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Sample records for phytochrome

  1. Chlorophyll formation and phytochrome

    NARCIS (Netherlands)

    Raven, C.W.

    1973-01-01

    The rôle of phytochrome in the regeneration of protochlorophyll (Pchl) in darkness following short exposures to light, as well as in the accumulation of chlorophyll- a (Chl- a ) in continuous light in previously dark-grown seedlings of pea, bean,

  2. Chlorophyll formation and phytochrome

    NARCIS (Netherlands)

    Raven, C.W.

    1973-01-01

    The rôle of phytochrome in the regeneration of protochlorophyll (Pchl) in darkness following short exposures to light, as well as in the accumulation of chlorophyll- a (Chl- a ) in continuous light in previously dark-grown seedlings of pea, bean, and maize has been the subject of the present investi

  3. Vibrational spectroscopy of phytochromes and phytochrome-related photoreceptors

    OpenAIRE

    Velázquez Escobar, Francisco Javier

    2015-01-01

    In dieser Arbeit wurde ein integrierter schwingungsspektroskopischer Ansatz zur Untersuchung der Mechanismen der Licht-induzierten Prozesse in Phytochromen angewandt. Diese Photorezeptor-Proteine binden ein offenkettiges Tetrapyrrol als Cofaktor. Hauptsächlich als kanonische (Pflanzen), prototypische (Bakterien, Pilze), Bathy-Phytochrome (Bakterien) und Cyanobakteriochrome (Cyanobakterien) klassifiziert, regulieren Phytochrome diverse biologische Prozesse (z. B. Blühverhalten, Phototaxis und ...

  4. Phytochromes in photosynthetically competent plants

    Energy Technology Data Exchange (ETDEWEB)

    Pratt, L.H.

    1990-07-01

    Plants utilize light as a source of information in photomorphogenesis and of free energy in photosynthesis, two processes that are interrelated in that the former serves to increase the efficiency with which plants can perform the latter. Only one pigment involved in photomorphogenesis has been identified unequivocally, namely phytochrome. The thrust of this proposal is to investigate this pigment and its mode(s) of action in photosynthetically competent plants. Our long term objective is to characterize phytochrome and its functions in photosynthetically competent plants from molecular, biochemical and cellular perspectives. It is anticipated that others will continue to contribute indirectly to these efforts at the physiological level. The ultimate goal will be to develop this information from a comparative perspective in order to learn whether the different phytochromes have significantly different physicochemical properties, whether they fulfill independent functions and if so what these different functions are, and how each of the different phytochromes acts at primary molecular and cellular levels.

  5. Synthetic Studies in Phytochrome Chemistry.

    Science.gov (United States)

    Jacobi, Peter A; Adel Odeh, Imad M; Buddhu, Subhas C; Cai, Guolin; Rajeswari, Sundaramoorthi; Fry, Douglas; Zheng, Wanjun; Desimone, Robert W; Guo, Jiasheng; Coutts, Lisa D; Hauck, Sheila I; Leung, Sam H; Ghosh, Indranath; Pippin, Douglas

    2005-01-01

    An account is given of the author's several approaches to the synthesis of the parent chromophore of phytochrome (1), a protein-bound linear tetrapyrrole derivative that controls photomorphogenesis in higher plants. These studies culminated in enantioselective syntheses of both 2R- and 2S-phytochromobilin (4), as well as several (13)C-labeled derivatives designed to probe the site of Z,E-isomerization during photoexcitation. When reacted in vitro, synthetic 2R-4 and recombinant-derived phytochrome apoprotein N-C produced a protein-bound chromophore with identical difference spectra to naturally occurring 1.

  6. Phytochrome and greening in etioplasts

    NARCIS (Netherlands)

    Kraak, H.L.

    1986-01-01

    This thesis is concerned with the role played by phytochrome (P) in the development of etioplasts into chloroplasts.

    Previously dark-grown maize seedlings are not as sensitive as pea seedlings to very low fluences of red light (R) with regard to induction of rapid chlorophyll (Chl)

  7. Temperature Effects on Agrobacterium Phytochrome Agp1

    OpenAIRE

    Ibrahim Njimona; Tilman Lamparter

    2014-01-01

    Phytochromes are widely distributed biliprotein photoreceptors with a conserved N-terminal chromophore-binding domain. Most phytochromes bear a light-regulated C-terminal His kinase or His kinase-like region. We investigated the effects of light and temperature on the His kinase activity of the phytochrome Agp1 from Agrobacterium tumefaciens. As in earlier studies, the phosphorylation activity of the holoprotein after far-red irradiation (where the red-light absorbing Pr form dominates) was s...

  8. MAS NMR study of the photoreceptor phytochrome

    NARCIS (Netherlands)

    Rohmer, Thierry

    2009-01-01

    Plants, algae and bacteria respond to light in various manners. The effect of light on the growth of plants is called photomorphogenesis and is regulated by the photoreceptor protein named phytochrome. Phytochrome is formed in the dark in its inactive red-absorbing (Pr) state and transformed upon ab

  9. Characterization of recombinant phytochrome from the cyanobacterium Synechocystis

    OpenAIRE

    Lamparter, Tilman; Mittmann, Franz; Gärtner, Wolfgang; Börner, Thomas; Hartmann, Elmar; Hughes, Jon

    1997-01-01

    The complete sequence of the Synechocystis chromosome has revealed a phytochrome-like sequence that yielded an authentic phytochrome when overexpressed in Escherichia coli. In this paper we describe this recombinant Synechocystis phytochrome in more detail. Islands of strong similarity to plant phytochromes were found throughout the cyanobacterial sequence whereas C-terminal homologies identify it as a likely sensory histidine kinase, a family to which plant phytochromes are related. An ≈300 ...

  10. Bottom-up Assembly of the Phytochrome Network

    Science.gov (United States)

    Sánchez-Lamas, Maximiliano; Lorenzo, Christian D.; Cerdán, Pablo D.

    2016-01-01

    Plants have developed sophisticated systems to monitor and rapidly acclimate to environmental fluctuations. Light is an essential source of environmental information throughout the plant’s life cycle. The model plant Arabidopsis thaliana possesses five phytochromes (phyA-phyE) with important roles in germination, seedling establishment, shade avoidance, and flowering. However, our understanding of the phytochrome signaling network is incomplete, and little is known about the individual roles of phytochromes and how they function cooperatively to mediate light responses. Here, we used a bottom-up approach to study the phytochrome network. We added each of the five phytochromes to a phytochrome-less background to study their individual roles and then added the phytochromes by pairs to study their interactions. By analyzing the 16 resulting genotypes, we revealed unique roles for each phytochrome and identified novel phytochrome interactions that regulate germination and the onset of flowering. Furthermore, we found that ambient temperature has both phytochrome-dependent and -independent effects, suggesting that multiple pathways integrate temperature and light signaling. Surprisingly, none of the phytochromes alone conferred a photoperiodic response. Although phyE and phyB were the strongest repressors of flowering, both phyB and phyC were needed to confer a flowering response to photoperiod. Thus, a specific combination of phytochromes is required to detect changes in photoperiod, whereas single phytochromes are sufficient to respond to light quality, indicating how phytochromes signal different light cues. PMID:27820825

  11. Light-induced import of the chromoprotein, phytochrome, into mitochondria

    Science.gov (United States)

    Serlin, B. S.; Roux, S. J.

    1986-01-01

    Mitochondria extracted from plants that were irradiated with actinic light in vivo have associated with them the chromoprotein, phytochrome. This phytochrome retains its native subunit size of 124 kDa after proteolytic treatment of the mitochondria with trypsin and chymotrypsin. This result suggests that phytochrome is not exposed on the outer surface of the outer mitochondrial membrane. Phytochrome, so protected, is not found to be associated with mitochondria derived from unirradiated plants. The possibility that the photoactivation of phytochrome induces a conformational change in its structure which facilitates its transport into the mitochondrion is discussed.

  12. Phytochrome, plant growth and flowering

    Science.gov (United States)

    King, R. W.; Bagnall, D. J.

    1994-01-01

    Attempts to use artificially lit cabinets to grow plants identical to those growing in sunlight have provided compelling evidence of the importance of light quality for plant growth. Changing the balance of red (R) to far-red (FR) radiation, but with a fixed photosynthetic input can shift the phytochrome photoequilibrium in a plant and generate large differences in plant growth. With FR enrichment the plants elongate, and may produce more leaf area and dry matter. Similar morphogenic responses are also obtained when light quality is altered only briefly (15-30 min) at the end-of-the-day. Conversely, for plants grown in natural conditions the response of plant form to selective spectral filtering has again shown that red and far-red wavebands are important as found by Kasperbauer and coworkers. Also, where photosynthetic photon flux densities (PPFD) of sunlight have been held constant, the removal of far-red alone alters plant growth. With FR depletion plants grown in sunlight are small, more branched and darker green. Here we examine the implications for plant growth and flowering when the far-red composition of incident radiation in plant growth chambers is manipulated.

  13. Phytochrome-regulated Gene Expression

    Institute of Scientific and Technical Information of China (English)

    Peter H. Quail

    2007-01-01

    Identification of all genes involved in the phytochrome (phy)-mediated responses of plants to their light environment is an important goal in providing an overall understanding of light-regulated growth and development. This article highlights and integrates the central findings of two recent comprehensive studies in Arabidopsis that have identified the genome-wide set of phy-regulated genes that respond rapidly to red-light signals upon first exposure of dark-grown seedlings, and have tested the functional relevance to normal seedling photomorphogenesis of an initial subset of these genes. The data: (a) reveal considerable complexity in the channeling of the light signals through the different phy-family members (phyA to phyE) to responsive genes; (b) identify a diversity of transcription-factor-encoding genes as major early, if not primary, targets of phy signaling, and, therefore, as potentially important regulators in the transcriptional-network hierarchy; and (c) identify auxin-related genes as the dominant class among rapidly-regulated, hormone-related genes. However, reverse-genetic functional profiling of a selected subset of these genes reveals that only a limited fraction are necessary for optimal phy-induced seedling deetiolation.

  14. Marine algae and land plants share conserved phytochrome signaling systems.

    Science.gov (United States)

    Duanmu, Deqiang; Bachy, Charles; Sudek, Sebastian; Wong, Chee-Hong; Jiménez, Valeria; Rockwell, Nathan C; Martin, Shelley S; Ngan, Chew Yee; Reistetter, Emily N; van Baren, Marijke J; Price, Dana C; Wei, Chia-Lin; Reyes-Prieto, Adrian; Lagarias, J Clark; Worden, Alexandra Z

    2014-11-04

    Phytochrome photosensors control a vast gene network in streptophyte plants, acting as master regulators of diverse growth and developmental processes throughout the life cycle. In contrast with their absence in known chlorophyte algal genomes and most sequenced prasinophyte algal genomes, a phytochrome is found in Micromonas pusilla, a widely distributed marine picoprasinophyte (algae and land plants. These analyses reveal a monophyletic clade containing streptophyte, prasinophyte, cryptophyte, and glaucophyte phytochromes implying an origin in the eukaryotic ancestor of the Archaeplastida. Transcriptomic measurements reveal diurnal regulation of phytochrome and bilin chromophore biosynthetic genes in Micromonas. Expression of these genes precedes both light-mediated phytochrome redistribution from the cytoplasm to the nucleus and increased expression of photosynthesis-associated genes. Prasinophyte phytochromes perceive wavelengths of light transmitted farther through seawater than the red/far-red light sensed by land plant phytochromes. Prasinophyte phytochromes also retain light-regulated histidine kinase activity lost in the streptophyte phytochrome lineage. Our studies demonstrate that light-mediated nuclear translocation of phytochrome predates the emergence of land plants and likely represents a widespread signaling mechanism in unicellular algae.

  15. Chromopeptides from phytochrome. The structure and linkage of the PR form of the phytochrome chromophore

    Energy Technology Data Exchange (ETDEWEB)

    Lagarias, J. Clark [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States); Rapoport, Henry [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States)

    1980-07-01

    The isolation and chromatographic purification of chromophore-containing peptides from the PR form of phytochrome treated with pepsin and thermolysin are described. From the amino acid sequence and 1H NMR spectral analysis of phytochromobiliundeca peptide (2), the structure of the PR phytochrome chromophore and the nature of the thioether linkage joining pigment to peptide have been established. Furthermore, confirmatory evidence was obtained from similar analysis of phytochromobilioctapeptide (3). The implications of this structural assignment with respect to the mechanism of the PR to PFR phototransformation are considered.

  16. The protein phosphatase 7 regulates phytochrome signaling in Arabidopsis.

    Directory of Open Access Journals (Sweden)

    Thierry Genoud

    Full Text Available The psi2 mutant of Arabidopsis displays amplification of the responses controlled by the red/far red light photoreceptors phytochrome A (phyA and phytochrome B (phyB but no apparent defect in blue light perception. We found that loss-of-function alleles of the protein phosphatase 7 (AtPP7 are responsible for the light hypersensitivity in psi2 demonstrating that AtPP7 controls the levels of phytochrome signaling. Plants expressing reduced levels of AtPP7 mRNA display reduced blue-light induced cryptochrome signaling but no noticeable deficiency in phytochrome signaling. Our genetic analysis suggests that phytochrome signaling is enhanced in the AtPP7 loss of function alleles, including in blue light, which masks the reduced cryptochrome signaling. AtPP7 has been found to interact both in yeast and in planta assays with nucleotide-diphosphate kinase 2 (NDPK2, a positive regulator of phytochrome signals. Analysis of ndpk2-psi2 double mutants suggests that NDPK2 plays a critical role in the AtPP7 regulation of the phytochrome pathway and identifies NDPK2 as an upstream element involved in the modulation of the salicylic acid (SA-dependent defense pathway by light. Thus, cryptochrome- and phytochrome-specific light signals synchronously control their relative contribution to the regulation of plant development. Interestingly, PP7 and NDPK are also components of animal light signaling systems.

  17. In vivo measurement of phytochrome in tomato fruit.

    Science.gov (United States)

    Jen, J J

    1977-04-01

    Presence of phytochrome in two kinds of tomatoes (Lycopersicon esculentum Mill.), the yellow lutescent strain and cherry tomatoes (L. esculentum Mill. var. cerasiformecv. Red Cherry), was established by measuring the absorption difference spectra of the whole fruit after irradiation with red and with far red light. Phytochrome content was determined in yellow lutescent tomatoes and decreased gradually during the ripening period.

  18. Mechanism for the selective conjugation of ubiquitin to phytochrome

    Energy Technology Data Exchange (ETDEWEB)

    Vierstra, R.D.

    1990-01-01

    The goal of this project is to understand at the molecular level how phytochrome functions and how intracellular proteins are degraded. Phytochrome is marked for degradation by covalent attachment of ubiquitin. Ubiquitin-phytochrome conjugates (UbP) were characterized with respect to formation kinetics, subcellular localization and site of ubiquitin attachment. UbP appears to be a general phenomenon during phytochrome degradation in a variety of species. UbP was isolated from oat seedlings and characterized. Residues 747-830 of phytochrome have been identified as a possible attachment site for ubiquitin. By placing the gene for etiolated phytochrome in tobacco we have created a transgenic system for over expressing phytochrome. The effects of this over expression are described, and it appears that tobacco degrades this foreign protein through formation of UbP. We have created a series of site-directed mutants of the oat phytochrome gene, and are in the process of characterizing them to determine sequence requirements for ubiquination. 8 refs., 1 fig. (MHB)

  19. Light-induced conformational changes of the chromophore and the protein in phytochromes: bacterial phytochromes as model systems.

    Science.gov (United States)

    Scheerer, Patrick; Michael, Norbert; Park, Jung Hee; Nagano, Soshichiro; Choe, Hui-Woog; Inomata, Katsuhiko; Borucki, Berthold; Krauss, Norbert; Lamparter, Tilman

    2010-04-26

    Recombinant phytochromes Agp1 and Agp2 from Agrobacterium tumefaciens are used as model phytochromes for biochemical and biophysical studies. In biliverdin binding phytochromes the site for covalent attachment of the chromophore lies in the N-terminal region of the protein, different from plant phytochromes. The issue which stereochemistry the chromophore adopts in the so-called Pr and Pfr forms is addressed by using a series of locked chromophores which form spectrally characteristic adducts with Agp1 and Agp2. Studies on light-induced conformational changes of Agp1 give an insight into how the intrinsic histidine kinase is modulated by light. Comparison of the crystal structure of an Agp1 fragment with other phytochrome crystal structures supports the idea that a light induced rearrangement of subunits within the homodimer modulates the activity of the kinase.

  20. Temperature effects on Agrobacterium phytochrome Agp1.

    Directory of Open Access Journals (Sweden)

    Ibrahim Njimona

    Full Text Available Phytochromes are widely distributed biliprotein photoreceptors with a conserved N-terminal chromophore-binding domain. Most phytochromes bear a light-regulated C-terminal His kinase or His kinase-like region. We investigated the effects of light and temperature on the His kinase activity of the phytochrome Agp1 from Agrobacterium tumefaciens. As in earlier studies, the phosphorylation activity of the holoprotein after far-red irradiation (where the red-light absorbing Pr form dominates was stronger than that of the holoprotein after red irradiation (where the far red-absorbing Pfr form dominates. Phosphorylation activities of the apoprotein, far red-irradiated holoprotein, and red-irradiated holoprotein decreased when the temperature increased from 25 °C to 35 °C; at 40 °C, almost no kinase activity was detected. The activity of a holoprotein sample incubated at 40 °C was nearly completely restored when the temperature returned to 25 °C. UV/visible spectroscopy indicated that the protein was not denatured up to 45 °C. At 50 °C, however, Pfr denatured faster than the dark-adapted sample containing the Pr form of Agp1. The Pr visible spectrum was unaffected by temperatures of 20-45 °C, whereas irradiated samples exhibited a clear temperature effect in the 30-40 °C range in which prolonged irradiation resulted in the photoconversion of Pfr into a new spectral species termed Prx. Pfr to Prx photoconversion was dependent on the His-kinase module of Agp1; normal photoconversion occurred at 40 °C in the mutant Agp1-M15, which lacks the C-terminal His-kinase module, and in a domain-swap mutant in which the His-kinase module of Agp1 is replaced by the His-kinase/response regulator module of the other A. tumefaciens phytochrome, Agp2. The temperature-dependent kinase activity and spectral properties in the physiological temperature range suggest that Agp1 serves as an integrated light and temperature sensor in A. tumefaciens.

  1. Temperature effects on Agrobacterium phytochrome Agp1.

    Science.gov (United States)

    Njimona, Ibrahim; Lamparter, Tilman

    2011-01-01

    Phytochromes are widely distributed biliprotein photoreceptors with a conserved N-terminal chromophore-binding domain. Most phytochromes bear a light-regulated C-terminal His kinase or His kinase-like region. We investigated the effects of light and temperature on the His kinase activity of the phytochrome Agp1 from Agrobacterium tumefaciens. As in earlier studies, the phosphorylation activity of the holoprotein after far-red irradiation (where the red-light absorbing Pr form dominates) was stronger than that of the holoprotein after red irradiation (where the far red-absorbing Pfr form dominates). Phosphorylation activities of the apoprotein, far red-irradiated holoprotein, and red-irradiated holoprotein decreased when the temperature increased from 25 °C to 35 °C; at 40 °C, almost no kinase activity was detected. The activity of a holoprotein sample incubated at 40 °C was nearly completely restored when the temperature returned to 25 °C. UV/visible spectroscopy indicated that the protein was not denatured up to 45 °C. At 50 °C, however, Pfr denatured faster than the dark-adapted sample containing the Pr form of Agp1. The Pr visible spectrum was unaffected by temperatures of 20-45 °C, whereas irradiated samples exhibited a clear temperature effect in the 30-40 °C range in which prolonged irradiation resulted in the photoconversion of Pfr into a new spectral species termed Prx. Pfr to Prx photoconversion was dependent on the His-kinase module of Agp1; normal photoconversion occurred at 40 °C in the mutant Agp1-M15, which lacks the C-terminal His-kinase module, and in a domain-swap mutant in which the His-kinase module of Agp1 is replaced by the His-kinase/response regulator module of the other A. tumefaciens phytochrome, Agp2. The temperature-dependent kinase activity and spectral properties in the physiological temperature range suggest that Agp1 serves as an integrated light and temperature sensor in A. tumefaciens.

  2. Oat Phytochrome Is Biologically Active in Transgenic Tomatoes.

    Science.gov (United States)

    Boylan, M. T.; Quail, P. H.

    1989-08-01

    To determine the functional homology between phytochromes from evolutionarily divergent species, we used the cauliflower mosaic virus 35S promoter to express a monocot (oat) phytochrome cDNA in a dicot plant (tomato). Immunoblot analysis shows that more than 50% of the transgenic tomato plants synthesize the full-length oat phytochrome polypeptide. Moreover, leaves of light-grown transgenic plants contain appreciably less oat phytochrome than leaves from dark-adapted plants, and etiolated R1 transgenic seedlings have higher levels of spectrally active phytochrome than wild-type tomato seedlings in direct proportion to the level of immunochemically detectable oat polypeptide present. These data suggest that the heterologous oat polypeptide carries a functional chromophore, allowing reversible photoconversion between the two forms of the molecule, and that the far-red absorbing form (Pfr) is recognized and selectively degraded by the Pfr-specific degradative machinery in the dicot cell. The overexpression of oat phytochrome has pleiotropic, phenotypic consequences at all major phases of the life cycle. Adult transgenic tomato plants expressing high levels of the oat protein tend to be dwarfed, with dark green foliage and fruits. R1 transgenic seedlings have short hypocotyls with elevated anthocyanin contents. We conclude that a monocot phytochrome can be synthesized and correctly processed to a biologically active form in a dicot cell, and that the transduction pathway components that interact with the photoreceptor are evolutionarily conserved.

  3. Novel Photodynamics in Phytochrome & Cyanobacteriochrome Photosensory Proteins

    Science.gov (United States)

    Larsen, Delmar

    2015-03-01

    The photodynamics of recently characterized phytochrome and cyanobacteriochrome photoreceptors are discussed. Phytochromes are red/far-red photosensory proteins that utilize the photoisomerization of a linear tetrapyrrole (bilin) chromophore to detect the red to far-red light ratio. Cyanobacteriochromes (CBCRs) are distantly related cyanobacterial photosensors with homologous bilin-binding GAF domains, but exhibit greater spectral diversity. The excited-state mechanisms underlying the initial photoisomerization in the forward reactions of the cyanobacterial photoreceptor Cph1 from Synechocystis, the RcaE CBCR from Fremyella diplosiphon, and Npr6012g4 CBCR from Nostoc punctiforme were contrasted via multipulse pump-dump-probe transient spectroscopy. A rich excited-state dynamics are resolved involving a complex interplay of excited-state proton transfer, photoisomerization, multilayered inhomogeneity, and reactive intermediates, and Le Chatelier redistribution. NpR6012g4 exhibits a high quantum yield for its forward photoreaction (40%) that was ascribed to the activity of hidden, productive ground-state intermediates via a ``second chance initiation dynamics'' (SCID) mechanism. This work was supported by a grant from the Chemical Sciences, Geosciences, and Biosciences Division, Office of Basic Energy Sciences, Office of Science, United States Department of Energy (DOE DE-FG02-09ER16117).

  4. Phytochrome from green plants: Assay, purification, and characterization

    Energy Technology Data Exchange (ETDEWEB)

    Quail, P.H. (California Univ., Berkeley, CA (United States). Dept. of Plant and Soil Biology Agricultural Research Service, Albany, CA (United States). Plant Gene Expression Center)

    1991-06-10

    This funding period was directed at developing an in-depth molecular analysis of the low-abundance, 118,000 M{sub r} green-tissue phytochrome that had at that time been relatively recently identified as being distinct from the better characterized 124,000 M{sub r} phytochrome abundant in etiolated tissue. The specific objectives as stated in the original proposal were: (1) To generate monoclonal antibodies specific to the 118,000 M{sub r} green-tissue phytochrome. (2) To develop additional and improved procedures to permit progress toward the ultimate goal of purifying green-tissue phytochrome to homogeneity. (3) To initiate an alternative approach to determining the structural properties of green-tissue phytochrome by isolating and sequencing cDNA cones representing the 118,000 M{sub r} green-tissue polypeptide in Avena. This approach is based on and will test hypothesis that the 118,000 M{sub r} polypeptide is encoded by a gene(s) distinct from those encoding etiolated-tissue 124,000 M{sub r} phytochrome. (4) To utilize any such 118,000 M{sub r} phytochrome specific cDNA clones as hybridization probes to begin to investigate the structure, organization, and regulation of the corresponding gene(s) in Avena. (5) To begin to investigate the possible presence in other higher plant and algal species of sequences homologous to the 118,000 M{sub r} Avena polypeptide using the Avena clones at hybridization probes. Most of these objectives have been accomplished, at least in principle, although the major breakthrough establishing that phytochrome is encoded by a multigene family came from the use of Arabidopsis rather than Avena. Similarly, much of the characterization subsequent to this discovery has been performed in Arabidopsis and rise as model dicot and monocot systems, respectively, rather than Avena. 13 refs., 9 figs.

  5. Calcium requirement of phytochrome-mediated fern-spore germination: no direct phytochrome-calcium interaction in the phytochrome-initiated transduction chain

    Science.gov (United States)

    Scheuerlein, R.; Wayne, R.; Roux, S. J.

    1989-01-01

    Phytochrome-mediated germination of fern spores of Dryopteris paleacea Sw. was initiated by a saturating red-light (R) irradiation after 20 h of imbibition. For its realization external Ca2+ was required, with a threshold at a submicromolar concentration, and an optimum was reached around 10(-4) M. At concentrations > or = 10(-1) M only a reduced response was obtained, based probably on an unspecific osmotic or ionic effect. The germination response was inhibited by La3+, an antagonist of Ca2+. From these results it is concluded that Ca2+ influx from the medium into the spores may be an important event in phytochrome-mediated germination. In the absence of Ca2+ the R-stimulated system remained capable of responding to Ca2+, added as late as 40 h after R. Moreover, Ca2+ was effective even if added after the active form of phytochrome, Pfr, had been abolished by far-red (FR) 24 h after R. Thus, the primary effect of Pfr, that initiates the transduction chain, does not require calcium. "Coupling" of Pfr to subsequent dark reactions has been investigated by R-FR irradiations with various dark intervals. The resulting "escape kinetics" were characterized by a lag phase (6 h) and half-maximal escape from FR reversibility (19 h). These kinetics were not significantly changed by the presence or absence of calcium. Thus, direct interaction of Pfr and calcium is not a step in the transduction chain initiated by the active form of phytochrome.

  6. Phytochrome-mediated regulation of plant respiration and photorespiration.

    Science.gov (United States)

    Igamberdiev, Abir U; Eprintsev, Alexander T; Fedorin, Dmitry N; Popov, Vasily N

    2014-02-01

    The expression of genes encoding various enzymes participating in photosynthetic and respiratory metabolism is regulated by light via the phytochrome system. While many photosynthetic, photorespiratory and some respiratory enzymes, such as the rotenone-insensitive NADH and NADPH dehydrogenases and the alternative oxidase, are stimulated by light, succinate dehydrogenase, subunits of the pyruvate dehydrogenase complex, cytochrome oxidase and fumarase are inhibited via the phytochrome mechanism. The effect of light, therefore, imposes limitations on the tricarboxylic acid cycle and on the mitochondrial electron transport coupled to ATP synthesis, while the non-coupled pathways become activated. Phytochrome-mediated regulation of gene expression also creates characteristic distribution patterns of photosynthetic, photorespiratory and respiratory enzymes across the leaf generating different populations of mitochondria, either enriched by glycine decarboxylase (in the upper part) or by succinate dehydrogenase (in the bottom part of the leaf).

  7. A Small GTPase Activator Protein Interacts with Cytoplasmic Phytochromes in Regulating Root Development*

    Science.gov (United States)

    Shin, Dong Ho; Cho, Man-Ho; Kim, Tae-Lim; Yoo, Jihye; Kim, Jeong-Il; Han, Yun-Jeong; Song, Pill-Soon; Jeon, Jong-Seong; Bhoo, Seong Hee; Hahn, Tae-Ryong

    2010-01-01

    Phytochromes enable plants to sense light information and regulate developmental responses. Phytochromes interact with partner proteins to transmit light signals to downstream components for plant development. PIRF1 (phytochrome-interacting ROP guanine-nucleotide exchange factor (RopGEF 1)) functions as a light-signaling switch regulating root development through the activation of ROPs (Rho-like GTPase of plant) in the cytoplasm. In vitro pulldown and yeast two-hybrid assays confirmed the interaction between PIRF1 and phytochromes. PIRF1 interacted with the N-terminal domain of phytochromes through its conserved PRONE (plant-specific ROP nucleotide exchanger) region. PIRF1 also interacted with ROPs and activated them in a phytochrome-dependent manner. The Pr form of phytochrome A enhanced the RopGEF activity of PIRF1, whereas the Pfr form inhibited it. A bimolecular fluorescence complementation analysis demonstrated that PIRF1 was localized in the cytoplasm and bound to the phytochromes in darkness but not in light. PIRF1 loss of function mutants (pirf1) of Arabidopsis thaliana showed a longer root phenotype in the dark. In addition, both PIRF1 overexpression mutants (PIRF1-OX) and phytochrome-null mutants (phyA-211 and phyB-9) showed retarded root elongation and irregular root hair formation, suggesting that PIRF1 is a negative regulator of phytochrome-mediated primary root development. We propose that phytochrome and ROP signaling are interconnected through PIRF1 in regulating the root growth and development in Arabidopsis. PMID:20551316

  8. The phytochrome B/phytochrome C heterodimer is necessary for phytochrome C-mediated responses in rice seedlings.

    Directory of Open Access Journals (Sweden)

    Xianzhi Xie

    Full Text Available BACKGROUND: PhyC levels have been observed to be markedly lower in phyB mutants than in Arabidopsis or rice wild type etiolated seedlings, but the mechanism of this phenomenon has not been fully elucidated. RESULTS: In the present study, we investigated the mechanism by which phyB affects the protein concentration and photo-sensing abilities of phyC and demonstrated that rice phyC exists predominantly as phyB/phyC heterodimers in etiolated seedlings. PHYC-GFP protein was detected when expressed in phyA phyC mutants, but not in phyA phyB mutants, suggesting that phyC requires phyB for its photo-sensing abilities. Interestingly, when a mutant PHYB gene that has no chromophore binding site, PHYB(C364A, was introduced into phyB mutants, the phyC level was restored. Moreover, when PHYB(C364A was introduced into phyA phyB mutants, the seedlings exhibited de-etiolation under both far-red light (FR and red light (R conditions, while the phyA phyB mutants were blind to both FR and R. These results are the first direct evidence that phyC is responsible for regulating seedling de-etiolation under both FR and R. These findings also suggest that phyB is indispensable for the expression and function of phyC, which depends on the formation of phyB/phyC heterodimers. SIGNIFICANCE: The present report clearly demonstrates the similarities and differences in the properties of phyC between Arabidopsis and rice and will advance our understanding of phytochrome functions in monocots and dicots.

  9. Labile phytochrome and photoperiodic flower induction in Pharbitis nil Chois. The irreversible phytochrome hypothesis

    Directory of Open Access Journals (Sweden)

    Mariusz Cymerski

    2014-01-01

    Full Text Available Seedlings of Pharbitis nil cultivated under non-inductive conditions of white light were subjected to generative induction applying one 16-hour-long period of inductive night. During the eighth hour the night was interrupted with 1 min of red light pulse which completely inhibited the flowering. Treating the plants with KCN blocked the inhibiting effect of red light. Because KCN lowers considerably the rate of destruction of labile Pfd in some plant systems, it seems probable that red light night-break irradiation (without KCN, which blocked the flowering, leads also to the accumulation of unknown Pfd destruction products (irreversible phytochrome. It also suggests that it is not the labile PfrI itself but the products of its irreversible transformation that could be active in the photoperiodic control of flowering.

  10. Phytochrome-mediated Carotenoids Biosynthesis in Ripening Tomatoes.

    Science.gov (United States)

    Thomas, R L; Jen, J J

    1975-09-01

    Red light induced and far red light inhibited carotenoid biosynthesis in ripening tomatoes (Lycopersicon esculentum Mill.) when compared to controls kept in the dark. Red illumination following far red illumination reversed the inhibitory action of far red light on carotenoid biosynthesis, suggesting a phytochrome-mediated process. Quantitation of individual carotenoids favored the hypothesis of two separate carotenoid biosynthetic pathways in tomatoes.

  11. Systematic analysis of how phytochrome B dimerization determines its specificity

    NARCIS (Netherlands)

    Klose, Cornelia; Venezia, Filippo; Hussong, Andrea; Kircher, Stefan; Schäfer, Eberhard; Fleck, Christian

    2015-01-01

    Phytochromes are red/far-red-light detecting photoreceptors that regulate plant growth and development. They photo-interconvert between an inactive Pr (red-light absorbing) and a physiologically active Pfr (far-red-light absorbing) form, acting as light-controlled molecular switches. Although the

  12. My Path from Chemistry to Phytochrome and Circadian Rhythms

    Science.gov (United States)

    Tobin, Elaine M.

    2016-01-01

    I summarize my scientific journey from my first interest in science to my career investigating how plants use the phytochrome photoreceptor to regulate what genes they express. I then describe how this work led to an understanding of how circadian rhythms function in plants and to the discovery of CCA1, a component of the plant central oscillator. PMID:27014288

  13. Phytochrome and endogenous gibberellin-like substances in etiolated and irradiated oat seedlings

    Directory of Open Access Journals (Sweden)

    Jan Kopcewicz

    2014-02-01

    Full Text Available The level of gibberellin-like substances was investigated in oat coleoptiles with different stationary states of phytochrome and in leaf segments which had been etiolated and irradiated with red light. Etiolated coleoptiles and leaves containing maximum amounts of the PR form of phytochrome were characterized by an increased level of bound gibberellins. Irradiation with red light resulting in the photoconversion of phytochrome into the Pt R form caused the appearance of a high content of free gibberellins. It seems that the releasing the hormones from bound forms correlated with the formation of phytochrome PFR may be an important aspect of the mechanism of phytochrome action in the processes of seedling deetiolation. The interrelation between phytochrome and plant hormones in the control of photomorphogenesis of young monocotyledonous seedlings is also discussed.

  14. Molecular dissection of the roles of phytochrome in photoperiodic flowering in rice.

    Science.gov (United States)

    Osugi, Asami; Itoh, Hironori; Ikeda-Kawakatsu, Kyoko; Takano, Makoto; Izawa, Takeshi

    2011-11-01

    Phytochromes mediate the photoperiodic control of flowering in rice (Oryza sativa), a short-day plant. Recent molecular genetics studies have revealed a genetic network that enables the critical daylength response of florigen gene expression. Analyses using a rice phytochrome chromophore-deficient mutant, photoperiod sensitivity5, have so far revealed that within this network, phytochromes are required for expression of Grain number, plant height and heading date7 (Ghd7), a floral repressor gene in rice. There are three phytochrome genes in rice, but the roles of each phytochrome family member in daylength response have not previously been defined. Here, we revealed multiple action points for each phytochrome in the critical daylength response of florigen expression by using single and double phytochrome mutant lines of rice. Our results show that either phyA alone or a genetic combination of phyB and phyC can induce Ghd7 mRNA, whereas phyB alone causes some reduction in levels of Ghd7 mRNA. Moreover, phyB and phyA can affect Ghd7 activity and Early heading date1 (a floral inducer) activity in the network, respectively. Therefore, each phytochrome gene of rice has distinct roles, and all of the phytochrome actions coordinately control the critical daylength response of florigen expression in rice.

  15. Adaptive evolution in the GAF domain of phytochromes in gymnosperms.

    Science.gov (United States)

    Wang, Jing; Yan, Boqian; Chen, Guopei; Su, Yingjuan; Wang, Ting

    2010-04-01

    The GAF domain of phytochrome is essential for photoconversion and signal transduction. In gymnosperms, it exists in all members of the phytochrome family that experience gene duplication. Maximum-likelihood models of codon substitution can provide a framework for constructing likelihood ratio tests of changes in selective pressure and make clear predictions about patterns of genetic change following gene duplication. In this study, 68 gymnosperm GAF sequences were analyzed to identify lineages and sites under positive selection. Our results indicate that (1) positive selection at a few sites (3.6%), rather than relaxation of selective constraints, has played a major role in the evolution of the gymnosperm GAF domain; (2) strong positive selective pressure tends to occur in the recent PHYP lineages of cogeneric species, but is absent in old lineages consisting of distantly related species; and (3) the selective pressure indicated by the omega ratio varies greatly among lineages and sites in the GAF domain.

  16. Fluorescence of Phytochrome Adducts with Synthetic Locked Chromophores*

    OpenAIRE

    Zienicke, Benjamin; Chen, Li-Yi; Khawn, Htoi; Hammam, Mostafa A. S.; Kinoshita, Hideki; Reichert, Johannes; Ulrich, Anne S.; Inomata, Katsuhiko; Lamparter, Tilman

    2010-01-01

    We performed steady state fluorescence measurements with phytochromes Agp1 and Agp2 of Agrobacterium tumefaciens and three mutants in which photoconversion is inhibited. These proteins were assembled with the natural chromophore biliverdin (BV), with phycoerythrobilin (PEB), which lacks a double bond in the ring C-D-connecting methine bridge, and with synthetic bilin derivatives in which the ring C-D-connecting methine bridge is locked. All PEB and locked chromophore adducts are photoinactive...

  17. A computational approach to discovering the functions of bacterial phytochromes by analysis of homolog distributions.

    Science.gov (United States)

    Lamparter, Tilman

    2006-03-16

    Phytochromes are photoreceptors, discovered in plants, that control a wide variety of developmental processes. They have also been found in bacteria and fungi, but for many species their biological role remains obscure. This work concentrates on the phytochrome system of Agrobacterium tumefaciens, a non-photosynthetic soil bacterium with two phytochromes. To identify proteins that might share common functions with phytochromes, a co-distribution analysis was performed on the basis of protein sequences from 138 bacteria. A database of protein sequences from 138 bacteria was generated. Each sequence was BLASTed against the entire database. The homolog distribution of each query protein was then compared with the homolog distribution of every other protein (target protein) of the same species, and the target proteins were sorted according to their probability of co-distribution under random conditions. As query proteins, phytochromes from Agrobacterium tumefaciens, Pseudomonas aeruginosa, Deinococcus radiodurans and Synechocystis PCC 6803 were chosen along with several phytochrome-related proteins from A. tumefaciens. The Synechocystis photosynthesis protein D1 was selected as a control. In the D1 analyses, the ratio between photosynthesis-related proteins and those not related to photosynthesis among the top 150 in the co-distribution tables was > 3:1, showing that the method is appropriate for finding partner proteins with common functions. The co-distribution of phytochromes with other histidine kinases was remarkably high, although most co-distributed histidine kinases were not direct BLAST homologs of the query protein. This finding implies that phytochromes and other histidine kinases share common functions as parts of signalling networks. All phytochromes tested, with one exception, also revealed a remarkably high co-distribution with glutamate synthase and methionine synthase. This result implies a general role of bacterial phytochromes in ammonium

  18. Phytochrome-controlled level of growth substances in etiolated oat seedlings

    Directory of Open Access Journals (Sweden)

    Jan Kopcewicz

    2014-02-01

    Full Text Available Irradiation with red light of coleoptiles and leaves of etiolated oat seedlings, causing photoconversion of phytochrome mainly into Pfr, leads to the release of free auxins and free gibberellins from conjugated forms. The effect of red light is reversible by far-red light irradiation. A correlation between the photostationary state of phytochrome and endogenous abscisic acid content was not found.

  19. Red Light-Induced Phytochrome Relocation into the Nucleus in Adiantum capillus-veneris

    Institute of Scientific and Technical Information of China (English)

    Hidenori Tsuboi; Sachihiko Nakamura; Eberhard Sch(a)fer; Masamitsu Wada

    2012-01-01

    Phytochromes in seed plants are known to move into nuclei in a red light-dependent manner with or without interacting factors.Here,we show phytochrome relocation to the nuclear region in phytochrome-dependent Adiantum capillus-veneris spore germination by partial spore-irradiation experiments.The nuclear or non-nuclear region of imbibed spores was irradiated with a microbeam of red and/or far-red light and the localization of phytochrome involved in spore germination was estimated from the germination rate.The phytochrome for spore germination existed throughout whole spore under darkness after imbibition,but gradually migrated to the nuclear region following red light irradiation.Intracellular distribution of PHY-GUS fusion proteins expressed in germinated spores by particle bombardment showed the migration of Acphy2,but not Acphy1,into nucleus in a red light-dependent manner,suggesting that Acphy2 is the photoreceptor for fern spore germination.

  20. Lack of influence of low temperature, light and growth substances on phytochrome resynthesis in coleoptiles of irradiated oat seedlings

    Directory of Open Access Journals (Sweden)

    Jan Kopcewicz

    2014-02-01

    Full Text Available The photoconversion of phytochrome PR into the PFR form causes at the same time the destruction of the initial large fraction of phytochrome found in the coleoptiles of etiolated oat seedlings. Factors such as low temperature, light of different wavelengths or growth substances are not capable of preventing the progressive destruction and restore the synthesis of phytochrome. Thus an abnormally high level of phytochrome is found only in etiolated seedlings. Such seedlings, on the other hand, are characterized by a very high rate of elongation growth. The role of phytochrome in the control of deetiolation of seedlings is discussed.

  1. The aurea mutant of tomato is deficient in spectrophotometrically and immunochemically detectable phytochrome.

    Science.gov (United States)

    Parks, B M; Jones, A M; Adamse, P; Koornneef, M; Kendrick, R E; Quail, P H

    1987-03-01

    The aurea locus mutant (au (w)) of tomato contains less than 5% of the level of phytochrome in wild-type tissue as measured by in vivo difference spectroscopy. Immunoblot analysis using antibodies directed against etiolated-oat phytochrome demonstrates that crude extracts of etiolated mutant tissue are deficient in a major immunodetectable protein (116 kDa) normally present in the parent wild type. Analyses of wild-type tissue extracts strongly indicate that the 116-kDa protein is phytochrome by showing that this protein: a) is degraded more rapidly in vitro after a brief far-red irradiation than after a brief red irradiation (Vierstra RD, Quail PH, Planta 156: 158-165, 1982); b) contains a covalently bound chromophore as detected by Zn-chromophore fluorescence on nitrocellulose blots; and c) has an apparent molecular mass comparable to phytochrome from other species on size exclusion chromatography under non-denaturing conditions. The demonstration that the aurea mutant is deficient in this 116-kDa phytochrome indicates that the lack of spectrally detectable phytochrome in this mutant is the result of a lesion which affects the abundance of the phytochrome molecule as opposed to its spectral integrity.

  2. Structure of the biliverdin cofactor in the Pfr state of bathy and prototypical phytochromes.

    Science.gov (United States)

    Salewski, Johannes; Escobar, Francisco Velazquez; Kaminski, Steve; von Stetten, David; Keidel, Anke; Rippers, Yvonne; Michael, Norbert; Scheerer, Patrick; Piwowarski, Patrick; Bartl, Franz; Frankenberg-Dinkel, Nicole; Ringsdorf, Simone; Gärtner, Wolfgang; Lamparter, Tilman; Mroginski, Maria Andrea; Hildebrandt, Peter

    2013-06-07

    Phytochromes act as photoswitches between the red- and far-red absorbing parent states of phytochromes (Pr and Pfr). Plant phytochromes display an additional thermal conversion route from the physiologically active Pfr to Pr. The same reaction pattern is found in prototypical biliverdin-binding bacteriophytochromes in contrast to the reverse thermal transformation in bathy bacteriophytochromes. However, the molecular origin of the different thermal stabilities of the Pfr states in prototypical and bathy bacteriophytochromes is not known. We analyzed the structures of the chromophore binding pockets in the Pfr states of various bathy and prototypical biliverdin-binding phytochromes using a combined spectroscopic-theoretical approach. For the Pfr state of the bathy phytochrome from Pseudomonas aeruginosa, the very good agreement between calculated and experimental Raman spectra of the biliverdin cofactor is in line with important conclusions of previous crystallographic analyses, particularly the ZZEssa configuration of the chromophore and its mode of covalent attachment to the protein. The highly homogeneous chromophore conformation seems to be a unique property of the Pfr states of bathy phytochromes. This is in sharp contrast to the Pfr states of prototypical phytochromes that display conformational equilibria between two sub-states exhibiting small structural differences at the terminal methine bridges A-B and C-D. These differences may mainly root in the interactions of the cofactor with the highly conserved Asp-194 that occur via its carboxylate function in bathy phytochromes. The weaker interactions via the carbonyl function in prototypical phytochromes may lead to a higher structural flexibility of the chromophore pocket opening a reaction channel for the thermal (ZZE → ZZZ) Pfr to Pr back-conversion.

  3. PHYTOCHROME KINASE SUBSTRATE1 regulates root phototropism and gravitropism.

    Science.gov (United States)

    Boccalandro, Hernán E; De Simone, Silvia N; Bergmann-Honsberger, Ariane; Schepens, Isabelle; Fankhauser, Christian; Casal, Jorge J

    2008-01-01

    Light promotes the expression of PHYTOCHROME KINASE SUBSTRATE1 (PKS1) in the root of Arabidopsis thaliana, but the function of PKS1 in this organ is unknown. Unilateral blue light induced a negative root phototropic response mediated by phototropin 1 in wild-type seedlings. This response was absent in pks1 mutants. In the wild type, unilateral blue light enhanced PKS1 expression in the subapical region of the root several hours before bending was detectable. The negative phototropism and the enhanced PKS1 expression in response to blue light required phytochrome A (phyA). In addition, the pks1 mutation enhanced the root gravitropic response when vertically oriented seedlings were placed horizontally. The negative regulation of gravitropism by PKS1 occurred even in dark-grown seedlings and did not require phyA. Blue light also failed to induce negative phototropism in pks1 under reduced gravitational stimulation, indicating that the effect of pks1 on phototropism is not simply the consequence of the counteracting effect of enhanced gravitropism. We propose a model where the background level of PKS1 reduces gravitropism. After a phyA-dependent increase in its expression, PKS1 positively affects root phototropism and both effects contribute to negative curvature in response to unilateral blue light.

  4. Phytochrome and retrograde signalling pathways coverage to antogonistically regulate a light-induced transcription network

    Science.gov (United States)

    Plastid-to-nucleus retrograde signals emitted by dysfunctional chloroplasts impact photomorphogenic development, but the molecular link between retrograde and photosensory-receptor signaling has remained undefined. Here, we show that the phytochrome (phy) and retrograde signaling pathways converge a...

  5. A computational approach to discovering the functions of bacterial phytochromes by analysis of homolog distributions

    Directory of Open Access Journals (Sweden)

    Lamparter Tilman

    2006-03-01

    Full Text Available Abstract Background Phytochromes are photoreceptors, discovered in plants, that control a wide variety of developmental processes. They have also been found in bacteria and fungi, but for many species their biological role remains obscure. This work concentrates on the phytochrome system of Agrobacterium tumefaciens, a non-photosynthetic soil bacterium with two phytochromes. To identify proteins that might share common functions with phytochromes, a co-distribution analysis was performed on the basis of protein sequences from 138 bacteria. Results A database of protein sequences from 138 bacteria was generated. Each sequence was BLASTed against the entire database. The homolog distribution of each query protein was then compared with the homolog distribution of every other protein (target protein of the same species, and the target proteins were sorted according to their probability of co-distribution under random conditions. As query proteins, phytochromes from Agrobacterium tumefaciens, Pseudomonas aeruginosa, Deinococcus radiodurans and Synechocystis PCC 6803 were chosen along with several phytochrome-related proteins from A. tumefaciens. The Synechocystis photosynthesis protein D1 was selected as a control. In the D1 analyses, the ratio between photosynthesis-related proteins and those not related to photosynthesis among the top 150 in the co-distribution tables was > 3:1, showing that the method is appropriate for finding partner proteins with common functions. The co-distribution of phytochromes with other histidine kinases was remarkably high, although most co-distributed histidine kinases were not direct BLAST homologs of the query protein. This finding implies that phytochromes and other histidine kinases share common functions as parts of signalling networks. All phytochromes tested, with one exception, also revealed a remarkably high co-distribution with glutamate synthase and methionine synthase. This result implies a general role of

  6. Tissue- and isoform-specific phytochrome regulation of light-dependent anthocyanin accumulation in Arabidopsis thaliana

    OpenAIRE

    2011-01-01

    Phytochromes regulate light- and sucrose-dependent anthocyanin synthesis and accumulation in many plants. Mesophyll-specific phyA alone has been linked to the regulation of anthocyanin accumulation in response to far-red light in Arabidopsis thaliana. However, multiple mesophyll-localized phytochromes were implicated in the photoregulation of anthocyanin accumulation in red-light conditions. Here, we report a role for mesophyll-specific phyA in blue-light-dependent regulation of anthocyanin l...

  7. Biochemische Untersuchungen mit dem prokaryotischen Phytochrom Agp1 aus Agrobacterium tumefaciens

    OpenAIRE

    Noack, Steffi

    2010-01-01

    Phytochromes are photoreceptors with a bilin chromophore in which light triggers the conversion between the red-absorbing form Pr and the far-red-absorbing form Pfr. The soil bacterium Agrobacterium tumefaciens has two phytochromes, Agp1 and Agp2, with antagonistic properties. In darkness, Agp1 converts slowly from Pfr to Pr, whereas Agp2 converts slowly from Pr to Pfr. Photoconversion is initiated by a change of the stereochemistry of the chromophore which induces structural changes of the p...

  8. Complex and shifting interactions of phytochromes regulate fruit development in tomato.

    Science.gov (United States)

    Gupta, Suresh Kumar; Sharma, Sulabha; Santisree, Parankusam; Kilambi, Himabindu Vasuki; Appenroth, Klaus; Sreelakshmi, Yellamaraju; Sharma, Rameshwar

    2014-07-01

    Tomato fruit ripening is a complex metabolic process regulated by a genetical hierarchy. A subset of this process is also modulated by light signalling, as mutants encoding negative regulators of phytochrome signal transduction show higher accumulation of carotenoids. In tomato, phytochromes are encoded by a multi-gene family, namely PHYA, PHYB1, PHYB2, PHYE and PHYF; however, their contribution to fruit development and ripening has not been examined. Using single phytochrome mutants phyA, phyB1 and phyB2 and multiple mutants phyAB1, phyB1B2 and phyAB1B2, we compared the on-vine transitory phases of ripening until fruit abscission. The phyAB1B2 mutant showed accelerated transitions during ripening, with shortest time to fruit abscission. Comparison of transition intervals in mutants indicated a phase-specific influence of different phytochrome species either singly or in combination on the ripening process. Examination of off-vine ripened fruits indicated that ripening-specific carotenoid accumulation was not obligatorily dependent upon light and even dark-incubated fruits accumulated carotenoids. The accumulation of transcripts and carotenoids in off-vine and on-vine ripened mutant fruits indicated a complex and shifting phase-dependent modulation by phytochromes. Our results indicate that, in addition to regulating carotenoid levels in tomato fruits, phytochromes also regulate the time required for phase transitions during ripening.

  9. Structural basis for the photoconversion of a phytochrome to the activated Pfr form.

    Science.gov (United States)

    Ulijasz, Andrew T; Cornilescu, Gabriel; Cornilescu, Claudia C; Zhang, Junrui; Rivera, Mario; Markley, John L; Vierstra, Richard D

    2010-01-14

    Phytochromes are a collection of bilin-containing photoreceptors that regulate numerous photoresponses in plants and microorganisms through their ability to photointerconvert between a red-light-absorbing, ground state (Pr) and a far-red-light-absorbing, photoactivated state (Pfr). Although the structures of several phytochromes as Pr have been determined, little is known about the structure of Pfr and how it initiates signalling. Here we describe the three-dimensional solution structure of the bilin-binding domain as Pfr, using the cyanobacterial phytochrome from Synechococcus OSB'. Contrary to predictions, light-induced rotation of the A pyrrole ring but not the D ring is the primary motion of the chromophore during photoconversion. Subsequent rearrangements within the protein then affect intradomain and interdomain contact sites within the phytochrome dimer. On the basis of our models, we propose that phytochromes act by propagating reversible light-driven conformational changes in the bilin to altered contacts between the adjacent output domains, which in most phytochromes direct differential phosphotransfer.

  10. Influence of growth regulators and respiration inhibitors on dark transformation of phytochrome in coleoptiles of oat seedlings

    Directory of Open Access Journals (Sweden)

    Jan Kopcewicz

    2014-02-01

    Full Text Available Irradiation with red light leads to the formation of an unstable, undergoing gradual destruction, physiologically active PFR form of phytochrome in the coleoptiles of oat seedlings. Growth substances: IAA, GA3, kinetin, ABA, ethrel as well acetylcholine do not influence the nature and rate of phytochrome dark transformation. Inhibitors of energy-producing processes such as KCN, 2,4-DNP, DCCD and antimycin A inhibit the process of dark destruction of the PFR form of phytochrome.

  11. Phytochrome from Agrobacterium tumefaciens has unusual spectral properties and reveals an N-terminal chromophore attachment site

    OpenAIRE

    Lamparter, Tilman; Michael, Norbert; Mittmann, Franz; Esteban, Berta

    2002-01-01

    Phytochromes are photochromic photoreceptors with a bilin chromophore that are found in plants and bacteria. The soil bacterium Agrobacterium tumefaciens contains two genes that code for phytochrome-homologous proteins, termed Agrobacterium phytochrome 1 and 2 (Agp1 and Agp2). To analyze its biochemical and spectral properties, Agp1 was purified from the clone of an E. coli overexpressor. The protein was assembled with the chromophores phycocyanobilin and biliverdin, which is the putative nat...

  12. Engineering of bacterial phytochromes for in vivo imaging (Conference Presentation)

    Science.gov (United States)

    Verkhusha, Vladislav; Shcherbakova, Daria M.; Kaberniuk, Andrii A.; Baloban, Mikhail

    2017-03-01

    Genetically encoded probes with absorbance and fluorescence spectra within a near-infrared tissue transparency window are preferable for deep-tissue imaging. On the basis of bacterial phytochromes we engineered several types of near-infrared absorbing probes for photoacoustic tomography and fluorescent probes for purely optical imaging. They can be used as protein and cell labels and as building blocks for biosensors. The probes enabled imaging of tumors and metastases, protein-protein interactions, RNA visualization, detection of apoptosis, cellular metabolites, signaling pathways and cell proliferation. The developed probes allow non-invasive visualization of biological processes across scales, from super-resolution microscopy to tissue and whole-body animal imaging.

  13. Phytochrome B promotes branching in Arabidopsis by suppressing auxin signaling.

    Science.gov (United States)

    Krishna Reddy, Srirama; Finlayson, Scott A

    2014-03-01

    Many plants respond to competition signals generated by neighbors by evoking the shade avoidance syndrome, including increased main stem elongation and reduced branching. Vegetation-induced reduction in the red light:far-red light ratio provides a competition signal sensed by phytochromes. Plants deficient in phytochrome B (phyB) exhibit a constitutive shade avoidance syndrome including reduced branching. Because auxin in the polar auxin transport stream (PATS) inhibits axillary bud outgrowth, its role in regulating the phyB branching phenotype was tested. Removing the main shoot PATS auxin source by decapitation or chemically inhibiting the PATS strongly stimulated branching in Arabidopsis (Arabidopsis thaliana) deficient in phyB, but had a modest effect in the wild type. Whereas indole-3-acetic acid (IAA) levels were elevated in young phyB seedlings, there was less IAA in mature stems compared with the wild type. A split plate assay of bud outgrowth kinetics indicated that low auxin levels inhibited phyB buds more than the wild type. Because the auxin response could be a result of either the auxin signaling status or the bud's ability to export auxin into the main shoot PATS, both parameters were assessed. Main shoots of phyB had less absolute auxin transport capacity compared with the wild type, but equal or greater capacity when based on the relative amounts of native IAA in the stems. Thus, auxin transport capacity was unlikely to restrict branching. Both shoots of young phyB seedlings and mature stem segments showed elevated expression of auxin-responsive genes and expression was further increased by auxin treatment, suggesting that phyB suppresses auxin signaling to promote branching.

  14. Detection of phytochrome-like genes from Rhazya stricta (Apocynaceae) using de novo genome assembly.

    Science.gov (United States)

    Sabir, Jamal S M; Baeshen, Nabih A; Shokry, Ahmed M; Gadalla, Nour O; Edris, Sherif; Mutwakil, Mohammed H; Ramadan, Ahmed M; Atef, Ahmed; Al-Kordy, Magdy A; Abuzinadah, Osama A; El-Domyati, Fotouh M; Jansen, Robert K; Bahieldin, Ahmed

    2013-01-01

    Phytochrome-like genes in the wild plant species Rhazya stricta Decne were characterized using a de novo genome assembly of next generation sequence data. Rhazya stricta contains more than 100 alkaloids with multiple pharmacological properties, and leaf extracts have been used to cure chronic rheumatism, to treat tumors, and in the treatment of several other diseases. Phytochromes are known to be involved in the light-regulated biosynthesis of some alkaloids. Phytochromes are soluble chromoproteins that function in the absorption of red and far-red light and the transduction of intracellular signals during light-regulated plant development. De novo assembly of the nuclear genome of R. stricta recovered 45,641 contigs greater than 1000bp long, which were used in constructing a local database. Five sequences belonging to Arabidopsis thaliana phytochrome gene family (i.e., AtphyABCDE) were used to identify R. stricta contigs with phytochrome-like sequences using BLAST. This led to the identification of three contigs with phytochrome-like sequences covering AtphyA-, AtphyC- and AtphyE-like full-length genes. Annotation of the three sequences showed that each contig consists of one phytochrome-like gene with three exons and two introns. BLASTn and BLASTp results indicated that RsphyA mRNA and protein sequences had homologues in Wrightia coccinea and and Solanum tuberosum, respectively. RsphyC-like mRNA and protein sequence were homologous to Vitis vinifera and Vitis riparia. RsphyE-like mRNA coding and protein sequences were homologous to Ipomoea nil. Multiple-sequence alignment of phytochrome proteins indicated a homology with 30 sequences from 23 different species of flowering plants. Phylogenetic analysis confirmed that each R. stricta phytochrome gene is related to the same phytochrome gene of other flowering plants. It is proposed that the absence of phyB gene in R. stricta is due to RsphyA gene taking over the role of phyB.

  15. High Resolution Structure of Deinococcus Bacteriophytochrome Yields New Insights into Phytochrome Architecture and Evolution

    Energy Technology Data Exchange (ETDEWEB)

    Wagner, Jeremiah R.; Zhang, Junrui; Brunzelle, Joseph S.; Vierstra, Richard D.; Forest, Katrina T. (NWU); (UW)

    2010-03-08

    Phytochromes are red/far red light photochromic photoreceptors that direct many photosensory behaviors in the bacterial, fungal, and plant kingdoms. They consist of an N-terminal domain that covalently binds a bilin chromophore and a C-terminal region that transmits the light signal, often through a histidine kinase relay. Using x-ray crystallography, we recently solved the first three-dimensional structure of a phytochrome, using the chromophore-binding domain of Deinococcus radiodurans bacterial phytochrome assembled with its chromophore, biliverdin IX{alpha}. Now, by engineering the crystallization interface, we have achieved a significantly higher resolution model. This 1.45 {angstrom} resolution structure helps identify an extensive buried surface between crystal symmetry mates that may promote dimerization in vivo. It also reveals that upon ligation of the C3{sup 2} carbon of biliverdin to Cys{sup 24}, the chromophore A-ring assumes a chiral center at C2, thus becoming 2(R),3(E)-phytochromobilin, a chemistry more similar to that proposed for the attached chromophores of cyanobacterial and plant phytochromes than previously appreciated. The evolution of bacterial phytochromes to those found in cyanobacteria and higher plants must have involved greater fitness using more reduced bilins, such as phycocyanobilin, combined with a switch of the attachment site from a cysteine near the N terminus to one conserved within the cGMP phosphodiesterase/adenyl cyclase/FhlA domain. From analysis of site-directed mutants in the D. radiodurans phytochrome, we show that this bilin preference was partially driven by the change in binding site, which ultimately may have helped photosynthetic organisms optimize shade detection. Collectively, these three-dimensional structural results better clarify bilin/protein interactions and help explain how higher plant phytochromes evolved from prokaryotic progenitors.

  16. Red light-induced acidification by pea leaf epidermal cells is regulated by more than one phytochrome

    NARCIS (Netherlands)

    Elzenga, J.T.M.; Staal, M; Prins, H.B A

    2000-01-01

    Leaves of pea (Pisum sativum L.) grown in red light develop normally, provided that functional phytochrome B is present. In the chromophore mutant pcd2 and in the phytochrome B mutant 1v the leaves remain small. Although some chlorophyll development takes place, the leaf size of red light-grown muta

  17. Phenotypic Characterization of Transgenic Miscanthus sinensis Plants Overexpressing Arabidopsis Phytochrome B

    Directory of Open Access Journals (Sweden)

    Ok-Jin Hwang

    2014-01-01

    Full Text Available Phytochromes are dimeric pigment proteins with reversible photochromism between red and far-red light-absorbing forms. They are photoreceptors that regulate various aspects of plant growth and development and have been used for biotechnological applications to improve agricultural performance of crops. Miscanthus species have been suggested as one of the most promising energy crops. In this paper, Arabidopsis phytochrome B (PHYB gene was introduced into Miscanthus sinensis using Agrobacterium-mediated transformation method that we developed recently, with the herbicide resistance gene (BAR as a selection marker. After putative transgenic plants were selected using the herbicide resistance assay, genomic integration of the transgene was confirmed by genomic PCR and Southern blot analysis, and transgene expression was validated by Northern blot analysis. Compared to nontransformed control plants, transgenic plants overexpressing PHYB showed phenotypes with increased phytochrome B function, which includes increased chlorophyll content, decreased plant height, and delayed flowering. Therefore, these results suggest that Arabidopsis phytochrome B is functional in M. sinensis and provide a method to develop Miscanthus varieties with enhanced agricultural performance using phytochromes.

  18. Intramolecular co-action of two independent photosensory modules in the fern phytochrome 3.

    Science.gov (United States)

    Kanegae, Takeshi

    2015-01-01

    Fern phytochrome3/neochrome1 (phy3/neo1) is a chimeric photoreceptor composed of a phytochrome-chromophore binding domain and an almost full-length phototropin. phy3 thus contains two different light-sensing modules; a red/far-red light receptor phytochrome and a blue light receptor phototropin. phy3 induces both red light- and blue light-dependent phototropism in phototropin-deficient Arabidopsis thaliana (phot1 phot2) seedlings. The red-light response is dependent on the phytochrome module of phy3, and the blue-light response is dependent on the phototropin module. We recently showed that both the phototropin-sensing module and the phytochrome-sensing module mediate the blue light-dependent phototropic response. Particularly under low-light conditions, these two light-sensing modules cooperate to induce the blue light-dependent phototropic response. This intramolecular co-action of two independent light-sensing modules in phy3 enhances light sensitivity, and perhaps allowed ferns to adapt to the low-light canopy conditions present in angiosperm forests.

  19. Prevention of Action of Far-Red-Absorbing Phytochrome in Rumex crispus L. Seeds by Ethanol.

    Science.gov (United States)

    Taylorson, R B

    1984-02-01

    Phytochrome-enhanced germination of curled dock (Rumex crispus L.) seeds is further stimulated by pretreatments in solutions of 0.5 to 2 molar methanol and 0.03 to >/= 0.3 molar 2-propanol during a 2-day 20 degrees C imbibition. Similar pretreatments in 0.1 molar ethanol, acetaldehyde, and n-propanol inhibit phytochrome-enhanced germination. If exposure to ethanol is delayed until 16 hours after a red irradiation, seeds escape the ethanol inhibition indicating a mechanism other than toxicity. The rate of escape from ethanol inhibition roughly parallels the escape from phytochrome control in seeds held in water only, indicating possible ethanol effects on phytochrome. It was found that ethanol pretreatment prevents the far-red absorbing form of phytochrome (Pfr) from acting but does not accelerate dark decay or prevent transformation. Ethanol inhibition may be prevented if ethanol pretreatment is at 10 degrees C instead of 20 degrees C, or may be overcome by transferring ethanol-pretreated seeds to 10 degrees C in water. Similarly, ethanol inhibition can be overcome by a 2-hour 40 degrees C temperature shift concluding the pretreatment. It is proposed that the ethanol causes perturbations at a membrane which prevent Pfr from acting.

  20. Evidence for involvement of phytochrome in tumor development on plants

    Science.gov (United States)

    Morrow, R. C.; Tibbitts, T. W.

    1988-01-01

    The regulation of nonpathogenic tumorous growths on tomato plants by red and far-red radiation was studied using leaf discs floated on water and irradiated from beneath. It was found that red light (600-700 nanometers) was required for the induction of tumors on tomato (Lycopersicon hirsutum Humb. & Bonpl. Plant Introduction LA 1625), while both blue (400-500 nanometers) and green (500-600 nanometers) light had little effect on tumor development. Detailed studies with red light demonstrated that tumor development increased with increasing photon flux and duration, though duration was the more significant factor. It was observed that tumor development could be prevented by the addition of far-red irradiance to red irradiance or by providing far-red irradiance immediately following red irradiance. The effectiveness of red and far-red irradiance in the regulation of tumor development indicates phytochrome involvement in this response. These findings should provide additional insight into the multiplicity of physiological factors regulating the development of nonpathogenic tumorous growths in plants.

  1. Fluorescence of Phytochrome Adducts with Synthetic Locked Chromophores*

    Science.gov (United States)

    Zienicke, Benjamin; Chen, Li-Yi; Khawn, Htoi; Hammam, Mostafa A. S.; Kinoshita, Hideki; Reichert, Johannes; Ulrich, Anne S.; Inomata, Katsuhiko; Lamparter, Tilman

    2011-01-01

    We performed steady state fluorescence measurements with phytochromes Agp1 and Agp2 of Agrobacterium tumefaciens and three mutants in which photoconversion is inhibited. These proteins were assembled with the natural chromophore biliverdin (BV), with phycoerythrobilin (PEB), which lacks a double bond in the ring C-D-connecting methine bridge, and with synthetic bilin derivatives in which the ring C-D-connecting methine bridge is locked. All PEB and locked chromophore adducts are photoinactive. According to fluorescence quantum yields, the adducts may be divided into four different groups: wild type BV adducts exhibiting a weak fluorescence, mutant BV adducts with about 10-fold enhanced fluorescence, adducts with locked chromophores in which the fluorescence quantum yields are around 0.02, and PEB adducts with a high quantum yield of around 0.5. Thus, the strong fluorescence of the PEB adducts is not reached by the locked chromophore adducts, although the photoconversion energy dissipation pathway is blocked. We therefore suggest that ring D of the bilin chromophore, which contributes to the extended π-electron system of the locked chromophores, provides an energy dissipation pathway that is independent on photoconversion. PMID:21071442

  2. Fluorescence of phytochrome adducts with synthetic locked chromophores.

    Science.gov (United States)

    Zienicke, Benjamin; Chen, Li-Yi; Khawn, Htoi; Hammam, Mostafa A S; Kinoshita, Hideki; Reichert, Johannes; Ulrich, Anne S; Inomata, Katsuhiko; Lamparter, Tilman

    2011-01-14

    We performed steady state fluorescence measurements with phytochromes Agp1 and Agp2 of Agrobacterium tumefaciens and three mutants in which photoconversion is inhibited. These proteins were assembled with the natural chromophore biliverdin (BV), with phycoerythrobilin (PEB), which lacks a double bond in the ring C-D-connecting methine bridge, and with synthetic bilin derivatives in which the ring C-D-connecting methine bridge is locked. All PEB and locked chromophore adducts are photoinactive. According to fluorescence quantum yields, the adducts may be divided into four different groups: wild type BV adducts exhibiting a weak fluorescence, mutant BV adducts with about 10-fold enhanced fluorescence, adducts with locked chromophores in which the fluorescence quantum yields are around 0.02, and PEB adducts with a high quantum yield of around 0.5. Thus, the strong fluorescence of the PEB adducts is not reached by the locked chromophore adducts, although the photoconversion energy dissipation pathway is blocked. We therefore suggest that ring D of the bilin chromophore, which contributes to the extended π-electron system of the locked chromophores, provides an energy dissipation pathway that is independent on photoconversion.

  3. Conformational heterogeneity of the Pfr chromophore in plant and cyanobacterial phytochromes.

    Science.gov (United States)

    Velazquez Escobar, Francisco; von Stetten, David; Günther-Lütkens, Mina; Keidel, Anke; Michael, Norbert; Lamparter, Tilman; Essen, Lars-Oliver; Hughes, Jon; Gärtner, Wolfgang; Yang, Yang; Heyne, Karsten; Mroginski, Maria A; Hildebrandt, Peter

    2015-01-01

    Phytochromes are biological photoreceptors that can be reversibly photoconverted between a dark and photoactivated state. The underlying reaction sequences are initiated by the photoisomerization of the tetrapyrrole cofactor, which in plant and cyanobacterial phytochromes are a phytochromobilin (PΦB) and a phycocyanobilin (PCB), respectively. The transition between the two states represents an on/off-switch of the output module activating or deactivating downstream physiological processes. In addition, the photoactivated state, i.e., Pfr in canonical phytochromes, can be thermally reverted to the dark state (Pr). The present study aimed to improve our understanding of the specific reactivity of various PΦB- and PCB-binding phytochromes in the Pfr state by analysing the cofactor structure by vibrational spectroscopic techniques. Resonance Raman (RR) spectroscopy revealed two Pfr conformers (Pfr-I and Pfr-II) forming a temperature-dependent conformational equilibrium. The two sub-states-found in all phytochromes studied, albeit with different relative contributions-differ in structural details of the C-D and A-B methine bridges. In the Pfr-I sub-state the torsion between the rings C and D is larger by ca. 10° compared to Pfr-II. This structural difference is presumably related to different hydrogen bonding interactions of ring D as revealed by time-resolved IR spectroscopic studies of the cyanobacterial phytochrome Cph1. The transitions between the two sub-states are evidently too fast (i.e., nanosecond time scale) to be resolved by NMR spectroscopy which could not detect a structural heterogeneity of the chromophore in Pfr. The implications of the present findings for the dark reversion of the Pfr state are discussed.

  4. Conformational heterogeneity of the Pfr chromophore in plant and cyanobacterial phytochromes

    Directory of Open Access Journals (Sweden)

    Francisco eVelazquez Escobar

    2015-07-01

    Full Text Available Phytochromes are biological photoreceptors that can be reversibly photoconverted between a dark and photoactivated state. The underlying reaction sequences are initiated by the photoisomerisation of the tetrapyrrole cofactor, which in plant and cyanobacterial phytochromes are a phytochromobilin (PB and a phycocyanobilin (PCB, respectively. The transition between the two states represents an on/off-switch of the output module activating or deactivating downstream physiological processes. In addition, the photoactivated state, i.e. Pfr in canonical phytochromes, can be thermally reverted to the dark state (Pr. The present study aimed to improve our understanding of the specific reactivity of various PB- and PCB-binding phytochromes in the Pfr state by analyzing the cofactor structure by vibrational spectroscopic techniques. Resonance Raman (RR spectroscopy revealed two Pfr conformers (Pfr-I and Pfr-II forming a temperature-dependent conformational equilibrium. The two sub-states - found in all phytochromes studied, albeit with different relative contributions - differ in structural details of the C-D and A-B methine bridges. In the Pfr-I sub-state the torsion between the rings C and D is larger by ca. 10o compared to Pfr-II. This structural difference is presumably related to different hydrogen bonding interactions of ring D as revealed by time-resolved IR spectroscopic studies of the cyanobacterial phytochrome Cph1. The transitions between the two sub-states are evidently too fast (i.e., nanosecond time scale to be resolved by NMR spectroscopy which could not detect a structural heterogeneity of the chromophore in Pfr. The implications of the present findings for the dark reversion of the Pfr state are discussed.

  5. Duplication, divergence and persistence in the Phytochrome photoreceptor gene family of cottons (Gossypium spp.

    Directory of Open Access Journals (Sweden)

    Abdukarimov Abdusattor

    2010-06-01

    Full Text Available Abstract Background Phytochromes are a family of red/far-red photoreceptors that regulate a number of important developmental traits in cotton (Gossypium spp., including plant architecture, fiber development, and photoperiodic flowering. Little is known about the composition and evolution of the phytochrome gene family in diploid (G. herbaceum, G. raimondii or allotetraploid (G. hirsutum, G. barbadense cotton species. The objective of this study was to obtain a preliminary inventory and molecular-evolutionary characterization of the phytochrome gene family in cotton. Results We used comparative sequence resources to design low-degeneracy PCR primers that amplify genomic sequence tags (GSTs for members of the PHYA, PHYB/D, PHYC and PHYE gene sub-families from A- and D-genome diploid and AD-genome allotetraploid Gossypium species. We identified two paralogous PHYA genes (designated PHYA1 and PHYA2 in diploid cottons, the result of a Malvaceae-specific PHYA gene duplication that occurred approximately 14 million years ago (MYA, before the divergence of the A- and D-genome ancestors. We identified a single gene copy of PHYB, PHYC, and PHYE in diploid cottons. The allotetraploid genomes have largely retained the complete gene complements inherited from both of the diploid genome ancestors, with at least four PHYA genes and two genes encoding PHYB, PHYC and PHYE in the AD-genomes. We did not identify a PHYD gene in any cotton genomes examined. Conclusions Detailed sequence analysis suggests that phytochrome genes retained after duplication by segmental duplication and allopolyploidy appear to be evolving independently under a birth-and-death-process with strong purifying selection. Our study provides a preliminary phytochrome gene inventory that is necessary and sufficient for further characterization of the biological functions of each of the cotton phytochrome genes, and for the development of 'candidate gene' markers that are potentially useful for

  6. Assembly of synthetic locked chromophores with Agrobacterium phytochromes Agp1 and Agp2

    OpenAIRE

    Inomata, Katsuhiko; Noack, Steffi; Hammam, Mostafa A. S.; Khawn, Htoi; Kinoshita, Hideki

    2006-01-01

    Phytochromes are photoreceptors with a bilin chromophore in which light triggers the conversion between the red-absorbing form Pr and the far-red-absorbing form Pfr. Agrobacterium tumefaciens has two phytochromes, Agp1 and Agp2, with antagonistic properties: in darkness, Agp1 converts slowly from Pfr to Pr, whereas Agp2 converts slowly from Pr to Pfr. In a previous study, we have assembled Agp1 with synthetic locked chromophores 15Za, 15Zs, 15Ea, and 15Es in which the C15=C16 double bond is f...

  7. Phytochrome from Agrobacterium tumefaciens has unusual spectral properties and reveals an N-terminal chromophore attachment site.

    Science.gov (United States)

    Lamparter, Tilman; Michael, Norbert; Mittmann, Franz; Esteban, Berta

    2002-09-03

    Phytochromes are photochromic photoreceptors with a bilin chromophore that are found in plants and bacteria. The soil bacterium Agrobacterium tumefaciens contains two genes that code for phytochrome-homologous proteins, termed Agrobacterium phytochrome 1 and 2 (Agp1 and Agp2). To analyze its biochemical and spectral properties, Agp1 was purified from the clone of an E. coli overexpressor. The protein was assembled with the chromophores phycocyanobilin and biliverdin, which is the putative natural chromophore, to photoactive holoprotein species. Like other bacterial phytochromes, Agp1 acts as light-regulated His kinase. The biliverdin adduct of Agp1 represents a previously uncharacterized type of phytochrome photoreceptor, because photoreversion from the far-red absorbing form to the red-absorbing form is very inefficient, a feature that is combined with a rapid dark reversion. Biliverdin bound covalently to the protein; blocking experiments and site-directed mutagenesis identified a Cys at position 20 as the binding site. This particular position is outside the region where plant and some cyanobacterial phytochromes attach their chromophore and thus represents a previously uncharacterized binding site. Sequence comparisons imply that the region around Cys-20 is a ring D binding motif in phytochromes.

  8. Recombinant phytochrome of the moss Ceratodon purpureus: heterologous expression and kinetic analysis of Pr-->Pfr conversion.

    Science.gov (United States)

    Zeidler, M; Lamparter, T; Hughes, J; Hartmann, E; Remberg, A; Braslavsky, S; Schaffner, K; Gärtner, W

    1998-12-01

    The phytochrome-encoding gene Cerpu;PHY;2 (CP2) of the moss Ceratodon purpureus was heterologously expressed in Saccharomyces cerevisiae as a polyhistidine-tagged apoprotein and assembled with phytochromobilin (P phi B) and phycocyanobilin (PCB). Nickel-affinity chromatography yielded a protein fraction containing approximately 80% phytochrome. The holoproteins showed photoreversibility with both chromophores. Difference spectra gave maxima at 644/716 nm (red-absorbing phytochrome [Pr]/far-red-absorbing phytochrome [Pfr]) for the PCB adduct, and 659/724 nm for the P phi B-adduct, the latter in close agreement with values for phytochrome extracted from Ceratodon itself, implying that P phi B is the native chromophore in this moss species. Immunoblots stained with the antiphytochrome antibody APC1 showed that the recombinant phytochrome had the same molecular size as phytochrome from Ceratodon extracts. Further, the mobility of recombinant CP2 holophytochrome on native size-exclusion chromatography was similar to that of native oat phytochrome, implying that CP2 forms a dimer. Kinetics of absorbance changes during the Pr-->Pfr photoconversion of the PCB adduct, monitored between 620 and 740 nm in the microsecond range, revealed the rapid formation of a red-shifted intermediate (I700), decaying with a time constant of approximately 110 microseconds. This is similar to the behavior of phytochromes from higher plants when assembled with the same chromophore. When following the formation of the Pfr state, two major processes were identified (with time constants of 3 and 18 ms) that are followed by slow reactions in the range of 166 ms and 8 s, respectively, albeit with very small amplitudes.

  9. Identification of photo-inactive phytochrome A in etiolated seedlings and photo-active phytochrome B in green leaves of the aurea mutant of tomato.

    Science.gov (United States)

    Sharma, R; López-Juez, E; Nagatani, A; Furuya, M

    1993-12-01

    The contents of spectrophotometrically measurable phytochrome A (PhyA) and phytochrome B (PhyB) and the corresponding immunochemically detectable apoproteins (PHYA and PHYB) were examined in dark- and light-grown tissues of the aurea mutant of tomato and its wild-type (WT). The amount of PHYA in etiolated aurea seedlings was found to be about 20% of that in the WT; this PHYA showed no photo-reversible changes in absorbance, no downregulation of the level of PHYA in light-grown seedlings, and no differential proteolysis of Pr and Pfr species in vitro which was seen in the case of the WT. By contrast, the amount of PHYB in aurea seedlings was not significantly different from that in WT seedlings. Phytochrome isolated from green leaves of the aurea mutant and purified by ion-exchange chromatography showed a red/far-red reversible spectral change, and its elution profile during chromatography was essentially similar to that of PHYB. The results indicate that aurea is a mutant that is deficient in photoactive PhyA at the etiolated stage, when it contains a spectrally inactive PHYA. However, the mutant contains spectrally active PhyB in its green tissue as does the WT.

  10. [Role of phytochrome in organ formation processes in Cucumis sativus L].

    Science.gov (United States)

    Sysoeva, M I; Marovskaia, E F

    2013-01-01

    The role of phytochrome B in the organogenesis process in the apical and axillary shoot meristems during early ontogenesis stages in cucumber Cucumis sativus L. at photoperiods (day/night) 10/14, 16/8 h, and continuous light in comparison with wild type plants and phytochrome B-deficient mutant (lh-mutant) was investigated. In mutant phytochrome B, deficiency caused inhibition of initiation of leaves both in the leading shoot and off-shoots and increased the number of flower buds (IV stage of organogenesis). With continuous light, the number of off-shoots and flowers during stage IV of organogenesis in wild-type plants increased twofold in comparison with the mutant. Short-term temperature drops did not induce floral ontogenesis in mutants but increased the number of off-shoots in both experimental variants during a long photoperiod and continuous light situations. We propose that phytochrome B, by increasing the compactness of chromatin, may facilitate coordination of ontogenesis processes with changing environmental conditions.

  11. Integration of Phytochrome and Cryptochrome Signals Determines Plant Growth during Competition for Light

    NARCIS (Netherlands)

    de Wit, Mieke; Keuskamp, Diederik H.; Bongers, Franca J.; Hornitschek, Patricia; Gommers, Charlotte M M; Reinen, Emilie; Martínez-Cerón, Carmen; Fankhauser, Christian; Pierik, Ronald

    2016-01-01

    Plants in dense vegetation perceive their neighbors primarily through changes in light quality. Initially, the ratio between red (R) and far-red (FR) light decreases due to reflection of FR by plant tissue well before shading occurs. Perception of low R:FR by the phytochrome photoreceptors induces

  12. Overexpression of homologous phytochrome genes in tomato: exploring the limits in photoperception

    NARCIS (Netherlands)

    Husaineid, S.H.; Kok, R.A.; Schreuder, M.E.L.; Plas, van der L.H.W.; Krol, van der A.R.

    2007-01-01

    Transgenic tomato [Lycopersicon esculentum (=Solanum lycopersicum)] lines overexpressing tomato PHYA, PHYB1, or PHYB2, under control of the constitutive double-35S promoter from cauliflower mosaic virus (CaMV) have been generated to test the level of saturation in individual phytochrome-signalling p

  13. Ca2+ transport in plant cells and mechanisms of transformation of phytochrome-induced photosignals

    Science.gov (United States)

    Volotovski, Igor D.

    1995-01-01

    The recent data on the influence of phytochrome on the efficiency of Ca2+ translocation across the membranes of oat protoplasts are given. Ca2+ uptake in the protoplasts was shown to be influenced by the red light (R) illumination. This effect was reverted by the following far-red light (FR) illumination. To elucidate the sensitivity to phytochrome-controlling action the screening between the mechanisms of Ca2+ transport across the plasma membranes of oat protoplasts, Na+/Ca2+ and Ca2+/H+ exchangers, Ca2+-pump and Ca2+-channel was done. It was established that phytochrome modulated the activity of Na+/Ca2+-exchanger and Ca2+-pump. The light-mediated oscillations of cytoplasmic Ca2+ concentration in the oat protoplasts were demonstrated using fluorescence probe quin2 loaded into the cells and laser monitoring of fluorescence signal. The evidences were obtained that the oscillations were not the result of the elevation of cytoplasmic Ca2+ concentration and had no connection with Ca2+ pool of mitochondria. The possibility of the relation between the Ca2+ oscillations and phosphoinositide metabolism in plant cell membranes is analyzed. The mechanisms of transformation of primary phytochrome signal into biological effects were discussed.

  14. Shedding (far-red) light on phytochrome mechanisms and responses in land plants

    NARCIS (Netherlands)

    Possart, A.; Fleck, C.; Hiltbrunner, A.

    2014-01-01

    In order to monitor ambient light conditions, plants rely on functionally diversified photoreceptors. Among these, phytochromes perceive red (R) and far-red (FR) light. FR light does not constitute a photosynthetic energy source; it however influences adaptive and developmental processes. In seed pl

  15. Minimal domain of bacterial phytochrome required for chromophore binding and fluorescence

    Science.gov (United States)

    Rumyantsev, Konstantin A.; Shcherbakova, Daria M.; Zakharova, Natalia I.; Emelyanov, Alexander V.; Turoverov, Konstantin K.; Verkhusha, Vladislav V.

    2015-12-01

    Fluorescent proteins (FP) are used to study various biological processes. Recently, a series of near-infrared (NIR) FPs based on bacterial phytochromes was developed. Finding ways to improve NIR FPs is becoming progressively important. By applying rational design and molecular evolution we have engineered R. palustris bacterial phytochrome into a single-domain NIR FP of 19.6 kDa, termed GAF-FP, which is 2-fold and 1.4-fold smaller than bacterial phytochrome-based NIR FPs and GFP-like proteins, respectively. Engineering of GAF-FP involved a substitution of 15% of its amino acids and a deletion of the knot structure. GAF-FP covalently binds two tetrapyrrole chromophores, biliverdin (BV) and phycocyanobilin (PCB). With the BV chromophore GAF-FP absorbs at 635 nm and fluoresces at 670 nm. With the PCB chromophore GAF-FP becomes blue-shifted and absorbs at 625 nm and fluoresces at 657 nm. The GAF-FP structure has a high tolerance to small peptide insertions. The small size of GAF-FP and its additional absorbance band in the violet range has allowed for designing a chimeric protein with Renilla luciferase. The chimera exhibits efficient non-radiative energy transfer from luciferase to GAF-FP, resulting in NIR bioluminescence. This study opens the way for engineering of small NIR FPs and NIR luciferases from bacterial phytochromes.

  16. Agrobacterium phytochrome as an enzyme for the production of ZZE bilins.

    Science.gov (United States)

    Lamparter, Tilman; Michael, Norbert

    2005-06-14

    Photoconversion of phytochrome from the red-absorbing form Pr to the far-red-absorbing form Pfr is initiated by a Z to E isomerization around the ring C-ring D connecting double bond; the chromophore undergoes a ZZZ to ZZE isomerization. In vivo, phytochrome chromophores are covalently bound to the protein, but several examples of noncovalent in vitro adducts have been reported which also undergo Pr to Pfr photoconversion. We show that free biliverdin or phycocyanobilin, highly enriched in the ZZE isomer, can easily be obtained from chromophores bound in a noncovalent manner to Agrobacterium phytochrome Agp1, and used for spectral assays. Photoconversion of free biliverdin in a methanol/HCl solution from ZZE to ZZZ proceeded with a quantum yield of 1.8%, but was negligible in neutral methanol solution, indicating that this process is proton-dependent. The ZZE form of biliverdin and phycocyanobilin were tested for their ability to assemble with Agp1 and cyanobacterial phytochrome Cph1, respectively. In both cases, a Pfr-like adduct was formed but the chromophore was bound in a noncovalent manner to the protein. Agp1 Pfr undergoes dark reversion to Pr; the same feature was found for the noncovalent ZZE adduct. After dark reversion, the chromophore became covalently bound to the protein. In analogy, the PCB chromophore became covalently bound to Cph1 upon irradiation with strong far-red light which initiated ZZE to ZZZ isomerization. Agrobacterium Agp2 belongs to a yet small group of phytochromes which also assemble in the Pr form but convert from Pr to Pfr in darkness. When the Agp2 apoprotein was assembled with the ZZE form of biliverdin, the formation of the final adduct was accelerated compared to the formation of the ZZZ control, indicating that the ZZE chromophore fits directly into the chromophore pocket of Agp2.

  17. Time courses for phytochrome-induced enzyme levels in phenylpropanoid metabolism (phenylalanine ammonia-lyase, naringenin-chalcone synthase) compared with time courses for phytochrome-mediated end-product accumulation (anthocyanin, quercetin).

    Science.gov (United States)

    Brödenfeldt, R; Mohr, H

    1988-12-01

    Time course for changes in the levels of enzymes characteristic of general phenylpropanoid metabolism (phenylalanine ammonia-lyase, PAL; EC 4.3.1.5) and of the flavonoid-glycoside branch pathway (naringenin-chalcone synthase, CHS; EC 2.3.1.74) were measured in the cotyledons of mustard (Sinapis alba L.) seedlings and compared with the rates of accumulation of related end products (anthocyanin and quercetin). Induction of enzyme levels and of end-product accumulation was carried out with red and far-red (FR) light, operating via phytochrome. The data are compatible with the concept that the phytochrome-mediated appearance of enzymes such as PAL and CHS is indeed a prerequisite for the appearance of anthocyanins and flavonols. However, there is no close correlation between enzyme levels and the rates of synthesis of end products which could justify the identification of specific rate-limiting enzymes. Rather, the data indicate that there is a second phytochrome-dependent step, beyond enzyme induction, where the actual rate of flavonoid accumulation is determined. Anthocyanin and quercetin accumulation respond differently to light. However, the relative action of continuous FR, red light pulses and 'stored phytochrome signal' is the same in both cases. This indicates that the mode of operation of phytochrome is the same in both cases. The two syntheses differ only in the degree of responsiveness towards phytochrome. The time course for changes in CHS levels in continuous FR, i.e. under conditions of phytochrome photosteady state, is similar to the time course for PAL levels whereas the time courses in darkness, following transfer from FR to darkness, are totally different. In the case of CHS, a transient rise is observed whereas, with PAL, an instantaneous drop in enzyme level occurs after transfer from FR to darkness. It is concluded that the 'stored phytochrome signal' operates in darkness in the case of CHS but not in the case of PAL.

  18. Phytochrome-mediated induction of phenylalanine ammonia-lyase in the cotyledons of tomato (Lycopersicon esculentum Mill.) plants.

    Science.gov (United States)

    Lercari, B; Sodi, F; Fastami, C

    1982-01-01

    Phenylalanine ammonia-lyase (PAL; EC 4.3.1.5.) induction in cotyledons from 96-h dark-grown Lycopersicon esculentum Mill. was studied in response to continuous light and hourly light pulses (blue, red, far red). The increases of PAL promoted by blue and red pulses are reversed completely by immediately following 758 nm irradiations. The response to continuous red light could be substituted for by hourly 6-min red light pulses. The effect of continuous red treatments is mainly due to a multiple induction effect of phytochrome. In contrast to red light, hourly light pulses with far red and blue, light can only partially substitute for continuous irradiation. The continuous blue response could be due to a combination of a multiple induction response and of a high irradiance response of phytochrome. The continuous far red response, could represent a high irradiance response of phytochrome. Dichromatic irradiations indicate that phytochrome is the photoreceptor controlling the light response (PAL) in tomato seedlings.

  19. Complete genome sequence of cyanobacterium Nostoc sp. NIES-3756, a potentially useful strain for phytochrome-based bioengineering.

    Science.gov (United States)

    Hirose, Yuu; Fujisawa, Takatomo; Ohtsubo, Yoshiyuki; Katayama, Mitsunori; Misawa, Naomi; Wakazuki, Sachiko; Shimura, Yohei; Nakamura, Yasukazu; Kawachi, Masanobu; Yoshikawa, Hirofumi; Eki, Toshihiko; Kanesaki, Yu

    2016-01-20

    To explore the diverse photoreceptors of cyanobacteria, we isolated Nostoc sp. strain NIES-3756 from soil at Mimomi-Park, Chiba, Japan, and determined its complete genome sequence. The Genome consists of one chromosome and two plasmids (total 6,987,571 bp containing no gaps). The NIES-3756 strain carries 7 phytochrome and 12 cyanobacteriochrome genes, which will facilitate the studies of phytochrome-based bioengineering. Copyright © 2015. Published by Elsevier B.V.

  20. Characterization of tobacco expressing functional oat phytochrome. Domains responsible for the rapid degradation of Pfr are conserved between monocots and dicots

    Energy Technology Data Exchange (ETDEWEB)

    Cherry, J.R.; Vierstra, R.D. (Univ. of Wisconsin, Madison (United States)); Hershey, H.P. (E.I.du Pont de Nemours and Co., Wilmington, DE (United States))

    1991-07-01

    Constitutive expression of a chimeric oat phytochrome gene in tobacco (Nicotiana tabacum) results in the accumulation of a functional 124-kilodalton photoreceptor that markedly alters the phenotype of light-grown tobacco. Here, we provide a detailed phenotypic and biochemical characterization of homozygous tobacco expressing high levels of oat phytochrome. Phenotypic changes include a substantial inhibition of stem elongation, decreased apical dominance, increased leaf chlorophyll content, and delayed leaf senescence. Oat phytochrome synthesized in tobacco is indistinguishable from that present in etiolated oats, having photoreversible difference spectrum maxima at 665 and 730 nanometers, exhibiting negligible dark reversion of phytochrome - far red-absorbing from (Pfr) to phytochrome - red-absorbing form (Pr), and existing as a dimer with an apparent size of approximately 300 kilodaltons. Heterodimers between the oat and tobacco chromoproteins were detected. Endogenous tobacco phytochrome and transgenically expressed oat phytochrome are rapidly degraded in vivo upon photoconversion of Pr to Pfr. Breakdown of both oat and tobacco Pfr is associated with the accumulation of ubiquitin-phytochrome conjugates, suggesting that degradation occurs via the ubiquitin-dependent proteolytic pathway. This result indicates that the factors responsible for selective recognition of Pfr by the ubiquitin pathway are conserved between monocot and dicot phytochromes. More broadly, it demonstrates that the domains(s) within a plant protein responsible for its selective breakdown can be recognized by the degradation machinery of heterologous species.

  1. Phytochrome from Green Plants: Properties and biological Function

    Energy Technology Data Exchange (ETDEWEB)

    Quail, Peter H.

    2014-07-25

    Plants constantly monitor the light environment for informational light signals used to direct adaptational responses to the prevailing conditions. One major such response, the Shade-Avaoidance Response (SAR), triggered when plants sense the presence of competing neighbors, results in enhanced channeling of photosynthetically-fixed carbon into stem elongation at the expense of deposition in reproductive tissues. This response has been selected against in many modern food crops to ensure maximum edible yield (e.g. seeds). Converse enhancement of the SAR, with consequent increased carbon channeling into vegetative cellulose, could contribute to the generation of crops with improved yield of tissues suitable for cellulosic biofuel production. The signal for this response is light enriched in far-red wavelengths. This signal is produced by sunlight filtered through, or reflected from, neighboring vegetation, as a result of preferential depletion of red photons through chlorophyll absorption. The plant phytochrome (phy) photoreceptor system (predominantly phyB) senses this signal through its capacity to switch reversibly, in milliseconds, between two molecular states: the biologically inactive Pr (red-light-absorbing) and biologically active Pfr (far-red-light-absorbing) conformers. The photoequilibrium established between these two conformers in light-grown plants is determined by the ratio of red-to-far-red wavelengths in the incoming signal. The levels of Pfr then dictate the recipient plant’s growth response: high levels suppress elongation growth; low levels promote elongation growth. Studies on seedling deetiolation have advanced our understanding considerably in recent years, of the mechanism by which the photoactivated phy molecule transduces its signal into cellular growth responses. The data show that a subfamily of phy-interacting bHLH transcription factors (PIFs) promote skotomorphogenic seedling development in post-germinative darkness, but that the phy

  2. Arabidopsis Phytochrome D Is Involved in Red Light-Induced Negative Gravitropism of Hypocotyles

    Institute of Scientific and Technical Information of China (English)

    LI Jian-ping; HOU Pei; ZHENG Xu; SONG Mei-fang; SU Liang; YANG Jian-ping

    2014-01-01

    The phytochrome gene family, which is in Arabidopsis thaliana, consists of phytochromes A-E (phyA to phyE), regulates plant responses to ambient light environments. PhyA and phyB have been characterized in detail, but studies on phyC to phyE have reported discrepant functions. In this study, we show that phyD regulates the Arabidopsis gravitropic response by inhibiting negative gravitropism of hypocotyls under red light condition. PhyD had only a limited effect on the gravitropic response of roots in red light condition. PhyD also enhanced phyB-regulated gravitropic responses in hypocotyls. Moreover, the regulation of hypocotyl gravitropic responses by phyD was dependent upon the red light lfuence rate.

  3. Phytochrome Control of Germination of Rumex crispus L. Seeds Induced by Temperature Shifts.

    Science.gov (United States)

    Taylorson, R B; Hendricks, S B

    1972-12-01

    High germination of curly dock (Rumex crispus L.) seeds is evident after suitable imbibition and temperature shift treatment, but germination at constant temperatures fails without an input of far red-absorbing form of phytochrome. Preliminary imbibitions at high temperatures (30 C) sharply reduce germination induced by temperature shifts. High germination may be restored by low energies of red radiation, or by brief far red adequate for the photosteady state. Prolonged far red during imbibition also nullifies temperature shift-induced germination. After prolonged far red, high germination may be restored by red radiation of an energy dependent upon the duration of the far red treatment. The evidence supports the conclusion that dark germination induced by temperature shifts arises from the interaction of pre-existent far red-absorbing form of phytochrome in the mature seeds with the temperature shift.

  4. Phytochrome Transformation and Action in Seeds of Rumex crispus L. during Secondary Dormancy.

    Science.gov (United States)

    Taylorson, R B; Hendricks, S B

    1973-11-01

    Promotion of germination by red light fails after prolonged dark imbibition of Rumex crispus L. seeds, indicative of a secondary dormancy. The degree and rate of inception of the dormancy increases with increasing temperature. Following establishment of the dormancy, germination response to red light can be restored by either prolonged cold treatment or brief high temperature shifts. Loss of phytochrome was not a factor in the initial establishment of the dormancy. When the seeds are in secondary dormancy, the chromophore of phytochrome can be transformed to the far red-absorbing form, but the far red-absorbing form cannot induce germination. The responses to changes in temperature suggested dependence of germination on order left arrow over right arrow disorder transitions in components of the seeds.

  5. cis-4-Cyclohexene-1,2-dicarboximide: Inhibitor of phytochrome-promoted seed germination.

    Science.gov (United States)

    Bewley, J D; Oaks, A

    1980-06-01

    cis-4-Cyclohexene-1,2-dicarboximide (CHDC) inhibits the germination of light-requiring seeds in both light and darkness but has no effect upon the germination of non-light-requiring seeds. In lettuce seeds, CHDC inhibits the action of far-red-absorbing form of phytochrome in breaking dormancy. This inhibition can be overcome by benzyladenine and red light together, but not by a combination of red light and gibberellic acid. Gibberellic acid-induced germination of lettuce seeds in darkness is inhibited also by CHDC. Embryos isolated from dark-imbibed lettuce seeds germinate on the inhibitor. CHDC was thought to be an "analogue" of cycloheximide, but it does not inhibit protein synthesis in lettuce seeds. Our results lead us to conclude that CHDC inhibits germination of seeds that require red light to break dormancy and interferes with some aspect of metabolism that is stimulated by far-red-absorbing form of phytochrome.

  6. Actions of gibberellic Acid and phytochrome on the germination of grand rapids lettuce seeds.

    Science.gov (United States)

    Vidaver, W; Hsiao, A I

    1974-02-01

    Red light and gibberellic acid were about equally effective in promoting germination of Grand Rapids lettuce (Lactuca sativa L.) seeds. With initial far red light treatment more than 80% remained dormant in subsequent dark storage. After 2 days of dark storage, red light effectively promoted germination, while gibberellic acid action was weak. With between 2 and 10 days of dark storage, gibberellic acid had little effect, while promotion by red light decreased slowly and finally disappeared. After 10 days of dark storage, both gibberellic acid and red light were required for germination. The dark storage treatment interferes with phytochrome-independent germination processes and cannot be overcome by added gibberellic acid. However, storage may also decrease the effectiveness of endogenous gibberellins. Phytochrome-dependent germination seems to require only low levels of endogenous gibberellin activity or the addition of gibberellic acid. Gibberellins and red light appear to act on germination by regulation of sequential sites of a branched-looped pathway.

  7. Reversibly switchable photoacoustic tomography using a genetically encoded near-infrared phytochrome

    Science.gov (United States)

    Yao, Junjie; Kaberniuk, Andrii A.; Li, Lei; Shcherbakova, Daria M.; Zhang, Ruiying; Wang, Lidai; Li, Guo; Verkhusha, Vladislav V.; Wang, Lihong V.

    2016-03-01

    Optical imaging of genetically encoded probes has revolutionized biomedical studies by providing valuable information about targeted biological processes. Here, we report a novel imaging technique, termed reversibly switchable photoacoustic tomography (RS-PAT), which exhibits large penetration depth, high detection sensitivity, and super-resolution. RS-PAT combines advanced photoacoustic imaging techniques with, for the first time, a nonfluorescent photoswitchable bacterial phytochrome. This bacterial phytochrome is the most near-infrared shifted genetically encoded probe reported so far. Moreover, this bacterial phytochrome is reversibly photoconvertible between its far-red and near-infrared light absorption states. Taking maximum advantage of the powerful imaging capability of PAT and the unique photochemical properties of the phytochrome, RS-PAT has broken through both the optical diffusion limit for deep-tissue imaging and the optical diffraction limit for super-resolution photoacoustic microscopy. Specifically, with RS-PAT we have achieved an unprecedented detection sensitivity of ~2 μM, or as few as ~20 tumor cells, at a centimeter depth. Such high sensitivity is fully demonstrated in our study by monitoring tumor growth and metastasis at whole-body level with ~100 μm resolution. Moreover, our microscopic implementation of RS-PAT is capable of imaging mammalian cells with a sub-diffraction lateral resolution of ~140 nm and axial resolution of ~400 nm, which are respectively ~2-fold and ~75-fold finer than those of our conventional photoacoustic microscopy. Overall, RS-PAT is a new and promising imaging technology for studying biological processes at different length scales.

  8. Altered Phytochrome Regulation of Greening in an aurea Mutant of Tomato.

    Science.gov (United States)

    Ken-Dror, S; Horwitz, B A

    1990-04-01

    A brief pulse of red light accelerates chlorophyll accumulation upon subsequent transfer of dark-grown tomato (Lycopersicon esculentum) seedlings to continuous white light. Such potentiation of greening was compared in wild type and an aurea mutant W616. This mutant has been the subject of recent studies of phytochrome phototransduction; its dark-grown seedlings are deficient in phytochrome, and light-grown plants have yellow-green leaves. The rate of greening was slower in the mutant, but the extent (relative to the dark control) of potentiation by the red pulse was similar to that in the wild type. In the wild type, the fluence-response curve for potentiation of greening indicates substantial components in the VLF (very low fluence) and LF (low fluence) ranges. Far-red light could only partially reverse the effect of red. In the aurea mutant, only red light in the LF range was effective, and the effect of red was completely reversed by far-red light. When grown in total darkness, aurea seedlings are also deficient in photoconvertible PChl(ide). Upon transfer to white light, the aurea mutant was defective in both the abundance and light regulation of the light-harvesting chlorophyll a/b binding polypeptide(s) [LHC(II)]. The results are consistent with the VLF response in greening being mediated by phytochrome. Furthermore, the data support the hypothesis that light modulates LHC(II) levels through its control of the synthesis of both chlorophyll and its LHC(II) apoproteins. Some, but not all, aspects of the aurea phenotype can be accounted for by the deficiency in photoreception by phytochrome.

  9. Far-red light-insensitive, phytochrome A-deficient mutants of tomato.

    Science.gov (United States)

    van Tuinen, A; Kerckhoffs, L H; Nagatani, A; Kendrick, R E; Koornneef, M

    1995-01-20

    We have selected two recessive mutants of tomato with slightly longer hypocotyls than the wild type, one under low fluence rate (3 mumol/m2/s) red light (R) and the other under low fluence rate blue light. These two mutants were shown to be allelic and further analysis revealed that hypocotyl growth was totally insensitive to far-red light (FR). We propose the gene symbol fri (far-red light insensitive) for this locus and have mapped it on chromosome 10. Immunochemically detectable phytochrome A polypeptide is essentially absent in the fri mutants as is the bulk spectrophotometrically detectable labile phytochrome pool in etiolated seedlings. A phytochrome B-like polypeptide is present in normal amounts and a small stable phytochrome pool can be readily detected by spectrophotometry in the fri mutants. Inhibition of hypocotyl growth by a R pulse given every 4 h is quantitatively similar in the fri mutants and wild type and the effect is to a large extent reversible if R pulses are followed immediately by a FR pulse. After 7 days in darkness, both fri mutants and the wild type become green on transfer to white light, but after 7 days in FR, the wild-type seedlings that have expanded their cotyledons lose their capacity to green in white light, while the fri mutants de-etiolate. Adult plants of the fri mutants show retarded growth and are prone to wilting, but exhibit a normal elongation response to FR given at the end of the daily photoperiod. The inhibition of seed germination by continuous FR exhibited by the wild type is normal in the fri mutants.(ABSTRACT TRUNCATED AT 250 WORDS)

  10. Functional analyses of the Physcomitrella patens phytochromes in regulating chloroplast avoidance movement.

    Science.gov (United States)

    Uenaka, Hidetoshi; Kadota, Akeo

    2007-09-01

    Red light-induced chloroplast movement in Physcomitrella patens (Pp) is mediated by dichroic phytochrome in the cytoplasm. To analyze the molecular function of the photoreceptor in the cytoplasm, we developed a protoplast system in which chloroplast photomovement was exclusively dependent on the expression of phytochrome cDNA constructs introduced by polyethylene glycol (PEG) transformation. YFP was fused to the phytochrome constructs and their expression was detected by fluorescence. The chloroplast avoidance response was induced in the protoplasts expressing a YFP fusion of PHY1-PHY3, but not of PHY4 or YFP alone. Phy::yfp fluorescence was detected in the cytoplasm. No change in the location of phy1::yfp or phy2::yfp was revealed before and after photomovement. When phy1::yfp and phy2::yfp were targeted to the nucleus by fusing a nuclear localization signal to the constructs, red light avoidance was not induced. To determine the domains of PHY2 essential for avoidance response, various partially-deleted PHY2::YFP constructs were tested. The N-terminal extension domain (NTE) was found to be necessary but the C-terminal histidine kinase-related domain (HKRD) was dispensable. An avoidance response was not induced under expression of phytochrome N-terminal half domain [deleting both the PAS (Per, Arnt, Sim)-related domain (PRD) and HKRD]. GUS fusion of this N-terminal half domain, reported to be fully functional in Arabidopsis for several phyA- and phyB-regulated responses was not effective in chloroplast avoidance movement. Domain requirement and GUS fusion effect were also confirmed in PHY1. These results indicate that Pp phy1-Pp phy3 in the cytoplasm mediate chloroplast avoidance movement, and that NTE and PRD, but not HKRD, are required for their function.

  11. Assembly of synthetic locked chromophores with agrobacterium phytochromes Agp1 and Agp2.

    Science.gov (United States)

    Inomata, Katsuhiko; Noack, Steffi; Hammam, Mostafa A S; Khawn, Htoi; Kinoshita, Hideki; Murata, Yasue; Michael, Norbert; Scheerer, Patrick; Krauss, Norbert; Lamparter, Tilman

    2006-09-22

    Phytochromes are photoreceptors with a bilin chromophore in which light triggers the conversion between the red-absorbing form Pr and the far-red-absorbing form Pfr. Agrobacterium tumefaciens has two phytochromes, Agp1 and Agp2, with antagonistic properties: in darkness, Agp1 converts slowly from Pfr to Pr, whereas Agp2 converts slowly from Pr to Pfr. In a previous study, we have assembled Agp1 with synthetic locked chromophores 15Za, 15Zs, 15Ea, and 15Es in which the C15=C16 double bond is fixed in either the E or Z configuration and the C14-C15 single bond is fixed in either the syn (s) or anti (a) conformation. In the present study, the locked chromophores 5Za and 5Zs were used for assembly with Agp1; in these chromophores, the C4=C5 double bond is fixed in the Z configuration, and the C5-C6 single bond is fixed in either the syn or anti conformation. All locked chromophores were also assembled with Agp2. The data showed that in both phytochromes the Pr chromophore adopts a C4=C5 Z C5-C6 syn C15=C16 Z C14-C15 anti stereochemistry and that in the Pfr chromophore the C15=C16 double bond has isomerized to the E configuration, whereas the C14-C15 single bond remains in the anti conformation. Photoconversion shifted the absorption maxima of the 5Zs adducts to shorter wavelengths, whereas the 5Za adducts were shifted to longer wavelengths. Thus, the C5-C6 single bond of the Pfr chromophore is rather in an anti conformation, supporting the previous suggestion that during photoconversion of phytochromes, a rotation around the ring A-B connecting single bond occurs.

  12. Photosynthetic photon flux density and phytochrome B interact to regulate branching in Arabidopsis.

    Science.gov (United States)

    Su, Hongwen; Abernathy, Scott D; White, Richard H; Finlayson, Scott A

    2011-11-01

    Branching is regulated by environmental signals including phytochrome B (phyB)-mediated responses to the ratio of red to far red light. While the mechanisms associated with phytochrome regulation of branching are beginning to be elucidated, there is little information regarding other light signals, including photosynthetic photon flux density (PPFD) and how it influences phytochrome-mediated responses. This study shows that Arabidopsis (Arabidopsis thaliana) branching is modified by both varying PPFD and phyB status and that significant interactions occur between these variables. While phyB deficiency decreased branching when the PPFD was low, the effect was suppressed by high PPFD and some branching aspects were actually promoted. Photosynthesis measurements showed that PPFD may influence branching in phyB-deficient plants at least partially through a specific signalling pathway rather than directly through energy effects on the shoot. The expression of various genes in unelongated buds of phyB-deficient and phyB-sufficient plants grown under high and low PPFD demonstrated potential roles for several hormones, including auxin, cytokinins and ABA, and also showed imperfect correlation between expression of the branching regulators BRC1 and BRC2 and bud fate. These results may implicate additional undiscovered bud autonomous mechanisms and/or components contributing to bud outgrowth regulation by environmental signals.

  13. Diatom Phytochromes Reveal the Existence of Far-Red-Light-Based Sensing in the Ocean.

    Science.gov (United States)

    Fortunato, Antonio Emidio; Jaubert, Marianne; Enomoto, Gen; Bouly, Jean-Pierre; Raniello, Raffaella; Thaler, Michael; Malviya, Shruti; Bernardes, Juliana Silva; Rappaport, Fabrice; Gentili, Bernard; Huysman, Marie J J; Carbone, Alessandra; Bowler, Chris; d'Alcalà, Maurizio Ribera; Ikeuchi, Masahiko; Falciatore, Angela

    2016-03-01

    The absorption of visible light in aquatic environments has led to the common assumption that aquatic organisms sense and adapt to penetrative blue/green light wavelengths but show little or no response to the more attenuated red/far-red wavelengths. Here, we show that two marine diatom species, Phaeodactylum tricornutum and Thalassiosira pseudonana, possess a bona fide red/far-red light sensing phytochrome (DPH) that uses biliverdin as a chromophore and displays accentuated red-shifted absorbance peaks compared with other characterized plant and algal phytochromes. Exposure to both red and far-red light causes changes in gene expression in P. tricornutum, and the responses to far-red light disappear in DPH knockout cells, demonstrating that P. tricornutum DPH mediates far-red light signaling. The identification of DPH genes in diverse diatom species widely distributed along the water column further emphasizes the ecological significance of far-red light sensing, raising questions about the sources of far-red light. Our analyses indicate that, although far-red wavelengths from sunlight are only detectable at the ocean surface, chlorophyll fluorescence and Raman scattering can generate red/far-red photons in deeper layers. This study opens up novel perspectives on phytochrome-mediated far-red light signaling in the ocean and on the light sensing and adaptive capabilities of marine phototrophs. © 2016 American Society of Plant Biologists. All rights reserved.

  14. Phytochrome intermediates and action spectra for light perception by dry seeds.

    Science.gov (United States)

    Bartley, M R; Frankland, B

    1984-03-01

    It has previously been demonstrated that far-red irradiation of dry Lactuca sativa L. seeds results in inhibition of subsequent germination. Although red has no effect on dry seeds, a red irradiation following a farred irradiation reverses the effect of far-red. This phenomenon is most noticeable in seeds with artificially raised levels of phytochrome in the far-red absorbing form. Qualitatively similar results have been found for the seeds of Plantago major L., Sinapis arvensis L., and Bromus sterilis L. Action spectra studies on Plantago seeds show that the action peaks for promotion and inhibition of germination of hydrated seeds are at 660 and 730 nanometers, respectively. The action spectrum for inhibition of subsequent germination following irradiation of dry seeds is qualitatively and quantitatively similar to that for hydrated seeds, with an action peak at 730 nanometers, indicating absorption by phytochrome in the far-red absorbing form. However, the action spectrum for the reversal of this far-red effect on dry seeds has a broad peak at 680 nanometers and subsidiary peaks at 650 and 600 nanometers. It is proposed that this effect is due to light absorption by the phytochrome intermediate complex meta-Fa, and that the action spectrum reflects the in vivo absorption properties of this intermediate.

  15. Phytochrome and retrograde signalling pathways converge to antagonistically regulate a light-induced transcriptional network.

    Science.gov (United States)

    Martín, Guiomar; Leivar, Pablo; Ludevid, Dolores; Tepperman, James M; Quail, Peter H; Monte, Elena

    2016-05-06

    Plastid-to-nucleus retrograde signals emitted by dysfunctional chloroplasts impact photomorphogenic development, but the molecular link between retrograde- and photosensory-receptor signalling has remained unclear. Here, we show that the phytochrome and retrograde signalling (RS) pathways converge antagonistically to regulate the expression of the nuclear-encoded transcription factor GLK1, a key regulator of a light-induced transcriptional network central to photomorphogenesis. GLK1 gene transcription is directly repressed by PHYTOCHROME-INTERACTING FACTOR (PIF)-class bHLH transcription factors in darkness, but light-activated phytochrome reverses this activity, thereby inducing expression. Conversely, we show that retrograde signals repress this induction by a mechanism independent of PIF mediation. Collectively, our data indicate that light at moderate levels acts through the plant's nuclear-localized sensory-photoreceptor system to induce appropriate photomorphogenic development, but at excessive levels, sensed through the separate plastid-localized RS system, acts to suppress such development, thus providing a mechanism for protection against photo-oxidative damage by minimizing the tissue exposure to deleterious radiation.

  16. Conditional involvement of constitutive photomorphogenic1 in the degradation of phytochrome A.

    Science.gov (United States)

    Debrieux, Dimitry; Trevisan, Martine; Fankhauser, Christian

    2013-04-01

    All higher plants possess multiple phytochrome photoreceptors, with phytochrome A (phyA) being light labile and other members of the family being relatively light stable (phyB-phyE in Arabidopsis [Arabidopsis thaliana]). phyA also differs from other members of the family because it enables plants to deetiolate in far-red light-rich environments typical of dense vegetational cover. Later in development, phyA counteracts the shade avoidance syndrome. Light-induced degradation of phyA favors the establishment of a robust shade avoidance syndrome and was proposed to be important for phyA-mediated deetiolation in far-red light. phyA is ubiquitylated and targeted for proteasome-mediated degradation in response to light. Cullin1 and the ubiquitin E3 ligase constitutive photomorphogenic1 (COP1) have been implicated in this process. Here, we systematically analyze the requirement of cullins in this process and show that only CULLIN1 plays an important role in light-induced phyA degradation. In addition, the role of COP1 in this process is conditional and depends on the presence of metabolizable sugar in the growth medium. COP1 acts with SUppressor of phytochrome A (SPA) proteins. Unexpectedly, the light-induced decline of phyA levels is reduced in spa mutants irrespective of the growth medium, suggesting a COP1-independent role for SPA proteins.

  17. Conditional Involvement of CONSTITUTIVE PHOTOMORPHOGENIC1 in the Degradation of Phytochrome A1[W][OA

    Science.gov (United States)

    Debrieux, Dimitry; Trevisan, Martine; Fankhauser, Christian

    2013-01-01

    All higher plants possess multiple phytochrome photoreceptors, with phytochrome A (phyA) being light labile and other members of the family being relatively light stable (phyB–phyE in Arabidopsis [Arabidopsis thaliana]). phyA also differs from other members of the family because it enables plants to deetiolate in far-red light-rich environments typical of dense vegetational cover. Later in development, phyA counteracts the shade avoidance syndrome. Light-induced degradation of phyA favors the establishment of a robust shade avoidance syndrome and was proposed to be important for phyA-mediated deetiolation in far-red light. phyA is ubiquitylated and targeted for proteasome-mediated degradation in response to light. Cullin1 and the ubiquitin E3 ligase CONSTITUTIVE PHOTOMORPHOGENIC1 (COP1) have been implicated in this process. Here, we systematically analyze the requirement of cullins in this process and show that only CULLIN1 plays an important role in light-induced phyA degradation. In addition, the role of COP1 in this process is conditional and depends on the presence of metabolizable sugar in the growth medium. COP1 acts with SUPPRESSOR OF PHYTOCHROME A (SPA) proteins. Unexpectedly, the light-induced decline of phyA levels is reduced in spa mutants irrespective of the growth medium, suggesting a COP1-independent role for SPA proteins. PMID:23391578

  18. Quaternary organization of a phytochrome dimer as revealed by cryoelectron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Li, H.; Li, H.; Zhang, J.; Vierstra, R. D.

    2010-06-15

    Phytochromes are a collection of dimeric photoreceptors that direct a diverse array of responses in plants and microorganisms through photoconversion between a red light-absorbing ground state Pr, and a far-red light-absorbing photoactivated state Pfr. Photoconversion from Pr to Pfr is initiated by a light-driven rotation within the covalently attached bilin, which then triggers a series of protein conformational changes in the binding pocket. These movements ultimately affect an appended output module, which often has reversible protein kinase activity. Propagation of the light signal from the bilin to the output module likely depends on the dimerization interface but its architecture and response to phototransformation remain unclear. Here, we used single particle cryoelectron microscopy to determine the quaternary arrangement of the phytochrome dimer as Pr, using the bacteriophytochrome (BphP) from Deinococcus radiodurans. Contrary to the long-standing view that the two monomers are held together solely via their C-terminal region, we provide unambiguous evidence that the N-terminal bilin-binding region of BphP also provides a dimerization interface with the C-terminal kinase domain appearing as a more flexible appendage. The BphP monomers dimerize in parallel with the polypeptides intimately twisting around each other in a right-handed fashion. Based on this electron microscopic picture, we propose that the light-driven conformational changes transmitted from the chromophore to the output module along the spine of this extensive dimer interface is the central feature underpinning phytochrome signaling.

  19. The room temperature crystal structure of a bacterial phytochrome determined by serial femtosecond crystallography

    Science.gov (United States)

    Edlund, Petra; Takala, Heikki; Claesson, Elin; Henry, Léocadie; Dods, Robert; Lehtivuori, Heli; Panman, Matthijs; Pande, Kanupriya; White, Thomas; Nakane, Takanori; Berntsson, Oskar; Gustavsson, Emil; Båth, Petra; Modi, Vaibhav; Roy-Chowdhury, Shatabdi; Zook, James; Berntsen, Peter; Pandey, Suraj; Poudyal, Ishwor; Tenboer, Jason; Kupitz, Christopher; Barty, Anton; Fromme, Petra; Koralek, Jake D.; Tanaka, Tomoyuki; Spence, John; Liang, Mengning; Hunter, Mark S.; Boutet, Sebastien; Nango, Eriko; Moffat, Keith; Groenhof, Gerrit; Ihalainen, Janne; Stojković, Emina A.; Schmidt, Marius; Westenhoff, Sebastian

    2016-01-01

    Phytochromes are a family of photoreceptors that control light responses of plants, fungi and bacteria. A sequence of structural changes, which is not yet fully understood, leads to activation of an output domain. Time-resolved serial femtosecond crystallography (SFX) can potentially shine light on these conformational changes. Here we report the room temperature crystal structure of the chromophore-binding domains of the Deinococcus radiodurans phytochrome at 2.1 Å resolution. The structure was obtained by serial femtosecond X-ray crystallography from microcrystals at an X-ray free electron laser. We find overall good agreement compared to a crystal structure at 1.35 Å resolution derived from conventional crystallography at cryogenic temperatures, which we also report here. The thioether linkage between chromophore and protein is subject to positional ambiguity at the synchrotron, but is fully resolved with SFX. The study paves the way for time-resolved structural investigations of the phytochrome photocycle with time-resolved SFX. PMID:27756898

  20. Phytochromes from Agrobacterium tumefaciens: difference spectroscopy with extracts of wild type and knockout mutants.

    Science.gov (United States)

    Oberpichler, Inga; Molina, Isabel; Neubauer, Olivia; Lamparter, Tilman

    2006-01-23

    Phytochromes are photoreceptors that occur in plants, fungi and bacteria, among others in the phytopathogen Agrobacterium tumefaciens. We constructed single and double knockout mutants of the two A. tumefaciens phytochromes Agp1 and Agp2. In liquid culture, the double mutant revealed a reduced growth rate, whereas the growth rates of the single mutants did not differ significantly from that of the wild type. Using these mutants, we analyzed the spectral properties of native A. tumefaciens phytochromes. A wild-type A. tumefaciens cell contains about 10 molecules of Agp1 and about 19 molecules of Agp2. Dark conversion of native Agp1 and Agp2 proceeds from Pfr to Pr and from Pr to Pfr, respectively, as has already been reported for the recombinant proteins. The spectral properties of recombinant and native Agp2 were significantly different. Mixing experiments with extracts from the double mutant and recombinant Agp2 imply that the spectral properties of Agp2 are modulated by components of the extract.

  1. Participation of labile and stabile phytochrome in the control of chlorophyll accumulation during the deetiolation of oat seedlings

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    Mariusz Cymerski

    2014-02-01

    Full Text Available The effect of the phytochrome system on the accumulation rate of chlorophyll-a and b in 96-hour-old oat seedlings during the first 3 hours of white light action was investigated. It was established that initial irradiation with red light stimulated the accumulation rate of both forms of chlorophyll. This effect depended on the level of the PFR form of phytochrome obtained during the initial irradiation and it reached the treshold value in the case of about 20% of PFR in relation to PR in etiolated seedlings. Far red light stimulated only the accumulation of chlorophyll-a. The effect of red light was reversible if far red light was applied directly after red light. The reversibility diminished gradually together with the extension of the dark period between red and far red light, disappearing completely after 6 hours. The results suggest the participation of two pools of phytochrome - a labile and a stabile one - in the reaction stimulating chlorophyll accumulation. A model of labile phytochrome action through the destruction products of phytochrome is proposed.

  2. The evolution of gymnosperms redrawn by phytochrome genes: the Gnetatae appear at the base of the gymnosperms.

    Science.gov (United States)

    Schmidt, Marion; Schneider-Poetsch, Hansjörg A W

    2002-06-01

    Gymnosperms possess two to four phytochrome types which apparently are the result of successive gene duplications in the genomes of their common ancestors. Phytochromes are nuclear-encoded proteins whose genes, contrary to chloroplast, mitochondrion, and rRNA genes, have hitherto rarely been used to examine gymnosperm phylogenies. Since the individual phytochrome gene types implied phylogenies that were not completely congruent to one another, conflicting branching orders were sorted by the number of gene lineages present in a taxon. The Gnetatae (two gene types) branched at the base of all gymnosperms, a position supported by bootstrap sampling (distance and character state trees, maximum likelihood). The Gnetatae were followed by Ginkgo, Cycadatae, and Pinaceae (three gene types) and the remaining conifers (four gene types). Therefore, in phytochrome trees, the most ancient branch of the conifers (Pinatae) seems to be the Pinaceae. The next split appears to have separated Araucariaceae plus Podocarpaceae from the Taxaceae/Taxodiaceae/Cupressaceae group. Structural arrangements in the plastid genomes (Raubeson and Jansen 1992) corroborate the finding that there is no close connection between Pinaceae and Gnetatae as suggested by some publications. The analyses are based on 60 phytochrome genes (579 positions in an alignment of PCR fragments) from 28 species. According to rough divergence time estimates, the last common ancestor of gymnosperms and angiosperms is likely to have existed in the Carboniferous.

  3. Phytochromes Regulate SA and JA Signaling Pathways in Rice and Are Required for Developmentally Controlled Resistance to Magnaporthe grisea

    Institute of Scientific and Technical Information of China (English)

    Xian-Zhi Xie; Yan-Jiu Xue; Jin-Jun Zhoua; Bin Zhang; Hong Chang; Makoto Takano

    2011-01-01

    Old leaves of wild-type rice plants (Oryza sativa L. Cv. Nipponbare)are more resistant to blast fungus (Mag-naporthe grisea)than new leaves. In contrast, both old and new leaves of the rice phytochrome triple mutant (phyAphyB-phyC)are susceptible to blast fungus. We demonstrate that pathogenesis-related class 1 (PR1)proteins are rapidly and strongly induced during M. Grisea infection and following exogenous jasmonate (JA)or salicylic acid (SA)exposure in the old leaves, but not in the new leaves of the wild-type. In contrast, the accumulation of PR1 proteins was significantly attenuated in old and new leaves of the phyAphyBphyC mutant. These results suggest that phytochromes are required for the induction of PR1 proteins in rice. Basal transcription levels of Prla and PRlb were substantially higher in the wild-type as compared to the phyAphyBphyC mutant, suggesting that phytochromes also are required for basal expression of PR1 genes. Moreover, the transcript levels of genes known to function in SA-or JA-dependent defense pathways were regulated by leaf age and functional phytochromes. Taken together, our findings demonstrate that phytochromes are required in rice for age-related resistance to M, grisea and may indirectly increase PR1 gene expression by regulating SA-and JA-dependent defense pathways.

  4. Biphasic fluence-response curves for phytochrome-mediated kalanchoë seed germination : sensitization by gibberellic Acid.

    Science.gov (United States)

    Rethy, R; Dedonder, A; De Petter, E; Van Wiemeersch, L; Fredericq, H; De Greef, J; Steyaert, H; Stevens, H

    1987-01-01

    The fluence-response curves for the effect of two red pulses separated by 24 hours on the germination of Kalanchoe blossfeldiana Poelln. cv Vesuv seeds, incubated on gibberellic acid (GA(3)) are biphasic for suboptimal concentrations. The response in the low fluence range corresponds with a classical red/far-red reversible phytochrome mediated reaction. GA(3) induces an additional response in the very low fluence range, which is also phytochrome mediated. The sensitivity to phytochrome-far-red absorbing form (Pfr), however, is increased about 20,000-fold, so that even far-red fluences become saturating. Both in the very low and low fluence response range, the maximal responses induced by saturating fluences are modulated by the GA(3) concentration. GA(3) having no direct influence on the phytochrome phototransformations, alters the Pfr requirement and determines the responding seed population fraction in the very low and low fluence range. The effet of GA(3) appears to be on the transduction chain of the phytochrome signal.

  5. Crystal Structure of Deinococcus Phytochrome in the Photoactivated State Reveals a Cascade of Structural Rearrangements during Photoconversion.

    Science.gov (United States)

    Burgie, E Sethe; Zhang, Junrui; Vierstra, Richard D

    2016-03-01

    Phytochromes are photochromic photoreceptors responsible for a myriad of red/far-red light-dependent processes in plants and microorganisms. Interconversion is initially driven by photoreversible isomerization of bilin, but how this alteration directs the photostate-dependent changes within the protein to actuate signaling is poorly understood. Here, we describe the structure of the Deinococcus phytochrome photosensory module in its near complete far-red light-absorbing Pfr state. In addition to confirming the 180° rotation of the D-pyrrole ring, the dimeric structure clearly identifies downstream rearrangements that trigger large-scale conformational differences between the dark-adapted and photoactivated states. Mutational analyses verified the importance of residues surrounding the bilin in Pfr stabilization, and protease sensitivity assays corroborated photostate alterations that propagate along the dimeric interface. Collectively, these data support a cooperative "toggle" model for phytochrome photoconversion and advance our understanding of the allosteric connection between the photosensory and output modules.

  6. Elucidating photoinduced structural changes in phytochromes by the combined application of resonance Raman spectroscopy and theoretical methods

    Science.gov (United States)

    Mroginski, M. A.; von Stetten, D.; Kaminski, S.; Escobar, F. Velazquez; Michael, N.; Daminelli-Widany, G.; Hildebrandt, P.

    2011-05-01

    Phytochromes constitute a family of red-light sensing photoreceptors in plants and microorganisms. The photoactive cofactor is an open-chain methine-bridged tetrapyrrole that, upon light absorption, undergoes a double bond isomerisation followed by series thermal relaxation processes which eventually lead to the functional structural change of the protein. Resonance Raman spectroscopy has contributed significantly to the understanding of the molecular functioning of these proteins although both the experiments and the interpretation of the spectra represent a considerable challenge. This account is dedicated to describe achievements, potential and limitations of combined resonance Raman spectroscopic and theoretical approaches for elucidating cofactor structures in phytochromes. Experimental approaches are discussed paying specific attention on strategies to overcome unwanted photochemical and photophysical processes when probing the various states of the photoinduced reaction cycle of phytochromes. The most comprehensive set of experimental data on phytochromes, including engineered protein variants and adducts formed with isotopically labelled tetrapyrroles, has been obtained by resonance Raman spectroscopy with near-infrared excitation that also allows probing phytochrome crystals without photo-induced destruction. Quantum mechanical calculations of Raman spectra of model compounds represent a first approximation for determining the methine bridge geometry of the protein-bound tetrapyrroles and constitute the basis for the identification of marker bands for specific structural properties such as the protonation state of the cofactor. Drawbacks of this theoretical method that inevitably neglects the protein environment have become evident with the first determinations of three-dimensional structures of phytochromes. These structural models can now be used for employing hybrid methods that combine quantum mechanical and molecular mechanics calculations of the

  7. Phytochromes A and B mediate red-light-induced positive phototropism in roots.

    Science.gov (United States)

    Kiss, John Z; Mullen, Jack L; Correll, Melanie J; Hangarter, Roger P

    2003-03-01

    The interaction of tropisms is important in determining the final growth form of the plant body. In roots, gravitropism is the predominant tropistic response, but phototropism also plays a role in the oriented growth of roots in flowering plants. In blue or white light, roots exhibit negative phototropism that is mediated by the phototropin family of photoreceptors. In contrast, red light induces a positive phototropism in Arabidopsis roots. Because this red-light-induced response is weak relative to both gravitropism and negative phototropism, we used a novel device to study phototropism without the complications of a counteracting gravitational stimulus. This device is based on a computer-controlled system using real-time image analysis of root growth and a feedback-regulated rotatable stage. Our data show that this system is useful to study root phototropism in response to red light, because in wild-type roots, the maximal curvature detected with this apparatus is 30 degrees to 40 degrees, compared with 5 degrees to 10 degrees without the feedback system. In positive root phototropism, sensing of red light occurs in the root itself and is not dependent on shoot-derived signals resulting from light perception. Phytochrome (Phy)A and phyB were severely impaired in red-light-induced phototropism, whereas the phyD and phyE mutants were normal in this response. Thus, PHYA and PHYB play a key role in mediating red-light-dependent positive phototropism in roots. Although phytochrome has been shown to mediate phototropism in some lower plant groups, this is one of the few reports indicating a phytochrome-dependent phototropism in flowering plants.

  8. Modulation of phytochrome signaling networks for improved biomass accumulation using a bioenergy crop model

    Energy Technology Data Exchange (ETDEWEB)

    Mockler, Todd C. [Donald Danforth Plant Science Center, Saint Louis, MO (United States)

    2016-11-07

    Plant growth and development, including stem elongation, flowering time, and shade-avoidance habits, are affected by wavelength composition (i.e., light quality) of the light environment. the molecular mechanisms underlying light perception and signaling pathways in plants have been best characterized in Arabidopsis thaliana where dozens of genes have been implicated in converging, complementary, and antagonistic pathways communicating light quality cues perceived by the phytochrome (red/far-red) cryptochrome (blue) and phototropin (blue) photorecptors. Light perception and signaling have been studied in grasses, including rice and sorghum but in much less detail than in Arabidopsis. During the course of the Mocker lab's DOE-funded wrok generating a gene expression atlas in Brachypodium distachyon we observed that Brachypodium plants grown in continuous monochromatic red light or continuous white light enriched in far-red light accumulated significantly more biomass and exhibited significantly greater seed yield than plants grown in monochromatic blue light or white light. This phenomenon was also observed in two other grasses, switchgrass and rice. We will systematically manipulate the expression of genes predicted to function in Brachypodium phytochrome signaling and assess the phenotypic consequences in transgenic Brachypodium plants in terms of morphology, stature, biomass accumulation, and cell wall composition. We will also interrogate direct interactions between candidate phytochrome signaling transcription factors and target promoters using a high-throughput yeast one-hybrid system. Brachypodium distachyon has emerged as a model grass species and is closely related to candidate feedstock crops for bioethanol production. Identification of genes capable of modifying growth characteristics of Brachypodium, when misexpressed, in particular increasing biomass accumulation, by modulating photoreceptor signaling will provide valuable candidates for

  9. Assembly of Agrobacterium phytochromes Agp1 and Agp2 with doubly locked bilin chromophores.

    Science.gov (United States)

    Inomata, Katsuhiko; Khawn, Htoi; Chen, Li-Yi; Kinoshita, Hideki; Zienicke, Benjamin; Molina, Isabel; Lamparter, Tilman

    2009-03-31

    The natural chromophore of most bacterial and fungal phytochromes is biliverdin (BV), which is incorporated in a covalent manner into the protein. Upon photoconversion between the red light-absorbing form Pr and the far-red light-absorbing form Pfr, the stereochemistry of the chromophore around the C15 methine bridge changes from Z anti to E anti. Recombinant phytochromes Agp1 and Agp2 from Agrobacterium tumefaciens were assembled with a set of synthetic chromophores, including 2,18-Et-BV, 3,18-Et-BV, and the doubly locked 5Ea15Ea-BV, 5Es15Ea-BV, 5Za15Ea-BV, and 5Zs15Ea-BV. In all chromophores, covalent bond formation is restricted. As shown by spectral changes and desalting column separation, all chromophores are bound to Agp1 and Agp2. Adducts with 2,18-Et-BV and 3,18-Et-BV undergo normal photoconversion between Pr and Pfr. As opposed to typical phytochromes, the BV-Agp2 adduct converts from Pr to Pfr in darkness. However, the 2,18-Et-BV-Agp2 and 3,18-Et-BV-Agp2 adducts can undergo dark conversion from Pr to Pfr and Pfr to Pr, showing that ring A of the chromophore has a direct impact on the direction of dark conversion. The doubly locked chromophores were designed to probe for the stereochemistry of the C5 methine bridge in the Pfr form. The adducts with 5Es15Ea-BV and 5Zs15Ea-BV absorbed in the blue spectral range only. Therefore, the C5 E syn and Z syn stereochemistries are unlikely for the Pfr chromophore of Agp1 and Agp2. According to our spectra, the Agp2 chromophore most likely adopts an E anti stereochemistry at its C5 methine bridge. Thus, during Pr to Pfr conversion, the C5 methine bridge of the chromophore might undergo a Hula-twist isomerization. In Agp1, the Pfr chromophore is most likely in the C5 Z anti stereochemistry. We propose that the stereochemistry of the C5 methine bridge might differ between different phytochromes, most particularly in the Pfr form.

  10. cis-4-Cyclohexene-1,2-dicarboximide: Inhibitor of phytochrome-promoted seed germination

    OpenAIRE

    BEWLEY, J. DEREK; Oaks, Ann

    1980-01-01

    cis-4-Cyclohexene-1,2-dicarboximide (CHDC) inhibits the germination of light-requiring seeds in both light and darkness but has no effect upon the germination of non-light-requiring seeds. In lettuce seeds, CHDC inhibits the action of far-red-absorbing form of phytochrome in breaking dormancy. This inhibition can be overcome by benzyladenine and red light together, but not by a combination of red light and gibberellic acid. Gibberellic acid-induced germination of lettuce seeds in darkness is ...

  11. Phytochrome and Seed Germination. I. Temperature Dependence and Relative P(FR) Levels in the Germination of Dark-germinating Tomato Seeds.

    Science.gov (United States)

    Mancinelli, A L; Yaniv, Z; Smith, P

    1967-03-01

    Germination of the dark-germinating seeds of 3 varieties of tomato is controlled by the phytochrome system. Germination is inhibited by far red radiation and repromoted by red applied after far red. At low temperatures, 17 to 20 degrees , a single, low energy far red irradiation is sufficient to inhibit germination in all 3 varieties. At higher temperatures far red is less effective in the inhibition of the germination of the tomato seeds. The phytochrome fraction present as P(FR) in the dark-germinating seeds of the Ace variety is about 40% of the total phytochrome present.

  12. Holophytochrome-Interacting Proteins in Physcomitrella: Putative Actors in Phytochrome Cytoplasmic Signaling.

    Science.gov (United States)

    Ermert, Anna Lena; Mailliet, Katharina; Hughes, Jon

    2016-01-01

    Phytochromes are the principle photoreceptors in light-regulated plant development, primarily acting via translocation of the light-activated photoreceptor into the nucleus and subsequent gene regulation. However, several independent lines of evidence indicate unambiguously that an additional cytoplasmic signaling mechanism must exist. Directional responses in filament tip cells of the moss Physcomitrella patens are steered by phy4 which has been shown to interact physically with the blue light receptor phototropin at the plasma membrane. This complex might perceive and transduce vectorial information leading to cytoskeleton reorganization and finally a directional growth response. We developed yeast two-hybrid procedures using photochemically functional, full-length phy4 as bait in Physcomitrella cDNA library screens and growth assays under different light conditions, revealing Pfr-dependent interactions possibly associated with phytochrome cytoplasmic signaling. Candidate proteins were then expressed in planta with fluorescent protein tags to determine their intracellular localization in darkness and red light. Of 14 candidates, 12 were confirmed to interact with phy4 in planta using bimolecular fluorescence complementation. We also used database information to study their expression patterns relative to those of phy4. We discuss the likely functional characteristics of these holophytochrome-interacting proteins (HIP's) and their possible roles in signaling.

  13. Evolutionary aspects of functional and pseudogene members of the phytochrome gene family in Scots pine.

    Science.gov (United States)

    García-Gil, Maria Rosario

    2008-08-01

    According to the neutral theory of evolution, mutation and genetic drift are the only forces that shape unconstrained, neutral, gene evolution. Thus, pseudogenes (which often evolve neutrally) provide opportunities to obtain direct estimates of mutation rates that are not biased by selection, and gene families comprising functional and pseudogene members provide useful material for both estimating neutral mutation rates and identifying sites that appear to be under positive or negative selection pressures. Conifers could be very useful for such analyses since they have large and complex genomes. There is evidence that pseudogenes make significant contributions to the size and complexity of gene families in pines, although few studies have examined the composition and evolution of gene families in conifers. In this work, I examine the complexity and rates of mutation of the phytochrome gene family in Pinus sylvestris and show that it includes not only functional genes but also pseudogenes. As expected, the functional PHYO does not appear to have evolved neutrally, while phytochrome pseudogenes show signs of unconstrained evolution.

  14. Shedding (far-red) light on phytochrome mechanisms and responses in land plants.

    Science.gov (United States)

    Possart, Anja; Fleck, Christian; Hiltbrunner, Andreas

    2014-03-01

    In order to monitor ambient light conditions, plants rely on functionally diversified photoreceptors. Among these, phytochromes perceive red (R) and far-red (FR) light. FR light does not constitute a photosynthetic energy source; it however influences adaptive and developmental processes. In seed plants, phytochrome A (phyA) acts as FR receptor and mediates FR high irradiance responses (FR-HIRs). It exerts a dual role by promoting e.g. germination and seedling de-etiolation in canopy shade and by antagonising shade avoidance growth. Even though cryptogam plants such as mosses and ferns do not have phyA, they show FR-induced responses. In the present review we discuss the mechanistic basis of phyA-dependent FR-HIRs as well as their dual role in seed plants. We compare FR responses in seed plants and cryptogam plants and conclude on different potential concepts for the detection of canopy shade. Scenarios for the evolution of FR perception and responses are discussed.

  15. Heterogeneous photodynamics of the pfr state in the cyanobacterial phytochrome Cph1.

    Science.gov (United States)

    Kim, Peter W; Rockwell, Nathan C; Martin, Shelley S; Lagarias, J Clark; Larsen, Delmar S

    2014-07-22

    Femtosecond photodynamics of the Pfr form of the red/far-red phytochrome N-terminal PAS-GAF-PHY photosensory core module of the cyanobacterial phytochrome Cph1 (termed Cph1Δ) from Synechocystis were resolved with visible broadband transient absorption spectroscopy. Multiphasic generation dynamics via global target analysis revealed parallel evolution of two pathways with distinct excited- and ground-state kinetics. These measurements resolved two subpopulations: a majority subpopulation with fast excited-state decay and slower ground-state dynamics, corresponding to previous descriptions of Pfr dynamics, and a minority subpopulation with slower excited-state decay and faster ground-state primary dynamics. Both excited-state subpopulations generated the isomerized, red-shifted Lumi-Ff photoproduct (715 nm); subsequent ground-state evolution to a blue-shifted Meta-Fr population (635 nm) proceeded on 3 ps and 1.5 ns time scales for the two subpopulations. Meta-Fr was spectrally similar to a recently described photoinactive fluorescent subpopulation of Pr ((Fluor)Pr). Thus, the reverse Pfr to Pr photoconversion of Cph1Δ involves minor structural deformation of Meta-Fr to generate the fluorescent, photochemically refractory form of Pr, with slower subsequent equilibration with the photoactive Pr subpopulation ((Photo)Pr).

  16. Subpicosecond midinfrared spectroscopy of the Pfr reaction of phytochrome Agp1 from Agrobacterium tumefaciens.

    Science.gov (United States)

    Schumann, Christian; Gross, Ruth; Wolf, Matthias M N; Diller, Rolf; Michael, Norbert; Lamparter, Tilman

    2008-04-15

    Phytochromes are light-sensing pigments found in plants and bacteria. For the first time, the P(fr) photoreaction of a phytochrome has been subject to ultrafast infrared vibrational spectroscopy. Three time constants of 0.3 ps, 1.3 ps, and 4.0 ps were derived from the kinetics of structurally specific marker bands of the biliverdin chromophore of Agp1-BV from Agrobacterium tumefaciens after excitation at 765 nm. VIS-pump-VIS-probe experiments yield time constants of 0.44 ps and 3.3 ps for the underlying electronic-state dynamics. A reaction scheme is proposed including two kinetic steps on the S(1) excited-state surface and the cooling of a vibrationally hot P(fr) ground state. It is concluded that the upper limit of the E-Z isomerization of the C(15) = C(16) methine bridge is given by the intermediate time constant of 1.3 ps. The reaction scheme is reminiscent of that of the corresponding P(r) reaction of Agp1-BV as published earlier.

  17. Initial characterization of shade avoidance response suggests functional diversity between Populus phytochrome B genes.

    Energy Technology Data Exchange (ETDEWEB)

    Karve, Abhijit A [ORNL; Weston, David [ORNL; Jawdy, Sara [ORNL; Gunter, Lee E [ORNL; Allen, Sara M [ORNL; Yang, Xiaohan [ORNL; Wullschleger, Stan D [ORNL; Tuskan, Gerald A [ORNL

    2012-01-01

    Shade avoidance signaling in higher plants involves perception of the incident red/far-red (R/FR) light by phytochromes and the modulation of downstream transcriptional networks to regulate developmental plasticity in relation to heterogeneous light environments. In this study, we characterized the expression and functional features of Populus phytochrome (PHY) gene family as well as the transcriptional responses of Populus to the changes in R/FR light. Expression data indicated that PHYA is the predominant PHY in the dark grown Populus seedling whereas PHYBs are most abundant in mature tissue types. Out of three Populus PHYs, PHYA is light labile and localized to cytosol in dark whereas both PHYB1 and PHYB2 are light stable and are localized to nucleus in mesophyll protoplasts. When expressed in Arabidopsis, PHYB1 rescued Arabidopsis phyB mutant phenotype whereas PHYB2 did not, suggesting functional diversification between these two gene family members. However, phenotypes of transgenic Populus lines with altered expression of PHYB1, PHYB2 or both and the expression of candidate shade response genes in these transgenic lines suggest that PHYB1 and PHYB2 may have distinct yet overlapping functions. The RNAseq results and analysis of Populus exposed to enriched-FR light indicate that genes associated in cell wall modification and brassinosteroid signaling were induced under far red light. Overall our data indicate that Populus transcriptional responses are at least partially conserved with Arabidopsis.

  18. Phytochromes play a role in phototropism and gravitropism in Arabidopsis roots

    Science.gov (United States)

    Correll, Melanie J.; Coveney, Katrina M.; Raines, Steven V.; Mullen, Jack L.; Hangarter, Roger P.; Kiss, John Z.

    2003-05-01

    Phototropism as well as gravitropism plays a role in the oriented growth of roots in flowering plants. In blue or white light, roots exhibit negative phototropism, but red light induces positive phototropism in Arabidopsis roots. Phytochrome A (phyA) and phyB mediate the positive red-light-based photoresponse in roots since single mutants (and the double phyAB mutant) were severely impaired in this response. In blue-light-based negative phototropism, phyA and phyAB (but not phyB) were inhibited in the response relative to the WT. In root gravitropism, phyB and phyAB (but not phyA) were inhibited in the response compared to the WT. The differences observed in tropistic responses were not due to growth limitations since the growth rates among all the mutants tested were not significantly different from that of the WT. Thus, our study shows that the blue-light and red-light systems interact in roots and that phytochrome plays a key role in plant development by integrating multiple environmental stimuli.

  19. The altered gravitropic response of the lazy-2 mutant of tomato is phytochrome regulated.

    Science.gov (United States)

    Gaiser, J C; Lomax, T L

    1993-06-01

    Shoots of the lazy-2 (lz-2) gravitropic mutant of tomato (Lycopersicon esculentum Mill.) have a normal gravitropic response when grown in the dark, but grow downward in response to gravity when grown in the light. Experiments were undertaken to investigate the nature of the light induction of the downward growth of lz-2 shoots. Red light was effective at causing downward growth of hypocotyls of lz-2 seedlings, whereas treatment with blue light did not alter the dark-grown (wild-type) gravity response. Downward growth of lz-2 seedlings is greatest 16 h after a 1-h red light irradiation, after which the seedlings begin to revert to the dark-grown phenotype. lz-2 seedlings irradiated with a far-red light pulse immediately after a red light pulse exhibited no downward growth. However, continuous red or far-red light both resulted in downward growth of lz-2 seedlings. Thus, the light induction of downward growth of lz-2 appears to involve the photoreceptor phytochrome. Fluence-response experiments indicate that the induction of downward growth of lz-2 by red light is a low-fluence phytochrome response, with a possible high-irradiance response component.

  20. Holophytochrome-interacting proteins in Physcomitrella: putative actors in phytochrome cytoplasmic signaling

    Directory of Open Access Journals (Sweden)

    Anna Lena eErmert

    2016-05-01

    Full Text Available Phytochromes are the principle photoreceptors in light-regulated plant development, primarily acting via translocation of the light-activated photoreceptor into the nucleus and subsequent gene regulation. However, several independent lines of evidence indicate unambiguously that an additional cytoplasmic signaling mechanism must exist. Directional responses in filament tip cells of the moss Physcomitrella patens are steered by phy4 which has been shown to interact physically with the blue light receptor phototropin at the plasma membrane. This complex might perceive and transduce vectorial information leading to cytoskeleton reorganization and finally a directional growth response. We developed yeast two-hybrid procedures using photochemically-functional, full-length phy4 as bait in Physcomitrella cDNA library screens and growth assays under different light conditions, revealing Pfr-dependent interactions possibly associated with phytochrome cytoplasmic signaling. Candidate proteins were then expressed in planta with fluorescent protein tags to determine their intracellular localization in darkness and red light. Of 14 candidates, 12 were confirmed to interact with phy4 in planta using bimolecular fluorescence complementation. We discuss the roles these putative holophytochrome-interacting proteins (HIP's might have in signaling.

  1. Real-time tracking of phytochrome's ring D orientational changes during Pr photoisomerization: Two Pr isoforms with different photoisomerization yields

    Directory of Open Access Journals (Sweden)

    González L.

    2013-03-01

    Full Text Available Phytochromes' ring D orientational changes are tracked during Z-to-E photoisomerization by polarization resolved femtosecond visible pump-infrared probe spectroscopy. Two distinct Pr isoforms Pr-I and Pr-II exhibit photoisomerization yields of 3% and 29%, respectively.

  2. Spectral properties of phytochrome Agp2 from Agrobacterium tumefaciens are specifically modified by a compound of the cell extract.

    Science.gov (United States)

    Krieger, Alexander; Molina, Isabel; Oberpichler, Inga; Michael, Norbert; Lamparter, Tilman

    2008-10-16

    Phytochromes are widely distributed photoreceptors that are converted by light between the red absorbing Pr and the far-red absorbing Pfr form. The soil bacterium Agrobacterium tumefaciens contains two phytochromes, Agp1 and Agp2, which act as light-regulated histidine kinases. Whereas most phytochromes are stable in the Pr form, Agp2 and few other phytochromes convert into Pfr in darkness. We have shown in a previous publication that the spectral properties of recombinant Agp2 are modified by compounds of the cell extract from an Agrobacterium agp1(-)/agp2(-) double knockout mutant. In the present work we performed concentration series which show that the interaction is specific and that the modifying factor has a concentration of ca. 0.2 microM. We have also performed a series of mixing experiments with the truncated protein Agp2-M2, which consists of the N-terminal chromophore module (501 amino acids). The cell extract inhibited the photoconversion of Agp2-M2 in an unspecific way. In concentration series, this negative effect was less pronounced when lower concentrations of Agp2-M2 were used. In the presence of excess Agp2-M2 apoprotein, the cell extract did no longer modify the spectral properties of Agp2. The data suggest that the factor of the cell extract interacts specifically with the N-terminal moiety of Agp2.

  3. Phytochrome controlled, long-day photoperiod-inducible protein in rice leaves

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A new protein in the leaves of NK58S and NK58 (Oryza sativa L. subsp. japonica), which can be induced by 10 d-long-day photoperiod (14 h light/d) and cannot be induced by 10 d-short-day photoperiod (10 h light/d), has been found by two-dimensional gel electrophoresis. The protein,whose molecular weight and isoelectric point are 36 ku and pH 5.2 respectively, is found to be controlled by phytochrome as shown by the experiment of red light induction-far red light reversion.The existence of this protein in both NK58S and NK58 reflects that some of the responses of NK58S and NK58 might be similar in response to long-day photoperiod, a mild stress.

  4. PHYTOCHROME C is an essential light receptor for photoperiodic flowering in the temperate grass, Brachypodium distachyon.

    Science.gov (United States)

    Woods, Daniel P; Ream, Thomas S; Minevich, Gregory; Hobert, Oliver; Amasino, Richard M

    2014-09-01

    We show that in the temperate grass, Brachypodium distachyon, PHYTOCHROME C (PHYC), is necessary for photoperiodic flowering. In loss-of-function phyC mutants, flowering is extremely delayed in inductive photoperiods. PHYC was identified as the causative locus by utilizing a mapping by sequencing pipeline (Cloudmap) optimized for identification of induced mutations in Brachypodium. In phyC mutants the expression of Brachypodium homologs of key flowering time genes in the photoperiod pathway such as GIGANTEA (GI), PHOTOPERIOD 1 (PPD1/PRR37), CONSTANS (CO), and florigen/FT are greatly attenuated. PHYC also controls the day-length dependence of leaf size as the effect of day length on leaf size is abolished in phyC mutants. The control of genes upstream of florigen production by PHYC was likely to have been a key feature of the evolution of a long-day flowering response in temperate pooid grasses.

  5. An integrative model for phytochrome B mediated photomorphogenesis: from protein dynamics to physiology.

    Directory of Open Access Journals (Sweden)

    Julia Rausenberger

    Full Text Available BACKGROUND: Plants have evolved various sophisticated mechanisms to respond and adapt to changes of abiotic factors in their natural environment. Light is one of the most important abiotic environmental factors and it regulates plant growth and development throughout their entire life cycle. To monitor the intensity and spectral composition of the ambient light environment, plants have evolved multiple photoreceptors, including the red/far-red light-sensing phytochromes. METHODOLOGY/PRINCIPAL FINDINGS: We have developed an integrative mathematical model that describes how phytochrome B (phyB, an essential receptor in Arabidopsis thaliana, controls growth. Our model is based on a multiscale approach and connects the mesoscopic intracellular phyB protein dynamics to the macroscopic growth phenotype. To establish reliable and relevant parameters for the model phyB regulated growth we measured: accumulation and degradation, dark reversion kinetics and the dynamic behavior of different nuclear phyB pools using in vivo spectroscopy, western blotting and Fluorescence Recovery After Photobleaching (FRAP technique, respectively. CONCLUSIONS/SIGNIFICANCE: The newly developed model predicts that the phyB-containing nuclear bodies (NBs (i serve as storage sites for phyB and (ii control prolonged dark reversion kinetics as well as partial reversibility of phyB Pfr in extended darkness. The predictive power of this mathematical model is further validated by the fact that we are able to formalize a basic photobiological observation, namely that in light-grown seedlings hypocotyl length depends on the total amount of phyB. In addition, we demonstrate that our theoretical predictions are in excellent agreement with quantitative data concerning phyB levels and the corresponding hypocotyl lengths. Hence, we conclude that the integrative model suggested in this study captures the main features of phyB-mediated photomorphogenesis in Arabidopsis.

  6. Phytochrome A and B Regulate Primary Metabolism in Arabidopsis Leaves in Response to Light

    Directory of Open Access Journals (Sweden)

    Xiaozhen Han

    2017-08-01

    Full Text Available Primary metabolism is closely linked to plant productivity and quality. Thus, a better understanding of the regulation of primary metabolism by photoreceptors has profound implications for agricultural practices and management. This study aims at identifying the role of light signaling in the regulation of primary metabolism, with an emphasis on starch. We first screened seven cryptochromes and phytochromes mutants for starch phenotype. The phyAB mutant showed impairment in starch accumulation while its biomass, chlorophyll fluorescence parameters, and leaf anatomy were unaffected, this deficiency being present over the whole vegetative growth period. Mutation of plastidial nucleoside diphosphate kinase-2 (NDPK2, acting downstream of phytochromes, also caused a deficit in starch accumulation. Besides, the glucose-1-phosphate adenylyltransferase small subunit (APS1 was down-regulated in phyAB. Those results suggest that PHYAB affect starch accumulation through NDPK2 and APS1. Then, we determined changes in starch and primary metabolites in single phyA, single phyB, double phyAB grown in light conditions differing in light intensity and/or light spectral content. PHYA is involved in starch accumulation in all the examined light conditions, whereas PHYB only exhibits a role under low light intensity (44 ± 1 μmol m-2 s-1 or low R:FR (11.8 ± 0.6. PCA analysis of the metabolic profiles in the mutants and wild type (WT suggested that PHYB acts as a major regulator of the leaf metabolic status in response to light intensity. Overall, we propose that PHYA and PHYB signaling play essential roles in the control of primary metabolism in Arabidopsis leaves in response to light.

  7. Mutant screen distinguishes between residues necessary for light-signal perception and signal transfer by phytochrome B.

    Directory of Open Access Journals (Sweden)

    Yoshito Oka

    2008-08-01

    Full Text Available The phytochromes (phyA to phyE are a major plant photoreceptor family that regulate a diversity of developmental processes in response to light. The N-terminal 651-amino acid domain of phyB (N651, which binds an open tetrapyrrole chromophore, acts to perceive and transduce regulatory light signals in the cell nucleus. The N651 domain comprises several subdomains: the N-terminal extension, the Per/Arnt/Sim (PAS-like subdomain (PLD, the cGMP phosphodiesterase/adenyl cyclase/FhlA (GAF subdomain, and the phytochrome (PHY subdomain. To define functional roles for these subdomains, we mutagenized an Arabidopsis thaliana line expressing N651 fused in tandem to green fluorescent protein, beta-glucuronidase, and a nuclear localization signal. A large-scale screen for long hypocotyl mutants identified 14 novel intragenic missense mutations in the N651 moiety. These new mutations, along with eight previously identified mutations, were distributed throughout N651, indicating that each subdomain has an important function. In vitro analysis of the spectral properties of these mutants enabled them to be classified into two principal classes: light-signal perception mutants (those with defective spectral activity, and signaling mutants (those normal in light perception but defective in intracellular signal transfer. Most spectral mutants were found in the GAF and PHY subdomains. On the other hand, the signaling mutants tend to be located in the N-terminal extension and PLD. These observations indicate that the N-terminal extension and PLD are mainly involved in signal transfer, but that the C-terminal GAF and PHY subdomains are responsible for light perception. Among the signaling mutants, R110Q, G111D, G112D, and R325K were particularly interesting. Alignment with the recently described three-dimensional structure of the PAS-GAF domain of a bacterial phytochrome suggests that these four mutations reside in the vicinity of the phytochrome light-sensing knot.

  8. A Temporarily Red Light-Insensitive Mutant of Tomato Lacks a Light-Stable, B-Like Phytochrome.

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    Van Tuinen, A.; Kerckhoffs, LHJ.; Nagatani, A.; Kendrick, R. E.; Koornneef, M.

    1995-07-01

    We have selected four recessive mutants in tomato (Lycopersicon esculentum Mill.) that, under continuous red light (R), have long hypocotyls and small cotyledons compared to wild type (WT), a phenotype typical of phytochrome B (phyB) mutants of other species. These mutants, which are allelic, are only insensitive to R during the first 2 days upon transition from darkness to R, and therefore we propose the gene symbol tri (temporarily red light insensitive). White light-grown mutant plants have a more elongated growth habit than that of the WT. An immunochemically and spectrophotometrically detectable phyB-like polypeptide detectable in the WT is absent or below detection limits in the tri1 mutant. In contrast to the absence of an elongation growth response to far-red light (FR) given at the end of the daily photoperiod (EODFR) in all phyB-deficient mutants so far characterized, the tri1 mutant responds to EODFR treatment. The tri1 mutant also shows a strong response to supplementary daytime far-red light. We propose that the phyB-like phytochrome deficient in the tri mutants plays a major role during de-etiolation and that other light-stable phytochromes can regulate the EODFR and shade-avoidance responses in tomato.

  9. Anatomia foliar de microtomateiros fitocromo-mutantes e ultra-estrutura de cloroplastos Leaf anatomy of micro-tomato phytochrome-mutants and chloroplast ultra-structure

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    Hyrandir Cabral de Melo

    2011-02-01

    Full Text Available Plantas fitocromo-mutantes têm sido utilizadas com o intuito de caracterizar isoladamente, dentre os demais fotorreceptores, a ação dos fitocromos sobre eventos ligados à fotomorfogênese. Raros são os estudos que relatam a ação dos fitocromos sobre aspectos estruturais, embora sejam fundamentais à compreensão do desenvolvimento das plantas. Neste trabalho, objetivou-se analisar características ultraestruturais de cloroplastos e aspectos anatômicos foliares dos microtomateiros (Solanum lycopersicum L. cv. Micro-Tom fitocromo-mutantes aurea (subexpressa fitocromos, hp1 e atroviolacea (ambos supra-responsivos a eventos mediados por fitocromo em plantas em estágio de floração. Observou-se que os fitocromos são responsáveis pela expressão de muitas características anatômicas da epiderme foliar, assim como do mesofilo e da ultraestrutura dos cloroplastos.Phytochrome-mutant plants have been used for phytochrome action characterization among all photoreceptors, in events of photomorphogenesis. Studies relating the phytochrome action on structural aspects, which are fundamental to the comprehension of plant development, are rare. The objective of this work was to analyze chloroplast ultra structure and leaf anatomical characteristics of micro-tomatos (Solanum lycopersicum L. cv. Micro-Tom phytochrome-mutants aurea (sub express phytochrome, hp1 and atroviolacea (both super express phytochrome events-mediated in plants in the flowering stage. The results show that phytochromes are responsible for the expression of many characteristics of leaf epidermis, mesophyll and chloroplast ultra-structure.

  10. Differential interactions of phytochrome A (Pr vs. Pfr) with monoclonal antibodies probed by a surface plasmon resonance technique.

    Science.gov (United States)

    Natori, Chihoko; Kim, Jeong-Il; Bhoo, Seong Hee; Han, Yun-Jeong; Hanzawa, Hiroko; Furuya, Masaki; Song, Pill-Soon

    2007-01-01

    Phytochromes are red- and far-red light-reversible photoreceptors for photomorphogenesis in plants. Phytochrome A is a dimeric chromopeptide that mediates very low fluence and high irradiance responses. To analyze the surface properties of phytochrome A (phyA), the epitopes of 21 anti-phyA monoclonal antibodies were determined by variously engineered recombinant phyA proteins and the dissociation constants of seven anti-phyA monoclonal antibodies with phyA were measured using a surface plasmon resonance (SPR)-based resonant mirror biosensor (IAsys). Purified oat phyA was immobilized on the sensor surface using a carboxymethyl dextran cuvette in advance, and the interactions of each chosen monoclonal antibody against phyA in either red light absorbing form (Pr) or far-red light absorbing form (Pfr) at different concentrations were monitored. The binding profiles were analyzed using the FAST Fit program of IAsys. The resultant values of dissociation constants clearly demonstrated the differential affinities between the phyA epitopes and the monoclonal antibodies dependent upon Pr vs. Pfr conformations. Monoclonal antibody mAP20 preferentially recognized the epitope at amino acids 653-731 in the Pr form, whereas mAA02, mAP21 and mAR07/mAR08 displayed preferential affinities for the Pfr's surfaces at epitopes 494-601 (the hinge region between the N- and C-terminal domains), 601-653 (hinge in PASI domain), and 772-1128 (C-terminal domain), respectively. The N-terminal extension (1-74) was not recognized by mAP09 and mAP15, suggesting that the N-terminal extreme is not exposed in the native conformation of phyA. On the other hand, the C-terminal domain becomes apparently exposed on Pr-to-Pfr phototransformation, suggesting an inter-domain cross-talk. The use of surface plasmon resonance spectroscopy offers a new approach to study the surface properties of phytochromes associated with the photoreversible structural changes, as well as for the study of protein

  11. Spectroscopic detection of a phytochrome-like photoreceptor in the myxomycete Physarum polycephalum and the kinetic mechanism for the photocontrol of sporulation by Pfr.

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    Lamparter, T; Marwan, W

    2001-06-01

    Sporulation of the true slime mold Physarum polycephalum (Myxomycetales) can be triggered by the far-red/red reversible Physarum phytochrome. Physarum plasmodia were analyzed with a purpose-built dual-wavelength photometer that is designed for phytochrome measurements. A photoreversible absorbance change at 670 nm was monitored after actinic red (R) and far-red (FR) irradiation of starved plasmodia, confirming the occurrence of a phytochrome-like photoreceptor in Physarum spectroscopically. These signals were not found in growing plasmodia, suggesting the Physarum phytochrome to be synthesized during starvation, which makes the cells competent for the photoinduction of sporulation. The photoconversion rates by R and FR light were similar in the phytochromes of Physarum and etiolated oat shoots. In dark-grown Physarum plasmodia that had not been preexposed to any light only R induced a detectable absorbance change while FR did not. This indicates that most (at least 90%) of the photoreversible pigment occurs in the red-absorbing form. Since the effectiveness of FR in triggering sporulation was enhanced by preirradiation with R, it is concluded that at least part of the Pr can be photoconverted to the active Pfr photoreceptor species. We propose a kinetic mechanism for the photocontrol of sporulation by photoconversion of Pfr, which may also hold for the high-irradiance response to FR in Arabidopsis and Cuscuta.

  12. Blue light is required for survival of the tomato phytochrome-deficient aurea mutant and the expression of four nuclear genes coding for plastidic proteins.

    Science.gov (United States)

    Oelmüller, R; Kendrick, R E

    1991-02-01

    When dark-grown aurea mutant tomato seedlings which lack more than 95% of the phytochrome present in isogenic wild-type seedlings are kept in white or blue light, four nuclear-encoded transcripts coding for plastidic proteins (the light-harvesting chlorophyll a/b-binding protein of photosystem I and II [cab-PSII], plastocyanin and subunit 2 of photosystem I) are present in comparable amounts. These transcript levels in red light are strongly reduced in aurea seedlings when compared with those of wild type. Thus, blue light is required for normal expression of these genes in the mutant, while red light alone is not sufficient. Red light-grown aurea seedlings are very sensitive to blue light, even 10 minutes of blue light every day suffices to cause a measurable increase in cab-PSII transcript level. The action of blue light on the expression of cab-PSII in the mutant is under phytochrome control. After 8 days of blue light, phytochrome is almost as effective in inducing cab-PSII mRNA as in the isogenic wild type, whereas after 8 days of red light, only a small phytochrome response was observed in the mutant. It is concluded that blue light sensitizes the mutant to the residual phytochrome which allows normal gene expression and survival of the mutant under daylight conditions.

  13. Light-activated phytochrome A and B interact with members of the SPA family to promote photomorphogenesis in Arabidopsis by reorganizing the COP1/SPA complex.

    Science.gov (United States)

    Sheerin, David J; Menon, Chiara; zur Oven-Krockhaus, Sven; Enderle, Beatrix; Zhu, Ling; Johnen, Philipp; Schleifenbaum, Frank; Stierhof, York-Dieter; Huq, Enamul; Hiltbrunner, Andreas

    2015-01-01

    Phytochromes function as red/far-red photoreceptors in plants and are essential for light-regulated growth and development. Photomorphogenesis, the developmental program in light, is the default program in seed plants. In dark-grown seedlings, photomorphogenic growth is suppressed by the action of the CONSTITUTIVELY PHOTOMORPHOGENIC1 (COP1)/SUPPRESSOR OF phyA-105 (SPA) complex, which targets positive regulators of photomorphogenic growth for degradation by the proteasome. Phytochromes inhibit the COP1/SPA complex, leading to the accumulation of transcription factors promoting photomorphogenesis; yet, the mechanism by which they inactivate COP1/SPA is still unknown. Here, we show that light-activated phytochrome A (phyA) and phytochrome B (phyB) interact with SPA1 and other SPA proteins. Fluorescence resonance energy transfer-fluorescence lifetime imaging microscopy analyses show that SPAs and phytochromes colocalize and interact in nuclear bodies. Furthermore, light-activated phyA and phyB disrupt the interaction between COP1 and SPAs, resulting in reorganization of the COP1/SPA complex in planta. The light-induced stabilization of HFR1, a photomorphogenic factor targeted for degradation by COP1/SPA, correlates temporally with the accumulation of phyA in the nucleus and localization of phyA to nuclear bodies. Overall, these data provide a molecular mechanism for the inactivation of the COP1/SPA complex by phyA- and phyB-mediated light perception. © 2015 American Society of Plant Biologists. All rights reserved.

  14. Abscisic Acid, High-Light, and Oxidative Stress Down-Regulate a Photosynthetic Gene via a Promoter Motif Not Involved in Phytochrome-Mediated Transcriptional Regulation

    Institute of Scientific and Technical Information of China (English)

    Roberto J. Staneloni; María José Rodriguez-Batiller; Jorge J. Casal

    2008-01-01

    In etiolated seedlings, light perceived by phytochrome promotes the expression of light-harvesting chlorophyll a/b protein of photosystem Ⅱ (Lhcb) genes. However, excess of photosynthetically active radiation can reduce Lhcb expression. Here, we investigate the convergence and divergence of phytochrome, high-light stress and abscisic acid (ABA)signaling, which could connect these processes. Etiolated Arabidopsis thaliana seedlings bearing an Lhcb promoter fused to a reporter were exposed to continuous far-red light to activate phytochrome and not photosynthesis, and treated with ABA. We identified a cis-acting region of the promoter required for down-regulation by ABA. This region contains a CCAC sequence recently found to be necessary for ABI4-binding to an Lhcb promoter. However, we did not find a G-box-binding core motif often associated with the ABI4-binding site in genes promoted by light and repressed by ABI4. Mutations involving this motif also impaired the responses to reduced water potential, the response to high photosynthetic light and the response to methyl viologen but not the response to low temperature or to Norflurazon. We propose a model based on current and previous findings, in which hydrogen peroxide produced in the chloroplasts under high light conditions interacts with the ABA signaling network to regulate Lhcb expression. Since the mutation that affects high-light and methyl viologen responses does not affect phytochrome-mediated responses, the regulation by retrograde and phytochrome signaling can finally be separated at the target promoter level.

  15. NMR chemical shift pattern changed by ammonium sulfate precipitation in cyanobacterial phytochrome Cph1

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    Chen eSong

    2015-07-01

    Full Text Available Phytochromes are dimeric biliprotein photoreceptors exhibiting characteristic red/far-red photocycles. Full-length cyanobacterial phytochrome Cph1 from Synechocystis 6803 is soluble initially but tends to aggregate in a concentration-dependent manner, hampering attempts to solve the structure using NMR and crystallization methods. Otherwise, the Cph1 sensory module (Cph1Δ2, photochemically indistinguishable from the native protein and used extensively in structural and other studies, can be purified to homogeneity in >10 mg amounts at mM concentrations quite easily. Bulk precipitation of full-length Cph1 by ammonium sulfate (AmS was expected to allow us to produce samples for solid-state magic-angle spinning (MAS NMR from dilute solutions before significant aggregation began. It was not clear, however, what effects the process of partial dehydration might have on the molecular structure. Here we test this by running solid-state MAS NMR experiments on AmS-precipitated Cph1Δ2 in its red-absorbing Pr state carrying uniformly 13C/15N-labeled phycocyanobilin (PCB chromophore. 2D 13C–13C correlation experiments allowed a complete assignment of 13C responses of the chromophore. Upon precipitation, 13C chemical shifts for most of PCB carbons move upfield, in which we found major changes for C4 and C6 atoms associated with the A-ring positioning. Further, the broad spectral lines seen in the AmS 13C spectrum reflect primarily the extensive homogeneous broadening presumably due to an increase in the distribution of conformational states in the protein, in which less free water is available to partake in the hydration shells. Our data suggest that dehydration indeed leads to motional and electronic structural changes of the bilin chromophore and its binding pocket and is not restricted to the protein surface. The extent of the changes induced differs from the freezing process of the solution samples routinely used in previous MAS NMR and

  16. NMR chemical shift pattern changed by ammonium sulfate precipitation in cyanobacterial phytochrome Cph1.

    Science.gov (United States)

    Song, Chen; Lang, Christina; Kopycki, Jakub; Hughes, Jon; Matysik, Jörg

    2015-01-01

    Phytochromes are dimeric biliprotein photoreceptors exhibiting characteristic red/far-red photocycles. Full-length cyanobacterial phytochrome Cph1 from Synechocystis 6803 is soluble initially but tends to aggregate in a concentration-dependent manner, hampering attempts to solve the structure using NMR and crystallization methods. Otherwise, the Cph1 sensory module (Cph1Δ2), photochemically indistinguishable from the native protein and used extensively in structural and other studies, can be purified to homogeneity in >10 mg amounts at mM concentrations quite easily. Bulk precipitation of full-length Cph1 by ammonium sulfate (AmS) was expected to allow us to produce samples for solid-state magic-angle spinning (MAS) NMR from dilute solutions before significant aggregation began. It was not clear, however, what effects the process of partial dehydration might have on the molecular structure. Here we test this by running solid-state MAS NMR experiments on AmS-precipitated Cph1Δ2 in its red-absorbing Pr state carrying uniformly (13)C/(15)N-labeled phycocyanobilin (PCB) chromophore. 2D (13)C-(13)C correlation experiments allowed a complete assignment of (13)C responses of the chromophore. Upon precipitation, (13)C chemical shifts for most of PCB carbons move upfield, in which we found major changes for C4 and C6 atoms associated with the A-ring positioning. Further, the broad spectral lines seen in the AmS (13)C spectrum reflect primarily the extensive inhomogeneous broadening presumably due to an increase in the distribution of conformational states in the protein, in which less free water is available to partake in the hydration shells. Our data suggest that the effect of dehydration process indeed leads to changes of electronic structure of the bilin chromophore and a decrease in its mobility within the binding pocket, but not restricted to the protein surface. The extent of the changes induced differs from the freezing process of the solution samples routinely

  17. The terminal phycobilisome emitter, LCM: A light-harvesting pigment with a phytochrome chromophore.

    Science.gov (United States)

    Tang, Kun; Ding, Wen-Long; Höppner, Astrid; Zhao, Cheng; Zhang, Lun; Hontani, Yusaku; Kennis, John T M; Gärtner, Wolfgang; Scheer, Hugo; Zhou, Ming; Zhao, Kai-Hong

    2015-12-29

    Photosynthesis relies on energy transfer from light-harvesting complexes to reaction centers. Phycobilisomes, the light-harvesting antennas in cyanobacteria and red algae, attach to the membrane via the multidomain core-membrane linker, L(CM). The chromophore domain of L(CM) forms a bottleneck for funneling the harvested energy either productively to reaction centers or, in case of light overload, to quenchers like orange carotenoid protein (OCP) that prevent photodamage. The crystal structure of the solubly modified chromophore domain from Nostoc sp. PCC7120 was resolved at 2.2 Å. Although its protein fold is similar to the protein folds of phycobiliproteins, the phycocyanobilin (PCB) chromophore adopts ZZZssa geometry, which is unknown among phycobiliproteins but characteristic for sensory photoreceptors (phytochromes and cyanobacteriochromes). However, chromophore photoisomerization is inhibited in L(CM) by tight packing. The ZZZssa geometry of the chromophore and π-π stacking with a neighboring Trp account for the functionally relevant extreme spectral red shift of L(CM). Exciton coupling is excluded by the large distance between two PCBs in a homodimer and by preservation of the spectral features in monomers. The structure also indicates a distinct flexibility that could be involved in quenching. The conclusions from the crystal structure are supported by femtosecond transient absorption spectra in solution.

  18. Phytochrome and temperature control of seed germination in Muntingia calabura L. (Elaeocarpaceae

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    Idalina T. de A. Leite

    2001-09-01

    Full Text Available The temperature range of germination of seeds of Muntingia calabura L. was 15-35° C and the optimum temperature at 35° C where more seeds germinated at short period. The fluence response curves demonstrated the involvement of phytochrome in the control of germination through the low fluence response. The effect of photoperiod showed that the species need long daily exposures to white light and that shade light inhibited completely seed germination, confirming as pioneer species that colonized only large gaps in the forest.As sementes de Muntingia calabura L. germinam nas temperaturas de 15 a 35C sendo a temperatura ótima de 35C onde maior número de sementes germinam em menor período. A curva de fluência-resposta demonstra que o fitocromo controla a germinação de sementes através da resposta de fluência baixa. A resposta da semente ao fotoperíodo e à completa inibição pela luz de sombreamento indicam que a espécies coloniza somente clareiras grandes de florestas, confirmando a espécie como pioneira.

  19. 14-3-3 Proteins Participate in Light Signaling through Association with PHYTOCHROME INTERACTING FACTORs

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    Eri Adams

    2014-12-01

    Full Text Available 14-3-3 proteins are regulatory proteins found in all eukaryotes and are known to selectively interact with phosphorylated proteins to regulate physiological processes. Through an affinity purification screening, many light-related proteins were recovered as 14-3-3 candidate binding partners. Yeast two-hybrid analysis revealed that the 14-3-3 kappa isoform (14-3-3κ could bind to PHYTOCHROME INTERACTING FACTOR3 (PIF3 and CONSTITUTIVE PHOTOMORPHOGENIC1 (COP1. Further analysis by in vitro pull-down assay confirmed the interaction between 14-3-3κ and PIF3. Interruption of putative phosphorylation sites on the 14-3-3 binding motifs of PIF3 was not sufficient to inhibit 14-3-3κ from binding or to disturb nuclear localization of PIF3. It was also indicated that 14-3-3κ could bind to other members of the PIF family, such as PIF1 and PIF6, but not to LONG HYPOCOTYL IN FAR-RED1 (HFR1. 14-3-3 mutants, as well as the PIF3 overexpressor, displayed longer hypocotyls, and a pif3 mutant displayed shorter hypocotyls than the wild-type in red light, suggesting that 14-3-3 proteins are positive regulators of photomorphogenesis and function antagonistically with PIF3. Consequently, our results indicate that 14-3-3 proteins bind to PIFs and initiate photomorphogenesis in response to a light signal.

  20. Phytochrome RNAi enhances major fibre quality and agronomic traits of the cotton Gossypium hirsutum L

    Science.gov (United States)

    Abdurakhmonov, Ibrokhim Y.; Buriev, Zabardast T.; Saha, Sukumar; Jenkins, Johnie N.; Abdukarimov, Abdusattor; Pepper, Alan E.

    2014-01-01

    Simultaneous improvement of fibre quality, early-flowering, early-maturity and productivity in Upland cotton (G. hirsutum) is a challenging task for conventional breeding. The influence of red/far-red light ratio on the fibre length prompted us to examine the phenotypic effects of RNA interference (RNAi) of the cotton PHYA1 gene. Here we show a suppression of up to ~70% for the PHYA1 transcript, and compensatory overexpression of up to ~20-fold in the remaining phytochromes in somatically regenerated PHYA1 RNAi cotton plants. Two independent transformants of three generations exhibited vigorous root and vegetative growth, early-flowering, significantly improved upper half mean fibre length and an improvement in other major fibre characteristics. Small decreases in lint traits were observed but seed cotton yield was increased an average 10-17% compared with controls. RNAi-associated phenotypes were heritable and transferable via sexual hybridization. These results should aid in the development of early-maturing and productive Upland cultivars with superior fibre quality.

  1. Genetic Dissection of Morphometric Traits Reveals That Phytochrome B Affects Nucleus Size and Heterochromatin Organization in Arabidopsis thaliana

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    Basten L. Snoek

    2017-08-01

    Full Text Available Microscopically visible chromatin is partitioned into two major components in Arabidopsis thaliana nuclei. On one hand, chromocenters are conspicuous foci of highly condensed “heterochromatic” domains that contain mostly repeated sequences. On the other hand, less condensed and gene-rich “euchromatin” emanates from these chromocenters. This differentiation, together with the dynamic nature of chromatin compaction in response to developmental and environmental stimuli, makes Arabidopsis a powerful system for studying chromatin organization and dynamics. Heterochromatin dynamics can be monitored by measuring the Heterochromatin Index, i.e., the proportion of nuclei displaying well-defined chromocenters, or the DNA fraction of chromocenters (relative heterochromatin fraction. Both measures are composite traits, thus their values represent the sum of effects of various underlying morphometric properties. We exploited genetic variation between natural occurring accessions to determine the genetic basis of individual nucleus and chromocenter morphometric parameters (area, perimeter, density, roundness, and heterogeneity that together determine chromatin compaction. Our novel reductionist genetic approach revealed quantitative trait loci (QTL for all measured traits. Genomic colocalization among QTL was limited, which suggests a complex genetic regulation of chromatin compaction. Yet genomic intervals of QTL for nucleus size (area and perimeter both overlap with a known QTL for heterochromatin compaction that is explained by natural polymorphism in the red/far-red light and temperature receptor Phytochrome B. Mutant analyses and genetic complementation assays show that Phytochrome B is a negative regulator of nucleus size, revealing that perception of climatic conditions by a Phytochrome-mediated hub is a major determinant for coordinating nucleus size and heterochromatin compaction.

  2. Sterically locked synthetic bilin derivatives and phytochrome Agp1 from Agrobacterium tumefaciens form photoinsensitive Pr- and Pfr-like adducts.

    Science.gov (United States)

    Inomata, Katsuhiko; Hammam, Mostafa A S; Kinoshita, Hideki; Murata, Yasue; Khawn, Htoi; Noack, Steffi; Michael, Norbert; Lamparter, Tilman

    2005-07-01

    Phytochrome photoreceptors undergo reversible photoconversion between the red-absorbing form, Pr, and the far-red-absorbing form, Pfr. The first step in the conversion from Pr to Pfr is a Z to E isomerization around the C15=C16 double bond of the bilin chromophore. We prepared four synthetic biliverdin (BV) derivatives in which rings C and D are sterically locked by cyclizing with an additional carbon chain. In these chromophores, which are termed 15Za, 15Zs, 15Ea, and 15Es, the C15=C16 double bond is in either the Z or E configuration and the C14-C15 single bond in either the syn or anti conformation. The chromophores were assembled with Agrobacterium phytochrome Agp1, which incorporates BV as natural chromophore. All locked BV derivatives bound covalently to the protein and formed adducts with characteristic spectral properties. The 15Za adduct was spectrally similar to the Pr form and the 15Ea adduct similar to the Pfr form of the BV adduct. Thus, the chromophore of Agp1 adopts a C15=C16 Z configuration and a C14-C15 anti conformation in the Pr form and a C15=C16 E configuration and a C14-C15 anti conformation in the Pfr form. Both the 15Zs and the 15Es adducts absorbed only in the blue region of the visible spectra. All chromophore adducts were analyzed by size exclusion chromatography and histidine kinase activity to probe for protein conformation. In either case, the 15Za adduct behaved like the Pr and the 15Ea adduct like the Pfr form of Agp1. Replacing the natural chromophore by a locked 15Ea derivative can thus bring phytochrome holoprotein in the Pfr form in darkness. In this way, physiological action of Pfr can be studied in vivo and separated from Pr/Pfr cycling and other light effects.

  3. A Rice Phytochrome A in Arabidopsis: The Role of the N-terminus under red and far-red light

    Institute of Scientific and Technical Information of China (English)

    Julia Kneissl; Tomoko Shinomura; Masaki Furuya; Cordelia Bolle

    2008-01-01

    The phytochrome (phy)A and phyB photoreceptors mediate three photobiological response modes in plants;whereas phyA can mediate the very-Iow-fluence response (VLFR), the high-irradiance response (HIR) and, to some extent, the low fluence response (LFR), phyB and other type Ⅱ phytochromes only mediate the LFR. To investigate to what level a rice phyA can complement for Arabidopsis phyA or phyB function and to evaluate the role of the serine residues in the first 20 amino acids of the N-terminus of phyA, we examined VLFRo LFR, and HIR responses in phyB and phyAphyB mutant plants transformed with rice PHYA cDNA or a mutant rice PHYA cDNA in which the first 10 serine residues were mutated to alanines (phyA SA). Utilizing mutants without endogenous phyB allowed the evaluation of red-light-derived responses sensed by the rice phyA. In summary, the WT rice phyA could complement VLFR and LFR responses such as inhibition of hypocotyl elongation under pulses of FR or continuous R light, induction of flowering and leaf expansion, whereas the phyA SA was more specific for HIR responses (e.g. inhibition of hypocotyl elongation and anthocyanin accumulation under continuous far-red light). As the N-terminal serines can no longer be phosphorylated in the phyA SA mutant, this suggests a role for phosphorylation discriminating between the different phyA-dependent responses. The efficacy of the rice phyA expressed in Arabidopsis was dependent upon the developmental age of the plants analyzed and on the physiological response, suggesting a stage-dependent downstream modulation of phytochrome signaling.

  4. Mechanism of Cph1 phytochrome assembly from stopped-flow kinetics and circular dichroism.

    Science.gov (United States)

    Borucki, Berthold; Otto, Harald; Rottwinkel, Gregor; Hughes, Jonathan; Heyn, Maarten P; Lamparter, Tilman

    2003-11-25

    The kinetics and mechanism of the autocatalytic assembly of holo-Cph1 phytochrome (from Synechocystis) from the apoprotein and the bilin chromophores phycocyanobilin (PCB) and phycoerythrobilin (PEB) were investigated by stopped flow and circular dichroism. At 1:1 stoichiometry, pH 7.9, and 10 degrees C, SVD analysis of the kinetic data for PCB revealed three spectral components involving three transitions with time constants tau(1) approximately 150 ms, tau(2) approximately 2.5 s, and tau(3) approximately 50 s. Tau(1) was associated with a major red shift and transfer of oscillator strength from the Soret region to the 680 nm region. When the sulfhydryl group of cysteine 259 was blocked with iodoacetamide, preventing the formation of a covalent adduct, a noncovalent red-shifted complex (680 nm) was formed with a time constant of 200 ms. Tau(1) could thus be assigned to the formation of a noncovalent complex. The absorption changes during tau(1) are due to the formation of the extended conformation of the linear tetrapyrrole and to its protonation in the binding pocket. From the concentration and pH dependence of the kinetics we obtained a value of 1.5 microM for the K(D) of this noncovalent complex and a value of 8.4 for the pK(a) of the proton donor. The tau(2) component was associated with a blue shift of about 25 nm and was attributed to the formation of the covalent bond (P(r)), accompanied with the loss of the 3-3' double bond to ring A. Tau(3) was due to photoconversion to P(fr). For PEB, which is not photochromic, the formation of the noncovalent complex is faster (tau(1) = 70 ms), but the covalent bond formation is about 80 times slower (tau(2) = 200 s) than with the natural chromophore PCB. The CD spectra of the PCB adduct in the 250-800 nm range show that the chromophore geometries in P(r) and P(fr) are similar to those in plant phytochrome. The opposite rotational strengths of P(r) and P(fr) in the longest wavelength band suggest that the

  5. Phytochrome controls achene germination in Bidens pilosa L. (Asteraceae by very low fluence response

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    Adriana Amaral-Baroli

    2001-06-01

    Full Text Available Achene without ornament of the tegument were light insensitive with germination under all tested light conditions. Achene with verrucose ornament of the tegument presented low germination under darkness and high germination under light conditions. By pre-incubation at 36° C for remotion of pre-existing Pfr and by comparison of results of counting of dark germinating achenes at the end of experiment and daily under dim green safe light (0.001mumol m-2 s-1 nm-1 we concluded that germination was controlled by phytochrome through very low fluence response.Aquênios sem ornamento do tegumento são insensíveis à luz com ocorrência de germinação sob todas as condições de luz testadas. Aquênios com ornamento verrucoso do tegumento apresentou baixa germinação sob escuro e alta germinação sob luz. A pré-incubação a 36° C para a remoção de Fve pré-existente e pela comparação dos resultados de contagem no final do experimento de aquênios que germinam no escuro e diárias sob luz verde de segurança (0.001mimol m-2s-1nm-1 concluimos que a germinação de Bidens pilosa é controlada pelo fitocromo através da resposta de fluência baixa.

  6. Heterotrimeric G-protein is involved in phytochrome A-mediated cell death of Arabidopsis hypocotyls

    Institute of Scientific and Technical Information of China (English)

    Qing Wei; Wenbin Zhou; Guangzhen Hu; Jiamian Wei; Hongquan Yang; Jirong Huang

    2008-01-01

    The heterotrimeric guanine nucleotide-binding protein (G-protein) has been demonstrated to mediate various signaling pathways in plants. However,its role in phytochrome A (phyA) signaling remains elusive. In this study,we discover a new phyA-mediated phenotype designated far-red irradiation (FR) preconditioned cell death,which occurs only in the hypocotyls of FR-grown seedlings following exposure to white light (WL). The cell death is mitigated in the Ga mutant gpal but aggravated in the Gβ mutant agbl in comparison with the wild type (WT),indicative of antagonistic roles of GPAI and AGB1 in the phyA-mediated cell-death pathway. Further investigation indicates that FR-induced accumulation of nonphotoconvertible protochlorophyllide (Pchlide633),which generates reactive oxygen species (ROS)on exposure to WL,is required for FR-preconditioned cell death. Moreover,ROS is mainly detected in chloroplasts using the fluorescent probe. Interestingly,the application of H2O2 to dark-grown seedlings results in a phenotype similar to FR-preconditioned cell death. This reveals that ROS is a critical mediator for the cell death. In addition,we observe that agbl is more sensitive to H2O2 than WT seedlings,indicating that the G-protein may also modify the sensitivity of the seedlings to ROS stress. Taking these results together,we infer that the G-protein may be involved in the phyA signaling pathway to regulate FR-preconditioned cell death of Arabidopsis hypocotyls.Apossible mechanism underlying the involvement of the G-protein in phyA signaling is discussed in this study.

  7. A Short Amino-Terminal Part of Arabidopsis Phytochrome A Induces Constitutive Photomorphogenic Response

    Institute of Scientific and Technical Information of China (English)

    András Viczián; (E)va (A)dám; Iris Wolf; János Bindics; Stefan Kircher; Marc Heijde; Roman UIm; Eberhard Sch(a)fer; Ferenc Nagy

    2012-01-01

    Phytochrome A (phyA) is the dominant photoreceptor of far-red light sensing in Arabidopsis thaliana.phyA accumulates at high levels in the cytoplasm of etiolated seedlings,and light-induced phyA signaling is mediated by a complex regulatory network.This includes light- and FHY1/FHL protein-dependent translocation of native phyA into the nucleus in vivo.It has also been shown that a short N-terminal fragment of phyA (PHYA406) is sufficient to phenocopy this highly regulated cellular process in vitro.To test the biological activity of this N-terminal fragment of phyA in planta,we produced transgenic phyA-201 plants expressing the PHYA406-YFP (YELLOW FLUORESCENT PROTEIN)-DD,PHYA406-YFP-DD-NLS (nuclear localization signal),and PHYA406-YFP-DD-NES (nuclear export signal) fusion proteins.Here,we report that PHYA406-YFP-DD is imported into the nucleus and this process is partially light-dependent whereas PHYA406-YFP-DD-NLS and PHYA406-YFP-DD-NES display the expected constitutive localization patterns.Our results show that these truncated phyA proteins are light-stable,they trigger a constitutive photomorphogenic-like response when localized in the nuclei,and neither of them induces proper phyA signaling.We demonstrate that in vitro and in vivo PHYA406 Pfr and Pr bind COP1,a general repressor of photomorphogenesis,and co-localize with it in nuclear bodies.Thus,we conclude that,in planta,the truncated PHYA406 proteins inactivate COP1 in the nuclei in a light-independent fashion.

  8. Recombinant phytochrome of the moss Ceratodon purpureus (CP2): fluorescence spectroscopy and photochemistry.

    Science.gov (United States)

    Sineshchekov, V; Koppel, L; Hughes, J; Lamparter, T; Zeidler, M

    2000-07-01

    The recombinant phytochrome of the moss Ceratodon purpureus (CP2) expressed in Saccharomyces cerevisiae and reconstituted with phycocyanobilin (PCB) was investigated using fluorescence spectroscopy. The pigment had an emission maximum at 670 nm at low temperature (85 K) and at 667 nm at room temperature (RT) and an excitation maximum at 650-652 nm at 85 K (excitation spectra could not be measured at RT). Both spectra had a half-band width of approx. 30-35 nm at 85 K. The fluorescence intensity revealed a steep temperature dependence with an activation energy of fluorescence decay (Ea) of 5.9-6.4 and 12.6-14.7 kJ mol(-1) in the interval from 85 to 210 K and from 210 to 275 K, respectively. The photochemical properties of CP2/PCB were characterised by the extent of the red-induced (lambda(a) = 639 nm) Pr conversion into the first photoproduct lumi-R at 85 K (gamma1) of approximately 0.07 and into Pfr at RT (gamma2) of approximately 0.7. From these characteristics, CP2/PCB can be attributed to the Pr" photochemical type with gamma1 < or = 0.05, which comprises the minor phyA fraction (phyA"), phyB, Adiantum phy1 and Synechocystis Cph1 in contrast to the major phyA' fraction (Pr' type with gamma1 = 0.5). Within the Pr" type, it is closer to phyA" than to phyB and Cph1.

  9. Resonance Raman analysis of the Pr and Pfr forms of phytochrome.

    Science.gov (United States)

    Fodor, S P; Lagarias, J C; Mathies, R A

    1990-12-18

    Resonance Raman vibrational spectra of the Pr and Pfr forms of oat phytochrome have been obtained at room temperature. When Pr is converted to Pfr, new bands appear in the C = C and C = N stretching region at 1622, 1599, and 1552 cm-1, indicating that a major structural change of the chromophore has occurred. The Pr to Pfr conversion results in an 11 cm-1 lowering of the N-H rocking band from 1323 to 1312 cm-1. Normal mode calculations correlate this frequency drop with a Z----E isomerization about the C15 = C16 bond. A line at 803 cm-1 in Pr is replaced by an unusually intense mode at 814 cm-1 in Pfr. Calculations on model tetrapyrrole chromophores suggest that these low-wavenumber modes are hydrogen out-of-plane (HOOP) wagging vibrations of the bridging C15 methine hydrogen and that both the intensity and frequency of the C15 HOOP mode are sensitive to the geometry around the C14-C15 and C15 = C16 bonds. The large intensity of the 814-cm-1 mode in Pfr indicates that the chromophore is highly distorted from planarity around the C15 methine bridge. If the Pr----Pfr conversion does involve a C15 = C16 Z----E isomerization, then the intensity of the C15 HOOP mode in Pfr argues that the chromophore has an E,anti conformation. On the basis of a comparison with the vibrational calculations, the low frequency (803 cm-1) and the reduced intensity of the C15 HOOP mode in Pr suggest that the chromophore in Pr adopts the C15-Z,syn conformation.

  10. Probing the photoreaction mechanism of phytochrome through analysis of resonance Raman vibrational spectra of recombinant analogues.

    Science.gov (United States)

    Andel, F; Murphy, J T; Haas, J A; McDowell, M T; van der Hoef, I; Lugtenburg, J; Lagarias, J C; Mathies, R A

    2000-03-14

    Resonance Raman spectra of native and recombinant analogues of oat phytochrome have been obtained and analyzed in conjunction with normal mode calculations. On the basis of frequency shifts observed upon methine bridge deuteration and vinyl and C(15)-methine bridge saturation of the chromophore, intense Raman lines at 805 and 814 cm(-)(1) in P(r) and P(fr), respectively, are assigned as C(15)-hydrogen out-of-plane (HOOP) wags, lines at 665 cm(-)(1) in P(r) and at 672 and 654 cm(-)(1) in P(fr) are assigned as coupled C=C and C-C torsions and in-plane ring twisting modes, and modes at approximately 1300 cm(-)(1) in P(r) are coupled N-H and C-H rocking modes. The empirical assignments and normal mode calculations support proposals that the chromophore structures in P(r) and P(fr) are C(15)-Z,syn and C(15)-E,anti, respectively. The intensities of the C(15)-hydrogen out-of-plane, C=C and C-C torsional, and in-plane ring modes in both P(r) and P(fr) suggest that the initial photochemistry involves simultaneous bond rotations at the C(15)-methine bridge coupled to C(15)-H wagging and D-ring rotation. The strong nonbonded interactions of the C- and D-ring methyl groups in the C(15)-E,anti P(fr) chromophore structure indicated by the intense 814 cm(-1) C(15) HOOP mode suggest that the excited state of P(fr) and its photoproduct states are strongly coupled.

  11. A Light-Independent Allele of Phytochrome B Faithfully Recapitulates Photomorphogenic Transcriptional Networks

    Institute of Scientific and Technical Information of China (English)

    Wei Hu; Yi-Shin Su; J. Clark Lagarias

    2009-01-01

    Dominant gain-of-function alleles of Arabidopsis phytochrome B were recently shown to confer lightindependent, constitutive photomorphogenic (cop) phenotypes to transgenic plants (Su and Lagarias, 2007). In the present study, comparative transcription profiling experiments were performed to assess whether the pattern of gene expression regulated by these alleles accurately reflects the process of photomorphogenesis in wild-type Arabidopsis. Wholegenome transcription profiles of dark-grown phyAphyB seedlings expressing the Y276H mutant of phyB (YHB) revealed that YHB reprograms about 13% of the Arabidopsis transcriptome in a light-independent manner. The YHB-regulated transcriptome proved qualitatively similar to but quantitatively greater than those of wild-type seedlings grown under 15 or 50 μmol m-2 m-1 continuous red light (Rc). Among the 2977 genes statistically significant two-fold (SSTF) regulated by YHB in the absence of light include those encoding components of the photosynthetic apparatus, tetrapyrrole/pigment biosynthetic pathways, and early light-responsive signaling factors. Approximately 80% of genes SSTF regulated by Rc were also YHB-regulated. Expression of a notable subset of 346 YHB-regulated genes proved to be strongly attenuated by Rc, indicating compensating regulation by phyC-E and/or other Rc-dependent processes. Since the majority of these 346 genes are regulated by the circadian clock, these results suggest that phyA- and phyB-independent light signaling pathway(s) strongly influence clock output. Together with the unique plastid morphology of dark-grown YHB seedlings, these analyses indicate that the YHB mutant induces constitutive photomorphogenesis via faithful reconstruction of phyB signaling pathways in a light-independent fashion.

  12. The phytochrome-interacting vascular plant one-zinc finger1 and VOZ2 redundantly regulate flowering in Arabidopsis.

    Science.gov (United States)

    Yasui, Yukiko; Mukougawa, Keiko; Uemoto, Mitsuhiro; Yokofuji, Akira; Suzuri, Ryota; Nishitani, Aiko; Kohchi, Takayuki

    2012-08-01

    The timing of the transition to flowering in plants is regulated by various environmental factors, including daylength and light quality. Although the red/far-red photoreceptor phytochrome B (phyB) represses flowering by indirectly regulating the expression of a key flowering regulator, FLOWERING LOCUS T (FT), the mechanism of phyB signaling for flowering is largely unknown. Here, we identified two Arabidopsis thaliana genes, VASCULAR PLANT ONE-ZINC FINGER1 (VOZ1) and VOZ2, which are highly conserved throughout land plant evolution, as phyB-interacting factors. voz1 voz2 double mutants, but neither single mutant, showed a late-flowering phenotype under long-day conditions, which indicated that VOZ1 and VOZ2 redundantly promote flowering. voz1 voz2 mutations suppressed the early-flowering phenotype of the phyB mutant, and FT expression was repressed in the voz1 voz2 mutant. Green fluorescent protein-VOZ2 signal was observed in the cytoplasm, and interaction of VOZ proteins with phyB was indicated to occur in the cytoplasm under far-red light. However, VOZ2 protein modified to localize constitutively in the nucleus promoted flowering. In addition, the stability of VOZ2 proteins in the nucleus was modulated by light quality in a phytochrome-dependent manner. We propose that partial translocation of VOZ proteins from the cytoplasm to the nucleus mediates the initial step of the phyB signal transduction pathway that regulates flowering.

  13. Trading direct for indirect defense? Phytochrome B inactivation in tomato attenuates direct anti-herbivore defenses whilst enhancing volatile-mediated attraction of predators

    NARCIS (Netherlands)

    Cortés, Leandro E.; Weldegergis, Berhane T.; Boccalandro, Hernán E.; Dicke, Marcel; Ballaré, Carlos L.

    2016-01-01

    Under conditions of competition for light, which lead to the inactivation of the photoreceptor phytochrome B (phyB), the growth of shade-intolerant plants is promoted and the accumulation of direct anti-herbivore defenses is down-regulated. Little is known about the effects of phyB on emissions o

  14. Trading direct for indirect defense? Phytochrome B inactivation in tomato attenuates direct anti-herbivore defenses whilst enhancing volatile-mediated attraction of predators

    NARCIS (Netherlands)

    Cortés, Leandro E.; Weldegergis, Berhane T.; Boccalandro, Hernán E.; Dicke, Marcel; Ballaré, Carlos L.

    2016-01-01

    Under conditions of competition for light, which lead to the inactivation of the photoreceptor phytochrome B (phyB), the growth of shade-intolerant plants is promoted and the accumulation of direct anti-herbivore defenses is down-regulated. Little is known about the effects of phyB on emissions o

  15. Choice of tracks, microtubules and/or actin filaments for chloroplast photo-movement is differentially controlled by phytochrome and a blue light receptor.

    Science.gov (United States)

    Sato, Y; Wada, M; Kadota, A

    2001-01-01

    Light induced chloroplast movement has been studied as a model system for photoreception and actin microfilament (MF)-based intracellular motilities in plants. Chloroplast photo-accumulation and -avoidance movement is mediated by phytochrome as well as blue light (BL) receptor in the moss Physcomitrella patens. Here we report the discovery of an involvement of a microtubule (MT)-based system in addition to an MF-based system in photorelocation of chloroplasts in this moss. In the dark, MTs provided tracks for rapid movement of chloroplasts in a longitudinal direction and MFs contributed the tracks for slow movement in any direction. We found that phytochrome responses utilized only the MT-based system, while BL responses had an alternative way of moving, either along MTs or MFs. MT-based systems were mediated by both photoreceptors, but chloroplasts showed movements with different velocity and pattern between them. No apparent difference in the behavior of chloroplast movement between the accumulation and avoidance movement was detected in phytochrome responses or BL responses, except for the direction of the movement. The results presented here demonstrate that chloroplasts use both MTs and MFs for motility and that phytochrome and a BL receptor control directional photo-movement of chloroplasts through the differential regulation of these motile systems.

  16. Physiological functions of phytochromes in tomato : a study using photomorphogenic mutants = [Fysiologische functies van fytochromen in tomaat : een studie gebruikmakend van fotomorfogenetische mutanten

    NARCIS (Netherlands)

    Kerckhoffs, L.H.J.

    1996-01-01


    Plant morphogenesis is influenced greatly by the irradiance, quality, direction and periodicity of the ambient light. At least three different photomorphogenic photoreceptors have been distinguished: (i) the red light (R)- and far-red light (FR)- absorbing phytochromes; (ii) the UV-A and

  17. Active and silent chromophore isoforms for phytochrome Pr photoisomerization: An alternative evolutionary strategy to optimize photoreaction quantum yields

    Directory of Open Access Journals (Sweden)

    Yang Yang

    2014-01-01

    Full Text Available Photoisomerization of a protein bound chromophore is the basis of light sensing of many photoreceptors. We tracked Z-to-E photoisomerization of Cph1 phytochrome chromophore PCB in the Pr form in real-time. Two different phycocyanobilin (PCB ground state geometries with different ring D orientations have been identified. The pre-twisted and hydrogen bonded PCBa geometry exhibits a time constant of 30 ps and a quantum yield of photoproduct formation of 29%, about six times slower and ten times higher than that for the non-hydrogen bonded PCBb geometry. This new mechanism of pre-twisting the chromophore by protein-cofactor interaction optimizes yields of slow photoreactions and provides a scaffold for photoreceptor engineering.

  18. Chromophore incorporation, Pr to Pfr kinetics, and Pfr thermal reversion of recombinant N-terminal fragments of phytochrome A and B chromoproteins.

    Science.gov (United States)

    Remberg, A; Ruddat, A; Braslavsky, S E; Gärtner, W; Schaffner, K

    1998-07-14

    N-Terminal apoprotein fragments of oat phytochrome A (phyA) of 65 kDa (amino acids 1-595) and potato phyB of 66 kDa (1-596) were heterologously expressed in Escherichia coli and in the yeasts Saccharomyces cerevisiae and Pichia pastoris, and assembled with phytochromobilin (PthetaB; native chromophore) and phycocyanobilin (PCB). The phyA65 apoprotein from yeast showed a monoexponential assembly kinetics after an initial steep rise, whereas the corresponding apoprotein from E. coli showed only a slow monoexponential assembly. The phyB66 apoprotein incorporated either chromophore more slowly than the phyA65s, with biexponential kinetics. With all apoproteins, PthetaB was incorporated faster than PCB. The thermal stabilities of the Pfr forms of the N-terminal halves are similar to those known for the full-length recombinant phytochromes: oat phyA65 Pfr is highly stable, whereas potato phyB66 Pfr is rapidly converted into Pr. Thus, neither the C-terminal domain nor homodimer formation regulates this property. Rather, it is a characteristic of the phytochrome indicating its origin from mono- or dicots. The Pr to Pfr kinetics of the N-terminal phyA65 and phyB66 are different. The primary photoproduct I700 of phyA65-PCB decayed monoexponentially and the PthetaB analogue biexponentially, whereas the phyB66 I700 decayed monoexponentially irrespective of the chromophore incorporated. The formation of Pfr from Pr is faster with the N-terminal halves than with the full-length phytochromes, indicating an involvement of the C-terminal domain in the relatively slow protein conformational changes.

  19. Stress responsive gene CIPK14 is involved in phytochrome A-mediated far-red light inhibition of greening in Arabidopsis

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    In this study, we show that CIPK14,a stress responsive CBL-interacting protein kinase gene,is involved in phytochrome A-mediated far-red light inhibition of greening in Arabidopsis seedlings. The CIPK14-impairment mutant cipk14 grown in continuous far-red (FR) light did not show greening when exposed to white light illumination for 15 h. By contrast, the FR-grown phytochrome A null mutant phyA greened within 0.5 h of exposure to white light. Although greening of Col-4 (wild-type) was not completely abolished by FR, it exhibited a significantly decreased greening capacity compared with that of phyA. Further analyses demonstrated that the expression of protochlorophyllide reductase (POR) genes was correlated with the greening ability of the genotypes. In addition, CIPK14 appeared to be regulated by both the circadian clock and PhyA. Taken together, these results suggest that CIPK14 plays a role in PhyA-mediated FR inhibition of seedling greening, and that a Ca-related kinase may be involved in a previously undefined branch point in the phytochrome A signaling pathway.

  20. Blue-light mediated accumulation of nuclear-encoded transcripts coding for proteins of the thylakoid membrane is absent in the phytochrome-deficient aurea mutant of tomato.

    Science.gov (United States)

    Oelmüller, R; Kendrick, R E; Briggs, W R

    1989-08-01

    Polyclonal antibodies against pea phytochrome detect 2 protein bands (about 116 and 120 kDa) on blots of crude protein extracts and protein of microsomal preparations of dark-grown tomato seedlings. Both protein bands are undetectable in Western blots of the aurea mutant extracts. Neither protein band is detectable after isogenic wild-type seedlings are illuminated with 3 h of red light, either in the crude extract or in the membrane fraction of the irradiated seedlings; this result is consistent with the hypothesis that both bands are phytochrome. When dark-grown wild-type seedlings are illuminated with 3 h of red light or blue light against a red light background, the transcript levels for chlorophyll a/b-binding proteins of photosystem I and II, plastocyanin, and the subunit II of photosystem I increase. In all cases, the same fluence rate of blue light is much more effective than red light alone, a result that indicates the involvement of a blue/UV-A light photoreceptor in addition to the involvement of the far-red-absorbing form of phytochrome, Pfr. The aurea mutant responds neither to red light nor to blue light. Thus, no Pfr-independent induction of the four transcripts by a blue/UV-A light photoreceptor can be measured in the aurea mutant.

  1. Jasmonic acid enhancement of anthocyanin accumulation is dependent on phytochrome A signaling pathway under far-red light in Arabidopsis.

    Science.gov (United States)

    Li, Ting; Jia, Kun-Peng; Lian, Hong-Li; Yang, Xu; Li, Ling; Yang, Hong-Quan

    2014-11-07

    Anthocyanins are critical for plants. It is shown that the expression of genes encoding the key enzymes such as dihydroflavonol 4-reductase (DFR), UDP-Glc: flavonoid 3-O-glucosyltransferase (UF3GT), and leucoanthocyanidin dioxygenase (LDOX) in anthocyanin biosynthesis pathway is regulated by MYB75, a R2R3 MYB transcription factor. The production of anthocyanin is known to be promoted by jasmonic acid (JA) in light but not in darkness. The photoreceptors cryptochrome 1 (CRY1), phytochrome B (phyB), and phytochrome A (phyA) are also shown to mediate light promotion of anthocyanin accumulation, respectively, whereas their downstream factor COP1, a master negative regulator of photomorphogensis, represses anthocyanin accumulation. However, whether JA coordinates with photoreceptors in the regulation of anthocyanin accumulation is unknown. Here, we show that under far-red light, JA promotes anthocyanin accumulation in a phyA signaling pathway-dependent manner. The phyA mutant is hyposensitive to jasmonic acid analog methyl jasmonic acid (MeJA) under far-red light. The dominant mutant of MYB75, pap1-D, accumulates significantly higher levels of anthocyanin than wild type under far-red light, whereas knockdown of MYBs (MYB75, MYB90, MYB113, and MYB114) through RNAi significantly reduces MeJA promotion of anthocyanin accumulation. The phyA pap1-D double mutant shows reduced responsiveness to MeJA, similar to phyA mutant under far-red light. In darkness, a mutant allele of cop1, cop1-4, shows enhanced responsiveness to MeJA, but pap1-D mutant is barely responsive to MeJA. Upon MeJA application, the cop1-4 pap1-D double mutant accumulates considerably higher levels of anthocyanin than cop1-4 in darkness. Protein studies indicate that MYB75 protein is stabilized by white light and far-red light. Further gene expression studies suggest that MeJA promotes the expression of DFR, UF3GT, and LDOX genes in a phyA- and MYB75-dependent manner under far-red light. Our findings suggest

  2. A Modified Reverse One-Hybrid Screen Identifies Transcriptional Activation Domains in PHYTOCHROME-INTERACTING FACTOR 3.

    Science.gov (United States)

    Dalton, Jutta C; Bätz, Ulrike; Liu, Jason; Curie, Gemma L; Quail, Peter H

    2016-01-01

    Transcriptional activation domains (TADs) are difficult to predict and identify, since they are not conserved and have little consensus. Here, we describe a yeast-based screening method that is able to identify individual amino acid residues involved in transcriptional activation in a high throughput manner. A plant transcriptional activator, PIF3 (phytochrome interacting factor 3), was fused to the yeast GAL4-DNA-binding Domain (BD), driving expression of the URA3 (Orotidine 5'-phosphate decarboxylase) reporter, and used for negative selection on 5-fluroorotic acid (5FOA). Randomly mutagenized variants of PIF3 were then selected for a loss or reduction in transcriptional activation activity by survival on FOA. In the process, we developed a strategy to eliminate false positives from negative selection that can be used for both reverse-1- and 2-hybrid screens. With this method we were able to identify two distinct regions in PIF3 with transcriptional activation activity, both of which are functionally conserved in PIF1, PIF4, and PIF5. Both are collectively necessary for full PIF3 transcriptional activity, but neither is sufficient to induce transcription autonomously. We also found that the TAD appear to overlap physically with other PIF3 functions, such as phyB binding activity and consequent phosphorylation. Our protocol should provide a valuable tool for identifying, analyzing and characterizing novel TADs in eukaryotic transcription factors, and thus potentially contribute to the unraveling of the mechanism underlying transcriptional activation.

  3. A Modified Reverse One-Hybrid Screen Identifies Transcriptional Activation Domains in PHYTOCHROME-INTERACTING FACTOR 3

    Science.gov (United States)

    Dalton, Jutta C.; Bätz, Ulrike; Liu, Jason; Curie, Gemma L.; Quail, Peter H.

    2016-01-01

    Transcriptional activation domains (TADs) are difficult to predict and identify, since they are not conserved and have little consensus. Here, we describe a yeast-based screening method that is able to identify individual amino acid residues involved in transcriptional activation in a high throughput manner. A plant transcriptional activator, PIF3 (phytochrome interacting factor 3), was fused to the yeast GAL4-DNA-binding Domain (BD), driving expression of the URA3 (Orotidine 5′-phosphate decarboxylase) reporter, and used for negative selection on 5-fluroorotic acid (5FOA). Randomly mutagenized variants of PIF3 were then selected for a loss or reduction in transcriptional activation activity by survival on FOA. In the process, we developed a strategy to eliminate false positives from negative selection that can be used for both reverse-1- and 2-hybrid screens. With this method we were able to identify two distinct regions in PIF3 with transcriptional activation activity, both of which are functionally conserved in PIF1, PIF4, and PIF5. Both are collectively necessary for full PIF3 transcriptional activity, but neither is sufficient to induce transcription autonomously. We also found that the TAD appear to overlap physically with other PIF3 functions, such as phyB binding activity and consequent phosphorylation. Our protocol should provide a valuable tool for identifying, analyzing and characterizing novel TADs in eukaryotic transcription factors, and thus potentially contribute to the unraveling of the mechanism underlying transcriptional activation. PMID:27379152

  4. Phytochrome as molecular machine: revealing chromophore action during the Pfr --> Pr photoconversion by magic-angle spinning NMR spectroscopy.

    Science.gov (United States)

    Rohmer, Thierry; Lang, Christina; Bongards, Christian; Gupta, Karthick Babu Sai Sankar; Neugebauer, Johannes; Hughes, Jon; Gärtner, Wolfgang; Matysik, Jörg

    2010-03-31

    The cyanobacterial phytochrome Cph1 can be photoconverted between two thermally stable states, Pr and Pfr. The photochemically induced Pfr --> Pr back-reaction has been followed at low temperature by magic-angle spinning (MAS) NMR spectroscopy, allowing two intermediates, Lumi-F and Meta-F, to be trapped. Employing uniformly (13)C- and (15)N-labeled open-chain tetrapyrrole chromophores, all four states-Pfr, Lumi-F, Meta-F, and Pr-have been structurally characterized. In the first step, the double bond photoisomerization forming Lumi-F occurs. The second step, the transformation to Meta-F, is driven by the release of the mechanical tension. This process leads to the break of the hydrogen bond of the ring D nitrogen to Asp-207 and triggers signaling. The third step is protonically driven allowing the hydrogen-bonding interaction of the ring D nitrogen to be restored. Compared to the forward reaction, the order of events is changed, probably caused by the different properties of the hydrogen bonding partners of N24, leading to the directionality of the photocycle.

  5. Resistance of Arabidopsis thaliana L. photosynthetic apparatus to UV-B is reduced by deficit of phytochromes B and A.

    Science.gov (United States)

    Khudyakova, Aleksandra Yu; Kreslavski, Vladimir D; Shirshikova, Galina N; Zharmukhamedov, Sergey K; Kosobryukhov, Anatoly A; Allakhverdiev, Suleyman I

    2017-03-01

    The photosynthetic responses of 25-day-old Arabidopsis phyA phyB double mutant (DM) compared with the wild type (WT) to UV-B radiation (1Wm(-2), 30min) were investigated. UV-B irradiation led to reduction of photosystem 2 (PS-2) activity and the photosynthetic rate. In plants grown under both white and red light (λm - 660nm) the reduction was greater in DM plants compared to the WT. Without UV-B irradiation a decrease in PS-2 activity was observed in DM grown under RL only. It is assumed that the lower content of UV-absorbing pigments and carotenoids observed in DM may be one of the reasons of reduced PS-2 resistance to UV-B. Higher decrease in activities under UV in DM plants grown under RL compared to DM plants grown under white light is likely due to the lack of activity of cryptochromes in plants grown under red light. Rates of post-stress recovery of photosynthetic activity of DM compared with WT plants under white and red light of low intensity were studied. Almost complete recovery of the activity was found which was not observed under dark conditions and in the presence of a protein synthesis inhibitor, chloramphenicol. It is assumed that phytochrome system participates in stress-protective mechanisms of the photosynthetic apparatus to UV-radiation.

  6. Synergistic and Antagonistic Action of Phytochrome (Phy A and PhyB during Seedling De-Etiolation in Arabidopsis thaliana

    Directory of Open Access Journals (Sweden)

    Liang Su

    2015-05-01

    Full Text Available It has been reported that Arabidopsis phytochrome (phy A and phyB are crucial photoreceptors that display synergistic and antagonistic action during seedling de-etiolation in multiple light signaling pathways. However, the functional relationship between phyA and phyB is not fully understood under different kinds of light and in response to different intensities of such light. In this work, we compared hypocotyl elongation of the phyA-211 phyB-9 double mutant with the wild type, the phyA-211 and phyB-9 single mutants under different intensities of far-red (FR, red (R, blue (B and white (W light. We confirmed that phyA and phyB synergistically promote seedling de-etiolation in B-, B plus R-, W- and high R-light conditions. The correlation of endogenous ELONGATED HYPOCOTYL 5 (HY5 protein levels with the trend of hypocotyl elongation of all lines indicate that both phyA and phyB promote seedling photomorphogenesis in a synergistic manner in high-irradiance white light. Gene expression analyses of RBCS members and HY5 suggest that phyB and phyA act antagonistically on seedling development under FR light.

  7. Overexpression of the phytochrome B gene from Arabidopsis thaliana increases plant growth and yield of cotton (Gossypium hirsutum)

    Institute of Scientific and Technical Information of China (English)

    Abdul Qayyum RAO; Muhammad IRFAN; Zafar SALEEM; Idrees Ahmad NASIR; Sheikh RIAZUDDIN; Tayyab HUSNAIN

    2011-01-01

    The phytochrome B (PHYB) gene of Arabidopsis thaliana was introduced into cotton through Agrobacterium tumefaciens. Integration and expression of PHYB gene in cotton plants were confirmed by molecular evidence.Messenger RNA (mRNA) expression in one of the transgenic lines, QCC11, was much higher than those of control and other transgenic lines. Transgenic cotton plants showed more than a two-fold increase in photosynthetic rate and more than a four-fold increase in transpiration rate and stomatal conductance. The increase in photosynthetic rate led to a 46% increase in relative growth rate and an 18% increase in net assimilation rate. Data recorded up to two generations,both in the greenhouse and in the field, revealed that overexpression ofArabidopsis thaliana PHYB gene in transgeniccotton plants resulted in an increase in the production of cotton by improving the cotton plant growth, with 35% more yield. Moreover, the presence of the Arabidopsis thaliana PHYB gene caused pleiotropic effects like semi-dwarfism,decrease in apical dominance, and increase in boll size.

  8. The shade avoidance syndrome in Arabidopsis: the antagonistic role of phytochrome a and B differentiates vegetation proximity and canopy shade.

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    Jaime F Martínez-García

    Full Text Available Light limitation caused by dense vegetation is one of the greatest threats to plant survival in natural environments. Plants detect such neighboring vegetation as a reduction in the red to far-red ratio (R:FR of the incoming light. The low R:FR signal, perceived by phytochromes, initiates a set of responses collectively known as the shade avoidance syndrome, intended to reduce the degree of current or future shade from neighbors by overtopping such competitors or inducing flowering to ensure seed production. At the seedling stage these responses include increased hypocotyl elongation. We have systematically analyzed the Arabidopsis seedling response and the contribution of phyA and phyB to perception of decreased R:FR, at three different levels of photosynthetically active radiation. Our results show that the shade avoidance syndrome, induced by phyB deactivation, is gradually antagonized by phyA, operating through the so-called FR-High Irradiance Response, in response to high FR levels in a range that simulates plant canopy shade. The data indicate that the R:FR signal distinguishes between the presence of proximal, but non-shading, neighbors and direct foliar shade, via a intrafamily photosensory attenuation mechanism that acts to suppress excessive reversion toward skotomorphogenic development under prolonged direct vegetation shade.

  9. Protonation state and structural changes of the tetrapyrrole chromophore during the Pr --> Pfr phototransformation of phytochrome: a resonance Raman spectroscopic study.

    Science.gov (United States)

    Kneip, C; Hildebrandt, P; Schlamann, W; Braslavsky, S E; Mark, F; Schaffner, K

    1999-11-16

    The photoconversion of phytochrome (phytochrome A from Avena satina) from the inactive (Pr) to the physiologically active form (Pfr) was studied by near-infrared Fourier transform resonance Raman spectroscopy at cryogenic temperatures, which allow us to trap the intermediate states. Nondeuterated and deuterated buffer solutions were used to determine the effect of H/D exchange on the resonance Raman spectra. For the first time, reliable spectra of the "bleached" intermediates meta-R(A) and meta-R(C) were obtained. The vibrational bands in the region 1300-1700 cm(-)(1), which is particularly indicative of structural changes in tetrapyrroles, were assigned on the basis of recent calculations of the Raman spectra of the chromophore in C-phycocyanin and model compounds [Kneip, C., Hildebrandt, P., Németh, K., Mark, F., Schaffner, K. (1999) Chem. Phys. Lett. 311, 479-485]. The experimental resonance Raman spectra Pr are compatible with the Raman spectra calculated for the protonated ZZZasa configuration, which hence is suggested to be the chromophore structure in this parent state of phytochrome. Furthermore, marker bands could be identified that are of high diagnostic value for monitoring structural changes in individual parts of the chromophore. Specifically, it could be shown that not only in the parent states Pr and Pfr but also in all intermediates the chromophore is protonated at the pyrroleninic nitrogen. The spectral changes observed for lumi-R confirm the view that the photoreaction of Pr is a Z --> E isomerization of the CD methine bridge. The subsequent thermal decay reaction to meta-R(A) includes relaxations of the CD methine bridge double bond, whereas the formation of meta-R(C) is accompanied by structural adaptations of the pyrrole rings B and C in the protein pocket. The far-reaching similarities between the chromophores of meta-R(A) and Pfr suggest that in the step meta-R(A) --> Pfr the ultimate structural changes of the protein matrix occur.

  10. Light-regulated expression of the nitrate-reductase and nitrite-reductase genes in tomato and in the phytochrome-deficient aurea mutant of tomato.

    Science.gov (United States)

    Becker, T W; Foyer, C; Caboche, M

    1992-08-01

    The phytochrome-deficient aurea mutant of tomato (Lycopersicon esculentum (L.) Mill) was used to investigate if phytochrome plays a role in the regulation of nitrate-reductase (NR, EC 1.6.6.1) and nitrite-reductase (NiR, EC 1.7.7.1) gene expression. We show that the expression of the tomato NR and NiR genes is stimulated by light and that this light response is mediated by the photoreceptor phytochrome. The red-light response of the NR and NiR genes was reduced in etiolated aurea seedlings when compared to isogenic wild-type cotyledons. The relative levels of NR mRNA and NiR transcripts and their diurnal fluctuations were identical in mature white-light-grown leaves of the wild-type and of the aurea mutant. The transcript levels for cab and RbcS (genes for the chlorophyll-a/b-binding protein of PSII and the small subunit of the enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase, respectively) in aurea leaves grown in white light were indistinguishable from the respective transcript levels in the leaves of the wildtype grown under the same conditions. Despite a severe reduction in the chlorophyll content, the rate of net CO2 uptake by leaves of the aurea mutant was only slightly reduced when compared to the rate of net photosynthesis of wild-type leaves. This difference in the photosynthetic performances of wild-type and aurea mutant plants disappeared during aging of the plants. The increase in zeaxanthin and the concomitant decrease in violaxanthin in leaves of the aurea mutant compared with the same pigment levels in leaves of the wild-type indicate that the activity of the xanthophyll cycle is increased in aurea leaves as a consequence of the reduced CO2-fixation capacity of the mutant leaves.

  11. Residues clustered in the light-sensing knot of phytochrome B are necessary for conformer-specific binding to signaling partner PIF3.

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    Elise A Kikis

    2009-01-01

    Full Text Available The bHLH transcription factor, Phytochrome Interacting Factor 3 (PIF3, interacts specifically with the photoactivated, Pfr, form of Arabidopsis phytochrome B (phyB. This interaction induces PIF3 phosphorylation and degradation in vivo and modulates phyB-mediated seedling deetiolation in response to red light. To identify missense mutations in the phyB N-terminal domain that disrupt this interaction, we developed a yeast reverse-hybrid screen. Fifteen individual mutations identified in this screen, or in previous genetic screens for Arabidopsis mutants showing reduced sensitivity to red light, were shown to also disrupt light-induced binding of phyB to PIF3 in in vitro co-immunoprecipitation assays. These phyB missense mutants fall into two general classes: Class I (eleven mutants containing those defective in light signal perception, due to aberrant chromophore attachment or photoconversion, and Class II (four mutants containing those normal in signal perception, but defective in the capacity to transduce this signal to PIF3. By generating a homology model for the three-dimensional structure of the Arabidopsis phyB chromophore-binding region, based on the crystal structure of Deinococcus radiodurans phytochrome, we predict that three of the four Class II mutated phyB residues are solvent exposed in a cleft between the presumptive PAS and GAF domains. This deduction suggests that these residues could be directly required for the physical interaction of phyB with PIF3. Because these three residues are also necessary for phyB-imposed inhibition of hypocotyl elongation in response to red light, they are functionally necessary for signal transfer from photoactivated phyB, not only to PIF3 and other related bHLH transcription factors tested here, but also to other downstream signaling components involved in regulating seedling deetiolation.

  12. Differential effects of mutations in the chromophore pocket of recombinant phytochrome on chromoprotein assembly and Pr-to-Pfr photoconversion.

    Science.gov (United States)

    Remberg, A; Schmidt, P; Braslavsky, S E; Gärtner, W; Schaffner, K

    1999-11-01

    Site-directed mutagenesis was performed with the chromophore-bearing N-terminal domain of oat phytochrome A apoprotein (amino acid residues 1-595). Except for Trp366, which was replaced by Phe (W366F), all the residues exchanged are in close proximity to the chromophore-binding Cys321 (i.e. P318A, P318K, H319L, S320K, H322L and the double mutant L323R/Q324D). The mutants were characterized by their absorption maxima, and the kinetics of chromophore-binding and the Pr-->Pfr conversion. The strongest effect of mutation on the chromoprotein assembly, leading to an almost complete loss of the chromophore binding capability, was found for the exchanges of His322 by Leu (H322L) and Pro318 by Lys (P318K), whereas a corresponding alanine mutant (P318A) showed wild-type behavior. The second histidine (H319) is also involved in chromophore fixation, as indicated by a slower assembly rate upon mutation (H319L). For the other mutants, an assembly process very similar to that of the wild-type protein was found. The light-induced Pr-->Pfr conversion kinetics is altered in the mutations H319L and S320K and in the double mutant L323R/Q324D, all of which exhibited a significantly faster I700 decay and accelerated Pfr formation. P318 is also involved in the Pr-->Pfr conversion, the millisecond steps (formation of Pfr) being significantly slower for P318A. Lacking sufficient amounts of W366F, assembly kinetics could not be determined in this case, while the fully assembled mutant underwent the Pr-->Pfr conversion with kinetics similar to wild-type protein.

  13. Sequences within both the N- and C-terminal domains of phytochrome A are required for PFR ubiquitination and degradation.

    Science.gov (United States)

    Clough, R C; Jordan-Beebe, E T; Lohman, K N; Marita, J M; Walker, J M; Gatz, C; Vierstra, R D

    1999-01-01

    Photoconversion of the plant photoreceptor phytochrome A (phyA) from its inactive Pr form to its biologically active Pfr from initiates its rapid proteolysis. Previous kinetic and biochemical studies implicated a role for the ubiquitin/26S proteasome pathway in this breakdown and suggested that multiple domains within the chromoprotein are involved. To further resolve the essential residues, we constructed a series of mutant PHY genes in vitro and analyzed the Pfr-specific degradation of the resulting photoreceptors expressed in transgenic tobacco. One important site is within the C-terminal half of the polypeptide as its removal stabilizes oat phyA as Pfr. Within this half is a set of conserved lysines that are potentially required for ubiquitin attachment. Substitution of these lysines did not prevent ubiquitination or breakdown of Pfr, suggesting either that they are not the attachment sites or that other lysines can be used in their absence. A small domain just proximal to the C-terminus is essential for the form-dependent breakdown of the holoprotein. Removal of just six amino acids in this domain generated a chromoprotein that was not rapidly degraded as Pfr. Using chimeric photoreceptors generated from potato PHYA and PHYB, we found that the N-terminal half of phyA is also required for Pfr-specific breakdown. Only those chimeras containing the N-terminal sequences from phyA were ubiquitinated and rapidly degraded as Pfr. Taken together, our data demonstrate that, whereas an intact C-terminal domain is essential for phyA degradation, the N-terminal domain is responsible for the selective recognition and ubiquitination of Pfr.

  14. Thermoperiodic control of hypocotyl elongation depends on auxin-induced ethylene signaling that controls downstream PHYTOCHROME INTERACTING FACTOR3 activity.

    Science.gov (United States)

    Bours, Ralph; Kohlen, Wouter; Bouwmeester, Harro J; van der Krol, Alexander

    2015-02-01

    We show that antiphase light-temperature cycles (negative day-night temperature difference [-DIF]) inhibit hypocotyl growth in Arabidopsis (Arabidopsis thaliana). This is caused by reduced cell elongation during the cold photoperiod. Cell elongation in the basal part of the hypocotyl under -DIF was restored by both 1-aminocyclopropane-1-carboxylic acid (ACC; ethylene precursor) and auxin, indicating limited auxin and ethylene signaling under -DIF. Both auxin biosynthesis and auxin signaling were reduced during -DIF. In addition, expression of several ACC Synthase was reduced under -DIF but could be restored by auxin application. In contrast, the reduced hypocotyl elongation of ethylene biosynthesis and signaling mutants could not be complemented by auxin, indicating that auxin functions upstream of ethylene. The PHYTOCHROME INTERACTING FACTORS (PIFs) PIF3, PIF4, and PIF5 were previously shown to be important regulators of hypocotyl elongation. We now show that, in contrast to pif4 and pif5 mutants, the reduced hypocotyl length in pif3 cannot be rescued by either ACC or auxin. In line with this, treatment with ethylene or auxin inhibitors reduced hypocotyl elongation in PIF4 overexpressor (PIF4ox) and PIF5ox but not PIF3ox plants. PIF3 promoter activity was strongly reduced under -DIF but could be restored by auxin application in an ACC Synthase-dependent manner. Combined, these results show that PIF3 regulates hypocotyl length downstream, whereas PIF4 and PIF5 regulate hypocotyl length upstream of an auxin and ethylene cascade. We show that, under -DIF, lower auxin biosynthesis activity limits the signaling in this pathway, resulting in low activity of PIF3 and short hypocotyls.

  15. Expression Patterns of OsPIL11, a Phytochrome-Interacting Factor in Rice, and Preliminary Analysis of Its Roles in Light Signal Transduction

    Institute of Scientific and Technical Information of China (English)

    LI Li; PENG Wei-feng; LIU Qian-qian; ZHOU Jin-jun; LIANG Wei-hong; XIE Xian-zhi

    2012-01-01

    The expression patterns of OsPlL11,one of six putative phytochrome-interacting factors,were analyzed in different organs of transgenic tobacco (Nicotiana tabacum).The expression of OsPIL 11 was organ-specific and was regulated by leaf development,abscisic acid (ABA),jasmonic acid (JA) and salicylic acid (SA).To further explore the role of OsPlL 11 in plant light signal transduction,a plant expression vector of OsPIL11 was constructed and introduced into tobacco.When grown under continuous red light,OsPIL11-overexpressed transgenic tobacco exhibited shorter hypocotyls and larger cotyledons and leaves compared to wild-type seedlings.When grown under continuous far-red light,however,transgenic and wild-type seedlings showed similar phenotypes.These results indicate that OsPIL11 is involved in red light induced de-etiolation,but not in far-red light induced de-etiolation in transgenic tobacco,which lays the foundation for dissecting the function of OsPIL 11 in phytochrome-mediated light signal transduction in rice.

  16. The Phytochrome-Interacting VASCULAR PLANT ONE–ZINC FINGER1 and VOZ2 Redundantly Regulate Flowering in Arabidopsis[C][W

    Science.gov (United States)

    Yasui, Yukiko; Mukougawa, Keiko; Uemoto, Mitsuhiro; Yokofuji, Akira; Suzuri, Ryota; Nishitani, Aiko; Kohchi, Takayuki

    2012-01-01

    The timing of the transition to flowering in plants is regulated by various environmental factors, including daylength and light quality. Although the red/far-red photoreceptor phytochrome B (phyB) represses flowering by indirectly regulating the expression of a key flowering regulator, FLOWERING LOCUS T (FT), the mechanism of phyB signaling for flowering is largely unknown. Here, we identified two Arabidopsis thaliana genes, VASCULAR PLANT ONE–ZINC FINGER1 (VOZ1) and VOZ2, which are highly conserved throughout land plant evolution, as phyB-interacting factors. voz1 voz2 double mutants, but neither single mutant, showed a late-flowering phenotype under long-day conditions, which indicated that VOZ1 and VOZ2 redundantly promote flowering. voz1 voz2 mutations suppressed the early-flowering phenotype of the phyB mutant, and FT expression was repressed in the voz1 voz2 mutant. Green fluorescent protein–VOZ2 signal was observed in the cytoplasm, and interaction of VOZ proteins with phyB was indicated to occur in the cytoplasm under far-red light. However, VOZ2 protein modified to localize constitutively in the nucleus promoted flowering. In addition, the stability of VOZ2 proteins in the nucleus was modulated by light quality in a phytochrome-dependent manner. We propose that partial translocation of VOZ proteins from the cytoplasm to the nucleus mediates the initial step of the phyB signal transduction pathway that regulates flowering. PMID:22904146

  17. Características fisiológicas de microtomateiros fitocromo-mutantes Physiological characteristics of micro-tomato (Lycopersicon esculentum P. Miller phytochrome-mutants

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    Hyrandir Cabral de Melo

    2009-10-01

    Full Text Available Objetivou-se, neste trabalho, caracterizar aspectos fisiológicos de microtomateiros (Lycopersicon esculentum P. Miller cv. Micro-Tom fitocromo-mutantes. A cultivar Micro-Tom e os mutantes aurea (deficiente na biossíntese do cromóforo dos fitocromos, atroviolacea (atv e high pigment1 (hp1;ambos superexpressam eventos mediados por fitocromos foram cultivados em condições controladas de luz e temperatura e caracterizados no estágio de floração. O mutante hp1 obteve as maiores taxas de fotossíntese potencial e de conteúdo de carotenóides. O mutante aurea manteve taxas de fotossíntese potencial similares à cultivar Micro-Tom, mesmo expressando o mais baixo conteúdo de clorofilas, e também expressou o maior conteúdo de nitrogênio entre os demais microtomateiros. Os mutantes aurea e hp1 obtiveram os menores conteúdos de açúcares solúveis totais. O mutante atv expressou o maior conteúdo de clorofilas e também a menor razão clorofila a/b.The objective of this work was to characterize physiological aspects of micro-tomato (Lycopersicon esculentum P. Miller cv. Micro-Tom phytochrome-mutants. Plants of Micro-Tom cultivar and aurea (deficient in phytochrome chromophore biosynthesis, high pigment1 (hp1 and atroviolacea (atv (both super express phytochrome events-mediated mutants were cultivated under controlled light and temperature and evaluated in flowering stage. The hp1 mutant expressed the highest rates of potential photosynthesis and also the content of total carotenoids. Aurea mutant maintained similar potential photosynthesis rates as the Micro-Tom cultivar, even containing low chlorophyll content, and expressed the highest content of nitrogen among all micro-tomatoes studied. Total soluble sugars were lower in aurea and hp1 mutants. The atv mutant expressed the highest content of chlorophylls and also the lowest rate of chlorophyll a/b.

  18. Ultrafast red light activation of Synechocystis phytochrome Cph1 triggers major structural change to form the Pfr signalling-competent state.

    Science.gov (United States)

    Heyes, Derren J; Khara, Basile; Sakuma, Michiyo; Hardman, Samantha J O; O'Cualain, Ronan; Rigby, Stephen E J; Scrutton, Nigel S

    2012-01-01

    Phytochromes are dimeric photoreceptors that regulate a range of responses in plants and microorganisms through interconversion of red light-absorbing (Pr) and far-red light-absorbing (Pfr) states. Photoconversion between these states is initiated by light-driven isomerization of a bilin cofactor, which triggers protein structural change. The extent of this change, and how light-driven structural changes in the N-terminal photosensory region are transmitted to the C-terminal regulatory domain to initiate the signalling cascade, is unknown. We have used pulsed electron-electron double resonance (PELDOR) spectroscopy to identify multiple structural transitions in a phytochrome from Synechocystis sp. PCC6803 (Cph1) by measuring distances between nitroxide labels introduced into the protein. We show that monomers in the Cph1 dimer are aligned in a parallel 'head-to-head' arrangement and that photoconversion between the Pr and Pfr forms involves conformational change in both the N- and C-terminal domains of the protein. Cryo-trapping and kinetic measurements were used to probe the extent and temporal properties of protein motions for individual steps during photoconversion of Cph1. Formation of the primary photoproduct Lumi-R is not affected by changes in solvent viscosity and dielectric constant. Lumi-R formation occurs at cryogenic temperatures, consistent with their being no major structural reorganization of Cph1 during primary photoproduct formation. All remaining steps in the formation of the Pfr state are affected by solvent viscosity and dielectric constant and occur only at elevated temperatures, implying involvement of a series of long-range solvent-coupled conformational changes in Cph1. We show that signalling is achieved through ultrafast photoisomerization where localized structural change in the GAF domain is transmitted and amplified to cause larger-scale and slower conformational change in the PHY and histidine kinase domains. This hierarchy of

  19. In response to partial plant shading, the lack of phytochrome A does not directly induce leaf senescence but alters the fine-tuning of chlorophyll biosynthesis.

    Science.gov (United States)

    Brouwer, Bastiaan; Gardeström, Per; Keech, Olivier

    2014-07-01

    Phytochrome is thought to control the induction of leaf senescence directly, however, the signalling and molecular mechanisms remain unclear. In the present study, an ecophysiological approach was used to establish a functional connection between phytochrome signalling and the physiological processes underlying the induction of leaf senescence in response to shade. With shade it is important to distinguish between complete and partial shading, during which either the whole or only a part of the plant is shaded, respectively. It is first shown here that, while PHYB is required to maintain chlorophyll content in a completely shaded plant, only PHYA is involved in maintaining the leaf chlorophyll content in response to partial plant shading. Second, it is shown that leaf yellowing associated with strong partial shading in phyA-mutant plants actually correlates to a decreased biosynthesis of chlorophyll rather than to an increase of its degradation. Third, it is shown that the physiological impact of this decreased biosynthesis of chlorophyll in strongly shaded phyA-mutant leaves is accompanied by a decreased capacity to adjust the Light Compensation Point. However, the increased leaf yellowing in phyA-mutant plants is not accompanied by an increase of senescence-specific molecular markers, which argues against a direct role of PHYA in inducing leaf senescence in response to partial shade. In conclusion, it is proposed that PHYA, but not PHYB, is essential for fine-tuning the chlorophyll biosynthetic pathway in response to partial shading. In turn, this mechanism allows the shaded leaf to adjust its photosynthetic machinery to very low irradiances, thus maintaining a positive carbon balance and repressing the induction of leaf senescence, which can occur under prolonged periods of shade.

  20. The Crystal Structures of the N-terminal Photosensory Core Module of Agrobacterium Phytochrome Agp1 as Parallel and Anti-parallel Dimers.

    Science.gov (United States)

    Nagano, Soshichiro; Scheerer, Patrick; Zubow, Kristina; Michael, Norbert; Inomata, Katsuhiko; Lamparter, Tilman; Krauß, Norbert

    2016-09-23

    Agp1 is a canonical biliverdin-binding bacteriophytochrome from the soil bacterium Agrobacterium fabrum that acts as a light-regulated histidine kinase. Crystal structures of the photosensory core modules (PCMs) of homologous phytochromes have provided a consistent picture of the structural changes that these proteins undergo during photoconversion between the parent red light-absorbing state (Pr) and the far-red light-absorbing state (Pfr). These changes include secondary structure rearrangements in the so-called tongue of the phytochrome-specific (PHY) domain and structural rearrangements within the long α-helix that connects the cGMP-specific phosphodiesterase, adenylyl cyclase, and FhlA (GAF) and the PHY domains. We present the crystal structures of the PCM of Agp1 at 2.70 Å resolution and of a surface-engineered mutant of this PCM at 1.85 Å resolution in the dark-adapted Pr states. Whereas in the mutant structure the dimer subunits are in anti-parallel orientation, the wild-type structure contains parallel subunits. The relative orientations between the PAS-GAF bidomain and the PHY domain are different in the two structures, due to movement involving two hinge regions in the GAF-PHY connecting α-helix and the tongue, indicating pronounced structural flexibility that may give rise to a dynamic Pr state. The resolution of the mutant structure enabled us to detect a sterically strained conformation of the chromophore at ring A that we attribute to the tight interaction with Pro-461 of the conserved PRXSF motif in the tongue. Based on this observation and on data from mutants where residues in the tongue region were replaced by alanine, we discuss the crucial roles of those residues in Pr-to-Pfr photoconversion.

  1. The role of phytochrome A and gibberellins in growth under long and short day conditions: Studies in hybrid aspen

    Energy Technology Data Exchange (ETDEWEB)

    Eriksson, M.E. [Swedish Univ. of Agricultural Sciences, Umeaa (Sweden). Dept. of Forest Genetics and Plant Physiology

    2000-07-01

    This thesis addresses questions concerning the regulation of growth and, specifically, the cessation of growth in response to short days in deciduous tree species. The model tree used in the studies was hybrid aspen (Populus tremula L. x P. tremuloides Michx.). We have exploited the possibility of transforming this species to modulate the level of expression of target genes using over-expression and antisense techniques. The target genes in the studies were the photoreceptor phytochrome A (phyA) and gibberellin 20-oxidase (GA 20-oxidase), the latter being a highly regulated enzyme involved in the biosynthesis of gibberellins (GAs). The photoreceptor phyA has been implicated in photoperiodic regulation of growth, while GAs may regulate the physiological response further downstream. The endogenous expression of these genes has been investigated in parallel with studies of various plants with ectopic and reduced levels of expression. The main focus has been on the early stages of induction of growth cessation and its physiological and molecular mechanisms. Studies of hybrid aspen plants with an increased or reduced expression of phyA, show this receptor to mediate the photoperiodic regulation of growth. Plants with ectopic expression could not stop growing despite drastically shortened photoperiods, while the antisense plants showed the reverse phenotype, with a higher sensitivity resulting in earlier cessation of growth. The role of GAs in growth inhibition was also addressed using plants with a reduction in GA levels. These plants showed early cessation of growth and dormancy, and thus an increased sensitivity toward daylength. Conversely, plants with increased rates of GA biosynthesis showed increased growth and stopped growing much later. Furthermore, increases in GA biosynthesis, resulting in high levels of GAs have a major impact on growth. Plants with high GA levels have increased elongation and diameter growth, due to higher rates of cell production in the

  2. Phytochrome-like responses in Euglena: A low fluence response that reorganizes the spectral dependence of the high irradiance response in long-day photoperiodic induction of cell division.

    Science.gov (United States)

    Bolige, Aoen; Goto, Ken

    2007-02-01

    Irradiance spectra change spatiotemporally, and angiosperms adapt accordingly, mainly through phytochromes. This study challenges the long-held belief that the flagellated alga Euglena gracilis lacks phytochromes and is therefore unaffected by spectral changes. We photoautotrophically cultured the alga under continuous light (LL), then transferred it to darkness. After about 26h in darkness, different irradiations for 3h enabled cell division in dark-arrested G2 cells evoking a high-irradiance response (HIR). The spectral characteristics of the irradiation during the LL period (pre-irradiation) defined the spectral sensitivity in the subsequent dark period. LL with light rich in the red spectrum led to a HIR to the red spectrum (R-HIR), whereas light rich in the far-red spectrum (FR) led to a FR-HIR. Finishing the period of pre-irradiation consisting of continuous cool-white fluorescent light (rich in R) by a FR pulse enhanced the characteristics of the FR-HIR 26h later. By contrast, a R pulse given at the end of the pre-irradiation rich in FR potentiated the R-HIR. The effects were completely photoreversible between R and FR with critical fluences of about 2mmolm(-2), satisfying the classic diagnostic feature of phytochromes. The action spectrum of the FR effect at the end of pre-irradiation consisting of continuous cool-white fluorescent light (rich in R) had a main peak at 740nm and a minor peak at 380nm, whereas antagonization of the FR effect had a main peak at 640nm and a minor peak at 480nm. Wavelengths of 610 and 670nm appeared in both spectra. We also demonstrated the photoreversibility of 380/640, 480/740, and (610 and 670)/(640 and 740) nm. We conclude that Euglena displays phytochrome-like responses similar to the 'shade avoidance' and 'end-of-day FR' effects reported in angiosperms.

  3. Ultrafast red light activation of Synechocystis phytochrome Cph1 triggers major structural change to form the Pfr signalling-competent state.

    Directory of Open Access Journals (Sweden)

    Derren J Heyes

    Full Text Available Phytochromes are dimeric photoreceptors that regulate a range of responses in plants and microorganisms through interconversion of red light-absorbing (Pr and far-red light-absorbing (Pfr states. Photoconversion between these states is initiated by light-driven isomerization of a bilin cofactor, which triggers protein structural change. The extent of this change, and how light-driven structural changes in the N-terminal photosensory region are transmitted to the C-terminal regulatory domain to initiate the signalling cascade, is unknown. We have used pulsed electron-electron double resonance (PELDOR spectroscopy to identify multiple structural transitions in a phytochrome from Synechocystis sp. PCC6803 (Cph1 by measuring distances between nitroxide labels introduced into the protein. We show that monomers in the Cph1 dimer are aligned in a parallel 'head-to-head' arrangement and that photoconversion between the Pr and Pfr forms involves conformational change in both the N- and C-terminal domains of the protein. Cryo-trapping and kinetic measurements were used to probe the extent and temporal properties of protein motions for individual steps during photoconversion of Cph1. Formation of the primary photoproduct Lumi-R is not affected by changes in solvent viscosity and dielectric constant. Lumi-R formation occurs at cryogenic temperatures, consistent with their being no major structural reorganization of Cph1 during primary photoproduct formation. All remaining steps in the formation of the Pfr state are affected by solvent viscosity and dielectric constant and occur only at elevated temperatures, implying involvement of a series of long-range solvent-coupled conformational changes in Cph1. We show that signalling is achieved through ultrafast photoisomerization where localized structural change in the GAF domain is transmitted and amplified to cause larger-scale and slower conformational change in the PHY and histidine kinase domains. This

  4. Bright blue-shifted fluorescent proteins with Cys in the GAF domain engineered from bacterial phytochromes: fluorescence mechanisms and excited-state dynamics

    Science.gov (United States)

    Hontani, Yusaku; Shcherbakova, Daria M.; Baloban, Mikhail; Zhu, Jingyi; Verkhusha, Vladislav V.; Kennis, John T. M.

    2016-11-01

    Near-infrared fluorescent proteins (NIR FPs) engineered from bacterial phytochromes (BphPs) are of great interest for in vivo imaging. They utilize biliverdin (BV) as a chromophore, which is a heme degradation product, and therefore they are straightforward to use in mammalian tissues. Here, we report on fluorescence properties of NIR FPs with key alterations in their BV binding sites. BphP1-FP, iRFP670 and iRFP682 have Cys residues in both PAS and GAF domains, rather than in the PAS domain alone as in wild-type BphPs. We found that NIR FP variants with Cys in the GAF or with Cys in both PAS and GAF show blue-shifted emission with long fluorescence lifetimes. In contrast, mutants with Cys in the PAS only or no Cys residues at all exhibit red-shifted emission with shorter lifetimes. Combining these results with previous biochemical and BphP1-FP structural data, we conclude that BV adducts bound to Cys in the GAF are the origin of bright blue-shifted fluorescence. We propose that the long fluorescence lifetime follows from (i) a sterically more constrained thioether linkage, leaving less mobility for ring A than in canonical BphPs, and (ii) that π-electron conjugation does not extend on ring A, making excited-state deactivation less sensitive to ring A mobility.

  5. Antiphase light and temperature cycles affect PHYTOCHROME B-controlled ethylene sensitivity and biosynthesis, limiting leaf movement and growth of Arabidopsis.

    Science.gov (United States)

    Bours, Ralph; van Zanten, Martijn; Pierik, Ronald; Bouwmeester, Harro; van der Krol, Alexander

    2013-10-01

    In the natural environment, days are generally warmer than the night, resulting in a positive day/night temperature difference (+DIF). Plants have adapted to these conditions, and when exposed to antiphase light and temperature cycles (cold photoperiod/warm night [-DIF]), most species exhibit reduced elongation growth. To study the physiological mechanism of how light and temperature cycles affect plant growth, we used infrared imaging to dissect growth dynamics under +DIF and -DIF in the model plant Arabidopsis (Arabidopsis thaliana). We found that -DIF altered leaf growth patterns, decreasing the amplitude and delaying the phase of leaf movement. Ethylene application restored leaf growth in -DIF conditions, and constitutive ethylene signaling mutants maintain robust leaf movement amplitudes under -DIF, indicating that ethylene signaling becomes limiting under these conditions. In response to -DIF, the phase of ethylene emission advanced 2 h, but total ethylene emission was not reduced. However, expression analysis on members of the 1-aminocyclopropane-1-carboxylic acid (ACC) synthase ethylene biosynthesis gene family showed that ACS2 activity is specifically suppressed in the petiole region under -DIF conditions. Indeed, petioles of plants under -DIF had reduced ACC content, and application of ACC to the petiole restored leaf growth patterns. Moreover, acs2 mutants displayed reduced leaf movement under +DIF, similar to wild-type plants under -DIF. In addition, we demonstrate that the photoreceptor PHYTOCHROME B restricts ethylene biosynthesis and constrains the -DIF-induced phase shift in rhythmic growth. Our findings provide a mechanistic insight into how fluctuating temperature cycles regulate plant growth.

  6. Spectroscopic Investigation on the Primary Photoreaction of Bathy Phytochrome Agp2-Pr of Agrobacterium fabrum: Isomerization in a pH-dependent H-bond Network.

    Science.gov (United States)

    Singer, Patrick; Wörner, Sybille; Lamparter, Tilman; Diller, Rolf

    2016-05-04

    Bathy phytochrome Agp2 from Agrobacterium fabrum exhibits an unusually low pKa =7.6 in the Pr state in contrast to a pKa >11 in the Pfr state, indicating a pH-dependent charge distribution and H-bond network in the Pr chromophore binding pocket around neutral pH. Here, we report on ultrafast UV/Vis absorption spectroscopy of the primary Pr photoisomerization of Agp2 at pH 6 and pH 9 and upon H2 O/D2 O buffer exchange. The triexponential Pr kinetics slows down at increased pH and pronounced pH-dependent kinetic isotope effects are observed. The results on the Pr photoreaction suggest: 1) component-wise hindered dynamics on the chromophore excited-state potential energy surface at high pH and 2) proton translocation processes either via single-proton transfer or via significant reorganization of H-bond networks. Both effects reflect the interplay between the pH-dependent charge distribution in the Pr chromophore binding pocket on the one hand and chromophore excitation and its Z→E isomerization on the other hand.

  7. Phytochrome B regulates Heading date 1 (Hd1)-mediated expression of rice florigen Hd3a and critical day length in rice.

    Science.gov (United States)

    Ishikawa, Ryo; Aoki, Mayumi; Kurotani, Ken-Ichi; Yokoi, Shuji; Shinomura, Tomoko; Takano, Makoto; Shimamoto, Ko

    2011-06-01

    Many plants require circadian clock and light information for the photoperiodic control of flowering. In Arabidopsis, a long-day plant (LDP), flowering is triggered by the circadian clock-controlled expression of CONSTANS (CO) and light stabilization of the CO protein to induce FT (FLOWERING LOCUS T). In rice, a short-day plant (SDP), the CO ortholog Heading date 1 (Hd1) regulates FT ortholog Hd3a, but regulation of Hd3a by Hd1 differs from that in Arabidopsis. Here, we report that phytochrome B (phyB)-mediated suppression of Hd3a is a primary cause of long-day suppression of flowering in rice, based on the three complementary discoveries. First, overexpression of Hd1 causes a delay in flowering under SD conditions and this effect requires phyB, suggesting that light modulates Hd1 control of Hd3a transcription. Second, a single extension of day length decreases Hd3a expression proportionately with the length of daylight. Third, Hd1 protein levels in Hd1-overexpressing plants are not altered in the presence of light. These results also suggest that phyB-mediated suppression of Hd3a expression is a component of the molecular mechanism for critical day length in rice.

  8. LEAFY COTYLEDON1-CASEIN KINASE I-TCP15-PHYTOCHROME INTERACTING FACTOR4 Network Regulates Somatic Embryogenesis by Regulating Auxin Homeostasis1[OPEN

    Science.gov (United States)

    Min, Ling; Hu, Qin; Li, Yaoyao; Xu, Jiao; Ma, Yizan; Zhu, Longfu; Yang, Xiyan; Zhang, Xianlong

    2015-01-01

    Somatic embryogenesis (SE) is an efficient tool for the propagation of plant species and also, a useful model for studying the regulatory networks in embryo development. However, the regulatory networks underlying the transition from nonembryogenic callus to somatic embryos during SE remain poorly understood. Here, we describe an upland cotton (Gossypium hirsutum) CASEIN KINASE I gene, GhCKI, which is a unique key regulatory factor that strongly affects SE. Overexpressing GhCKI halted the formation of embryoids and plant regeneration because of a block in the transition from nonembryogenic callus to somatic embryos. In contrast, defective GhCKI in plants facilitated SE. To better understand the mechanism by which GhCKI regulates SE, the regulatory network was analyzed. A direct upstream negative regulator protein, cotton LEAFY COTYLEDON1, was identified to be targeted to a cis-element, CTTTTC, in the promoter of GhCKI. Moreover, GhCKI interacted with and phosphorylated cotton CINCINNATA-like TEOSINTE BRANCHED1-CYCLOIDEA-PCF transcription factor15 by coordinately regulating the expression of cotton PHYTOCHROME INTERACTING FACTOR4, finally disrupting auxin homeostasis, which led to increased cell proliferation and aborted somatic embryo formation in GhCKI-overexpressing somatic cells. Our results show a complex process of SE that is negatively regulated by GhCKI through a complex regulatory network. PMID:26491146

  9. LEAFY COTYLEDON1-CASEIN KINASE I-TCP15-PHYTOCHROME INTERACTING FACTOR4 Network Regulates Somatic Embryogenesis by Regulating Auxin Homeostasis.

    Science.gov (United States)

    Min, Ling; Hu, Qin; Li, Yaoyao; Xu, Jiao; Ma, Yizan; Zhu, Longfu; Yang, Xiyan; Zhang, Xianlong

    2015-12-01

    Somatic embryogenesis (SE) is an efficient tool for the propagation of plant species and also, a useful model for studying the regulatory networks in embryo development. However, the regulatory networks underlying the transition from nonembryogenic callus to somatic embryos during SE remain poorly understood. Here, we describe an upland cotton (Gossypium hirsutum) CASEIN KINASE I gene, GhCKI, which is a unique key regulatory factor that strongly affects SE. Overexpressing GhCKI halted the formation of embryoids and plant regeneration because of a block in the transition from nonembryogenic callus to somatic embryos. In contrast, defective GhCKI in plants facilitated SE. To better understand the mechanism by which GhCKI regulates SE, the regulatory network was analyzed. A direct upstream negative regulator protein, cotton LEAFY COTYLEDON1, was identified to be targeted to a cis-element, CTTTTC, in the promoter of GhCKI. Moreover, GhCKI interacted with and phosphorylated cotton CINCINNATA-like TEOSINTE BRANCHED1-CYCLOIDEA-PCF transcription factor15 by coordinately regulating the expression of cotton PHYTOCHROME INTERACTING FACTOR4, finally disrupting auxin homeostasis, which led to increased cell proliferation and aborted somatic embryo formation in GhCKI-overexpressing somatic cells. Our results show a complex process of SE that is negatively regulated by GhCKI through a complex regulatory network.

  10. 裸子植物PHY基因GAF结构域纯化选择位点的研究%Purifying selection sites in the GAF domain of phytochromes in gymnosperms

    Institute of Scientific and Technical Information of China (English)

    王静; 李万昌; 王艇

    2012-01-01

    Phytochromes consist of a N-terminal photosensory module and a C-terminal regulatory module. The photosensory core possesses three distinct domains: PAS, GAF and PHY; and the regulatory module is composed of PAS1、 PAS2 and HKRD domains. The bilin chromophore, which functions for light harvesting, is covalently attached to GAF domain whose conservation is one of the functional prerequisites for phytochrome photoconversion and signal transduction. PHY domain is crucial for tuning spectroscopic properties of the bound bilin. To make sure the purifying selection sites, the molecular evolution of 68 gymnosperm GAF domain sequences are assayed under the site model established. Results indicate there are 41 purifying selection sites found in GAF domain, 16 sites among them are located to the helical hairpin region of phytochrome. 15 sites lay within the beta strand region, and 3 sites are in the lasso loop region. The rest sites are beyond these regions.%光敏色素分子由位于N端的光感受区和位于C端的光调节区组成,光感受区包括PAS(Per/Arndt/Sim)、GAF(cG-MP phosphodiesterase/adenyl cyclase/FhlA)以及PHY(phytochrome domain)结构域,光调节区包括PAS1、PAS2以及HKRD(histidine kinase related domain)结构域.GAF结构域是发色团结合的部位,高度保守,该结构域的保守性是确保光敏色素光逆转和光信号转导等功能正常运行的先决条件之一.为了研究裸子植物PHY的GAF结构域经历纯化选择作用的位点,本文基于位点模型对裸子植物中68条GAF结构域序列所受到的选择压力进行分析.结果表明:在GAF结构域中,有41个位点经历了纯化选择作用,其中有16个位于α螺旋结构区,有15个位于β折叠结构区,有3个位于套索区,另外7个位点位于这些结构之间,这说明,相对于其他区域,a区和β区在功能上更为保守.

  11. Highly conserved residues Asp-197 and His-250 in Agp1 phytochrome control the proton affinity of the chromophore and Pfr formation.

    Science.gov (United States)

    von Stetten, David; Seibeck, Sven; Michael, Norbert; Scheerer, Patrick; Mroginski, Maria Andrea; Murgida, Daniel H; Krauss, Norbert; Heyn, Maarten P; Hildebrandt, Peter; Borucki, Berthold; Lamparter, Tilman

    2007-01-19

    The mutants H250A and D197A of Agp1 phytochrome from Agrobacterium tumefaciens were prepared and investigated by different spectroscopic and biochemical methods. Asp-197 and His-250 are highly conserved amino acids and are part of the hydrogen-bonding network that involves the chromophore. Both substitutions cause a destabilization of the protonated chromophore in the Pr state as revealed by resonance Raman and UV-visible absorption spectroscopy. Titration experiments demonstrate a lowering of the pK(a) from 11.1 (wild type) to 8.8 in H250A and 7.2 in D197A. Photoconversion of the mutants does not lead to the Pfr state. H250A is arrested in a meta-Rc-like state in which the chromophore is deprotonated. For H250A and the wild-type protein, deprotonation of the chromophore in meta-Rc is coupled to the release of a proton to the external medium, whereas the subsequent proton re-uptake, linked to the formation of the Pfr state in the wild-type protein, is not observed for H250A. No transient proton exchange with the external medium occurs in D197A, suggesting that Asp-197 may be the proton release group. Both mutants do not undergo the photo-induced protein structural changes that in the wild-type protein are detectable by size exclusion chromatography. These conformational changes are, therefore, attributed to the meta-Rc --> Pfr transition and most likely coupled to the transient proton re-uptake. The present results demonstrate that Asp-197 and His-250 are essential for stabilizing the protonated chromophore structure in the parent Pr state, which is required for the primary photochemical process, and for the complete photo-induced conversion to the Pfr state.

  12. Polar distribution of annexin-like proteins during phytochrome-mediated initiation and growth of rhizoids in the ferns Dryopteris and Anemia

    Science.gov (United States)

    Clark, G. B.; Turnwald, S.; Tirlapur, U. K.; Haas, C. J.; von der Mark, K.; Roux, S. J.; Scheuerlein, R.

    1995-01-01

    Although the calcium requirement of phytochrome-mediated fern spore germination and early rhizoid growth is well established, the calcium-binding proteins that serve as transducers for these responses are not known. Here we report the presence of annexin-like proteins in germinating spores of Dryopteris filix-mas (L.) Schott and Anemia phyllitidis (L.) Sw. and evidence that they may be important participants in early photomorphogenic changes in gametophytes. Immunolocalization and immunoblot assays of these proteins were carried out using polyclonal antibodies raised either against a 35-kDa annexin-like protein from pea or against anchorin CII from chicken. Western-blot analysis showed that crude protein extracts obtained from both species after red-light treatment contained two cross-reactive protein bands with molecular weights around 70 kDa. These proteins were annexin-like in that they bound to a phosphatidylserine affinity column in a calcium-dependent fashion. Using this column, two protein bands around 70 kDa, i.e. 67 and 73 kDa, were partially purified together with proteins at 36 kDa and a doublet at 54 kDa. Proteins of these latter molecular weights are suggested to be members of the annexin family, but no cross-reactivity could be found between these and the two antibodies used in our investigations. Immunodetectable levels of these proteins were observed only after light-mediated induction of spore germination. Imaging of the immuno-localization patterns observed with both antibodies showed that the annexin-like proteins are concentrated at the extreme tips of the rhizoids in D. filix-mas and A. phyllitidis during rhizoid initiation and all stages of elongation. We suggest that these proteins may play a major role in the tip-oriented exocytosis events that are critical for the initiation and growth of fern rhizoids.

  13. Assignments of the Pfr-Pr FTIR difference spectrum of cyanobacterial phytochrome Cph1 using 15N and 13C isotopically labeled phycocyanobilin chromophore.

    Science.gov (United States)

    van Thor, Jasper J; Fisher, Nicholas; Rich, Peter R

    2005-11-03

    The reversible red and far-red light-induced transitions of cyanobacterial phytochrome Cph1 from Synechocystis PCC 6803 were investigated by Fourier transform infrared (FTIR) difference spectroscopy. High-quality light-induced Pfr-Pr difference FTIR spectra were recorded for the 58 kDa N-terminal domain of Cph1 by repetitive photochemical cycling and signal averaging. The Pfr-Pr difference spectra in H(2)O and D(2)O were very similar to those previously reported for full-length 85 kDa Cph1.(1) Published assignments were extended by analysis of the effects of (13)C and (15)N isotope substitutions at selected sites in the phycocyanobilin chromophore and by (15)N global labeling of the protein. The Pfr-Pr difference spectra were dominated by an amide I peak/trough at 1653 cm(-1)(+)/1631 cm(-1)(-) and a smaller amide II band at 1554 cm(-1). Labeling effects allowed specific chromophore assignments for the C(1)=O (1736 cm(-1)(-)/1724 cm(-1)(+)) and C(19)=O (1704 cm(-1)(-)) carbonyl vibrations, C=C vibrations at 1589 cm(-1)(+), and bands at 1537(-), 1512(+), 1491(-), 1163(+), 1151(-), 1134(+), 1109(-), and 1072(-) cm(-1) that must involve chromophore C-N bonds. A variety of additional changes were insensitive to isotope labeling of the chromophore. Effects of (15)N labeling of the protein were used to tentatively assign some of these to specific amino acid changes. Those insensitive to (15)N labeling included a protonated aspartic or glutamic acid at 1734 cm(-1)(-)/1722 cm(-1)(+) and a cysteine at 2575 cm(-1)(+)/2557 cm(-1)(-). Bands sensitive to (15)N protein labeling at 1487 cm(-1)(+)/1502 cm(-1)(-) might arise from trytophan and bands at 1261 cm(-1)(+)/1244 cm(-1)(-) and 1107 cm(-1)(-)/1095 cm(-1)(+) might arise from a histidine environment or protonation change. These assignments are discussed in light of the 15Z-E photoisomerization model of phototransformation and the associated protein conformational changes.

  14. Dynamic antagonism between phytochromes and PIF family basic helix-loop-helix factors induces selective reciprocal responses to light and shade in a rapidly responsive transcriptional network in Arabidopsis.

    Science.gov (United States)

    Leivar, Pablo; Tepperman, James M; Cohn, Megan M; Monte, Elena; Al-Sady, Bassem; Erickson, Erika; Quail, Peter H

    2012-04-01

    Plants respond to shade-modulated light signals via phytochrome (phy)-induced adaptive changes, termed shade avoidance. To examine the roles of Phytochrome-Interacting basic helix-loop-helix Factors, PIF1, 3, 4, and 5, in relaying such signals to the transcriptional network, we compared the shade-responsive transcriptome profiles of wild-type and quadruple pif (pifq) mutants. We identify a subset of genes, enriched in transcription factor-encoding loci, that respond rapidly to shade, in a PIF-dependent manner, and contain promoter G-box motifs, known to bind PIFs. These genes are potential direct targets of phy-PIF signaling that regulate the primary downstream transcriptional circuitry. A second subset of PIF-dependent, early response genes, lacking G-box motifs, are enriched for auxin-responsive loci, and are thus potentially indirect targets of phy-PIF signaling, mediating the rapid cell expansion induced by shade. Comparing deetiolation- and shade-responsive transcriptomes identifies another subset of G-box-containing genes that reciprocally display rapid repression and induction in response to light and shade signals. These data define a core set of transcriptional and hormonal processes that appear to be dynamically poised to react rapidly to light-environment changes via perturbations in the mutually antagonistic actions of the phys and PIFs. Comparing the responsiveness of the pifq and triple pif mutants to light and shade confirms that the PIFs act with overlapping redundancy on seedling morphogenesis and transcriptional regulation but that each PIF contributes differentially to these responses.

  15. Regulation of Phytochrome Interacting Factors (PIFs) on Plant Growth and Development%光敏色素互作因子(PIFs)对植物生长发育的调控

    Institute of Scientific and Technical Information of China (English)

    潘教文; 赵术珍; 张烨; 李长生; 王玉红; 王兴军

    2014-01-01

    Phytochrome interacting factors ( PIFs ) belonging to Arabidopsis basic helix -loop -helix ( bHLH) transcription factors subgroup 15 are key regulators in light signal transduction .Light -activated phytochromes regulate plant growth and development by promoting the degradation of PIFs and directly or indi -rectly inhibiting their DNA binding activity .Studies showed that PIFs played important roles in the regulation of seed germination, seedling morphogenesis , shade avoidance , circadian clock, phytohormone biosynthesis and signal transduction .PIFs have broader roles than previously expected and work as a cellular signaling hub that integrates multiple signals to orchestrate the transcriptional network of plants .%光敏色素相互作用因子( PIFs)属于拟南芥bHLH转录因子家族的第15亚族,是光信号响应过程中的关键负调控因子。光激活的光敏色素通过促进PIFs蛋白降解,直接或间接抑制它们与DNA的结合,从而实现光对植物生长发育的调控。研究发现PIFs在调控种子萌发、幼苗形态建成、避荫反应、昼夜节律以及各种植物激素响应过程中起着重要作用。此外,PIFs作为细胞信号传导的“枢纽”具有更为广泛的作用,能够整合不同信号,精细调控整个转录网络。

  16. Mid-infrared picosecond pump-dump-probe and pump-repump-probe experiments to resolve a ground-state intermediate in cyanobacterial phytochrome Cph1.

    Science.gov (United States)

    van Wilderen, Luuk J G W; Clark, Ian P; Towrie, Michael; van Thor, Jasper J

    2009-12-24

    Multipulse picosecond mid-infrared spectroscopy has been used to study photochemical reactions of the cyanobacterial phytochrome photoreceptor Cph1. Different photophysical schemes have been discussed in the literature to describe the pathways after photoexcitation, particularly, to identify reaction phases that are linked to photoisomerisation and electronic decay in the 1566-1772 cm(-1) region that probes C=C and C=O stretching modes of the tetrapyrrole chromophore. Here, multipulse spectroscopy is employed, where, compared to conventional visible pump-mid-infrared probe spectroscopy, an additional visible pulse is incorporated that interacts with populations that are evolving on the excited- and ground-state potential energy surfaces. The time delays between the pump and the dump pulse are chosen such that the dump pulse interacts with different phases in the reaction process. The pump and dump pulses are at the same wavelength, 640 nm, and are resonant with the Pr ground state as well as with the excited state and intermediates. Because the dump pulse additionally pumps the remaining, partially recovered, and partially oriented ground-state population, theory is developed for estimating the fraction of excited-state molecules. The calculations take into account the model-dependent ground-state recovery fraction, the angular dependence of the population transfer resulting from the finite bleach that occurs with linearly polarized intense femtosecond optical excitation, and the partially oriented population for the dump field. Distinct differences between the results from the experiments that use a 1 or a 14 ps dump time favor a branching evolution from S1 to an excited state or reconfigured chromophore and to a newly identified ground-state intermediate (GSI). Optical dumping at 1 ps shows the instantaneous induced absorption of a delocalized C=C stretching mode at 1608 cm(-1), where the increased cross section is associated with the electronic ground

  17. Sorghum phytochrome B inhibits flowering in long days by activating expression of SbPRR37 and SbGHD7, repressors of SbEHD1, SbCN8 and SbCN12.

    Directory of Open Access Journals (Sweden)

    Shanshan Yang

    Full Text Available Light signaling by phytochrome B in long days inhibits flowering in sorghum by increasing expression of the long day floral repressors PSEUDORESPONSE REGULATOR PROTEIN (SbPRR37, Ma1 and GRAIN NUMBER, PLANT HEIGHT AND HEADING DATE 7 (SbGHD7, Ma6. SbPRR37 and SbGHD7 RNA abundance peaks in the morning and in the evening of long days through coordinate regulation by light and output from the circadian clock. 58 M, a phytochrome B deficient (phyB-1, ma3R genotype, flowered ∼60 days earlier than 100 M (PHYB, Ma3 in long days and ∼11 days earlier in short days. Populations derived from 58 M (Ma1, ma3R, Ma5, ma6 and R.07007 (Ma1, Ma3, ma5, Ma6 varied in flowering time due to QTL aligned to PHYB/phyB-1 (Ma3, Ma5, and GHD7/ghd7-1 (Ma6. PHYC was proposed as a candidate gene for Ma5 based on alignment and allelic variation. PHYB and Ma5 (PHYC were epistatic to Ma1 and Ma6 and progeny recessive for either gene flowered early in long days. Light signaling mediated by PhyB was required for high expression of the floral repressors SbPRR37 and SbGHD7 during the evening of long days. In 100 M (PHYB the floral activators SbEHD1, SbCN8 and SbCN12 were repressed in long days and de-repressed in short days. In 58 M (phyB-1 these genes were highly expressed in long and short days. Furthermore, SbCN15, the ortholog of rice Hd3a (FT, is expressed at low levels in 100 M but at high levels in 58 M (phyB-1 regardless of day length, indicating that PhyB regulation of SbCN15 expression may modify flowering time in a photoperiod-insensitive manner.

  18. Ectopic expression of a phytochrome B gene from Chinese cabbage (Brassica rapa L. ssp. pekinensis) in Arabidopsis thaliana promotes seedling de-etiolation, dwarfing in mature plants, and delayed flowering.

    Science.gov (United States)

    Song, Mei-Fang; Zhang, Shu; Hou, Pei; Shang, Hong-Zhong; Gu, Hai-Ke; Li, Jing-Juan; Xiao, Yang; Guo, Lin; Su, Liang; Gao, Jian-Wei; Yang, Jian-Ping

    2015-04-01

    Phytochrome B (phyB) is an essential red light receptor that predominantly mediates seedling de-etiolation, shade-avoidance response, and flowering time. In this study, we isolate a full-length cDNA of PHYB, designated BrPHYB, from Chinese cabbage (Brassica rapa L. ssp. pekinensis), and we find that BrphyB protein has high amino acid sequence similarity and the closest evolutionary relationship to Arabidopsis thaliana phyB (i.e., AtphyB). Quantitative reverse transcription (RT)-PCR results indicate that the BrPHYB gene is ubiquitously expressed in different tissues under all light conditions. Constitutive expression of the BrPHYB gene in A. thaliana significantly enhances seedling de-etiolation under red- and white-light conditions, and causes dwarf stature in mature plants. Unexpectedly, overexpression of BrPHYB in transgenic A. thaliana resulted in reduced expression of gibberellins biosynthesis genes and delayed flowering under short-day conditions, whereas AtPHYB overexpression caused enhanced expression of FLOWERING LOCUS T and earlier flowering. Our results suggest that BrphyB might play an important role in regulating the development of Chinese cabbage. BrphyB and AtphyB have conserved functions during de-etiolation and vegetative plant growth and divergent functions in the regulation of flowering time.

  19. The molecular mechanisms of phytochrome interacting factors (PIFs) in phy-tohormone signaling transduction%光敏色素作用因子PIFs参与植物激素信号转导的分子机制

    Institute of Scientific and Technical Information of China (English)

    任小芸; 吴美琴; 陈建民; 张冬平; 高勇

    2016-01-01

    Phytochrome interacting factors (PIFs) belonging to basic helix-loop-helix (bHLH) transcription fac-tors family, play an important role in plant growth and development. As the hubs of signal network in plant, PIFs integrate multiple plant hormone signals to regulate the transcriptional network. Existing research shows that PIFs can not only affect the synthesis of GA, ABA and IAA, but also regulate signal transmission of GA, BR, JA, IAA, ABA and ethylene. This review summarizes the research progress of function of PIFs in plant homone, and provides help for the further study of PIFs.%光敏色素作用因子(PIFs)属于bHLH 转录因子家族,在植物的生长发育中起到重要调节作用。作为一个关键的胞内信号调控组分, PIFs扮演着整合不同激素信号通路“枢纽”的角色。现有研究表明, PIFs能影响GA、ABA、IAA等激素的合成,调控GA、BR、JA、IAA、ABA、乙烯等激素的信号传递。本文重点阐述PIFs在植物激素信号中调控功能的研究进展,以期为进一步探索PIFs的功能及机制提供帮助。

  20. Pump-dump-probe and pump-repump-probe ultrafast spectroscopy resolves cross section of an early ground state intermediate and stimulated emission in the photoreactions of the Pr ground state of the cyanobacterial phytochrome Cph1.

    Science.gov (United States)

    Fitzpatrick, Ann E; Lincoln, Craig N; van Wilderen, Luuk J G W; van Thor, Jasper J

    2012-01-26

    The primary photoreactions of the red absorbing ground state (Pr) of the cyanobacterial phytochrome Cph1 from Synechocystis PCC 6803 involve C15═C16 Z-E photoisomerization of its phycocyanobilin chromophore. The first observable product intermediate in pump-probe measurements of the photocycle, "Lumi-R", is formed with picosecond kinetics and involves excited state decay reactions that have 3 and 14 ps time constants. Here, we have studied the photochemical formation of the Lumi-R intermediate using multipulse picosecond visible spectroscopy. Pump-dump-probe (PDP) and pump-repump-probe (PRP) experiments were carried out by employing two femtosecond visible pulses with 1, 14, and 160 ps delays, together with a broadband dispersive visible probe. The time delays between the two excitation pulses have been selected to allow interaction with the dominant (3 and 14 ps) kinetic phases of Lumi-R formation. The frequency dependence of the PDP and PRP amplitudes was investigated at 620, 640, 660, and 680 nm, covering excited state absorption (λ(max) = 620 nm), ground state absorption (λ(max) = 660 nm), and stimulated emission (λ(max) = 680 nm) cross sections. Experimental double difference transient absorbance signals (ΔΔOD), from the PDP and PRP measurements, required corrections to remove contributions from ground state repumping. The sensitivity of the resulting ΔΔOD signals was systematically investigated for possible connectivity schemes and photochemical parameters. When applying a homogeneous (sequentially decaying) connectivity scheme in both the 3 and 14 ps kinetic phases, evidence for repumping of an intermediate that has an electronic ground state configuration (GSI) is taken from the dump-induced S1 formation with 620, 640, and 660 nm wavelengths and 1 and 14 ps repump delays. Evidence for repumping a GSI is also seen, for the same excitation wavelengths, when imposing a target connectivity scheme proposed in the literature for the 1 ps repump delay. In

  1. 光敏色素B介导光信号影响水稻的脱落酸途径%Light signals mediated by phytochrome B affect abscisic acid pathway in rice

    Institute of Scientific and Technical Information of China (English)

    顾建伟; 张方; 赵杰; 周晋军; 钱凤芹; 闫丽华; 臧新; 谢先芝

    2012-01-01

    Several evidences revealed the interaction between phytochrome-mediated light signals and plant hormones abscisic acid (ABA) pathway in Arabidopsis. However, interaction between ABA signaling and phytochrome-mediated light signaling in mediating rice growth and development remain unclear. In the present study, we analyzed effects of P/nB-mediated light signals on ABA metabolism and ABA responses using rice wild type (WT) and the phyB mutant. It was observed that transcript levels of ABA biosynthetic genes (including OsNCEDl, 0sNCED2, OsNCED3 and 0sNCED4) were higher in the phyB mutant than those in WT, whereas transcript level of ABA deactivating gene OsABA8OXl was lower in the phyB mutant than that in WT, which probably contributed to the relatively high ABA content in the phyB mutant. ABA treatment inhibited germination of rice seeds grown either in the dark or under light. However, inhibitory effects of ABA treatment on seed germination were more obvious in phyB mutants relative to that in WT when seeds were grown under light conditions, suggesting that PhyB-mediated light signals attenuated the inhibitory effects triggered by ABA. Meantime, we compared the expression patterns of genes related to seed germination in WT and the phyB mutant grown in the medium with or without ABA. It was deduced that these genes is unlikely to contribute for the promotive effects of phyB-mediated light signals on seed germination. In addition, ABA treatment inhibited growth of both above-ground part and seminal root in rice seedlings. PhyB-mediated light signals did not affect the ABA-induced inhibition of above-ground part growth, but negatively regulate the inhibition of root growth. Taken together, our results suggest that PhyB-mediated light signals negatively regulate ABA accumulation and ABA responses in rice. This work reveals the influence of PhyB-mediated light signals on ABA pathway, which lays the foundation for dissecting the molecular mechanism of coordinated

  2. Blue Rhythms Between GIGANTEA and Phytochromes

    National Research Council Canada - National Science Library

    María Crepy; Jorge J. Casal; Marcelo J. Yanovsky

    2007-01-01

    GIGANTEA (GI) is involved in the promotion of flowering by long days, in light input to the circadian clock, and in seedling de-etiolation under continuous red light or blue light but not under continuous far-red light (FR...

  3. Leaf senescence in alstroemeria: regulation by phytochrome gibberellins and cytokinins.

    NARCIS (Netherlands)

    Kappers, I.

    1998-01-01

    Leaf senescence in plants is a regulated process influenced by light as well as phytohormones. In the present study the putative role of the phytohormones cytokinins and gibberellins as mediators for the light signal on leaf senescence in alstroemeria was studied. It was found that low photon fluenc

  4. New proposal of classification of seeds based on forms of phytochrome instead of photoblastism

    OpenAIRE

    Takaki,Massanori

    2001-01-01

    Propomos no presente trabalho a classificação das sementes em relação às formas do fitocromo em vez de fotoblastimo. Com base nos dados publicados podemos afirmar que todas as sementes contém fitocromo e o termo fotoblastismo deve ser substituído pelas formas do fitocromo que controlam a germinação. 1. Sementes fotoblásticas positivas tem fiB (e, em menor extensão, fiD e fiE) controlando o processo de germinação através da resposta de fluência baixa (RFB); 2. Sementes fotoblásticas negativas ...

  5. Phytochrome mediates red-light-based positive phototropism in Arabidopsis roots

    Science.gov (United States)

    Correll, M.; Mullen, J.; Hangarter, R.; Kiss, J.

    Plants rely on sophisticated mechanisms to interpret the constant bombardment of incoming signals so they can adjust their growth accordingly. The environmental cues of gravity and light are particularly important for plant growth and development. While gravitropism has been extensively studied in roots, there has been increased emphasis on understanding the cellular and molecular basis of root phototropism. In addition to the blue-light-based negative phototropism, roots also exhibit a recently discovered positive phototropism in response to red light. In this paper, we characterize this red-light-based phototropism in roots of Arabidopsis.

  6. Effects of light and phytochrome in heterotrophic growth of Lemna minor L

    NARCIS (Netherlands)

    Rombach, J.

    1976-01-01

    Axenic cultures of Lemna minor L. were grown on a medium containing sugars and amino acids. In continuous darkness the growth rate was one-tenth of the maximum in continuous light. In darkness early death revealed a thiamine deficiency; this deficiency was counteracted, without increasing the multi

  7. Role of CBFs as Integrators of Chloroplast Redox, Phytochrome and Plant Hormone Signaling during Cold Acclimation

    Directory of Open Access Journals (Sweden)

    Norman P. A. Hüner

    2013-06-01

    Full Text Available Cold acclimation of winter cereals and other winter hardy species is a prerequisite to increase subsequent freezing tolerance. Low temperatures upregulate the expression of C-repeat/dehydration-responsive element binding transcription factors (CBF/DREB1 which in turn induce the expression of COLD-REGULATED (COR genes. We summarize evidence which indicates that the integration of these interactions is responsible for the dwarf phenotype and enhanced photosynthetic performance associated with cold-acclimated and CBF-overexpressing plants. Plants overexpressing CBFs but grown at warm temperatures mimic the cold-tolerant, dwarf, compact phenotype; increased photosynthetic performance; and biomass accumulation typically associated with cold-acclimated plants. In this review, we propose a model whereby the cold acclimation signal is perceived by plants through an integration of low temperature and changes in light intensity, as well as changes in light quality. Such integration leads to the activation of the CBF-regulon and subsequent upregulation of COR gene and GA 2-oxidase (GA2ox expression which results in a dwarf phenotype coupled with increased freezing tolerance and enhanced photosynthetic performance. We conclude that, due to their photoautotrophic nature, plants do not rely on a single low temperature sensor, but integrate changes in light intensity, light quality, and membrane viscosity in order to establish the cold-acclimated state. CBFs appear to act as master regulators of these interconnecting sensing/signaling pathways.

  8. The germination of seeds of Epiphyllum phyllanthus (L.) Haw. (Cactaceae) is controlled by phytochrome and by nonphytochrome related process

    OpenAIRE

    Simão, Edson [UNESP; Nakamura, Adriana Tiemi [UNESP; Takaki,Massanori

    2010-01-01

    As sementes de Epiphyllum phyllanthus apresentam alta sensibilidade à luz e a sua germinação pode ser promovida pela luz verde de segurança por meio da resposta de fluência muito baixa mediada pelo fitocromo A. Parte da população de sementes tem fitocromo B na forma ativa (Fve) suficiente para promover a germinação no escuro. Sementes de Epiphyllum phyllanthus germinam em uma ampla faixa de temperatura de 10 a 40°C, atingindo germinação completa na faixa de 15 a 30°C. Acima de 35°C a velocida...

  9. First steps in the phytochrome phototransformation: a comparative femtosecond study on the forward (Pr --> Pfr) and back reaction (Pfr --> Pr).

    Science.gov (United States)

    Bischoff, M; Hermann, G; Rentsch, S; Strehlow, D

    2001-01-09

    The primary light-induced events in the reversible Pr right harpoon over left harpoon Pfr phototransformation are investigated by femtosecond absorption spectroscopy using a pump-probe technique. After the selective electronic excitation of Pr and Pfr with pulses at 610 and 730 nm, respectively, the transient absorption spectra were measured as a function of the delay time and subjected to a global fit analysis. As a result of this analysis, the decay-associated spectra of the kinetic components involved in the formation of the first photoproducts in the forward and back reaction are obtained. These spectra provide a more detailed understanding of the primary stages in the light-induced transformations. In addition, the influence of the solvent viscosity on the initial reaction steps was studied. In each direction of reaction, a short-lifetime component is found to be strongly viscosity-dependent, indicating that the primary photochemistry encompasses intramolecular motions of the chromophore or its proximal amino acid side chains. H-D exchange has no significant effect on the kinetics of the initial photoprocesses. This suggests that the isomerization reaction in both directions is not accompanied by a rate-limiting proton transfer.

  10. Phytochrome and Seed Germination. III. Action of Prolonged Far Red Irradiation on the Germination of Tomato and Cucumber Seeds.

    Science.gov (United States)

    Yaniv, Z; Mancinelli, A L; Smith, P

    1967-11-01

    Prolonged irradiation with continuous or intermittent far red prevents the germination of tomato and cucumber seeds. The inhibitory efficiency of intermittent far red decreases with the lengthening of the interval between successive irradiations, and with the increase of temperature. If each far red irradiation is followed by red, germination is restored. Intermittent far red is less inhibitory than intermittent red-far red when red is given immediately before each far red. This effect is more evident when the interval between successive irradiation becomes longer.

  11. Genetic Dissection of Morphometric Traits Reveals that Phytochrome B Affects Nucleus Size and Heterochromatin Organization in Arabidopsis thaliana

    NARCIS (Netherlands)

    Snoek, L.B.; Pavlova, P.; Tessadori, F.; Fransz, P.F.; Zanten, van M.; Peeters, A.J.M.; Bourbousse, Clara; Barneche, Fredy; Jong, de J.H.S.G.M.; Fransz, Paul; Zanten, van M.

    2017-01-01

    Microscopically visible chromatin is partitioned into two major components in Arabidopsis thaliana nuclei. Chromocenters on one hand are conspicuous foci of highly condensed 'heterochromatic' domains that contain mostly repeated sequences. On the other hand, less condensed and gene-rich

  12. Phytochrome Signaling in Green Arabidopsis Seedlings: Impact Assessment of a Mutually Negative phyB-PIF Feedback Loop

    Institute of Scientific and Technical Information of China (English)

    Pablo Leivar; Elena Monte; Megan M. Cohn; Peter H. Quail

    2012-01-01

    The reversibly red (R)/far-red (FR)-Iight-responsive phytoch rome (phy) photosensory system initiates both the deetiolation process in dark-germinated seedlings upon first exposure to light,and the shade-avoidance process in fully deetiolated seedlings upon exposure to vegetational shade.The intracellular signaling pathway from the light-activated photoreceptor conformer (Pfr) to the transcriptional network that drives these responses involves direct,physical interaction of Pfr with a small subfamily of bHLH transcription factors,termed Phy-lnteracting Factors (PIFs),which induces rapid PIF proteolytic degradation.In addition,there is evidence of further complexity in light-grown seedlings,whereby phyB-PIF interaction reciprocally induces phyB degradation,in a mutually-negative,feedback-loop configuration.Here,to assess the relative contributions of these antagonistic activities to the net phenotypic readout in light-grown seedlings,we have examined the magnitude of the light- and simulated-shade-induced responses of a pentuple phyBpif1pif3pif4pif5 (phyBpifq) mutant and various multiple pif-mutant combinations.The data (1) reaffirm that phyB is the predominant,if not exclusive,photoreceptor imposing the inhibition of hypocotyl elongation in deetiolating seedlings in response to prolonged continuous R irradiation and (2) show that the PIF quartet (PIF1,PIF3,PIF4,and PIF5) retain and exert a dual capacity to modulate hypocotyl elongation under these conditions,by concomitantly promoting cell elongation through intrinsic transcriptional-regulatory activity,and reducing phyB-inhibitory capacity through feedback-loop-induced phyB degradation.In shade-exposed seedlings,immunoblot analysis shows that the shade-imposed reduction in Pfr levels induces increases in the abundance of PIF3,and mutant analysis indicates that PIF3 acts,in conjunction with PIF4 and PIF5,to promote the known shade-induced acceleration of hypocotyl elongation.Conversely,although the quadruple pifq mutant displays clearly reduced hypocotyl elongation compared to wild-type in response to prolonged shade,immunoblot analysis detects no elevation in phyB levels in the mutant seedlings compared to the wild-type during the majority of the shade-induced growth period,and phyB levels are not robustly correlated with the growth phenotype across the pif-mutant combinations compared.These results suggest that PIF feedback modulation of phyB abundance does not play a dominant role in modulating the magnitude of the PIF-promoted,shade-responsive phenotype under these conditions.In seedlings grown under diurnal light-dark cycles,the data show that FR-pulse-induced removal of Pfr at the beginning of the dark period (End-of-Day-FR (EOD-FR) treatment) results in longer hypocotyls relative to no EOD-FR treatment and that this effect is attenuated in the pif-mutant combinations tested.This result similarly indicates that the PIF quartet members are capable of intrinsically promoting hypocotyl cell elongation in light-grown plants,independently of the effects of PIF feedback modulation of photoactivated-phyB abundance.

  13. Anatomia foliar de microtomateiros fitocromo-mutantes e ultra-estrutura de cloroplastos Leaf anatomy of micro-tomato phytochrome-mutants and chloroplast ultra-structure

    OpenAIRE

    Hyrandir Cabral de Melo; Evaristo Mauro de Castro; Eduardo Alves; Fabiano José Perina

    2011-01-01

    Plantas fitocromo-mutantes têm sido utilizadas com o intuito de caracterizar isoladamente, dentre os demais fotorreceptores, a ação dos fitocromos sobre eventos ligados à fotomorfogênese. Raros são os estudos que relatam a ação dos fitocromos sobre aspectos estruturais, embora sejam fundamentais à compreensão do desenvolvimento das plantas. Neste trabalho, objetivou-se analisar características ultraestruturais de cloroplastos e aspectos anatômicos foliares dos microtomateiros (Solanum lycoper...

  14. Características fisiológicas de microtomateiros fitocromo-mutantes Physiological characteristics of micro-tomato (Lycopersicon esculentum P. Miller) phytochrome-mutants

    National Research Council Canada - National Science Library

    Hyrandir Cabral de Melo; Evaristo Mauro de Castro; Ângela Maria Soares; Cynthia de Oliveira; Sílvio Júnio Ramos

    2009-01-01

    ... (Lycopersicon esculentum P. Miller cv. Micro-Tom) fitocromo-mutantes. A cultivar Micro-Tom e os mutantes aurea (deficiente na biossíntese do cromóforo dos fitocromos), atroviolacea (atv) e high pigment1 (hp1...

  15. Functional Genomic Analysis of the HY2 Family of Ferredoxin-Dependent Bilin Reductases from Oxygenic Photosynthetic Organisms

    National Research Council Canada - National Science Library

    Nicole Frankenberg; Keiko Mukougawa; Takayuki Kohchi; J. Clark Lagarias

    2001-01-01

    Phytobilins are linear tetrapyrrole precursors of the light-harvesting prosthetic groups of the phytochrome photoreceptors of plants and the phycobiliprotein photosynthetic antennae of cyanobacteria...

  16. Photo-biotechnology as a tool to improve agronomic traits in crops.

    Science.gov (United States)

    Gururani, Mayank Anand; Ganesan, Markkandan; Song, Pill-Soon

    2015-01-01

    Phytochromes are photosensory phosphoproteins with crucial roles in plant developmental responses to light. Functional studies of individual phytochromes have revealed their distinct roles in the plant's life cycle. Given the importance of phytochromes in key plant developmental processes, genetically manipulating phytochrome expression offers a promising approach to crop improvement. Photo-biotechnology refers to the transgenic expression of phytochrome transgenes or variants of such transgenes. Several studies have indicated that crop cultivars can be improved by modulating the expression of phytochrome genes. The improved traits include enhanced yield, improved grass quality, shade-tolerance, and stress resistance. In this review, we discuss the transgenic expression of phytochrome A and its hyperactive mutant (Ser599Ala-PhyA) in selected crops, such as Zoysia japonica (Japanese lawn grass), Agrostis stolonifera (creeping bentgrass), Oryza sativa (rice), Solanum tuberosum (potato), and Ipomea batatas (sweet potato). The transgenic expression of PhyA and its mutant in various plant species imparts biotechnologically useful traits. Here, we highlight recent advances in the field of photo-biotechnology and review the results of studies in which phytochromes or variants of phytochromes were transgenically expressed in various plant species. We conclude that photo-biotechnology offers an excellent platform for developing crops with improved properties. Copyright © 2014 Elsevier Inc. All rights reserved.

  17. Plant Respiration and Lipid Metabolism

    DEFF Research Database (Denmark)

    Sunlight has replaced the two Fifth-Edition chapters on Phytochrome and Blue Light Responses. This chapter includes phytochrome, as well as the blue and UV light receptors and their signaling pathways, including phototropins, cryptochromes, and UVR8. The subsequent chapters in Unit III are devoted...

  18. Picosecond spectroscopy of dihydro biliverdin

    Science.gov (United States)

    Ditto, Manfred; Brunner, Harald; Lippitsch, Max E.

    1991-10-01

    Picosecond time-resolved fluorescence and absorption spectroscopy was performed on dihydro biliverdin, a model for the chromophore in the plant pigment phytochrome, a chromoprotein governing plant growth. Close agreement between the model compound and the native chromophore proves the importance of the saturated pyrrol ring for the decay kinetics and renders chromophore protonation in phytochrome unlikely.

  19. Main: REBETALGLHCB21 [PLACE

    Lifescience Database Archive (English)

    Full Text Available REBETALGLHCB21 S000363 16-Feb-2001 (last modified) seki REbeta found in Lemna gibba...am could replace the function of REbeta; Required for phytochrome regulation; See S000362; REalpha; Lhcb21; phytochrome; REbeta; Lemna gibba CGGATA ...

  20. Light-induced structural changes in a monomeric bacteriophytochrome

    Directory of Open Access Journals (Sweden)

    Heikki Takala

    2016-09-01

    Full Text Available Phytochromes sense red light in plants and various microorganism. Light absorption causes structural changes within the protein, which alter its biochemical activity. Bacterial phytochromes are dimeric proteins, but the functional relevance of this arrangement remains unclear. Here, we use time-resolved X-ray scattering to reveal the solution structural change of a monomeric variant of the photosensory core module of the phytochrome from Deinococcus radiodurans. The data reveal two motions, a bend and a twist of the PHY domain with respect to the chromophore-binding domains. Infrared spectroscopy shows the refolding of the PHY tongue. We conclude that a monomer of the phytochrome photosensory core is sufficient to perform the light-induced structural changes. This implies that allosteric cooperation with the other monomer is not needed for structural activation. The dimeric arrangement may instead be intrinsic to the biochemical output domains of bacterial phytochromes.

  1. Photoreceptor effects on plant biomass, resource allocation, and metabolic state.

    Science.gov (United States)

    Yang, Deyue; Seaton, Daniel D; Krahmer, Johanna; Halliday, Karen J

    2016-07-05

    Plants sense the light environment through an ensemble of photoreceptors. Members of the phytochrome class of light receptors are known to play a critical role in seedling establishment, and are among the best-characterized plant signaling components. Phytochromes also regulate adult plant growth; however, our knowledge of this process is rather fragmented. This study demonstrates that phytochrome controls carbon allocation and biomass production in the developing plant. Phytochrome mutants have a reduced CO2 uptake, yet overaccumulate daytime sucrose and starch. This finding suggests that even though carbon fixation is impeded, the available carbon resources are not fully used for growth during the day. Supporting this notion, phytochrome depletion alters the proportion of day:night growth. In addition, phytochrome loss leads to sizeable reductions in overall growth, dry weight, total protein levels, and the expression of CELLULOSE SYNTHASE-LIKE genes. Because cellulose and protein are major constituents of plant biomass, our data point to an important role for phytochrome in regulating these fundamental components of plant productivity. We show that phytochrome loss impacts core metabolism, leading to elevated levels of tricarboxylic acid cycle intermediates, amino acids, sugar derivatives, and notably the stress metabolites proline and raffinose. Furthermore, the already growth-retarded phytochrome mutants are less responsive to growth-inhibiting abiotic stresses and have elevated expression of stress marker genes. This coordinated response appears to divert resources from energetically costly biomass production to improve resilience. In nature, this strategy may be activated in phytochrome-disabling, vegetation-dense habitats to enhance survival in potentially resource-limiting conditions.

  2. Mobilization of storage materials during light-induced germination of tomato (Solanum lycopersicum) seeds.

    Science.gov (United States)

    Eckstein, Aleksandra; Jagiełło-Flasińska, Dominika; Lewandowska, Aleksandra; Hermanowicz, Paweł; Appenroth, Klaus-J; Gabryś, Halina

    2016-08-01

    The aim of this study was to analyze the metabolism of storage materials in germinating tomato (Solanum lycopersicum) seeds and to determine whether it is regulated by light via phytochromes. Wild type, single and multiple phytochrome A, B1 and B2 mutants were investigated. Imbibed seeds were briefly irradiated with far-red or far-red followed by red light, and germinated in darkness. Triacylglycerols and starch were quantified using biochemical assays in germinating seeds and seedlings during the first 5 days of growth. To investigate the process of fat-carbohydrate transformation, the activity of the glyoxylate cycle was assessed. Our results confirm the role of phytochrome in the control of tomato seed germination. Phytochromes A and B2 were shown to play specific roles, acting antagonistically in far-red light. While the breakdown of triacylglycerols proceeded independently of light, phytochrome control was visible in the next stages of the lipid-carbohydrate transformation. The key enzymes of the glyoxylate cycle, isocitrate lyase and malate synthase, were regulated by phytochrome(s). This was reflected in a greater increase of starch content during seedling growth in response to additional red light treatment. This study is the first attempt to build a comprehensive image of storage material metabolism regulation by light in germinating dicotyledonous seeds. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

  3. 2396-IJBCS-Article-Gideon Olarewaju Okunlola (Enregistré ...

    African Journals Online (AJOL)

    hp

    Keywords: Tomato, crop, morphology, biomass, Leaf area, physiology. INTRODUCTION. Any change in ..... This will result to lower photosynthetic activity in the affected leaves. ... sensitive phytochrome pigments (chlorophyll pigmentation) that ...

  4. Reference: 707 [Arabidopsis Phenome Database[Archive

    Lifescience Database Archive (English)

    Full Text Available hibiting elongation. Although these effects seem to be partially caused via the r...chromes. Our current results therefore indicate that the phytochromes and cryptochromes have at least two effects

  5. Quantum simulations of materials and biological systems

    CERN Document Server

    Zeng, Jun; Treutlein, Herbert

    2012-01-01

    This book details applications of DFT methods to large materials and biological systems, such optical and electronic properties of nanoparticles, X-ray structure refinement of proteins, the catalytic process of enzymes and photochemistry of phytochromes.

  6. Study of light signal receptor of Stephanopyxis palmeriana during sexual reproduction

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    We collected centric diatom Stephanopyxis palmeriana samples in coastal waters of Xiamen for characteristic red light/far red light (R/FR) phytochrome reactions to identify its photoreceptor in the course of sexual reproduction. The result showed that pre-illumination of 2-3h red light before darkness could induce sexualization of S.palmeriana, while the follow-up illumination of far red light could reverse the effect of red light, which is a featured reaction of phytochrome. The Southern Dot Blot was carried out to identify the type of phytochrome that induces the sexualization. The result also showed high homogeneity of DNA fragment of S. palmeriana with phyB, but phyA. This means the photoreceptor in the process of sexual reproduction of S. palmeriana is phytochrome B (phyB).

  7. Main: DE1PSPRA2 [PLACE

    Lifescience Database Archive (English)

    Full Text Available DE1PSPRA2 S000379 21-May-2001 (last modified) uchi DE1 found in the pea(P.S) pra2 gene pr...omoter; Involved in pra2 down-regulation by phytochrome A, phytochrome B and blue-light photoreceptors; pr... to two types of DNA sequences, DE1 and GT2; pra2; light response; dark induction; down regulation; DF1; pea (Pisum sativum) GGATTTTACAGT ...

  8. Protein identification and mRNA analysis of phyto- chrome-regulated genes in Arabidopsis under red light

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Phytochromes are a family of plant photoreceptors that mediate physiological and developmental re- sponses to red and far-red light. According to the affymetrix ATH1 microarray, phytochrome A (phyA) and phytochrome B (phyB) together play a key role in transducing the Rc signals to light-responsive genes. In order to select those red light-responsive genes associated with phyA or phyB, a proteomic approach based on two-dimensional gel electrophoresis (2-DE) was used to compare the protein ex- pression patterns of the phyAphyB double mutant and the wild type of Arabidopsis thaliana (col-4) which grew under constant red light conditions for 7 d. Thirty-two protein spots which exhibited dif- ferences in protein abundance were identified by matrix-assisted laser desorption/ionization-time of flight/time of flight mass spectrometry. The expression of ten genes corresponding to ten protein spots was analyzed by a semiquantitative reverse transcription-polymerase chain reaction. Two of the ten genes were confirmed by quantitative PCR (Q-PCR). The results showed that phytochromes may exert their function by regulating mRNA or protein expressions. Proteomic analysis may provide a novel pathway for identifying phytochrome-dependent genes.

  9. Protein identification and mRNA analysis of phyto-chrome-regulated genes in Arabidopsis under red light

    Institute of Scientific and Technical Information of China (English)

    LI Xu; YANG YueJun; LI Yan; WANG Jie; XIAO XiaoJuan; GUO XinHong; TANG DongYing; LIU XuanMing

    2009-01-01

    Phytochromes are a family of plant photoreceptors that mediate physiological and developmental re-sponses to red and far-red light. According to the affymetrix ATH1 microarray, phytochrome A (phyA)and phytochrome B (phyB) together play a key role in transducing the Rc signals to light-responsive genes. In order to select those red light-responsive genes associated with phyA or phyB, a proteomic approach based on two-dimensional gel electrophoresis (2-DE) was used to compare the protein ex-pression patterns of the phyAphyB double mutant and the wild type of Arabidopsis thaliana (col-4)which grew under constant red light conditions for 7 d. Thirty-two protein spots which exhibited dif-ferences in protein abundance were identified by matrix-assisted laser desorption/ionization-time of flight/time of flight mass spectrometry. The expression of ten genes corresponding to ten protein spots was analyzed by a semiquantitative reverse transcription-polymerase chain reaction. Two of the ten genes were confirmed by quantitative PCR (Q-PCR). The results showed that phytochromes may exert their function by regulating mRNA or protein expressions. Proteomic analysis may provide a novel pathway for identifying phytochrome-dependent genes.

  10. History and applications in controlled environments

    Science.gov (United States)

    Downs, R. J.

    1994-01-01

    The widespread application of electric (often called artificial) light in greenhouses, growing rooms, and plant growth chambers would presuppose that the role of phytochrome would be considered in the selection and use of such lighting systems. Unfortunately this is not usually the case. Part of the problem is that many students, and indeed an unfortunate number of senior scientists, seem to regard phytochrome as a laboratory phenomenon without much application in the real world. They simply have not grasped the concept that phytochrome is functioning through all stages of plant development, wherever plants are grown. It is certainly true, as Meijer (1971) stated, that one cannot compare experimental results obtained under very strict laboratory conditions with plant irradiation in glasshouses and in growth rooms. When Karl Norris developed the first practical portable spectroradiometer about 1962, some of the first measurements were to determine the red/far-red ratios under tree canopies. These measurements showed clearly the predominance of far-red in the understory and suggested that far-red was contributing to the elongation exhibited by many species growing in the shade, and possibly was a factor in the induction of light requirements in seeds. Subsequently we used Catalpa leaves as far-red filters to make light-insensitive lettuce seed light requiring. Much more detailed work has since been done on phytochrome effects in the natural environment, and it is encouraging to note that efforts are bring made to apply phytochrome research to horticulture.

  11. Ethylene Signaling Influences Light-Regulated Development in Pea.

    Science.gov (United States)

    Weller, James L; Foo, Eloise M; Hecht, Valérie; Ridge, Stephen; Vander Schoor, Jacqueline K; Reid, James B

    2015-09-01

    Plant responses to light involve a complex network of interactions among multiple plant hormones. In a screen for mutants showing altered photomorphogenesis under red light, we identified a mutant with dramatically enhanced leaf expansion and delayed petal senescence. We show that this mutant exhibits reduced sensitivity to ethylene and carries a nonsense mutation in the single pea (Pisum sativum) ortholog of the ethylene signaling gene ETHYLENE INSENSITIVE2 (EIN2). Consistent with this observation, the ein2 mutation rescues the previously described effects of ethylene overproduction in mature phytochrome-deficient plants. In seedlings, ein2 confers a marked increase in leaf expansion under monochromatic red, far-red, or blue light, and interaction with phytochromeA, phytochromeB, and long1 mutants confirms that ein2 enhances both phytochrome- and cryptochrome-dependent responses in a LONG1-dependent manner. In contrast, minimal effects of ein2 on seedling development in darkness or high-irradiance white light show that ethylene is not limiting for development under these conditions. These results indicate that ethylene signaling constrains leaf expansion during deetiolation in pea and provide further evidence that down-regulation of ethylene production may be an important component mechanism in the broader control of photomorphogenic development by phytochrome and cryptochrome.

  12. Unusual Spectral Properties of Bacteriophytochrome Agp2 Result from a Deprotonation of the Chromophore in the Red-absorbing Form Pr*

    Science.gov (United States)

    Zienicke, Benjamin; Molina, Isabel; Glenz, René; Singer, Patrick; Ehmer, Dorothee; Escobar, Francisco Velazquez; Hildebrandt, Peter; Diller, Rolf; Lamparter, Tilman

    2013-01-01

    Phytochromes are widely distributed photoreceptors with a bilin chromophore that undergo a typical reversible photoconversion between the two spectrally different forms, Pr and Pfr. The phytochrome Agp2 from Agrobacterium tumefaciens belongs to the group of bathy phytochromes that have a Pfr ground state as a result of the Pr to Pfr dark conversion. Agp2 has untypical spectral properties in the Pr form reminiscent of a deprotonated chromophore as confirmed by resonance Raman spectroscopy. UV/visible absorption spectroscopy showed that the pKa is >11 in the Pfr form and ∼7.6 in the Pr form. Unlike other phytochromes, photoconversion thus results in a pKa shift of more than 3 units. The Pr/Pfr ratio after saturating irradiation with monochromatic light is strongly pH-dependent. This is partially due to a back-reaction of the deprotonated Pr chromophore at pH 9 after photoexcitation as found by flash photolysis. The chromophore protonation and dark conversion were affected by domain swapping and site-directed mutagenesis. A replacement of the PAS or GAF domain by the respective domain of the prototypical phytochrome Agp1 resulted in a protonated Pr chromophore; the GAF domain replacement afforded an inversion of the dark conversion. A reversion was also obtained with the triple mutant N12S/Q190L/H248Q, whereas each single point mutant is characterized by decelerated Pr to Pfr dark conversion. PMID:24036118

  13. Unusual spectral properties of bacteriophytochrome Agp2 result from a deprotonation of the chromophore in the red-absorbing form Pr.

    Science.gov (United States)

    Zienicke, Benjamin; Molina, Isabel; Glenz, René; Singer, Patrick; Ehmer, Dorothee; Escobar, Francisco Velazquez; Hildebrandt, Peter; Diller, Rolf; Lamparter, Tilman

    2013-11-01

    Phytochromes are widely distributed photoreceptors with a bilin chromophore that undergo a typical reversible photoconversion between the two spectrally different forms, Pr and Pfr. The phytochrome Agp2 from Agrobacterium tumefaciens belongs to the group of bathy phytochromes that have a Pfr ground state as a result of the Pr to Pfr dark conversion. Agp2 has untypical spectral properties in the Pr form reminiscent of a deprotonated chromophore as confirmed by resonance Raman spectroscopy. UV/visible absorption spectroscopy showed that the pKa is >11 in the Pfr form and ∼7.6 in the Pr form. Unlike other phytochromes, photoconversion thus results in a pKa shift of more than 3 units. The Pr/Pfr ratio after saturating irradiation with monochromatic light is strongly pH-dependent. This is partially due to a back-reaction of the deprotonated Pr chromophore at pH 9 after photoexcitation as found by flash photolysis. The chromophore protonation and dark conversion were affected by domain swapping and site-directed mutagenesis. A replacement of the PAS or GAF domain by the respective domain of the prototypical phytochrome Agp1 resulted in a protonated Pr chromophore; the GAF domain replacement afforded an inversion of the dark conversion. A reversion was also obtained with the triple mutant N12S/Q190L/H248Q, whereas each single point mutant is characterized by decelerated Pr to Pfr dark conversion.

  14. YUCCA auxin biosynthetic genes are required for Arabidopsis shade avoidance

    Directory of Open Access Journals (Sweden)

    Patricia Müller-Moulé

    2016-10-01

    Full Text Available Plants respond to neighbor shade by increasing stem and petiole elongation. Shade, sensed by phytochrome photoreceptors, causes stabilization of PHYTOCHROME INTERACTING FACTOR proteins and subsequent induction of YUCCA auxin biosynthetic genes. To investigate the role of YUCCA genes in phytochrome-mediated elongation, we examined auxin signaling kinetics after an end-of-day far-red (EOD-FR light treatment, and found that an auxin responsive reporter is rapidly induced within 2 hours of far-red exposure. YUCCA2, 5, 8, and 9 are all induced with similar kinetics suggesting that they could act redundantly to control shade-mediated elongation. To test this hypothesis we constructed a yucca2, 5, 8, 9 quadruple mutant and found that the hypocotyl and petiole EOD-FR and shade avoidance responses are completely disrupted. This work shows that YUCCA auxin biosynthetic genes are essential for detectable shade avoidance and that YUCCA genes are important for petiole shade avoidance.

  15. YUCCA auxin biosynthetic genes are required for Arabidopsis shade avoidance

    Science.gov (United States)

    Müller-Moulé, Patricia; Nozue, Kazunari; Pytlak, Melissa L.; Palmer, Christine M.; Covington, Michael F.; Wallace, Andreah D.; Harmer, Stacey L.

    2016-01-01

    Plants respond to neighbor shade by increasing stem and petiole elongation. Shade, sensed by phytochrome photoreceptors, causes stabilization of PHYTOCHROME INTERACTING FACTOR proteins and subsequent induction of YUCCA auxin biosynthetic genes. To investigate the role of YUCCA genes in phytochrome-mediated elongation, we examined auxin signaling kinetics after an end-of-day far-red (EOD-FR) light treatment, and found that an auxin responsive reporter is rapidly induced within 2 hours of far-red exposure. YUCCA2, 5, 8, and 9 are all induced with similar kinetics suggesting that they could act redundantly to control shade-mediated elongation. To test this hypothesis we constructed a yucca2, 5, 8, 9 quadruple mutant and found that the hypocotyl and petiole EOD-FR and shade avoidance responses are completely disrupted. This work shows that YUCCA auxin biosynthetic genes are essential for detectable shade avoidance and that YUCCA genes are important for petiole shade avoidance. PMID:27761349

  16. Nitric Oxide, Ethylene, and Auxin Cross Talk Mediates Greening and Plastid Development in Deetiolating Tomato Seedlings.

    Science.gov (United States)

    Melo, Nielda K G; Bianchetti, Ricardo E; Lira, Bruno S; Oliveira, Paulo M R; Zuccarelli, Rafael; Dias, Devisson L O; Demarco, Diego; Peres, Lazaro E P; Rossi, Magdalena; Freschi, Luciano

    2016-04-01

    The transition from etiolated to green seedlings involves the conversion of etioplasts into mature chloroplasts via a multifaceted, light-driven process comprising multiple, tightly coordinated signaling networks. Here, we demonstrate that light-induced greening and chloroplast differentiation in tomato (Solanum lycopersicum) seedlings are mediated by an intricate cross talk among phytochromes, nitric oxide (NO), ethylene, and auxins. Genetic and pharmacological evidence indicated that either endogenously produced or exogenously applied NO promotes seedling greening by repressing ethylene biosynthesis and inducing auxin accumulation in tomato cotyledons. Analysis performed in hormonal tomato mutants also demonstrated that NO production itself is negatively and positively regulated by ethylene and auxins, respectively. Representing a major biosynthetic source of NO in tomato cotyledons, nitrate reductase was shown to be under strict control of both phytochrome and hormonal signals. A close NO-phytochrome interaction was revealed by the almost complete recovery of the etiolated phenotype of red light-grown seedlings of the tomato phytochrome-deficient aurea mutant upon NO fumigation. In this mutant, NO supplementation induced cotyledon greening, chloroplast differentiation, and hormonal and gene expression alterations similar to those detected in light-exposed wild-type seedlings. NO negatively impacted the transcript accumulation of genes encoding phytochromes, photomorphogenesis-repressor factors, and plastid division proteins, revealing that this free radical can mimic transcriptional changes typically triggered by phytochrome-dependent light perception. Therefore, our data indicate that negative and positive regulatory feedback loops orchestrate ethylene-NO and auxin-NO interactions, respectively, during the conversion of colorless etiolated seedlings into green, photosynthetically competent young plants. © 2016 American Society of Plant Biologists. All Rights

  17. Retention of Photoinduction of Cytosolic Enzymes in aurea Mutant of Tomato (Lycopersicon esculentum).

    Science.gov (United States)

    Goud, K. V.; Sharma, R.

    1994-06-01

    The tomato (Lycopersicon esculentum Mill.) aurea (au) mutant has been characterized as a phytochrome-deficient mutant lacking spectrally detectable phytochrome A in etiolated seedlings. Seedlings of au grown under red light (RL) lack phytochrome regulation of nuclear genes encoding plastidic proteins, possess ill-developed chloroplasts, and are slow to de-etiolate. In the present study, the effect of phytochrome deficiency on photoinduction of enzymes in etiolated au seedlings was investigated. The photoinduction of the cytosolic enzymes amylase and nitrate reductase (NR) and of the plastidic enzyme nitrite reductase (NiR) in au was compared with that in the isogenic wild-type (WT) tomato and the high-pigment (hp) mutant with exaggerated phytochrome response. In WT and hp, both brief RL pulses and continuous RL induced amylase, NR, and NiR activities, whereas in au no photoinduction of enzymes was observed with brief RL pulses, and continuous RL induced only amylase and NR activities. The time courses of photoinduction of NR and amylase in au under continuous RL followed patterns qualitatively similar to hp and WT. A blue-light pretreatment prior to continuous RL exposure was ineffective in inducing NiR activity in au. Only continuous white light could elicit a photoinduction of NiR in au seedlings. The norflurazon-triggered loss of photoinduction of NiR in WT and hp indicated that NiR photoinduction depended on chloroplast biogenesis. The results indicate that observed photoinduction of NR and amylase in au may be mediated by a residual phytochrome pool.

  18. ZEITLUPE positively regulates hypocotyl elongation at warm temperature under light in Arabidopsis thaliana.

    Science.gov (United States)

    Miyazaki, Yuji; Takase, Tomoyuki; Kiyosue, Tomohiro

    2015-01-01

    Hypocotyl cell elongation has been studied as a model to understand how cellular expansion contributes to plant organ growth. Hypocotyl elongation is affected by multiple environmental factors, including light quantity and light quality. Red light inhibits hypocotyl growth via the phytochrome signaling pathways. Proteins of the flavin-binding KELCH repeat F-box 1 / LOV KELCH protein 2 / ZEITLUPE family are positive regulators of hypocotyl elongation under red light in Arabidopsis. These proteins were suggested to reduce phytochrome-mediated inhibition of hypocotyl elongation. Here, we show that ZEITLUPE also functions as a positive regulator in warmth-induced hypocotyl elongation under light in Arabidopsis.

  19. Main: D1GMAUX28 [PLACE

    Lifescience Database Archive (English)

    Full Text Available D1GMAUX28 S000328 20-Feb-2002 (last modified) uchi D1; DNase I protected sequence f...ound in the soybean (G.m.) auxin responsive gene, Aux28, promoter; D1 and D4 share a very similar core seque...nce TAGTXXCTGT and TAGTXCTGT, respectively; D1/D4-like sequence were identified in several other auxin-respo...tors; GmGT-2 are down-regulated by light in a phytochrome-dependent manner; See 000331; Auxin; Aux28; GT-2; phytochrome; D1; hypocotyl; soybean (Glycine max) ACAGTTACTA ...

  20. Reference: 768 [Arabidopsis Phenome Database[Archive

    Lifescience Database Archive (English)

    Full Text Available odulates abscisic acid (ABA) and gibberellic acid (GA) signaling pathways at least partly via PHYTOCHROME-IN...TERACTING FACTOR3-LIKE5 (PIL5), a phytochrome-interacting basic helix-loop-helix ...transcription factor. Here, we report a new mutant, somnus (som), that germinates in darkness, independently of various light re...s lower levels of ABA and elevated levels of GA due to expressional changes in AB...A and GA metabolic genes. Unlike PIL5, however, SOM does not regulate the expression of GA-INSENSITIVE and R

  1. Reference: 537 [Arabidopsis Phenome Database[Archive

    Lifescience Database Archive (English)

    Full Text Available loss-of-function ga2ox2 mutation causes an increase in GA(4) levels and partly suppresses the germination i...nability during dark imbibition after inactivation of phytochrome. Experiments using 2,2-dimethylGA(4), a GA

  2. Main: RE1ASPHYA3 [PLACE

    Lifescience Database Archive (English)

    Full Text Available RE1ASPHYA3 S000195 17-May-1998 (last modified) kehi RE1 (putative repressor element...) responsible for Pfr-directed repression of oat (A.s.) phyA3 phytochrome gene; Also found in pea AS1 (asparagine synthetas

  3. Reference: SORLIP1AT [PLACE

    Lifescience Database Archive (English)

    Full Text Available SORLIP1AT Hudson ME, Quail PH. Identification of promoter motifs involved in the ne...twork of phytochrome A-regulated gene expression by combined analysis of genomic sequence and microarray dat...a. Plant Physiol. 133: 1605-1616 (2003) in silico; over-represented motif; PubMed: 14681527 ...

  4. Reference: SORLIP2AT [PLACE

    Lifescience Database Archive (English)

    Full Text Available SORLIP2AT Hudson ME, Quail PH. Identification of promoter motifs involved in the ne...twork of phytochrome A-regulated gene expression by combined analysis of genomic sequence and microarray dat...a. Plant Physiol. 133: 1605-1616 (2003) in silico; over-represented motif; PubMed: 14681527 ...

  5. Reference: SORLREP4AT [PLACE

    Lifescience Database Archive (English)

    Full Text Available SORLREP4AT Hudson ME, Quail PH. Identification of promoter motifs involved in the n...etwork of phytochrome A-regulated gene expression by combined analysis of genomic sequence and microarray da...ta. Plant Physiol. 133: 1605-1616 (2003) in silico; over-represented motif; PubMed: 14681527 ...

  6. Reference: PE3ASPHYA3 [PLACE

    Lifescience Database Archive (English)

    Full Text Available PE3ASPHYA3 Bruce WB, Deng X-W, Quial PH A negatively acting DNA sequence element mediates phytochrome-dire...cted repression of phyA gene transcription. EMBO J 10:3015-3024 (1991) PubMed: 1915276; ...

  7. Reference: 325 [Arabidopsis Phenome Database[Archive

    Lifescience Database Archive (English)

    Full Text Available 325 http://metadb.riken.jp/db/SciNetS_ria224i/cria224u4ria224u16412087i Marrocco Katia et al. 2006 Fe...box protein involved in phytochrome A-dependent light signal transduction. 3 423-38 16412087 2006 Feb The Pl

  8. An Injectable Method for Posterior Lateral Spine Fusion

    Science.gov (United States)

    2013-09-01

    West, and E. A. Olmsted-Davis, “An injectable method for noninvasive spine fusion,” Spine J. 11(6), 545–556 (2011). 15. R. Y. Tsien , “Constructing...Lev-Ram, P. A. Steinbach, and R. Y. Tsien , “Mammalian expression of infrared fluorescent proteins engineered from a bacterial phytochrome,” Science

  9. AcEST: BP915880 [AcEST

    Lifescience Database Archive (English)

    Full Text Available oxide stress-activated histidine kinase ... 53 9e-07 >sp... bvgS OS=Bordetella... 55 2e-07 sp|P33529|PHY_MOUSC Phytochrome OS=Mougeotia scalaris GN=PHY PE=... 54 7e-07 sp|Q9P7Q7|MAK1_SCHPO Per

  10. Photoreceptor proteins from purple bacteria

    NARCIS (Netherlands)

    Hendriks, J.; van der Horst, M.A.; Chua, T.K.; Ávila Pérez, M.; van Wilderen, L.J.; Alexandre, M.T.A.; Groot, M.-L.; Kennis, J.T.M.; Hellingwerf, K.J.; Hunter, C.N.; Daldal, F.; Thurnauer, M.C.; Beatty, J.T.

    2009-01-01

    Purple bacteria contain representatives of four of the six main families of photoreceptor proteins: phytochromes, BLUF domain containing proteins, xanthopsins (i.e., photoactive yellow proteins), and phototropins (containing one or more light, oxygen, or voltage (LOV) domains). Most of them have a

  11. UV-A/Blue-Light responses in algae

    Science.gov (United States)

    Senger, Horst; Hermsmeier, Dieter

    1994-01-01

    All life on earth depends on light. A variety of photoreceptors capture the light for a wide range of reactions. Photosynthetic organisms absorb the light necessary for energy transformation and charge separation facilitating photosynthesis. In addition to the bulk pigments there is a great diversity of photoreceptors present in minute concentrations that control development, metabolism and orientation of plants and microorganisms. Based on its spectral absorbance, the well-studied phytochrome system acts in the RL (red light) region as well as in the UV-A/BL (blue light) region where the above mentioned reactions are mediated by a variety of photoreceptors whose natures are largely unknown. Phyllogenetically the UV-A/BL photoreceptors seem to be more ancient pigments that eventually were replaced by the phytochrome system. However, there are many reports that suggest a coaction between the UV-A/BL receptors and the phytochrome system. In several cases the UV-A/BL activation is the prerequisite for the phytochrome reaction. Historically it was the German botanist Julius Sachs who first discovered in 1864 that phototropism in plants was due to BL reactions. It took over 70 years until Bunning (1937) and Galston and Baker (1949) rediscovered the BL response. Since then, an ever-increasing attention has been paid to this effect. In this contribution, the general aspect of UV-A/BL responses and especially the responsiveness of algae will be covered.

  12. Bacteriophytochromes control conjugation in Agrobacterium fabrum.

    Science.gov (United States)

    Bai, Yingnan; Rottwinkel, Gregor; Feng, Juan; Liu, Yiyao; Lamparter, Tilman

    2016-08-01

    Bacterial conjugation, the transfer of single stranded plasmid DNA from donor to recipient cell, is mediated through the type IV secretion system. We performed conjugation assays using a transmissible artificial plasmid as reporter. With this assay, conjugation in Agrobacterium fabrum was modulated by the phytochromes Agp1 and Agp2, photoreceptors that are most sensitive in the red region of visible light. In conjugation studies with wild-type donor cells carrying a pBIN-GUSINT plasmid as reporter that lacked the Ti (tumor inducing) plasmid, no conjugation was observed. When either agp1(-) or agp2(-) knockout donor strains were used, plasmid DNA was delivered to the recipient, indicating that both phytochromes suppress conjugation in the wild type donor. In the recipient strains, the loss of Agp1 or Agp2 led to diminished conjugation. When wild type cells with Ti plasmid and pBIN-GUS reporter plasmid were used as donor, a high rate of conjugation was observed. The DNA transfer was down regulated by red or far-red light by a factor of 3.5. With agp1(-) or agp2(-) knockout donor cells, conjugation in the dark was about 10 times lower than with the wild type donor, and with the double knockout donor no conjugation was observed. These results imply that the phytochrome system has evolved to inhibit conjugation in the light. The decrease of conjugation under different temperature correlated with the decrease of phytochrome autophosphorylation.

  13. A second conserved GAF domain cysteine is required for the blue/green photoreversibility of cyanobacteriochrome Tlr0924 from Thermosynechococcus elongatus.

    Science.gov (United States)

    Rockwell, Nathan C.; Njuguna, Stephanie Lane; Roberts, Laurel; Castillo, Elenor; Parson, Victoria L.; Dwojak, Sunshine; Lagarias, J. Clark; Spiller, Susan C.

    2008-01-01

    Phytochromes are widely occurring red/far-red photoreceptors that utilize a linear tetrapyrrole (bilin) chromophore covalently bound within a knotted PAS-GAF domain pair. Cyanobacteria also contain more distant relatives of phytochromes that lack this knot, such as the phytochrome-related cyanobacteriochromes implicated to function as blue/green switchable photoreceptors. In this study, we characterize the cyanobacteriochrome Tlr0924 from the thermophilic cyanobacterium Thermosynechococcus elongatus. Full-length Tlr0924 exhibits blue/green photoconversion across a broad range of temperatures, including physiologically relevant temperatures for this organism. Spectroscopic characterization of Tlr0924 demonstrates that its green-absorbing state is in equilibrium with a labile, spectrally distinct blue-absorbing species. The photochemically generated blue-absorbing state is in equilibrium with another species absorbing at longer wavelengths, giving a total of 4 states. Cys499 is essential for this behavior, because mutagenesis of this residue results in red-absorbing mutant biliproteins. Characterization of the C499D mutant protein by absorbance and CD spectroscopy supports the conclusion that its bilin chromophore adopts a similar conformation to the red-light-absorbing Pr form of phytochrome. We propose a model photocycle in which Z/E photoisomerization of the 15/16 bond modulates formation of a reversible thioether linkage between Cys499 and C10 of the chromophore, providing the basis for the blue/green switching of cyanobacteriochromes. PMID:18549244

  14. Photocontrol of germination in Amaranthus caudatus.

    Science.gov (United States)

    Kendrick, R E; Frankland, B

    1969-12-01

    Germination of Amaranthus caudatus is inhibited by light, far-red being the most effective part of the spectrum. At temperatures of 25° and below there is a low final germination percentage under continuous far-red whereas above 25° there is only a delaying effect. In the presence of a saturating concentration of gibberellic acid (GA3) at 25° seeds germinate under continuous far-red although they are delayed. At 25° seeds exposed to 48 hr far-red fail to germinate when transferred to darkness. This induced dormancy can be broken by a single short exposure to red light given at any time after the far-red illumination. This effect of short red can be reversed by a subsequent short period of far-red indicating that the seeds are phytochrome controlled. Although most seeds have escaped from the reversing effect of short far-red after an intervening dark period of 5 hours, germination is greatly reduced by continuous far-red at this time. Results of exposing seeds to varying periods of far-red before and after dark imbibition are interpreted in terms of a continual production of phytochrome in its active P fr form and a requirement for P fr action over a long period of time. Effects of intermittent and continuous low intensity far-red on the inhibition of germination provides further evidence for a low energy photoreaction involving phytochrome. Effects on Germination Index of continuous illumination with various light sources maintaining different P fr /P total ratios have been investigated. The results suggest that the proportion of phytochrome in the P fr form is the most important factor in the regulation of germination. A scheme for the phytochrome control of germination in Amaranthus caudatus is presented and possible explanations for the dependence on P fr /P total ratio are discussed.

  15. Repression of shade-avoidance reactions by sunfleck induction of HY5 expression in Arabidopsis.

    Science.gov (United States)

    Sellaro, Romina; Yanovsky, Marcelo J; Casal, Jorge J

    2011-12-01

    The light environment provides signals that play a critical role in the control of stem growth in plants. The reduced irradiance and altered spectral composition of shade light promote stem growth compared with unfiltered sunlight. However, whereas most studies have used seedlings exposed to contrasting but constant light treatments, the natural light environment may exhibit strong fluctuations. As a result of gaps in the canopy, plants shaded by neighbours may experience sunflecks, i.e., brief periods of exposure to unfiltered sunlight. Here, we show that sunflecks are perceived by phytochromes A and B, and inhibit hypocotyl growth in Arabidopsis thaliana mainly if they occur during the final portion of the photoperiod. By using forward and reverse genetic approaches we found that ELONGATED HYPOCOTYL 5, LATE ELONGATED HYPOCOTYL, PHYTOCHROME KINASE SUBSTRATE 4 and auxin signalling are key players in this response. © 2011 The Authors. The Plant Journal © 2011 Blackwell Publishing Ltd.

  16. Model for variable light sensitivity in imbibed dark-dormant seeds.

    Science.gov (United States)

    Duke, S O; Egley, G H; Reger, B J

    1977-02-01

    The level of light-induced germination of the seed of common purslane (Portulaca oleracea L.) and curly dock (Rumex crispus L.) changes with dark incubation time prior to brief, low energy, red light treatment. The rate at which phytochrome-far red-absorbing form (Pfr) acts in the light-induced population of seeds was measured by quantitating per cent reversals of the red light effect with saturating far red light exposures at successive times after the red light exposure. A linear positive correlation was found between this rate and the final germination level. These results are compatible with a model involving changing levels, during dark incubation, of a component with which Pfr interacts. In this model, germination is initiated after attainment of a certain level of interaction between Pfr and this component. These findings also support the view that the Pfr to Pr decay rate constant and total phytochrome level are stable during dark incubation.

  17. A few aspects of the physiology of flowering in photoperiodic sensitive plants

    Directory of Open Access Journals (Sweden)

    E. G. Groenewald

    2003-09-01

    Full Text Available Three aspects of the physiology of flowering in photoperiodic sensitive plants are discussed. These are the florigen hypothesis, phytochrome and the time measurement mechanism of flowering and genetic-molecular studies involved in flowering. There is evidence that the hypothetical compound, florigen, occurs in plants, but it has never been characterised. There is a family of phytochromes discovered in plants and some of them are involved with the circadian clock and thus with the time measurement mechanism of flowering. The molecular networks that interact to control flowering are being elucidated, by means of genetic-molecular techniques although at an early stage. It has not yet been possible to pinpoint florigen by these methods, but the future looks promising.

  18. Morphology and Hydraulic Architecture of Vitis vinifera L. cv. Syrah and Torrontés Riojano Plants Are Unaffected by Variations in Red to Far-Red Ratio

    OpenAIRE

    González, Carina Verónica; Jofré, María Florencia; Vila, Hernán F.; Stoffel, Markus; Bottini, Rubén; Giordano, Carla Valeria

    2016-01-01

    Plants have evolved an array of specific photoreceptors to acclimate to the light environment. By sensing light signals, photoreceptors modulate plant morphology, carbon- and water-physiology, crop yield and quality of harvestable organs, among other responses. Many cultural practices and crop management decisions alter light quantity and quality perceived by plants cultivated in the field. Under full sunlight, phytochromes perceive high red to far red ratios (R:FR; 1.1), whereas overhead or ...

  19. Conformational differences between the Pfr and Pr states in Pseudomonas aeruginosa bacteriophytochrome

    OpenAIRE

    2009-01-01

    Phytochromes are red-light photoreceptors that regulate light responses in plants, fungi, and bacteria by means of reversible photoconversion between red (Pr) and far-red (Pfr) light-absorbing states. Here, we report the crystal structure of the Q188L mutant of Pseudomonas aeruginosa bacteriophytochrome (PaBphP) photosensory core module, which exhibits altered photoconversion behavior and different crystal packing from wild type. We observe two distinct chromophore conformations in the Q188L ...

  20. SwissProt search result: AK105637 [KOME

    Lifescience Database Archive (English)

    Full Text Available AK105637 001-200-E02 (Q9FE22) Long hypocotyl in far-red 1 (bHLH-like protein HFR1) (Reduced... phytochrome signaling) (Basic helix-loop-helix FBI1 protein) (Basic helix-loop-helix protein 26) (bHLH26) (AtbHLH026) (Reduced sensitivity to far-red light) HFR1_ARATH 4e-13 ...

  1. SwissProt search result: AK102252 [KOME

    Lifescience Database Archive (English)

    Full Text Available AK102252 J033088H11 (Q9FE22) Long hypocotyl in far-red 1 (bHLH-like protein HFR1) (Reduced... phytochrome signaling) (Basic helix-loop-helix FBI1 protein) (Basic helix-loop-helix protein 26) (bHLH26) (AtbHLH026) (Reduced sensitivity to far-red light) HFR1_ARATH 8e-12 ...

  2. SwissProt search result: AK060505 [KOME

    Lifescience Database Archive (English)

    Full Text Available AK060505 001-018-H11 (Q9FE22) Long hypocotyl in far-red 1 (bHLH-like protein HFR1) (Reduced... phytochrome signaling) (Basic helix-loop-helix FBI1 protein) (Basic helix-loop-helix protein 26) (bHLH26) (AtbHLH026) (Reduced sensitivity to far-red light) HFR1_ARATH 2e-11 ...

  3. Main: SORLIP3AT [PLACE

    Lifescience Database Archive (English)

    Full Text Available SORLIP3AT S000484 18-November-2005 (last modified) kehi one of Sequences Over-Repre...sented in Light-Induced Promoters (SORLIPs) in Arabidopsis; Computationally identified phyA-induced motifs; ...See also S000482, S000483, S000485, S000486 (all SORLIPs), and also S000487, S000488, S000489, S000490 (all SORLREPs); phyA; phytochrome; light; Arabidopsis thaliana CTCAAGTGA ...

  4. Main: SORLREP4AT [PLACE

    Lifescience Database Archive (English)

    Full Text Available SORLREP4AT S000489 18-November-2005 (last modified) kehi one of Sequences Over-Repr...esented in Light-Repressed Promoters (SORLREPs) in Arabidopsis; Computationally identified phyA-repressed mo...tifs; Common in circadian-regulated promoters; See also S000487, S000488, S000490 (all SORLREPs); and also S...000482, S000483, S000484, S000485, S000486 (all SORLIPs); phyA; phytochrome; light; Arabidopsis thaliana CTCCTAATT ...

  5. Main: SORLREP5AT [PLACE

    Lifescience Database Archive (English)

    Full Text Available SORLREP5AT S000490 18-November-2005 (last modified) kehi one of Sequences Over-Repr...esented in Light-Repressed Promoters (SORLREPs) in Arabidopsis; Computationally identified phyA-repressed mo...tifs; See also S000487, S000488, S000489 (all SORLREPs); and also S000482, S000483, S000484, S000485, S000486 (all SORLIPs); phyA; phytochrome; light; Arabidopsis thaliana TTGCATGACT ...

  6. Main: SORLIP2AT [PLACE

    Lifescience Database Archive (English)

    Full Text Available SORLIP2AT S000483 18-November-2005 (last modified) kehi one of Sequences Over-Repre...sented in Light-Induced Promoters (SORLIPs) in Arabidopsis; Computationally identified phyA-induced motifs; ...See also S000482, S000484, S000485, S000486 (all SORLIPs), and also S000487, S000488, S000489, S000490 (all SORLREPs); phyA; phytochrome; light; Arabidopsis thaliana GGGCC ...

  7. Main: SORLREP3AT [PLACE

    Lifescience Database Archive (English)

    Full Text Available SORLREP3AT S000488 18-November-2005 (last modified) kehi one of Sequences Over-Repr...esented in Light-Repressed Promoters (SORLREPs) in Arabidopsis; Computationally identified phyA-repressed mo...tifs; See also S000487, S000489, S000490 (all SORLREPs); and also S000482, S000483, S000484, S000485, S000486 (all SORLIPs); phyA; phytochrome; light; Arabidopsis thaliana TGTATATAT ...

  8. Main: SORLREP2AT [PLACE

    Lifescience Database Archive (English)

    Full Text Available SORLREP2AT S000487 18-November-2005 (last modified) kehi one of Sequences Over-Repr...esented in Light-Repressed Promoters (SORLREPs) in Arabidopsis; Computationally identified phyA-repressed mo...tifs; See also S000488, S000489, S000490 (all SORLREPs); and also S000482, S000483, S000484, S000485, S000486 (all SORLIPs); phyA; phytochrome; light; Arabidopsis thaliana ATAAAACGT ...

  9. Main: SORLIP4AT [PLACE

    Lifescience Database Archive (English)

    Full Text Available SORLIP4AT S000485 18-November-2005 (last modified) kehi one of Sequences Over-Repre...sented in Light-Induced Promoters (SORLIPs) in Arabidopsis; Computationally identified phyA-induced motifs; ...See also S000482, S000483, S000484, S000486 (all SORLIPs), and also S000487, S000488, S000489, S000490 (all SORLREPs); phyA; phytochrome; light; Arabidopsis thaliana GTATGATGG ...

  10. Adaptive Molecular Evolution of PHYE in Primulina, a Karst Cave Plant

    OpenAIRE

    Junjie Tao; Qingwen Qi; Ming Kang; Hongwen Huang

    2015-01-01

    Limestone Karst areas possess high levels of biodiversity and endemism. Primulina is a typical component of Karst endemic floras. The high species richness and wide distribution in various Karst microenvironments make the genus an idea model for studying speciation and local adaptation. In this study, we obtained 10 full-length sequences of the phytochrome PHYE from available transcriptome resources of Primulina and amplified partial sequences of PHYE from the genomic DNA of 74 Primulina spec...

  11. Reference: 692 [Arabidopsis Phenome Database[Archive

    Lifescience Database Archive (English)

    Full Text Available also failed to induce negative phototropism in pks1 under reduced gravitational stimulation, indicating that...nt increase in its expression, PKS1 positively affects root phototropism and both... the effect of pks1 on phototropism is not simply the consequence of the counteracting effect of enhanced gr... effects contribute to negative curvature in response to unilateral blue light. PHYTOCHROME KINASE SUBSTRATE1 regulates root phototro...otropism and the enhanced PKS1 expression in response to

  12. Biosynthesis of open-chain tetrapyrroles in plants, algae, and cyanobacteria.

    Science.gov (United States)

    Beale, S I

    1994-01-01

    Phycobilins are open-chain tetrapyrroles of plants and algae which act as the chromophores of phycobiliproteins where they function as light energy-harvesting pigments. Phytochromobilin, another open-chain tetrapyrrole, is the chromophore of phytochrome, which functions as a light-sensing pigment in plant development. These open-chain tetrapyrroles are biosynthetically derived from protohaem. Enzyme reactions that convert protohaem to biliverdin IX alpha, and biliverdin IX alpha to phycocyanobilin, have been detected and characterized in extracts of the unicellular rhodophyte Cyanidium caldarium. Algal haem oxygenase and algal biliverdin-IX alpha reductase are both soluble enzymes that use electrons derived from reduced ferredoxin. Biochemical intermediates in the conversion of biliverdin IX alpha to (3E)-phycocyanobilin were identified as 15, 16-dihydrobiliverdin IX alpha, (3Z)-phycoerythrobilin and (3Z)-phycocyanobilin. Separate enzymes catalyse the two two-electron reduction steps in the conversion of biliverdin IX alpha to (3Z)-phycoerythrobilin. Z-to-E isomerization of the phycobilin ethylidine group is catalysed by an enzyme that requires glutathione for activity. Protein-bound phycoerythrobilin can be chemically converted to phytochromobilin which can then be released from the protein by methanolysis. This procedure was used to produce phytochromobilin in quantities sufficient to allow its chemical characterization and use in phytochrome reconstitution experiments. The results indicate that (2R,3E)-phytochromobilin spontaneously condenses with recombinant oat apophytochrome to form photoreversible holoprotein that is spectrally identical to native phytochrome.

  13. Signal transduction pathways that regulate CAB gene expression. Progress report

    Energy Technology Data Exchange (ETDEWEB)

    Chory, J.

    1993-12-31

    We have completed the initial genetic and phenotypic characterization of several classes of new mutants that affect CAB gene expression. The doc mutants (for dark overexpression of cab) are characterized by elevated levels of CAB gene expression in the dark; however, unlike the previously isolated de-etiolated mutants (also isolated in my lab), the doc mutants still appear etiolated. The doc alleles define 3 loci, each of which maps to a separate chromosome. The details of the mutant isolation scheme and the genetic and phenotypic description of these new mutants are described. The second class of mutants, the gun mutants (for genomes uncoupled) show accumulation of CAB mRNA in the absence of chloroplast gene expression and development. Thus, the normally tightly coordinated expression between the chloroplast and nuclear genes that encode chloroplast-destined proteins has been uncoupled. We have shown that the Arabidopsis HY3 locus encodes the type B phytochrome apoprotein gene and have characterized the phenotypes of null hy3 alleles to ascertain a role for this phytochrome in Arabidopsis development. We have also isolated and characterized a number of alleles of the phytochrome A gene.

  14. The HY5-PIF regulatory module coordinates light and temperature control of photosynthetic gene transcription.

    Directory of Open Access Journals (Sweden)

    Gabriela Toledo-Ortiz

    2014-06-01

    Full Text Available The ability to interpret daily and seasonal alterations in light and temperature signals is essential for plant survival. This is particularly important during seedling establishment when the phytochrome photoreceptors activate photosynthetic pigment production for photoautotrophic growth. Phytochromes accomplish this partly through the suppression of phytochrome interacting factors (PIFs, negative regulators of chlorophyll and carotenoid biosynthesis. While the bZIP transcription factor long hypocotyl 5 (HY5, a potent PIF antagonist, promotes photosynthetic pigment accumulation in response to light. Here we demonstrate that by directly targeting a common promoter cis-element (G-box, HY5 and PIFs form a dynamic activation-suppression transcriptional module responsive to light and temperature cues. This antagonistic regulatory module provides a simple, direct mechanism through which environmental change can redirect transcriptional control of genes required for photosynthesis and photoprotection. In the regulation of photopigment biosynthesis genes, HY5 and PIFs do not operate alone, but with the circadian clock. However, sudden changes in light or temperature conditions can trigger changes in HY5 and PIFs abundance that adjust the expression of common target genes to optimise photosynthetic performance and growth.

  15. Root phototropism: how light and gravity interact in shaping plant form.

    Science.gov (United States)

    Kiss, John Z; Correll, Melanie J; Mullen, Jack L; Hangarter, Roger P; Edelmann, Richard E

    2003-06-01

    The interactions among tropisms can be critical in determining the final growth form of plants and plant organs. We have studied tropistic responses in roots as an example of these type of interactions. While gravitropism is the predominant tropistic response in roots, phototropism also plays a role in the oriented growth in this organ in flowering plants. In blue or white light, roots exhibit negative phototropism, but red light induces positive phototropism. In the flowering plant Arabidopsis, the photosensitive pigments phytochrome A (phyA) and phytochrome B (phyB) mediate this positive red-light-based photoresponse in roots since single mutants (and the double phyAB mutant) were severely impaired in this response. While blue-light-based negative phototropism is primarily mediated by the phototropin family of photoreceptors, the phyA and phyAB mutants (but not phyB) were inhibited in this response relative to the WT. The differences observed in phototropic responses were not due to growth limitations since the growth rates among all the mutants tested were not significantly different from that of the WT. Thus, our study shows that the blue-light and red-light systems interact in plants and that phytochrome plays a key role in integrating multiple environmental stimuli.

  16. Root phototropism: how light and gravity interact in shaping plant form

    Science.gov (United States)

    Kiss, John Z.; Correll, Melanie J.; Mullen, Jack L.; Hangarter, Roger P.; Edelmann, Richard E.

    2003-01-01

    The interactions among tropisms can be critical in determining the final growth form of plants and plant organs. We have studied tropistic responses in roots as an example of these type of interactions. While gravitropism is the predominant tropistic response in roots, phototropism also plays a role in the oriented growth in this organ in flowering plants. In blue or white light, roots exhibit negative phototropism, but red light induces positive phototropism. In the flowering plant Arabidopsis, the photosensitive pigments phytochrome A (phyA) and phytochrome B (phyB) mediate this positive red-light-based photoresponse in roots since single mutants (and the double phyAB mutant) were severely impaired in this response. While blue-light-based negative phototropism is primarily mediated by the phototropin family of photoreceptors, the phyA and phyAB mutants (but not phyB) were inhibited in this response relative to the WT. The differences observed in phototropic responses were not due to growth limitations since the growth rates among all the mutants tested were not significantly different from that of the WT. Thus, our study shows that the blue-light and red-light systems interact in plants and that phytochrome plays a key role in integrating multiple environmental stimuli.

  17. Light differentially regulates cell division and the mRNA abundance of pea nucleolin during de-etiolation

    Science.gov (United States)

    Reichler, S. A.; Balk, J.; Brown, M. E.; Woodruff, K.; Clark, G. B.; Roux, S. J.

    2001-01-01

    The abundance of plant nucleolin mRNA is regulated during de-etiolation by phytochrome. A close correlation between the mRNA abundance of nucleolin and mitosis has also been previously reported. These results raised the question of whether the effects of light on nucleolin mRNA expression were a consequence of light effects on mitosis. To test this we compared the kinetics of light-mediated increases in cell proliferation with that of light-mediated changes in the abundance of nucleolin mRNA using plumules of dark-grown pea (Pisum sativum) seedlings. These experiments show that S-phase increases 9 h after a red light pulse, followed by M-phase increases in the plumule leaves at 12 h post-irradiation, a time course consistent with separately measured kinetics of red light-induced increases in the expression of cell cycle-regulated genes. These increases in cell cycle-regulated genes are photoreversible, implying that the light-induced increases in cell proliferation are, like nucleolin mRNA expression, regulated via phytochrome. Red light stimulates increases in the mRNA for nucleolin at 6 h post-irradiation, prior to any cell proliferation changes and concurrent with the reported timing of phytochrome-mediated increases of rRNA abundance. After a green light pulse, nucleolin mRNA levels increase without increasing S-phase or M-phase. Studies in animals and yeast indicate that nucleolin plays a significant role in ribosome biosynthesis. Consistent with this function, pea nucleolin can rescue nucleolin deletion mutants of yeast that are defective in rRNA synthesis. Our data show that during de-etiolation, the increased expression of nucleolin mRNA is more directly regulated by light than by mitosis.

  18. Effects of light quality on somatic embryogenesis in Araujia sericifera.

    Science.gov (United States)

    Torné, Josep M.; Moysset, Luisa; Santos, Mireya; Simón, Esther

    2001-03-01

    The effects of photoperiod, light quality and end-of-day (EOD) phytochrome photoconversion on somatic embryogenesis (SE) of Araujia sericifera petals have been studied. Petals from immature flowers were cultured under 8- and 16-h photoperiods using Gro-lux fluorescent lamps. The photon fluence rate was 90-100 µmol m-2 s-1 and the red (R):far-red (FR) ratio was 98. R, FR, R followed by FR (R-FR) and FR followed by R (FR-R) light treatments were applied for 3 weeks at the end of the photoperiods. In a set of experiments, DL-alpha-difluoromethylarginine (DFMA) or methylglyoxal bis(guanylhydrazone) (MGBG), both inhibitors of polyamine biosynthesis, were added to the culture medium in order to study the involvement of polyamine metabolism. The level of SE was the same in long (LD) and short (SD) days. Thus, the light effect was accomplished after 8 h. All EOD treatments that decreased the Pfr level inhibited SE when applied after SD, but not after LD. The FR-R treatment after LD caused an additional stimulatory effect on SE, even in the presence of polyamine inhibitors. DFMA inhibited SE in both SD and LD, but MGBG did not modify SE in either SD or LD. The R, FR and R-FR treatments did not alter the level of SE when applied after LD in the presence of DFMA or MGBG. However, these treatments decreased SE after SD when the medium contained polyamine inhibitors. Our results suggest that Gro-lux lamps, which produce an extremely high R:FR ratio, promote SE in A. sericifera and a timing response to phytochrome photoconversion during photoperiodic induction. Thus, our data corroborate the involvement of phytochromes and polyamines in SE in A. sericifera, which responded as a light-dominant long-day plant.

  19. Phototropism of Arabidopsis thaliana in microgravity and fractional gravity on the International Space Station.

    Science.gov (United States)

    Kiss, John Z; Millar, Katherine D L; Edelmann, Richard E

    2012-08-01

    While there is a great deal of knowledge regarding plant growth and development in microgravity aboard orbiting spacecraft, there is little information available about these parameters in reduced or fractional gravity conditions (less than the nominal 1g on Earth). Thus, in these experiments using the European Modular Cultivation System on the International Space Station, we studied the interaction between phototropism and gravitropism in the WT and mutants of phytochrome A and B of Arabidopis thaliana. Fractional gravity and the 1 g control were provided by centrifuges in the spaceflight hardware, and unidirectional red and blue illumination followed a white light growth period in the time line of the space experiments. The existence of red-light-based positive phototropism in hypocotyls of seedlings that is mediated by phytochrome was confirmed in these microgravity experiments. Fractional gravity studies showed an attenuation of red-light-based phototropism in both roots and hypocotyls of seedlings occurring due to gravitational accelerations ranging from 0.l to 0.3 g. In contrast, blue-light negative phototropism in roots, which was enhanced in microgravity compared with the 1g control, showed a significant attenuation at 0.3 g. In addition, our studies suggest that the well-known red-light enhancement of blue-light-induced phototropism in hypocotyls is likely due to an indirect effect by the attenuation of gravitropism. However, red-light enhancement of root blue-light-based phototropism may occur via a more direct effect on the phototropism system itself, most likely through the phytochrome photoreceptors. To our knowledge, these experiments represent the first to examine the behavior of flowering plants in fractional or reduced gravity conditions.

  20. 拟南芥铁氧还蛋白基因缺失促进花期提前的初步研究%Loss of Function of Ferredoxin2 Can Promote Flowering in Arabidopsis thaliana

    Institute of Scientific and Technical Information of China (English)

    刘兵; 魏海轩; 苏建斌; 张洋; 王金发; 王宏斌; 冯冬茹

    2013-01-01

    In Arabidopsis thaliana, the red and far-red light photoreceptors phytochromes (PHYs) act to involve in regulating flowering.Phytochromobilin synthase (HY2) synthesizes the open chain tetrapyrrole chromophore which is essential to the light-sensing function of phytochromes , and it is a member of the ferredoxin-dependent bilin reductases (FDBRs).Here, we found a Ds-T-DNA insertion line of Arabidop-sis thaliana for the gene encoding the most major ferredoxin (Fd2, At1g60950), which can promote flowering in the process of growth both under long-day and short-day conditions.In this report we show that loss of AtFd2c an promote flowering, AtFd2 interacts with AtHY2 in the chloroplast, and Fd2-KO mutants are impaired in the responses mediated by phytochromes .Together, these results implicate that loss of AtFd2 may promote flowering by impairing the physiology function of phytochromes .%  拟南芥的红光/远红光受体光敏色素(PHYs)参与花期调节过程,而铁氧还蛋白色素还原酶(FD-BRs)的一种---植物色素合成酶(HY2)对于光敏色素的合成是必不可少的。研究发现拟南芥铁氧还蛋白---AtFd2的基因缺失突变体(Fd2-KO突变体)在长日照与短日照培养条件下,较其野生型而言均表现出花期提前的表型,而且显示AtFd2与AtHY2在叶绿体中发生互作,并且Fd2突变体对光敏色素的反应受到抑制。推测At-Fd2基因的缺失可能通过影响光敏色素介导的相关生理功能进而对植株的花期进行调节。

  1. Light-dependent reversion gravitropism of the moss Pohlia nutans

    Science.gov (United States)

    Khorkavtsiv, O.

    Plants have evolved highly sensitive mechanisms adapting their growth to the environmental conditions. Light and gravity are critical importance factors, which exerts an essential and specific influence on the determination of the growth direction and regulation of the early stages of plants ontogeny, sometimes effects of these factors being independent. The negative gravitropic resp onse of moss protonemata causes their spatial orientation towards light, which in its turn is the source of photosynthetic efficiency and phototropism. The gravitropism system does not function independently of other sensory response systems in plants. The competence of protonemata to gravity might be altered and the gravitropic response be reversed from negative to positive by light. It has been shown that response of apical cells to light depend on wavelenght: red light (max = 660 nm) represses the gravitropism and blue ( = 450 nm) inverts the protonemal gravitropism. Light, has also been shown for seed plants to modulate gravitropism of roots and stems through the action of phy B in red/far-red reversible way and by phy A in a non-reversible, very - low-fluence response (Hangarter, 1997). In P. nutans blue light reversed the gravitropism protonemal filaments. The mean angle after 24 h blue irradiation was 83 0, like that of negative gravitropic protonemata in darkness. We compared the effect of blue light on gravitropism of chloronemal filaments of Funaria hygrometrica having very low sensitivity to gravity. After action of blue light, however, the positive gravitropism of F. hygrometrica chloronemata was fairly high - 370 . Among blue light spectrum the highest reversion effectiveness in P. nutans had the UV light ( = 350 nm) initiated bends in 90% of protonemata. If a far-red pulse (5 min per h) was added to the blue/UV the gravitropic growth of protonemata resembled that in the dark control. Phytochrome has maxima of absorption in blue and red spectrum region and in our

  2. Main: 1U8W [RPSD[Archive

    Lifescience Database Archive (English)

    Full Text Available 1U8W シロイヌナズナ Arabidopsis Arabidopsis thaliana (L.) Heynh. Nucleoside Diphosphate Kin...ase I Name=Ndpk1; Orderedlocusnames=At4g09320; Orfnames=T30a10.80; Arabidopsis Thaliana Molecule: Nucleoside Diphosphate Kin...ase I; Chain: A, B, C, D, E, F; Synonym: Ndk I, Ndp Kinase I, Ndpk I; Engineered: Yes Trans...ferase 2.7.4.6 (Nucleoside Diphosphate Kinase I) Y.J.Im, J.-I.Kim, Y.Shen, Y.Na, ...m Structural Analysis Of Arabidopsis Thaliana Nucleoside Diphosphate Kinase-2 For Phytochrome-Mediated Light Signalin

  3. Two-component systems and their co-option for eukaryotic signal transduction.

    Science.gov (United States)

    Schaller, G Eric; Shiu, Shin-Han; Armitage, Judith P

    2011-05-10

    Two-component signaling pathways involve histidine kinases, response regulators, and sometimes histidine-containing phosphotransfer proteins. Prevalent in prokaryotes, these signaling elements have also been co-opted to meet the needs of signal transduction in eukaryotes such as fungi and plants. Here we consider the evolution of such regulatory systems, with a particular emphasis on the roles they play in signaling by the plant hormones cytokinin and ethylene, in phytochrome-mediated perception of light, and as integral components of the circadian clock. Copyright © 2011 Elsevier Ltd. All rights reserved.

  4. Inhibition of blue-light-dependent binding of 14-3-3 proteins to phototropins by hydrogen peroxide

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xiao; SHIMAZAKI Kenichiro

    2005-01-01

    @@ Phototropins, following the discovery of phytochromes[1,2] and cryptochromes[3,4], are the most recently characterized blue-light (BL) receptors in plants. The N- terminal regions of the proteins contain two light oxygen and voltage (LOV)――LOV1 and LOV2, which belong to PAS domain involved in protein-protein interaction and ligand binding, possessing non-covalent binding sites for the chromophore FMN[5]. The C-terminal regions contain Ser/Thr kinase domains[6].

  5. Physiological and genetic characterization of plant growth and gravitropism in LED light sources

    Science.gov (United States)

    Deitzer, Gerald F.

    1994-01-01

    Among the many problems of growing plants in completely controlled environments, such as those anticipated for the space station and the CELSS program, is the need to provide light that is both adequate for photosynthesis and of proper quality for normal growth and development. NASA scientists and engineers have recently become interested in the possibility of utilizing densely packed, solid state, light emitting diodes (LED's) as a source for this light. Unlike more conventional incandescent or electrical discharge lamps, these sources are highly monochromatic and lack energy in spectral regions thought to be important for normal plant development. In addition, a recent observation by NASA scientist has suggested that infra-red LED's, that are routinely used as photographic safelights for plants grown in darkness, may interact with the ability of plants to detect gravity. In order to establish how plants respond to light from these LED light sources we carried out a series of experiments with known pigment mutants of the model mustard plant, Arabidopsis thaliana, growing in either a gravity field or on a clinostat to simulate a micro-gravity environment. Results indicate that only red light from the 665 nm LED's disrupts the ability of normal wildtype seedlings to detect a gravity stimulus. There was no consistent effect found for the far-red (735 nm) LED's or either of the infrared (880 nm or 935 nm) LED sources but both showed some effect in one or more of the genotypes tested. Of these five members of the phytochrome multigene family in Arabidopsis, only the phytochrome B pigment mutant (hy3) lacked the ability to detect gravity under all conditions. There was no effect of either micro-gravity (clinostat) or the infra-red LED's on the light induced inhibition of hypocotyl elongation. Measurements of the pigment phytochrome in oats also showed no photoconversion by 15 min irradiations with the infra-red LED's. We conclude that phytochrome B is required for the

  6. Florigen: One Found, More to Follow?

    Institute of Scientific and Technical Information of China (English)

    Xuhong Yu; John Klejnot; Chentao Lin

    2006-01-01

    Florigen(s) are molecules that are synthesized in response to appropriate photoperiods and transmitted from leaves to shoot apices to promote floral initiation. It has been recently discovered in Arabidopsis that mRNA of the FT gene acts as a florigen. In Arabidopsis, cryptochromes and phytochromes mediate longday promotion of CO protein expression, which activates FT mRNA expression in leaves. FT mRNA is transmitted to the shoot apex, where it acts together with FD to activate transcription of floral meristem identity genes, resulting in floral initiation. The discovery of the molecular nature of a florigen was a major scientific breakthrough in 2005.

  7. Retrograde bilin signaling enables Chlamydomonas greening and phototrophic survival

    Science.gov (United States)

    Duanmu, Deqiang; Casero, David; Dent, Rachel M.; Gallaher, Sean; Yang, Wenqiang; Rockwell, Nathan C.; Martin, Shelley S.; Pellegrini, Matteo; Niyogi, Krishna K.; Merchant, Sabeeha S.; Grossman, Arthur R.; Lagarias, J. Clark

    2013-01-01

    The maintenance of functional chloroplasts in photosynthetic eukaryotes requires real-time coordination of the nuclear and plastid genomes. Tetrapyrroles play a significant role in plastid-to-nucleus retrograde signaling in plants to ensure that nuclear gene expression is attuned to the needs of the chloroplast. Well-known sites of synthesis of chlorophyll for photosynthesis, plant chloroplasts also export heme and heme-derived linear tetrapyrroles (bilins), two critical metabolites respectively required for essential cellular activities and for light sensing by phytochromes. Here we establish that Chlamydomonas reinhardtii, one of many chlorophyte species that lack phytochromes, can synthesize bilins in both plastid and cytosol compartments. Genetic analyses show that both pathways contribute to iron acquisition from extracellular heme, whereas the plastid-localized pathway is essential for light-dependent greening and phototrophic growth. Our discovery of a bilin-dependent nuclear gene network implicates a widespread use of bilins as retrograde signals in oxygenic photosynthetic species. Our studies also suggest that bilins trigger critical metabolic pathways to detoxify molecular oxygen produced by photosynthesis, thereby permitting survival and phototrophic growth during the light period. PMID:23345435

  8. Dynamic structural changes underpin photoconversion of a blue/green cyanobacteriochrome between its dark and photoactivated states.

    Science.gov (United States)

    Cornilescu, Claudia C; Cornilescu, Gabriel; Burgie, E Sethe; Markley, John L; Ulijasz, Andrew T; Vierstra, Richard D

    2014-01-31

    The phytochrome superfamily of photoreceptors exploits reversible light-driven changes in the bilin chromophore to initiate a variety of signaling cascades. The nature of these alterations and how they impact the protein moiety remain poorly resolved and might include several species-specific routes. Here, we provide a detailed picture of photoconversion for the photosensing cGMP phosphodiesterase/adenylyl cyclase/FhlA (GAF) domain from Thermosynechococcus elongatus (Te) PixJ, a member of the cyanobacteriochrome clade. Solution NMR structures of the blue light-absorbing dark state Pb and green light-absorbing photoactivated state Pg, combined with paired crystallographic models, revealed that the bilin and GAF domain dynamically transition via breakage of the C10/Cys-494 thioether bond, opposite rotations of the A and D pyrrole rings, sliding of the bilin in the GAF pocket, and the appearance of an extended region of disorder that includes Cys-494. Changes in GAF domain backbone dynamics were also observed that are likely important for inter-domain signal propagation. Taken together, photoconversion of T. elongatus PixJ from Pb to Pg involves complex structural changes within the GAF domain pocket that transduce light into a mechanical signal, many aspects of which should be relevant to others within the extended phytochrome superfamily.

  9. Evolutionary recycling of light signaling components in fleshy fruits: new insights on the role of pigments to monitor ripening

    Directory of Open Access Journals (Sweden)

    Briardo eLlorente

    2016-03-01

    Full Text Available Besides an essential source of energy, light provides environmental information to plants. Photosensory pathways are thought to have occurred early in plant evolution, probably at the time of the Archaeplastida ancestor, or perhaps even earlier. Manipulation of individual components of light perception and signaling networks in tomato (Solanum lycopersicum affects the metabolism of ripening fruit at several levels. Most strikingly, recent experiments have shown that some of the molecular mechanisms originally devoted to sense and respond to environmental light cues have been re-adapted during evolution to provide plants with useful information on fruit ripening progression. In particular, the presence of chlorophylls in green fruit can strongly influence the spectral composition of the light filtered through the fruit pericarp. The concomitant changes in light quality can be perceived and transduced by phytochromes and phytochrome-interacting factors, respectively, to regulate gene expression and in turn modulate the production of carotenoids, a family of metabolites that are relevant for the final pigmentation of ripe fruits. We raise the hypothesis that the evolutionary recycling of light-signaling components to finely adjust pigmentation to the actual ripening stage of the fruit may have represented a selective advantage for primeval fleshy-fruited plants even before the extinction of dinosaurs.

  10. Genomic Survey and Biochemical Analysis of Recombinant Candidate Cyanobacteriochromes Reveals Enrichment for Near UV/Violet Sensors in the Halotolerant and Alkaliphilic Cyanobacterium Microcoleus IPPAS B353.

    Science.gov (United States)

    Cho, Sung Mi; Jeoung, Sae Chae; Song, Ji-Young; Kupriyanova, Elena V; Pronina, Natalia A; Lee, Bong-Woo; Jo, Seong-Whan; Park, Beom-Seok; Choi, Sang-Bong; Song, Ji-Joon; Park, Youn-Il

    2015-11-20

    Cyanobacteriochromes (CBCRs), which are exclusive to and widespread among cyanobacteria, are photoproteins that sense the entire range of near-UV and visible light. CBCRs are related to the red/far-red phytochromes that utilize linear tetrapyrrole (bilin) chromophores. Best characterized from the unicellular cyanobacterium Synechocystis sp. PCC 6803 and the multicellular heterocyst forming filamentous cyanobacteria Nostoc punctiforme ATCC 29133 and Anabaena sp. PCC 7120, CBCRs have been poorly investigated in mat-forming, nonheterocystous cyanobacteria. In this study, we sequenced the genome of one of such species, Microcoleus IPPAS B353 (Microcoleus B353), and identified two phytochromes and seven CBCRs with one or more bilin-binding cGMP-specific phosphodiesterase, adenylyl cyclase and FhlA (GAF) domains. Biochemical and spectroscopic measurements of 23 purified GAF proteins from phycocyanobilin (PCB) producing recombinant Escherichia coli indicated that 13 of these proteins formed near-UV and visible light-absorbing covalent adducts: 10 GAFs contained PCB chromophores, whereas three contained the PCB isomer, phycoviolobilin (PVB). Furthermore, the complement of Microcoleus B353 CBCRs is enriched in near-UV and violet sensors, but lacks red/green and green/red CBCRs that are widely distributed in other cyanobacteria. We hypothesize that enrichment in short wavelength-absorbing CBCRs is critical for acclimation to high-light environments where this organism is found.

  11. A Photo-Labile Thioether Linkage to Phycoviolobilin Provides the Foundation for the Blue/Green Photocycles in DXCF-Cyanobacteriochromes

    Energy Technology Data Exchange (ETDEWEB)

    Burgie, E. Sethe [Univ. of Wisconsin, Madison, WI (United States); Walker, Joseph M. [Univ. of Wisconsin, Madison, WI (United States); Phillips Jr., George N. [Univ. of Wisconsin, Madison, WI (United States); Rice Univ., Houston, TX (United States); Vierstra, Richard D. [Univ. of Wisconsin, Madison, WI (United States)

    2013-01-08

    The phytochrome superfamily encompasses a diverse collection of photochromic photoreceptors in plants and microorganisms that employ a covalently linked bilin cradled in a cGMP-phosphodiesterase/adenylyl-cyclase/FhlA (GAF) domain to detect light. Whereas most interconvert between red- and far-red-light-absorbing states, cyanobacteria also express variants called cyanobacteriochromes (CBCRs) that modify bilin absorption to collectively perceive the entire visible spectrum. Here, we present two X-ray crystallographic structures of the GAF domain from the blue/green photochromic CBCR PixJ from Thermosynechococcus elongatus. Moreover, these structures confirm the hypothesis that CBCRs variably manipulate the chromophore π-conjugation system through isomerization and a second thioether linkage, in this case involving the bilin C10 carbon and Cys494 within a DXCF sequence characteristic of blue/green CBCRs. Biochemical studies support a mechanism for photoconversion whereby the second linkage ruptures on route to the green-light-absorbing state. All together, theTePixJ(GAF) models illustrate the remarkable structural and photochemical versatility among phytochromes and CBCRs in driving light perception.

  12. The ELF4-ELF3-LUX complex links the circadian clock to diurnal control of hypocotyl growth.

    Science.gov (United States)

    Nusinow, Dmitri A; Helfer, Anne; Hamilton, Elizabeth E; King, Jasmine J; Imaizumi, Takato; Schultz, Thomas F; Farré, Eva M; Kay, Steve A

    2011-07-13

    The circadian clock is required for adaptive responses to daily and seasonal changes in environmental conditions. Light and the circadian clock interact to consolidate the phase of hypocotyl cell elongation to peak at dawn under diurnal cycles in Arabidopsis thaliana. Here we identify a protein complex (called the evening complex)--composed of the proteins encoded by EARLY FLOWERING 3 (ELF3), ELF4 and the transcription-factor-encoding gene LUX ARRHYTHMO (LUX; also known as PHYTOCLOCK 1)--that directly regulates plant growth. ELF3 is both necessary and sufficient to form a complex between ELF4 and LUX, and the complex is diurnally regulated, peaking at dusk. ELF3, ELF4 and LUX are required for the proper expression of the growth-promoting transcription factors encoded by PHYTOCHROME INTERACTING FACTOR 4 (PIF4) and PIF5 (also known as PHYTOCHROME INTERACTING FACTOR 3-LIKE 6) under diurnal conditions. LUX targets the complex to the promoters of PIF4 and PIF5 in vivo. Mutations in PIF4 and/or PIF5 are epistatic to the loss of the ELF4-ELF3-LUX complex, suggesting that regulation of PIF4 and PIF5 is a crucial function of the complex. Therefore, the evening complex underlies the molecular basis for circadian gating of hypocotyl growth in the early evening.

  13. Hormonal networks involved in apical hook development in darkness and their response to light

    Directory of Open Access Journals (Sweden)

    Maria Agustina Mazzella

    2014-02-01

    Full Text Available In darkness, the dicot seedlings produces an apical hook as result of differential cell division and extension at opposite sides of the hypocotyl. This hook protects the apical meristem from mechanical damage during seedling emergence from the soil. In darkness, gibberellins act via the DELLA-PIF (PHYTOCHROME INTERACTING FACTORs pathway, and ethylene acts via the EIN3/EIL1 (ETHYLENE INSENSITIE 3/EIN3 like 1-HLS1 (HOOKLESS 1 pathway to control the asymmetric accumulation of auxin required for apical hook formation and maintenance. These core pathways form a network with multiple points of connection. Light perception by phytochromes and cryptochromes reduces the activity of PIFs and CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1 --both required for hook formation in darkness--, lowers the levels of gibberellins, and triggers hook opening as a component of the switch between heterotrophic and photoautotrophic development. Apical hook opening is thus a suitable model to study the convergence of endogenous and exogenous signals on the control of cell division and cell growth.

  14. Crystal structure of Pseudomonas aeruginosa bacteriophytochrome: Photoconversion and signal transduction

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Xiaojing; Kuk, Jane; Moffat, Keith (UC)

    2008-11-12

    Phytochromes are red-light photoreceptors that regulate light responses in plants, fungi, and bacteria via reversible photoconversion between red (Pr) and far-red (Pfr) light-absorbing states. Here we report the crystal structure at 2.9 {angstrom} resolution of a bacteriophytochrome from Pseudomonas aeruginosa with an intact, fully photoactive photosensory core domain in its dark-adapted Pfr state. This structure reveals how unusual interdomain interactions, including a knot and an 'arm' structure near the chromophore site, bring together the PAS (Per-ARNT-Sim), GAF (cGMP phosphodiesterase/adenyl cyclase/FhlA), and PHY (phytochrome) domains to achieve Pr/Pfr photoconversion. The PAS, GAF, and PHY domains have topologic elements in common and may have a single evolutionary origin. We identify key interactions that stabilize the chromophore in the Pfr state and provide structural and mutational evidence to support the essential role of the PHY domain in efficient Pr/Pfr photoconversion. We also identify a pair of conserved residues that may undergo concerted conformational changes during photoconversion. Modeling of the full-length bacteriophytochrome structure, including its output histidine kinase domain, suggests how local structural changes originating in the photosensory domain modulate interactions between long, cross-domain signaling helices at the dimer interface and are transmitted to the spatially distant effector domain, thereby regulating its histidine kinase activity.

  15. The counteracting effect of potassium cyanide in sodium azide-inhibited germination of Paulownia tomentosa  Steud. seeds

    Directory of Open Access Journals (Sweden)

    Živković Suzana

    2005-01-01

    Full Text Available The effect of some respiratory inhibitors on light-induced Paulownia tomentosa Steud. seed germination was studied. Millimolar solution of sodium azide was sufficient to completely prevent germination induced by a 5-min red light pulse. The inhibitory effect of azide was absent if seeds were rinsed before phytochrome activation by light. Sodium azide was effective only if present in the period of Pfr activity. The escape time from azide inhibition compared to the escape from far-red light action, was delayed for about 24 hours. When azide was applied after phytochrome activation, its effect depended on how long it was present in the incubation medium. The removal of azide allowed full restoration of germination by another red light pulse and the far-red escape time did not differ from the escape of untreated, i.e. water-imbibed seeds. Potassium cyanide alone did not produce any effect in light-stimulated germination of these seeds. However, it counteracted the inhibitory effect of azide in light-stimulated germination, if applied simultaneously at a concentration three times higher.

  16. HFR1 sequesters PIF1 to govern the transcriptional network underlying light-initiated seed germination in Arabidopsis.

    Science.gov (United States)

    Shi, Hui; Zhong, Shangwei; Mo, Xiaorong; Liu, Na; Nezames, Cynthia D; Deng, Xing Wang

    2013-10-01

    Seed germination is the first step for seed plants to initiate a new life cycle. Light plays a predominant role in promoting seed germination, where the initial phase is mediated by photoreceptor phytochrome B (phyB). Previous studies showed that phytochrome-interacting factor1 (PIF1) represses seed germination downstream of phyB. Here, we identify a positive regulator of phyB-dependent seed germination, long hypocotyl in far-red1 (HFR1). HFR1 blocks PIF1 transcriptional activity by forming a heterodimer with PIF1 that prevents PIF1 from binding to DNA. Our whole-genomic analysis shows that HFR1 and PIF1 oppositely mediate the light-regulated transcriptome in imbibed seeds. Through the HFR1-PIF1 module, light regulates expression of numerous genes involved in cell wall loosening, cell division, and hormone pathways to initiate seed germination. The functionally antagonistic HFR1-PIF1 pair constructs a fail-safe mechanism for fine-tuning seed germination during low-level illumination, ensuring a rapid response to favorable environmental changes. This study identifies the HFR1-PIF1 pair as a central module directing the whole genomic transcriptional network to rapidly initiate light-induced seed germination.

  17. Hormone-controlled UV-B responses in plants.

    Science.gov (United States)

    Vanhaelewyn, Lucas; Prinsen, Els; Van Der Straeten, Dominique; Vandenbussche, Filip

    2016-08-01

    Ultraviolet B (UV-B) light is a portion of solar radiation that has significant effects on the development and metabolism of plants. Effects of UV-B on plants can be classified into photomorphogenic effects and stress effects. These effects largely rely on the control of, and interactions with, hormonal pathways. The fairly recent discovery of the UV-B-specific photoreceptor UV RESISTANCE LOCUS 8 (UVR8) allowed evaluation of the role of downstream hormones, leading to the identification of connections with auxin and gibberellin. Moreover, a substantial overlap between UVR8 and phytochrome responses has been shown, suggesting that part of the responses caused by UVR8 are under PHYTOCHROME INTERACTING FACTOR control. UV-B effects can also be independent of UVR8, and affect different hormonal pathways. UV-B affects hormonal pathways in various ways: photochemically, affecting biosynthesis, transport, and/or signaling. This review concludes that the effects of UV-B on hormonal regulation can be roughly divided in two: inhibition of growth-promoting hormones; and the enhancement of environmental stress-induced defense hormones.

  18. Alteration of PHYA expression change circadian rhythms and timing of bud set in Populus.

    Science.gov (United States)

    Kozarewa, Iwanka; Ibáñez, Cristian; Johansson, Mikael; Ogren, Erling; Mozley, David; Nylander, Eva; Chono, Makiko; Moritz, Thomas; Eriksson, Maria E

    2010-05-01

    In many temperate woody species, dormancy is induced by short photoperiods. Earlier studies have shown that the photoreceptor phytochrome A (phyA) promotes growth. Specifically, Populus plants that over-express the oat PHYA gene (oatPHYAox) show daylength-independent growth and do not become dormant. However, we show that oatPHYAox plants could be induced to set bud and become cold hardy by exposure to a shorter, non-24 h diurnal cycle that significantly alters the relative position between endogenous rhythms and perceived light/dark cycles. Furthermore, we describe studies in which the expression of endogenous Populus tremula x P. tremuloides PHYTOCHROME A (PttPHYA) was reduced in Populus trees by antisense inhibition. The antisense plants showed altered photoperiodic requirements, resulting in earlier growth cessation and bud formation in response to daylength shortening, an effect that was explained by an altered innate period that leads to phase changes of clock-associated genes such as PttCO2. Moreover, gene expression studies following far-red light pulses show a phyA-mediated repression of PttLHY1 and an induction of PttFKF1 and PttFT. We conclude that the level of PttPHYA expression strongly influences seasonally regulated growth in Populus and is central to co-ordination between internal clock-regulated rhythms and external light/dark cycles through its dual effect on the pace of clock rhythms and in light signaling.

  19. Reduced phenylalanine ammonia-lyase and tyrosine ammonia-lyase activities and lignin synthesis in wheat grown under low pressure sodium lamps

    Science.gov (United States)

    Guerra, D.; Anderson, A. J.; Salisbury, F. B.

    1985-01-01

    Wheat (Triticum aestivum L. cv Fremont) grown in hydroponic culture under 24-hour continuous irradiation at 560 to 580 micromoles per square meter per second from either metalhalide (MH), high pressure sodium (HPS), or low pressure sodium (LPS) lamps reached maturity in 70 days. Grain yields were similar under all three lamps, although LPS-grown plants lodged at maturity. Phenylalanine ammonia-lyase (PAL) and a tyrosine ammonia lyase (TAL) with lesser activity were detected in all extracts of leaf, inflorescence, and stem. Ammonia-lyase activities increased with age of the plant, and plants grown under the LPS lamp displayed PAL and TAL activities lower than wheat cultured under MH and HPS radiation. Greenhouse solar-grown wheat had the highest PAL and TAL activities. Lignin content of LPS-grown wheat was also significantly reduced from that of plants grown under MH or HPS lamps or in the greenhouse, showing a correlation with the reduced PAL and TAL activities. Ratios of far red-absorbing phytochrome to total phytochrome were similar for all three lamps, but the data do not yet warrant a conclusion about specific wavelengths missing from the LPS lamps that might have induced PAL and TAL activities in plants under the other lamps.

  20. SPA proteins: SPAnning the gap between visible light and gene expression.

    Science.gov (United States)

    Menon, Chiara; Sheerin, David J; Hiltbrunner, Andreas

    2016-08-01

    In this review we focus on the role of SPA proteins in light signalling and discuss different aspects, including molecular mechanisms, specificity, and evolution. The ability of plants to perceive and respond to their environment is key to their survival under ever-changing conditions. The abiotic factor light is of particular importance for plants. Light provides plants energy for carbon fixation through photosynthesis, but also is a source of information for the adaptation of growth and development to the environment. Cryptochromes and phytochromes are major photoreceptors involved in control of developmental decisions in response to light cues, including seed germination, seedling de-etiolation, and induction of flowering. The SPA protein family acts in complex with the E3 ubiquitin ligase COP1 to target positive regulators of light responses for degradation by the 26S proteasome to suppress photomorphogenic development in darkness. Light-activated cryptochromes and phytochromes both repress the function of COP1, allowing accumulation of positive photomorphogenic factors in light. In this review, we highlight the role of the SPA proteins in this process and discuss recent advances in understanding how SPAs link light-activation of photoreceptors and downstream signaling.

  1. Phototropins mediate blue and red light-induced chloroplast movements in Physcomitrella patens.

    Science.gov (United States)

    Kasahara, Masahiro; Kagawa, Takatoshi; Sato, Yoshikatsu; Kiyosue, Tomohiro; Wada, Masamitsu

    2004-07-01

    Phototropin is the blue-light receptor that mediates phototropism, chloroplast movement, and stomatal opening in Arabidopsis. Blue and red light induce chloroplast movement in the moss Physcomitrella patens. To study the photoreceptors for chloroplast movement in P. patens, four phototropin genes (PHOTA1, PHOTA2, PHOTB1, and PHOTB2) were isolated by screening cDNA libraries. These genes were classified into two groups (PHOTA and PHOTB) on the basis of their deduced amino acid sequences. Then phototropin disruptants were generated by homologous recombination and used for analysis of chloroplast movement. Data revealed that blue light-induced chloroplast movement was mediated by phototropins in P. patens. Both photA and photB groups were able to mediate chloroplast avoidance, as has been reported for Arabidopsis phot2, although the photA group contributed more to the response. Red light-induced chloroplast movement was also significantly reduced in photA2photB1photB2 triple disruptants. Because the primary photoreceptor for red light-induced chloroplast movement in P. patens is phytochrome, phototropins may be downstream components of phytochromes in the signaling pathway. To our knowledge, this work is the first to show a function for the phototropin blue-light receptor in a response to wavelengths that it does not absorb.

  2. Integration of Phot1, Phot2, and PhyB signalling in light-induced chloroplast movements.

    Science.gov (United States)

    Luesse, Darron R; DeBlasio, Stacy L; Hangarter, Roger P

    2010-10-01

    In Arabidopsis thaliana, chloroplasts move towards the periclinal cell walls upon exposure to low blue light intensities and to anticlinal walls under high light. The regulation of these chloroplast movements involves members of both the phototropin and phytochrome families of photoreceptors. Examination of fluence-rate response dependencies in phot1 and phot2 mutants revealed that although both photoreceptors are capable of inducing chloroplast accumulation under low-light conditions, the signals from these photoreceptors appear to be antagonistic. Chloroplast movements in wild-type plants were intermediate between those of the single phot mutants, consistent with each operating through separate signalling cascades. Mutants in phot2 showed transient chloroplast avoidance responses upon exposure to intense blue light, and slow but sustained chloroplast avoidance under intense white light, indicating that in the absence of phot2, phot1 is capable of generating both a low and a high-light response signal. Mutations in phytochrome B (phyB) caused an enhanced avoidance response at intermediate and high light intensities. Examination of phyB, phot1phyB, and phot2phyB mutants indicated that this enhancement is caused by PhyB inhibition of the high-light avoidance response in wild-type plants. In addition, our results suggest that the inhibition by PhyB is not exclusive to either of the phot1 or phot2 signalling pathways.

  3. Diurnal Regulation of the Brassinosteroid-Biosynthetic CPD Gene in Arabidopsis1[W

    Science.gov (United States)

    Bancos, Simona; Szatmári, Anna-Mária; Castle, Julie; Kozma-Bognár, László; Shibata, Kyomi; Yokota, Takao; Bishop, Gerard J.; Nagy, Ferenc; Szekeres, Miklós

    2006-01-01

    Plant steroid hormones, brassinosteroids (BRs), are essential for normal photomorphogenesis. However, the mechanism by which light controls physiological functions via BRs is not well understood. Using transgenic plants carrying promoter-luciferase reporter gene fusions, we show that in Arabidopsis (Arabidopsis thaliana) the BR-biosynthetic CPD and CYP85A2 genes are under diurnal regulation. The complex diurnal expression profile of CPD is determined by dual, light-dependent, and circadian control. The severely decreased expression level of CPD in phytochrome-deficient background and the red light-specific induction in wild-type plants suggest that light regulation of CPD is primarily mediated by phytochrome signaling. The diurnal rhythmicity of CPD expression is maintained in brassinosteroid insensitive 1 transgenic seedlings, indicating that its transcriptional control is independent of hormonal feedback regulation. Diurnal changes in the expression of CPD and CYP85A2 are accompanied by changes of the endogenous BR content during the day, leading to brassinolide accumulation at the middle of the light phase. We also show that CPD expression is repressed in extended darkness in a BR feedback-dependent manner. In the dark the level of the bioactive hormone did not increase; therefore, our data strongly suggest that light also influences the sensitivity of plants to BRs. PMID:16531479

  4. Diurnal regulation of the brassinosteroid-biosynthetic CPD gene in Arabidopsis.

    Science.gov (United States)

    Bancos, Simona; Szatmári, Anna-Mária; Castle, Julie; Kozma-Bognár, László; Shibata, Kyomi; Yokota, Takao; Bishop, Gerard J; Nagy, Ferenc; Szekeres, Miklós

    2006-05-01

    Plant steroid hormones, brassinosteroids (BRs), are essential for normal photomorphogenesis. However, the mechanism by which light controls physiological functions via BRs is not well understood. Using transgenic plants carrying promoter-luciferase reporter gene fusions, we show that in Arabidopsis (Arabidopsis thaliana) the BR-biosynthetic CPD and CYP85A2 genes are under diurnal regulation. The complex diurnal expression profile of CPD is determined by dual, light-dependent, and circadian control. The severely decreased expression level of CPD in phytochrome-deficient background and the red light-specific induction in wild-type plants suggest that light regulation of CPD is primarily mediated by phytochrome signaling. The diurnal rhythmicity of CPD expression is maintained in brassinosteroid insensitive 1 transgenic seedlings, indicating that its transcriptional control is independent of hormonal feedback regulation. Diurnal changes in the expression of CPD and CYP85A2 are accompanied by changes of the endogenous BR content during the day, leading to brassinolide accumulation at the middle of the light phase. We also show that CPD expression is repressed in extended darkness in a BR feedback-dependent manner. In the dark the level of the bioactive hormone did not increase; therefore, our data strongly suggest that light also influences the sensitivity of plants to BRs.

  5. Mutants of phospholipase A (pPLA-I) have a red light and auxin phenotype.

    Science.gov (United States)

    Effendi, Yunus; Radatz, Katrin; Labusch, Corinna; Rietz, Steffen; Wimalasekera, Rinukshi; Helizon, Hanna; Zeidler, Mathias; Scherer, Günther F E

    2014-07-01

    pPLA-I is the evolutionarily oldest patatin-related phospholipase A (pPLA) in plants, which have previously been implicated to function in auxin and defence signalling. Molecular and physiological analysis of two allelic null mutants for pPLA-I [ppla-I-1 in Wassilewskija (Ws) and ppla-I-3 in Columbia (Col) ] revealed pPLA-I functions in auxin and light signalling. The enzyme is localized in the cytosol and to membranes. After auxin application expression of early auxin-induced genes is significantly slower compared with wild type and both alleles show a slower gravitropic response of hypocotyls, indicating compromised auxin signalling. Additionally, phytochrome-modulated responses like abrogation of gravitropism, enhancement of phototropism and growth in far red-enriched light are decreased in both alleles. While early flowering, root coils and delayed phototropism are only observed in the Ws mutant devoid of phyD, the light-related phenotypes observed in both alleles point to an involvement of pPLA-I in phytochrome signalling.

  6. NETS FOR PEACH PROTECTED CULTIVATION

    Directory of Open Access Journals (Sweden)

    Evelia Schettini

    2012-06-01

    Full Text Available The aim of this paper was to investigate the radiometric properties of coloured nets used to protect a peach cultivation. The modifications of the solar spectral distribution, mainly in the R and FR wavelength band, influence plant photomorphogenesis by means of the phytochrome and cryptochrome. The phytochrome response is characterized in terms of radiation rate in the red wavelengths (R, 600-700 nm to that in the farred radiation (FR, 700-800 nm, i.e. the R/FR ratio. The effects of the blue radiation (B, 400-500 nm is investigated by the ratio between the blue radiation and the far-red radiation, i.e. the B/FR ratio. A BLUE net, a RED net, a YELLOW net, a PEARL net, a GREY net and a NEUTRAL net were tested in Bari (Italy, latitude 41° 05’ N. Peach trees were located in pots inside the greenhouses and in open field. The growth of the trees cultivated in open field was lower in comparison to the growth of the trees grown under the nets. The RED, PEARL, YELLOW and GREY nets increased the growth of the trees more than the other nets. The nets positively influenced the fruit characteristics, such as fruit weight and flesh firmness.

  7. Integration of light signaling with photoperiodic flowering and circadian rhythm

    Institute of Scientific and Technical Information of China (English)

    Min NI

    2005-01-01

    Plants become photosynthetic through de-etiolation, a developmental process regulated by red/far-red light-absorbing phytochromes and blue/ultraviolet A light-absorbing cryptochromes. Genetic screens have identified in the last decade many far-red light signaling mutants and several red and blue light signaling mutants, suggesting the existence of distinct red, far-red, or blue light signaling pathways downstream of phytochromes and cryptochromes. However, genetic screens have also identified mutants with defective de-etiolation responses under multiple wavelengths. Thus, the optimal de-etiolation responses of a plant depend on coordination among the different light signaling pathways. This review intends to discuss several recently identified signaling components that have a potential role to integrate red, far-red, and blue light signalings. This review also highlights the recent discoveries on proteolytic degradation in the desensitization of light signal transmission, and the tight connection of light signaling with photoperiodic flowering and circadian rhythm. Studies on the controlling mechanisms of de-etiolation, photoperiodic flowering, and circadian rhythm have been the fascinating topics in Arabidopsis research. The knowledge obtained from Arabidopsis can be readily applied to food crops and ornamental species, and can be contributed to our general understanding of signal perception and transduction in all organisms.

  8. Maize (Zea mays) seeds can detect above-ground weeds; thiamethoxam alters the view.

    Science.gov (United States)

    Afifi, Maha; Lee, Elizabeth; Lukens, Lewis; Swanton, Clarence

    2015-09-01

    Far red light is known to penetrate soil and delay seed germination. Thiamethoxam as a seed treatment has been observed to enhance seed germination. No previous work has explored the effect of thiamethoxam on the physiological response of buried maize seed when germinating in the presence of above-ground weeds. We hypothesised that the changes in red:far red reflected from above-ground weeds would be detected by maize seed phytochrome and delay seed germination by decreasing the level of GA and increasing ABA. We further hypothesised that thiamethoxam would overcome this delay in germination. Thiamethoxam enhanced seed germination in the presence of above-ground weeds by increasing GA signalling and downregulating DELLA protein and ABA signalling genes. An increase in amylase activity and a degradation of starch were also observed. Far red reflected from the above-ground weeds was capable of penetrating below the soil surface and was detected by maize seed phytochrome. Thiamethoxam altered the effect of far red on seed germination by stimulating GA and inhibiting ABA synthesis. This is the first study to suggest that the mode of action of thiamethoxam involves both GA synthesis and ABA inhibition. © 2014 Society of Chemical Industry.

  9. Horizontal transfer of an adaptive chimeric photoreceptor from bryophytes to ferns.

    Science.gov (United States)

    Li, Fay-Wei; Villarreal, Juan Carlos; Kelly, Steven; Rothfels, Carl J; Melkonian, Michael; Frangedakis, Eftychios; Ruhsam, Markus; Sigel, Erin M; Der, Joshua P; Pittermann, Jarmila; Burge, Dylan O; Pokorny, Lisa; Larsson, Anders; Chen, Tao; Weststrand, Stina; Thomas, Philip; Carpenter, Eric; Zhang, Yong; Tian, Zhijian; Chen, Li; Yan, Zhixiang; Zhu, Ying; Sun, Xiao; Wang, Jun; Stevenson, Dennis W; Crandall-Stotler, Barbara J; Shaw, A Jonathan; Deyholos, Michael K; Soltis, Douglas E; Graham, Sean W; Windham, Michael D; Langdale, Jane A; Wong, Gane Ka-Shu; Mathews, Sarah; Pryer, Kathleen M

    2014-05-06

    Ferns are well known for their shade-dwelling habits. Their ability to thrive under low-light conditions has been linked to the evolution of a novel chimeric photoreceptor--neochrome--that fuses red-sensing phytochrome and blue-sensing phototropin modules into a single gene, thereby optimizing phototropic responses. Despite being implicated in facilitating the diversification of modern ferns, the origin of neochrome has remained a mystery. We present evidence for neochrome in hornworts (a bryophyte lineage) and demonstrate that ferns acquired neochrome from hornworts via horizontal gene transfer (HGT). Fern neochromes are nested within hornwort neochromes in our large-scale phylogenetic reconstructions of phototropin and phytochrome gene families. Divergence date estimates further support the HGT hypothesis, with fern and hornwort neochromes diverging 179 Mya, long after the split between the two plant lineages (at least 400 Mya). By analyzing the draft genome of the hornwort Anthoceros punctatus, we also discovered a previously unidentified phototropin gene that likely represents the ancestral lineage of the neochrome phototropin module. Thus, a neochrome originating in hornworts was transferred horizontally to ferns, where it may have played a significant role in the diversification of modern ferns.

  10. Map-Based Cloning of the Gene Associated With the Soybean Maturity Locus E3

    Science.gov (United States)

    Watanabe, Satoshi; Hideshima, Rumiko; Xia, Zhengjun; Tsubokura, Yasutaka; Sato, Shusei; Nakamoto, Yumi; Yamanaka, Naoki; Takahashi, Ryoji; Ishimoto, Masao; Anai, Toyoaki; Tabata, Satoshi; Harada, Kyuya

    2009-01-01

    Photosensitivity plays an essential role in the response of plants to their changing environments throughout their life cycle. In soybean [Glycine max (L.) Merrill], several associations between photosensitivity and maturity loci are known, but only limited information at the molecular level is available. The FT3 locus is one of the quantitative trait loci (QTL) for flowering time that corresponds to the maturity locus E3. To identify the gene responsible for this QTL, a map-based cloning strategy was undertaken. One phytochrome A gene (GmPhyA3) was considered a strong candidate for the FT3 locus. Allelism tests and gene sequence comparisons showed that alleles of Misuzudaizu (FT3/FT3; JP28856) and Harosoy (E3/E3; PI548573) were identical. The GmPhyA3 alleles of Moshidou Gong 503 (ft3/ft3; JP27603) and L62-667 (e3/e3; PI547716) showed weak or complete loss of function, respectively. High red/far-red (R/FR) long-day conditions enhanced the effects of the E3/FT3 alleles in various genetic backgrounds. Moreover, a mutant line harboring the nonfunctional GmPhyA3 flowered earlier than the original Bay (E3/E3; PI553043) under similar conditions. These results suggest that the variation in phytochrome A may contribute to the complex systems of soybean flowering response and geographic adaptation. PMID:19474204

  11. There and Back Again: Loss and Reacquisition of Two-Cys Photocycles in Cyanobacteriochromes.

    Science.gov (United States)

    Rockwell, Nathan C; Martin, Shelley S; Lagarias, John Clark

    2017-05-01

    Cyanobacteriochromes (CBCRs) are cyanobacterial photoreceptors distantly related to phytochromes. Both families use linear tetrapyrrole (bilin) chromophores that are covalently attached to a conserved Cys residue. CBCRs are more spectrally diverse than phytochromes, with known examples detecting light from the near ultraviolet to the edge of the infrared (370-750 nm). Detection of ultraviolet to blue light by CBCRs is mediated by a second Cys residue, which forms a covalent linkage to the bilin C10 atom. Second linkage formation is best understood in a subfamily possessing a conserved Asp-Xaa-Cys-Phe (DXCF) motif. Some DXCF CBCRs can isomerize their phycocyanobilin (PCB) chromophores into phycoviolobilin (PVB), a property not reported for other lineages. Both the DXCF Cys and PVB formation have been lost during evolution of other CBCR subfamilies. Using phylogenetic analysis and characterization of recombinantly expressed CBCRs, we show that the DXCF Cys residue has also been reacquired during CBCR evolution. Guided by this knowledge, we successfully reintroduced a second cysteine into a red/green CBCR, restoring blue-light sensing and PVB formation with two additional substitutions. Our results validate the roles of these residues in CBCR spectral tuning and thus provide new insight into the molecular basis of their spectral diversity. © 2017 The American Society of Photobiology.

  12. Drop-on-demand sample delivery for studying biocatalysts in action at X-ray free-electron lasers.

    Science.gov (United States)

    Fuller, Franklin D; Gul, Sheraz; Chatterjee, Ruchira; Burgie, E Sethe; Young, Iris D; Lebrette, Hugo; Srinivas, Vivek; Brewster, Aaron S; Michels-Clark, Tara; Clinger, Jonathan A; Andi, Babak; Ibrahim, Mohamed; Pastor, Ernest; de Lichtenberg, Casper; Hussein, Rana; Pollock, Christopher J; Zhang, Miao; Stan, Claudiu A; Kroll, Thomas; Fransson, Thomas; Weninger, Clemens; Kubin, Markus; Aller, Pierre; Lassalle, Louise; Bräuer, Philipp; Miller, Mitchell D; Amin, Muhamed; Koroidov, Sergey; Roessler, Christian G; Allaire, Marc; Sierra, Raymond G; Docker, Peter T; Glownia, James M; Nelson, Silke; Koglin, Jason E; Zhu, Diling; Chollet, Matthieu; Song, Sanghoon; Lemke, Henrik; Liang, Mengning; Sokaras, Dimosthenis; Alonso-Mori, Roberto; Zouni, Athina; Messinger, Johannes; Bergmann, Uwe; Boal, Amie K; Bollinger, J Martin; Krebs, Carsten; Högbom, Martin; Phillips, George N; Vierstra, Richard D; Sauter, Nicholas K; Orville, Allen M; Kern, Jan; Yachandra, Vittal K; Yano, Junko

    2017-04-01

    X-ray crystallography at X-ray free-electron laser sources is a powerful method for studying macromolecules at biologically relevant temperatures. Moreover, when combined with complementary techniques like X-ray emission spectroscopy, both global structures and chemical properties of metalloenzymes can be obtained concurrently, providing insights into the interplay between the protein structure and dynamics and the chemistry at an active site. The implementation of such a multimodal approach can be compromised by conflicting requirements to optimize each individual method. In particular, the method used for sample delivery greatly affects the data quality. We present here a robust way of delivering controlled sample amounts on demand using acoustic droplet ejection coupled with a conveyor belt drive that is optimized for crystallography and spectroscopy measurements of photochemical and chemical reactions over a wide range of time scales. Studies with photosystem II, the phytochrome photoreceptor, and ribonucleotide reductase R2 illustrate the power and versatility of this method.

  13. Photoregulated expression of the PsPK3 and PsPK5 genes in pea seedlings.

    Science.gov (United States)

    Khanna, R; Lin, X; Watson, J C

    1999-01-01

    The PsPK3 and PsPK5 genes of the garden pea encode protein-serine/threonine kinases whose catalytic domains are closely related to known signal transducing kinases from animals and fungi. The PsPK3 polypeptide is predicted to be located in the nucleus, whereas PsPK5 is a homologue of NPH1, the probable blue light receptor for phototropism from Arabidopsis. We found previously that when etiolated pea seedlings are illuminated with continuous white light, PsPK3 and PsPK5 transcript levels within apical buds decline substantially, reaching their minimum levels within one day of exposure to light. The role of light in regulating the expression of the PsPK3 and PsPK5 genes was investigated further. To gain insight into the rapidity with which expression changes, 6-day old, dark-grown pea seedlings were transferred to continuous white light, and PsPK3 and PsPK5 RNA levels monitored over the ensuing 24 h. While transcripts from the RbcS gene family increase, the PsPK3 and PsPK5 mRNAs decline rapidly to their minimum levels. PsPK5 mRNA declines 10-fold in ca. 2 h, whereas PsPK3 mRNA declines 4-fold in ca. 8 h. We used single pulses of light to elucidate which photoreceptor triggers the negative regulation of PsPK3 and PsPK5 gene expression. To assess phytochrome involvement, etiolated seedlings were treated with single pulses of red light, red followed by far-red light, or far-red light alone. RbcS induction by a red light pulse is reversible with a subsequent far-red light pulse, clearly showing that phytochrome mediates its induction. Likewise, RbcS expression is induced with a single pulse of blue light or a dichromatic pulse of red+blue light. However, none of these pulses trigger the PsPK3 and PsPK5 mRNA levels to decline. Given the lack of effectiveness of light pulses, etiolated seedlings were transferred to continuous light of three different qualities to determine the spectral sensitivity of PsPK3 and PsPK5 gene expression. Exposure to continuous red, continuous

  14. Drop-on-Demand Sample Delivery for Studying Biocatalysts in Action at XFELs

    Science.gov (United States)

    Fuller, Franklin D.; Gul, Sheraz; Chatterjee, Ruchira; Burgie, Ernest S.; Young, Iris D.; Lebrette, Hugo; Srinivas, Vivek; Brewster, Aaron S.; Michels-Clark, Tara; Clinger, Jonathan A.; Andi, Babak; Ibrahim, Mohamed; Pastor, Ernest; de Lichtenberg, Casper; Hussein, Rana; Pollock, Christopher J.; Zhang, Miao; Stan, Claudiu A.; Kroll, Thomas; Fransson, Thomas; Weninger, Clemens; Kubin, Markus; Aller, Pierre; Lassalle, Louise; Bräuer, Philipp; Miller, Mitchell D.; Amin, Muhamed; Koroidov, Sergey; Roessler, Christian G.; Allaire, Marc; Sierra, Raymond G.; Docker, Peter T.; Glownia, James M.; Nelson, Silke; Koglin, Jason E.; Zhu, Diling; Chollet, Matthieu; Song, Sanghoon; Lemke, Henrik; Liang, Mengning; Sokaras, Dimosthenis; Alonso-Mori, Roberto; Zouni, Athina; Messinger, Johannes; Bergmann, Uwe; Boal, Amie K.; Bollinger, J. Martin; Krebs, Carsten; Högbom, Martin; Phillips, George N.; Vierstra, Richard D.; Sauter, Nicholas K.; Orville, Allen M.; Kern, Jan; Yachandra, Vittal K.; Yano, Junko

    2017-01-01

    X-ray crystallography at X-ray free-electron laser (XFEL) sources is a powerful method for studying macromolecules at biologically relevant temperatures. Moreover, when combined with complementary techniques like X-ray emission spectroscopy (XES), both global structures and chemical properties of metalloenzymes can be obtained concurrently, providing new insights into the interplay between the protein structure/dynamics and chemistry at an active site. Implementing such a multimodal approach can be compromised by conflicting requirements to optimize each individual method. In particular, the method used for sample delivery greatly impacts the data quality. We present here a new, robust way of delivering controlled sample amounts on demand using acoustic droplet ejection coupled with a conveyor belt drive that is optimized for crystallography and spectroscopy measurements of photochemical and chemical reactions over a wide range of time scales. Studies with photosystem II, the phytochrome photoreceptor, and ribonucleotide reductase R2 illustrate the power and versatility of this method. PMID:28250468

  15. Molecular genetic analysis of activation-tagged transcription factors thought to be involved in photomorphogenesis

    Energy Technology Data Exchange (ETDEWEB)

    Neff, Michael M.

    2011-06-23

    This is a final report for Department of Energy Grant No. DE-FG02-08ER15927 entitled “Molecular Genetic Analysis of Activation-Tagged Transcription Factors Thought to be Involved in Photomorphogenesis”. Based on our preliminary photobiological and genetic analysis of the sob1-D mutant, we hypothesized that OBP3 is a transcription factor involved in both phytochrome and cryptochrome-mediated signal transduction. In addition, we hypothesized that OBP3 is involved in auxin signaling and root development. Based on our preliminary photobiological and genetic analysis of the sob2-D mutant, we also hypothesized that a related gene, LEP, is involved in hormone signaling and seedling development.

  16. Thermodynamic and structural properties of tuber starches from transgenic potato plants grown in vitro and in vivo.

    Science.gov (United States)

    Wasserman, Luybov A; Sergeev, Andrey I; Vasil'ev, Viktor G; Plashchina, Irina G; Aksenova, Nina P; Konstantinova, Tatyana N; Golyanovskaya, Svetlana A; Sergeeva, Lidiya I; Romanov, Georgy A

    2015-07-10

    Potato plants harboring Phytochrome B (PHYB) gene from Arabidopsis thaliana or rol genes from Agrobacterium rhizogenes were used to study the effect of transgene expression on structure and properties of starch in tubers. Thermodynamic characteristics of starch (melting temperature, enthalpy of melting, thickness of crystalline lamellae) were shown to be variable depending on the transgene expression and plant culturing mode: in vitro or in soil. The expression of rolB or rolC genes in in vitro cultured plants evoked opposite effects on starch melting temperature and crystalline lamellae thickness. AtPHYB or rolB expression in the soil-grown potato led to the formation of more defective or more ordered starch structures, respectively, in comparison with starches of the same lines grown in vitro. On the whole, our study revealed genotype-dependent differences between starches extracted from tubers of in vitro or in vivo grown plants.

  17. FAR-RED ELONGATED HYPOCOTYL3 promotes floral meristem determinacy in Arabidopsis.

    Science.gov (United States)

    Liu, Luping; Li, Bo; Liu, Xigang

    2016-10-02

    The transposase-derived transcription factor genes FAR-RED ELONGATED HYPOCOTYL3 (FHY3) and FAR-RED IMPAIRED RESPONSE1 (FAR1) have redundant and multifaceted roles in plant growth and development during the vegetative stage, including phytochrome A-mediated far-red light (FR) signaling and circadian clock entrainment. Little is known about their functions in the reproductive stage. We recently demonstrated that FHY3 plays important roles in shoot apical meristem (SAM) maintenance and floral meristem (FM) determinacy through its target genes CLAVATA3 (CLV3), SEPALLATA1 (SEP1) and SEP2. Here we present data that FHY3 but not its homolog, FAR1, has a distinct role in FM determinacy in a manner independent of its light signaling and circadian pathway functions. Moreover, genome-wide gene expression profiling showed that the homeostasis of the FM is critical for the regulation of FM activity.

  18. The Arabidopsis SWI/SNF protein BAF60 mediates seedling growth control by modulating DNA accessibility

    KAUST Repository

    Jégu, Teddy

    2017-06-15

    Plant adaptive responses to changing environments involve complex molecular interplays between intrinsic and external signals. Whilst much is known on the signaling components mediating diurnal, light, and temperature controls on plant development, their influence on chromatin-based transcriptional controls remains poorly explored.In this study we show that a SWI/SNF chromatin remodeler subunit, BAF60, represses seedling growth by modulating DNA accessibility of hypocotyl cell size regulatory genes. BAF60 binds nucleosome-free regions of multiple G box-containing genes, opposing in cis the promoting effect of the photomorphogenic and thermomorphogenic regulator Phytochrome Interacting Factor 4 (PIF4) on hypocotyl elongation. Furthermore, BAF60 expression level is regulated in response to light and daily rhythms.These results unveil a short path between a chromatin remodeler and a signaling component to fine-tune plant morphogenesis in response to environmental conditions.

  19. Photoregulation of Anthocyanin Synthesis : VIII. Effect of Light Pretreatments.

    Science.gov (United States)

    Mancinelli, A L

    1984-06-01

    A comparative study of the spectral sensitivity of anthocyanin production in dark-grown and light-pretreated systems was carried out in Brassica oleracea L., Lycopersicon esculentum Mill., Secale cereale L. and Spirodela polyrrhiza L. Light pretreatments bring about an enhancement of the inductive, red-far red reversible response in all systems, a decrease of the continuous irradiation response in cabbage, rye, and tomato seedlings, and an enhancement of the continuous irradiation response in cabbage leaf disks. Light pretreatments also bring about a marked change in the spectral sensitivity of the continuous irradiation response. The different effect of light pretreatments on the photosensitivity of the response to short and long wavelength irradiations suggests that two photoreceptors, phytochrome and cryptochrome, may be involved in the photoregulation of anthocyanin production.

  20. Light-Regulated Stomatal Aperture in Arabidopsis

    Institute of Scientific and Technical Information of China (English)

    Chen Chen; Yu-Guo Xiao; Xin Li; Min Ni

    2012-01-01

    The stomatal pores of plant leaves,situated in the epidermis and surrounded by a pair of guard cells,allow CO2 uptake for photosynthesis and water loss through transpiration.Blue light is one of the dominant environmental signals that control stomatal movements in leaves of plants in a natural environment.This blue light response is mediated by blue/UV A light-absorbing phototropins (phots) and cryptochromes (crys).Red/far-red light-absorbing phytochromes (phys) also play a role in the control of stomatal aperture.The signaling components that link the perception of light signals to the stomatal opening response are largely unknown.This review discusses a few newly discovered nuclear genes,their function with respect to the phot-,cry-,and phy-mediated signal transduction cascades,and possible involvement of circadian clock.

  1. The activities of the E3 ubiquitin ligase COP1/SPA, a key repressor in light signaling.

    Science.gov (United States)

    Hoecker, Ute

    2017-06-01

    Light is a critical signal to integrate plant growth and development with the environment. Downstream of photoreceptors, the E3 ubiquitin ligase COP1/SPA is a key repressor of photomorphogenesis which targets many positive regulators of light signaling, mainly transcription factors, for degradation in darkness. In light-grown plants COP1/SPA activity is repressed, allowing light responses to occur. This review provides an overview on our current knowledge on COP1/SPA repressor function, focusing in particular on the roles of the respective protein domains and the mechanisms of light-induced inactivation of COP1/SPA. Moreover, we summarize how COP1 activity is regulated by other interacting proteins, such as a SUMO E3 ligase and Phytochrome-Interacting Factors (PIFs), as well as by hormones. At last, several novel functions of COP1 that were recently revealed are included. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. Ambient temperature signalling in plants.

    Science.gov (United States)

    Wigge, Philip A

    2013-10-01

    Plants are exposed to daily and seasonal fluctuations in temperature. Within the 'ambient' temperature range (about 12-27°C for Arabidopsis) temperature differences have large effects on plant growth and development, disease resistance pathways and the circadian clock without activating temperature stress pathways. It is this developmental sensing and response to non-stressful temperatures that will be covered in this review. Recent advances have revealed key players in mediating temperature signals. The bHLH transcription factor PHYTOCHROME INTERACTING FACTOR4 (PIF4) has been shown to be a hub for multiple responses to warmer temperature in Arabidopsis, including flowering and hypocotyl elongation. Changes in chromatin state are involved in transmitting temperature signals to the transcriptome. Determining the precise mechanisms of temperature perception represents an exciting goal for the field.

  3. Chloroplast movement: dissection of events downstream of photo- and mechano-perception.

    Science.gov (United States)

    Sato, Yoshikatsu; Kadota, Akeo; Wada, Masamitsu

    2003-02-01

    The study of chloroplast photorelocation movement is progressing rapidly now that mutants for chloroplast movement have become available in Arabidopsis thaliana. However, mechanistic approaches in cell biology still stand to elucidate the mechanisms and regulations of such movement. The fern Adiantum capillus-veneris and the moss Physcomitrella patens are particularly suitable materials for analyzing the kinetics of intracellular chloroplast movement. In these plants, chloroplast movement is induced by red light as well as blue light, mediated by phytochrome and blue light receptor, respectively. In this paper, we review the unique force-generating system for chloroplast motility in P. patens. In addition to light-induced chloroplast movement, we also summarize mechanically induced chloroplast movement in these plants and the motility systems involved. Finally, the different dependency of mechano- and photo-relocation movement on external Ca(2+) is discussed.

  4. Recent advances in understanding the molecular mechanism of chloroplast photorelocation movement.

    Science.gov (United States)

    Kong, Sam-Geun; Wada, Masamitsu

    2014-04-01

    Plants are photosynthetic organisms that have evolved unique systems to adapt fluctuating environmental light conditions. In addition to well-known movement responses such as phototropism, stomatal opening, and nastic leaf movements, chloroplast photorelocation movement is one of the essential cellular responses to optimize photosynthetic ability and avoid photodamage. For these adaptations, chloroplasts accumulate at the areas of cells illuminated with low light (called accumulation response), while they scatter from the area illuminated with strong light (called avoidance response). Plant-specific photoreceptors (phototropin, phytochrome, and/or neochrome) mediate these dynamic directional movements in response to incident light position and intensity. Several factors involved in the mechanisms underlying the processes from light perception to actin-based movements have also been identified through molecular genetic approach. This review aims to discuss recent findings in the field relating to how chloroplasts move at molecular levels. This article is part of a Special Issue entitled: Dynamic and ultrastructure of bioenergetic membranes and their components.

  5. Responding to color: the regulation of complementary chromatic adaptation.

    Science.gov (United States)

    Kehoe, David M; Gutu, Andrian

    2006-01-01

    The acclimation of photosynthetic organisms to changes in light color is ubiquitous and may be best illustrated by the colorful process of complementary chromatic adaptation (CCA). During CCA, cyanobacterial cells change from brick red to bright blue green, depending on their light color environment. The apparent simplicity of this spectacular, photoreversible event belies the complexity of the cellular response to changes in light color. Recent results have shown that the regulation of CCA is also complex and involves at least three pathways. One is controlled by a phytochrome-class photoreceptor that is responsive to green and red light and a complex two-component signal transduction pathway, whereas another is based on sensing redox state. Studies of CCA are uncovering the strategies used by photosynthetic organisms during light acclimation and the means by which they regulate these responses.

  6. A molecular understanding of complementary chromatic adaptation.

    Science.gov (United States)

    Grossman, Arthur R

    2003-01-01

    Photosynthetic activity and the composition of the photosynthetic apparatus are strongly regulated by environmental conditions. Some visually dramatic changes in pigmentation of cyanobacterial cells that occur during changing nutrient and light conditions reflect marked alterations in components of the major light-harvesting complex in these organisms, the phycobilisome. As noted well over 100 years ago, the pigment composition of some cyanobacteria is very sensitive to ambient wavelengths of light; this sensitivity reflects molecular changes in polypeptide constituents of the phycobilisome. The levels of different pigmented polypeptides or phycobiliproteins that become associated with the phycobilisome are adjusted to optimize absorption of excitation energy present in the environment. This process, called complementary chromatic adaptation, is controlled by a bilin-binding photoreceptor related to phytochrome of vascular plants; however, many other regulatory elements also play a role in chromatic adaptation. My perspectives and biases on the history and significance of this process are presented in this essay.

  7. Functional interconnection of MYC2 and SPA1 in the photomorphogenic seedling development of Arabidopsis.

    Science.gov (United States)

    Gangappa, Sreeramaiah N; Prasad, V Babu Rajendra; Chattopadhyay, Sudip

    2010-11-01

    MYC2 is a basic helix-loop-helix transcription factor that cross talks with light, abscisic acid (ABA), and jasmonic acid (JA) signaling pathways. Here, we have shown that Arabidopsis (Arabidopsis thaliana) MYC2 directly binds to the G-box present in the SUPPRESSOR OF PHYTOCHROME A1 (SPA1) promoter and that it controls the expression of SPA1 in a COP1-dependent manner. Analyses of atmyc2 spa1 double mutants suggest that whereas MYC2 and SPA1 act redundantly to suppress photomorphogenic growth in the dark, they function synergistically for the suppression of photomorphogenic growth in the light. Our studies have also revealed that MYC2-mediated ABA and JA responses are further modulated by SPA1. Taken together, this study demonstrates the molecular and physiological interrelations of MYC2 and SPA1 in light, ABA, and JA signaling pathways.

  8. Phylogenetic relationships of annual and perennial wild rice: probing by direct DNA sequencing.

    Science.gov (United States)

    Barbier, P; Morishima, H; Ishihama, A

    1991-05-01

    The phylogenetic relationships between Asian wild rice strains were analyzed by direct sequencing of PCR-amplified DNA fragments. The sequence of three introns located in the phytochrome gene was determined for eight strains of the Asian wild rice, Oryza rufipogon, and one strain of the related African species, Oryza longistaminata. The number of nucleotide substitutions per site between various strains within a single species, O. rufipogon, ranged between 0.0017 and 0.0050, while those between two related species, O. rufipogon and O. longistaminate, were 0.043-0.049 (23-26 within 532 bp). Taken together with the sequence differences of the 10-kDa prolamin gene, a model is proposed for the phylogenetic relationships and evolutionary history of annuals and perennials within O. rufipogon.

  9. Equivalence between Pfr and Cyclic AMP in the Induction of d-Usnic Acid Dehydrogenase in the Lichen Evernia prunastri.

    Science.gov (United States)

    Avalos, A; Vicente, C

    1987-07-01

    d-Usnic acid dehydrogenase is induced in Evernia prunastri thalli by a supply of exogenous d-usnic acid in light. This effect is enhanced by red light pulses through a two step way: a very rapid increase of activity after the first 10 minutes of red light, which is not reversed by far-red light, and a slow enhancement following successive red light pulses at the beginning of each hour of incubation. The last response is completely reversed by far-red following red light. Although induction of the enzyme is not achieved in the dark, 0.1 and 0.5 millimolar cyclic AMP, or 0.1 millimolar dibutyryl cyclic AMP substitutes light action and, then, the enzyme is produced. In addition, phytochrome-far red-absorbing form-increases the amount of endogenously produced cyclic AMP and this effect is shown to be photoreversible when ethylenediaminetetraacetic acid is inhibiting adenylate cyclase.

  10. The Transcriptional Coregulator LEUNIG_HOMOLOG Inhibits Light-Dependent Seed Germination in Arabidopsis.

    Science.gov (United States)

    Lee, Nayoung; Park, Jeongmoo; Kim, Keunhwa; Choi, Giltsu

    2015-08-01

    PHYTOCHROME-INTERACTING FACTOR1 (PIF1) is a basic helix-loop-helix transcription factor that inhibits light-dependent seed germination in Arabidopsis thaliana. However, it remains unclear whether PIF1 requires other factors to regulate its direct targets. Here, we demonstrate that LEUNIG_HOMOLOG (LUH), a Groucho family transcriptional corepressor, binds to PIF1 and coregulates its targets. Not only are the transcriptional profiles of the luh and pif1 mutants remarkably similar, more than 80% of the seeds of both genotypes germinate in the dark. We show by chromatin immunoprecipitation that LUH binds a subset of PIF1 targets in a partially PIF1-dependent manner. Unexpectedly, we found LUH binds and coregulates not only PIF1-activated targets but also PIF1-repressed targets. Together, our results indicate LUH functions with PIF1 as a transcriptional coregulator to inhibit seed germination.

  11. High-resolution mapping and genetic characterization of the Lazy-2 gravitropic mutant of tomato

    Science.gov (United States)

    Behringer, F. J.; Lomax, T. L.

    1999-01-01

    Mutation of the Lazy-2 (Lz-2) gene in tomato (Lycopersicon esculentum mill.) produces a phytochrome-dependent reversal of shoot gravitropism, providing a unique genetic resource for investigating how signals from light modulate gravitropism. We mapped the Lz-2 gene using RFLPs and a PCR-based technique to assess the feasibility of positional cloning. Analysis of a 1338 plant backcross population between L. esculentum and L. pennellii placed Lz-2 within a 1.2 cM interval on chromosome 5, 0.4 cM from TG504-CT201A interval. The inabililty to resolve these markers indicates that Lz-2 resides in a centromeric region in which recombination is highly suppressed. Lazy-2 is tightly linked to but does not encode the gene for ACC4, an enzyme involved in ethylene biosynthesis. We also observed that Lz-2 is partially dominant under certain conditions and stages of development.

  12. Stimulation of steviol glycoside accumulation in Stevia rebaudiana by red LED light.

    Science.gov (United States)

    Ceunen, Stijn; Werbrouck, Stefaan; Geuns, Jan M C

    2012-05-01

    The aim of this study was to determine whether steviol glycoside accumulation is under phytochrome control. The results indicate that Stevia rebaudiana Bertoni plants grown under short-day conditions showed precocious flowering and stagnation of steviol glycoside accumulation. Long night interruption by red LED light stimulated and sustained the vegetative growth as well as the accumulation of steviol glycosides in the leaves. After 7 weeks of treatment, steviol glycoside content was about two-fold higher in LED-treated plants than in the short-day control group. The effects of red LED light were measured both in a greenhouse and in a phytotron, irrespective of cultivar-specific differences. Therefore, it can be concluded that a mid-night interruption by red LED light during short photoperiods provides an easy and inexpensive method to increase vegetative leaf biomass production with an increased steviol glycoside yield.

  13. Photosynthesis-dependent anthocyanin pigmentation in Arabidopsis.

    Science.gov (United States)

    Das, Prasanta Kumar; Geul, Bang; Choi, Sang-Bong; Yoo, Sang-Dong; Park, Youn-Il

    2011-01-01

    Light is the ultimate energy source for photo-autotrophs on earth. For green plants, however, it can also be toxic under certain stressful environmental conditions and at critical developmental stages. Anthocyanins, a class of flavonoids, act as an effective screening mechanism that allows plant survival and proliferation under occasional periods of harmful irradiation through modulation of light absorption. Apart from light-sensing through photoreceptors such as phytochrome and cryptochrome, plants use the photosynthetic electron transfer (PET) chain to integrate light information. The redox status of the plastoquinone (PQ) pool of the PET chain regulates anthocyanin biosynthesis genes, together with the plant hormone ethylene and plant hormone-like sugars. A complex signaling apparatus in acyanic cells appears to transduce information to cyanic cells to regulate anthocyanin production through an intercellular signaling pathway that remains largely uncharacterized. This review will highlight recent advances in this field and their implications for the regulation of anthocyanin pigmentation.

  14. Effect of Temperature, Oxygen, and Gibberellic Acid on the Development of Photosensitivity in Oldenlandia corymbosa L. Seeds during Their Incubation in Darkness.

    Science.gov (United States)

    Corbineau, F; Côme, D

    1985-10-01

    Two successive phases can be distinguished in the development of the responsiveness to light in Oldenlandia corymbosa L. seeds during their incubation in darkness. During phase I, the responsiveness to light increases with time if there is sufficient O(2), and the higher the temperature, the faster the increase. This phase is stimulated by gibberellic acid. During the following phase (II), seeds remain responsive to light at 10 or 20 degrees C, but lose their responsiveness at higher temperature (>/=30 degrees C). This second phase depends on O(2): loss of responsiveness is accelerated at lower O(2) concentration. Phase II is only slightly affected by gibberellic acid. The results are discussed in terms of variation of phytochrome and of a reaction along the transduction chain initiated by phototransformation of this pigment, which is finally expressed in germination.

  15. Morphology and Hydraulic Architecture of Vitis vinifera L. cv. Syrah and Torrontés Riojano Plants Are Unaffected by Variations in Red to Far-Red Ratio.

    Science.gov (United States)

    González, Carina Verónica; Jofré, María Florencia; Vila, Hernán F; Stoffel, Markus; Bottini, Rubén; Giordano, Carla Valeria

    2016-01-01

    Plants have evolved an array of specific photoreceptors to acclimate to the light environment. By sensing light signals, photoreceptors modulate plant morphology, carbon- and water-physiology, crop yield and quality of harvestable organs, among other responses. Many cultural practices and crop management decisions alter light quantity and quality perceived by plants cultivated in the field. Under full sunlight, phytochromes perceive high red to far red ratios (R:FR; 1.1), whereas overhead or lateral low R:FR (below 1.1) are sensed in the presence of plant shade or neighboring plants, respectively. Grapevine is one of the most important fruit crops in the world. To date, studies on grapevine response to light focused on different Photosynthetic Active Radiation (PAR) levels; however, limited data exist about its response to light quality. In this study we aimed to investigate morphological, biochemical, and hydraulic responses of Vitis vinifera to variations in R:FR. Therefore, we irradiated Syrah and Torrontés Riojano plants, grown in a glasshouse, with lateral FR light (low lateral R:FR treatment), while others, that were kept as controls, were not irradiated (ambient lateral R:FR treatment). In response to the low lateral R:FR treatment, grapevine plants did not display any of the SAS morphological markers (i.e. stem length, petiole length and angle, number of lateral shoots) in any of the cultivars assessed, despite an increase in gibberelins and auxin concentrations in leaf tissues. Low lateral R:FR did not affect dry matter partitioning, water-related traits (stomata density and index, wood anatomy), or water-related physiology (plant conductance, transpiration rate, stem hydraulic conductivity, stomatal conductance). None of the Vitis vinifera varieties assessed displayed the classical morphological and hydraulic responses associated to SAS induced by phytochromes. We discuss these results in the context of natural grapevine environment and agronomical

  16. Morphology and Hydraulic Architecture of Vitis vinifera L. cv. Syrah and Torrontés Riojano Plants Are Unaffected by Variations in Red to Far-Red Ratio

    Science.gov (United States)

    González, Carina Verónica; Jofré, María Florencia; Vila, Hernán F.; Stoffel, Markus; Bottini, Rubén; Giordano, Carla Valeria

    2016-01-01

    Plants have evolved an array of specific photoreceptors to acclimate to the light environment. By sensing light signals, photoreceptors modulate plant morphology, carbon- and water-physiology, crop yield and quality of harvestable organs, among other responses. Many cultural practices and crop management decisions alter light quantity and quality perceived by plants cultivated in the field. Under full sunlight, phytochromes perceive high red to far red ratios (R:FR; 1.1), whereas overhead or lateral low R:FR (below 1.1) are sensed in the presence of plant shade or neighboring plants, respectively. Grapevine is one of the most important fruit crops in the world. To date, studies on grapevine response to light focused on different Photosynthetic Active Radiation (PAR) levels; however, limited data exist about its response to light quality. In this study we aimed to investigate morphological, biochemical, and hydraulic responses of Vitis vinifera to variations in R:FR. Therefore, we irradiated Syrah and Torrontés Riojano plants, grown in a glasshouse, with lateral FR light (low lateral R:FR treatment), while others, that were kept as controls, were not irradiated (ambient lateral R:FR treatment). In response to the low lateral R:FR treatment, grapevine plants did not display any of the SAS morphological markers (i.e. stem length, petiole length and angle, number of lateral shoots) in any of the cultivars assessed, despite an increase in gibberelins and auxin concentrations in leaf tissues. Low lateral R:FR did not affect dry matter partitioning, water-related traits (stomata density and index, wood anatomy), or water-related physiology (plant conductance, transpiration rate, stem hydraulic conductivity, stomatal conductance). None of the Vitis vinifera varieties assessed displayed the classical morphological and hydraulic responses associated to SAS induced by phytochromes. We discuss these results in the context of natural grapevine environment and agronomical

  17. MAP-kinase activity in etiolated Cucumis sativus cotyledons: the effect of red and far-red light irradiation.

    Science.gov (United States)

    Alvarez-Flórez, Fagua; Vidal, Dolors; Simón, Esther

    2013-02-01

    Phytochrome (phy) signalling in plants may be transduced through protein phosphorylation. Mitogen-activated protein kinase (MAP-kinase, MAPK) activity and the effect of R (red) and FR (far-red) light irradiation on MAPK activity were studied in etiolated Cucumis sativus L. cotyledons. By in vitro protein phosphorylation and in-gel assays with myelin basic protein (MBP), a protein band (between 48 and 45 kDa) with MAPK-like activity was detected. The addition to the phosphorylation buffer of specific protein phosphatase (PTP) inhibitors (Na(3)VO(4) and NaF) and genistein, apigenin or PD98059 as MAPK inhibitors allowed us to confirm the MAPK activity of the protein band. Irradiation of etiolated cotyledons with FR light for 5, 10 or 60 min rapidly and transiently stimulated the MAPK activity of the protein band. This suggests that there was a very low fluence response (VLFR) of phys. In addition, 15 min of R light irradiation or a sequential treatment of 15 min of R plus 5 min of FR also increased MAPK activity. The stimulatory effect of R light was also attributed to the same photoreceptor, which suggests that MAPKs are involved in phytochrome signal transduction. Protein immunoprecipitation and immunoblotting analysis with the polyclonal antibody anti-pERK1/2 (Tyr 204) and the monoclonal antibody anti-phosphotyrosine PY20 allowed us to recognize the above mentioned protein band as two proteins with molecular masses (M(r)) of approximately 47 and 45 kDa, and MAPK activity. The biochemical and immunological properties showed by the proteins detected indicated that they were members of the MAPK family phosphorylated in tyrosine residues.

  18. High irradiance responses involving photoreversible multiple photoreceptors as related to photoperiodic induction of cell division in Euglena.

    Science.gov (United States)

    Bolige, Aoen; Goto, Ken

    2007-02-01

    Little is known about the photoreceptors involved in the photoperiodism of unicellular organisms, which we elucidated by deriving their action spectra. The flagellated alga Euglena gracilis exhibits photoperiodism, with a long-day response in cell reproduction. The underlying clock is a circadian rhythm with photoinductive capability, peaking at subjective dusk and occurring at the 26th hour in continuous darkness (DD) when transferred from continuous light (LL); it regulates photoinduction, a high-irradiance response (HIR), of a dark-capability of progressing through cell division. We derived the action spectra by irradiating E. gracilis with monochromatic light for 3h at around the 26th hour; the action maxima occurred at 380, 450-460, 480, 610, 640, 660, 680, and 740nm. Except for the maximum at 450-460nm, which was always a major maximum, the maxima greatly depended on the red (R)/far-red (FR) ratio of the prior LL. The high R/FR ratio resulted in a dominant major peak at 640nm and minor peaks at 480 and 680nm, whereas the low ratio resulted in dominant major peaks at 610 and 740nm and minor peaks at 380 and 660nm; the critical fluence was minimally about 60mmolm(-2). These HIRs resulted from the accumulation of corresponding low-fluence responses (LFRs) because we found that repetition of a 3-min light/dark cycle, with critical fluences of 1mmolm(-2), lasting for 3h resulted in the same photoinduction as the continuous 3-h irradiation. Moreover, these LFRs expressed photoreversibility. Thus, photoperiodic photoinduction involves Euglena-phytochrome (640 and 740nm) and blue photoreceptor (460nm). Although 380, 480, 610, 660, and 680nm may also represent Euglena-phytochrome, a definite conclusion awaits further study.

  19. A Heme-based Redox Sensor in the Methanogenic Archaeon Methanosarcina acetivorans*

    Science.gov (United States)

    Molitor, Bastian; Stassen, Marc; Modi, Anuja; El-Mashtoly, Samir F.; Laurich, Christoph; Lubitz, Wolfgang; Dawson, John H.; Rother, Michael; Frankenberg-Dinkel, Nicole

    2013-01-01

    Based on a bioinformatics study, the protein MA4561 from the methanogenic archaeon Methanosarcina acetivorans was originally predicted to be a multidomain phytochrome-like photosensory kinase possibly binding open-chain tetrapyrroles. Although we were able to show that recombinantly produced and purified protein does not bind any known phytochrome chromophores, UV-visible spectroscopy revealed the presence of a heme tetrapyrrole cofactor. In contrast to many other known cytoplasmic heme-containing proteins, the heme was covalently attached via one vinyl side chain to cysteine 656 in the second GAF domain. This GAF domain by itself is sufficient for covalent attachment. Resonance Raman and magnetic circular dichroism data support a model of a six-coordinate heme species with additional features of a five-coordination structure. The heme cofactor is redox-active and able to coordinate various ligands like imidazole, dimethyl sulfide, and carbon monoxide depending on the redox state. Interestingly, the redox state of the heme cofactor has a substantial influence on autophosphorylation activity. Although reduced protein does not autophosphorylate, oxidized protein gives a strong autophosphorylation signal independent from bound external ligands. Based on its genomic localization, MA4561 is most likely a sensor kinase of a two-component system effecting regulation of the Mts system, a set of three homologous corrinoid/methyltransferase fusion protein isoforms involved in methyl sulfide metabolism. Consistent with this prediction, an M. acetivorans mutant devoid of MA4561 constitutively synthesized MtsF. On the basis of our results, we postulate a heme-based redox/dimethyl sulfide sensory function of MA4561 and propose to designate it MsmS (methyl sulfide methyltransferase-associated sensor). PMID:23661702

  20. FAR-RED ELONGATED HYPOCOTYL3 activates SEPALLATA2 but inhibits CLAVATA3 to regulate meristem determinacy and maintenance in Arabidopsis.

    Science.gov (United States)

    Li, Dongming; Fu, Xing; Guo, Lin; Huang, Zhigang; Li, Yongpeng; Liu, Yang; He, Zishan; Cao, Xiuwei; Ma, Xiaohan; Zhao, Meicheng; Zhu, Guohui; Xiao, Langtao; Wang, Haiyang; Chen, Xuemei; Liu, Renyi; Liu, Xigang

    2016-08-16

    Plant meristems are responsible for the generation of all plant tissues and organs. Here we show that the transcription factor (TF) FAR-RED ELONGATED HYPOCOTYL3 (FHY3) plays an important role in both floral meristem (FM) determinacy and shoot apical meristem maintenance in Arabidopsis, in addition to its well-known multifaceted roles in plant growth and development during the vegetative stage. Through genetic analyses, we show that WUSCHEL (WUS) and CLAVATA3 (CLV3), two central players in the establishment and maintenance of meristems, are epistatic to FHY3 Using genome-wide ChIP-seq and RNA-seq data, we identify hundreds of FHY3 target genes in flowers and find that FHY3 mainly acts as a transcriptional repressor in flower development, in contrast to its transcriptional activator role in seedlings. Binding motif-enrichment analyses indicate that FHY3 may coregulate flower development with three flower-specific MADS-domain TFs and four basic helix-loop-helix TFs that are involved in photomorphogenesis. We further demonstrate that CLV3, SEPALLATA1 (SEP1), and SEP2 are FHY3 target genes. In shoot apical meristem, FHY3 directly represses CLV3, which consequently regulates WUS to maintain the stem cell pool. Intriguingly, CLV3 expression did not change significantly in fhy3 and phytochrome B mutants before and after light treatment, indicating that FHY3 and phytochrome B are involved in light-regulated meristem activity. In FM, FHY3 directly represses CLV3, but activates SEP2, to ultimately promote FM determinacy. Taken together, our results reveal insights into the mechanisms of meristem maintenance and determinacy, and illustrate how the roles of a single TF may vary in different organs and developmental stages.

  1. Regulation of Carotenoid Biosynthesis by Shade Relies on Specific Subsets of Antagonistic Transcription Factors and Cofactors1[OPEN

    Science.gov (United States)

    Bou-Torrent, Jordi; Toledo-Ortiz, Gabriela; Ortiz-Alcaide, Miriam; Cifuentes-Esquivel, Nicolas; Halliday, Karen J.; Martinez-García, Jaime F.; Rodriguez-Concepcion, Manuel

    2015-01-01

    Carotenoids are photosynthetic pigments essential for the protection against excess light. During deetiolation, their production is regulated by a dynamic repression-activation module formed by PHYTOCHROME-INTERACTING FACTOR1 (PIF1) and LONG HYPOCOTYL5 (HY5). These transcription factors directly and oppositely control the expression of the gene encoding PHYTOENE SYNTHASE (PSY), the first and main rate-determining enzyme of the carotenoid pathway. Antagonistic modules also regulate the responses of deetiolated plants to vegetation proximity and shade (i.e. to the perception of far-red light-enriched light filtered through or reflected from neighboring plants). These responses, aimed to adapt to eventual shading from plant competitors, include a reduced accumulation of carotenoids. Here, we show that PIF1 and related photolabile PIFs (but not photostable PIF7) promote the shade-triggered decrease in carotenoid accumulation. While HY5 does not appear to be required for this process, other known PIF antagonists were found to modulate the expression of the Arabidopsis (Arabidopsis thaliana) PSY gene and the biosynthesis of carotenoids early after exposure to shade. In particular, PHYTOCHROME-RAPIDLY REGULATED1, a transcriptional cofactor that prevents the binding of true transcription factors to their target promoters, was found to interact with PIF1 and hence directly induce PSY expression. By contrast, a change in the levels of the transcriptional cofactor LONG HYPOCOTYL IN FAR RED1, which also binds to PIF1 and other PIFs to regulate shade-related elongation responses, did not impact PSY expression or carotenoid accumulation. Our data suggest that the fine-regulation of carotenoid biosynthesis in response to shade relies on specific modules of antagonistic transcriptional factors and cofactors. PMID:26082398

  2. Different blue-light requirement for the accumulation of transcripts from nuclear genes for thylakoid proteins in Nicotiana tabacum and Lycopersicon esculentum.

    Science.gov (United States)

    Palomares, R; Herrmann, R G; Oelmüller, R

    1991-11-01

    We have isolated recombinant lambda gt11 phages which carry cDNA clones for the major light-harvesting chlorophyll a/b-binding proteins of photosystem I (LHCPI) and II (LHCPII), subunit II of photosystem I, a chlorophyll a/b-binding protein of photosystem II (CP24), the Rieske iron-sulphur protein of the cytochrome b6/f complex, and the 33, 23 and 16 kDa proteins of the water-oxidizing complex of photosystem II from Nicotiana tabacum. The nucleotide sequences of cDNA clones encoding the precursors for LHCPI and the FeS protein are presented. If tobacco or tomato seedlings, or seedlings of a phytochrome-deficient aurea mutant of tomato which lacks more than 95% of the phytochrome of the isogenic wild type, are kept in blue light, the transcript level of each of these genes is higher than in seedlings grown in red light suggesting the involvement of a blue-UVA-light photoreceptor. In the case of LHCPI, a 1 min blue-light pulse applied to red-light-grown seedlings is sufficient to increase the transcript levels to those present in blue-light-grown seedlings, whereas almost no increase is observed for transcripts encoding the FeS and 33 kDa proteins. If dark-grown tomato seedlings receive a single far-red-light pulse, significant stimulation is detected for LHCPI transcripts, whereas transcripts encoding the FeS and 33 kDa proteins are not stimulated. It is concluded that the lower light requirement for the increase in the LHCPI transcript level is not specific for one of the light-dependent signal transduction chains.

  3. A novel high-throughput in vivo molecular screen for shade avoidance mutants identifies a novel phyA mutation.

    Science.gov (United States)

    Wang, Xuewen; Roig-Villanova, Irma; Khan, Safina; Shanahan, Hugh; Quail, Peter H; Martinez-Garcia, Jaime F; Devlin, Paul F

    2011-05-01

    The shade avoidance syndrome (SAS) allows plants to anticipate and avoid shading by neighbouring plants by initiating an elongation growth response. The phytochrome photoreceptors are able to detect a reduction in the red:far red ratio in incident light, the result of selective absorption of red and blue wavelengths by proximal vegetation. A shade-responsive luciferase reporter line (PHYB::LUC) was used to carry out a high-throughput screen to identify novel SAS mutants. The dracula 1 (dra1) mutant, that showed no avoidance of shade for the PHYB::LUC response, was the result of a mutation in the PHYA gene. Like previously characterized phyA mutants, dra1 showed a long hypocotyl in far red light and an enhanced hypocotyl elongation response to shade. However, dra1 additionally showed a long hypocotyl in red light. Since phyB levels are relatively unaffected in dra1, this gain-of-function red light phenotype strongly suggests a disruption of phyB signalling. The dra1 mutation, G773E within the phyA PAS2 domain, occurs at a residue absolutely conserved among phyA sequences. The equivalent residue in phyB is absolutely conserved as a threonine. PAS domains are structurally conserved domains involved in molecular interaction. Structural modelling of the dra1 mutation within the phyA PAS2 domain shows some similarity with the structure of the phyB PAS2 domain, suggesting that the interference with phyB signalling may be the result of non-functional mimicry. Hence, it was hypothesized that this PAS2 residue forms a key distinction between the phyA and phyB phytochrome species.

  4. No time for candy: passionfruit (Passiflora edulis) plants down-regulate damage-induced extra floral nectar production in response to light signals of competition.

    Science.gov (United States)

    Izaguirre, Miriam M; Mazza, Carlos A; Astigueta, María S; Ciarla, Ana M; Ballaré, Carlos L

    2013-09-01

    Plant fitness is often defined by the combined effects of herbivory and competition, and plants must strike a delicate balance between their ability to capture limiting resources and defend against herbivore attack. Many plants use indirect defenses, such as volatile compounds and extra floral nectaries (EFN), to attract canopy arthropods that are natural enemies of herbivorous organisms. While recent evidence suggests that upon perception of low red to far-red (R:FR) ratios, which signal the proximity of competitors, plants down-regulate resource allocation to direct chemical defenses, it is unknown if a similar phytochrome-mediated response occurs for indirect defenses. We evaluated the interactive effects of R:FR ratio and simulated herbivory on nectar production by EFNs of passion fruit (Passiflora edulis f. flavicarpa). The activity of petiolar EFNs dramatically increased in response to simulated herbivory and hormonal treatment with methyl jasmonate (MeJA). Low R:FR ratios, which induced a classic "shade-avoidance" repertoire of increased stem elongation in P. edulis, strongly suppressed the EFN response triggered by simulated herbivory or MeJA application. Strikingly, the EFN response to wounding and light quality was localized to the branches that received the treatments. In vines like P. edulis, a local response would allow the plants to precisely adjust their light harvesting and defense phenotypes to the local conditions encountered by individual branches when foraging for resources in patchy canopies. Consistent with the emerging paradigm that phytochrome regulation of jasmonate signaling is a central modulator of adaptive phenotypic plasticity, our results demonstrate that light quality is a strong regulator of indirect defenses.

  5. Arabidopsis DET1 degrades HFR1 but stabilizes PIF1 to precisely regulate seed germination

    Science.gov (United States)

    Shi, Hui; Wang, Xin; Mo, Xiaorong; Tang, Chao; Zhong, Shangwei; Deng, Xing Wang

    2015-01-01

    Seed is an essential propagation organ and a critical strategy adopted by terrestrial flowering plants to colonize the land. The ability of seeds to accurately respond to light is vital for plant survival. However, the underlying mechanism is largely unknown. In this study, we reveal a circuit of triple feed-forward loops adopted by Arabidopsis seeds to exclusively repress germination in dark conditions and precisely initiate germination under diverse light conditions. We identify that de-etiolated 1 (DET1), an evolutionarily conserved protein, is a central repressor of light-induced seed germination. Genetic analysis demonstrates that DET1 functions upstream of long hypocotyl in far-red 1 (HFR1) and phytochrome interacting factor 1 (PIF1), the key positive and negative transcription regulators in seed germination. We further find that DET1 and constitutive photomorphogenic 10 (COP10) target HFR1 for protein degradation by assembling a COP10–DET1–damaged DNA binding protein 1–cullin4 E3 ligase complex. Moreover, DET1 and COP10 directly interact with and promote the protein stability of PIF1. Computational modeling reveals that phytochrome B (phyB)–DET1–HFR1–PIF1 and phyB–DET1–Protease–PIF1 are new signaling pathways, independent of the previously identified phyB-PIF1 pathway, respectively mediating the rapid and time-lapse responses to light irradiation. The model-simulated results are highly consistent with their experimental validations, suggesting that our mathematical model captures the essence of Arabidopsis seed germination networks. Taken together, this study provides a comprehensive molecular framework for light-regulated seed germination, improving our understanding of how plants respond to changeable environments. PMID:25775589

  6. Arabidopsis DET1 degrades HFR1 but stabilizes PIF1 to precisely regulate seed germination.

    Science.gov (United States)

    Shi, Hui; Wang, Xin; Mo, Xiaorong; Tang, Chao; Zhong, Shangwei; Deng, Xing Wang

    2015-03-24

    Seed is an essential propagation organ and a critical strategy adopted by terrestrial flowering plants to colonize the land. The ability of seeds to accurately respond to light is vital for plant survival. However, the underlying mechanism is largely unknown. In this study, we reveal a circuit of triple feed-forward loops adopted by Arabidopsis seeds to exclusively repress germination in dark conditions and precisely initiate germination under diverse light conditions. We identify that de-etiolated 1 (DET1), an evolutionarily conserved protein, is a central repressor of light-induced seed germination. Genetic analysis demonstrates that DET1 functions upstream of long hypocotyl in far-red 1 (HFR1) and phytochrome interacting factor 1 (PIF1), the key positive and negative transcription regulators in seed germination. We further find that DET1 and constitutive photomorphogenic 10 (COP10) target HFR1 for protein degradation by assembling a COP10-DET1-damaged DNA binding protein 1-cullin4 E3 ligase complex. Moreover, DET1 and COP10 directly interact with and promote the protein stability of PIF1. Computational modeling reveals that phytochrome B (phyB)-DET1-HFR1-PIF1 and phyB-DET1-Protease-PIF1 are new signaling pathways, independent of the previously identified phyB-PIF1 pathway, respectively mediating the rapid and time-lapse responses to light irradiation. The model-simulated results are highly consistent with their experimental validations, suggesting that our mathematical model captures the essence of Arabidopsis seed germination networks. Taken together, this study provides a comprehensive molecular framework for light-regulated seed germination, improving our understanding of how plants respond to changeable environments.

  7. A LOV protein modulates the physiological attributes of Xanthomonas axonopodis pv. citri relevant for host plant colonization.

    Directory of Open Access Journals (Sweden)

    Ivana Kraiselburd

    Full Text Available Recent studies have demonstrated that an appropriate light environment is required for the establishment of efficient vegetal resistance responses in several plant-pathogen interactions. The photoreceptors implicated in such responses are mainly those belonging to the phytochrome family. Data obtained from bacterial genome sequences revealed the presence of photosensory proteins of the BLUF (Blue Light sensing Using FAD, LOV (Light, Oxygen, Voltage and phytochrome families with no known functions. Xanthomonas axonopodis pv. citri is a Gram-negative bacterium responsible for citrus canker. The in silico analysis of the X. axonopodis pv. citri genome sequence revealed the presence of a gene encoding a putative LOV photoreceptor, in addition to two genes encoding BLUF proteins. This suggests that blue light sensing could play a role in X. axonopodis pv. citri physiology. We obtained the recombinant Xac-LOV protein by expression in Escherichia coli and performed a spectroscopic analysis of the purified protein, which demonstrated that it has a canonical LOV photochemistry. We also constructed a mutant strain of X. axonopodis pv. citri lacking the LOV protein and found that the loss of this protein altered bacterial motility, exopolysaccharide production and biofilm formation. Moreover, we observed that the adhesion of the mutant strain to abiotic and biotic surfaces was significantly diminished compared to the wild-type. Finally, inoculation of orange (Citrus sinensis leaves with the mutant strain of X. axonopodis pv. citri resulted in marked differences in the development of symptoms in plant tissues relative to the wild-type, suggesting a role for the Xac-LOV protein in the pathogenic process. Altogether, these results suggest the novel involvement of a photosensory system in the regulation of physiological attributes of a phytopathogenic bacterium. A functional blue light receptor in Xanthomonas spp. has been described for the first time, showing

  8. Two Cyanobacterial Photoreceptors Regulate Photosynthetic Light Harvesting by Sensing Teal, Green, Yellow, and Red Light.

    Science.gov (United States)

    Wiltbank, Lisa B; Kehoe, David M

    2016-02-09

    The genomes of many photosynthetic and nonphotosynthetic bacteria encode numerous phytochrome superfamily photoreceptors whose functions and interactions are largely unknown. Cyanobacterial genomes encode particularly large numbers of phytochrome superfamily members called cyanobacteriochromes. These have diverse light color-sensing abilities, and their functions and interactions are just beginning to be understood. One of the best characterized of these functions is the regulation of photosynthetic light-harvesting antenna composition in the cyanobacterium Fremyella diplosiphon by the cyanobacteriochrome RcaE in response to red and green light, a process known as chromatic acclimation. We have identified a new cyanobacteriochrome named DpxA that maximally senses teal (absorption maximum, 494 nm) and yellow (absorption maximum, 568 nm) light and represses the accumulation of a key light-harvesting protein called phycoerythrin, which is also regulated by RcaE during chromatic acclimation. Like RcaE, DpxA is a two-component system kinase, although these two photoreceptors can influence phycoerythrin expression through different signaling pathways. The peak responsiveness of DpxA to teal and yellow light provides highly refined color discrimination in the green spectral region, which provides important wavelengths for photosynthetic light harvesting in cyanobacteria. These results redefine chromatic acclimation in cyanobacteria and demonstrate that cyanobacteriochromes can coordinately impart sophisticated light color sensing across the visible spectrum to regulate important photosynthetic acclimation processes. The large number of cyanobacteriochrome photoreceptors encoded by cyanobacterial genomes suggests that these organisms are capable of extremely complex light color sensing and responsiveness, yet little is known about their functions and interactions. Our work uncovers previously undescribed cooperation between two photoreceptors with very different light

  9. The epiphytic Cactaceae Hylocereus setaceus (Salm-Dick ex DC. ralf bauer seed germination is controlled by light and temperature

    Directory of Open Access Journals (Sweden)

    Edson Simão

    2007-07-01

    Full Text Available The effect of light and temperature on seed germination in Hylocereus setaceus was analyzed by isothermic incubations under continuous white light and darkness. The minimum temperature for germination was between 5 to 10°C and the maximum between 45 to 50°C. The optimum temperaturewais between 25 and 30°C. The involvement of phytochrome, by very low fluence response, in controlled seed germination was attained by incubation in a gradient of photoequilibrium of phytochrome. The results indicated that seeds of H. setaceus germinated in a wide range of temperature, under canopy and in open areas, but in complete darkness they did not germinate.O efeito da luz e da temperatura sobre a germinação de sementes de Hylocereus setaceus foi analisado sob condições de incubações isotérmicas. Hylocereus setaceus é uma espécie ameaçada de extinção, que ocorre na Mata Atlântica e florestas estacionais semideciduais. A temperatura mínima para a germinação está entre 5 e 10°C e a máxima entre 45 e 50°C. A temperatura ótima está entre 25ºC e 30°C. A participação do fitocromo, através da resposta de fluência muito baixa, no controle da germinação de sementes foi determinada através de incubações das sementes em um gradiente de fotoequilíbrio do fitocromo. Os resultados apresentados no presente trabalho indicam que sementes de Hylocereus setaceus germinam em uma ampla faixa de temperatura, sob a sombra de vegetação e em áreas abertas, embora não germinem em condições de ausência completa de luz.

  10. A transcriptional analysis of carotenoid, chlorophyll and plastidial isoprenoid biosynthesis genes during development and osmotic stress responses in Arabidopsis thaliana

    KAUST Repository

    Meier, Stuart

    2011-05-19

    Background: The carotenoids are pure isoprenoids that are essential components of the photosynthetic apparatus and are coordinately synthesized with chlorophylls in chloroplasts. However, little is known about the mechanisms that regulate carotenoid biosynthesis or the mechanisms that coordinate this synthesis with that of chlorophylls and other plastidial synthesized isoprenoid-derived compounds, including quinones, gibberellic acid and abscisic acid. Here, a comprehensive transcriptional analysis of individual carotenoid and isoprenoid-related biosynthesis pathway genes was performed in order to elucidate the role of transcriptional regulation in the coordinated synthesis of these compounds and to identify regulatory components that may mediate this process in Arabidopsis thaliana.Results: A global microarray expression correlation analysis revealed that the phytoene synthase gene, which encodes the first dedicated and rate-limiting enzyme of carotenogenesis, is highly co-expressed with many photosynthesis-related genes including many isoprenoid-related biosynthesis pathway genes. Chemical and mutant analysis revealed that induction of the co-expressed genes following germination was dependent on gibberellic acid and brassinosteroids (BR) but was inhibited by abscisic acid (ABA). Mutant analyses further revealed that expression of many of the genes is suppressed in dark grown plants by Phytochrome Interacting transcription Factors (PIFs) and activated by photoactivated phytochromes, which in turn degrade PIFs and mediate a coordinated induction of the genes. The promoters of PSY and the co-expressed genes were found to contain an enrichment in putative BR-auxin response elements and G-boxes, which bind PIFs, further supporting a role for BRs and PIFs in regulating expression of the genes. In osmotically stressed root tissue, transcription of Calvin cycle, methylerythritol 4-phosphate pathway and carotenoid biosynthesis genes is induced and uncoupled from that of

  11. Review on influence mechanisms of light in seed germination%光对种子萌发的影响机理研究进展

    Institute of Scientific and Technical Information of China (English)

    张敏; 朱教君; 闫巧玲

    2012-01-01

    Seed germination is a key process in the natural regeneration of plant populations and is mainly controlled by favorable temperature, water or light conditions. Light plays a critical role in determining the ability and rate of germination of photoblastic seeds. Furthermore, the regulation of seed germination by light involves not only complicated physiological processes but also rigorous signal transductions and gene expression pathways. We summarized available data on the relationships between seed germination and other factors (i.e., light attributes, coupling of light and water/heat and phytochromes in seeds). To assess the effects of light on seed germination, we also comprehensively summarized the physiological reaction and light signal transduction mechanisms regulated by phytochromes in seed germination.%种子萌发是植物成功实现天然更新的关键环节,需要适宜的温度、水分或光照条件.对于需光性种子,光照是决定其萌发与否或萌发率高低的主要因素.光对植物种子萌发的影响不仅是一个复杂的生理过程,也是受到调控的信号传递和基因表达过程.该文系统总结了影响种子萌发的光照属性、光与水/热耦合作用和种子的光属性(光敏色素)与种子萌发的关系,明确了光调控种子萌发的生态意义;重点综述了种子内光敏色素调控种子萌发的生理反应模式和光敏色素的光信号转导途径.试图为全面评估光对种子萌发的影响和将来开展更深入的研究提供参考.

  12. Nucleotide sequence of a tobacco cDNA encoding plastidic glutamine synthetase and light inducibility, organ specificity and diurnal rhythmicity in the expression of the corresponding genes of tobacco and tomato.

    Science.gov (United States)

    Becker, T W; Caboche, M; Carrayol, E; Hirel, B

    1992-06-01

    A full-length cDNA encoding glutamine synthetase (GS) was cloned from a lambda gt10 library of tobacco leaf RNA, and the nucleotide sequence was determined. An open reading frame accounting for a primary translation product consisting of 432 amino acids has been localized on the cDNA. The calculated molecular mass of the encoded protein is 47.2 kDa. The predicted amino acid sequence of this precursor shows higher homology to GS-2 protein sequences from other species than to a leaf GS-1 polypeptide sequence, indicating that the cDNA isolated encodes the chloroplastic isoform (GS-2) of tobacco GS. The presence of C- and N-terminal extensions which are characteristic of GS-2 proteins supports this conclusion. Genomic Southern blot analysis indicated that GS-2 is encoded by a single gene in the diploid genomes of both tomato and Nicotiana sylvestris, while two GS-2 genes are very likely present in the amphidiploid tobacco genome. Western blot analysis indicated that in etiolated and in green tomato cotyledons GS-2 subunits are represented by polypeptides of similar size, while in green tomato leaves an additional GS-2 polypeptide of higher apparent molecular weight is detectable. In contrast, tobacco GS-2 is composed of subunits of identical size in all organs examined. GS-2 transcripts and GS-2 proteins could be detected at high levels in the leaves of both tobacco or tomato. Lower amounts of GS-2 mRNA were detected in stems, corolla, and roots of tomato, but not in non-green organs of tobacco. The GS-2 transcript abundance exhibited a diurnal fluctuation in tomato leaves but not in tobacco leaves. White or red light stimulated the accumulation of GS-2 transcripts and GS-2 protein in etiolated tomato cotyledons. Far-red light cancelled this stimulation. The red light response of the GS-2 gene was reduced in etiolated seedlings of the phytochrome-deficient aurea mutant of tomato. These results indicate a phytochrome-mediated light stimulation of GS-2 gene expression

  13. A transcriptional analysis of carotenoid, chlorophyll and plastidial isoprenoid biosynthesis genes during development and osmotic stress responses in Arabidopsis thaliana

    Directory of Open Access Journals (Sweden)

    Vallabhaneni Ratnakar

    2011-05-01

    Full Text Available Abstract Background The carotenoids are pure isoprenoids that are essential components of the photosynthetic apparatus and are coordinately synthesized with chlorophylls in chloroplasts. However, little is known about the mechanisms that regulate carotenoid biosynthesis or the mechanisms that coordinate this synthesis with that of chlorophylls and other plastidial synthesized isoprenoid-derived compounds, including quinones, gibberellic acid and abscisic acid. Here, a comprehensive transcriptional analysis of individual carotenoid and isoprenoid-related biosynthesis pathway genes was performed in order to elucidate the role of transcriptional regulation in the coordinated synthesis of these compounds and to identify regulatory components that may mediate this process in Arabidopsis thaliana. Results A global microarray expression correlation analysis revealed that the phytoene synthase gene, which encodes the first dedicated and rate-limiting enzyme of carotenogenesis, is highly co-expressed with many photosynthesis-related genes including many isoprenoid-related biosynthesis pathway genes. Chemical and mutant analysis revealed that induction of the co-expressed genes following germination was dependent on gibberellic acid and brassinosteroids (BR but was inhibited by abscisic acid (ABA. Mutant analyses further revealed that expression of many of the genes is suppressed in dark grown plants by Phytochrome Interacting transcription Factors (PIFs and activated by photoactivated phytochromes, which in turn degrade PIFs and mediate a coordinated induction of the genes. The promoters of PSY and the co-expressed genes were found to contain an enrichment in putative BR-auxin response elements and G-boxes, which bind PIFs, further supporting a role for BRs and PIFs in regulating expression of the genes. In osmotically stressed root tissue, transcription of Calvin cycle, methylerythritol 4-phosphate pathway and carotenoid biosynthesis genes is induced

  14. What have we learned about phototropism from spaceflight experiments? Novel responses to light discovered during the Seedling Growth project on the ISS.

    Science.gov (United States)

    Kiss, John Z.; Edelmann, Richard; Herranz, Raul; Medina, Francisco Javier; Vandenbrink, Joshua

    2016-07-01

    In response to external stimuli, plants exhibit directed growth responses termed tropisms. Phototropism is directed growth of plants in response to light while gravitropism is the tropistic movement of plants in response to gravity. The integration of these tropisms (along with other growth movements) results in the overall growth form of the plant. Utilizing the European Modular Cultivation System (EMCS) on the International Space Station (ISS), we were able to decouple phototropism from the effects of gravitropism. The Seedling Growth (SG-1, 2, 3) series of experiments employed the centrifuge in the EMCS to create fractional/reduced gravity environments (0, 0.3, 0.5, 0.8 and 1g) to help discern the relationship between the phototropic response and gravitropism in seedlings of Arabidopsis thaliana. In SG, seedlings were exposed to continuous red light, continuous blue light, and red-to-blue light cycles at various gravity levels in order to characterize the phototropic response. Image downlinks from the ISS allowed for analysis of growth and curvature measurements under differential light and gravity conditions. Previous results from our space experiments identified a unique red-light-based phototropism in roots and shoots. The most recent results from SG-1 and SG-2 (2015) reveal a novel positive phototropic curvature in roots of seedlings illuminated with blue light under microgravity conditions. In addition, a positive phototropic response of roots and shoots exposed to red light was observed in microgravity, confirming our previous observations. The phototropic response of shoots to blue light appears to be largely unaffected by fractional gravity. In addition to the WT (Landsberg ecotype), phytochrome A and B mutants were utilized to elucidate the role phytochromes play in blue and red light perception and the resulting phototropic responses. Understanding the relationship between phototropic and gravitropic responses is an important first step in being able

  15. Function and distribution of bilin biosynthesis enzymes in photosynthetic organisms.

    Science.gov (United States)

    Dammeyer, Thorben; Frankenberg-Dinkel, Nicole

    2008-10-01

    Bilins are open-chain tetrapyrrole molecules essential for light-harvesting and/or sensing in many photosynthetic organisms. While they serve as chromophores in phytochrome-mediated light-sensing in plants, they additionally function in light-harvesting in cyanobacteria, red algae and cryptomonads. Associated to phycobiliproteins a variety of bile pigments is responsible for the specific light-absorbance properties of the organisms enabling efficient photosynthesis under different light conditions. The initial step of bilin biosynthesis is the cleavage of heme by heme oxygenases (HO) to afford the first linear molecule biliverdin. This reaction is ubiquitously found also in non-photosynthetic organisms. Biliverdin is then further reduced by site specific reductases most of them belonging to the interesting family of ferredoxin-dependent bilin reductases (FDBRs)-a new family of radical oxidoreductases. In recent years much progress has been made in the field of heme oxygenases but even more in the widespread family of FDBRs, revealing novel biochemical FDBR activities, new crystal structures and new ecological aspects, including the discovery of bilin biosynthesis genes in wild marine phage populations. The aim of this review is to summarize and discuss the recent progress in this field and to highlight the new and remaining questions.

  16. Light quality and temperature effects on antirrhinum growth and development

    Institute of Scientific and Technical Information of China (English)

    KHATTAK Abdul Mateen; PEARSON Simon

    2005-01-01

    An experiment was carried out to examine the effects of light quality on the growth and development of antirrhinum under three different temperatures 19℃, 24℃ and 27℃ in glasshouses. Five different colour filters (i.e. 'Red absorbing', 'Blue absorbing', 'Blue and Red absorbing' and two 'partially Blue absorbing' materials) were tested, with one clear polythene as a control. Plant height, internode length and leaf area were significantly affected by the spectral filters as well as the temperature.Analysis of color filter's effect on presumed photoreceptors to exist indicated that antirrhinum plant height was regulated by the action of a blue acting photoreceptor (BAP) and not the phytochrome. There was no evidence for an effect ofphytochrome or BAP on time to flowering, however, increasing temperature levels effectively decreased the time to flowering. To predict the effects of different spectral qualities and temperature, simple models were created from data on plant height, internode length and time to flowering. These models were then applied to simulate the potential benefits of spectral filters and temperature in manipulation of growth control and flowering in antirrhinum.

  17. Comprehensive Analysis of DWARF14-LIKE2 (DLK2 Reveals Its Functional Divergence from Strigolactone-Related Paralogs

    Directory of Open Access Journals (Sweden)

    Attila Végh

    2017-09-01

    Full Text Available Strigolactones (SLs and related butenolides, originally identified as active seed germination stimulants of parasitic weeds, play important roles in many aspects of plant development. Two members of the D14 α/β hydrolase protein family, DWARF14 (D14 and KARRIKIN INSENSITIVE2 (KAI2 are essential for SL/butenolide signaling. The third member of the family in Arabidopsis, DWARF 14-LIKE2 (DLK2 is structurally very similar to D14 and KAI2, but its function is unknown. We demonstrated that DLK2 does not bind nor hydrolyze natural (+5-deoxystrigol [(+5DS], and weakly hydrolyzes non-natural strigolactone (-5DS. A detailed genetic analysis revealed that DLK2 does not affect SL responses and can regulate seedling photomorphogenesis. DLK2 is upregulated in the dark dependent upon KAI2 and PHYTOCHROME INTERACTING FACTORS (PIFs, indicating that DLK2 might function in light signaling pathways. In addition, unlike its paralog proteins, DLK2 is not subject to rac-GR24-induced degradation, suggesting that DLK2 acts independently of MORE AXILLARY GROWTH2 (MAX2; however, regulation of DLK2 transcription is mostly accomplished through MAX2. In conclusion, these data suggest that DLK2 represents a divergent member of the DWARF14 family.

  18. Blue-Light-Independent Activity of Arabidopsis Cryptochromes in the Regulation of Steady-State Levels of Protein and mRNA Expression

    Institute of Scientific and Technical Information of China (English)

    Yue-Jun Yang; Xuan-Ming Liu; Chen-Tao Lin; Ze-Cheng Zuo; Xiao-Ying Zhao; Xu Li; John Klejnot; Yan Li; Ping Chen; Song-Ping Liang; Xu-Hong Yu

    2008-01-01

    Cryptochromes are blue-light receptors that mediate blue-light inhibition of hypocotyl elongation and bluelight stimulation of floral initiation in Arabidopsis. In addition to their blue-light-dependent functions, cryptochromes are also involved in blue-light-independent regulation of the circadian clock, cotyledon unfolding, and hypocotyl inhibition.However, the molecular mechanism associated with the blue-light-independent function of cryptochromes remains unclear. We reported here a comparative proteomics study of the light regulation of protein expression. We showed that, as expected, the protein expression of many metabolic enzymes changed in response to both blue light and red light. Surprisingly, some light-regulated protein expression changes are impaired in the cry1cry2 mutant in both blue light and red light. This result suggests that, in addition to mediating blue-light-dependent regulation of protein expression, cryptochromes are also involved in the blue-light-independent regulation of gene expression. Consistent with this hypothesis,the cry1cry2 mutant exhibited reduced changes of mRNA expression in response to not only blue light, but also red light,although the cryptochrome effects on the red-light-dependent gene expression changes are generally less pronounced.These results support a hypothesis that, in addition to their blue-light-specific functions, cryptochromes also play roles in the control of gene expression mediated by the red/far-red-light receptor phytochromes.

  19. Photoreceptor Mediated Plant Growth Responses: Implications for Photoreceptor Engineering toward Improved Performance in Crops

    Directory of Open Access Journals (Sweden)

    Ophilia I. L. Mawphlang

    2017-07-01

    Full Text Available Rising temperatures during growing seasons coupled with altered precipitation rates presents a challenging task of improving crop productivity for overcoming such altered weather patterns and cater to a growing population. Light is a critical environmental factor that exerts a powerful influence on plant growth and development ranging from seed germination to flowering and fruiting. Higher plants utilize a suite of complex photoreceptor proteins to perceive surrounding red/far-red (phytochromes, blue/UV-A (cryptochromes, phototropins, ZTL/FKF1/LKP2, and UV-B light (UVR8. While genomic studies have also shown that light induces extensive reprogramming of gene expression patterns in plants, molecular genetic studies have shown that manipulation of one or more photoreceptors can result in modification of agronomically beneficial traits. Such information can assist researchers to engineer photoreceptors via genome editing technologies to alter expression or even sensitivity thresholds of native photoreceptors for targeting aspects of plant growth that can confer superior agronomic value to the engineered crops. Here we summarize the agronomically important plant growth processes influenced by photoreceptors in crop species, alongwith the functional interactions between different photoreceptors and phytohormones in regulating these responses. We also discuss the potential utility of synthetic biology approaches in photobiology for improving agronomically beneficial traits of crop plants by engineering designer photoreceptors.

  20. Diurnal Dependence of Growth Responses to Shade in Arabidopsis: Role of Hormone, Clock,and Light Signaling

    Institute of Scientific and Technical Information of China (English)

    Romina Sellaro; Manuel Pacín; Jorge J. Casal

    2012-01-01

    We investigated the diurnal dependence of the hypocotyl-growth responses to shade under sunlight-night cycles in Arabidopsis thaliana.Afternoon shade events promoted hypocotyl growth,while morning shade was ineffective.The Ihy-D,elf3,lux,pif4 pif5,toc1,and quadruple della mutants retained the response to afternoon shade and the lack of response to morning shade while the Ihy cca 1 mutant responded to both morning and afternoon shade.The phyB mutant,plants overexpressing the multidrug resistance-like membrane protein ABCB19,and the iaa17/axr3 loss-of-function mutant failed to respond to shade.Transient exposure of sunlight-grown seedlings to synthetic auxin in the afternoon caused a stronger promotion of hypocotyl growth than morning treatments.The promotion of hypocotyl growth by afternoon shade or afternoon auxin required light perceived by phytochrome A or cryptochromes during the previous hours of the photoperiod.Although the ELF4-ELF3-LUX complex,PIF4,PIF5,and DELLA are key players in the generation of diurnal hypocotyl-growth patterns,they exert a minor role in the control of the diurnal pattern of growth responses to shade.We conclude that the strong diurnal dependency of hypocotyl-growth responses to shade relates to the balance between the antagonistic actions of LHY-CCA1 and a light-derived signal.

  1. A red and far-red light receptor mutation confers resistance to the herbicide glyphosate

    Science.gov (United States)

    Sharkhuu, Altanbadralt; Narasimhan, Meena L; Merzaban, Jasmeen S; Bressan, Ray A; Weller, Steve; Gehring, Chris

    2014-01-01

    Glyphosate is a widely applied broad-spectrum systemic herbicide that inhibits competitively the penultimate enzyme 5-enolpyruvylshikimate 3-phosphate synthase (EPSPS) from the shikimate pathway, thereby causing deleterious effects. A glyphosate-resistant Arabidopsis mutant (gre1) was isolated and genetic analyses indicated that a dysfunctional red (R) and far-red (FR) light receptor, phytochrome B (phyB), caused this phenotype. This finding is consistent with increased glyphosate sensitivity and glyphosate-induced shikimate accumulation in low R:FR light, and the induction of genes encoding enzymes of the shikimate pathway in high R:FR light. Expression of the shikimate pathway genes exhibited diurnal oscillation and this oscillation was altered in the phyB mutant. Furthermore, transcript analysis suggested that this diurnal oscillation was not only dependent on phyB but was also due to circadian regulatory mechanisms. Our data offer an explanation of the well documented observation that glyphosate treatment at various times throughout the day, with their specific composition of light quality and intensity, results in different efficiencies of the herbicide. PMID:24654847

  2. LOV Domain-Containing F-Box Proteins:Light-Dependent Protein Degradation Modules in Arabidopsis

    Institute of Scientific and Technical Information of China (English)

    Shogo Ito; Young Hun Song; Takato Imaizumi

    2012-01-01

    Plants constantly survey the surrounding environment using several sets of photoreceptors.They can sense changes in the quantity (=intensity) and quality (=wavelength) of light and use this information to adjust their physiological responses,growth,and developmental patterns.In addition to the classical photoreceptors,such as phytochromes,cryptochromes,and phototropins,ZEITLUPE (ZTL),FLAVIN-BINDING,KELCH REPEAT,F-BOX 1 (FKF1),and LOV KELCH PROTEIN 2 (LKP2) proteins have been recently identified as blue-light photoreceptors that are important for regulation of the circadian clock and photoperiodic flowering.The ZTL/FKF1/LKP2 protein family possesses a unique combination of domains:a blue-light-absorbing LOV (Light,Oxygen,or Voltage) domain along with domains involved in protein degradation.Here,we summarize recent advances in our understanding of the function of the Arabidopsis ZTL/FKF1/LKP2 proteins.We summarize the distinct photochemical properties of their LOV domains and discuss the molecular mechanisms by which the ZTL/FKF1/LKP2 proteins regulate the circadian clock and photoperiodic flowering by controlling blue-light-dependent protein degradation.

  3. The genome of the seagrass Zostera marina reveals angiosperm adaptation to the sea.

    Science.gov (United States)

    Olsen, Jeanine L; Rouzé, Pierre; Verhelst, Bram; Lin, Yao-Cheng; Bayer, Till; Collen, Jonas; Dattolo, Emanuela; De Paoli, Emanuele; Dittami, Simon; Maumus, Florian; Michel, Gurvan; Kersting, Anna; Lauritano, Chiara; Lohaus, Rolf; Töpel, Mats; Tonon, Thierry; Vanneste, Kevin; Amirebrahimi, Mojgan; Brakel, Janina; Boström, Christoffer; Chovatia, Mansi; Grimwood, Jane; Jenkins, Jerry W; Jueterbock, Alexander; Mraz, Amy; Stam, Wytze T; Tice, Hope; Bornberg-Bauer, Erich; Green, Pamela J; Pearson, Gareth A; Procaccini, Gabriele; Duarte, Carlos M; Schmutz, Jeremy; Reusch, Thorsten B H; Van de Peer, Yves

    2016-02-18

    Seagrasses colonized the sea on at least three independent occasions to form the basis of one of the most productive and widespread coastal ecosystems on the planet. Here we report the genome of Zostera marina (L.), the first, to our knowledge, marine angiosperm to be fully sequenced. This reveals unique insights into the genomic losses and gains involved in achieving the structural and physiological adaptations required for its marine lifestyle, arguably the most severe habitat shift ever accomplished by flowering plants. Key angiosperm innovations that were lost include the entire repertoire of stomatal genes, genes involved in the synthesis of terpenoids and ethylene signalling, and genes for ultraviolet protection and phytochromes for far-red sensing. Seagrasses have also regained functions enabling them to adjust to full salinity. Their cell walls contain all of the polysaccharides typical of land plants, but also contain polyanionic, low-methylated pectins and sulfated galactans, a feature shared with the cell walls of all macroalgae and that is important for ion homoeostasis, nutrient uptake and O2/CO2 exchange through leaf epidermal cells. The Z. marina genome resource will markedly advance a wide range of functional ecological studies from adaptation of marine ecosystems under climate warming, to unravelling the mechanisms of osmoregulation under high salinities that may further inform our understanding of the evolution of salt tolerance in crop plants.

  4. Light and gravity signals synergize in modulating plant development

    Science.gov (United States)

    Vandenbrink, Joshua P.; Kiss, John Z.; Herranz, Raul; Medina, F. Javier

    2014-01-01

    Tropisms are growth-mediated plant movements that help plants to respond to changes in environmental stimuli. The availability of water and light, as well as the presence of a constant gravity vector, are all environmental stimuli that plants sense and respond to via directed growth movements (tropisms). The plant response to gravity (gravitropism) and the response to unidirectional light (phototropism) have long been shown to be interconnected growth phenomena. Here, we discuss the similarities in these two processes, as well as the known molecular mechanisms behind the tropistic responses. We also highlight research done in a microgravity environment in order to decouple two tropisms through experiments carried out in the absence of a significant unilateral gravity vector. In addition, alteration of gravity, especially the microgravity environment, and light irradiation produce important effects on meristematic cells, the undifferentiated, highly proliferating, totipotent cells which sustain plant development. Microgravity produces the disruption of meristematic competence, i.e., the decoupling of cell proliferation and cell growth, affecting the regulation of the cell cycle and ribosome biogenesis. Light irradiation, especially red light, mediated by phytochromes, has an activating effect on these processes. Phytohormones, particularly auxin, also are key mediators in these alterations. Upcoming experiments on the International Space Station will clarify some of the mechanisms and molecular players of the plant responses to these environmental signals involved in tropisms and the cell cycle. PMID:25389428

  5. VASCULAR PLANT ONE-ZINC FINGER1 and VOZ2 repress the FLOWERING LOCUS C clade members to control flowering time in Arabidopsis.

    Science.gov (United States)

    Yasui, Yukiko; Kohchi, Takayuki

    2014-01-01

    Floral transition is regulated by environmental and endogenous signals. Previously, we identified VASCULAR PLANT ONE-ZINC FINGER1 (VOZ1) and VOZ2 as phytochrome B-interacting factors. VOZ1 and VOZ2 redundantly promote flowering and have pivotal roles in the downregulation of FLOWERING LOCUS C (FLC), a central repressor of flowering in Arabidopsis. Here, we showed that the late-flowering phenotypes of the voz1 voz2 mutant were suppressed by vernalization in the Columbia and FRIGIDA (FRI)-containing accessions, which indicates that the late-flowering phenotype of voz1 voz2 mutants was caused by upregulation of FLC. We also showed that the other FLC clade members, MADS AFFECTING FLOWERING (MAF) genes, were also a downstream target of VOZ1 and VOZ2 as their expression levels were also increased in the voz1 voz2 mutant. Our results suggest that the FLC clade genes integrate signals from VOZ1/VOZ2 and vernalization to regulate flowering.

  6. Comprehensive Analysis of the Green-to-Blue Photoconversion of Full-Length Cyanobacteriochrome Tlr0924

    Science.gov (United States)

    Hardman, Samantha J.O.; Hauck, Anna F.E.; Clark, Ian P.; Heyes, Derren J.; Scrutton, Nigel S.

    2014-01-01

    Cyanobacteriochromes are members of the phytochrome superfamily of photoreceptors and are of central importance in biological light-activated signaling mechanisms. These photoreceptors are known to reversibly convert between two states in a photoinitiated process that involves a basic E/Z isomerization of the bilin chromophore and, in certain cases, the breakage of a thioether linkage to a conserved cysteine residue in the bulk protein structure. The exact details and timescales of the reactions involved in these photoconversions have not been conclusively shown. The cyanobacteriochrome Tlr0924 contains phycocyanobilin and phycoviolobilin chromophores, both of which photoconvert between two species: blue-absorbing and green-absorbing, and blue-absorbing and red-absorbing, respectively. Here, we followed the complete green-to-blue photoconversion process of the phycoviolobilin chromophore in the full-length form of Tlr0924 over timescales ranging from femtoseconds to seconds. Using a combination of time-resolved visible and mid-infrared transient absorption spectroscopy and cryotrapping techniques, we showed that after photoisomerization, which occurs with a lifetime of 3.6 ps, the phycoviolobilin twists or distorts slightly with a lifetime of 5.3 μs. The final step, the formation of the thioether linkage with the protein, occurs with a lifetime of 23.6 ms. PMID:25418104

  7. Photoconversion and fluorescence properties of a red/green-type cyanobacteriochrome AM1_C0023g2 that binds not only phycocyanobilin but also biliverdin.

    Directory of Open Access Journals (Sweden)

    Keiji eFushimi

    2016-04-01

    Full Text Available Cyanobacteriochromes (CBCRs are distantly related to the red/far-red responsive phytochromes. Red/green-type CBCRs are widely distributed among various cyanobacteria. The red/green-type CBCRs covalently bind phycocyanobilin (PCB and show red/green reversible photoconversion. Recent studies revealed that some red/green-type CBCRs from chlorophyll d-bearing cyanobacterium Acaryochloris marina covalently bind not only PCB but also biliverdin (BV. The BV-binding CBCRs show far-red/orange reversible photoconversion. Here, we identified another CBCR (AM1_C0023g2 from A. marina that also covalently binds not only PCB but also BV with high binding efficiencies, although BV chromophore is unstable in the presence of urea. Replacement of Ser334 with Gly resulted in significant improvement in the yield of the BV-binding holoprotein, thereby ensuring that the mutant protein is a fine platform for future development of optogenetic switches. We also succeeded in detecting near-infrared fluorescence from mammalian cells harboring PCB-binding AM1_C0023g2 whose fluorescence quantum yield is 3.0%. Here the PCB-binding holoprotein is shown as a platform for future development of fluorescent probes.

  8. A red and far-red light receptor mutation confers resistance to the herbicide glyphosate

    KAUST Repository

    Sharkhuu, Altanbadralt

    2014-06-01

    Glyphosate is a widely applied broad-spectrum systemic herbicide that inhibits competitively the penultimate enzyme 5-enolpyruvylshikimate 3-phosphate synthase (EPSPS) from the shikimate pathway, thereby causing deleterious effects. A glyphosate-resistant Arabidopsis mutant (gre1) was isolated and genetic analyses indicated that a dysfunctional red (R) and far-red (FR) light receptor, phytochrome B (phyB), caused this phenotype. This finding is consistent with increased glyphosate sensitivity and glyphosate-induced shikimate accumulation in low R:FR light, and the induction of genes encoding enzymes of the shikimate pathway in high R:FR light. Expression of the shikimate pathway genes exhibited diurnal oscillation and this oscillation was altered in the phyB mutant. Furthermore, transcript analysis suggested that this diurnal oscillation was not only dependent on phyB but was also due to circadian regulatory mechanisms. Our data offer an explanation of the well documented observation that glyphosate treatment at various times throughout the day, with their specific composition of light quality and intensity, results in different efficiencies of the herbicide.

  9. Efeitos da luz, temperatura e estresse de água na germinação de sementes de Caesalpinia peltophoroides Benth. (Caesalpinoideae Effects of light, temperature and water stress on seed germination in Caesalpinia peltophoroides Benth. Caesalpinoideae

    Directory of Open Access Journals (Sweden)

    Fernanda Gollo A. Ferraz-Grande

    2006-01-01

    Full Text Available As sementes de Caesalpinia peltophoroides absorvem água rapidamente e após 9 horas acumulam o conteúdo de 56% de água e perdem mais lentamente, necessitando de cerca de 20 horas para perder completamente a água absorvida. As sementes de Caesalpinia peltophoroides germinam na faixa de temperaturas de 15 a 25 °C, e não possuem fotossensibilidade independentemente dos tratamentos luminosos e das temperaturas testadas. Verificou-se que com a diminuição do potencial de água, ocorre nas sementes uma redução na germinabilidade e na velocidade de germinação sob luz branca. Sob condições de estresse de água, observa-se fotossensibilidade, em sementes de Caesalpinia peltophoroides, sendo a germinação inibida pela luz branca mediada pelo pigmento fitocromo.Seeds of Caesalpinia peltophoroides absorb water and reach rapidly 56% of their water content after 9 hours. They lose water slowly, requiring 20 hours to completely lose imbibed water. Seeds of Caesalpinia peltophoroides germinated in the temperature range 15 to 25ºC. They did not show light sensitivity under different light types. We observed that low water potential reduced the germinability and germination rate. Under water stress those seeds were inhibited by white light mediated by phytochrome.

  10. Identification of photoperception and light signal transduction pathways in citrus

    Directory of Open Access Journals (Sweden)

    Vera Quecini

    2007-01-01

    Full Text Available Studies employing model species have elucidated several aspects of photoperception and light signal transduction that control plant development. However, the information available for economically important crops is scarce. Citrus genome databases of expressed sequence tags (EST were investigated in order to identify genes coding for functionally characterized proteins responsible for light-regulated developmental control in model plants. Approximately 176,200 EST sequences from 53 libraries were queried and all bona fide and putative photoreceptor gene families were found in citrus species. We have identified 53 orthologs for several families of transcriptional regulators and cytoplasmic proteins mediating photoreceptor-induced responses although some important Arabidopsis phytochrome- and cryptochrome-signaling components are absent from citrus sequence databases. The main gene families responsible for phototropin-mediated signal transduction were present in citrus transcriptome, including general regulatory factors (14-3-3 proteins, scaffolding elements and auxin-responsive transcription factors and transporters. A working model of light perception, signal transduction and response-eliciting in citrus is proposed based on the identified key components. These results demonstrate the power of comparative genomics between model systems and economically important crop species to elucidate several aspects of plant physiology and metabolism.

  11. Partial purification and characterization of a Ca(2+)-dependent protein kinase from pea nuclei

    Science.gov (United States)

    Li, H.; Dauwalder, M.; Roux, S. J.

    1991-01-01

    Almost all the Ca(2+)-dependent protein kinase activity in nuclei purified from etiolated pea (Pisum sativum, L.) plumules is present in a single enzyme that can be extracted from chromatin by 0.3 molar NaCl. This protein kinase can be further purified 80,000-fold by salt fractionation and high performance liquid chromatography, after which it has a high specific activity of about 100 picomoles per minute per microgram in the presence of Ca2+ and reaches half-maximal activation at about 3 x 10(-7) molar free Ca2+, without calmodulin. It is a monomer with a molecular weight near 90,000. It can efficiently use histone III-S, ribosomal S6 protein, and casein as artificial substrates, but it phosphorylates phosvitin only weakly. Its Ca(2+)-dependent kinase activity is half-maximally inhibited by 0.1 millimolar chlorpromazine, by 35 nanomolar K-252a and by 7 nanomolar staurosporine. It is insensitive to sphingosine, an inhibitor of protein kinase C, and to basic polypeptides that block other Ca(2+)-dependent protein kinases. It is not stimulated by exogenous phospholipids or fatty acids. In intact isolated pea nuclei it preferentially phosphorylates several chromatin-associated proteins, with the most phosphorylated protein band being near the same molecular weight (43,000) as a nuclear protein substrate whose phosphorylation has been reported to be stimulated by phytochrome in a calcium-dependent fashion.

  12. Conformational differences between the Pfr and Pr states in Pseudomonas aeruginosa bacteriophytochrome

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Xiaojing; Kuk, Jane; Moffat, Keith; (UC)

    2009-09-16

    Phytochromes are red-light photoreceptors that regulate light responses in plants, fungi, and bacteria by means of reversible photoconversion between red (Pr) and far-red (Pfr) light-absorbing states. Here, we report the crystal structure of the Q188L mutant of Pseudomonas aeruginosa bacteriophytochrome (PaBphP) photosensory core module, which exhibits altered photoconversion behavior and different crystal packing from wild type. We observe two distinct chromophore conformations in the Q188L crystal structure that we identify with the Pfr and Pr states. The Pr/Pfr compositions, varying from crystal to crystal, seem to correlate with light conditions under which the Q188L crystals are cryoprotected. We also compare all known Pr and Pfr structures. Using site-directed mutagenesis, we identify residues that are involved in stabilizing the 15Ea (Pfr) and 15Za (Pr) configurations of the biliverdin chromophore. Specifically, Ser-261 appears to be essential to form a stable Pr state in PaBphP, possibly by means of its interaction with the propionate group of ring C. We propose a 'flip-and-rotate' model that summarizes the major conformational differences between the Pr and Pfr states of the chromophore and its binding pocket.

  13. Plant resistance to cold stress: Mechanisms and environmental signals triggering frost hardening and dehardening

    Indian Academy of Sciences (India)

    Erwin H Beck; Richard Heim; Jens Hansen

    2004-12-01

    This introductory overview shows that cold, in particular frost, stresses a plant in manifold ways and that the plant’s response, being injurious or adaptive, must be considered a syndrome rather than a single reaction. In the course of the year perennial plants of the temperate climate zones undergo frost hardening in autumn and dehardening in spring. Using Scots pine (Pinus sylvestris L.) as a model plant the environmental signals inducing frost hardening and dehardening, respectively, were investigated. Over 2 years the changes in frost resistance of Scots pine needles were recorded together with the annual courses of day-length and ambient temperature. Both act as environmental signals for frost hardening and dehardening. Climate chamber experiments showed that short day-length as a signal triggering frost hardening could be replaced by irradiation with far red light, while red light inhibited hardening. The involvement of phytochrome as a signal receptor could be corroborated by respective night-break experiments. More rapid frost hardening than by short day or far red treatment was achieved by applying a short period (6 h) of mild frost which did not exceed the plant’s cold resistance. Both types of signals were independently effective but the rates of frost hardening were not additive. The maximal rate of hardening was – 0.93°C per day and frost tolerance of < – 72°C was achieved. For dehardening, temperature was an even more effective signal than day-length.

  14. A red and far-red light receptor mutation confers resistance to the herbicide glyphosate.

    Science.gov (United States)

    Sharkhuu, Altanbadralt; Narasimhan, Meena L; Merzaban, Jasmeen S; Bressan, Ray A; Weller, Steve; Gehring, Chris

    2014-06-01

    Glyphosate is a widely applied broad-spectrum systemic herbicide that inhibits competitively the penultimate enzyme 5-enolpyruvylshikimate 3-phosphate synthase (EPSPS) from the shikimate pathway, thereby causing deleterious effects. A glyphosate-resistant Arabidopsis mutant (gre1) was isolated and genetic analyses indicated that a dysfunctional red (R) and far-red (FR) light receptor, phytochrome B (phyB), caused this phenotype. This finding is consistent with increased glyphosate sensitivity and glyphosate-induced shikimate accumulation in low R:FR light, and the induction of genes encoding enzymes of the shikimate pathway in high R:FR light. Expression of the shikimate pathway genes exhibited diurnal oscillation and this oscillation was altered in the phyB mutant. Furthermore, transcript analysis suggested that this diurnal oscillation was not only dependent on phyB but was also due to circadian regulatory mechanisms. Our data offer an explanation of the well documented observation that glyphosate treatment at various times throughout the day, with their specific composition of light quality and intensity, results in different efficiencies of the herbicide.

  15. Conformational differences between the Pfr and Pr states in Pseudomonas aeruginosa bacteriophytochrome.

    Science.gov (United States)

    Yang, Xiaojing; Kuk, Jane; Moffat, Keith

    2009-09-15

    Phytochromes are red-light photoreceptors that regulate light responses in plants, fungi, and bacteria by means of reversible photoconversion between red (Pr) and far-red (Pfr) light-absorbing states. Here, we report the crystal structure of the Q188L mutant of Pseudomonas aeruginosa bacteriophytochrome (PaBphP) photosensory core module, which exhibits altered photoconversion behavior and different crystal packing from wild type. We observe two distinct chromophore conformations in the Q188L crystal structure that we identify with the Pfr and Pr states. The Pr/Pfr compositions, varying from crystal to crystal, seem to correlate with light conditions under which the Q188L crystals are cryoprotected. We also compare all known Pr and Pfr structures. Using site-directed mutagenesis, we identify residues that are involved in stabilizing the 15Ea (Pfr) and 15Za (Pr) configurations of the biliverdin chromophore. Specifically, Ser-261 appears to be essential to form a stable Pr state in PaBphP, possibly by means of its interaction with the propionate group of ring C. We propose a "flip-and-rotate" model that summarizes the major conformational differences between the Pr and Pfr states of the chromophore and its binding pocket.

  16. Reduced phototropism in pks mutants may be due to altered auxin-regulated gene expression or reduced lateral auxin transport.

    Science.gov (United States)

    Kami, Chitose; Allenbach, Laure; Zourelidou, Melina; Ljung, Karin; Schütz, Frédéric; Isono, Erika; Watahiki, Masaaki K; Yamamoto, Kotaro T; Schwechheimer, Claus; Fankhauser, Christian

    2014-02-01

    Phototropism allows plants to orient their photosynthetic organs towards the light. In Arabidopsis, phototropins 1 and 2 sense directional blue light such that phot1 triggers phototropism in response to low fluence rates, while both phot1 and phot2 mediate this response under higher light conditions. Phototropism results from asymmetric growth in the hypocotyl elongation zone that depends on an auxin gradient across the embryonic stem. How phototropin activation leads to this growth response is still poorly understood. Members of the phytochrome kinase substrate (PKS) family may act early in this pathway, because PKS1, PKS2 and PKS4 are needed for a normal phototropic response and they associate with phot1 in vivo. Here we show that PKS proteins are needed both for phot1- and phot2-mediated phototropism. The phototropic response is conditioned by the developmental asymmetry of dicotyledonous seedlings, such that there is a faster growth reorientation when cotyledons face away from the light compared with seedlings whose cotyledons face the light. The molecular basis for this developmental effect on phototropism is unknown; here we show that PKS proteins play a role at the interface between development and phototropism. Moreover, we present evidence for a role of PKS genes in hypocotyl gravi-reorientation that is independent of photoreceptors. pks mutants have normal levels of auxin and normal polar auxin transport, however they show altered expression patterns of auxin marker genes. This situation suggests that PKS proteins are involved in auxin signaling and/or lateral auxin redistribution.

  17. Light Regulation of Gibberellins Metabolism in Seedling Development

    Institute of Scientific and Technical Information of China (English)

    Xiao-Ying Zhao; Xu-Hong Yu; Xuan-Ming Liu; Chen-Tao Lin

    2007-01-01

    Light affects many aspects of plant development, including seed germination, stem elongation, and floral initiation. How photoreceptors control photomorphogenic processes is not yet fully understood. Because phytohormones are chemical regulators of plant development, it may not be surprising that light affects,directly or indirectly, cellular levels and signaling processes of various phytohormones, such as auxin,gibberellins (GA), cytokinin, ethylene, abscisic acid (ABA), and brassinosteroids (BR). Among those phytohormones, light regulation of GA metabolism has probably attracted more attention among photobiologists and it is arguably the most extensively studied plant hormone at present with respect to its role in photomorphogenesis. It has become increasingly clear that phytochromes and cryptochromes are the major photoreceptors mediating light regulation of GA homeostasis. This short article attempts to examine some recent developments in our understanding of how light and photoreceptors regulate GA biosynthesis and catabolism during seedling development. It is not our intention to carry out a comprehensive review of the field, and readers are referred to recent review articles for a more complete view of this area of study (Kamiya and Garcia-Martinez 1999; Hedden and Phillips 2000; Garcia-Martinez and Gil 2001; Olszewski et al. 2002; Halliday and Fankhauser 2003; Sun and Gubler 2004).

  18. Gibberellin and auxin influence the diurnal transcription pattern of photoreceptor genes via CRY1a in tomato.

    Directory of Open Access Journals (Sweden)

    Paolo Facella

    Full Text Available BACKGROUND: Plant photoreceptors, phytochromes and cryptochromes, regulate many aspects of development and growth, such as seed germination, stem elongation, seedling de-etiolation, cotyledon opening, flower induction and circadian rhythms. There are several pieces of evidence of interaction between photoreceptors and phyto-hormones in all of these physiological processes, but little is known about molecular and genetic mechanisms underlying hormone-photoreceptor crosstalk. METHODOLOGY/PRINCIPAL FINDINGS: In this work, we investigated the molecular effects of exogenous phyto-hormones to photoreceptor gene transcripts of tomato wt, as well as transgenic and mutant lines with altered cryptochromes, by monitoring day/night transcript oscillations. GA and auxin alter the diurnal expression level of different photoreceptor genes in tomato, especially in mutants that lack a working form of cryptochrome 1a: in those mutants the expression of some (IAA or most (GA photoreceptor genes is down regulated by these hormones. CONCLUSIONS/SIGNIFICANCE: Our results highlight the presence of molecular relationships among cryptochrome 1a protein, hormones, and photoreceptors' gene expression in tomato, suggesting that manipulation of cryptochromes could represent a good strategy to understand in greater depth the role of phyto-hormones in the plant photoperceptive mechanism.

  19. Light and gravity signals synergize in modulating plant development

    Directory of Open Access Journals (Sweden)

    Joshua P. Vandenbrink

    2014-10-01

    Full Text Available Tropisms are growth-mediated plant movements that help plants to respond to changes in environmental stimuli. The availability of water and light, as well as the presence of a constant gravity vector, are all environmental stimuli that plants sense and respond to via directed growth movements (tropisms. The plant response to gravity (gravitropism and the response to unidirectional light (phototropism have long been shown to be interconnected growth phenomena. Here, we discuss the similarities in these two processes, as well as the known molecular mechanisms behind the tropistic responses. We also highlight experiments done in a microgravity environment in order to decouple two tropisms through experiments carried out in the absence of a significant unilateral gravity vector. In addition, alteration of gravity, especially the microgravity environment, and light irradiation produce important effects on meristematic cells, the undifferentiated, highly proliferating, totipotent cells which sustain plant development. Microgravity produces the disruption of meristematic competence, i.e. the decoupling of cell proliferation and cell growth, affecting the regulation of cell cycle and ribosome biogenesis. Light irradiation, especially red light, mediated by phytochromes, has an activating effect on these processes. Phytohormones, particularly auxin, are key mediators in these alterations. Upcoming experiments on the International Space Station will clarify some of the unknown mechanisms and molecular players of the plant responses to these environmental signals involved in tropisms and the cell cycle.

  20. Root phototropism: from dogma to the mechanism of blue light perception.

    Science.gov (United States)

    Kutschera, Ulrich; Briggs, Winslow R

    2012-03-01

    In roots, the "hidden half" of all land plants, gravity is an important signal that determines the direction of growth in the soil. Hence, positive gravitropism has been studied in detail. However, since the 19th century, the response of roots toward unilateral light has also been analyzed. Based on studies on white mustard (Sinapis alba) seedlings, botanists have concluded that all roots are negatively phototropic. This "Sinapis-dogma" was refuted in a seminal study on root phototropism published a century ago, where it was shown that less then half of the 166 plant species investigated behave like S. alba, whereas 53% displayed no phototropic response at all. Here we summarize the history of research on root phototropism, discuss this phenomenon with reference to unpublished data on garden cress (Lepidium sativum) seedlings, and describe the effects of blue light on the negative bending response in Thale cress (Arabidopsis thaliana). The ecological significance of root phototropism is discussed and the relationships between gravi- and phototropism are outlined, with respect to the starch-statolith-theory of gravity perception. Finally, we present an integrative model of gravi- and blue light perception in the root tip of Arabidopsis seedlings. This hypothesis is based on our current view of the starch-statolith-concept and light sensing via the cytoplasmic red/blue light photoreceptor phytochrome A and the plasma membrane-associated blue light receptor phototropin-1. Open questions and possible research agendas for the future are summarized.

  1. Spaceflight studies of tropisms in the European Modular Cultivation System

    Science.gov (United States)

    Kiss, J. Z.; Correll, M. J.; Edelmann, R. E.

    Phototropism and gravitropism play key roles in the oriented growth of roots in flowering plants. In blue or white light, roots exhibit negative phototropism, but red light induces positive phototropism in Arabidopsis roots. The blue-light response is controlled by the phototropins while the red-light response is mediated by the phytochrome family of photoreceptors. In order to better characterize root phototropism, we plan to perform experiments in microgravity so that this tropism can be more effectively studied without the interactions with the gravity response. Our experiments are to be performed on the European Modular Cultivation System (EMCS), which provides an incubator, lighting system, and high resolution video that are on a centrifuge palette. These experiments will be performed at μ g, 1g (control) and fractional g-levels. In order to ensure success of this mission on the International Space Station (ISS), we have been performing ground-based studies on growth, phototropism, and gravitropism in experimental unique equipment (EUE) that was designed for our experiments that will use Arabidopsis seedlings. Currently, the EMCS and our EUE are scheduled for launch on space shuttle mission STS-121. This project should provide insight into how the blue-light and red-light signaling systems interact with each other, and also with the gravisensing system.

  2. Ground-based studies of tropisms in hardware developed for the European Modular Cultivation System (EMCS)

    Science.gov (United States)

    Correll, Melanie J.; Edelmann, Richard E.; Hangarter, Roger P.; Mullen, Jack L.; Kiss, John Z.

    Phototropism and gravitropism play key roles in the oriented growth of roots in flowering plants. In blue or white light, roots exhibit negative phototropism, but red light induces positive phototropism in Arabidopsis roots. The blue-light response is controlled by the phototropins while the red-light response is mediated by the phytochrome family of photoreceptors. In order to better characterize root phototropism, we plan to perform experiments in microgravity so that this tropism can be more effectively studied without the interactions with the gravity response. Our experiments are to be performed on the European Modular Cultivation System (EMCS), which provides an incubator, lighting system, and high resolution video that are on a centrifuge palette. These experiments will be performed at μg, 1g (control) and fractional g-levels. In order to ensure success of this mission on the International Space Station, we have been conducting ground-based studies on growth, phototropism, and gravitropism in experimental unique equipment (EUE) that was designed for our experiments with Arabidopsis seedlings. Currently, the EMCS and our EUE are scheduled for launch on space shuttle mission STS-121. This project should provide insight into how the blue- and red-light signaling systems interact with each other and with the gravisensing system.

  3. O-GlcNAcylation of master growth repressor DELLA by SECRET AGENT modulates multiple signaling pathways in Arabidopsis

    Science.gov (United States)

    Zentella, Rodolfo; Hu, Jianhong; Hsieh, Wen-Ping; Matsumoto, Peter A.; Dawdy, Andrew; Barnhill, Benjamin; Oldenhof, Harriëtte; Hartweck, Lynn M.; Maitra, Sushmit; Thomas, Stephen G.; Cockrell, Shelley; Boyce, Michael; Shabanowitz, Jeffrey; Hunt, Donald F.; Olszewski, Neil E.; Sun, Tai-ping

    2016-01-01

    The DELLA family of transcription regulators functions as master growth repressors in plants by inhibiting phytohormone gibberellin (GA) signaling in response to developmental and environmental cues. DELLAs also play a central role in mediating cross-talk between GA and other signaling pathways via antagonistic direct interactions with key transcription factors. However, how these crucial protein–protein interactions can be dynamically regulated during plant development remains unclear. Here, we show that DELLAs are modified by the O-linked N-acetylglucosamine (O-GlcNAc) transferase (OGT) SECRET AGENT (SEC) in Arabidopsis. O-GlcNAcylation of the DELLA protein REPRESSOR OF ga1-3 (RGA) inhibits RGA binding to four of its interactors—PHYTOCHROME-INTERACTING FACTOR3 (PIF3), PIF4, JASMONATE-ZIM DOMAIN1, and BRASSINAZOLE-RESISTANT1 (BZR1)—that are key regulators in light, jasmonate, and brassinosteroid signaling pathways, respectively. Consistent with this, the sec-null mutant displayed reduced responses to GA and brassinosteroid and showed decreased expression of several common target genes of DELLAs, BZR1, and PIFs. Our results reveal a direct role of OGT in repressing DELLA activity and indicate that O-GlcNAcylation of DELLAs provides a fine-tuning mechanism in coordinating multiple signaling activities during plant development. PMID:26773002

  4. RNAseq reveals weed-induced PIF3-like as a candidate target to manipulate weed stress response in soybean.

    Science.gov (United States)

    Horvath, David P; Hansen, Stephanie A; Moriles-Miller, Janet P; Pierik, Ronald; Yan, Changhui; Clay, David E; Scheffler, Brian; Clay, Sharon A

    2015-07-01

    Weeds reduce yield in soybeans (Glycine max) through incompletely defined mechanisms. The effects of weeds on the soybean transcriptome were evaluated in field conditions during four separate growing seasons. RNASeq data were collected from six biological samples of soybeans growing with or without weeds. Weed species and the methods to maintain weed-free controls varied between years to mitigate treatment effects, and to allow detection of general soybean weed responses. Soybean plants were not visibly nutrient- or water-stressed. We identified 55 consistently downregulated genes in weedy plots. Many of the downregulated genes were heat shock genes. Fourteen genes were consistently upregulated. Several transcription factors including a PHYTOCHROME INTERACTING FACTOR 3-like gene (PIF3) were included among the upregulated genes. Gene set enrichment analysis indicated roles for increased oxidative stress and jasmonic acid signaling responses during weed stress. The relationship of this weed-induced PIF3 gene to genes involved in shade avoidance responses in Arabidopsis provide evidence that this gene may be important in the response of soybean to weeds. These results suggest that the weed-induced PIF3 gene will be a target for manipulating weed tolerance in soybean.

  5. Differentially Phased Leaf Growth and Movements in Arabidopsis Depend on Coordinated Circadian and Light Regulation[W

    Science.gov (United States)

    Dornbusch, Tino; Michaud, Olivier; Xenarios, Ioannis; Fankhauser, Christian

    2014-01-01

    In contrast to vastly studied hypocotyl growth, little is known about diel regulation of leaf growth and its coordination with movements such as changes in leaf elevation angle (hyponasty). We developed a 3D live-leaf growth analysis system enabling simultaneous monitoring of growth and movements. Leaf growth is maximal several hours after dawn, requires light, and is regulated by daylength, suggesting coupling between growth and metabolism. We identify both blade and petiole positioning as important components of leaf movements in Arabidopsis thaliana and reveal a temporal delay between growth and movements. In hypocotyls, the combination of circadian expression of PHYTOCHROME INTERACTING FACTOR4 (PIF4) and PIF5 and their light-regulated protein stability drives rhythmic hypocotyl elongation with peak growth at dawn. We find that PIF4 and PIF5 are not essential to sustain rhythmic leaf growth but influence their amplitude. Furthermore, EARLY FLOWERING3, a member of the evening complex (EC), is required to maintain the correct phase between growth and movement. Our study shows that the mechanisms underlying rhythmic hypocotyl and leaf growth differ. Moreover, we reveal the temporal relationship between leaf elongation and movements and demonstrate the importance of the EC for the coordination of these phenotypic traits. PMID:25281688

  6. Differentially phased leaf growth and movements in Arabidopsis depend on coordinated circadian and light regulation.

    Science.gov (United States)

    Dornbusch, Tino; Michaud, Olivier; Xenarios, Ioannis; Fankhauser, Christian

    2014-10-01

    In contrast to vastly studied hypocotyl growth, little is known about diel regulation of leaf growth and its coordination with movements such as changes in leaf elevation angle (hyponasty). We developed a 3D live-leaf growth analysis system enabling simultaneous monitoring of growth and movements. Leaf growth is maximal several hours after dawn, requires light, and is regulated by daylength, suggesting coupling between growth and metabolism. We identify both blade and petiole positioning as important components of leaf movements in Arabidopsis thaliana and reveal a temporal delay between growth and movements. In hypocotyls, the combination of circadian expression of PHYTOCHROME INTERACTING FACTOR4 (PIF4) and PIF5 and their light-regulated protein stability drives rhythmic hypocotyl elongation with peak growth at dawn. We find that PIF4 and PIF5 are not essential to sustain rhythmic leaf growth but influence their amplitude. Furthermore, EARLY FLOWERING3, a member of the evening complex (EC), is required to maintain the correct phase between growth and movement. Our study shows that the mechanisms underlying rhythmic hypocotyl and leaf growth differ. Moreover, we reveal the temporal relationship between leaf elongation and movements and demonstrate the importance of the EC for the coordination of these phenotypic traits.

  7. Light-induced degradation of storage starch in turions of Spirodela polyrhiza depends on nitrate.

    Science.gov (United States)

    Appenroth, Klaus-J; Ziegler, Paul

    2008-10-01

    Light induces both the germination of turions of the duckweed Spirodela polyrhiza and the degradation of the reserve starch stored in the turions. The germination photoresponse requires nitrate, and we show here that nitrate is also needed for the light-induced degradation of the turion starch. Ammonium cannot substitute for nitrate in this regard, and nitrate thus acts specifically as signal to promote starch degradation in the turions. Irradiation with continuous red light leads to starch degradation via auto-phosphorylation of starch-associated glucan, water dikinase (GWD), phosphorylation of the turion starch and enhanced binding of alpha-amylase to starch granules. The present study shows that all of these processes require the presence of nitrate, and that nitrate exerts its effect on starch degradation at a point between the absorption of light by phytochrome and the auto-phosphorylation of the GWD. Nitrate acts to coordinate carbon and nitrogen metabolism in germinating turions: starch will only be broken down when sufficient nitrogen is present to ensure appropriate utilization of the released carbohydrate. These data constitute the first report of control over the initiation of reserve starch degradation by nitrate.

  8. Transcriptome reprogramming during developmental switching in Physarum polycephalum involves extensive remodeling of intracellular signaling networks.

    Science.gov (United States)

    Glöckner, Gernot; Marwan, Wolfgang

    2017-09-26

    Activation of a phytochrome photoreceptor triggers a program of Physarum polycephalum plasmodial cell differentiation through which a mitotic multinucleate protoplasmic mass synchronously develops into haploid spores formed by meiosis and rearrangement of cellular components. We have performed a transcriptome-wide RNAseq study of cellular reprogramming and developmental switching. RNAseq analysis revealed extensive remodeling of intracellular signaling and regulation in switching the expression of sets of genes encoding transcription factors, kinases, phosphatases, signal transduction proteins, RNA-binding proteins, ubiquitin ligases, regulators of the mitotic and meiotic cell cycle etc. in conjunction with the regulation of genes encoding metabolic enzymes and cytoskeletal proteins. About 15% of the differentially expressed genes shared similarity with members of the evolutionary conserved set of core developmental genes of social amoebae. Differential expression of genes encoding regulators that act at the transcriptional, translational, and post-translational level indicates the establishment of a new state of cellular function and reveals evolutionary deeply conserved molecular changes involved in cellular reprogramming and differentiation in a prototypical eukaryote.

  9. A complex photoreceptor system mediates the regulation by light of the conidiation genes con-10 and con-6 in Neurospora crassa.

    Science.gov (United States)

    Olmedo, María; Ruger-Herreros, Carmen; Luque, Eva M; Corrochano, Luis M

    2010-04-01

    Genes con-10 and con-6 in Neurospora crassa are activated during conidiation or after illumination of vegetative mycelia. Light activation requires the white-collar complex (WCC), a transcription factor complex composed of the photoreceptor WC-1 and its partner WC-2. We have characterized the photoactivation of con-10 and con-6, and we have identified 300bp required for photoactivation in the con-10 promoter. A complex stimulus-response relationship for con-10 and con-6 photoactivation suggested the activity of a complex photoreceptor system. The WCC is the key element for con-10 activation by light, but we suggest that other photoreceptors, the cryptochrome CRY-1, the rhodopsin NOP-1, and the phytochrome PHY-2, modify the activity of the WCC for con-10 photoactivation, presumably through a repressor. In addition we show that the regulatory protein VE-1 is required for full photocarotenogenesis. We propose that these proteins may modulate the WCC in a gene-specific way.

  10. Targeting Proteins for Degradation by Arabidopsis COP1: Teamwork Is What Matters

    Institute of Scientific and Technical Information of China (English)

    Rongcheng Lin; Haiyang Wang

    2007-01-01

    Arabidopsis COP1 (Constitutive Photomorphogenic 1) defines a key repressor of photomorphogenesis in darkness by acting as an E3 ubiquitin ligase in the nucleus, and is responsible for the targeted degradation of a number of photomorphogenesis-promoting factors, including phyA, HY5, LAF1, and HFR1. Light activation of multiple classes of photoreceptors (including both phytochromes and cryptochromes) inactivates COP1 and reduces its nuclear abundance, allowing the accumulation of these positively acting light signaling intermediates to promote photomorphogenic development. Recent studies suggest that Arabidopsis COP1 teams up with a family of SPA proteins (SPA1-SPA4) to form the physiologically active COP1-SPA E3 ubiquitin ligase complexes. These COP1-SPA complexes play overlapping and distinct functions in regulating seedling photomorphogenesis under different light conditions and adult plant growth. Further, the COP1-SPA complexes act in concert at a biochemical level with the CDD (COP10, DET1, and DDB1) complex and COP9 signalosome (CSN) to orchestrate the repression of photomorphogenesis.

  11. PIF genes mediate the effect of sucrose on seedling growth dynamics.

    Directory of Open Access Journals (Sweden)

    Jodi L Stewart

    Full Text Available As photoautotrophs, plants can use both the form and amount of fixed carbon as a measure of the light environment. In this study, we used a variety of approaches to elucidate the role of exogenous sucrose in modifying seedling growth dynamics. In addition to its known effects on germination, high-resolution temporal analysis revealed that sucrose could extend the number of days plants exhibited rapid hypocotyl elongation, leading to dramatic increases in ultimate seedling height. In addition, sucrose changed the timing of daily growth maxima, demonstrating that diel growth dynamics are more plastic than previously suspected. Sucrose-dependent growth promotion required function of multiple phytochrome-interacting factors (PIFs, and overexpression of PIF5 led to growth dynamics similar to plants exposed to sucrose. Consistent with this result, sucrose was found to increase levels of PIF5 protein. PIFs have well-established roles as integrators of response to light levels, time of day and phytohormone signaling. Our findings strongly suggest that carbon availability can modify the known photomorphogenetic signaling network.

  12. HYPOSENSITIVE TO LIGHT,an Alpha/Beta Fold Protein,Acts Downstream of ELONGATED HYPOCOTYL 5 to Regulate Seedling De-Etiolation

    Institute of Scientific and Technical Information of China (English)

    Xiao-Dong Sun; Min Ni

    2011-01-01

    Ambient light has profound effects on early seedling de-etiolation through red and far-red light-absorbing phytochromes and blue and UV-A light-absorbing cryptochromes.Subsequent integration of various light signal transduction pathways leads to changes in gene expression and morphogenic responses.Here,we report the isolation of a new Arabidopsis light-signaling component,HYPOSENSITIVE TO LIGHT or HTL.Both htl-1 and htl-2 alleles displayed a long hypocotyl phenotype under red,far-red,and blue light,whereas overexpression of HTL caused a short hypocotyl phenotype under similar light conditions.The mutants also showed other photomorphogenic defects such as elongated petioles,retarded cotyledon and leaf expansion,reduced accumulation of chlorophyll and anthocyanin pigments,and attenuated expression of light-responsive CHLOROPHYLL A/B BINDING PROTEIN 3 and CHALCONE SYNTHASE genes.HTL belongs to an alpha/beta fold protein family and is localized strongly in the nucleus and weakly in the cytosol.The expression of HTL was strongly induced by light of various wavelengths and this light induction was impaired in elongated hypocotyl 5.HY5directly bound to both a C/G-box and a G-box in the HTL promoter but with a greater affinity toward the C/G-box.HTL.therefore,represents a new signaling step downstream of HY5 in phy-and cry-mediated de-etiolation responses.

  13. Photocontrol of Anthocyanin Synthesis: VII. Factors Affecting the Spectral Sensitivity of Anthocyanin Synthesis in Young Seedlings.

    Science.gov (United States)

    Mancinelli, A L; Walsh, L

    1979-05-01

    Light-dependent anthocyanin synthesis is a typical high irradiance response (HIR) of plant photomorphogenesis. The spectral sensitivity of this response in young seedlings of cabbage and tomato is strongly affected by the length and mode of application of the light treatments. This observation suggests that the different experimental conditions, used in different action spectroscopy studies, might have been responsible, at least in part, for some of the reported differences in the characteristics of the HIR action spectra of different response-system combinations. In both cabbage and tomato, the values of the far red/blue, far red/red, and blue/red action ratios increase with increasing durations of the light treatments; this finding is in agreement with hypotheses of K. M. Hartmann (1966, 1967) and E. Schäfer (1975) for phytochrome action in the HIR. The similarity in the trend of change of the values of the action ratios suggests the possibility that the photomorphogenic pigment system, involved in the photoregulation of anthocyanin synthesis, may be the same in cabbage and tomato, even though there are some differences in the spectral sensitivity of the response between the two species.

  14. Photocontrol of Anthocyanin Synthesis: VI. Spectral Sensitivity, Irradiance Dependence, and Reciprocity Relationships.

    Science.gov (United States)

    Rabino, I; Mancinelli, A L; Kuzmanoff, K M

    1977-04-01

    The spectral sensitivity and the irradiance dependence of anthocyanin synthesis, a "high irradiance response," in cabbage (Brassica oleracea, cv. Red Acre) and tomato (Lycopersicon esculentum, cv. Beefsteak) seedlings exposed to continuous irradiation depend upon the length of the exposure. In cabbage, blue and red are more effective than far red when the irradiations are shorter than 12 hours and less effective than far red when the irradiations are longer than 12 hours. The irradiance dependence is negligible under red and becomes evident under blue and far red red only for exposures longer than 12 hours. Anthocyanin synthesis under intermittent light treatments, of efficiency comparable to that of continuous treatments, obeys the Bunsen-Roscoe reciprocity law and is a function of the dose (irradiance x time), rather than of the irradiance alone. The validity of the reciprocity relationships suggests that only one photoreceptor is responsible for the photocontrol of the response in the blue, red, and far red spectral regions. The characteristics of the response suggest that the photoreceptor is phytochrome, at least in cabbage.

  15. Stem transcriptome reveals mechanisms to reduce the energetic cost of shade-avoidance responses in tomato.

    Science.gov (United States)

    Cagnola, Juan Ignacio; Ploschuk, Edmundo; Benech-Arnold, Tomás; Finlayson, Scott A; Casal, Jorge José

    2012-10-01

    While the most conspicuous response to low red/far-red ratios (R:FR) of shade light perceived by phytochrome is the promotion of stem growth, additional, less obvious effects may be discovered by studying changes in the stem transcriptome. Here, we report rapid and reversible stem transcriptome responses to R:FR in tomato (Solanum lycopersicum). As expected, low R:FR promoted the expression of growth-related genes, including those involved in the metabolism of cell wall carbohydrates and in auxin responses. In addition, genes involved in flavonoid synthesis, isoprenoid metabolism, and photosynthesis (dark reactions) were overrepresented in clusters showing reduced expression in the stem of low R:FR-treated plants. Consistent with these responses, low R:FR decreased the levels of flavonoids (anthocyanin, quercetin, kaempferol) and selected isoprenoid derivatives (chlorophyll, carotenoids) in the stem and severely reduced the photosynthetic capacity of this organ. However, lignin contents were unaffected. Low R:FR reduced the stem levels of jasmonate, which is a known inducer of flavonoid synthesis. The rate of stem respiration was also reduced in low R:FR-treated plants, indicating that by downsizing the stem photosynthetic apparatus and the levels of photoprotective pigments under low R:FR, tomato plants reduce the energetic cost of shade-avoidance responses.

  16. The origin and evolution of phototropins

    Directory of Open Access Journals (Sweden)

    Fay-Wei eLi

    2015-08-01

    Full Text Available Plant phototropism, the ability to bend toward or away from light, is predominantly controlled by blue-light photoreceptors, the phototropins. Although phototropins have been well-characterized in Arabidopsis thaliana, their evolutionary history is largely unknown. In this study, we complete an in-depth survey of phototropin homologs across land plants and algae using newly available transcriptomic and genomic data. We show that phototropins originated in an ancestor of Viridiplantae (land plants + green algae. Phototropins repeatedly underwent independent duplications in most major land-plant lineages (mosses, lycophytes, ferns, and seed plants, but remained single-copy genes in liverworts and hornworts—an evolutionary pattern shared with another family of photoreceptors, the phytochromes. Following each major duplication event, the phototropins differentiated in parallel, resulting in two specialized, yet partially overlapping, functional forms that primarily mediate either low- or high-light responses. Our detailed phylogeny enables us to not only uncover new phototropin lineages, but also link our understanding of phototropin function in Arabidopsis with what is known in Adiantum and Physcomitrella (the major model organisms outside of flowering plants. We propose that the convergent functional divergences of phototropin paralogs likely contributed to the success of plants through time in adapting to habitats with diverse and heterogeneous light conditions.

  17. Tomato fruit carotenoid biosynthesis is adjusted to actual ripening progression by a light-dependent mechanism.

    Science.gov (United States)

    Llorente, Briardo; D'Andrea, Lucio; Ruiz-Sola, M Aguila; Botterweg, Esther; Pulido, Pablo; Andilla, Jordi; Loza-Alvarez, Pablo; Rodriguez-Concepcion, Manuel

    2016-01-01

    Carotenoids are isoprenoid compounds that are essential for plants to protect the photosynthetic apparatus against excess light. They also function as health-promoting natural pigments that provide colors to ripe fruit, promoting seed dispersal by animals. Work in Arabidopsis thaliana unveiled that transcription factors of the phytochrome-interacting factor (PIF) family regulate carotenoid gene expression in response to environmental signals (i.e. light and temperature), including those created when sunlight reflects from or passes though nearby vegetation or canopy (referred to as shade). Here we show that PIFs use a virtually identical mechanism to modulate carotenoid biosynthesis during fruit ripening in tomato (Solanum lycopersicum). However, instead of integrating environmental information, PIF-mediated signaling pathways appear to fulfill a completely new function in the fruit. As tomatoes ripen, they turn from green to red due to chlorophyll breakdown and carotenoid accumulation. When sunlight passes through the flesh of green fruit, a self-shading effect within the tissue maintains high levels of PIFs that directly repress the master gene of the fruit carotenoid pathway, preventing undue production of carotenoids. This effect is attenuated as chlorophyll degrades, causing degradation of PIF proteins and boosting carotenoid biosynthesis as ripening progresses. Thus, shade signaling components may have been co-opted in tomato fruit to provide information on the actual stage of ripening (based on the pigment profile of the fruit at each moment) and thus finely coordinate fruit color change. We show how this mechanism may be manipulated to obtain carotenoid-enriched fruits.

  18. Noncanonical role of Arabidopsis COP1/SPA complex in repressing BIN2-mediated PIF3 phosphorylation and degradation in darkness.

    Science.gov (United States)

    Ling, Jun-Jie; Li, Jian; Zhu, Danmeng; Deng, Xing Wang

    2017-03-28

    The E3 ligase CONSTITUTIVELY PHOTOMORPHOGENIC 1 (COP1) has been known to mediate key signaling factors for degradation via the ubiquitin/26S proteasome pathway in both plants and animals. Here, we report a noncanonical function of Arabidopsis COP1, the central repressor of photomorphogenesis, in the form of a COP1/ SUPPRESSOR of phyA-105 (SPA) complex. We show that the COP1/SPA complex associates with and stabilizes PHYTOCHROME INTERACTING FACTOR 3 (PIF3) to repress photomorphogenesis in the dark. We identify the GSK3-like kinase BRASSINOSTEROID-INSENSITIVE 2 (BIN2) as a kinase of PIF3, which induces PIF3 degradation via 26S proteasome during skotomorphogenesis. Mutations on two typical BIN2 phosphorylation motifs of PIF3 lead to a strong stabilization of the protein in the dark. We further show that the COP1/SPA complex promotes PIF3 stability by repressing BIN2 activity. Intriguingly, without affecting BIN2 expression, the COP1/SPA complex modulates BIN2 activity through interfering with BIN2-PIF3 interaction, thereby inhibiting BIN2-mediated PIF3 phosphorylation and degradation. Taken together, our results suggest another paradigm for COP1/SPA complex action in the precise control of skotomorphogenesis.

  19. Photoreceptive sites in the photocontrol of oat seedling growth

    Directory of Open Access Journals (Sweden)

    Kazimierz Madela

    2014-01-01

    Full Text Available The influence of red light on the growth of coleoptiles and mesocotyles of etiolated and pre-irradiated oat seedlings was investigated. Red light (15 min. applied on whole seedlings stimulated the elongation of coleoptiles and inhibited the growth of mesocotyles both in etiolated and in pre-irradiated plants. Irradiation with red light (2 min of various 2-mm-long regions of etiolated and pre-irradiated oat seedlings was carried out in order to locate their light reception regions. On the basis of growth reactions after such treatment it was found that in completely etiolated seedlings the light reception sites involved in the stimulation of coleoptile elongation and inhibition of mesocotyle growth lie directly above and below the seedling node, whereas in pre-irradiated seedlings, in the top of the seedling. These results point to the existence of different growth photoregulation systems in etiolated and pre-irradiated oat seedlings. The role of phytochrome in these phenomena is discussed.

  20. Application of color vision tests on the diagnosis and treatment for common ocular fundus diseases%色觉检查在常见眼底病诊疗中的应用

    Institute of Scientific and Technical Information of China (English)

    苏捷; 敖明昕; 王薇

    2016-01-01

    ?Color vision has been an important part of the human visual function.It is determined by the phytochrome of cone.In many clinical cases of ocular fundus diseases, patients had color vision loss, which shows that color visions tests is necessary and meaningful.At present, doctors have not paid attention to it and adopt the tests rarely. The article summarizes the tests of color in common use and applications on the diagnosis and treatment for common ocular fundus diseases to be a theory basis.%色觉是视觉功能一个基本而重要的组成部分,人类的色觉由视锥细胞的光敏色素决定。在很多眼底病病例中,患者色觉出现异常,提示色觉检查在眼底病诊疗中有一定意义。目前,色觉检查在目前眼底病诊疗中的价值尚未引起重视,临床应用较少。本文就色觉检查的常用方法,其在各类眼底病中的应用及研究进展进行综述,希望在临床工作中引起重视。

  1. Early quantitative method for measuring germination in non-green spores of Dryopteris paleacea using an epifluorescence-microscope technique

    Science.gov (United States)

    Scheuerlein, R.; Wayne, R.; Roux, S. J.

    1988-01-01

    A method is described to determine germination by blue-light excited red fluorescence in the positively photoblastic spores of Dryopteris paleacea Sw. This fluorescence is due to chlorophyll as evidenced from 1) a fluorescence-emission spectrum in vivo, where a bright fluorescence around 675 nm is obtained only in red light (R)-irradiated spores and 2) in vitro measurements with acetone extracts prepared from homogenized spores. Significant amounts of chlorophyll can be found only in R-treated spores; this chlorophyll exhibits an emission band around 668 nm, when irradiated with 430 nm light at 21 degrees C. Compared to other criteria for germination, such as swelling of the cell, coat splitting, greening, and rhizoid formation, which require longer periods after induction for their expression, chlorophyll fluorescence can be used to quantify germination after two days. This result is confirmed by fluence-response curves for R-induced spore germination; the same relationship between applied R and germination is obtained by the evaluation with the epifluorescence method 2 days after the light treatment as compared with the evaluation with bright-field microscopy 5 days after the inducing R. Using this technique we show for the first time that Ca2+ contributes to the signal-transduction chain in phytochrome-mediated chlorophyll synthesis in spores of Dryopteris paleacea.

  2. Adaptive Molecular Evolution of PHYE in Primulina, a Karst Cave Plant.

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    Tao, Junjie; Qi, Qingwen; Kang, Ming; Huang, Hongwen

    2015-01-01

    Limestone Karst areas possess high levels of biodiversity and endemism. Primulina is a typical component of Karst endemic floras. The high species richness and wide distribution in various Karst microenvironments make the genus an idea model for studying speciation and local adaptation. In this study, we obtained 10 full-length sequences of the phytochrome PHYE from available transcriptome resources of Primulina and amplified partial sequences of PHYE from the genomic DNA of 74 Primulina species. Then, we used maximum-likelihood approaches to explore molecular evolution of PHYE in this Karst cave plant. The results showed that PHYE was dominated by purifying selection in both data sets, and two sites were identified as potentially under positive selection. Furthermore, the ω ratio varies greatly among different functional domains of PHYE and among different species lineages. These results suggest that potential positive selection in PHYE might have played an important role in the adaption of Primulina to heterogeneous light environments in Karst regions, and different species lineages might have been subjected to different selective pressures.

  3. Adaptive Molecular Evolution of PHYE in Primulina, a Karst Cave Plant.

    Directory of Open Access Journals (Sweden)

    Junjie Tao

    Full Text Available Limestone Karst areas possess high levels of biodiversity and endemism. Primulina is a typical component of Karst endemic floras. The high species richness and wide distribution in various Karst microenvironments make the genus an idea model for studying speciation and local adaptation. In this study, we obtained 10 full-length sequences of the phytochrome PHYE from available transcriptome resources of Primulina and amplified partial sequences of PHYE from the genomic DNA of 74 Primulina species. Then, we used maximum-likelihood approaches to explore molecular evolution of PHYE in this Karst cave plant. The results showed that PHYE was dominated by purifying selection in both data sets, and two sites were identified as potentially under positive selection. Furthermore, the ω ratio varies greatly among different functional domains of PHYE and among different species lineages. These results suggest that potential positive selection in PHYE might have played an important role in the adaption of Primulina to heterogeneous light environments in Karst regions, and different species lineages might have been subjected to different selective pressures.

  4. Verification at the protein level of the PIF4-mediated external coincidence model for the temperature-adaptive photoperiodic control of plant growth in Arabidopsis thaliana.

    Science.gov (United States)

    Yamashino, Takafumi; Nomoto, Yuji; Lorrain, Séverine; Miyachi, Miki; Ito, Shogo; Nakamichi, Norihito; Fankhauser, Christian; Mizuno, Takeshi

    2013-03-01

    Plant circadian clock controls a wide variety of physiological and developmental events, which include the short-days (SDs)-specific promotion of the elongation of hypocotyls during de-etiolation and also the elongation of petioles during vegetative growth. In A. thaliana, the PIF4 gene encoding a phytochrome-interacting basic helix-loop-helix (bHLH) transcription factor plays crucial roles in this photoperiodic control of plant growth. According to the proposed external coincidence model, the PIF4 gene is transcribed precociously at the end of night specifically in SDs, under which conditions the protein product is stably accumulated, while PIF4 is expressed exclusively during the daytime in long days (LDs), under which conditions the protein product is degraded by the light-activated phyB and also the residual proteins are inactivated by the DELLA family of proteins. A number of previous reports provided solid evidence to support this coincidence model mainly at the transcriptional level of the PIF 4 and PIF4-traget genes. Nevertheless, the diurnal oscillation profiles of PIF4 proteins, which were postulated to be dependent on photoperiod and ambient temperature, have not yet been demonstrated. Here we present such crucial evidence on PIF4 protein level to further support the external coincidence model underlying the temperature-adaptive photoperiodic control of plant growth in A. thaliana.

  5. Circadian clock and PIF4-mediated external coincidence mechanism coordinately integrates both of the cues from seasonal changes in photoperiod and temperature to regulate plant growth in Arabidopsis thaliana.

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    Nomoto, Yuji; Kubozono, Saori; Miyachi, Miki; Yamashino, Takafumi; Nakamichi, Norihito; Mizuno, Takeshi

    2013-02-01

    In Arabidopsis thaliana, the circadian clock regulates the photoperiodic plant growth including the elongation of hypocotyls in a short-days (SDs)-specific manner. The clock-controlled PHYTOCHROME-INTERACTING FACTOR 4 (PIF4) gene encoding a basic helix-loop-helix (bHLH) transcription factor plays crucial roles in this regulation. The SDs-specific elongation of hypocotyls is best explained by accumulation of the active PIF4 proteins at the end of night specifically in SDs due to coincidence between internal (circadian clock) and external (photoperiod) cues. However, this external coincidence model was challenged with the recent finding that the elongation of hypocotyls is markedly promoted at high growth temperature (28˚C) even in long-days (LDs), implying that the model to explain the photoperiodic response of plant architecture appears to be conditional on ambient temperature. With regard to this problem, the results of this and previous studies showed that the model holds under a wide range of ambient temperature conditions (16˚C to 28˚C). We propose that the circadian clock and PIF4-mediated external coincidence mechanism coordinately integrates both of the cues from seasonal changes in photoperiod and temperature to regulate plant growth in natural habitats.

  6. SPATULA links daytime temperature and plant growth rate.

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    Sidaway-Lee, Kate; Josse, Eve-Marie; Brown, Alanna; Gan, Yinbo; Halliday, Karen J; Graham, Ian A; Penfield, Steven

    2010-08-24

    Plants exhibit a wide variety of growth rates that are known to be determined by genetic and environmental factors, and different plants grow optimally at different temperatures, indicating that this is a genetically determined character. Moderate decreases in ambient temperature inhibit vegetative growth, but the mechanism is poorly understood, although a decrease in gibberellin (GA) levels is known to be required. Here we demonstrate that the basic helix-loop-helix transcription factor SPATULA (SPT), previously known to be a regulator of low temperature-responsive germination, mediates the repression of growth by cool daytime temperatures but has little or no growth-regulating role under warmer conditions. We show that only daytime temperatures affect vegetative growth and that SPT couples morning temperature to growth rate. In seedlings, warm temperatures inhibit the accumulation of the SPT protein, and SPT autoregulates its own transcript abundance in conjunction with diurnal effects. Genetic data show that repression of growth by SPT is independent of GA signaling and phytochrome B, as previously shown for PIF4. Our data suggest that SPT integrates time of day and temperature signaling to control vegetative growth rate.

  7. Chloroplast photorelocation movement mediated by phototropin family proteins in green plants.

    Science.gov (United States)

    Suetsugu, Noriyuki; Wada, Masamitsu

    2007-09-01

    Chloroplasts gather in areas irradiated with weak light to maximize photosynthesis (the accumulation response). They move away from areas irradiated with strong light to minimize damage of the photosynthetic apparatus (the avoidance response). The processes underlying these chloroplast movements can be divided into three parts: photoperception, signal transduction, and chloroplast movement. Photoreceptors for chloroplast movement have been identified recently in various plant species. A blue light receptor phototropin (phot) mediates chloroplast photorelocation movement in the seed plant Arabidopsis thaliana, the fern Adiantum capillus-veneris, the moss Physcomitrella patens and possibly the green alga Mougeotia scalaris. A chimeric photoreceptor between phytochrome and phototropin, neochrome (neo), was found in some advanced ferns and in the green alga M. scalaris. While the mechanism of chloroplast movement is not well understood, it is known that actin filaments play an important role in this process. To understand the molecular mechanisms associated with chloroplast movement, several mutants were isolated in A. thaliana (jac1 and chup1) and the corresponding genes were cloned. In this review, recent progress in photoreceptor research into chloroplast movement in various plant species and the possible factors functioning in signal transduction or the regulation of actin filaments identified in A. thaliana is discussed.

  8. Gustav Senn (1875-1945): the pioneer of chloroplast movement research.

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    Kataoka, Hironao

    2015-01-01

    Gustav Senn analyzed for the first time light-induced movement and arrangement of chloroplasts. Using many plant species he performed physiological analyses of chloroplast migration in response to external stimuli, with emphasis on light. He determined light paths within a cell by measuring refractive indices and optical thickness of cellular compartments and confirmed that chloroplasts migrate towards the region where the light intensity is optimum. After 6 to 7 years' concentrated study, Senn published the famous monograph "Die Gestalts- und Lageveränderung der Pflanzen- Chromatophoren" (The Changes in Shape and Position of Plant Chloroplasts) in 1908. This book has stimulated many plant physiologists and photobiologists, because Senn not only thoroughly classified and defined various types of light-induced chloroplast migration but also already described possible interaction of different photoreceptor systems in Mougeotia more than 50 years before the discovery of phytochrome. This book also contains still useful experimental hints and overlooked findings on the interaction between light and other factors, such as temperature, water content, and nourishment. After publishing this book, Senn retreated from the study of chloroplasts and became a researcher of the Greek philosopher, Theophrastus. In this review, I introduce his biographical background and then summarize some of his key research accomplishment.

  9. PIF4 Promotes Expression of LNG1 and LNG2 to Induce Thermomorphogenic Growth in Arabidopsis

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    Geonhee Hwang

    2017-07-01

    Full Text Available Arabidopsis plants adapt to high ambient temperature by a suite of morphological changes including elongation of hypocotyls and petioles and leaf hyponastic growth. These morphological changes are collectively called thermomorphogenesis and are believed to increase leaf cooling capacity by enhancing transpiration efficiency, thereby increasing tolerance to heat stress. The bHLH transcription factor PHYTOCHROME INTERACTING FACTOR4 (PIF4 has been identified as a major regulator of thermomorphogenic growth. Here, we show that PIF4 promotes the expression of two homologous genes LONGIFOLIA1 (LNG1 and LONGIFOLIA2 (LNG2 that have been reported to regulate leaf morphology. ChIP-Seq analyses and ChIP assays showed that PIF4 directly binds to the promoters of both LNG1 and LNG2. The expression of LNG1 and LNG2 is induced by high temperature in wild type plants. However, the high temperature activation of LNG1 and LNG2 is compromised in the pif4 mutant, indicating that PIF4 directly regulates LNG1 and LNG2 expression in response to high ambient temperatures. We further show that the activities of LNGs support thermomorphogenic growth. The expression of auxin biosynthetic and responsive genes is decreased in the lng quadruple mutant, implying that LNGs promote thermomorphogenic growth by activating the auxin pathway. Together, our results demonstrate that LNG1 and LNG2 are directly regulated by PIF4 and are new components for the regulation of thermomorphogenesis.

  10. From Charles Darwin's botanical country-house studies to modern plant biology.

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    Kutschera, U; Briggs, W R

    2009-11-01

    As a student of theology at Cambridge University, Charles Darwin (1809-1882) attended the lectures of the botanist John S. Henslow (1796-1861). This instruction provided the basis for his life-long interest in plants as well as the species question. This was a major reason why in his book On the Origin of Species, which was published 150 years ago, Darwin explained his metaphorical phrase 'struggle for life' with respect to animals and plants. In this article, we review Darwin's botanical work with reference to the following topics: the struggle for existence in the vegetable kingdom with respect to the phytochrome-mediated shade avoidance response; the biology of flowers and Darwin's plant-insect co-evolution hypothesis; climbing plants and the discovery of action potentials; the power of movement in plants and Darwin's conflict with the German plant physiologist Julius Sachs; and light perception by growing grass coleoptiles with reference to the phototropins. Finally, we describe the establishment of the scientific discipline of Plant Biology that took place in the USA 80 years ago, and define this area of research with respect to Darwin's work on botany and the physiology of higher plants.

  11. Cryptochrome as a sensor of the blue/green ratio of natural radiation in Arabidopsis.

    Science.gov (United States)

    Sellaro, Romina; Crepy, María; Trupkin, Santiago Ariel; Karayekov, Elizabeth; Buchovsky, Ana Sabrina; Rossi, Constanza; Casal, Jorge José

    2010-09-01

    Green light added to blue light has been proposed to shift cryptochromes from their semireduced active form to the reduced, inactive state. Whether the increased proportion of green light observed under leaf canopies compared to open places reduces cryptochrome-mediated effects remained to be elucidated. Here we report that the length of the hypocotyl of Arabidopsis (Arabidopsis thaliana) seedlings grown under controlled conditions decreased linearly with increasing blue/green ratios of the light within the range of ratios found in natural environments. This effect was stronger under higher irradiances. We developed a model, parameterized on the basis of field experiments including photoreceptor mutants, where hypocotyl growth of seedlings exposed to different natural radiation environments was related to the action and interaction of phytochromes and cryptochromes. Adding the blue/green ratio of the light in the term involving cryptochrome activity improved the goodness of fit of the model, thus supporting a role of the blue/green ratio under natural radiation. The blue/green ratio decreased sharply with increasing shade by green grass leaves to one-half of the values observed in open places. The impact of blue/green ratio on cryptochrome-mediated inhibition of hypocotyl growth was at least as large as that of irradiance. We conclude that cryptochrome is a sensor of blue irradiance and blue/green ratio.

  12. The DET1-COP1-HY5 Pathway Constitutes a Multipurpose Signaling Module Regulating Plant Photomorphogenesis and Thermomorphogenesis

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    Carolin Delker

    2014-12-01

    Full Text Available Developmental plasticity enables plants to respond to elevated ambient temperatures by adapting their shoot architecture. On the cellular level, the basic-helix-loop-helix (bHLH transcription factor PHYTOCHROME INTERACTING FACTOR 4 (PIF4 coordinates this response by activating hormonal modules that in turn regulate growth. In addition to an unknown temperature-sensing mechanism, it is currently not understood how temperature regulates PIF4 activity. Using a forward genetic approach in Arabidopsis thaliana, we present extensive genetic evidence demonstrating that the DE-ETIOLATED 1 (DET1-CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1-ELONGATED HYPOCOTYL 5 (HY5-dependent photomorphogenesis pathway transcriptionally regulates PIF4 to coordinate seedling growth in response to elevated temperature. Our findings demonstrate that two of the most prevalent environmental cues, light and temperature, share a much larger set of signaling components than previously assumed. Similar to the toolbox concept in animal embryonic patterning, multipurpose signaling modules might have evolved in plants to translate various environmental stimuli into adaptational growth processes.

  13. Phototropin 2 is involved in blue light-induced anthocyanin accumulation in Fragaria x ananassa fruits.

    Science.gov (United States)

    Kadomura-Ishikawa, Yasuko; Miyawaki, Katsuyuki; Noji, Sumihare; Takahashi, Akira

    2013-11-01

    Anthocyanins are widespread, essential secondary metabolites in higher plants during color development in certain flowers and fruits. In strawberries, anthocyanins are also key contributors to fruit antioxidant capacity and nutritional value. However, the effects of different light qualities on anthocyanin accumulation in strawberry (Fragaria x ananassa, cv. Sachinoka) fruits remain elusive. In the present study, we showed the most efficient increase in anthocyanin content occurred by blue light irradiation. Light sensing at the molecular level was investigated by isolation of two phototropin (FaPHOT1 and FaPHOT2), two cryptochrome (FaCRY1 and FaCRY2), and two phytochrome (FaPHYA and FaPHYB) homologs. Expression analysis revealed only FaPHOT2 transcripts markedly increased depending on fruit developmental stage, and a corresponding increase in anthocyanin content was detected. FaPHOT2 knockdown resulted in decreased anthocyanin content; however, overexpression increased anthocyanin content. These findings suggested blue light induced anthocyanin accumulation, and FaPHOT2 may play a role in sensing blue light, and mediating anthocyanin biosynthesis in strawberry fruits. This is the first report to find a relationship between visible light sensing, and color development in strawberry fruits.

  14. Comparative Transcriptome Analysis Reveals Effects of Exogenous Hematin on Anthocyanin Biosynthesis during Strawberry Fruit Ripening

    Science.gov (United States)

    Li, Huayin; Li, Jingjuan; Zhang, Yihui

    2016-01-01

    Anthocyanin in strawberries has a positive effect on fruit coloration. In this study, the role of exogenous hematin on anthocyanin biosynthesis was investigated. Our result showed that the white stage of strawberries treated with exogenous hematin had higher anthocyanin content, compared to the control group. Among all treatments, 5 μM of hematin was the optimal condition to promote color development. In order to explore the molecular mechanism of fruit coloring regulated by hematin, transcriptomes in the hematin- and non-hematin-treated fruit were analyzed. A large number of differentially expressed genes (DEGs) were identified in regulating anthocyanin synthesis, including the DEGs involved in anthocyanin biosynthesis, hormone signaling transduction, phytochrome signaling, starch and sucrose degradation, and transcriptional pathways. These regulatory networks may play an important role in regulating the color process of strawberries treated with hematin. In summary, exogenous hematin could promote fruit coloring by increasing anthocyanin content in the white stage of strawberries. Furthermore, transcriptome analysis suggests that hematin-promoted fruit coloring occurs through multiple related metabolic pathways, which provides valuable information for regulating fruit color via anthocyanin biosynthesis in strawberries. PMID:28074176

  15. Perception of photoperiod in individual buds of mature trees regulates leaf-out.

    Science.gov (United States)

    Zohner, Constantin M; Renner, Susanne S

    2015-12-01

    Experimental data on the perception of day length and temperature in dormant temperate zone trees are surprisingly scarce. In order to investigate when and where these environmental signals are perceived, we carried out bagging experiments in which buds on branches of Fagus sylvatica, Aesculus hippocastanum and Picea abies trees were exposed to natural light increase or kept at constant 8-h days from December until June. Parallel experiments used twigs cut from the same trees, harvesting treated and control twigs seven times and then exposing them to 8- or 16-h days in a glasshouse. Under 8-h days, budburst in Fagus outdoors was delayed by 41 d and in Aesculus by 4 d; in Picea, day length had no effect. Buds on nearby branches reacted autonomously, and leaf primordia only reacted to light cues in late dormancy after accumulating warm days. Experiments applying different wavelength spectra and high-resolution spectrometry to buds indicate a phytochrome-mediated photoperiod control. By demonstrating local photoperiodic control of buds, revealing the time when these signals are perceived, and showing the interplay between photoperiod and chilling, this study contributes to improved modelling of the impact of climate warming on photosensitive species.

  16. Release of reactive oxygen intermediates (superoxide radicals, hydrogen peroxide, and hydroxyl radicals) and peroxidase in germinating radish seeds controlled by light, gibberellin, and abscisic acid.

    Science.gov (United States)

    Schopfer, P; Plachy, C; Frahry, G

    2001-04-01

    Germination of radish (Raphanus sativus cv Eterna) seeds can be inhibited by far-red light (high-irradiance reaction of phytochrome) or abscisic acid (ABA). Gibberellic acid (GA3) restores full germination under far-red light. This experimental system was used to investigate the release of reactive oxygen intermediates (ROI) by seed coats and embryos during germination, utilizing the apoplastic oxidation of 2',7'-dichlorofluorescin to fluorescent 2',7'-dichlorofluorescein as an in vivo assay. Germination in darkness is accompanied by a steep rise in ROI release originating from the seed coat (living aleurone layer) as well as the embryo. At the same time as the inhibition of germination, far-red light and ABA inhibit ROI release in both seed parts and GA3 reverses this inhibition when initiating germination under far-red light. During the later stage of germination the seed coat also releases peroxidase with a time course affected by far-red light, ABA, and GA3. The participation of superoxide radicals, hydrogen peroxide, and hydroxyl radicals in ROI metabolism was demonstrated with specific in vivo assays. ROI production by germinating seeds represents an active, developmentally controlled physiological function, presumably for protecting the emerging seedling against attack by pathogens.

  17. Light-mediated self-organization of sunflower stands increases oil yield in the field.

    Science.gov (United States)

    López Pereira, Mónica; Sadras, Victor O; Batista, William; Casal, Jorge J; Hall, Antonio J

    2017-07-25

    Here, we show a unique crop response to intraspecific interference, whereby neighboring sunflower plants in a row avoid each other by growing toward a more favorable light environment and collectively increase production per unit land area. In high-density stands, a given plant inclined toward one side of the interrow space, and the immediate neighbors inclined in the opposite direction. This process started early as an incipient inclination of pioneer plants, and the arrangement propagated gradually as a "wave" of alternate inclination that persisted until maturity. Measurements and experimental manipulation of light spectral composition indicate that these responses are mediated by changes in the red/far-red ratio of the light, which is perceived by phytochrome. Cellular automata simulations reproduced the patterns of stem inclination in field experiments, supporting the proposition of self-organization of stand structure. Under high crop population densities (10 and 14 plants per m(2)), as yet unachievable in commercial farms with current hybrids due to lodging and diseases, self-organized crops yielded between 19 and 47% more oil than crops forced to remain erect.

  18. Salt tolerance (STO), a stress-related protein, has a major role in light signalling.

    Science.gov (United States)

    Indorf, Martin; Cordero, Julio; Neuhaus, Gunther; Rodríguez-Franco, Marta

    2007-08-01

    The salt tolerance protein (STO) of Arabidopsis was identified as a protein conferring salt tolerance to yeast cells. In order to uncover its function, we isolated an STO T-DNA insertion line and generated RNAi and overexpressor Arabidopsis plants. Here we present data on the hypocotyl growth of these lines indicating that STO acts as a negative regulator in phytochrome and blue-light signalling. Transcription analysis of STO uncovered a light and circadian dependent regulation of gene expression, and analysis of light-regulated genes revealed that STO is involved in the regulation of CHS expression during de-etiolation. In addition, we could show that CONSTITUTIVE PHOTOMORPHOGENESIS 1 (COP1) represses the transcription of STO and contributes to the destabilization of the protein in etiolated seedlings. Microscopic analysis revealed that the STO:eGFP fusion protein is located in the nucleus, accumulates in a light-dependent manner, and, in transient transformation assays in onion epidermal cells, co-localizes with COP1 in nuclear and cytoplasmic aggregations. However, the analysis of gain- and loss-of-function STO mutants in the cop1-4 background points towards a COP1-independent role during photomorphogenesis.

  19. Tomato plants overexpressing cryptochrome 2 reveal altered expression of energy and stress-related gene products in response to diurnal cues.

    Science.gov (United States)

    Lopez, Loredana; Carbone, Fabrizio; Bianco, Linda; Giuliano, Giovanni; Facella, Paolo; Perrotta, Gaetano

    2012-05-01

    In order to sense and respond to the fluctuating light conditions, higher plants possess several families of photoreceptors, such as phytochromes (PHYs), cryptochromes (CRYs) and phototropins. CRYs are responsible for photomorphogenesis and play a role in circadian, developmental and adaptive growth regulation of plants. In tomato (Solanum lycopersicum), CRY2 controls vegetative development, flowering time, fruit antioxidant content as well as the diurnal transcription of several other photoreceptor genes. We applied large-scale molecular approaches to identify altered transcripts and proteins in tomato wild-type (WT) versus a CRY2 overexpressing transgenic genotype, under a diurnal rhythm. Our results showed that tomato CRY2 profoundly affects both gene and protein expression in response to daily light cycle. Particularly altered molecular pathways are related to biotic/abiotic stress, photosynthesis, including components of the light and dark reactions and of starch and sucrose biosynthesis, as well as to secondary metabolism, such as phenylpropanoid, phenolic and flavonoid/anthocyanin biosynthesis pathways. One of the most interesting results is the coordinated up-regulation, in the transgenic genotype, of a consistent number of transcripts and proteins involved in photorespiration and photosynthesis. It is conceivable that light modulates the energetic metabolism of tomato through a fine CRY2-mediated transcriptional control.

  20. A blue-light photoreceptor mediates the feedback regulation of photosynthesis.

    Science.gov (United States)

    Petroutsos, Dimitris; Tokutsu, Ryutaro; Maruyama, Shinichiro; Flori, Serena; Greiner, Andre; Magneschi, Leonardo; Cusant, Loic; Kottke, Tilman; Mittag, Maria; Hegemann, Peter; Finazzi, Giovanni; Minagawa, Jun

    2016-09-22

    In plants and algae, light serves both as the energy source for photosynthesis and a biological signal that triggers cellular responses via specific sensory photoreceptors. Red light is perceived by bilin-containing phytochromes and blue light by the flavin-containing cryptochromes and/or phototropins (PHOTs), the latter containing two photosensory light, oxygen, or voltage (LOV) domains. Photoperception spans several orders of light intensity, ranging from far below the threshold for photosynthesis to values beyond the capacity of photosynthetic CO2 assimilation. Excess light may cause oxidative damage and cell death, processes prevented by enhanced thermal dissipation via high-energy quenching (qE), a key photoprotective response. Here we show the existence of a molecular link between photoreception, photosynthesis, and photoprotection in the green alga Chlamydomonas reinhardtii. We show that PHOT controls qE by inducing the expression of the qE effector protein LHCSR3 (light-harvesting complex stress-related protein 3) in high light intensities. This control requires blue-light perception by LOV domains on PHOT, LHCSR3 induction through PHOT kinase, and light dissipation in photosystem II via LHCSR3. Mutants deficient in the PHOT gene display severely reduced fitness under excessive light conditions, indicating that the sensing, utilization, and dissipation of light is a concerted process that plays a vital role in microalgal acclimation to environments of variable light intensities.

  1. LSD1 and HY5 Antagonistically Regulate Red Light induced-Programmed Cell Death in Arabidopsis

    Directory of Open Access Journals (Sweden)

    Tingting eChai

    2015-05-01

    Full Text Available Programmed cell death (PCD in plant is triggered by abiotic and biotic stress. Light-dependent PCD is unique to plants. Light-induced PCD also requires reactive oxygen species (ROS and salicylic acid (SA. In this study, lesion simulating disease1 (LSD1 and elongated hypocotyl 5 (HY5 perform opposite roles to regulate excess red light (RL-triggered PCD associated with ROS and SA production. Under RL, the lsd1 mutant released more ROS and SA and displayed a stronger cell death rate than the hy5 mutant. It was shown that active LSD1 converted into inactive form by changing the redox status of the plastoquinone pool, and HY5 interacted with phytochrome B (phyB to promote PCD in response to RL. LSD1 inhibited the enhanced disease susceptibility 1 (EDS1 expression by upregulating SR1, whereas HY5 enhanced the enhanced EDS1 expression by binding to the G-box of the EDS1 promoter. This study suggested that LSD1 and HY5 antagonistically modulated EDS1-dependent ROS and SA signaling; thus, PCD was mediated in response to RL.

  2. LSD1 and HY5 antagonistically regulate red light induced-programmed cell death in Arabidopsis.

    Science.gov (United States)

    Chai, Tingting; Zhou, Jun; Liu, Jian; Xing, Da

    2015-01-01

    Programmed cell death (PCD) in plant is triggered by abiotic and biotic stress. Light-dependent PCD is unique to plants. Light-induced PCD also requires reactive oxygen species (ROS) and salicylic acid (SA). In this study, lesion simulating disease1 (LSD1) and elongated hypocotyl 5 (HY5) perform opposite roles to regulate excess red light (RL)-triggered PCD associated with ROS and SA production. Under RL, the lsd1 mutant released more ROS and SA and displayed a stronger cell death rate than the hy5 mutant. It was shown that active LSD1 converted into inactive form by changing the redox status of the plastoquinone pool, and HY5 interacted with phytochrome B (phyB) to promote PCD in response to RL. LSD1 inhibited the enhanced disease susceptibility 1 (EDS1) expression by upregulating SR1, whereas HY5 enhanced the enhanced EDS1 expression by binding to the G-box of the EDS1 promoter. This study suggested that LSD1 and HY5 antagonistically modulated EDS1-dependent ROS and SA signaling; thus, PCD was mediated in response to RL.

  3. Characterization of a calcium/calmodulin-dependent protein kinase homolog from maize roots showing light-regulated gravitropism

    Science.gov (United States)

    Lu, Y. T.; Hidaka, H.; Feldman, L. J.

    1996-01-01

    Roots of many species respond to gravity (gravitropism) and grow downward only if illuminated. This light-regulated root gravitropism is phytochrome-dependent, mediated by calcium, and inhibited by KN-93, a specific inhibitor of calcium/calmodulin-dependent protein kinase II (CaMK II). A cDNA encoding MCK1, a maize homolog of mammalian CaMK, has been isolated from roots of maize (Zea mays L.). The MCK1 gene is expressed in root tips, the site of perception for both light and gravity. Using the [35S]CaM gel-overlay assay we showed that calmodulin-binding activity of the MCK1 is abolished by 50 microM KN-93, but binding is not affected by 5 microM KN-93, paralleling physiological findings that light-regulated root gravitropism is inhibited by 50 microM KN-93, but not by 5 microM KN-93. KN-93 inhibits light-regulated gravitropism by interrupting transduction of the light signal, not light perception, suggesting that MCK1 may play a role in transducing light. This is the first report suggesting a physiological function for a CaMK homolog in light signal transduction.

  4. Engineering of a red-light-activated human cAMP/cGMP-specific phosphodiesterase.

    Science.gov (United States)

    Gasser, Carlos; Taiber, Sandra; Yeh, Chen-Min; Wittig, Charlotte Helene; Hegemann, Peter; Ryu, Soojin; Wunder, Frank; Möglich, Andreas

    2014-06-17

    Sensory photoreceptors elicit vital physiological adaptations in response to incident light. As light-regulated actuators, photoreceptors underpin optogenetics, which denotes the noninvasive, reversible, and spatiotemporally precise perturbation by light of living cells and organisms. Of particular versatility, naturally occurring photoactivated adenylate cyclases promote the synthesis of the second messenger cAMP under blue light. Here, we have engineered a light-activated phosphodiesterase (LAPD) with complementary light sensitivity and catalytic activity by recombining the photosensor module of Deinococcus radiodurans bacterial phytochrome with the effector module of Homo sapiens phosphodiesterase 2A. Upon red-light absorption, LAPD up-regulates hydrolysis of cAMP and cGMP by up to sixfold, whereas far-red light can be used to down-regulate activity. LAPD also mediates light-activated cAMP and cGMP hydrolysis in eukaryotic cell cultures and in zebrafish embryos; crucially, the biliverdin chromophore of LAPD is available endogenously and does not need to be provided exogenously. LAPD thus establishes a new optogenetic modality that permits light control over diverse cAMP/cGMP-mediated physiological processes. Because red light penetrates tissue more deeply than light of shorter wavelengths, LAPD appears particularly attractive for studies in living organisms.

  5. Signalling cascades integrating light-enhanced nitrate metabolism.

    Science.gov (United States)

    Lillo, Cathrine

    2008-10-01

    In higher plants, light is crucial for regulation of nitrate uptake, translocation and assimilation into organic compounds. Part of this metabolism is tightly coupled to photosynthesis because the enzymes involved, nitrite reductase and glutamate synthase, are localized to the chloroplasts and receive reducing power from photosynthetic electron transport. However, important enzymes in nitrate acquisition and reduction are localized to cellular compartments other than chloroplasts and are also up-regulated by light, i.e. transporters in cell and organellar membranes and nitrate reductase in the cytosol. This review describes the different light-dependent signalling cascades regulating nitrate metabolism at the transcriptional as well as post-transcriptional level, and how reactions in different compartments of the cell are co-ordinated. Essential players in this network are phytochrome and HY5 (long hypocotyls 5)/HYH (HY5 homologue)-dependent signalling pathways, the energy-related AMPK (AMP-activated protein kinase) protein kinase homologue SNRK1 (sucrose non-fermenting kinase 1-related kinase), chloroplastic thioredoxins and the prokaryotically originated PII protein. A complex light-dependent network of regulation emerges, which appears to be necessary for optimal nitrogen assimilation and for avoiding the accumulation of toxic intermediates and side products, such as nitrite and reactive oxygen compounds.

  6. Light-stimulated cell expansion in bean (Phaseolus vulgaris L.) leaves. II. Quantity and quality of light required

    Science.gov (United States)

    Van Volkenburgh, E.; Cleland, R. E.; Watanabe, M.

    1990-01-01

    The quantity and quality of light required for light-stimulated cell expansion in leaves of Phaseolus vulgaris L. have been determined. Seedlings were grown in dim red light (RL; 4 micromoles photons m-2 s-1) until cell division in the primary leaves was completed, then excised discs were incubated in 10 mM sucrose plus 10 mM KCl in a variety of light treatments. The growth response of discs exposed to continuous white light (WL) for 16 h was saturated at 100 micromoles m-2 s-1, and did not show reciprocity. Extensive, but not continuous, illumination was needed for maximal growth. The wavelength dependence of disc expansion was determined from fluence-response curves obtained from 380 to 730 nm provided by the Okazaki Large Spectrograph. Blue (BL; 460 nm) and red light (RL; 660 nm) were most effective in promoting leaf cell growth, both in photosynthetically active and inhibited leaf discs. Far-red light (FR; 730 nm) reduced the effectiveness of RL, but not BL, indicating that phytochrome and a separate blue-light receptor mediate expansion of leaf cells.

  7. The REVEILLE clock genes inhibit growth of juvenile and adult plants by control of cell size.

    Science.gov (United States)

    Gray, Jennifer A; Shalit-Kaneh, Akiva; Chu, Dalena Nhu; Hsu, Polly Yingshan; Harmer, Stacey

    2017-03-02

    The circadian clock is a complex regulatory network that enhances plant growth and fitness in a constantly changing environment. In Arabidopsis thaliana, the clock is comprised of numerous regulatory feedback loops in which REVEILLE8 (RVE8) and its homologs RVE4 and RVE6 act in a partially redundant manner to promote clock pace. Here, we report that the remaining members of the RVE8 clade, RVE3 and RVE5, play only minor roles in regulation of clock function. However, we find that RVE8 clade proteins have unexpected functions in modulation of light input to the clock and control of plant growth at multiple stages of development. In seedlings, these proteins repress hypocotyl elongation in a day-length and sucrose dependent manner. Strikingly, adult rve4 6 8 and rve3 4 5 6 8 mutants are much larger than wild type, with both increased leaf area and biomass. This size phenotype is associated with a faster growth rate and larger cell size and is not simply due to a delay in the transition to flowering. Gene expression and epistasis analysis reveal that the growth phenotypes of rve mutants are due to misregulation of PHYTOCHROME INTERACTING FACTOR4 (PIF4) and PIF5 expression. Our results shows that even small changes in PIF gene expression caused by perturbation of clock gene function can have large effects on the growth of adult plants.

  8. Gustav Senn (1875-1945):The pioneer of chloroplast movement research

    Institute of Scientific and Technical Information of China (English)

    Hironao Kataoka

    2015-01-01

    Gustav Senn analyzed for the first time light-induced movement and arrangement of chloroplasts. Using many plant species he performed physiological analyses of chloroplast migration in response to external stimuli, with emphasis on light. He determined light paths within a cel by measuring refractive indices and optical thickness of cel ular compartments and confirmed that chloroplasts migrate towards the region where the light intensity is optimum. After 6 to 7 years’ concentrated study, Senn published the famous monograph “Die Gestalts- und Lageveränderung der Pflanzen-Chromatophoren”(The Changes in Shape and Position of Plant Chloroplasts) in 1908. This book has stimulated many plant physiologists and photobiologists, because Senn not only thoroughly classified and defined various types of light-induced chloroplast migration but also already described possible interaction of different photoreceptor systems in Mougeotia more than 50 years before the discovery of phytochrome. This book also contains stil useful experimental hints and over-looked findings on the interaction between light and other factors, such as temperature, water content, and nourishment. After publishing this book, Senn retreated from the study of chloroplasts and became a researcher of the Greek philoso-pher, Theophrastus. In this review, I introduce his biographical background and then summarize some of his key research accomplishment.

  9. Transcription factor PIF4 controls the thermosensory activation of flowering

    KAUST Repository

    Kumar, S. Vinod

    2012-03-21

    Plant growth and development are strongly affected by small differences in temperature. Current climate change has already altered global plant phenology and distribution, and projected increases in temperature pose a significant challenge to agriculture. Despite the important role of temperature on plant development, the underlying pathways are unknown. It has previously been shown that thermal acceleration of flowering is dependent on the florigen, FLOWERING LOCUS T (FT). How this occurs is, however, not understood, because the major pathway known to upregulate FT, the photoperiod pathway, is not required for thermal acceleration of flowering. Here we demonstrate a direct mechanism by which increasing temperature causes the bHLH transcription factor PHYTOCHROME INTERACTING FACTOR4 (PIF4) to activate FT. Our findings provide a new understanding of how plants control their timing of reproduction in response to temperature. Flowering time is an important trait in crops as well as affecting the life cycles of pollinator species. A molecular understanding of how temperature affects flowering will be important for mitigating the effects of climate change. © 2012 Macmillan Publishers Limited. All rights reserved.

  10. 植物血红素加氧酶生理功能研究进展(综述)%Research Advance of Heme Oxygenase Physiological Function in Plant

    Institute of Scientific and Technical Information of China (English)

    王光辉; 吴黄铭; 郑岩; 李成梁; 陈惠萍

    2014-01-01

    Heme oxygenase (HO) is a key enzyme that catalyzes the oxidative degradation of heme to carbon monoxide (CO), free iron, and biliverdin (BV).This review focuses on the recent advances of HO research made in plant including HO playing the role in phytochrome synthesis,regulating the constitution in morphological architecture of root,raising the resistance of plant against stress,and promoting the germination of seeds and regulating the closure of stoma, etc. Forthmore,the direction of coming research is made a discussion.%血红素加氧酶(heme oxygenase, HO)是血红素分解代谢的关键酶类,在植物体内起着重要的作用。本文从HO在植物光敏色素合成中的作用、对植物根形态建成、提高植物抗胁迫反应能力、促进植物种子萌发和调节植物气孔关闭等方面,综述植物HO生理功能的最新研究进展,并对HO未来研究方向进行展望。

  11. Effect of Light Quality on Photosynthesis and Chlorophyll Fluorescence in Strawberry Leaves

    Institute of Scientific and Technical Information of China (English)

    XU Kai; GUO Yan-ping; ZHANG Shang-long; ZHANG Liang-cheng; ZHANG Ling-xiao

    2004-01-01

    The photosynthetic characteristics of strawberry(Fragaria x ananassa Duch. cv. Toyonoka)leaves under illumination of identical light intensity(55-57% natural light)with different light quality were studied. It was showed that the chlorophyll content,maximal photochemical efficiency of PS Ⅱ(Fv/Fm),Fm/Fo,amount of inactive PS Ⅱ reaction centers(Fi-Fo)and rate of QAreduction were positively correlated with the red-light/blue-light ratios,but the chlorophyll(a/b)ratios were negatively correlated with them. Carotenoid content of the leaves was maximum under the blue film,than under green film,red film,white film and yellow film,and negatively correlated with the red/farred ratios. The apparent quantum yield(AQY),photorespiratory rate(Pr)and carboxylation efficiency(CE)were also strongly affected by light quality. The photosynthetic rate(Pn)in strawberry leaves under green film was significantly lower than under all other film. Our results suggested that light quality is an essential factor regulating the development of PS Ⅱ and phytochrome and an independent blue light photoreceptor,possibly a cryptochrome,can regulate photosynthetic performance.

  12. The genome of the seagrass Zostera marina reveals angiosperm adaptation to the sea

    KAUST Repository

    Olsen, Jeanine L.

    2016-01-27

    Seagrasses colonized the sea1 on at least three independent occasions to form the basis of one of the most productive and widespread coastal ecosystems on the planet2. Here we report the genome of Zostera marina (L.), the first, to our knowledge, marine angiosperm to be fully sequenced. This reveals unique insights into the genomic losses and gains involved in achieving the structural and physiological adaptations required for its marine lifestyle, arguably the most severe habitat shift ever accomplished by flowering plants. Key angiosperm innovations that were lost include the entire repertoire of stomatal genes3, genes involved in the synthesis of terpenoids and ethylene signalling, and genes for ultraviolet protection and phytochromes for far-red sensing. Seagrasses have also regained functions enabling them to adjust to full salinity. Their cell walls contain all of the polysaccharides typical of land plants, but also contain polyanionic, low-methylated pectins and sulfated galactans, a feature shared with the cell walls of all macroalgae4 and that is important for ion homoeostasis, nutrient uptake and O2/CO2 exchange through leaf epidermal cells. The Z. marina genome resource will markedly advance a wide range of functional ecological studies from adaptation of marine ecosystems under climate warming5, 6, to unravelling the mechanisms of osmoregulation under high salinities that may further inform our understanding of the evolution of salt tolerance in crop plants7.

  13. GT-2: in vivo transcriptional activation activity and definition of novel twin DNA binding domains with reciprocal target sequence selectivity.

    Science.gov (United States)

    Ni, M; Dehesh, K; Tepperman, J M; Quail, P H

    1996-06-01

    GT-2 is a novel DNA binding protein that interacts with a triplet functionally defined, positively acting GT-box motifs (GT1-bx, GT2-bx, and GT3-bx) in the rice phytochrome A gene (PHYA) promoter. Data from a transient transfection assay used here show that recombinant GT-2 enhanced transcription from both homologous and heterologous GT-box-containing promoters, thereby indicating that this protein can function as a transcriptional activator in vivo. Previously, we have shown that GT-2 contains separate DNA binding determinants in its N- and C-terminal halves, with binding site preferences for the GT3-bx and GT2-bx promoter motifs, respectively. Here, we demonstrate that the minimal DNA binding domains reside within dual 90-amino acid polypeptide segments encompassing duplicated sequences, termed trihelix regions, in each half of the molecule, plus 15 additional immediately adjacent amino acids downstream. These minimal binding domains retained considerable target sequence selectivity for the different GT-box motifs, but this selectivity was enhanced by a separate polypeptide segment farther downstream on the C-terminal side of each trihelix region. Therefore, the data indicate that the twin DNA binding domains of GT-2 each consist of a general GT-box recognition core with intrinsic differential binding activity toward closely related target motifs and a modified sequence conferring higher resolution reciprocal selectivity between these motifs.

  14. Leaf-Mediated Light Responses in Petunia Flowers.

    Science.gov (United States)

    Moscovici, S.; Moalem-Beno, D.; Weiss, D.

    1996-01-01

    In the present work we studied the role of light in the regulation of flavonoid gene expression and anthocyanin synthesis in petunia (Petunia hybrida) corollas. We found that light is required for chalcone synthase gene (chs) expression, anthocyanin synthesis, and growth of detached and attached petunia corollas. Although direct illumination induced chs expression, pigmentation, and elongation of the detached corollas, irradiation of green leaves or sepals played the main role in the attached corollas. The duration, intensity, and spectrum of the light reaction suggest that phytochrome-mediated high-irradiance reactions are involved in the regulation of corolla development. Using the photosynthesis inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethylurea, we showed that photosynthesis does not significantly contribute to the leaf-mediated light responses. When sepals were removed or covered. [14C]sucrose up-take by the corolla of detached intact flowers was inhibited. The results of this study suggest that light is perceived by leaves and sepals and enhances corolla sink activity, elongation, pigmentation, and chs expression. The role of leaves and sepals in the light regulation of petunia corolla development is discussed. PMID:12226259

  15. A pair of floral regulators sets critical day length for Hd3a florigen expression in rice.

    Science.gov (United States)

    Itoh, Hironori; Nonoue, Yasunori; Yano, Masahiro; Izawa, Takeshi

    2010-07-01

    The critical day length triggering photoperiodic flowering is set as an acute, accurate threshold in many short-day plants, including rice. Here, we show that, unlike the Arabidopsis florigen gene FT, the rice florigen gene Hd3a (Heading date 3a) is toggled by only a 30-min day-length reduction. Hd3a expression is induced by Ehd1 (Early heading date 1) expression when blue light coincides with the morning phase set by OsGIGANTEA(OsGI)-dependent circadian clocks. Ehd1 expression is repressed by both night breaks under short-day conditions and morning light signals under long-day conditions. Ghd7 (Grain number, plant height and heading date 7) was acutely induced when phytochrome signals coincided with a photosensitive phase set differently by distinct photoperiods and this induction repressed Ehd1 the next morning. Thus, two distinct gating mechanisms--of the floral promoter Ehd1 and the floral repressor Ghd7--could enable manipulation of slight differences in day length to control Hd3a transcription with a critical day-length threshold.

  16. Gibberellic acid nitrite stimulates germination of two species of light-requiring seeds via the nitric oxide pathway.

    Science.gov (United States)

    Jovanović, Vladan; Giba, Zlatko; Djoković, Dejan; Milosavljević, Slobodan; Grubisić, Dragoljub; Konjević, Radomir

    2005-06-01

    We used two species of light-requiring seeds, Paulownia tomentosa, which have absolute light requirement (no germination in darkness), and Stellaria media seeds, which germinate in darkness to a certain extent because of presence of preformed active phytochrome, to obtain results strongly suggesting that gibberellic acid nitrite stimulates seed germination via its capability as a functional NO donor. Exogenous application of gibberellic acid nitrite stimulates gibberellin-insensitive Stellaria media seed germination in darkness as do a wide variety of NO donors. Pure gibberellic acid could replace the light requirement of P. tomentosa seeds, thus enabling them to germinate in darkness. Gibberellic acid nitrite did not have this effect. A stimulative effect from gibberellic acid nitrite could be detected only after exposure of these seeds to short, 10 min, pulse of red light. Taken together, these results suggest that gibberellic activity of gibberellic acid nitrite is lost after nitrosation but, regarding to the presence of -O-NO moiety in the molecule, gibberellic acid nitrite shares stimulative properties in seed germination with other compounds with NO-releasing properties.

  17. Green light induces shade avoidance symptoms.

    Science.gov (United States)

    Zhang, Tingting; Maruhnich, Stefanie A; Folta, Kevin M

    2011-11-01

    Light quality and quantity affect plant adaptation to changing light conditions. Certain wavelengths in the visible and near-visible spectrum are known to have discrete effects on plant growth and development, and the effects of red, far-red, blue, and ultraviolet light have been well described. In this report, an effect of green light on Arabidopsis (Arabidopsis thaliana) rosette architecture is demonstrated using a narrow-bandwidth light-emitting diode-based lighting system. When green light was added to a background of constant red and blue light, plants exhibited elongation of petioles and upward leaf reorientation, symptoms consistent with those observed in a shaded light environment. The same green light-induced phenotypes were also observed in phytochrome (phy) and cryptochrome (cry) mutant backgrounds. To explore the molecular mechanism underlying the green light-induced response, the accumulation of shade-induced transcripts was measured in response to enriched green light environments. Transcripts that have been demonstrated to increase in abundance under far-red-induced shade avoidance conditions either decrease or exhibit no change when green light is added. However, normal far-red light-associated transcript accumulation patterns are observed in cryptochrome mutants grown with supplemental green light, indicating that the green-absorbing form of cryptochrome is the photoreceptor active in limiting the green light induction of shade-associated transcripts. These results indicate that shade symptoms can be induced by the addition of green light and that cryptochrome receptors and an unknown light sensor participate in acclimation to the enriched green environment.

  18. Green Light Induces Shade Avoidance Symptoms1[C][W][OA

    Science.gov (United States)

    Zhang, Tingting; Maruhnich, Stefanie A.; Folta, Kevin M.

    2011-01-01

    Light quality and quantity affect plant adaptation to changing light conditions. Certain wavelengths in the visible and near-visible spectrum are known to have discrete effects on plant growth and development, and the effects of red, far-red, blue, and ultraviolet light have been well described. In this report, an effect of green light on Arabidopsis (Arabidopsis thaliana) rosette architecture is demonstrated using a narrow-bandwidth light-emitting diode-based lighting system. When green light was added to a background of constant red and blue light, plants exhibited elongation of petioles and upward leaf reorientation, symptoms consistent with those observed in a shaded light environment. The same green light-induced phenotypes were also observed in phytochrome (phy) and cryptochrome (cry) mutant backgrounds. To explore the molecular mechanism underlying the green light-induced response, the accumulation of shade-induced transcripts was measured in response to enriched green light environments. Transcripts that have been demonstrated to increase in abundance under far-red-induced shade avoidance conditions either decrease or exhibit no change when green light is added. However, normal far-red light-associated transcript accumulation patterns are observed in cryptochrome mutants grown with supplemental green light, indicating that the green-absorbing form of cryptochrome is the photoreceptor active in limiting the green light induction of shade-associated transcripts. These results indicate that shade symptoms can be induced by the addition of green light and that cryptochrome receptors and an unknown light sensor participate in acclimation to the enriched green environment. PMID:21852417

  19. Light-dependent attenuation of phycoerythrin gene expression reveals convergent evolution of green light sensing in cyanobacteria.

    Science.gov (United States)

    Bezy, Ryan P; Wiltbank, Lisa; Kehoe, David M

    2011-11-08

    The colorful process of chromatic acclimation allows many cyanobacteria to change their pigmentation in response to ambient light color changes. In red light, cells produce red-absorbing phycocyanin (PC), whereas in green light, green-absorbing phycoerythrin (PE) is made. Controlling these pigment levels increases fitness by optimizing photosynthetic activity in different light color environments. The light color sensory system controlling PC expression is well understood, but PE regulation has not been resolved. In the filamentous cyanobacterium Fremyella diplosiphon UTEX 481, two systems control PE synthesis in response to light color. The first is the Rca pathway, a two-component system controlled by a phytochrome-class photoreceptor, which transcriptionally represses cpeCDESTR (cpeC) expression during growth in red light. The second is the Cgi pathway, which has not been characterized. We determined that the Cgi system also regulates PE synthesis by repressing cpeC expression in red light, but acts posttranscriptionally, requiring the region upstream of the CpeC translation start codon. cpeC RNA stability was comparable in F. diplosiphon cells grown in red and green light, and a short transcript that included the 5' region of cpeC was detected, suggesting that the Cgi system operates by transcription attenuation. The roles of four predicted stem-loop structures within the 5' region of cpeC RNA were analyzed. The putative stem-loop 31 nucleotides upstream of the translation start site was required for Cgi system function. Thus, the Cgi system appears to be a unique type of signal transduction pathway in which the attenuation of cpeC transcription is regulated by light color.

  20. Growth and photomorphogenesis of pepper plants under red light-emitting diodes with supplemental blue or far-red lighting

    Science.gov (United States)

    Brown, C. S.; Schuerger, A. C.; Sager, J. C.

    1995-01-01

    Light-emitting diodes (LEDs) are a potential irradiation source for intensive plant culture systems and photobiological research. They have small size, low mass, a long functional life, and narrow spectral output. In this study, we measured the growth and dry matter partitioning of 'Hungarian Wax' pepper (Capsicum annuum L.) plants grown under red LEDs compared with similar plants grown under red LEDs with supplemental blue or far-red radiation or under broad spectrum metal halide (MH) lamps. Additionally, we describe the thermal and spectral characteristics of these sources. The LEDs used in this study had a narrow bandwidth at half peak height (25 nm) and a focused maximum spectral output at 660 nm for the red and 735 nm for the far-red. Near infrared radiation (800 to 3000 nm) was below detection and thermal infrared radiation (3000 to 50,000 nm) was lower in the LEDs compared to the MH source. Although the red to far-red ratio varied considerably, the calculated phytochrome photostationary state (phi) was only slightly different between the radiation sources. Plant biomass was reduced when peppers were grown under red LEDs in the absence of blue wavelengths compared to plants grown under supplemental blue fluorescent lamps or MH lamps. The addition of far-red radiation resulted in taller plants with greater stem mass than red LEDs alone. There were fewer leaves under red or red plus far-red radiation than with lamps producing blue wavelengths. These results indicate that red LEDs may be suitable, in proper combination with other wavelengths of light, for the culture of plants in tightly controlled environments such as space-based plant culture systems.

  1. Footprints of natural and artificial selection for photoperiod pathway genes in Oryza.

    Science.gov (United States)

    Huang, Chao-Li; Hung, Cheng-Yu; Chiang, Yu-Chung; Hwang, Chi-Chuan; Hsu, Tsai-Wen; Huang, Chi-Chun; Hung, Kuo-Hsiang; Tsai, Kun-Chan; Wang, Kuo-Hsiung; Osada, Naoki; Schaal, Barbara Anna; Chiang, Tzen-Yuh

    2012-06-01

    Asian rice, Oryza sativa, consists of two major subspecies, indica and japonica, which are physiologically differentiated and adapted to different latitudes. Genes for photoperiod sensitivity are likely targets of selection along latitude. We examined the footprints of natural and artificial selections for four major genes of the photoperiod pathway, namely PHYTOCHROME B (PhyB), HEADING DATE 1 (Hd1), HEADING DATE 3a (Hd3a), and EARLY HEADING DATE 1 (Ehd1), by investigation of the patterns of nucleotide polymorphisms in cultivated and wild rice. Geographical subdivision between tropical and subtropical O. rufipogon was found for all of the photoperiod genes in plants divided by the Tropic of Cancer (TOC). All of these genes, except for PhyB, were characterized by the existence of clades that split a long time ago and that corresponded to latitudinal subdivisions, and revealed a likely diversifying selection. Ssp. indica showed close affinity to tropical O. rufipogon for all genes, while ssp. japonica, which has a much wider range of distribution, displayed complex patterns of differentiation from O. rufipogon, which reflected various agricultural needs in relation to crop yield. In japonica, all genes, except Hd3a, were genetically differentiated at the TOC, while geographical subdivision occurred at 31°N in Hd3a, probably the result of varying photoperiods. Many other features of the photoperiod genes revealed domestication signatures, which included high linkage disequilibrium (LD) within genes, the occurrence of frequent and recurrent non-functional Hd1 mutants in cultivated rice, crossovers between subtropical and tropical alleles of Hd1, and significant LD between Hd1 and Hd3a in japonica and indica.

  2. specific and unspecific responses of plants to cold and drought stress

    Indian Academy of Sciences (India)

    Erwin H Beck; Sebastian Fettig; Claudia Knake; Katja Hartig; Tribikram Bhattarai

    2007-04-01

    Different environmental stresses to a plant may result in similar responses at the cellular and molecular level. This is due to the fact that the impacts of the stressors trigger similar strains and downstream signal transduction chains. A good example for an unspecific response is the reaction to stressors which induce water deficiency e.g. drought, salinity and cold, especially frost. The stabilizing effect of liquid water on the membrane bilayer can be supported by compatible solutes and special proteins. At the metabolic level, osmotic adjustment by synthesis of low-molecular osmolytes (carbohydrates, betains, proline) can counteract cellular dehydration and turgor loss. Taking the example of Pinus sylvestris, changes at the level of membrane composition, and concomitantly of photosynthetic capacity during frost hardening is shown. Additionally the effect of photoperiod as measured via the phytochrome system and the effect of subfreezing temperatures on the incidence of frost hardening is discussed. Extremely hydrophilic proteins such as dehydrins are common products protecting not only the biomembranes in ripening seeds (late embryogenesis abundant proteins) but accumulate also in the shoots and roots during cold adaptation, especially in drought tolerant plants. Dehydrins are characterized by conserved amino acid motifs, called the K-, Y- or S-segments. Accumulation of dehydrins can be induced not only by drought, but also by cold, salinity, treatment with abscisic acid and methyl jasmonate. Positive effects of the overexpression of a wild chickpea (Cicer pinnatifidum) dehydrin in tobacco plants on the dehydration tolerance is shown. The presentation discusses the perception of cold and drought, the subsequent signal transduction and expression of genes and their products. Differences and similarities between the plant responses to both stressors are also discussed.

  3. The role of the seed coat in the light sensivity in Raphanus sativus L. cv. redondo gigante seeds O papel do tegumento na sensibilidade à luz em sementes de Raphanus sativus L. cv. redondo gigante

    Directory of Open Access Journals (Sweden)

    Maura Lúcia Costa Gonçalves

    1997-07-01

    Full Text Available The role of the seed coat in the light sensitivity of seeds of Raphanus sativus L. cv. redondo gigante was analysed by germination tests of intact and naked seeds. Far-red light caused high inhibition of seed germination, while under white and red lights low inhibition was found. Naked seeds presented no light sensitivity with high percentage germination under light and darkness. However, incubation of naked seeds in -0.6MPa polyethylene glycol solution resulted in light inhibition as observed in intact seeds. The analysis of the seed coat transmitted light indicated that the filtered light presented the same photoequilibrium of phytochrome when compared to the white light, with a decrease of only 33% in the light irradiance which reaches the embryo.O papel do tegumento sobre a sensibilidade à luz em sementes de Raphanus sativus L. cv. redondo gigante foi analisado por testes de germinação de sementes intactas e nuas. A luz vermelho-extremo inibiu fortemente a germinação, enquanto as luzes branca e vermelha apresentaram baixa inibição. Por outro lado, sementes nuas não apresentaram sensibilidade à luz, com alta porcentagem de germinação tanto na luz como no escuro. Entretanto, a incubação das sementes nuas em condições de estresse em solução de polietilenoglicol a -0,6MPa, resultou em inibição na luz, como observadas em sementes intactas. A análise da luz transmitida pelo tegumento das sementes indicou que a luz filtrada apresenta o mesmo fotoequilíbrio teórico do fitocromo obtido na luz branca, com um decréscimo em apenas 33% da irradiância que atinge o embrião.

  4. Influence of light on DNA content of Helianthus annuus Linnaeus.

    Science.gov (United States)

    Price, H J; Johnston, J S

    1996-10-01

    Mean nuclear 2C DNA content (C equaling haploid DNA per nucleus) of the first leaf of the sunflower, Helianthus annuus L., is influenced by the quality and the quantity of light. Seedlings of two inbred lines, RHA 299 and RHA 271 were germinated and grown in controlled environmental conditions. Lighting was adjusted to provide different combinations of photon flux densities and red to far red (R:FR) ratios. At R:FR = 5.8 and photon flux densities of 170 mumol.m-2.s-1, 200 mumol.m-2.s-1, and 230 mumol.m-2.s-1, DNA content remained high and relatively constant (x = 6.97 pg for RHA 271 and x = 7.32 pg for RHA 299). When the photon flux density range (R:FR = 5.8) was elevated to 350 mumol.m-2.s-1, 410 mumol.m-2.s-1, and 470 mumol.m-2.s-1, mean DNA content was reduced to 6.23 pg (RHA 271) and 6.46 pg (RHA 299). At R:FR = 1.5, mean DNA content was consistently high (7.2-7.9 pg) only at the lowest photon flux density of 170 mumol.m-2.s-1. Significant decreases in DNA content (densities of 200 mumol.m-2.s-1 and 230 mumol.m-2.s-1. At the higher photon flux densities (350 mumol.m-2.s-1, 410 mumol.m-2.s-1, and 470 mumol.m-2.s-1) and R:RF = 1.5, the plants had extremely low DNA contents (mean x = 3.36 pg for RHA 271 and 3.41 pg for RHA 299) and high between-plant variance. The instability of DNA content, particularly for plants grown under light that is far red rich, suggests that phytochromes may be involved in regulating DNA content of the sunflower.

  5. Drought and salt stress tolerance of an Arabidopsis glutathione S-transferase U17 knockout mutant are attributed to the combined effect of glutathione and abscisic acid.

    Science.gov (United States)

    Chen, Jui-Hung; Jiang, Han-Wei; Hsieh, En-Jung; Chen, Hsing-Yu; Chien, Ching-Te; Hsieh, Hsu-Liang; Lin, Tsan-Piao

    2012-01-01

    Although glutathione S-transferases (GSTs) are thought to play major roles in oxidative stress metabolism, little is known about the regulatory functions of GSTs. We have reported that Arabidopsis (Arabidopsis thaliana) GLUTATHIONE S-TRANSFERASE U17 (AtGSTU17; At1g10370) participates in light signaling and might modulate various aspects of development by affecting glutathione (GSH) pools via a coordinated regulation with phytochrome A. Here, we provide further evidence to support a negative role of AtGSTU17 in drought and salt stress tolerance. When AtGSTU17 was mutated, plants were more tolerant to drought and salt stresses compared with wild-type plants. In addition, atgstu17 accumulated higher levels of GSH and abscisic acid (ABA) and exhibited hyposensitivity to ABA during seed germination, smaller stomatal apertures, a lower transpiration rate, better development of primary and lateral root systems, and longer vegetative growth. To explore how atgstu17 accumulated higher ABA content, we grew wild-type plants in the solution containing GSH and found that they accumulated ABA to a higher extent than plants grown in the absence of GSH, and they also exhibited the atgstu17 phenotypes. Wild-type plants treated with GSH also demonstrated more tolerance to drought and salt stresses. Furthermore, the effect of GSH on root patterning and drought tolerance was confirmed by growing the atgstu17 in solution containing l-buthionine-(S,R)-sulfoximine, a specific inhibitor of GSH biosynthesis. In conclusion, the atgstu17 phenotype can be explained by the combined effect of GSH and ABA. We propose a role of AtGSTU17 in adaptive responses to drought and salt stresses by functioning as a negative component of stress-mediated signal transduction pathways.

  6. Gibberellins negatively regulate light-induced nitrate reductase activity in Arabidopsis seedlings.

    Science.gov (United States)

    Zhang, Yongqiang; Liu, Zhongjuan; Liu, Rongzhi; Wang, Liguang; Bi, Yurong

    2011-12-15

    In the present study, the role of phytohormone gibberellins (GAs) on regulating the nitrate reductase (NR) activity was tested in Arabidopsis seedlings. The NR activity in light-grown Col-0 seedlings was reduced by exogenous GA₃ (an active form of GAs), but enhanced by exogenous paclobutrazol (PAC, a gibberellin biosynthesis inhibitor), suggesting that GAs negatively regulate the NR activity in light-grown seedlings. Light is known to influence the NR activity through both photosynthesis and phytochromes. When etiolated seedlings were transferred to white or red light, both exogenously applied GA₃ and PAC were found to function on the NR activity only in the presence of sucrose, implying that GAs are not involved in light signaling-induced but negatively regulate photoproducts-induced NR activity. NR is regulated by light mainly at two levels: transcript level and post-translational level. Our reverse transcription (RT)-PCR assays showed that GAs did not affect the transcript levels of NIA1 and NIA2, two genes that encode NR proteins. But the divalent cations (especially Mg²⁺) were required for GAs negative regulation of NR activity, in view of the importance of divalent cations during the process of post-translational regulation of NR activity, which indicates that GAs very likely regulate the NR activity at the post-translational level. In the following dark-light shift analyses, GAs were found to accelerate dark-induced decrease, but retard light-induced increase of the NR activity. Furthermore, it was observed that application of G₃ or PAC could impair diurnal variation of the NR activity. These results collectively indicate that GAs play a negative role during light regulation of NR activity in nature.

  7. The blue-light receptor CmWC-1 mediates fruit body development and secondary metabolism in Cordyceps militaris.

    Science.gov (United States)

    Yang, Tao; Guo, Mingmin; Yang, Huaijun; Guo, Suping; Dong, Caihong

    2016-01-01

    Light is an essential factor for pigment formation and fruit body development in Cordyceps militaris, a well-known edible and medicinal fungus. Cmwc-1, a homolog of the blue-light receptor gene white collar-1 (wc-1) in Neurospora crassa, was cloned from the C. militaris genome in our previous study. Here, Cmwc-1 gene inactivation results in thicker aerial hyphae, disordered fruit body development, a significant reduction in conidial formation, and carotenoid and cordycepin production. These characteristics were restored when the ΔCmwc-1 strains were hybridized with wild-type strains of the opposite mating type. A genome-wide expression analysis revealed that there were 1042 light-responsive genes in the wild-type strain and only 458 in the ΔCmwc-1 strain. Among five putative photoreceptors identified, Vivid, cryptochrome-1, and cyclobutane pyrimidine dimer photolyase are strongly induced by light in a Cmwc-1-dependent manner, while phytochrome and cryptochrome-2 were not induced. The transcription factors involved in the fungal light reaction were mainly of the Zn2Cys6 type. CmWC-1 regulates adenylosuccinate synthase, an important enzyme for adenosine de novo synthesis, which could explain the reduction in cordycepin production. Some G protein-coupled receptors that control fungal fruit body formation and the sexual cycle were regulated by CmWC-1, and the cAMP pathway involved in light signal transduction in N. crassa was not critical for the photoreaction in the fungus here. A transcriptional analysis indicated that steroid biosynthesis was more active in the ΔCmwc-1 strain, suggesting that CmWC-1 might switch the vegetative growth state to primordia differentiation by suppressing the expression of related genes.

  8. The Clock Protein CCA1 and the bZIP Transcription Factor HY5 Physically Interact to Regulate Gene Expression in Arabidopsis

    Institute of Scientific and Technical Information of China (English)

    Christos Andronis; Simon Barak; Stephen M.Knowles; Shoji Sugano; Elaine M.Tobin

    2008-01-01

    The circadian clock regulates the expression of an array of Arabidopsis genes such as those encoding the LIGHT-HARVESTING CHLOROPHYLL A/B (Lhcb) proteins. We have previously studied the promoters of two of these Arabidopsis genes-Lhcb1*1 and Lhcb1*3-and identified a sequence that binds the clock protein CIRCADIAN CLOCK ASSOCIATED 1 (CCA1). This sequence, designated CCAl-binding site (CBS), is necessary for phytochrome and circadian responsiveness of these genes. In close proximity to this sequence, there exists a G-box core element that has been shown to bind the bZIP transcription factor HY5 in other light-regulated plant promoters. In the present study, we examined the importance of the interaction of transcription factors binding the CBS and the G-box core element in the control of normal circadian rhythmic expression of Lhcb genes. Our results show that HY5 is able to specifically bind the G-box element in the Lhcb promoters and that CCA1 can alter the binding activity of HY5. We further show that CCA1 and HY5 can physically interact and that they can act synergistically on transcription in a yeast reporter gene assay. An absence of HY5 leads to a shorter period of Lhcb1*1 circadian expression but does not affect the circadian expression of CATALASE3 (CAT3), whose promoter lacks a G-box element. Our results suggest that interaction of the HY5 and CCA1 proteins on Lhcb promoters is necessary for normal circadian expression of the Lhcb genes.

  9. Diurnal and circadian rhythms in the tomato transcriptome and their modulation by cryptochrome photoreceptors.

    Directory of Open Access Journals (Sweden)

    Paolo Facella

    Full Text Available BACKGROUND: Circadian clocks are internal molecular time-keeping mechanisms that provide living organisms with the ability to adjust their growth and physiology and to anticipate diurnal environmental changes. Circadian clocks, without exception, respond to light and, in plants, light is the most potent and best characterized entraining stimulus. The capacity of plants to respond to light is achieved through a number of photo-perceptive proteins including cryptochromes and phytochromes. There is considerable experimental evidence demonstrating the roles of photoreceptors in providing light input to the clock. METHODOLOGY: In order to identify genes regulated by diurnal and circadian rhythms, and to establish possible functional relations between photoreceptors and the circadian clock in tomato, we monitored the temporal transcription pattern in plants entrained to long-day conditions, either by large scale comparative profiling, or using a focused approach over a number of photosensory and clock-related genes by QRT-PCR. In parallel, focused transcription analyses were performed in cry1a- and in CRY2-OX tomato genotypes. CONCLUSIONS: We report a large series of transcript oscillations that shed light on the complex network of interactions among tomato photoreceptors and clock-related genes. Alteration of cryptochrome gene expression induced major changes in the rhythmic oscillations of several other gene transcripts. In particular, over-expression of CRY2 had an impact not only on day/night fluctuations but also on rhythmicity under constant light conditions. Evidence was found for widespread diurnal oscillations of transcripts encoding specific enzyme classes (e.g. carotenoid biosynthesis enzymes as well as for post-transcriptional diurnal and circadian regulation of the CRY2 transcript.

  10. A multi-locus analysis of phylogenetic relationships within grass subfamily Pooideae (Poaceae) inferred from sequences of nuclear single copy gene regions compared with plastid DNA.

    Science.gov (United States)

    Hochbach, Anne; Schneider, Julia; Röser, Martin

    2015-06-01

    To investigate phylogenetic relationships within the grass subfamily Pooideae we studied about 50 taxa covering all recognized tribes, using one plastid DNA (cpDNA) marker (matK gene-3'trnK exon) and for the first time four nuclear single copy gene loci. DNA sequence information from two parts of the nuclear genes topoisomerase 6 (Topo6) spanning the exons 8-13 and 17-19, the exons 9-13 encoding plastid acetyl-CoA-carboxylase (Acc1) and the partial exon 1 of phytochrome B (PhyB) were generated. Individual and nuclear combined data were evaluated using maximum parsimony, maximum likelihood and Bayesian methods. All of the phylogenetic results show Brachyelytrum and the tribe Nardeae as earliest diverging lineages within the subfamily. The 'core' Pooideae (Hordeeae and the Aveneae/Poeae tribe complex) are also strongly supported, as well as the monophyly of the tribes Brachypodieae, Meliceae and Stipeae (except PhyB). The beak grass tribe Diarrheneae and the tribe Duthieeae are not monophyletic in some of the analyses. However, the combined nuclear DNA (nDNA) tree yields the highest resolution and the best delimitation of the tribes, and provides the following evolutionary hypothesis for the tribes: Brachyelytrum, Nardeae, Duthieeae, Meliceae, Stipeae, Diarrheneae, Brachypodieae and the 'core' Pooideae. Within the individual datasets, the phylogenetic trees obtained from Topo6 exon 8-13 shows the most interesting results. The divergent positions of some clone sequences of Ampelodesmos mauritanicus and Trikeraia pappiformis, for instance, may indicate a hybrid origin of these stipoid taxa. Copyright © 2015 Elsevier Inc. All rights reserved.

  11. A molecular framework for seasonal growth-dormancy regulation in perennial plants.

    Science.gov (United States)

    Shim, Donghwan; Ko, Jae-Heung; Kim, Won-Chan; Wang, Qijun; Keathley, Daniel E; Han, Kyung-Hwan

    2014-01-01

    The timing of the onset and release of dormancy impacts the survival, productivity and spatial distribution of temperate horticultural and forestry perennials and is mediated by at least three main regulatory programs involving signal perception and processing by phytochromes (PHYs) and PHY-interacting transcription factors (PIFs). PIF4 functions as a key regulator of plant growth in response to both external and internal signals. In poplar, the expression of PIF4 and PIF3-LIKE1 is upregulated in response to short days, while PHYA and PHYB are not regulated at the transcriptional level. Integration of light and environmental signals is achieved by gating the expression and transcriptional activity of PIF4. During this annual cycle, auxin promotes the degradation of Aux/IAA transcriptional repressors through the SKP-Cullin-F-boxTIR1 complex, relieving the repression of auxin-responsive genes by allowing auxin response factors (ARFs) to activate the transcription of auxin-responsive genes involved in growth responses. Analyses of transcriptome changes during dormancy transitions have identified MADS-box transcription factors associated with endodormancy induction. Previous studies show that poplar dormancy-associated MADS-box (DAM) genes PtMADS7 and PtMADS21 are differentially regulated during the growth-dormancy cycle. Endodormancy may be regulated by internal factors, which are specifically localized in buds. PtMADS7/PtMADS21 may function as an internal regulator in poplar. The control of flowering time shares certain regulatory hierarchies with control of the dormancy/growth cycle. However, the particularities of different stages of the dormancy/growth cycle warrant comprehensive approaches to identify the causative genes for the entire cycle. A growing body of knowledge also indicates epigenetic regulation plays a role in these processes in perennial horticultural and forestry plants. The increased knowledge contributes to better understanding of the dormancy

  12. The Physarum polycephalum Genome Reveals Extensive Use of Prokaryotic Two-Component and Metazoan-Type Tyrosine Kinase Signaling.

    Science.gov (United States)

    Schaap, Pauline; Barrantes, Israel; Minx, Pat; Sasaki, Narie; Anderson, Roger W; Bénard, Marianne; Biggar, Kyle K; Buchler, Nicolas E; Bundschuh, Ralf; Chen, Xiao; Fronick, Catrina; Fulton, Lucinda; Golderer, Georg; Jahn, Niels; Knoop, Volker; Landweber, Laura F; Maric, Chrystelle; Miller, Dennis; Noegel, Angelika A; Peace, Rob; Pierron, Gérard; Sasaki, Taeko; Schallenberg-Rüdinger, Mareike; Schleicher, Michael; Singh, Reema; Spaller, Thomas; Storey, Kenneth B; Suzuki, Takamasa; Tomlinson, Chad; Tyson, John J; Warren, Wesley C; Werner, Ernst R; Werner-Felmayer, Gabriele; Wilson, Richard K; Winckler, Thomas; Gott, Jonatha M; Glöckner, Gernot; Marwan, Wolfgang

    2015-11-27

    Physarum polycephalum is a well-studied microbial eukaryote with unique experimental attributes relative to other experimental model organisms. It has a sophisticated life cycle with several distinct stages including amoebal, flagellated, and plasmodial cells. It is unusual in switching between open and closed mitosis according to specific life-cycle stages. Here we present the analysis of the genome of this enigmatic and important model organism and compare it with closely related species. The genome is littered with simple and complex repeats and the coding regions are frequently interrupted by introns with a mean size of 100 bases. Complemented with extensive transcriptome data, we define approximately 31,000 gene loci, providing unexpected insights into early eukaryote evolution. We describe extensive use of histidine kinase-based two-component systems and tyrosine kinase signaling, the presence of bacterial and plant type photoreceptors (phytochromes, cryptochrome, and phototropin) and of plant-type pentatricopeptide repeat proteins, as well as metabolic pathways, and a cell cycle control system typically found in more complex eukaryotes. Our analysis characterizes P. polycephalum as a prototypical eukaryote with features attributed to the last common ancestor of Amorphea, that is, the Amoebozoa and Opisthokonts. Specifically, the presence of tyrosine kinases in Acanthamoeba and Physarum as representatives of two distantly related subdivisions of Amoebozoa argues against the later emergence of tyrosine kinase signaling in the opisthokont lineage and also against the acquisition by horizontal gene transfer. © The Author(s) 2015. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

  13. Light controls growth and development via a conserved pathway in the fungal kingdom.

    Directory of Open Access Journals (Sweden)

    Alexander Idnurm

    2005-04-01

    Full Text Available Light inhibits mating and haploid fruiting of the human fungal pathogen Cryptococcus neoformans, but the mechanisms involved were unknown. Two genes controlling light responses were discovered through candidate gene and insertional mutagenesis approaches. Deletion of candidate genes encoding a predicted opsin or phytochrome had no effect on mating, while strains mutated in the white collar 1 homolog gene BWC1 mated equally well in the light or the dark. The predicted Bwc1 protein shares identity with Neurospora crassa WC-1, but lacks the zinc finger DNA binding domain. BWC1 regulates cell fusion and repression of hyphal development after fusion in response to blue light. In addition, bwc1 mutant strains are hypersensitive to ultraviolet light. To identify other components required for responses to light, a novel self-fertile haploid strain was created and subjected to Agrobacterium-mediated insertional mutagenesis. One UV-sensitive mutant that filaments equally well in the light and the dark was identified and found to have an insertion in the BWC2 gene, whose product is structurally similar to N. crassa WC-2. The C. neoformans Bwc1 and Bwc2 proteins interact in the yeast two-hybrid assay. Deletion of BWC1 or BWC2 reduces the virulence of C. neoformans in a murine model of infection; the Bwc1-Bwc2 system thus represents a novel protein complex that influences both development and virulence in a pathogenic fungus. These results demonstrate that a role for blue/UV light in controlling development is an ancient process that predates the divergence of the fungi into the ascomycete and basidiomycete phyla.

  14. Light Controls Growth and Development via a Conserved Pathway in the Fungal Kingdom

    Directory of Open Access Journals (Sweden)

    Idnurm Alexander

    2005-01-01

    Full Text Available Light inhibits mating and haploid fruiting of the human fungal pathogen Cryptococcus neoformans, but the mechanisms involved were unknown. Two genes controlling light responses were discovered through candidate gene and insertional mutagenesis approaches. Deletion of candidate genes encoding a predicted opsin or phytochrome had no effect on mating, while strains mutated in the white collar 1 homolog gene BWC1 mated equally well in the light or the dark. The predicted Bwc1 protein shares identity with Neurospora crassa WC-1, but lacks the zinc finger DNA binding domain. BWC1 regulates cell fusion and repression of hyphal development after fusion in response to blue light. In addition, bwc1 mutant strains are hypersensitive to ultraviolet light. To identify other components required for responses to light, a novel self-fertile haploid strain was created and subjected to Agrobacterium-mediated insertional mutagenesis. One UV-sensitive mutant that filaments equally well in the light and the dark was identified and found to have an insertion in the BWC2 gene, whose product is structurally similar to N. crassa WC-2. The C. neoformans Bwc1 and Bwc2 proteins interact in the yeast two-hybrid assay. Deletion of BWC1 or BWC2 reduces the virulence of C. neoformans in a murine model of infection; the Bwc1-Bwc2 system thus represents a novel protein complex that influences both development and virulence in a pathogenic fungus. These results demonstrate that a role for blue/UV light in controlling development is an ancient process that predates the divergence of the fungi into the ascomycete and basidiomycete phyla.

  15. Effect of end-of-day irradiations on polyamine accumulation in petal cultures of Araujia sericifera.

    Science.gov (United States)

    Moysset, Luisa; Trull, Olga; Santos, M. Asunción; Simón, Esther; Torné, Josep M

    2002-01-01

    We have studied photoperiodic control and the effect of phytochrome photoconversion at the end-of-day (EOD) on polyamine (PA) accumulation in petal explants of Araujia sericifera. Petals from immature flowers were cultured under long (LD) and short (SD) days. Light was provided by Gro-lux fluorescent lamps (90-100 &mgr;mol m-2 s-1). Red (R), far red (FR), red followed by far-red (R-FR) and far-red followed by red (FR-R) light treatments were applied daily at the end of the photoperiod. The free and bound putrescine (Put), spermidine (Spd) and spermine (Spm) fractions in petal explants were determined 40 days after the beginning of the culture. We also aimed to clarify the involvement of PA changes by using two inhibitors of PA biosynthesis: D-l-alpha-difluoromethylarginine (DFMA) and methylglyoxal bis(guanylhydrazone) (MGBG). We found PA accumulation to be under photoperiodic control, and the inhibitory effect of DFMA on this accumulation suggests that arginine decarboxylase (ADC) is the major pathway for Put biosynthesis. Polyamine levels were higher under LD, mainly as a result of the accumulation of free and bound Put. FR-EOD treatment, which dramatically reduced the R : FR ratio after LD, increased the accumulation of PA, mainly as free Put and free and bound Spd. Sequential R-FR and FR-R-EOD treatments strongly increased bound Spd. The concentration of MGBG used increased total PA accumulation, mainly as Put. However, all EOD light treatments dramatically reduced Put accumulation in the presence of MGBG. This may be due to a dual role of FR light in PA accumulation: (1) FR per se stimulates PA production, probably via ADC, and (2) in the presence of MGBG, FR inhibits Put accumulation, probably via ethylene production.

  16. Photocontrol of the Accumulation of Plastid Polypeptides during Greening of Tomato Cotyledons : Potentiation by a Pulse of Red Light.

    Science.gov (United States)

    Pauncz, Y; Gepstein, S; Horwitz, B A

    1992-12-01

    A pulse of red light acting through phytochrome accelerates the formation of chlorophyll upon subsequent transfer of dark-grown seedlings to continuous white light. Specific antibodies were used to follow the accumulation of representative subunits of the major photosynthetic complexes during greening of seedlings of tomato (Lycopersicon esculentum). The time course for accumulation of the various subunits was compared in seedlings that received a red light pulse 4 h prior to transfer to continuous white light and parallel controls that did not receive a red light pulse. The light-harvesting chlorophyll-binding proteins of photosystem II (LHC II), the 33-kD extrinsic polypeptide of the oxygen-evolving complex (OEC1), and subunit II of photosystem I (psaD gene product) all increased in the light, and did so much faster in seedlings that received the inductive red light pulse. The red light pulse had no significant effect on the abundance of the small subunit of ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco), nor on several plastid-encoded polypeptides: the large subunit of Rubisco, the beta subunit of the CF(1) complex of plastid ATPase, and the 43- and 47-kD subunits of photosystem II (CP43, CP47). Subunits I (cytochrome b(6)f) and III (Rieske Fe-S protein) of the cytochrome b(6)f complex showed a small or no increase as a result of the red pulse. The potentiation of greening by a pulse of red light, therefore, is not expressed uniformly in the abundance of all the photosynthetic complexes and their subunits.

  17. Low-fluence red light increases the transport and biosynthesis of auxin.

    Science.gov (United States)

    Liu, Xing; Cohen, Jerry D; Gardner, Gary

    2011-10-01

    In plants, light is an important environmental signal that induces photomorphogenesis and interacts with endogenous signals, including hormones. We found that light increased polar auxin transport in dark-grown Arabidopsis (Arabidopsis thaliana) and tomato (Solanum lycopersicum) hypocotyls. In tomato, this increase was induced by low-fluence red or blue light followed by 1 d of darkness. It was reduced in phyA, phyB1, and phyB2 tomato mutants and was reversed by far-red light applied immediately after the red or blue light exposure, suggesting that phytochrome is involved in this response. We further found that the free indole-3-acetic acid (IAA) level in hypocotyl regions below the hook was increased by red light, while the level of conjugated IAA was unchanged. Analysis of IAA synthesized from [¹³C]indole or [¹³C]tryptophan (Trp) revealed that both Trp-dependent and Trp-independent IAA biosynthesis were increased by low-fluence red light in the top section (meristem, cotyledons, and hook), and the Trp-independent pathway appears to become the primary route for IAA biosynthesis after red light exposure. IAA biosynthesis in tissues below the top section was not affected by red light, suggesting that the increase of free IAA in this region was due to increased transport of IAA from above. Our study provides a comprehensive view of light effects on the transport and biosynthesis of IAA, showing that red light increases both IAA biosynthesis in the top section and polar auxin transport in hypocotyls, leading to unchanged free IAA levels in the top section and increased free IAA levels in the lower hypocotyl regions.

  18. Physics and the molecular revolution in plant biology: union needed for managing the future

    Directory of Open Access Journals (Sweden)

    Ulrich Lüttge

    2016-10-01

    Full Text Available The question was asked if there is still a prominent role of biophysics in plant biology in an age when molecular biology appears to be dominating. Mathematical formation of theory is essential in systems biology, and mathematics is more inherent in biophysics than in molecular biology. A survey is made identifying and briefly characterizing fields of plant biology where approaches of biophysics remain essential. In transport at membranes electrophysiology and thermodynamics are biophysical topics. Water is a special molecule. Its transport follows the physical laws of osmosis and gradients of water potential on the background of physics of hydraulic architecture. Photobiology needs understanding of the physics of electro-magnetic radiation of quantitative nature in photosynthesis and of qualitative nature in perception by the photo-sensors cryptochromes, phototropins and phytochrome in environmental responses and development. Biophysical oscillators can play a role in biological timing by the circadian clock. Integration in the self-organization of modules, such as roots, stems and leaves, for the emergence of whole plants as unitary organisms needs storage and transport of information where physical modes of signaling are essential with cross talks between electrical and hydraulic signals and with chemical signals. Examples are gravitropism and root-shoot interactions in water relations. All of these facets of plant biophysics overlie plant molecular biology and exchange with it. It is advocated that a union of approaches of plant molecular biology and biophysics needs to be cultivated. In many cases it is already operative. In bionics biophysics is producing output for practical applications linking biology with technology. Biomimetic engineering intrinsically uses physical approaches. An extreme biophysical perspective is looking out for life in space. Sustained and increased practice of biophysics with teaching and research deserves strong

  19. Light Regulation of Swarming Motility in Pseudomonas syringae Integrates Signaling Pathways Mediated by a Bacteriophytochrome and a LOV Protein

    Science.gov (United States)

    Wu, Liang; McGrane, Regina S.; Beattie, Gwyn A.

    2013-01-01

    ABSTRACT The biological and regulatory roles of photosensory proteins are poorly understood for nonphotosynthetic bacteria. The foliar bacterial pathogen Pseudomonas syringae has three photosensory protein-encoding genes that are predicted to encode the blue-light-sensing LOV (light, oxygen, or voltage) histidine kinase (LOV-HK) and two red/far-red-light-sensing bacteriophytochromes, BphP1 and BphP2. We provide evidence that LOV-HK and BphP1 form an integrated network that regulates swarming motility in response to multiple light wavelengths. The swarming motility of P. syringae B728a deletion mutants indicated that LOV-HK positively regulates swarming motility in response to blue light and BphP1 negatively regulates swarming motility in response to red and far-red light. BphP2 does not detectably regulate swarming motility. The histidine kinase activity of each LOV-HK and BphP1 is required for this regulation based on the loss of complementation upon mutation of residues key to their kinase activity. Surprisingly, mutants lacking both lov and bphP1 were similar in motility to a bphP1 single mutant in blue light, indicating that the loss of bphP1 is epistatic to the loss of lov and also that BphP1 unexpectedly responds to blue light. Moreover, whereas expression of bphP1 did not alter motility under blue light in a bphP1 mutant, it reduced motility in a mutant lacking lov and bphP1, demonstrating that LOV-HK positively regulates motility by suppressing negative regulation by BphP1. These results are the first to show cross talk between the LOV protein and phytochrome signaling pathways in bacteria, and the similarity of this regulatory network to that of photoreceptors in plants suggests a possible common ancestry. PMID:23760465

  20. Chemical-Induced Inhibition of Blue Light-Mediated Seedling Development Caused by Disruption of Upstream Signal Transduction Involving Cryptochromes in Arabidopsis thaliana.

    Science.gov (United States)

    Ong, Wen-Dee; Okubo-Kurihara, Emiko; Kurihara, Yukio; Shimada, Setsuko; Makita, Yuko; Kawashima, Mika; Honda, Kaori; Kondoh, Yasumitsu; Watanabe, Nobumoto; Osada, Hiroyuki; Cutler, Sean R; Sudesh, Kumar; Matsui, Minami

    2017-01-01

    Plants have a remarkable ability to perceive and respond to various wavelengths of light and initiate regulation of different cascades of light signaling and molecular components. While the perception of red light and the mechanisms of its signaling involving phytochromes are largely known, knowledge of the mechanisms of blue light signaling is still limited. Chemical genetics involves the use of diverse small active or synthetic molecules to evaluate biological processes. By combining chemicals and analyzing the effects they have on plant morphology, we identified a chemical, 3-bromo-7-nitroindazole (3B7N), that promotes hypocotyl elongation of wild-type Arabidopsis only under continuous blue light. Further evaluation with loss-of-function mutants confirmed that 3B7N inhibits photomorphogenesis through cryptochrome-mediated light signaling. Microarray analysis demonstrated that the effect of 3B7N treatment on gene expression in cry1cry2 is considerably smaller than that in the wild type, indicating that 3B7N specifically interrupts cryptochrome function in the control of seedling development in a light-dependent manner. We demonstrated that 3B7N directly binds to CRY1 protein using an in vitro binding assay. These results suggest that 3B7N is a novel chemical that directly inhibits plant cryptochrome function by physical binding. The application of 3B7N can be used on other plants to study further the blue light mechanism and the genetic control of cryptochromes in the growth and development of plant species. © The Author 2016. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oup.com.

  1. Identification of an arsenic tolerant double mutant with a thiol-mediated component and increased arsenic tolerance in phyA mutants.

    Science.gov (United States)

    Sung, Dong-Yul; Lee, David; Harris, Hugh; Raab, Andrea; Feldmann, Jörg; Meharg, Andrew; Kumabe, Bryan; Komives, Elizabeth A; Schroeder, Julian I

    2007-03-01

    A genetic screen was performed to isolate mutants showing increased arsenic tolerance using an Arabidopsis thaliana population of activation tagged lines. The most arsenic-resistant mutant shows increased arsenate and arsenite tolerance. Genetic analyses of the mutant indicate that the mutant contains two loci that contribute to arsenic tolerance, designated ars4 and ars5. The ars4ars5 double mutant contains a single T-DNA insertion, ars4, which co-segregates with arsenic tolerance and is inserted in the Phytochrome A (PHYA) gene, strongly reducing the expression of PHYA. When grown under far-red light conditions ars4ars5 shows the same elongated hypocotyl phenotype as the previously described strong phyA-211 allele. Three independent phyA alleles, ars4, phyA-211 and a new T-DNA insertion allele (phyA-t) show increased tolerance to arsenate, although to a lesser degree than the ars4ars5 double mutant. Analyses of the ars5 single mutant show that ars5 exhibits stronger arsenic tolerance than ars4, and that ars5 is not linked to ars4. Arsenic tolerance assays with phyB-9 and phot1/phot2 mutants show that these photoreceptor mutants do not exhibit phyA-like arsenic tolerance. Fluorescence HPLC analyses show that elevated levels of phytochelatins were not detected in ars4, ars5 or ars4ars5, however increases in the thiols cysteine, gamma-glutamylcysteine and glutathione were observed. Compared with wild type, the total thiol levels in ars4, ars5 and ars4ars5 mutants were increased up to 80% with combined buthionine sulfoximine and arsenic treatments, suggesting the enhancement of mechanisms that mediate thiol synthesis in the mutants. The presented findings show that PHYA negatively regulates a pathway conferring arsenic tolerance, and that an enhanced thiol synthesis mechanism contributes to the arsenic tolerance of ars4ars5.

  2. Sugar and auxin signaling pathways respond to high-temperature stress during anther development as revealed by transcript profiling analysis in cotton.

    Science.gov (United States)

    Min, Ling; Li, Yaoyao; Hu, Qin; Zhu, Longfu; Gao, Wenhui; Wu, Yuanlong; Ding, Yuanhao; Liu, Shiming; Yang, Xiyan; Zhang, Xianlong

    2014-03-01

    Male reproduction in flowering plants is highly sensitive to high temperature (HT). To investigate molecular mechanisms of the response of cotton (Gossypium hirsutum) anthers to HT, a relatively complete comparative transcriptome analysis was performed during anther development of cotton lines 84021 and H05 under normal temperature and HT conditions. In total, 4,599 differentially expressed genes were screened; the differentially expressed genes were mainly related to epigenetic modifications, carbohydrate metabolism, and plant hormone signaling. Detailed studies showed that the deficiency in S-adenosyl-L-homocysteine hydrolase1 and the inhibition of methyltransferases contributed to genome-wide hypomethylation in H05, and the increased expression of histone constitution genes contributed to DNA stability in 84021. Furthermore, HT induced the expression of casein kinasei (GhCKI) in H05, coupled with the suppression of starch synthase activity, decreases in glucose level during anther development, and increases in indole-3-acetic acid (IAA) level in late-stage anthers. The same changes also were observed in Arabidopsis (Arabidopsis thaliana) GhCKI overexpression lines. These results suggest that GhCKI, sugar, and auxin may be key regulators of the anther response to HT stress. Moreover, phytochrome-interacting factor genes (PIFs), which are involved in linking sugar and auxin and are regulated by sugar, might positively regulate IAA biosynthesis in the cotton anther response to HT. Additionally, exogenous IAA application revealed that high background IAA may be a disadvantage for late-stage cotton anthers during HT stress. Overall, the linking of HT, sugar, PIFs, and IAA, together with our previously reported data on GhCKI, may provide dynamic coordination of plant anther responses to HT stress.

  3. Light-regulated plant growth and development.

    Science.gov (United States)

    Kami, Chitose; Lorrain, Séverine; Hornitschek, Patricia; Fankhauser, Christian

    2010-01-01

    Plants are sessile and photo-autotrophic; their entire life cycle is thus strongly influenced by the ever-changing light environment. In order to sense and respond to those fluctuating conditions higher plants possess several families of photoreceptors that can monitor light from UV-B to the near infrared (far-red). The molecular nature of UV-B sensors remains unknown, red (R) and far-red (FR) light is sensed by the phytochromes (phyA-phyE in Arabidopsis) while three classes of UV-A/blue photoreceptors have been identified: cryptochromes, phototropins, and members of the Zeitlupe family (cry1, cry2, phot1, phot2, ZTL, FKF1, and LKP2 in Arabidopsis). Functional specialization within photoreceptor families gave rise to members optimized for a wide range of light intensities. Genetic and photobiological studies performed in Arabidopsis have shown that these light sensors mediate numerous adaptive responses (e.g., phototropism and shade avoidance) and developmental transitions (e.g., germination and flowering). Some physiological responses are specifically triggered by a single photoreceptor but in many cases multiple light sensors ensure a coordinated response. Recent studies also provide examples of crosstalk between the responses of Arabidopsis to different external factors, in particular among light, temperature, and pathogens. Although the different photoreceptors are unrelated in structure, in many cases they trigger similar signaling mechanisms including light-regulated protein-protein interactions or light-regulated stability of several transcription factors. The breath and complexity of this topic forced us to concentrate on specific aspects of photomorphogenesis and we point the readers to recent reviews for some aspects of light-mediated signaling (e.g., transition to flowering).

  4. Emerging Perspectives on the Mechanisms,Regulation, and Distribution of Light Color Acclimation in Cyanobacteria

    Institute of Scientific and Technical Information of China (English)

    Andrian Gutu; David M. Kehoe

    2012-01-01

    Chromatic acclimation (CA) provides many cyanobacteria with the ability to tailor the properties of their lightharvesting antennae to the spectral distribution of ambient light.CA was originally discovered as a result of its dramatic cellular phenotype in red and green light.However,discoveries over the past decade have revealed that many pairs of light colors,ranging from blue to infrared,can trigger CA responses.The capacity to undergo CA is widespread geographically,occurs in most habitats around the world,and is found within all major cyanobacterial groups.In addition,many other cellular activities have been found to be under CA control,resulting in distinct physiological and morphological states for cells under different light-color conditions.Several types of CA appear to be the result of convergent evolution,where different strategies are used to achieve the final goal of optimizing light-harvesting antenna composition to maximize photon capture.The regulation of CA has been found to occur primarily at the level of RNA abundance.The CA-regulatory pathways uncovered thus far are two-component systems that use phytochrome-class photoreceptors with sensor-kinase domains to control response regulators that function as transcription factors.However,there is also at least one CAregulatory pathway that operates at the post-transcriptional level.It is becoming increasingly clear that large numbers of cyanobacterial species have the capacity to acclimate to a wide variety of light colors through the use of a range of different CA processes.

  5. Light-modulated abundance of an mRNA encoding a calmodulin-regulated, chromatin-associated NTPase in pea

    Science.gov (United States)

    Hsieh, H. L.; Tong, C. G.; Thomas, C.; Roux, S. J.

    1996-01-01

    A CDNA encoding a 47 kDa nucleoside triphosphatase (NTPase) that is associated with the chromatin of pea nuclei has been cloned and sequenced. The translated sequence of the cDNA includes several domains predicted by known biochemical properties of the enzyme, including five motifs characteristic of the ATP-binding domain of many proteins, several potential casein kinase II phosphorylation sites, a helix-turn-helix region characteristic of DNA-binding proteins, and a potential calmodulin-binding domain. The deduced primary structure also includes an N-terminal sequence that is a predicted signal peptide and an internal sequence that could serve as a bipartite-type nuclear localization signal. Both in situ immunocytochemistry of pea plumules and immunoblots of purified cell fractions indicate that most of the immunodetectable NTPase is within the nucleus, a compartment proteins typically reach through nuclear pores rather than through the endoplasmic reticulum pathway. The translated sequence has some similarity to that of human lamin C, but not high enough to account for the earlier observation that IgG against human lamin C binds to the NTPase in immunoblots. Northern blot analysis shows that the NTPase MRNA is strongly expressed in etiolated plumules, but only poorly or not at all in the leaf and stem tissues of light-grown plants. Accumulation of NTPase mRNA in etiolated seedlings is stimulated by brief treatments with both red and far-red light, as is characteristic of very low-fluence phytochrome responses. Southern blotting with pea genomic DNA indicates the NTPase is likely to be encoded by a single gene.

  6. Physiological asymmetry in etiolated pea epicotyls: relation to patterns of auxin distribution and phototropic behavior

    Science.gov (United States)

    Kuhn, H.; Galston, A. W.

    1992-01-01

    Etiolated pea seedlings require transformation of Pr phytochrome to Pfr before they display optimal phototropic response to unilateral blue light. This study investigates the possible role of auxin transport in explaining these phenomena. Labeled [2-14C]IAA applied to the intact terminal buds of dark-grown and red light-treated pea seedlings was measured 210 min later on the shaded and illuminated sides of the epicotyl as a function of direction and duration of irradiation with blue light. Totally darkened epicotyls show an asymmetry in distribution of radioactivity in the upper growth zone of the epicotyl, in favor of the side under the concave part of the apical hook. Red light, which greatly potentiates curvature toward subsequent unilateral blue light, lowers this asymmetry. Blue light directed to the epicotyl of red-pretreated plants in a plane parallel to the hook and from the side bearing the convex portion of the hook induces positive phototropic curvature as well as a surplus of radioactivity on the illuminated side of the upper epicotyl and on the shaded side of the lower growth zone of the epicotyl. Light directed to the side bearing the concave part of the hook also causes an accumulation of counts in the upper part of the lighted side but produces neither curvature of the epicotyl nor accumulation of counts in the lower shaded side. Because of this built-in physiological asymmetry in the growth zone just below the apical hook, it is difficult to explain the effects of red and blue light on curvature in terms of patterns of auxin distribution alone.

  7. Identification of An Arsenic Tolerant Double Mutant With a Thiol-Mediated Component And Increased Arsenic Tolerance in PhyA Mutants

    Energy Technology Data Exchange (ETDEWEB)

    Sung, D.Y.; Lee, D.; Harris, H.; Raab, A.; Feldmann, J.; Meharg, A.; Kumabe, B.; Komives, E.A.; Schroeder, J.I.; /SLAC, SSRL /Sydney U. /Aberdeen U. /UC, San Diego

    2007-04-06

    A genetic screen was performed to isolate mutants showing increased arsenic tolerance using an Arabidopsis thaliana population of activation tagged lines. The most arsenic-resistant mutant shows increased arsenate and arsenite tolerance. Genetic analyses of the mutant indicate that the mutant contains two loci that contribute to arsenic tolerance, designated ars4 and ars5. The ars4ars5 double mutant contains a single T-DNA insertion, ars4, which co-segregates with arsenic tolerance and is inserted in the Phytochrome A (PHYA) gene, strongly reducing the expression of PHYA. When grown under far-red light conditions ars4ars5 shows the same elongated hypocotyl phenotype as the previously described strong phyA-211 allele. Three independent phyA alleles, ars4, phyA-211 and a new T-DNA insertion allele (phyA-t) show increased tolerance to arsenate, although to a lesser degree than the ars4ars5 double mutant. Analyses of the ars5 single mutant show that ars5 exhibits stronger arsenic tolerance than ars4, and that ars5 is not linked to ars4. Arsenic tolerance assays with phyB-9 and phot1/phot2 mutants show that these photoreceptor mutants do not exhibit phyA-like arsenic tolerance. Fluorescence HPLC analyses show that elevated levels of phytochelatins were not detected in ars4, ars5 or ars4ars5, however increases in the thiols cysteine, gamma-glutamylcysteine and glutathione were observed. Compared with wild type, the total thiol levels in ars4, ars5 and ars4ars5 mutants were increased up to 80% with combined buthionine sulfoximine and arsenic treatments, suggesting the enhancement of mechanisms that mediate thiol synthesis in the mutants. The presented findings show that PHYA negatively regulates a pathway conferring arsenic tolerance, and that an enhanced thiol synthesis mechanism contributes to the arsenic tolerance of ars4ars5.

  8. Fruit-localized photoreceptors increase phenolic compounds in berry skins of field-grown Vitis vinifera L. cv. Malbec.

    Science.gov (United States)

    González, Carina Verónica; Fanzone, Martín Leandro; Cortés, Leandro Emanuel; Bottini, Rubén; Lijavetzky, Diego Claudio; Ballaré, Carlos Luis; Boccalandro, Hernán Esteban

    2015-02-01

    Sunlight exposure has multiple effect on fruits, as it affects the light climate perceived by fruit photoreceptors and fruit tissue temperature. In grapes (Vitis vinifera L.), light exposure can have a strong effect on fruit quality and commercial value; however, the mechanisms of light action are not well understood. The role of fruit-localized photoreceptors in the control of berry quality traits was evaluated under field conditions in a commercial vineyard in Mendoza (Argentina). Characterization of the diurnal dynamics of the fruit light environment in a vertical trellis system indicated that clusters were shaded by leaves during most of the photoperiod. Supplementation of the fruit light environment from 20 days before veraison until technological harvest showed that red (R, 660 nm) and blue (B, 470 nm) light strongly increased total phenolic compound levels at harvest in the berry skins without affecting sugar content, acidity or berry size. Far-red (FR, 730 nm) and green (G, 560 nm) light supplementation had relatively small effects. The stimulation of berry phytochromes and cryptochromes favored accumulation of flavonoid and non-flavonoid compounds, including anthocyanins, flavonols, flavanols, phenolic acids and stilbenes. These results demonstrate that the chemical composition of grape berries is modulated by the light quality received by the clusters under field conditions, and that fruit photoreceptors are not saturated even in areas of high insolation and under management systems that are considered to result in a relatively high exposure of fruits to solar radiation. Therefore, manipulation of the light environment or the light sensitivity of fruits could have significant effects on critical grape quality traits. Published by Elsevier Ltd.

  9. Primary photodynamics of the green/red-absorbing photoswitching regulator of the chromatic adaptation E domain from Fremyella diplosiphon.

    Science.gov (United States)

    Gottlieb, Sean M; Kim, Peter W; Rockwell, Nathan C; Hirose, Yuu; Ikeuchi, Masahiko; Lagarias, J Clark; Larsen, Delmar S

    2013-11-19

    Phytochromes are red/far-red photosensory proteins that utilize the photoisomerization of a linear tetrapyrrole (bilin) chromophore to detect the red to far-red light ratio. Cyanobacteriochromes (CBCRs) are distantly related cyanobacterial photosensors with homologous bilin-binding GAF domains, but they exhibit greater spectral diversity. Different CBCR subfamilies have been described, with spectral sensitivity varying across the near-ultraviolet and throughout the visible spectrum, but all known CBCRs utilize photoisomerization of the bilin 15,16-double bond as the primary photochemical event. The first CBCR discovered was RcaE, responsible for tuning light harvesting to the incident color environment (complementary chromatic adaptation) in Fremyella diplosiphon. The green/red RcaE photocycle has recently been described in detail. We now extend this analysis by examining femtosecond photodynamics using ultrafast transient absorption techniques with broadband detection and multicomponent global analysis. Excited-state dynamics in both directions are significantly slower than those recently published for the red/green CBCR NpR6012g4. In the forward reaction, the primary Lumi-G photoproduct arises from the longer-lived excited-state populations, leading to a low photoproduct quantum yield. Using dual-excitation wavelength interleaved pump-probe spectroscopy, we observe multiphasic excited-state dynamics in the forward reaction ((15Z)Pg → (15E)Pr), which we interpret as arising from ground-state inhomogeneity with different tautomers of the PCB chromophore. The reverse reaction ((15E)Pr → (15Z)Pg) is characterized via pump-probe spectroscopy and also exhibits slow excited-state decay dynamics and a low photoproduct yield. These results provide the first description of excited-state dynamics for a green/red CBCR.

  10. Deletion of the Synechocystis sp. PCC 6803 kaiAB1C1 gene cluster causes impaired cell growth under light-dark conditions.

    Science.gov (United States)

    Dörrich, Anja K; Mitschke, Jan; Siadat, Olga; Wilde, Annegret

    2014-11-01

    In contrast to Synechococcus elongatus PCC 7942, few data exist on the timing mechanism of the widely used cyanobacterium Synechocystis sp. PCC 6803. The standard kaiAB1C1 operon present in this organism was shown to encode a functional KaiC protein that interacted with KaiA, similar to the S. elongatus PCC 7942 clock. Inactivation of this operon in Synechocystis sp. PCC 6803 resulted in a mutant with a strong growth defect when grown under light-dark cycles, which was even more pronounced when glucose was added to the growth medium. In addition, mutants showed a bleaching phenotype. No effects were detected in mutant cells grown under constant light. Microarray experiments performed with cells grown for 1 day under a light-dark cycle revealed many differentially regulated genes with known functions in the ΔkaiABC mutant in comparison with the WT. We identified the genes encoding the cyanobacterial phytochrome Cph1 and the light-repressed protein LrtA as well as several hypothetical ORFs with a complete inverse behaviour in the light cycle. These transcripts showed a stronger accumulation in the light but a weaker accumulation in the dark in ΔkaiABC cells in comparison with the WT. In general, we found a considerable overlap with microarray data obtained for hik31 and sigE mutants. These genes are known to be important regulators of cell metabolism in the dark. Strikingly, deletion of the ΔkaiABC operon led to a much stronger phenotype under light-dark cycles in Synechocystis sp. PCC 6803 than in Synechococcus sp. PCC 7942. © 2014 The Authors.

  11. Photoperiodic and thermosensory pathways interact through CONSTANS to promote flowering at high temperature under short days.

    Science.gov (United States)

    Fernández, Virginia; Takahashi, Yasuyuki; Le Gourrierec, José; Coupland, George

    2016-06-01

    Plants detect changes in day length to induce seasonal patterns of flowering. The photoperiodic pathway accelerates the flowering of Arabidopsis thaliana under long days (LDs) whereas it is inactive under short days (SDs), resulting in delayed flowering. This delay is overcome by exposure of plants to high temperature (27°C) under SDs (27°C-SD). Previously, the high-temperature flowering response was proposed to involve either the impaired activity of MADS-box transcription factor (TF) floral repressors or PHYTOCHROME-INTERACTING FACTOR 4 (PIF4) TF-mediated activation of FLOWERING LOCUS T (FT), which encodes the output signal of the photoperiodic pathway. We integrate these observations by studying several PIFs, the MADS-box SHORT VEGETATIVE PHASE (SVP) and the photoperiodic pathway under 27°C-SD. We find that the mRNAs of FT and its paralogue TWIN SISTER OF FT (TSF) are increased at dusk under 27°C-SD compared with 21°C-SD, and that this requires PIF4 and PIF5 as well as CONSTANS (CO), a TF that promotes flowering under LDs. The CO and PIF4 proteins are present at dusk under 27°C-SD, and they physically interact. Although Col-0 plants flower at similar times under 27°C-SD and 21°C-LD the expression level of FT is approximately 10-fold higher under 21°C-LD, suggesting that responsiveness to FT is also increased under 27°C-SD, perhaps as a result of the reduced activity of SVP in the meristem. Accordingly, only svp-41 ft-10 tsf-1 plants flowered at the same time under 21°C-SD and 27°C-SD. Thus, we propose that under non-inductive SDs, elevated temperatures increase the activity and sensitize the response to the photoperiod pathway.

  12. PAPP2C Interacts with the Atypical Disease Resistance Protein RPW8.2 and Negatively Regulates Salicylic Acid-Dependent Defense Responses in Arabidopsis

    Institute of Scientific and Technical Information of China (English)

    Wen-Ming Wang; Xian-Feng Ma; Yi Zhang; Ming-Cheng Luo; Guo-Liang Wang; Maria Bellizzi; Xing-Yao Xiong; Shun-Yuan Xiao

    2012-01-01

    Many fungal and oomycete pathogens differentiate a feeding structure named the haustorium to extract nutrition from the plant epidermal cell.The atypical resistance (R) protein RPW8.2 activates salicylic acid (SA)-dependent,haustorium-targeted defenses against Golovinomyces spp.,the causal agents of powdery mildew diseases on multiple plant species.How RPW8.2 activates defense remains uncharacterized.Here,we report that RPW8.2 interacts with the phytochrome-associated protein phosphatase type 2C (PAPP2C) in yeast and in planta as evidenced by coimmunoprecipitation and bimolecular fluorescence complementation assays.Down-regulation of PAPP2C by RNA interference (RNAi) in Col-0 plants lacking RPW8.2 leads to leaf spontaneous cell death and enhanced disease resistance to powdery mildew via the SA-dependent signaling pathway.Moreover,down-regulation of PAPP2C by RNAi in the RPW8.2 background results in strong HR-like cell death,which correlates with elevated RPW8.2 expression.We further demonstrate that hemagglutinin (HA)-tagged PAPP2C prepared from tobacco leaf cells transiently transformed with HA-PAPP2C possesses phosphatase activity.In addition,silencing a rice gene (Os04g0452000) homologous to PAPP2C also results in spontaneous cell death in rice.Combined,our results suggest that RPW8.2 is functionally connected with PAPP2C and that PAPP2C negatively regulates SA-dependent basal defense against powdery mildew in Arabidopsis.

  13. A histone methyltransferase inhibits seed germination by increasing PIF1 mRNA expression in imbibed seeds.

    Science.gov (United States)

    Lee, Nayoung; Kang, Hyojin; Lee, Daeyoup; Choi, Giltsu

    2014-04-01

    Phytochrome-interacting factor 1 (PIF1) inhibits light-dependent seed germination. The specific function of PIF1 in seed germination is partly due to its high level of expression in imbibed seeds, but the associated regulatory factors have not been identified. Here we show that mutation of the early flowering in short days (EFS) gene, encoding an H3K4 and H3K36 methyltransferase, decreases the level of H3K36me2 and H3K36me3 but not H3K4me3 at the PIF1 locus, reduces the targeting of RNA polymerase II to the PIF1 locus, and reduces mRNA expression of PIF1 in imbibed seeds. Consistently, the efs mutant geminated even under the phyBoff condition, and had an expression profile of PIF1 target genes similar to that of the pif1 mutant. Introduction of an EFS transgene into the efs mutant restored the level of H3K36me2 and H3K36me3 at the PIF1 locus, the high-level expression of PIF1 mRNA, the expression pattern of PIF1 target genes, and the light-dependent germination of these seeds. Introduction of a PIF1 transgene into the efs mutant also restored the expression pattern of PIF1 target genes and light-dependent germination in imbibed seeds, but did not restore the flowering phenotype. Taken together, our results indicate that EFS is necessary for high-level expression of PIF1 mRNA in imbibed seeds.

  14. Identification of a hydrogen peroxide signalling pathway in the control of light-dependent germination in Arabidopsis.

    Science.gov (United States)

    Lariguet, Patricia; Ranocha, Philippe; De Meyer, Mireille; Barbier, Odile; Penel, Claude; Dunand, Christophe

    2013-08-01

    Germination is controlled by external factors, such as temperature, water, light and by hormone balance. Recently, reactive oxygen species (ROS) have been shown to act as messengers during plant development, stress responses and programmed cell death. We analyzed the role of ROS during germination and demonstrated that ROS in addition to their role as cell wall loosening factor are essential signalling molecules in this process. Indeed, we showed that ROS are released prior to endosperm rupture, that their production is required for germination, and that class III peroxidases, as ROS level regulators, colocalized with ROS production. Among ROS, H2O2 modifies, during germination early steps, the expression of genes encoding for enzymes regulating ROS levels. This pointing out a regulatory feedback loop for ROS production. Measurements of endogenous levels of ROS following application of GA and ABA suggested that ABA inhibits germination by repressing ROS accumulation, and that, conversely, GA triggers germination by promoting an increase of ROS levels. We followed the early visible steps of germination (testa and endosperm rupture) in Arabidopsis seeds treated by specific ROS scavengers and as the light quality perception is necessary for a regular germination, we examined the germination in presence of exogenous H2O2 in different light qualities. H2O2 either promoted germination or repressed germination depending on the light wavelengths, showing that H2O2 acts as a signal molecule regulating germination in a light-dependent manner. Using photoreceptors null-mutants and GA-deficient mutants, we showed that H2O2-dependent promotion of germination relies on phytochrome signalling, but not on cryptochrome signalling, and that ROS signalling requires GA signalling.

  15. A third phytoene synthase is devoted to abiotic stress-induced abscisic acid formation in rice and defines functional diversification of phytoene synthase genes.

    Science.gov (United States)

    Welsch, Ralf; Wüst, Florian; Bär, Cornelia; Al-Babili, Salim; Beyer, Peter

    2008-05-01

    We here report on the characterization of a novel third phytoene synthase gene (PSY) in rice (Oryza sativa), OsPSY3, and on the differences among all three PSY genes with respect to the tissue-specific expression and regulation upon various environmental stimuli. The two already known PSYs are under phytochrome control and involved in carotenoid biosynthesis in photosynthetically active tissues and exhibit different expression patterns during chloroplast development. In contrast, OsPSY3 transcript levels are not affected by light and show almost no tissue-specific differences. Rather, OsPSY3 transcripts are up-regulated during increased abscisic acid (ABA) formation upon salt treatment and drought, especially in roots. The simultaneous induction of genes encoding 9-cis-epoxycarotenoid dioxygenases (NCEDs), involved in the initial steps of ABA biosynthesis, indicate that decreased xanthophyll levels are compensated by the induction of the third PSY gene. Furthermore, OsPSY3 and the OsNCEDs investigated were also induced by the application of ABA, indicating positive feedback regulation. The regulatory differences are mirrored by cis-acting elements in the corresponding promoter regions, with light-responsive elements for OsPSY1 and OsPSY2 and an ABA-response element as well as a coupling element for OsPSY3. The investigation of the gene structures and 5' untranslated regions revealed that OsPSY1 represents a descendant of an ancient PSY gene present in the common ancestor of monocots and dicots. Since the genomic structures of OsPSY2 and OsPSY3 are comparable, we conclude that they originated from the most recent common ancestor, OsPSY1.

  16. Loss of the ETR1 ethylene receptor reduces the inhibitory effect of far-red light and darkness on seed germination of Arabidopsis thaliana

    Directory of Open Access Journals (Sweden)

    Rebecca L Wilson

    2014-08-01

    Full Text Available When exposed to far-red light followed by darkness, wild-type Arabidopsis thaliana seeds fail to germinate or germinate very poorly. We have previously shown that the ethylene receptor ETR1 (ETHYLENE RESPONSE1 inhibits and ETR2 stimulates seed germination of Arabidopsis during salt stress. This function of ETR1 requires the full-length receptor. These roles are independent of ethylene levels and sensitivity and are mainly mediated by a change in abscisic acid (ABA sensitivity. In the current study we find that etr1-6 and etr1-7 loss-of-function mutant seeds germinate better than wild-type seeds after illumination with far-red light or when germinated in the dark indicating an inhibitory role for ETR1. Surprisingly, this function of ETR1 does not require the receiver domain. No differences between these mutants and wild-type are seen when germination proceeds after treatment with white, blue, green, or red light. Loss of any of the other four ethylene receptor isoforms has no measurable effect on germination after far-red light treatment. An analysis of the transcript abundance for genes encoding ABA and gibberellic acid (GA metabolic enzymes indicates that etr1-6 mutants may produce more GA and less ABA than wild-type seeds after illumination with far-red light which correlates with the better germination of the mutants. Epistasis analysis suggests that ETR1 may genetically interact with the phytochromes (phy, PHYA and PHYB to control germination and growth. This study shows that of the five ethylene receptor isoforms in Arabidopsis, ETR1 has a unique role in modulating the effects of red and far-red light on plant growth and development.

  17. Loss of the ETR1 ethylene receptor reduces the inhibitory effect of far-red light and darkness on seed germination of Arabidopsis thaliana.

    Science.gov (United States)

    Wilson, Rebecca L; Bakshi, Arkadipta; Binder, Brad M

    2014-01-01

    When exposed to far-red light followed by darkness, wild-type Arabidopsis thaliana seeds fail to germinate or germinate very poorly. We have previously shown that the ethylene receptor ETR1 (ETHYLENE RESPONSE1) inhibits and ETR2 stimulates seed germination of Arabidopsis during salt stress. This function of ETR1 requires the full-length receptor. These roles are independent of ethylene levels and sensitivity and are mainly mediated by a change in abscisic acid (ABA) sensitivity. In the current study we find that etr1-6 and etr1-7 loss-of-function mutant seeds germinate better than wild-type seeds after illumination with far-red light or when germinated in the dark indicating an inhibitory role for ETR1. Surprisingly, this function of ETR1 does not require the receiver domain. No differences between these mutants and wild-type are seen when germination proceeds after treatment with white, blue, green, or red light. Loss of any of the other four ethylene receptor isoforms has no measurable effect on germination after far-red light treatment. An analysis of the transcript abundance for genes encoding ABA and gibberellic acid (GA) metabolic enzymes indicates that etr1-6 mutants may produce more GA and less ABA than wild-type seeds after illumination with far-red light which correlates with the better germination of the mutants. Epistasis analysis suggests that ETR1 may genetically interact with the phytochromes (phy), PHYA and PHYB to control germination and growth. This study shows that of the five ethylene receptor isoforms in Arabidopsis, ETR1 has a unique role in modulating the effects of red and far-red light on plant growth and development.

  18. Resposta à qualidade de luz como estratégia para estabelecimento de Bidens gardneri Response to the quality of light as a strategy for establishment of Bidens gardneri

    Directory of Open Access Journals (Sweden)

    Josimara Nolasco Rondon

    2012-12-01

    de invasão e sobrevivência no cerrado: em locais com baixa disponibilidade de luz poderá ocorrer a germinação dos aquênios longos, ainda na estação chuvosa, (fevereiro. Enquanto os aquênios curtos podem permanecer armazenados no solo, vindo a germinar apenas no final da estação seca (em setembro. Portanto, o aquênio curto persiste no banco de sementes no solo por sete meses e é o que possibilita o estabelecimento de Bidens gardneri em campos de cerrado e pastagens.The objective of this study was to investigate the involvement of phytochrome on the germination of achenes of Bidens gardneri Baker., known as black tick. The seeds were separated into short, medium and long sizes. Two experiments used only achenes medium due to differences in the response of germination in the dark, when they were artificially stored in Cerrado soil, in a previous study. The response of achenes short, medium and long to increase flow of white light was observed under a white light gradient from 0 to 46.44 µmol m-2 s-1 creep. The reversal of phytochrome far red (Pfr in phytochrome red (Pr in the dark, achenes medium newly collected and stored for 14 months at 4 °C, which were imbibed in water for 24 hours and incubated at 35 °C for 24, 48 and 72 hours in the dark and germination was 25 ° C in the dark and observed after 15 and 30 days. Finally, a gradient was constructed photoequilibrium for each size and age of achene in petri dishes moistened with distilled water, and the germination was observed every two days. In irradiances from 0 to 46.44 µmol m-2 s-1, germinability of achenes long and medium sizes increased with irradiance, but the seeds had low germination always short. Achenes medium stored imbibed for 24 h and incubated in the dark for 24 h, 48 h and 72 h at 35 °C remained response photoblastic when germination was observed every two days and after 15 and 30 days therefore showed no reversion Pfr for Pr in the dark. However, achenes medium newly collected and

  19. 玉米光敏色素A1与A2在各种光处理下的转录表达特性%Transcription Characteristics ofZmPHYA1 and ZmPHYA2 under Different Light Treatments in Maize

    Institute of Scientific and Technical Information of China (English)

    杨宗举; 闫蕾; 宋梅芳; 苏亮; 孟凡华; 李红丹; 白建荣; 郭林; 杨建平

    2016-01-01

    光敏色素是一类红光/远红光受体,它们在植物体内有非活性形式的红光吸收型(Pr)和活性形式远红光吸收型(Pfr)2种状态,通常其活性形式负责调控植物的种子萌发、株高、开花时间和避荫性等生长发育过程。在禾本科中,光敏色素只有 PHYA、PHYB 和 PHYC 三个基因亚家族,古四倍体化造成的玉米光敏色素基因有6个成员,即PHYA1、PHYA2、PHYB1、PHYB2、PHYC1和PHYC2。光敏色素A参与抑制下胚轴的伸长、促进张开子叶和花青素的积累、阻断持续远红光条件下的变绿。为了评价ZmPHYA1和ZmPHYA2对光的响应能力及其功能差异,本研究采用实时定量PCR技术分析玉米自交系B73和Mo17中ZmPHYA1和ZmPHYA2对不同光照处理响应的表达模式。结果表明玉米光敏色素A主要在叶片和花丝中表达,并且ZmPHYA1转录丰度是ZmPHYA2的2~8倍;玉米自交系B73和Mo17中胚轴在黑暗、远红光和蓝光条件下较红光和白光下更长。ZmPHYA1和ZmPHYA2的转录水平在持续远红光和蓝光条件下均较高;并且均较迅速响应黑暗到远红光和蓝光光质转换,但是前者的丰度显著高于后者, ZmPHYA1在远红光下更重要,而ZmPHYA2在蓝光下更重要。ZmPHYA1和ZmPHYA2同样响应于黑暗到红光和白光的转换,并且ZmPHYA1和ZmPHYA2表达模式基本一致。ZmPHYA1和ZmPHYA2的表达均能响应长日照和短日照处理,但是ZmPHYA1转录丰度高于ZmPHYA2的2~5倍。以上结果表明, ZmPHYA1和ZmPHYA2的转录能有效地响应各种光处理,可能ZmPHYA1在作物改良上比ZmPHYA2更有效。本研究为进一步了解ZmPHYA1和ZmPHYA2基因功能以及评价二者的光反应能力提供了理论基础。%Plant phytochromes are a family of red/far-red light photoreceptors, which have two forms in plant: inactive red light ab-sorbing form (Pr) and active far-red light absorbing form (Pfr). During plant growth and developmental

  20. Transcriptomic analysis of the underground renewal buds during dormancy transition and release in 'Hangbaishao' peony (Paeonia lactiflora.

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    Jiaping Zhang

    Full Text Available Paeonia lactiflora is one of the most famous species of herbaceous peonies with gorgeous flowers. Bud dormancy is a crucial developmental process that allows P. lactiflora to survive unfavorable environmental conditions. However, little information is available on the molecular mechanism of the bud dormancy in P. lactiflora. We performed de novo transcriptome sequencing using the Illumina RNA sequencing platform for the underground renewal buds of P. lactiflora 'Hangbaishao' to study the molecular mechanism underlying its bud dormancy transition (the period from endodormancy to ecodormancy and release (the period from ecodormancy to bud elongation and sprouting. Approximately 300 million high-quality clean reads were generated and assembled into 207,827 (mean length = 828 bp and 51,481 (mean length = 1250 bp unigenes using two assembly methods named "Trinity" and "Trinity+PRICE", respectively. Based on the data obtained by the latter method, 32,316 unigenes were annotated by BLAST against various databases. Approximately 1,251 putative transcription factors were obtained, of which the largest number of unique transcripts belonged to the basic helix-loop-helix protein (bHLH transcription factor family, and five of the top ten highly expressed transcripts were annotated as dehydrin (DHN. A total of 17,705 simple sequence repeat (SSR motifs distributed in 13,797 sequences were obtained. The budbreak morphology, levels of indole-3-acetic acid (IAA and abscisic acid (ABA, and activities of guaiacol peroxidase (POD and catalase (CAT were observed. The expression of 20 interested unigenes, which annotated as DHN, heat shock protein (HSP, histone, late elongated hypocotyl (LHY, and phytochrome (PHY, and so on, were also analyzed. These studies were based on morphological, physiological, biochemical, and molecular levels and provide comprehensive insight into the mechanism of dormancy transition and release in P. lactiflora. Transcriptome dataset can be

  1. Meristematic competence is disrupted by microgravity, real or simulated, in seedlings and cultured cells of Arabidopsis

    Science.gov (United States)

    Medina, Francisco Javier; Herranz, Raul; Van Loon, ing.. Jack J. W. A.; Kiss, John; Valbuena, Miguel A.; Youssef, Khaled

    phytochromes, the red light receptors, will be analyzed by using specific mutants. However, interestingly, studies performed on synchronized in vitro cell cultures grown in the RPM in absence of auxin transport alterations and of any change in the auxin levels, showed also disruption of meristematic competence. The cell cycle was shortened (specifically the G2 period) and ribosome production was depleted, as shown by flow cytometry, immunocytochemistry and qPCR estimation of the expression of relevant genes. This strongly suggests that the effects of altered gravity on cell growth and proliferation are not only the consequence of the transduction of the gravitropic signal mediated by auxin, but they may also be achieved using additional mechanisms of gravity sensing and additional transduction mediators. Supported by ESA, NASA and Spanish “Plan Nacional de I+D+I” (AYA2012-33982).

  2. Evaluation of intrinsic chemical kinetics and transient product spectra from time-resolved spectroscopic data.

    Science.gov (United States)

    Dioumaev, A K

    1997-09-01

    This communication is devoted to the evaluation of true spectra and intrinsic (microscopic) rate constants from apparent kinetics measured in time-resolved spectroscopic experiments monitoring complex relaxation dynamics of multi-intermediate systems. Retinal proteins, cytochrom c oxidase, phytochrome, hemoglobin, and photoactive yellow protein are examples of natural systems in which several transient states (intermediates) overlap so strongly, both in time and spectral domains, that their isolation and full characterization by classical biochemical methods is impossible, and mathematical evaluation of their true spectra and microscopic kinetic constants is required. Most of the popular methods for analysis of kinetic data, global fitting (GF), singular value decomposition (SVD), principal component analysis (PCA) and factor analysis (FA), are applicable to two-dimensional (2D, in time and spectral domains) arrays of data. All these methods produce only a phenomenological description of data, that approximates the measured data only with apparent kinetics. A fundamental limitation, namely, insufficient information in 2D data, does not allow any of these methods to reach the final goal: to recalculate from apparent to intrinsic values in any but the most trivial cases. A strategy was proposed (J.F. Nagle, Biophys. J.. 59 (1991) 476-487) to include an additional (third) information-rich dimension, temperature, into the simultaneous computer analysis. A simultaneous direct fitting of 3D data arrays to systems of differential rate equations allows recalculation of apparent kinetics into true spectra and intrinsic rate constants. In spite of its evident theoretical advantages, this strategy has not been successful on real data. Here we describe another custom-built program, SCHEMEFIT, developed for the same purpose: to fit measured kinetics directly to the system of coupled differential rate equations describing the photochrome's relaxation dynamics. Though sharing the

  3. The effect of red light on the germination of a Brazilian Pteridophyte

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    Áurea M. T. Colli

    1999-01-01

    Full Text Available The effects of red light on the germination of spores of Cheilantes concolor Langsd & Fisch were investigated in this study. The spores were spread in the Mohr (1956 nutritional solution after Dyer’s modifications (1979. Three Petri dishes were used for each treatment, three slides per dish were made for each day of treatment, and one hundred spores per slide were counted . Germination of the spores in the dark was not observed. In relation to the photoperiods, the highest germination percentage and index values were obtained with the exposure of the spores to photoperiods of 8h, and the lowest values were obtained with their exposure to photoperiods of 2h. The phytochrome pigment acts in the germination of the spores through low fluency response. The highest germination percentage and index values were obtained with the highest irradiation while the lowest with the lowest irradiation.Neste estudo foi verificado o efeito da luz vermelha na germinação dos esporos de Cheilantes concolor. Os esporos foram semeados na solução nutritiva de Mohr (1956 modificada por Dyer (1979. Foram utilizadas três placas de Petri por cada tratamento, e contadas três lâminas por placa e cem esporos por lâmina. A germinação dos esporos no escuro não foi observada. Com relação aos fotoperíodos os maiores valores de porcentagem e índice de germinação foram obtidos com a exposição dos esporos a fotoperíodos de 10h, e os menores valores com a sua exposição a fotoperíodos de 2h. O pigmento fitocromo atua na germinação dos esporos através da resposta de baixa fluência. Com relação a irradiância, os maiores valores de porcentagem e índice de germinação foram observados nas maiores irradiâncias e os menores nas menores irradiâncias.

  4. Transcriptome Analysis Reveals that Red and Blue Light Regulate Growth and Phytohormone Metabolism in Norway Spruce [Picea abies (L. Karst].

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    Fangqun OuYang

    yielded the higher IAA level. DELLA and phytochrome-interacting factor 3 (PIF3, involved in negative GA signaling, were also upregulated under blue light, which may be related to the lower GA level. Light quality also affects endogenous hormones by influencing secondary metabolism. Blue light promoted phenylpropanoid biosynthesis, phenylalanine metabolism, flavonoid biosynthesis and flavone and flavonol biosynthesis, accompanied by upregulation of most of the genes in their pathways. In conclusion, red light may promote stem growth by regulating biosynthesis of GAs, and blue light may promote flavonoid, lignin, phenylpropanoid and some hormones (such as jasmonic acid which were related to plant defense in Norway spruce, which might reduce the primary metabolites available for plant growth.

  5. Arm-in-Arm Response Regulator Dimers Promote Intermolecular Signal Transduction

    Science.gov (United States)

    Baker, Anna W.; Satyshur, Kenneth A.; Moreno Morales, Neydis

    2016-01-01

    ABSTRACT Bacteriophytochrome photoreceptors (BphPs) and their cognate response regulators make up two-component signal transduction systems which direct bacteria to mount phenotypic responses to changes in environmental light quality. Most of these systems utilize single-domain response regulators to transduce signals through unknown pathways and mechanisms. Here we describe the photocycle and autophosphorylation kinetics of RtBphP1, a red light-regulated histidine kinase from the desert bacterium Ramlibacter tataouinensis. RtBphP1 undergoes red to far-red photoconversion with rapid thermal reversion to the dark state. RtBphP1 is autophosphorylated in the dark; this activity is inhibited under red light. The RtBphP1 cognate response regulator, the R. tataouinensis bacteriophytochrome response regulator (RtBRR), and a homolog, AtBRR from Agrobacterium tumefaciens, crystallize unexpectedly as arm-in-arm dimers, reliant on a conserved hydrophobic motif, hFWAhL (where h is a hydrophobic M, V, L, or I residue). RtBRR and AtBRR dimerize distinctly from four structurally characterized phytochrome response regulators found in photosynthetic organisms and from all other receiver domain homodimers in the Protein Data Bank. A unique cacodylate-zinc-histidine tag metal organic framework yielded single-wavelength anomalous diffraction phases and may be of general interest. Examination of the effect of the BRR stoichiometry on signal transduction showed that phosphorylated RtBRR is accumulated more efficiently than the engineered monomeric RtBRR (RtBRRmon) in phosphotransfer reactions. Thus, we conclude that arm-in-arm dimers are a relevant signaling intermediate in this class of two-component regulatory systems. IMPORTANCE BphP histidine kinases and their cognate response regulators comprise widespread red light-sensing two-component systems. Much work on BphPs has focused on structural understanding of light sensing and on enhancing the natural infrared fluorescence of these

  6. The white collar complex is involved in sexual development of Fusarium graminearum.

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    Hun Kim

    Full Text Available Sexual spores (ascospores of Fusarium graminearum, a homothallic ascomycetous fungus, are believed to be the primary inocula for epidemics of the diseases caused by this species in cereal crops. Based on the light requirement for the formation of fruiting bodies (perithecia of F. graminearum under laboratory conditions, we explored whether photoreceptors play an important role in sexual development. Here, we evaluated the roles of three genes encoding putative photoreceptors [a phytochrome gene (FgFph and two white collar genes (FgWc-1 and FgWc-2] during sexual development in F. graminearum. For functional analyses, we generated transgenic strains lacking one or two genes from the self-fertile Z3643 strain. Unlike the wild-type (WT and add-back strains, the single deletion strains (ΔFgWc-1 and ΔFgWc-2 produced fertile perithecia under constant light on complete medium (CM, an unfavorable medium for sexual development as well as on carrot agar (a perithecial induction condition. The expression of mating-type (MAT genes increased significantly in the gene deletion strains compared to the WT under both conditions. Deletion of FgFph had no significant effect on sexual development or MAT gene expression. In contrast, all of the deletion strains examined did not show significant changes in other traits such as hyphal growth, mycotoxin production, and virulence. A split luciferase assay confirmed the in vivo protein-protein interactions among three photoreceptors along with FgLaeA, a global regulator of secondary metabolism and fungal development. Introduction of an intact copy of the A. nidulans LreA and LreB genes, which are homologs of FgWc-1 and FgWc-2, into the ΔFgWc-1 and ΔFgWc-2 strains, respectively, failed to repress perithecia formation on CM in the gene deletion strains. Taken together, these results demonstrate that FgWc-1 and FgWc-2, two central components of the blue-light sensing system, negatively regulate sexual development in F

  7. Comparative genomic analysis of light-regulated transcripts in the Solanaceae

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    Yanovsky Marcelo J

    2009-02-01

    Full Text Available Abstract Background Plants use different light signals to adjust their growth and development to the prevailing environmental conditions. Studies in the model species Arabidopsis thaliana and rice indicate that these adjustments are mediated by large changes in the transcriptome. Here we compared transcriptional responses to light in different species of the Solanaceae to investigate common as well as species-specific changes in gene expression. Results cDNA microarrays were used to identify genes regulated by a transition from long days (LD to short days (SD in the leaves of potato and tobacco plants, and by phytochrome B (phyB, the photoreceptor that represses tuberization under LD in potato. We also compared transcriptional responses to photoperiod in Nicotiana tabacum Maryland Mammoth (MM, which flowers only under SD, with those of Nicotiana sylvestris, which flowers only under LD conditions. Finally, we identified genes regulated by red compared to far-red light treatments that promote germination in tomato. Conclusion Most of the genes up-regulated in LD were associated with photosynthesis, the synthesis of protective pigments and the maintenance of redox homeostasis, probably contributing to the acclimatization to seasonal changes in irradiance. Some of the photoperiodically regulated genes were the same in potato and tobacco. Others were different but belonged to similar functional categories, suggesting that conserved as well as convergent evolutionary processes are responsible for physiological adjustments to seasonal changes in the Solanaceae. A β-ZIP transcription factor whose expression correlated with the floral transition in Nicotiana species with contrasting photoperiodic responses was also regulated by photoperiod and phyB in potato, and is a candidate gene to act as a general regulator of photoperiodic responses. Finally, GIGANTEA, a gene that controls flowering time in Arabidopsis thaliana and rice, was regulated by

  8. PAPP5 is involved in the tetrapyrrole mediated plastid signalling during chloroplast development.

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    Juan de Dios Barajas-López

    Full Text Available The initiation of chloroplast development in the light is dependent on nuclear encoded components. The nuclear genes encoding key components in the photosynthetic machinery are regulated by signals originating in the plastids. These plastid signals play an essential role in the regulation of photosynthesis associated nuclear genes (PhANGs when proplastids develop into chloroplasts. One of the plastid signals is linked to the tetrapyrrole biosynthesis and accumulation of the intermediates the Mg-ProtoIX and its methyl ester Mg-ProtoIX-ME. Phytochrome-Associated Protein Phosphatase 5 (PAPP5 was isolated in a previous study as a putative Mg-ProtoIX interacting protein. In order to elucidate if there is a biological link between PAPP5 and the tetrapyrrole mediated signal we generated double mutants between the Arabidopsis papp5 and the crd mutants. The crd mutant over-accumulates Mg-ProtoIX and Mg-ProtoIX-ME and the tetrapyrrole accumulation triggers retrograde signalling. The crd mutant exhibits repression of PhANG expression, altered chloroplast morphology and a pale phenotype. However, in the papp5crd double mutant, the crd phenotype is restored and papp5crd accumulated wild type levels of chlorophyll, developed proper chloroplasts and showed normal induction of PhANG expression in response to light. Tetrapyrrole feeding experiments showed that PAPP5 is required to respond correctly to accumulation of tetrapyrroles in the cell and that PAPP5 is most likely a component in the plastid signalling pathway down stream of the tetrapyrrole Mg-ProtoIX/Mg-ProtoIX-ME. Inhibition of phosphatase activity phenocopied the papp5crd phenotype in the crd single mutant demonstrating that PAPP5 phosphatase activity is essential to mediate the retrograde signal and to suppress PhANG expression in the crd mutant. Thus, our results suggest that PAPP5 receives an inbalance in the tetrapyrrole biosynthesis through the accumulation of Mg-ProtoIX and acts as a negative

  9. Characterizing two inter-specific bin maps for the exploration of the QTLs/genes that confer three soybean evolutionary traits

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    Tuanjie Zhao

    2016-08-01

    Full Text Available Annual wild soybean (Glycine soja Sieb. & Zucc., the wild progenitor of the cultivated soybean (G. max (L. Merr., is valuable for improving the later. The construction of a linkage map is crucial for studying the genetic differentiation between these species, but marker density is the main factor limiting the accuracy of such a map. Recent advances in next-generation sequencing technologies allow for the generation of high-density linkage maps. Here, two sets of inter-specific recombinant inbred line populations, named NJIRNP and NJIR4P, composed of 284 and 161 lines, respectively, were generated from the same wild male parent, PI 342618B, and genotyped by restriction-site-associated DNA sequencing (RAD-seq. Two linkage maps containing 5,728 and 4,354 bins were constructed based on 89,680 and 80,995 SNPs, spanning a total genetic distance of 2204.6 and 2136.7 cM, with an average distance of 0.4 and 0.5 cM between neighboring bins in NJRINP and NJRI4P, respectively. With the two maps, seven well-studied loci, B1 for seed bloom (SB; G and I for seed coat color (SCC; E2, E3, qDTF16.1 and two linked FLOWERING LOCUS T for days to flowering (DTF, were detected. In addition, two SB and two DTF loci were newly identified in wild soybean. Using two high-density maps, the mapping resolution was enhanced, e.g., G was narrowed to a region of 0.4 Mb on chromosome 1, encompassing 54 gene models, among which only Glyma01g40590 was predicted to be involved in anthocyanin accumulation, and its interaction with I was verified in both populations. In addition, five genes, Glyma16g03030, orthologous to Arabidopsis Phytochrome A (PHYA; Glyma13g28810, Glyma13g29920 and Glyma13g30710 predicted to encode the APETALA 2 (AP2 domain; and Glyma02g00300, involved in response to red or far red light, might be candidate DTF genes. Our results demonstrate that RAD-seq is a cost-effective approach for constructing high-density and high-quality bin maps that can be used to map

  10. Arm-in-Arm Response Regulator Dimers Promote Intermolecular Signal Transduction.

    Science.gov (United States)

    Baker, Anna W; Satyshur, Kenneth A; Moreno Morales, Neydis; Forest, Katrina T

    2016-04-01

    Bacteriophytochrome photoreceptors (BphPs) and their cognate response regulators make up two-component signal transduction systems which direct bacteria to mount phenotypic responses to changes in environmental light quality. Most of these systems utilize single-domain response regulators to transduce signals through unknown pathways and mechanisms. Here we describe the photocycle and autophosphorylation kinetics of RtBphP1, a red light-regulated histidine kinase from the desert bacterium Ramlibacter tataouinensis RtBphP1 undergoes red to far-red photoconversion with rapid thermal reversion to the dark state. RtBphP1 is autophosphorylated in the dark; this activity is inhibited under red light. The RtBphP1 cognate response regulator, the R. tataouinensis bacteriophytochrome response regulator (RtBRR), and a homolog, AtBRR from Agrobacterium tumefaciens, crystallize unexpectedly as arm-in-arm dimers, reliant on a conserved hydrophobic motif, hFWAhL (where h is a hydrophobic M, V, L, or I residue). RtBRR and AtBRR dimerize distinctly from four structurally characterized phytochrome response regulators found in photosynthetic organisms and from all other receiver domain homodimers in the Protein Data Bank. A unique cacodylate-zinc-histidine tag metal organic framework yielded single-wavelength anomalous diffraction phases and may be of general interest. Examination of the effect of the BRR stoichiometry on signal transduction showed that phosphorylated RtBRR is accumulated more efficiently than the engineered monomeric RtBRR (RtBRRmon) in phosphotransfer reactions. Thus, we conclude that arm-in-arm dimers are a relevant signaling intermediate in this class of two-component regulatory systems. BphP histidine kinases and their cognate response regulators comprise widespread red light-sensing two-component systems. Much work on BphPs has focused on structural understanding of light sensing and on enhancing the natural infrared fluorescence of these proteins, rather than

  11. Exciton coherence and energy transport in the light-harvesting dimers of allophycocyanin.

    Science.gov (United States)

    Womick, Jordan M; Moran, Andrew M

    2009-12-03

    line shape and open channels for fast internal conversion. The dominant internal conversion channel is assigned to a promoting mode near 800 cm(-1) involving hydrogen out-of-plane (HOOP) wagging motion similar to that observed in phytochrome and retinal. This rate enhancement ensures that all photoexcitations quickly and efficiently relax to the electronic origin of the lower energy exciton state from which energy transfer to the reaction center occurs.

  12. Nature of excited states and relaxation mechanisms in C-phycocyanin.

    Science.gov (United States)

    Womick, Jordan M; Moran, Andrew M

    2009-12-03

    The electronic structure and photoinduced relaxation dynamics of the cyanobacterial light harvesting protein, C-Phycocyanin (CPC), are examined using transient grating and two-dimensional (2D) photon echo spectroscopies possessing sub-20 fs time resolution. In combination with linear absorption and fluorescence measurements, these time-resolved experiments are used to constrain the parameters of a Frenkel exciton Hamiltonian. Particular emphasis is placed on elucidating the nature of excited states involving the alpha84 and beta84 phycocyanobilin pigme