WorldWideScience

Sample records for basipetal auxin transport

  1. N-glycan containing a core α1,3-fucose residue is required for basipetal auxin transport and gravitropic response in rice (Oryza sativa).

    Science.gov (United States)

    Harmoko, Rikno; Yoo, Jae Yong; Ko, Ki Seong; Ramasamy, Nirmal Kumar; Hwang, Bo Young; Lee, Eun Ji; Kim, Ho Soo; Lee, Kyung Jin; Oh, Doo-Byoung; Kim, Dool-Yi; Lee, Sanghun; Li, Yang; Lee, Sang Yeol; Lee, Kyun Oh

    2016-10-01

    In plants, α1,3-fucosyltransferase (FucT) catalyzes the transfer of fucose from GDP-fucose to asparagine-linked GlcNAc of the N-glycan core in the medial Golgi. To explore the physiological significance of this processing, we isolated two Oryza sativa (rice) mutants (fuct-1 and fuct-2) with loss of FucT function. Biochemical analyses of the N-glycan structure confirmed that α1,3-fucose is missing from the N-glycans of allelic fuct-1 and fuct-2. Compared with the wild-type cv Kitaake, fuct-1 displayed a larger tiller angle, shorter internode and panicle lengths, and decreased grain filling as well as an increase in chalky grains with abnormal shape. The mutant allele fuct-2 gave rise to similar developmental abnormalities, although they were milder than those of fuct-1. Restoration of a normal tiller angle in fuct-1 by complementation demonstrated that the phenotype is caused by the loss of FucT function. Both fuct-1 and fuct-2 plants exhibited reduced gravitropic responses. Expression of the genes involved in tiller and leaf angle control was also affected in the mutants. We demonstrate that reduced basipetal auxin transport and low auxin accumulation at the base of the shoot in fuct-1 account for both the reduced gravitropic response and the increased tiller angle. PMID:27241276

  2. Regulation of auxin transport during gravitropism

    Science.gov (United States)

    Rashotte, A.; Brady, S.; Kirpalani, N.; Buer, C.; Muday, G.

    Plants respond to changes in the gravity vector by differential growth across the gravity-stimulated organ. The plant hormone auxin, which is normally basipetally transported, changes in direction and auxin redistribution has been suggested to drive this differential growth or gravitropism. The mechanisms by which auxin transport directionality changes in response to a change in gravity vector are largely unknown. Using the model plant, Arabidopsis thaliana, we have been exploring several regulatory mechanisms that may control auxin transport. Mutations that alter protein phosphorylation suggest that auxin transport in arabidopsis roots may be controlled via phosphorylation and this signal may facilitate gravitropic bending. The protein kinase mutant pinoid (pid9) has reduced auxin transport; whereas the protein phosphatase mutant, rcn1, has elevated transport, suggesting reciprocal regulation of auxin transport by reversible protein phosphorylation. In both of these mutants, the auxin transport defects are accompanied by gravitropic defects, linking phosphorylation signaling to gravity-induced changes in auxin transport. Additionally, auxin transport may be regulated during gravity response by changes in an endogenous auxin efflux inhibitor. Flavonoids, such as quercetin and kaempferol, have been implicated in regulation of auxin transport in vivo and in vitro. Mutants that make no flavonoids have reduced root gravitropic bending. Furthermore, changes in auxin-induced gene expression and flavonoid accumulation patterns have been observed during gravity stimulation. Current studies are examining whether there are spatial and temporal changes in flavonoid accumulation that precede gravitropic bending and whether the absence of these changes are the cause of the altered gravity response in plants with mutations that block flavonoid synthesis. These results support the idea that auxin transport may be regulated during gravity response by several mechanisms including

  3. Action of Abscisic Acid on Auxin Transport and its Relation to Phototropism

    DEFF Research Database (Denmark)

    Naqvi, S. M.; Engvild, Kjeld Christensen

    1974-01-01

    The action of abscisic acid on the kinetics of auxin transport through Zea mays L. (cv. Goudster) coleoptiles has been investigated. Abscisic acid applied simultaneously with indoleacetic acid-2-14C in the donor block reduced the transport intensity without materially affecting the basipetal...

  4. Cellular Auxin Transport in Algae

    Science.gov (United States)

    Zhang, Suyun; van Duijn, Bert

    2014-01-01

    The phytohormone auxin is one of the main directors of plant growth and development. In higher plants, auxin is generated in apical plant parts and transported from cell-to-cell in a polar fashion. Auxin is present in all plant phyla, and the existence of polar auxin transport (PAT) is well established in land plants. Algae are a group of relatively simple, autotrophic, photosynthetic organisms that share many features with land plants. In particular, Charophyceae (a taxon of green algae) are closest ancestors of land plants. In the study of auxin function, transport and its evolution, the algae form an interesting research target. Recently, proof for polar auxin transport in Chara species was published and auxin related research in algae gained more attention. In this review we discuss auxin transport in algae with respect to land plants and suggest directions for future studies.

  5. The Transport of Auxins

    Czech Academy of Sciences Publication Activity Database

    Morris, David; Friml, J.; Zažímalová, Eva

    Dordrecht : Kluwer, 2004 - (Davies, P.), s. 437-470 ISBN 1-4020-2685-4 R&D Projects: GA AV ČR(CZ) IAA6038303 Institutional research plan: CEZ:AV0Z5038910 Keywords : auxins * developmental process * transmembrane transport Subject RIV: ED - Physiology

  6. Auxin transporters controlling plant development

    Czech Academy of Sciences Publication Activity Database

    Petrášek, Jan; Malínská, Kateřina; Zažímalová, Eva

    Heidelberg: Springer Verlag, 2010 - (Geisler, M.; Venema, K.), s. 255-290 ISBN 978-3-642-14368-7 R&D Projects: GA MŠk(CZ) LC06034 Institutional research plan: CEZ:AV0Z50380511 Keywords : Auxin * polar auxin transport * auxin carriers Subject RIV: ED - Physiology

  7. Maintenance of asymmetric cellular localization of an auxin transport protein through interaction with the actin cytoskeleton

    Science.gov (United States)

    Muday, G. K.

    2000-01-01

    In shoots, polar auxin transport is basipetal (that is, from the shoot apex toward the base) and is driven by the basal localization of the auxin efflux carrier complex. The focus of this article is to summarize the experiments that have examined how the asymmetric distribution of this protein complex is controlled and the significance of this polar distribution. Experimental evidence suggests that asymmetries in the auxin efflux carrier may be established through localized secretion of Golgi vesicles, whereas an attachment of a subunit of the efflux carrier to the actin cytoskeleton may maintain this localization. In addition, the idea that this localization of the efflux carrier may control both the polarity of auxin movement and more globally regulate developmental polarity is explored. Finally, evidence indicating that the gravity vector controls auxin transport polarity is summarized and possible mechanisms for the environmentally induced changes in auxin transport polarity are discussed.

  8. Genotypical differences in aluminum resistance of maize are expressed in the distal part of the transition zone. Is reduced basipetal auxin flow involved in inhibition of root elongation by aluminum?

    Science.gov (United States)

    Kollmeier, M; Felle, H H; Horst, W J

    2000-03-01

    Short-term Al treatment (90 microM Al at pH 4.5 for 1 h) of the distal transition zone (DTZ; 1-2 mm from the root tip), which does not contribute significantly to root elongation, inhibited root elongation in the main elongation zone (EZ; 2.5-5 mm from the root tip) to the same extent as treatment of the entire maize (Zea mays) root apex. Application of Al to the EZ had no effect on root elongation. Higher genotypical resistance to Al applied to the entire root apex, and specifically to the DTZ, was expressed by less inhibition of root elongation, Al accumulation, and Al-induced callose formation, primarily in the DTZ. A characteristic pH profile along the surface of the root apex with a maximum of pH 5.3 in the DTZ was demonstrated. Al application induced a substantial flattening of the pH profile moreso in the Al-sensitive than in the Al-resistant cultivar. Application of indole-3-acetic acid to the EZ but not to the meristematic zone significantly alleviated the inhibition of root elongation induced by the application of Al to the DTZ. Basipetal transport of exogenously applied [(3)H]indole-3-acetic acid to the meristematic zone was significantly inhibited by Al application to the DTZ in the Al-sensitive maize cv Lixis. Our results provide evidence that the primary mechanisms of genotypical differences in Al resistance are located within the DTZ, and suggest a signaling pathway in the root apex mediating the Al signal between the DTZ and the EZ through basipetal auxin transport. PMID:10712559

  9. Gravity-regulated differential auxin transport from columella to lateral root cap cells

    Science.gov (United States)

    Ottenschlager, Iris; Wolff, Patricia; Wolverton, Chris; Bhalerao, Rishikesh P.; Sandberg, Goran; Ishikawa, Hideo; Evans, Mike; Palme, Klaus

    2003-01-01

    Gravity-induced root curvature has long been considered to be regulated by differential distribution of the plant hormone auxin. However, the cells establishing these gradients, and the transport mechanisms involved, remain to be identified. Here, we describe a GFP-based auxin biosensor to monitor auxin during Arabidopsis root gravitropism at cellular resolution. We identify elevated auxin levels at the root apex in columella cells, the site of gravity perception, and an asymmetric auxin flux from these cells to the lateral root cap (LRC) and toward the elongation zone after gravistimulation. We differentiate between an efflux-dependent lateral auxin transport from columella to LRC cells, and an efflux- and influx-dependent basipetal transport from the LRC to the elongation zone. We further demonstrate that endogenous gravitropic auxin gradients develop even in the presence of an exogenous source of auxin. Live-cell auxin imaging provides unprecedented insights into gravity-regulated auxin flux at cellular resolution, and strongly suggests that this flux is a prerequisite for root gravitropism.

  10. Polar auxin transport: models and mechanisms

    NARCIS (Netherlands)

    Berkel, van K.; Boer, de R.J.; Scheres, B.; Tusscher, ten K.

    2013-01-01

    Spatial patterns of the hormone auxin are important drivers of plant development. The observed feedback between the active, directed transport that generates auxin patterns and the auxin distribution that influences transport orientation has rendered this a popular subject for modelling studies. Her

  11. Auxin apical control of the auxin polar transport and its oscillation - a suggested cellular transduction mechanism

    Directory of Open Access Journals (Sweden)

    Tomasz J. Wodzicki

    2014-02-01

    Full Text Available The proposed hypothesis concerns the transduction of auxin molecular signals arriving from the apoplast at the plasma membrane or recognized by the proteineous receptors of the responding cell, to the concentration gradients oscillating in the supracellular space, associated usually with the specific plant growth and differentiation. Acting as an agonist from outside the target cell auxin stimulates in this cell: (1 the liberation of auxin from the cytosolic pool of its conjugates directly into the basipetal efflux; (2 the synthesis of new auxin which restores the cytosolic reserve of auxin conjugates. The functioning of such a system may be effective in a series of processes initiated by the changing concentration of cytosolic calcium. The hypothesis suggests a molecular mechanism for the development and effective operation of the morphogenetic field in the supracellular space of the plant body, such as the field resulting from auxin waves discovered in cambium.

  12. The role of auxin transporters in monocots development

    OpenAIRE

    Sara eBalzan; Johal, Gurmukh S; Nicola eCarraro

    2014-01-01

    Auxin is a key regulator of plant growth and development, orchestrating cell division, elongation and differentiation, embryonic development, root and stem tropisms, apical dominance and transition to flowering. Auxin levels are higher in undifferentiated cell populations and decrease following organ initiation and tissue differentiation. This differential auxin distribution is achieved by polar auxin transport (PAT) mediated by auxin transport proteins. There are 4 major families of auxin tr...

  13. Auxin transport and growth in intact roots of Vicia faba

    International Nuclear Information System (INIS)

    Transport of IAA applied to the intact root of Vicia seedlings was investigated in relation to root growth. The root was treated at 3-4,4-5 or 7-8mm from the tip with a narrow ring of lanolin paste containing IAA or IAA-2-14C in growth or transport experiments, repectively. The growth process along the root axis was examined in every 1-mm part from the tip at 30 min, 1 or 4 hr intervals. The elongation zone of the control root was 1-9mm from the tip. IAA treatment brought about no significant change in the growth of the region apical to the treated site, whereas distinct inhibition of growth occurred in the region basal to the treated site within 1 hr. The transport of radioactivity was observed in both acropetal and basipetal directions within 1 hr, but the later predominated for 8 hr or more; the nearer to the tip the treatment site, the longer the predominance lasted. The velocities of acropetal and basipetal transport were estimated at about 4 and 8 mm/hr, respectively. Autoradiographs of transverse section of roots showed that basipetal transport occurred mainly through the outer part of the root, whereas acropetal transport occurred mainly through the inner part, the central cylinder. It may be concluded that the basipetally transported IAA which passed cylinder. It may be concluded that the basipetally transported IAA which passed through the outer part of the root inhibited the elongation of the intact root. (auth.)

  14. Loss of GSNOR1 Function Leads to Compromised Auxin Signaling and Polar Auxin Transport.

    Science.gov (United States)

    Shi, Ya-Fei; Wang, Da-Li; Wang, Chao; Culler, Angela Hendrickson; Kreiser, Molly A; Suresh, Jayanti; Cohen, Jerry D; Pan, Jianwei; Baker, Barbara; Liu, Jian-Zhong

    2015-09-01

    Cross talk between phytohormones, nitric oxide (NO), and auxin has been implicated in the control of plant growth and development. Two recent reports indicate that NO promoted auxin signaling but inhibited auxin transport probably through S-nitrosylation. However, genetic evidence for the effect of S-nitrosylation on auxin physiology has been lacking. In this study, we used a genetic approach to understand the broader role of S-nitrosylation in auxin physiology in Arabidopsis. We compared auxin signaling and transport in Col-0 and gsnor1-3, a loss-of-function GSNOR1 mutant defective in protein de-nitrosylation. Our results showed that auxin signaling was impaired in the gsnor1-3 mutant as revealed by significantly reduced DR5-GUS/DR5-GFP accumulation and compromised degradation of AXR3NT-GUS, a useful reporter in interrogating auxin-mediated degradation of Aux/IAA by auxin receptors. In addition, polar auxin transport was compromised in gsnor1-3, which was correlated with universally reduced levels of PIN or GFP-PIN proteins in the roots of the mutant in a manner independent of transcription and 26S proteasome degradation. Our results suggest that S-nitrosylation and GSNOR1-mediated de-nitrosylation contribute to auxin physiology, and impaired auxin signaling and compromised auxin transport are responsible for the auxin-related morphological phenotypes displayed by the gsnor1-3 mutant. PMID:25917173

  15. The role of auxin transporters in monocots development

    OpenAIRE

    Balzan, Sara; Johal, Gurmukh S; Carraro, Nicola

    2014-01-01

    Auxin is a key regulator of plant growth and development, orchestrating cell division, elongation and differentiation, embryonic development, root and stem tropisms, apical dominance, and transition to flowering. Auxin levels are higher in undifferentiated cell populations and decrease following organ initiation and tissue differentiation. This differential auxin distribution is achieved by polar auxin transport (PAT) mediated by auxin transport proteins. There are four major families of auxi...

  16. Determination of Auxin Transport Parameters on the Cellular Level

    Czech Academy of Sciences Publication Activity Database

    Petrášek, Jan; Laňková, Martina; Zažímalová, Eva

    Totowa: Humana Press, 2014 - (Hicks, G.; Robert, S.), s. 241-253. (Methods in Molecular Biology). ISBN 978-1-62703-591-0 Institutional support: RVO:61389030 Keywords : Auxin transport assay * Plant cell cultures * Auxin influx Subject RIV: ED - Physiology

  17. Strigolactone Inhibition of Branching Independent of Polar Auxin Transport.

    Science.gov (United States)

    Brewer, Philip B; Dun, Elizabeth A; Gui, Renyi; Mason, Michael G; Beveridge, Christine A

    2015-08-01

    The outgrowth of axillary buds into branches is regulated systemically via plant hormones and the demand of growing shoot tips for sugars. The plant hormone auxin is thought to act via two mechanisms. One mechanism involves auxin regulation of systemic signals, cytokinins and strigolactones, which can move into axillary buds. The other involves suppression of auxin transport/canalization from axillary buds into the main stem and is enhanced by a low sink for auxin in the stem. In this theory, the relative ability of the buds and stem to transport auxin controls bud outgrowth. Here, we evaluate whether auxin transport is required or regulated during bud outgrowth in pea (Pisum sativum). The profound, systemic, and long-term effects of the auxin transport inhibitor N-1-naphthylphthalamic acid had very little inhibitory effect on bud outgrowth in strigolactone-deficient mutants. Strigolactones can also inhibit bud outgrowth in N-1-naphthylphthalamic acid-treated shoots that have greatly diminished auxin transport. Moreover, strigolactones can inhibit bud outgrowth despite a much diminished auxin supply in in vitro or decapitated plants. These findings demonstrate that auxin sink strength in the stem is not important for bud outgrowth in pea. Consistent with alternative mechanisms of auxin regulation of systemic signals, enhanced auxin biosynthesis in Arabidopsis (Arabidopsis thaliana) can suppress branching in yucca1D plants compared with wild-type plants, but has no effect on bud outgrowth in a strigolactone-deficient mutant background. PMID:26111543

  18. Gradual shifts in sites of free-auxin production during leaf-primordium development and their role in vascular differentiation and leaf morphogenesis in Arabidopsis.

    Science.gov (United States)

    Aloni, Roni; Schwalm, Katja; Langhans, Markus; Ullrich, Cornelia I

    2003-03-01

    The major regulatory shoot signal is auxin, whose synthesis in young leaves has been a mystery. To test the leaf-venation hypothesis [R. Aloni (2001) J Plant Growth Regul 20: 22-34], the patterns of free-auxin production, movement and accumulation in developing leaf primordia of DR5::GUS-transformed Arabidopsis thaliana (L.) Heynh. were visualized. DR5::GUS expression was regarded to reflect sites of free auxin, while immunolocalization with specific monoclonal antibodies indicated total auxin distribution. The mRNA expression of key enzymes involved in the synthesis, conjugate hydrolysis, accumulation and basipetal transport of auxin, namely indole-3-glycerol-phosphate-synthase, nitrilase, IAA-amino acid hydrolase, chalcone synthase and PIN1 as an essential component of the basipetal IAA carrier, was investigated by reverse transcription-polymerase chain reaction. Near the shoot apex, stipules were the earliest sites of high free-auxin production. During early stages of primordium development, leaf apical dominance was evident from strong beta-glucuronidase activity in the elongating tip, possibly suppressing the production of free auxin in the leaf tissues below it. Hydathodes, which develop in the tip and later in the lobes, were apparently primary sites of high free-auxin production, the latter supported by auxin-conjugate hydrolysis, auxin retention by the chalcone synthase-dependent action of flavonoids and also by the PIN1-component of the carrier-mediated basipetal transport. Trichomes and mesophyll cells were secondary sites of free-auxin production. During primordium development there are gradual shifts in sites and concentrations of free-auxin production occurring first in the tip of a leaf primordium, then progressing basipetally along the margins, and finally appearing also in the central regions of the lamina. This developmental pattern of free-auxin production is suggested to control the basipetal maturation sequence of leaf development and vascular

  19. Auxin transport in an auxin-resistant mutant of arabidopsis thaliana

    Energy Technology Data Exchange (ETDEWEB)

    Lincoln, C.; Benning, C.; Estelle, M.

    1987-04-01

    The authors are studying a group of allelic recessive mutations in Arabidopsis called axr-1. Homozygous axr-1 plants are resistant to exogenously applied auxin. In addition, axr-1 mutations all confer a number of development abnormalities including an apparent reduction in apical dominance, loss of normal geotropic response, and a failure to self-fertilize due to a decrease in stamen elongation. In order to determine whether this pleiotropic phenotype is due to an alteration in auxin transport they have adapted the agar block transport assay for use in Arabidopsis stem segments. Their results indicate that as in other plant species, auxin transport is strongly polar in Arabidopsis stem segments. In addition transport is inhibited by the well characterized auxin transport inhibitor N-1-naphthylphthalamic acid and the artificial auxin 2,4-D. These results as well as the characterization of transport in axr-1 plants will be presented.

  20. Molecular modeling of auxin transport inhibitors

    Energy Technology Data Exchange (ETDEWEB)

    Gardner, G.; Black-Schaefer, C.; Bures, M.G. (Abbott Labs, North Chicago, IL (USA))

    1990-05-01

    Molecular modeling techniques have been used to study the chemical and steric properties of auxin transport inhibitors. These bind to a specific site on the plant plasma membrane characterized by its affinity for N-1-naphthylphthalamic acid (NPA). A three-dimensional model was derived from critical features of ligands for the NPA receptor, and a suggested binding conformation is proposed. This model, along with three-dimensional structural searching techniques, was then used to search the Abbott corporate database of chemical structures. Of the 467 compounds that satisfied the search criteria, 77 representative molecules were evaluated for their ability to compete for ({sup 3}H)NPA binding to corn microsomal membranes. Nineteen showed activity that ranged from 16 to 85% of the maximum NPA binding. Four of the most active of these, from chemical classes not included in the original compound set, also inhibited polar auxin transport through corn coleoptile sections.

  1. The role of auxin transporters in monocots development.

    Science.gov (United States)

    Balzan, Sara; Johal, Gurmukh S; Carraro, Nicola

    2014-01-01

    Auxin is a key regulator of plant growth and development, orchestrating cell division, elongation and differentiation, embryonic development, root and stem tropisms, apical dominance, and transition to flowering. Auxin levels are higher in undifferentiated cell populations and decrease following organ initiation and tissue differentiation. This differential auxin distribution is achieved by polar auxin transport (PAT) mediated by auxin transport proteins. There are four major families of auxin transporters in plants: PIN-FORMED (PIN), ATP-binding cassette family B (ABCB), AUXIN1/LIKE-AUX1s, and PIN-LIKES. These families include proteins located at the plasma membrane or at the endoplasmic reticulum (ER), which participate in auxin influx, efflux or both, from the apoplast into the cell or from the cytosol into the ER compartment. Auxin transporters have been largely studied in the dicotyledon model species Arabidopsis, but there is increasing evidence of their role in auxin regulated development in monocotyledon species. In monocots, families of auxin transporters are enlarged and often include duplicated genes and proteins with high sequence similarity. Some of these proteins underwent sub- and neo-functionalization with substantial modification to their structure and expression in organs such as adventitious roots, panicles, tassels, and ears. Most of the present information on monocot auxin transporters function derives from studies conducted in rice, maize, sorghum, and Brachypodium, using pharmacological applications (PAT inhibitors) or down-/up-regulation (over-expression and RNA interference) of candidate genes. Gene expression studies and comparison of predicted protein structures have also increased our knowledge of the role of PAT in monocots. However, knockout mutants and functional characterization of single genes are still scarce and the future availability of such resources will prove crucial to elucidate the role of auxin transporters in monocots

  2. Seven Things We Think We Know about Auxin Transport

    Institute of Scientific and Technical Information of China (English)

    Wendy Ann Peer; Joshua J. Blakeslee; Haibing Yang; Angus S. Murphy

    2011-01-01

    T Polar transport of the phytohormone auxin and the establishment of localized auxin maxima regulate embryonic development, stem cell maintenance, root and shoot architecture, and tropic growth responses. The past decade has been marked by dramatic progress in efforts to elucidate the complex mechanisms by which auxin transport regulates plant growth. As the understanding of auxin transport regulation has been increasingly elaborated, it has become clear that this process is involved in almost all plant growth and environmental responses in some way. However, we still lack information about some basic aspects of this fundamental regulatory mechanism. In this review, we present what we know (or what we think we know) and what we do not know about seven auxin-regulated processes. We discuss the role of auxin transport in gravitropism in primary and lateral roots, phototropism, shoot branching, leaf expansion, and venation. We also discuss the auxin reflux/fountain model at the root tip, flavonoid modulation of auxin transport processes, and outstanding aspects of post-translational regulation of auxin transporters. This discussion is not meant to be exhaustive, but highlights areas in which generally held assumptions require more substantive validation.

  3. The role of auxin transporters in monocots development

    Directory of Open Access Journals (Sweden)

    Sara eBalzan

    2014-08-01

    Full Text Available Auxin is a key regulator of plant growth and development, orchestrating cell division, elongation and differentiation, embryonic development, root and stem tropisms, apical dominance and transition to flowering. Auxin levels are higher in undifferentiated cell populations and decrease following organ initiation and tissue differentiation. This differential auxin distribution is achieved by polar auxin transport (PAT mediated by auxin transport proteins. There are 4 major families of auxin transporters in plants: PINs, ABCBs, AUX/LAXs and PILS. These families include proteins located at the plasma membrane (PM or at the Endoplasmic Reticulum (ER, which participate in auxin influx, efflux or both, from the apoplast into the cell or from the cytosol into the ER compartment. Auxin transporters have been largely studied in the dicotyledon model species Arabidopsis, but there is increasing evidence of their role in auxin regulated development in monocotyledon species. In monocots, families of auxin transporters are enlarged and often include duplicated genes and proteins with high sequence similarity. Some of these proteins underwent sub- and neo-functionalization with substantial modification to their structure and expression in organs such as adventitious roots, panicles, tassels and ears. Most of the present information on monocot auxin transporters function derives from studies conducted in rice, maize, sorghum and Brachypodium using pharmacological applications (PAT inhibitors or down-/up-regulation (over-expression and RNAi of candidate genes. Gene expression studies and comparison of predicted protein structures have also increased our knowledge of the role of PAT in monocots. However, knockout mutants and functional characterization of single genes are still scarce and the future availability of such resources will prove crucial to elucidate the role of auxin transporters in monocot development.

  4. Diversification and expression of the PIN, AUX/LAX and ABCB families of putative auxin transporters in Populus

    Directory of Open Access Journals (Sweden)

    Nicola eCarraro

    2012-02-01

    Full Text Available Intercellular transport of the plant hormone auxin is mediated by three families of membrane-bound protein carriers, with the PIN and ABCB families coding primarily for efflux proteins and the AUX/LAX family coding for influx proteins. In the last decade our understanding of gene and protein function for these transporters in Arabidopsis has expanded rapidly but very little is known about their role in woody plant development. Here we present a comprehensive account of all three families in the model woody species Populus, including chromosome distribution, protein structure, quantitative gene expression, and evolutionary relationships. The PIN and AUX/LAX gene families in Populus comprise 16 and 8 members respectively, and show evidence for the retention of paralogs following a relatively recent whole genome duplication. There is also evidence for differential expression across tissues within many gene pairs. The ABCB family is previously undescribed in Populus and includes 20 members, showing a much deeper evolutionary history including both tandem and whole genome duplication as well as probable loss. A striking number of these transporters are expressed in developing Populus stems and we suggest that evolutionary and structural relationships with known auxin transporters in Arabidopsis can point toward candidate genes for further study in Populus. This is especially important for the ABCBs, which is a large family and includes members in Arabidopsis that are able to transport other substrates in addition to auxin. Protein modeling, sequence alignment and expression data all point to ABCB1.1 as a likely auxin transport protein in Populus. Given that basipetal auxin flow through the cambial zone shapes the development of woody stems, it is important that we identify the full complement of proteins involved in this process. This work should lay the foundation for studies targeting specific proteins for functional characterization and in situ

  5. myo-Inositol-1-phosphate synthase is required for polar auxin transport and organ development

    KAUST Repository

    Chen, Hao

    2010-06-01

    myo-Inositol-1-phosphate synthase is a conserved enzyme that catalyzes the first committed and rate-limiting step in inositol biosynthesis. Despite its wide occurrence in all eukaryotes, the role of myo-inositol-1-phosphate synthase and de novo inositol biosynthesis in cell signaling and organism development has been unclear. In this study, we isolated loss-of-function mutants in the Arabidopsis MIPS1 gene from different ecotypes. It was found that all mips1 mutants are defective in embryogenesis, cotyledon venation patterning, root growth, and root cap development. The mutant roots are also agravitropic and have reduced basipetal auxin transport. mips1 mutants have significantly reduced levels of major phosphatidylinositols and exhibit much slower rates of endocytosis. Treatment with brefeldin A induces slower PIN2 protein aggregation in mips1, indicating altered PIN2 trafficking. Our results demonstrate that MIPS1 is critical for maintaining phosphatidylinositol levels and affects pattern formation in plants likely through regulation of auxin distribution. © 2010 by The American Society for Biochemistry and Molecular Biology, Inc.

  6. Regulation of polar auxin transport by protein and lipid kinases.

    Science.gov (United States)

    Armengot, Laia; Marquès-Bueno, Maria Mar; Jaillais, Yvon

    2016-07-01

    The directional transport of auxin, known as polar auxin transport (PAT), allows asymmetric distribution of this hormone in different cells and tissues. This system creates local auxin maxima, minima, and gradients that are instrumental in both organ initiation and shape determination. As such, PAT is crucial for all aspects of plant development but also for environmental interaction, notably in shaping plant architecture to its environment. Cell to cell auxin transport is mediated by a network of auxin carriers that are regulated at the transcriptional and post-translational levels. Here we review our current knowledge on some aspects of the 'non-genomic' regulation of auxin transport, placing an emphasis on how phosphorylation by protein and lipid kinases controls the polarity, intracellular trafficking, stability, and activity of auxin carriers. We describe the role of several AGC kinases, including PINOID, D6PK, and the blue light photoreceptor phot1, in phosphorylating auxin carriers from the PIN and ABCB families. We also highlight the function of some receptor-like kinases (RLKs) and two-component histidine kinase receptors in PAT, noting that there are probably RLKs involved in co-ordinating auxin distribution yet to be discovered. In addition, we describe the emerging role of phospholipid phosphorylation in polarity establishment and intracellular trafficking of PIN proteins. We outline these various phosphorylation mechanisms in the context of primary and lateral root development, leaf cell shape acquisition, as well as root gravitropism and shoot phototropism. PMID:27242371

  7. Polar auxin transport is essential for gall formation by Pantoea agglomerans on Gypsophila.

    Science.gov (United States)

    Chalupowicz, Laura; Weinthal, Dan; Gaba, Victor; Sessa, Guido; Barash, Isaac; Manulis-Sasson, Shulamit

    2013-02-01

    The virulence of the bacterium Pantoea agglomerans pv. gypsophilae (Pag) on Gypsophila paniculata depends on a type III secretion system (T3SS) and its effectors. The hypothesis that plant-derived indole-3-acetic acid (IAA) plays a major role in gall formation was examined by disrupting basipetal polar auxin transport with the specific inhibitors 2,3,5-triiodobenzoic acid (TIBA) and N-1-naphthylphthalamic acid (NPA). On inoculation with Pag, galls developed in gypsophila stems above but not below lanolin rings containing TIBA or NPA, whereas, in controls, galls developed above and below the rings. In contrast, TIBA and NPA could not inhibit tumour formation in tomato caused by Agrobacterium tumefaciens. The colonization of gypsophila stems by Pag was reduced below, but not above, the lanolin-TIBA ring. Following Pag inoculation and TIBA treatment, the expression of hrpL (a T3SS regulator) and pagR (a quorum-sensing transcriptional regulator) decreased four-fold and that of pthG (a T3SS effector) two-fold after 24 h. Expression of PIN2 (a putative auxin efflux carrier) increased 35-fold, 24 h after Pag inoculation. However, inoculation with a mutant in the T3SS effector pthG reduced the expression of PIN2 by two-fold compared with wild-type infection. The results suggest that pthG might govern the elevation of PIN2 expression during infection, and that polar auxin transport-derived IAA is essential for gall initiation. PMID:23083316

  8. PIN6 auxin transporter at endoplasmic reticulum and plasma membrane mediates auxin homeostasis and organogenesis in Arabidopsis.

    Science.gov (United States)

    Simon, Sibu; Skůpa, Petr; Viaene, Tom; Zwiewka, Marta; Tejos, Ricardo; Klíma, Petr; Čarná, Mária; Rolčík, Jakub; De Rycke, Riet; Moreno, Ignacio; Dobrev, Petre I; Orellana, Ariel; Zažímalová, Eva; Friml, Jiří

    2016-07-01

    Plant development mediated by the phytohormone auxin depends on tightly controlled cellular auxin levels at its target tissue that are largely established by intercellular and intracellular auxin transport mediated by PIN auxin transporters. Among the eight members of the Arabidopsis PIN family, PIN6 is the least characterized candidate. In this study we generated functional, fluorescent protein-tagged PIN6 proteins and performed comprehensive analysis of their subcellular localization and also performed a detailed functional characterization of PIN6 and its developmental roles. The localization study of PIN6 revealed a dual localization at the plasma membrane (PM) and endoplasmic reticulum (ER). Transport and metabolic profiling assays in cultured cells and Arabidopsis strongly suggest that PIN6 mediates both auxin transport across the PM and intracellular auxin homeostasis, including the regulation of free auxin and auxin conjugates levels. As evidenced by the loss- and gain-of-function analysis, the complex function of PIN6 in auxin transport and homeostasis is required for auxin distribution during lateral and adventitious root organogenesis and for progression of these developmental processes. These results illustrate a unique position of PIN6 within the family of PIN auxin transporters and further add complexity to the developmentally crucial process of auxin transport. PMID:27240710

  9. Use of membrane vesicles as a simplified system for studying auxin transport of auxin: Progress report

    International Nuclear Information System (INIS)

    Indoleacetic acid (IAA), the auxin regulating growth, is transported polarly in plants. IAA stimulates a rapid increase in the rate of electrogenic proton secretion by the plasma membrane. This not only increases the magnitude of the pH and electrical gradients providing the driving force for polar auxin transport and uptake of sugars, amino acids and inorganic ions, but, by acidifying the cell wall, also leads to growth. We find that auxin uptake by membrane vesicles isolated from actively growing plant tissues exhibits some of the same properties as by cells: the accumulation depends on the pH gradient, is saturable and specific for auxin, and enhanced by herbicides that inhibit polar auxin transport. We are using accumulation of a radioactive weak acid to quantify the pH gradient and distribution of fluorescent cyanine dyes to monitor the membrane potential. The magnitude of IAA accumulation exceeds that predicted from the pH gradient, and in the absence of a pH gradient, a membrane potential fails to support any auxin accumulation, leading to the conclusion that the transmembrane potential is not a significant driving force for auxin accumulation in this system. Since increasing the external ionic strength decreases saturable auxin accumulation, we are investigating how modifying the surface potential of the vesicles affects the interaction of the amphipathic IAA molecules with the membranes and whether protein modifying reagents affect the saturability and stimulation by NPA. These studies should provide information on the location and function of the auxin binding site and may enable us to identify the solubilized protein. 5 refs

  10. Use of membrane vesicles as a simplified system for studying auxin transport of auxin: Progress report

    Energy Technology Data Exchange (ETDEWEB)

    Goldsmith, M.H.M.

    1986-01-01

    Indoleacetic acid (IAA), the auxin regulating growth, is transported polarly in plants. IAA stimulates a rapid increase in the rate of electrogenic proton secretion by the plasma membrane. This not only increases the magnitude of the pH and electrical gradients providing the driving force for polar auxin transport and uptake of sugars, amino acids and inorganic ions, but, by acidifying the cell wall, also leads to growth. We find that auxin uptake by membrane vesicles isolated from actively growing plant tissues exhibits some of the same properties as by cells: the accumulation depends on the pH gradient, is saturable and specific for auxin, and enhanced by herbicides that inhibit polar auxin transport. We are using accumulation of a radioactive weak acid to quantify the pH gradient and distribution of fluorescent cyanine dyes to monitor the membrane potential. The magnitude of IAA accumulation exceeds that predicted from the pH gradient, and in the absence of a pH gradient, a membrane potential fails to support any auxin accumulation, leading to the conclusion that the transmembrane potential is not a significant driving force for auxin accumulation in this system. Since increasing the external ionic strength decreases saturable auxin accumulation, we are investigating how modifying the surface potential of the vesicles affects the interaction of the amphipathic IAA molecules with the membranes and whether protein modifying reagents affect the saturability and stimulation by NPA. These studies should provide information on the location and function of the auxin binding site and may enable us to identify the solubilized protein. 5 refs.

  11. Uptake of auxins into membrane vesicles isolated from pea stems: an in vitro auxin transport system

    Energy Technology Data Exchange (ETDEWEB)

    Slone, J.H.

    1985-01-01

    The objective of this research was to test the applicability of the chemiosmotic theory of auxin transport to a subcellular system. Membrane vesicles were isolated from the basal portion of the third internode of etiolated pea plants (Pisum sativum L. var. Alaska) by differential centrifugation. Uptake of auxin was determined by adding /sup 14/C-labeled indoleacetic acid (IAA) to vesicles. Nigericin, a monovalent cation ionophore, and the electrogenic protonophore, carbonyl-cyanide m-chlorophenylhydrazone (CCCP), at micromolar concentrations abolished saturable uptake. Bursting vesicles by sonication, osmotic shock and freeze/thawing also eliminated saturable uptake. As the temperature increased from 0 to 30/sup 0/C, saturable uptake decreased markedly. Nonsaturable auxin uptake was less affected by these treatments. The pH gradient-dependent uptake of auxin appeared to be a transmembrane uptake of auxin into the vesicles rather than surface binding. Unlabeled IAA, 2,4-dichlorophenoxyacetic acid (2,4-D) and 2-naphthaleneacetic acid (NAA) at low concentrations reduced the saturable accumulation of (/sup 14/C)IAA in vesicles, while phenylacetic acid, benzoic acid, and 1-NAA were effective only at high concentrations. Kinetic analysis revealed two types of sites: a high affinity site with an uptake capacity of 25 to 40 pmoles/g tissue, and a low affinity site with an uptake capacity of 260 to 600 pmole/g tissue, fresh wt. In conclusion, several principal elements of an auxin transport system, as specific by the chemiosmotic theory of polar auxin transport, were present in membrane vesicles isolated from relatively mature pea stem tissue. However, one important aspect of the theory was not demonstrated in this in vitro system - a TIBA/NPA-sensitive auxin efflux. The kinetics and specificity of auxin uptake strongly suggested that this system was physiologically significant.

  12. Role of actin in auxin transport and transduction of gravity

    Science.gov (United States)

    Hu, S.; Basu, S.; Brady, S.; Muday, G.

    Transport of the plant hormone auxin is polar and the direction of the hormone movement appears to be controlled by asymmetric distribution of auxin transport protein complexes. Changes in the direction of auxin transport are believed to drive asymmetric growth in response to changes in the gravity vector. To test the possibility that asymmetric distribution of the auxin transport protein complex is mediated by attachment to the actin cytoskeleton, a variety of experimental approaches have been used. The most direct demonstration of the role of the actin cytoskeleton in localization of the protein complex is the ability of one protein in this complex to bind to affinity columns containing actin filaments. Additionally, treatments of plant tissues with drugs that fragment the actin c toskeleton reducey polar transport. In order to explore this actin interaction and the affect of gravity on auxin transport and developmental polarity, embryos of the brown alga, Fucus have been examined. Fucus zygotes are initially symmetrical, but develop asymmetry in response to environmental gradients, with light gradients being the best- characterized signal. Gravity will polarize these embryos and gravity-induced polarity is randomized by clinorotation. Auxin transport also appears necessary for environmental controls of polarity, since auxin efflux inhibitors perturb both photo- and gravity-polarization at a very discrete temporal window within six hours after fertilization. The actin cytoskeleton has previously been shown to reorganize after fertilization of Fucus embryos leading to formation of an actin patch at the site of polar outgrowth. These actin patches still form in Fucus embryos treated with auxin efflux inhibitors, yet the position of these patches is randomized. Together, these results suggest that there are connections between the actin cytoskeleton, auxin transport, and gravity oriented growth and development. (Supported by NASA Grant: NAG2-1203)

  13. Close relationships between polar auxin transport and graviresponse in plants.

    Science.gov (United States)

    Ueda, J; Miyamoto, K; Uheda, E; Oka, M; Yano, S; Higashibata, A; Ishioka, N

    2014-01-01

    Gravitational force on Earth is one of the major environmental factors affecting plant growth and development. Spacecraft and the International Space Station (ISS), and a three-dimensional (3-D) clinostat have been available to clarify the effects of gravistimulation on plant growth and development in space and on ground conditions, respectively. Under a stimulus-free environment such as space conditions, plants show a growth and developmental habit designated as 'automorphosis' or 'automorphogenesis'. Recent studies in hormonal physiology, together with space and molecular biology, have demonstrated the close relationships between automorphosis and polar auxin transport. Reduced polar auxin transport in space conditions, or induced by the application of polar auxin transport inhibitors, substantially induced automorphosis or automorphosis-like growth and development, indicating that polar auxin transport is responsible for graviresponse in plants. This concise review covers graviresponse in plants and automorphosis observed in space conditions, and polar auxin transport related to graviresponse in etiolated Alaska and ageotropum pea seedlings. Molecular aspects of polar auxin transport clarified in recent studies are also described. PMID:24128007

  14. Cell wall pH and auxin transport velocity

    Science.gov (United States)

    Hasenstein, K. H.; Rayle, D.

    1984-01-01

    According to the chemiosmotic polar diffusion hypothesis, auxin pulse velocity and basal secretion should increase with decreasing cell wall pH. Experiments were designed to test this prediction. Avena coleoptile sections were preincubated in either fusicoccin (FC), cycloheximide, pH 4.0, or pH 8.0 buffer and subsequently their polar transport capacities were determined. Relative to controls, FC enhanced auxin (IAA) uptake while CHI and pH 8.0 buffer reduced IAA uptake. Nevertheless, FC reduced IAA pulse velocity while cycloheximide increased velocity. Additional experiments showed that delivery of auxin to receivers is enhanced by increased receiver pH. This phenomenon was overcome by a pretreatment of the tissue with IAA. Our data suggest that while acidic wall pH values facilitate cellular IAA uptake, they do not enhance pulse velocity or basal secretion. These findings are inconsistent with the chemiosmotic hypothesis for auxin transport.

  15. S-nitrosylation mediates nitric oxide -auxin crosstalk in auxin signaling and polar auxin transport

    Science.gov (United States)

    Nitric oxide (NO) and auxin phytohormone cross talk has been implicated in plant development and growth. Addition and removal of NO moieties to cysteine residues of proteins, is termed S-nitrosylation and de-nitrosylation, respectively and functions as an on/off switch of protein activity. This dyna...

  16. Auxin transport is sufficient to generate a maximumand gradient guiding root growth

    NARCIS (Netherlands)

    Grieneisen, V.; Xu, J.; Marée, A.F.M.; Hogeweg, P.; Scheres, B.J.G.

    2007-01-01

    The plant growth regulator auxin controls cell identity, cell division and cell expansion. Auxin efflux facilitators (PINs) are associated with auxin maxima in distal regions of both shoots and roots. Here we model diffusion and PIN-facilitated auxin transport in and across cells within a structured

  17. The acropetal effects of indole-3-acetic acid in isolated shoot segments of Acer pseudoplatanus L. II. Possible regulation by a vectorial fieid of auxin waves

    Directory of Open Access Journals (Sweden)

    Jacek A. Adamczyk

    2014-02-01

    Full Text Available The acropetal effects of auxin on elongation of axillary buds and on modulation of the wave-like pattern of basipetal efflux of natural auxin to agar from Acer pseudoplatanus L. shoots were studied. When synthetic IAA was applied to cut surfaces of one of two branches the elongation growth of buds situated on the opposite branch was retarded, suggesting regulation independent of the direct action of the molecules of the applied IAA. Oscillations in basipetal transport of natural auxin along the stem segments were observed corroborating the results of other authors using different tree species. Apical application of synthetic IAA for 1 hour to the lateral branch caused a phase shift of the wave-like pattern of basipetal efflux of natural auxin, when the stem segment above the treated branch was sectioned. The same effect was observed evoked by the laterally growing branch which is interpreted as an effect of natural auxin produced by the actively growing shoot. These modulations could be propagated acropetally at a rate excluding direct action of auxin molecules at the sites of measurement. The results seem to corroborate the hypothesis suggesting that auxin is involved in acropetal regulation of shoot apex growth through its effect upon modulation of the vectorial field which arises when the auxin-waves translocate in cambium.

  18. Auxin physiology of the tomato mutant diageotropica

    Science.gov (United States)

    Daniel, S. G.; Rayle, D. L.; Cleland, R. E.

    1989-01-01

    The tomato (Lycopersicon esculentum, Mill.) mutant diageotropica (dgt) exhibits biochemical, physiological, and morphological abnormalities that suggest the mutation may have affected a primary site of auxin perception or action. We have compared two aspects of the auxin physiology of dgt and wild-type (VFN8) seedlings: auxin transport and cellular growth parameters. The rates of basipetal indole-3-acetic acid (IAA) polar transport are identical in hypocotyl sections of the two genotypes, but dgt sections have a slightly greater capacity for IAA transport. 2,3,5-Triiodobenzoic acid and ethylene reduce transport in both mutant and wild-type sections. The kinetics of auxin uptake into VFN8 and dgt sections are nearly identical. These results make it unlikely that an altered IAA efflux carrier or IAA uptake symport are responsible for the pleiotropic effects resulting from the dgt mutation. The lack of auxin-induced cell elongation in dgt plants is not due to insufficient turgor, as the osmotic potential of dgt cell sap is less (more negative) than that of VFN8. An auxin-induced increase in wall extensibility, as measured by the Instron technique, only occurs in the VFN8 plants. These data suggest dgt hypocotyls suffer a defect in the sequence of events culminating in auxin-induced cell wall loosening.

  19. Auxin physiology of the tomato mutant diageotropical

    Energy Technology Data Exchange (ETDEWEB)

    Daniel, S.G.; Rayle, D.L. (San Diego State Univ., CA (USA)); Cleland, R.E. (Univ. of Washington, Seattle (USA))

    1989-11-01

    The tomato (Lycopersicon esculentum, Mill.) mutant diageotropica (dgt) exhibits biochemical, physiological, and morphological abnormalities that suggest the mutation may have affected a primary site of auxin perception or action. We have compared two aspects of the auxin physiology of dgt and wild-type (VFN8) seedlings: auxin transport and cellular growth parameters. The rates of basipetal indole-3-acetic acid (IAA) polar transport are identical in hypocotyl sections of the two genotypes, but dgt sections have a slightly greater capacity for IAA transport. 2,3,5-Triiodobenzoic acid and ethylene reduce transport in both mutant and wild-type sections. The kinetics of auxin uptake into VFN8 and dgt sections are nearly identical. These results make it unlikely that an altered IAA efflux carrier or IAA uptake symport are responsible for the pleiotropic effects resulting from the dgt mutation. The lack of auxin-induced cell elongation in dgt plants is not due to insufficient turgor, as the osmotic potential of dgt cell sap is less (more negative) than that of VFN8. An auxin-induced increase in wall extensibility, as measured by the Instron technique, only occurs in the VFN8 plants. These data suggest dgt hypocotyls suffer a defect in the sequence of events culminating in auxin-induced cell wall loosening.

  20. The Role of PIN Auxin Efflux Carriers in Polar Auxin Transport and Accumulation and Their Effect on Shaping Maize Development

    Institute of Scientific and Technical Information of China (English)

    Cristian Forestan; Serena Varotto

    2012-01-01

    In plants,proper seed development and the continuing post-embryonic organogenesis both require that different cell types are correctly differentiated in response to internal and external stimuli.Among internal stimuli,plant hormones and particularly auxin and its polar transport(PAT)have been shown to regulate a multitude of plant physiological processes during vegetative and reproductive development.Although our current auxin knowledge is almost based on the results from researches on the eudicot Arabidopsis thaliana,during the last few years,many studies tried to transfer this knowledge from model to crop species,maize in particular.Applications of auxin transport inhibitors,mutant characterization,and molecular and cell biology approaches,facilitated by the sequencing of the maize genome,allowed the identification of genes involved in auxin metabolism,signaling,and particularly in polar auxin transport.PIN auxin efflux carriers have been shown to play an essential role in regulating PAT during both seed and post-embryonic development in maize.In this review,we provide a summary of the recent findings on PIN-mediated polar auxin transport during maize development.Similarities and differences between maize and Arabidopsis are analyzed and discussed,also considering that their different plant architecture depends on the differentiation of structures whose development is controlled by auxins.

  1. The role of PIN auxin efflux carriers in polar auxin transport and accumulation and their effect on shaping maize development.

    Science.gov (United States)

    Forestan, Cristian; Varotto, Serena

    2012-07-01

    In plants, proper seed development and the continuing post-embryonic organogenesis both require that different cell types are correctly differentiated in response to internal and external stimuli. Among internal stimuli, plant hormones and particularly auxin and its polar transport (PAT) have been shown to regulate a multitude of plant physiological processes during vegetative and reproductive development. Although our current auxin knowledge is almost based on the results from researches on the eudicot Arabidopsis thaliana, during the last few years, many studies tried to transfer this knowledge from model to crop species, maize in particular. Applications of auxin transport inhibitors, mutant characterization, and molecular and cell biology approaches, facilitated by the sequencing of the maize genome, allowed the identification of genes involved in auxin metabolism, signaling, and particularly in polar auxin transport. PIN auxin efflux carriers have been shown to play an essential role in regulating PAT during both seed and post-embryonic development in maize. In this review, we provide a summary of the recent findings on PIN-mediated polar auxin transport during maize development. Similarities and differences between maize and Arabidopsis are analyzed and discussed, also considering that their different plant architecture depends on the differentiation of structures whose development is controlled by auxins. PMID:22186966

  2. Effects of cations on hormone transport in primary roots of Zea mays

    Science.gov (United States)

    Hasenstein, K. H.; Evans, M. L.

    1988-01-01

    We examined the influence of aluminum and calcium (and certain other cations) on hormone transport in corn roots. When aluminum was applied unilaterally to the caps of 15 mm apical root sections the roots curved strongly away from the aluminum. When aluminum was applied unilaterally to the cap and 3H-indole-3-acetic acid was applied to the basal cut surface twice as much radioactivity (assumed to be IAA) accumulated on the concave side of the curved root as on the convex side. Auxin transport in the apical region of intact roots was preferentially basipetal, with a polarity (basipetal transport divided by acropetal transport) of 6.3. In decapped 5 mm apical root segments, auxin transport was acropetally polar (polarity = 0.63). Application of aluminum to the root cap strongly promoted acropetal transport of auxin reducing polarity from 6.3 to 2.1. Application of calcium to the root cap enhanced basipetal movement of auxin, increasing polarity from 6.3 to 7.6. Application of the calcium chelator, ethylene-glycol-bis-(beta-aminoethylether)-N,N,N',N'-tetraacetic acid, greatly decreased basipetal auxin movement, reducing polarity from 6.3 to 3.7. Transport of label after application of tritiated abscisic acid showed no polarity and was not affected by calcium or aluminum. The results indicate that the root cap is particularly important in maintaining basipetal polarity of auxin transport in primary roots of corn. The induction of root curvature by unilateral application of aluminum or calcium to root caps is likely to result from localized effects of these ions on auxin transport. The findings are discussed relative to the possible role of calcium redistribution in the gravitropic curvature of roots and the possibility of calmodulin involvement in the action of calcium and aluminum on auxin transport.

  3. Effects of auxin transport inhibitors on gibberellins in pea

    International Nuclear Information System (INIS)

    The effects of the auxin transport inhibitors 2,3,5-triiodobenzoic acid (TIBA), 9-hydroxyfluorene-9-carboxylic acid (HFCA), and 1-N-naphthylphthalamic acid (NPA) on gibberellins (GAs) in the garden pea (Pisum sativum L.) were studied. Application of these compounds to elongating internodes of intact wild type plants reduced markedly the endogenous level of the bioactive gibberellin A1. (GA1) below the application site. Indole-3-acetic acid (IAA) levels were also reduced, as was internode elongation. The auxin transport inhibitors did not affect the level of endogenous GA1 above the application site markedly, nor that of GA1 precursors above or below it. When plants were treated with [13C,3H]GA20, TIBA reduced dramatically the level of [13C,3H]GA1 recovered below the TIBA application site. The internodes treated with auxin transport inhibitors appeared to be still in the phase where endogenous GA1 affects elongation, as indicated by the strong response to applied GA1 by internodes of a GA1-deficient line at the same stage of expansion. On the basis of the present results it is suggested that caution be exercised when attributing the developmental effects of auxin transport inhibitors to changes in IAA level alone

  4. Flavonoids act as negative regulators of auxin transport in vivo in arabidopsis

    Science.gov (United States)

    Brown, D. E.; Rashotte, A. M.; Murphy, A. S.; Normanly, J.; Tague, B. W.; Peer, W. A.; Taiz, L.; Muday, G. K.

    2001-01-01

    Polar transport of the plant hormone auxin controls many aspects of plant growth and development. A number of synthetic compounds have been shown to block the process of auxin transport by inhibition of the auxin efflux carrier complex. These synthetic auxin transport inhibitors may act by mimicking endogenous molecules. Flavonoids, a class of secondary plant metabolic compounds, have been suggested to be auxin transport inhibitors based on their in vitro activity. The hypothesis that flavonoids regulate auxin transport in vivo was tested in Arabidopsis by comparing wild-type (WT) and transparent testa (tt4) plants with a mutation in the gene encoding the first enzyme in flavonoid biosynthesis, chalcone synthase. In a comparison between tt4 and WT plants, phenotypic differences were observed, including three times as many secondary inflorescence stems, reduced plant height, decreased stem diameter, and increased secondary root development. Growth of WT Arabidopsis plants on naringenin, a biosynthetic precursor to those flavonoids with auxin transport inhibitor activity in vitro, leads to a reduction in root growth and gravitropism, similar to the effects of synthetic auxin transport inhibitors. Analyses of auxin transport in the inflorescence and hypocotyl of independent tt4 alleles indicate that auxin transport is elevated in plants with a tt4 mutation. In hypocotyls of tt4, this elevated transport is reversed when flavonoids are synthesized by growth of plants on the flavonoid precursor, naringenin. These results are consistent with a role for flavonoids as endogenous regulators of auxin transport.

  5. Disruption of the polar auxin transport system in cotton seedlings following treatment with the defoliant thidiazuron. [Gossypium hirsutum L. cv LG102

    Energy Technology Data Exchange (ETDEWEB)

    Suttle, J.C.

    1988-01-01

    The effect of the defoliant thidiazuron (TDZ) on basipetal auxin transport in petiole segments isolated from cotton (Gossypium hirsutum L. cv LG102) seedlings was examined using the donor/receiver agar block technique. Treatment of intact seedlings with TDZ at concentrations of 1 micromolar or greater resulted in a dose-dependent inhibition of /sup 14/C-IAA transport in petiole segment isolated 1 or 2 days after treatment. Using 100 micromolar TDZ, the inhibition was detectable 19 hours after treatment and was complete by 27 hours. Both leaves and petiole segments exhibited a marked increase in ethylene production following treatment with TDZ at concentrations of 0.1 micromolar or greater. The involvement of ethylene in this TDA response was evaluated by examining the effects of two inhibitors of ethylene action: silver thiosulfate, 2,5-norbornadiene. One day after treatment, both inhibitors effectively antagonized the TDZ-induced inhibition of auxin transport. Two days after TDZ treatment both inhibitors were ineffective. The decrease in IAA transport in TDZ treated tissues was associated with increased metabolism of IAA. The transport of /sup 14/C-2,4-dichlorophenoxyacetic acid was also inhibited by TDZ treatment. This inhibition was not accompanied by increased metabolism. Incorporation of TDZ into the receiver blocks had no effect on auxin transport. The ability of the phytotropin N-1-naphthylphthalamic acid to stimulate IAA uptake from a bathing medium was reduced in TDZ-treated tissues. This reduction is thought to reflect a decline in the auxin efflux system following TDZ treatment.

  6. Calcium elicited asymmetric auxin transport in gravity influenced root segments

    Science.gov (United States)

    Edwards, K. L.

    1984-01-01

    Auxin is a prime candidate for regulating and modulating the differential growth response of primary corn roots to gravity. Auxin, indole-3-acetic acid (IAA), both promotes and inhibits root elongation rapidly within a narrow concentration range. Thus growth regulation would require only small changes in the short lag period for initiation of gravitropism. Since auxin is transported to/through the zone of elongation toward the meristem, it may serve as a direct communication link between the zone of elongation, site of gravitropic response, and the root cap (RC), site of gravity perception. When auxin transport is inhibited, gravitropism is also inhibited. Napthylpthalamic acid (NPA) is one such inhibitor. It inhibits gravitropism only when applied to the apical growing and dividing region of the root. Application at the basal end of the root does not influence gravitropic NPA causes upward curvature when applied to the upper surface of horizontal, two day-old, intact corn roots. This effect is countered by application of IAA to the opposite side.

  7. PIN protein phosphorylation by plant AGC3 kinases and its role in polar auxin transport

    NARCIS (Netherlands)

    Huang, Fang

    2010-01-01

    Polar cell-to-cell transport of plant hormone auxin mediated by plasma membrane (PM)-localized PIN-FORMED (PIN) auxin efflux carriers generates auxin gradients that provide positional information for various plant developmental processes. The apical-basal polar localization of the PIN proteins that

  8. The exocyst complex contributes to PIN auxin efflux carrier recycling and polar auxin transport in Arabidopsis

    Czech Academy of Sciences Publication Activity Database

    Drdová, Edita; Synek, Lukáš; Pečenková, Tamara; Hála, Michal; Kulich, I.; Fowler, J.E.; Murphy, A.S.; Žárský, Viktor

    2013-01-01

    Roč. 73, č. 5 (2013), s. 709-719. ISSN 0960-7412 R&D Projects: GA ČR GPP501/11/P853; GA ČR(CZ) GAP305/11/1629; GA MŠk(CZ) LC06034; GA AV ČR KJB600380802 Grant ostatní: GA MŠk(CZ) ME10033 Institutional research plan: CEZ:AV0Z50380511 Keywords : exocyst * polar auxin transport * PIN recycling Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 6.815, year: 2013

  9. Auxin distribution and transport during embryogenesis and seed germi-nation of Arabidopsis

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Auxin distribution during embryogenesis and seed germination were studied with transgenic Arabidopsis plants expressing GUS gene driven by a synthetic DR5 promoter, an auxin responsive promoter. The results showed that GUS activity is higher in ends of hypophysis and cotyledon primordia of heart-, torpedo- and cotyledon-stage embryos, leaf tip area, lateral root primordia, root apex and cotyledon of young seedlings.And GUS accumulated in root apex of the seedlings grown on auxin transport inhibitor containing media.All these suggested that above-mentioned part of the organs and tissues have a higher level of auxin, and auxin polar transport inhibitor could cause the accumulation of auxin in root apex. And auxin transport inhibitor also resulted in aberration of Arabidopsis leaf pattern formation, root gravitropism and elongation.

  10. Connective Auxin Transport in the Shoot Facilitates Communication between Shoot Apices.

    Science.gov (United States)

    Bennett, Tom; Hines, Geneviève; van Rongen, Martin; Waldie, Tanya; Sawchuk, Megan G; Scarpella, Enrico; Ljung, Karin; Leyser, Ottoline

    2016-04-01

    The bulk polar movement of the plant signaling molecule auxin through the stem is a long-recognized but poorly understood phenomenon. Here we show that the highly polar, high conductance polar auxin transport stream (PATS) is only part of a multimodal auxin transport network in the stem. The dynamics of auxin movement through stems are inconsistent with a single polar transport regime and instead suggest widespread low conductance, less polar auxin transport in the stem, which we term connective auxin transport (CAT). The bidirectional movement of auxin between the PATS and the surrounding tissues, mediated by CAT, can explain the complex auxin transport kinetics we observe. We show that the auxin efflux carriers PIN3, PIN4, and PIN7 are major contributors to this auxin transport connectivity and that their activity is important for communication between shoot apices in the regulation of shoot branching. We propose that the PATS provides a long-range, consolidated stream of information throughout the plant, while CAT acts locally, allowing tissues to modulate and be modulated by information in the PATS. PMID:27119525

  11. Connective Auxin Transport in the Shoot Facilitates Communication between Shoot Apices

    Science.gov (United States)

    Bennett, Tom; Hines, Geneviève; van Rongen, Martin; Sawchuk, Megan G.; Scarpella, Enrico; Ljung, Karin

    2016-01-01

    The bulk polar movement of the plant signaling molecule auxin through the stem is a long-recognized but poorly understood phenomenon. Here we show that the highly polar, high conductance polar auxin transport stream (PATS) is only part of a multimodal auxin transport network in the stem. The dynamics of auxin movement through stems are inconsistent with a single polar transport regime and instead suggest widespread low conductance, less polar auxin transport in the stem, which we term connective auxin transport (CAT). The bidirectional movement of auxin between the PATS and the surrounding tissues, mediated by CAT, can explain the complex auxin transport kinetics we observe. We show that the auxin efflux carriers PIN3, PIN4, and PIN7 are major contributors to this auxin transport connectivity and that their activity is important for communication between shoot apices in the regulation of shoot branching. We propose that the PATS provides a long-range, consolidated stream of information throughout the plant, while CAT acts locally, allowing tissues to modulate and be modulated by information in the PATS. PMID:27119525

  12. A chemical pollen suppressant inhibits auxin-induced growth in maize coleoptile sections

    Energy Technology Data Exchange (ETDEWEB)

    Vesper, M.J. (Univ. of Dayton, OH (USA)); Cross, J.W. (Sogetal, Inc., Hayward, CA (USA))

    1990-05-01

    Chemical inhibitors of pollen development having a phenylcinnoline carboxylate structure were found to inhibit IAA- and 1-NAA-induced growth in maize coleoptile sections. The inhibitor (100 {mu}M) used in these experiments caused approx. 35% reduction in auxin-induced growth over the auxin concentration range of 0.3 to 100 {mu}M. Growth inhibition was noted as a lengthening of the latent period and a decrease in the rate of an auxin-induced growth response. An acid growth response to pH 5 buffer in abraded sections was not impaired. The velocity of basipetal transport of ({sup 3}H)IAA through the coleoptile sections also was not inhibited by the compound, nor was uptake of ({sup 3}H)IAA. Similarly, the inhibitor does not appear to alter auxin-induced H{sup +} secretion. We suggest that the agent targets some other process necessary for auxin-dependent growth.

  13. Auxin transport through non-hair cells sustains root-hair development

    OpenAIRE

    Jones, Angharad R.; Kramer, Eric M.; Knox, Kirsten; Swarup, Ranjan; Bennett, Malcolm J; Lazarus, Colin M.; Leyser, H. M. Ottoline; Grierson, Claire S.

    2008-01-01

    The plant hormone auxin controls root epidermal cell development in a concentration-dependent manner 1-3. Root hairs are produced on a subset of epidermal cells as they increase in distance from the root tip. Auxin is required for their initiation 4-7 and continued growth 8-11, but little is known about its distribution in this region of the root. Counter to the expectation that hair cells might require active auxin influx to ensure auxin supply, we did not detect the auxin-influx transporter...

  14. Auxin dynamics after decapitation are not correlated with the initial growth of axillary buds.

    Science.gov (United States)

    Morris, Suzanne E; Cox, Marjolein C H; Ross, John J; Krisantini, Santi; Beveridge, Christine A

    2005-07-01

    One of the first and most enduring roles identified for the plant hormone auxin is the mediation of apical dominance. Many reports have claimed that reduced stem indole-3-acetic acid (IAA) levels and/or reduced basipetal IAA transport directly or indirectly initiate bud growth in decapitated plants. We have tested whether auxin inhibits the initial stage of bud release, or subsequent stages, in garden pea (Pisum sativum) by providing a rigorous examination of the dynamics of auxin level, auxin transport, and axillary bud growth. We demonstrate that after decapitation, initial bud growth occurs prior to changes in IAA level or transport in surrounding stem tissue and is not prevented by an acropetal supply of exogenous auxin. We also show that auxin transport inhibitors cause a similar auxin depletion as decapitation, but do not stimulate bud growth within our experimental time-frame. These results indicate that decapitation may trigger initial bud growth via an auxin-independent mechanism. We propose that auxin operates after this initial stage, mediating apical dominance via autoregulation of buds that are already in transition toward sustained growth. PMID:15965021

  15. Auxin transport at cellular level: new insights supported by mathematical modelling

    Czech Academy of Sciences Publication Activity Database

    Hošek, Petr; Kubeš, Martin; Laňková, Martina; Dobrev, Petre; Klíma, Petr; Kohoutová, M.; Petrášek, Jan; Hoyerová, Klára; Jiřina, M.; Zažímalová, Eva

    2012-01-01

    Roč. 63, č. 10 (2012), s. 3815-3827. ISSN 0022-0957 R&D Projects: GA MŠk(CZ) LC06034; GA ČR GAP305/11/0797 Institutional research plan: CEZ:AV0Z50380511 Keywords : auxin metabolism * auxin transport * auxin transport inhibitors Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 5.242, year: 2012

  16. The Maize PIN Gene Family of Auxin Transporters.

    Science.gov (United States)

    Forestan, Cristian; Farinati, Silvia; Varotto, Serena

    2012-01-01

    Auxin is a key regulator of plant development and its differential distribution in plant tissues, established by a polar cell to cell transport, can trigger a wide range of developmental processes. A few members of the two families of auxin efflux transport proteins, PIN-formed (PIN) and P-glycoprotein (ABCB/PGP), have so far been characterized in maize. Nine new Zea mays auxin efflux carriers PIN family members and two maize PIN-like genes have now been identified. Four members of PIN1 (named ZmPIN1a-d) cluster, one gene homologous to AtPIN2 (ZmPIN2), three orthologs of PIN5 (ZmPIN5a-c), one gene paired with AtPIN8 (ZmPIN8), and three monocot-specific PINs (ZmPIN9, ZmPIN10a, and ZmPIN10b) were cloned and the phylogenetic relationships between early-land plants, monocots, and eudicots PIN proteins investigated, including the new maize PIN proteins. Tissue-specific expression patterns of the 12 maize PIN genes, 2 PIN-like genes and ZmABCB1, an ABCB auxin efflux carrier, were analyzed together with protein localization and auxin accumulation patterns in normal conditions and in response to drug applications. ZmPIN gene transcripts have overlapping expression domains in the root apex, during male and female inflorescence differentiation and kernel development. However, some PIN family members have specific tissue localization: ZmPIN1d transcript marks the L1 layer of the shoot apical meristem and inflorescence meristem during the flowering transition and the monocot-specific ZmPIN9 is expressed in the root endodermis and pericycle. The phylogenetic and gene structure analyses together with the expression pattern of the ZmPIN gene family indicate that subfunctionalization of some maize PINs can be associated to the differentiation and development of monocot-specific organs and tissues and might have occurred after the divergence between dicots and monocots. PMID:22639639

  17. TWISTED DWARF1 Mediates the Action of Auxin Transport Inhibitors on Actin Cytoskeleton Dynamics.

    Science.gov (United States)

    Zhu, Jinsheng; Bailly, Aurelien; Zwiewka, Marta; Sovero, Valpuri; Di Donato, Martin; Ge, Pei; Oehri, Jacqueline; Aryal, Bibek; Hao, Pengchao; Linnert, Miriam; Burgardt, Noelia Inés; Lücke, Christian; Weiwad, Matthias; Michel, Max; Weiergräber, Oliver H; Pollmann, Stephan; Azzarello, Elisa; Mancuso, Stefano; Ferro, Noel; Fukao, Yoichiro; Hoffmann, Céline; Wedlich-Söldner, Roland; Friml, Jiří; Thomas, Clément; Geisler, Markus

    2016-04-01

    Plant growth and architecture is regulated by the polar distribution of the hormone auxin. Polarity and flexibility of this process is provided by constant cycling of auxin transporter vesicles along actin filaments, coordinated by a positive auxin-actin feedback loop. Both polar auxin transport and vesicle cycling are inhibited by synthetic auxin transport inhibitors, such as 1-N-naphthylphthalamic acid (NPA), counteracting the effect of auxin; however, underlying targets and mechanisms are unclear. Using NMR, we map the NPA binding surface on the Arabidopsis thaliana ABCB chaperone TWISTED DWARF1 (TWD1). We identify ACTIN7 as a relevant, although likely indirect, TWD1 interactor, and show TWD1-dependent regulation of actin filament organization and dynamics and that TWD1 is required for NPA-mediated actin cytoskeleton remodeling. The TWD1-ACTIN7 axis controls plasma membrane presence of efflux transporters, and as a consequence act7 and twd1 share developmental and physiological phenotypes indicative of defects in auxin transport. These can be phenocopied by NPA treatment or by chemical actin (de)stabilization. We provide evidence that TWD1 determines downstream locations of auxin efflux transporters by adjusting actin filament debundling and dynamizing processes and mediating NPA action on the latter. This function appears to be evolutionary conserved since TWD1 expression in budding yeast alters actin polarization and cell polarity and provides NPA sensitivity. PMID:27053424

  18. Foliar modifications induced by inhibition of polar transport of auxin

    Institute of Scientific and Technical Information of China (English)

    NIDIAN; LINGJIANWANG; 等

    1999-01-01

    The effects of auxin polar transport inhibitors,9-hydroxy-fluorene-9-carboxylic acid (HFCA);2,3,5-triiodobenzoic acid(TIBA) and trans-cinnamic acid (CA) on leaf pattern formation were investigated with shoots formed from cultured leaf explants of tobacco and cultured pedicel explants of Orychophragmus violaceus,and the seedlings of tobacco and Brassica chinensis,Although the effective concentration varies with the inhibitors used,all of the inhibitors induced the formation of trumpet-shaped and/or fused leaves.The frequency of trumpet-shaped leaf formation was related to the concentration of inhibitors in the medium.Histological observation of tobacco seedlings showed that there was only one main vascular bundle and several minor vascular bundles in normal leaves of the control,but there were several vascular bundles of more or less the same size in the trumpet-shaped leaves of treated ones.These results indicated that auxin polar transport played an important role on bilateral symmetry of leaf growth.

  19. Shoot-supplied ammonium targets the root auxin influx carrier AUX1 and inhibits lateral root emergence in Arabidopsis

    KAUST Repository

    Li, Baohai

    2011-03-24

    Deposition of ammonium (NH4 +) from the atmosphere is a substantial environmental problem. While toxicity resulting from root exposure to NH4 + is well studied, little is known about how shoot-supplied ammonium (SSA) affects root growth. In this study, we show that SSA significantly affects lateral root (LR) development. We show that SSA inhibits lateral root primordium (LRP) emergence, but not LRP initiation, resulting in significantly impaired LR number. We show that the inhibition is independent of abscisic acid (ABA) signalling and sucrose uptake in shoots but relates to the auxin response in roots. Expression analyses of an auxin-responsive reporter, DR5:GUS, and direct assays of auxin transport demonstrated that SSA inhibits root acropetal (rootward) auxin transport while not affecting basipetal (shootward) transport or auxin sensitivity of root cells. Mutant analyses indicated that the auxin influx carrier AUX1, but not the auxin efflux carriers PIN-FORMED (PIN)1 or PIN2, is required for this inhibition of LRP emergence and the observed auxin response. We found that AUX1 expression was modulated by SSA in vascular tissues rather than LR cap cells in roots. Taken together, our results suggest that SSA inhibits LRP emergence in Arabidopsis by interfering with AUX1-dependent auxin transport from shoot to root. © 2011 Blackwell Publishing Ltd.

  20. Influences of polar auxin transport on polarity of adventitious bud formation in hybrid populas

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Myung Won (Yonsei Univ. Kangwondo (Korea)); Hackett, W. (Univ of Minnesota, St. Paul (USA))

    1989-04-01

    The role of auxin and cytokinin distribution of polar regeneration of adventitious bud has been investigated. Explants from leaf midvein were labelled with {sup 14}C-NAA and {sup 14}C-BA and the radioactivity in proximal, mid, and distal portions was counted after 24h and 48h. Explants showing polar regeneration of buds on the proximal end showed a clear polar distribution of {sup 14}CNAA. Auxin transport inhibitors (NPA, TIBA) eliminated polar distribution of auxin and reduced polarity of bud formation and the total number of buds formed, but did not reduce callus formation. Increased concentration of Ca(NO{sub 3}){sub 2} decreased polarity of bud formation and increased the number of buds formed but did not affect the distribution of auxin of cytokinin. Some factor in addition to polar distribution of auxin or cytokinin-auxin ratio appears to influence the polarity of adventitious bud formation.

  1. Membrane vesicles: A simplified system for studying auxin transport

    Energy Technology Data Exchange (ETDEWEB)

    Goldsmith, M.H.M.

    1989-01-01

    Indoleacetic acid (IAA), the auxin responsible for regulation of growth, is transported polarly in plants. Several different models have been suggested to account for IAA transport by cells and its accumulation by membrane vesicles. One model sees diffusion of IAA driven by a pH gradient. The anion of a lipophilic weak acid like IAA or butyrate accumulates in an alkaline compartment in accord with the size of the pH gradient The accumulation of IAA may be diminished by the permeability of its lipophilic anion. This anion leak may be blocked by NPA. With anion efflux blocked, a gradient of two pH units would support an IAA accumulation of less than 50-fold at equilibrium (2) Another model sees diffusion of IAA in parallel with a saturable symport (IAA[sup [minus

  2. Tomato root growth, gravitropism, and lateral development: correlation with auxin transport

    Science.gov (United States)

    Muday, G. K.; Haworth, P.

    1994-01-01

    Tomato (Lycopersicon esculentum, Mill.) roots were analyzed during growth on agar plates. Growth of these roots was inhibited by the auxin transport inhibitors naphthylphthalamic acid (NPA) and semicarbazone derivative I (SCB-1). The effect of auxin transport inhibitors on root gravitropism was analyzed by measurement of the angle of gravitropic curvature after the roots were reoriented 90 degrees from the vertical. NPA and SCB-1 abolished both the response of these roots to gravity and the formation of lateral roots, with SCB-1 being the more effective at inhibition. Auxins also inhibited root growth. Both auxins tested has a slight effect on the gravity response, but this effect is probably indirect, since auxins reduced the growth rate. Auxins also stimulated lateral root growth at concentration where primary root growth was inhibited. When roots were treated with both IAA and NPA simultaneously, a cumulative inhibition of root growth was found. When both compounds were applied together, analysis of gravitropism and lateral root formation indicated that the dominant effect was exerted by auxin transport inhibitors. Together, these data suggest a model for the role of auxin transport in controlling both primary and lateral root growth.

  3. Redirection of auxin flow in Arabidopsis thaliana roots after infection by root-knot nematodes.

    Science.gov (United States)

    Kyndt, Tina; Goverse, Aska; Haegeman, Annelies; Warmerdam, Sonja; Wanjau, Cecilia; Jahani, Mona; Engler, Gilbert; de Almeida Engler, Janice; Gheysen, Godelieve

    2016-08-01

    Plant-parasitic root-knot nematodes induce the formation of giant cells within the plant root, and it has been recognized that auxin accumulates in these feeding sites. Here, we studied the role of the auxin transport system governed by AUX1/LAX3 influx proteins and different PIN efflux proteins during feeding site development in Arabidopsis thaliana roots. Data generated via promoter-reporter line and protein localization analyses evoke a model in which auxin is being imported at the basipetal side of the feeding site by the concerted action of the influx proteins AUX1 and LAX3, and the efflux protein PIN3. Mutants in auxin influx proteins AUX1 and LAX3 bear significantly fewer and smaller galls, revealing that auxin import into the feeding sites is needed for their development and expansion. The feeding site development in auxin export (PIN) mutants was only slightly hampered. Expression of some PINs appears to be suppressed in galls, probably to prevent auxin drainage. Nevertheless, a functional PIN4 gene seems to be a prerequisite for proper nematode development and gall expansion, most likely by removing excessive auxin to stabilize the hormone level in the feeding site. Our data also indicate a role of local auxin peaks in nematode attraction towards the root. PMID:27312670

  4. Gravity-induced modification of auxin transport and distribution for peg formation in cucumber seedlings

    Science.gov (United States)

    Kamada, M.; Fujii, N.; Higashitani, A.; Takahashi, H.

    Cucumber seedlings grown in microgravity developed a peg on each side of the transition zone between hypocotyl and root, whereas seedlings grown in a horizontal position on the ground developed a peg on the concave (lower) side of the gravitropically bending transition zone. Using an auxin-inducible gene, CS-IAA1, we showed that upon gravistimulation the auxin concentration on the upper side of the horizontally placed transition zone is reduced to a level below the threshold necessary for peg formation. In this study, to elucidate the role of auxin in the lateral placement of peg formation, we measured the contents of endogenous auxin in the transition zone. The content of free IAA was lower and conjugated IAA was more abundant on the upper side of the transition zone of the gravistimulated seedlings compared with the lower side. These results support the idea that a decrease in auxin level due to a modification of auxin transport or metabolism causes the suppression of peg formation on the upper side of the transition zone in a horizontal position. Cucumber seedlings treated with auxin transport inhibitors exhibited agravitropic growth and developed a peg on each side of the transition zone. Application of auxin transport inhibitors caused an increase in CS-IAA1 mRNA (an auxin-inducible gene) at the transition zone. To analyze auxin transport system for peg formation, we isolated auxin influx carrier, CS-AUX1, and auxin efflux carrier, CS-PIN1, from cucumber plants. The accumulation of CS-AUX1 and CS-PIN1 mRNAs was observed at vascular tissue and epidermis in the transition zone. The level of CS-AUX1 mRNA was lower on the upper side of the transition zone in a horizontal position. The results suggest that the transition zone is an additional source of auxin, and that both influx and efflux of auxin in the cells of the transition zone control cytoplasmic concentration of auxin for peg formation.

  5. Evidence that the mature leaves contribute auxin to the immature tissues of pea (Pisum sativum L.).

    Science.gov (United States)

    Jager, Corinne E; Symons, Gregory M; Glancy, Naomi E; Reid, James B; Ross, John J

    2007-07-01

    In plants such as the garden pea (Pisum sativum L.), it is widely thought that the auxin indole-3-acetic acid (IAA) is synthesised mainly in the immature tissues of the apical bud and then transported basipetally to other parts of the plant. Consistent with this belief are results showing that removal of the apical bud markedly reduces the IAA content in the stem. However, it has also been suggested that the mature leaves may synthesise substantial amounts of IAA, which enters the basipetal transport stream after being transported to the shoot apex in the phloem (Cambridge and Morris in Planta 99:583-588, 1996). To examine this theory, we defoliated pea plants and measured the effect on IAA content in the remaining shoot tissues. IAA levels were reduced in the internodes, and to a lesser extent in the apical bud, after defoliation, suggesting that mature leaves are indeed an important source of auxin for the shoot. Consistent with this idea, we have demonstrated that mature, fully expanded leaves are capable of de novo IAA synthesis. Furthermore, we report evidence for the presence of IAA in the phloem sap of pea. Together these results support those of Cambridge and Morris, suggesting that mature leaves are a source of the IAA in the basipetal transport stream. PMID:17308928

  6. Models of long-distance transport: how is carrier-dependent auxin transport regulated in the stem?

    Science.gov (United States)

    Renton, Michael; Hanan, Jim; Ferguson, Brett J; Beveridge, Christine A

    2012-05-01

    • This paper presents two models of carrier-dependent long-distance auxin transport in stems that represent the process at different scales. • A simple compartment model using a single constant auxin transfer rate produced similar data to those observed in biological experiments. The effects of different underlying biological assumptions were tested in a more detailed model representing cellular and intracellular processes that enabled discussion of different patterns of carrier-dependent auxin transport and signalling. • The output that best fits the biological data is produced by a model where polar auxin transport is not limited by the number of transporters/carriers and hence supports biological data showing that stems have considerable excess capacity to transport auxin. • All results support the conclusion that auxin depletion following apical decapitation in pea (Pisum sativum) occurs too slowly to be the initial cause of bud outgrowth. Consequently, changes in auxin content in the main stem and changes in polar auxin transport/carrier abundance in the main stem are not correlated with axillary bud outgrowth. PMID:22443265

  7. Master and servant: Regulation of auxin transporters by FKBPs and cyclophilins.

    Science.gov (United States)

    Geisler, Markus; Bailly, Aurélien; Ivanchenko, Maria

    2016-04-01

    Plant development and architecture are greatly influenced by the polar distribution of the essential hormone auxin. The directional influx and efflux of auxin from plant cells depends primarily on AUX1/LAX, PIN, and ABCB/PGP/MDR families of auxin transport proteins. The functional analysis of these proteins has progressed rapidly within the last decade thanks to the establishment of heterologous auxin transport systems. Heterologous co-expression allowed also for the testing of protein-protein interactions involved in the regulation of transporters and identified relationships with members of the FK506-Binding Protein (FKBP) and cyclophilin protein families, which are best known in non-plant systems as cellular receptors for the immunosuppressant drugs, FK506 and cyclosporin A, respectively. Current evidence that such interactions affect membrane trafficking, and potentially the activity of auxin transporters is reviewed. We also propose that FKBPs andcyclophilins might integrate the action of auxin transport inhibitors, such as NPA, on members of the ABCB and PIN family, respectively. Finally, we outline open questions that might be useful for further elucidation of the role of immunophilins as regulators (servants) of auxin transporters (masters). PMID:26940487

  8. The microtubule cytoskeleton does not integrate auxin transport and gravitropism in maize roots

    Science.gov (United States)

    Hasenstein, K. H.; Blancaflor, E. B.; Lee, J. S.

    1999-01-01

    The Cholodny-Went hypothesis of gravitropism suggests that the graviresponse is controlled by the distribution of auxin. However, the mechanism of auxin transport during the graviresponse of roots is still unresolved. To determine whether the microtubule (MT) cytoskeleton is participating in auxin transport, the cytoskeleton was examined and the movement of 3H-IAA measured in intact and excised taxol, oryzalin, and naphthylphthalamic acid (NPA)-treated roots of Zea mays cv. Merit. Taxol and oryzalin did not inhibit the graviresponse of roots but the auxin transport inhibitor NPA greatly inhibited both auxin transport and graviresponse. NPA had no effect on MT organization in vertical roots, but caused MT reorientation in horizontally placed roots. Regardless of treatment, the organization of MTs in intact roots differed from that in root segments. The MT inhibitors, taxol and oryzalin had opposite effects on the MTs, namely, depolymerization (oryzalin) and stabilization and thickening (taxol), but both treatments caused swelling of the roots. The data indicate that the MT cytoskeleton does not directly interfere with auxin transport or auxin-mediated growth responses in maize roots.

  9. A mutation in protein phosphatase 2A regulatory subunit A affects auxin transport in Arabidopsis

    Science.gov (United States)

    Garbers, C.; DeLong, A.; Deruere, J.; Bernasconi, P.; Soll, D.; Evans, M. L. (Principal Investigator)

    1996-01-01

    The phytohormone auxin controls processes such as cell elongation, root hair development and root branching. Tropisms, growth curvatures triggered by gravity, light and touch, are also auxin-mediated responses. Auxin is synthesized in the shoot apex and transported through the stem, but the molecular mechanism of auxin transport is not well understood. Naphthylphthalamic acid (NPA) and other inhibitors of auxin transport block tropic curvature responses and inhibit root and shoot elongation. We have isolated a novel Arabidopsis thaliana mutant designated roots curl in NPA (rcn1). Mutant seedlings exhibit altered responses to NPA in root curling and hypocotyl elongation. Auxin efflux in mutant seedlings displays increased sensitivity to NPA. The rcn1 mutation was transferred-DNA (T-DNA) tagged and sequences flanking the T-DNA insert were cloned. Analysis of the RCN1 cDNA reveals that the T-DNA insertion disrupts a gene for the regulatory A subunit of protein phosphatase 2A (PP2A-A). The RCN1 gene rescues the rcn1 mutant phenotype and also complements the temperature-sensitive phenotype of the Saccharomyces cerevisiae PP2A-A mutation, tpd3-1. These data implicate protein phosphatase 2A in the regulation of auxin transport in Arabidopsis.

  10. Identification of the cells involved in auxin transport in maize mesocotyl

    Energy Technology Data Exchange (ETDEWEB)

    Jones, A.M. (Univ. of North Carolina, Chapel Hill (USA))

    1989-04-01

    A study was undertaken to identify by a direct method the cells involved in auxin transport through maize mesocotyl tissue. The auxin photoaffinity labeling agent, 7-({sup 3}H), 5-azidoindole 3-acetic acid (N{sub 3}IAA), was loaded into excised stem tissue from a cut end. Polar transport of this analog was demonstrated over 4 hours by comparing uptake into tissue loaded with N{sub 3}IAA from the apical vs. the basal end. Triiodobenzoic acid, an auxin transport inhibitor, inhibited N{sub 3}IAA uptake into tissue. Tissue which had taken up the photoaffinity labeling agent was photolyzed to covalently fix the radioisotope within cells. This tissue was sectioned and subjected to in situ autoradiography. The outermost cell of epidermal tissue and certain files of cells in vascular tissue were densely labeled indicating that on a per cell basis these two cell types are most actively transporting auxin.

  11. Simulation of organ patterning on the floral meristem using a polar auxin transport model.

    Directory of Open Access Journals (Sweden)

    Simon van Mourik

    Full Text Available An intriguing phenomenon in plant development is the timing and positioning of lateral organ initiation, which is a fundamental aspect of plant architecture. Although important progress has been made in elucidating the role of auxin transport in the vegetative shoot to explain the phyllotaxis of leaf formation in a spiral fashion, a model study of the role of auxin transport in whorled organ patterning in the expanding floral meristem is not available yet. We present an initial simulation approach to study the mechanisms that are expected to play an important role. Starting point is a confocal imaging study of Arabidopsis floral meristems at consecutive time points during flower development. These images reveal auxin accumulation patterns at the positions of the organs, which strongly suggests that the role of auxin in the floral meristem is similar to the role it plays in the shoot apical meristem. This is the basis for a simulation study of auxin transport through a growing floral meristem, which may answer the question whether auxin transport can in itself be responsible for the typical whorled floral pattern. We combined a cellular growth model for the meristem with a polar auxin transport model. The model predicts that sepals are initiated by auxin maxima arising early during meristem outgrowth. These form a pre-pattern relative to which a series of smaller auxin maxima are positioned, which partially overlap with the anlagen of petals, stamens, and carpels. We adjusted the model parameters corresponding to properties of floral mutants and found that the model predictions agree with the observed mutant patterns. The predicted timing of the primordia outgrowth and the timing and positioning of the sepal primordia show remarkable similarities with a developing flower in nature.

  12. Simulation of Organ Patterning on the Floral Meristem Using a Polar Auxin Transport Model

    OpenAIRE

    Simon van Mourik; Kerstin Kaufmann; Aalt D J van Dijk; Angenent, Gerco C.; Merks, Roeland M H; Jaap Molenaar

    2012-01-01

    An intriguing phenomenon in plant development is the timing and positioning of lateral organ initiation, which is a fundamental aspect of plant architecture. Although important progress has been made in elucidating the role of auxin transport in the vegetative shoot to explain the phyllotaxis of leaf formation in a spiral fashion, a model study of the role of auxin transport in whorled organ patterning in the expanding floral meristem is not available yet. We present an initial simulation app...

  13. Auxin polar transport in arabidopsis under simulated microgravity conditions - relevance to growth and development

    Science.gov (United States)

    Miyamoto, K.; Oka, M.; Yamamoto, R.; Masuda, Y.; Hoson, T.; Kamisaka, S.; Ueda, J.

    1999-01-01

    Activity of auxin polar transport in inflorescence axes of Arabidopsis thaliana grown under simulated microgravity conditions was studied in relation to the growth and development. Seeds were germinated and allowed to grow on an agar medium in test tubes on a horizontal clinostat. Horizontal clinostat rotation substantially reduced the growth of inflorescence axes and the productivity of seeds of Arabidopsis thaliana (ecotypes Landsberg erecta and Columbia), although it little affected seed germination, development of rosette leaves and flowering. The activity of auxin polar transport in inflorescence axes decreased when Arabidopsis plants were grown on a horizontal clinostat from germination stage, being ca. 60% of 1 g control. On the other hand, the auxin polar transport in inflorescence axes of Arabidopsis grown in 1 g conditions was not affected when the segments were exposed to various gravistimuli, including 3-dimensional clinorotation, during transport experiments. Pin-formed mutant of Arabidopsis, having a unique structure of the inflorescence axis with no flower and extremely low levels of the activity of auxin polar transport in inflorescence axes and endogenous auxin, did not continue its vegetative growth under clinostat rotation. These facts suggest that the development of the system of auxin polar transport in Arabidopsis is affected by microgravity, resulting in the inhibition of growth and development, especially during reproductive growth.

  14. Loss of GSNOR1 function leads to compromised auxin signaling and polar auxin transport

    Science.gov (United States)

    Nitric oxide (NO) and auxin phytohormone cross talk has been implicated in plant development and growth. Addition and removal of NO to cysteine residues of proteins, is termed S-nitrosylation and de-nitrosylation, respectively and functions as an on/off switch of protein activity. This dynamic proce...

  15. Roles of auxin transport and action in the gravity-regulated morphogenesis of cucumber seedlings

    Science.gov (United States)

    Saito, Y.; Shimizu, M.; Hotta, T.; Dai-Hee, K.; Yanai, K.; Kamada, M.; Fujii, N.; Miyazawa, Y.; Takahashi, H.

    Cucumber Cucumis sativus L seedlings develop a specialized protuberance peg on the lower side of the transition zone between the hypocotyl and the root when seeds germinate in a horizontal position The peg plays an important role in pulling seedling out from the seed coat We have reported that cucumber seedlings potentially develop a peg on each side of the transition zone but peg development on the upper side is suppressed in response to gravity Auxin is the primary factor responsible for the induction or the suppression of peg formation Here we investigated the roles of auxin transport and action in the gravity-regulated formation suppression of the peg in cucumber seedlings When cucumber seedlings were treated with inhibitors of auxin efflux carrier a peg was formed not only on the lower side but also on the upper side of the gravistimulated transition zone suggesting that activation of auxin efflux carriers is required for the suppression of peg formation To identify auxin efflux carriers involved in the suppression of peg formation by graviresponse we isolated six cucumber cDNAs of PIN auxin efflux carrier genes and investigated their mRNA accumulation and protein expression Our results show that CsPIN1 and CsPIN6 could play a role in the redistribution of auxin in the transition zone To understand auxin action on peg formation suppression we next examined the transcriptional regulators for the expressions of auxin-responsive genes The results suggest that a higher level of auxin in the lower side of the

  16. Automorphosis and auxin polar transport of etiolated pea seedlings under microgravity conditions.

    Science.gov (United States)

    Hoshino, Tomoki; Miyamoto, Kensuke; Ueda, Junichi

    2004-11-01

    On STS-95 space experiment, etiolated pea (Pisum sativum L. cv. Alaska) seedlings showed automorphosis and activities of auxin polar transport in epicotyls were substantially suppressed. These results together with the fact that inhibitors of auxin polar transport induced automorphosis-like growth and development strongly suggested that there are close relationships between automorphosis and auxin polar transport in etiolated pea seedlings. In order to know how gravistimuli control auxin polar transport at molecular levels, we isolated novel cDNAs of PsPIN2 and PsAUX1 encoding putative auxin efflux and influx carriers from etiolated pea seedlings. Significantly high levels in homology were found on nucleotide and deduced amino acid sequences among PsPIN2, PsPIN1 (accession no. AY222857) and AtPINs, and between PsAUX1 and AtAUX1. Exogenously applied auxin substantially enhanced the expression of PsAUX1 and PsPIN2 as well as PsPIN1. Simulated microgravity conditions on a 3-dimensional clinostat remarkably increased gene expression of PsPIN1 and PsAUX1 in the hook and the 1st internode of pea epicotyls, while the increase of expression of PsPIN2 in both organs was not so much. These results suggest that PsPINs and PsAUX1 are auxin-inducible genes, and the expression of PsPINs and PsAUX1 is under the control of gravistimulation. A possible role of these genes in regulating auxin transport relevant to automorphosis of etiolated pea seedlings is also discussed. PMID:15858337

  17. Ethylene regulates root growth through effects on auxin biosynthesis and transport-dependent auxin distribution

    OpenAIRE

    Ruzicka, Kamil; Ljung, Karin; Vanneste, Steffen; Podhorská, Radka; Beeckman, Tom; Friml, Jiri; Benkova, Eva

    2007-01-01

    In plants, each developmental process integrates a network of signaling events that are regulated by different phytohormones, and interactions among hormonal pathways are essential to modulate their effect. Continuous growth of roots results from the postembryonic activity of cells within the root meristem that is controlled by the coordinated action of several phytohormones, including auxin and ethylene. Although their interaction has been studied intensively, the molecular and cellular mech...

  18. Overexpression of the Auxin Binding PROTEIN1 Modulates PIN-Dependent Auxin Transport in Tobacco Cells

    Czech Academy of Sciences Publication Activity Database

    Čovanová, Milada; Sauer, M.; Rychtář, J.; Friml, J.; Petrášek, Jan; Zažímalová, Eva

    2013-01-01

    Roč. 8, č. 7 (2013). E-ISSN 1932-6203 R&D Projects: GA ČR(CZ) GAP305/11/0797; GA ČR(CZ) GPP501/12/P951 Institutional research plan: CEZ:AV0Z50380511 Keywords : ZEA-MAYS-L * PLANT HORMONE AUXIN * MEMBRANE H+-ATPASE Subject RIV: ED - Physiology Impact factor: 3.534, year: 2013

  19. Comprehensive Analysis of the Soybean (Glycine max) GmLAX Auxin Transporter Gene Family.

    Science.gov (United States)

    Chai, Chenglin; Wang, Yongqin; Valliyodan, Babu; Nguyen, Henry T

    2016-01-01

    The phytohormone auxin plays a critical role in regulation of plant growth and development as well as plant responses to abiotic stresses. This is mainly achieved through its uneven distribution in plant via a polar auxin transport process. Auxin transporters are major players in polar auxin transport. The AUXIN RESISTENT 1/LIKE AUX1 (AUX/LAX) auxin influx carriers belong to the amino acid permease family of proton-driven transporters and function in the uptake of indole-3-acetic acid (IAA). In this study, genome-wide comprehensive analysis of the soybean AUX/LAX (GmLAX) gene family, including phylogenic relationships, chromosome localization, and gene structure, was carried out. A total of 15 GmLAX genes, including seven duplicated gene pairs, were identified in the soybean genome. They were distributed on 10 chromosomes. Despite their higher percentage identities at the protein level, GmLAXs exhibited versatile tissue-specific expression patterns, indicating coordinated functioning during plant growth and development. Most GmLAXs were responsive to drought and dehydration stresses and auxin and abscisic acid (ABA) stimuli, in a tissue- and/or time point- sensitive mode. Several GmLAX members were involved in responding to salt stress. Sequence analysis revealed that promoters of GmLAXs contained different combinations of stress-related cis-regulatory elements. These studies suggest that the soybean GmLAXs were under control of a very complex regulatory network, responding to various internal and external signals. This study helps to identity candidate GmLAXs for further analysis of their roles in soybean development and adaption to adverse environments. PMID:27014306

  20. Comprehensive analysis of the soybean (Glycine max GmLAX auxin transporter gene family

    Directory of Open Access Journals (Sweden)

    Chenglin eChai

    2016-03-01

    Full Text Available The phytohormone auxin plays a critical role in regulation of plant growth and development as well as plant responses to abiotic stresses. This is mainly achieved through its uneven distribution in plants via a polar auxin transport process. Auxin transporters are major players in polar auxin transport. The AUXIN RESISTANT 1 ⁄ LIKE AUX1 (AUX⁄LAX auxin influx carriers belong to the amino acid permease family of proton-driven transporters and function in the uptake of indole-3-acetic acid (IAA. In this study, genome-wide comprehensive analysis of the soybean AUX⁄LAX (GmLAX gene family, including phylogenic relationships, chromosome localization, and gene structure, were carried out. A total of 15 GmLAX genes, including seven duplicated gene pairs, were identified in the soybean genome. They were distributed on 10 chromosomes. Despite their higher percentage identities at the protein level, GmLAXs exhibited versatile tissue-specific expression patterns, indicating coordinated functioning during plant growth and development. Most GmLAXs were responsive to drought and dehydration stresses and auxin and abscisic acid (ABA stimuli, in a tissue- and/or time point- sensitive mode. Several GmLAX members were involved in responding to salt stress. Sequence analysis revealed that promoters of GmLAXs contained different combinations of stress-related cis-regulatory elements. These studies suggest that the soybean GmLAXs were under control of a very complex regulatory network, responding to various internal and external signals. This study helps to identity candidate GmLAXs for further analysis of their roles in soybean development and adaption to adverse environments.

  1. Odyssey of Auxin

    OpenAIRE

    Abel, Steffen; Theologis, Athanasios

    2010-01-01

    The history of plant biology is inexorably intertwined with the conception and discovery of auxin, followed by the many decades of research to comprehend its action during growth and development. Growth responses to auxin are complex and require the coordination of auxin production, transport, and perception. In this overview of past auxin research, we limit our discourse to the mechanism of auxin action. We attempt to trace the almost epic voyage from the birth of the hormonal concept in pla...

  2. The BY-2 Cell Line as a Tool to Study Auxin Transport

    Czech Academy of Sciences Publication Activity Database

    Petrášek, Jan; Zažímalová, Eva

    Vol. 58. Heidelberg: Springer-Verlag, 2006 - (Nagata, T.; Matsuoka, K.; Inzé, D.), s. 107-117 ISBN 3-540-32673-1 R&D Projects: GA AV ČR IAA6038303 Institutional research plan: CEZ:AV0Z50380511 Keywords : Auxin Transport * BY-2 Cell Line * cell membrane Subject RIV: ED - Physiology

  3. The arabidopsis thaliana AGRAVITROPIC 1 gene encodes a component of the polar-auxin-transport efflux carrier

    Science.gov (United States)

    Chen, R.; Hilson, P.; Sedbrook, J.; Rosen, E.; Caspar, T.; Masson, P. H.

    1998-01-01

    Auxins are plant hormones that mediate many aspects of plant growth and development. In higher plants, auxins are polarly transported from sites of synthesis in the shoot apex to their sites of action in the basal regions of shoots and in roots. Polar auxin transport is an important aspect of auxin functions and is mediated by cellular influx and efflux carriers. Little is known about the molecular identity of its regulatory component, the efflux carrier [Estelle, M. (1996) Current Biol. 6, 1589-1591]. Here we show that mutations in the Arabidopsis thaliana AGRAVITROPIC 1 (AGR1) gene involved in root gravitropism confer increased root-growth sensitivity to auxin and decreased sensitivity to ethylene and an auxin transport inhibitor, and cause retention of exogenously added auxin in root tip cells. We used positional cloning to show that AGR1 encodes a putative transmembrane protein whose amino acid sequence shares homologies with bacterial transporters. When expressed in Saccharomyces cerevisiae, AGR1 promotes an increased efflux of radiolabeled IAA from the cells and confers increased resistance to fluoro-IAA, a toxic IAA-derived compound. AGR1 transcripts were localized to the root distal elongation zone, a region undergoing a curvature response upon gravistimulation. We have identified several AGR1-related genes in Arabidopsis, suggesting a global role of this gene family in the control of auxin-regulated growth and developmental processes.

  4. Transport and Metabolism of the Endogenous Auxin Precursor lndole-3-Butyric Acid

    Institute of Scientific and Technical Information of China (English)

    Lucia C. Strader; Bonnie Bartel

    2011-01-01

    T Plant growth and morphogenesis depend on the levels and distribution of the plant hormone auxin. Plants tightly regulate cellular levels of the active auxin indole-3-acetic acid (IAA) through synthesis, inactivation, and transport. Although the transporters that move IAA into and out of cells are well characterized and play important roles in development, little is known about the transport of IAA precursors. In this review, we discuss the accumulating evidence suggesting that the IAA precursor indole-3-butyric acid (IBA) is transported independently of the characterized IAA transport machinery along with the recent identification of specific IBA efflux carriers and enzymes suggested to metabolize IBA. These studies have revealed important roles for IBA in maintaining IAA levels and distribution within the plant to support normal development.

  5. Suppression of asymmetric acid efflux and gravitropism in maize roots treated with auxin transport inhibitors of sodium orthovanadate

    Science.gov (United States)

    Mulkey, T. J.; Evans, M. L.

    1982-01-01

    In gravitropically stimulated roots of maize (Zea mays L., hybrid WF9 x 38MS), there is more acid efflux on the rapidly growing upper side than on the slowly growing lower side. In light of the Cholodny/Went hypothesis of gravitropism which states that gravitropic curvature results from lateral redistribution of auxin, the effects of auxin transport inhibitors on the development of acid efflux asymmetry and curvature in gravistimulated roots were examined. All the transport inhibitors tested prevented both gravitropism and the development of asymmetric acid efflux in gravistimulated roots. The results indicate that auxin redistribution may cause the asymmetry of acid efflux, a finding consistent with the Cholodny/Went hypothesis of gravitropism. As further evidence that auxin-induced acid efflux asymmetry may mediate gravitropic curvature, sodium orthovanadate, an inhibitor of auxin-induced H+ efflux was found to prevent both gravitropism and the development of asymmetric acid efflux in gravistimulated roots.

  6. Evidence for regulation of polar auxin transport at the efflux carrier in maize coleoptile sections

    Energy Technology Data Exchange (ETDEWEB)

    Vesper, M.J. (Univ. of Dayton, OH (USA))

    1989-04-01

    Previously we have shown that conditions which result in an increased auxin-induced growth response in maize (Zea mays L.) coleoptile sections also result in a decrease in the velocity of polar auxin transport. Coleoptile sections given conditions which result in slower transport of IAA have different kinetics for net IAA accumulation compared to sections given conditions which result in faster transport. In further experiments, sections were loaded with 30 nM ({sup 3}H)IAA in the presence of increasing unlabeled IAA at low pH. Efflux of ({sup 3}H)IAA was then followed as a function of unlabeled IAA. Saturation of efflux appears to occur at a lower conc. of IAA in sections showing slower transport.

  7. The Shape of an Auxin Pulse, and What It Tells Us about the Transport Mechanism.

    Directory of Open Access Journals (Sweden)

    Graeme Mitchison

    2015-10-01

    Full Text Available Auxin underlies many processes in plant development and physiology, and this makes it of prime importance to understand its movements through plant tissues. In stems and coleoptiles, classic experiments showed that the peak region of a pulse of radio-labelled auxin moves at a roughly constant velocity down a stem or coleoptile segment. As the pulse moves it becomes broader, at a roughly constant rate. It is shown here that this 'spreading rate' is larger than can be accounted for by a single channel model, but can be explained by coupling of channels with differing polar transport rates. An extreme case is where strongly polar channels are coupled to completely apolar channels, in which case auxin in the apolar part is 'dragged along' by the polar part in a somewhat diffuse distribution. The behaviour of this model is explored, together with others that can account for the experimentally observed spreading rates. It is also shown that saturation of carriers involved in lateral transport can explain the characteristic shape of pulses that result from uptake of large amounts of auxin.

  8. Auxin signaling

    OpenAIRE

    Quint, Marcel; Gray, William M.

    2006-01-01

    Auxin regulates a host of plant developmental and physiological processes, including embryogenesis, vascular differentiation, organogenesis, tropic growth, and root and shoot architecture. Genetic and biochemical studies carried out over the past decade have revealed that much of this regulation involves the SCFTIR1/AFB-mediated proteolysis of the Aux/IAA family of transcriptional regulators. With the recent finding that the TRANSPORT INHIBITOR RESPONSE1 (TIR1)/AUXIN SIGNALING F-BOX (AFB) pro...

  9. Modelling the dynamics of polar auxin transport in inflorescence stems of Arabidopsis thaliana.

    Science.gov (United States)

    Boot, Kees J M; Hille, Sander C; Libbenga, Kees R; Peletier, Lambertus A; van Spronsen, Paulina C; van Duijn, Bert; Offringa, Remko

    2016-02-01

    The polar transport of the plant hormone auxin has been the subject of many studies, several involving mathematical modelling. Unfortunately, most of these models have not been experimentally verified. Here we present experimental measurements of long-distance polar auxin transport (PAT) in segments of inflorescence stems of Arabidopsis thaliana together with a descriptive mathematical model that was developed from these data. It is based on a general advection-diffusion equation for auxin density, as suggested by the chemiosmotic theory, but is extended to incorporate both immobilization of auxin and exchange with the surrounding tissue of cells involved in PAT, in order to account for crucial observations. We found that development of the present model assisted effectively in the analysis of experimental observations. As an example, we discuss the analysis of a quadruple mutant for all four AUX1/LAX1-LAX3 influx carriers genes. We found a drastic change in the parameters governing the exchange of PAT channels with the surrounding tissue, whereas the velocity was still of the order of magnitude of the wild type. In addition, the steady-state flux of auxin through the PAT system of the mutant did not exhibit a saturable component, as we found for the wild type, suggesting that the import carriers are responsible for the saturable component in the wild type. In the accompanying Supplementary data available at JXB online, we describe in more detail the data-driven development of the model, review and derive predictions from a mathematical model of the chemiosmotic theory, and explore relationships between parameters in our model and processes and parameters at the cellular level. PMID:26531101

  10. Modelling the dynamics of polar auxin transport in inflorescence stems of Arabidopsis thaliana

    Science.gov (United States)

    Boot, Kees J.M.; Hille, Sander C.; Libbenga, Kees R.; Peletier, Lambertus A.; van Spronsen, Paulina C.; van Duijn, Bert; Offringa, Remko

    2016-01-01

    The polar transport of the plant hormone auxin has been the subject of many studies, several involving mathematical modelling. Unfortunately, most of these models have not been experimentally verified. Here we present experimental measurements of long-distance polar auxin transport (PAT) in segments of inflorescence stems of Arabidopsis thaliana together with a descriptive mathematical model that was developed from these data. It is based on a general advection–diffusion equation for auxin density, as suggested by the chemiosmotic theory, but is extended to incorporate both immobilization of auxin and exchange with the surrounding tissue of cells involved in PAT, in order to account for crucial observations. We found that development of the present model assisted effectively in the analysis of experimental observations. As an example, we discuss the analysis of a quadruple mutant for all four AUX1/LAX1–LAX3 influx carriers genes. We found a drastic change in the parameters governing the exchange of PAT channels with the surrounding tissue, whereas the velocity was still of the order of magnitude of the wild type. In addition, the steady-state flux of auxin through the PAT system of the mutant did not exhibit a saturable component, as we found for the wild type, suggesting that the import carriers are responsible for the saturable component in the wild type. In the accompanying Supplementary data available at JXB online, we describe in more detail the data-driven development of the model, review and derive predictions from a mathematical model of the chemiosmotic theory, and explore relationships between parameters in our model and processes and parameters at the cellular level. PMID:26531101

  11. Differential effects of auxin polar transport inhibitors on rooting in some Crassulaceae species

    OpenAIRE

    Marian Saniewski; Justyna Góraj; Elżbieta Węgrzynowicz-Lesiak; Kensuke Miyamoto; Junichi Ueda

    2014-01-01

    Effects of auxin polar transport inhibitors, 2,3,5-triio-dobenzoic acid (TIBA), 1-N-naphthylphthalamic acid (NPA) and methyl 2-chloro-9-hydroxyfluorene-9-carboxylate (morphactin IT 3456), as a lanolin paste, on root formation in cuttings of some species of Crassulaceae, such as Bryophyllum daigremontianum, B. calycinum, Kalanchoe blossfeldiana and K. tubiflora, were studied. Cuttings of these plants were easily rooted in water without any treatment. TIBA and morphactin IT 3456 completely inhi...

  12. Simulation of organ patterning on the floral meristem using a polar auxin transport model

    OpenAIRE

    Mourik, van, J.A.; Kauffman, K.; Dijk, van, G.; Angenent, G.C.; Merks, Roeland; Molenaar, Gijs

    2012-01-01

    An intriguing phenomenon in plant development is the timing and positioning of lateral organ initiation, which is a fundamental aspect of plant architecture. Although important progress has been made in elucidating the role of auxin transport in the vegetative shoot to explain the phyllotaxis of leaf formation in a spiral fashion, a model that explains the whorled organ patterning in the expanding floral meristem is not available yet. We present an initial simulation approach to study the mech...

  13. Convergences and divergences in polar auxin transport and shoot development in land plant evolution

    OpenAIRE

    Fujita, Tomomichi; Hasebe, Mitsuyasu

    2009-01-01

    A shoot is a reiterated structure consisting of stems and leaves and is the prevailing body plan in most land plant lineages. Vascular plants form shoots in the diploid generation, whereas mosses do so in the haploid generation.1 However, whether these plants use similar molecular mechanisms in shoot development and how the genetic networks for shoot development evolved is not clear. In our recent paper,2 we examined polar auxin transport in several mosses, which is essential for shoot develo...

  14. Differential effects of auxin polar transport inhibitors on rooting in some Crassulaceae species

    Directory of Open Access Journals (Sweden)

    Marian Saniewski

    2014-07-01

    Full Text Available Effects of auxin polar transport inhibitors, 2,3,5-triio-dobenzoic acid (TIBA, 1-N-naphthylphthalamic acid (NPA and methyl 2-chloro-9-hydroxyfluorene-9-carboxylate (morphactin IT 3456, as a lanolin paste, on root formation in cuttings of some species of Crassulaceae, such as Bryophyllum daigremontianum, B. calycinum, Kalanchoe blossfeldiana and K. tubiflora, were studied. Cuttings of these plants were easily rooted in water without any treatment. TIBA and morphactin IT 3456 completely inhibited root formation in the cuttings of these plants but NPA did not when these inhibitors were applied around the stem below the leaves. When TIBA and morphactin were applied around the stem near the top, but leaves were present below the treatment, the root formation was observed in B. calycinum and K. blossfeldiana but in a smaller degree than in control cuttings. These results strongly suggest that endogenous auxin is required for root formation in cuttings of Crassulaceae plants. The differential mode of action of NPA is discussed together with its effect on auxin polar transport.

  15. Inhibition of polar calcium movement and gravitropism in roots treated with auxin-transport inhibitors

    Science.gov (United States)

    Lee, J. S.; Mulkey, T. J.; Evans, M. L.

    1984-01-01

    Primary roots of maize (Zea mays L.) and pea (Pisum sativum L.) exhibit strong positive gravitropism. In both species, gravistimulation induces polar movement of calcium across the root tip from the upper side to the lower side. Roots of onion (Allium cepa L.) are not responsive to gravity and gravistimulation induces little or no polar movement of calcium across the root tip. Treatment of maize or pea roots with inhibitors of auxin transport (morphactin, naphthylphthalamic acid, 2,3,5-triiodobenzoic acid) prevents both gravitropism and gravity-induced polar movement of calcium across the root tip. The results indicate that calcium movement and auxin movement are closely linked in roots and that gravity-induced redistribution of calcium across the root cap may play an important role in the development of gravitropic curvature.

  16. The Arabidopsis concentration-dependent influx/efflux transporter ABCB4 regulates cellular auxin levels in the root epidermis

    Czech Academy of Sciences Publication Activity Database

    Kubeš, Martin; Yang, H.; Richter, G.L.; Cheng, Y.; Młodzińska, E.; Wang, X.; Blakeslee, J.J.; Carraro, N.; Petrášek, Jan; Zažímalová, Eva; Hoyerová, Klára; Ann Peer, W.; Murphy, A. S.

    2012-01-01

    Roč. 69, č. 4 (2012), s. 640-654. ISSN 0960-7412 R&D Projects: GA MŠk(CZ) LC06034; GA ČR(CZ) GAP305/11/0797 Institutional research plan: CEZ:AV0Z50380511 Keywords : auxin * auxin transporters * ATP-binding cassette B4 Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 6.582, year: 2012

  17. Regulation of ABCB1/PGP1-catalysed auxin transport by linker phosphorylation

    DEFF Research Database (Denmark)

    Henrichs, Sina; Wang, Bangjun; Fukao, Yoichiro;

    2012-01-01

    Polar transport of the plant hormone auxin is controlled by PIN-and ABCB/PGP-efflux catalysts. PIN polarity is regulated by the AGC protein kinase, PINOID (PID), while ABCB activity was shown to be dependent on interaction with the FKBP42, TWISTED DWARF1 (TWD1). Using co-immunoprecipitation (co......-IP) and shotgun LC-MS/MS analysis, we identified PID as a valid partner in the interaction with TWD1. In-vitro and yeast expression analyses indicated that PID specifically modulates ABCB1-mediated auxin efflux in an action that is dependent on its kinase activity and that is reverted by quercetin binding...... and thus inhibition of PID autophosphorylation. Triple ABCB1/PID/TWD1 co-transfection in tobacco revealed that PID enhances ABCB1-mediated auxin efflux but blocks ABCB1 in the presence of TWD1. Phospho-proteomic analyses identified S634 as a key residue of the regulatory ABCB1 linker and a very likely...

  18. Mutations in exocyst complex subunit SEC6 gene impaired polar auxin transport and PIN protein recycling in Arabidopsis primary root.

    Science.gov (United States)

    Tan, Xiaoyun; Feng, Yihong; Liu, Yulong; Bao, Yiqun

    2016-09-01

    Polar auxin transport, which is critical for land plant pattern formation and directional growth, is largely depended on asymmetric distribution of PIN proteins at the plasma membrane (PM). Endocytosis and recycling processes play important roles in regulating PIN protein distribution and abundance at the PM. Two subunits (SEC8, EXO70A1) of exocyst, an octameric vesicle-tethering complex, have been reported to be involved in PIN protein recycling in Arabidopsis. However, the function of exocyst complex in PIN protein recycling and polar auxin transport remains incompletely understood. In this study, we utilized two SEC6 down-regulation mutants (PRsec6-1 and PRsec6-2) to investigate the role of exocyst subunit SEC6 in the primary root development, polar auxin transport and PIN proteins recycling. We found that in PRsec6 mutants: 1. Primary root growth was retarded, and lateral root initiation were compromised. 2. Primary roots were sensitive to exogenous auxin 1-napthalene acetic acid (NAA) but not 2,4-dichlorophenoxy (2.4-D). 3. Recycling of PIN1 and PIN2 proteins from the Brefeldin A (BFA) compartment to the PM was delayed. 4. Vesicles accumulated in the primary root tip cells, especially accumulated in the cytosol closed to the PM. These results further demonstrated that the exocyst complex plays an important role in PIN protein recycling and polar auxin transport in Arabidopsis primary root. PMID:27457987

  19. Roles for auxin during morphogenesis of the compound leaves of pea ( Pisum sativum).

    Science.gov (United States)

    DeMason, Darleen A; Chawla, Rekha

    2004-01-01

    The goal of this study was to explore the impact of the plant growth regulator auxin on the development of compound leaves in pea. Wildtype ( WT) plantlets, as well as those of two leaf mutants, acacia ( tl) and tendrilled acacia ( uni-tac) of pea ( Pisum sativum L.), were grown on media containing the auxin-transport inhibitors 2,3,5-triiodobenzoic acid (TIBA), N-(1-naphthyl)phthalamic acid (NPA), or the auxin antagonist, p-chlorophenoxyisobutyric acid (PCIB). The resulting plantlets were carefully analyzed morphologically, by scanning electron microscopy and for Uni gene expression using quantitative reverse transcription-polymerase chain reaction. Auxin transport was measured in WT leaf parts using [(14)C]indole-3-acetic acid. Relative Uni gene expression was determined in shoot tips of a range of leaf-form mutants. Morphological abnormalities were observed for all genotypes examined. The terminal tendrils on WT plants were converted to leaflets, stubs or were aborted. The number of pinna pairs produced on leaves was reduced, with the distal forms being eliminated before the proximal ones. Some leaves were converted to simple, including tri-and bilobed, forms. These treatments phenocopy the uni-tac and unifoliata ( uni) mutants of pea. In the most extreme situations, leaf blades were completely lost leaving only a pair of stipules or scale leaves. Polar auxin transport was basipetal for all leaf parts. Uni gene expression in shoot tips was significantly reduced in 60 microM NPA and TIBA. Uni mRNA was more abundant in tl, af and af tl and reduced in the uni mutants compared to WT. These results indicate that an auxin gradient plays fundamental roles in controlling morphogenesis in the compound leaves of pea and specifically it: (i). is the driving force for leaf growth and pinna determination; (ii). is necessary for pinna initiation; and (iii). controls subsequent pinna development. PMID:12942326

  20. WOX2 and polar auxin transport during spruce embryo pattern formation

    OpenAIRE

    Palovaara, Joakim; Hakman, Inger

    2009-01-01

    The WOX family of transcription factors and polar auxin transport (PAT) are both essential for embryonic patterning and thus normal embryo development in angiosperms. Recent analysis by us of WOX-related genes in Picea and Pinus suggests that they play fundamental roles during embryo development also in conifers.1 It has been proposed that there is a connection between the spatial separation of WOX2 and WOX8, and PAT in the formation of the apical-basal axis in Arabidopsis embryos and that bo...

  1. A Role for Auxin in Flower Development

    Institute of Scientific and Technical Information of China (English)

    Youfa Cheng; Yunde Zhao

    2007-01-01

    Auxin has long been implicated in many aspects of plant growth and development including flower development. However, the exact roles of auxin in flower development have not been well defined until the recent identification of auxin biosynthesis mutants. Auxin is necessary for the initiation of floral primordia,and the disruption of auxin biosynthesis, polar auxin transport or auxin signaling leads to the failure of flower formation. Auxin also plays an essential role in specifying the number and identity of floral organs.Further analysis of the relationship between the auxin pathways and the known flower development genes will provide critical information regarding mechanisms of organogenesis and pattern formation in plants.

  2. The Twisted Dwarf's ABC: How Immunophilins Regulate Auxin Transport

    OpenAIRE

    Bailly, Aurélien; Sovero, Valpuri; Geisler, Markus

    2006-01-01

    There is increasing evidence that immunophilins function as key regulators of plant development. One of the best investigated members, the multi-domain FKBP TWISTED DWARF1 (TWD1)/FKBP42, has been shown to reside on both the vacuolar and plasma membranes where it interacts in mirror image with two pairs of ABC transporters, MRP1/ MRP2 and PGP1/PGP19(MDR1), respectively. Twisted dwarf1 and pgp1/pgp19 mutants display strongly overlapping phenotypes, including reduction and disorientation of grow...

  3. Stochastic and deterministic multiscale models for systems biology: an auxin-transport case study

    Directory of Open Access Journals (Sweden)

    King John R

    2010-03-01

    Full Text Available Abstract Background Stochastic and asymptotic methods are powerful tools in developing multiscale systems biology models; however, little has been done in this context to compare the efficacy of these methods. The majority of current systems biology modelling research, including that of auxin transport, uses numerical simulations to study the behaviour of large systems of deterministic ordinary differential equations, with little consideration of alternative modelling frameworks. Results In this case study, we solve an auxin-transport model using analytical methods, deterministic numerical simulations and stochastic numerical simulations. Although the three approaches in general predict the same behaviour, the approaches provide different information that we use to gain distinct insights into the modelled biological system. We show in particular that the analytical approach readily provides straightforward mathematical expressions for the concentrations and transport speeds, while the stochastic simulations naturally provide information on the variability of the system. Conclusions Our study provides a constructive comparison which highlights the advantages and disadvantages of each of the considered modelling approaches. This will prove helpful to researchers when weighing up which modelling approach to select. In addition, the paper goes some way to bridging the gap between these approaches, which in the future we hope will lead to integrative hybrid models.

  4. Requirement for the gravity-controlled transport of auxin for a negative gravitropic response of epicotyls in the early growth stage of etiolated pea seedlings.

    Science.gov (United States)

    Hoshino, Tomoki; Miyamoto, Kensuke; Ueda, Junichi

    2006-11-01

    Gravity-controlled transport of auxin was studied for a negative gravitropic response in the early growth stage of etiolated pea (Pisum sativum L. cv. Alaska) seedlings, in which epicotyl bending was observed near the cotyledon nodes of the seedlings grown continuously from seeds germinated in a horizontal or an inclined position. Increased expression of an auxin-inducible gene, PsIAA4/5, was observed in the elongated side of epicotyls grown in a horizontal or an inclined position. Regardless of the conditions of seed germination, polar auxin transport in the proximal side of the first internodes of the seedlings was significantly higher than in the distal side. Polar auxin transport in the proximal side of epicotyls grown in an inclined position was significantly lower than in those grown in a horizontal position. In contrast, lateral auxin distribution from the proximal to distal sides in epicotyls grown in an inclined position was significantly higher than in epicotyls grown in a horizontal position. Accumulation of PsPIN1 mRNA encoding a putative auxin efflux facilitator, which was observed in vascular tissue, cortex and epidermis in the proximal and distal sides of epicotyls, was markedly influenced by gravistimulation. These results strongly suggest that gravistimulation induces changeable polar auxin transport and one-way lateral auxin distribution in epicotyls as well as asymmetric auxin accumulation in the proximal and distal sides of epicotyls, resulting in a negative gravitropic response of epicotyls in the early growth stage of pea seedlings. PMID:17008444

  5. Gravistimulation changes expression of genes encoding putative carrier proteins of auxin polar transport in etiolated pea epicotyls

    Science.gov (United States)

    Hoshino, T.; Hitotsubashi, R.; Miyamoto, K.; Tanimoto, E.; Ueda, J.

    STS-95 space experiment has showed that auxin polar transport in etiolated epicotyls of pea (Pisum sativum L. cv. Alaska) seedlings is controlled by gravistimulation. In Arabidopsis thaliana auxin polar transport has considered to be regulated by efflux and influx carrier proteins in plasma membranes, AtPIN1 and AtAUX1, respectively. In order to know how gravistimuli control auxin polar transport in etiolated pea epicotyls at molecular levels, strenuous efforts have been made, resulting in successful isolation of full-length cDNAs of a putative auxin efflux and influx carriers, PsPIN2 and PsAUX1, respectively. Significantly high levels in homology were found on nucleotide and deduced amino acid sequences among PsPIN2, PsPIN1 (accession no. AY222857, Chawla and DeMason, 2003) and AtPINs, and also among PsAUX1, AtAUX1 and their related genes. Phylogenetic analyses based on the deduced amino acid sequences revealed that PsPIN2 belonged to a subclade including AtPIN3, AtPIN4 relating to lateral transport of auxin, while PsPIN1 belonged to the same clade as AtPIN1 relating to auxin polar transport. In the present study, we examined the effects of gravistimuli on the expression of PsPINs and PsAUX1 in etiolated pea seedlings by northern blot analysis. Expression of PsPIN1, PsPIN2 and PsAUX1 in hook region of 3.5-d-old etiolated pea seedlings grown under simulated microgravity conditions on a 3-D clinostat increased as compared with that of the seedlings grown under 1 g conditions. On the other hand, that of PsPIN1 and PsAUX1 in the 1st internode region under simulated microgravity conditions on a 3-D clinostat also increased, while that of PsPIN2 was affected little. These results suggest that expression of PsPIN1, PsPIN2 and PsAUX1 regulating polar/lateral transport of auxin is substantially under the control of gravity. A possible role of PsPINs and PsAUX1 of auxin polar transport in etiolated pea seedlings will also be discussed.

  6. Characterization of transmembrane auxin transport in Arabidopsis suspension-cultured cells

    Czech Academy of Sciences Publication Activity Database

    Seifertová, Daniela; Skůpa, Petr; Rychtář, J.; Laňková, Martina; Pařezová, Markéta; Dobrev, Petre; Hoyerová, Klára; Petrášek, Jan; Zažímalová, Eva

    2014-01-01

    Roč. 171, č. 6 (2014), s. 429-437. ISSN 0176-1617 R&D Projects: GA ČR(CZ) GAP305/11/0797 Institutional support: RVO:61389030 Keywords : Auxin influx * Auxin efflux * Auxin metabolic profiling Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 2.557, year: 2014

  7. Auxin and Monocot Development

    OpenAIRE

    McSteen, Paula

    2010-01-01

    Monocots are known to respond differently to auxinic herbicides; hence, certain herbicides kill broadleaf (i.e., dicot) weeds while leaving lawns (i.e., monocot grasses) intact. In addition, the characters that distinguish monocots from dicots involve structures whose development is controlled by auxin. However, the molecular mechanisms controlling auxin biosynthesis, homeostasis, transport, and signal transduction appear, so far, to be conserved between monocots and dicots, although there ar...

  8. Evolution and Structural Diversification of PILS Putative Auxin Carriers in Plants

    OpenAIRE

    Feraru, Elena; Vosolsobě, Stanislav; Feraru, Mugurel I.; Petrášek, Jan; Kleine-Vehn, Jürgen

    2012-01-01

    The phytohormone auxin contributes to virtually every aspect of the plant development. The spatiotemporal distribution of auxin depends on a complex interplay between auxin metabolism and intercellular auxin transport. Intracellular auxin compartmentalization provides another link between auxin transport processes and auxin metabolism. The PIN-LIKES (PILS) putative auxin carriers localize to the endoplasmic reticulum (ER) and contribute to cellular auxin homeostasis. PILS proteins regulate in...

  9. ROTUNDA3 function in plant development by phosphatase 2A-mediated regulation of auxin transporter recycling

    Science.gov (United States)

    Karampelias, Michael; Neyt, Pia; De Groeve, Steven; Aesaert, Stijn; Coussens, Griet; Rolčík, Jakub; Bruno, Leonardo; De Winne, Nancy; Van Minnebruggen, Annemie; Van Montagu, Marc; Ponce, María Rosa; Micol, José Luis; Friml, Jiří; De Jaeger, Geert; Van Lijsebettens, Mieke

    2016-01-01

    The shaping of organs in plants depends on the intercellular flow of the phytohormone auxin, of which the directional signaling is determined by the polar subcellular localization of PIN-FORMED (PIN) auxin transport proteins. Phosphorylation dynamics of PIN proteins are affected by the protein phosphatase 2A (PP2A) and the PINOID kinase, which act antagonistically to mediate their apical–basal polar delivery. Here, we identified the ROTUNDA3 (RON3) protein as a regulator of the PP2A phosphatase activity in Arabidopsis thaliana. The RON3 gene was map-based cloned starting from the ron3-1 leaf mutant and found to be a unique, plant-specific gene coding for a protein with high and dispersed proline content. The ron3-1 and ron3-2 mutant phenotypes [i.e., reduced apical dominance, primary root length, lateral root emergence, and growth; increased ectopic stages II, IV, and V lateral root primordia; decreased auxin maxima in indole-3-acetic acid (IAA)-treated root apical meristems; hypergravitropic root growth and response; increased IAA levels in shoot apices; and reduced auxin accumulation in root meristems] support a role for RON3 in auxin biology. The affinity-purified PP2A complex with RON3 as bait suggested that RON3 might act in PIN transporter trafficking. Indeed, pharmacological interference with vesicle trafficking processes revealed that single ron3-2 and double ron3-2 rcn1 mutants have altered PIN polarity and endocytosis in specific cells. Our data indicate that RON3 contributes to auxin-mediated development by playing a role in PIN recycling and polarity establishment through regulation of the PP2A complex activity. PMID:26888284

  10. Membrane vesicles: A simplified system for studying auxin transport. Final technical report

    Energy Technology Data Exchange (ETDEWEB)

    Goldsmith, M.H.M.

    1989-12-31

    Indoleacetic acid (IAA), the auxin responsible for regulation of growth, is transported polarly in plants. Several different models have been suggested to account for IAA transport by cells and its accumulation by membrane vesicles. One model sees diffusion of IAA driven by a pH gradient. The anion of a lipophilic weak acid like IAA or butyrate accumulates in an alkaline compartment in accord with the size of the pH gradient The accumulation of IAA may be diminished by the permeability of its lipophilic anion. This anion leak may be blocked by NPA. With anion efflux blocked, a gradient of two pH units would support an IAA accumulation of less than 50-fold at equilibrium (2) Another model sees diffusion of IAA in parallel with a saturable symport (IAA{sup {minus}} + nH{sup +}), driven by both the pH gradient and membrane voltage. Such a symport should be highly accumulative, however, with a lipophilic weak acid such as IAA, net diffusive efflux of IAAH whenever IAAHI{sub i} > IAAH{sub o} would constitute a leak. (3) A third model sees a pH change driven IAA uptake and saturable symport enhanced by internal binding sites. Following pH gradient-driven accumulation of IAA, the anion may bind to an intravesicular site, permitting further uptake of IAA. NPA, by blocking anion efflux, enhances this binding. We have reported that membrane vesicles isolated from actively growing plant tissues are a good system for studying the mechanisms involved in the transport and accumulation of auxin.

  11. Location of transported auxin in etiolated maize shoots using 5-azidoindole-3-acetic acid. [Zea mays L

    Energy Technology Data Exchange (ETDEWEB)

    Jones, A.M. (Univ. of North Carolina, Chapel Hill (USA))

    1990-07-01

    A study was undertaken using the photoaffinity labeling agent, tritiated 5-azidoindole-3-acetic acid (({sup 3}H),5-N{sub 3}IAA), to identify cells in the etiolated maize (Zea mays L.) shoot which transport auxin. Transport of ({sup 3}H),5-N{sub 3}IAA was shown to be polar, inhibited by 2,3,5-triiodobenzoic acid (TIBA) and essentially freely mobile. There was no detectable radiodecomposition of ({sup 3}H),5-N{sub 3}IAA within tissue kept in darkness for 4 hours. Shoot tissue which had taken up ({sup 3}H),5-N{sub 3}IAA was irradiated with ultraviolet light to covalently fix the photoaffinity labeling agent within cells that contained it at the time of photolysis. Subsequent microautoradiography showed that all cells contained radioactivity; however, the amount of radioactivity varied among different cell types. Epidermal cells contained the most radioactivity per area, approximately twofold more than other cells. Parenchyma cells in the mature stelar region contained the next largest amount and cortical cells, sieve tube cells, tracheary cells, and all cells in the leaf base contained the least amount of the radioactive label. Two observations suggest that the auxin within the epidermal cells is transported in a polar manner: (a) the amount of auxin in the epidermal cells is greatly reduced in the presence of TIBA, and (b) auxin accumulates on the apical side of a wound in the epidermis and is absent on the basal side. While these results indicate that auxin in the epidermis is polarly transported, this tissue cannot be the only pathway since the epidermis is only a small fraction of the shoot volume.

  12. Inhibition of auxin transport and auxin signaling and treatment with far red light induces root coiling in the phospholipase-A mutant ppla-I-1. Significance for surface penetration?

    Science.gov (United States)

    Perrineau, F; Wimalasekera, R; Effendi, Y; Scherer, G F E

    2016-06-01

    When grown on a non-penetretable at a surface angle of 45°, Arabidopsis roots form wave-like structures and, in wild type rarely, but in certain mutants the tip root even may form circles. These circles are called coils. The formation of coils depends on the complex interaction of circumnutation, gravitropism and negative thigmotropism where - at least - gravitropism is intimately linked to auxin transport and signaling. The knockout mutant of patatin-related phospholipase-AI-1 (pplaI-1) is an auxin-signaling mutant which forms moderately increased numbers of coils on tilted agar plates. We tested the effects of the auxin efflux transport inhibitor NPA (1-naphthylphtalamic acid) and of the influx transport inhibitor 1-NOA (1-naphthoxyacetic acid) which both further increased root coil formation. The pPLAI-1 inhibitors HELSS (haloenol lactone suicide substrate=E-6-(bromomethylene)tetrahydro-3-(1-naphthalenyl)-2H-pyran-2-one) and ETYA (eicosatetraynoic acid) which are auxin signaling inhibitors also increased coil formation. In addition, far red light treatment increased coil formation. The results point out that a disturbance of auxin transport and signaling is one potential cause for root coils. As we show that the mutant pplaI-1 penetrates horizontal agar plates better than wild type plants root movements may help penetrating the soil. PMID:27058428

  13. Effect of an auxin transport inhibitor on aggregation and attachment processes during ectomycorrhiza formation between Laccaria bicolo S238N and Picea abies

    OpenAIRE

    Rincón, Ana; Gérard, Joëlle; Dexheimer, Jean; Le Tacon, François

    2001-01-01

    Transmission electron microscopy observations performed with cytochemical stains to detect polysaccharides and cysteine-rich proteins have been done to study the effect of an auxin transport inhibitor (2,3,5-triidobenzoic acid), TIBA) on Laccaria bicolor (Marie) Orton.

  14. Non-invasive quantification of endogenous root auxin transport using an integrated flux microsensor technique.

    Science.gov (United States)

    McLamore, Eric S; Diggs, Alfred; Calvo Marzal, Percy; Shi, Jin; Blakeslee, Joshua J; Peer, Wendy A; Murphy, Angus S; Porterfield, D Marshall

    2010-09-01

    Indole-3-acetic acid (IAA) is a primary phytohormone that regulates multiple aspects of plant development. Because polar transport of IAA is an essential determinant of organogenesis and dynamic tropic growth, methods to monitor IAA movement in vivo are in demand. A self-referencing electrochemical microsensor was optimized to non-invasively measure endogenous IAA flux near the surface of Zea mays roots without the addition of exogenous IAA. Enhanced sensor surface modification, decoupling of acquired signals, and integrated flux analyses were combined to provide direct, real time quantification of endogenous IAA movement in B73 maize inbred and brachytic2 (br2) auxin transport mutant roots. BR2 is localized in epidermal and hypodermal tissues at the root apex. br2 roots exhibit reduced shootward IAA transport at the root apex in radiotracer experiments and reduced gravitropic growth. IAA flux data indicates that maximal transport occurs in the distal elongation zone of maize roots, and net transport in/out of br2 roots was decreased compared to B73. Integration of short term real time flux data in this zone revealed oscillatory patterns, with B73 exhibiting shorter oscillatory periods and greater amplitude than br2. IAA efflux and influx were inhibited using 1-N-naphthylphthalamic acid (NPA), and 2-naphthoxyacetic acid (NOA), respectively. A simple harmonic oscillation model of these data produced a correlation between modeled and measured values of 0.70 for B73 and 0.69 for br2. These results indicate that this technique is useful for real-time IAA transport monitoring in surface tissues and that this approach can be performed simultaneously with current live imaging techniques. PMID:20626658

  15. Cellular Auxin Homeostasis:Gatekeeping Is Housekeeping

    Institute of Scientific and Technical Information of China (English)

    Michel Ruiz Rosquete; Elke Barbez; Jürgen Kleine-Vehn

    2012-01-01

    The phytohormone auxin is essential for plant development and contributes to nearly every aspect of the plant life cycle.The spatio-temporal distribution of auxin depends on a complex interplay between auxin metabolism and cell-to-cell auxin transport.Auxin metabolism and transport are both crucial for plant development;however,it largely remains to be seen how these processes are integrated to ensure defined cellular auxin levels or even gradients within tissues or organs.In this review,we provide a glance at very diverse topics of auxin biology,such as biosynthesis,conjugation,oxidation,and transport of auxin.This broad,but certainly superficial,overview highlights the mutual importance of auxin metabolism and transport.Moreover,it allows pinpointing how auxin metabolism and transport get integrated to jointly regulate cellular auxin homeostasis.Even though these processes have been so far only separately studied,we assume that the phytohormonal crosstalk integrates and coordinates auxin metabolism and transport.Besides the integrative power of the global hormone signaling,we additionally introduce the hypothetical concept considering auxin transport components as gatekeepers for auxin responses.

  16. Analyzing the In Vivo Status of Exogenously Applied Auxins: A HPLC-Based Method to Characterize the Intracellularly Localized Auxin Transporters

    Czech Academy of Sciences Publication Activity Database

    Simon, Sibu; Skůpa, Petr; Dobrev, Petre; Petrášek, Jan; Zažímalová, Eva; Friml, J.

    Totowa: Humana Press, 2014 - (Hicks, G.; Robert, S.), s. 255-264. (Methods in Molecular Biology). ISBN 978-1-62703-591-0 R&D Projects: GA ČR(CZ) GAP305/11/0797 Institutional support: RVO:61389030 Keywords : Auxin * Auxin metabolism * BY-2 tobacco cells Subject RIV: EB - Genetics ; Molecular Biology

  17. Comprehensive Analysis and Expression Profiling of the OsLAX and OsABCB Auxin Transporter Gene Families in Rice (Oryza sativa under Phytohormone Stimuli and Abiotic Stresses

    Directory of Open Access Journals (Sweden)

    Chenglin eChai

    2016-05-01

    Full Text Available The plant hormone auxin regulates many aspects of plant growth and developmental processes. Auxin gradient is formed in plant as a result of polar auxin transportation by three types of auxin transporters such as OsLAX, OsPIN, and OsABCB. We report here the analysis of two rice auxin transporter gene families, OsLAX and OsABCB, using bioinformatics tools, publicly accessible microarray data, and quantitative RT-PCR. There are 5 putative OsLAXs and 22 putative OsABCBs in rice genome, which were mapped on 8 chromosomes. The exon-intron structure of OsLAX genes and properties of deduced proteins were relatively conserved within grass family, while that of OsABCB genes varied greatly. Both constitutive and organ/tissue specific expression patterns were observed in OsLAXs and OsABCBs. Analysis of evolutionarily closely related gene pairs together with organ/tissue specific expression revealed possible function gaining and function losing events during rice evolution. Most OsLAX and OsABCB genes were regulated by drought and salt stress, as well as hormonal stimuli [auxin and Abscisic Acid (ABA], which suggests extensive crosstalk between abiotic stresses and hormone signaling pathways. The existence of large number of auxin and stress related cis-regulatory elements in promoter regions might account for their massive responsiveness of these genes to these environmental stimuli, indicating complexity of regulatory networks involved in various developmental and physiological processes. The comprehensive analysis of OsLAX and OsABCB auxin transporter genes in this study would be helpful for understanding the biological significance of these gene families in hormone signaling and adaptation of rice plants to unfavorable environments.

  18. Comprehensive Analysis and Expression Profiling of the OsLAX and OsABCB Auxin Transporter Gene Families in Rice (Oryza sativa) under Phytohormone Stimuli and Abiotic Stresses.

    Science.gov (United States)

    Chai, Chenglin; Subudhi, Prasanta K

    2016-01-01

    The plant hormone auxin regulates many aspects of plant growth and developmental processes. Auxin gradient is formed in plant as a result of polar auxin transportation by three types of auxin transporters such as OsLAX, OsPIN, and OsABCB. We report here the analysis of two rice auxin transporter gene families, OsLAX and OsABCB, using bioinformatics tools, publicly accessible microarray data, and quantitative RT-PCR. There are 5 putative OsLAXs and 22 putative OsABCBs in rice genome, which were mapped on 8 chromosomes. The exon-intron structure of OsLAX genes and properties of deduced proteins were relatively conserved within grass family, while that of OsABCB genes varied greatly. Both constitutive and organ/tissue specific expression patterns were observed in OsLAXs and OsABCBs. Analysis of evolutionarily closely related "gene pairs" together with organ/tissue specific expression revealed possible "function gaining" and "function losing" events during rice evolution. Most OsLAX and OsABCB genes were regulated by drought and salt stress, as well as hormonal stimuli [auxin and Abscisic Acid (ABA)], which suggests extensive crosstalk between abiotic stresses and hormone signaling pathways. The existence of large number of auxin and stress related cis-regulatory elements in promoter regions might account for their massive responsiveness of these genes to these environmental stimuli, indicating complexity of regulatory networks involved in various developmental and physiological processes. The comprehensive analysis of OsLAX and OsABCB auxin transporter genes in this study would be helpful for understanding the biological significance of these gene families in hormone signaling and adaptation of rice plants to unfavorable environments. PMID:27200061

  19. Auxin polar transport of etiolated Ageotropum pea epicotyls is not affected by gravistimulation: Relevance to automorphosis-like growth and development

    Science.gov (United States)

    Miyamoto, Kensuke; Hoshino, Tomoki; Takahashi, Yoshinori; Ueda, Junichi

    There appears to be a close relationship between automorphosis and changes in auxin polar transport due to the fact that microgravity conditions cause both changes in the activity of auxin polar transport and in automorphosis of etiolated Alaska pea epicotyls. In addition, the application of inhibitors of auxin polar transport results in automorphosis-like growth and development. To elucidate the role of auxin polar transport in gravimorphogenesis in etiolated pea seedlings, we have studied the effects of gravistimulation on growth and development, and auxin polar transport in epicotyls of an agravitropic pea mutant " Ageotropum" seedlings and the normal "Alaska" seedlings. When the embryo axes in seeds of Alaska pea were set in a vertical (parallel to the direction of gravity) or a horizontal (vertical to the direction of gravity) position, and allowed to germinate and grow under 1 g conditions in the dark for 3 or 6.5 days, the epicotyls grew upward due to negative gravitropic responses regardless of gravistimulation during seed germination. On the other hand, epicotyls of etiolated Ageotropum pea seedlings showed automorphosis-like bending away from the cotyledons regardless of gravistimulation during seed germination. Automorphosis-like epicotyl bending of etiolated Ageotropum pea seedlings was also unaffected by clinorotation on a three-dimensional (3-D) clinostat. The activity of auxin polar transport in the 2nd internodes of 6.5-d-old etiolated Ageotropum pea seedlings was lower than those of Alaska pea seedlings, and was not affected by clinorotation on a 3-D clinostat or by changes in gravity conditions during seed germination. These findings strongly support our previous studies that showed that normal auxin polar transport is required for the normal graviresponse of epicotyls in etiolated pea seedlings.

  20. [Graviresponse in higher plants and its regulation in molecular bases: relevance to growth and development, and auxin polar transport in etiolated pea seedlings].

    Science.gov (United States)

    Ueda, Junichi; Miyamoto, Kensuke

    2003-08-01

    We review the graviresponse under true and simulated microgravity conditions on a clinostat in higher plants, and its regulation in molecular bases, especially on the aspect of auxin polar transport in etiolated pea (Pisum sativum L. cv. Alaska) seedlings which were the plant materials subjected to STS-95 space experiments. True and simulated microgravity conditions substantially affected growth and development in etiolated pea seedlings, especially the direction of growth of stems and roots, resulting in automorphosis. In etiolated pea seedlings grown in space, epicotyls were the most oriented toward the direction far from the cotyledons, and roots grew toward the aerial space of Plant Growth Chamber. Automorphosis observed in space were well simulated by a clinorotation on a 3-dimensional clinostat and also phenocopied by the application of auxin polar transport inhibitors of 2,3,5-triiodobenzoic acid, N-(1-naphtyl)phthalamic acid and 9-hydroxyfluorene-9-carboxylic acid. Judging from the results described above together with the fact that activities of auxin polar transport in epicotyls of etiolated pea seedlings grown in space substantially were reduced, auxin polar transport seems to be closely related to automorphosis. Strenuous efforts to learn in molecular levels how gravity contributes to the auxin polar transport in etiolated pea epicotyls resulted in successful identification of PsPIN2 and PsAUX1 genes located in plasma membrane which products are considered to be putative efflux and influx carriers of auxin, respectively. Based on the results of expression of PsPIN2 and PsAUX1 genes under various gravistimulations, a possible role of PsPIN2 and PsAUX1 genes for auxin polar transport in etiolated pea seedlings will be discussed. PMID:14555809

  1. Auxin polar transport of etiolated epicotyls of ageotropum pea seedlings is not affected by gravistimulation: Relevance to automorphosis-like growth and development

    Science.gov (United States)

    Miyamoto, K.; Hoshino, T.; Takahashi, Y.; Ueda, J.

    Both true microgravity conditions in space STS-95 space experiment and simulated ones on a three-dimensional 3-D clinostat have been demonstrated to induce automorphosis in etiolated pea Pisum sativum L cv Alaska seedlings represented as epicotyl bending as well as changes in root growth direction and inhibition of hook formation and to alter the activities of auxin polar transport of epicotyls The fact that the application of inhibitors of auxin polar transport phenocopied automorphosis together with the result of detail kinetic analyses of epicotyl bending on the 3-D clinostat suggests that automorphosis of etiolated pea epicotyls is due to suppression of a negative gravitropic response on 1 g conditions and graviresponse of etiolated pea seedlings under 1 g conditions requires normal activities of auxin polar transport To study the role of auxin polar transport in graviresponse in early growth stage of etiolated pea seedlings effect of gravistimulation on auxin polar transport in epicotyls of Alaska pea seedlings was studied in comparison with that of the agravitropic pea mutant ageotropum seedlings Dry pea seeds whose embryo axes were set in a horizontal position referred to as horizontal position or an inclinational one to the gravity vector referred to as inclinational position allowed to germinate and grow in the dark for 2 5 days Epicotyls of etiolated Alaska pea seedlings grown under horizontal position showed negative gravitropisum due to relatively larger elongation in the proximal side to the cotyledons

  2. Ca2+-Transport through Plasma Membrane as a Test of Auxin Sensitivity

    Directory of Open Access Journals (Sweden)

    Anastasia A. Kirpichnikova

    2014-03-01

    Full Text Available Auxin is one of the crucial regulators of plant growth and development. The discovered auxin cytosolic receptor (TIR1 is not involved in the perception of the hormone signal at the plasma membrane. Instead, another receptor, related to the ABP1, auxin binding protein1, is supposed to be responsible for the perception at the plasma membrane. One of the fast and sensitive auxin-induced reactions is an increase of Ca2+ cytosolic concentration, which is suggested to be dependent on the activation of Ca2+ influx through the plasma membrane. This investigation was carried out with a plasmalemma enriched vesicle fraction, obtained from etiolated maize coleoptiles. The magnitude of Ca2+ efflux through the membrane vesicles was estimated according to the shift of potential dependent fluorescent dye diS-C3-(5. The obtained results showed that during coleoptiles ageing (3rd, 4th and 5th days of seedling etiolated growth the magnitude of Ca2+ efflux from inside-out vesicles was decreased. Addition of ABP1 led to a recovery of Ca2+ efflux to the level of the youngest and most sensitive cells. Moreover, the efflux was more sensitive, responding from 10−8 to 10−6 M 1-NAA, in vesicles containing ABP1, whereas native vesicles showed the highest efflux at 10−6 M 1-NAA. We suggest that auxin increases plasma membrane permeability to Ca2+ and that ABP1 is involved in modulation of this reaction.

  3. Use of membrane vesicles as a simplified system for studying transport of auxin. Progress report

    Energy Technology Data Exchange (ETDEWEB)

    Goldsmith, M.H.

    1985-01-01

    The accumulation of indoleacetic acid (IAA) inside microsomal vesicles depends on the presence of a pH gradient and is reversible when the ..delta..pH is collapsed by ionosphores. Accumulation is stimulated by either napthylphthalamic acid or TIBA. The accumulation of IAA by the vesicles can be saturated. At concentrations of 1 ..mu..M or less, IAA, synthetic auxins, or auxin antagonists do not affect the pH gradient, but decrease the accumulation of /sup 3/H-IAA, and therefore compete specifically for uptake. Concentrations of 10 ..mu..M and above, uptake of either the auxins or weak acids is sufficient to overcome the buffering capacity of the solution within the vesicles. The collapse of the pH gradient by such high concentrations affects uptake of either /sup 3/H-IAA or /sup 14/C-BA to similar extents and thus is nonspecific. 3 refs.

  4. Modeling Auxin-regulated Development

    OpenAIRE

    Krupinski, Pawel; Jönsson, Henrik

    2010-01-01

    The phytohormone auxin plays an essential role in many aspects of plant growth and development. Its patterning, intercellular transport, and means of signaling have been extensively studied both in experiments and computational models. Here, we present a review of models of auxin-regulated development in different plant tissues. This includes models of organ initiation in the shoot apical meristem, development of vascular strands in leafs and stems, and auxin-related functioning in roots. The...

  5. Differential behavior within a grapevine cluster: decreased ethylene-related gene expression dependent on auxin transport is correlated with low abscission of first developed berries.

    Directory of Open Access Journals (Sweden)

    Nathalie Kühn

    Full Text Available In grapevine, fruit abscission is known to occur within the first two to three weeks after flowering, but the reason why some berries in a cluster persist and others abscise is not yet understood. Ethylene sensitivity modulates abscission in several fruit species, based on a mechanism where continuous polar auxin transport across the pedicel results in a decrease in ethylene perception, which prevents abscission. In grapevine, flowering takes about four to seven days in a single cluster, thus while some flowers are developing into berries, others are just starting to open. So, in this work it was assessed whether uneven flowering accounted for differences in berry abscission dependent on polar auxin transport and ethylene-related gene expression. For this, flowers that opened in a cluster were tagged daily, which allowed to separately analyze berries, regarding their ability to persist. It was found that berries derived from flowers that opened the day that flowering started--named as "first berries"--had lower abscission rate than berries derived from flowers that opened during the following days--named as "late berries". Use of radiolabeled auxin showed that "first berries" had higher polar auxin transport, correlated with lower ethylene content and lower ethylene-related transcript abundance than "late berries". When "first berries" were treated with a polar auxin transport inhibitor they showed higher ethylene-related transcript abundance and were more prone to abscise than control berries. This study provides new insights on fruit abscission control. Our results indicate that polar auxin transport sustains the ability of "first berries" to persist in the cluster during grapevine abscission and also suggest that this could be associated with changes in ethylene-related gene expression.

  6. Graviresponse and its regulation from the aspect of molecular levels in higher plants: growth and development, and auxin polar transport in etiolated pea seedlings under microgravity.

    Science.gov (United States)

    Miyamoto, Kensuke; Hoshino, Tomoki; Hitotsubashi, Reiko; Tanimoto, Eiichi; Ueda, Junichi

    2003-10-01

    In STS-95 space experiments we have demonstrated that microgravity conditions resulted in automorphosis in etiolated pea (Pisum sativum L. cv. Alaska) seedlings (Ueda et al. 1999). Automorphosis-like growth and development in etiolated pea seedlings were also induced under simulated microgravity conditions on a 3-dimensional (3-D) clinostat, epicotyls being the most oriented toward the direction far from the cotyledons. Detail analysis of epicotyl bending revealed that within 36 h after watering, no significant difference in growth direction of epicotyls was observed in between seedlings grown on the 3-D clinostat and under 1 g conditions, differential growth near the cotyledonary node resulting in epicotyl bending of ca. 45 degrees toward the direction far from the cotyledons. Thereafter epicotyls continued to grow almost straightly keeping this orientation on the 3-D clinostat. On the other hand, the growth direction in etiolated seedlings changed to antigravity direction by negative gravitropic response under 1 g conditions. Automorphological epicotyl bending was also phenocopied by the application of auxin polar transport inhibitors such as 9-hydroxyfluorene-9-carboxylic acid, N-(1-naphtyl)phthalamic acid and 2,3,5-triiodobenzoic acid. These results together with the fact that auxin polar transport activity in etiolated pea epicotyls was substantially reduced in space suggested that reduced auxin polar transport is closely related to automorphosis. Strenuous efforts to learn how gravity contributes to the auxin polar transport in etiolated pea epicotyls in molecular bases resulted in successful identification of PsPIN2 and PsAUX1 encoding putative auxin-efflux and influx carrier proteins, respectively. Based on the results of these gene expression under simulated microgravity conditions, a possible role of PsPIN2 and PsAUX1 genes for auxin polar transport in etiolated pea seedlings will be discussed. PMID:14676393

  7. Auxin Biosynthesis

    OpenAIRE

    Zhao, Yunde

    2014-01-01

    lndole-3-acetic acid (IAA), the most important natural auxin in plants, is mainly synthesized from the amino acid tryptophan (Trp). Recent genetic and biochemical studies in Arabidopsis have unambiguously established the first complete Trp-dependent auxin biosynthesis pathway. The first chemical step of auxin biosynthesis is the removal of the amino group from Trp by the TRYPTOPHAN AMINOTRANSFERASE OF ARABIDOPSIS (TAA) family of transaminases to generate indole-3-pyruvate (IPA). IPA then unde...

  8. Aluminium toxicity targets PIN2 in Arabidopsis root apices: Effects on PIN2 endocytosis, vesicular recycling,and polar auxin transport

    Institute of Scientific and Technical Information of China (English)

    SHEN Hong; HOU NingYan; Markus SCHLICHT; WAN YingLang; Stefano MANCUSO; Frantisek BALUSKA

    2008-01-01

    The most obvious symptom of AI toxicity is the inhibition of root growth.However,the mechanism of AI-inhibiting root growth remains to be elucidated.In this study,auxin transport and vesicle movement of an auxin-efflux carrier (PIN2) were investigated in Arabidopsis roots in response to AI stress.Results indicated that AI inhibited the apical transport of auxin in root tips of Arabidopsis significantly.The severe inhibition was localized in the cells of transition zone,where the concentration of auxin was only 34% that of the control.Brefeldin A (BFA),an inhibitor of vesicle transport,induced the dot-like structure of PIN2 vesicle significantly.Al decreased the size of dot-like structure of PIN2 vesicles.Re-sults of real-time RT-PCR and Western-blotting analysis showed that Al increased the transcript level of PIN2 and the accumulation of PIN2 protein in horizontal direction of plasma membrane,but decreased its distribution in endosomes,suggesting that AI inhibited the transport of PIN2 vesicles from plasma membrane to endosomes.Results of cytoskeleton-depolymering drugs indicated that it was via the pathway of disruption of actin microfilaments that AI inhibited the transport of PIN2 vesicles.Exposed to AI stress,the cells of elongation zone had less AI uptake and less transport frequency of vesicles than cells of transition zone.Taken together,our results suggested that AI inhibited root growth mainly by modulating the transport of PIN2 vesicles between plasma membrane and endosomes,thus block-ing auxin transport and root growth.

  9. Overexpression of OsWRKY72 gene interferes in the abscisic acid signal and auxin transport pathway of Arabidopsis

    Indian Academy of Sciences (India)

    Song Yu; Chen Ligang; Zhang Liping; Yu Diqiu

    2010-09-01

    Through activating specific transcriptional programmes, plants can launch resistance mechanisms to stressful environments and acquire a new equilibrium between development and defence. To screen the rice WRKY transcription factor which functions in abiotic stress tolerance and modulates the abscisic acid (ABA) response, we generated a whole array of 35S-OsWRKY transgenic Arabidopsis. In this study, we report that 35S-OsWRKY72 transgenic Arabidopsis, whose seed germination was retarded under normal conditions, emerged more sensitive to mannitol, NaCl, ABA stresses and sugar starvation than vector plants. Meanwhile, 35S-OsWRKY72 transgenic Arabidopsis displayed early flowering, reduced apical dominance, lost high temperature-induced hypocotyl elongation response, and enhanced gravitropism response, which were similar to the auxin-related gene mutants aux1, axr1 and bud1. Further, semi-quantitative RT-PCR showed that the expression patterns of three auxin-related genes AUX1, AXR1 and BUD1 were significantly altered in rosette leaves and inflorescences of 35S-OsWRKY72 plants compared with control Arabidopsis, and two ABA-related genes ABA2 and ABI4 were induced in 35S-OsWRKY72 seedlings. In addition, northern blot analysis indicated that, in rice, OsWRKY72 was inducible by polyethylene glycol (PEG), NaCl, naphthalene acetic acid (NAA), ABA and 42°C, similar to its orthologue AtWRKY75 in Arabidopsis, implying that these two WRKY genes might be required for multiple physiological processes in their plants. Together, these results suggest that OsWRKY72 interferes in the signal cross-talk between the ABA signal and auxin transport pathway in transgenic Arabidopsis.

  10. Effect of root application of 6-benzylamine purine on auxin transport in Malus domestica

    Energy Technology Data Exchange (ETDEWEB)

    Stutte, G.

    1987-04-01

    The effect of 6-benzylamine purine (BA) on movement of napthalene acetic acid (NAA) applied to the shoot was investigated. Three-month-old York apple seedlings in sand culture were placed under mercury halide lamps (285 ..mu..mol m/sup -2/ s/sup -1/) at 22/sup 0/C for 24 hours; then 13.8, 27.5 or 55 ..mu..Mol of BA was applied as a soil drench. (/sup 14/C)-NAA was injected into the shoot at petiole base of 4th mature leaf. After 24 hours plants were harvested and movement of label acropetally to new shoot growth and basipetally to old shoot growth or roots determined. Seventeen (S.E. 3.3) percent of applied label was recovered away from application site. In controls, 67% of /sup 14/C that moved was recovered from new shoot growth, 9% in roots and 24% in old shoot tissue. The 13.8 ..mu..Mol treatment resulted in 37% of label being recovered in root tissue and 48% in new growth. The 27.5 and 55 ..mu..Mol applications increased the amount recovered in old shoot tissue but did not increase labelling of root tissues.

  11. Arabidopsis phosphatidylinositol monophosphate 5-kinase 2 is involved in root gravitropism through regulation of polar auxin transport by affecting the cycling of PIN proteins

    Institute of Scientific and Technical Information of China (English)

    Yu Mei; Wen-Jing Jia; Yu-Jia Chu; Hong-Wei Xue

    2012-01-01

    Phosphatidylinositol monophosphate 5-kinase(PIP5K)catalyzes the synthesis of PI-4,5-bisphosphate(PtdIns(4,5)P2)by phosphorylation of PI-4-phosphate at the 5 position of the inositol ring,and is involved in regulating multiple developmental processes and stress responses.We here report on the functional characterization of Arabidopsis PIP5K2,which is expressed during lateral root initiation and elongation,and whose expression is enhanced by exogenous auxin.The knockout mutant pip5k2 shows reduced lateral root formation,which could be recovered with exogenous auxin,and interestingly,delayed root gravity response that could not be recovered with exogenous auxin.Crossing with the DR5-GUS marker line and measurement of free IAA content confirmed the reduced auxin accumulation in pip5k2.In addition,analysis using the membrane-selective dye FM4-64 revealed the decelerated vesicle trafficking caused by PtdIns(4,5)P2 reduction,which hence results in suppressed cycling of PIN proteins(PIN2 and 3),and delayed redistribution of PIN2 and auxin under gravistimulation in pipSk2 roots.On the contrary,PtdIns(4,5)P2 significantly enhanced the vesicle trafficking and cycling of PIN proteins.These results demonstrate that PIP5K2 is involved in regulating lateral root formation and root gravity response,and reveal a critical role of PIP5K2/Ptdlns(4,5)P2 in root development through regulation of PIN proteins,providing direct evidence of crosstalk between the phosphatidylinositol signaling pathway and auxin response,and new insights into the control of polar auxin transport.

  12. Arabidopsis phosphatidylinositol monophosphate 5-kinase 2 is involved in root gravitropism through regulation of polar auxin transport by affecting the cycling of PIN proteins.

    Science.gov (United States)

    Mei, Yu; Jia, Wen-Jing; Chu, Yu-Jia; Xue, Hong-Wei

    2012-03-01

    Phosphatidylinositol monophosphate 5-kinase (PIP5K) catalyzes the synthesis of PI-4,5-bisphosphate (PtdIns(4,5)P(2)) by phosphorylation of PI-4-phosphate at the 5 position of the inositol ring, and is involved in regulating multiple developmental processes and stress responses. We here report on the functional characterization of Arabidopsis PIP5K2, which is expressed during lateral root initiation and elongation, and whose expression is enhanced by exogenous auxin. The knockout mutant pip5k2 shows reduced lateral root formation, which could be recovered with exogenous auxin, and interestingly, delayed root gravity response that could not be recovered with exogenous auxin. Crossing with the DR5-GUS marker line and measurement of free IAA content confirmed the reduced auxin accumulation in pip5k2. In addition, analysis using the membrane-selective dye FM4-64 revealed the decelerated vesicle trafficking caused by PtdIns(4,5)P(2) reduction, which hence results in suppressed cycling of PIN proteins (PIN2 and 3), and delayed redistribution of PIN2 and auxin under gravistimulation in pip5k2 roots. On the contrary, PtdIns(4,5)P(2) significantly enhanced the vesicle trafficking and cycling of PIN proteins. These results demonstrate that PIP5K2 is involved in regulating lateral root formation and root gravity response, and reveal a critical role of PIP5K2/PtdIns(4,5)P(2) in root development through regulation of PIN proteins, providing direct evidence of crosstalk between the phosphatidylinositol signaling pathway and auxin response, and new insights into the control of polar auxin transport. PMID:21894193

  13. Fusarium oxysporum volatiles enhance plant growth via affecting auxin transport and signaling

    Directory of Open Access Journals (Sweden)

    Vasileios eBitas

    2015-11-01

    Full Text Available Volatile organic compounds (VOCs have well-documented roles in plant-plant communication and directing animal behavior. In this study, we examine the less understood roles of VOCs in plant-fungal relationships. Phylogenetically and ecologically diverse strains of Fusarium oxysporum, a fungal species complex that often resides in the rhizosphere of assorted plants, produce volatile compounds that augment shoot and root growth of Arabidopsis thaliana and tobacco. Growth responses of A. thaliana hormone signaling mutants and expression patterns of a GUS reporter gene under the auxin-responsive DR5 promoter supported the involvement of auxin signaling in F. oxysporum volatile-mediated growth enhancement. In addition, 1-naphthylthalamic acid, an inhibitor of auxin efflux, negated F. oxysporum volatile-mediated growth enhancement in both plants. Comparison of the profiles of volatile compounds produced by F. oxysporum strains that differentially affected plant growth suggests that the relative compositions of both growth inhibitory and stimulatory compounds may determine the degree of plant growth enhancement. Volatile-mediated signaling between fungi and plants may represent a potentially conserved, yet mostly overlooked, mechanism underpinning plant-fungus interactions and fungal niche adaption.

  14. Alignment between PIN1 polarity and microtubule orientation in the shoot apical meristem reveals a tight coupling between morphogenesis and auxin transport.

    Directory of Open Access Journals (Sweden)

    Marcus G Heisler

    Full Text Available Morphogenesis during multicellular development is regulated by intercellular signaling molecules as well as by the mechanical properties of individual cells. In particular, normal patterns of organogenesis in plants require coordination between growth direction and growth magnitude. How this is achieved remains unclear. Here we show that in Arabidopsis thaliana, auxin patterning and cellular growth are linked through a correlated pattern of auxin efflux carrier localization and cortical microtubule orientation. Our experiments reveal that both PIN1 localization and microtubule array orientation are likely to respond to a shared upstream regulator that appears to be biomechanical in nature. Lastly, through mathematical modeling we show that such a biophysical coupling could mediate the feedback loop between auxin and its transport that underlies plant phyllotaxis.

  15. Auxin response under osmotic stress.

    Science.gov (United States)

    Naser, Victoria; Shani, Eilon

    2016-08-01

    The phytohormone auxin (indole-3-acetic acid, IAA) is a small organic molecule that coordinates many of the key processes in plant development and adaptive growth. Plants regulate the auxin response pathways at multiple levels including biosynthesis, metabolism, transport and perception. One of the most striking aspects of plant plasticity is the modulation of development in response to changing growth environments. In this review, we explore recent findings correlating auxin response-dependent growth and development with osmotic stresses. Studies of water deficit, dehydration, salt, and other osmotic stresses point towards direct and indirect molecular perturbations in the auxin pathway. Osmotic stress stimuli modulate auxin responses by affecting auxin biosynthesis (YUC, TAA1), transport (PIN), perception (TIR/AFB, Aux/IAA), and inactivation/conjugation (GH3, miR167, IAR3) to coordinate growth and patterning. In turn, stress-modulated auxin gradients drive physiological and developmental mechanisms such as stomata aperture, aquaporin and lateral root positioning. We conclude by arguing that auxin-mediated growth inhibition under abiotic stress conditions is one of the developmental and physiological strategies to acclimate to the changing environment. PMID:27052306

  16. Defining the selectivity of processes along the auxin response chain: a study using auxin analogues

    Czech Academy of Sciences Publication Activity Database

    Simon, Sibu; Kubeš, Martin; Baster, P.; Robert, S.; Dobrev, Petre; Friml, J.; Petrášek, Jan; Zažímalová, Eva

    2013-01-01

    Roč. 200, č. 4 (2013), s. 1034-1048. ISSN 0028-646X R&D Projects: GA ČR(CZ) GAP305/11/0797 Institutional research plan: CEZ:AV0Z50380511 Keywords : auxin analogues * auxin signalling * auxin transport Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 6.736, year: 2012

  17. Auxin Transport and Ribosome Biogenesis Mutant/Reporter Lines to Study Plant Cell Growth and Proliferation under Altered Gravity

    Science.gov (United States)

    Valbuena, Miguel A.; Manzano, Ana I.; van Loon, Jack JWA.; Saez-Vasquez, Julio; Carnero-Diaz, Eugenie; Herranz, Raul; Medina, F. J.

    2013-02-01

    We tested different Arabidopsis thaliana strains to check their availability for space use in the International Space Station (ISS). We used mutants and reporter gene strains affecting factors of cell proliferation and cell growth, to check variations induced by an altered gravity vector. Seedlings were grown either in a Random Positioning Machine (RPM), under simulated microgravity (μg), or in a Large Diameter Centrifuge (LDC), under hypergravity (2g). A combination of the two devices (μgRPM+LDC) was also used. Under all gravity alterations, seedling roots were longer than in control 1g conditions, while the levels of the nucleolar protein nucleolin were depleted. Alterations in the pattern of expression of PIN2, an auxin transporter, and of cyclin B1, a cell cycle regulator, were shown. All these alterations are compatible with previous space data, so the use of these strains will be useful in the next experiments in ISS, under real microgravity.

  18. Ectopic expression of the Brassica SHOOTMERISTEMLESS attenuates the deleterious effects of the auxin transport inhibitor TIBA on somatic embryo number and morphology.

    Science.gov (United States)

    Elhiti, Mohamed; Stasolla, Claudio

    2011-02-01

    The auxin transport inhibitor 2,3,5-triiodobenzoic acid (TIBA) is a useful compound for investigating the role of auxin flow during plant growth and development. In Arabidopsis lines, applications of TIBA during the induction phase of somatic embryogenesis inhibit embryo development and induce the differentiation of the meristematic cells of the shoot apical meristem (SAM), leading to the fusion of the cotyledons. These abnormalities were associated to changes in the expression levels of auxin transporter genes (PINs) and endogenous distribution of IAA. Treatments of TIBA caused a rapid accumulation of IAA within the epidermal and cortical root cells of the explants (bent-cotyledon zygotic embryos), as well as in the apical and sub-apical cells of the callus generated by the surface of the cotyledons of the explants. Within the callus only a few cells acquired meristematic characteristics, and this was associated to low expression levels of genes involved in embryogenic cell fate acquisition, such as WUSCHEL (WUS), LEAFY COTYLEDON 1 and 2. All these deleterious effects were attenuated when TIBA was administered to lines over-expressing SHOOT MERISTEMLESS (STM) isolated from Brassica oleracea (Bo), B. napus (Bn), and B. rapa (Br). Of interest, TIBA-treated explants of Arabidopsis lines over-expressing the Brassica STM were able to produce a large number of embryogenic cells and somatic embryos which exhibited a normal morphology and two distinct cotyledons. A proposed reason for this behaviour was ascribed to the ability of the transformed tissue to retain a normal distribution of auxin in the presence of TIBA. Proper localization of auxin might be required for the normal expression of several genes needed for the acquisition of embryogenic competence and formation of somatic embryos. PMID:21421384

  19. Auxin influx inhibitors 1-NOA, 2-NOA, and CHPAA interfere with membrane dynamics in tobacco cells

    OpenAIRE

    Laňková, M. (Martina); Smith, R. S.; Pešek, B. (Bedřich); Kubeš, M. (Martin); Zažímalová, E. (Eva); Petrášek, J. (Jan); Hoyerová, K.

    2010-01-01

    The phytohormone auxin is transported through the plant body either via vascular pathways or from cell to cell by specialized polar transport machinery. This machinery consists of a balanced system of passive diffusion combined with the activities of auxin influx and efflux carriers. Synthetic auxins that differ in the mechanisms of their transport across the plasma membrane together with polar auxin transport inhibitors have been used in many studies on particular auxin carriers and their ro...

  20. Transport and concentration of abscisic acid (ABA) and auxin (IAA) in deciduous and coniferous trees. Transport und Gehalt von Abscisinsaeure (ABA) und Auxin (IAA) in Laub- und Nadelblaettern

    Energy Technology Data Exchange (ETDEWEB)

    Hartung, W.

    1988-09-01

    Abscisic acid and indoleacetic acid were chosen to examine whether intact deciduous and coniferous tissues from spruce, hemlock fir, spinage, barley and sorrel or isolated mesophyll protoplasts from barley and closing cell preparations from Valerianella locusta are affected by sulphur dioxide in terms of changes in the concentration, transportation and distribution of such plant hormones. The distribution of phytohormones like ABA and IAA over the individual cell compartments is determined by the different pH gradients of the latter. Owing to their acidity these hormones are accumulated in alkaline cell inclusion bodies like chloroplasts and cytosol. Potentially acid air pollutants like SO{sub 2} and NO{sub x} lead to acidification of previously alkaline cell compartments, due to which fact the cellular pH gradients are reduced. This, in turn, gives rise to a redistribution of phytohormones to the effect that certain target cells such as closing cells of leaves or meristem cells come under the influence of altered hormone concentrations and compositions. This is bound to affect the processes controlling the development, growth and stress behaviour of plants. (orig.) With 55 refs., 2 tabs., 16 figs.

  1. Kaempferol 3-O-rhamnoside-7-O-rhamnoside is an endogenous flavonol inhibitor of polar auxin transport in Arabidopsis shoots

    OpenAIRE

    Yin, R.H.; Han, K.; Heller, W; Albert, A.; Dobrev, P. (Petre); Zažímalová, E. (Eva); Schaffner, A.R.

    2014-01-01

    Polar auxin transport (PAT) plays key roles in the regulation of plant growth and development. Flavonoids have been implicated in the inhibition of PAT. However, the active flavonoid derivative(s) involved in this process in vivo has not yet been identified. Here, we provide evidence that a specific flavonol bis-glycoside is correlated with shorter plant stature and reduced PAT. Specific flavonoid-biosynthetic or flavonoid-glycosylating steps were genetically blocked in Arabidopsis thaliana. ...

  2. Auxin transport in leafy pea stem cuttings is partially driven by photosynthesis

    Energy Technology Data Exchange (ETDEWEB)

    Kumpula, C.L.; Potter, J.R.

    1987-04-01

    When /sup 14/C-IAA was applied to the apex of disbudded leafy pea stem cuttings (15 cm long), the movement of /sup 14/C-IAA to the base of the cuttings after 24 h was influenced by the photosynthetic rate. In the absence of photosynthesis, light did not influence /sup 14/C-IAA movement. Photosynthesis was altered by varying light, CO/sub 2/ concentration, or stomatal aperature (blocked with an antitranspirant). Radioactivity (identified by co-chromatography) was 25, 60, and 5% IAA, IAA-aspartate, and indolealdehyde respectively regardless of treatment. Adventitious root formation was reduced 50 to 95% and movement of IAA was inhibited 50 to 70% by decreasing gross photosynthesis 90 to 100%. Apparently, photosynthesis partially drives the movement of IAA from the apex to the base where roots arise. This gives a probably role of photosynthesis in rooting, because in this system virtually no rooting will take place without exogenous auxin and at least a low level of gross photosynthesis.

  3. The role of polar auxin transport through pedicels of Prunus avium L. in relation to fruit development and retention.

    Science.gov (United States)

    Else, Mark A; Stankiewicz-Davies, Anna P; Crisp, Carol M; Atkinson, Christopher J

    2004-09-01

    It was investigated whether premature fruit abscission in Prunus avium L. was triggered by a reduction in polar auxin transport (PAT). The capacity of pedicels to transport tritiated IAA ([3H]-IAA) via the PAT pathway was measured at intervals throughout flower and fruit development. The extent of passive diffusion, assessed by concurrent applications of [14C]-benzoic acid ([14C]-BA), was negligible. Transported radioactivity recovered from agar blocks eluted at the same retention time as authentic [3H]-IAA during HPLC fractionation. The capacity for PAT was already high 7 d before anthesis and increased further following the fertilization of flowers at anthesis. PAT intensity was greatest immediately following fertilization and at the beginning of the cell expansion phase of fruit growth; the transport intensity in fruitlets destined to abscind was negligible. The amount of endogenous IAA moving through the PAT pathway was greatest during the first 3 weeks after fertilization and was again high at the beginning of the fruit expansion stage. IAA export in the phloem increased following fertilization then declined below detectable levels. ABA export in the phloem increased markedly during stone formation and at the onset of fruit expansion. TIBA applied to pedicels of fruit in situ promoted fruitlet abscission in 2000 but not in 2001, despite PAT capacity being reduced by over 98% in the treated pedicels. The application of TIBA to pedicels did not affect fruit expansion. The role of PAT and IAA in relation to the development and retention of Prunus avium fruit is discussed. PMID:15310825

  4. Automorphosis of etiolated pea seedlings in space is simulated by a three-dimensional clinostat and the application of inhibitors of auxin polar transport.

    Science.gov (United States)

    Miyamoto, Kensuke; Hoshino, Tomoki; Yamashita, Masamichi; Ueda, Junichi

    2005-04-01

    Etiolated pea (Pisum sativum L. cv. Alaska) seedlings grown under microgravity conditions in space show automorphosis: bending of epicotyls, inhibition of hook formation and changes in root growth direction. In order to determine the mechanisms of microgravity conditions that induce automorphosis, we used a three-dimensional clinostat and obtained the successful induction of automorphosis-like growth of etiolated pea seedlings. Kinetic studies revealed that epicotyls bent at their basal region towards the clockwise direction far from the cotyledons from the vertical line (0 degrees) at approximately 40 degrees in seedlings grown both at 1 g and in the clinostat within 48 h after watering. Thereafter, epicotyls retained this orientation during growth in the clinostat, whereas those at 1 g changed their growth direction against the gravity vector and exhibited a negative gravitropic response. On the other hand, the plumular hook that had already formed in the embryo axis tended to open continuously by growth at the inner basal portion of the elbow; thus, the plumular hook angle initially increased; this was followed by equal growth on the convex and concave sides at 1 g, resulting in normal hook formation; in contrast, hook formation was inhibited on the clinostat. The automorphosis-like growth and development of etiolated pea seedlings was induced by auxin polar transport inhibitors (9-hydroxyfluorene-9-carboxylic acid, N-(1-naphthyl)phthalamic acid and 2,3,5-triiodobenzoic acid), but not by anti-auxin (p-chlorophenoxyisobutyric acid) at 1 g. An ethylene biosynthesis inhibitor, 1-aminooxyacetic acid, inhibited hook formation at 1 g, and ethylene production of etiolated seedlings was suppressed on the clinostat. Clinorotation on the clinostat strongly reduced the activity of auxin polar transport of epicotyls in etiolated pea seedlings, similar to that observed in space experiments (Ueda J, Miyamoto K, Yuda T, Hoshino T, Fujii S, Mukai C, Kamigaichi S, Aizawa S

  5. Competitive canalization of PIN-dependent auxin flow from axillary buds controls pea bud outgrowth.

    Science.gov (United States)

    Balla, Jozef; Kalousek, Petr; Reinöhl, Vilém; Friml, Jiří; Procházka, Stanislav

    2011-02-01

    Shoot branching is one of the major determinants of plant architecture. Polar auxin transport in stems is necessary for the control of bud outgrowth by a dominant apex. Here, we show that following decapitation in pea (Pisum sativum L.), the axillary buds establish directional auxin export by subcellular polarization of PIN auxin transporters. Apical auxin application on the decapitated stem prevents this PIN polarization and canalization of laterally applied auxin. These results support a model in which the apical and lateral auxin sources compete for primary channels of auxin transport in the stem to control the outgrowth of axillary buds. PMID:21219506

  6. Interactions of Oryza sativa OsCONTINUOUS VASCULAR RING-LIKE 1 (OsCOLE1) and OsCOLE1-INTERACTING PROTEIN reveal a novel intracellular auxin transport mechanism.

    Science.gov (United States)

    Liu, Fei; Zhang, Lan; Luo, Yanzhong; Xu, Miaoyun; Fan, Yunliu; Wang, Lei

    2016-10-01

    Little is known about the transport mechanism of intracellular auxin. Here, we report two vacuole-localized proteins, Oryza sativa OsCONTINUOUS VASCULAR RING-LIKE 1 (OsCOLE1) and OsCOLE1-INTERACTING PROTEIN (OsCLIP), that regulate intracellular auxin transport and homoeostasis. Overexpression of OsCOLE1 markedly increased the internode length and auxin content of the stem base, whereas these parameters were decreased in RNA interference (RNAi) plants. OsCOLE1 was localized on the tonoplast and preferentially expressed in mature tissues. We further identified its interacting protein OsCLIP, which was co-localized on the tonoplast. Protein-protein binding assays demonstrated that the N-terminus of OsCOLE1 directly interacted with OsCLIP in yeast cells and the rice protoplast. Furthermore, (3) H-indole-3-acetic acid ((3) H-IAA) transport assays revealed that OsCLIP transported IAA into yeast cells, which was promoted by OsCOLE1. The results indicate that OsCOLE1 affects rice development by regulating intracellular auxin transport through interaction with OsCLIP, which provides a new insight into the regulatory mechanism of intracellular transport of auxin and the roles of vacuoles in plant development. PMID:27265035

  7. The role of auxin signaling in early embryo pattern formation

    NARCIS (Netherlands)

    Smit, Margot E.; Weijers, Dolf

    2015-01-01

    Pattern formation of the early Arabidopsis embryo generates precursors to all major cell types, and is profoundly controlled by the signaling molecule auxin. Here we discuss recent milestones in our understanding of auxin-dependent embryo patterning. Auxin biosynthesis, transport and response mec

  8. The signal transducer NPH3 integrates the phototropin1 photosensor with PIN2-based polar auxin transport in Arabidopsis root phototropism.

    Science.gov (United States)

    Wan, Yinglang; Jasik, Jan; Wang, Li; Hao, Huaiqing; Volkmann, Dieter; Menzel, Diedrik; Mancuso, Stefano; Baluška, František; Lin, Jinxing

    2012-02-01

    Under blue light (BL) illumination, Arabidopsis thaliana roots grow away from the light source, showing a negative phototropic response. However, the mechanism of root phototropism is still unclear. Using a noninvasive microelectrode system, we showed that the BL sensor phototropin1 (phot1), the signal transducer NONPHOTOTROPIC HYPOCOTYL3 (NPH3), and the auxin efflux transporter PIN2 were essential for BL-induced auxin flux in the root apex transition zone. We also found that PIN2-green fluorescent protein (GFP) localized to vacuole-like compartments (VLCs) in dark-grown root epidermal and cortical cells, and phot1/NPH3 mediated a BL-initiated pathway that caused PIN2 redistribution to the plasma membrane. When dark-grown roots were exposed to brefeldin A (BFA), PIN2-GFP remained in VLCs in darkness, and BL caused PIN2-GFP disappearance from VLCs and induced PIN2-GFP-FM4-64 colocalization within enlarged compartments. In the nph3 mutant, both dark and BL BFA treatments caused the disappearance of PIN2-GFP from VLCs. However, in the phot1 mutant, PIN2-GFP remained within VLCs under both dark and BL BFA treatments, suggesting that phot1 and NPH3 play different roles in PIN2 localization. In conclusion, BL-induced root phototropism is based on the phot1/NPH3 signaling pathway, which stimulates the shootward auxin flux by modifying the subcellular targeting of PIN2 in the root apex transition zone. PMID:22374399

  9. 26S Proteasome: Hunter and Prey in Auxin Signaling.

    Science.gov (United States)

    Kong, Xiangpei; Zhang, Liangran; Ding, Zhaojun

    2016-07-01

    Auxin binds to TRANSPORT INHIBITOR RESPONSE 1 and AUXIN SIGNALLING F-BOX proteins (TIR1/AFBs) and promotes the degradation of Aux/IAA transcriptional repressors. The proteasome regulator PROTEASOME REGULATOR1 (PTRE1) has now been shown to be required for auxin-mediated repression of 26S proteasome activity, thus providing new insights into the fine-tuning of the homoeostasis of Aux/IAA proteins and auxin signaling. PMID:27246455

  10. Transcriptional Responses to the Auxin Hormone

    NARCIS (Netherlands)

    Weijers, Dolf; Wagner, Doris

    2016-01-01

    Auxin is arguably the most important signaling molecule in plants, and the last few decades have seen remarkable breakthroughs in understanding its production, transport, and perception. Recent investigations have focused on transcriptional responses to auxin, providing novel insight into the fun

  11. Expression of PIN and AUX1 genes encoding putative carrier proteins for auxin polar transport in etiolated pea epicotyls [correction of epicotyles] under simulated microgravity conditions on a three-dimensional clinostat.

    Science.gov (United States)

    Hoshino, Tomoki; Hitotsubashi, Reiko; Miyamoto, Kensuke; Tanimoto, Eiichi; Ueda, Junichi

    2003-10-01

    Etiolated pea (Pisum sativum L. cv. Alaska) seedlings grown under simulated microgravity conditions on a 3-dimensional clinostat showed automorphosis-like growth and development similar to that observed in true microgravity conditions in space. Application of inhibitors of auxin polar transport phenocopied automorphosis-like growth on 1 g conditions, suggesting that automorophosis is closely related to auxin polar transport. Strenuous efforts to know the relationships between automorphosis and auxin polar transport in pea seedlings at molecular bases resulted in successful identification of PsPIN2 and PsAUX1 encoding putative auxin efflux and influx carrier protein, respectively. Significantly high levels in homology were found on nucleotide and deduced amino acid sequences among PsPIN2, PsPIN1 and AtPINs, and between PsAUX1 and AtAUX1. Expression of PsPIN1 and PsAUX1 genes in etiolated pea seedlings grown on the clinostat were substantially affected, but that of PsPIN2 was not. Roles of these genes in auxin polar transport and automorphosis of etiolated pea seedlings are also described. PMID:14676360

  12. Gravity-controlled asymmetrical transport of auxin regulates a gravitropic response in the early growth stage of etiolated pea (Pisum sativum) epicotyls: studies using simulated microgravity conditions on a three-dimensional clinostat and using an agravitropic mutant, ageotropum.

    Science.gov (United States)

    Hoshino, Tomoki; Miyamoto, Kensuke; Ueda, Junichi

    2007-09-01

    Increased expression of the auxin-inducible gene PsIAA4/5 was observed in the elongated side of epicotyls in early growth stages of etiolated pea (Pisum sativum L. cv. Alaska) seedlings grown in a horizontal or an inclined position under 1 g conditions. Under simulated microgravity conditions on a 3D clinostat, accumulation of PsIAA4/5 mRNA was found throughout epicotyls showing automorphosis. Polar auxin transport in the proximal side of epicotyls changed when the seedlings were grown in a horizontal or an inclined position under 1 g conditions, but that under clinorotation did not, regardless of the direction of seed setting. Accumulation of PsPIN1 and PsPIN2 mRNAs in epicotyls was affected by gravistimulation, but not by clinorotation. Under 1 g conditions, auxin-transport inhibitors made epicotyls of seedlings grown in a horizontal or inclined position grow toward the proximal direction to cotyledons. These inhibitors led to epicotyl bending toward the cotyledons in seedlings grown in an inclined position under clinorotation. Polar auxin transport, as well as growth direction, of epicotyls of the agravitropic mutant ageotropum did not respond to various gravistimulation. These results suggest that alteration of polar auxin transport in the proximal side of epicotyls regulates the graviresponse of pea epicotyls. PMID:17712525

  13. Comprehensive Transcriptome Analysis of Auxin Responses in Arabidopsis

    Institute of Scientific and Technical Information of China (English)

    Ivan A.Paponov; Martina Paponov; William Teale; Margit Menges; Sohini Chakrabortee; James A.H.Murray; Klaus Palme

    2008-01-01

    In plants,the hormone auxin shapes gene expression to regulate growth and development.Despite the detailed characterization of auxin-inducible genes,a comprehensive overview of the temporal and spatial dynamics of auxinregulated gene expression is lacking.Here,we analyze transcriptome data from many publicly available Arabidopsis profiling experiments and assess tissue-specific gene expression both in response to auxin concentration and exposure time and in relation to other plant growth regulators.Our analysis shows that the primary response to auxin over a wide range of auxin application conditions and in specific tissues comprises almost exclusively the up-regulation of genes and identifies the most robust auxin marker genes.Tissue-specific auxin responses correlate with differential expression of Aux/IAA genes and the subsequent regulation of context- and sequence-specific patterns of gene expression.Changes in transcript levels were consistent with a distinct sequence of conjugation,increased transport capacity and down-regulation of biosynthesis in the temperance of high cellular auxin concentrations.Our data show that auxin regulates genes associated with the biosynthesis,catabolism and signaling pathways of other phytohormones.We present a transcriptional overview of the auxin response.Specific interactions between auxin and other phytohormones are highlighted,particularly the regulation of their metabolism.Our analysis provides a roadmap for auxin-dependent processes that underpins the concept of an 'auxin code'-a tissue-specific fingerprint of gene expression that initiates specific developmental processes.

  14. WOX5–IAA17 feedback circuit-mediated cellular auxin response is crucial for the patterning of root stem cell niches in Arabidopsis

    OpenAIRE

    Tian, Huiyu; Wabnik, Krzysztof; Niu, Tiantian; Li, Hanbing; Yu, Qianqian; Pollmann, Stephan; Vanneste, Steffen; Govaerts, Willy; Rolčík, Jakub; Geisler, Markus; Friml, Jiří; Ding, Zhaojun

    2014-01-01

    In plants, the patterning of stem cell-enriched meristems requires a graded auxin response maximum that emerges from the concerted action of polar auxin transport, auxin biosynthesis, auxin metabolism, and cellular auxin response machinery. However, mechanisms underlying this auxin response maximum-mediated root stem cell maintenance are not fully understood. Here, we present unexpected evidence that WUSCHEL-RELATED HOMEOBOX 5 (WOX5) transcription factor modulates expression of auxin biosynth...

  15. Up in the air: Untethered Factors of Auxin Response

    Science.gov (United States)

    Powers, Samantha K.; Strader, Lucia C.

    2016-01-01

    As a prominent regulator of plant growth and development, the hormone auxin plays an essential role in controlling cell division and expansion. Auxin-responsive gene transcription is mediated through the TRANSPORT INHIBITOR RESPONSE1/AUXIN SIGNALING F-BOX (TIR1/AFB) pathway. Roles for TIR1/AFB pathway components in auxin response are understood best, but additional factors implicated in auxin responses require more study. The function of these factors, including S-Phase Kinase-Associated Protein 2A (SKP2A), SMALL AUXIN UP RNAs (SAURs), INDOLE 3-BUTYRIC ACID RESPONSE5 (IBR5), and AUXIN BINDING PROTEIN1 (ABP1), has remained largely obscure. Recent advances have begun to clarify roles for these factors in auxin response while also raising additional questions to be answered. PMID:26918184

  16. Pattern formation in a cell based auxin transport model with numerical bifurcation analysis

    CERN Document Server

    Draelants, Delphine; Beemster, Gerrit T S; Vanroose, Wim

    2012-01-01

    Transport models of growth hormones can be used to reproduce the hormone accumulations that occur in plant organs. Mostly, these accumulation patterns are calculated using time step methods, even though only the resulting steady state patterns of the model are of interest. We examine the steady state solutions of the hormone transport model of Smith et al (2006) for a one-dimensional row of plant cells. We search for the steady state solutions as a function of three of the model parameters by using numerical continuation methods and bifurcation analysis. These methods are more adequate for solving steady state problems than time step methods. We discuss a trivial solution where the concentrations of hormones are equal in all cells and examine its stability region. We identify two generic bifurcation scenarios through which the trivial solution loses its stability. The trivial solution becomes either a steady state pattern with regular spaced peaks or a pattern where the concentration is periodic in time.

  17. Genome-wide identification and expression profiling analysis of ZmPIN, ZmPILS, ZmLAX and ZmABCB auxin transporter gene families in maize (Zea mays L. under various abiotic stresses.

    Directory of Open Access Journals (Sweden)

    Runqing Yue

    Full Text Available The auxin influx carriers auxin resistant 1/like aux 1 (AUX/LAX, efflux carriers pin-formed (PIN (together with PIN-like proteins and efflux/conditional P-glycoprotein (ABCB are major protein families involved in auxin polar transport. However, how they function in responses to exogenous auxin and abiotic stresses in maize is largely unknown. In this work, the latest updated maize (Zea mays L. reference genome sequence was used to characterize and analyze the ZmLAX, ZmPIN, ZmPILS and ZmABCB family genes from maize. The results showed that five ZmLAXs, fifteen ZmPINs, nine ZmPILSs and thirty-five ZmABCBs were mapped on all ten maize chromosomes. Highly diversified gene structures, nonconservative transmembrane helices and tissue-specific expression patterns suggested the possibility of function diversification for these genes. Quantitative real-time polymerase chain reaction (qRT-PCR was used to analyze the expression patterns of ZmLAX, ZmPIN, ZmPILS and ZmABCB genes under exogenous auxin and different environmental stresses. The expression levels of most ZmPIN, ZmPILS, ZmLAX and ZmABCB genes were induced in shoots and were reduced in roots by various abiotic stresses (drought, salt and cold stresses. The opposite expression response patterns indicated the dynamic auxin transport between shoots and roots under abiotic stresses. Analysis of the expression patterns of ZmPIN, ZmPILS, ZmLAX and ZmABCB genes under drought, salt and cold treatment may help us to understand the possible roles of maize auxin transporter genes in responses and tolerance to environmental stresses.

  18. A ROP GTPase-dependent auxin signaling pahtway regulates the subcellular distribution of PIN2 in Arabidopsis roots

    NARCIS (Netherlands)

    Lin, D.; Nagawa, S.; Chen, J.; Cao, L.; Scheres, B.

    2012-01-01

    PIN-FORMED (PIN) protein-mediated auxin polar transport is critically important for development, pattern formation, and morphogenesis in plants. Auxin has been implicated in the regulation of polar auxin transport by inhibiting PIN endocytosis [1 and 2], but how auxin regulates this process is poorl

  19. Irrepressible, truncated Auxin Response Factors: Natural roles and applications in dissecting auxin gene regulation pathways

    OpenAIRE

    Ckurshumova, Wenzislava; Krogan, Naden T.; Marcos, Danielle; Caragea, Adriana E.; Berleth, Thomas

    2012-01-01

    The molecularly well-characterized auxin signal transduction pathway involves two evolutionarily conserved families interacting through their C-terminal domains III and IV: the Auxin Response Factors (ARFs) and their repressors the Aux/IAAs, to control auxin-responsive genes, among them genes involved in auxin transport.1,2 We have developed a new genetic tool to study ARF function. Using MONOPTEROS (MP)/ARF5, we have generated a truncated version of MP (MPΔ),3 which has lost the target domai...

  20. The effect of low temperature, nitrogen atmosphere and uncouplers on longitudinal distribution of radioactivity after acropetal and basipetal application of (2-14C) ABA in long root segments of Phaseolus coccineus L

    International Nuclear Information System (INIS)

    Acropetal movement of [2-14C] abscisic acid (ABA) in long root segments of P.coccineus is drastically reduced by destruction of the tissue, low temperature, anaerobic conditions and pretreatment with CCCP (carbonyl-cyanide-m-chloro-phenylhydrazone) at uncoupling concentrations. Basipetal transport is not affected by destruction of the tissue but markedly inhibited by the other treatments. Consequently polarity of ABA-transport disappears only after the roots have been killed. The importance of using long segments for hormone transport studies is discussed. (orig.)

  1. Auxin-Cytokinin Interaction Regulates Meristem Development

    Institute of Scientific and Technical Information of China (English)

    Ying-Hua Su; Yu-Bo Liu; Xian-Sheng Zhang

    2011-01-01

    Plant hormones regulate many aspects of plant growth and development. Both auxin and cytokinin have been known for a long time to act either synergistically or antagonistically to control several significant developmental processes, such as the formation and maintenance of meristem. Over the past few years, exciting progress has been made to reveal the molecular mechanisms underlying the auxin-cytokinin action and interaction. In this review, we shall briefly discuss the major progress made in auxin and cytokinin biosynthesis, auxin transport, and auxin and cytokinin signaling.The frameworks for the complicated interaction of these two hormones in the control of shoot apical meristem and root apical meristem formation as well as their roles in in vitro organ regeneration are the major focus of this review.

  2. Auxin biology revealed by small molecules.

    Science.gov (United States)

    Ma, Qian; Robert, Stéphanie

    2014-05-01

    The plant hormone auxin regulates virtually every aspect of plant growth and development and unraveling its molecular and cellular modes of action is fundamental for plant biology research. Chemical genomics is the use of small molecules to modify protein functions. This approach currently rises as a powerful technology for basic research. Small compounds with auxin-like activities or affecting auxin-mediated biological processes have been widely used in auxin research. They can serve as a tool complementary to genetic and genomic methods, facilitating the identification of an array of components modulating auxin metabolism, transport and signaling. The employment of high-throughput screening technologies combined with informatics-based chemical design and organic chemical synthesis has since yielded many novel small molecules with more instantaneous, precise and specific functionalities. By applying those small molecules, novel molecular targets can be isolated to further understand and dissect auxin-related pathways and networks that otherwise are too complex to be elucidated only by gene-based methods. Here, we will review examples of recently characterized molecules used in auxin research, highlight the strategies of unraveling the mechanisms of these small molecules and discuss future perspectives of small molecule applications in auxin biology. PMID:24252105

  3. Auxin metabolism rates and implications for plant development

    Directory of Open Access Journals (Sweden)

    Eric M Kramer

    2015-03-01

    Full Text Available Studies of auxin metabolism rarely express their results as a metabolic rate, although the data obtained would often permit such a calculation to be made. We analyze data from 31 previously published papers to quantify the rates of auxin biosynthesis, conjugation, conjugate hydrolysis, and catabolism in seed plants. Most metabolic pathways have rates in the range 10 nM/h to 1 μM/h, with the exception of auxin conjugation, which has rates as high as ~100 μM/h. The highest rates of auxin conjugation suggests that auxin metabolic sinks may be very small, perhaps as small as a single cell. By contrast, the relatively low rate of auxin biosynthesis requires plants to conserve and recycle auxin during long-distance transport. The consequences for plant development are discussed.

  4. Plant embryogenesis requires AUX/LAX-mediated auxin influx

    NARCIS (Netherlands)

    Robert, H.S.; Grunewald, W.; Cannoot, B.; Soriano, M.; Swarup, R.; Weijers, D.; Bennett, M.; Boutilier, K.A.; Friml, J.

    2015-01-01

    The plant hormone auxin and its directional transport are known to play a crucial role in defining the embryonic axis and subsequent development of the body plan. Although the role of PIN auxin efflux transporters has been clearly assigned during embryonic shoot and root specification, the role of t

  5. Irrepressible, truncated auxin response factors: natural roles and applications in dissecting auxin gene regulation pathways.

    Science.gov (United States)

    Ckurshumova, Wenzislava; Krogan, Naden T; Marcos, Danielle; Caragea, Adriana E; Berleth, Thomas

    2012-08-01

    The molecularly well-characterized auxin signal transduction pathway involves two evolutionarily conserved families interacting through their C-terminal domains III and IV: the Auxin Response Factors (ARFs) and their repressors the Aux/IAAs, to control auxin-responsive genes, among them genes involved in auxin transport. ( 1) (,) ( 2) We have developed a new genetic tool to study ARF function. Using MONOPTEROS (MP)/ARF5, we have generated a truncated version of MP (MPΔ), ( 3) which has lost the target domains for repression by Aux/IAA proteins. Besides exploring genetic interactions between MP and Aux/IAAs, we used this construct to trace MP's role in vascular patterning, a previously characterized auxin dependent process. ( 4) (,) ( 5) Here we summarize examples of naturally occurring truncated ARFs and summarize potential applications of truncated ARFs as analytical tools. PMID:22827953

  6. 5'-azido-N-1-naphthylphthalamic acid, a photolabile analog of the auxin transport inhibitor, N-1-naphthylphthalamic acid: synthesis and binding properties

    Energy Technology Data Exchange (ETDEWEB)

    Voet, J.G.; Howley, K.; Shumsky, J.S.

    1987-05-01

    The polar transport of the plant growth regulator, auxin (indole-3-acetic acid, IAAH), is thought to involve the participation of several proteins in the plasma membrane, including a specific, saturable, voltage independent H/sup +//IAA/sup -/ efflux carrier located preferentially at the basal end of each cell. Auxin transport is specifically inhibited by the herbicide, N-1-naphthylphthalamic acid (NPA), which binds specifically to a protein in the plasma membrane, thought to be either the IAA/sup -/ efflux carrier or an allosteric effector protein. They have synthesized and characterized a photolabile analog of NPA, 5'-azido-N-1-naphthylphthalamic acid (Az-NPA). This potential photoaffinity label for the NPA binding protein competes with /sup 3/H-NPA for binding sites on Curcurbita pepo L. (zucchini) stem cell membranes with K/sub j/ = 1.5 x 10/sup -7/ M. The K/sub i/ for NPA under these conditions is 2 x 10/sup -8/M, indicating that the affinity of Az-NPA for the membranes is only 7.5 fold lower than NPA. While the binding of 4.6 x 10/sup -6/ M Az-NPA to NPA binding sites is reversible in the dark, exposure to light results in a 30% loss in /sup 3/H-NPA binding ability. Pretreatment with 10/sup -4/ M NPA protects the membranes against photodestruction of /sup 3/H-NPA binding sites by Az-NPA, supporting the conclusion that Az-NPA destroys these sites by specific covalent attachment.

  7. Strigolactone acts downstream of auxin to regulate bud outgrowth in pea and Arabidopsis.

    Science.gov (United States)

    Brewer, Philip B; Dun, Elizabeth A; Ferguson, Brett J; Rameau, Catherine; Beveridge, Christine A

    2009-05-01

    During the last century, two key hypotheses have been proposed to explain apical dominance in plants: auxin promotes the production of a second messenger that moves up into buds to repress their outgrowth, and auxin saturation in the stem inhibits auxin transport from buds, thereby inhibiting bud outgrowth. The recent discovery of strigolactone as the novel shoot-branching inhibitor allowed us to test its mode of action in relation to these hypotheses. We found that exogenously applied strigolactone inhibited bud outgrowth in pea (Pisum sativum) even when auxin was depleted after decapitation. We also found that strigolactone application reduced branching in Arabidopsis (Arabidopsis thaliana) auxin response mutants, suggesting that auxin may act through strigolactones to facilitate apical dominance. Moreover, strigolactone application to tiny buds of mutant or decapitated pea plants rapidly stopped outgrowth, in contrast to applying N-1-naphthylphthalamic acid (NPA), an auxin transport inhibitor, which significantly slowed growth only after several days. Whereas strigolactone or NPA applied to growing buds reduced bud length, only NPA blocked auxin transport in the bud. Wild-type and strigolactone biosynthesis mutant pea and Arabidopsis shoots were capable of instantly transporting additional amounts of auxin in excess of endogenous levels, contrary to predictions of auxin transport models. These data suggest that strigolactone does not act primarily by affecting auxin transport from buds. Rather, the primary repressor of bud outgrowth appears to be the auxin-dependent production of strigolactones. PMID:19321710

  8. Phyllotaxis involves auxin drainage through leaf primordia

    DEFF Research Database (Denmark)

    Deb, Yamini; Marti, Dominik; Frenz, Martin;

    2015-01-01

    The spatial arrangement of leaves and flowers around the stem, known as phyllotaxis, is controlled by an auxin-dependent reiterative mechanism that leads to regular spacing of the organs and thereby to remarkably precise phyllotactic patterns. The mechanism is based on the active cellular transport...... of the phytohormone auxin by cellular influx and efflux carriers, such as AUX1 and PIN1. Their important role in phyllotaxis is evident from mutant phenotypes, but their exact roles in space and time are difficult to address due to the strong pleiotropic phenotypes of most mutants in phyllotaxis. Models...... of phyllotaxis invoke the accumulation of auxin at leaf initials and removal of auxin through their developing vascular strand, the midvein. We have developed a precise microsurgical tool to ablate the midvein at high spatial and temporal resolution in order to test its function in leaf formation and phyllotaxis...

  9. Interactions between auxin and strigolactone in shoot branching control.

    Science.gov (United States)

    Hayward, Alice; Stirnberg, Petra; Beveridge, Christine; Leyser, Ottoline

    2009-09-01

    In Arabidopsis (Arabidopsis thaliana), the carotenoid cleavage dioxygenases MORE AXILLARY GROWTH3 (MAX3) and MAX4 act together with MAX1 to produce a strigolactone signaling molecule required for the inhibition of axillary bud outgrowth. We show that both MAX3 and MAX4 transcripts are positively auxin regulated in a manner similar to the orthologous genes from pea (Pisum sativum) and rice (Oryza sativa), supporting evolutionary conservation of this regulation in plants. This regulation is important for branching control because large auxin-related reductions in these transcripts are associated with increased axillary branching. Both transcripts are up-regulated in max mutants, and consistent with max mutants having increased auxin in the polar auxin transport stream, this feedback regulation involves auxin signaling. We suggest that both auxin and strigolactone have the capacity to modulate each other's levels and distribution in a dynamic feedback loop required for the coordinated control of axillary branching. PMID:19641034

  10. Points of regulation for auxin action.

    Science.gov (United States)

    Zazimalova, E; Napier, R M

    2003-03-01

    There have been few examples of the application of our growing knowledge of hormone action to crop improvement. In this review we discuss what is known about the critical points regulating auxin action. We examine auxin metabolism, transport, perception and signalling and identify genes and proteins that might be keys to regulation, particularly the rate-limiting steps in various pathways. Certain mutants show that substrate flow in biosynthesis can be limiting. To date there is little information available on the genes and proteins of catabolism. There have been several auxin transport proteins and some elegant transport physiology described recently, and the potential for using transport proteins to manage free indole-3-acetic acid (IAA) concentrations is discussed. Free IAA is very mobile, and so while it may be more practical to control auxin action through managing the receptor and signalling pathways, the candidate genes and proteins through which this can be done remain largely unknown. From the available evidence, it is clear that the reason for so few commercial applications arising from the control of auxin action is that knowledge is still limited. PMID:12789411

  11. THE MODEL FOR AUXIN REGULATED ATPIN1 EXPRESSION IN THE ROOT APICAL MERISTEM

    OpenAIRE

    Ermakov A.A.; V.V. Chernova; Doroshkov, A. V.; S.S. Sangaev; Omelyanchuk, N. A.; Kochetov, A. V.; Mironova, V. V.

    2012-01-01

    Plant hormone auxin regulates many aspects of plant growth and development. PIN-FORMED (PIN) gene family encodes transmembrane proteins, which mediate auxin efflux. PIN proteins are asymmetrically localized within cells, thereby forming in tissue auxin concentration gradients and maxima. Auxin has various effects on PIN1 expression in a cell providing for both positive and negative feedbacks on its own transport [1]. Earlier we proposed that this dual regulation determines stem cell niche mai...

  12. Auxin response factors.

    Science.gov (United States)

    Chandler, John William

    2016-05-01

    Auxin signalling involves the activation or repression of gene expression by a class of auxin response factor (ARF) proteins that bind to auxin response elements in auxin-responsive gene promoters. The release of ARF repression in the presence of auxin by the degradation of their cognate auxin/indole-3-acetic acid repressors forms a paradigm of transcriptional response to auxin. However, this mechanism only applies to activating ARFs, and further layers of complexity of ARF function and regulation are being revealed, which partly reflect their highly modular domain structure. This review summarizes our knowledge concerning ARF binding site specificity, homodimer and heterodimer multimeric ARF association and cooperative function and how activator ARFs activate target genes via chromatin remodelling and evolutionary information derived from phylogenetic comparisons from ARFs from diverse species. ARFs are regulated in diverse ways, and their importance in non-auxin-regulated pathways is becoming evident. They are also embedded within higher-order transcription factor complexes that integrate signalling pathways from other hormones and in response to the environment. The ways in which new information concerning ARFs on many levels is causing a revision of existing paradigms of auxin response are discussed. PMID:26487015

  13. Effect of Polar Auxin Transport on Rice Root Development%生长素极性运输在水稻根发育中的作用

    Institute of Scientific and Technical Information of China (English)

    周大喜; 殷珂; 许智宏; 薛红卫

    2003-01-01

    Polar auxin transport (PAT) is critical in plant growth and development, especially polardifferentiation and pattern formation. Lots of studies have been performed in dicots while relative less inmonocots. Using two kinds of PAT inhibitors, 2, 3, 5-triiodobenzoic acid (TIBA) and 9-hydroxyfluorene-9-carboxylic acid (HFCA), it was shown that PAT is important for rice (Oryza sativa L cv. Zhonghua 11) rootdevelopment, including elongation of the primary roots, initiation and elongation of lateral roots, andformation of adventitious roots. Inhibition of PAT resulted in the shortened primary roots, less and short-ened lateral and adventitious roots. Exogenously supplemented NAA can partially rescue the formation ofadventitious roots but not lateral roots, while low concentration of NAA (0.1 μmol/L) could not rescueeither of them, suggesting the possible different mechanisms of lateral and adventitious root initiations.Treatment of 30 μrnol/L TIBA did not completely inhibit the initiation of lateral roots, and survival capaci-ties of which were demonstrated through cross section experiments revealing the presence of primordialof lateral roots at different stages. Further studies through localized application of PAT inhibitors indicatedthat auxin flow, transported from coleoptiles to the base, is not only responsible for the auxin contents instem nodes but also critical for initiation and elongation of adventitious roots.%生长素极性运输(PAT)在植物生长发育尤其是极性发育和模式建成中起重要作用.采用2种PAT抑制剂TIBA(2,3,5-triiodobenzoic acid)和HFCA(9-hydroxyfluorene-9-carboxylic acid)处理水稻(Oryza sativa L. cv.Zhonghua)幼苗,结果表明:PAT影响水稻根发育包括主根的伸长、侧根的起始和伸长以及不定根的发育.PAT的抑制导致主根变短、侧根和不定根数目减少.外源附加生长素(NAA)可以部分恢复不定根的形成但不能恢复侧根的形成,表明在侧根和不定根的形成上可

  14. A plausible mechanism for auxin patterning along the developing root

    Directory of Open Access Journals (Sweden)

    Kolchanov Nikolai A

    2010-07-01

    with which auxin inhibits its own transport in different species, thereby distinguishing two main types of plant root architecture: taproot vs. fibrous.

  15. Auxin efflux by PIN-FORMED proteins is activated by two different protein kinases, D6 PROTEIN KINASE and PINOID

    KAUST Repository

    Zourelidou, Melina

    2014-06-19

    The development and morphology of vascular plants is critically determined by synthesis and proper distribution of the phytohormone auxin. The directed cell-to-cell distribution of auxin is achieved through a system of auxin influx and efflux transporters. PIN-FORMED (PIN) proteins are proposed auxin efflux transporters, and auxin fluxes can seemingly be predicted based on the-in many cells-asymmetric plasma membrane distribution of PINs. Here, we show in a heterologous Xenopus oocyte system as well as in Arabidopsis thaliana inflorescence stems that PIN-mediated auxin transport is directly activated by D6 PROTEIN KINASE (D6PK) and PINOID (PID)/WAG kinases of the Arabidopsis AGCVIII kinase family. At the same time, we reveal that D6PKs and PID have differential phosphosite preferences. Our study suggests that PIN activation by protein kinases is a crucial component of auxin transport control that must be taken into account to understand auxin distribution within the plant.

  16. Rice WUSCHEL-related homeobox 3A (OsWOX3A) modulates auxin-transport gene expression in lateral root and root hair development.

    Science.gov (United States)

    Yoo, Soo-Cheul; Cho, Sung-Hwan; Paek, Nam-Chon

    2013-10-01

    Coordinated regulation of the many genes controlling leaf, flower, and root development determines the phenotypes of plants; this regulation requires exquisite control of many transcription factors, including the WUSCHEL-related homeobox (WOX) family. We recently reported that rice (Oryza sativa) WUSCHEL-related homeobox 3A (OsWOX3A) plays important roles in organ development, including lateral-axis outgrowth and vasculature patterning in leaves, lemma and palea morphogenesis in spikelets, and the numbers of tillers and lateral roots. OsWOX3A is encoded by NARROW LEAF2 (NAL2) and NAL3, a pair of duplicated genes. In this study, further analysis of nal2 nal3 (hereafter nal2/3) double mutants revealed that, in addition to its role in lateral root development, OsWOX3A also acts in the control of root hair formation. Based on this new finding, we describe a possible mechanism by which OsWOX3A regulation of auxin transport genes acts in root development. PMID:24002214

  17. Auxin Perception—Structural Insights

    OpenAIRE

    Calderon-Villalobos, Luz Irina; Tan, Xu; Zheng, Ning; Estelle, Mark

    2010-01-01

    The identity of the auxin receptor(s) and the mechanism of auxin perception has been a subject of intense interest since the discovery of auxin almost a century ago. The development of genetic approaches to the study of plant hormone signaling led to the discovery that auxin acts by promoting degradation of transcriptional repressors called Aux/IAA proteins. This process requires a ubiquitin protein ligase (E3) called SCFTIR1 and related SCF complexes. Surprisingly, auxin works by directly bi...

  18. Lateral root stimulation in the early interaction between Arabidopsis thaliana and the ectomycorrhizal fungus Laccaria bicolor: Is fungal auxin the trigger?

    OpenAIRE

    Felten, Judith; Legué, Valérie; Ditengou, Franck Anicet

    2010-01-01

    Lateral root (LR) stimulation during early signal exchange between plant roots and ectomycorrhizal (ECM) fungi has recently been shown to be achieved by modulation of auxin gradients. We suggested that this modulation could occur through altered polar auxin transport (PAT) and through activation of auxin signalling pathways in the root. However, it remains unclear, which fungal molecules alter auxin pathways inside the plant partner. It has been suggested in previous studies that auxin releas...

  19. Auxin-cytokinin and auxin-gibberellin interactions during morphogenesis of the compound leaves of pea (Pisum sativum).

    Science.gov (United States)

    DeMason, Darleen A

    2005-09-01

    A number of mutations that alter the form of the compound leaf in pea (Pisum sativum) has proven useful in elucidating the role that auxin might play in pea leaf development. The goals of this study were to determine if auxin application can rescue any of the pea leaf mutants and if gibberellic acid (GA) plays a role in leaf morphogenesis in pea. A tissue culture system was used to determine the effects of various auxins, GA or a GA biosynethesis inhibitor (paclobutrazol) on leaf development. The GA mutant, nana1 (na1) was analyzed. The uni-tac mutant was rescued by auxin and GA and rescue involved both a conversion of the terminal leaflet into a tendril and an addition of a pair of lateral tendrils. This rescue required the presence of cytokinin. The auxins tested varied in their effectiveness, although methyl-IAA worked best. The terminal tendrils of wildtype plantlets grown on paclobutrazol were converted into leaflets, stubs or were aborted. The number of lateral pinna pairs produced was reduced and leaf initiation was impaired. These abnormalities resembled those caused by auxin transport inhibitors and phenocopy the uni mutants. The na1 mutant shared some morphological features with the uni mutants; including, flowering late and producing leaves with fewer lateral pinna pairs. These results show that both auxin and GA play similar and significant roles in pea leaf development. Pea leaf morphogenesis might involve auxin regulation of GA biosynthesis and GA regulation of Uni expression. PMID:15809864

  20. Localization and interactions between Arabidopsis auxin biosynthetic enzymes in the TAA/YUC-dependent pathway.

    Science.gov (United States)

    Kriechbaumer, Verena; Botchway, Stanley W; Hawes, Chris

    2016-07-01

    The growth regulator auxin is involved in all key developmental processes in plants. A complex network of a multiplicity of potential biosynthetic pathways as well as transport, signalling plus conjugation and deconjugation lead to a complex and multifaceted system system for auxin function. This raises the question how such a system can be effectively organized and controlled. Here we report that a subset of auxin biosynthetic enzymes in the TAA/YUC route of auxin biosynthesis is localized to the endoplasmic reticulum (ER). ER microsomal fractions also contain a significant percentage of auxin biosynthetic activity. This could point toward a model of auxin function using ER membrane location and subcellular compartmentation for supplementary layers of regulation. Additionally we show specific protein-protein interactions between some of the enzymes in the TAA/YUC route of auxin biosynthesis. PMID:27208541

  1. Aintegumenta and Aintegumenta-Like6 regulate auxin-mediated flower development in Arabidopsis

    Directory of Open Access Journals (Sweden)

    Krizek Beth A

    2011-06-01

    Full Text Available Abstract Background Two related genes encoding AP2/ERF-type transcription factors, AINTEGUMENTA (ANT and AINTEGUMENTA-LIKE6 (AIL6, are important regulators of floral growth and patterning in Arabidopsis. Evidence suggests that these genes promote several aspects of flower development in response to auxin. To investigate the interplay of ANT, AIL6 and auxin during floral development, I have examined the phenotypic consequences of disrupting polar auxin transport in ant, ail6 and ant ail6 mutants by either genetic or chemical means. Results Plants containing mutations in ANT or AIL6 alone or in both genes together exhibit increased sensitivity to disruptions in polar auxin transport. Both genes promote shoot growth, floral meristem initiation and floral meristem patterning in combination with auxin transport. However, differences in the responses of ant and ail6 single mutants to perturbations in auxin transport suggest that these two genes also have non-overlapping activities in each of these developmental processes. Conclusions The enhanced sensitivity of ant and ail6 mutants to alterations in polar auxin transport suggests that these mutants have defects in some aspect of auxin physiology. The inability of ant ail6 double mutants to initiate flowers in backgrounds disrupted for auxin transport confirm the proposed roles for these two genes in floral meristem initiation.

  2. Phospholipase Dζ2 Drives Vesicular Secretion of Auxin for Its Polar Cell-Cell Transport in the Transition Zone of the Root Apex

    Czech Academy of Sciences Publication Activity Database

    Mancuso, S.; Marras, A.M.; Mugnai, S.; Schlicht, M.; Žárský, Viktor; Li, G.; Song, L.; Xue, H.W.; Baluška, F.

    2007-01-01

    Roč. 2, č. 4 (2007), s. 240-244. ISSN 1559-2316 Institutional research plan: CEZ:AV0Z50380511 Keywords : auxin * Brefeldin A * plant synapse * phospholipase D Subject RIV: EB - Genetics ; Molecular Biology www.landesbioscience.com/journals/psb/abstract.php?id=4566

  3. Auxin influx carriers control vascular patterning and xylem differentiation in Arabidopsis thaliana.

    Directory of Open Access Journals (Sweden)

    Norma Fàbregas

    2015-04-01

    Full Text Available Auxin is an essential hormone for plant growth and development. Auxin influx carriers AUX1/LAX transport auxin into the cell, while auxin efflux carriers PIN pump it out of the cell. It is well established that efflux carriers play an important role in the shoot vascular patterning, yet the contribution of influx carriers to the shoot vasculature remains unknown. Here, we combined theoretical and experimental approaches to decipher the role of auxin influx carriers in the patterning and differentiation of vascular tissues in the Arabidopsis inflorescence stem. Our theoretical analysis predicts that influx carriers facilitate periodic patterning and modulate the periodicity of auxin maxima. In agreement, we observed fewer and more spaced vascular bundles in quadruple mutants plants of the auxin influx carriers aux1lax1lax2lax3. Furthermore, we show AUX1/LAX carriers promote xylem differentiation in both the shoot and the root tissues. Influx carriers increase cytoplasmic auxin signaling, and thereby differentiation. In addition to this cytoplasmic role of auxin, our computational simulations propose a role for extracellular auxin as an inhibitor of xylem differentiation. Altogether, our study shows that auxin influx carriers AUX1/LAX regulate vascular patterning and differentiation in plants.

  4. Auxin regulates distal stem cell differentiation in Arabidopsis roots

    OpenAIRE

    Ding, Zhaojun; Friml, Jiří

    2010-01-01

    The stem cell niche in the root meristem is critical for the development of the plant root system. The plant hormone auxin acts as a versatile trigger in many developmental processes, including the regulation of root growth, but its role in the control of the stem cell activity remains largely unclear. Here we show that local auxin levels, determined by biosynthesis and intercellular transport, mediate maintenance or differentiation of distal stem cells in the Arabidopsis thaliana roots. Gene...

  5. Context, Specificity, and Self-Organization in Auxin Response

    OpenAIRE

    Del Bianco, Marta; Kepinski, Stefan

    2011-01-01

    Auxin is a simple molecule with a remarkable ability to control plant growth, differentiation, and morphogenesis. The mechanistic basis for this versatility appears to stem from the highly complex nature of the networks regulating auxin metabolism, transport and response. These heavily feedback-regulated and inter-dependent mechanisms are complicated in structure and complex in operation giving rise to a system with self-organizing properties capable of generating highly context-specific resp...

  6. The auxin influx carriers AUX1 and LAX3 are involved in auxin-ethylene interactions during apical hook development in Arabidopsis thaliana seedlings

    Czech Academy of Sciences Publication Activity Database

    Vandenbussche, F.; Petrášek, Jan; Žádníková, P.; Hoyerová, Klára; Pešek, Bedřich; Raz, V.; Swarup, R.; Bennett, M.; Zažímalová, Eva; Benková, E.; Van Der Straeten, D.

    2010-01-01

    Roč. 137, č. 4 (2010), s. 597-606. ISSN 0950-1991 R&D Projects: GA MŠk(CZ) LC06034 Institutional research plan: CEZ:AV0Z50380511 Keywords : Apical hook * Auxin biosynthesis * Auxin transport Subject RIV: ED - Physiology Impact factor: 6.898, year: 2010

  7. Auxin influx inhibitors 1-NOA, 2-NOA, and CHPAA interfere with membrane dynamics in tobacco cells

    Czech Academy of Sciences Publication Activity Database

    Laňková, Martina; Smith, R. S.; Pešek, Bedřich; Kubeš, Martin; Zažímalová, Eva; Petrášek, Jan; Hoyerová, Klára

    2010-01-01

    Roč. 61, č. 13 (2010), s. 3589-3598. ISSN 0022-0957 R&D Projects: GA AV ČR KJB600380702; GA MŠk(CZ) LC06034 Grant ostatní: _(CZ) CZ.2.16/3.1.00/21159 Institutional research plan: CEZ:AV0Z50380511 Keywords : Auxin efflux carrier * auxin influx carrier * auxin transport Subject RIV: EF - Botanics Impact factor: 4.818, year: 2010

  8. Perturbation of auxin homeostasis by overexpression of wild-type IAA15 results in impaired stem cell differentiation and gravitropism in roots.

    Directory of Open Access Journals (Sweden)

    Da-Wei Yan

    Full Text Available Aux/IAAs interact with auxin response factors (ARFs to repress their transcriptional activity in the auxin signaling pathway. Previous studies have focused on gain-of-function mutations of domain II and little is known about whether the expression level of wild-type Aux/IAAs can modulate auxin homeostasis. Here we examined the perturbation of auxin homeostasis by ectopic expression of wild-type IAA15. Root gravitropism and stem cell differentiation were also analyzed. The transgenic lines were less sensitive to exogenous auxin and exhibited low-auxin phenotypes including failures in gravity response and defects in stem cell differentiation. Overexpression lines also showed an increase in auxin concentration and reduced polar auxin transport. These results demonstrate that an alteration in the expression of wild-type IAA15 can disrupt auxin homeostasis.

  9. Auxins in defense strategies

    Czech Academy of Sciences Publication Activity Database

    Čarná, Mária; Repka, V.; Skůpa, Petr; Šturdík, E.

    2014-01-01

    Roč. 69, č. 10 (2014), s. 1255-1263. ISSN 0006-3088 R&D Projects: GA TA ČR TA01011802 Institutional support: RVO:61389030 Keywords : auxin * defense responses * JA Subject RIV: GF - Plant Pathology, Vermin, Weed, Plant Protection Impact factor: 0.827, year: 2014

  10. Identification of auxin responsive genes in Arabidopsis by cDNA array

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The plant hormone auxin influences a variety of developmental and physiological processes. But the mechanism of its action is quite unclear. In order to identify and analyze the expression of auxin responsive genes, a cDNA array approach was used to screen for genes with altered expression from Arabidopsis suspension culture after IAA treatment and was identified 50 differentially expressed genes from 13824 cDNA clones. These genes were related to signal transduction, stress responses, senescence, photosynthesis, protein biosynthesis and transportation. The results provide the molecular evidence that auxin influences a variety of physiological processes and pave a way for further investigation of the mechanism of auxin action. Furthermore,we found that the expression of a ClpC (regulation subunit of Clp protease) was repressed by exogenous auxin, but increased in dark-induced senescing leaves. This suggests that ClpC may be a senescence-associated gene and can be regulated by auxin.

  11. A rho scaffold integrates the secretory system with feedback mechanisms in regulation of auxin distribution.

    Directory of Open Access Journals (Sweden)

    Ora Hazak

    2010-01-01

    Full Text Available Development in multicellular organisms depends on the ability of individual cells to coordinate their behavior by means of small signaling molecules to form correctly patterned tissues. In plants, a unique mechanism of directional transport of the signaling molecule auxin between cells connects cell polarity and tissue patterning and thus is required for many aspects of plant development. Direction of auxin flow is determined by polar subcellular localization of PIN auxin efflux transporters. Dynamic PIN polar localization results from the constitutive endocytic cycling to and from the plasma membrane, but it is not well understood how this mechanism connects to regulators of cell polarity. The Rho family small GTPases ROPs/RACs are master regulators of cell polarity, however their role in regulating polar protein trafficking and polar auxin transport has not been established. Here, by analysis of mutants and transgenic plants, we show that the ROP interactor and polarity regulator scaffold protein ICR1 is required for recruitment of PIN proteins to the polar domains at the plasma membrane. icr1 mutant embryos and plants display an a array of severe developmental aberrations that are caused by compromised differential auxin distribution. ICR1 functions at the plasma membrane where it is required for exocytosis but does not recycle together with PINs. ICR1 expression is quickly induced by auxin but is suppressed at the positions of stable auxin maxima in the hypophysis and later in the embryonic and mature root meristems. Our results imply that ICR1 is part of an auxin regulated positive feedback loop realized by a unique integration of auxin-dependent transcriptional regulation into ROP-mediated modulation of cell polarity. Thus, ICR1 forms an auxin-modulated link between cell polarity, exocytosis, and auxin transport-dependent tissue patterning.

  12. Antagonistic regulation of PIN phosphorylation by PP2A and PINOID directs auxin flux

    NARCIS (Netherlands)

    Michniewicz, M.; Zago, M.K.; Abas, L.; Weijers, D.; Schweighofer, A.; Meskiene, I.; Heisler, M.G.; Ohno, C.; Zhang, J.; Huang, F.; Schwab, R.; Weigel, D.; Meyerowitz, E.M.; Luschnig, C.; Offringa, R.; Friml, J.

    2007-01-01

    In plants, cell polarity and tissue patterning are connected by intercellular flow of the phytohormone auxin, whose directional signaling depends on polar subcellular localization of PIN auxin transport proteins. The mechanism of polar targeting of PINs or other cargos in plants is largely unidentif

  13. Redirection of auxin flow in Arabidopsis thaliana roots after infection by root-knot nematodes

    NARCIS (Netherlands)

    Kyndt, Tina; Goverse, Aska; Haegeman, Annelies; Warmerdam, Sonja; Wanjau, Cecilia; Jahani, Mona; Engler, Gilbert; Almeida Engler, De Janice; Gheysen, Godelieve

    2016-01-01

    Plant-parasitic root-knot nematodes induce the formation of giant cells within the plant root, and it has been recognized that auxin accumulates in these feeding sites. Here, we studied the role of the auxin transport system governed by AUX1/LAX3 influx proteins and different PIN efflux proteins dur

  14. Local Auxin Sources Orient the Apical-Basal Axis in Arabidopsis Embryos

    NARCIS (Netherlands)

    Robert, H.S.; Grones, P.; Stepanova, A.N.; Robles, L.M.; Lokerse, A.S.; Alonso, J.M.; Weijers, D.; Friml, J.

    2013-01-01

    Establishment of the embryonic axis foreshadows the main body axis of adults both in plants and in animals, but underlying mechanisms are considered distinct. Plants utilize directional, cell-to-cell transport of the growth hormone auxin [1 and 2] to generate an asymmetric auxin response that specif

  15. Arabidopsis phosphatidylinositol monophosphate 5-kinase 2 is involved in root gravitropism through regulation of polar auxin transport by affecting the cycling of PIN proteins

    OpenAIRE

    Mei, Yu; Jia, Wen-Jing; Chu, Yu-Jia; Xue, Hong-Wei

    2011-01-01

    Phosphatidylinositol monophosphate 5-kinase (PIP5K) catalyzes the synthesis of PI-4,5-bisphosphate (PtdIns(4,5)P2) by phosphorylation of PI-4-phosphate at the 5 position of the inositol ring, and is involved in regulating multiple developmental processes and stress responses. We here report on the functional characterization of Arabidopsis PIP5K2, which is expressed during lateral root initiation and elongation, and whose expression is enhanced by exogenous auxin. The knockout mutant pip5k...

  16. Auxins in defense strategies

    OpenAIRE

    Čarná, M. (Mária); Repka, V.; Skůpa, P. (Petr); Šturdík, E.

    2014-01-01

    Plant hormones operate in a very complex network where they regulate and control different vital mechanisms. They coordinate growth, development and defense via signaling involving different interactions of molecules. Activation of molecules responsible for regulation of plant immunity is mainly provided by salicylic and jasmonic acid signaling pathways. Similar to the signaling of these defense-associated plant hormones, auxin can also affect resistance to different pathogen groups and disea...

  17. Transport and distribution of basally applied indoleaceticacid-2-14C in bean (Phaseolus vulgaris L.) cuttings in relation to interaction of auxin and indole in adventitious root formation

    International Nuclear Information System (INIS)

    Negative interaction or antagonism between IAA and high concentration of indole in rooting of bean cuttings was associated with significant increase in upward movement and accumulation of radiocarbon of IAA-2-14C in upper parts of the cuttings. Positive interaction or synergism observed with lower concentrations of indole was not associated with such increased acropetal transport. There was also no significant difference in total radioactivity per cutting among the different concentrations of indole. The results suggest that non-promotion of upward movement of basally applied auxin from the root forming region or its increased upward movement out of the root forming region may be an important factor in the mechanism of synergism or antagonism respectively. (author)

  18. Transport and distribution of basally applied indoleaceticacid-2-/sup 14/C in bean (Phaseolus vulgaris L. ) cuttings in relation to interaction of auxin and indole in adventitious root formation

    Energy Technology Data Exchange (ETDEWEB)

    Ghosh Choudhary, K.; Basu, R.N. (University Coll. of Agriculture, Calcutta (India))

    1981-07-01

    Negative interaction or antagonism between IAA and high concentration of indole in rooting of bean cuttings was associated with significant increase in upward movement and accumulation of radiocarbon of IAA-2-/sup 14/C in upper parts of the cuttings. Positive interaction or synergism observed with lower concentrations of indole was not associated with such increased acropetal transport. There was also no significant difference in total radioactivity per cutting among the different concentrations of indole. The results suggest that non-promotion of upward movement of basally applied auxin from the root forming region or its increased upward movement out of the root forming region may be an important factor in the mechanism of synergism or antagonism respectively.

  19. Auxin can act independently of CRC, LUG, SEU, SPT and STY1 in style development but not apical-basal patterning of the Arabidopsis gynoecium.

    Science.gov (United States)

    Ståldal, Veronika; Sohlberg, Joel J; Eklund, D Magnus; Ljung, Karin; Sundberg, Eva

    2008-01-01

    Patterning of the Arabidopsis thaliana gynoecium is dependent on the localization and concentration of the plant hormone auxin and it has been previously reported that STYLISH1 (STY1) activates transcription of the auxin biosynthesis gene YUCCA4 (YUC4) and affects gynoecium development. Here, the relationship between auxin, STY1 and other regulators of gynoecium development was examined. Exogenous auxin in droplets of lanolin paste were applied to young gynoecia; auxin biosynthesis rate was measured and STY1 overexpression or chemically mediated polar auxin transport (PAT) inhibition were induced in various mutants. The style phenotype of sty1-1sty2-1 mutants was restored by exogenous application of auxin, and STY1 over-activation resulted in an elevated auxin biosynthesis rate. Both over-activation of STY1 and inhibition of PAT restored the stylar defects of several unrelated mutants, but with regard to gynoecium apical-basal patterning the mutants responded differently to inhibition of PAT. These results suggest that reduced auxin concentrations cause the sty1-1 sty2-1 phenotype, that STY1 induces auxin biosynthesis, that elevated apical auxin concentrations can compensate for the loss of several style-promoting factors, and that auxin may act downstream of, or in parallel with these during style development but is dependent on their action in apical-basal patterning. PMID:18811619

  20. WOX5-1AA17 Feedback Circuit-Mediated CellularAuxin Response Is Crucial for the Patterning ofRoot Stem Cell Niches in Arabidopsis

    Institute of Scientific and Technical Information of China (English)

    2014-01-01

    In plants, the patterning of stem cell-enriched meristems requires a graded auxin response maximum thatemerges from the concerted action of polar auxin transport, auxin biosynthesis, auxin metabolism, and cellular auxinresponse machinery. However, mechanisms underlying this auxin response maximum-mediated root stem cell mainte-nance are not fully understood. Here, we present unexpected evidence that WUSCHEL-RELATED HOMEOBOX 5 (WOX5)transcription factor modulates expression of auxin biosynthetic genes in the quiescent center (QC) of the root and thusprovides a robust mechanism for the maintenance of auxin response maximum in the root tip. This WOX5 action is bal-anced through the activity of indole-3-acetic acid 17 (IAA17) auxin response repressor. Our combined genetic, cell biol-ogy, and computational modeling studies revealed a previously uncharacterized feedback loop linking WOX5-mediatedauxin production to IAA17-dependent repression of auxin responses. This WOX5-1AA17 feedback circuit further assuresthe maintenance of auxin response maximum in the root tip and thereby contributes to the maintenance of distal stemcell (DSC) populations. Our experimental studies and in silico computer simulations both demonstrate that the WOX5-iAA17 feedback circuit is essential for the maintenance of auxin gradient in the root tip and the auxin-mediated root DSCdifferentiation.

  1. Auxin inhibits endocytosis and promotes its own efflux from cells

    Czech Academy of Sciences Publication Activity Database

    Paciorek, T.; Zažímalová, Eva; Ruthardt, N.; Petrášek, Jan; Stierhof, Y. D.; Kleine-Vehn, J.; Morris, David; Emans, N.; Jürgens, G.; Geldner, N.; Friml, J.

    2005-01-01

    Roč. 435, č. 7046 (2005), s. 1251-1256. ISSN 0028-0836 R&D Projects: GA AV ČR IAA6038303 Institutional research plan: CEZ:AV0Z50380511 Keywords : Phytohormones * polar auxin transport * plasma membrane Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 29.273, year: 2005

  2. Auxin and plant-microbe interactions.

    Science.gov (United States)

    Spaepen, Stijn; Vanderleyden, Jos

    2011-04-01

    Microbial synthesis of the phytohormone auxin has been known for a long time. This property is best documented for bacteria that interact with plants because bacterial auxin can cause interference with the many plant developmental processes regulated by auxin. Auxin biosynthesis in bacteria can occur via multiple pathways as has been observed in plants. There is also increasing evidence that indole-3-acetic acid (IAA), the major naturally occurring auxin, is a signaling molecule in microorganisms because IAA affects gene expression in some microorganisms. Therefore, IAA can act as a reciprocal signaling molecule in microbe-plant interactions. Interest in microbial synthesis of auxin is also increasing in yet another recently discovered property of auxin in Arabidopsis. Down-regulation of auxin signaling is part of the plant defense system against phytopathogenic bacteria. Exogenous application of auxin, e.g., produced by the pathogen, enhances susceptibility to the bacterial pathogen. PMID:21084388

  3. The auxin response factor MONOPTEROS controls meristem function and organogenesis in both the shoot and root through the direct regulation of PIN genes.

    Science.gov (United States)

    Krogan, Naden T; Marcos, Danielle; Weiner, Aaron I; Berleth, Thomas

    2016-10-01

    The regulatory effect auxin has on its own transport is critical in numerous self-organizing plant patterning processes. However, our understanding of the molecular mechanisms linking auxin signal transduction and auxin transport is still fragmentary, and important regulatory genes remain to be identified. To track a key link between auxin signaling and auxin transport in development, we established an Arabidopsis thaliana genetic background in which fundamental patterning processes in both shoot and root were essentially abolished and the expression of PIN FORMED (PIN) auxin efflux facilitators was dramatically reduced. In this background, we demonstrate that activating a steroid-inducible variant of the auxin response factor (ARF) MONOPTEROS (MP) is sufficient to restore patterning and PIN gene expression. Further, we show that MP binds to distinct promoter elements of multiple genetically defined PIN genes. Our work identifies a direct regulatory link between central, well-characterized genes involved in auxin signal transduction and auxin transport. The steroid-inducible MP system directly demonstrates the importance of this molecular link in multiple patterning events in embryos, shoots and roots, and provides novel options for interrogating the properties of self-regulated auxin-based patterning in planta. PMID:27441727

  4. Glucose and auxin signaling interaction in controlling Arabidopsis thaliana seedlings root growth and development.

    Directory of Open Access Journals (Sweden)

    Bhuwaneshwar S Mishra

    Full Text Available BACKGROUND: Plant root growth and development is highly plastic and can adapt to many environmental conditions. Sugar signaling has been shown to affect root growth and development by interacting with phytohormones such as gibberellins, cytokinin and abscisic acid. Auxin signaling and transport has been earlier shown to be controlling plant root length, number of lateral roots, root hair and root growth direction. PRINCIPAL FINDINGS: Increasing concentration of glucose not only controls root length, root hair and number of lateral roots but can also modulate root growth direction. Since root growth and development is also controlled by auxin, whole genome transcript profiling was done to find out the extent of interaction between glucose and auxin response pathways. Glucose alone could transcriptionally regulate 376 (62% genes out of 604 genes affected by IAA. Presence of glucose could also modulate the extent of regulation 2 fold or more of almost 63% genes induced or repressed by IAA. Interestingly, glucose could affect induction or repression of IAA affected genes (35% even if glucose alone had no significant effect on the transcription of these genes itself. Glucose could affect auxin biosynthetic YUCCA genes family members, auxin transporter PIN proteins, receptor TIR1 and members of a number of gene families including AUX/IAA, GH3 and SAUR involved in auxin signaling. Arabidopsis auxin receptor tir1 and response mutants, axr2, axr3 and slr1 not only display a defect in glucose induced change in root length, root hair elongation and lateral root production but also accentuate glucose induced increase in root growth randomization from vertical suggesting glucose effects on plant root growth and development are mediated by auxin signaling components. CONCLUSION: Our findings implicate an important role of the glucose interacting with auxin signaling and transport machinery to control seedling root growth and development in changing nutrient

  5. Role of auxin during intercellular infection of Discaria trinervis by Frankia

    Directory of Open Access Journals (Sweden)

    Leandro eImanishi

    2014-08-01

    Full Text Available Nitrogen-fixing nodules induced by Frankia in the actinorhizal plant Discaria trinervis result from a primitive intercellular root invasion pathway that does not involve root hair deformation and infection threads. Here, we analyzed the role of auxin in this intercellular infection pathway at the molecular level and compared it with our previous work in the intracellular infected actinorhizal plant Casuarina glauca. Immunolocalisation experiments showed that auxin accumulated in Frankia-infected cells in both systems. We then characterized the expression of auxin transporters in D. trinervis nodules. No activation of the heterologous CgAUX1 promoter was detected in infected cells in D. trinervis. These results were confirmed with the endogenous D. trinervis gene, DtAUX1. However, DtAUX1 was expressed in the nodule meristem. Consistently, transgenic D. trinervis plants containing the auxin response marker DR5:VENUS showed expression of the reporter gene in the meristem. Immunolocalisation experiments using an antibody against the auxin efflux carrier PIN1, revealed the presence of this transporter in the plasma membrane of infected cells. Finally, we used in silico cellular models to analyse auxin fluxes in D. trinervis nodules. Our results point to the existence of divergent roles of auxin in intercellularly- and intracellularly-infected actinorhizal plants, an ancestral infection pathways leading to root nodule symbioses.

  6. Phospholipases and the network of auxin signal transduction with ABP1 and TIR1 as two receptors: a comprehensive and provocative model

    Directory of Open Access Journals (Sweden)

    Günther F. E. Scherer

    2012-04-01

    Full Text Available Phospholipase D (PLD, secreted phospholipase A2 (sPLA2 and patatin-related phospholipase A (pPLA are important elements in auxin signal transduction. PLDζ2 has a function in auxin transport. PLD's potential link to upstream receptors ABP1 or TIR1, and to cytosolic calcium as an activator of PLDζ2, is outlined. A link from PLDζ2 to activation of PINOID, a kinase activating PIN proteins, is suggested. The activation mechanism of sPLA2, also involved in auxin transport-related functions, is unknown. New experiments show that not only ABP1 but also pPLA isoforms are tied to rapid activation of early auxin-induced genes, the functional domain of the other auxin receptor TIR1. Post-translational activation mechanisms for pPLAs are suggested to be tied to ABP1. We propose pPLAs and PLDζ2 are mediators in auxin signaling. The downstream targets of regulation by ABP1 as the receptor we propose to be primarily PIN proteins. This coordinates gene expression regulation by TIR1 in the nucleus. A clear separation of cytosolic mechanisms of auxin signalling is suggested with ABP1 as receptor, and phospholipases A and D and PIN proteins as downstream targets on the on hand, and TIR1 and regulation of early auxin-induced genes on the other. At the same time, this separation is coordinated by auxin transport creating the auxin concentration in the nucleus suitable for gene regulation.

  7. Roles for auxin, cytokinin, and strigolactone in regulating shoot branching.

    Science.gov (United States)

    Ferguson, Brett J; Beveridge, Christine A

    2009-04-01

    Many processes have been described in the control of shoot branching. Apical dominance is defined as the control exerted by the shoot tip on the outgrowth of axillary buds, whereas correlative inhibition includes the suppression of growth by other growing buds or shoots. The level, signaling, and/or flow of the plant hormone auxin in stems and buds is thought to be involved in these processes. In addition, RAMOSUS (RMS) branching genes in pea (Pisum sativum) control the synthesis and perception of a long-distance inhibitory branching signal produced in the stem and roots, a strigolactone or product. Auxin treatment affects the expression of RMS genes, but it is unclear whether the RMS network can regulate branching independently of auxin. Here, we explore whether apical dominance and correlative inhibition show independent or additive effects in rms mutant plants. Bud outgrowth and branch lengths are enhanced in decapitated and stem-girdled rms mutants compared with intact control plants. This may relate to an RMS-independent induction of axillary bud outgrowth by these treatments. Correlative inhibition was also apparent in rms mutant plants, again indicating an RMS-independent component. Treatments giving reductions in RMS1 and RMS5 gene expression, auxin transport, and auxin level in the main stem were not always sufficient to promote bud outgrowth. We suggest that this may relate to a failure to induce the expression of cytokinin biosynthesis genes, which always correlated with bud outgrowth in our treatments. We present a new model that accounts for apical dominance, correlative inhibition, RMS gene action, and auxin and cytokinin and their interactions in controlling the progression of buds through different control points from dormancy to sustained growth. PMID:19218361

  8. Auxin Biology: Applications and the Mechanisms Behind

    OpenAIRE

    Skůpa, P. (Petr); Opatrný, Z.; Petrášek, J. (Jan)

    2014-01-01

    This chapter describes the state of the contemporary knowledge of auxin action reflected in its applications in agriculture and biotechnology. We summarise the current understanding of the mechanism of action for endogenous and major synthetic auxins highlighting their morphogenic character that modulates numerous aspects of plant development. Various auxins and auxin-like compounds are used in techniques of plant vegetative propagation, in vitro culture and regeneration, and they play also a...

  9. Transport of 14C-labeled indoleacetic acid in Vicia root segments

    International Nuclear Information System (INIS)

    IAA transport in Vicia root segments was investigated for comparison with that in intact roots. Lanolin paste (1-mm-wide ring) or agar blocks (3 x 3 x 1.5 mm), both containing IAA-2-14C, were applied to the surface or a cut end of the root segments, respectively; transported 14C was collected in receiver agar blocks placed on the cut end of the segments. When lanolin paste was applied to 5-mm segments, basipetal transport of IAA redominated over acropetal transport. When agar blocks were applied to 1- and 2-mm segments, the same was true; in longer segments (3 and 5 mm long), however, basipetal movement occurred predominantly at first but was surpassed by acropetal movement after 2 - 3 hr. Among the segments tested (regions 2 - 4, 4 - 6 and 8 - 10 mm from the tip), the most apical one showed the distinctest predominancy of basipetal movement. The velocities of the acropetal and basipetal movement of the 14C were estimated at 3 - 3.8 and 8 - 12 mm/hr, respectively. Autoradiographic study and the experiment in which wire was inserted longitudinally through the central part of the segments showed that basipetal movement occurred mainly through the outer part of the roots and acropetal movement mainly through the central cylinder. The present results were compatible with those obtained previously with intact roots. Some properties of polar movement, such as its specificity, inhibition by TIBA, and dependency on temperature are described. (author)

  10. ADP1 affects plant architecture by regulating local auxin biosynthesis.

    Directory of Open Access Journals (Sweden)

    Ruixi Li

    2014-01-01

    Full Text Available Plant architecture is one of the key factors that affect plant survival and productivity. Plant body structure is established through the iterative initiation and outgrowth of lateral organs, which are derived from the shoot apical meristem and root apical meristem, after embryogenesis. Here we report that ADP1, a putative MATE (multidrug and toxic compound extrusion transporter, plays an essential role in regulating lateral organ outgrowth, and thus in maintaining normal architecture of Arabidopsis. Elevated expression levels of ADP1 resulted in accelerated plant growth rate, and increased the numbers of axillary branches and flowers. Our molecular and genetic evidence demonstrated that the phenotypes of plants over-expressing ADP1 were caused by reduction of local auxin levels in the meristematic regions. We further discovered that this reduction was probably due to decreased levels of auxin biosynthesis in the local meristematic regions based on the measured reduction in IAA levels and the gene expression data. Simultaneous inactivation of ADP1 and its three closest homologs led to growth retardation, relative reduction of lateral organ number and slightly elevated auxin level. Our results indicated that ADP1-mediated regulation of the local auxin level in meristematic regions is an essential determinant for plant architecture maintenance by restraining the outgrowth of lateral organs.

  11. Transcription of TIR1-Controlled Genes Can be Regulated within 10 Min by an Auxin-Induced Process. Can TIR1 be the Receptor?

    Science.gov (United States)

    Labusch, Corinna; Effendi, Yunus; Fulda, Martin; Scherer, Günther F E

    2016-01-01

    ABP1 and TIR1/AFBs are known as auxin receptors. ABP1 is linked to auxin responses several of which are faster than 10 min. TIR1 regulates auxin-induced transcription of early auxin genes also within minutes. We use transcription of such TIR1-dependent genes as indicator of TIR1 activity to show the rapid regulation of TIR1 by exogenous auxin. To this end, we used quantification of transcription of a set of fifteen early auxin-induced reporter genes at t = 10 and t = 30 min to measure this as a TIR1-dependent auxin response. We conducted this study in 22 mutants of auxin transporters (pin5, abcb1, abcb19, and aux1/lax3), protein kinases and phosphatases (ibr5, npr1, cpk3, CPK3-OX, d6pk1, d6pkl1-1, d6pkl3-2, d6pkl1-1/d6pkl2-2, and d6pkl1-1/d6pkl3-2), of fatty acid metabolism (fad2-1, fad6-1, ssi2, lacs4, lacs9, and lacs4/lacs9) and receptors (tir1, tir1/afb2, and tir1/afb3) and compared them to the wild type. After 10 min auxin application, in 18 out of 22 mutants mis-regulated expression of at least one reporter was found, and in 15 mutants transcription of two-to-three out of five selected auxin reporter genes was mis-regulated. After 30 min of auxin application to mutant plants, mis-regulation of reporter genes ranged from one to 13 out of 15 tested reporter genes. Those genes chosen as mutants were themselves not regulated in their expression by auxin for at least 1 h, excluding an influence of TIR1/AFBs on their transcription. The expression of TIR1/AFB genes was also not modulated by auxin for up to 3 h. Together, this excludes a feedback or feedforward of these mutant genes/proteins on TIR1/AFBs output of transcription in this auxin-induced response. However, an auxin-induced response needed an as yet unknown auxin receptor. We suggest that the auxin receptor necessary for the fast auxin-induced transcription modulation could be, instead, ABP1. The alternative hypothesis would be that auxin-induced expression of a protein, initiated by TIR1/AFBs receptors

  12. Repression of the Auxin Response Pathway Increases Arabidopsis Susceptibility to Necrotrophic Fungi

    Institute of Scientific and Technical Information of China (English)

    Francisco Llorente; Paul Muskett; Andrea Sánchez-Vallet; Gemma López; Brisa Ramos; Clara Sánchez-Rodríguez; Lucia Jordá; Jane Parker; Antonio Molina

    2008-01-01

    In plants, resistance to necrotrophic pathogens depends on the interplay between different hormone systems, such as those regulated by salicylic acid (SA), jasmonic acid (JA), ethylene, and abscisic acid. Repression of auxin signaling by the SA pathway was recently shown to contribute to antibacterial resistance. Here, we demonstrate that Arabidopsis auxin signaling mutants axrl, axr2, and axr6 that have defects in the auxin-stimulated SCF (Skpl-Cullin-F-box) ubiquitination pathway exhibit increased susceptibility to the necrotrophic fungi Plectosphaerella cucumerina and Botrytis cinerea. Also, stabilization of the auxin transcriptional repressor AXR3 that is normally targeted for removal by the SCF-ubiquitin/proteasome machinery occurs upon P. cucumerina infection. Pharmacological inhibition of auxin transport or proteasome function each compromise necrotroph resistance of wild-type plants to a similar extent as in non-treated auxin response mutants. These results suggest that auxin signaling is important for resistance to the necrotrophic fungi P. cucumerina and B. cinerea. SGTlb (one of two Arabidopsis SGT1 genes encoding HSP90/HSC70 co-chaperones) promotes the functions of SCF E3-ubiquitin ligase complexes in auxin and JA responses and resistance conditioned by certain Resistance (R) genes to biotrophic pathogens. We find that sgtlb mutants are as resistant to P. cucumerina as wild-type plants. Conversely, auxin/SCF signaling mutants are uncompromised in RPP4-triggered resistance to the obligate biotrophic oomycete, Hyaloperonospora parasitica. Thus, the predominant action of SGTlb in R gene-conditioned resistance to oomycetes appears to be at a site other than assisting SCF E3-ubiquitin ligases. However, genetic additivity of sgtlb axr1 double mutants in susceptibility to H. parasitica suggests that SCF-mediated ubiquitination contributes to limiting biotrophic pathogen colonization once plant-pathogen compatibility is established.

  13. Rice Dwarf Virus P2 Protein Hijacks Auxin Signaling by Directly Targeting the Rice OsIAA10 Protein, Enhancing Viral Infection and Disease Development.

    Science.gov (United States)

    Jin, Lian; Qin, Qingqing; Wang, Yu; Pu, Yingying; Liu, Lifang; Wen, Xing; Ji, Shaoyi; Wu, Jianguo; Wei, Chunhong; Ding, Biao; Li, Yi

    2016-09-01

    The phytohormone auxin plays critical roles in regulating myriads of plant growth and developmental processes. Microbe infection can disturb auxin signaling resulting in defects in these processes, but the underlying mechanisms are poorly understood. Auxin signaling begins with perception of auxin by a transient co-receptor complex consisting of an F-box transport inhibitor response 1/auxin signaling F-box (TIR1/AFB) protein and an auxin/indole-3-acetic acid (Aux/IAA) protein. Auxin binding to the co-receptor triggers ubiquitination and 26S proteasome degradation of the Aux/IAA proteins, leading to subsequent events, including expression of auxin-responsive genes. Here we report that Rice dwarf virus (RDV), a devastating pathogen of rice, causes disease symptoms including dwarfing, increased tiller number and short crown roots in infected rice as a result of reduced sensitivity to auxin signaling. The RDV capsid protein P2 binds OsIAA10, blocking the interaction between OsIAA10 and OsTIR1 and inhibiting 26S proteasome-mediated OsIAA10 degradation. Transgenic rice plants overexpressing wild-type or a dominant-negative (degradation-resistant) mutant of OsIAA10 phenocopy RDV symptoms are more susceptible to RDV infection; however, knockdown of OsIAA10 enhances the resistance of rice to RDV infection. Our findings reveal a previously unknown mechanism of viral protein reprogramming of a key step in auxin signaling initiation that enhances viral infection and pathogenesis. PMID:27606959

  14. CgOpt1, a putative oligopeptide transporter from Colletotrichum gloeosporioides that is involved in responses to auxin and pathogenicity

    OpenAIRE

    Maor Rudy; Chagué Véronique; Sharon Amir

    2009-01-01

    Abstract Background The fungus Colletotrichum gloeosporioides f. sp. aeschynomene produces high levels of indole-3-acetic acid (IAA) in axenic cultures and during plant infection. We generated a suppression subtractive hybridization library enriched for IAA-induced genes and identified a clone, which was highly expressed in IAA-containing medium. Results The corresponding gene showed similarity to oligopeptide transporters of the OPT family and was therefore named CgOPT1. Expression of CgOPT1...

  15. Aluminium-induced reduction of plant growth in alfalfa (Medicago sativa) is mediated by interrupting auxin transport and accumulation in roots.

    Science.gov (United States)

    Wang, Shengyin; Ren, Xiaoyan; Huang, Bingru; Wang, Ge; Zhou, Peng; An, Yuan

    2016-01-01

    The objective of this study was to investigate Al(3+)-induced IAA transport, distribution, and the relation of these two processes to Al(3+)-inhibition of root growth in alfalfa. Alfalfa seedlings with or without apical buds were exposed to 0 or 100 μM AlCl3 and were foliar sprayed with water or 6 mg L(-1) IAA. Aluminium stress resulted in disordered arrangement of cells, deformed cell shapes, altered cell structure, and a shorter length of the meristematic zone in root tips. Aluminium stress significantly decreased the IAA concentration in apical buds and root tips. The distribution of IAA fluorescence signals in root tips was disturbed, and the IAA transportation from shoot base to root tip was inhibited. The highest intensity of fluorescence signals was detected in the apical meristematic zone. Exogenous application of IAA markedly alleviated the Al(3+)-induced inhibition of root growth by increasing IAA accumulation and recovering the damaged cell structure in root tips. In addition, Al(3+) stress up-regulated expression of AUX1 and PIN2 genes. These results indicate that Al(3+)-induced reduction of root growth could be associated with the inhibitions of IAA synthesis in apical buds and IAA transportation in roots, as well as the imbalance of IAA distribution in root tips. PMID:27435109

  16. The glucosinolate breakdown product indole-3-carbinol acts as an auxin antagonist in roots of Arabidopsis thaliana.

    Science.gov (United States)

    Katz, Ella; Nisani, Sophia; Yadav, Brijesh S; Woldemariam, Melkamu G; Shai, Ben; Obolski, Uri; Ehrlich, Marcelo; Shani, Eilon; Jander, Georg; Chamovitz, Daniel A

    2015-05-01

    The glucosinolate breakdown product indole-3-carbinol functions in cruciferous vegetables as a protective agent against foraging insects. While the toxic and deterrent effects of glucosinolate breakdown on herbivores and pathogens have been studied extensively, the secondary responses that are induced in the plant by indole-3-carbinol remain relatively uninvestigated. Here we examined the hypothesis that indole-3-carbinol plays a role in influencing plant growth and development by manipulating auxin signaling. We show that indole-3-carbinol rapidly and reversibly inhibits root elongation in a dose-dependent manner, and that this inhibition is accompanied by a loss of auxin activity in the root meristem. A direct interaction between indole-3-carbinol and the auxin perception machinery was suggested, as application of indole-3-carbinol rescues auxin-induced root phenotypes. In vitro and yeast-based protein interaction studies showed that indole-3-carbinol perturbs the auxin-dependent interaction of Transport Inhibitor Response (TIR1) with auxin/3-indoleacetic acid (Aux/IAAs) proteins, further supporting the possibility that indole-3-carbinol acts as an auxin antagonist. The results indicate that chemicals whose production is induced by herbivory, such as indole-3-carbinol, function not only to repel herbivores, but also as signaling molecules that directly compete with auxin to fine tune plant growth and development. PMID:25758811

  17. Transcriptomic analysis reveals ethylene as stimulator and auxin as regulator of adventitious root formation in petunia cuttings

    Directory of Open Access Journals (Sweden)

    Uwe eDruege

    2014-09-01

    Full Text Available Adventitious root (AR formation in the stem base of cuttings is the basis for propagation of many plant species and petunia is used as model to study this developmental process. Following AR formation from 2 to 192 hours after excision (hpe of cuttings, transcriptome analysis by microarray revealed a change of the character of the rooting zone from stem base to root identity. The greatest shift in the number of differentially expressed genes was observed between 24 and 72 hpe, when the categories storage, mineral nutrient acquisition, anti-oxidative and secondary metabolism, and biotic stimuli showed a notable high number of induced genes. Analyses of phytohormone-related genes disclosed multifaceted changes of the auxin transport system, auxin conjugation and the auxin signal perception machinery indicating a reduction in auxin sensitivity and phase-specific responses of particular auxin-regulated genes. Genes involved in ethylene biosynthesis and action showed a more uniform pattern as a high number of respective genes were generally induced during the whole process of AR formation. The important role of ethylene for stimulating AR formation was demonstrated by the application of inhibitors of ethylene biosynthesis and perception as well as of the precursor aminocyclopropane-1-carboxylic acid, all changing the number and length of AR. A model is proposed showing the putative role of polar auxin transport and resulting auxin accumulation in initiation of subsequent changes in auxin homeostasis and signal perception with a particular role of Aux/IAA expression. These changes might in turn guide the entrance into the different phases of AR formation. Ethylene biosynthesis, which is stimulated by wounding and does probably also respond to other stresses and auxin, acts as important stimulator of AR formation probably via the expression of ethylene responsive transcription factor genes, whereas the timing of different phases seems to be controlled

  18. Auxin-responsive SAUR39 gene modulates auxin level in rice

    OpenAIRE

    Kant, Surya; Rothstein, Steven

    2009-01-01

    The signaling molecule auxin plays a central role in several aspects of plant growth and developmental processes. Underlying optimization of these processes are complex mechanisms orchestrating the expression of genes involved in controlling auxin level, movement and signalling. The small auxin-up RNA (SAUR) family comprises a large set of genes whose expressions are early auxin-responsive. However, the function of these genes is largely unknown. Loss-of-function mutants in a number of Arabid...

  19. Multi-Scale Characean Experimental System: From Electrophysiology of Membrane Transporters to Cell-to-Cell Connectivity, Cytoplasmic Streaming and Auxin Metabolism.

    Science.gov (United States)

    Beilby, Mary J

    2016-01-01

    The morphology of characean algae could be mistaken for a higher plant: stem-like axes with leaf-like branchlets anchored in the soil by root-like rhizoids. However, all of these structures are made up of giant multinucleate cells separated by multicellular nodal complexes. The excised internodal cells survive long enough for the nodes to give rise to new thallus. The size of the internodes and their thick cytoplasmic layer minimize impalement injury and allow specific micro-electrode placement. The cell structure can be manipulated by centrifugation, perfusion of cell contents or creation of cytoplasmic droplets, allowing access to both vacuolar and cytoplasmic compartments and both sides of the cell membranes. Thousands of electrical measurements on intact or altered cells and cytoplasmic droplets laid down basis to modern plant electrophysiology. Furthermore, the giant internodal cells and whole thalli facilitate research into many other plant properties. As nutrients have to be transported from rhizoids to growing parts of the thallus and hormonal signals need to pass from cell to cell, Characeae possess very fast cytoplasmic streaming. The mechanism was resolved in the characean model. Plasmodesmata between the internodal cells and nodal complexes facilitate transport of ions, nutrients and photosynthates across the nodes. The internal structure was found to be similar to those of higher plants. Recent experiments suggest a strong circadian influence on metabolic pathways producing indole-3-acetic acid (IAA) and serotonin/melatonin. The review will discuss the impact of the characean models arising from fragments of cells, single cells, cell-to-cell transport or whole thalli on understanding of plant evolution and physiology. PMID:27504112

  20. The AUXIN BINDING PROTEIN 1 is required for differential auxin responses mediating root growth.

    Directory of Open Access Journals (Sweden)

    Alexandre Tromas

    Full Text Available BACKGROUND: In plants, the phytohormone auxin is a crucial regulator sustaining growth and development. At the cellular level, auxin is interpreted differentially in a tissue- and dose-dependent manner. Mechanisms of auxin signalling are partially unknown and the contribution of the AUXIN BINDING PROTEIN 1 (ABP1 as an auxin receptor is still a matter of debate. METHODOLOGY/PRINCIPAL FINDINGS: Here we took advantage of the present knowledge of the root biological system to demonstrate that ABP1 is required for auxin response. The use of conditional ABP1 defective plants reveals that the protein is essential for maintenance of the root meristem and acts at least on the D-type CYCLIN/RETINOBLASTOMA pathway to control entry into the cell cycle. ABP1 affects PLETHORA gradients and confers auxin sensitivity to root cells thus defining the competence of the cells to be maintained within the meristem or to elongate. ABP1 is also implicated in the regulation of gene expression in response to auxin. CONCLUSIONS/SIGNIFICANCE: Our data support that ABP1 is a key regulator for root growth and is required for auxin-mediated responses. Differential effects of ABP1 on various auxin responses support a model in which ABP1 is the major regulator for auxin action on the cell cycle and regulates auxin-mediated gene expression and cell elongation in addition to the already well known TIR1-mediated ubiquitination pathway.

  1. PHABULOSA Mediates an Auxin Signaling Loop to Regulate Vascular Patterning in Arabidopsis1[OPEN

    Science.gov (United States)

    Valdés, Ana Elisa; Wang, Guodong

    2016-01-01

    Plant vascular tissues, xylem and phloem, differentiate in distinct patterns from procambial cells as an integral transport system for water, sugars, and signaling molecules. Procambium formation is promoted by high auxin levels activating class III homeodomain leucine zipper (HD-ZIP III) transcription factors (TFs). In the root of Arabidopsis (Arabidopsis thaliana), HD-ZIP III TFs dose-dependently govern the patterning of the xylem axis, with higher levels promoting metaxylem cell identity in the central axis and lower levels promoting protoxylem at its flanks. It is unclear, however, by what mechanisms the HD-ZIP III TFs control xylem axis patterning. Here, we present data suggesting that an important mechanism is their ability to moderate the auxin response. We found that changes in HD-ZIP III TF levels affect the expression of genes encoding core auxin response molecules. We show that one of the HD-ZIP III TFs, PHABULOSA, directly binds the promoter of both MONOPTEROS (MP)/AUXIN RESPONSE FACTOR5, a key factor in vascular formation, and IAA20, encoding an auxin/indole acetic acid protein that is stable in the presence of auxin and able to interact with and repress MP activity. The double mutant of IAA20 and its closest homolog IAA30 forms ectopic protoxylem, while overexpression of IAA30 causes discontinuous protoxylem and occasional ectopic metaxylem, similar to a weak loss-of-function mp mutant. Our results provide evidence that HD-ZIP III TFs directly affect the auxin response and mediate a feed-forward loop formed by MP and IAA20 that may focus and stabilize the auxin response during vascular patterning and the differentiation of xylem cell types. PMID:26637548

  2. Characterization of auxin-binding proteins from zucchini plasma membrane

    Science.gov (United States)

    Hicks, G. R.; Rice, M. S.; Lomax, T. L.

    1993-01-01

    We have previously identified two auxin-binding polypeptides in plasma membrane (PM) preparations from zucchini (Cucurbita pepo L.) (Hicks et al. 1989, Proc. Natl. Acad. Sci. USA 86, 4948-4952). These polypeptides have molecular weights of 40 kDa and 42 kDa and label specifically with the photoaffinity auxin analog 5-N3-7-3H-IAA (azido-IAA). Azido-IAA permits both the covalent and radioactive tagging of auxin-binding proteins and has allowed us to characterize further the 40-kDa and 42-kDa polypeptides, including the nature of their attachment to the PM, their relationship to each other, and their potential function. The azido-IAA-labeled polypeptides remain in the pelleted membrane fraction following high-salt and detergent washes, which indicates a tight and possibly integral association with the PM. Two-dimensional electrophoresis of partially purified azido-IAA-labeled protein demonstrates that, in addition to the major isoforms of the 40-kDa and 42-kDa polypeptides, which possess isoelectric points (pIs) of 8.2 and 7.2, respectively, several less abundant isoforms that display unique pIs are apparent at both molecular masses. Tryptic and chymotryptic digestion of the auxin-binding proteins indicates that the 40-kDa and 42-kDa polypeptides are closely related or are modifications of the same polypeptide. Phase extraction with the nonionic detergent Triton X-114 results in partitioning of the azido-IAA-labeled polypeptides into the aqueous (hydrophilic) phase. This apparently paradoxical behavior is also exhibited by certain integral membrane proteins that aggregate to form channels. The results of gel filtration indicate that the auxin-binding proteins do indeed aggregate strongly and that the polypeptides associate to form a dimer or multimeric complex in vivo. These characteristics are consistent with the hypothesis that the 40-kDa and 42-kDa polypeptides are subunits of a multimeric integral membrane protein which has an auxin-binding site, and which may

  3. Auxin regulation of cell polarity in plants.

    Science.gov (United States)

    Pan, Xue; Chen, Jisheng; Yang, Zhenbiao

    2015-12-01

    Auxin is well known to control pattern formation and directional growth at the organ/tissue levels via the nuclear TIR1/AFB receptor-mediated transcriptional responses. Recent studies have expanded the arena of auxin actions as a trigger or key regulator of cell polarization and morphogenesis. These actions require non-transcriptional responses such as changes in the cytoskeleton and vesicular trafficking, which are commonly regulated by ROP/Rac GTPase-dependent pathways. These findings beg for the question about the nature of auxin receptors that regulate these responses and renew the interest in ABP1 as a cell surface auxin receptor, including the work showing auxin-binding protein 1 (ABP1) interacts with the extracellular domain of the transmembrane kinase (TMK) receptor-like kinases in an auxin-dependent manner, as well as the debate on this auxin binding protein discovered about 40 years ago. This review highlights recent work on the non-transcriptional auxin signaling mechanisms underscoring cell polarity and shape formation in plants. PMID:26599954

  4. NCP1/AtMOB1A Plays Key Roles in Auxin-Mediated Arabidopsis Development

    Science.gov (United States)

    Song, Lizhen; Wang, Yanli; Cheng, Youfa

    2016-01-01

    MOB1 protein is a core component of the Hippo signaling pathway in animals where it is involved in controlling tissue growth and tumor suppression. Plant MOB1 proteins display high sequence homology to animal MOB1 proteins, but little is known regarding their role in plant growth and development. Herein we report the critical roles of Arabidopsis MOB1 (AtMOB1A) in auxin-mediated development in Arabidopsis. We found that loss-of-function mutations in AtMOB1A completely eliminated the formation of cotyledons when combined with mutations in PINOID (PID), which encodes a Ser/Thr protein kinase that participates in auxin signaling and transport. We showed that atmob1a was fully rescued by its Drosophila counterpart, suggesting functional conservation. The atmob1a pid double mutants phenocopied several well-characterized mutant combinations that are defective in auxin biosynthesis or transport. Moreover, we demonstrated that atmob1a greatly enhanced several other known auxin mutants, suggesting that AtMOB1A plays a key role in auxin-mediated plant development. The atmob1a single mutant displayed defects in early embryogenesis and had shorter root and smaller flowers than wild type plants. AtMOB1A is uniformly expressed in embryos and suspensor cells during embryogenesis, consistent with its role in embryo development. AtMOB1A protein is localized to nucleus, cytoplasm, and associated to plasma membrane, suggesting that it plays roles in these subcellular localizations. Furthermore, we showed that disruption of AtMOB1A led to a reduced sensitivity to exogenous auxin. Our results demonstrated that AtMOB1A plays an important role in Arabidopsis development by promoting auxin signaling. PMID:26942722

  5. Research Progresses on Auxin Response Factors

    Institute of Scientific and Technical Information of China (English)

    Hai-Bin Wei; Bai-Ming Cui; Yan-Li Ren; Juan-Hua Li; Wei-Bin Liao; Nan-Fei Xu; Ming Peng

    2006-01-01

    Auxin response factors (ARFs), a family of transcription factors, have been discovered recently. The ARFs bind specifically to the auxin response elements (AuxREs) within promoters of primary auxin responsive genes and function as activators or repressors. The ARFs contain three domains, namely a conserved Nterminal DNA-binding domain, a non-conserved middle region, and a conserved C-terminal dirnerization domain. The ARFs can form a protein complex with auxin/indoleacetic acid through homodimerization or heterodimerization. The particular protein-protein interaction may play a key role in modulating the expression of early auxin responsive genes. The identification of ARF mutations in Arabidopsis helps to demonstrate/dissect the function of ARFs in the normal growth and development of plants. Phylogenetic analysis also reveals some interesting protein evolution points in the ARF family.

  6. Auxin efflux facilitator and auxin dynamism responsible for the gravity-regulated development of peg in cucumber seedlings

    Science.gov (United States)

    Takahashi, Hideyuki; Watanabe, Chiaki; Fujii, Nobuharu; Miyazawa, Yutaka

    next to the cortex. This CsPIN1 localization could play a role in transporting auxin from cortex to vascular bundle. In both vascular and pith tissues, CsPIN1 was localized on the bottom plasma membrane of the cells, which could allow auxin to move toward the roots. In the seedlings grown in a horizontal position, endoder-mal cells situated above the vascular bundle localized CsPIN1 on the lower plasma membrane, whereas the polarized localization of CsPIN1 in endodermal cells situated below the vascular bundle became less clear. This differential expression of CsPIN1 in the endodermis commenced within 30 min after gravistimulation. We measured endogenous IAA contents in the transi-tion zone of the 24-hour-old seedlings. In the longitudinally halved transition zone of seedlings grown in a horizontal position, free IAA content was significantly lowered in the upper side, compared to that of the lower side or either side of the transition zone in a vertical position. When 24-hour-old seedlings grown in a vertical position were gravistimulated by reorienting them to the horizontal, free IAA in the lower side of the transition zone increased by 30 min after gravistimulation and eventually decreased to the control level by 180 min after gravistim-ulation. IAA content in the upper side of the transition zone did not change much and was comparable to that in the vertical transition zone during 180 min after gravistimulation. Thus, it appears that gravistimulation causes an immediate increase of IAA level in the lower side and its eventual decrease in the upper side of the transition zone. The gravity-induced changes in CsPIN1 localization in endodermal cells could be involved in auxin redistribution that leads to unilateral positioning of a peg in cucumber seedlings.

  7. Auxin regulation of cytokinin biosynthesis in Arabidopsis thaliana: A factor of potential importance for auxin–cytokinin-regulated development

    OpenAIRE

    Nordström, Anders; Tarkowski, Petr; Tarkowska, Danuse; Norbaek, Rikke; Åstot, Crister; Dolezal, Karel; Sandberg, Göran

    2004-01-01

    One of the most long-lived models in plant science is the belief that the long-distance transport and ratio of two plant hormones, auxin and cytokinin, at the site of action control major developmental events such as apical dominance. We have used in vivo deuterium labeling and mass spectrometry to investigate the dynamics of homeostatic cross talk between the two plant hormones. Interestingly, auxin mediates a very rapid negative control of the cytokinin pool by mainly suppressing the biosyn...

  8. Studies on the mode of action of auxin in plant development:analysis of the PIN6 gene in meristem function and cell differentiation

    OpenAIRE

    Medeiros, Violante de Faria e Maia Pacheco de, 1979-

    2007-01-01

    A proteína PIN6 é um dos membros menos caracterizados da família de proteínas PIN, associadas ao transporte de auxina em Arabidopsis thaliana. Nesta planta modelo, o transporte polar auxínico tem sido associado a diversos processos fisiológicos. Por exemplo, o movimento acropetal de IAA, do caule para a raíz, tem sido implicado no desenvolvimento de raízes laterais, enquanto que o movimento basipetal de IAA, do ápice radicular para a junção caule-raíz, tem sido associado à resposta à gravidad...

  9. Small-molecule auxin inhibitors that target YUCCA are powerful tools for studying auxin function.

    Science.gov (United States)

    Kakei, Yusuke; Yamazaki, Chiaki; Suzuki, Masashi; Nakamura, Ayako; Sato, Akiko; Ishida, Yosuke; Kikuchi, Rie; Higashi, Shouichi; Kokudo, Yumiko; Ishii, Takahiro; Soeno, Kazuo; Shimada, Yukihisa

    2015-11-01

    Auxin is essential for plant growth and development, this makes it difficult to study the biological function of auxin using auxin-deficient mutants. Chemical genetics have the potential to overcome this difficulty by temporally reducing the auxin function using inhibitors. Recently, the indole-3-pyruvate (IPyA) pathway was suggested to be a major biosynthesis pathway in Arabidopsis thaliana L. for indole-3-acetic acid (IAA), the most common member of the auxin family. In this pathway, YUCCA, a flavin-containing monooxygenase (YUC), catalyzes the last step of conversion from IPyA to IAA. In this study, we screened effective inhibitors, 4-biphenylboronic acid (BBo) and 4-phenoxyphenylboronic acid (PPBo), which target YUC. These compounds inhibited the activity of recombinant YUC in vitro, reduced endogenous IAA content, and inhibited primary root elongation and lateral root formation in wild-type Arabidopsis seedlings. Co-treatment with IAA reduced the inhibitory effects. Kinetic studies of BBo and PPBo showed that they are competitive inhibitors of the substrate IPyA. Inhibition constants (Ki ) of BBo and PPBo were 67 and 56 nm, respectively. In addition, PPBo did not interfere with the auxin response of auxin-marker genes when it was co-treated with IAA, suggesting that PPBo is not an inhibitor of auxin sensing or signaling. We propose that these compounds are a class of auxin biosynthesis inhibitors that target YUC. These small molecules are powerful tools for the chemical genetic analysis of auxin function. PMID:26402640

  10. Functionally different PIN proteins control auxin flux during bulbil development in Agave tequilana.

    Science.gov (United States)

    Abraham Juárez, María Jazmín; Hernández Cárdenas, Rocío; Santoyo Villa, José Natzul; O'Connor, Devin; Sluis, Aaron; Hake, Sarah; Ordaz-Ortiz, José; Terry, Leon; Simpson, June

    2015-07-01

    In Agave tequilana, reproductive failure or inadequate flower development stimulates the formation of vegetative bulbils at the bracteoles, ensuring survival in a hostile environment. Little is known about the signals that trigger this probably unique phenomenon in agave species. Here we report that auxin plays a central role in bulbil development and show that the localization of PIN1-related proteins is consistent with altered auxin transport during this process. Analysis of agave transcriptome data led to the identification of the A. tequilana orthologue of PIN1 (denoted AtqPIN1) and a second closely related gene from a distinct clade reported as 'Sister of PIN1' (denoted AtqSoPIN1). Quantitative real-time reverse transcription-PCR (RT-qPCR) analysis showed different patterns of expression for each gene during bulbil formation, and heterologous expression of the A. tequilana PIN1 and SoPIN1 genes in Arabidopsis thaliana confirmed functional differences between these genes. Although no free auxin was detected in induced pedicel samples, changes in the levels of auxin precursors were observed. Taken as a whole, the data support the model that AtqPIN1 and AtqSoPIN1 have co-ordinated but distinct functions in relation to auxin transport during the initial stages of bulbil formation. PMID:25911746

  11. Auxin transport routes in plant development

    Czech Academy of Sciences Publication Activity Database

    Petrášek, Jan; Friml, J.

    2009-01-01

    Roč. 136, č. 16 (2009), s. 2675-2688. ISSN 0950-1991 R&D Projects: GA AV ČR KJB600380604 Institutional research plan: CEZ:AV0Z50380511 Keywords : ROOT- HAIR DEVELOPMENT * ARABIDOPSIS-THALIANA * LATERAL ROOT Subject RIV: ED - Physiology Impact factor: 7.194, year: 2009

  12. Specificity patterns indicate that auxin exporters and receptors are the same proteins.

    Science.gov (United States)

    Hössel, D; Schmeiser, C; Hertel, R

    2005-01-01

    A study of transport and action of synthetic auxin analogues can help to identify transporters and receptors of this plant hormone. Both aspects--transportability and action on growth--were tested with 2-naphthoxyacetic acid (2-NOA) and compared across several plant species. 2-NOA stimulates elongation effectively at low concentrations in petioles of the gymnosperm Ginkgo biloba L., in hypocotyls or internodes of the dicot legumes, mung bean (Vigna mungo L.) and pea (Pisum sativum L.), in cotyledons of onion (Allium cepa L.) and in leaf bases of chive (Allium schoenoprasum L.), the latter two of the monocot order Asparagales. In contrast, elongation of coleoptile segments of maize (Zea mays L.) is poorly responsive to 2-NOA. Significant auxin-like transport of 2-NOA was observed in segments of mung bean hypocotyls, pea internodes, and chive leaf bases, but not in segments of the grass coleoptiles. Thus, for the two assays, elongation and polar transportability, the same difference in ligand specificity was observed between the grass and all other species assayed. This finding supports the hypothesis that a common protein mediates auxin efflux as well as auxin action on elongation. PMID:15666213

  13. Auxin influences strigolactones in pea mycorrhizal symbiosis.

    Science.gov (United States)

    Foo, E

    2013-03-15

    Hormone interactions are essential for the control of many developmental processes, including intracellular symbioses. The interaction between auxin and the new plant hormone strigolactone in the regulation of arbuscular mycorrhizal symbiosis was examined in one of the few auxin deficient mutants available in a mycorrhizal species, the auxin-deficient bsh mutant of pea (Pisum sativum). Mycorrhizal colonisation with the fungus Glomus intraradices was significantly reduced in the low auxin bsh mutant. The bsh mutant also exhibited a reduction in strigolactone exudation and the expression of a key strigolactone biosynthesis gene (PsCCD8). Strigolactone exudation was also reduced in wild type plants when the auxin content was reduced by stem girdling. Low strigolactone levels appear to be at least partially responsible for the reduced colonisation of the bsh mutant, as application of the synthetic strigolactone GR24 could partially rescue the mycorrhizal phenotype of bsh mutants. Data presented here indicates root auxin content was correlated with strigolactone exudation in both mutant and wild type plants. Mutant studies suggest that auxin may regulate early events in the formation of arbuscular mycorrhizal symbiosis by controlling strigolactone levels, both in the rhizosphere and possibly during early root colonisation. PMID:23219475

  14. Modeling a cortical auxin maximum for nodulation: different signatures of potential strategies.

    Science.gov (United States)

    Deinum, Eva Elisabeth; Geurts, René; Bisseling, Ton; Mulder, Bela M

    2012-01-01

    Lateral organ formation from plant roots typically requires the de novo creation of a meristem, initiated at the location of a localized auxin maximum. Legume roots can form both root nodules and lateral roots. From the basic principles of auxin transport and metabolism only a few mechanisms can be inferred for increasing the local auxin concentration: increased influx, decreased efflux, and (increased) local production. Using computer simulations we investigate the different spatio-temporal patterns resulting from each of these mechanisms in the context of a root model of a generalized legume. We apply all mechanisms to the same group of preselected cells, dubbed the controlled area. We find that each mechanism leaves its own characteristic signature. Local production by itself can not create a strong auxin maximum. An increase of influx, as is observed in lateral root formation, can result in an auxin maximum that is spatially more confined than the controlled area. A decrease of efflux on the other hand leads to a broad maximum, which is more similar to what is observed for nodule primordia. With our prime interest in nodulation, we further investigate the dynamics following a decrease of efflux. We find that with a homogeneous change in the whole cortex, the first auxin accumulation is observed in the inner cortex. The steady state lateral location of this efflux reduced auxin maximum can be shifted by slight changes in the ratio of central to peripheral efflux carriers. We discuss the implications of this finding in the context of determinate and indeterminate nodules, which originate from different cortical positions. The patterns we have found are robust under disruption of the (artificial) tissue layout. The same patterns are therefore likely to occur in many other contexts. PMID:22654886

  15. THE MODEL FOR AUXIN REGULATED AtPIN1 EXPRESSION IN THE ROOT APICAL MERISTEM

    Directory of Open Access Journals (Sweden)

    Ermakov A.A.

    2012-08-01

    Full Text Available Plant hormone auxin regulates many aspects of plant growth and development. PIN-FORMED (PIN gene family encodes transmembrane proteins, which mediate auxin efflux. PIN proteins are asymmetrically localized within cells, thereby forming in tissue auxin concentration gradients and maxima. Auxin has various effects on PIN1 expression in a cell providing for both positive and negative feedbacks on its own transport [1]. Earlier we proposed that this dual regulation determines stem cell niche maintenance in root apical meristem [2].Using two reporter lines of Arabidopsis thaliana we investigated dose-response auxin regulation of PIN1 expression at the levels of RNA and protein. PIN1::PIN1-GFP containing part of PIN1 coding region reveals both transcriptional and posttranscriptional regulation, whereas pPIN1::GUS displays only transcriptional regulation. The reporter line pPIN1::GUS[-1388;+82] was created by authors; PIN1::PIN1-GFP was provided by Alexis Peaucelle (INRA, France. PIN1::PIN1-GFP and pPIN1::GUS seedlings were grown in a 16 hours light/8 hours dark cycle at 25/22°C on 1/2MS with sucrose. Before microscopic analysis 3 dag seedlings were incubated for 24 h in liquid 1/2MS supplemented with different IAA concentrations. The experimental images were analyzed using ImageJ program.We found the following changes in PIN1 expression pattern in the root for both lines under low and moderate auxin treatments: (1 increased domain of PIN1 expression in the root meristem; (2 ectopic expression in epidermis and cortex, (3 increased level of PIN1 expression in provascular cells. However, we observed differences in PIN1 expression between the lines: in columella and under high auxin concentrations. The experimental data suggests posttranslational PIN1 regulation by high auxin concentrations. A mathematical model [2] was extended to describe the observed phenomena. The model simulation well agrees with the experimental data and predicts new aspects on the

  16. The role of Phe82 and Phe351 in auxin-induced substrate perception by TIR1 ubiquitin ligase: a novel insight from molecular dynamics simulations.

    Directory of Open Access Journals (Sweden)

    Ge-Fei Hao

    Full Text Available It is well known that Auxin plays a key role in controlling many aspects of plant growth and development. Crystal structures of Transport inhibitor response 1 (TIR1, a true receptor of auxin, were very recently determined for TIR1 alone and in complexes with auxin and different synthetic analogues and an Auxin/Indole-3-Acetic Acid (Aux/IAA substrate peptide. However, the dynamic conformational changes of the key residues of TIR1 that take place during the auxin and substrate perception by TIR1 and the detailed mechanism of these changes are still unclear. In the present study, various computational techniques were integrated to uncover the detailed molecular mechanism of the auxin and Aux/IAA perception process; these simulations included molecular dynamics (MD simulations on complexes and the free enzyme, the molecular mechanics Poisson Boltzmann surface area (MM-PBSA calculations, normal mode analysis, and hydrogen bond energy (HBE calculations. The computational simulation results provided a reasonable explanation for the structure-activity relationships of auxin and its synthetic analogues in view of energy. In addition, a more detailed model for auxin and Aux/IAA perception was also proposed, indicating that Phe82 and Phe351 played a pivotal role in Aux/IAA perception. Upon auxin binding, Phe82 underwent conformational changes to accommodate the subsequent binding of Aux/IAA. As a result, auxin enhances the TIR1-Aux/IAA interactions by acting as a "molecular glue". Besides, Phe351 acts as a "fastener" to further improve the substrate binding. The structural and mechanistic insights obtained from the present study will provide valuable clues for the future design of promising auxin analogues.

  17. Abscisic acid regulates root growth under osmotic stress conditions via an interacting hormonal network with cytokinin, ethylene and auxin.

    Science.gov (United States)

    Rowe, James H; Topping, Jennifer F; Liu, Junli; Lindsey, Keith

    2016-07-01

    Understanding the mechanisms regulating root development under drought conditions is an important question for plant biology and world agriculture. We examine the effect of osmotic stress on abscisic acid (ABA), cytokinin and ethylene responses and how they mediate auxin transport, distribution and root growth through effects on PIN proteins. We integrate experimental data to construct hormonal crosstalk networks to formulate a systems view of root growth regulation by multiple hormones. Experimental analysis shows: that ABA-dependent and ABA-independent stress responses increase under osmotic stress, but cytokinin responses are only slightly reduced; inhibition of root growth under osmotic stress does not require ethylene signalling, but auxin can rescue root growth and meristem size; osmotic stress modulates auxin transporter levels and localization, reducing root auxin concentrations; PIN1 levels are reduced under stress in an ABA-dependent manner, overriding ethylene effects; and the interplay among ABA, ethylene, cytokinin and auxin is tissue-specific, as evidenced by differential responses of PIN1 and PIN2 to osmotic stress. Combining experimental analysis with network construction reveals that ABA regulates root growth under osmotic stress conditions via an interacting hormonal network with cytokinin, ethylene and auxin. PMID:26889752

  18. Plant AGC protein kinases orient auxin-mediated differential growth and organogenesis

    NARCIS (Netherlands)

    Galván Ampudia, Carlos Samuel

    2009-01-01

    In view of their predominant sessile lifestyle, plants need to be able to adapt to changes in their environment. Environmental signals such as light and gravity modulate plant growth and architecture by redirecting polar cell-to-cell transport of auxin, thus causing changes in the distribution of th

  19. Light can rescue auxin-dependent synchrony of cell division in a tobacco cell line

    Czech Academy of Sciences Publication Activity Database

    Qiao, F.; Petrášek, Jan; Nick, P.

    2010-01-01

    Roč. 61, č. 2 (2010), s. 503-510. ISSN 0022-0957 Institutional research plan: CEZ:AV0Z50380511 Keywords : Auxin transport * cell division * NPA Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 4.818, year: 2010 http://jxb.oxfordjournals.org/content/61/2/503.abstract

  20. Immunophilin-like TWISTED DWARF1 modulates auxin efflux activities of Arabidopsis p-glycoproteins

    OpenAIRE

    BOUCHARD R; Bailly, A; Blakeslee, J.J.; VINCENZETTI V; Paponov, I.; Palme, K; S. Mancuso; Murphy, A.S.; Schulz, B.; Geisler, M.

    2006-01-01

    The immunophilin-like protein TWISTED DWARF1 (TWD1/FKBP42) has been shown to physically interact with the multidrug resistance/P-glycoprotein (PGP) ATP-binding cassette transporters PGP1 and PGP19 (MDR1). Overlapping phenotypes of pgp1/pgp19 and twd1 mutant plants suggested a positive regulatory role of TWD1 in PGP-mediated export of the plant hormone auxin, which controls plant development. Here, we provide evidence at the cellular and plant levels that TWD1 controls PGP-mediated auxin trans...

  1. Auxin at the Shoot Apical Meristem

    OpenAIRE

    Vernoux, Teva; Besnard, Fabrice; Traas, Jan,

    2010-01-01

    Plants continuously generate new tissues and organs through the activity of populations of undifferentiated stem cells, called meristems. Here, we discuss the so-called shoot apical meristem (SAM), which generates all the aerial parts of the plant. It has been known for many years that auxin plays a central role in the functioning of this meristem. Auxin is not homogeneously distributed at the SAM and it is thought that this distribution is interpreted in terms of differential gene expression...

  2. Is ABP1 an Auxin Receptor Yet?

    Institute of Scientific and Technical Information of China (English)

    Jing-Hua Shi; Zhen-Biao Yang

    2011-01-01

    AUXIN BINDING PROTEIN 1 (ABP1)has long been proposed as an auxin receptor to regulate cell expansion. The embryo lethality of ABPI-null mutants demonstrates its fundamental role in plant development, but also hinders inves-tigation of its involvement in post-embryonic processes and its mode of action. By taking advantage of weak alleles and inducible systems, several recent studies have revealed a role for ABP1 in organ development, cell polarization, and shape formation. In addition to its role in the regulation of auxin-induced gene expression, ABP1 has now been shown to mod-ulate non-transcriptional auxin responses. ABP1 is required for activating two antagonizing ROP GTPase signaling path-ways involved in cytoskeletal reorganization and cell shape formation, and participates in the regulation of clathrin-mediated endocytosis to subsequently affect PIN protein distribution. These exciting discoveries provide indisputable ev-idence for the auxin-induced signaling pathways that are downstream of ABP1 function, and suggest intriguing mech-anisms for ABPl-mediated polar cell expansion and spatial coordination in response to auxin.

  3. SCFTIR1/AFB-auxin signalling regulates PIN vacuolar trafficking and auxin fluxes during root gravitropism

    NARCIS (Netherlands)

    Baster, P.; Robert, S.; Kleine-Vehn, J.; Vanneste, S.; Kania, U.; Grunewald, W.; Rybel, de B.P.M.; Beeckman, T.; Friml, J.

    2013-01-01

    The distribution of the phytohormone auxin regulates many aspects of plant development including growth response to gravity. Gravitropic root curvature involves coordinated and asymmetric cell elongation between the lower and upper side of the root, mediated by differential cellular auxin levels. Th

  4. Examination of the auxin hypothesis of phytomelatonin action in classical auxin assay systems in maize.

    Science.gov (United States)

    Kim, Minjae; Seo, Hyesu; Park, Chanwoo; Park, Woong June

    2016-01-15

    Melatonin has been found in a wide range of plant groups. Its physiological roles have been suggested to be diverse in stress protection and plant growth regulation. An attractive hypothesis is that phytomelatonin acts as an auxin to regulate plant development. However, the auxin hypothesis is controversial, since both supporting and contradictory evidence has been reported. We systematically investigated whether melatonin fulfilled the definition for auxin in maize (Zea mays). Melatonin did not affect coleoptile elongation, root growth or ACC synthase gene expression, contrary to 10(-5)M IAA in our assay system. The auxin hypothesis of phytomelatonin action is not supported in maize, because melatonin appeared inactive in all of the auxin activity tests. On the other hand, melatonin was active in the protection of maize growth against salt stress, suggesting its importance in another context. PMID:26681269

  5. Carbohydrate Stress Affecting Fruitlet Abscission and Expression of Genes Related to Auxin Signal Transduction Pathway in Litchi

    Directory of Open Access Journals (Sweden)

    Wang-Jin Lu

    2012-11-01

    Full Text Available Auxin, a vital plant hormone, regulates a variety of physiological and developmental processes. It is involved in fruit abscission through transcriptional regulation of many auxin-related genes, including early auxin responsive genes (i.e., auxin/indole-3-acetic acid (AUX/IAA, Gretchen Hagen3 (GH3 and small auxin upregulated (SAUR and auxin response factors (ARF, which have been well characterized in many plants. In this study, totally five auxin-related genes, including one AUX/IAA (LcAUX/IAA1, one GH3 (LcGH3.1, one SAUR (LcSAUR1 and two ARFs (LcARF1 and LcARF2, were isolated and characterized from litchi fruit. LcAUX/IAA1, LcGH3.1, LcSAUR1, LcARF1 and LcARF2 contain open reading frames (ORFs encoding polypeptides of 203, 613, 142, 792 and 832 amino acids, respectively, with their corresponding molecular weights of 22.67, 69.20, 11.40, 88.20 and 93.16 kDa. Expression of these genes was investigated under the treatment of girdling plus defoliation which aggravated litchi fruitlet abscission due to the blockage of carbohydrates transport and the reduction of endogenous IAA content. Results showed that transcript levels of LcAUX/IAA1, LcGH3.1 and LcSAUR1 mRNAs were increased after the treatment in abscission zone (AZ and other tissues, in contrast to the decreasing accumulation of LcARF1 mRNA, suggesting that LcAUX/IAA1, LcSAUR1 and LcARF1 may play more important roles in abscission. Our results provide new insight into the process of fruitlet abscission induced by carbohydrate stress and broaden our understanding of the auxin signal transduction pathway in this process at the molecular level.

  6. Mutant analysis in Arabidopsis provides insight into the molecular mode of action of the auxinic herbicide dicamba.

    Directory of Open Access Journals (Sweden)

    Cynthia Gleason

    Full Text Available Herbicides that mimic the natural auxin indole-3-acetic acid are widely used in weed control. One common auxin-like herbicide is dicamba, but despite its wide use, plant gene responses to dicamba have never been extensively studied. To further understand dicamba's mode of action, we utilized Arabidopsis auxin-insensitive mutants and compared their sensitivity to dicamba and the widely-studied auxinic herbicide 2,4-dichlorophenoxyacetic acid (2,4-D. The mutant axr4-2, which has disrupted auxin transport into cells, was resistant to 2,4-D but susceptible to dicamba. By comparing dicamba resistance in auxin signalling F-box receptor mutants (tir1-1, afb1, afb2, afb3, and afb5, only tir1-1 and afb5 were resistant to dicamba, and this resistance was additive in the double tir1-1/afb5 mutant. Interestingly, tir1-1 but not afb5 was resistant to 2,4-D. Whole genome analysis of dicamba-induced gene expression showed that 10 hours after application, dicamba stimulated many stress-responsive and signalling genes, including those involved in biosynthesis or signalling of auxin, ethylene, and abscisic acid (ABA, with TIR1 and AFB5 required for the dicamba-responsiveness of some genes. Research into dicamba-regulated gene expression and the selectivity of auxin receptors has provided molecular insight into dicamba-regulated signalling and could help in the development of novel herbicide resistance in crop plants.

  7. Effects of ethylene on the kinetics of curvature and auxin redistribution in gravistimulated roots of Zea mays

    Science.gov (United States)

    Lee, J. S.; Evans, M. L.

    1990-01-01

    We tested the involvement of ethylene in maize (Zea mays L.) root gravitropism by measuring the kinetics of curvature and lateral auxin movement in roots treated with ethylene, inhibitors of ethylene synthesis, or inhibitors of ethylene action. In the presence of ethylene the latent period of gravitropic curvature appeared to be increased somewhat. However, ethylene-treated roots continued to curve after control roots had reached their final angle of curvature. Consequently, maximum curvature in the presence of ethylene was much greater in ethylene-treated roots than in controls. Inhibitors of ethylene biosynthesis or action had effects on the kinetics of curvature opposite to that of ethylene, i.e. the latent period appeared to be shortened somewhat while total curvature was reduced relative to that of controls. Label from applied 3H-indole-3-acetic acid was preferentially transported toward the lower side of stimulated roots. In parallel with effects on curvature, ethylene treatment delayed the development of gravity-induced asymmetric auxin movement across the root but extended its duration once initiated. The auxin transport inhibitor, 1-N-naphthylphthalamic acid reduced both gravitropic curvature and the effect of ethylene on curvature. Since neither ethylene nor inhibitors of ethylene biosynthesis or action prevented curvature, we conclude that ethylene does not mediate the primary differential growth response causing curvature. Because ethylene affects curvature and auxin transport in parallel, we suggest that ethylene modifies curvature by affecting gravity-induced lateral transport of auxin, perhaps by interfering with adaptation of the auxin transport system to the gravistimulus.

  8. The promoting effects of alginate oligosaccharides on root development in Oryza sativa L. mediated by auxin signaling.

    Science.gov (United States)

    Zhang, Yunhong; Yin, Heng; Zhao, Xiaoming; Wang, Wenxia; Du, Yuguang; He, Ailing; Sun, Kegang

    2014-11-26

    Alginate oligosaccharides (AOS), which are marine oligosaccharides, are involved in regulating plant root growth, but the promotion mechanism for AOS remains unclear. Here, AOS (10-80 mg/L) induced the expression of auxin-related gene (OsYUCCA1, OsYUCCA5, OsIAA11 and OsPIN1) in rice (Oryza sativa L.) tissues to accelerate auxin biosynthesis and transport, and reduced indole-3-acetic acid (IAA) oxidase activity in rice roots. These changes resulted in the increase of 37.8% in IAA concentration in rice roots, thereby inducing the expression of root development-related genes, promoting root growth in a dose-dependent manner, which were inhibited by auxin transport inhibitor 2,3,5-triiodo benzoic acid (TIBA) and calcium-chelating agent ethylene glycol bis (2-aminoethyl) tetraacetic acid (EGTA). AOS also induced calcium signaling generation in rice roots. Those results indicated that auxin mediated AOS regulation of root development, and calcium signaling may act mainly in the upstream of auxin in the regulation of AOS on rice root development. PMID:25256506

  9. Osmotic properties of pea internodes in relation to growth and auxin action

    Energy Technology Data Exchange (ETDEWEB)

    Cosgrove, D.J.; Cleland, R.E.

    1983-01-01

    The water transport properties of etiolated pea (Pisum sativum L.) internodes were studied using both dynamic and steady-state methods to determine (a) whether water transport through the growing tissue limits the rate of cell enlargement, and (b) whether auxin stimulates growth in part by increasing the hydraulic conductance of the growing tissue. Measurements using the pressure probe technique showed that the hydraulic conductivity of cortical cell membranes was the same for both slowly growing and auxin-induced rapidly growing cells (membrane hydraulic conductivity, about 1.5 x 10/sup -5/ centimeters per second per bar). In a second technique which measured the rate of water movement through the entire pea internode, the half-time for radial water flow was about 60 seconds and was not altered by auxin application. These results indicate that auxin does not alter the hydraulic conductance of pea stem tissue, either at the cellular or the whole tissue level. When the growth rate was altered by various treatments, including decapitation, auxin application, cold temperature, and KCN treatment, the water potential was independent of the growth rate of the stem. We attribute the depression of the water potential in young pea stems to the presence of solutes in the cell wall free space of the tissue. From the results of these dynamic and steady-state experiments, we conclude that the internal gradient in water potential (from the xylem to the epidermis) needed to sustain cell enlargement is small (no greater than 0.5 bar). Thus, the hydraulic conductance of the tissue is sufficiently large that it does not control or limit the rate of cell enlargement. 30 references, 5 figures, 4 tables.

  10. In vitro oxidation of indoleacetic acid by soluble auxin-oxidases and peroxidases from maize roots

    International Nuclear Information System (INIS)

    Soluble auxin-oxidases were extracted from Zea mays L. cv LG11 apical root segments and partially separated from peroxidases (EC 1.11.1.7) by size-exclusion chromatography. Auxin-oxidases were resolved into one main peak corresponding to a molecular mass of 32.5 kilodaltons and a minor peak at 54.5 kilodaltons. Peroxidases were separated into at least four peaks, with molecular masses from 32.5 to 78 kilodaltons. In vitro activity of indoleacetic acid-oxidases was dependent on the presence of MnCl2 and p-coumaric acid. Compound(s) present in the crude extract and several synthetic auxin transport inhibitors (including 2,3,5-triiodobenzoic acid and N-1-naphthylphthalamic acid) inhibited auxin-oxidase activity, but had no effect on peroxidases. The products resulting from the in vitro enzymatic oxidation of [3H]indoleacetic acid were separated by HPLC and the major metabolite was found to cochromatograph with indol-3yl-methanol

  11. Isolation and functional analysis of a Brassica juncea gene encoding a component of auxin efflux carrier

    Institute of Scientific and Technical Information of China (English)

    WEI; MIN; NI; XIAO; YA; CHEN; ZHI; HONG; XU; HONG; WEI; XUE

    2002-01-01

    Polar auxin transport plays a divergent role in plant growth and developmental processes including rootand embryo development, vascular pattern formation and cell elongation. Recently isolated Arabidopsispin gene family was believed to encode a component of auxin efflux carrier (Galweiler et al, 1998). Basedon the Arabidopsis pin1 sequence we have isolated a Brassica juncea cDNA (designated Bjpinl), whichencoded a 70-kDa putative auxin efflux carrier. Deduced BjPIN1 shared 65% identities at protein level withAtPIN1 and was highly homologous to other putative PIN proteins of Arabidopsis (with highest homologyto AtPIN3). Hydrophobic analysis showed similar structures between BjPIN1 and AtPIN proteins. Presenceof 6 exons (varying in size between 65 bp and 1229 bp) and 5 introns (sizes between 89 bp and 463 bp)in the genomic fragment was revealed by comparing the genomic and cDNA sequences. Northern blotanalysis indicated that Bjpinl was expressed in most of the tissues tested, with a relatively higher levelof transcript in flowers and a lower level in root tissues. Promoter-reporter gene fusion studies furtherrevealed the expression of Bjpinl in the mature pollen grains, young seeds, root tip, leaf vascular tissue andtrace bundle, stem epidermis, cortex and vascular cells. BjPIN1 was localized on the plasma membraneas demonstrated through fusion expression of green fluorescent protein (GFP). Auxin efflux carrier activitywas elevated in transgenic Arabidopsis expressing BjPIN1.

  12. Phloem development in nematode-induced feeding sites: The implications of auxin and cytokinin

    Directory of Open Access Journals (Sweden)

    Birgit eAbsmanner

    2013-07-01

    Full Text Available Sedentary plant parasitic nematodes such as root-knot nematodes and cyst nematodes induce giant cells or syncytia, respectively, in their host plant’s roots. These highly specialized structures serve as feeding sites from which exclusively the nematodes withdraw nutrients. While giant cells are symplastically isolated and obtain assimilates by transporter-mediated processes syncytia are massively connected to the phloem by plasmodesmata. To support the feeding sites and the nematode during their development, phloem is induced around syncytia and giant cells. In the case of syncytia the unloading phloem consists of sieve elements and companion cells and in the case of root knots it consists exclusively of sieve elements. We applied immunohistochemistry to identify the cells within the developing phloem that responded to auxin and cytokinin. Both feeding sites themselves did not respond to either hormone. We were able to show that in root knots an auxin response precedes the differentiation of these auxin responsive cells into phloem elements. This process appears to be independent of B-type Arabidopsis response regulators. Using additional markers for tissue identity we provide evidence that around giant cells protophloem is formed and proliferates dramatically. In contrast, the phloem around syncytia responded to both hormones. The presence of companion cells as well as hormone-responsive sieve elements suggests that metaphloem development occurs. The implication of auxin and cytokinin in the further development of the metaphloem is discussed.

  13. The Clubroot Pathogen (Plasmodiophora brassicae Influences Auxin Signaling to Regulate Auxin Homeostasis in Arabidopsis

    Directory of Open Access Journals (Sweden)

    Linda Jahn

    2013-11-01

    Full Text Available The clubroot disease, caused by the obligate biotrophic protist Plasmodiophora brassicae, affects cruciferous crops worldwide. It is characterized by root swellings as symptoms, which are dependent on the alteration of auxin and cytokinin metabolism. Here, we describe that two different classes of auxin receptors, the TIR family and the auxin binding protein 1 (ABP1 in Arabidopsis thaliana are transcriptionally upregulated upon gall formation. Mutations in the TIR family resulted in more susceptible reactions to the root pathogen. As target genes for the different pathways we have investigated the transcriptional regulation of selected transcriptional repressors (Aux/IAA and transcription factors (ARF. As the TIR pathway controls auxin homeostasis via the upregulation of some auxin conjugate synthetases (GH3, the expression of selected GH3 genes was also investigated, showing in most cases upregulation. A double gh3 mutant showed also slightly higher susceptibility to P. brassicae infection, while all tested single mutants did not show any alteration in the clubroot phenotype. As targets for the ABP1-induced cell elongation the effect of potassium channel blockers on clubroot formation was investigated. Treatment with tetraethylammonium (TEA resulted in less severe clubroot symptoms. This research provides evidence for the involvement of two auxin signaling pathways in Arabidopsis needed for the establishment of the root galls by P. brassicae.

  14. Auxins and cytokinins in plant development

    Czech Academy of Sciences Publication Activity Database

    Kamínek, Miroslav; Ludwig-Müller, J.; Vaňková, Radomíra; Zažímalová, Eva

    2006-01-01

    Roč. 25, č. 1 (2006), s. 89-97. ISSN 0721-7595 R&D Projects: GA ČR GA206/98/1510 Institutional research plan: CEZ:AV0Z50380511 Keywords : Cytokinins * Auxins * Plant Development Subject RIV: EF - Botanics Impact factor: 2.107, year: 2006

  15. Hormonal control of root development on epiphyllous plantlets of Bryophyllum (Kalanchoe) marnierianum: role of auxin and ethylene.

    Science.gov (United States)

    Kulka, Richard G

    2008-01-01

    Epiphyllous plantlets develop on leaves of Bryophyllum marnierianum when they are excised from the plant. Shortly after leaf excision, plantlet shoots develop from primordia located near the leaf margin. After the shoots have enlarged for several days, roots appear at their base. In this investigation, factors regulating plantlet root development were studied. The auxin transport inhibitor 2,3,5-triiodobenzoic acid (TIBA) abolished root formation without markedly affecting shoot growth. This suggested that auxin transport from the plantlet shoot induces root development. Excision of plantlet apical buds inhibits root development. Application of indole-3-acetic acid (IAA) in lanolin at the site of the apical buds restores root outgrowth. Naphthalene acetic acid (NAA), a synthetic auxin, reverses TIBA inhibition of plantlet root emergence on leaf explants. Both of these observations support the hypothesis that auxin, produced by the plantlet, induces root development. Exogenous ethylene causes precocious root development several days before that of a control without hormone. Ethylene treatment cannot bypass the TIBA block of root formation. Therefore, ethylene does not act downstream of auxin in root induction. However, ethylene amplifies the effects of low concentrations of NAA, which in the absence of ethylene do not induce roots. Ag(2)S(2)O(3), an ethylene blocker, and CoCl(2), an ethylene synthesis inhibitor, do not abolish plantlet root development. It is therefore unlikely that ethylene is essential for root formation. Taken together, the experiments suggest that roots develop when auxin transport from the shoot reaches a certain threshold. Ethylene may augment this effect by lowering the threshold and may come into play when the parent leaf senesces. PMID:18544609

  16. Arabidopsis TWISTED DWARF1 functionally interacts with Auxin Exporter ABCB1 on the root plasma membrane

    DEFF Research Database (Denmark)

    Wang, Bangjun; Bailly, Aurélien; Zwiewka, Marta;

    2013-01-01

    . In planta bioluminescence resonance energy transfer analysis was used to verify specific ABC transporter B1 (ABCB1)-TWD1 interaction. Our data support a model in which TWD1 promotes lateral ABCB-mediated auxin efflux via protein-protein interaction at the plasma membrane, minimizing reflux from the root...

  17. Regulation of the gibberellin pathway by auxin and DELLA proteins.

    Science.gov (United States)

    O'Neill, Damian P; Davidson, Sandra E; Clarke, Victoria C; Yamauchi, Yukika; Yamaguchi, Shinjiro; Kamiya, Yuji; Reid, James B; Ross, John J

    2010-10-01

    The synthesis and deactivation of bioactive gibberellins (GA) are regulated by auxin and by GA signalling. The effect of GA on its own pathway is mediated by DELLA proteins. Like auxin, the DELLAs promote GA synthesis and inhibit its deactivation. Here, we investigate the relationships between auxin and DELLA regulation of the GA pathway in stems, using a pea double mutant that is deficient in DELLA proteins. In general terms our results demonstrate that auxin and DELLAs independently regulate the GA pathway, contrary to some previous suggestions. The extent to which DELLA regulation was able to counteract the effects of auxin regulation varied from gene to gene. For Mendel's LE gene (PsGA3ox1) no counteraction was observed. However, for another synthesis gene, a GA 20-oxidase, the effect of auxin was weak and in WT plants appeared to be completely over-ridden by DELLA regulation. For a key GA deactivation (2-oxidase) gene, PsGA2ox1, the up-regulation induced by auxin deficiency was reduced to some extent by DELLA regulation. A second pea 2-oxidase gene, PsGA2ox2, was up-regulated by auxin, in a DELLA-independent manner. In Arabidopsis also, one 2-oxidase gene was down-regulated by auxin while another was up-regulated. Monitoring the metabolism pattern of GA(20) showed that in Arabidopsis, as in pea, auxin can promote the accumulation of bioactive GA. PMID:20706734

  18. Auxins and Cytokinins in Plant Development ... and Interactions with Other Phytohormones 2014

    OpenAIRE

    Vaňková, R. (Radomíra); Petrášek, J. (Jan); Zažímalová, E. (Eva); Kamínek, M; Motyka, V.; Ludwig-Müller, J.

    2014-01-01

    The ACPD Symposium (2014) followed the line of previous ones by presenting up-to-date achievements in auxin and cytokinin research including their mutual cross-talk and co-operation with other plant hormones. It becomes increasingly evident that thanks to this complexity the control of an amazingly wide spectrum of developmental processes is possible. The co-operation presumes transport of plant hormones on a cellular, tissue, and whole plant level. Novel approaches presented during t...

  19. Glucose and Auxin Signaling Interaction in Controlling Arabidopsis thaliana Seedlings Root Growth and Development

    OpenAIRE

    Mishra, Bhuwaneshwar S.; Manjul Singh; Priyanka Aggrawal; Ashverya Laxmi

    2009-01-01

    BACKGROUND: Plant root growth and development is highly plastic and can adapt to many environmental conditions. Sugar signaling has been shown to affect root growth and development by interacting with phytohormones such as gibberellins, cytokinin and abscisic acid. Auxin signaling and transport has been earlier shown to be controlling plant root length, number of lateral roots, root hair and root growth direction. PRINCIPAL FINDINGS: Increasing concentration of glucose not only controls root ...

  20. Developmental anatomy and auxin response of lateral root formation in Ceratopteris richardii.

    Science.gov (United States)

    Hou, Guichuan; Hill, Jeffrey P; Blancaflor, Elison B

    2004-03-01

    The homosporous fern Ceratopteris richardii exhibits a homorhizic root system where roots originate from the shoot system. These shoot-borne roots form lateral roots (LRs) that arise from the endodermis adjacent to the xylem poles, which is in contrast to flowering plants where LR formation arises from cell division in the pericycle. A detailed study of the fifth shoot-borne root showed that one lateral root mother cell (LRMC) develops in each two out of three successive merophytes. As a result, LRs emerge alternately in two ranks from opposite positions on a parent root. From LRMC initiation to LR emergence, three developmental stages were identified based on anatomical criteria. The addition of auxins (either indole-3-acetic acid or indole-3-butyric acid) to the growth media did not induce additional LR formation, but exogenous applications of both auxins inhibited parent root growth rate. Application of the polar auxin-transport inhibitor N-(1-naphthyl)phthalamic acid (NPA) also inhibited parent root growth without changing the LR initiation pattern. The results suggest that LR formation does not depend on root growth rate per se. The result that exogenous auxins do not promote LR formation in C. richardii is similar to reports for certain species of flowering plants, in which there is an acropetal LR population and the formation of the LRs is insensitive to the application of auxins. It also may indicate that different mechanisms control LR development in non-seed vascular plants compared with angiosperms, taking into consideration the long and independent evolutionary history of the two groups. PMID:14754921

  1. Auxin autonomy in cultured tobacco teratoma tissues transformed by an auxin-mutant strain of Agrobacterium tumefaciens.

    Science.gov (United States)

    Campell, B R; Su, L Y; Pengelly, W L

    1992-08-01

    We have studied the mechanism of auxin autonomy in tobacco (Nicotiana tabacum L.) crowngall tissues transformed by the auxin-mutant (tms (-)) A66 strain of Agrobacterium tumefaciens. Normally, tms (-) tobacco tumor tissues require the formation of shoots to exhibit auxin-independent growth in culture. We have isolated from tms (-) tobacco cells several stable variants that are fully hormone-independent and grow rapidly as friable, unorganized tissues, thus mimicking the growth and morphology of tms (+) tobacco cells that produce high levels of auxin. However, none of the variants contained the high levels of auxin found in tms (+) tumor cells. The variants could be divided into two classes with respect to their response to applied auxin. The first class was highly sensitive to applied auxin: low concentrations (1 μM) of α-naphthaleneacetic acid (NAA) severely inhibited growth and markedly stimulated the accumulation of the ethylene precursor, 1-aminocyclopropane-1-carboxylic acid (ACC). The second class of variants showed a low sensitivity to applied auxin: growth was promoted by concentrations of NAA up to 10 μM, and growth inhibition and high ACC levels were observed only at high NAA concentrations (100 μM). Unorganized variants with low auxin sensitivity were also isolated from a variant line with high auxin sensitivity. The isolation of tumor cells that exhibited the growth phenotype of tms (+) cells while retaining the low auxin content and low auxin sensitivity of tms (-) cells indicates that full hormone autonomy, characteristic of wild-type crown-gall tumors, can be achieved by a mechanism that is independent of changes in the auxin physiology of the cells. PMID:24178208

  2. Maize AUXIN-BINDING PROTEIN 1 and AUXIN-BINDING PROTEIN 4 impact on leaf growth, elongation, and seedling responsiveness to auxin and light

    Czech Academy of Sciences Publication Activity Database

    Jurišić-Knežev, Dejana; Čudejková, Mária; Zalabák, David; Hlobilová, Marta; Rolčík, Jakub; Pěnčík, Aleš; Bergougnoux, Véronique; Fellner, Martin

    2012-01-01

    Roč. 90, č. 10 (2012), s. 990-1006. ISSN 1916-2790 R&D Projects: GA MŠk(CZ) 1P05ME792 Institutional research plan: CEZ:AV0Z50380511 Keywords : auxin * auxin-binding protein * growth Subject RIV: EF - Botanics Impact factor: 1.225, year: 2012

  3. Onset of cell division in maize germination: action of auxins

    International Nuclear Information System (INIS)

    Seed germination implies metabolic reactivation, synthesis of macromolecules and onset of cell division. During maize germination, meristematic tissues of embryos re-initiate cell division asynchronically. Since auxins are known to stimulate cell division, they asked how auxins might regulate cell cycle re-initiation. Embryonic tissues were incubated with and without auxins. A pulse of either 3H-thymidine or 32P-ortophosphate was given to the tissues. Mitotic indexes were determined and % of labeled mitotic cells recorded. Results indicated that meristematic cells re-initiate cell division either from G1 or G2 phases. Auxin stimulated differentially the cell division process of these cells. 32P incorporation into cytoplasmic or nucleic histones was measured. Auxins stimulated this incorporation. Active turnover of histone phosphorylation occurred simultaneously to the cell division process. It is suggested that auxins might regulate the cell cycle by phosphorylation-dephosphorylation of histones

  4. Role of auxin-responsive genes in biotic stress responses

    OpenAIRE

    Ghanashyam, Challa; Jain, Mukesh

    2009-01-01

    Although the phytohormone auxin has been implicated primarily in developmental processes, some recent studies suggest its involvement in stress/defense responses as well. Recently, we identified auxin-responsive genes and reported their comprehensive transcript profiling during various stages of development and abiotic stress responses in crop plant rice. The analysis revealed tissue-specific and overlapping expression profiles of auxin-responsive genes during various stages of reproductive d...

  5. Auxin acts independently of DELLA proteins in regulating gibberellin levels

    OpenAIRE

    Reid, James B; Davidson, Sandra E.; Ross, John J.

    2011-01-01

    Shoot elongation is a vital process for plant development and productivity, in both ecological and economic contexts. Auxin and bioactive gibberellins (GAs), such as GA1, play critical roles in the control of elongation,1–3 along with environmental and endogenous factors, including other hormones such as the brassinosteroids.4,5 The effect of auxins, such as indole-3-acetic acid (IAA), is at least in part mediated by its effect on GA metabolism,6 since auxin upregulates biosynthesis genes suc...

  6. Hairy roots are more sensitive to auxin than normal roots.

    Science.gov (United States)

    Shen, W H; Petit, A; Guern, J; Tempé, J

    1988-05-01

    Responses to auxin of Lotus corniculatus root tips or protoplasts transformed by Agrobacterium rhizogenes strains 15834 and 8196 were compared to those of their normal counterparts. Three different types of experiments were performed, involving long-term, medium-term, or short-term responses to a synthetic auxin, 1-naphthaleneacetic acid. Root tip elongation, proton excretion by root tips, and transmembrane electrical potential difference of root protoplasts were measured as a function of exogenous auxin concentration. The sensitivity of hairy root tips or protoplasts to exogenous auxin was found to be 100-1000 times higher than that of untransformed material. PMID:16593928

  7. The circadian clock regulates auxin signaling and responses in Arabidopsis.

    Directory of Open Access Journals (Sweden)

    Michael F Covington

    2007-08-01

    Full Text Available The circadian clock plays a pervasive role in the temporal regulation of plant physiology, environmental responsiveness, and development. In contrast, the phytohormone auxin plays a similarly far-reaching role in the spatial regulation of plant growth and development. Went and Thimann noted 70 years ago that plant sensitivity to auxin varied according to the time of day, an observation that they could not explain. Here we present work that explains this puzzle, demonstrating that the circadian clock regulates auxin signal transduction. Using genome-wide transcriptional profiling, we found many auxin-induced genes are under clock regulation. We verified that endogenous auxin signaling is clock regulated with a luciferase-based assay. Exogenous auxin has only modest effects on the plant clock, but the clock controls plant sensitivity to applied auxin. Notably, we found both transcriptional and growth responses to exogenous auxin are gated by the clock. Thus the circadian clock regulates some, and perhaps all, auxin responses. Consequently, many aspects of plant physiology not previously thought to be under circadian control may show time-of-day-specific sensitivity, with likely important consequences for plant growth and environmental responses.

  8. Auxin-Oxylipin Crosstalk: Relationship of Antagonists

    Institute of Scientific and Technical Information of China (English)

    Maik Hoffmann; Mathias Hentrich; Stephan Pollmann

    2011-01-01

    Phytohormones regulate a wide array of developmental processes throughout the life cycle of plants. Herein, the various plant hormones may interact additively, synergistically, or antagonistically. By their cooperation they create a delicate regulatory network whose net output largely depends on the action of specific phytohormone combinations rather than on the independent activities of separate hormones. While most classical studies of plant hormonal control have focused mainly on the action of single hormones or on the synergistic interaction of hormones in regulating various developmental processes, recent work is beginning to shed light on the crosstalk of nominally antagonistic plant hormones, such as gibberellins and auxins with oxylipins or abscisic acid. In this review, we summarize our current understanding of how two of the first sight antagonistic plant hormones, i.e. auxins and oxylipins,interact in controlling plant responses and development.

  9. Mechanism of auxin-induced ethylene production

    Energy Technology Data Exchange (ETDEWEB)

    Kang, B.G.; Newcomb, W.; Burg, S.P.

    1971-01-01

    Indoleacetic acid-induced ethylene production and growth in excised segments of etiolated pea shoots (Pisum sativum L. var. Alaska) parallels the free indoleacetic acid level in the tissue which in turn depends upon the rate of indoleacetic acid conjugation and decarboxylation. Both ethylene synthesis and growth require the presence of more than a threshold level of free endogenous indoleacetic acid, but in etiolated tissue the rate of ethylene production saturates at a high concentration and the rate of growth at a lower concentration of indoleacetic acid. Auxin stimulation of ethylene synthesis is not mediated by induction of peroxidase; to the contrary, the products of the auxin action which induce growth and ethylene synthesis are highly labile. 33 references, 8 figures, 3 tables.

  10. Points of regulation for auxin action

    Czech Academy of Sciences Publication Activity Database

    Zažímalová, Eva; Napier, R. M.

    2003-01-01

    Roč. 21, č. 7 (2003), s. 625-634. ISSN 0721-7714 R&D Projects: GA MŠk LN00A081 Grant ostatní: EU INCO COPERNICUS(XE) ERBIC15 CT98 0118 Institutional research plan: CEZ:AV0Z5038910 Keywords : Plant hormone * Homeostasis * Auxin Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 1.423, year: 2003

  11. Auxin Activity: Past, present, and Future1

    OpenAIRE

    Enders, Tara A.; Strader, Lucia C.

    2015-01-01

    Long before its chemical identity was known, the phytohormone auxin was postulated to regulate plant growth. In the late 1800s, Sachs hypothesized that plant growth regulators, present in small amounts, move differentially throughout the plant to regulate growth. Concurrently, Charles Darwin and Francis Darwin were discovering that light and gravity were perceived by the tips of shoots and roots and that the stimulus was transmitted to other tissues, which underwent a growth response. These i...

  12. Plasma membrane-bound AGC3 kinases phosphorylate PIN auxin carriers at TPRXS(N/S) motifs to direct apical PIN recycling

    NARCIS (Netherlands)

    P. Dhonukshe; F. Huang; C.S. Galvan-Ampudia; A.P. Mähönen; J. Kleine-Vehn; J. Xu; A. Quint; K. Prasad; J. Friml; B. Scheres; R. Offringa

    2010-01-01

    Polar membrane cargo delivery is crucial for establishing cell polarity and for directional transport processes. In plants, polar trafficking mediates the dynamic asymmetric distribution of PIN FORMED (PIN) carriers, which drive polar cell-to-cell transport of the hormone auxin, thereby generating a

  13. ROP GTPase-mediated auxin signaling regulates pavement cell interdigitation in Arabidopsis thaliana

    Institute of Scientific and Technical Information of China (English)

    Deshu Lin; Huibo Ren; Ying Fu

    2015-01-01

    In multicel ular plant organs, cel shape formation depends on molecular switches to transduce developmental or environmental signals and to coordinate cel‐to‐cel communi-cation. Plants have a specific subfamily of the Rho GTPase family, usual y cal ed Rho of Plants (ROP), which serve as a critical signal transducer involved in many cel ular processes. In the last decade, important advances in the ROP‐mediated regulation of plant cel morphogenesis have been made by using Arabidopsis thaliana leaf and cotyledon pavement cel s. Especial y, the auxin‐ROP signaling networks have been demonstrated to control interdigitated growth of pavement cel s to form jigsaw‐puzzle shapes. Here, we review findings related to the discovery of this novel auxin‐signaling mecha-nism at the cel surface. This signaling pathway is to a large extent independent of the wel‐known Transport Inhibitor Response (TIR)–Auxin Signaling F‐Box (AFB) pathway, and instead requires Auxin Binding Protein 1 (ABP1) interaction with the plasma membrane‐localized, transmembrane kinase (TMK) receptor‐like kinase to regulate ROP proteins. Once activated, ROP influences cytoskeletal organization and inhibits endocytosis of the auxin transporter PIN1. The present review focuses on ROP signaling and its self‐organizing feature al owing ROP proteins to serve as a bustling signal decoder and integrator for plant cel morphogenesis.

  14. Auxin regulation of a proton translocating ATPase in pea root plasma membrane vesicles. [Pisum sativum. L

    Energy Technology Data Exchange (ETDEWEB)

    Gabathuler, R.; Cleland, R.E.

    1985-12-01

    Pea root microsomal vesicles have been fractionated on a Dextran step gradient to give three fractions, each of which carries out ATP-dependent proton accumulation as measured by fluorescence quenching of quinacrine. The fraction at the 4/6% Dextran interface is enriched in plasma membrane, as determined by UDPG sterol glucosyltransferase and vanadate-inhibited ATPase. The vanadate-sensitive phosphohydrolase is not specific for ATP, has a K/sub m/ of about 0.23 millimolar for MgATP, is only slightly affected by K/sup +/ or Cl/sup -/ and is insensitive to auxin. Proton transport, on the other hand, is more specific for ATP, enhanced by anions (NO/sub 3//sup -/ > Cl/sup -/) and has a K/sub m/ of about 0.7 millimolar. Auxins decrease the K/sub m/ to about 0.35 millimolar, with no significant effect on the V/sub max/, while antiauxins or weak acids have no such effect. It appears that auxin has the ability to alter the efficiency of the ATP-driven proton transport.

  15. Auxin producing non-heterocystous Cyanobacteria and their impact on the growth and endogenous auxin homeostasis of wheat.

    Science.gov (United States)

    Mazhar, Sumaira; Cohen, Jerry D; Hasnain, Shahida

    2013-12-01

    Four non-heterocystous cyanobacterial strains isolated from rhizosphere and soil surface mat of rice, wheat, and maize were identified by 16S rRNA gene sequencing and evaluated for auxin production as well as growth promotion of wheat. Isolated strains produced a diverse amount of auxin in BG11 media supplemented with different concentrations of L-tryptophan. The amount of auxin detected with colorimetric methods was higher as compared to GC-MS analysis. Auxin production by cyanobacterial strains in BG 11 medium supplemented with 250 µg ml(-1) L-tryptophan ranged from 0.20 to 1.63 µg ml(-1) IAA as revealed by gas chromatography and mass spectrometric (GC-MS) analysis. In a hydroponic growth system, the vegetative growth of wheat was stimulated appreciably by inoculation with cyanobacterial strains. The endogenous auxin content of wheat was significantly correlated with the exogenous auxin production of the cyanobacterial strains. It was observed that cyanobacterial strains produced more endogenous and exogenous auxin in the presence of a plant, showing that plants might be releasing some signals responsible for higher auxin production by cyanobacterial cultures. It was concluded that the auxin producing potential of cyanobacterial strains can be exploited for the promotion of wheat growth. PMID:23765374

  16. The PIN1 family gene PvPIN1 is involved in auxin-dependent root emergence and tillering in switchgrass.

    Science.gov (United States)

    Xu, Kaijie; Sun, Fengli; Wang, Yongfeng; Shi, Lili; Liu, Shudong; Xi, Yajun

    2016-03-01

    Switchgrass (Panicum virgatum L.; family Poaceae) is a warm-season C4 perennial grass. Tillering plays an important role in determining the morphology of aboveground parts and the final biomass yield of switchgrass. Auxin distribution in plants can affect a variety of important growth and developmental processes, including the regulation of shoot and root branching, plant resistance and biological yield. Auxin transport and gradients in plants are mediated by influx and efflux carriers. PvPIN1, a switchgrass PIN1-like gene that is involved in regulating polar transport, is a putative auxin efflux carrier. Neighbor-joining analysis using sequences deposited in NCBI databases showed that the PvPIN1gene belongs to the PIN1 family and is evolutionarily closer to the Oryza sativa japonica group. Tiller emergence and development was significantly promoted in plants subjected toPvPIN1 RNA interference (RNAi), which yielded a phenotype similar to that of wild-type plants treated with the auxin transport inhibitor TIBA (2,3,5-triiodobenzoic acid). A transgenic approach that inducedPvPIN1 gene overexpression or suppression altered tiller number and the shoot/root ratio. These data suggest that PvPIN1plays an important role in auxin-dependent adventitious root emergence and tillering. PMID:27007900

  17. The PIN1 family gene PvPIN1 is involved in auxin-dependent root emergence and tillering in switchgrass

    Directory of Open Access Journals (Sweden)

    Kaijie Xu

    2016-03-01

    Full Text Available Abstract Switchgrass (Panicum virgatum L.; family Poaceae is a warm-season C4 perennial grass. Tillering plays an important role in determining the morphology of aboveground parts and the final biomass yield of switchgrass. Auxin distribution in plants can affect a variety of important growth and developmental processes, including the regulation of shoot and root branching, plant resistance and biological yield. Auxin transport and gradients in plants are mediated by influx and efflux carriers. PvPIN1, a switchgrass PIN1-like gene that is involved in regulating polar transport, is a putative auxin efflux carrier. Neighbor-joining analysis using sequences deposited in NCBI databases showed that the PvPIN1gene belongs to the PIN1 family and is evolutionarily closer to the Oryza sativa japonica group. Tiller emergence and development was significantly promoted in plants subjected toPvPIN1 RNA interference (RNAi, which yielded a phenotype similar to that of wild-type plants treated with the auxin transport inhibitor TIBA (2,3,5-triiodobenzoic acid. A transgenic approach that inducedPvPIN1 gene overexpression or suppression altered tiller number and the shoot/root ratio. These data suggest that PvPIN1plays an important role in auxin-dependent adventitious root emergence and tillering.

  18. The role of auxin and cytokinin signalling in specifying the root architecture of Arabidopsis thaliana

    KAUST Repository

    Muraro, Daniele

    2013-01-01

    Auxin and cytokinin are key hormonal signals that control the cellular architecture of the primary root and the initiation of new lateral root organs in the plant Arabidopsis thaliana. Both developmental processes are regulated by cross-talk between these hormones and their signalling pathways. In this paper, sub-cellular and multi-cellular mathematical models are developed to investigate how interactions between auxin and cytokinin influence the size and location of regions of division and differentiation within the primary root, and describe how their cross-regulation may cause periodic branching of lateral roots. We show how their joint activity may influence tissue-specific oscillations in gene expression, as shown in Moreno-Risueno et al. (2010) and commented upon in Traas and Vernoux (2010), and we propose mechanisms that may generate synchronisation of such periodic behaviours inside a cell and with its neighbours. Using a multi-cellular model, we also analyse the roles of cytokinin and auxin in specifying the three main regions of the primary root (elongation, transition and division zones), our simulation results being in good agreement with independent experimental observations. We then use our model to generate testable predictions concerning the effect of varying the concentrations of the auxin efflux transporters on the sizes of the different root regions. In particular, we predict that over-expression of the transporters will generate a longer root with a longer elongation zone and a smaller division zone than that of a wild type root. This root will contain fewer cells than its wild type counterpart. We conclude that our model can provide a useful tool for investigating the response of cell division and elongation to perturbations in hormonal signalling. © 2012 Elsevier Ltd.

  19. A proteomics study of auxin effects in Arabidopsis thaliana

    Institute of Scientific and Technical Information of China (English)

    Meiqing Xing; Hongwei Xue

    2012-01-01

    Many phytohormones regulate plant growth and development through modulating protein degradation.In this study,a proteome study based on multidimensional non-gel shotgun approach was performed to analyze the auxin-induced protein degradation via ubiquitinproteasome pathway of Arabidopsis thaliana,with the emphasis to study the overall protein changes after auxin treatment (1 nM or 1 μM indole-3-acetic acid for 6,12,or 24 h).More than a thousand proteins were detected by using label-free shotgun method,and 386 increased proteins and 370 decreased ones were identified after indole-3-acetic acid treatment.By using the auxin receptor-deficient mutant,tir1-1,as control,comparative analysis revealed that 69 and 79 proteins were significantly decreased and increased,respectively.Detailed analysis showed that among the altered proteins,some were previously reported to be associated with auxin regulation and others are potentially involved in mediating the auxin effects on specific cellular and physiological processes by regulating photosynthesis,chloroplast development,cytoskeleton,and intracellular signaling.Our results demonstrated that label-free shotgun proteomics is a powerful tool for large-scale protein identification and the analysis of the proteomic profiling of auxin-regulated biological processes will provide informative clues of underlying mechanisms of auxin effects.These results will help to expand the understanding of how auxin regulates plant growth and development via protein degradation.

  20. The role of auxin in cell specification during arabidopsis embryogenesis

    NARCIS (Netherlands)

    Lokerse, A.S.

    2011-01-01

    Auxin is a structurally simple molecule, yet it elicits many different responses in plants. In Chapter 1 we have reviewed how specificity in the output of auxin signaling could be generated by distinct regulation and the unique properties of the members of the Aux/IAA and ARF transcription factor fa

  1. Auxin, H/sup +/-excretion and cell elongation

    Energy Technology Data Exchange (ETDEWEB)

    Cleland, R.E.; Rayle, D.L.

    1978-01-01

    By the use of Avena coleoptiles, the biochemical reactions of auxin-induced plant cell elongation are studied. A biological model of H/sup +/ as a cell wall loosening factor is presented for auxin-induced plant growth in the acid-growth theory. (DS)

  2. Arabidopsis PROTEASOME REGULATOR1 is required for auxin-mediated suppression of proteasome activity and regulates auxin signalling.

    Science.gov (United States)

    Yang, Bao-Jun; Han, Xin-Xin; Yin, Lin-Lin; Xing, Mei-Qing; Xu, Zhi-Hong; Xue, Hong-Wei

    2016-01-01

    The plant hormone auxin is perceived by the nuclear F-box protein TIR1 receptor family and regulates gene expression through degradation of Aux/IAA transcriptional repressors. Several studies have revealed the importance of the proteasome in auxin signalling, but details on how the proteolytic machinery is regulated and how this relates to degradation of Aux/IAA proteins remains unclear. Here we show that an Arabidopsis homologue of the proteasome inhibitor PI31, which we name PROTEASOME REGULATOR1 (PTRE1), is a positive regulator of the 26S proteasome. Loss-of-function ptre1 mutants are insensitive to auxin-mediated suppression of proteasome activity, show diminished auxin-induced degradation of Aux/IAA proteins and display auxin-related phenotypes. We found that auxin alters the subcellular localization of PTRE1, suggesting this may be part of the mechanism by which it reduces proteasome activity. Based on these results, we propose that auxin regulates proteasome activity via PTRE1 to fine-tune the homoeostasis of Aux/IAA repressor proteins thus modifying auxin activity. PMID:27109828

  3. A modular analysis of the auxin signalling network.

    Directory of Open Access Journals (Sweden)

    Etienne Farcot

    Full Text Available Auxin is essential for plant development from embryogenesis onwards. Auxin acts in large part through regulation of transcription. The proteins acting in the signalling pathway regulating transcription downstream of auxin have been identified as well as the interactions between these proteins, thus identifying the topology of this network implicating 54 Auxin Response Factor (ARF and Aux/IAA (IAA transcriptional regulators. Here, we study the auxin signalling pathway by means of mathematical modeling at the single cell level. We proceed analytically, by considering the role played by five functional modules into which the auxin pathway can be decomposed: the sequestration of ARF by IAA, the transcriptional repression by IAA, the dimer formation amongst ARFs and IAAs, the feedback loop on IAA and the auxin induced degradation of IAA proteins. Focusing on these modules allows assessing their function within the dynamics of auxin signalling. One key outcome of this analysis is that there are both specific and overlapping functions between all the major modules of the signaling pathway. This suggests a combinatorial function of the modules in optimizing the speed and amplitude of auxin-induced transcription. Our work allows identifying potential functions for homo- and hetero-dimerization of transcriptional regulators, with ARF:IAA, IAA:IAA and ARF:ARF dimerization respectively controlling the amplitude, speed and sensitivity of the response and a synergistic effect of the interaction of IAA with transcriptional repressors on these characteristics of the signaling pathway. Finally, we also suggest experiments which might allow disentangling the structure of the auxin signaling pathway and analysing further its function in plants.

  4. Noncoding transcription by alternative rna polymerases dynamically regulates an auxin-driven chromatin loop

    KAUST Repository

    Ariel, Federico D.

    2014-08-01

    The eukaryotic epigenome is shaped by the genome topology in three-dimensional space. Dynamic reversible variations in this epigenome structure directly influence the transcriptional responses to developmental cues. Here, we show that the Arabidopsis long intergenic noncoding RNA (lincRNA) APOLO is transcribed by RNA polymerases II and V in response to auxin, a phytohormone controlling numerous facets of plant development. This dual APOLO transcription regulates the formation of a chromatin loop encompassing the promoter of its neighboring gene PID, a key regulator of polar auxin transport. Altering APOLO expression affects chromatin loop formation, whereas RNA-dependent DNA methylation, active DNA demethylation, and Polycomb complexes control loop dynamics. This dynamic chromatin topology determines PID expression patterns. Hence, the dual transcription of a lincRNA influences local chromatin topology and directs dynamic auxin-controlled developmental outputs on neighboring genes. This mechanism likely underscores the adaptive success of plants in diverse environments and may be widespread in eukaryotes. © 2014 Elsevier Inc.

  5. Carbon Monoxide Interacts with Auxin and Nitric Oxide to Cope with Iron Deficiency in Arabidopsis

    Science.gov (United States)

    Yang, Liming; Ji, Jianhui; Wang, Hongliang; Harris-Shultz, Karen R.; Abd_Allah, Elsayed F.; Luo, Yuming; Guan, Yanlong; Hu, Xiangyang

    2016-01-01

    To clarify the roles of carbon monoxide (CO), nitric oxide (NO), and auxin in the plant response to iron deficiency (–Fe), and to establish how the signaling molecules interact to enhance Fe acquisition, we conducted physiological, genetic, and molecular analyses that compared the responses of various Arabidopsis mutants, including hy1 (CO deficient), noa1 (NO deficient), nia1/nia2 (NO deficient), yuc1 (auxin over-accumulation), and cue1 (NO over-accumulation) to –Fe stress. We also generated a HY1 over-expression line (named HY1-OX) in which CO is over-produced compared to wild-type. We found that the suppression of CO and NO generation using various inhibitors enhanced the sensitivity of wild-type plants to Fe depletion. Similarly, the hy1, noa1, and nia1/nia2 mutants were more sensitive to Fe deficiency. By contrast, the yuc1, cue1, and HY1-OX lines were less sensitive to Fe depletion. The hy1 mutant with low CO content exhibited no induced expression of the Fe uptake-related genes FIT1 and FRO2 as compared to wild-type plants. On the other hand, the treatments of exogenous CO and NO enhanced Fe uptake. Likewise, cue1 and HY1-OX lines with increased endogenous content of NO and CO, respectively, also exhibited enhanced Fe uptake and increased expression of bHLH transcriptional factor FIT1as compared to wild-type plants. Furthermore, we found that CO affected auxin accumulation and transport in the root tip by altering the PIN1 and PIN2 proteins distribution that control lateral root structure under –Fe stress. Our results demonstrated the integration of CO, NO, and auxin signaling to cope with Fe deficiency in Arabidopsis. PMID:27014280

  6. Carbon Monoxide Interacts with Auxin and Nitric Oxide to Cope with Iron Deficiency in Arabidopsis.

    Science.gov (United States)

    Yang, Liming; Ji, Jianhui; Wang, Hongliang; Harris-Shultz, Karen R; Abd Allah, Elsayed F; Luo, Yuming; Guan, Yanlong; Hu, Xiangyang

    2016-01-01

    To clarify the roles of carbon monoxide (CO), nitric oxide (NO), and auxin in the plant response to iron deficiency (-Fe), and to establish how the signaling molecules interact to enhance Fe acquisition, we conducted physiological, genetic, and molecular analyses that compared the responses of various Arabidopsis mutants, including hy1 (CO deficient), noa1 (NO deficient), nia1/nia2 (NO deficient), yuc1 (auxin over-accumulation), and cue1 (NO over-accumulation) to -Fe stress. We also generated a HY1 over-expression line (named HY1-OX) in which CO is over-produced compared to wild-type. We found that the suppression of CO and NO generation using various inhibitors enhanced the sensitivity of wild-type plants to Fe depletion. Similarly, the hy1, noa1, and nia1/nia2 mutants were more sensitive to Fe deficiency. By contrast, the yuc1, cue1, and HY1-OX lines were less sensitive to Fe depletion. The hy1 mutant with low CO content exhibited no induced expression of the Fe uptake-related genes FIT1 and FRO2 as compared to wild-type plants. On the other hand, the treatments of exogenous CO and NO enhanced Fe uptake. Likewise, cue1 and HY1-OX lines with increased endogenous content of NO and CO, respectively, also exhibited enhanced Fe uptake and increased expression of bHLH transcriptional factor FIT1as compared to wild-type plants. Furthermore, we found that CO affected auxin accumulation and transport in the root tip by altering the PIN1 and PIN2 proteins distribution that control lateral root structure under -Fe stress. Our results demonstrated the integration of CO, NO, and auxin signaling to cope with Fe deficiency in Arabidopsis. PMID:27014280

  7. Correlations between gravitropic curvature and auxin movement across gravistimulated roots of Zea mays

    Science.gov (United States)

    Young, L. M.; Evans, M. L.; Hertel, R.

    1990-01-01

    We compared the kinetics of auxin redistribution across the caps of primary roots of 2-day-old maize (Zea mays, cv Merit) seedlings with the time course of gravitropic curvature. [3H] indoleacetic acid was applied to one side of the cap in an agar donor and radioactivity moving across the cap was collected in an agar receiver applied to the opposite side. Upon gravistimulation the roots first curved upward slightly, then returned to the horizontal and began curving downward, reaching a final angle of about 67 degrees. Movement of label across the caps of gravistimulated roots was asymmetric with preferential downward movement (ratio downward/upward = ca. 1.6, radioactivity collected during the 90 min following beginning of gravistimulation). There was a close correlation between the development of asymmetric auxin movement across the root cap and the rate of curvature, with both values increasing to a maximum and then declining as the roots approached the final angle of curvature. In roots preadapted to gravity (alternate brief stimulation on opposite flanks over a period of 1 hour) the initial phase of upward curvature was eliminated and downward bending began earlier than for controls. The correlation between asymmetric auxin movement and the kinetics of curvature also held in comparisons between control and preadapted roots. Both downward auxin transport asymmetry and downward curvature occurred earlier in preadapted roots than in controls. These findings are consistent with suggestions that the root cap is not only the site of perception but also the location of the initial redistribution of effectors that ultimately leads to curvature.

  8. Auxin gradient is crucial for the maintenance of root distal stem cell identity in Arabidopsis

    OpenAIRE

    Tian, Huiyu; Niu, Tiantian; Yu, Qianqian; Quan, Taiyong; Ding, Zhaojun

    2013-01-01

    The plant hormone auxin plays a critical role in the maintenance of root stem cell niches in Arabidopsis. We have recently reported that WUSCHEL-RELATED HOMEOBOX 5 (WOX5) transcription factor modulates free auxin production in the quiescent center (QC) of the root and its expression is inhibited in a feedback-dependent manner by canonical auxin signaling that involves indole-3-acetic acid 17 (IAA17) auxin response repressor. WOX5-IAA17 feedback circuit assures the maintenance of auxin respons...

  9. L-Cysteine inhibits root elongation through auxin/PLETHORA and SCR/SHR pathway in Arabidopsis thaliana

    Institute of Scientific and Technical Information of China (English)

    Zhen Wang; Jie-Li Mao; Ying-Jun Zhao; Chuan-You Li; Cheng-Bin Xiang

    2015-01-01

    L‐Cysteine plays a prominent role in sulfur metabo-lism of plants. However, its role in root development is largely unknown. Here, we report that L‐cysteine reduces primary root growth in a dosage‐dependent manner. Elevating cel ular L‐cysteine level by exposing Arabidopsis thaliana seedlings to high L‐cysteine, buthionine sulphoximine, or O‐acetylserine leads to altered auxin maximum in root tips, the expression of quiescent center cel marker as wel as the decrease of the auxin carriers PIN1, PIN2, PIN3, and PIN7 of primary roots. We also show that high L‐cysteine significantly reduces the protein level of two sets of stem cel specific transcription factors PLETHORA1/2 and SCR/SHR. However, L‐cysteine does not downregulate the transcript level of PINs, PLTs, or SCR/SHR, suggesting that an uncharacterized post‐transcriptional mech-anism may regulate the accumulation of PIN, PLT, and SCR/SHR proteins and auxin transport in the root tips. These results suggest that endogenous L‐cysteine level acts to maintain root stem cel niche by regulating basal‐and auxin‐induced expression of PLT1/2 and SCR/SHR. L‐Cysteine may serve as a link between sulfate assimilation and auxin in regulating root growth.

  10. In vitro oxidation of indoleacetic acid by soluble auxin-oxidases and peroxidases from maize roots. [Zea mays L

    Energy Technology Data Exchange (ETDEWEB)

    Beffa, R.; Martin, H.V.; Pilet, P.E. (Institute of Plant Biology and Physiology of the University, Lausanne (Switzerland))

    1990-10-01

    Soluble auxin-oxidases were extracted from Zea mays L. cv LG11 apical root segments and partially separated from peroxidases (EC 1.11.1.7) by size-exclusion chromatography. Auxin-oxidases were resolved into one main peak corresponding to a molecular mass of 32.5 kilodaltons and a minor peak at 54.5 kilodaltons. Peroxidases were separated into at least four peaks, with molecular masses from 32.5 to 78 kilodaltons. In vitro activity of indoleacetic acid-oxidases was dependent on the presence of MnCl{sub 2} and p-coumaric acid. Compound(s) present in the crude extract and several synthetic auxin transport inhibitors (including 2,3,5-triiodobenzoic acid and N-1-naphthylphthalamic acid) inhibited auxin-oxidase activity, but had no effect on peroxidases. The products resulting from the in vitro enzymatic oxidation of ({sup 3}H)indoleacetic acid were separated by HPLC and the major metabolite was found to cochromatograph with indol-3yl-methanol.

  11. WOX4 imparts auxin responsiveness to cambium cells in Arabidopsis.

    Science.gov (United States)

    Suer, Stefanie; Agusti, Javier; Sanchez, Pablo; Schwarz, Martina; Greb, Thomas

    2011-09-01

    Multipotent stem cell populations, the meristems, are fundamental for the indeterminate growth of plant bodies. One of these meristems, the cambium, is responsible for extended root and stem thickening. Strikingly, although the pivotal role of the plant hormone auxin in promoting cambium activity has been known for decades, the molecular basis of auxin responsiveness on the level of cambium cells has so far been elusive. Here, we reveal that auxin-dependent cambium stimulation requires the homeobox transcription factor WOX4. In Arabidopsis thaliana inflorescence stems, 1-N-naphthylphthalamic acid-induced auxin accumulation stimulates cambium activity in the wild type but not in wox4 mutants, although basal cambium activity is not abolished. This conclusion is confirmed by the analysis of cellular markers and genome-wide transcriptional profiling, which revealed only a small overlap between WOX4-dependent and cambium-specific genes. Furthermore, the receptor-like kinase PXY is required for a stable auxin-dependent increase in WOX4 mRNA abundance and the stimulation of cambium activity, suggesting a concerted role of PXY and WOX4 in auxin-dependent cambium stimulation. Thus, in spite of large anatomical differences, our findings uncover parallels between the regulation of lateral and apical plant meristems by demonstrating the requirement for a WOX family member for auxin-dependent regulation of lateral plant growth. PMID:21926336

  12. A Review of Auxin Response Factors (ARFs) in Plants

    Science.gov (United States)

    Li, Si-Bei; Xie, Zong-Zhou; Hu, Chun-Gen; Zhang, Jin-Zhi

    2016-01-01

    Auxin is a key regulator of virtually every aspect of plant growth and development from embryogenesis to senescence. Previous studies have indicated that auxin regulates these processes by controlling gene expression via a family of functionally distinct DNA-binding auxin response factors (ARFs). ARFs are likely components that confer specificity to auxin response through selection of target genes as transcription factors. They bind to auxin response DNA elements (AuxRE) in the promoters of auxin-regulated genes and either activate or repress transcription of these genes depending on a specific domain in the middle of the protein. Genetic studies have implicated various ARFs in distinct developmental processes through loss-of-function mutant analysis. Recent advances have provided information on the regulation of ARF gene expression, the role of ARFs in growth and developmental processes, protein–protein interactions of ARFs and target genes regulated by ARFs in plants. In particular, protein interaction and structural studies of ARF proteins have yielded novel insights into the molecular basis of auxin-regulated transcription. These results provide the foundation for predicting the contributions of ARF genes to the biology of other plants. PMID:26870066

  13. A crosstalk of auxin and GA during tuber development.

    Science.gov (United States)

    Roumeliotis, Efstathios; Visser, Richard G F; Bachem, Christian W B

    2012-10-01

    Several hormones have been studied for their effect on tuber initiation and development. Until recently, the hormone with the most prominent role in tuber initiation was attributed to GA. Genes involved in GA degradation do exhibit an upregulated profile during early stages of tuber development, leading to a rapid decrease of active GA content, thereby facilitating stolon-tip swelling. While GA is known to be involved in shoot and stolon elongation, the development of the new tuberorgan requires changes in meristem identity and the reorientation ofthe plane of cell division. In other developmental processes, such as embryo patterning, flower development and lateral root initiation auxin plays a key role. Recent evidence on the involvement of auxin in tuber formation was providedby the measurement of auxin content in swelling stolons. Auxin content in the stolon tips increased several fold prior to tuber swelling. In vitro tuberisation experiments with auxin applications support the role of auxin during tuber initiation. Taken together, it is becoming clear that the initiation and induction of tubers in potato is a developmental process that appears to be regulated by a crosstalk between GA and auxin. PMID:22902700

  14. Hormonal control of root development on epiphyllous plantlets of Bryophyllum (Kalanchoë) marnierianum: role of auxin and ethylene

    OpenAIRE

    Kulka, Richard G.

    2008-01-01

    Epiphyllous plantlets develop on leaves of Bryophyllum marnierianum when they are excised from the plant. Shortly after leaf excision, plantlet shoots develop from primordia located near the leaf margin. After the shoots have enlarged for several days, roots appear at their base. In this investigation, factors regulating plantlet root development were studied. The auxin transport inhibitor 2,3,5-triiodobenzoic acid (TIBA) abolished root formation without markedly affecting shoot growth. This ...

  15. The Protein Kinase CK2 Mediates Cross-Talk between Auxin- and Salicylic Acid-Signaling Pathways in the Regulation of PINOID Transcription.

    Science.gov (United States)

    Armengot, Laia; Caldarella, Eleonora; Marquès-Bueno, Maria Mar; Martínez, M Carmen

    2016-01-01

    The protein kinase CK2 is a ubiquitous and highly conserved enzyme, the activity of which is vital for eukaryotic cells. We recently demonstrated that CK2 modulates salicylic acid (SA) homeostasis in Arabidopsis thaliana, and that functional interplay between CK2 and SA sustains transcriptional expression of PIN-FORMED (PIN) genes. In this work, we show that CK2 also plays a key role in the transcriptional regulation of PINOID (PID), an AGC protein kinase that modulates the apical/basal localization of auxin-efflux transporters. We show that PID transcription is up-regulated by auxin and by SA and that CK2 is involved in both pathways. On the one hand, CK2 activity is required for proteosome-dependent degradation of AXR3, a member of the AUX/IAA family of auxin transcriptional repressors that must be degraded to activate auxin-responsive gene expression. On the other hand, the role of CK2 in SA homeostasis and, indirectly, in SA-driven PID transcription, was confirmed by using Arabidopsis NahG transgenic plants, which cannot accumulate SA. In conclusion, our results evidence a role for CK2 as a functional link in the negative cross-talk between auxin- and SA-signaling. PMID:27275924

  16. The Protein Kinase CK2 Mediates Cross-Talk between Auxin- and Salicylic Acid-Signaling Pathways in the Regulation of PINOID Transcription.

    Directory of Open Access Journals (Sweden)

    Laia Armengot

    Full Text Available The protein kinase CK2 is a ubiquitous and highly conserved enzyme, the activity of which is vital for eukaryotic cells. We recently demonstrated that CK2 modulates salicylic acid (SA homeostasis in Arabidopsis thaliana, and that functional interplay between CK2 and SA sustains transcriptional expression of PIN-FORMED (PIN genes. In this work, we show that CK2 also plays a key role in the transcriptional regulation of PINOID (PID, an AGC protein kinase that modulates the apical/basal localization of auxin-efflux transporters. We show that PID transcription is up-regulated by auxin and by SA and that CK2 is involved in both pathways. On the one hand, CK2 activity is required for proteosome-dependent degradation of AXR3, a member of the AUX/IAA family of auxin transcriptional repressors that must be degraded to activate auxin-responsive gene expression. On the other hand, the role of CK2 in SA homeostasis and, indirectly, in SA-driven PID transcription, was confirmed by using Arabidopsis NahG transgenic plants, which cannot accumulate SA. In conclusion, our results evidence a role for CK2 as a functional link in the negative cross-talk between auxin- and SA-signaling.

  17. SUPPRESSOR OF PHYTOCHROME B4-#3 Represses Genes Associated with Auxin Signaling to Modulate Hypocotyl Growth.

    Science.gov (United States)

    Favero, David S; Jacques, Caitlin N; Iwase, Akira; Le, Kimberly Ngan; Zhao, Jianfei; Sugimoto, Keiko; Neff, Michael M

    2016-08-01

    Developing seedlings are well equipped to alter their growth in response to external factors in order to maximize their chances of survival. SUPPRESSOR OF PHYTOCHROME B4-#3 (SOB3) and other members of the AT-HOOK MOTIF CONTAINING NUCLEAR LOCALIZED (AHL) family of transcription factors modulate the development of Arabidopsis (Arabidopsis thaliana) by repressing hypocotyl elongation in young seedlings growing in light. However, the molecular mechanism behind how AHLs influence seedling development is largely unknown. We have identified genes associated with auxin-mediated hypocotyl elongation as downstream targets of SOB3. We found that YUCCA8 (YUC8) as well as members of the SMALL AUXIN UP-REGULATED RNA19 (SAUR19) subfamily were down-regulated in the short-hypocotyl, gain-of-function SOB3-D mutant and up-regulated in the dominant-negative, tall-hypocotyl sob3-6 mutant. SOB3-D and sob3-6 hypocotyls also exhibited altered sensitivity to the polar auxin transport inhibitor N-1-napthylphthalamic acid, suggesting a critical connection between auxin and the modulation of seedling elongation by SOB3 Finally, we found that overexpression of GREEN FLUORESCENT PROTEIN-SAUR19 in the SOB3-D line partially rescued defects in hypocotyl elongation, and SOB3 bound directly to the promoters of YUC8 and SAUR19 subfamily members. Taken together, these data indicate that SOB3 modulates hypocotyl elongation in young seedlings by directly repressing the transcription of genes associated with auxin signaling. PMID:27342309

  18. SUPPRESSOR OF PHYTOCHROME B4-#3 Represses Genes Associated with Auxin Signaling to Modulate Hypocotyl Growth1[OPEN

    Science.gov (United States)

    Iwase, Akira

    2016-01-01

    Developing seedlings are well equipped to alter their growth in response to external factors in order to maximize their chances of survival. SUPPRESSOR OF PHYTOCHROME B4-#3 (SOB3) and other members of the AT-HOOK MOTIF CONTAINING NUCLEAR LOCALIZED (AHL) family of transcription factors modulate the development of Arabidopsis (Arabidopsis thaliana) by repressing hypocotyl elongation in young seedlings growing in light. However, the molecular mechanism behind how AHLs influence seedling development is largely unknown. We have identified genes associated with auxin-mediated hypocotyl elongation as downstream targets of SOB3. We found that YUCCA8 (YUC8) as well as members of the SMALL AUXIN UP-REGULATED RNA19 (SAUR19) subfamily were down-regulated in the short-hypocotyl, gain-of-function SOB3-D mutant and up-regulated in the dominant-negative, tall-hypocotyl sob3-6 mutant. SOB3-D and sob3-6 hypocotyls also exhibited altered sensitivity to the polar auxin transport inhibitor N-1-napthylphthalamic acid, suggesting a critical connection between auxin and the modulation of seedling elongation by SOB3. Finally, we found that overexpression of GREEN FLUORESCENT PROTEIN-SAUR19 in the SOB3-D line partially rescued defects in hypocotyl elongation, and SOB3 bound directly to the promoters of YUC8 and SAUR19 subfamily members. Taken together, these data indicate that SOB3 modulates hypocotyl elongation in young seedlings by directly repressing the transcription of genes associated with auxin signaling. PMID:27342309

  19. Design, Synthesis, and Evaluation of Novel Auxin Mimic Herbicides.

    Science.gov (United States)

    Do-Thanh, Chi-Linh; Vargas, Jose J; Thomas, Joseph W; Armel, Gregory R; Best, Michael D

    2016-05-11

    Due to the key roles of auxins as master regulators of plant growth, there is considerable interest in the development of compounds with auxin-like properties for growth management and weed control applications. Herein, we describe the design and multistep synthesis of ten compounds bearing combinations of functional groups commonly associated with auxin-type properties. Following synthesis, these compounds were tested against multiple weed species as well as sweet corn. In general, while these structures were not quite as active as commercial auxin mimic herbicides, multiple compounds exhibited broadleaf weed activity with concurrent selectivity in sweet corn (Zea mays L. var. saccharum). In addition, differential results were observed upon subtle changes to structure, providing insights into the structural properties required for activity. PMID:27086840

  20. High-temperature injury and auxin biosynthesis in microsporogenesis.

    Directory of Open Access Journals (Sweden)

    Atsushi eHigashitani

    2013-03-01

    Full Text Available Plant reproductive development is more sensitive than vegetative growth to many environmental stresses. With global warming, in particular, plant high temperature injury is becoming an increasingly serious problem. In wheat, barley, and various other commercially important crops, the early phase of anther development is especially susceptible to high temperatures. We recently demonstrated that high temperature causes cell-proliferation arrest and represses auxin signaling in a tissue-specific manner of the anther cells of barley and Arabidopsis. These phenomena were accompanied by comprehensive alterations in transcription including repression of cell-proliferation related genes and YUCCA auxin biosynthesis genes. Moreover, application of auxin completely improved the transcriptional alterations, the production of normal pollen grains, and seed setting rate under increasing temperatures. These denote that auxin, which has been used widely as potent and selective herbicides, is useful for the promotion of plant fertility and maintenance of crop yields under the global warming conditions.

  1. Plant development, auxin, and the subsystem incompleteness theorem.

    Science.gov (United States)

    Niklas, Karl J; Kutschera, Ulrich

    2012-01-01

    Plant morphogenesis (the process whereby form develops) requires signal cross-talking among all levels of organization to coordinate the operation of metabolic and genomic subsystems operating in a larger network of subsystems. Each subsystem can be rendered as a logic circuit supervising the operation of one or more signal-activated system. This approach simplifies complex morphogenetic phenomena and allows for their aggregation into diagrams of progressively larger networks. This technique is illustrated here by rendering two logic circuits and signal-activated subsystems, one for auxin (IAA) polar/lateral intercellular transport and another for IAA-mediated cell wall loosening. For each of these phenomena, a circuit/subsystem diagram highlights missing components (either in the logic circuit or in the subsystem it supervises) that must be identified experimentally if each of these basic plant phenomena is to be fully understood. We also illustrate the "subsystem incompleteness theorem," which states that no subsystem is operationally self-sufficient. Indeed, a whole-organism perspective is required to understand even the most simple morphogenetic process, because, when isolated, every biological signal-activated subsystem is morphogenetically ineffective. PMID:22645582

  2. Distribution and regulation of auxin in Arabidopsis root cells

    OpenAIRE

    Petersson, Sara

    2011-01-01

    The plant hormone auxin (IAA) coordinates many of the important processes in plant development. For example, IAA is critical for normal embryogenesis, root development, cell elongation, and the tropic responses such as gravitropism and phototropism. IAA gradients are established and maintained in many tissues and it is thought that these gradients act as developmental cues, determining the fate of cells and tissues. Descriptions of auxin distribution patterns with cellular resolution h...

  3. Hairy roots are more sensitive to auxin than normal roots

    OpenAIRE

    Shen, Wen Hui; Petit, Annik; Guern, Jean; Tempé, Jacques

    1988-01-01

    Responses to auxin of Lotus corniculatus root tips or protoplasts transformed by Agrobacterium rhizogenes strains 15834 and 8196 were compared to those of their normal counterparts. Three different types of experiments were performed, involving long-term, medium-term, or short-term responses to a synthetic auxin, 1-naphthaleneacetic acid. Root tip elongation, proton excretion by root tips, and transmembrane electrical potential difference of root protoplasts were measured as a function of exo...

  4. Auxin modulation of salt stress signaling in Arabidopsis seed germination

    OpenAIRE

    Jung, Jae-Hoon; Park, Chung-Mo

    2011-01-01

    Seed germination is an elaborate developmental process that is regulated through intricate signaling networks integrating diverse environmental cues into endogenous hormonal signaling pathways. Accumulating evidence in recent years supports the role of auxin in seed germination. Whereas the roles of gibberellic acid (GA) and abscisic acid (ABA) in the germination process have been studied extensively, how auxin modulates seed germination is largely unknown. We found that a membrane-bound NAC ...

  5. Synergistic action of auxin and ethylene on root elongation inhibition is caused by a reduction of epidermal cell length

    OpenAIRE

    Alarcón, M. Victoria; Lloret, Pedro G; Salguero, Julio

    2014-01-01

    Auxin and ethylene have been largely reported to reduce root elongation in maize primary root. However the effects of auxin are greater than those caused by ethylene. Although auxin stimulates ethylene biosynthesis through the specific increase of ACC synthase, the auxin inhibitory effect on root elongation is not mediated by the auxin-induced increase of ethylene production. Recently it has been demonstrated that root inhibition by the application of the synthetic auxin NAA (1-naphtalenaceti...

  6. Auxin Control in the Formation of Adventitious Roots

    Directory of Open Access Journals (Sweden)

    Tiberia I. POP

    2011-05-01

    Full Text Available Adventitious rooting is a complex process and a key step in the vegetative propagation of economically important woody, horticultural and agricultural species, playing an important role in the successful production of elite clones. The formation of adventitious roots is a quantitative genetic trait regulated by both environmental and endogenous factors. Among phytohormones, auxin plays an essential role in regulating roots development and it has been shown to be intimately involved in the process of adventitious rooting. Great progress has been made in elucidating the auxin-induced genes and auxin signaling pathway, especially in auxin response Aux/IAA and Auxin Response Factor gene families. Although some important aspects of adventitious and lateral rooting signaling have been revealed, the intricate signaling network remains poorly understood. This review summarizes some of the current knowledge on the physiological aspects of adventitious root formation and highlights the recent progress made in the identification of putative molecular players involved in the control of adventitious rooting. Despite much has been discovered regarding the effects and regulation of auxins on plant growth since the Darwin experiments, there is much that remains unknown.

  7. Nitric Oxide-Mediated Maize Root Apex Responses to Nitrate are Regulated by Auxin and Strigolactones

    Science.gov (United States)

    Manoli, Alessandro; Trevisan, Sara; Voigt, Boris; Yokawa, Ken; Baluška, František; Quaggiotti, Silvia

    2016-01-01

    Nitrate (NO3-) is a key element for crop production but its levels in agricultural soils are limited. Plants have developed mechanisms to cope with these NO3- fluctuations based on sensing nitrate at the root apex. Particularly, the transition zone (TZ) of root apex has been suggested as a signaling-response zone. This study dissects cellular and molecular mechanisms underlying NO3- resupply effects on primary root (PR) growth in maize, confirming nitric oxide (NO) as a putative modulator. Nitrate restoration induced PR elongation within the first 2 h, corresponding to a stimulation of cell elongation at the basal border of the TZ. Xyloglucans (XGs) immunolocalization together with Brefeldin A applications demonstrated that nitrate resupply induces XG accumulation. This effect was blocked by cPTIO (NO scavenger). Transcriptional analysis of ZmXET1 confirmed the stimulatory effect of nitrate on XGs accumulation in cells of the TZ. Immunolocalization analyses revealed a positive effect of nitrate resupply on auxin and PIN1 accumulation, but a transcriptional regulation of auxin biosynthesis/transport/signaling genes was excluded. Short-term nitrate treatment repressed the transcription of genes involved in strigolactones (SLs) biosynthesis and transport, mainly in the TZ. Enhancement of carotenoid cleavage dioxygenases (CCDs) transcription in presence of cPTIO indicated endogenous NO as a negative modulator of CCDs activity. Finally, treatment with the SLs-biosynthesis inhibitor (TIS108) restored the root growth in the nitrate-starved seedlings. Present report suggests that the NO-mediated root apex responses to nitrate are accomplished in cells of the TZ via integrative actions of auxin, NO and SLs. PMID:26834770

  8. Nitric Oxide-Mediated Maize Root Apex Responses to Nitrate are Regulated by Auxin and Strigolactones

    Directory of Open Access Journals (Sweden)

    Alessandro eManoli

    2016-01-01

    Full Text Available Nitrate (NO3- is a key element for crop production but its levels in agricultural soils are limited. Plants have developed mechanisms to cope with these NO3- fluctuations based on sensing nitrate at the root apex. Particularly, the transition zone (TZ of root apex has been suggested as a signalling-response zone. This study dissects cellular and molecular mechanisms underlying NO3- resupply effects on primary root growth in maize, confirming nitric oxide (NO as a putative modulator. Nitrate restoration induced primary root elongation within the first 2 h, corresponding to a stimulation of cell elongation at the basal border of the TZ. Xyloglucans (XGs immunolocalization together with Brefeldin A applications demonstrated that nitrate resupply induces XG accumulation. This effect was blocked by cPTIO (NO scavenger. Transcriptional analysis of ZmXET1 confirmed the stimulatory effect of nitrate on XGs accumulation in cells of the TZ. Immunolocalization analyses revealed a positive effect of nitrate resupply on auxin and PIN1 accumulation, but a transcriptional regulation of auxin biosynthesis/transport/signalling genes was excluded. Short-term nitrate treatment repressed the transcription of genes involved in strigolactones (SLs biosynthesis and transport, mainly in the TZ. Enhancement of carotenoid cleavage dioxygenases (CCDs transcription in presence of cPTIO indicated endogenous NO as a negative modulator of CCDs activity. Finally, treatment with the SLs-biosynthesis inhibitor (TIS108 restored the root growth in the nitrate-starved seedlings. Present report suggests that the NO-mediated root apex responses to nitrate are accomplished in cells of the TZ via integrative actions of auxin, NO and SLs.

  9. Nitric Oxide-Mediated Maize Root Apex Responses to Nitrate are Regulated by Auxin and Strigolactones.

    Science.gov (United States)

    Manoli, Alessandro; Trevisan, Sara; Voigt, Boris; Yokawa, Ken; Baluška, František; Quaggiotti, Silvia

    2015-01-01

    Nitrate (NO3 (-)) is a key element for crop production but its levels in agricultural soils are limited. Plants have developed mechanisms to cope with these NO3 (-) fluctuations based on sensing nitrate at the root apex. Particularly, the transition zone (TZ) of root apex has been suggested as a signaling-response zone. This study dissects cellular and molecular mechanisms underlying NO3 (-) resupply effects on primary root (PR) growth in maize, confirming nitric oxide (NO) as a putative modulator. Nitrate restoration induced PR elongation within the first 2 h, corresponding to a stimulation of cell elongation at the basal border of the TZ. Xyloglucans (XGs) immunolocalization together with Brefeldin A applications demonstrated that nitrate resupply induces XG accumulation. This effect was blocked by cPTIO (NO scavenger). Transcriptional analysis of ZmXET1 confirmed the stimulatory effect of nitrate on XGs accumulation in cells of the TZ. Immunolocalization analyses revealed a positive effect of nitrate resupply on auxin and PIN1 accumulation, but a transcriptional regulation of auxin biosynthesis/transport/signaling genes was excluded. Short-term nitrate treatment repressed the transcription of genes involved in strigolactones (SLs) biosynthesis and transport, mainly in the TZ. Enhancement of carotenoid cleavage dioxygenases (CCDs) transcription in presence of cPTIO indicated endogenous NO as a negative modulator of CCDs activity. Finally, treatment with the SLs-biosynthesis inhibitor (TIS108) restored the root growth in the nitrate-starved seedlings. Present report suggests that the NO-mediated root apex responses to nitrate are accomplished in cells of the TZ via integrative actions of auxin, NO and SLs. PMID:26834770

  10. Synthesis of Plant Auxin Derivatives and Their Effects on Ceratopteris Richardii

    Science.gov (United States)

    Stilts, Corey E.; Fisher, Roxanne

    2007-01-01

    Bioassays are commonly used to test the biological activity of chemicals and other exercises are presented in which students synthesize plant hormones. Lab exercise is conducted using commercially available auxins and auxin regulating compounds.

  11. Auxin acts independently of DELLA proteins in regulating gibberellin levels.

    Science.gov (United States)

    Reid, James B; Davidson, Sandra E; Ross, John J

    2011-03-01

    Shoot elongation is a vital process for plant development and productivity, in both ecological and economic contexts. Auxin and bioactive gibberellins (GAs), such as GA1, play critical roles in the control of elongation, along with environmental and endogenous factors, including other hormones such as the brassinosteroids. The effect of auxins, such as indole-3-acetic acid (IAA), is at least in part mediated by its effect on GA metabolism, since auxin up-regulates biosynthesis genes such as GA 3-oxidase and GA 20-oxidase and down regulates GA catabolism genes such as GA 2-oxidases, leading to elevated levels of bioactive GA 1. In our recent paper, we have provided evidence that this action of IAA is largely independent of DELLA proteins, the negative regulators of GA action, since the auxin effects are still present in the DELLA-deficient la cry-s genotype of pea. This was a crucial issue to resolve, since like auxin, the DELLAs also promote GA 1 synthesis and inhibit its deactivation. DELLAs are deactivated by GA, and thereby mediate a feedback system by which bioactive GA regulates its own level. However, our recent results, in themselves, do not show the generality of the auxin-GA relationship across species and phylogenetic groups or across different tissue types and responses. Further, they do not touch on the ecological benefits of the auxin-GA interaction. These issues are discussed below as well as the need for the development of suitable experimental systems to allow this process to be examined. PMID:21358281

  12. Tomato fruit development in the auxin-resistant dgt mutant is induced by pollination but not by auxin treatment.

    Science.gov (United States)

    Mignolli, Francesco; Mariotti, Lorenzo; Lombardi, Lara; Vidoz, María Laura; Ceccarelli, Nello; Picciarelli, Piero

    2012-08-15

    In tomato (Solanum lycopersicum Mill.), auxin is believed to play a pivotal role in controlling fruit-set and early ovary growth. In this paper we investigated the effect of the reduced auxin sensitivity exhibited by the diageotropica (dgt) tomato mutant on ovary growth during early stage of fruit development. Here we show that in hand-pollinated ovaries fruit-set was not affected by the dgt lesion while fruit growth was reduced. This reduction was associated with a smaller cell size of mesocarp cells, with a lower mean C values and with a lower gene expression of the expansin gene LeExp2. When a synthetic auxin (4-CPA, chlorophenoxyacetic acid) was applied to the flowers of wild type plants, parthenocarpic ovary growth was induced. On the contrary, auxin application to the flowers of dgt plants failed to induce parthenocarpy. Hand-pollinated ovaries of dgt contained higher levels of IAA compared to wild type and this was not associated with high transcript levels of genes encoding a key regulatory enzyme of IAA biosynthesis (ToFZYs) but with lower expression levels of GH3, a gene involved in the conjugation of IAA to amino acids. The expression of diverse Aux/IAA genes and SAUR (small auxin up-regulated RNA) was also altered in the dgt ovaries. The dgt lesion does not seem to affect specific Aux/IAA genes in terms of transcript occurrence but rather in terms of relative levels of expression. Transcript levels of Aux/IAA genes were up regulated in auxin-treated ovaries of wild-type but not in dgt. Together, our results suggest that dgt ovary cells are not able to sense and/or transduce the external auxin signal, whereas pollinated dgt ovary cells are able to detect the IAA present in fertilized ovules promoting fruit development. PMID:22608080

  13. Q&A: Auxin: the plant molecule that influences almost anything.

    Science.gov (United States)

    Paque, Sebastien; Weijers, Dolf

    2016-01-01

    Auxin is an essential molecule that controls almost every aspect of plant development. Although the core signaling components that control auxin response are well characterized, the precise mechanisms enabling specific responses are not yet fully understood. Considering the significance of auxin in plant growth and its potential applications, deciphering further aspects of its biology is an important and exciting challenge. PMID:27510039

  14. ROS Homeostasis Regulates Somatic Embryogenesis via the Regulation of Auxin Signaling in Cotton.

    Science.gov (United States)

    Zhou, Ting; Yang, Xiyan; Guo, Kai; Deng, Jinwu; Xu, Jiao; Gao, Wenhui; Lindsey, Keith; Zhang, Xianlong

    2016-06-01

    Somatic embryogenesis (S.E.) is a versatile model for understanding the mechanisms of plant embryogenesis and a useful tool for plant propagation. To decipher the intricate molecular program and potentially to control the parameters affecting the frequency of S.E., a proteomics approach based on two-dimensional gel electrophoresis (2-DE) combined with MALDI-TOF/TOF was used. A total of 149 unique differentially expressed proteins (DEPs) were identified at different stages of cotton S.E. compared with the initial control (0 h explants). The expression profile and functional annotation of these DEPs revealed that S.E. activated stress-related proteins, including several reactive oxygen species (ROS)-scavenging enzymes. Proteins implicated in metabolic, developmental, and reproductive processes were also identified. Further experiments were performed to confirm the role of ROS-scavenging enzymes, suggesting the involvement of ROS homeostasis during S.E. in cotton. Suppressing the expression of specifically identified GhAPX proteins resulted in the inhibition of dedifferentiation. Accelerated redifferentiation was observed in the suppression lines of GhAPXs or GhGSTL3 in parallel with the alteration of endogenous ascorbate metabolism and accumulation of endogenous H2O2 content. Moreover, disrupting endogenous redox homeostasis through the application of high concentrations of DPI, H2O2, BSO, or GSH inhibited the dedifferentiation of cotton explants. Mild oxidation induced through BSO treatment facilitated the transition from embryogenic calluses (ECs) to somatic embryos. Meanwhile, auxin homeostasis was altered through the perturbation of ROS homeostasis by chemical treatments or suppression of ROS-scavenging proteins, along with the activating/suppressing the transcription of genes related to auxin transportation and signaling. These results show that stress responses are activated during S.E. and may regulate the ROS homeostasis by interacting with auxin signaling

  15. Cytokinin response factors regulate PIN-FORMED auxin transporters

    Czech Academy of Sciences Publication Activity Database

    Šimášková, M.; O'Brien, J.A.; Khan, M.; Van Noorden, G.; Ötvös, K.; Vieten, A.; De Clercq, E.; Van Haperen, J.M.A.; Cuesta, C.; Hoyerová, Klára; Vanneste, S.; Marhavý, P.; Wabnik, K.; Van Breusegem, F.; Nowack, M.; Murphy, A.; Friml, J.; Weijers, D.; Beeckman, T.; Benková, E.

    2015-01-01

    Roč. 6, NOV (2015), s. 8717. ISSN 2041-1723 Institutional support: RVO:61389030 Keywords : ARABIDOPSIS-THALIANA * ROOT-MERISTEM * TRANSCRIPTION FACTORS Subject RIV: ED - Physiology Impact factor: 11.470, year: 2014

  16. The roles of auxin in seed dormancy and germination.

    Science.gov (United States)

    Haiwei, Shuai; Yongjie, Meng; Xiaofeng, Luo; Feng, Chen; Ying, Qi; Wenyu, Yang; Kai, Shu

    2016-04-01

    Seed dormancy and germination are attractive topics in the fields of plant molecular biology as they are key stages during plant growth and development. Seed dormancy is intricately regulated by complex networks of phytohormones and numerous key genes, combined with diverse environmental cues. The transition from dormancy to germination is a very important biological process, and extensive studies have demonstrated that phytohormones abscisic acid (ABA) and gibberellin acid (GA) are major determinants. Consequently, the precise balance between ABA and GA can ensure that the seeds remain dormant under stress conditions and germinate at optimal times. Here we review the role of auxin in seed dormancy and germination. Auxin is one of the classic phytohormones effective during tropism growth and tissue differentiation. Recent studies, however, show that auxin possesses positive effects on seed dormancy, which suggests that auxin is the second phytohormone that induces seed dormancy, besides ABA. We will focus on the synthetic effects in detail between auxin and ABA pathways on seed dormancy and propose future research directions. PMID:27103455

  17. Local auxin metabolism regulates environment-induced hypocotyl elongation.

    Science.gov (United States)

    Zheng, Zuyu; Guo, Yongxia; Novák, Ondřej; Chen, William; Ljung, Karin; Noel, Joseph P; Chory, Joanne

    2016-01-01

    A hallmark of plants is their adaptability of size and form in response to widely fluctuating environments. The metabolism and redistribution of the phytohormone auxin play pivotal roles in establishing active auxin gradients and resulting cellular differentiation. In Arabidopsis thaliana, cotyledons and leaves synthesize indole-3-acetic acid (IAA) from tryptophan through indole-3-pyruvic acid (3-IPA) in response to vegetational shade. This newly synthesized auxin moves to the hypocotyl where it induces elongation of hypocotyl cells. Here we show that loss of function of VAS2 (IAA-amido synthetase Gretchen Hagen 3 (GH3).17) leads to increases in free IAA at the expense of IAA-Glu (IAA-glutamate) in the hypocotyl epidermis. This active IAA elicits shade- and high temperature-induced hypocotyl elongation largely independently of 3-IPA-mediated IAA biosynthesis in cotyledons. Our results reveal an unexpected capacity of local auxin metabolism to modulate the homeostasis and spatial distribution of free auxin in specialized organs such as hypocotyls in response to shade and high temperature. PMID:27249562

  18. Auxin production by the plant trypanosomatid Phytomonas serpens and auxin homoeostasis in infected tomato fruits.

    Science.gov (United States)

    Ienne, Susan; Freschi, Luciano; Vidotto, Vanessa F; De Souza, Tiago A; Purgatto, Eduardo; Zingales, Bianca

    2014-09-01

    Previously we have characterized the complete gene encoding a pyruvate decarboxylase (PDC)/indolepyruvate decarboxylase (IPDC) of Phytomonas serpens, a trypanosomatid highly abundant in tomato fruits. Phylogenetic analyses indicated that the clade that contains the trypanosomatid protein behaves as a sister group of IPDCs of γ-proteobacteria. Since IPDCs are key enzymes in the biosynthesis of the plant hormone indole-3-acetic acid (IAA), the ability for IAA production by P. serpens was investigated. Similar to many microorganisms, the production of IAA and related indolic compounds, quantified by high performance liquid chromatography, increased in P. serpens media in response to amounts of tryptophan. The auxin functionality was confirmed in the hypocotyl elongation assay. In tomato fruits inoculated with P. serpens the concentration of free IAA had no significant variation, whereas increased levels of IAA-amide and IAA-ester conjugates were observed. The data suggest that the auxin produced by the flagellate is converted to IAA conjugates, keeping unaltered the concentration of free IAA. Ethanol also accumulated in P. serpens-conditioned media, as the result of a PDC activity. In the article we discuss the hypothesis of the bifunctionality of P. serpens PDC/IPDC and provide a three-dimensional model of the enzyme. PMID:24805281

  19. Transport and degradation of 2-14C abscicine acid in the coleus rehneltianus berger sprout

    International Nuclear Information System (INIS)

    1 μg ABA-2-14C aqueous solution was injected into the youngest or into a fully grown leaf of young and older coleus plants. The activity quantity in the various sprout parts is investigated after 2, 24 and 72 h; as well as which labelled substances other than abscisic acid (ABA) occur. The activity in the ethanol extracts was detected with the help of liquid scintillation measurements. Thin layer chromatography and gas chromatography were used to characterize the radioactive substances. The results show that ABA is degraded into three metabolites which are characterized by their relative Rsub(F) values using chromatography with LM 2 as substance 0.2, 0.5a, 0.5b and 0.8. Comparing with the literature shows that it could be 6'-hydroxy methyl ABA, ABA glucoside, phaseic acid and dihydrophaseic acid. Young and old leaves in older plants have the same ability to degrade ABA taking the occurence of the 0.8 metabolite as standard. The degradation in younger plants is firstly very slight. However, within 72 h the ability of ABA degradation is induced in older leaves of younger plants, so that finally the degradation rate is as big as in older plants. Activity is essentially exported by adult leaves of older plants. The basipetal transport is considerably greater than the acropetal one. Results show that mainly ABA is transported in the acropetal test, whereas ABA and fraction 0.5 are transported in the basipetal direction. A reversed transport direction is observed after applying ABA to a young leaf. The transport basipetal is polarized in the first two hours, after 72 hours of transport there is a definite acropetal polarity. (orig./MG)

  20. Contrasting growth responses in lamina and petiole during neighbor detection depend on differential auxin responsiveness rather than different auxin levels.

    Science.gov (United States)

    de Wit, Mieke; Ljung, Karin; Fankhauser, Christian

    2015-10-01

    Foliar shade triggers rapid growth of specific structures that facilitate access of the plant to direct sunlight. In leaves of many plant species, this growth response is complex because, although shade triggers the elongation of petioles, it reduces the growth of the lamina. How the same external cue leads to these contrasting growth responses in different parts of the leaf is not understood. Using mutant analysis, pharmacological treatment and gene expression analyses, we investigated the role of PHYTOCHROME INTERACTING FACTOR7 (PIF7) and the growth-promoting hormone auxin in these contrasting leaf growth responses. Both petiole elongation and lamina growth reduction are dependent on PIF7. The induction of auxin production is both necessary and sufficient to induce opposite growth responses in petioles vs lamina. However, these contrasting growth responses are not caused by different auxin concentrations in the two leaf parts. Our work suggests that a transient increase in auxin levels triggers tissue-specific growth responses in different leaf parts. We provide evidence suggesting that this may be caused by the different sensitivity to auxin in the petiole vs the blade and by tissue-specific gene expression. PMID:25963518

  1. A Glimpse beyond Structures in Auxin-Dependent Transcription.

    Science.gov (United States)

    Parcy, François; Vernoux, Teva; Dumas, Renaud

    2016-07-01

    Auxin response factors (ARFs), transcription factors (TFs), and their Aux/IAA (IAA) repressors are central components of the auxin signalling pathway. They interact as homo- and heteromultimers. The structure of their interacting domains revealed a PB1 fold mediating electrostatic interactions through positive and negative faces. Detailed structural analysis revealed additional hydrophobic and polar determinants and started unveiling an ARF/IAA interaction code. Structural progress also shed new light on the DNA binding mode of ARFs showing how they dimerize to bind repeated DNA elements. Here, we discuss the in vitro and in vivo significance of these structural properties for the ARF family of TFs and identify some critical missing information on how specificity might be achieved in the auxin signalling pathway. PMID:26994657

  2. Protein synthesis and auxin-induced growth: inhibitor studies

    Energy Technology Data Exchange (ETDEWEB)

    Bates, G.T.; Cleland, R.E.

    1979-01-01

    We have compared the effects of cycloheximide (CHI) and two other rapid and effective inhibitors of protein synthesis, pactamycin and 2-(4-methyl-2,6-dinitroanilino)-N-methyl proprionamide (MDMP), on protein synthesis, respiration, auxin-induced growth and H/sup +/-excretion of Avena sativa L. coleoptiles. All three compounds inhibit protein synthesis without affecting respiration. The effectiveness of the inhibitors against H/sup +/-excretion and growth correlates with their ability to inhibit protein synthesis. Both CHI and MDMP inhibit auxin-induced H/sup +/-excretion after a latent period of 5 to 8 min, and inhibit growth after a 8 to 10 min lag. These results support the idea that continued protein synthesis is required in the initial stages of the growth-promoting action of auxin.

  3. Seek and Ye Shall [eventually] Find: The End of the Search for the Auxin Receptor

    Institute of Scientific and Technical Information of China (English)

    Lawrence HOBBIE

    2005-01-01

    The mechanism by which the plant hormone auxin regulates gene expression has been shown to involve regulated degradation, through the ubiquitin-proteasome pathway, of transcriptional repressor proteins. However, the key first component in this pathway, the receptor that binds auxin and initiates auxin signaling, has remained a mystery. Two recent papers identify the F-box protein TIR1, part of the complex that attaches ubiquitin to its targets, as an auxin receptor. This breakthrough reveals a new mode of signal transduction and lays the groundwork for a more complete understanding of auxin physiology.

  4. ABP1: An auxin receptor for fast responses at the plasma membrane

    OpenAIRE

    Dahlke, Renate I.; Luethen, Hartwig; Steffens, Bianka

    2010-01-01

    Auxin-binding protein 1 (ABP1) is an auxin receptor for responses not primarily regulated by gene regulation. One fast response is protoplast swelling. By using immunological ABP1 tools we showed that the highly conserved box a is not alone important for auxin binding. Box c is another part of the auxin binding domain.1 Here we present a novel method to analyze auxin-induced, ABP1-mediated effects at the plasma membrane on single cell level in vivo. The fluorescence of FM4-64 in the plasma me...

  5. Promoting Roles of Melatonin in Adventitious Root Development of Solanum lycopersicum L. by Regulating Auxin and Nitric Oxide Signaling.

    Science.gov (United States)

    Wen, Dan; Gong, Biao; Sun, Shasha; Liu, Shiqi; Wang, Xiufeng; Wei, Min; Yang, Fengjuan; Li, Yan; Shi, Qinghua

    2016-01-01

    Melatonin (MT) plays integral roles in regulating several biological processes including plant growth, seed germination, flowering, senescence, and stress responses. This study investigated the effects of MT on adventitious root formation (ARF) of de-rooted tomato seedlings. Exogenous MT positively or negatively influenced ARF, which was dependent on the concentration of MT application. In the present experiment, 50 μM MT showed the best effect on inducing ARF. Interestingly, exogenous MT promoted the accumulation of endogenous nitric oxide (NO) by down-regulating the expression of S-nitrosoglutathione reductase (GSNOR). To determine the interaction of MT and NO in ARF, MT synthesis inhibitor p-chlorophenylalanine, NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide potassium salt as well as GSNOR-overexpression plants with low NO levels were used. The function of MT was removed by NO scavenger or GSNOR-overexpression plants. However, application of MT synthesis inhibitor did little to abolish the function of NO. These results indicate that NO, as a downstream signal, was involved in the MT-induced ARF. Concentrations of indole-3-acetic acid and indole-3-butyric acid, as well as the expression of several genes related to the auxin signaling pathway (PIN1, PIN3, PIN7, IAA19, and IAA24), showed that MT influenced auxin transport and signal transduction as well as auxin accumulation through the NO signaling pathway. Collectively, these strongly suggest that elevated NO levels resulting from inhibited GSNOR activity and auxin signaling were involved in the MT-induced ARF in tomato plants. This can be applied in basic research and breeding. PMID:27252731

  6. Promoting Roles of Melatonin in Adventitious Root Development of Solanum lycopersicum L. by Regulating Auxin and Nitric Oxide Signaling

    Directory of Open Access Journals (Sweden)

    Dan eWen

    2016-05-01

    Full Text Available Melatonin (MT plays integral roles in regulating several biological processes including plant growth, seed germination, flowering, senescence and stress responses. This study investigated the effects of MT on adventitious root formation (ARF of de-rooted tomato seedlings. Exogenous MT positively or negatively influenced ARF, which was dependent on the concentration of MT application. In the present experiment, 50 µM MT showed the best effect on inducing ARF. Interestingly, exogenous MT promoted the accumulation of endogenous nitric oxide (NO by down-regulating the expression of S-nitrosoglutathione reductase (GSNOR. To determine the interaction of MT and NO in ARF, MT synthesis inhibitor p-chlorophenylalanine, NO scavenger 2-(4-carboxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide potassium salt as well as GSNOR-overexpression plants with low NO levels were used. The function of MT was removed by NO scavenger or GSNOR-overexpression plants. However, application of MT synthesis inhibitor did little to abolish the function of NO. These results indicate that NO, as a downstream signal, was involved in the MT-induced ARF. Concentrations of indole-3-acetic acid and indole-3-butyric acid, as well as the expression of several genes related to the auxin signaling pathway (PIN1, PIN3, PIN7, IAA19 and IAA24, showed that MT influenced auxin transport and signal transduction as well as auxin accumulation through the NO signaling pathway. Collectively, these strongly suggest that elevated NO levels resulting from inhibited GSNOR activity and auxin signaling were involved in the MT-induced ARF in tomato plants. This can be applied in basic research and breeding.

  7. Auxin and ABA act as central regulators of developmental networks associated with paradormancy in Canada thistle (Cirsium arvense)

    KAUST Repository

    Anderson, James V.

    2012-05-13

    Abstract Dormancy in underground vegetative buds of Canada thistle, an herbaceous perennial weed, allows escape from current control methods and contributes to its invasive nature. In this study, ∼65 % of root sections obtained from greenhouse propagated Canada thistle produced new vegetative shoots by 14 days post-sectioning. RNA samples obtained from sectioned roots incubated 0, 24, 48, and 72 h at 25°C under 16:8 h light-dark conditions were used to construct four MID-tagged cDNA libraries. Analysis of in silico data obtained using Roche 454 GS-FLX pyrosequencing technologies identified molecular networks associated with paradormancy release in underground vegetative buds of Canada thistle. Sequencing of two replicate plates produced ∼2.5 million ESTs with an average read length of 362 bases. These ESTs assembled into 67358 unique sequences (21777 contigs and 45581 singlets) and annotation against the Arabidopsis database identified 15232 unigenes. Among the 15232 unigenes, we identified processes enriched with transcripts involved in plant hormone signaling networks. To follow-up on these results, we examined hormone profiles in roots, which identified changes in abscisic acid (ABA) and ABA metabolites, auxins, and cytokinins post-sectioning. Transcriptome and hormone profiling data suggest that interaction between auxin- and ABA-signaling regulate paradormancy maintenance and release in underground adventitious buds of Canada thistle. Our proposed model shows that sectioning-induced changes in polar auxin transport alters ABA metabolism and signaling, which further impacts gibberellic acid signaling involving interactions between ABA and FUSCA3. Here we report that reduced auxin and ABA-signaling, in conjunction with increased cytokinin biosynthesis post-sectioning supports a model where interactions among hormones drives molecular networks leading to cell division, differentiation, and vegetative outgrowth. ©Springer-Verlag (outside the USA) 2012.

  8. Development of the Poplar-Laccaria bicolor Ectomycorrhiza Modifies Root Auxin Metabolism, Signaling, and Response.

    Science.gov (United States)

    Vayssières, Alice; Pěnčík, Ales; Felten, Judith; Kohler, Annegret; Ljung, Karin; Martin, Francis; Legué, Valérie

    2015-09-01

    Root systems of host trees are known to establish ectomycorrhizae (ECM) interactions with rhizospheric fungi. This mutualistic association leads to dramatic developmental modifications in root architecture, with the formation of numerous short and swollen lateral roots ensheathed by a fungal mantle. Knowing that auxin plays a crucial role in root development, we investigated how auxin metabolism, signaling, and response are affected in poplar (Populus spp.)-Laccaria bicolor ECM roots. The plant-fungus interaction leads to the arrest of lateral root growth with simultaneous attenuation of the synthetic auxin response element DR5. Measurement of auxin-related metabolites in the free-living partners revealed that the mycelium of L. bicolor produces high concentrations of the auxin indole-3-acetic acid (IAA). Metabolic profiling showed an accumulation of IAA and changes in the indol-3-pyruvic acid-dependent IAA biosynthesis and IAA conjugation and degradation pathways during ECM formation. The global analysis of auxin response gene expression and the regulation of AUXIN SIGNALING F-BOX PROTEIN5, AUXIN/IAA, and AUXIN RESPONSE FACTOR expression in ECM roots suggested that symbiosis-dependent auxin signaling is activated during the colonization by L. bicolor. Taking all this evidence into account, we propose a model in which auxin signaling plays a crucial role in the modification of root growth during ECM formation. PMID:26084921

  9. Comprehensive RNA-Seq Analysis on the Regulation of Tomato Ripening by Exogenous Auxin.

    Science.gov (United States)

    Li, Jiayin; Tao, Xiaoya; Li, Li; Mao, Linchun; Luo, Zisheng; Khan, Zia Ullah; Ying, Tiejin

    2016-01-01

    Auxin has been shown to modulate the fruit ripening process. However, the molecular mechanisms underlying auxin regulation of fruit ripening are still not clear. Illumina RNA sequencing was performed on mature green cherry tomato fruit 1 and 7 days after auxin treatment, with untreated fruit as a control. The results showed that exogenous auxin maintained system 1 ethylene synthesis and delayed the onset of system 2 ethylene synthesis and the ripening process. At the molecular level, genes associated with stress resistance were significantly up-regulated, but genes related to carotenoid metabolism, cell degradation and energy metabolism were strongly down-regulated by exogenous auxin. Furthermore, genes encoding DNA demethylases were inhibited by auxin, whereas genes encoding cytosine-5 DNA methyltransferases were induced, which contributed to the maintenance of high methylation levels in the nucleus and thus inhibited the ripening process. Additionally, exogenous auxin altered the expression patterns of ethylene and auxin signaling-related genes that were induced or repressed in the normal ripening process, suggesting significant crosstalk between these two hormones during tomato ripening. The present work is the first comprehensive transcriptome analysis of auxin-treated tomato fruit during ripening. Our results provide comprehensive insights into the effects of auxin on the tomato ripening process and the mechanism of crosstalk between auxin and ethylene. PMID:27228127

  10. Chemical control of xylem differentiation by thermospermine, xylemin, and auxin

    Science.gov (United States)

    Yoshimoto, Kaori; Takamura, Hiroyoshi; Kadota, Isao; Motose, Hiroyasu; Takahashi, Taku

    2016-01-01

    The xylem conducts water and minerals from the root to the shoot and provides mechanical strength to the plant body. The vascular precursor cells of the procambium differentiate to form continuous vascular strands, from which xylem and phloem cells are generated in the proper spatiotemporal pattern. Procambium formation and xylem differentiation are directed by auxin. In angiosperms, thermospermine, a structural isomer of spermine, suppresses xylem differentiation by limiting auxin signalling. However, the process of auxin-inducible xylem differentiation has not been fully elucidated and remains difficult to manipulate. Here, we found that an antagonist of spermidine can act as an inhibitor of thermospermine biosynthesis and results in excessive xylem differentiation, which is a phenocopy of a thermospermine-deficient mutant acaulis5 in Arabidopsis thaliana. We named this compound xylemin owing to its xylem-inducing effect. Application of a combination of xylemin and thermospermine to wild-type seedlings negates the effect of xylemin, whereas co-treatment with xylemin and a synthetic proauxin, which undergoes hydrolysis to release active auxin, has a synergistic inductive effect on xylem differentiation. Thus, xylemin may serve as a useful transformative chemical tool not only for the study of thermospermine function in various plant species but also for the control of xylem induction and woody biomass production. PMID:26879262

  11. Alterations in auxin homeostasis suppress defects in cell wall function.

    Directory of Open Access Journals (Sweden)

    Blaire J Steinwand

    Full Text Available The plant cell wall is a highly dynamic structure that changes in response to both environmental and developmental cues. It plays important roles throughout plant growth and development in determining the orientation and extent of cell expansion, providing structural support and acting as a barrier to pathogens. Despite the importance of the cell wall, the signaling pathways regulating its function are not well understood. Two partially redundant leucine-rich-repeat receptor-like kinases (LRR-RLKs, FEI1 and FEI2, regulate cell wall function in Arabidopsis thaliana roots; disruption of the FEIs results in short, swollen roots as a result of decreased cellulose synthesis. We screened for suppressors of this swollen root phenotype and identified two mutations in the putative mitochondrial pyruvate dehydrogenase E1α homolog, IAA-Alanine Resistant 4 (IAR4. Mutations in IAR4 were shown previously to disrupt auxin homeostasis and lead to reduced auxin function. We show that mutations in IAR4 suppress a subset of the fei1 fei2 phenotypes. Consistent with the hypothesis that the suppression of fei1 fei2 by iar4 is the result of reduced auxin function, disruption of the WEI8 and TAR2 genes, which decreases auxin biosynthesis, also suppresses fei1 fei2. In addition, iar4 suppresses the root swelling and accumulation of ectopic lignin phenotypes of other cell wall mutants, including procuste and cobra. Further, iar4 mutants display decreased sensitivity to the cellulose biosynthesis inhibitor isoxaben. These results establish a role for IAR4 in the regulation of cell wall function and provide evidence of crosstalk between the cell wall and auxin during cell expansion in the root.

  12. Auxinic herbicides, mechanisms of action, and weed resistance: A look into recent plant science advances

    Directory of Open Access Journals (Sweden)

    Pedro Jacob Christoffoleti

    2015-08-01

    Full Text Available Auxin governs dynamic cellular processes involved at several stages of plant growth and development. In this review, we discuss the mechanisms employed by auxin in light of recent scientific advances, with a focus on synthetic auxins as herbicides and synthetic auxin resistance mechanisms. Two auxin receptors were reported. The plasma membrane receptor ABP1 (Auxin Binding Protein 1 alters the structure and arrangement of actin filaments and microtubules, leading to plant epinasty and reducing peroxisomes and mitochondria mobility in the cell environment. The second auxin receptor is the gene transcription pathway regulated by the SCFTir/AFB ubiquitination complex, which destroys transcription repressor proteins that interrupt Auxin Response Factor (ARF activation. As a result mRNA related with Abscisic Acid (ABA and ethylene are transcribed, producing high quantities of theses hormones. Their associated action leads to high production of Reactive Oxygen Species (ROS, leading to tissue and plant death. Recently, another ubiquitination pathway which is described as a new auxin signaling route is the F-box protein S-Phase Kinase-Associated Protein 2A (SKP2A. It is active in cell division regulation and there is evidence that auxin herbicides can deregulate the SKP2A pathway, which leads to severe defects in plant development. In this discussion, we propose that SFCSKP2A auxin binding site alteration could be a new auxinic herbicide resistance mechanism, a concept which may contribute to the current progress in plant biology in its quest to clarify the many questions that still surround auxin herbicide mechanisms of action and the mechanisms of weed resistance.

  13. Transport

    International Nuclear Information System (INIS)

    Transport is one of the major causes of environmental damage in Austria. Energy consumption, pollutants emissions, noise emissions, use of surfaces, sealing of surfaces, dissection of ecosystems and impact on landscape are the most significant environmental impacts caused by it. An overview of the transport development of passengers and freight in Austria is presented. Especially the energy consumption growth, carbon dioxide and nitrogen oxide emissions by type of transport, and the emissions development (HC, particle and carbon monoxide) of goods and passengers transport are analyzed covering the years 1980 - 1999. The health cost resulting from transport-related air pollution in Austria is given and measures to be taken for an effective control of the transport sector are mentioned. Figs. 8, Table 1. (nevyjel)

  14. The epidermis coordinates auxin-induced stem growth in response to shade.

    Science.gov (United States)

    Procko, Carl; Burko, Yogev; Jaillais, Yvon; Ljung, Karin; Long, Jeff A; Chory, Joanne

    2016-07-01

    Growth of a complex multicellular organism requires coordinated changes in diverse cell types. These cellular changes generate organs of the correct size, shape, and functionality. In plants, the growth hormone auxin induces stem elongation in response to shade; however, which cell types of the stem perceive the auxin signal and contribute to organ growth is poorly understood. Here, we blocked the transcriptional response to auxin within specific tissues to show that auxin signaling is required in many cell types for correct hypocotyl growth in shade, with a key role for the epidermis. Combining genetic manipulations in Arabidopsis thaliana with transcriptional profiling of the hypocotyl epidermis from Brassica rapa, we show that auxin acts in the epidermis in part by inducing activity of the locally acting, growth-promoting brassinosteroid pathway. Our findings clarify cell-specific auxin function in the hypocotyl and highlight the complexity of cell type interactions within a growing organ. PMID:27401556

  15. An Integrative Analysis of the Effects of Auxin on Jasmonic Acid Biosynthesis in Arabidopsis thaliana

    Institute of Scientific and Technical Information of China (English)

    Jun Liu; Xiu-Jie Wang

    2006-01-01

    Auxin and jasmonic acid (JA) are two plant phytohormones that both participate in the regulation of many developmental processes. Jasmonic acid also plays important roles in plant stress response reactions.Although extensive investigations have been undertaken to study the biological functions of auxin and JA,little attention has been paid to the cross-talk between their regulated pathways. In the few available reports examining the effects of auxin on the expression of JA or JA-responsive genes, both synergetic and antagonistic results have been found. To further investigate the relationship between auxin and JA, we adopted an integrative method that combines microarray expression data with pathway information to study the behavior of the JA biosynthesis pathway under auxin treatment. Our results showed an overall downregulation of genes involved in JA biosynthesis, providing the first report of a relationship between auxin and the JA synthesis pathway in Arabidopsis seedlings.

  16. Auxin-induced modifications of cell wall polysaccharides in cat coleoptile segments. Effect of galactose

    International Nuclear Information System (INIS)

    Galactose inhibits auxin-induced cell elongation in oat coleoptile segments. Cell elongation induced by exogenously applied auxin is controlled by factors such as auxin uptake, cell wall loosening, osmotic concentration of sap and hydraulic conductivity. However, galactose does not have any effect on these factors. The results discussed in this paper led to the conclusion that galactose does not affect cell wall loosening which controls rapid growth, but inhibits cell wall synthesis which is required to maintain long-term growth

  17. An auxin responsive CLE gene regulates shoot apical meristem development in Arabidopsis

    OpenAIRE

    Guo, Hongyan; Zhang, Wei; Tian, Hainan; Zheng, Kaijie; Dai, Xuemei; Liu, Shanda; Hu, Qingnan; Wang, Xianling; Liu, Bao; Wang, Shucai

    2015-01-01

    Plant hormone auxin regulates most, if not all aspects of plant growth and development, including lateral root formation, organ pattering, apical dominance, and tropisms. Peptide hormones are peptides with hormone activities. Some of the functions of peptide hormones in regulating plant growth and development are similar to that of auxin, however, the relationship between auxin and peptide hormones remains largely unknown. Here we report the identification of OsCLE48, a rice (Oryza sativa) CL...

  18. An auxin responsive CLE gene regulates shoot apical meristem development in Arabidopsis

    OpenAIRE

    Hongyan eGuo; Wei eZhang; Hainan eTian; Kaijie eZheng; Xuemei eDai; Shanda eLiu; Qingnan eHu; Xianling eWang; Bao eLiu; Shucai eWang

    2015-01-01

    Plant hormone auxin regulates most, if not all aspects of plant growth and development, including lateral root formation, organ pattering, apical dominance and tropisms. Peptide hormones are peptides with hormone activities. Some of the functions of peptide hormones in regulating plant growth and development are similar to that of auxin, however, the relationship between auxin and peptide hormones remains largely unknown. Here we report the identification of OsCLE48, a rice (Oryza sativa) CLE...

  19. Genome-wide identification and expression profiling of auxin response factor (ARF) gene family in maize

    OpenAIRE

    Xing, Hongyan; Pudake, Ramesh N.; Guo, Ganggang; Xing, Guofang; Hu, Zhaorong; Zhang, Yirong; Sun, Qixin; Ni, Zhongfu

    2011-01-01

    Background Auxin signaling is vital for plant growth and development, and plays important role in apical dominance, tropic response, lateral root formation, vascular differentiation, embryo patterning and shoot elongation. Auxin Response Factors (ARFs) are the transcription factors that regulate the expression of auxin responsive genes. The ARF genes are represented by a large multigene family in plants. The first draft of full maize genome assembly has recently been released, however, to our...

  20. Investigating a Potential Auxin-Related Mode of Hormetic/Inhibitory Action of the Phytotoxin Parthenin.

    Science.gov (United States)

    Belz, Regina G

    2016-01-01

    Parthenin is a metabolite of Parthenium hysterophorus and is believed to contribute to the weed's invasiveness via allelopathy. Despite the potential of parthenin to suppress competitors, low doses stimulate plant growth. This biphasic action was hypothesized to be auxin-like and, therefore, an auxin-related mode of parthenin action was investigated using two approaches: joint action experiments with Lactuca sativa, and dose-response experiments with auxin/antiauxin-resistant Arabidopsis thaliana genotypes. The joint action approach comprised binary mixtures of subinhibitory doses of the auxin 3-indoleacetic acid (IAA) mixed with parthenin or one of three reference compounds [indole-3-butyric acid (IBA), 2,3,5-triiodobenzoic acid (TIBA), 2-(p-chlorophenoxy)-2-methylpropionic acid (PCIB)]. The reference compounds significantly interacted with IAA at all doses, but parthenin interacted only at low doses indicating that parthenin hormesis may be auxin-related, in contrast to its inhibitory action. The genetic approach investigated the response of four auxin/antiauxin-resistant mutants and a wildtype to parthenin or two reference compounds (IAA, PCIB). The responses of mutant plants to the reference compounds confirmed previous reports, but differed from the responses observed for parthenin. Parthenin stimulated and inhibited all mutants independent of resistance. This provided no indication for an auxin-related action of parthenin. Therefore, the hypothesis of an auxin-related inhibitory action of parthenin was rejected in two independent experimental approaches, while the hypothesis of an auxin-related stimulatory effect could not be rejected. PMID:26686984

  1. Influence of lead on auxin-induced cell elongation

    Directory of Open Access Journals (Sweden)

    Marek Burzyński

    2014-02-01

    Full Text Available The influence of lead chloride on plant tissue growth is described. Lead reduced elongation of etiolated wheat coleoptile segments, green pea epicotyl fragments and etiolated and green sunflower hypocotyls. Green tissues were more susceptible to lead than etiolated ones. PbCl2 in a 10-4 M concentration significantly reduced plastic and elastic extensibility of the wheat coleoptile cell walls and diminished the hydration of sunflower hypocotyl segments. Auxin (indolyl-3-acetic acid - IAA applied in concentration optimal for growth of the particular tissues partly attenuated the inhibitory action of lead on elongation, plastic and elastic extensibility and water absorption. Auxin applied in supraoptimal concentrations did not abolish the inhibitory action of lead on tissue growth.

  2. How Auxin and Cytokinin Phytohormones Modulate Root Microbe Interactions.

    Science.gov (United States)

    Boivin, Stéphane; Fonouni-Farde, Camille; Frugier, Florian

    2016-01-01

    A large range of microorganisms can associate with plants, resulting in neutral, friendly or hostile interactions. The ability of plants to recognize compatible and incompatible microorganisms and to limit or promote their colonization is therefore crucial for their survival. Elaborated communication networks determine the degree of association between the host plant and the invading microorganism. Central to these regulations of plant microbe interactions, phytohormones modulate microorganism plant associations and coordinate cellular and metabolic responses associated to the progression of microorganisms across different plant tissues. We review here hormonal regulations, focusing on auxin and cytokinin phytohormones, involved in the interactions between plant roots and soil microorganisms, including bacterial and fungi associations, either beneficial (symbiotic) or detrimental (pathogenic). The aim is to highlight similarities and differences in cytokinin/auxin functions amongst various compatible versus incompatible associations. PMID:27588025

  3. The role of auxin and gibberellin in tomato fruit set.

    Science.gov (United States)

    de Jong, Maaike; Mariani, Celestina; Vriezen, Wim H

    2009-01-01

    The initiation of tomato fruit growth, fruit set, is very sensitive to environmental conditions. Therefore, an understanding of the mechanisms that regulate this process can facilitate the production of this agriculturally valuable fruit crop. Over the years, it has been well established that tomato fruit set depends on successful pollination and fertilization, which trigger the fruit developmental programme through the activation of the auxin and gibberellin signalling pathways. However, the exact role of each of these two hormones is still poorly understood, probably because only few of the signalling components involved have been identified so far. Recent research on fruit set induced by hormone applications has led to new insights into hormone biosynthesis and signalling. The aim of this review is to consolidate the current knowledge on the role of auxin and gibberellin in tomato fruit set. PMID:19321650

  4. Biosynthesis of the halogenated auxin, 4-chloroindole-3-acetic acid.

    Science.gov (United States)

    Tivendale, Nathan D; Davidson, Sandra E; Davies, Noel W; Smith, Jason A; Dalmais, Marion; Bendahmane, Abdelhafid I; Quittenden, Laura J; Sutton, Lily; Bala, Raj K; Le Signor, Christine; Thompson, Richard; Horne, James; Reid, James B; Ross, John J

    2012-07-01

    Seeds of several agriculturally important legumes are rich sources of the only halogenated plant hormone, 4-chloroindole-3-acetic acid. However, the biosynthesis of this auxin is poorly understood. Here, we show that in pea (Pisum sativum) seeds, 4-chloroindole-3-acetic acid is synthesized via the novel intermediate 4-chloroindole-3-pyruvic acid, which is produced from 4-chlorotryptophan by two aminotransferases, TRYPTOPHAN AMINOTRANSFERASE RELATED1 and TRYPTOPHAN AMINOTRANSFERASE RELATED2. We characterize a tar2 mutant, obtained by Targeting Induced Local Lesions in Genomes, the seeds of which contain dramatically reduced 4-chloroindole-3-acetic acid levels as they mature. We also show that the widespread auxin, indole-3-acetic acid, is synthesized by a parallel pathway in pea. PMID:22573801

  5. Ethylene and auxin in the control of wood formation

    OpenAIRE

    Hellgren, Jenny Maria

    2003-01-01

    This thesis considers aspects of the regulation of growth rate and fibre properties in forest trees. These properties are both genetically determined and influenced by environmental stimuli. Induction of reaction wood is an environmentally induced process involving changes in growth rate and fibre properties that can be readily studied. Plant hormones are signalling agents that play important roles in the initiation and coordination of wood formation; in this thesis the plant hormones auxin a...

  6. Soluble Carbohydrates Regulate Auxin Biosynthesis via PIF Proteins in Arabidopsis

    OpenAIRE

    Sairanen, Ilkka; Novak, Ondrej; Pencik, Ales; Ikeda, Yoshihisa; Jones, Brian; Sandberg, Göran; Ljung, Karin

    2012-01-01

    Plants are necessarily highly competitive and have finely tuned mechanisms to adjust growth and development in accordance with opportunities and limitations in their environment. Sugars from photosynthesis form an integral part of this growth control process, acting as both an energy source and as signaling molecules in areas targeted for growth. The plant hormone auxin similarly functions as a signaling molecule and a driver of growth and developmental processes. Here, we show that not only ...

  7. Auxin Control in the Formation of Adventitious Roots

    OpenAIRE

    Tiberia I. POP; Pamfil, Doru; Bellini, Catherine

    2011-01-01

    Adventitious rooting is a complex process and a key step in the vegetative propagation of economically important woody, horticultural and agricultural species, playing an important role in the successful production of elite clones. The formation of adventitious roots is a quantitative genetic trait regulated by both environmental and endogenous factors. Among phytohormones, auxin plays an essential role in regulating roots development and it has been shown to be intimately involved in the pro...

  8. Auxin-binding pocket of ABP1 is crucial for its gain-of-function cellular and developmental roles

    Czech Academy of Sciences Publication Activity Database

    Grones, P.; Chen, X.; Simon, S.; Kaufmann, W.A.; De Rycke, R.; Nodzyński, T.; Zažímalová, Eva; Friml, J.

    2015-01-01

    Roč. 66, č. 16 (2015), s. 5055-5065. ISSN 0022-0957 Institutional support: RVO:61389030 Keywords : Auxin * ABP1 * Auxin binding Subject RIV: EB - Genetic s ; Molecular Biology Impact factor: 5.526, year: 2014

  9. Truffles regulate plant root morphogenesis via the production of auxin and ethylene.

    Science.gov (United States)

    Splivallo, Richard; Fischer, Urs; Göbel, Cornelia; Feussner, Ivo; Karlovsky, Petr

    2009-08-01

    Truffles are symbiotic fungi that form ectomycorrhizas with plant roots. Here we present evidence that at an early stage of the interaction, i.e. prior to physical contact, mycelia of the white truffle Tuber borchii and the black truffle Tuber melanopsorum induce alterations in root morphology of the host Cistus incanus and the nonhost Arabidopsis (Arabidopsis thaliana; i.e. primary root shortening, lateral root formation, root hair stimulation). This was most likely due to the production of indole-3-acetic acid (IAA) and ethylene by the mycelium. Application of a mixture of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid and IAA fully mimicked the root morphology induced by the mycelium for both host and nonhost plants. Application of the single hormones only partially mimicked it. Furthermore, primary root growth was not inhibited in the Arabidopsis auxin transport mutant aux1-7 by truffle metabolites while root branching was less effected in the ethylene-insensitive mutant ein2-LH. The double mutant aux1-7;ein2-LH displayed reduced sensitivity to fungus-induced primary root shortening and branching. In agreement with the signaling nature of truffle metabolites, increased expression of the auxin response reporter DR5GFP in Arabidopsis root meristems subjected to the mycelium could be observed, confirming that truffles modify the endogenous hormonal balance of plants. Last, we demonstrate that truffles synthesize ethylene from l-methionine probably through the alpha-keto-gamma-(methylthio)butyric acid pathway. Taken together, these results establish the central role of IAA and ethylene as signal molecules in truffle/plant interactions. PMID:19535471

  10. 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.

  11. A Complex Molecular Interplay of Auxin and Ethylene Signaling Pathways Is Involved in Arabidopsis Growth Promotion by Burkholderia phytofirmans PsJN

    Science.gov (United States)

    Poupin, María J.; Greve, Macarena; Carmona, Vicente; Pinedo, Ignacio

    2016-01-01

    Modulation of phytohormones homeostasis is one of the proposed mechanisms to explain plant growth promotion induced by beneficial rhizobacteria (PGPR). However, there is still limited knowledge about the molecular signals and pathways underlying these beneficial interactions. Even less is known concerning the interplay between phytohormones in plants inoculated with PGPR. Auxin and ethylene are crucial hormones in the control of plant growth and development, and recent studies report an important and complex crosstalk between them in the regulation of different plant developmental processes. The objective of this work was to study the role of both hormones in the growth promotion of Arabidopsis thaliana plants induced by the well-known PGPR Burkholderia phytofirmans PsJN. For this, the spatiotemporal expression patterns of several genes related to auxin biosynthesis, perception and response and ethylene biosynthesis were studied, finding that most of these genes showed specific transcriptional regulations after inoculation in roots and shoots. PsJN-growth promotion was not observed in Arabidopsis mutants with an impaired ethylene (ein2-1) or auxin (axr1–5) signaling. Even, PsJN did not promote growth in an ethylene overproducer (eto2), indicating that a fine regulation of both hormones signaling and homeostasis is necessary to induce growth of the aerial and root tissues. Auxin polar transport is also involved in growth promotion, since PsJN did not promote primary root growth in the pin2 mutant or under chemical inhibition of transport in wild type plants. Finally, a key role for ethylene biosynthesis was found in the PsJN-mediated increase in root hair number. These results not only give new insights of PGPR regulation of plant growth but also are also useful to understand key aspects of Arabidopsis growth control.

  12. A complex molecular interplay of auxin and ethylene signaling pathways is involved in Arabidopsis growth promotion by Burkholderia phytofirmans PsJN

    Directory of Open Access Journals (Sweden)

    María Josefina Poupin

    2016-04-01

    Full Text Available Modulation of phytohormones homeostasis is one of the proposed mechanisms to explain plant growth promotion induced by beneficial rhizobacteria (PGPR. However, there is still limited knowledge about the molecular signals and pathways underlying these beneficial interactions. Even less is known concerning the interplay between phytohormones in plants inoculated with PGPR. Auxin and ethylene are crucial hormones in the control of plant growth and development, and recent studies report an important and complex crosstalk between them in the regulation of different plant developmental processes. The objective of this work was to study the role of both hormones in the growth promotion of Arabidopsis thaliana plants induced by the well-known PGPR Burkholderia phytofirmans PsJN. For this, the spatiotemporal expression patterns of several genes related to auxin biosynthesis, perception and response and ethylene biosynthesis were studied, finding that most of these genes showed specific transcriptional regulations after inoculation in roots and shoots. PsJN-growth promotion was not observed in Arabidopsis mutants with an impaired ethylene (ein2-1 or auxin (axr1-5 signaling. Even, PsJN did not promote growth in an ethylene overproducer (eto2, indicating that a fine regulation of both hormones signaling and homeostasis is necessary to induce growth of the aerial and root tissues. Auxin polar transport is also involved in growth promotion, since PsJN did not promote primary root growth in the pin2 mutant or under chemical inhibition of transport in wild type plants. Finally, a key role for ethylene biosynthesis was found in the PsJN-mediated increase in root hair number. These results not only give new insights of PGPR regulation of plant growth but also are also useful to understand key aspects of Arabidopsis growth control.

  13. A Complex Molecular Interplay of Auxin and Ethylene Signaling Pathways Is Involved in Arabidopsis Growth Promotion by Burkholderia phytofirmans PsJN.

    Science.gov (United States)

    Poupin, María J; Greve, Macarena; Carmona, Vicente; Pinedo, Ignacio

    2016-01-01

    Modulation of phytohormones homeostasis is one of the proposed mechanisms to explain plant growth promotion induced by beneficial rhizobacteria (PGPR). However, there is still limited knowledge about the molecular signals and pathways underlying these beneficial interactions. Even less is known concerning the interplay between phytohormones in plants inoculated with PGPR. Auxin and ethylene are crucial hormones in the control of plant growth and development, and recent studies report an important and complex crosstalk between them in the regulation of different plant developmental processes. The objective of this work was to study the role of both hormones in the growth promotion of Arabidopsis thaliana plants induced by the well-known PGPR Burkholderia phytofirmans PsJN. For this, the spatiotemporal expression patterns of several genes related to auxin biosynthesis, perception and response and ethylene biosynthesis were studied, finding that most of these genes showed specific transcriptional regulations after inoculation in roots and shoots. PsJN-growth promotion was not observed in Arabidopsis mutants with an impaired ethylene (ein2-1) or auxin (axr1-5) signaling. Even, PsJN did not promote growth in an ethylene overproducer (eto2), indicating that a fine regulation of both hormones signaling and homeostasis is necessary to induce growth of the aerial and root tissues. Auxin polar transport is also involved in growth promotion, since PsJN did not promote primary root growth in the pin2 mutant or under chemical inhibition of transport in wild type plants. Finally, a key role for ethylene biosynthesis was found in the PsJN-mediated increase in root hair number. These results not only give new insights of PGPR regulation of plant growth but also are also useful to understand key aspects of Arabidopsis growth control. PMID:27148317

  14. Protocol: High-throughput and quantitative assays of auxin and auxin precursors from minute tissue samples

    Directory of Open Access Journals (Sweden)

    Liu Xing

    2012-08-01

    Full Text Available Abstract Background The plant hormone auxin, indole-3-acetic acid (IAA, plays important roles in plant growth and development. The signaling response to IAA is largely dependent on the local concentration of IAA, and this concentration is regulated by multiple mechanisms in plants. Therefore, the precise quantification of local IAA concentration provides insights into the regulation of IAA and its biological roles. Meanwhile, pathways and genes involved in IAA biosynthesis are not fully understood, so it is necessary to analyze the production of IAA at the metabolite level for unbiased studies of IAA biosynthesis. Results We have developed high-throughput methods to quantify plant endogenous IAA and its biosynthetic precursors including indole, tryptophan, indole-3-pyruvic acid (IPyA, and indole-3-butyric acid (IBA. The protocol starts with homogenizing plant tissues with stable-labeled internal standards added, followed by analyte purification using solid phase extraction (SPE tips and analyte derivatization. The derivatized analytes are finally analyzed by selected reaction monitoring on a gas chromatograph-mass spectrometer (GC-MS/MS to determine the precise abundance of analytes. The amount of plant tissue required for the assay is small (typically 2–10 mg fresh weight, and the use of SPE tips is simple and convenient, which allows preparation of large sets of samples within reasonable time periods. Conclusions The SPE tips and GC-MS/MS based method enables high-throughput and accurate quantification of IAA and its biosynthetic precursors from minute plant tissue samples. The protocol can be used for measurement of these endogenous compounds using isotope dilution, and it can also be applied to analyze IAA biosynthesis and biosynthetic pathways using stable isotope labeling. The method will potentially advance knowledge of the role and regulation of IAA.

  15. The Solanum lycopersicum auxin response factor 7 (SlARF7) regulates auxin signaling during tomato fruit set and development.

    Science.gov (United States)

    de Jong, Maaike; Wolters-Arts, Mieke; Feron, Richard; Mariani, Celestina; Vriezen, Wim H

    2009-01-01

    Auxin response factors (ARFs) are encoded by a gene family of transcription factors that specifically control auxin-dependent developmental processes. A tomato ARF gene, homologous to Arabidopsis NPH4/ARF7 and therefore designated as Solanum lycopersicum ARF7 (SlARF7), was found to be expressed at a high level in unpollinated mature ovaries. More detailed analysis of tomato ovaries showed that the level of SlARF7 transcript increases during flower development, remains at a constant high level in mature flowers, and is down-regulated within 48 h after pollination. Transgenic plants with decreased SlARF7 mRNA levels formed seedless (parthenocarpic) fruits. These fruits were heart-shaped and had a rather thick pericarp due to increased cell expansion, compared with the pericarp of wild-type fruits. The expression analysis, together with the parthenocarpic fruit phenotype of the transgenic lines, suggests that, in tomato, SlARF7 acts as a negative regulator of fruit set until pollination and fertilization have taken place, and moderates the auxin response during fruit growth. PMID:18778404

  16. Maximizing adhesion of auxin solutions to stem cuttings using sodium cellulose glycolate

    Science.gov (United States)

    Auxin solutions prepared with sodium cellulose glycolate (SCG; a thickening agent, also known as sodium carboxymethylcellulose) and applied to stem cuttings using a basal quick-dip extend the duration of exposure of cuttings to the auxin and have previously been shown to increase root number and/or ...

  17. Single-cell-based system to monitor carrier driven cellular auxin homeostasis

    Czech Academy of Sciences Publication Activity Database

    Barbez, E.; Laňková, Martina; Pařezová, Markéta; Maizel, A.; Zažímalová, Eva; Petrášek, Jan; Friml, J.; Kleine-Vehn, J.

    2013-01-01

    Roč. 13, FEB 4 (2013). ISSN 1471-2229 R&D Projects: GA ČR(CZ) GAP305/11/0797; GA ČR(CZ) GAP305/11/2476 Institutional research plan: CEZ:AV0Z50380511 Keywords : Auxin homeostasis * DR5 * Auxin carrier Subject RIV: ED - Physiology Impact factor: 3.942, year: 2013

  18. Isolation of transcription factors binding auxin response elements using a yeast one-hybrid system

    Institute of Scientific and Technical Information of China (English)

    齐眉; 黄美娟; 陈凡

    2002-01-01

    Plant hormones play an important role during higher plant embryogenesis. Auxin is central to the development of vascular tissues, formation of lateral and adventitious roots, control of apical dominance, and tropic responses. Auxin response element (AuxRE), present in the promoters of many auxin-induced genes, can confer auxin responsiveness. Using carrot somatic embryo under specific developmental phase, a cDNA expression library was constructed. Several plasmids were recombined containing the tetramer of AuxRE as a bait. After screening by a yeast one-hy- brid system, one positive clone was confirmed and characterized. Electrophoretic mobility shift assay showed that AxRF1 protein expressed in yeast cell could bind AuxRE in vitro. It suggests that AxRF1 participates in regulation of the expression of auxin responsive gene during carrot somatic embryogenesis.

  19. Auxin-regulated changes in protein phosphorylation in pea epicotyl segments

    International Nuclear Information System (INIS)

    Auxin-regulated changes in protein phosphorylation were studied by labeling pea epicotyl segments with (32P) PO43- and analyzing the phosphoproteins by two dimensional (2-D) gel electrophoresis. Analysis of phosphoproteins revealed auxin-regulated changes in the phosphorylation of specific polypeptides. In the presence of auxin, phosphorylation of 23,000, 82,000, 105,000 and 110,000 molecular weight polypeptides was markedly decreased whereas phosphorylation of 19,000, 24,000, 28,000 molecular weight polypeptides was increased. Some of these changes are very rapid and could be observed within minutes. Furthermore, their studies with calmodulin antagonists indicate the possible involvement of calmodulin-dependent protein kinases and/or phosphatases in auxin-regulated changes in protein phosphorylation. In view of these results, they suggest that auxin-regulated protein phosphorylation could be the one of the earliest events in regulating diverse physiological processes by this hormone

  20. Expression characteristics of GFP driven by NAC1 promoter and its responses to auxin and gibberellin

    Institute of Scientific and Technical Information of China (English)

    WANG Youhua; DUAN Liusheng; LU Mengzhu; LI Zhaohu; WANG Minjie; ZHAI Zhixi

    2006-01-01

    A 1050 bp fragment upstream transcription start site of a transcription factor gene NAC1 in Arabidopsis thaliana was amplified and cloned into plasmid pRD420 to construct a green fluorescent protein(GFP) fusion system under the control of NAC1 promoter. Plasmids were introduced into tobacco by Agrobacterium mediated method to regenerate plants with NAC1-GFP gene, and expression pattern of NAC1-GFP and its responses to auxin and gibberellin (GA) were observed. GFP was found to accumulate specifically in root, and was detected after treatment of auxin, N-1-Naphthylphthalamic acid (NPA, an auxin antagonist) or GA3. It was indicated that the expression of GFP driven by NAC1 promoter was induced not only by auxin but also by GAs, suggesting that NAC1 mediated both the auxin signaling and the GAs signaling involved in lateral roots development.

  1. Evidence that auxin-induced growth of soybean hypocotyls involves proton excretion

    Energy Technology Data Exchange (ETDEWEB)

    Rayle, D.L. (San Diego State Univ., CA); Cleland, R.E.

    1980-09-01

    The role of H/sup +/ excretion in auxin-induced growth of soybean hypocotyl tissues has been investigated, using tissues whose cuticle was rendered permeable to protons or buffers by scarification (scrubbing). Indoleacetic acid induces both elongation and H/sup +/ excretion after a lag of 10 to 12 minutes. Cycloheximide inhibits growth and causes the tissues to remove protons from the medium. Neutral buffers (pH 7.0) inhibit auxin-induced growth of scrubbed but not intact sections; the inhibition increases as the buffers strength is increased. Both live and frozen-thawed sections, in the absence of auxin, extend in response to exogenously supplied protons. Fusicoccin induces both elongation and H/sup +/ excretion at rates greater than does auxin. These results indicate that H/sup +/ excretion is involved in the initiation of auxin-induced elongation in soybean hypocotyl tissue.

  2. Auxin-regulated changes in protein phosphorylation in pea epicotyl segments

    Energy Technology Data Exchange (ETDEWEB)

    Reddy, A.S.N.; Chengappa, S.; Raghothama, K.G.; Poovaiah, B.W.

    1987-04-01

    Auxin-regulated changes in protein phosphorylation were studied by labeling pea epicotyl segments with (/sup 32/P) PO/sub 4//sup 3 -/ and analyzing the phosphoproteins by two dimensional (2-D) gel electrophoresis. Analysis of phosphoproteins revealed auxin-regulated changes in the phosphorylation of specific polypeptides. In the presence of auxin, phosphorylation of 23,000, 82,000, 105,000 and 110,000 molecular weight polypeptides was markedly decreased whereas phosphorylation of 19,000, 24,000, 28,000 molecular weight polypeptides was increased. Some of these changes are very rapid and could be observed within minutes. Furthermore, their studies with calmodulin antagonists indicate the possible involvement of calmodulin-dependent protein kinases and/or phosphatases in auxin-regulated changes in protein phosphorylation. In view of these results, they suggest that auxin-regulated protein phosphorylation could be the one of the earliest events in regulating diverse physiological processes by this hormone.

  3. UGT74D1 is a novel auxin glycosyltransferase from Arabidopsis thaliana.

    Directory of Open Access Journals (Sweden)

    Shang-Hui Jin

    Full Text Available Auxin is one type of phytohormones that plays important roles in nearly all aspects of plant growth and developmental processes. The glycosylation of auxins is considered to be an essential mechanism to control the level of active auxins. Thus, the identification of auxin glycosyltransferases is of great significance for further understanding the auxin regulation. In this study, we biochemically screened the group L of Arabidopsis thaliana glycosyltransferase superfamily for enzymatic activity toward auxins. UGT74D1 was identified to be a novel auxin glycosyltransferase. Through HPLC and LC-MS analysis of reaction products in vitro by testing eight substrates including auxins and other compounds, we found that UGT74D1 had a strong glucosylating activity toward indole-3-butyric acid [IBA], indole-3-propionic acid [IPA], indole-3-acetic acid [IAA] and naphthaleneacetic acid [NAA], catalyzing them to form corresponding glucose esters. Biochemical characterization showed that this enzyme had a maximum activity in HEPES buffer at pH 6.0 and 37°C. In addition, the enzymatic activity analysis of crude protein and the IBA metabolite analysis from transgenic Arabidopsis plants overexpressing UGT74D1 gene were also carried out. Experimental results indicated that over-production of the UGT74D1 in plants indeed led to increased level of the glucose conjugate of IBA. Moreover, UGT74D1 overexpression lines displayed curling leaf phenotype, suggesting a physiological role of UGT74D1 in affecting the activity of auxins. Our current data provide a new target gene for further genetic studies to understand the auxin regulation by glycosylation in plants.

  4. The Arabidopsis Auxin Receptor F-Box Proteins AFB4 and AFB5 Are Required for Response to the Synthetic Auxin Picloram

    Directory of Open Access Journals (Sweden)

    Michael J. Prigge

    2016-05-01

    Full Text Available The plant hormone auxin is perceived by a family of F-box proteins called the TIR1/AFBs. Phylogenetic studies reveal that these proteins fall into four clades in flowering plants called TIR1, AFB2, AFB4, and AFB6. Genetic studies indicate that members of the TIR1 and AFB2 groups act as positive regulators of auxin signaling by promoting the degradation of the Aux/IAA transcriptional repressors. In this report, we demonstrate that both AFB4 and AFB5 also function as auxin receptors based on in vitro assays. We also provide genetic evidence that AFB4 and AFB5 are targets of the picloram family of auxinic herbicides in addition to indole-3-acetic acid. In contrast to previous studies we find that null afb4 alleles do not exhibit obvious defects in seedling morphology or auxin hypersensitivity. We conclude that AFB4 and AFB5 act in a similar fashion to other members of the family but exhibit a distinct auxin specificity.

  5. Hydrolases of the ILR1-like family of Arabidopsis thaliana modulate auxin response by regulating auxin homeostasis in the endoplasmic reticulum.

    Science.gov (United States)

    Sanchez Carranza, Ana Paula; Singh, Aparajita; Steinberger, Karoline; Panigrahi, Kishore; Palme, Klaus; Dovzhenko, Alexander; Dal Bosco, Cristina

    2016-01-01

    Amide-linked conjugates of indole-3-acetic acid (IAA) have been identified in most plant species. They function in storage, inactivation or inhibition of the growth regulator auxin. We investigated how the major known endogenous amide-linked IAA conjugates with auxin-like activity act in auxin signaling and what role ILR1-like proteins play in this process in Arabidopsis. We used a genetically encoded auxin sensor to show that IAA-Leu, IAA-Ala and IAA-Phe act through the TIR1-dependent signaling pathway. Furthermore, by using the sensor as a free IAA reporter, we followed conjugate hydrolysis mediated by ILR1, ILL2 and IAR3 in plant cells and correlated the activity of the hydrolases with a modulation of auxin response. The conjugate preferences that we observed are in agreement with available in vitro data for ILR1. Moreover, we identified IAA-Leu as an additional substrate for IAR3 and showed that ILL2 has a more moderate kinetic performance than observed in vitro. Finally, we proved that IAR3, ILL2 and ILR1 reside in the endoplasmic reticulum, indicating that in this compartment the hydrolases regulate the rates of amido-IAA hydrolysis which results in activation of auxin signaling. PMID:27063913

  6. The Arabidopsis Auxin Receptor F-Box Proteins AFB4 and AFB5 Are Required for Response to the Synthetic Auxin Picloram

    Science.gov (United States)

    Prigge, Michael J.; Greenham, Kathleen; Zhang, Yi; Santner, Aaron; Castillejo, Cristina; Mutka, Andrew M.; O’Malley, Ronan C.; Ecker, Joseph R.; Kunkel, Barbara N.; Estelle, Mark

    2016-01-01

    The plant hormone auxin is perceived by a family of F-box proteins called the TIR1/AFBs. Phylogenetic studies reveal that these proteins fall into four clades in flowering plants called TIR1, AFB2, AFB4, and AFB6. Genetic studies indicate that members of the TIR1 and AFB2 groups act as positive regulators of auxin signaling by promoting the degradation of the Aux/IAA transcriptional repressors. In this report, we demonstrate that both AFB4 and AFB5 also function as auxin receptors based on in vitro assays. We also provide genetic evidence that AFB4 and AFB5 are targets of the picloram family of auxinic herbicides in addition to indole-3-acetic acid. In contrast to previous studies we find that null afb4 alleles do not exhibit obvious defects in seedling morphology or auxin hypersensitivity. We conclude that AFB4 and AFB5 act in a similar fashion to other members of the family but exhibit a distinct auxin specificity. PMID:26976444

  7. Tricho- and atrichoblast cell files show distinct PIN2 auxin efflux carrier exploitations and are jointly required for defined auxin-dependent root organ growth.

    Science.gov (United States)

    Löfke, Christian; Scheuring, David; Dünser, Kai; Schöller, Maria; Luschnig, Christian; Kleine-Vehn, Jürgen

    2015-08-01

    The phytohormone auxin is a vital growth regulator in plants. In the root epidermis auxin steers root organ growth. However, the mechanisms that allow adjacent tissues to integrate growth are largely unknown. Here, the focus is on neighbouring epidermal root tissues to assess the integration of auxin-related growth responses. The pharmacologic, genetic, and live-cell imaging approaches reveal that PIN2 auxin efflux carriers are differentially controlled in tricho- and atrichoblast cells. PIN2 proteins show lower abundance at the plasma membrane of trichoblast cells, despite showing higher rates of intracellular trafficking in these cells. The data suggest that PIN2 proteins display distinct cell-type-dependent trafficking rates to the lytic vacuole for degradation. Based on this insight, it is hypothesized that auxin-dependent processes are distinct in tricho- and atrichoblast cells. Moreover, genetic interference with epidermal patterning supports this assumption and suggests that tricho- and atrichoblasts have distinct importance for auxin-sensitive root growth and gravitropic responses. PMID:26041320

  8. Effect of Auxins and Light on Rooting Stem Cuttings of Populus nigra Salix tetrasperma, Ipomea fistulosa and Hibiscus notodus in Relation to Polarity.

    Science.gov (United States)

    Nanda, K K; Purohit, A N; Kochhar, V K

    1969-01-01

    The apical and basal ends of stem cuttings of Populus nigra, Salix tetrasperma, Ipomoea fistulosa and Hibiscus notodus were treated with 10 mg/l solutions of IAA and IBA for 24 hours and were planted either erect or inverted both in light and dark. Observations for the number of cuttings that rooted and the roots produced on them were recorded at weekly intervals. In Salix, Ipomoea and Hibiscus rooting was more on cuttings planted erect, while in populus it did not differ much with the manner of planting. The reduced rooting in inverted cuttings may be ascribed to the low level of endogenous auxin at the apex due to polar transport. An exogenous application of auxins enhanced rooting on inverted cuttings. In dark, roots on Populus and Salix cuttings were produced both above and within the rooting medium. The weak polarity of these two plants may be due to the potential root primordia reported in their stem. The formation of callus occurred on the top of Populus cuttings whether planted erect or inverted but it differentiated into branches on erect cuttings only. In those planted in an inverted position the callus failed to differentiate in spite of the application of kinetin, auxins, TIBA, coumarin and sucrose, and dried ultimately. PMID:20925659

  9. cis-Cinnamic acid selective suppressors distinct from auxin inhibitors.

    Science.gov (United States)

    Okuda, Katsuhiro; Nishikawa, Keisuke; Fukuda, Hiroshi; Fujii, Yoshiharu; Shindo, Mitsuru

    2014-01-01

    The activity of cis-cinnamic acid (cis-CA), one of the allelochemicals, in plants is very similar to that of indole-3-acetic acid (IAA), a natural auxin, and thus cis-CA has long been believed to be an analog of auxin. We have reported some structure-activity relationships studies by synthesizing over 250 cis-CA derivatives and estimating their inhibitory activities on root growth inhibition in lettuce. In this study, the compounds that showed low- or no-activity on root growth inhibition were recruited as candidates suppressors against cis-CA and/or auxin and tested for their activity. In the presence of cis-CA, lettuce root growth was inhibited; however, the addition of some cis-CA derivatives restored control-level root growth. Four compounds, (Z)-3-(4-isopropylphenyl)acrylic acid, (Z)-3-(3-butoxyphenyl)acrylic acid, (Z)-3-[3-(pentyloxy)phenyl]acrylic acid, and (Z)-3-(naphthalen-1-yl)acrylic acid were selected as candidates for a cis-CA selective suppressor they allowed the recovery of root growth from inhibition by cis-CA treatment without any effects on the IAA-induced effect or elongating activity by themselves. Three candidates significantly ameliorated the root shortening by the potent inhibitor derived from cis-CA. In brief, we have found some cis-CA selective suppressors which have never been reported from inactive cis-CA derivatives for root growth inhibition. cis-CA selective suppressors will play an important role in elucidating the mechanism of plant growth regulation. PMID:24881667

  10. Involvement of auxin and CKs in boron deficiency induced changes in apical dominance of pea plants (Pisum sativum L.).

    Science.gov (United States)

    Wang, Guoying; Römheld, Volker; Li, Chunjian; Bangerth, Fritz

    2006-04-01

    It has previously been shown that boron (B) deficiency inhibits growth of the plant apex, which consequently results in a relatively weak apical dominance, and a subsequent sprouting of lateral buds. Auxin and cytokinins (CKs) are the two most important phytohormones involved in the regulation of apical dominance. In this study, the possible involvement of these two hormones in B-deficiency-induced changes in apical dominance was investigated by applying B or the synthetic CK CPPU to the shoot apex of pea plants grown in nutrient solution without B supply. Export of IAA out of the shoot apex, as well as the level of IAA, Z/ZR and isopentenyl-adenine/isopentenyl-adenosine (i-Ade/i-Ado) in the shoot apex were assayed. In addition, polar IAA transport capacity was measured in two internodes of different ages using 3H-IAA. In B-deficient plants, both the level of auxin and CKs were reduced, and the export of auxin from the shoot apex was considerably decreased relative to plants well supplied with B. Application of B to the shoot apex restored the endogenous Z/ZR and IAA level to control levels and increased the export of IAA from the shoot apex, as well as the 3H-IAA transport capacity in the newly developed internodes. Further, B application to the shoot apex inhibited lateral bud growth and stimulated lateral root formation, presumably by stimulated polar IAA transport. Applying CPPU to the shoot apex, a treatment that stimulates IAA export under adequate B supply, considerably reduced the endogenous Z/ZR concentration in the shoot apex, but had no stimulatory effect on IAA concentration and transport in B-deficient plants. A similar situation appeared to exist in lateral buds of B-deficient plants as, in contrast to plants well supplied with B, application of CKs to these plants did not stimulate lateral bud growth. In contrast to the changes of Z/ZR levels in the shoot apex, which occurred after application of B or CPPU, the levels of i-Ade/i-Ado stayed more or

  11. Constitutive expression of pathogen-inducible OsWRKY31 enhances disease resistance and affects root growth and auxin response in transgenic rice plants

    Institute of Scientific and Technical Information of China (English)

    Juan Zhang; Youliang Peng; Zejian Guo

    2008-01-01

    WRKY transcription factors have many regulatory roles in response to biotic and abiotic stresses. In this study, we isolated a rice WRKY gene (OsWRKY31) that is induced by the rice blast fungus Magnaporthe grisea and auxin. This gene encodes a polypeptide of 211 amino-acid residues and belongs to a subgroup of the rice WRKY gene family that probably originated after the divergence of monocot and dicot plants. OsWRKY31 was found to be localized to the nucleus of onion epidermis cells to transiently express OsWRKY31-eGFP fusion protein. Analysis of 0sWRKY31 and its mutants fused with a Cal4 DNA-binding domain indicated that OsWRKY31 has transactivation activity in yeast. Overexpression of the OsWRKY31 gene was found to enhance resistance against infection with M. grisea, and the transgenic lines exhibited reduced lateral root formation and elongation compared with wild-type and RNAi plants. The lines with overexpression showed constitutive expression of many defense-related genes, such as PBZ1 and OsSci2, as well as early auxin-response genes, such as OsIAA4 and OsCrll genes. Furthermore, the plants with overexpression were less sensitive to exogenously supplied IBA, NAA and 2,4-D at high concentrations, suggesting that overexpression of the OsWRKY31 gene might alter the auxin response or transport. These results also suggest that OsWRKY31 might be a common component in the signal transduction pathways of the auxin response and the defense response in rice.

  12. Auxin and plant morphogenesis - a model of regulation

    Directory of Open Access Journals (Sweden)

    Stefan Zajączkowski

    2015-05-01

    Full Text Available In the presented model cells of the plant body form a spatial medium in which three-dimensional morphogenic waves of auxin are propagated. Points in the same phase of oscillation form isophasic surfaces and the vectors of wave propagation form a three-dimensional vector field. The vectors in the case of local inhomogeneities of the medium deviate from organ polarity, providing positional information recognized by cells. Models of functioning of such a supracellular oscillatory system in regulation of tissue differentiation, tropic responses and plant form are discussed.

  13. Auxin Is Rapidly Induced by Herbivore Attack and Regulates a Subset of Systemic, Jasmonate-Dependent Defenses.

    Science.gov (United States)

    Machado, Ricardo A R; Robert, Christelle A M; Arce, Carla C M; Ferrieri, Abigail P; Xu, Shuqing; Jimenez-Aleman, Guillermo H; Baldwin, Ian T; Erb, Matthias

    2016-09-01

    Plant responses to herbivore attack are regulated by phytohormonal networks. To date, the role of the auxin indole-3-acetic acid (IAA) in this context is not well understood. We quantified and manipulated the spatiotemporal patterns of IAA accumulation in herbivore-attacked Nicotiana attenuata plants to unravel its role in the regulation of plant secondary metabolism. We found that IAA is strongly, rapidly, and specifically induced by herbivore attack. IAA is elicited by herbivore oral secretions and fatty acid conjugate elicitors and is accompanied by a rapid transcriptional increase of auxin biosynthetic YUCCA-like genes. IAA accumulation starts 30 to 60 s after local induction and peaks within 5 min after induction, thereby preceding the jasmonate (JA) burst. IAA accumulation does not require JA signaling and spreads rapidly from the wound site to systemic tissues. Complementation and transport inhibition experiments reveal that IAA is required for the herbivore-specific, JA-dependent accumulation of anthocyanins and phenolamides in the stems. In contrast, IAA does not affect the accumulation of nicotine or 7-hydroxygeranyllinalool diterpene glycosides in the same tissue. Taken together, our results uncover IAA as a rapid and specific signal that regulates a subset of systemic, JA-dependent secondary metabolites in herbivore-attacked plants. PMID:27485882

  14. The Arabidopsis gene DIG6 encodes a large 60S subunit nuclear export GTPase 1 that is involved in ribosome biogenesis and affects multiple auxin-regulated development processes

    KAUST Repository

    Zhao, Huayan

    2015-08-13

    The circularly permuted GTPase large subunit GTPase 1 (LSG1) is involved in the maturation step of the 60S ribosome and is essential for cell viability in yeast. Here, an Arabidopsis mutant dig6 (drought inhibited growth of lateral roots) was isolated. The mutant exhibited multiple auxin-related phenotypes, which included reduced lateral root number, altered leaf veins, and shorter roots. Genetic mapping combined with next-generation DNA sequencing identified that the mutation occurred in AtLSG1-2. This gene was highly expressed in regions of auxin accumulation. Ribosome profiling revealed that a loss of function of AtLSG1-2 led to decreased levels of monosomes, further demonstrating its role in ribosome biogenesis. Quantitative proteomics showed that the expression of certain proteins involved in ribosome biogenesis was differentially regulated, indicating that ribosome biogenesis processes were impaired in the mutant. Further investigations showed that an AtLSG1-2 deficiency caused the alteration of auxin distribution, response, and transport in plants. It is concluded that AtLSG1-2 is integral to ribosome biogenesis, consequently affecting auxin homeostasis and plant development.

  15. Auxin-mediated lamina growth in tomato leaves is restricted by two parallel mechanisms.

    Science.gov (United States)

    Ben-Gera, Hadas; Dafna, Asaf; Alvarez, John Paul; Bar, Maya; Mauerer, Mareike; Ori, Naomi

    2016-06-01

    In the development of tomato compound leaves, local auxin maxima points, separated by the expression of the Aux/IAA protein SlIAA9/ENTIRE (E), direct the formation of discrete leaflets along the leaf margin. The local auxin maxima promote leaflet initiation, while E acts between leaflets to inhibit auxin response and lamina growth, enabling leaflet separation. Here, we show that a group of auxin response factors (ARFs), which are targeted by miR160, antagonizes auxin response and lamina growth in conjunction with E. In wild-type leaf primordia, the miR160-targeted ARFs SlARF10A and SlARF17 are expressed in leaflets, and SlmiR160 is expressed in provascular tissues. Leaf overexpression of the miR160-targeted ARFs SlARF10A, SlARF10B or SlARF17, led to reduced lamina and increased leaf complexity, and suppressed auxin response in young leaves. In agreement, leaf overexpression of miR160 resulted in simplified leaves due to ectopic lamina growth between leaflets, reminiscent of e leaves. Genetic interactions suggest that E and miR160-targeted ARFs act partially redundantly but are both required for local inhibition of lamina growth between initiating leaflets. These results show that different types of auxin signal antagonists act cooperatively to ensure leaflet separation in tomato leaf margins. PMID:27121172

  16. Auxins Induce Tryptophan Decarboxylase Activity in Radicles of Catharanthus Seedlings 1

    Science.gov (United States)

    Aerts, Rob J.; Alarco, Anne-Marie; De Luca, Vincenzo

    1992-01-01

    Germinating seedlings of Catharanthus roseus produce monoterpenoid indole alkaloids as a result of a transient increase of tryptophan decarboxylase (TDC) activity. The influence of auxins on this transient rise of TDC activity was studied. External application of indolebutyric acid or 2,4-dichlorophenoxyacetic acid at a concentration of 20 to 40 μm enhanced and prolonged the rise in TDC activity in developing seedlings. Auxin treatment also influenced the morphology of the seedlings; it induced a shortening and thickening of the hypocotyl and the radicle and promoted the initiation of lateral roots in the radicle. During development, the radicles of auxin-treated seedlings displayed a gradual increase in TDC activity that was absent in the radicles of untreated controls. Examination of immunoblots revealed anti-TDC reactive proteins in extracts from radicles of auxin-treated seedlings, but none in extracts from radicles of control seedlings. In contrast, TDC activity and immunoreactive protein levels in the aerial parts of controls and auxin-treated seedlings were comparable. Our results indicate that externally applied auxins induce both abnormal development and TDC activity in the radicles of Catharanthus seedlings. Although auxins slightly delayed the light-mediated induction of the cotyledon-specific last step in vindoline biosynthesis (i.e. acetylcoenzyme A: deacetylvindolin-O-acetyltransferase activity), seedlings still synthesized vindoline, one of the major alkaloid end products. Images Figure 2 PMID:16653009

  17. Effects of natural and synthetic auxins on the gravitropic growth habit of roots in two auxin-resistant mutants of Arabidopsis, axr1 and axr4: evidence for defects in the auxin influx mechanism of axr4

    Science.gov (United States)

    Yamamoto, M.; Yamamoto, K. T.

    1999-01-01

    The partially agravitropic growth habit of roots of an auxin-resistant mutant of Arabidopsis thaliana, axr4, was restored by the addition of 30-300 nM 1-naphthaleneacetic acid (NAA) to the growth medium. Neither indole 3-acetic acid (IAA) nor 2,4-dichlorophenoxyacetic acid (2,4-D) showed such an effect. Growth of axr4 roots was resistant to IAA and 2,4-D, but not at all to NAA. The differential effects of the three auxins suggest that the defects of axr4 result from a lower auxin influx into its cells. The partially agravitropic growth habit of axr1 roots, which was less severe than that of axr4 roots, was only slightly affected by the three auxins in the growth medium at concentrations up to 300 nM; growth of axr1 roots was resistant to all three of the auxins. These results suggest that the lesion of axrl mutants is different from that of axr4.

  18. Auxin synthesis-encoding transgene enhances grape fecundity.

    Science.gov (United States)

    Costantini, Elisa; Landi, Lucia; Silvestroni, Oriana; Pandolfini, Tiziana; Spena, Angelo; Mezzetti, Bruno

    2007-04-01

    Grape (Vitis vinifera) yield is largely dependent on the fecundity of the cultivar. The average number of inflorescences per shoot (i.e. shoot fruitfulness) is a trait related to fecundity of each grapevine. Berry number and weight per bunch are other features affecting grape yield. An ovule-specific auxin-synthesizing (DefH9-iaaM) transgene that increases the indole-3-acetic acid content of grape transgenic berries was transformed into cultivars Silcora and Thompson Seedless, which differ in the average number of inflorescences per shoots. Thompson Seedless naturally has very low shoot fruitfulness, whereas Silcora has medium shoot fruitfulness. The average number of inflorescences per shoot in DefH9-iaaM Thompson Seedless was doubled compared to its wild-type control. Berry number per bunch was increased in both transgenic cultivars. The quality and nutritional value of transgenic berries were substantially equivalent to their control fruits. The data presented indicate that auxin enhances fecundity in grapes, thus enabling to increase yield with lower production costs. PMID:17337528

  19. Auxin, ethylene and light in gravitropic growth: new insights

    Science.gov (United States)

    Edelmann, Hg; Sabovljevic, A.; Njio, G.; Roth, U.

    The regulation mechanism of gravitropic differential plant growth is commonly divided into three sequential processes: the perception of the gravistimulus (generally attributed to amyloplast sedimentation), the transduction of the perceived signal (of which very little is known), and the adequate differential growth response (generally attributed to asymmetric auxin redistribution). The detailled mechanism is still unresolved and remains to be elucidated in significant parts. Employing 2D SDS-PAGE /Q-TOF amongst other methods and strategies we studied the effect of different auxins on gravitropism of coleoptiles and hypocotyls. We also analyzed the effects of light and ethylene (synthesis and perception) on gravitropic growth of primary shoots and roots and analyzed the protein pattern with respect to the observed physiological effects. In coleoptiles, under the applied experimental conditions the effect of 2,4-dichlorophenoxy acetic acid (2,4 D) on gravitropism differed from the effect of indolylacetic acid (IAA), which was similar to the one observed in sunflower hypocotyls. In roots, the relevance of ethylene for gravitropic differential growth and the capacity to evade mechanical barriers during horizontal gravistimulation was analyzed in detail. A special focus was addressed on the physiological significance of the root cap. We will show that the relevance of ethylene for gravitropism has hitherto been misjudged. Further new findings and their implications for the regulation mechanism of gravitropism will be presented and discussed. Kramer et al., (2003) J. Ex. Bot. 54, (393), 2723-2732 Edelmann, H.G., (2002) J. Ex. Bot. 53, (375), 1825-1828

  20. Two distinct signaling pathways participate in auxin-induced swelling of pea epidermal protoplasts.

    Science.gov (United States)

    Yamagami, Mutsumi; Haga, Ken; Napier, Richard M; Iino, Moritoshi

    2004-02-01

    Protoplast swelling was used to investigate auxin signaling in the growth-limiting stem epidermis. The protoplasts of epidermal cells were isolated from elongating internodes of pea (Pisum sativum). These protoplasts swelled in response to auxin, providing the clearest evidence that the epidermis can directly perceive auxin. The swelling response to the natural auxin IAA showed a biphasic dose response curve but that to the synthetic auxin 1-naphthalene acetic acid (NAA) showed a simple bell-shaped dose response curve. The responses to IAA and NAA were further analyzed using antibodies raised against ABP1 (auxin-binding protein 1), and their dependency on extracellular ions was investigated. Two signaling pathways were resolved for IAA, an ABP1-dependent pathway and an ABP1-independent pathway that is much more sensitive to IAA than the former. The response by the ABP1 pathway was eliminated by anti-ABP1 antibodies, had a higher sensitivity to NAA, and did not depend on extracellular Ca(2+). In contrast, the response by the non-ABP1 pathway was not affected by anti-ABP1 antibodies, had no sensitivity to NAA, and depended on extracellular Ca(2+). The swelling by either pathway required extracellular K(+) and Cl(-). The auxin-induced growth of pea internode segments showed similar response patterns, including the occurrence of two peaks in the dose response curve for IAA and the difference in Ca(2+) requirements. It is suggested that two signaling pathways participate in auxin-induced internode growth and that the non-ABP1 pathway is more likely to be involved in the control of growth by constitutive concentrations of endogenous auxin. PMID:14764902

  1. Regulation of cell division and expansion by sugar and auxin signaling

    Directory of Open Access Journals (Sweden)

    Lu eWang

    2013-05-01

    Full Text Available Plant growth and development are modulated by concerted actions of a variety of signaling molecules. In recent years, evidence has emerged on the roles of sugar and auxin signals in diverse aspects of plant growth and development. Here, based on recent progress of genetic analyses and gene expression profiling studies, we summarize the functional similarities, diversities and their interactions of sugar and auxin signals in regulating two major processes of plant development: cell division and cell expansion. We focus on roles of sugar and auxin signaling in both vegetative and reproductive tissues including developing seed.

  2. Vanadate inhibition of auxin-enhanced H+ secretion and elongation in pea epicotyls and oat coleoptiles

    OpenAIRE

    Jacobs, Mark; Taiz, Lincoln

    1980-01-01

    In experiments carried out to investigate the acid secretion theory of auxin action, we utilized sodium orthovanadate, an agent found to be a selective inhibitor of a plasma membrane-associated H+-pumping ATPase in Neurospora [Bowman, B. J. & Slayman, C. W. (1979) J. Biol. Chem. 245, 2928-2934]. At 1 mM, vanadate inhibited auxin-enhanced medium acidification by pea epicotyl segments within 5 min, whether added 0.5 or 2.5 hr after auxin. Inhibition of acidification was total after 10-15 min bu...

  3. A genomics approach to understanding the role of auxin in apple (Malus x domestica fruit size control

    Directory of Open Access Journals (Sweden)

    Devoghalaere Fanny

    2012-01-01

    Full Text Available Abstract Background Auxin is an important phytohormone for fleshy fruit development, having been shown to be involved in the initial signal for fertilisation, fruit size through the control of cell division and cell expansion, and ripening related events. There is considerable knowledge of auxin-related genes, mostly from work in model species. With the apple genome now available, it is possible to carry out genomics studies on auxin-related genes to identify genes that may play roles in specific stages of apple fruit development. Results High amounts of auxin in the seed compared with the fruit cortex were observed in 'Royal Gala' apples, with amounts increasing through fruit development. Injection of exogenous auxin into developing apples at the start of cell expansion caused an increase in cell size. An expression analysis screen of auxin-related genes involved in auxin reception, homeostasis, and transcriptional regulation showed complex patterns of expression in each class of gene. Two mapping populations were phenotyped for fruit size over multiple seasons, and multiple quantitative trait loci (QTLs were observed. One QTL mapped to a region containing an Auxin Response Factor (ARF106. This gene is expressed during cell division and cell expansion stages, consistent with a potential role in the control of fruit size. Conclusions The application of exogenous auxin to apples increased cell expansion, suggesting that endogenous auxin concentrations are at least one of the limiting factors controlling fruit size. The expression analysis of ARF106 linked to a strong QTL for fruit weight suggests that the auxin signal regulating fruit size could partially be modulated through the function of this gene. One class of gene (GH3 removes free auxin by conjugation to amino acids. The lower expression of these GH3 genes during rapid fruit expansion is consistent with the apple maximising auxin concentrations at this point.

  4. AUXIN-PRODUCING BACTERIA AND UREASE ACTIVITY IN THE RHIZOSPHERE OF GLYPHOSATE-RESISTANT SOYBEAN

    Science.gov (United States)

    Repeated use of glyphosate on glyphosate-resistant crops has raised concerns regarding the potential environmental impacts of this herbicide. Glyphosate may affect microbial production of plant-growth-regulating compounds including hydrogen cyanide, phytohormones including auxins, and other unidenti...

  5. Comparison of auxin activty in tumourous and normal callus cultures from sunflower and tobacco plants

    Directory of Open Access Journals (Sweden)

    Z. Chirek

    2015-05-01

    Full Text Available In normal and tumourous calluses of sunflower and tobacco the level of extractable auxins was determined by Avena coleoptile straight growth test. Auxin activity was detected practically in two zones: I - at position with Rf 0.2-0.4 and II - at position with Rf 0.6-0.9. The tumour tissues of sunflower and tobacco plants, representing different types of neoplastic growth exhibit a 3 times higher auxin activity as compared with that of the corresponding normal tissues. Tobacco tissues, on the other hand, had a higher auxin level than the corresponding sunflower tissues and they exhibited different proportions in the activity of zones I and II, which points to a dominance of genetic regulation of hormone metabolism in these plants.

  6. Auxin, the organizer of the environmental/hormonal signals for root hair growth

    Directory of Open Access Journals (Sweden)

    Hyung-Taeg eCho

    2013-11-01

    Full Text Available The root hair development is controlled by diverse factors such as fate-determining developmental cues, auxin-related environmental factors, and hormones. In particular, the soil environmental factors are important as they maximize their absorption by modulating root hair development. These environmental factors affect the root hair developmental process by making use of diverse hormones. These hormonal factors interact with each other to modulate root hair development in which auxin appears to form the most intensive networks with the pathways from environmental factors and hormones. Moreover, auxin action for root hair development is genetically located immediately upstream of the root hair-morphogenetic genes. These observations suggest that auxin plays as an organizing node for environmental/hormonal pathways to modulate root hair growth.

  7. Auxin, the organizer of the hormonal/environmental signals for root hair growth

    OpenAIRE

    Lee, Richard D.-W.; Cho, Hyung-Taeg

    2013-01-01

    The root hair development is controlled by diverse factors such as fate-determining developmental cues, auxin-related environmental factors, and hormones. In particular, the soil environmental factors are important as they maximize their absorption by modulating root hair development. These environmental factors affect the root hair developmental process by making use of diverse hormones. These hormonal factors interact with each other to modulate root hair development in which auxin appears ...

  8. Epinasty of Poinsettias-the Role of Auxin and Ethylene.

    Science.gov (United States)

    Reid, M S; Mor, Y; Kofranek, A M

    1981-05-01

    Upward physical restraint of the normally horizontal bracts of poinsettia (Euphorbia pulcherrima Willd.) resulted in increased ethylene production and epinastic curvature of the petioles after 5 days. Downward restraint caused little change in ethylene production or epinasty, indicating that the enhanced ethylene production observed in petioles bent upwards is not due to the bending stress alone. Epinasty, measured upon removal of upward physical restraint, was not affected by spraying plants with aminoxyacetic acid to reduce ethylene production or with silver thiosulfate to prevent ethylene action. Removal of the bract blades prevented the epinastic response of the petiole, and the response was restored by applying indoleacetic acid to the cut petiole end. Redistribution of auxin appears to be responsible for both the epinasty and the increased ethylene production of reoriented poinsettia bracts. PMID:16661798

  9. Epinasty of Poinsettias—the Role of Auxin and Ethylene

    Science.gov (United States)

    Reid, Michael S.; Mor, Yoram; Kofranek, Anton M.

    1981-01-01

    Upward physical restraint of the normally horizontal bracts of poinsettia (Euphorbia pulcherrima Willd.) resulted in increased ethylene production and epinastic curvature of the petioles after 5 days. Downward restraint caused little change in ethylene production or epinasty, indicating that the enhanced ethylene production observed in petioles bent upwards is not due to the bending stress alone. Epinasty, measured upon removal of upward physical restraint, was not affected by spraying plants with aminoxyacetic acid to reduce ethylene production or with silver thiosulfate to prevent ethylene action. Removal of the bract blades prevented the epinastic response of the petiole, and the response was restored by applying indoleacetic acid to the cut petiole end. Redistribution of auxin appears to be responsible for both the epinasty and the increased ethylene production of reoriented poinsettia bracts. Images PMID:16661798

  10. An auxin-responsive endogenous peptide regulates root development in Arabidopsis

    Institute of Scientific and Technical Information of China (English)

    Fengxi Yang; Yu Song; Hao Yang; Zhibin Liu; Genfa Zhu; Yi Yang

    2014-01-01

    Auxin plays critical roles in root formation and development. The components involved in this process, however, are not well understood. Here, we newly identified a peptide encoding gene, auxin-responsive endogenous polypeptide 1 (AREP1), which is induced by auxin, and mediates root development in Arabidopsis. Expression of AREP1 was specific to the cotyledon and to root and shoot meristem tissues. Amounts of AREP1 transcripts and AREP1-green fluorescent protein fusion proteins were elevated in response to indoleacetic acid treatment. Suppression of AREP1 through RNAi silencing resulted in reduction of primary root length, increase of lateral root number, and expansion of adventitious roots, compared to the observations in wild-type plants in the presence of auxin. By contrast, transgenic plants overexpressing AREP1 showed enhanced growth of the primary root under auxin treatment. Additionally, rootmorphology, including lateral root number and adventitious roots, differed greatly between transgenic and wildtype plants. Further analysis indicated that the expression of auxin-responsive genes, such as IAA3, IAA7, IAA17, GH3.2, GH3.3, and SAUR-AC1, was significantly higher in AREP1 RNAi plants, and was slightly lower in AREP1 overexpressing plants than in wildtype plants. These results suggest that the novel endogenous peptide AREP1 plays an important role in the process of auxinmediated root development.

  11. Auxin-dependent compositional change in Mediator in ARF7- and ARF19-mediated transcription.

    Science.gov (United States)

    Ito, Jun; Fukaki, Hidehiro; Onoda, Makoto; Li, Lin; Li, Chuanyou; Tasaka, Masao; Furutani, Masahiko

    2016-06-01

    Mediator is a multiprotein complex that integrates the signals from transcription factors binding to the promoter and transmits them to achieve gene transcription. The subunits of Mediator complex reside in four modules: the head, middle, tail, and dissociable CDK8 kinase module (CKM). The head, middle, and tail modules form the core Mediator complex, and the association of CKM can modify the function of Mediator in transcription. Here, we show genetic and biochemical evidence that CKM-associated Mediator transmits auxin-dependent transcriptional repression in lateral root (LR) formation. The AUXIN/INDOLE 3-ACETIC ACID 14 (Aux/IAA14) transcriptional repressor inhibits the transcriptional activity of its binding partners AUXIN RESPONSE FACTOR 7 (ARF7) and ARF19 by making a complex with the CKM-associated Mediator. In addition, TOPLESS (TPL), a transcriptional corepressor, forms a bridge between IAA14 and the CKM component MED13 through the physical interaction. ChIP assays show that auxin induces the dissociation of MED13 but not the tail module component MED25 from the ARF7 binding region upstream of its target gene. These findings indicate that auxin-induced degradation of IAA14 changes the module composition of Mediator interacting with ARF7 and ARF19 in the upstream region of their target genes involved in LR formation. We suggest that this regulation leads to a quick switch of signal transmission from ARFs to target gene expression in response to auxin. PMID:27217573

  12. Protein patterns in the oat coleoptile as influenced by auxin and by protein turnover

    Energy Technology Data Exchange (ETDEWEB)

    Bates, G.W.; Cleland, R.E.

    1980-01-01

    Synthesis of growth-limiting proteins is required for continued auxin-induced elongation of oat coleoptiles. In order to determine whether GLP synthesis is dependent or independent of auxin, a double-labeling ratio technique, coupled with disc-gel electrophoresis, has been used to assess the effect of auxin on the pattern of protein synthesis. Sections were peeled to enhance amino-acid uptake; proteins were labeled with (/sup 14/C)- or (/sup 3/H) leucine in the presence or absence of indole-3-acetic acid for 40 min to 6 h, and were separated into soluble, membrane-associated, and wall-associated fractions. Regardless of the conditions used, or the protein fraction examined, no changes in response to auxin were detected in the pattern or protein synthesis. In order to escape detection by this technique an auxin-induced protein would have to comprise less than 0.75% of the total newly synthesized protein. Thus the synthesis of GLP appears to be independent of auxin. The same technique has been used to follow protein turnover. During the chase, proteins are initially degraded at an average rate of 8% H/sup -1/, and some protein bands showed as much as 14% h/sup -1/ degradation. No protein was detected which had a turnover rate as rapid as the BLP.

  13. 水稻冠根数目多样性与生长素的关系%Auxin and genetic diversity of crown root number in rice

    Institute of Scientific and Technical Information of China (English)

    陈雅; 包亮; 王利凯; 赵磊; 余四斌; 须健

    2012-01-01

    Using an improved rice root research system, crown root numbers in 42 cultivated rice were analyzed. Results showed that different cultivars have different crown root numbers, ranging from 2 to 12 at average. Two cultivars with extremely few crown roots and 2 cultivars with large numbers of crown roots were selected for further analysis with the polar auxin transport inhibitor NPA. By localized application of NPA at the shoot-root junction of the 4 selected cultivars,we found that NPA appeared to reduce crown root numbers in general. Cultivars with large number of crown roots were more sensitive to low concentration of NPA than cultivars with small numbers. These data indicated that auxin and polar auxin transport determines crown root number in rice.%采用改进的水稻根系鉴定体系考察42个生态型水稻的冠根数目,发现水稻冠根数目存在多样性;从中选择2个冠根数目极端多和2个冠根数目极端少的生态型,利用定点施加生长素极性运输抑制剂NPA,以冠根数目为指标,分析冠根数目不同的生态型对NPA的敏感性,发现NPA处理导致冠根数目减少.在低浓度NPA处理时,冠根数目多的品种比冠根数目少的品种对NPA更敏感;在高浓度NPA处理时,不同生态型水稻冠根数目趋于接近.说明在不同根系类型的水稻中,生长素对冠根数目都有着重要的影响.

  14. Transfer of auxinic herbicide resistance from Brassica kaber to Brassica juncea and Brassica rapa through embryo rescue

    OpenAIRE

    Mithila, J.; Hall, J Christopher

    2013-01-01

    Auxinic herbicides are widely used in agriculture to selectively control broadleaf weeds. Prolonged use of auxinic herbicides has resulted in the evolution of resistance to these herbicides in some biotypes of Brassica kaber (wild mustard), a common weed in agricultural crops. In this study, auxinic herbicide resistance from B. kaber was transferred to Brassica juncea and Brassica rapa, two commercially important Brassica crops, by traditional breeding coupled with in vitro embryo rescue. A h...

  15. The IBR5 phosphatase promotes Arabidopsis auxin responses through a novel mechanism distinct from TIR1-mediated repressor degradation

    OpenAIRE

    Bartel Bonnie; Monroe-Augustus Melanie; Strader Lucia C

    2008-01-01

    Abstract Background In Arabidopsis, INDOLE-3-BUTYRIC ACID RESPONSE5 (IBR5), a putative dual-specificity protein phosphatase, is a positive regulator of auxin response. Mutations in IBR5 result in decreased plant height, defective vascular development, increased leaf serration, fewer lateral roots, and resistance to the phytohormones auxin and abscisic acid. However, the pathways through which IBR5 influences auxin responses are not fully understood. Results We analyzed double mutants of ibr5 ...

  16. Synergistic action of auxin and ethylene on root elongation inhibition is caused by a reduction of epidermal cell length.

    Science.gov (United States)

    Alarcón, M Victoria; Lloret, Pedro G; Salguero, Julio

    2014-01-01

    Auxin and ethylene have been largely reported to reduce root elongation in maize primary root. However the effects of auxin are greater than those caused by ethylene. Although auxin stimulates ethylene biosynthesis through the specific increase of ACC synthase, the auxin inhibitory effect on root elongation is not mediated by the auxin-induced increase of ethylene production. Recently it has been demonstrated that root inhibition by the application of the synthetic auxin NAA (1-naphtalenacetic acid) is increased if combined with the ethylene precursor ACC (1-aminocyclopropane-1-carboxilic acid) when both compounds are applied at very low concentrations.   Root elongation is basically the result of two processes: a) cell divisions in the meristem where meristematic cells continuously generate new cells and b) subsequently polarized growth by elongation along the root axis as cells leave the meristem and enter the root elongation zone. Our results indicate that exogenous auxin reduced both root elongation and epidermal cell length. In a different way, ethylene at very low concentrations only inhibited root elongation without affecting significantly epidermal cell length. However, these concentrations of ethylene increased the inhibitory effect of auxin on root elongation and cell length. Consequently the results support the hypothesis that ethylene acts synergistically with auxin in the regulation of root elongation and that inhibition by both hormones is due, at least partially, to the reduction of cell length in the epidermal layer. PMID:24598313

  17. Sterol Methyl Oxidases Affect Embryo Development via Auxin-Associated Mechanisms.

    Science.gov (United States)

    Zhang, Xia; Sun, Shuangli; Nie, Xiang; Boutté, Yohann; Grison, Magali; Li, Panpan; Kuang, Susu; Men, Shuzhen

    2016-05-01

    Sterols are essential molecules for multiple biological processes, including embryogenesis, cell elongation, and endocytosis. The plant sterol biosynthetic pathway is unique in the involvement of two distinct sterol 4α-methyl oxidase (SMO) families, SMO1 and SMO2, which contain three and two isoforms, respectively, and are involved in sequential removal of the two methyl groups at C-4. In this study, we characterized the biological functions of members of the SMO2 gene family. SMO2-1 was strongly expressed in most tissues during Arabidopsis (Arabidopsis thaliana) development, whereas SMO2-2 showed a more specific expression pattern. Although single smo2 mutants displayed no obvious phenotype, the smo2-1 smo2-2 double mutant was embryonic lethal, and the smo2-1 smo2-2/+ mutant was dwarf, whereas the smo2-1/+ smo2-2 mutant exhibited a moderate phenotype. The phenotypes of the smo2 mutants resembled those of auxin-defective mutants. Indeed, the expression of DR5rev:GFP, an auxin-responsive reporter, was reduced and abnormal in smo2-1 smo2-2 embryos. Furthermore, the expression and subcellular localization of the PIN1 auxin efflux facilitator also were altered. Consistent with these observations, either the exogenous application of auxin or endogenous auxin overproduction (YUCCA9 overexpression) partially rescued the smo2-1 smo2-2 embryonic lethality. Surprisingly, the dwarf phenotype of smo2-1 smo2-2/+ was completely rescued by YUCCA9 overexpression. Gas chromatography-mass spectrometry analysis revealed a substantial accumulation of 4α-methylsterols, substrates of SMO2, in smo2 heterozygous double mutants. Together, our data suggest that SMO2s are important for correct sterol composition and function partially through effects on auxin accumulation, auxin response, and PIN1 expression to regulate Arabidopsis embryogenesis and postembryonic development. PMID:27006488

  18. YUCCA6 over-expression demonstrates auxin function in delaying leaf senescence in Arabidopsis thaliana

    KAUST Repository

    Kim, Jeong Im

    2011-04-21

    The Arabidopsis thaliana YUCCA family of flavin monooxygenase proteins catalyses a rate-limiting step in de novo auxin biosynthesis. A YUCCA6 activation mutant, yuc6-1D, has been shown to contain an elevated free IAA level and to display typical high-auxin phenotypes. It is reported here that Arabidopsis plants over-expressing YUCCA6, such as the yuc6-1D activation mutant and 35S:YUC6 transgenic plants, displayed dramatic longevity. In addition, plants over-expressing YUCCA6 exhibited classical, delayed dark-induced and hormone-induced senescence in assays using detached rosette leaves. However, plants over-expressing an allele of YUCCA6, that carries mutations in the NADPH cofactor binding site, exhibited neither delayed leaf senescence phenotypes nor phenotypes typical of auxin overproduction. When the level of free IAA was reduced in yuc6-1D by conjugation to lysine, yuc6-1D leaves senesced at a rate similar to the wild-type leaves. Dark-induced senescence in detached leaves was accompanied by a decrease in their free IAA content, by the reduced expression of auxin biosynthesis enzymes such as YUCCA1 and YUCCA6 that increase cellular free IAA levels, and by the increased expression of auxin-conjugating enzymes encoded by the GH3 genes that reduce the cellular free auxin levels. Reduced transcript abundances of SAG12, NAC1, and NAC6 during senescence in yuc6-1D compared with the wild type suggested that auxin delays senescence by directly or indirectly regulating the expression of senescence-associated genes. 2011 The Author(s).

  19. Actin as deathly switch? How auxin can suppress cell-death related defence.

    Directory of Open Access Journals (Sweden)

    Xiaoli Chang

    Full Text Available Plant innate immunity is composed of two layers--a basal immunity, and a specific effector-triggered immunity, which is often accompanied by hypersensitive cell death. Initiation of cell death depends on a complex network of signalling pathways. The phytohormone auxin as central regulator of plant growth and development represents an important component for the modulation of plant defence. In our previous work, we showed that cell death is heralded by detachment of actin from the membrane. Both, actin response and cell death, are triggered by the bacterial elicitor harpin in grapevine cells. In this study we investigated, whether harpin-triggered actin bundling is necessary for harpin-triggered cell death. Since actin organisation is dependent upon auxin, we used different auxins to suppress actin bundling. Extracellular alkalinisation and transcription of defence genes as the basal immunity were examined as well as cell death. Furthermore, organisation of actin was observed in response to pharmacological manipulation of reactive oxygen species and phospholipase D. We find that induction of defence genes is independent of auxin. However, auxin can suppress harpin-induced cell death and also counteract actin bundling. We integrate our findings into a model, where harpin interferes with an auxin dependent pathway that sustains dynamic cortical actin through the activity of phospholipase D. The antagonism between growth and defence is explained by mutual competition for signal molecules such as superoxide and phosphatidic acid. Perturbations of the auxin-actin pathway might be used to detect disturbed integrity of the plasma membrane and channel defence signalling towards programmed cell death.

  20. Transcript profiles of auxin efflux carrier and IAA-amido synthetase genes suggest the role of auxin on apple (Malus x domestica) fruit maturation patterns

    Science.gov (United States)

    Plant growth regulators are known to regulate fruit development at various stages including flowering, fruit growth, maturation and ripening. Recent transcriptome studies indicated that auxin might play an essential role in regulating apple fruit maturation and ripening beside the well-defined role...

  1. AUXIN BINDING PROTEIN 4 is involved in the Ca2+/auxin-regulated expression of ZCAX3 gene in maize (Zea mays)

    Czech Academy of Sciences Publication Activity Database

    Jurišić-Knežev, Dejana; Bergougnoux, Véronique; Milde, D.; Fellner, Martin

    2014-01-01

    Roč. 92, č. 5 (2014), s. 332-339. ISSN 1916-2790 R&D Projects: GA MŠk 1P05ME792 Institutional support: RVO:61389030 Keywords : auxin-binding protein * ABP4 * AtCAX1 Subject RIV: EF - Botanics Impact factor: 1.278, year: 2014

  2. Compensation for a Mutated Auxin Biosynthesis Gene of Agrobacterium Ti Plasmid A66 in Nicotiana glutinosa Does Not Result from Increased Auxin Accumulation.

    Science.gov (United States)

    Campell, B R; Su, L Y; Pengelly, W L

    1989-04-01

    Nicotiana glutinosa compensated for a mutated tumor-morphology-shooty (tms) (auxin biosynthesis) locus of Agrobacterlum tumefaciens strain A66 and showed the same virulent tumor response to infection by strain A66 or the wild-type strain A6. Cloned cell lines transformed by strains A6 or A66 were fully hormone independent in culture and grew rapidly as friable, unorganized tissues on hormone-free growth medium. Growth of N. glutinosa tumor cells was inhibited by addition of alpha-naphthaleneacetic acid to the growth medium, and A6- and A66-transformed cells showed similar dose responses to this auxin. On the other hand, A6-transformed cells contained much higher levels of indole-3-acetic acid (IAA) and 1-aminocyclopropane-1-carboxylic acid (ACC) than A66-transformed cells. Differences in IAA and ACC levels in N. glutinosa tumor lines were consistent with the expected activity of the tms locus and were quantitatively similar to results obtained previously with A6- and A66-transformed cells of Nicotiana tabacum, which does not compensate for mutated tms genes. Thus, compensation for mutated tms genes in N. glutinosa did not result from increased auxin accumulation and did not appear to be related to the capacity of this host for auxin biosynthesis. PMID:16666706

  3. Long-distance transport of 35S-sulphur in 3-year-old beech trees (Fagus sylvatica)

    International Nuclear Information System (INIS)

    35S-L-cysteine was fed to a mature leaf of 3-year-old beech trees via a flap. After 1 to 4 h the distribution of 35S-radioactivity was analysed in the leaves as well as the bark and wood of the trunk and the main root. Transport of 35S out of the fed leaf amounted to 0.3–1.2% of the total 35S taken up. The branches of the trees did not act as sink organs for the exported radioactivity. The main portion of the 35S-radioactivity transported out of the fed leaf was found in basipetal parts of the trunk. Only a small portion of 35S-radioactivity was transported in acropetal direction. The distribution of the 35S-radioactivity within the trunk showed a higher portion of 35S in the bark than in the wood. In both tissues, bark (70 to 80%) and wood (60 to 70%), the 35S was predominantly found in the HCl soluble fraction. However, 35S-cysteine, the compound fed to the leaves was not exported out of the fed leaf. Along the trunk 35S-cysteine was neither determined in bark nor in wood sections. The only low molecular mass S-compounds found was 35S-glutathione (GSH). The 35S-sulphate detected in bark and wood origined from cysteine oxidation in the leaf tissue and from contamination of the 35S-cysteine feeding solution. The ratio of GSH to sulphate decreased with increasing distance from the fed leaf. Apparently, 35S-radioactivity was transported as sulphate and GSH in the phloem in basipetal direction, but GSH was removed preferentially out of the phloem along the transport path. 35S-radioactivity exported out of the phloem and transported into the wood of the trunk was not retranslocated in the xylem. It may therefore be assumed that part of the 35S translocated was stored in ray cells, medullary sheath cells and/or pith parenchyma cells. Girdling experiments in which the bark of the trunk was peeled off basipetal to the branch containing the fed leaf support these assumptions. (author)

  4. Auxin-induced regulation of protein synthesis in tobacco mesophyll protoplasts cultivated in vitro: I. Characteristics of auxin-sensitive proteins.

    Science.gov (United States)

    Meyer, Y; Aspart, L; Chartier, Y

    1984-08-01

    The presence of auxin (2,4-D), in the culture medium of tobacco (Nicotiana tabacum var Maryland) mesophyll protoplasts is necessary both for cell wall regeneration and for passage of the cells from phase G(0) to phase G(1) of the cell cycle. Among about 250 proteins synthesized by protoplasts and characterized by their migration in a two-dimensional electrophoresis gel, 2,4-dichlorophenoxyacetic acid affects the synthesis of 11.Nine proteins are synthesized at a reduced level in the presence of the hormone, of which three are rapidly labeled and short-lived, while the others, which are long-lived, become detectable only after 2 hours of radioactive labeling, suggesting that they undergo slow posttranslational maturation. These nine proteins are proline-rich but the proline radicals are not strongly hydroxylated. The synthesis of these proteins is no longer inhibited by auxin if dichlorobenzonitril, a weed-killer which inhibits cell wall reformation of tobacco protoplasts, is added to the culture medium.Two proteins are only synthesized if protoplasts are cultivated in an auxin-containing medium. These polypeptides are rapidly labeled, and are long-lived. The inhibition of cell wall reformation by dichlorobenzonitril does not modify their synthesis.These results suggest that proteins whose synthesis is reduced by auxin are related to cell wall reformation and that they do not play a role in the induction of the cell cycle. In contrast, proteins whose synthesis is stimulated in the presence of auxin are good candidates for a role in the induction of the cell cycle. PMID:16663728

  5. Pengaruh penambahan auxin terhadap pertunasan dan perakaran kopi arabika perbanyakan Somatic Embryogenesis (The effects of shooting and rooting of arabica coffee propagation through Embryogenesis Somatic auxin uses.

    Directory of Open Access Journals (Sweden)

    Rina Arimarsetiowati

    2012-08-01

    Full Text Available Plantlet that has developed shoots and roots will have a high level adaptation in the field. The objective of this experiment was to improve the ability of planlet in shooting and rooting so that it is ready for acclimatization in the field. The increase ability in shooting and rooting of the planlet were conducted by adding various types of auxin in the media. The arabica coffee embryo of clone AS 2K which has entered the phase of the cotyledons was transfered into the treatment media containing half-strength of MS (Murashige & Skoog macro and micro nutrient, vitamin B5, 30 g/L glucose, 100 ml/L coconut water, 50 mg/L AgNO3 added with the combination of IAA, IBA and NAA. The research was conducted by using completely randomized design with seven combined treatment i.e. 0.1 mg/L IBA, 0.1 mg/L NAA, 0.1 mg/L IAA; 0 , 1 mg/L IBA + 0.1 mg/L NAA, 0.1 mg/L IBA + 0.1 mg/L IAA, 0.1 mg/L NAA + 0.1 mg/L IAA; without auxin. There were 12 replications in every treatment and each replication consisted of five cotyledonary embryos. The parameters of observation were the root length, leaf number, leaf area, stem diameter, and height of plantlets. The observations were conducted in eighth weeks after cotyledonary embryo had shoots. The results showed that in the number of leaves and height of planlet parameters, the treatment without auxin was the best result compared to planlet with auxin addition. The addition of auxin varians and their combination did not significantly influent leaf area, root length and stem diameter parameters. The medium tested was optimum for the growth of shoots and roots of AS 2K arabica coffee.

  6. Auxin biosynthesis by the YUCCA6 flavin monooxygenase gene in woodland strawberry.

    Science.gov (United States)

    Liu, Hong; Xie, Wei-Fa; Zhang, Ling; Valpuesta, Victoriano; Ye, Zheng-Wen; Gao, Qing-Hua; Duan, Ke

    2014-04-01

    Auxin has been regarded as the main signal molecule coordinating the growth and ripening of fruits in strawberry, the reference genomic system for Rosaceae. The mechanisms regulating auxin biosynthesis in strawberry are largely elusive. Recently, we demonstrated that two YUCCA genes are involved in flower and fruit development in cultivated strawberry. Here, we show that the woodland strawberry (Fragaria vesca L.) genome harbors nine loci for YUCCA genes and eight of them encode functional proteins. Transcription pattern in different plant organs was different for all eight FvYUCs. Functionality of the FvYUC6 gene was studied in transgenic strawberry overexpressing FvYUC6, which showed typical high-auxin phenotypes. Overexpression of FvYUC6 also delayed flowering and led to complete male sterility in F. vesca. Additionally, specific repression of FvYUC6 expression by RNA interference significantly inhibited vegetative growth and reduced plant fertility. The development of leaves, roots, flowers, and fruits was greatly affected in FvYUC6-repressed plants. Expression of a subset of auxin-responsive genes was well correlated with the changes of FvYUC6 transcript levels and free indole-3-acetic acid levels in transgenic strawberry. These observations are consistent with an important role of FvYUC6 in auxin synthesis, and support a main role of the gene product in vegetative and reproductive development in woodland strawberry. PMID:24373096

  7. Effect of auxins and associated biochemical changes during clonal propagation of the biofuel plant - Jatropha curcas

    Energy Technology Data Exchange (ETDEWEB)

    Kochhar, Sunita; Singh, S.P.; Kochhar, V.K. [National Botanical Research Institute, Lucknow 226001 (India)

    2008-12-15

    Rooting and sprouting behaviour of stem cuttings of biofuel plant Jatropha curcas and their performance under field conditions have been studied in relation to auxin application. Pretreatment with indole-3-butyric acid (IBA) and 1-naphthalene acetic acid (NAA) increased both the rooting and sprouting. Sprouting of buds on the cuttings preceded rooting. The rooting and sprouting in J. curcas was more with IBA than NAA. The endogenous auxin contents were found to increase almost 15 days prior to rooting, indicating that mobilization of auxin rather than the absolute contents of auxin may be involved in root initiation. Indole acetic acid oxidase (IAA-oxidase) seems to be involved for triggering and initiating the roots/root primordia, whereas peroxidase is involved in both root initiation and the elongation processes as supported by the peroxidase and IAA-oxidase isoenzyme analysis in the cuttings. The clonally propagated plants (cutting-raised plants) performed better in the field as compared to those raised from the seeds. The plants produced from auxin-treated cuttings produced fruits and seeds in the same year as compared to the plants raised from seeds or from untreated or control cuttings that did not produce any seeds in 1 year of this study. Jatropha plants in general produce seeds after 2-3 years. (author)

  8. Constitutive auxin response in Physcomitrella reveals complex interactions between Aux/IAA and ARF proteins.

    Science.gov (United States)

    Lavy, Meirav; Prigge, Michael J; Tao, Sibo; Shain, Stephanie; Kuo, April; Kirchsteiger, Kerstin; Estelle, Mark

    2016-01-01

    The coordinated action of the auxin-sensitive Aux/IAA transcriptional repressors and ARF transcription factors produces complex gene-regulatory networks in plants. Despite their importance, our knowledge of these two protein families is largely based on analysis of stabilized forms of the Aux/IAAs, and studies of a subgroup of ARFs that function as transcriptional activators. To understand how auxin regulates gene expression we generated a Physcomitrella patens line that completely lacks Aux/IAAs. Loss of the repressors causes massive changes in transcription with misregulation of over a third of the annotated genes. Further, we find that the aux/iaa mutant is blind to auxin indicating that auxin regulation of transcription occurs exclusively through Aux/IAA function. We used the aux/iaa mutant as a simplified platform for studies of ARF function and demonstrate that repressing ARFs regulate auxin-induced genes and fine-tune their expression. Further the repressing ARFs coordinate gene induction jointly with activating ARFs and the Aux/IAAs. PMID:27247276

  9. The Effects of High Steady State Auxin Levels on Root Cell Elongation in Brachypodium.

    Science.gov (United States)

    Pacheco-Villalobos, David; Díaz-Moreno, Sara M; van der Schuren, Alja; Tamaki, Takayuki; Kang, Yeon Hee; Gujas, Bojan; Novak, Ondrej; Jaspert, Nina; Li, Zhenni; Wolf, Sebastian; Oecking, Claudia; Ljung, Karin; Bulone, Vincent; Hardtke, Christian S

    2016-05-01

    The long-standing Acid Growth Theory of plant cell elongation posits that auxin promotes cell elongation by stimulating cell wall acidification and thus expansin action. To date, the paucity of pertinent genetic materials has precluded thorough analysis of the importance of this concept in roots. The recent isolation of mutants of the model grass species Brachypodium distachyon with dramatically enhanced root cell elongation due to increased cellular auxin levels has allowed us to address this question. We found that the primary transcriptomic effect associated with elevated steady state auxin concentration in elongating root cells is upregulation of cell wall remodeling factors, notably expansins, while plant hormone signaling pathways maintain remarkable homeostasis. These changes are specifically accompanied by reduced cell wall arabinogalactan complexity but not by increased proton excretion. On the contrary, we observed a tendency for decreased rather than increased proton extrusion from root elongation zones with higher cellular auxin levels. Moreover, similar to Brachypodium, root cell elongation is, in general, robustly buffered against external pH fluctuation in Arabidopsis thaliana However, forced acidification through artificial proton pump activation inhibits root cell elongation. Thus, the interplay between auxin, proton pump activation, and expansin action may be more flexible in roots than in shoots. PMID:27169463

  10. An INDEHISCENT-Controlled Auxin Response Specifies the Separation Layer in Early Arabidopsis Fruit.

    Science.gov (United States)

    van Gelderen, Kasper; van Rongen, Martin; Liu, An'an; Otten, Anne; Offringa, Remko

    2016-06-01

    Seed dispersal is an important moment in the life cycle of a plant species. In Arabidopsis thaliana, it is dependent on transcription factor INDEHISCENT (IND)-mediated specification of a separation layer in the dehiscence zone found in the margin between the valves (carpel walls) and the central replum of the developing fruit. It was proposed that IND specifies the separation layer by inducing a local auxin minimum at late stages of fruit development. Here we show that morphological differences between the ind mutant and wild-type fruit already arise at early stages of fruit development, coinciding with strong IND expression in the valve margin. We show that IND-reduced PIN-FORMED3 (PIN3) auxin efflux carrier abundance leads to an increased auxin response in the valve margin during early fruit development, and that the concomitant cell divisions that form the dehiscence zone are lacking in ind mutant fruit. Moreover, IND promoter-driven ectopic expression of the AGC kinases PINOID (PID) and WAG2 induced indehiscence by expelling auxin from the valve margin at stages 14-16 of fruit development through increased PIN3 abundance. Our results show that IND, besides its role at late stages of Arabidopsis fruit development, functions at early stages to facilitate the auxin-triggered cell divisions that form the dehiscence zone. PMID:26995296

  11. Arabidopsis GLP4 is localized to the Golgi and binds auxin in vitro

    Institute of Scientific and Technical Information of China (English)

    Ke Yin; Xinxin Han; Zhihong Xu; Hongwei Xue

    2009-01-01

    Hormones are critical for cell differentiation,elongation, and division. The plant hormone auxin plays vital roles in plant growth and development and is essential for various physiologic processes. Previous studies showed that germin-like proteins (GLPs) are involved in multiple physiologic and developmental processes and that several GLP members could bind different auxin molecules. Here we showed that Arabidopsis thaliana GLP4 gene, which has a length of 660 bp and encodes a 219-aa polypeptide, contains the conserved auxin-binding region box A and hinds indole-3-acetic acid and 2,4-dichlorophenoxyacetic acid (2,4-D) with low affinity, but not α-naphthaleneacetic acid, in vitro,by using assays equilibrium dialysis and nuclear magnetic resonance. This hinding character is different from that of auxin-binding protein 1, which does not hind 2,4-D. GLP4 is highly transcribed in various tissues, but it shows low transcription in roots and during embryo development. In addition, transcription of GLP4 is stimulated by auxin treatment. Suhcellular localization studies indicated that GLP4 protein is localized in the Golgi compartment and the N-terminus of GLP4 is crucial for its proper localization, which suggests that GLP4 may be involved in Goigi-dependent developmental processes.

  12. The Effects of High Steady State Auxin Levels on Root Cell Elongation in Brachypodium[OPEN

    Science.gov (United States)

    Pacheco-Villalobos, David; Tamaki, Takayuki; Gujas, Bojan; Jaspert, Nina; Oecking, Claudia; Bulone, Vincent; Hardtke, Christian S.

    2016-01-01

    The long-standing Acid Growth Theory of plant cell elongation posits that auxin promotes cell elongation by stimulating cell wall acidification and thus expansin action. To date, the paucity of pertinent genetic materials has precluded thorough analysis of the importance of this concept in roots. The recent isolation of mutants of the model grass species Brachypodium distachyon with dramatically enhanced root cell elongation due to increased cellular auxin levels has allowed us to address this question. We found that the primary transcriptomic effect associated with elevated steady state auxin concentration in elongating root cells is upregulation of cell wall remodeling factors, notably expansins, while plant hormone signaling pathways maintain remarkable homeostasis. These changes are specifically accompanied by reduced cell wall arabinogalactan complexity but not by increased proton excretion. On the contrary, we observed a tendency for decreased rather than increased proton extrusion from root elongation zones with higher cellular auxin levels. Moreover, similar to Brachypodium, root cell elongation is, in general, robustly buffered against external pH fluctuation in Arabidopsis thaliana. However, forced acidification through artificial proton pump activation inhibits root cell elongation. Thus, the interplay between auxin, proton pump activation, and expansin action may be more flexible in roots than in shoots. PMID:27169463

  13. Regulated protein depletion by the auxin-inducible degradation system in Drosophila melanogaster.

    Science.gov (United States)

    Trost, Martina; Blattner, Ariane C; Lehner, Christian F

    2016-01-01

    The analysis of consequences resulting after experimental elimination of gene function has been and will continue to be an extremely successful strategy in biological research. Mutational elimination of gene function has been widely used in the fly Drosophila melanogaster. RNA interference is used extensively as well. In the fly, exceptionally precise temporal and spatial control over elimination of gene function can be achieved in combination with sophisticated transgenic approaches and clonal analyses. However, the methods that act at the gene and transcript level cannot eliminate protein products which are already present at the time when mutant cells are generated or RNA interference is started. Targeted inducible protein degradation is therefore of considerable interest for controlled rapid elimination of gene function. To this end, a degradation system was developed in yeast exploiting TIR1, a plant F box protein, which can recruit proteins with an auxin-inducible degron to an E3 ubiquitin ligase complex, but only in the presence of the phytohormone auxin. Here we demonstrate that the auxin-inducible degradation system functions efficiently also in Drosophila melanogaster. Neither auxin nor TIR1 expression have obvious toxic effects in this organism, and in combination they result in rapid degradation of a target protein fused to the auxin-inducible degron. PMID:27010248

  14. Targeted cell elimination reveals an auxin-guided biphasic mode of lateral root initiation

    Science.gov (United States)

    Marhavý, Peter; Montesinos, Juan Carlos; Abuzeineh, Anas; Van Damme, Daniel; Vermeer, Joop E.M.; Duclercq, Jerôme; Rakusová, Hana; Nováková, Petra; Friml, Jiři; Geldner, Niko; Benková, Eva

    2016-01-01

    To sustain a lifelong ability to initiate organs, plants retain pools of undifferentiated cells with a preserved proliferation capacity. The root pericycle represents a unique tissue with conditional meristematic activity, and its tight control determines initiation of lateral organs. Here we show that the meristematic activity of the pericycle is constrained by the interaction with the adjacent endodermis. Release of these restraints by elimination of endodermal cells by single-cell ablation triggers the pericycle to re-enter the cell cycle. We found that endodermis removal substitutes for the phytohormone auxin-dependent initiation of the pericycle meristematic activity. However, auxin is indispensable to steer the cell division plane orientation of new organ-defining divisions. We propose a dual, spatiotemporally distinct role for auxin during lateral root initiation. In the endodermis, auxin releases constraints arising from cell-to-cell interactions that compromise the pericycle meristematic activity, whereas, in the pericycle, auxin defines the orientation of the cell division plane to initiate lateral roots. PMID:26883363

  15. Osmoregulation in the Avena coleoptile in relation to auxin and growth

    Energy Technology Data Exchange (ETDEWEB)

    Stevenson, T.T.; Cleland, R.E.

    1981-04-01

    A study has been made of the effects of auxin and growth on the ability of Avena coleoptile sections to osmoregulate, i.e., to take up solutes so as to maintain their osmotic concentration, turgor pressure, and growth rate. The high auxin-induced growth rate of Avena coleoptiles is maintained when cells are provided sucrose, glucose, NaCl, or KCl as a source of absorbable solutes, but not when 2-deoxy-O-glucose or 3-O-methyl-O-glucose is used. In the absence of auxin, cells take up solutes from a 2% sucrose solution and the osmotic concentration increases. Solute uptake is not stimulated by auxin when growth is inhibited osmotically or by calcium ions. Solute uptake appears to have two components: a basal rate, independent of auxin or growth, and an additional uptake which is proportional to growth. Osmoregulation of sections may be limited by the rate of entry of solutes into the tissue rather than by their rate of uptake into the cells.

  16. Something old, something new: auxin and strigolactone interact in the ancient mycorrhizal symbiosis.

    Science.gov (United States)

    Foo, Eloise

    2013-04-01

    Arbuscular mycorrhizal symbiosis, formed between more than 80% of land plants and fungi from the phylum Glomeromycota, is an ancient association that is believed to have evolved as plants moved onto land more than 400 mya. Similarly ancient, the plant hormones auxin and strigolactone are thought to have been present in the plant lineage since before the divergence of the bryophytes in the case of auxin and before the colonisation of land in the case of strigolactones. The discovery of auxin in the 1930s predates the discovery of strigolactones as a plant hormone in 2008 by over 70 y. Recent studies in pea suggest that these two signals may interact to regulate mycorrhizal symbiosis. Furthermore, the first quantitative studies are presented that show that low auxin content of the root is correlated with low strigolactone production, an interaction that has implications for how these plant hormones regulate several developmental programs including shoot branching, secondary growth and root development. With recent advances in our understanding of auxin and strigolactone biosynthesis, together with the discovery of the fungal signals that activate the plant host, the stage is set for real breakthroughs in our understanding of the interactions between plant and fungal signals in mycorrhizal symbiosis. PMID:23333973

  17. Constitutive auxin response in Physcomitrella reveals complex interactions between Aux/IAA and ARF proteins

    Science.gov (United States)

    Lavy, Meirav; Prigge, Michael J; Tao, Sibo; Shain, Stephanie; Kuo, April; Kirchsteiger, Kerstin; Estelle, Mark

    2016-01-01

    The coordinated action of the auxin-sensitive Aux/IAA transcriptional repressors and ARF transcription factors produces complex gene-regulatory networks in plants. Despite their importance, our knowledge of these two protein families is largely based on analysis of stabilized forms of the Aux/IAAs, and studies of a subgroup of ARFs that function as transcriptional activators. To understand how auxin regulates gene expression we generated a Physcomitrella patens line that completely lacks Aux/IAAs. Loss of the repressors causes massive changes in transcription with misregulation of over a third of the annotated genes. Further, we find that the aux/iaa mutant is blind to auxin indicating that auxin regulation of transcription occurs exclusively through Aux/IAA function. We used the aux/iaa mutant as a simplified platform for studies of ARF function and demonstrate that repressing ARFs regulate auxin-induced genes and fine-tune their expression. Further the repressing ARFs coordinate gene induction jointly with activating ARFs and the Aux/IAAs. DOI: http://dx.doi.org/10.7554/eLife.13325.001 PMID:27247276

  18. Auxin increases the hydrogen peroxide (H2O2) concentration in tomato (Solanum lycopersicum) root tips while inhibiting root growth

    NARCIS (Netherlands)

    Ivanchenko, Maria G.; den Os, Desiree; Monshausen, Gabriele B.; Dubrovsky, Joseph G.; Bednarova, Andrea; Krishnan, Natraj

    2013-01-01

    The hormone auxin and reactive oxygen species (ROS) regulate root elongation, but the interactions between the two pathways are not well understood. The aim of this study was to investigate how auxin interacts with ROS in regulating root elongation in tomato, Solanum lycopersicum. Wild-type and auxi

  19. Expression of auxin synthesis gene tms1 under control of tuber-specific promoter enhances potato tuberization in vitro

    Institute of Scientific and Technical Information of China (English)

    Oksana O Kolachevskaya; Valeriya V Alekseeva; Lidiya I Sergeeva; Elena B Rukavtsova; Irina A Getman; Dick Vreugdenhil; Yaroslav I Buryanov; Georgy A Romanov

    2015-01-01

    Phytohormones, auxins in particular, play an important role in plant development and productivity. Earlier data showed positive impact of exogenous auxin on potato (Solanum tuberosum L.) tuberization. The aim of this study was to generate potato plants with increased auxin level predominantly in tubers. To this end, a pBinB33-tms1 vector was constructed harboring the Agrobacterium auxin biosynthesis gene tms1 fused to tuber-specific promoter of the class I patatin gene (B33-promoter) of potato. Among numerous independently generated B33:tms1 lines, those without visible differences from control were selected for detailed studies. In the majority of transgenic lines, tms1 gene transcription was detected, mostly in tubers rather than in shoots. Indoleacetic acid (IAA) content in tubers and the auxin tuber-to-shoot ratio were increased in tms1-expressing transformants. The organ-specific increase in auxin synthesis in B33:tms1-transformants accelerated and intensified the process of tuber formation, reduced the dose of carbohydrate supply required for in vitro tuber-ization, and decreased the photoperiodic dependence of tuber initiation. Overall, a positive correlation was observed between tms1 expression, IAA content in tubers, and stimulation of tuber formation. The revealed proper-ties of B33:tms1 transformants imply an important role for auxin in potato tuberization and offer prospects to magnify potato productivity by a moderate organ-specific enhance-ment of auxin content.

  20. Inhibition of auxin-induced ethylene production by lycoricidinol

    International Nuclear Information System (INIS)

    Lycoricidinol, a natural growth inhibitor isolated from bulbs of Lycoris radiata Herb. strongly suppressed auxin-induced ethylene production from the hypocotyl segments of etiolated mung bean (Vigna radiata Wilczek) seedlings. The inhibitor did not significantly inhibit ethylene formation from its immediate precursor, 1-aminocyclopropane-1-carboxylic acid (ACC), during short-term (up to 4h) incubation. The ACC content in tissue treated with IAA was reduced by lycoricidinol in close parallel with the inhibition of ethylene production. Examination of radioactive metabolites in tissues labeled with 3,4-14C-methionine indicated that reduction of the ACC content was not due to any possible promotive effect of lycoricidinol on conjugation of ACC with malonate. Lycoricidinol showed no inhibitory effect on the activity of ACC synthase if applied in vitro, but it almost completely abolished the increase in the enzyme activity when applied in vivo during incubation of the tissue with IAA. Lycoricidinol also strongly inhibited incorporation of 14C-leucine into protein in the tissue. The suppression of the enzyme induction and, in turn, that of ethylene production by lycoricidinol were interpreted as being due to the inhibition of protein synthesis. (author)

  1. Inhibition of auxin-induced ethylene production by lycoricidinol

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Bin-G.; Lee, June-S.; Oh, Seung-Eun (Yonsei Univ., Seoul (Republic of Korea)); Horiuchi, Yuko; Imaseki, Hidemasa

    1984-03-01

    Lycoricidinol, a natural growth inhibitor isolated from bulbs of Lycoris radiata Herb. strongly suppressed auxin-induced ethylene production from the hypocotyl segments of etiolated mung bean (Vigna radiata Wilczek) seedlings. The inhibitor did not significantly inhibit ethylene formation from its immediate precursor, 1-aminocyclopropane-1-carboxylic acid (ACC), during short-term (up to 4h) incubation. The ACC content in tissue treated with IAA was reduced by lycoricidinol in close parallel with the inhibition of ethylene production. Examination of radioactive metabolites in tissues labeled with 3,4-/sup 14/C-methionine indicated that reduction of the ACC content was not due to any possible promotive effect of lycoricidinol on conjugation of ACC with malonate. Lycoricidinol showed no inhibitory effect on the activity of ACC synthase if applied in vitro, but it almost completely abolished the increase in the enzyme activity when applied in vivo during incubation of the tissue with IAA. Lycoricidinol also strongly inhibited incorporation of /sup 14/C-leucine into protein in the tissue. The suppression of the enzyme induction and, in turn, that of ethylene production by lycoricidinol were interpreted as being due to the inhibition of protein synthesis.

  2. Reassessing the role of N-hydroxytryptamine in auxin biosynthesis.

    Science.gov (United States)

    Tivendale, Nathan D; Davies, Noel W; Molesworth, Peter P; Davidson, Sandra E; Smith, Jason A; Lowe, Edwin K; Reid, James B; Ross, John J

    2010-12-01

    The tryptamine pathway is one of five proposed pathways for the biosynthesis of indole-3-acetic acid (IAA), the primary auxin in plants. The enzymes AtYUC1 (Arabidopsis thaliana), FZY (Solanum lycopersicum), and ZmYUC (Zea mays) are reported to catalyze the conversion of tryptamine to N-hydroxytryptamine, putatively a rate-limiting step of the tryptamine pathway for IAA biosynthesis. This conclusion was based on in vitro assays followed by mass spectrometry or HPLC analyses. However, there are major inconsistencies between the mass spectra reported for the reaction products. Here, we present mass spectral data for authentic N-hydroxytryptamine, 5-hydroxytryptamine (serotonin), and tryptamine to demonstrate that at least some of the published mass spectral data for the YUC in vitro product are not consistent with N-hydroxytryptamine. We also show that tryptamine is not metabolized to IAA in pea (Pisum sativum) seeds, even though a PsYUC-like gene is strongly expressed in these organs. Combining these findings, we propose that at present there is insufficient evidence to consider N-hydroxytryptamine an intermediate for IAA biosynthesis. PMID:20974893

  3. Auxin biosynthesis in pea: characterization of the tryptamine pathway.

    Science.gov (United States)

    Quittenden, Laura J; Davies, Noel W; Smith, Jason A; Molesworth, Peter P; Tivendale, Nathan D; Ross, John J

    2009-11-01

    One pathway leading to the bioactive auxin, indole-3-acetic acid (IAA), is known as the tryptamine pathway, which is suggested to proceed in the sequence: tryptophan (Trp), tryptamine, N-hydroxytryptamine, indole-3-acetaldoxime, indole-3-acetaldehyde (IAAld), IAA. Recently, this pathway has been characterized by the YUCCA genes in Arabidopsis (Arabidopsis thaliana) and their homologs in other species. YUCCA is thought to be responsible for the conversion of tryptamine to N-hydroxytryptamine. Here we complement the genetic findings with a compound-based approach in pea (Pisum sativum), detecting potential precursors by gas chromatography/tandem-mass spectrometry. In addition, we have synthesized deuterated forms of many of the intermediates involved, and have used them to quantify the endogenous compounds, and to investigate their metabolic fates. Trp, tryptamine, IAAld, indole-3-ethanol, and IAA were detected as endogenous constituents, whereas indole-3-acetaldoxime and one of its products, indole-3-acetonitrile, were not detected. Metabolism experiments indicated that the tryptamine pathway to IAA in pea roots proceeds in the sequence: Trp, tryptamine, IAAld, IAA, with indole-3-ethanol as a side-branch product of IAAld. N-hydroxytryptamine was not detected, but we cannot exclude that it is an intermediate between tryptamine and IAAld, nor can we rule out the possibility of a Trp-independent pathway operating in pea roots. PMID:19710233

  4. The epidermis of the pea epicotyl is not a unique target tissue for auxin-induced growth

    Science.gov (United States)

    Rayle, D. L.; Nowbar, S.; Cleland, R. E.

    1991-01-01

    Previous research has suggested that the epidermis of dicotyledonous stems is the primary site of auxin action in elongation growth. We show for pea (Pisum sativum L.) epicotyl sections that this hypothesis is incorrect. In buffer (pH 6.5), sections from which the outer cell layers were removed (peeled) elongated slowly and to the same extent as intact sections. Addition of 10 micromolar indoleacetic acid to this incubation medium caused peeled sections to grow to the same extent and with the same kinetics as auxin-treated nonpeeled sections. This indicates that both epidermis and cortical tissues have the ability to respond rapidly to auxin and that the epidermis is not the sole site of auxin action in dicotyledonous stems. Previous reports that peeled pea sections respond poorly to auxin may have resulted from an acid extension of these sections due to the use of distilled water as the incubation medium.

  5. Sorting Motifs Involved in the Trafficking and Localization of the PIN1 Auxin Efflux Carrier.

    Science.gov (United States)

    Sancho-Andrés, Gloria; Soriano-Ortega, Esther; Gao, Caiji; Bernabé-Orts, Joan Miquel; Narasimhan, Madhumitha; Müller, Anna Ophelia; Tejos, Ricardo; Jiang, Liwen; Friml, Jiří; Aniento, Fernando; Marcote, María Jesús

    2016-07-01

    In contrast with the wealth of recent reports about the function of μ-adaptins and clathrin adaptor protein (AP) complexes, there is very little information about the motifs that determine the sorting of membrane proteins within clathrin-coated vesicles in plants. Here, we investigated putative sorting signals in the large cytosolic loop of the Arabidopsis (Arabidopsis thaliana) PIN-FORMED1 (PIN1) auxin transporter, which are involved in binding μ-adaptins and thus in PIN1 trafficking and localization. We found that Phe-165 and Tyr-280, Tyr-328, and Tyr-394 are involved in the binding of different μ-adaptins in vitro. However, only Phe-165, which binds μA(μ2)- and μD(μ3)-adaptin, was found to be essential for PIN1 trafficking and localization in vivo. The PIN1:GFP-F165A mutant showed reduced endocytosis but also localized to intracellular structures containing several layers of membranes and endoplasmic reticulum (ER) markers, suggesting that they correspond to ER or ER-derived membranes. While PIN1:GFP localized normally in a μA (μ2)-adaptin mutant, it accumulated in big intracellular structures containing LysoTracker in a μD (μ3)-adaptin mutant, consistent with previous results obtained with mutants of other subunits of the AP-3 complex. Our data suggest that Phe-165, through the binding of μA (μ2)- and μD (μ3)-adaptin, is important for PIN1 endocytosis and for PIN1 trafficking along the secretory pathway, respectively. PMID:27208248

  6. The chloroindole auxins of pea, strong plant growth hormones or endogenous herbicides

    International Nuclear Information System (INIS)

    In this work the three theses below are discussed: 1) Identification and quantitative determination of the very strong plant hormone, the auxin 4-chloroindole-3-acetic acid methyl ester, in immature seeds of Pisum, Vicia, Lathyrus, and Lens spp. by incorporation of radioactive 36Cl, thin layer chromatography, autoradiography, colour reactions, and gas chromatography/mass spectrometry. 2) The strong biological activity of 4-chloroindole-3-acetic acid and its analogues and its ability to induce strong, almost irreversible, ethylene evolution. 3) The possible role of chloroindole auxin in plants, particularly if it might be the hypothetical death hormone, secreted from developing seeds, which induces senescence and kills the mother plant at maturity; if plants generally have several auxin types, growth promoters and endogenous herbicides; and if other chlorine-containing plant hormones occur in developing seeds of other crop species. (au) (7 tabs., 8 ills., 144 refs.)

  7. The diageotropica mutant of tomato lacks high specific activity auxin sites

    Energy Technology Data Exchange (ETDEWEB)

    Hicks, G.R.; Lomax, T.L. (Oregon State Univ., Corvallis (USA)); Rayle, D.L. (San Diego State Univ., CA (USA))

    1989-04-01

    Tomato (Lycopersicum esculentum, Mill) plants homozygous for the single gene diageotropica (dgt) mutation have reduced shoot growth, abnormal vascular tissue, altered leaf morphology, and lack of lateral root branching. These and other morphological and physiological abnormalities suggest that dgt plants are unable to respond to the plant growth hormone auxin (indole-3-acetic acid, IAA). The photoaffinity auxin analogue {sup 3}H-5N{sub 3}-IAA specifically labels a polypeptide doublet of 40 ad 42 kD in membrane preparations from stems of the parental variety VFN8, but not from stems of dgt. In elongation tests, excised dgt roots respond in the same manner to IAA an VFN8 roots. These data suggest that the two polypeptides are part of a physiologically important auxin receptor system which is altered in a tissue-specific manner in the mutant.

  8. Evidence That Chlorinated Auxin Is Restricted to the Fabaceae But Not to the Fabeae.

    Science.gov (United States)

    Lam, Hong Kiat; McAdam, Scott A M; McAdam, Erin L; Ross, John J

    2015-07-01

    Auxin is a pivotal plant hormone, usually occurring in the form of indole-3-acetic acid (IAA). However, in maturing pea (Pisum sativum) seeds, the level of the chlorinated auxin, 4-chloroindole-3-acetic acid (4-Cl-IAA), greatly exceeds that of IAA. A key issue is how plants produce halogenated compounds such as 4-Cl-IAA. To better understand this topic, we investigated the distribution of the chlorinated auxin. We show for the first time, to our knowledge, that 4-Cl-IAA is found in the seeds of Medicago truncatula, Melilotus indicus, and three species of Trifolium. Furthermore, we found no evidence that Pinus spp. synthesize 4-Cl-IAA in seeds, contrary to a previous report. The evidence indicates a single evolutionary origin of 4-Cl-IAA synthesis in the Fabaceae, which may provide an ideal model system to further investigate the action and activity of halogenating enzymes in plants. PMID:25971549

  9. The chloroindole auxins of pea, strong plant growth hormones or endogenous herbicides

    Energy Technology Data Exchange (ETDEWEB)

    Engvild, K.C.

    1994-02-01

    In this work the three theses below are discussed: (1) Identification and quantitative determination of the very strong plant hormone, the auxin 4-chloroindole-3-acetic acid methyl ester, in immature seeds of Pisum, Vicia, Lathyrus, and Lens spp. by incorporation of radioactive {sup 36}Cl, thin layer chromatography, autoradiography, colour reactions, and gas chromatography/mass spectrometry. (2) The strong biological activity of 4-chloroindole-3-acetic acid and its analogues and its ability to induce strong, almost irreversible, ethylene evolution. (3) The possible role of chloroindole auxin in plants, particularly if it might be the hypothetical death hormone, secreted from developing seeds, which induces senescence and kills the mother plant at maturity; if plants generally have several auxin types, growth promoters and endogenous herbicides; and if other chlorine-containing plant hormones occur in developing seeds of other crop species. (au) (7 tabs., 8 ills., 144 refs.).

  10. Disruptions in AUX1-Dependent Auxin Influx Alter Hypocotyl Phototropism in Arabidopsis

    Institute of Scientific and Technical Information of China (English)

    Bethany B.Stone; Emily L.Stowe-Evans; Reneé M.Harper; R.Brandon Celaya; Karin Ljung; G(o)ran Sandberg; Emmanuel Liscum

    2008-01-01

    Phototropism represents a differential growth response by which plant organs can respond adaptively to changes in the direction of incident light to optimize leaf/stem positioning for photosynthetic light capture and root growth orientation for water/nutrient acquisition. Studies over the past few years have identified a number of components in the signaling pathway(s) leading to development of phototropic curvatures in hypocotyls. These include the phototropin photoreceptors (phot1 and phot2) that perceive directional blue-light (BL) cues and then stimulate signaling,leading to relocalization of the plant hormone auxin, as well as the auxin response factor NPH4/ARF7 that responds to changes in local auxin concentrations to directly mediate expression of genes likely encoding proteins necessary for development of phototropic curvatures. While null mutations in NPH4/ARF7 condition an aphototropic response to unidirectional BL, seedlings carrying the same mutations recover BL-dependent phototropic responsiveness if coirradiated with red light (RL) or pre-treated with either ethylene. In the present study, we identify second-site enhancer mutations in the nph4 background that abrogate these recovery responses. One of these mutations-map1 ((m)odifier of (a)rf7 (p)henotypes (1))-was found to represent a missense allele of AUX1-a gene encoding a high-affinity auxin influx carrier previously associated with a number of root responses. Pharmocological studies and analyses of additional aux1 mutants confirmed that AUX1 functions as a modulator of hypocotyl phototropism. Moreover, we have found that the strength of dependence of hypocotyl phototropism on AUX1-mediated auxin influx is directly related to the auxin responsiveness of the seedling in question.

  11. An auxin responsive CLE gene regulates shoot apical meristem development in Arabidopsis

    Directory of Open Access Journals (Sweden)

    Hongyan eGuo

    2015-05-01

    Full Text Available Plant hormone auxin regulates most, if not all aspects of plant growth and development, including lateral root formation, organ pattering, apical dominance and tropisms. Peptide hormones are peptides with hormone activities. Some of the functions of peptide hormones in regulating plant growth and development are similar to that of auxin, however, the relationship between auxin and peptide hormones remains largely unknown. Here we report the identification of OsCLE48, a rice (Oryza sativa CLE (CLAVATA3/ENDOSPERM SURROUNDING REGION gene, as an auxin response gene, and the functional characterization of OsCLE48 in Arabidopsis and rice. OsCLE48 encodes a CLE peptide hormone that is similar to Arabidopsis CLEs. RT-PCR analysis showed that OsCLE48 was induced by exogenously application of IAA (indole-3-acetic acid, a naturally occurred auxin. Expression of integrated OsCLE48p:GUS reporter gene in transgenic Arabidopsis plants was also induced by exogenously IAA treatment. These results indicate that OsCLE48 is an auxin responsive gene. Histochemical staining showed that GUS activity was detected in all the tissue and organs of the OsCLE48p:GUS transgenic Arabidopsis plants. Expression of OsCLE48 under the control of the 35S promoter in Arabidopsis inhibited shoot apical meristem development. Expression of OsCLE48 under the control of the CLV3 native regulatory elements almost completely complemented clv3-2 mutant phenotypes, suggesting that OsCLE48 is functionally similar to CLV3. On the other hand, expression of OsCLE48 under the control of the 35S promoter in Arabidopsis has little, if any effects on root apical meristem development, and transgenic rice plants overexpressing OsCLE48 are morphologically indistinguishable from wild type plants, suggesting that the functions of some CLE peptides may not be fully conserved in Arabidopsis and rice.

  12. Simple Identification of the Neutral Chlorinated Auxin in Pea by Thin Layer Chromatography

    DEFF Research Database (Denmark)

    Engvild, Kjeld Christensen

    1980-01-01

    One of the neutral chlorinated auxins of immature pea seeds was readily identified by thin layer procedures simple enough to serve in student's laboratory courses. 4-Chloroindole-3-acetic acid methyl ester was extracted from 50 g of commercial, frozen peas by either water or acetone, concentrated...... to small volumes and chromatographed in CHCl3 or CCl4 solvent systems separating the chlorinated auxin from indoleacetonitrile and the methyl or ethyl esters of indoleacetic acid. Colour reaction was carried out with some of the Salkowski FeCl3 sprays of which Ehmann's FeCl3/dimethylaminobenzaldehyde...

  13. Changes in auxin level in the course of growth of a sunflower crown-gall suspension culture

    Directory of Open Access Journals (Sweden)

    Zofia Chirek

    2014-02-01

    Full Text Available The auxin level in the cell mass and culture medium was determined by means of the Avena straight caleoptile test in various periods of the suspension culture cycle of the sunflower crown-gall tumour. The investigations were performed in the course of the zero passage (PO and first one (Pl, differing in their time of duration of maximum growth and its intensity. In both passages the intra- and extra-cellular auxin levels reach values of the same order. At the beginning of the maximal growth phase the activity corresponding to IAA in the cells prevails over that of the other auxin-like compounds. This disproportion diminishes with further development of the culture, and with the beginning of the stationary phase the cellular IAA level is lower than that of the remaining auxin-like compounds. The short phase of maximal growth (PO occurs with an auxin level decreasing in the cell mass and increasing in the medium, and towards the end of the cycle these levels become equal. During the long phase of maximal growth (Pl the total amount of auxins in the cells increases and is 2-3 times higher than in the medium, whereas IAA in the cells remains at a constant level. These results suggest that the participation of IAA in the intracellular pool of auxin-like substances is decisive for the mitotic activity of the cells and maintenance of growth in the culture.

  14. Complete disintegration of the microtubular cytoskeleton precedes its auxin-mediated reconstruction in postmitotic maize root cells

    Science.gov (United States)

    Baluska, F.; Barlow, P. W.; Volkmann, D.

    1996-01-01

    The inhibitory action of 0.1 microM auxin (IAA) on maize root growth was closely associated with a rapid and complete disintegration of the microtubular (MT) cytoskeleton, as visualized by indirect immunofluorescence of tubulin, throughout the growth region. After 30 min of this treatment, only fluorescent spots were present in root cells, accumulating either around nuclei or along cell walls. Six h later, in addition to some background fluorescence, dense but partially oriented oblique or longitudinal arrays of cortical MTs (CMTs) were found in most growing cells of the root apex. After 24 h of treatment, maize roots had adapted to the auxin, as inferred from the slowly recovering elongation rate and from the reassembly of a dense and well-ordered MT cytoskeleton which showed only slight deviations from that of the control root cells. Taxol pretreatment (100 microM, 24 h) prevented not only the rapid auxin-mediated disintegration of the MT cytoskeleton but also a reorientation of the CMT arrays, from transversal to longitudinal. The only tissue to show MTs in their cells throughout the auxin treatment was the epidermis. Significant resistance of transverse CMT arrays in these cells towards auxin was confirmed using a higher auxin concentration (100 microM, 24 h). The latter auxin dose also revealed inter-tissue-specific responses to auxin: outer cortical cell files reoriented their CMTs from the transversal to longitudinal orientation, whereas inner cortical cell files lost their MTs. This high auxin-mediated response, associated with the swelling of root apices, was abolished with the pretreatment of maize root with taxol.

  15. 7-Rhamnosylated Flavonols Modulate Homeostasis of the Plant Hormone Auxin and Affect Plant Development

    Czech Academy of Sciences Publication Activity Database

    Kuhn, B.M.; Errafi, S.; Bucher, R.; Dobrev, Petre; Geisler, M.; Bigler, L.; Zažímalová, Eva; Ringli, Ch.

    2016-01-01

    Roč. 291, č. 10 (2016), s. 5385-5395. ISSN 0021-9258 R&D Projects: GA ČR(CZ) GAP305/11/0797 Institutional support: RVO:61389030 Keywords : Arabidopsis thaliana * auxin * flavonoid Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 4.573, year: 2014

  16. Transcriptional regulation of auxin metabolism and ethylene biosynthesis activation during apple (Malus × domestica) fruit maturation

    Science.gov (United States)

    Variation exists among apple genotypes in fruit maturation and ripening patterns that influences at13 harvest fruit firmness and postharvest storability. Based on the results from our previous large-scale 14 transcriptome profiling on apple fruit maturation and well-documented auxin-ethylene crossta...

  17. Role of phytohormones ethylene and auxin in plant-nematode interactions: mini-review

    Science.gov (United States)

    The phytohormones ethylene and auxin regulate many important processes in plants, including cell differentiation, cell expansion, and responses to abiotic stresses. These hormones also play important roles in many plant-pathogen interactions, including regulation of plant defense responses and symp...

  18. Cytokinin Modulates Endocytic Trafficking of PIN1 Auxin Efflux Carrier to Control Plant Organogenesis

    Czech Academy of Sciences Publication Activity Database

    Marhavý, P.; Bielach, A.; Abas, L.; Abuzeineh, A.; Duclercq, J.; Tanaka, H.; Pařezová, Markéta; Petrášek, Jan; Friml, J.; Kleine-Vehn, J.; Benková, E.

    2011-01-01

    Roč. 21, č. 4 (2011), s. 796-804. ISSN 1534-5807 R&D Projects: GA AV ČR(CZ) IAA601630703; GA MŠk(CZ) LC06034 Institutional research plan: CEZ:AV0Z50380511 Keywords : auxin efflux * cytokinin * vacuoles * membrane trafficking Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 14.030, year: 2011

  19. Auxin is required for pollination-induced ovary growth in Dendrobium orchids

    NARCIS (Netherlands)

    Ketsa, S.; Wisutiamonkul, A.; Doorn, van W.G.

    2006-01-01

    In Dendrobium and other orchids the ovule becomes mature long after pollination, whereas the ovary starts growing within two days of pollination. The signalling pathway that induces rapid ovary growth after pollination has remained elusive. We placed the auxin antagonist ¿-(p-chlorophenoxy) isobutyr

  20. Auxin-induced degradation dynamics set the pace for lateral root development

    Science.gov (United States)

    Auxin elicits diverse cell behaviors through a simple nuclear signaling pathway initiated by degradation of Aux/IAA co-repressors. Our previous work revealed that members of the large Arabidopsis Aux/IAA family exhibit a range of degradation rates in synthetic contexts. However, it remained an unr...

  1. Endogenous auxin regulates the sensitivity of Dendrobium (cv. Miss Teen) flower pedicel abscission to ethylene

    NARCIS (Netherlands)

    Rungruchkanont, K.; Ketsa, S.; Chatchawankanphanich, O.; Doorn, van W.G.

    2007-01-01

    Dendrobium flower buds and flowers have an abscission zone at the base of the pedicel (flower stalk). Ethylene treatment of cv. Miss Teen inflorescences induced high rates of abscission in flower buds but did not affect abscission once the flowers had opened. It is not known if auxin is a regulator

  2. Leafy head formation of the progenies of transgenic plants of Chinese cabbage with exogenous auxin genes

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The experiment was performed to evaluate the progenies of plant lines transgenic for auxin synthesis genes derived from Ri T-DNA. Four lines of the transgenic plants were self-crossed and the foreign auxin genes in plants of T5 generation were confirmed by Southern hybridization. Two lines, D1232 and D1653, showed earlier folding of expanding leaves than untransformed line and therefore had early initiation of leafy head. Leaf cuttings derived from plant of transgenic line D1653 produced more adventitious roots than the control whereas the cuttings from folding leaves had much more roots than rosette leaves at folding stage, and the cuttings from head leaves had more roots than rosette leaves at heading stage. It is demonstrated that early folding of transgenic leaf may be caused by the relatively higher concentration of auxin. These plant lines with auxin transgenes can be used for the study of hormonal regulation in differentiation and development of plant organs and for the breeding of new variety with rapid growth trait.

  3. AUXIN RESPONSE FACTOR 2 Intersects Hormonal Signals in the Regulation of Tomato Fruit Ripening

    Science.gov (United States)

    Meir, Sagit; Panizel, Irina; Puig, Clara Pons; Hao, Yanwei; Yifhar, Tamar; Yasuor, Hagai; Zouine, Mohamed; Bouzayen, Mondher; Granell Richart, Antonio; Rogachev, Ilana; Aharoni, Asaph

    2016-01-01

    The involvement of ethylene in fruit ripening is well documented, though knowledge regarding the crosstalk between ethylene and other hormones in ripening is lacking. We discovered that AUXIN RESPONSE FACTOR 2A (ARF2A), a recognized auxin signaling component, functions in the control of ripening. ARF2A expression is ripening regulated and reduced in the rin, nor and nr ripening mutants. It is also responsive to exogenous application of ethylene, auxin and abscisic acid (ABA). Over-expressing ARF2A in tomato resulted in blotchy ripening in which certain fruit regions turn red and possess accelerated ripening. ARF2A over-expressing fruit displayed early ethylene emission and ethylene signaling inhibition delayed their ripening phenotype, suggesting ethylene dependency. Both green and red fruit regions showed the induction of ethylene signaling components and master regulators of ripening. Comprehensive hormone profiling revealed that altered ARF2A expression in fruit significantly modified abscisates, cytokinins and salicylic acid while gibberellic acid and auxin metabolites were unaffected. Silencing of ARF2A further validated these observations as reducing ARF2A expression let to retarded fruit ripening, parthenocarpy and a disturbed hormonal profile. Finally, we show that ARF2A both homodimerizes and interacts with the ABA STRESS RIPENING (ASR1) protein, suggesting that ASR1 might be linking ABA and ethylene-dependent ripening. These results revealed that ARF2A interconnects signals of ethylene and additional hormones to co-ordinate the capacity of fruit tissue to initiate the complex ripening process. PMID:26959229

  4. Leafy head formation of the progenies of transgenic plants of Chinese cabbage with exogenous auxin genes

    Institute of Scientific and Technical Information of China (English)

    HEYUKE; WANXINXUE; 等

    2000-01-01

    The experiment was performed to evaluate the progenies of plant lines transgenic for auxin synthesis genes derived from Ri T-DNA.Four lines of the transgenic plants were self-crossed and the foreign auxin genes in plants of T5 generation were confirmed by Southern hybridization.Two lines,D1232 and D1653,showed earlier folding of expanding leaves than untransformed line and therefore had early initiation of leafy head.Leaf cuttings derived from plant of transgenic line D1653 produced more adventitious roots than the control whereas the cuttings from folding leaves had much more roots than rosette leaves at folding stage,and the cuttings from head leaves had more roots than rosette leaves at heading stage.It is demonstrated that early folding of transgenic leaf may be caused by the relatively higher concentration of auxin.These plant lines with auxin transgenes can be used for the study of hormonal regulation in differentiation and development of plant orgens and for the breeding of new variety with rapid growth trait.

  5. Carbon monoxide interacts with auxin and nitric oxide to cope with iron deficiency in Arabidopsis

    Science.gov (United States)

    To clarify the roles of CO, NO and auxin in the plant response to iron deficiency and to establish how the signaling molecules interact to enhance Fe acquisition, we conducted physiological, genetic, and molecular analyses that compared the responses of various Arabidopsis mutants, including hy1 (CO...

  6. Auxin effects on in vitro and in vivo protein phosphorylation in pea. [Pisum sativum

    Energy Technology Data Exchange (ETDEWEB)

    Gallagher, S.R.; Ray, P.M.

    1987-04-01

    Terminal 8mm sections from the third internode of dark grown 7 day old Pisum sativum cv Alaska seedlings were separated into membrane and soluble fractions. SDS gradient PAGE identified approximately 50 in vivo phosphorylated proteins and proved superior to 2-D SDS PAGE in terms of resolution and repeatability. Addition of indoleacetic acid (IAA), fusicoccin, or 2,4 dichlorophenoxyacetic acid to membranes resulted in no detectable change in the number or phosphorylation level of the labeled proteins during in vitro phosphorylation in the presence of submicromolar concentrations of calcium. Similar results were obtained with soluble proteins. In the absence of calcium, the level of in vitro protein phosphorylation was much less, but not auxin effects could be identified. Furthermore, treatment of the sections with IAA in vivo followed by cell fractionation and in vitro phosphorylation failed to identify auxin responsive proteins. Lastly, when sections were labeled with /sup 32/P inorganic phosphate in the presence of 17 uM IAA, no auxin specific changes were found in the level of phosphorylation or in the number of phosphorylated proteins. Auxin effects on phosphorylation are thus slight or below their detection limit.

  7. Endogenous cytokinins, auxins, and abscisic acid in red algae from Brazil

    Czech Academy of Sciences Publication Activity Database

    Yokoya, N. S.; Stirk, W. A.; van Staden, J.; Novák, Ondřej; Turečková, Veronika; Pěnčík, Aleš; Strnad, Miroslav

    2010-01-01

    Roč. 46, č. 6 (2010), s. 1198-1205. ISSN 0022-3646 R&D Projects: GA ČR GA301/08/1649 Institutional research plan: CEZ:AV0Z50380511 Keywords : ENDOGENOUS * CYTOKININS * AUXINS * ABSCISIC ACID * RED * ALGAE * BRAZIL Subject RIV: EF - Botanics Impact factor: 2.239, year: 2010

  8. Changes in cytokinin and auxin concentrations in seaweed concentrates when stored at an elevated temperature

    Czech Academy of Sciences Publication Activity Database

    Stirk, W. A.; Arthur, G. D.; Lourens, A. F.; Novák, Ondřej; Strnad, Miroslav; van Staden, J.

    2004-01-01

    Roč. 16, č. 1 (2004), s. 31-39. ISSN 0022-3646 R&D Projects: GA ČR GA522/03/0323 Institutional research plan: CEZ:AV0Z5038910 Keywords : accelerated storage * auxins * cytokinins Subject RIV: EF - Botanics Impact factor: 2.490, year: 2004

  9. Boron and blue light reduce responsiveness of Arabidopsis hypocotyls to exogenous auxins

    Czech Academy of Sciences Publication Activity Database

    Stočes, Štěpán; Karlická, Marie; Fellner, Martin

    2012-01-01

    Roč. 66, č. 3 (2012), s. 293-301. ISSN 0167-6903 R&D Projects: GA ČR GA521/09/0445 Institutional research plan: CEZ:AV0Z50380511 Keywords : Arabidopsis thaliana * Auxin * Boron Subject RIV: EF - Botanics Impact factor: 1.670, year: 2012

  10. Diurnal variation of cytokinin, auxin and abscisic acid levels in tobacco leaves

    Czech Academy of Sciences Publication Activity Database

    Nováková, Marie; Motyka, Václav; Dobrev, Petre; Malbeck, Jiří; Gaudinová, Alena

    2005-01-01

    Roč. 56, č. 421 (2005), s. 2877-2883. ISSN 0022-0957 R&D Projects: GA ČR GA206/03/0369; GA MŠk LN00A081 Institutional research plan: CEZ:AV0Z50380511 Keywords : abscisic acid * auxin * cytokinin Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 3.336, year: 2005

  11. Simple Identification of the Neutral Chlorinated Auxin in Pea by Thin Layer Chromatography

    DEFF Research Database (Denmark)

    Engvild, Kjeld Christensen

    1980-01-01

    One of the neutral chlorinated auxins of immature pea seeds was readily identified by thin layer procedures simple enough to serve in student's laboratory courses. 4-Chloroindole-3-acetic acid methyl ester was extracted from 50 g of commercial, frozen peas by either water or acetone, concentrated...

  12. Under-expression of the Auxin Response Factor Sl-ARF4 improves post-harvest behavior of tomato fruits

    OpenAIRE

    Sagar, Maha; Chervin, Christian; Roustan, Jean-Paul; Bouzayen, Mondher; Zouine, Mohamed

    2013-01-01

    Auxin is one of the most prominent phytohormones regulating many aspects of fleshy fruit development including fruit set, fruit size through the control of cell division and cell expansion, and fruit ripening. To shed light on the role of auxin fruit ripening, we have previously shown that Sl-ARF4 is a major player in mediating the auxin control of sugar metabolism in tomato fruit (cv MicroTom). Further extending this study, we show here that down-regulation of Sl-ARF4 in tomato alters some r...

  13. An auxin responsive CLE gene regulates shoot apical meristem development in Arabidopsis.

    Science.gov (United States)

    Guo, Hongyan; Zhang, Wei; Tian, Hainan; Zheng, Kaijie; Dai, Xuemei; Liu, Shanda; Hu, Qingnan; Wang, Xianling; Liu, Bao; Wang, Shucai

    2015-01-01

    Plant hormone auxin regulates most, if not all aspects of plant growth and development, including lateral root formation, organ pattering, apical dominance, and tropisms. Peptide hormones are peptides with hormone activities. Some of the functions of peptide hormones in regulating plant growth and development are similar to that of auxin, however, the relationship between auxin and peptide hormones remains largely unknown. Here we report the identification of OsCLE48, a rice (Oryza sativa) CLE (CLAVATA3/ENDOSPERM SURROUNDING REGION) gene, as an auxin response gene, and the functional characterization of OsCLE48 in Arabidopsis and rice. OsCLE48 encodes a CLE peptide hormone that is similar to Arabidopsis CLEs. RT-PCR analysis showed that OsCLE48 was induced by exogenously application of IAA (indole-3-acetic acid), a naturally occurred auxin. Expression of integrated OsCLE48p:GUS reporter gene in transgenic Arabidopsis plants was also induced by exogenously IAA treatment. These results indicate that OsCLE48 is an auxin responsive gene. Histochemical staining showed that GUS activity was detected in all the tissue and organs of the OsCLE48p:GUS transgenic Arabidopsis plants. Expression of OsCLE48 under the control of the 35S promoter in Arabidopsis inhibited shoot apical meristem development. Expression of OsCLE48 under the control of the CLV3 native regulatory elements almost completely complemented clv3-2 mutant phenotypes, suggesting that OsCLE48 is functionally similar to CLV3. On the other hand, expression of OsCLE48 under the control of the 35S promoter in Arabidopsis has little, if any effects on root apical meristem development, and transgenic rice plants overexpressing OsCLE48 are morphologically indistinguishable from wild type plants, suggesting that the functions of some CLE peptides may not be fully conserved in Arabidopsis and rice. Taken together, our results showed that OsCLE48 is an auxin responsive peptide hormone gene, and it regulates shoot apical

  14. Genome-wide identification and expression profiling of auxin response factor (ARF gene family in maize

    Directory of Open Access Journals (Sweden)

    Zhang Yirong

    2011-04-01

    Full Text Available Abstract Background Auxin signaling is vital for plant growth and development, and plays important role in apical dominance, tropic response, lateral root formation, vascular differentiation, embryo patterning and shoot elongation. Auxin Response Factors (ARFs are the transcription factors that regulate the expression of auxin responsive genes. The ARF genes are represented by a large multigene family in plants. The first draft of full maize genome assembly has recently been released, however, to our knowledge, the ARF gene family from maize (ZmARF genes has not been characterized in detail. Results In this study, 31 maize (Zea mays L. genes that encode ARF proteins were identified in maize genome. It was shown that maize ARF genes fall into related sister pairs and chromosomal mapping revealed that duplication of ZmARFs was associated with the chromosomal block duplications. As expected, duplication of some ZmARFs showed a conserved intron/exon structure, whereas some others were more divergent, suggesting the possibility of functional diversification for these genes. Out of these 31 ZmARF genes, 14 possess auxin-responsive element in their promoter region, among which 7 appear to show small or negligible response to exogenous auxin. The 18 ZmARF genes were predicted to be the potential targets of small RNAs. Transgenic analysis revealed that increased miR167 level could cause degradation of transcripts of six potential targets (ZmARF3, 9, 16, 18, 22 and 30. The expressions of maize ARF genes are responsive to exogenous auxin treatment. Dynamic expression patterns of ZmARF genes were observed in different stages of embryo development. Conclusions Maize ARF gene family is expanded (31 genes as compared to Arabidopsis (23 genes and rice (25 genes. The expression of these genes in maize is regulated by auxin and small RNAs. Dynamic expression patterns of ZmARF genes in embryo at different stages were detected which suggest that maize ARF genes may

  15. Auxin involvement in tepal senescence and abscission in Lilium: a tale of two lilies.

    Science.gov (United States)

    Lombardi, Lara; Arrom, Laia; Mariotti, Lorenzo; Battelli, Riccardo; Picciarelli, Piero; Kille, Peter; Stead, Tony; Munné-Bosch, Sergi; Rogers, Hilary J

    2015-02-01

    Petal wilting and/or abscission terminates the life of the flower. However, how wilting and abscission are coordinated is not fully understood. There is wide variation in the extent to which petals wilt before abscission, even between cultivars of the same species. For example, tepals of Lilium longiflorum wilt substantially, while those of the closely related Lilium longiflorum×Asiatic hybrid (L.A.) abscise turgid. Furthermore, close comparison of petal death in these two Lilium genotypes shows that there is a dramatic fall in fresh weight/dry weight accompanied by a sharp increase in ion leakage in late senescent L. longiflorum tepals, neither of which occur in Lilium L.A. Despite these differences, a putative abscission zone was identified in both lilies, but while the detachment force was reduced to zero in Lilium L.A., wilting of the fused tepals in L. longiflorum occurred before abscission was complete. Abscission is often negatively regulated by auxin, and the possible role of auxin in regulating tepal abscission relative to wilting was tested in the two lilies. There was a dramatic increase in auxin levels with senescence in L. longiflorum but not in Lilium L.A. Fifty auxin-related genes were expressed in early senescent L. longiflorum tepals including 12 ARF-related genes. In Arabidopsis, several ARF genes are involved in the regulation of abscission. Expression of a homologous transcript to Arabidopsis ARF7/19 was 8-fold higher during senescence in L. longiflorum compared with abscising Lilium L.A., suggesting a conserved role for auxin-regulated abscission in monocotyledonous ethylene-insensitive flowers. PMID:25422499

  16. Auxins differentially regulate root system architecture and cell cycle protein levels in maize seedlings.

    Science.gov (United States)

    Martínez-de la Cruz, Enrique; García-Ramírez, Elpidio; Vázquez-Ramos, Jorge M; Reyes de la Cruz, Homero; López-Bucio, José

    2015-03-15

    Maize (Zea mays) root system architecture has a complex organization, with adventitious and lateral roots determining its overall absorptive capacity. To generate basic information about the earlier stages of root development, we compared the post-embryonic growth of maize seedlings germinated in water-embedded cotton beds with that of plants obtained from embryonic axes cultivated in liquid medium. In addition, the effect of four different auxins, namely indole-3-acetic acid (IAA), 1-naphthaleneacetic acid (NAA), indole-3-butyric acid (IBA) and 2,4-dichlorophenoxyacetic acid (2,4-D) on root architecture and levels of the heat shock protein HSP101 and the cell cycle proteins CKS1, CYCA1 and CDKA1 were analyzed. Our data show that during the first days after germination, maize seedlings develop several root types with a simultaneous and/or continuous growth. The post-embryonic root development started with the formation of the primary root (PR) and seminal scutellar roots (SSR) and then continued with the formation of adventitious crown roots (CR), brace roots (BR) and lateral roots (LR). Auxins affected root architecture in a dose-response fashion; whereas NAA and IBA mostly stimulated crown root formation, 2,4-D showed a strong repressing effect on growth. The levels of HSP101, CKS1, CYCA1 and CDKA in root and leaf tissues were differentially affected by auxins and interestingly, HSP101 registered an auxin-inducible and root specific expression pattern. Taken together, our results show the timing of early branching patterns of maize and indicate that auxins regulate root development likely through modulation of the HSP101 and cell cycle proteins. PMID:25615607

  17. Cytokinin and Auxin Display Distinct but Interconnected Distribution and Signaling Profiles to Stimulate Cambial Activity.

    Science.gov (United States)

    Immanen, Juha; Nieminen, Kaisa; Smolander, Olli-Pekka; Kojima, Mikiko; Alonso Serra, Juan; Koskinen, Patrik; Zhang, Jing; Elo, Annakaisa; Mähönen, Ari Pekka; Street, Nathaniel; Bhalerao, Rishikesh P; Paulin, Lars; Auvinen, Petri; Sakakibara, Hitoshi; Helariutta, Ykä

    2016-08-01

    Despite the crucial roles of phytohormones in plant development, comparison of the exact distribution profiles of different hormones within plant meristems has thus far remained scarce. Vascular cambium, a wide lateral meristem with an extensive developmental zonation, provides an optimal system for hormonal and genetic profiling. By taking advantage of this spatial resolution, we show here that two major phytohormones, cytokinin and auxin, display different yet partially overlapping distribution profiles across the cambium. In contrast to auxin, which has its highest concentration in the actively dividing cambial cells, cytokinins peak in the developing phloem tissue of a Populus trichocarpa stem. Gene expression patterns of cytokinin biosynthetic and signaling genes coincided with this hormonal gradient. To explore the functional significance of cytokinin signaling for cambial development, we engineered transgenic Populus tremula × tremuloides trees with an elevated cytokinin biosynthesis level. Confirming that cytokinins function as major regulators of cambial activity, these trees displayed stimulated cambial cell division activity resulting in dramatically increased (up to 80% in dry weight) production of the lignocellulosic trunk biomass. To connect the increased growth to hormonal status, we analyzed the hormone distribution and genome-wide gene expression profiles in unprecedentedly high resolution across the cambial zone. Interestingly, in addition to showing an elevated cambial cytokinin content and signaling level, the cambial auxin concentration and auxin-responsive gene expression were also increased in the transgenic trees. Our results indicate that cytokinin signaling specifies meristematic activity through a graded distribution that influences the amplitude of the cambial auxin gradient. PMID:27426519

  18. Structural basis for the auxin-induced transcriptional regulation by Aux/IAA17.

    Science.gov (United States)

    Han, Mookyoung; Park, Yangshin; Kim, Iktae; Kim, Eun-Hee; Yu, Tae-Kyung; Rhee, Sangkee; Suh, Jeong-Yong

    2014-12-30

    Auxin is the central hormone that regulates plant growth and organ development. Transcriptional regulation by auxin is mediated by the auxin response factor (ARF) and the repressor, AUX/IAA. Aux/IAA associates with ARF via domain III-IV for transcriptional repression that is reversed by auxin-induced Aux/IAA degradation. It has been known that Aux/IAA and ARF form homo- and hetero-oligomers for the transcriptional regulation, but what determines their association states is poorly understood. Here we report, to our knowledge, the first solution structure of domain III-IV of Aux/IAA17 (IAA17), and characterize molecular interactions underlying the homotypic and heterotypic oligomerization. The structure exhibits a compact β-grasp fold with a highly dynamic insert helix that is unique in Aux/IAA family proteins. IAA17 associates to form a heterogeneous ensemble of front-to-back oligomers in a concentration-dependent manner. IAA17 and ARF5 associate to form homo- or hetero-oligomers using a common scaffold and binding interfaces, but their affinities vary significantly. The equilibrium dissociation constants (KD) for homo-oligomerization are 6.6 μM and 0.87 μM for IAA17 and ARF5, respectively, whereas hetero-oligomerization reveals a ∼ 10- to ∼ 100-fold greater affinity (KD = 73 nM). Thus, individual homo-oligomers of IAA17 and ARF5 spontaneously exchange their subunits to form alternating hetero-oligomers for transcriptional repression. Oligomerization is mainly driven by electrostatic interactions, so that charge complementarity at the interface determines the binding affinity. Variable binding affinity by surface charge modulation may effectively regulate the complex interaction network between Aux/IAA and ARF family proteins required for the transcriptional control of auxin-response genes. PMID:25512488

  19. Meta-analysis of transcriptome data identified TGTCNN motif variants associated with the response to plant hormone auxin in Arabidopsis thaliana L.

    Science.gov (United States)

    Zemlyanskaya, Elena V; Wiebe, Daniil S; Omelyanchuk, Nadezhda A; Levitsky, Victor G; Mironova, Victoria V

    2016-04-01

    Auxin is the major regulator of plant growth and development. It regulates gene expression via a family of transcription factors (ARFs) that bind to auxin responsive elements (AuxREs) in the gene promoters. The canonical AuxREs found in regulatory regions of many auxin responsive genes contain the TGTCTC core motif, whereas ARF binding site is a degenerate TGTCNN with TGTCGG strongly preferred. Thereby two questions arise: which TGTCNN variants are functional AuxRE cores and whether different TGTCNN variants have distinct functional roles? In this study, we performed meta-analysis of microarray data to reveal TGTCNN variants essential for auxin response and to characterize their functional features. Our results indicate that four TGTCNN motifs (TGTCTC, TGTCCC, TGTCGG, and TGTCTG) are associated with auxin up-regulation and two (TGTCGG, TGTCAT) with auxin down-regulation, but to a lesser extent. The genes having some of these motifs in their regulatory regions showed time-specific auxin response. Functional annotation of auxin up- and down-regulated genes also revealed GO terms specific for the auxin-regulated genes with certain TGTCNN variants in their promoters. Our results provide an idea that various TGTCNN motifs may play distinct roles in the auxin regulation of gene expression. PMID:27122321

  20. Function of type-2 Arabidopsis hemoglobin in the auxin-mediated formation of embryogenic cells during morphogenesis

    DEFF Research Database (Denmark)

    Elhiti, Mohamed; Hebelstrup, Kim; Wang, Aiming;

    2013-01-01

    Suppression of the Arabidopsis GLB2, a type-2 nonsymbiotic hemoglobin, enhances somatic embryogenesis by increasing auxin production. In the glb2 knock-out line (GLB2 -/-) polarization of PIN1 proteins and auxin maxima occurred at the base of the cotyledons of the zygotic explants, which...... are the sites of embryogenic tissue formation. These changes were also accompanied by a transcriptional up-regulation of WUSCHEL (WUS) and SOMATIC EMBRYOGENESIS RECEPTOR KINASE (SERK1), markers of embryogenic competence. The increased auxin levels in the GLB2 -/- line were ascribed to the induction of several...... the embryogenic cells, which repress the expression of the transcription factor MYC2, a well characterized repressor of the auxin biosynthetic pathway. A model is proposed in which the suppression of GLB2 reduces the degree of NO scavenging by oxyhemoglobin, thereby increasing the cellular NO concentration...

  1. Establishment of embryonic shoot–root axis is involved in auxin and cytokinin response during Arabidopsis somatic embryogenesis

    OpenAIRE

    Su, Ying Hua; Liu, Yu Bo; Bai, Bo; Zhang, Xian Sheng

    2015-01-01

    Auxin and cytokinin signaling participates in regulating a large spectrum of developmental and physiological processes in plants. The shoots and roots of plants have specific and sometimes even contrary responses to these hormones. Recent studies have clearly shown that establishing the spatiotemporal distribution of auxin and cytokinin response signals is central for the control of shoot apical meristem (SAM) induction in cultured tissues. However, little is known about the role of these hor...

  2. microRNA160 dictates stage-specific auxin and cytokinin sensitivities and directs soybean nodule development.

    Science.gov (United States)

    Nizampatnam, Narasimha Rao; Schreier, Spencer John; Damodaran, Suresh; Adhikari, Sajag; Subramanian, Senthil

    2015-10-01

    Legume nodules result from coordinated interactions between the plant and nitrogen-fixing rhizobia. The phytohormone cytokinin promotes nodule formation, and recent findings suggest that the phytohormone auxin inhibits nodule formation. Here we show that microRNA160 (miR160) is a key signaling element that determines the auxin/cytokinin balance during nodule development in soybean (Glycine max). miR160 appears to promote auxin activity by suppressing the levels of the ARF10/16/17 family of repressor ARF transcription factors. Using quantitative PCR assays and a fluorescence miRNA sensor, we show that miR160 levels are relatively low early during nodule formation and high in mature nodules. We had previously shown that ectopic expression of miR160 in soybean roots led to a severe reduction in nodule formation, coupled with enhanced sensitivity to auxin and reduced sensitivity to cytokinin. Here we show that exogenous cytokinin restores nodule formation in miR160 over-expressing roots. Therefore, low miR160 levels early during nodule development favor cytokinin activity required for nodule formation. Suppression of miR160 levels using a short tandem target mimic (STTM160) resulted in reduced sensitivity to auxin and enhanced sensitivity to cytokinin. In contrast to miR160 over-expressing roots, STTM160 roots had increased nodule formation, but nodule maturation was significantly delayed. Exogenous auxin partially restored proper nodule formation and maturation in STTM160 roots, suggesting that high miR160 activity later during nodule development favors auxin activity and promotes nodule maturation. Therefore, miR160 dictates developmental stage-specific sensitivities to auxin and cytokinin to direct proper nodule formation and maturation in soybean. PMID:26287653

  3. YUCCA-mediated auxin biogenesis is required for cell fate transition occurring during de novo root organogenesis in Arabidopsis.

    Science.gov (United States)

    Chen, Lyuqin; Tong, Jianhua; Xiao, Langtao; Ruan, Ying; Liu, Jingchun; Zeng, Minhuan; Huang, Hai; Wang, Jia-Wei; Xu, Lin

    2016-07-01

    Many plant organs have the ability to regenerate a new plant after detachment or wounding via de novo organogenesis. During de novo root organogenesis from Arabidopsis thaliana leaf explants, endogenic auxin is essential for the fate transition of regeneration-competent cells to become root founder cells via activation of WUSCHEL-RELATED HOMEOBOX 11 (WOX11). However, the molecular events from leaf explant detachment to auxin-mediated cell fate transition are poorly understood. In this study, we used an assay to determine the concentration of indole-3-acetic acid (IAA) to provide direct evidence that auxin is produced after leaf explant detachment, a process that involves YUCCA (YUC)-mediated auxin biogenesis. Inhibition of YUC prevents expression of WOX11 and fate transition of competent cells, resulting in the blocking of rooting. Further analysis showed that YUC1 and YUC4 act quickly (within 4 hours) in response to wounding after detachment in both light and dark conditions and promote auxin biogenesis in both mesophyll and competent cells, whereas YUC5, YUC8, and YUC9 primarily respond in dark conditions. In addition, YUC2 and YUC6 contribute to rooting by providing a basal auxin level in the leaf. Overall, our study indicates that YUC genes exhibit a division of labour during de novo root organogenesis from leaf explants in response to multiple signals. PMID:27255928

  4. Target of Rapamycin Is a Key Player for Auxin Signaling Transduction in Arabidopsis.

    Science.gov (United States)

    Deng, Kexuan; Yu, Lihua; Zheng, Xianzhe; Zhang, Kang; Wang, Wanjing; Dong, Pan; Zhang, Jiankui; Ren, Maozhi

    2016-01-01

    Target of rapamycin (TOR), a master sensor for growth factors and nutrition availability in eukaryotic species, is a specific target protein of rapamycin. Rapamycin inhibits TOR kinase activity viaFK506 binding protein 12 kDa (FKBP12) in all examined heterotrophic eukaryotic organisms. In Arabidopsis, several independent studies have shown that AtFKBP12 is non-functional under aerobic condition, but one study suggests that AtFKBP12 is functional during anaerobic growth. However, the functions of AtFKBP12 have never been examined in parallel under aerobic and anaerobic growth conditions so far. To this end, we cloned the FKBP12 gene of humans, yeast, and Arabidopsis, respectively. Transgenic plants were generated, and pharmacological examinations were performed in parallel with Arabidopsis under aerobic and anaerobic conditions. ScFKBP12 conferred plants with the strongest sensitivity to rapamycin, followed by HsFKBP12, whereas AtFKBP12 failed to generate rapamycin sensitivity under aerobic condition. Upon submergence, yeast and human FKBP12 can significantly block cotyledon greening while Arabidopsis FKBP12 only retards plant growth in the presence of rapamycin, suggesting that hypoxia stress could partially restore the functions of AtFKBP12 to bridge the interaction between rapamycin and TOR. To further determine if communication between TOR and auxin signaling exists in plants, yeast FKBP12 was introduced into DR5::GUS homozygous plants. The transgenic plants DR5/BP12 were then treated with rapamycin or KU63794 (a new inhibitor of TOR). GUS staining showed that the auxin content of root tips decreased compared to the control. DR5/BP12 plants lost sensitivity to auxin after treatment with rapamycin. Auxin-defective phenotypes, including short primary roots, fewer lateral roots, and loss of gravitropism, occurred in DR5/BP12 plants when seedlings were treated with rapamycin+KU63794. This indicated that the combination of rapamycin and KU63794 can significantly

  5. Genome-wide identification and expression profiling of auxin response factor (ARF) gene family in maize

    OpenAIRE

    Zhang Yirong; Hu Zhaorong; Xing Guofang; Guo Ganggang; Pudake Ramesh N; Xing Hongyan; Sun Qixin; Ni Zhongfu

    2011-01-01

    Abstract Background Auxin signaling is vital for plant growth and development, and plays important role in apical dominance, tropic response, lateral root formation, vascular differentiation, embryo patterning and shoot elongation. Auxin Response Factors (ARFs) are the transcription factors that regulate the expression of auxin responsive genes. The ARF genes are represented by a large multigene family in plants. The first draft of full maize genome assembly has recently been released, howeve...

  6. Polar transport of plant hormone auxin – the role of PIN-FORMED (PIN) proteins

    Czech Academy of Sciences Publication Activity Database

    Zažímalová, Eva; Křeček, Pavel; Skůpa, Petr; Hoyerová, Klára; Petrášek, Jan

    2007-01-01

    Roč. 64, č. 13 (2007), s. 1621-1637. ISSN 1420-682X R&D Projects: GA AV ČR IAA6038303; GA AV ČR KJB600380604; GA MŠk(CZ) LC06034 Institutional research plan: CEZ:AV0Z50380511 Source of funding: V - iné verejné zdroje ; V - iné verejné zdroje ; V - iné verejné zdroje Keywords : Plant hormone * phytohormone * plant growth regulator Subject RIV: ED - Physiology Impact factor: 5.239, year: 2007

  7. Pengaruh penambahan auxin terhadap pertunasan dan perakaran kopi arabika perbanyakan Somatic Embryogenesis (The effects of shooting and rooting of arabica coffee propagation through Embryogenesis Somatic auxin uses).

    OpenAIRE

    Rina Arimarsetiowati; Fitria Ardiyani

    2012-01-01

    Plantlet that has developed shoots and roots will have a high level adaptation in the field. The objective of this experiment was to improve the ability of planlet in shooting and rooting so that it is ready for acclimatization in the field. The increase ability in shooting and rooting of the planlet were conducted by adding various types of auxin in the media. The arabica coffee embryo of clone AS 2K which has entered the phase of the cotyledons was transfered into the treatment media contai...

  8. The Pseudomonas syringae Type III Effector AvrRpt2 Promotes Pathogen Virulence via Stimulating Arabidopsis Auxin/Indole Acetic Acid Protein Turnover1[C][W][OA

    Science.gov (United States)

    Cui, Fuhao; Wu, Shujing; Sun, Wenxian; Coaker, Gitta; Kunkel, Barbara; He, Ping; Shan, Libo

    2013-01-01

    To accomplish successful infection, pathogens deploy complex strategies to interfere with host defense systems and subvert host physiology to favor pathogen survival and multiplication. Modulation of plant auxin physiology and signaling is emerging as a common virulence strategy for phytobacteria to cause diseases. However, the underlying mechanisms remain largely elusive. We have previously shown that the Pseudomonas syringae type III effector AvrRpt2 alters Arabidopsis (Arabidopsis thaliana) auxin physiology. Here, we report that AvrRpt2 promotes auxin response by stimulating the turnover of auxin/indole acetic acid (Aux/IAA) proteins, the key negative regulators in auxin signaling. AvrRpt2 acts additively with auxin to stimulate Aux/IAA turnover, suggesting distinct, yet proteasome-dependent, mechanisms operated by AvrRpt2 and auxin to control Aux/IAA stability. Cysteine protease activity is required for AvrRpt2-stimulated auxin signaling and Aux/IAA degradation. Importantly, transgenic plants expressing the dominant axr2-1 mutation recalcitrant to AvrRpt2-mediated degradation ameliorated the virulence functions of AvrRpt2 but did not alter the avirulent function mediated by the corresponding RPS2 resistance protein. Thus, promoting auxin response via modulating the stability of the key transcription repressors Aux/IAA is a mechanism used by the bacterial type III effector AvrRpt2 to promote pathogenicity. PMID:23632856

  9. Rapid Protein Depletion in Human Cells by Auxin-Inducible Degron Tagging with Short Homology Donors

    Directory of Open Access Journals (Sweden)

    Toyoaki Natsume

    2016-04-01

    Full Text Available Studying the role of essential proteins is dependent upon a method for rapid inactivation, in order to study the immediate phenotypic consequences. Auxin-inducible degron (AID technology allows rapid depletion of proteins in animal cells and fungi, but its application to human cells has been limited by the difficulties of tagging endogenous proteins. We have developed a simple and scalable CRISPR/Cas-based method to tag endogenous proteins in human HCT116 and mouse embryonic stem (ES cells by using donor constructs that harbor synthetic short homology arms. Using a combination of AID tagging with CRISPR/Cas, we have generated conditional alleles of essential nuclear and cytoplasmic proteins in HCT116 cells, which can then be depleted very rapidly after the addition of auxin to the culture medium. This approach should greatly facilitate the functional analysis of essential proteins, particularly those of previously unknown function.

  10. Rapid Protein Depletion in Human Cells by Auxin-Inducible Degron Tagging with Short Homology Donors.

    Science.gov (United States)

    Natsume, Toyoaki; Kiyomitsu, Tomomi; Saga, Yumiko; Kanemaki, Masato T

    2016-04-01

    Studying the role of essential proteins is dependent upon a method for rapid inactivation, in order to study the immediate phenotypic consequences. Auxin-inducible degron (AID) technology allows rapid depletion of proteins in animal cells and fungi, but its application to human cells has been limited by the difficulties of tagging endogenous proteins. We have developed a simple and scalable CRISPR/Cas-based method to tag endogenous proteins in human HCT116 and mouse embryonic stem (ES) cells by using donor constructs that harbor synthetic short homology arms. Using a combination of AID tagging with CRISPR/Cas, we have generated conditional alleles of essential nuclear and cytoplasmic proteins in HCT116 cells, which can then be depleted very rapidly after the addition of auxin to the culture medium. This approach should greatly facilitate the functional analysis of essential proteins, particularly those of previously unknown function. PMID:27052166

  11. Auxin Biosynthesis: Are the Indole-3-Acetic Acid and Phenylacetic Acid Biosynthesis Pathways Mirror Images?

    Science.gov (United States)

    Cook, Sam D; Nichols, David S; Smith, Jason; Chourey, Prem S; McAdam, Erin L; Quittenden, Laura; Ross, John J

    2016-06-01

    The biosynthesis of the main auxin in plants (indole-3-acetic acid [IAA]) has been elucidated recently and is thought to involve the sequential conversion of Trp to indole-3-pyruvic acid to IAA However, the pathway leading to a less well studied auxin, phenylacetic acid (PAA), remains unclear. Here, we present evidence from metabolism experiments that PAA is synthesized from the amino acid Phe, via phenylpyruvate. In pea (Pisum sativum), the reverse reaction, phenylpyruvate to Phe, is also demonstrated. However, despite similarities between the pathways leading to IAA and PAA, evidence from mutants in pea and maize (Zea mays) indicate that IAA biosynthetic enzymes are not the main enzymes for PAA biosynthesis. Instead, we identified a putative aromatic aminotransferase (PsArAT) from pea that may function in the PAA synthesis pathway. PMID:27208245

  12. Auxin-induced acidification is not due to the hydration of respiratory CO/sub 2/

    Energy Technology Data Exchange (ETDEWEB)

    Oberbauer, S.; Rayle, D.; Johnson, K.; Cleland, R.

    1978-01-01

    Sloane and Sadava, in 1975, proposed that auxin-induced cell wall acidification is largely due to carbonic acid derived from respired CO/sub 2/. In this paper we show that the pH values calculated by Sloane and Sadava from measured CO/sub 2/ concentrations do not agree with either theoretical or measured pH values. In addition we show that in an open beaker system the speed with which CO/sub 2/ escapes to the atmosphere is too rapid to allow any substantial accumulation of carbonic acid. Lastly, vigorous bubbling with N/sub 2/ of the acidified medium surrounding auxin-treated pea stem segments does not cause a substantial increase in the pH of the medium. For these reasons we feel that the hypothesis which states that growth-regulator-enhanced wall acidification arises largely from the hydration of respiratory-derived CO/sub 2/ is disproved.

  13. Effect of auxin on Golgi-mediated cell wall synthesis in pea stem segments

    Energy Technology Data Exchange (ETDEWEB)

    Brummell, D.A.; Maclachlan, G.A.

    1986-04-01

    Stem segments of 7 day-old etiolated Pisum sativum seedlings were abraded using carborundum powder. Batches of segments were pulsed in (/sup 3/H) glucose followed by a chase in cold glucose in the presence or absence of 1AA, then homogenized by chopping with a razor blade. A rate-zonal centrifugation on a linear sucrose gradient was used to separate dictyosomes and secretory vesicles, and membrane-bound radioactivity determined as a measure of Golgi material in the cytoplasm. The amount of membrane-bound radioactivity was increased in tissues treated with 1AA for 30 min, indicative of an enhanced Golgi content in such segments. This increase thus precedes the sustained increase in auxin-stimulated growth of stem segments which occurs around 35-45 min after exposure to auxin and which is thought to be due to increased cell wall synthesis.

  14. 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. PMID:26829981

  15. Auxin gradients trigger de novo formation of stem cells during somatic embryogenesis

    OpenAIRE

    Su, Ying Hua; Zhang, Xian Sheng

    2009-01-01

    Single or a group of somatic cells could give rise to the whole plant, which require hormones, or plant growth regulators. Although many studies have been done during past years, how hormones specify cell fate during in vitro organogenesis is still unknown. To uncover this mechanism, Arabidopsis somatic embryogenesis has been recognized as a model for studying in vitro plant organogenesis. In this paper, we showed that establishment of auxin gradients within embryonic callus is essential for ...

  16. Quantification of Abscisic Acid, Cytokinin, and Auxin Content in Salt-Stressed Plant Tissues

    OpenAIRE

    Dobrev, P.; Vaňková, R. (Radomíra)

    2012-01-01

    Plant hormones cytokinins, auxin (indole-3-acetic acid), and abscisic acid are central to regulation of plant growth and defence to abiotic stresses such as salinity. Quantification of the hormone levels and determination of their ratios can reveal different plant strategies to cope with the stress, e.g., suppression of growth or mobilization of plant metabolism. This chapter describes a procedure enabling such quantification. Due to the high variability of these hormones in plant tissues, it...

  17. Genetic basis of cytokinin and auxin functions during root nodule development

    OpenAIRE

    Suzaki, Takuya; Ito, Momoyo; Kawaguchi, Masayoshi

    2013-01-01

    The phytohormones cytokinin and auxin are essential for the control of diverse aspects of cell proliferation and differentiation processes in plants. Although both phytohormones have been suggested to play key roles in the regulation of root nodule development, only recently, significant progress has been made in the elucidation of the molecular genetic basis of cytokinin action in the model leguminous species, Lotus japonicus and Medicago truncatula. Identification and functional analyses of...

  18. Activation of Shikimate, Phenylpropanoid, Oxylipins, and Auxin Pathways in Pectobacterium carotovorum Elicitors-Treated Moss.

    Science.gov (United States)

    Alvarez, Alfonso; Montesano, Marcos; Schmelz, Eric; Ponce de León, Inés

    2016-01-01

    Plants have developed complex defense mechanisms to cope with microbial pathogens. Pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs) are perceived by pattern recognition receptors (PRRs), leading to the activation of defense. While substantial progress has been made in understanding the activation of plant defense by PAMPs and DAMPs recognition in tracheophytes, far less information exists on related processes in early divergent plants like mosses. The aim of this study was to identify genes that were induced in P. patens in response to elicitors of Pectobacterium carotovorum subsp. carotovorum, using a cDNA suppression subtractive hybridization (SSH) method. A total of 239 unigenes were identified, including genes involved in defense responses related to the shikimate, phenylpropanoid, and oxylipin pathways. The expression levels of selected genes related to these pathways were analyzed using quantitative RT-PCR, confirming their rapid induction by P.c. carotovorum derived elicitors. In addition, P. patens induced cell wall reinforcement after elicitor treatment by incorporation of phenolic compounds, callose deposition, and elevated expression of Dirigent-like encoding genes. Small molecule defense markers and phytohormones such as cinnamic acid, 12-oxo-phytodienoic acid, and auxin levels all increased in elicitor-treated moss tissues. In contrast, salicylic acid levels decreased while abscisic acid levels remained unchanged. P. patens reporter lines harboring an auxin-inducible promoter fused to β-glucuronidase revealed GUS activity in protonemal and gametophores tissues treated with elicitors of P.c. carotovorum, consistent with a localized activation of auxin signaling. These results indicate that P. patens activates the shikimate, phenylpropanoid, oxylipins, and auxin pathways upon treatment with P.c. carotovorum derived elicitors. PMID:27047509

  19. Quantification of Abscisic Acid, Cytokinin, and Auxin Content in Salt-Stressed Plant Tissues

    Czech Academy of Sciences Publication Activity Database

    Dobrev, Petre; Vaňková, Radomíra

    Vol. 913. New York: Humana Press, 2012 - (Shabala, S.; Cuin, T.), s. 251-261. (Methods in Molecular Biology). ISBN 978-1-61779-985-3 R&D Projects: GA MŠk(CZ) LD11073 Institutional research plan: CEZ:AV0Z50380511 Keywords : Abscisic acid * Auxin * Cytokinin Subject RIV: ED - Physiology http://home.ueb.cas.cz/publikace/2012_Dobrev.pdf

  20. Auxin depletion from the leaf axil conditions competence for axillary meristem formation in Arabidopsis and tomato

    OpenAIRE

    Wang, Quan; Kohlen, Wouter; Rossmann, Susanne; Vernoux, Teva

    2014-01-01

    The enormous variation in architecture of flowering plants is based to a large extent on their ability to form new axes of growth throughout their life span. Secondary growth is initiated from groups of pluripotent cells, called meristems, which are established in the axils of leaves. Such meristems form lateral organs and develop into a side shoot or a flower, depending on the developmental status of the plant and environmental conditions. The phytohormone auxin is well known to play an impo...

  1. Phyllotaxy: Beyond the Meristem and Auxin Comes the miRNA

    OpenAIRE

    Peaucelle, Alexis; Laufs, Patrick

    2007-01-01

    Phyllotaxy, the arrangement of organs along the stem, has puzzled scientists for centuries. The shoot apical meristem plays a crucial role in the formation of this pattern, by initiating organ primordia on its flanks in a temporally and spatially controlled manner. Recent studies have shown that primordium position at the meristem is governed by local auxin gradients, but little is known about the subsequent events leading to the phyllotaxy along the mature stem.

  2. stem fasciated, a Recessive Mutation in Sunflower (Helianthus annuus), Alters Plant Morphology and Auxin Level

    OpenAIRE

    FAMBRINI, MARCO; BONSIGNORI, ELISA; RAPPARINI, FRANCESCA; CIONINI, GIULIANO; Michelotti, Vania; BERTINI, DANIELE; BARALDI, RITA; PUGLIESI, CLAUDIO

    2006-01-01

    • Background and Aims Plant lateral organs such as leaves arise from a group of initial cells within the flanks of the shoot apical meristem (SAM). Alterations in the initiation of lateral organs are often associated with changes in the dimension and arrangement of the SAM as well as with abnormal hormonal homeostasis. A mutation named stem fasciated (stf) that affects various aspects of plant development, including SAM shape and auxin level, was characterized in sunflower (Helianthus annuus).

  3. Regulation of cytokinin and auxin levels in developing wheat grains and its use for crop improvement

    Czech Academy of Sciences Publication Activity Database

    Kamínek, Miroslav; Trčková, M.; Gaudinová, Alena; Dobrev, Petre; Motyka, Václav; Albrechtová, J.; Votrubová, O.

    Ústav experimentální botaniky AV ČR, v. v. i.. Roč. 42, Supplement (1999), s. S85 ISSN 0006-3134. [Auxin and Cytokinins in Plant Development. 26.07.1999-30.07.1999, Praha] R&D Projects: GA ČR GA206/96/1032; GA ČR GV206/96/K188 Subject RIV: EF - Botanics

  4. Growth-limiting proteins in maize coleoptiles and the auxin-brassinosteroid hypothesis of mesocotyl elongation.

    Science.gov (United States)

    Kutschera, Ulrich; Wang, Zhi-Yong

    2016-01-01

    The shoot of grass coleoptiles consists of the mesocotyl, the node, and the coleoptile (with enclosed primary leaf). Since the 1930s, it is known that auxin (indole-3-acetic acid, IAA), produced in the tip of the coleoptile, is the central regulator of turgor-driven organ growth. Fifty years ago, it was discovered that antibiotics that suppress protein biosynthesis, such as cycloheximide, inhibit auxin (IAA)-induced cell elongation in excised sections of coleoptiles and stems. Based on such inhibitor studies, the concept of "growth-limiting proteins (GLPs)" emerged that was subsequently elaborated and modified. Here, we summarize the history of this idea with reference to IAA-mediated shoot elongation in maize (Zea mays) seedlings and recent studies on the molecular mechanism underlying auxin action in Arabidopsis thaliana. In addition, the analysis of light-induced inhibition of shoot elongation in intact corn seedlings is discussed. We propose a concept to account for the GLP-mediated epidermal wall-loosening process in coleoptile segments and present a more general model of growth regulation in intact maize seedlings. Quantitative proteomic and genomic studies led to a refinement of the classic "GLP concept" to explain phytohormone-mediated cell elongation at the molecular level (i.e., the recently proposed theory of a "central growth regulation network," CGRN). Novel data show that mesocotyl elongation not only depends on auxin but also on brassinosteroids (BRs). However, the biochemical key processes that regulate the IAA/BR-mediated loosening of the expansion-limiting epidermal wall(s) have not yet been elucidated. PMID:25772679

  5. Auxin response factors mediate Arabidopsis organ asymmetry via modulation of KANADI activity.

    Science.gov (United States)

    Pekker, Irena; Alvarez, John Paul; Eshed, Yuval

    2005-11-01

    Members of the KANADI gene family in Arabidopsis thaliana regulate abaxial identity and laminar growth of lateral organs. Promoter APETALA3-mediated ectopic expression of KANADI restricts petal expansion and was used in a genetic screen for factors involved in KANADI-mediated signaling. Through this screen, mutations in ETTIN (ETT; also known as Auxin Response Factor3 [ARF3]) were isolated as second site suppressors and found to ameliorate ectopic KANADI activity throughout the plant as well. Mutant phenotypes of ett are restricted to flowers; however, double mutants with a closely related gene ARF4 exhibit transformation of abaxial tissues into adaxial ones in all aerial parts, resembling mutations in KANADI. Accordingly, the common RNA expression domain of both ARFs was found to be on the abaxial side of all lateral organs. Truncated, negatively acting gene products of strong ett alleles map to an ARF-specific, N-terminal domain of ETT. Such gene products strongly enhance abaxial tissue loss only when ARF activities are compromised. As KANADI is not required for either ETT or ARF4 transcription, and their overexpression cannot rescue kanadi mutants, cooperative activity is implied. ARF proteins are pivotal in mediating auxin responses; thus, we present a model linking transient local auxin gradients and gradual partitioning of lateral organs along the abaxial/adaxial axis. PMID:16199616

  6. Auxin effects on somaclonal variation and plant regeneration from mature embryo of barley (hordeum vulgare L.)

    International Nuclear Information System (INIS)

    Crop improvement through genetic engineering depends on effective and reproducible plant regeneration systems. In barley (Hordeum vulgare L.), immature embryos are the most commonly used as explant source for In vitro regeneration and genetic transformation but, mature embryos are alternative to immature embryo due to the fact that they have advantages such as easy storage and ready availability throughout the year. The effects of different concentrations (2, 4, 6, 8, 10 and 12 mg/l) of three auxins (2,4-D, dicamba and picloram) were evaluated in mature embryo culture of barley. Calli, embryogenic calli and regenerated plants were observed in all of the studied auxins. The MS (Murashige and Skoog basal medium) containing 12 mg/l dicamba was found to be the most effective for embryogenic callus, responded embryogenic callus and regeneration efficiency. Plant tissue culture can bring about genetic changes that are known as somaclonal variation. Genetic and epigenetic changes were examined by RAPD (Randomly Amplified Polymorphic DNA) and CRED-RA (Coupled Restriction Enzyme Digestion-Random Amplification) techniques, respectively. Increased auxin concentration led to the decrease in the GTS (Genomic Template Stability) value. DNA hypermethylation occurred in higher concentrations of 2,4-D and picloram, while DNA hypomethylation was observed in dicamba. (author)

  7. Time course and auxin sensitivity of cortical microtubule reorientation in maize roots

    Science.gov (United States)

    Blancaflor, E. B.; Hasenstein, K. H.

    1995-01-01

    The kinetics of MT [microtubule] reorientation in primary roots of Zea mays cv. Merit, were examined 15, 30, 45, and 60 min after horizontal positioning. Confocal microscopy of longitudinal tissue sections showed no change in MT orientation 15 and 30 min after horizontal placement. However, after 45 and 60 min, MTs of the outer 4-5 cortical cell layers along the lower side were reoriented. In order to test whether MT reorientation during graviresponse is caused by an auxin gradient, we examined the organization of MTs in roots that were incubated for 1 h in solutions containing 10(-9) to 10(-6) M IAA. IAA treatment at 10(-8) M or less showed no major or consistent changes but 10(-7) M IAA resulted in MT reorientation in the cortex. The auxin effect does not appear to be acid-induced since benzoic acid (10(-5) M) did not cause MT reorientation. The region closest to the maturation zone was most sensitive to IAA. The data indicate that early stages of gravity induced curvature occur in the absence of MT reorientation but sustained curvature leads to reoriented MTs in the outer cortex. Growth inhibition along the lower side of graviresponding roots appears to result from asymmetric distribution of auxin following gravistimulation.

  8. Auxin-induced nitric oxide, cGMP and gibberellins were involved in the gravitropism

    Science.gov (United States)

    Cai, Weiming; Hu, Liwei; Hu, Xiangyang; Cui, Dayong; Cai, Weiming

    Gravitropism is the asymmetric growth or curvature of plant organs in response to gravistimulation. There is a complex signal transduction cascade which involved in the differential growth of plants in response to changes in the gravity vector. The role of auxin in gravitropism has been demonstrated by many experiments, but little is known regarding the molecular details of such effects. In our studies before, mediation of the gravitropic bending of soybean roots and rice leaf sheath bases by nitric oxide, cGMP and gibberellins, are induced by auxin. The asymmetrical distribution of nitric oxide, cGMP and gibberellins resulted from the asymmetrical synthesis of them in bending sites. In soybean roots, inhibitions of NO and cGMP synthesis reduced differential NO and cGMP accumulation respectively, which both of these effects can lead to the reduction of gravitropic bending. Gibberellin-induced OsXET, OsEXPA4 and OsRWC3 were also found involved in the gravitropic bending. These data indicated that auxin-induced nitric oxide, cGMP and gibberellins were involved in the gravitropism. More experiments need to prove the more detailed mechanism of them.

  9. A theoretical model for ROP localisation by auxin in Arabidopsis root hair cells.

    Directory of Open Access Journals (Sweden)

    Robert J H Payne

    Full Text Available Local activation of Rho GTPases is important for many functions including cell polarity, morphology, movement, and growth. Although a number of molecules affecting Rho-of-Plants small GTPase (ROP signalling are known, it remains unclear how ROP activity becomes spatially organised. Arabidopsis root hair cells produce patches of ROP at consistent and predictable subcellular locations, where root hair growth subsequently occurs.We present a mathematical model to show how interaction of the plant hormone auxin with ROPs could spontaneously lead to localised patches of active ROP via a Turing or Turing-like mechanism. Our results suggest that correct positioning of the ROP patch depends on the cell length, low diffusion of active ROP, a gradient in auxin concentration, and ROP levels. Our theory provides a unique explanation linking the molecular biology to the root hair phenotypes of multiple mutants and transgenic lines, including OX-ROP, CA-rop, aux1, axr3, tip1, eto1, etr1, and the triple mutant aux1 ein2 gnom(eb.We show how interactions between Rho GTPases (in this case ROPs and regulatory molecules (in this case auxin could produce characteristic subcellular patterning that subsequently affects cell shape. This has important implications for research on the morphogenesis of plants and other eukaryotes. Our results also illustrate how gradient-regulated Turing systems provide a particularly robust and flexible mechanism for pattern formation.

  10. Specific photoaffinity labeling of two plasma membrane polypeptides with an azido auxin

    Energy Technology Data Exchange (ETDEWEB)

    Hicks, G.R.; Rayle, D.L.; Jones, A.M.; Lomax, T.L. (Oregon State Univ., Corvallis (USA))

    1989-07-01

    Plasma membrane vesicles were isolated from zucchini (Cucurbita pepo) hypocotyl tissue by aqueous phase partitioning and assessed for homogeneity by the use of membrane-specific enzyme assays. The highly pure plasma membrane vesicles maintained a pH differential across the membrane and accumulated a tritiated azido analogue of 3-indoleacetic acid (IAA), 5-azido-(7-{sup 3}H)IAA(({sup 3}H)N{sub 3}IAA), in a manner similar to the accumulation of ({sup 3}H)IAA. The association of the ({sup 3}H)N{sub 3}IAA with membrane vesicles was saturable and subject to competition by IAA and auxin analogues. Auxin-binding proteins were photoaffinity labeled by addition of ({sup 3}H)N{sub 3}IAA to plasma membrane vesicles prior to exposure to UV light and detected by subsequent NaDodSO{sub 4}/PAGE and fluorography. When the reaction temperature was lowered to {minus}196{degree}C, high-specific-activity labeling of a 40-kDa and a 42-kDa polypeptide was observed. Collectively, these results suggest that the radiolabeled polypeptides are auxin receptors. The covalent nature of the label should facilitate purification and further characterization of the receptors.

  11. Actin-dependent vacuolar occupancy of the cell determines auxin-induced growth repression

    Science.gov (United States)

    Scheuring, David; Löfke, Christian; Krüger, Falco; Kittelmann, Maike; Eisa, Ahmed; Hughes, Louise; Smith, Richard S.; Hawes, Chris; Schumacher, Karin; Kleine-Vehn, Jürgen

    2016-01-01

    The cytoskeleton is an early attribute of cellular life, and its main components are composed of conserved proteins. The actin cytoskeleton has a direct impact on the control of cell size in animal cells, but its mechanistic contribution to cellular growth in plants remains largely elusive. Here, we reveal a role of actin in regulating cell size in plants. The actin cytoskeleton shows proximity to vacuoles, and the phytohormone auxin not only controls the organization of actin filaments but also impacts vacuolar morphogenesis in an actin-dependent manner. Pharmacological and genetic interference with the actin–myosin system abolishes the effect of auxin on vacuoles and thus disrupts its negative influence on cellular growth. SEM-based 3D nanometer-resolution imaging of the vacuoles revealed that auxin controls the constriction and luminal size of the vacuole. We show that this actin-dependent mechanism controls the relative vacuolar occupancy of the cell, thus suggesting an unanticipated mechanism for cytosol homeostasis during cellular growth. PMID:26715743

  12. Investigating organic molecules responsible of auxin-like activity of humic acid fraction extracted from vermicompost.

    Science.gov (United States)

    Scaglia, Barbara; Nunes, Ramom Rachide; Rezende, Maria Olímpia Oliveira; Tambone, Fulvia; Adani, Fabrizio

    2016-08-15

    This work studied the auxin-like activity of humic acids (HA) obtained from vermicomposts produced using leather wastes plus cattle dung at different maturation stages (fresh, stable and mature). Bioassays were performed by testing HA concentrations in the range of 100-6000mgcarbonL(-1). (13)C CPMAS-NMR and GC-MS instrumental methods were used to assess the effect of biological processes and starting organic mixtures on HA composition. Not all HAs showed IAA-like activity and in general, IAA-like activity increased with the length of the vermicomposting process. The presence of leather wastes was not necessary to produce the auxin-like activity of HA, since HA extracted from a mix of cattle manure and sawdust, where no leather waste was added, showed IAA-like activity as well. CPMAS (13)CNMR revealed that HAs were similar independently of the mix used and that the humification process involved the increasing concentration of pre-existing alkali soluble fractions in the biomass. GC/MS allowed the identification of the molecules involved in IAA-like effects: carboxylic acids and amino acids. The concentration of active molecules, rather than their simple presence in HA, determined the bio-stimulating effect, and a good linear regression between auxin-like activity and active stimulating molecules concentration was found (R(2)=-0.85; p<0.01, n=6). PMID:27100009

  13. Changes in auxin activity in tumourous and normal tobacco calluses treated with morphactin IT 3233

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    Z. Chirek

    2015-05-01

    Full Text Available The addition of morphactin IT 3233 in 1-40 mg/dm3 concentrations to the medium inhibited the growth in vitro of normal and tumourous tobacco calluses. The auxin activity (estimated by the Avena coleoptile straight growth test of the acid ether extracts from these tissues increased. The activity of zone I (Rf 0.2-0.4, 0.5, solvent system: butanol:water:ammonia 10:10:1 in normal tissues increased more intensively than that of zone II (Rf 0.6-0.8, 0.9. In tumourous tissues, however, these changes were smaller and they concerned merely zone I of auxin activity (Rf 0.0-0.5. It seems that the mechanism of morphactin activity in both kinds of tissue is different. It may be supposed that the excessive accumulation of auxins induces growth inhibition of tissues. A previously found increase in the activity of IAA-oxidase influenced by morphactin might be considered as an adaptation to a higher level of IAA.

  14. Auxin controls local cytokinin biosynthesis in the nodal stem in apical dominance.

    Science.gov (United States)

    Tanaka, Mina; Takei, Kentaro; Kojima, Mikiko; Sakakibara, Hitoshi; Mori, Hitoshi

    2006-03-01

    In intact plants, the shoot apex grows predominantly and inhibits outgrowth of axillary buds. After decapitation of the shoot apex, outgrowth of axillary buds begins. This phenomenon is called an apical dominance. Although the involvement of auxin, which represses outgrowth of axillary buds, and cytokinin (CK), which promotes outgrowth of axillary buds, has been proposed, little is known about the underlying molecular mechanisms. In the present study, we demonstrated that auxin negatively regulates local CK biosynthesis in the nodal stem by controlling the expression level of the pea (Pisum sativum L.) gene adenosine phosphate-isopentenyltransferase (PsIPT), which encodes a key enzyme in CK biosynthesis. Before decapitation, PsIPT1 and PsIPT2 transcripts were undetectable; after decapitation, they were markedly induced in the nodal stem along with accumulation of CK. Expression of PsIPT was repressed by the application of indole-3-acetic acid (IAA). In excised nodal stem, PsIPT expression and CK levels also increased under IAA-free conditions. Furthermore, beta-glucuronidase expression, under the control of the PsIPT2 promoter region in transgenic Arabidopsis, was repressed by an IAA. Our results indicate that in apical dominance one role of auxin is to repress local biosynthesis of CK in the nodal stem and that, after decapitation, CKs, which are thought to be derived from the roots, are locally biosynthesized in the nodal stem rather than in the roots. PMID:16507092

  15. Deliberate ROS production and auxin synergistically trigger the asymmetrical division generating the subsidiary cells in Zea mays stomatal complexes.

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    Livanos, Pantelis; Galatis, Basil; Apostolakos, Panagiotis

    2016-07-01

    Subsidiary cell generation in Poaceae is an outstanding example of local intercellular stimulation. An inductive stimulus emanates from the guard cell mother cells (GMCs) towards their laterally adjacent subsidiary cell mother cells (SMCs) and triggers the asymmetrical division of the latter. Indole-3-acetic acid (IAA) immunolocalization in Zea mays protoderm confirmed that the GMCs function as local sources of auxin and revealed that auxin is polarly accumulated between GMCs and SMCs in a timely-dependent manner. Besides, staining techniques showed that reactive oxygen species (ROS) exhibit a closely similar, also time-dependent, pattern of appearance suggesting ROS implication in subsidiary cell formation. This phenomenon was further investigated by using the specific NADPH-oxidase inhibitor diphenylene iodonium, the ROS scavenger N-acetyl-cysteine, menadione which leads to ROS overproduction, and H2O2. Treatments with diphenylene iodonium, N-acetyl-cysteine, and menadione specifically blocked SMC polarization and asymmetrical division. In contrast, H2O2 promoted the establishment of SMC polarity and subsequently subsidiary cell formation in "younger" protodermal areas. Surprisingly, H2O2 favored the asymmetrical division of the intervening cells of the stomatal rows leading to the creation of extra apical subsidiary cells. Moreover, H2O2 altered IAA localization, whereas synthetic auxin analogue 1-napthaleneacetic acid enhanced ROS accumulation. Combined treatments with ROS modulators along with 1-napthaleneacetic acid or 2,3,5-triiodobenzoic acid, an auxin efflux inhibitor, confirmed the crosstalk between ROS and auxin functioning during subsidiary cell generation. Collectively, our results demonstrate that ROS are critical partners of auxin during development of Z. mays stomatal complexes. The interplay between auxin and ROS seems to be spatially and temporarily regulated. PMID:26250135

  16. Characterization of a Pinus pinaster cDNA encoding an auxin up-regulated putative peroxidase in roots.

    Science.gov (United States)

    Charvet-Candela, V; Hitchin, S; Reddy, M S; Cournoyer, B; Marmeisse, R; Gay, G

    2002-03-01

    As part of a study to identify host plant genes regulated by fungal auxin during ectomycorrhiza formation, we differentially screened a cDNA library constructed from roots of auxin-treated Pinus pinaster (Ait.) Sol. seedlings. We identified three cDNAs up-regulated by auxin. Sequence analysis of one of these cDNAs, PpPrx75, revealed the presence of an open reading frame of 216 amino acids with the characteristic consensus sequences of plant peroxidases. The deduced amino acid sequence showed homology with Arabidopsis thaliana (L.) Heynh., Arachis hypogaea L. and Stylosanthes humilis HBK cationic peroxidases. Amino acid sequence identities in the conserved domains of plant peroxidases ranged from 60 to 100%. In PpPrx75, there are five cysteine residues and one histidine residue that are found at conserved positions among other peroxidases. A potential glycosylation site (NTS) is present in the deduced sequence. Phylogenetic analysis showed that PpPrx75 is closely related to two A. thaliana peroxidases. The PpPrx75 cDNA was induced by active auxins, ethylene, abscisic acid and quercetin, a flavonoid possibly involved in plant-microorganism interactions. Transcript accumulation was detected within 3 h following root induction by auxin, and the amount of mRNA increased over the following 24 h. The protein synthesis inhibitor cycloheximide did not inhibit indole-3-acetic acid-induced transcript accumulation, suggesting that PpPrx75 induction is a primary (direct) response to auxin. This cDNA can be used to study expression of an auxin-regulated peroxidase during ectomycorrhiza formation. PMID:11874719

  17. Phloem-specific expression of a melon Aux/IAA in tomato plants alters auxin sensitivity and plant development

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    Guy eGolan

    2013-08-01

    Full Text Available Phloem sap contains a large repertoire of macromolecules in addition to sugars, amino acids, growth substances and ions. The transcription profile of melon phloem sap contains over 1,000 mRNA molecules, most of them associated with signal transduction, transcriptional control, and stress and defense responses. Heterografting experiments have established the long-distance trafficking of numerous mRNA molecules. Interestingly, several trafficking transcripts are involved in the auxin response, including two molecules coding for auxin/indole acetic acid (Aux/IAA. To further explore the biological role of the melon Aux/IAA transcript CmF-308 in the vascular tissue, a cassette containing the coding sequence of this gene under a phloem-specific promoter was introduced into tomato plants. The number of lateral roots was significantly higher in transgenic plants expressing CmF-308 under the AtSUC2 promoter than in controls. A similar effect on root development was obtained after transient expression of CmF-308 in source leaves of N. benthamiana plants. An auxin-response assay showed that CmF-308-transgenic roots are more sensitive to auxin than control roots. In addition to the altered root development, phloem-specific expression of CmF-308 resulted in shorter plants, a higher number of lateral shoots and delayed flowering, a phenotype resembling reduced apical dominance. In contrast to the root response, cotyledons of the transgenic plants were less sensitive to auxin than control cotyledons. The reduced auxin sensitivity in the shoot tissue was confirmed by lower relative expression of several Aux/IAA genes in leaves and an increase in the relative expression of a cytokinin-response regulator, TRR8/9b. The accumulated data suggest that expression of Aux/IAA in the phloem modifies auxin sensitivity in a tissue-specific manner, thereby altering plant development.

  18. Grapevine Rootstocks Differentially Affect the Rate of Ripening and Modulate Auxin-Related Genes in Cabernet Sauvignon Berries.

    Science.gov (United States)

    Corso, Massimiliano; Vannozzi, Alessandro; Ziliotto, Fiorenza; Zouine, Mohamed; Maza, Elie; Nicolato, Tommaso; Vitulo, Nicola; Meggio, Franco; Valle, Giorgio; Bouzayen, Mondher; Müller, Maren; Munné-Bosch, Sergi; Lucchin, Margherita; Bonghi, Claudio

    2016-01-01

    In modern viticulture, grafting commercial grapevine varieties on interspecific rootstocks is a common practice required for conferring resistance to many biotic and abiotic stresses. Nevertheless, the use of rootstocks to gain these essential traits is also known to impact grape berry development and quality, although the underlying mechanisms are still poorly understood. In grape berries, the onset of ripening (véraison) is regulated by a complex network of mobile signals including hormones such as auxins, ethylene, abscisic acid, and brassinosteroids. Recently, a new rootstock, designated M4, was selected based on its enhanced tolerance to water stress and medium vigor. This study investigates the effect of M4 on Cabernet Sauvignon (CS) berry development in comparison to the commercial 1103P rootstock. Physical and biochemical parameters showed that the ripening rate of CS berries is faster when grafted onto M4. A multifactorial analysis performed on mRNA-Seq data obtained from skin and pulp of berries grown in both graft combinations revealed that genes controlling auxin action (ARF and Aux/IAA) represent one of main categories affected by the rootstock genotype. Considering that the level of auxin tightly regulates the transcription of these genes, we investigated the behavior of the main gene families involved in auxin biosynthesis and conjugation. Molecular and biochemical analyses confirmed a link between the rate of berry development and the modulation of auxin metabolism. Moreover, the data indicate that this phenomenon appears to be particularly pronounced in skin tissue in comparison to the flesh. PMID:26904046

  19. Genome-wide characterization and expression profiling of the AUXIN RESPONSE FACTOR (ARF gene family in Eucalyptus grandis.

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    Hong Yu

    Full Text Available Auxin is a central hormone involved in a wide range of developmental processes including the specification of vascular stem cells. Auxin Response Factors (ARF are important actors of the auxin signalling pathway, regulating the transcription of auxin-responsive genes through direct binding to their promoters. The recent availability of the Eucalyptus grandis genome sequence allowed us to examine the characteristics and evolutionary history of this gene family in a woody plant of high economic importance. With 17 members, the E. grandis ARF gene family is slightly contracted, as compared to those of most angiosperms studied hitherto, lacking traces of duplication events. In silico analysis of alternative transcripts and gene truncation suggested that these two mechanisms were preeminent in shaping the functional diversity of the ARF family in Eucalyptus. Comparative phylogenetic analyses with genomes of other taxonomic lineages revealed the presence of a new ARF clade found preferentially in woody and/or perennial plants. High-throughput expression profiling among different organs and tissues and in response to environmental cues highlighted genes expressed in vascular cambium and/or developing xylem, responding dynamically to various environmental stimuli. Finally, this study allowed identification of three ARF candidates potentially involved in the auxin-regulated transcriptional program underlying wood formation.

  20. Grapevine Rootstocks Differentially Affect the Rate of Ripening and Modulate Auxin-Related Genes in Cabernet Sauvignon Berries

    Science.gov (United States)

    Corso, Massimiliano; Vannozzi, Alessandro; Ziliotto, Fiorenza; Zouine, Mohamed; Maza, Elie; Nicolato, Tommaso; Vitulo, Nicola; Meggio, Franco; Valle, Giorgio; Bouzayen, Mondher; Müller, Maren; Munné-Bosch, Sergi; Lucchin, Margherita; Bonghi, Claudio

    2016-01-01

    In modern viticulture, grafting commercial grapevine varieties on interspecific rootstocks is a common practice required for conferring resistance to many biotic and abiotic stresses. Nevertheless, the use of rootstocks to gain these essential traits is also known to impact grape berry development and quality, although the underlying mechanisms are still poorly understood. In grape berries, the onset of ripening (véraison) is regulated by a complex network of mobile signals including hormones such as auxins, ethylene, abscisic acid, and brassinosteroids. Recently, a new rootstock, designated M4, was selected based on its enhanced tolerance to water stress and medium vigor. This study investigates the effect of M4 on Cabernet Sauvignon (CS) berry development in comparison to the commercial 1103P rootstock. Physical and biochemical parameters showed that the ripening rate of CS berries is faster when grafted onto M4. A multifactorial analysis performed on mRNA-Seq data obtained from skin and pulp of berries grown in both graft combinations revealed that genes controlling auxin action (ARF and Aux/IAA) represent one of main categories affected by the rootstock genotype. Considering that the level of auxin tightly regulates the transcription of these genes, we investigated the behavior of the main gene families involved in auxin biosynthesis and conjugation. Molecular and biochemical analyses confirmed a link between the rate of berry development and the modulation of auxin metabolism. Moreover, the data indicate that this phenomenon appears to be particularly pronounced in skin tissue in comparison to the flesh. PMID:26904046