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Sample records for chlamydomonas lacking photosystem

  1. Carbon dioxide fixation and photoevolution of hydrogen and oxygen in a mutant of Chlamydomonas lacking Photosystem I

    Energy Technology Data Exchange (ETDEWEB)

    Greenbaum, E.; Lee, J.W.; Tevault, C.V. [Oak Ridge National Lab., TN (United States)] [and others

    1995-09-01

    Sustained photoassimilation of atmospheric CO{sub 2} and simultaneous photoevolution of molecular hydrogen and oxygen has been observed in a Photosystem I deficient mutant B4 of Chlamydomonas reinhardtii that contains only Photosystem II. The data indicate that Photosystem II alone is capable of spanning the potential difference between water oxidation/oxygen evolution and ferredoxin reduction. The rates of both CO{sub 2} fixation and hydrogen and oxygen evolution are similar in the mutant to that of the wild-type C. reinhardtii 137c containing both photosystems. The wild-type had stable photosynthetic activity, measured as CO{sub 2} fixation, under both air and anaerobic conditions, while the mutant was stable only under anaerobic conditions. The results are discussed in terms of the fundamental mechanisms and energetics of photosynthesis and possible implications for the evolution of oxygenic photosynthesis.

  2. Loss of phylloquinone in Chlamydomonas affects plastoquinone pool size and photosystem II synthesis.

    Science.gov (United States)

    Lefebvre-Legendre, Linnka; Rappaport, Fabrice; Finazzi, Giovanni; Ceol, Mauro; Grivet, Chantal; Hopfgartner, Gérard; Rochaix, Jean-David

    2007-05-01

    Phylloquinone functions as the electron transfer cofactor at the A(1) site of photosystem I. We have isolated and characterized a mutant of Chlamydomonas reinhardtii, menD1, that is deficient in MenD, which encodes 2-succinyl-6-hydroxy-2,4-cyclohexadiene-1-carboxylate synthase, an enzyme that catalyzes the first specific step of the phylloquinone biosynthetic pathway. The mutant is photosynthetically active but light-sensitive. Analysis of total pigments by mass spectrometry reveals that phylloquinone is absent in menD1, but plastoquinone levels are not affected. This is further confirmed by the rescue of menD1 by addition of phylloquinone to the growth medium. Analysis of electron transfer by absorption spectroscopy indicates that plastoquinone replaces phylloquinone in photosystem I and that electron transfer from A(1) to the iron-sulfur centers is slowed down at least 40-fold. Consistent with a replacement of phylloquinone by plastoquinone, the size of the free plastoquinone pool of menD1 is reduced by 20-30%. In contrast to cyanobacterial MenD-deficient mutants, photosystem I accumulates normally in menD1, whereas the level of photosystem II declines. This decrease is because of reduced synthesis of the photosystem II core subunits. The relationship between plastoquinone occupancy of the A(1) site in photosystem I and the reduced accumulation of photosystem II is discussed. PMID:17339322

  3. Expression of the nuclear encoded OEE1 protein is required for oxygen evolution and stability of photosystem II particles in Chlamydomonas reinhardtii.

    OpenAIRE

    Mayfield, S P; Bennoun, P; Rochaix, J D

    1987-01-01

    In Chlamydomonas reinhardtii the oxygen evolving enhancer protein 1 (OEE1), which is part of the oxygen evolving complex of photosystem II (PS II), is coded for by a single nuclear gene (psb1). The nuclear mutant FuD44 specifically lacks the OEE1 polypeptide and is completely deficient in photosynthetic oxygen evolution. In this mutant a 5 kb DNA insertion into the 5' region of the psb1 gene results in the complete absence of OEE1 mRNA and protein. A revertant, FuD44-R 2, which is capable of ...

  4. TEF30 Interacts with Photosystem II Monomers and Is Involved in the Repair of Photodamaged Photosystem II in Chlamydomonas reinhardtii.

    Science.gov (United States)

    Muranaka, Ligia Segatto; Rütgers, Mark; Bujaldon, Sandrine; Heublein, Anja; Geimer, Stefan; Wollman, Francis-André; Schroda, Michael

    2016-02-01

    The remarkable capability of photosystem II (PSII) to oxidize water comes along with its vulnerability to oxidative damage. Accordingly, organisms harboring PSII have developed strategies to protect PSII from oxidative damage and to repair damaged PSII. Here, we report on the characterization of the THYLAKOID ENRICHED FRACTION30 (TEF30) protein in Chlamydomonas reinhardtii, which is conserved in the green lineage and induced by high light. Fractionation studies revealed that TEF30 is associated with the stromal side of thylakoid membranes. By using blue native/Deriphat-polyacrylamide gel electrophoresis, sucrose density gradients, and isolated PSII particles, we found TEF30 to quantitatively interact with monomeric PSII complexes. Electron microscopy images revealed significantly reduced thylakoid membrane stacking in TEF30-underexpressing cells when compared with control cells. Biophysical and immunological data point to an impaired PSII repair cycle in TEF30-underexpressing cells and a reduced ability to form PSII supercomplexes after high-light exposure. Taken together, our data suggest potential roles for TEF30 in facilitating the incorporation of a new D1 protein and/or the reintegration of CP43 into repaired PSII monomers, protecting repaired PSII monomers from undergoing repeated repair cycles or facilitating the migration of repaired PSII monomers back to stacked regions for supercomplex reassembly. PMID:26644506

  5. Hydrogen Production in Chlamydomonas: Photosystem II-Dependent and -Independent Pathways Differ in Their Requirement for Starch Metabolism1[W

    Science.gov (United States)

    Chochois, Vincent; Dauvillée, David; Beyly, Audrey; Tolleter, Dimitri; Cuiné, Stéphan; Timpano, Hélène; Ball, Steven; Cournac, Laurent; Peltier, Gilles

    2009-01-01

    Under sulfur deprivation conditions, the green alga Chlamydomonas reinhardtii produces hydrogen in the light in a sustainable manner thanks to the contribution of two pathways, direct and indirect. In the direct pathway, photosystem II (PSII) supplies electrons to hydrogenase through the photosynthetic electron transport chain, while in the indirect pathway, hydrogen is produced in the absence of PSII through a photosystem I-dependent process. Starch metabolism has been proposed to contribute to both pathways by feeding respiration and maintaining anoxia during the direct pathway and by supplying reductants to the plastoquinone pool during the indirect pathway. At variance with this scheme, we report that a mutant lacking starch (defective for sta6) produces similar hydrogen amounts as the parental strain in conditions of sulfur deprivation. However, when PSII is inhibited by 3-(3,4-dichlorophenyl)-1,1-dimethylurea, conditions where hydrogen is produced by the indirect pathway, hydrogen production is strongly reduced in the starch-deficient mutant. We conclude that starch breakdown contributes to the indirect pathway by feeding electrons to the plastoquinone pool but is dispensable for operation of the direct pathway that prevails in the absence of DCMU. While hydrogenase induction was strongly impaired in the starch-deficient mutant under dark anaerobic conditions, wild-type-like induction was observed in the light. Because this light-driven hydrogenase induction is DCMU insensitive and strongly inhibited by carbonyl cyanide-p-trifluoromethoxyphenylhydrazone or 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone, we conclude that this process is regulated by the proton gradient generated by cyclic electron flow around PSI. PMID:19700559

  6. Posttranslational events leading to the assembly of photosystem II protein complex: a study using photosynthesis mutants from Chlamydomonas reinhardtii

    OpenAIRE

    1989-01-01

    We studied the assembly of photosystem II (PSII) in several mutants from Chlamydomonas reinhardtii which were unable to synthesize either one PSII core subunit (P6 [43 kD], D1, or D2) or one oxygen-evolving enhancer (OEE1 or OEE2) subunit. Synthesis of the PSII subunits was analyzed on electrophoretograms of cells pulse labeled with [14C]acetate. Their accumulation in thylakoid membranes was studied on immunoblots, their chlorophyll-binding ability on nondenaturating gels, their assembly by d...

  7. A Nucleus-Encoded Chloroplast Phosphoprotein Governs Expression of the Photosystem I Subunit PsaC in Chlamydomonas reinhardtii.

    Science.gov (United States)

    Douchi, Damien; Qu, Yujiao; Longoni, Paolo; Legendre-Lefebvre, Linnka; Johnson, Xenie; Schmitz-Linneweber, Christian; Goldschmidt-Clermont, Michel

    2016-05-01

    The nucleo-cytoplasmic compartment exerts anterograde control on chloroplast gene expression through numerous proteins that intervene at posttranscriptional steps. Here, we show that the maturation of psaC mutant (mac1) of Chlamydomonas reinhardtii is defective in photosystem I and fails to accumulate psaC mRNA. The MAC1 locus encodes a member of the Half-A-Tetratricopeptide (HAT) family of super-helical repeat proteins, some of which are involved in RNA transactions. The Mac1 protein localizes to the chloroplast in the soluble fraction. MAC1 acts through the 5' untranslated region of psaC transcripts and is required for their stability. Small RNAs that map to the 5'end of psaC RNA in the wild type but not in the mac1 mutant are inferred to represent footprints of MAC1-dependent protein binding, and Mac1 expressed in bacteria binds RNA in vitro. A coordinate response to iron deficiency, which leads to dismantling of the photosynthetic electron transfer chain and in particular of photosystem I, also causes a decrease of Mac1. Overexpression of Mac1 leads to a parallel increase in psaC mRNA but not in PsaC protein, suggesting that Mac1 may be limiting for psaC mRNA accumulation but that other processes regulate protein accumulation. Furthermore, Mac 1 is differentially phosphorylated in response to iron availability and to conditions that alter the redox balance of the electron transfer chain. PMID:27113776

  8. Light-Harvesting Complex Protein LHCBM9 Is Critical for Photosystem II Activity and Hydrogen Production in Chlamydomonas reinhardtii.

    Science.gov (United States)

    Grewe, Sabrina; Ballottari, Matteo; Alcocer, Marcelo; D'Andrea, Cosimo; Blifernez-Klassen, Olga; Hankamer, Ben; Mussgnug, Jan H; Bassi, Roberto; Kruse, Olaf

    2014-04-01

    Photosynthetic organisms developed multiple strategies for balancing light-harvesting versus intracellular energy utilization to survive ever-changing environmental conditions. The light-harvesting complex (LHC) protein family is of paramount importance for this function and can form light-harvesting pigment protein complexes. In this work, we describe detailed analyses of the photosystem II (PSII) LHC protein LHCBM9 of the microalga Chlamydomonas reinhardtii in terms of expression kinetics, localization, and function. In contrast to most LHC members described before, LHCBM9 expression was determined to be very low during standard cell cultivation but strongly increased as a response to specific stress conditions, e.g., when nutrient availability was limited. LHCBM9 was localized as part of PSII supercomplexes but was not found in association with photosystem I complexes. Knockdown cell lines with 50 to 70% reduced amounts of LHCBM9 showed reduced photosynthetic activity upon illumination and severe perturbation of hydrogen production activity. Functional analysis, performed on isolated PSII supercomplexes and recombinant LHCBM9 proteins, demonstrated that presence of LHCBM9 resulted in faster chlorophyll fluorescence decay and reduced production of singlet oxygen, indicating upgraded photoprotection. We conclude that LHCBM9 has a special role within the family of LHCII proteins and serves an important protective function during stress conditions by promoting efficient light energy dissipation and stabilizing PSII supercomplexes. PMID:24706511

  9. State transitions redistribute rather than dissipate energy between the two photosystems in Chlamydomonas.

    Science.gov (United States)

    Nawrocki, Wojciech J; Santabarbara, Stefano; Mosebach, Laura; Wollman, Francis-André; Rappaport, Fabrice

    2016-01-01

    Photosynthesis converts sunlight into biologically useful compounds, thus fuelling practically the entire biosphere. This process involves two photosystems acting in series powered by light harvesting complexes (LHCs) that dramatically increase the energy flux to the reaction centres. These complexes are the main targets of the regulatory processes that allow photosynthetic organisms to thrive across a broad range of light intensities. In microalgae, one mechanism for adjusting the flow of energy to the photosystems, state transitions, has a much larger amplitude than in terrestrial plants, whereas thermal dissipation of energy, the dominant regulatory mechanism in plants, only takes place after acclimation to high light. Here we show that, at variance with recent reports, microalgal state transitions do not dissipate light energy but redistribute it between the two photosystems, thereby allowing a well-balanced influx of excitation energy. PMID:27249564

  10. Posttranslational events leading to the assembly of photosystem II protein complex: a study using photosynthesis mutants from Chlamydomonas reinhardtii.

    Science.gov (United States)

    de Vitry, C; Olive, J; Drapier, D; Recouvreur, M; Wollman, F A

    1989-09-01

    We studied the assembly of photosystem II (PSII) in several mutants from Chlamydomonas reinhardtii which were unable to synthesize either one PSII core subunit (P6 [43 kD], D1, or D2) or one oxygen-evolving enhancer (OEE1 or OEE2) subunit. Synthesis of the PSII subunits was analyzed on electrophoretograms of cells pulse labeled with [14C]acetate. Their accumulation in thylakoid membranes was studied on immunoblots, their chlorophyll-binding ability on nondenaturating gels, their assembly by detergent fractionation, their stability by pulse-chase experiments and determination of in vitro protease sensitivity, and their localization by immunocytochemistry. In Chlamydomonas, the PSII core subunits P5 (47 kD), D1, and D2 are synthesized in a concerted manner while P6 synthesis is independent. P5 and P6 accumulate independently of each other in the stacked membranes. They bind chlorophyll soon after, or concomitantly with, their synthesis and independently of the presence of the other PSII subunits. Resistance to degradation increases step by step: beginning with assembly of P5, D1, and D2, then with binding of P6, and, finally, with binding of the OEE subunits on two independent high affinity sites (one for OEE1 and another for OEE2 to which OEE3 binds). In the absence of PSII cores, the OEE subunits accumulate independently in the thylakoid lumen and bind loosely to the membranes; OEE1 was found on stacked membranes, but OEE2 was found on either stacked or unstacked membranes depending on whether or not P6 was synthesized. PMID:2670960

  11. Two Chlamydomonas OPR proteins stabilize chloroplast mRNAs encoding small subunits of photosystem II and cytochrome b6 f.

    Science.gov (United States)

    Wang, Fei; Johnson, Xenie; Cavaiuolo, Marina; Bohne, Alexandra-Viola; Nickelsen, Joerg; Vallon, Olivier

    2015-06-01

    In plants and algae, chloroplast gene expression is controlled by nucleus-encoded proteins that bind to mRNAs in a specific manner, stabilizing mRNAs or promoting their splicing, editing, or translation. Here, we present the characterization of two mRNA stabilization factors of the green alga Chlamydomonas reinhardtii, which both belong to the OctotricoPeptide Repeat (OPR) family. MCG1 is necessary to stabilize the petG mRNA, encoding a small subunit of the cytochrome b6 f complex, while MBI1 stabilizes the psbI mRNA, coding for a small subunit of photosystem II. In the mcg1 mutant, the small RNA footprint corresponding to the 5'-end of the petG transcript is reduced in abundance. In both cases, the absence of the small subunit perturbs assembly of the cognate complex. Whereas PetG is essential for formation of a functional cytochrome b6 f dimer, PsbI appears partly dispensable as a low level of PSII activity can still be measured in its absence. Thus, nuclear control of chloroplast gene expression is not only exerted on the major core subunits of the complexes, but also on small subunits with a single transmembrane helix. While OPR proteins have thus far been involved in translation or trans-splicing of plastid mRNAs, our results expand the potential roles of this repeat family to their stabilization. PMID:25898982

  12. Refactoring the Six-Gene Photosystem II Core in the Chloroplast of the Green Algae Chlamydomonas reinhardtii.

    Science.gov (United States)

    Gimpel, Javier A; Nour-Eldin, Hussam H; Scranton, Melissa A; Li, Daphne; Mayfield, Stephen P

    2016-07-15

    Oxygenic photosynthesis provides the energy to produce all food and most of the fuel on this planet. Photosystem II (PSII) is an essential and rate-limiting component of this process. Understanding and modifying PSII function could provide an opportunity for optimizing photosynthetic biomass production, particularly under specific environmental conditions. PSII is a complex multisubunit enzyme with strong interdependence among its components. In this work, we have deleted the six core genes of PSII in the eukaryotic alga Chlamydomonas reinhardtii and refactored them in a single DNA construct. Complementation of the knockout strain with the core PSII synthetic module from three different green algae resulted in reconstitution of photosynthetic activity to 85, 55, and 53% of that of the wild-type, demonstrating that the PSII core can be exchanged between algae species and retain function. The strains, synthetic cassettes, and refactoring strategy developed for this study demonstrate the potential of synthetic biology approaches for tailoring oxygenic photosynthesis and provide a powerful tool for unraveling PSII structure-function relationships. PMID:26214707

  13. Site Energies of Active and Inactive Pheophytins in the Reaction Center of Photosystem II from Chlamydomonas Reinhardtii

    International Nuclear Information System (INIS)

    It is widely accepted that the primary electron acceptor in various Photosystem II (PSII) reaction center (RC) preparations is pheophytin α (Pheo α) within the D1 protein (PheoD1), while PheoD2 (within the D2 protein) is photochemically inactive. The Pheo site energies, however, have remained elusive, due to inherent spectral congestion. While most researchers over the past two decades placed the Qy-states of PheoD1 and PheoD2 bands near 678-684 and 668-672 nm, respectively, recent modeling (Raszewski et al. Biophys. J. 2005, 88, 986-998; Cox et al. J. Phys. Chem. B 2009, 113, 12364-12374) of the electronic structure of the PSII RC reversed the assignment of the active and inactive Pheos, suggesting that the mean site energy of PheoD1 is near 672 nm, whereas PheoD2 (∼677.5 nm) and ChlD1 (∼680 nm) have the lowest energies (i.e., the PheoD2-dominated exciton is the lowest excited state). In contrast, chemical pigment exchange experiments on isolated RCs suggested that both pheophytins have their Qy absorption maxima at 676-680 nm (Germano et al. Biochemistry 2001, 40, 11472-11482; Germano et al. Biophys. J. 2004, 86, 1664-1672). To provide more insight into the site energies of both PheoD1 and PheoD2 (including the corresponding Qx transitions, which are often claimed to be degenerate at 543 nm) and to attest that the above two assignments are most likely incorrect, we studied a large number of isolated RC preparations from spinach and wild-type Chlamydomonas reinhardtii (at different levels of intactness) as well as the Chlamydomonas reinhardtii mutant (D2-L209H), in which the active branch PheoD1 is genetically replaced with chlorophyll α (Chl α). We show that the Qx-/Qy-region site energies of PheoD1 and PheoD2 are ∼545/680 nm and ∼541.5/670 nm, respectively, in good agreement with our previous assignment (Jankowiak et al. J. Phys. Chem. B 2002, 106, 8803?8814). The latter values should be used to model excitonic structure and excitation energy

  14. Site Energies of Active and Inactive Pheophytins in the Reaction Center of Photosystem II from Chlamydomonas Reinhardtii

    Energy Technology Data Exchange (ETDEWEB)

    Acharya, K.; Neupane, B.; Zazubovich, V.; Sayre, R. T.; Picorel, R.; Seibert, M.; Jankowiak, R.

    2012-03-29

    It is widely accepted that the primary electron acceptor in various Photosystem II (PSII) reaction center (RC) preparations is pheophytin {alpha} (Pheo {alpha}) within the D1 protein (Pheo{sub D1}), while Pheo{sub D2} (within the D2 protein) is photochemically inactive. The Pheo site energies, however, have remained elusive, due to inherent spectral congestion. While most researchers over the past two decades placed the Q{sub y}-states of Pheo{sub D1} and Pheo{sub D2} bands near 678-684 and 668-672 nm, respectively, recent modeling [Raszewski et al. Biophys. J. 2005, 88, 986-998; Cox et al. J. Phys. Chem. B 2009, 113, 12364-12374] of the electronic structure of the PSII RC reversed the assignment of the active and inactive Pheos, suggesting that the mean site energy of Pheo{sub D1} is near 672 nm, whereas Pheo{sub D2} ({approx}677.5 nm) and Chl{sub D1} ({approx}680 nm) have the lowest energies (i.e., the Pheo{sub D2}-dominated exciton is the lowest excited state). In contrast, chemical pigment exchange experiments on isolated RCs suggested that both pheophytins have their Q{sub y} absorption maxima at 676-680 nm [Germano et al. Biochemistry 2001, 40, 11472-11482; Germano et al. Biophys. J. 2004, 86, 1664-1672]. To provide more insight into the site energies of both Pheo{sub D1} and Pheo{sub D2} (including the corresponding Q{sub x} transitions, which are often claimed to be degenerate at 543 nm) and to attest that the above two assignments are most likely incorrect, we studied a large number of isolated RC preparations from spinach and wild-type Chlamydomonas reinhardtii (at different levels of intactness) as well as the Chlamydomonas reinhardtii mutant (D2-L209H), in which the active branch Pheo{sub D1} is genetically replaced with chlorophyll {alpha} (Chl {alpha}). We show that the Q{sub x}-/Q{sub y}-region site energies of Pheo{sub D1} and Pheo{sub D2} are {approx}545/680 nm and {approx}541.5/670 nm, respectively, in good agreement with our previous assignment

  15. The Ultrastructure of a Chlamydomonas reinhardtii Mutant Strain Lacking Phytoene Synthase Resembles that of a Colorless Alga

    OpenAIRE

    Inwood, William; Yoshihara, Corinne; Zalpuri, Reena; Kim, Kwang-Seo; Kustu, Sydney

    2008-01-01

    Chlamydomonas reinhardtii strains lacking phytoene synthase, the first enzyme of carotenoid biosynthesis, are white. They lack carotenoid pigments, have very low levels of chlorophyll, and can grow only heterotrophically in the dark. Our electron and fluorescence microscopic studies showed that such a mutant strain (lts1-204) had a proliferated plastid envelope membrane but no stacks of thylakoid membranes within the plastid. It accumulated cytoplasmic compartments that appeared to be autopha...

  16. Effect of core-shell copper oxide nanoparticles on cell culture morphology and photosynthesis (photosystem II energy distribution) in the green alga, Chlamydomonas reinhardtii

    International Nuclear Information System (INIS)

    The effect of core-shell copper oxide nanoparticles with sizes smaller than 100 nm on cellular systems is still not well understood. Documenting these effects is pressing since core-shell copper oxide nanoparticles are currently components of pigments used frequently as antifouling paint protecting boats from crustacean, weed and slime fouling. However, the use of such paints may induce strong deteriorative effects on different aquatic trophic levels that are not the intended targets. Here, the toxic effect of core-shell copper oxide nanoparticles on the green alga, Chlamydomonas reinhardtii was investigated with regards to the change of algal cellular population structure, primary photochemistry of photosystem II and reactive oxygen species formation. Algal cultures were exposed to 0.004, 0.01 and 0.02 g/l of core-shell copper oxide nanoparticles for 6 h and a change in algal population structure was observed, while the formation of reactive oxygen species was determined using the 2',7'-dichlorodihydrofluorescein diacetate marker measured by flow cytometry. For the study of the photosystem II primary photochemistry we investigated the change in chlorophyll a rapid rise of fluorescence. We found that core-shell copper oxide nanoparticles induced cellular aggregation processes and had a deteriorative effect on chlorophyll by inducing the photoinhibition of photosystem II. The inhibition of photosynthetic electron transport induced a strong energy dissipation process via non-photochemical pathways. The deterioration of photosynthesis was interpreted as being caused by the formation of reactive oxygen species induced by core-shell copper oxide nanoparticles. However, no formation of reactive oxygen species was observed when C. reinhardtii was exposed to the core without the shell or to the shell only.

  17. Effect of core-shell copper oxide nanoparticles on cell culture morphology and photosynthesis (photosystem II energy distribution) in the green alga, Chlamydomonas reinhardtii

    Energy Technology Data Exchange (ETDEWEB)

    Saison, Cyril; Perreault, Francois [Department of Chemistry, Universite du Quebec a Montreal, 2101, Rue Jeanne Mance, Montreal, QC, H2X 2J6 (Canada); Daigle, Jean-Christophe [Department of Chemistry, Universite du Quebec a Montreal, 2101, Rue Jeanne Mance, Montreal, QC, H2X 2J6 (Canada); NanoQAM Research Center, Department of Chemistry, Universite du Quebec a Montreal, 2101, Rue Jeanne Mance, Montreal, QC, H2X 2J6 (Canada); Fortin, Claude [Institut National de la Recherche Scientifique, Centre Eau, Terre et Environnement, Universite du Quebec, 490, rue de la Couronne, Quebec, QC, G1K 9A9 (Canada); Claverie, Jerome; Morin, Mario [Department of Chemistry, Universite du Quebec a Montreal, 2101, Rue Jeanne Mance, Montreal, QC, H2X 2J6 (Canada); NanoQAM Research Center, Department of Chemistry, Universite du Quebec a Montreal, 2101, Rue Jeanne Mance, Montreal, QC, H2X 2J6 (Canada); Popovic, Radovan, E-mail: popovic.radovan@uqam.ca [Department of Chemistry, Universite du Quebec a Montreal, 2101, Rue Jeanne Mance, Montreal, QC, H2X 2J6 (Canada)

    2010-01-31

    The effect of core-shell copper oxide nanoparticles with sizes smaller than 100 nm on cellular systems is still not well understood. Documenting these effects is pressing since core-shell copper oxide nanoparticles are currently components of pigments used frequently as antifouling paint protecting boats from crustacean, weed and slime fouling. However, the use of such paints may induce strong deteriorative effects on different aquatic trophic levels that are not the intended targets. Here, the toxic effect of core-shell copper oxide nanoparticles on the green alga, Chlamydomonas reinhardtii was investigated with regards to the change of algal cellular population structure, primary photochemistry of photosystem II and reactive oxygen species formation. Algal cultures were exposed to 0.004, 0.01 and 0.02 g/l of core-shell copper oxide nanoparticles for 6 h and a change in algal population structure was observed, while the formation of reactive oxygen species was determined using the 2',7'-dichlorodihydrofluorescein diacetate marker measured by flow cytometry. For the study of the photosystem II primary photochemistry we investigated the change in chlorophyll a rapid rise of fluorescence. We found that core-shell copper oxide nanoparticles induced cellular aggregation processes and had a deteriorative effect on chlorophyll by inducing the photoinhibition of photosystem II. The inhibition of photosynthetic electron transport induced a strong energy dissipation process via non-photochemical pathways. The deterioration of photosynthesis was interpreted as being caused by the formation of reactive oxygen species induced by core-shell copper oxide nanoparticles. However, no formation of reactive oxygen species was observed when C. reinhardtii was exposed to the core without the shell or to the shell only.

  18. Refactoring the six-gene photosystem II core in the chloroplast of the green algae chlamydomonas reinhardtii

    DEFF Research Database (Denmark)

    Gimpel, Javier A; Nour-Eldin, Hussam Hassan; Scranton, Melissa A;

    2016-01-01

    production, particularly under specific environmental conditions. PSII is a complex multisubunit enzyme with strong interdependence among its components. In this work, we have deleted the six core genes of PSII in the eukaryotic alga Chlamydomonas reinhardtii and refactored them in a single DNA construct...

  19. Mutation of Photosystem II D1 protein that empower efficient phenotypes of Chlamydomonas Reinhardtii under extreme environment in space

    Science.gov (United States)

    Oxygenic photosynthesis involves capture and conversion of light energy into chemical energy, a process fundamental to life including plant productivity on Earth. Photosynthetic electron transport is catalyzed by two photochemical reaction centres in series, photosystem II (PS II) and photosytem I (...

  20. Role of the photosystem II-associated CAH3 in the oxygen evolving machinery in Chlamydomonas reinhardtii

    OpenAIRE

    Rende, Umut

    2012-01-01

    One of the most abundant proteins on the Earth is ribulose-1,5-biphosphate carboxylase/oxygenase (RUBISCO). RUBISCO is a CO2 fixing enzyme in oxygenic photosynthetic organisms that it has low affinity for CO2. When CO2 is the limiting factor in the environment, RUBISCO works inefficiently due to its oxygenase activity. Some higher plants and aquatic photosynthetic organisms, such as the green alga Chlamydomonas reinhardtii; therefore, evolved Carbon Concentrating Mechanisms to acquire and to ...

  1. Production of superoxide from Photosystem II in a rice (Oryza sativa L.) mutant lacking PsbS

    OpenAIRE

    Zulfugarov, Ismayil S; Tovuu, Altanzaya; Eu, Young-Jae; Dogsom, Bolormaa; Poudyal, Roshan Sharma; Nath, Krishna; Hall, Michael; Banerjee, Mainak; Yoon, Ung Chan; Moon, Yong-Hwan; An, Gynheung; Jansson, Stefan; Lee, Choon-Hwan

    2014-01-01

    Background PsbS is a 22-kDa Photosystem (PS) II protein involved in non-photochemical quenching (NPQ) of chlorophyll fluorescence. Rice (Oryza sativa L.) has two PsbS genes, PsbS1 and PsbS2. However, only inactivation of PsbS1, through a knockout (PsbS1-KO) or in RNAi transgenic plants, results in plants deficient in qE, the energy-dependent component of NPQ. Results In studies presented here, under fluctuating high light, growth of young seedlings lacking PsbS is retarded, and PSII in detach...

  2. Ascorbate accumulation during sulphur deprivation and its effects on photosystem II activity and H2 production of the green alga Chlamydomonas reinhardtii.

    Science.gov (United States)

    Nagy, Valéria; Vidal-Meireles, André; Tengölics, Roland; Rákhely, Gábor; Garab, Győző; Kovács, László; Tóth, Szilvia Z

    2016-07-01

    In nature, H2 production in Chlamydomonas reinhardtii serves as a safety valve during the induction of photosynthesis in anoxia, and it prevents the over-reduction of the photosynthetic electron transport chain. Sulphur deprivation of C. reinhardtii also triggers a complex metabolic response resulting in the induction of various stress-related genes, down-regulation of photosynthesis, the establishment of anaerobiosis and expression of active hydrogenase. Photosystem II (PSII) plays dual role in H2 production because it supplies electrons but the evolved O2 inhibits the hydrogenase. Here, we show that upon sulphur deprivation, the ascorbate content in C. reinhardtii increases about 50-fold, reaching the mM range; at this concentration, ascorbate inactivates the Mn-cluster of PSII, and afterwards, it can donate electrons to tyrozin Z(+) at a slow rate. This stage is followed by donor-side-induced photoinhibition, leading to the loss of charge separation activity in PSII and reaction centre degradation. The time point at which maximum ascorbate concentration is reached in the cell is critical for the establishment of anaerobiosis and initiation of H2 production. We also show that ascorbate influenced H2 evolution via altering the photosynthetic electron transport rather than hydrogenase activity and starch degradation. PMID:26714836

  3. Photosystem II Subunit PsbS Is Involved in the Induction of LHCSR Protein-dependent Energy Dissipation in Chlamydomonas reinhardtii.

    Science.gov (United States)

    Correa-Galvis, Viviana; Redekop, Petra; Guan, Katharine; Griess, Annika; Truong, Thuy B; Wakao, Setsuko; Niyogi, Krishna K; Jahns, Peter

    2016-08-12

    Non-photochemical quenching of excess excitation energy is an important photoprotective mechanism in photosynthetic organisms. In Arabidopsis thaliana, a high quenching capacity is constitutively present and depends on the PsbS protein. In the green alga Chlamydomonas reinhardtii, non-photochemical quenching becomes activated upon high light acclimation and requires the accumulation of light harvesting complex stress-related (LHCSR) proteins. Expression of the PsbS protein in C. reinhardtii has not been reported yet. Here, we show that PsbS is a light-induced protein in C. reinhardtii, whose accumulation under high light is further controlled by CO2 availability. PsbS accumulated after several hours of high light illumination at low CO2 At high CO2, however, PsbS was only transiently expressed under high light and was degraded after 1 h of high light exposure. PsbS accumulation correlated with an enhanced non-photochemical quenching capacity in high light-acclimated cells grown at low CO2 However, PsbS could not compensate for the function of LHCSR in an LHCSR-deficient mutant. Knockdown of PsbS accumulation led to reduction of both non-photochemical quenching capacity and LHCSR3 accumulation. Our data suggest that PsbS is essential for the activation of non-photochemical quenching in C. reinhardtii, possibly by promoting conformational changes required for activation of LHCSR3-dependent quenching in the antenna of photosystem II. PMID:27358399

  4. Mutation of Residue Arginine18 of Cytochrome b559 α-Subunit and its Effects on Photosystem Ⅱ Activities in Chlamydomonas reinhardtii

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    It has been known that arginine is used as the basic amino acid in the ?subunit of cytochrome b559 (Cyt b559) except histidine. However, previous studies have focused on the function of histidine in the activities of photosystem (PS) Ⅱ and there are no reports regarding the structural and/or functional roles of arginine in PSII complexes. In the present study,two arginine18 (R18) mutants of Chlamydomonas reinhardtii were constructed using site-directed mutagenesis, in which R18 was replaced by glutamic acid (E) and glycine (G). The results show that the oxygen evolution of the PSII complex in the R18G and R18E mutants was approximately 60% of wild-type (WT) levels and that, after irradiation at high light intensity, oxygen evolution for the PSII of mutants was reduced to zero compared with 40% in WT cells. The efficiency of light capture by PSII (Fv/Fm) of R18G and R18E mutants was approximately 42%-46% that of WT cells. Furthermore, levels of the ?subunit of Cyt b559 and PsbO proteins were reduced in thylakoid membranes compared with WT. Overall, these data suggest that R18 plays a significant role in helping Cyt b559 maintain the structure of the PSII complex and its activity,although it is not directly bound to the heme group.

  5. Site Energies of Active and Inactive Pheophytins in the Reaction Center of Photosystem II from Chlamydomonas Reinhardtii

    OpenAIRE

    Acharya, Khem; Neupane, Bhanu; Zazubovich, Valter; Sayre, R. T.; Picorel Castaño, Rafael; Seibert, Michael; Jankowiak, Ryszard J.

    2012-01-01

    It is widely accepted that the primary electron acceptor in various Photosystem II (PSII) reaction centers (RCs) is pheophytin a (Pheo a) within the D1 protein (PheoD1), while PheoD2 (within the D2 protein) is photochemically inactive. The Pheo site energies, however, have remained elusive, due to inherent spectral congestion. While most researchers over the last two decades assigned the Qy-states of PheoD1 and PheoD2 bands near 678–684 nm and 668–672 nm, respectively, recent modeling [Raszew...

  6. Transient inactivation of the thylakoid photosystem II light-harvesting protein kinase system and concomitant changes in intramembrane particle size during photoinhibition of Chlamydomonas reinhardtii

    International Nuclear Information System (INIS)

    Light-dependent reduction of the plastoquinone pool regulates the activity of the thylakoid-bound protein kinase which phosphorylates the light harvesting chlorophyll a,b-protein complex (LHC II) and regulates energy distribution between photosystems II (PS II) and I. Since reduction of plastoquinone by PS II is abolished in photoinhibited thylakoids due to loss of the secondary electron acceptor QB protein, it was of interest to examine the activity of the LHC II protein kinase system during photoinhibition and recovery of PS II activity. The kinase activity was assessed both in vivo and in vitro in Chlamydomonas cells exposed to high light intensity (photoinhibition) and recovery at low light intensity. The kinase activity was progressively reduced during photoinhibition and became undetectable after 90 min. The inactive LHC II-kinase system could not be reactivated in vitro either by light or by reduction of the plastoquinone pool following addition of reduced duroquinone (TMQH2). The LHC II polypeptides were dephosphorylated in vivo when cells, prelabeled with [32P]orthophosphate before exposure to high light intensity, were transferred to photoinhibiting light in the presence of [32P]orthophosphate. In vivo recovery of the LHC II-kinase activity, elicited by the addition of TMQH2 to the assay system, did not require restoration of QB-dependent electron flow or de novo protein synthesis, either in the cytoplasm or in the chloroplast. Mild sonication of thylakoids isolated from photoinhibited cells restored the ability of the LHC II protein kinase system to be activated in vitro by addition to TMQH2. Restoration of the light-activated LHC-II kinase required recovery of QB-dependent electron flow. At the structural level, photoinhibition did not affect the ratio of grana/stroma thylakoids

  7. Effect of chromium oxide (III) nanoparticles on the production of reactive oxygen species and photosystem II activity in the green alga Chlamydomonas reinhardtii.

    Science.gov (United States)

    Costa, Cristina Henning da; Perreault, François; Oukarroum, Abdallah; Melegari, Sílvia Pedroso; Popovic, Radovan; Matias, William Gerson

    2016-09-15

    With the growth of nanotechnology and widespread use of nanomaterials, there is an increasing risk of environmental contamination by nanomaterials. However, the potential implications of such environmental contamination are hard to evaluate since the toxicity of nanomaterials if often not well characterized. The objective of this study was to evaluate the toxicity of a chromium-based nanoparticle, Cr2O3-NP, used in a wide diversity of industrial processes and commercial products, on the unicellular green alga Chlamydomonas reinhardtii. The deleterious impacts of Cr2O3-NP were characterized using cell density measurements, production of reactive oxygen species (ROS), esterase enzymes activity, and photosystem II electron transport as indicators of toxicity. Cr2O3-NP exposure inhibited culture growth and significantly lowered cellular Chlorophyll a content. From cell density measurements, EC50 values of 2.05±0.20 and 1.35±0.06gL(-1) Cr2O3-NP were obtained after 24 and 72h of exposure, respectively. In addition, ROS levels were increased to 160.24±2.47% and 59.91±0.15% of the control value after 24 and 72h of exposition to 10gL(-1) Cr2O3-NP. At 24h of exposure, the esterase activity increased to 160.24% of control value, revealing a modification of the short-term metabolic response of algae to Cr2O3-NP exposure. In conclusion, the metabolism of C. reinhardtii was the most sensitive to Cr2O3-NP after 24h of treatment. PMID:26803219

  8. Alteration of proteins and pigments influence the function of photosystem I under iron deficiency from Chlamydomonas reinhardtii.

    Directory of Open Access Journals (Sweden)

    Venkateswarlu Yadavalli

    Full Text Available BACKGROUND: Iron is an essential micronutrient for all organisms because it is a component of enzyme cofactors that catalyze redox reactions in fundamental metabolic processes. Even though iron is abundant on earth, it is often present in the insoluble ferric [Fe (III] state, leaving many surface environments Fe-limited. The haploid green alga Chlamydomonas reinhardtii is used as a model organism for studying eukaryotic photosynthesis. This study explores structural and functional changes in PSI-LHCI supercomplexes under Fe deficiency as the eukaryotic photosynthetic apparatus adapts to Fe deficiency. RESULTS: 77K emission spectra and sucrose density gradient data show that PSI and LHCI subunits are affected under iron deficiency conditions. The visible circular dichroism (CD spectra associated with strongly-coupled chlorophyll dimers increases in intensity. The change in CD signals of pigments originates from the modification of interactions between pigment molecules. Evidence from sucrose gradients and non-denaturing (green gels indicates that PSI-LHCI levels were reduced after cells were grown for 72 h in Fe-deficient medium. Ultrafast fluorescence spectroscopy suggests that red-shifted pigments in the PSI-LHCI antenna were lost during Fe stress. Further, denaturing gel electrophoresis and immunoblot analysis reveals that levels of the PSI subunits PsaC and PsaD decreased, while PsaE was completely absent after Fe stress. The light harvesting complexes were also susceptible to iron deficiency, with Lhca1 and Lhca9 showing the most dramatic decreases. These changes in the number and composition of PSI-LHCI supercomplexes may be caused by reactive oxygen species, which increase under Fe deficiency conditions. CONCLUSIONS: Fe deficiency induces rapid reduction of the levels of photosynthetic pigments due to a decrease in chlorophyll synthesis. Chlorophyll is important not only as a light-harvesting pigment, but also has a structural role

  9. Altered Fermentative Metabolism in Chlamydomonas reinhardtii Mutants Lacking Pyruvate Formate Lyase and Both Pyruvate Formate Lyase and Alcohol Dehydrogenase

    Energy Technology Data Exchange (ETDEWEB)

    Catalanotti, C.; Dubini, A.; Subramanian, V.; Yang, W. Q.; Magneschi, L.; Mus, F.; Seibert, M.; Posewitz, M. C.; Grossman, A. R.

    2012-02-01

    Chlamydomonas reinhardtii, a unicellular green alga, often experiences hypoxic/anoxic soil conditions that activate fermentation metabolism. We isolated three Chlamydomonas mutants disrupted for the pyruvate formate lyase (PFL1) gene; the encoded PFL1 protein catalyzes a major fermentative pathway in wild-type Chlamydomonas cells. When the pfl1 mutants were subjected to dark fermentative conditions, they displayed an increased flux of pyruvate to lactate, elevated pyruvate decarboxylation, ethanol accumulation, diminished pyruvate oxidation by pyruvate ferredoxin oxidoreductase, and lowered H2 production. The pfl1-1 mutant also accumulated high intracellular levels of lactate, succinate, alanine, malate, and fumarate. To further probe the system, we generated a double mutant (pfl1-1 adh1) that is unable to synthesize both formate and ethanol. This strain, like the pfl1 mutants, secreted lactate, but it also exhibited a significant increase in the levels of extracellular glycerol, acetate, and intracellular reduced sugars and a decrease in dark, fermentative H2 production. Whereas wild-type Chlamydomonas fermentation primarily produces formate and ethanol, the double mutant reroutes glycolytic carbon to lactate and glycerol. Although the metabolic adjustments observed in the mutants facilitate NADH reoxidation and sustained glycolysis under dark, anoxic conditions, the observed changes could not have been predicted given our current knowledge of the regulation of fermentation metabolism.

  10. Flexibility in Anaerobic Metabolism as Revealed in a Mutant of Chlamydomonas reinhardtii Lacking Hydrogenase Activity*S⃞

    OpenAIRE

    Dubini, Alexandra; Mus, Florence; Seibert, Michael; Grossman, Arthur R.; Posewitz, Matthew C.

    2009-01-01

    The green alga Chlamydomonas reinhardtii has a network of fermentation pathways that become active when cells acclimate to anoxia. Hydrogenase activity is an important component of this metabolism, and we have compared metabolic and regulatory responses that accompany anaerobiosis in wild-type C. reinhardtii cells and a null mutant strain for the HYDEF gene (hydEF-1 mutant), which encodes an [FeFe] hydrogenase maturation protein. This mutant has no hydrogenase activity...

  11. A novel screening method for hydrogenase-deficient mutants in Chlamydomonas reinhardtii based on in vivo chlorophyll fluorescence and photosystem II quantum yield

    OpenAIRE

    Godaux, Damien; Emonds-Alt, Barbara; Berne, Nicolas; Ghysels, Bart(*); Alric, Jean; Remacle, Claire; Cardol, Pierre

    2013-01-01

    In Chlamydomonas reinhardtii, prolonged anaerobiosis leads to the expression of enzymes Received 30 August 2012 belonging to various fermentative pathways. Among them, oxygen-sensitive hydrogenases Received in revised form (HydA1/2) catalyze the synthesis of molecular hydrogen from protons and reduced ferre- 12 November 2012 doxin in the stroma. In this work, by analyzing wild type and mutants affected in H2 Accepted 16 November 2012 production, we show that maximal PSII photosynt...

  12. Photosystem II Repair and Plant Immunity: Lessons Learned from Arabidopsis Mutant Lacking the THYLAKOID LUMEN PROTEIN 18.3.

    Science.gov (United States)

    Järvi, Sari; Isojärvi, Janne; Kangasjärvi, Saijaliisa; Salojärvi, Jarkko; Mamedov, Fikret; Suorsa, Marjaana; Aro, Eva-Mari

    2016-01-01

    Chloroplasts play an important role in the cellular sensing of abiotic and biotic stress. Signals originating from photosynthetic light reactions, in the form of redox and pH changes, accumulation of reactive oxygen and electrophile species or stromal metabolites are of key importance in chloroplast retrograde signaling. These signals initiate plant acclimation responses to both abiotic and biotic stresses. To reveal the molecular responses activated by rapid fluctuations in growth light intensity, gene expression analysis was performed with Arabidopsis thaliana wild type and the tlp18.3 mutant plants, the latter showing a stunted growth phenotype under fluctuating light conditions (Biochem. J, 406, 415-425). Expression pattern of genes encoding components of the photosynthetic electron transfer chain did not differ between fluctuating and constant light conditions, neither in wild type nor in tlp18.3 plants, and the composition of the thylakoid membrane protein complexes likewise remained unchanged. Nevertheless, the fluctuating light conditions repressed in wild-type plants a broad spectrum of genes involved in immune responses, which likely resulted from shade-avoidance responses and their intermixing with hormonal signaling. On the contrary, in the tlp18.3 mutant plants there was an imperfect repression of defense-related transcripts upon growth under fluctuating light, possibly by signals originating from minor malfunction of the photosystem II (PSII) repair cycle, which directly or indirectly modulated the transcript abundances of genes related to light perception via phytochromes. Consequently, a strong allocation of resources to defense reactions in the tlp18.3 mutant plants presumably results in the stunted growth phenotype under fluctuating light. PMID:27064270

  13. Manganese deficiency in Chlamydomonas results in loss of photosystem II and MnSOD function, sensitivity to peroxides, and secondary phosphorus and iron deficiency.

    Science.gov (United States)

    Allen, Michael D; Kropat, Janette; Tottey, Stephen; Del Campo, José A; Merchant, Sabeeha S

    2007-01-01

    For photoheterotrophic growth, a Chlamydomonas reinhardtii cell requires at least 1.7 x 10(7) manganese ions in the medium. At lower manganese ion concentrations (typically OEE proteins from the membrane. Assay of Mn superoxide dismutase (MnSOD) indicates loss of activity of two isozymes in proportion to the Mn deficiency. The expression of MSD3 through MSD5, encoding various isoforms of the MnSODs, is up-regulated severalfold in Mn-deficient cells, but neither expression nor activity of the plastid Fe-containing superoxide dismutase is changed, which contrasts with the dramatically increased MSD3 expression and plastid MnSOD activity in Fe-deficient cells. Mn-deficient cells are selectively sensitive to peroxide but not methyl viologen or Rose Bengal, and GPXs, APX, and MSRA2 genes (encoding glutathione peroxidase, ascorbate peroxidase, and methionine sulfoxide reductase 2) are slightly up-regulated. Elemental analysis indicates that the Mn, Fe, and P contents of cells in the Mn-deficient cultures were reduced in proportion to the deficiency. A natural resistance-associated macrophage protein homolog and one of five metal tolerance proteins were induced in Mn-deficient cells but not in Fe-deficient cells, suggesting that the corresponding gene products may be components of a Mn(2+)-selective assimilation pathway. PMID:17085511

  14. Ultrafast transient absorption studies on photosystem I reaction centers from Chlamydomonas reinhardtii. 2: mutations near the P700 reaction center chlorophylls provide new insight into the nature of the primary electron donor.

    Science.gov (United States)

    Holzwarth, Alfred R; Müller, Marc G; Niklas, Jens; Lubitz, Wolfgang

    2006-01-15

    The energy transfer and charge separation kinetics in several core Photosystem I particles of Chlamydomonas reinhardtii with point mutations around the PA and PB reaction center chlorophylls (Chls) have been studied using ultrafast transient absorption spectroscopy in the femtosecond to nanosecond time range to characterize the influence on the early electron transfer processes. The data have been analyzed in terms of kinetic compartment models. The adequate description of the transient absorption kinetics requires three different radical pairs in the time range up to approximately 100 ps. Also a charge recombination process from the first radical pair back to the excited state is present in all the mutants, as already shown previously for the wild-type (Müller, M. G., J. Niklas, W. Lubitz, and A. R. Holzwarth. 2003. Biophys. J. 85:3899-3922; and Holzwarth, A. R., M. G. Müller, J. Niklas, and W. Lubitz. 2005. J. Phys. Chem. B. 109:5903-59115). In all mutants, the primary charge separation occurs with the same effective rate constant within the error limits as in the wild-type (>350 ns(-1)), which implies an intrinsic rate constant of charge separation of hydrogen bond to the keto carbonyl of Chl PA, only a slight slowing down of the secondary electron transfer is observed. Finally for mutant A-W679A, which has the Trp near the PA Chl replaced, either no pronounced effect or, at best, a slight increase on the secondary electron transfer rate constants is observed. The effective charge recombination rate constant is modified in all mutants to some extent, with the strongest effect observed in mutant B-H656C. Our data strongly suggest that the Chls of the PA and PB pair, constituting what is traditionally called the "primary electron donor P700", are not oxidized in the first electron transfer process, but rather only in the secondary electron transfer step. We thus propose a new electron transfer mechanism for Photosystem I where the accessory Chl(s) function as

  15. Iron economy in Chlamydomonas reinhardtii

    Science.gov (United States)

    Glaesener, Anne G.; Merchant, Sabeeha S.; Blaby-Haas, Crysten E.

    2013-01-01

    While research on iron nutrition in plants has largely focused on iron-uptake pathways, photosynthetic microbes such as the unicellular green alga Chlamydomonas reinhardtii provide excellent experimental systems for understanding iron metabolism at the subcellular level. Several paradigms in iron homeostasis have been established in this alga, including photosystem remodeling in the chloroplast and preferential retention of some pathways and key iron-dependent proteins in response to suboptimal iron supply. This review presents our current understanding of iron homeostasis in Chlamydomonas, with specific attention on characterized responses to changes in iron supply, like iron-deficiency. An overview of frequently used methods for the investigation of iron-responsive gene expression, physiology and metabolism is also provided, including preparation of media, the effect of cell size, cell density and strain choice on quantitative measurements and methods for the determination of metal content and assessing the effect of iron supply on photosynthetic performance. PMID:24032036

  16. Correlation between changes in light energy distribution and changes in thylakoid membrane polypeptide phosphorylation in Chlamydomonas reinhardtii

    International Nuclear Information System (INIS)

    We have used a new method to extensively modify the redox state of the plastoquinone pool in Chlamydomonas reinhardtii intact cells. This was achieved by an anaerobic treatment that inhibits the chlororespiratory pathway recently described by P. Bennoun. A state I (plus 3,4-dichlorophenyl-1,1-dimethylurea) → anaerobic state transition induced a decrease in the maximal fluorescence yield at room temperature and in the F/sub PSII//F/sub PSI/ ratio at 770K, which was three times larger than in a classical state I → state II transition. The fluorescence changes observed in vivo were similar in amplitude to those observed in vitro upon transfer to the light of dark-adapted, broken chloroplasts incubated in the presence of ATP. We then compared the phosphorylation pattern of thylakoid polypeptides in C. reinhardtii in vitro and in vivo using γ-[32P]ATP and [32P]orthophosphate labeling, respectively. The same set of polypeptides, mainly light-harvesting complex polypeptides, was phosphorylated in both cases. We observed that this phosphorylation process is reversible and is mediated by the redox state of the plastoquinone pool in vivo as well as in vitro. Similar changes of even larger amplitude were observed with the F34 mutant intact cells lacking in photosystem II centers. The presence of the photosystem II centers is then not required for the occurrence of the plastoquinone-mediated phosphorylation of light-harvesting complex polypeptides

  17. Biogenesis of photosystem II complexes: transcriptional, translational, and posttranslational regulation

    International Nuclear Information System (INIS)

    The integral membrane proteins of photosystem II (PS II) reaction center complexes are encoded by chloroplast genomes. These proteins are absent from thylakoids of PS II mutants of algae and vascular plants as a result of either chloroplast or nuclear gene mutations. To resolve the molecular basis and the concurrent absence of the PS II polypeptides, protein synthesis rates and mRNA levels were measured in mutants of Chlamydomonas reinhardtii that lack PS II. The analyses show that one nuclear gene product regulates the levels of transcripts from the chloroplast gene encoding the 51-kD chlorophyll α-binding polypeptide (polypeptide 5) but is not involved in the synthesis of other chloroplast mRNAs. The other nuclear product is specifically required for translation of mRNA encoding the 32-34-kD polypeptide, D1. The absence of either D1 or polypeptide 5 does not eliminate the synthesis and thylakoid insertion of two other integral membrane proteins of PS II, the chlorophyll α-binding polypeptide of 46 kD (polypeptide 6) and the 30-kD D1-like protein, D2. However, these two unassembled subunits cannot be properly processed and/or are degraded in the mutants even though they reside in the membrane. In addition, pulse labeling of the nuclear mutants and a chloroplast mutant that does not synthesize D1 mRNA indicates that synthesis of polypeptide 5 and D1 is coordinated at the translational level. A model is presented to explain how absence of one of the two proteins could lead to translational arrest of the other

  18. Photo-oxidative stress in a xanthophyll-deficient mutant of Chlamydomonas.

    Science.gov (United States)

    Baroli, Irene; Gutman, Benjamin L; Ledford, Heidi K; Shin, Jai W; Chin, Brian L; Havaux, Michel; Niyogi, Krishna K

    2004-02-20

    When there is an imbalance between the light energy absorbed by a photosynthetic organism and that which can be utilized in photosynthesis, photo-oxidative stress can damage pigments, proteins, lipids, and nucleic acids. In this work we compared the wild type and a xanthophyll-deficient mutant of Chlamydomonas reinhardtii in their response to high amounts of light. Wild-type Chlamydomonas cells were able to acclimate to high amounts of light following transfer from low light conditions. In contrast, the npq1 lor1 double mutant, which lacks protective xanthophylls (zeaxanthin and lutein) in the chloroplast, progressively lost viability and photosynthetic capacity along with destruction of thylakoid membrane protein-pigment complexes and accumulation of reactive oxygen species and membrane lipid peroxides. Loss of viability was partially rescued by lowered oxygen tension, suggesting that the high sensitivity of the mutant to light stress is caused by the production of reactive oxygen species in the chloroplast. Cell death was not prevented by the addition of an organic carbon source to the growth medium, demonstrating that the photo-oxidative damage can target other essential chloroplast processes besides photosynthesis. From the differential sensitivity of the mutant to exogenously added pro-oxidants, we infer that the reactive oxygen species produced during light stress in npq1 lor1 may be singlet oxygen and/or superoxide but not hydrogen peroxide. The bleaching phenotype of npq1 lor1 was not due to enhanced photodamage to photosystem II but rather to a less localized phenomenon of accumulation of photo-oxidation products in chloroplast membranes. PMID:14665619

  19. UV-B Perception and Acclimation in Chlamydomonas reinhardtii.

    Science.gov (United States)

    Tilbrook, Kimberley; Dubois, Marine; Crocco, Carlos D; Yin, Ruohe; Chappuis, Richard; Allorent, Guillaume; Schmid-Siegert, Emanuel; Goldschmidt-Clermont, Michel; Ulm, Roman

    2016-04-01

    Plants perceive UV-B, an intrinsic component of sunlight, via a signaling pathway that is mediated by the photoreceptor UV RESISTANCE LOCUS8 (UVR8) and induces UV-B acclimation. To test whether similar UV-B perception mechanisms exist in the evolutionarily distant green alga Chlamydomonas reinhardtii, we identified Chlamydomonas orthologs of UVR8 and the key signaling factor CONSTITUTIVELY PHOTOMORPHOGENIC1 (COP1). Cr-UVR8 shares sequence and structural similarity to Arabidopsis thaliana UVR8, has conserved tryptophan residues for UV-B photoreception, monomerizes upon UV-B exposure, and interacts with Cr-COP1 in a UV-B-dependent manner. Moreover, Cr-UVR8 can interact with At-COP1 and complement the Arabidopsis uvr8 mutant, demonstrating that it is a functional UV-B photoreceptor. Chlamydomonas shows apparent UV-B acclimation in colony survival and photosynthetic efficiency assays. UV-B exposure, at low levels that induce acclimation, led to broad changes in the Chlamydomonas transcriptome, including in genes related to photosynthesis. Impaired UV-B-induced activation in the Cr-COP1 mutant hit1 indicates that UVR8-COP1 signaling induces transcriptome changes in response to UV-B. Also, hit1 mutants are impaired in UV-B acclimation. Chlamydomonas UV-B acclimation preserved the photosystem II core proteins D1 and D2 under UV-B stress, which mitigated UV-B-induced photoinhibition. These findings highlight the early evolution of UVR8 photoreceptor signaling in the green lineage to induce UV-B acclimation and protection. PMID:27020958

  20. Tetratricopeptide repeat protein protects photosystem I from oxidative disruption during assembly.

    Science.gov (United States)

    Heinnickel, Mark; Kim, Rick G; Wittkopp, Tyler M; Yang, Wenqiang; Walters, Karim A; Herbert, Stephen K; Grossman, Arthur R

    2016-03-01

    A Chlamydomonas reinhardtii mutant lacking CGL71, a thylakoid membrane protein previously shown to be involved in photosystem I (PSI) accumulation, exhibited photosensitivity and highly reduced abundance of PSI under photoheterotrophic conditions. Remarkably, the PSI content of this mutant declined to nearly undetectable levels under dark, oxic conditions, demonstrating that reduced PSI accumulation in the mutant is not strictly the result of photodamage. Furthermore, PSI returns to nearly wild-type levels when the O2 concentration in the medium is lowered. Overall, our results suggest that the accumulation of PSI in the mutant correlates with the redox state of the stroma rather than photodamage and that CGL71 functions under atmospheric O2 conditions to allow stable assembly of PSI. These findings may reflect the history of the Earth's atmosphere as it transitioned from anoxic to highly oxic (1-2 billion years ago), a change that required organisms to evolve mechanisms to assist in the assembly and stability of proteins or complexes with O2-sensitive cofactors. PMID:26903622

  1. Tools for regulated gene expression in the chloroplast of Chlamydomonas.

    Science.gov (United States)

    Rochaix, Jean-David; Surzycki, Raymond; Ramundo, Silvia

    2014-01-01

    The green unicellular alga Chlamydomonas reinhardtii has emerged as a very attractive model system for chloroplast genetic engineering. Algae can be transformed readily at the chloroplast level through bombardment of cells with a gene gun, and transformants can be selected using antibiotic resistance or phototrophic growth. An inducible chloroplast gene expression system could be very useful for several reasons. First, it could be used to elucidate the function of essential chloroplast genes required for cell growth and survival. Second, it could be very helpful for expressing proteins which are toxic to the algal cells. Third, it would allow for the reversible depletion of photosynthetic complexes thus making it possible to study their biogenesis in a controlled fashion. Fourth, it opens promising possibilities for hydrogen production in Chlamydomonas. Here we describe an inducible/repressible chloroplast gene expression system in Chlamydomonas in which the copper-regulated Cyc6 promoter drives the expression of the nuclear Nac2 gene encoding a protein which is targeted to the chloroplast where it acts specifically on the chloroplast psbD 5'-untranslated region and is required for the stable accumulation of the psbD mRNA and photosystem II. The system can be used for any chloroplast gene or transgene by placing it under the control of the psbD 5'-untranslated region. PMID:24599871

  2. Toxicity of PAMAM dendrimers to Chlamydomonas reinhardtii

    International Nuclear Information System (INIS)

    In recent decades, a new class of polymeric materials, PAMAM dendrimers, has attracted marked interest owing to their unique nanoscopic architecture and their hopeful perspectives in nanomedicine and therapeutics. However, the potential release of dendrimers into the aquatic environment raises the issue about their toxicity on aquatic organisms. Our investigation sought to estimate the toxicity of cationic PAMAM dendrimers on the green alga, Chlamydomonas reinhardtii. Algal cultures were exposed to different concentrations (0.3-10 mg L-1) of low dendrimer generations (G2, G4 and G5) for 72 h. Potential adverse effects on Chlamydomonas were assessed using esterase activity (cell viability), photosynthetic O2 evolution, pigments content and chlorophyll a fluorescence transient. According to the median inhibitory concentration (IC50) appraised from esterase activity, toxicity on cell viability decreased with dendrimer generation number (2, 3 and 5 mg L-1 for G2, G4 and G5 dendrimers, respectively). Moreover, the three generations of dendrimers did not induce the same changes in the photosynthetic metabolism of the green alga. O2 evolution was stimulated in cultures exposed to the lowest generations tested (i.e. G2 and G4) whereas no significant effects were observed with G5. In addition, total chlorophyll content was increased after G2 treatment at 2.5 mg L-1. Finally, G2 and G4 had positive effects on photosystem II (PSII): the amount of active PSII reaction centers, the primary charge separation and the electron transport between QA and QB were all increased inducing activation of the photosynthetic electron transport chain. These changes resulted in stimulation of full photosynthetic performance.

  3. A new method to identify flanking sequence tags in chlamydomonas using 3’-RACE

    OpenAIRE

    Meslet-Cladière Laurence; Vallon Olivier

    2012-01-01

    Abstract Background The green alga Chlamydomonas reinhardtii, although a premier model organism in biology, still lacks extensive insertion mutant libraries with well-identified Flanking Sequence Tags (FSTs). Rapid and efficient methods are needed for FST retrieval. Results Here, we present a novel method to identify FSTs in insertional mutants of Chlamydomonas. Transformants can be obtained with a resistance cassette lacking a 3’ untranslated region (UTR), suggesting that the RNA that is pro...

  4. Excitation energy transfer in Chlamydomonas reinhardtii deficient in the PSI core or the PSII core under conditions mimicking state transitions.

    Science.gov (United States)

    Wlodarczyk, Lucyna M; Dinc, Emine; Croce, Roberta; Dekker, Jan P

    2016-06-01

    The efficient use of excitation energy in photosynthetic membranes is achieved by a dense network of pigment-protein complexes. These complexes fulfill specific functions and interact dynamically with each other in response to rapidly changing environmental conditions. Here, we studied how in the intact cells of Chlamydomonas reinhardtii (C.r.) the lack of the photosystem I (PSI) core or the photosystem II (PSII) core affects these interactions. To that end the mutants F15 and M18 (both PSI-deficient) and FUD7 (PSII-deficient) were incubated under conditions known to promote state transitions in wild-type. The intact cells were then instantly frozen to 77K and the full-spectrum time-resolved fluorescence emission of the cells was measured by means of streak camera. In the PSI-deficient mutants excitation energy transfer (EET) towards light-harvesting complexes of PSI (Lhca) occurs in less than 0.5 ns, and fluorescence from Lhca decays in 3.1 ns. Decreased trapping by PSII and increased fluorescence of Lhca upon state 1 (S1)→state 2 (S2) transition appears in the F15 and less in the M18 mutant. In the PSII-deficient mutant FUD7, quenched (0.5 ns) and unquenched (2 ns) light-harvesting complexes of PSII (LHCII) are present in both states, with the quenched form more abundant in S2 than in S1. Moreover, EET of 0.4 ns from the remaining LHCII to PSI increases upon S1→S2 transition. We relate the excitation energy kinetics observed in F15, M18 and FUD7 to the remodeling of the photosynthetic apparatus in these mutants under S1 and S2 conditions. PMID:26946087

  5. Unraveling photosystems. Progress report

    International Nuclear Information System (INIS)

    Each of the three cyanobacteria examined contains two or more genes for the B protein of photosystem II of photosynthesis. One of these genes from the cyanobacterium Fremyella diplosiphon has been sequenced. Synthetic oliogopeptides were used to raise antibodies to two ten amino acid-long sequences of the 32 kilodalton B protein. To examine whether chloroplast promoter sequences (and hence possibly chloroplast genes) can function in cyanobacteria, we have used a series of plasmids containing the chloramphenicol acetyl transferase (CAT) gene minus its bacterial promoter. It appears that chloroplast promoters are recognized in cyanobacteria and act efficiently

  6. Sensitivity evaluation of the green alga Chlamydomonas reinhardtii to uranium by pulse amplitude modulated (PAM) fluorometry

    International Nuclear Information System (INIS)

    Highlights: •Our study addressed the toxicity thresholds of uranium on microalgae using PAM fluorometry. •The oxygen-evolving complex (OEC) of PSII was identified as the primary action site of uranium. •Uranium impaired the electron flux between the photosystems until almost complete inhibition. •Non-photochemical quenching was identified as the most sensitive fluorescence parameter. •PAM fluorometry provided a rapid and reasonably sensitive method for assessing stress response. -- Abstract: Although ecotoxicological studies tend to address the toxicity thresholds of uranium in freshwaters, there is a lack of information on the effects of the metal on physiological processes, particularly in aquatic plants. Knowing that uranium alters photosynthesis via impairment of the water photo-oxidation process, we determined whether pulse amplitude modulated (PAM) fluorometry was a relevant tool for assessing the impact of uranium on the green alga Chlamydomonas reinhardtii and investigated how and to what extent uranium hampered photosynthetic performance. Photosynthetic activity and quenching were assessed from fluorescence induction curves generated by PAM fluorometry, after 1 and 5 h of uranium exposure in controlled conditions. The oxygen-evolving complex (OEC) of PSII was identified as the primary action site of uranium, through alteration of the water photo-oxidation process as revealed by F0/Fv. Limiting re-oxidation of the plastoquinone pool, uranium impaired the electron flux between the photosystems until almost complete inhibition of the PSII quantum efficiency (F′q/F′m, EC50 = 303 ± 64 μg U L−1 after 5 h of exposure) was observed. Non-photochemical quenching (qN) was identified as the most sensitive fluorescence parameter (EC50 = 142 ± 98 μg U L−1 after 5 h of exposure), indicating that light energy not used in photochemistry was dissipated in non-radiative processes. It was shown that parameters which stemmed from fluorescence induction

  7. Sensitivity evaluation of the green alga Chlamydomonas reinhardtii to uranium by pulse amplitude modulated (PAM) fluorometry

    Energy Technology Data Exchange (ETDEWEB)

    Herlory, Olivier, E-mail: olivier.herlory@gmail.com [IRSN-Laboratoire d’Ecotoxicologie des Radionucléides, Centre de Cadarache, BP3, 13115 Saint Paul lez Durance (France); Bonzom, Jean-Marc, E-mail: jean-marc.bonzom@irsn.fr [IRSN-Laboratoire d’Ecotoxicologie des Radionucléides, Centre de Cadarache, BP3, 13115 Saint Paul lez Durance (France); Gilbin, Rodolphe, E-mail: rodolphe.gilbin@irsn.fr [IRSN-Laboratoire de Biogéochimie, Biodisponibilité et Transferts des Radionucléides, Centre de Cadarache, BP3, 13115 Saint Paul lez Durance (France)

    2013-09-15

    Highlights: •Our study addressed the toxicity thresholds of uranium on microalgae using PAM fluorometry. •The oxygen-evolving complex (OEC) of PSII was identified as the primary action site of uranium. •Uranium impaired the electron flux between the photosystems until almost complete inhibition. •Non-photochemical quenching was identified as the most sensitive fluorescence parameter. •PAM fluorometry provided a rapid and reasonably sensitive method for assessing stress response. -- Abstract: Although ecotoxicological studies tend to address the toxicity thresholds of uranium in freshwaters, there is a lack of information on the effects of the metal on physiological processes, particularly in aquatic plants. Knowing that uranium alters photosynthesis via impairment of the water photo-oxidation process, we determined whether pulse amplitude modulated (PAM) fluorometry was a relevant tool for assessing the impact of uranium on the green alga Chlamydomonas reinhardtii and investigated how and to what extent uranium hampered photosynthetic performance. Photosynthetic activity and quenching were assessed from fluorescence induction curves generated by PAM fluorometry, after 1 and 5 h of uranium exposure in controlled conditions. The oxygen-evolving complex (OEC) of PSII was identified as the primary action site of uranium, through alteration of the water photo-oxidation process as revealed by F{sub 0}/F{sub v}. Limiting re-oxidation of the plastoquinone pool, uranium impaired the electron flux between the photosystems until almost complete inhibition of the PSII quantum efficiency (F{sup ′}{sub q}/F{sup ′}{sub m}, EC{sub 50} = 303 ± 64 μg U L{sup −1} after 5 h of exposure) was observed. Non-photochemical quenching (qN) was identified as the most sensitive fluorescence parameter (EC{sub 50} = 142 ± 98 μg U L{sup −1} after 5 h of exposure), indicating that light energy not used in photochemistry was dissipated in non-radiative processes. It was shown

  8. Phosphorylation controls the localization and activation of the lumenal carbonic anhydrase in Chlamydomonas reinhardtii.

    Directory of Open Access Journals (Sweden)

    Amaya Blanco-Rivero

    Full Text Available BACKGROUND: Cah3 is the only carbonic anhydrase (CA isoform located in the thylakoid lumen of Chlamydomonas reinhardtii. Previous studies demonstrated its association with the donor side of the photosystem II (PSII where it is required for the optimal function of the water oxidizing complex. However this enzyme has also been frequently proposed to perform a critical function in inorganic carbon acquisition and CO(2 fixation and all mutants lacking Cah3 exhibit very poor growth after transfer to low CO(2 conditions. RESULTS/CONCLUSIONS: In the present work we demonstrate that after transfer to low CO(2, Cah3 is phosphorylated and that phosphorylation is correlated to changes in its localization and its increase in activity. When C. reinhardtii wild-type cells were acclimated to limiting CO(2 conditions, the Cah3 activity increased about 5-6 fold. Under these conditions, there were no detectable changes in the level of the Cah3 polypeptide. The increase in activity was specifically inhibited in the presence of Staurosporine, a protein kinase inhibitor, suggesting that the Cah3 protein was post-translationally regulated via phosphorylation. Immunoprecipitation and in vitro dephosphorylation experiments confirm this hypothesis. In vivo phosphorylation analysis of thylakoid polypeptides indicates that there was a 3-fold increase in the phosphorylation signal of the Cah3 polypeptide within the first two hours after transfer to low CO(2 conditions. The increase in the phosphorylation signal was correlated with changes in the intracellular localization of the Cah3 protein. Under high CO(2 conditions, the Cah3 protein was only associated with the donor side of PSII in the stroma thylakoids. In contrast, in cells grown at limiting CO(2 the protein was partly concentrated in the thylakoids crossing the pyrenoid, which did not contain PSII and were surrounded by Rubisco molecules. SIGNIFICANCE: This is the first report of a CA being post

  9. Association of chlorophyll a/c(2) complexes to photosystem I and photosystem II in the cryptophyte Rhodomonas CS24.

    Science.gov (United States)

    Kereïche, Sami; Kouril, Roman; Oostergetel, Gert T; Fusetti, Fabrizia; Boekema, Egbert J; Doust, Alexander B; van der Weij-de Wit, Chantal D; Dekker, Jan P

    2008-09-01

    Photosynthetic supercomplexes from the cryptophyte Rhodomonas CS24 were isolated by a short detergent treatment of membranes from the cryptophyte Rhodomonas CS24 and studied by electron microscopy and low-temperature absorption and fluorescence spectroscopy. At least three different types of supercomplexes of photosystem I (PSI) monomers and peripheral Chl a/c(2) proteins were found. The most common complexes have Chl a/c(2) complexes at both sides of the PSI core monomer and have dimensions of about 17x24 nm. The peripheral antenna in these supercomplexes shows no obvious similarities in size and/or shape with that of the PSI-LHCI supercomplexes from the green plant Arabidopsis thaliana and the green alga Chlamydomonas reinhardtii, and may be comprised of about 6-8 monomers of Chl a/c(2) light-harvesting complexes. In addition, two different types of supercomplexes of photosystem II (PSII) dimers and peripheral Chl a/c(2) proteins were found. The detected complexes consist of a PSII core dimer and three or four monomeric Chl a/c(2) proteins on one side of the PSII core at positions that in the largest complex are similar to those of Lhcb5, a monomer of the S-trimer of LHCII, Lhcb4 and Lhcb6 in green plants. PMID:18513489

  10. Structure and dynamics in Photosystem I

    Science.gov (United States)

    Jolley, Craig Charles

    Photosystem I (PSI) is a transmembrane protein complex that uses incident light energy to drive an energetically unfavorable electron transfer reaction across a membrane in the early steps of oxygenic photosynthesis. This electron transfer reaction provides energy for the fixing of carbon dioxide and for the subsequent synthesis of nearly all biological material on Earth. Despite the morphological variety of oxygenic photosynthetic organisms---ranging from single-celled aquatic cyanobacteria to large, complex terrestrial plants---the structure and function of PSI are remarkably well-conserved across phyla. PSI has been the subject of extensive interdisciplinary research involving fields ranging from molecular genetics to condensed matter physics, and many aspects of its function still remain unclear. This study presents a variety of theoretical and experimental approaches to aspects of PSI structure and dynamics. An atomic-level structural model of higher plant PSI has been constructed based on recent protein crystal structures, and provides insight into the evolution of eukaryotic PSI. Time-resolved optical spectroscopic studies of PSI supercomplexes from the green freshwater alga Chlamydomonas reinhardtii illustrate how this organism adapts its photosynthetic apparatus to deal with changing environmental conditions and highlight the importance of structure-function relationships in light-harvesting systems. A novel computational approach using constrained geometric simulations has been used to model a portion of the PSI assembly process, shedding some light on how the heterodimeric PSI reaction center evolved from the more ancient homodimeric photosynthetic reaction centers found in green sulfur bacteria and heliobacteria. A new method is also demonstrated in which constrained geometric simulations are used to flexibly fit a high-resolution protein structure to a low-resolution density map obtained with cryo-electron microscopy (cryo-EM) or low-resolution x

  11. Induction and Characterization of Mitochondrial DNA Mutants in Chlamydomonas Reinhardtii

    OpenAIRE

    Matagne, René-Fernand; Michel-Wolwertz, M.R.; Munaut, Carine; Duyckaerts, Claire; Sluse, Francis

    1989-01-01

    In addition to lethal minute colony mutations which correspond to loss of mitochondrial DNA, acriflavin induces in Chlamydomonas reinhardtii a low percentage of cells that grow in the light but do not divide under heterotrophic conditions. Two such obligate photoautotrophic mutants were shown to lack the cyanide-sensitive cytochrome pathway of the respiration and to have a reduced cytochrome c oxidase activity. In crosses to wild type, the mutations are transmitted almost exclusively from the...

  12. Mechanosensitive physiology of chlamydomonas reinhardtii under direct membrane distortion

    OpenAIRE

    Seul Ki Min; Gwang Heum Yoon; Jung Hyun Joo; Sang Jun Sim; Hwa Sung Shin

    2014-01-01

    Cellular membrane distortion invokes variations in cellular physiology. However, lack of an appropriate system to control the stress and facilitate molecular analyses has hampered progress of relevant studies. In this study, a microfluidic system that finely manipulates membrane distortion of Chlamydomonas reinhardtii (C. reinhardtii) was developed. The device facilitated a first-time demonstration that directs membrane distortion invokes variations in deflagellation, cell cycle, and lipid me...

  13. Unraveling photosystems. Final technical report

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-09-01

    This report highlights four main points. (1) A residue substitution in phosphoribulokinase of Synechocystis PCC 6803 renders the mutant light-sensitive. The authors isolated a light-sensitive mutant (BRLS) of the photosynthetic cyanobacterium Synechocystis 6803 that does not survive exposure to bright light; 70% of BRLS cells die upon exposure to light of > 3000 lux for 2 hr. (2) Excitation energy transfer from phycocyanin to chlorophyll in an apcA-defective mutant of Synechocystis sp. PCC 6803. A greenish mutant of the normally bule-green cyanobacterium Synechocystis sp. PC 6803, designated UV6p, was isolated and characterized. UV6p possesses functional photosystems I and II but lacks normal light harvesting phycobilisomes because allophycocyanin is absent and core-specific linker proteins are almost entirely absent. (3) Deletion of the psbG1 gene of the cyanobacterium Synechocystis sp. PCC 6803 leads to the activation of the cryptic psbG2 gene. The genes psbG1 and psbG2 in cyanobacterium Synechocystis sp. PCC 6803 are homologous. The psbG1 gene is located on the chromosome and is part of the ndhC-psbG1-ORF157 operon, while psbG2 is located on a plasmid and is not flanked by equivalent ndhC or ORF157 genes. (4) Deletion of the structural gene for the NADH-dehydrogenase subunit 4 of Synechocystis 6803 alters respiratory properties. Chloroplasts and cyanobacteria contain genes encoding polypeptides homologous to some subunits of the mitochondrial respiratory NADH-ubiquinol oxidoreductase complex (NADH dehydrogenase). Nothing is known of the role of the NADH dehydrogenase complex in photosynthesis, respiration, or other functions in chloroplasts, and little is known about their specific roles in the perhaps 42 subunits of this complex in the mitochondrion.

  14. Chlamydomonas: A Model Green Plant.

    Science.gov (United States)

    Sheffield, E.

    1985-01-01

    Discusses the instructional potential of Chlamydomonas in providing a basis for a range of experimental investigations to illustrate basic biological phenomena. Describes the use of this algae genus in studies of population growth, photosynthesis, and mating behavior. Procedures for laboratory exercises are included. (ML)

  15. Electron transport and photophosphorylation by Photosystem I in vivo in plants and cyanobacteria.

    Science.gov (United States)

    Fork, D C; Herbert, S K

    1993-06-01

    Recently, a number of techniques, some of them relatively new and many often used in combination, have given a clearer picture of the dynamic role of electron transport in Photosystem I of photosynthesis and of coupled cyclic photophosphorylation. For example, the photoacoustic technique has detected cyclic electron transport in vivo in all the major algal groups and in leaves of higher plants. Spectroscopic measurements of the Photosystem I reaction center and of the changes in light scattering associated with thylakoid membrane energization also indicate that cyclic photophosphorylation occurs in living plants and cyanobacteria, particularly under stressful conditions.In cyanobacteria, the path of cyclic electron transport has recently been proposed to include an NAD(P)H dehydrogenase, a complex that may also participate in respiratory electron transport. Photosynthesis and respiration may share common electron carriers in eukaryotes also. Chlororespiration, the uptake of O2 in the dark by chloroplasts, is inhibited by excitation of Photosystem I, which diverts electrons away from the chlororespiratory chain into the photosynthetic electron transport chain. Chlororespiration in N-starved Chlamydomonas increases ten fold over that of the control, perhaps because carbohydrates and NAD(P)H are oxidized and ATP produced by this process.The regulation of energy distribution to the photosystems and of cyclic and non-cyclic phosphorylation via state 1 to state 2 transitions may involve the cytochrome b 6-f complex. An increased demand for ATP lowers the transthylakoid pH gradient, activates the b 6-f complex, stimulates phosphorylation of the light-harvesting chlorophyll-protein complex of Photosystem II and decreases energy input to Photosystem II upon induction of state 2. The resulting increase in the absorption by Photosystem I favors cyclic electron flow and ATP production over linear electron flow to NADP and 'poises' the system by slowing down the flow of

  16. 13th International Conference on Chlamydomonas

    Energy Technology Data Exchange (ETDEWEB)

    Silflow, Carolyn D. [University of Minnesota

    2014-03-11

    The 13th International Conference on Chlamydomonas (EMBO Workshop on the Cell and Molecular Biology of Chlamydomonas) was held May 27 to June 1, 2008 in Hyeres, France. The conference was the biennial meeting for all researchers studying the green algal systems Chlamydomonas and Volvox. The conference brought together approximately 200 investigators from around the world (North America, Asia, Europe and Australia) representing different fields and disciplines (cell biology, genetics, biochemistry, biophysics, plant physiology, genomics). It provided an opportunity for investigators from different countries to share methodologies and to discuss recent results with a focus on the Chlamydomonas experimental system.

  17. Selenoprotein-Transgenic Chlamydomonas reinhardtii

    OpenAIRE

    Jiazuan Ni; Zhangli Hu; Jing Tian; Qintang Hou; Qiong Liu; Shi Qiu

    2013-01-01

    Selenium (Se) deficiency is associated with the occurrence of many diseases. However, excessive Se supplementation, especially with inorganic Se, can result in toxicity. Selenoproteins are the major forms of Se in vivo to exert its biological function. Expression of those selenoproteins, especially with the application of a newly developed system, is thus very important for studying the mechanism of Se in nutrition. The use of Chlamydomonas reinhardtii (C. reinhardtii) as a biological vector ...

  18. Temperature-sensitive rubisco mutant of Chlamydomonas

    International Nuclear Information System (INIS)

    The Chlamydomonas reinhardtii mutant 68-4PP is a temperature-sensitive mutant that lacks photosynthetic ability at 350C, but is able to grow photosynthetically at 250C. Genetic analysis indicated that 68-4PP is a chloroplast mutant that is allelic with known Rubisco large-subunit structural-gene mutants, implying that 68-4PP also resulted from a mutation in the large-subunit gene. The 68-4PP mutant has about 35% of the wild-type level of Rubisco holoenzyme and carboxylase activity when grown at 250C, but it has less than 10% of normal holoenzyme and carboxylase activity when grown at 350C. However, [35S]-sulfate pulse labeling showed that Rubisco subunits were synthesized at normal rates at both temperatures. More significantly, the ratio of carboxylase activity in the absence and presence of oxygen at a limiting CO2 concentration (6.6 μM) was about 2.2 for the mutant enzyme, as compared to about 3.0 for the wild-type enzyme. The decreased ratio of the mutant enzyme is maternally inherited, indicating that this reduced oxygen sensitivity results from a mutation in chloroplast DNA. The authors have recently cloned the 68-4PP Rubisco large-subunit gene, and DNA sequencing is in progress

  19. The PsbW protein stabilizes the supramolecular organization of photosystem II in higher plants

    NARCIS (Netherlands)

    Garcia-Cerdan, Jose G.; Kovacs, Laszlo; Toth, Tuende; Kereiche, Sami; Aseeva, Elena; Boekema, Egbert J.; Mamedov, Fikret; Funk, Christiane; Schroder, Wolfgang P.; Tóth, Tünde; Kereïche, Sami; Schröder, Wolfgang P.

    2011-01-01

    P>PsbW, a 6.1-kDa low-molecular-weight protein, is exclusive to photosynthetic eukaryotes, and associates with the photosystem II (PSII) protein complex. In vivo and in vitro comparison of Arabidopsis thaliana wild-type plants with T-DNA insertion knock-out mutants completely lacking the PsbW protei

  20. Brownian dynamics and molecular dynamics study of the association between hydrogenase and ferredoxin from Chlamydomonas reinhardtii.

    Science.gov (United States)

    Long, Hai; Chang, Christopher H; King, Paul W; Ghirardi, Maria L; Kim, Kwiseon

    2008-10-01

    The [FeFe] hydrogenase from the green alga Chlamydomonas reinhardtii can catalyze the reduction of protons to hydrogen gas using electrons supplied from photosystem I and transferred via ferredoxin. To better understand the association of the hydrogenase and the ferredoxin, we have simulated the process over multiple timescales. A Brownian dynamics simulation method gave an initial thorough sampling of the rigid-body translational and rotational phase spaces, and the resulting trajectories were used to compute the occupancy and free-energy landscapes. Several important hydrogenase-ferredoxin encounter complexes were identified from this analysis, which were then individually simulated using atomistic molecular dynamics to provide more details of the hydrogenase and ferredoxin interaction. The ferredoxin appeared to form reasonable complexes with the hydrogenase in multiple orientations, some of which were good candidates for inclusion in a transition state ensemble of configurations for electron transfer. PMID:18621810

  1. The basal bodies of Chlamydomonas reinhardtii

    OpenAIRE

    Dutcher, Susan K.; O’Toole, Eileen T.

    2016-01-01

    The unicellular green alga, Chlamydomonas reinhardtii, is a biflagellated cell that can swim or glide. C. reinhardtii cells are amenable to genetic, biochemical, proteomic, and microscopic analysis of its basal bodies. The basal bodies contain triplet microtubules and a well-ordered transition zone. Both the mother and daughter basal bodies assemble flagella. Many of the proteins found in other basal body-containing organisms are present in the Chlamydomonas genome, and mutants in these genes...

  2. A codon-optimized luciferase from Gaussia princeps facilitates the in vivo monitoring of gene expression in the model alga Chlamydomonas reinhardtii

    OpenAIRE

    N Shao; R. Bock

    2008-01-01

    The unicellular green alga Chlamydomonas reinhardtii has emerged as a superb model species in plant biology. Although the alga is easily transformable, the low efficiency of transgene expression from the Chlamydomonas nuclear genome has severely hampered functional genomics research. For example, poor transgene expression is held responsible for the lack of sensitive reporter genes to monitor gene expression in vivo, analyze subcellular protein localization or study protein–protein interactio...

  3. Solar energy conversion by green microalgae: a photosystem for hydrogen peroxide production.

    Science.gov (United States)

    de la Rosa, F F; Montes, O; Galván, F

    2001-09-20

    A photosystem for solar energy conversion, comprised of a culture of green microalgae supplemented with methyl viologen, is proposed. The capture of solar energy is based on the Mehler reaction. The reduction of methyl viologen by the photosynthetic apparatus and its subsequent reoxidation by oxygen produces hydrogen peroxide. This is a rich-energy compound that can be used as a nonpollutant and efficient fuel. Four different species of green microalgae, Chlamydomonas reinhardtii (21gr) C. reinhardtii (CW15), Chlorella fusca, and Monoraphidium braunii, were tested as a possible biocatalyst. Each species presented a different efficiency level in the transformation of energy. Azide was an efficient inhibitor of the hydrogen peroxide scavenging system while maintaining photosynthetic activity of the microalgae, and thus significantly increasing the production of the photosystem. The strain C. reinhardtii (21gr), among the species studied, was the most efficient with an initial production rate of 185 micromol H(2)O(2)/h x mg Chl and reaching a maximum of 42.5 micromol H(2)O(2)/mg Chl when assayed in the presence of azide inhibitor. PMID:11494222

  4. Antenna complexes protect Photosystem I from Photoinhibition

    Directory of Open Access Journals (Sweden)

    Hienerwadel Rainer

    2009-06-01

    Full Text Available Abstract Background Photosystems are composed of two moieties, a reaction center and a peripheral antenna system. In photosynthetic eukaryotes the latter system is composed of proteins belonging to Lhc family. An increasing set of evidences demonstrated how these polypeptides play a relevant physiological function in both light harvesting and photoprotection. Despite the sequence similarity between antenna proteins associated with the two Photosystems, present knowledge on their physiological role is mostly limited to complexes associated to Photosystem II. Results In this work we analyzed the physiological role of Photosystem I antenna system in Arabidopsis thaliana both in vivo and in vitro. Plants depleted in individual antenna polypeptides showed a reduced capacity for photoprotection and an increased production of reactive oxygen species upon high light exposure. In vitro experiments on isolated complexes confirmed that depletion of antenna proteins reduced the resistance of isolated Photosystem I particles to high light and that the antenna is effective in photoprotection only upon the interaction with the core complex. Conclusion We show that antenna proteins play a dual role in Arabidopsis thaliana Photosystem I photoprotection: first, a Photosystem I with an intact antenna system is more resistant to high light because of a reduced production of reactive oxygen species and, second, antenna chlorophyll-proteins are the first target of high light damages. When photoprotection mechanisms become insufficient, the antenna chlorophyll proteins act as fuses: LHCI chlorophylls are degraded while the reaction center photochemical activity is maintained. Differences with respect to photoprotection strategy in Photosystem II, where the reaction center is the first target of photoinhibition, are discussed.

  5. Expression of the nuclear gene encoding oxygen-evolving enhancer protein 2 is required for high levels of photosynthetic oxygen evolution in Chlamydomonas reinhardtii.

    OpenAIRE

    Mayfield, S P; Rahire, M; Frank, G.; Zuber, H.; Rochaix, J D

    1987-01-01

    We have cloned a cDNA encoding a 20-kDa polypeptide, oxygen-evolving enhancer protein 2 (OEE2), in Chlamydomonas reinhardtii. This polypeptide has been implicated in photosynthetic oxygen evolution, and it is associated with the photosystem II complex, the site of oxygen evolution in all higher plants and algae. The sequence of OEE2 cDNA, the deduced amino acid sequence of the preprotein, the N-terminal protein sequence of mature OEE2 protein, and the coding regions of the single OEE2 gene ar...

  6. A dual strategy to cope with high light in Chlamydomonas reinhardtii.

    Science.gov (United States)

    Allorent, Guillaume; Tokutsu, Ryutaro; Roach, Thomas; Peers, Graham; Cardol, Pierre; Girard-Bascou, Jacqueline; Seigneurin-Berny, Daphné; Petroutsos, Dimitris; Kuntz, Marcel; Breyton, Cécile; Franck, Fabrice; Wollman, Francis-André; Niyogi, Krishna K; Krieger-Liszkay, Anja; Minagawa, Jun; Finazzi, Giovanni

    2013-02-01

    Absorption of light in excess of the capacity for photosynthetic electron transport is damaging to photosynthetic organisms. Several mechanisms exist to avoid photodamage, which are collectively referred to as nonphotochemical quenching. This term comprises at least two major processes. State transitions (qT) represent changes in the relative antenna sizes of photosystems II and I. High energy quenching (qE) is the increased thermal dissipation of light energy triggered by lumen acidification. To investigate the respective roles of qE and qT in photoprotection, a mutant (npq4 stt7-9) was generated in Chlamydomonas reinhardtii by crossing the state transition-deficient mutant (stt7-9) with a strain having a largely reduced qE capacity (npq4). The comparative phenotypic analysis of the wild type, single mutants, and double mutants reveals that both state transitions and qE are induced by high light. Moreover, the double mutant exhibits an increased photosensitivity with respect to the single mutants and the wild type. Therefore, we suggest that besides qE, state transitions also play a photoprotective role during high light acclimation of the cells, most likely by decreasing hydrogen peroxide production. These results are discussed in terms of the relative photoprotective benefit related to thermal dissipation of excess light and/or to the physical displacement of antennas from photosystem II. PMID:23424243

  7. Potassium fluxes in Chlamydomonas reinhardtii. II. Compartmental analysis

    International Nuclear Information System (INIS)

    42K+ and 86Rb+ were used to determine the subcellular distribution of potassium in Chlamydomonas reinhardtii by compartmental analysis. In both wild type and a mutant strain, three distinct compartments (referred to as I, II, and III) were apparent. Using 42K+, we found that these had half-lives for K+ exchange of 1.07 min, 12.8 min, and 2.9 h, respectively, in wild-type cells and 0.93 min, 14.7 min, and 9.8 h, respectively, for the mutants. Half-lives were not significantly different when 86Rb+ was used to trace K+. Compartments I and II probably correspond to the cell wall and cytoplasm, respectively. Based on the lack of a large central vacuole in Chlamydomonas, the effect of a dark pretreatment on the kinetic properties of compartment III and the similarity between the [K+] of compartment III and that of isolated chloroplasts, this slowly exchanging compartment was identified as the chloroplast. Growth of wild-type cells at 100 micromolars (instead of 10 mM K+) caused no change of cytoplasmic [K+] but reduced chloroplast [K+] very substantially. The mutants failed to grow at 100 micromolars K+

  8. Photosynthetic H2 metabolism in Chlamydomonas reinhardtii (unicellular green algae).

    Science.gov (United States)

    Melis, Anastasios

    2007-10-01

    Unicellular green algae have the ability to operate in two distinctly different environments (aerobic and anaerobic), and to photosynthetically generate molecular hydrogen (H2). A recently developed metabolic protocol in the green alga Chlamydomonas reinhardtii permitted separation of photosynthetic O2-evolution and carbon accumulation from anaerobic consumption of cellular metabolites and concomitant photosynthetic H2-evolution. The H2 evolution process was induced upon sulfate nutrient deprivation of the cells, which reversibly inhibits photosystem-II and O2-evolution in their chloroplast. In the absence of O2, and in order to generate ATP, green algae resorted to anaerobic photosynthetic metabolism, evolved H2 in the light and consumed endogenous substrate. This study summarizes recent advances on green algal hydrogen metabolism and discusses avenues of research for the further development of this method. Included is the mechanism of a substantial tenfold starch accumulation in the cells, observed promptly upon S-deprivation, and the regulated starch and protein catabolism during the subsequent H2-evolution. Also discussed is the function of a chloroplast envelope-localized sulfate permease, and the photosynthesis-respiration relationship in green algae as potential tools by which to stabilize and enhance H2 metabolism. In addition to potential practical applications of H2, approaches discussed in this work are beginning to address the biochemistry of anaerobic H2 photoproduction, its genes, proteins, regulation, and communication with other metabolic pathways in microalgae. Photosynthetic H2 production by green algae may hold the promise of generating a renewable fuel from nature's most plentiful resources, sunlight and water. The process potentially concerns global warming and the question of energy supply and demand. PMID:17721788

  9. The basal bodies of Chlamydomonas reinhardtii.

    Science.gov (United States)

    Dutcher, Susan K; O'Toole, Eileen T

    2016-01-01

    The unicellular green alga, Chlamydomonas reinhardtii, is a biflagellated cell that can swim or glide. C. reinhardtii cells are amenable to genetic, biochemical, proteomic, and microscopic analysis of its basal bodies. The basal bodies contain triplet microtubules and a well-ordered transition zone. Both the mother and daughter basal bodies assemble flagella. Many of the proteins found in other basal body-containing organisms are present in the Chlamydomonas genome, and mutants in these genes affect the assembly of basal bodies. Electron microscopic analysis shows that basal body duplication is site-specific and this may be important for the proper duplication and spatial organization of these organelles. Chlamydomonas is an excellent model for the study of basal bodies as well as the transition zone. PMID:27252853

  10. Photomixing of chlamydomonas rheinhardtii suspensions

    Science.gov (United States)

    Dervaux, Julien; Capellazzi Resta, Marina; Abou, Bérengère; Brunet, Philippe

    2014-11-01

    Chlamydomonas rheinhardtii is a fast swimming unicellular alga able to bias its swimming direction in gradients of light intensity, an ability know as phototaxis. We have investigated experimentally both the swimming behavior of individual cells and the macroscopic response of shallow suspensions of these micro-organisms in response to a localized light source. At low light intensity, algae exhibit positive phototaxis and accumulate beneath the excitation light. In weakly concentrated thin layers, the balance between phototaxis and cell motility results in steady symmetrical patterns compatible with a purely diffusive model using effective diffusion coefficients extracted from the analysis of individual cell trajectories. However, at higher cell density and layer depth, collective effects induce convective flows around the light source. These flows disturb the cell concentration patterns which spread and may then becomes unstable. Using large passive tracer particles, we have characterized the velocity fields associated with this forced bioconvection and their dependence on the cell density and layer depth. By tuning the light distribution, this mechanism of photo-bioconvection allows a fine control over the local fluid flows, and thus the mixing efficiency, in algal suspensions.

  11. Selenoprotein-Transgenic Chlamydomonas reinhardtii

    Directory of Open Access Journals (Sweden)

    Jiazuan Ni

    2013-02-01

    Full Text Available Selenium (Se deficiency is associated with the occurrence of many diseases. However, excessive Se supplementation, especially with inorganic Se, can result in toxicity. Selenoproteins are the major forms of Se in vivo to exert its biological function. Expression of those selenoproteins, especially with the application of a newly developed system, is thus very important for studying the mechanism of Se in nutrition. The use of Chlamydomonas reinhardtii (C. reinhardtii as a biological vector to express an heterogeneous protein is still at the initial stages of development. In order to investigate the possibility of using this system to express selenoproteins, human 15-KDa selenoprotein (Sep15, a small but widely distributed selenoprotein in mammals, was chosen for the expression platform test. Apart from the wild-type human Sep15 gene fragment, two Sep15 recombinants were constructed containing Sep15 open reading frame (ORF and the selenocysteine insertion sequence (SECIS element from either human Sep15 or C. reinhardtii selenoprotein W1, a highly expressed selenoprotein in this alga. Those Sep15-containing plasmids were transformed into C. reinhardtii CC-849 cells. Results showed that Sep15 fragments were successfully inserted into the nuclear genome and expressed Sep15 protein in the cells. The transgenic and wild-type algae demonstrated similar growth curves in low Se culture medium. To our knowledge, this is the first report on expressing human selenoprotein in green alga.

  12. An improved ARS2-derived nuclear reporter enhances the efficiency and ease of genetic engineering in Chlamydomonas

    DEFF Research Database (Denmark)

    Specht, Elizabeth A; Nour-Eldin, Hussam Hassan; Hoang, Kevin T D;

    2015-01-01

    The model alga Chlamydomonas reinhardtii has been used to pioneer genetic engineering techniques for high-value protein and biofuel production from algae. To date, most studies of transgenic Chlamydomonas have utilized the chloroplast genome due to its ease of engineering, with a sizeable suite o...... nuclear promoters. This enhanced arylsulfatase reporter construct improves the efficiency and ease of genetic engineering within the Chlamydomonas nuclear genome, with potential application to other algal strains.......The model alga Chlamydomonas reinhardtii has been used to pioneer genetic engineering techniques for high-value protein and biofuel production from algae. To date, most studies of transgenic Chlamydomonas have utilized the chloroplast genome due to its ease of engineering, with a sizeable suite...... of reporters and well-characterized expression constructs. The advanced manipulation of algal nuclear genomes has been hampered by limited strong expression cassettes, and a lack of high-throughput reporters. We have improved upon an endogenous reporter gene - the ARS2 gene encoding an arylsulfatase enzyme...

  13. A steering mechanism for phototaxis in Chlamydomonas

    CERN Document Server

    Bennett, Rachel R

    2014-01-01

    Chlamydomonas shows both positive and negative phototaxis. It has a single eyespot near its equator and as the cell rotates during forward motion the light signal received by the eyespot varies. We use a simple mechanical model of Chlamydomonas that couples the flagellar beat pattern to the light intensity at the eyespot to demonstrate a mechanism for phototactic steering that is consistent with observations. The direction of phototaxis is controlled by a parameter in our model and the steering mechanism is robust to noise. Our model shows switching between directed phototaxis when the light is on and run-and-tumble behaviour in the dark.

  14. Chlamydomonas reinhardtii PsbS Protein Is Functional and Accumulates Rapidly and Transiently under High Light.

    Science.gov (United States)

    Tibiletti, Tania; Auroy, Pascaline; Peltier, Gilles; Caffarri, Stefano

    2016-08-01

    Photosynthetic organisms must respond to excess light in order to avoid photo-oxidative stress. In plants and green algae the fastest response to high light is non-photochemical quenching (NPQ), a process that allows the safe dissipation of the excess energy as heat. This phenomenon is triggered by the low luminal pH generated by photosynthetic electron transport. In vascular plants the main sensor of the low pH is the PsbS protein, while in the green alga Chlamydomonas reinhardtii LhcSR proteins appear to be exclusively responsible for this role. Interestingly, Chlamydomonas also possesses two PsbS genes, but so far the PsbS protein has not been detected and its biological function is unknown. Here, we reinvestigated the kinetics of gene expression and PsbS and LhcSR3 accumulation in Chlamydomonas during high light stress. We found that, unlike LhcSR3, PsbS accumulates very rapidly but only transiently. In order to determine the role of PsbS in NPQ and photoprotection in Chlamydomonas, we generated transplastomic strains expressing the algal or the Arabidopsis psbS gene optimized for plastid expression. Both PsbS proteins showed the ability to increase NPQ in Chlamydomonas wild-type and npq4 (lacking LhcSR3) backgrounds, but no clear photoprotection activity was observed. Quantification of PsbS and LhcSR3 in vivo indicates that PsbS is much less abundant than LhcSR3 during high light stress. Moreover, LhcSR3, unlike PsbS, also accumulates during other stress conditions. The possible role of PsbS in photoprotection is discussed. PMID:27329221

  15. Evidence for multiple photosystems in jellyfish

    DEFF Research Database (Denmark)

    Garm, Anders Lydik; Ekström, Peter

    2010-01-01

    Cnidarians are often used as model animals in studies of eye and photopigment evolution. Most cnidarians display photosensitivity at some point in their lifecycle ranging from extraocular photoreception to image formation in camera-type eyes. The available information strongly suggests that some...... cnidarians even possess multiple photosystems. The evidence is strongest within Cubomedusae where all known species posses 24 eyes of four morphological types. Physiological experiments show that each cubomedusan eye type likely constitutes a separate photosystem controlling separate visually guided...... behaviors. Further, the visual system of cubomedusae also includes extraocular photoreception. The evidence is supported by immunocytochemical and molecular data indicating multiple photopigments in cubomedusae as well as in other cnidarians. Taken together, available data suggest that multiple photosystems...

  16. A new method to identify flanking sequence tags in chlamydomonas using 3’-RACE

    Directory of Open Access Journals (Sweden)

    Meslet-Cladière Laurence

    2012-06-01

    Full Text Available Abstract Background The green alga Chlamydomonas reinhardtii, although a premier model organism in biology, still lacks extensive insertion mutant libraries with well-identified Flanking Sequence Tags (FSTs. Rapid and efficient methods are needed for FST retrieval. Results Here, we present a novel method to identify FSTs in insertional mutants of Chlamydomonas. Transformants can be obtained with a resistance cassette lacking a 3’ untranslated region (UTR, suggesting that the RNA that is produced from the resistance marker terminates in the flanking genome when it encounters a cleavage/polyadenylation signal. We have used a robust 3’-RACE method to specifically amplify such chimeric cDNAs. Out of 38 randomly chosen transformants, 27 (71% yielded valid FSTs, of which 23 could be unambiguously mapped to the genome. Eighteen of the mutants lie within a predicted gene. All but two of the intragenic insertions occur in the sense orientation with respect to transcription, suggesting a bias against situations of convergent transcription. Among the 14 insertion sites tested by genomic PCR, 12 could be confirmed. Among these are insertions in genes coding for PSBS3 (possibly involved in non-photochemical quenching, the NimA-related protein kinase CNK2, the mono-dehydroascorbate reductase MDAR1, the phosphoglycerate mutase PGM5 etc.. Conclusion We propose that our 3’-RACE FST method can be used to build large scale FST libraries in Chlamydomonas and other transformable organisms.

  17. Excitation energy transfer in the photosystem I

    Energy Technology Data Exchange (ETDEWEB)

    Webber, Andrew N

    2012-09-25

    Photosystem I is a multimeric pigment protein complex in plants, green alage and cyanobacteria that functions in series with Photosystem II to use light energy to oxidize water and reduce carbon dioxide. The Photosystem I core complex contains 96 chlorophyll a molecules and 22 carotenoids that are involved in light harvesting and electron transfer. In eucaryotes, PSI also has a peripheral light harvesting complex I (LHCI). The role of specific chlorophylls in excitation and electron transfer are still unresolved. In particular, the role of so-called bridging chlorophylls, located between the bulk antenna and the core electron transfer chain, in the transfer of excitation energy to the reaction center are unknown. During the past funding period, site directed mutagenesis has been used to create mutants that effect the physical properties of these key chlorophylls, and to explore how this alters the function of the photosystem. Studying these mutants using ultrafast absorption spectroscopy has led to a better understanding of the process by which excitation energy is transferred from the antenna chlorophylls to the electron transfer chain chlorophylls, and what the role of connecting chlorophylls and A_0 chlorophylls is in this process. We have also used these mutants to investigate whch of the central group of six chlorophylls are involved in the primary steps of charge separation and electron transfer.

  18. A comparison of hydrogen photoproduction by sulfur-deprived Chlamydomonas reinhardtii under different growth conditions.

    Science.gov (United States)

    Kosourov, Sergey; Patrusheva, Elena; Ghirardi, Maria L; Seibert, Michael; Tsygankov, Anatoly

    2007-03-10

    Continuous photoproduction of H(2) by the green alga, Chlamydomonas reinhardtii, is observed after incubating the cultures for about a day in the absence of sulfate and in the presence of acetate. Sulfur deprivation causes the partial and reversible inactivation of photosynthetic O(2) evolution in algae, resulting in the light-induced establishment of anaerobic conditions in sealed photobioreactors, expression of two [FeFe]-hydrogenases in the cells, and H(2) photoproduction for several days. We have previously demonstrated that sulfur-deprived algal cultures can produce H(2) gas in the absence of acetate, when appropriate experimental protocols were used (Tsygankov, A.A., Kosourov, S.N., Tolstygina, I.V., Ghirardi, M.L., Seibert, M., 2006. Hydrogen production by sulfur-deprived Chlamydomonas reinhardtii under photoautotrophic conditions. Int. J. Hydrogen Energy 31, 1574-1584). We now report the use of an automated photobioreactor system to compare the effects of photoautotrophic, photoheterotrophic and photomixotrophic growth conditions on the kinetic parameters associated with the adaptation of the algal cells to sulfur deprivation and H(2) photoproduction. This was done under the experimental conditions outlined in the above reference, including controlled pH. From this comparison we show that both acetate and CO(2) are required for the most rapid inactivation of photosystem II and the highest yield of H(2) gas production. Although, the presence of acetate in the system is not critical for the process, H(2) photoproduction under photoautotrophic conditions can be increased by optimizing the conditions for high starch accumulation. These results suggest ways of engineering algae to improve H(2) production, which in turn may have a positive impact on the economics of applied systems for H(2) production. PMID:17275940

  19. A steering mechanism for phototaxis in Chlamydomonas

    Science.gov (United States)

    Bennett, Rachel; Golestanian, Ramin

    2015-03-01

    Chlamydomonas shows both positive and negative phototaxis. It has a single eyespot near its equator and as the cell rotates during forward motion the light signal received by the eyespot varies. We use a simple mechanical model of Chlamydomonas that couples the flagellar beat pattern to the light intensity at the eyespot to demonstrate a mechanism for phototactic steering that is consistent with observations. The direction of phototaxis is controlled by a parameter in our model and the steering mechanism is robust to noise. In the dark, our model shows emergent run-and-tumble behavior and we see switching between directed phototaxis and run-and-tumble when we switch the light on and off.

  20. Inheritance of chloroplast DNA in Chlamydomonas reinhardtii

    OpenAIRE

    Grant, David M; Nicholas W. Gillham; Boynton, John E.

    1980-01-01

    Two symmetrically located deletions of approximately 100 base pairs each have been identified in chloroplast DNA of Chlamydomonas reinhardtii. Although present in a mutant strain that requires acetate for growth, both deletions have been shown to be distinct from the nonphotosynthetic phenotype of this strain. These physical markers in the chloroplast genome and maternally inherited genetic markers showed strict cotransmission in reciprocal crosses. Thus, our results are consistent with the l...

  1. Chlamydomonas sajao nov. sp. (Chlorophyta, Volvocales)

    Science.gov (United States)

    Lewin, Ralph A.

    1984-06-01

    A new species of Chlamydomonas, namely, C. sajao nov. sp. of the Volvocales, Chlorophyta was isolated from a duckweed growing near a ricefield in the vicinity of Guangzhou, China. This interesting unicellular green alga, similar to C. mexicana from Mexico, secretes quantities of extracellular mucilaginous polysaccharides, and may be employed in improving soil quality. The new species resembles C. waldenburgensis Moewus in most characteristics but differs in three important features.

  2. Modulation of the light-harvesting chlorophyll antenna size in Chlamydomonas reinhardtii by TLA1 gene over-expression and RNA interference

    Science.gov (United States)

    Mitra, Mautusi; Kirst, Henning; Dewez, David; Melis, Anastasios

    2012-01-01

    Truncated light-harvesting antenna 1 (TLA1) is a nuclear gene proposed to regulate the chlorophyll (Chl) antenna size in Chlamydomonas reinhardtii. The Chl antenna size of the photosystems and the chloroplast ultrastructure were manipulated upon TLA1 gene over-expression and RNAi downregulation. The TLA1 over-expressing lines possessed a larger chlorophyll antenna size for both photosystems and contained greater levels of Chl b per cell relative to the wild type. Conversely, TLA1 RNAi transformants had a smaller Chl antenna size for both photosystems and lower levels of Chl b per cell. Western blot analyses of the TLA1 over-expressing and RNAi transformants showed that modulation of TLA1 gene expression was paralleled by modulation in the expression of light-harvesting protein, reaction centre D1 and D2, and VIPP1 genes. Transmission electron microscopy showed that modulation of TLA1 gene expression impacts the organization of thylakoid membranes in the chloroplast. Over-expressing lines showed well-defined grana, whereas RNAi transformants possessed loosely held together and more stroma-exposed thylakoids. Cell fractionation suggested localization of the TLA1 protein in the inner chloroplast envelope and potentially in association with nascent thylakoid membranes, indicating a role in Chl antenna assembly and thylakoid membrane biogenesis. The results provide a mechanistic understanding of the Chl antenna size regulation by the TLA1 gene. PMID:23148270

  3. Mutants of Chlamydomonas: tools to study thylakoid membrane structure, function and biogenesis.

    Science.gov (United States)

    de Vitry, C; Vallon, O

    1999-06-01

    The unicellular green alga Chlamydomonas reinhardtii is a model system for the study of photosynthesis and chloroplast biogenesis. C. reinhardtii has a photosynthesis apparatus similar to that of higher plants and it grows at rapid rate (generation time about 8 h). It is a facultative phototroph, which allows the isolation of mutants unable to perform photosynthesis and its sexual cycle allows a variety of genetic studies. Transformation of the nucleus and chloroplast genomes is easily performed. Gene transformation occurs mainly by homologous recombination in the chloroplast and heterologous recombination in the nucleus. Mutants are precious tools for studies of thylakoid membrane structure, photosynthetic function and assembly. Photosynthesis mutants affected in the biogenesis of a subunit of a protein complex usually lack the entire complex; this pleiotropic effect has been used in the identification of the other subunits, in the attribution of spectroscopic signals and also as a 'genetic cleaning' process which facilitates both protein complex purification, absorption spectroscopy studies or freeze-fracture analysis. The cytochrome b6f complex is not required for the growth of C. reinhardtii, unlike the case of photosynthetic prokaryotes in which the cytochrome complex is also part of the respiratory chain, and can be uniquely studied in Chlamydomonas by genetic approaches. We describe in greater detail the use of Chlamydomonas mutants in the study of this complex. PMID:10433117

  4. Expression of chloroplast protein genes during the cell cycle of Chlamydomonas reinhardtii: evidence for transcriptional and translocational control

    International Nuclear Information System (INIS)

    Chlamydomonas reinhardtii cells, growing synchronously under a repeating 12 h light:12 h dark cycle, were used to investigate the synthesis and regulation of chloroplast proteins. The cells accumulate chlorophyll, the major thylakoid membrane proteins, and ribulose-1,5-bisphosphate carboxylase (RuBPCase) during the light (G1) period of the cell cycle. Pulse-labeling in vivo with [3H]arginine, and analysis of the protein synthetic capacity of thylakoid-bound polysomes in vitro, shows that these proteins are synthesized de novo during the light. Specific antibody and cloned DNA probes were obtained and used to estimate translatable and/or steady-state mRNA levels for light-harvesting (LHCII) and reaction center (D-1 and D-2) polypeptides of photosystem II, a light-harvesting polypeptide of photosystem I (LHCI), and the large (LS) and small (SS) subunits of RuBPCase. Levels of mRNA for the nuclear-encoded LHCI, LHCII and SS correlated with the synthesis of these polypeptides in vivo; they were higher in the light period and several-folded lower or absent during the dark period. The results suggest that synthesis of nuclear-encoded chloroplast proteins are regulated primarily by the level of mRNA. In contrast, regulation of chloroplast-encoded genes is achieved by controlling the translation of mRNA that is constitutively present, and by transcriptional mechanisms during light induction

  5. A Light Switch Based on Protein S-Nitrosylation Fine-Tunes Photosynthetic Light Harvesting in Chlamydomonas.

    Science.gov (United States)

    Berger, Hanna; De Mia, Marcello; Morisse, Samuel; Marchand, Christophe H; Lemaire, Stéphane D; Wobbe, Lutz; Kruse, Olaf

    2016-06-01

    Photosynthetic eukaryotes are challenged by a fluctuating light supply, demanding for a modulated expression of nucleus-encoded light-harvesting proteins associated with photosystem II (LHCII) to adjust light-harvesting capacity to the prevailing light conditions. Here, we provide clear evidence for a regulatory circuit that controls cytosolic LHCII translation in response to light quantity changes. In the green unicellular alga Chlamydomonas reinhardtii, the cytosolic RNA-binding protein NAB1 represses translation of certain LHCII isoform mRNAs. Specific nitrosylation of Cys-226 decreases NAB1 activity and could be demonstrated in vitro and in vivo. The less active, nitrosylated form of NAB1 is found in cells acclimated to limiting light supply, which permits accumulation of light-harvesting proteins and efficient light capture. In contrast, elevated light supply causes its denitrosylation, thereby activating the repression of light-harvesting protein synthesis, which is needed to control excitation pressure at photosystem II. Denitrosylation of recombinant NAB1 is efficiently performed by the cytosolic thioredoxin system in vitro. To our knowledge, NAB1 is the first example of stimulus-induced denitrosylation in the context of photosynthetic acclimation. By identifying this novel redox cross-talk pathway between chloroplast and cytosol, we add a new key element required for drawing a precise blue print of the regulatory network of light harvesting. PMID:27208221

  6. A rapid, modular and marker-free chloroplast expression system for the green alga Chlamydomonas reinhardtii.

    Science.gov (United States)

    Bertalan, Ivo; Munder, Matthias C; Weiß, Caroline; Kopf, Judith; Fischer, Dirk; Johanningmeier, Udo

    2015-02-10

    In search of alternative expression platforms heterologous protein production in microalgae has gained increasing importance in the last years. Particularly, the chloroplast of the green alga Chlamydomonas reinhardtii has been adopted to successfully express foreign proteins like vaccines and antibodies. However, when compared with other expression systems, the development of the algal chloroplast to a powerful production platform for recombinant proteins is still in its early stages. In an effort to further improve methods for a reliable and rapid generation of transplastomic Chlamydomonas strains we constructed the key plasmid pMM2 containing the psbA gene and a multiple cloning site for foreign gene insertion. The psbA gene allows a marker-free selection procedure using as a recipient the Fud7 strain of Chlamydomonas, which grows on media containing acetate as a carbon source, but is unable to grow photoautotrophically due to the lack of an intact psbA gene. Biolistic transformation of Fud7 with vectors containing this gene restores photoautotrophic growth and thus permits selection in the light on media without carbon sources and antibiotics. The multiple cloning site with a BsaI recognition sequence allows type IIs restriction enzyme-based modular cloning which rapidly generates new gene constructs without sequences, which could influence the expression and characteristics of the foreign protein. In order to demonstrate the feasibility of this approach, a codon optimized version of the gene for the bacterial protein MPT64 has been integrated into the plastome. Several strains with different promoter/UTR combinations show a stable expression of the HA tagged MPT64 protein in Chlamydomonas chloroplasts. PMID:25554634

  7. Crystal structure of plant photosystem I

    Science.gov (United States)

    Ben-Shem, Adam; Frolow, Felix; Nelson, Nathan

    2003-12-01

    Oxygenic photosynthesis is the principal producer of both oxygen and organic matter on Earth. The conversion of sunlight into chemical energy is driven by two multisubunit membrane protein complexes named photosystem I and II. We determined the crystal structure of the complete photosystem I (PSI) from a higher plant (Pisum sativum var. alaska) to 4.4Å resolution. Its intricate structure shows 12 core subunits, 4 different light-harvesting membrane proteins (LHCI) assembled in a half-moon shape on one side of the core, 45 transmembrane helices, 167 chlorophylls, 3 Fe-S clusters and 2 phylloquinones. About 20 chlorophylls are positioned in strategic locations in the cleft between LHCI and the core. This structure provides a framework for exploration not only of energy and electron transfer but also of the evolutionary forces that shaped the photosynthetic apparatus of terrestrial plants after the divergence of chloroplasts from marine cyanobacteria one billion years ago.

  8. MEETING: Chlamydomonas Annotation Jamboree - October 2003

    Energy Technology Data Exchange (ETDEWEB)

    Grossman, Arthur R

    2007-04-13

    Shotgun sequencing of the nuclear genome of Chlamydomonas reinhardtii (Chlamydomonas throughout) was performed at an approximate 10X coverage by JGI. Roughly half of the genome is now contained on 26 scaffolds, all of which are at least 1.6 Mb, and the coverage of the genome is ~95%. There are now over 200,000 cDNA sequence reads that we have generated as part of the Chlamydomonas genome project (Grossman, 2003; Shrager et al., 2003; Grossman et al. 2007; Merchant et al., 2007); other sequences have also been generated by the Kasuza sequence group (Asamizu et al., 1999; Asamizu et al., 2000) or individual laboratories that have focused on specific genes. Shrager et al. (2003) placed the reads into distinct contigs (an assemblage of reads with overlapping nucleotide sequences), and contigs that group together as part of the same genes have been designated ACEs (assembly of contigs generated from EST information). All of the reads have also been mapped to the Chlamydomonas nuclear genome and the cDNAs and their corresponding genomic sequences have been reassembled, and the resulting assemblage is called an ACEG (an Assembly of contiguous EST sequences supported by genomic sequence) (Jain et al., 2007). Most of the unique genes or ACEGs are also represented by gene models that have been generated by the Joint Genome Institute (JGI, Walnut Creek, CA). These gene models have been placed onto the DNA scaffolds and are presented as a track on the Chlamydomonas genome browser associated with the genome portal (http://genome.jgi-psf.org/Chlre3/Chlre3.home.html). Ultimately, the meeting grant awarded by DOE has helped enormously in the development of an annotation pipeline (a set of guidelines used in the annotation of genes) and resulted in high quality annotation of over 4,000 genes; the annotators were from both Europe and the USA. Some of the people who led the annotation initiative were Arthur Grossman, Olivier Vallon, and Sabeeha Merchant (with many individual

  9. Hole burning study of cyanobacterial Photosystem II complexes differing in the content of small putative chlorophyll-binding proteins

    International Nuclear Information System (INIS)

    This contribution presents low-temperature absorption, both broad-band and site-selective excited fluorescence, and persistent hole burning spectra of Photosystem II complexes from the Photosystem I-lacking strains of the cyanobacterium Synechocystis sp. PCC 6803 differing in the content of small putative chlorophyll-binding proteins (Scps). These proteins are homologous to light-harvesting complex of higher plants and may bind pigments. The excited state lifetimes of the complexes were determined from zero-phonon hole widths extrapolated to zero-burning dose. The area and spectral position of a phonon side-band with respect to the zero-phonon hole provided additional information concerning chlorophyll-protein coupling and the Stokes shift. Decrease of three absorption subbands at (670.0, 672.9, and 675.7 nm) in the Photosystem II isolated from the strain lacking ScpC and ScpD is in agreement with a hypothesis about the role of Scps in the chlorophyll binding. In addition, narrowing of the zero-phonon hole in Photosystem II without both Scps indicates slowering of the excitation energy transfer which may be explained by the absence of a protective excitation energy quenching related to the presence of Scps

  10. Real-time monitoring of genetically modified Chlamydomonas reinhardtii during the Foton M3 space mission

    Science.gov (United States)

    Lambreva, M.; Rea, G.; Antonacci, A.; Serafini, A.; Damasso, M.; Pastorelli, S.; Margonelli, A.; Johanningmeier, U.; Bertalan, I.; Pezzotti, G.; Giardi, M. T.

    2008-09-01

    Long-term space exploration, colonization or habitation requires biological life support systems capable to cope with the deleterious space environment. The use of oxygenic photosynthetic microrganisms is an intriguing possibility mainly for food, O2 and nutraceutical compounds production. The critical points of utilizing plants- or algae-based life support systems are the microgravity and the ionizing radiation, which can influence the performance of these organisms. The aim of the present study was to assess the effects of space environment on the photosynthetic activity of various microrganisms and to select space stresstolerant strains. Photosystem II D1 protein sitedirected and random mutants of the unicellular green alga Chlamydomonas reinhardtii [1] were used as a model system to test and select the amino acid substitutions capable to account for space stress tolerance. We focussed our studies also on the accumulation of the Photosystem II photoprotective carotenoids (the xantophylls violaxanthin, anteraxanthin and zeaxanthin), powerful antioxidants that epidemiological studies demonstrated to be human vision protectors. For this purpose some mutants modified at the level of enzymes involved in the biosynthesis of xanthophylls were included in the study [2]. To identify the consequences of the space environment on the photosynthetic apparatus the changes in the Photosystem II efficiency were monitored in real time during the ESA-Russian Foton- M3 mission in September 2007. For the space flight a high-tech, multicell fluorescence detector, Photo-II, was designed and built by the Centre for Advanced Research in Space Optics in collaboration with Kayser-Italy, Biosensor and DAS. Photo-II is an automatic device developed to measure the chlorophyll fluorescence and to provide a living conditions for several different algae strains (Fig.1). Twelve different C. reinhardti strains were analytically selected and two replications for each strain were brought to space

  11. The oxygen evolving enhancer protein 1 (OEE) of photosystem II in green algae exhibits thioredoxin activity.

    Science.gov (United States)

    Heide, Heinrich; Kalisz, Henryk M; Follmann, Hartmut

    2004-02-01

    A thioredoxin-like chloroplast protein of the fructosebisphosphatase-stimulating f-type, but with an unusually high molecular mass of 28 kDa has previously been identified and purified to homogeneity in a fractionation scheme for resolution of the acid- and heat-stable, regular-size (12kDa) thioredoxins of the unicellular green algae, Scenedesmus obliquus. An apparently analogous protein of 26 kDa was described in a cyanobacterium, Anabaena sp., but no such large thioredoxin species f exists in the thioredoxin profiles of higher plants. The structure of the 28 kDa protein, which had been envisaged to represent a precursor, or fusion product of the two more specialized, common chloroplast thioredoxins f and m has now been determined by amino acid sequencing. Although it exhibits virtually all the properties and enzyme-modulating activities of a thioredoxin proper this algal protein, surprisingly, does not belong to the thioredoxin family of small redox proteins but is identical with OEE (oxygen evolving enhancer) protein 1, an auxiliary component of the photosystem II manganese cluster. Extracts of Chlorella vulgaris and Chlamydomonas reinhardtii also contain heat-stable protein fractions of 23-26 kDa capable of specifically stimulating chloroplast fructosebisphosphatase in vitro. In contrast, OEE protein 1 from spinach is not able to modulate FbPase or NADP malate dehydrogenase from spinach chloroplasts. A dual function of the OEE protein in algal photosynthesis is envisaged. PMID:15022827

  12. Advances in the biotechnology of hydrogen production with the microalga Chlamydomonas reinhardtii.

    Science.gov (United States)

    Torzillo, Giuseppe; Scoma, Alberto; Faraloni, Cecilia; Giannelli, Luca

    2015-01-01

    Biological hydrogen production is being evaluated for use as a fuel, since it is a promising substitute for carbonaceous fuels owing to its high conversion efficiency and high specific energy content. The basic advantages of biological hydrogen production over other "green" energy sources are that it does not compete for agricultural land use, and it does not pollute, as water is the only by-product of the combustion. These characteristics make hydrogen a suitable fuel for the future. Among several biotechnological approaches, photobiological hydrogen production carried out by green microalgae has been intensively investigated in recent years. A select group of photosynthetic organisms has evolved the ability to harness light energy to drive hydrogen gas production from water. Of these, the microalga Chlamydomonas reinhardtii is considered one of the most promising eukaryotic H2 producers. In this model microorganism, light energy, H2O and H2 are linked by two excellent catalysts, the photosystem 2 (PSII) and the [FeFe]-hydrogenase, in a pathway usually referred to as direct biophotolysis. This review summarizes the main advances made over the past decade as an outcome of the discovery of the sulfur-deprivation process. Both the scientific and technical barriers that need to be overcome before H2 photoproduction can be scaled up to an industrial level are examined. Actual and theoretical limits of the efficiency of the process are also discussed. Particular emphasis is placed on algal biohydrogen production outdoors, and guidelines for an optimal photobioreactor design are suggested. PMID:24754449

  13. Process development for hydrogen production with Chlamydomonas reinhardtii based on growth and product formation kinetics.

    Science.gov (United States)

    Lehr, Florian; Morweiser, Michael; Rosello Sastre, Rosa; Kruse, Olaf; Posten, Clemens

    2012-11-30

    Certain strains of microalgae are long known to produce hydrogen under anaerobic conditions. In Chlamydomonas reinhardtii the oxygen-sensitive hydrogenase enzyme recombines electrons from the chloroplast electron transport chain with protons to form molecular hydrogen directly inside the chloroplast. A sustained hydrogen production can be obtained under low sulfur conditions in C. reinhardtii, reducing the net oxygen evolution by reducing the photosystem II activity and thereby overcoming the inhibition of the hydrogenases. The development of specially adapted hydrogen production strains led to higher yields and optimized biological process preconditions. So far sustainable hydrogen production required a complete exchange of the growth medium to establish sulfur-deprived conditions after biomass growth. In this work we demonstrate the transition from the biomass growth phase to the hydrogen production phase in a single batch culture only by exact dosage of sulfur. This eliminates the elaborate and energy intensive solid-liquid separation step and establishes a process strategy to proceed further versus large scale production. This strategy has been applied to determine light dependent biomass growth and hydrogen production kinetics to assess the potential of H₂ production with C. reinhardtii as a basis for scale up and further process optimization. PMID:22750091

  14. Retrograde Signaling and Photoprotection in a gun4 Mutant of Chlamydomonas reinhardtii

    Institute of Scientific and Technical Information of China (English)

    Cinzia Formighieri; Mauro Ceol; Giulia Bonente; Jean-David Rochaix; Roberto Bassi

    2012-01-01

    GUN4 is a regulatory subunit of Mg-chelatase involved in the control of tetrapyrrole synthesis in plants and cyanobacteria.Here,we report the first characterization of a gun4 insertion mutant of the unicellular green alga Chlamydomonas reinhardtii.The mutant contains 50% of chlorophyll as compared to wild-type and accumulates ProtolX.In contrast to the increase in LHCtranscription,the accumulation of most LHC proteins is drastically diminished,implying posttranscriptional down-regulation in the absence of transcriptional coordination.We found that 803 genes change their expression level in gun4 as compared to wild-type,by RNA-Seq,and this wide-ranging effect on transcription is apparent under physiological conditions.Besides LHCs,we identified transcripts encoding enzymes of the tetrapyrrole pathway and factors involved in signal transduction,transcription,and chromatin remodeling.Moreover,we observe perturbations in electron transport with a strongly decreased PSI-to-PSII ratio.This is accompanied by an enhanced activity of the plastid terminal oxidase (PTOX) that could have a physiological role in decreasing photosystem Ⅱ excitation pressure.

  15. Characterization of Chlamydomonas reinhardtii phosphatidylglycerophosphate synthase in Synechocystis sp. PCC 6803

    Directory of Open Access Journals (Sweden)

    Chun-Hsien eHung

    2015-08-01

    Full Text Available Phosphatidylglycerol (PG is an indispensable phospholipid class with photosynthetic function in plants and cyanobacteria. However, its biosynthesis in eukaryotic green microalgae is poorly studied. Here, we report the isolation and characterization of two homologs (CrPGP1 and CrPGP2 of phosphatidylglycerophosphate synthase (PGPS, the rate-limiting enzyme in PG biosynthesis, in Chlamydomonas reinhardtii. Heterologous complementation of Synechocystis sp. PCC 6803 pgsA mutant by CrPGP1 and CrPGP2 rescued the PG-dependent growth phenotype, but the PG level and its fatty acid composition were not fully rescued in the complemented strains. As well, oxygen evolution activity was not fully recovered, although electron transport activity of photosystem II was restored to the wild-type level. Gene expression study of CrPGP1 and CrPGP2 in nutrient-starved C. reinhardtii showed differential response to phosphorus and nitrogen deficiency. Taken together, these results highlight the distinct and overlapping function of PGPS in cyanobacteria and eukaryotic algae.

  16. Mutagenesis of Ser24 of cytochrome b559 α subunit affects PSⅡ activities in Chlamydomonas reinhardtii

    Institute of Scientific and Technical Information of China (English)

    MA JingJing; LI LiangBi; JING YuXiang; KUANG TingYun

    2007-01-01

    In order to study the functions of cytochrome b559 (Cyt b559) in photosystem two (PSⅡ) activity, mutant S24F of Chlamydomonas reinhardtii was constructed using site directed mutagenesis, in which Serine24 (Ser24) locating downstream of Histidine23 (His23) in c subunit of Cyt b559 was replaced by Phenylalanine (Phe). Physiological and biochemical analysis showed that mutant S24F could be grown photoautotrophically or photoheterotrophically. However, their growth rate was slower either on HSM or TAP medium than that of the control; Analysis of PSⅡ activity revealed that its oxygen evolution was about 71% of wild type (WT); The Photochemical efficiency of PSll (Fv/Fm) of S24F was reduced 0.23 compared with WT; S24F was more sensitive to strong light irradiance than the wild type; Furthermore,SDS-PAGE and Western-blotting analysis indicated that the expression levels of c subunit of Cyt b559,LHCⅡ and PsbO of S24F were a little less than those of the wild type. Overall, these data suggests that Ser24 plays a significant role in making Cyt b559 structure maintain PSⅡ complex activity of oxygen evolution although it is not directly bound to heme group.

  17. [An experiment with Chlamydomonas reinhardtii on the Kosmos-2044 biosatellite].

    Science.gov (United States)

    Gavrilova, O V; Gabova, A V; Goriainova, L N; Filatova, E V

    1992-01-01

    Space experiment with Chlamydomonas reinhardtii demonstrated that the microgravity effects were noted in Chlamydomonas at both cellular and population levels: in space the cell size is increased, stage of active growth of the culture is extended, it contains the juvenile vegetative motile cells in greater quantities. Ultrastructural analysis indicated that in microgravity the changes in shape, structure and distribution of intracellular organelles and in volume ratio of organelles and cytoplasma are absent. Chlamydomonas data are in line with the results of the Infusoria and Chlorella experiments. PMID:1307032

  18. Paternal inheritance of mitochondria in Chlamydomonas.

    Science.gov (United States)

    Nakamura, Soichi

    2010-03-01

    To analyze mitochondrial DNA (mtDNA)inheritance, differences in mtDNA between Chlamydomonas reinhardtii and Chlamydomonas smithii, respiration deficiency and antibiotic resistance were used to distinguish mtDNA origins. The analyses indicated paternal inheritance. However, these experiments raised questions regarding whether paternal inheritance occurred normally.Mitochondrial nucleoids were observed in living zygotes from mating until 3 days after mating and then until progeny formation. However, selective disappearance of nucleoids was not observed. Subsequently, experimental serial backcrosses between the two strains demonstrated strict paternal inheritance. The fate of mt+ and mt- mtDNA was followed using the differences in mtDNA between the two strains. The slow elimination of mt+ mtDNA through zygote maturation in darkness was observed, and later the disappearance of mt+ mtDNA was observed at the beginning of meiosis. To explain the different fates of mtDNA, methylation status was investigated; however, no methylation was detected. Variously constructed diploid cells showed biparental inheritance. Thus, when the mating process occurs normally, paternal inheritance occurs. Mutations disrupting mtDNA inheritance have not yet been isolated. Mutations that disrupt maternal inheritance of chloroplast DNA (cpDNA) do not disrupt inheritance of mtDNA. The genes responsible for mtDNA inheritance are different from those of chloroplasts. PMID:20069335

  19. Carbonic anhydrase activity in isolated chloroplasts of chlamydomonas reinhardtii

    International Nuclear Information System (INIS)

    In a new assay of carbonic anhydrase, NaH14CO3 solution at the bottom of a sealed vessel releases 14CO3 which diffuses to the top of the vessel to be assimilated by actively photosynthesizing Chlamydomonas cells. The assay is initiated by illuminating cells and stopped by turning the light off and killing the cells with acid. Enzyme activity was estimated from acid stable radioactivity above the uncatalyzed background level. With bovine carbonic anhydrase, 1.5 Wilbur Anderson Unit (WAU) can be consistantly measured at 5-6 fold above background. Sonicated whole cells of air adapted wild type (+)gave 741.1 ± 12.4 WAU/mg chl. Intact washed cells of mixotrophically grown wall-less mutant CWD(-) and a high CO2 requiring wall-less double mutant CIA-3/CW15 (-) gave 7.1 ± 1.9 and 2.8 ± 7.8 WAU/mg chl respectively. Chloroplasts isolated from CWD and CIA-3/CW15 and subsequently disrupted gave 64.0 ± 14.7 and 2.8 ± 3.2 WAU/mg chl respectively. Chloroplast sonicate from another wall-less mutant CW15(-) gave activity comparable to CWD. Thus on a chlorophyll basis, enzyme activity in chloroplasts from mixotrophically grown cells is about 1/10th of the level found in air adapted wild type cells. CIA-3 seems to lack this activity

  20. Vegetative and gametic flagellum membranes of Chlamydomonas reinhardtii

    OpenAIRE

    Sikorski, Aleksander F

    2015-01-01

    Differences were demonstrated in the composition, electrophoretic patterns of polypeptide chains and neutral sugar composition between vegetative and gametic flagellum membranes of two strains (89 and 90) of Chlamydomonas reinhardtii.

  1. Vegetative and gametic flagellum membranes of Chlamydomonas reinhardtii

    Directory of Open Access Journals (Sweden)

    Aleksander F. Sikorski

    2015-05-01

    Full Text Available Differences were demonstrated in the composition, electrophoretic patterns of polypeptide chains and neutral sugar composition between vegetative and gametic flagellum membranes of two strains (89 and 90 of Chlamydomonas reinhardtii.

  2. The involvement of hydrogen-producing and ATP-dependent NADPH-consuming pathways in setting the redox poise in the chloroplast of Chlamydomonas reinhardtii in anoxia.

    Science.gov (United States)

    Clowez, Sophie; Godaux, Damien; Cardol, Pierre; Wollman, Francis-André; Rappaport, Fabrice

    2015-03-27

    Photosynthetic microalgae are exposed to changing environmental conditions. In particular, microbes found in ponds or soils often face hypoxia or even anoxia, and this severely impacts their physiology. Chlamydomonas reinhardtii is one among such photosynthetic microorganisms recognized for its unusual wealth of fermentative pathways and the extensive remodeling of its metabolism upon the switch to anaerobic conditions. As regards the photosynthetic electron transfer, this remodeling encompasses a strong limitation of the electron flow downstream of photosystem I. Here, we further characterize the origin of this limitation. We show that it stems from the strong reducing pressure that builds up upon the onset of anoxia, and this pressure can be relieved either by the light-induced synthesis of ATP, which promotes the consumption of reducing equivalents, or by the progressive activation of the hydrogenase pathway, which provides an electron transfer pathway alternative to the CO2 fixation cycle. PMID:25691575

  3. Introduction of exogenous DNA into Chlamydomonas reinhardtii by electroporation.

    OpenAIRE

    Brown, L. E.; Sprecher, S L; Keller, L R

    1991-01-01

    The fate of exogenous DNA introduced into Chlamydomonas reinhardtii by electroporation was analyzed. With single and double electrical pulses, plasmids as large as 14 kb were introduced into cells with and without intact cell walls. Within hours after introduction, exogenous plasmid DNA was associated with nuclei isolated from cells; several weeks after introduction, exogenous DNA was stably integrated into the Chlamydomonas genome. These studies establish electroporation as a method for intr...

  4. Identification of an NADP/thioredoxin system in Chlamydomonas reinhardtii

    Science.gov (United States)

    Huppe, H. C.; Picaud, A.; Buchanan, B. B.; Miginiac-Maslow, M.

    1991-01-01

    The protein components of the NADP/thioredoxin system, NADP-thioredoxin reductase (NTR) and thioredoxin h, have been purified and characterized from the green alga, Chlamydomonas reinhardtii. The analysis of this system confirms that photoautotrophic Chlamydomonas cells resemble leaves in having both an NADP- and ferrodoxin-linked thioredoxin redox system. Chlamydomonas thioredoxin h, which is smaller on sodium dodecyl sulfate-polyacrylamide gel electrophoresis than thioredoxin m from the same source, cross-reacted with antisera to thioredoxin h from spinach (Spinacia oleracea L.) and wheat germ (Triticum vulgaris L.) but not with antisera to m or f thioredoxins. In these properties, the thioredoxin h resembled a thioredoxin from Chlamydomonas, designated Ch1, whose sequence was reported recently (P. Decottignies et al., 1991, Eur. J. Biochem. 198, 505-512). The differential reactivity of thioredoxin h with antisera was used to demonstrate that thioredoxin h is enriched outside the chloroplast. The NTR was purified from Chlamydomonas using thioredoxin h from the same source. Similar to its counterpart from other organisms, Chlamydomonas NTR had a subunit size of approx. 36 kDa and was specific for NADPH. Chlamydomonas NTR effectively reduced thioredoxin h from the same source but showed little activity with the other thioredoxins tested, including spinach thioredoxin h and Escherichia coli thioredoxin. Comparison of the reduction of Chlamydomonas thioredoxins m and h by each of the endogenous thioredoxin reductases, NTR and ferredoxin-thioredoxin reductase, revealed a differential specificity of each enzyme for thioredoxin. Thus, NTR showed increased activity with thioredoxin h and ferredoxin-thioredoxin reductase with thioredoxins m and f.

  5. A brief introduction to the model microswimmer {\\it Chlamydomonas reinhardtii}

    CERN Document Server

    Jeanneret, Raphaël; Polin, Marco

    2016-01-01

    The unicellular biflagellate green alga {\\it Chlamydomonas reinhardtii} has been an important model system in biology for decades, and in recent years it has started to attract growing attention also within the biophysics community. Here we provide a concise review of some of the aspects of {\\it Chlamydomonas} biology and biophysics most immediately relevant to physicists that might be interested in starting to work with this versatile microorganism.

  6. Studies on flagellar shortening in Chlamydomonas reinhardtii

    International Nuclear Information System (INIS)

    Flagellar shortening of Chlamydomonas reinhardtii was promoted by sodium chloride, pyrophosphate (sodium, potassium and ammonium salts), EDTA and EGTA, succinate, citrate and oxalate (sodium salts), caffeine and aminophylline. Removal of calcium from the medium potentiated the effects of these agents in inducing shortening. Investigations of the release of phosphorylated compounds to the medium during pyrophosphate-induced flagellar shortening of cells pre-labelled with 32P, revealed an as yet unidentified 32P-labelled compound with distinct chromatographic properties. Chromatography and electrophoresis indicates that it is a small, highly polar molecule with a high charge to mass ratio, containing thermo- and acid-labile phosphate linkages. Investigations showed of the release of 35S-labelled protein to the medium from cells pre-labelled with 35S-sulfate showed that flagellated cells released two prominent polypeptides which comigrated with α- and β-flagellar tubulin on SDS polyacrylamide gel electrophoresis, while deflagellated cells did not

  7. Cilia and ciliopathies: From Chlamydomonas and beyond

    Institute of Scientific and Technical Information of China (English)

    PAN JunMin

    2008-01-01

    The biological function of motile cilia/flagella has long been recognized. The non-motile primary cilium, once regarded as a vestigial organelle;however, has been found recently to play unexpected roles in mammalian physiology and development. Defects in cilia have profound impact on human health. Diseases related to cilia, collectively called ciliopathies include male infertility, primary cilia dyskinesia, renal cyst formation, blindness, polydactyly, obesity, hypertension, and even mental retardation. Our current understanding of cilia and ciliopathies has been fueled by basic research employing various model organisms including Chlamydomonas, a unicellular green alga. This review article provides a general introduction to the cell biology of cilia and an overview of various cilia-relateddiseases.

  8. A photorespiratory mutant of Chlamydomonas reinhardtii

    International Nuclear Information System (INIS)

    A mutant strain of Chlamydomonas reinhardtii, designated 18-7F, has been isolated and characterized. 18-7F requires a high CO2 concentration for photoautrophic growth in spite of the apparent induction of a functional CO2 concentrating mechanism in air-adapted cells. In 2% O2 the photosynthetic characteristics of 18-7F and wild type are similar. In 21% O2, photosynthetic O2 evolution is severely inhibited in the mutant by preillumination in limiting CO2, although the apparent photosynthetic affinity for inorganic carbon is similar in preilluminated cells and in cells incubated in the dark prior to O2 evolution measurements. Net CO2 uptake is also inhibited when the cells are exposed to air (21% O2, 0.035% CO2, balance N2) for longer than a few minutes. [14C]Phosphoglycolate accumulates within 5 minutes of photosynthetic 14CO2 fixation in cells of 18-7F. Phosphoglycolate does not accumulate in wild type. Phosphoglycolate phosphatase activity in extracts from air-adapted cells of 18-7F is 10 to 20% of that in wild-type Chlamydomonas. The activity of phosphoglycolate phosphatase in heterozygous diploids is intermediate between that of homozygous mutant and wild-type diploids. It was concluded that the high-CO2 requiring phenotype in 18-7F results from a phosphoglycolate phosphatase deficiency. Genetic analyses indicate that this deficiency results from a single-gene, nuclear mutation. We have named the locus pgp-1

  9. Interaction of photosystem I from Phaeodactylum tricornutum with plastocyanins as compared with its native cytochrome c6: Reunion with a lost donor.

    Science.gov (United States)

    Bernal-Bayard, Pilar; Pallara, Chiara; Carmen Castell, M; Molina-Heredia, Fernando P; Fernández-Recio, Juan; Hervás, Manuel; Navarro, José A

    2015-12-01

    In the Phaeodactylum tricornutum alga, as in most diatoms, cytochrome c6 is the only electron donor to photosystem I, and thus they lack plastocyanin as an alternative electron carrier. We have investigated, by using laser-flash absorption spectroscopy, the electron transfer to Phaeodactylum photosystem I from plastocyanins from cyanobacteria, green algae and plants, as compared with its own cytochrome c6. Diatom photosystem I is able to effectively react with eukaryotic acidic plastocyanins, although with less efficiency than with Phaeodactylum cytochrome c6. This efficiency, however, increases in some green alga plastocyanin mutants mimicking the electrostatics of the interaction site on the diatom cytochrome. In addition, the structure of the transient electron transfer complex between cytochrome c6 and photosystem I from Phaeodactylum has been analyzed by computational docking and compared to that of green lineage and mixed systems. Taking together, the results explain why the Phaeodactylum system shows a lower efficiency than the green systems, both in the formation of the properly arranged [cytochrome c6-photosystem I] complex and in the electron transfer itself. PMID:26407632

  10. Reciprocal expression of two candidate di-iron enzymes affecting photosystem I and light-harvesting complex accumulation.

    Science.gov (United States)

    Moseley, Jeffrey L; Page, M Dudley; Alder, Nancy P; Eriksson, Mats; Quinn, Jeanette; Soto, Feiris; Theg, Steven M; Hippler, Michael; Merchant, Sabeeha

    2002-03-01

    Crd1 (Copper response defect 1), which is required for the maintenance of photosystem I and its associated light-harvesting complexes in copper-deficient (-Cu) and oxygen-deficient (-O(2)) Chlamydomonas reinhardtii cells, is localized to the thylakoid membrane. A related protein, Cth1 (Copper target homolog 1), is shown to have a similar but not identical function by genetic suppressor analysis of gain-of-function sct1 (suppressor of copper target 1) strains that are transposon-containing alleles at CTH1. The pattern of Crd1 versus Cth1 accumulation is reciprocal; Crd1 abundance is increased in -Cu or -O(2) cells, whereas Cth1 accumulates in copper-sufficient (+Cu), oxygenated cells. This expression pattern is determined by a single trans-acting regulatory locus, CRR1 (COPPER RESPONSE REGULATOR 1), which activates transcription in -Cu cells. In +Cu cells, a 2.1-kb Cth1 mRNA is produced and translated, whereas Crd1 is transcribed only at basal levels, leading to Cth1 accumulation in +Cu cells. In -Cu cells, CRR1 function determines the activation of Crd1 expression and the production of an alternative 3.1-kb Cth1 mRNA that is extended at the 5' end relative to the 2.1-kb mRNA. Synthesis of the 3.1-kb mRNA, which encodes six small upstream open reading frames that possibly result in poor translation, blocks the downstream promoter through transcriptional occlusion. Fluorescence analysis of wild-type, crd1, and sct1 strains indicates that copper-responsive adjustment of the Cth1:Crd1 ratio results in modification of the interactions between photosystem I and associated light-harvesting complexes. The tightly coordinated CRR1-dependent regulation of isoenzymes Cth1 and Crd1 reinforces the notion that copper plays a specific role in the maintenance of chlorophyll proteins. PMID:11910013

  11. The mechanism of anthracene interaction with photosynthetic apparatus: A study using intact cells, thylakoid membranes and PS II complexes isolated from Chlamydomonas reinhardtii

    Energy Technology Data Exchange (ETDEWEB)

    Aksmann, Anna, E-mail: bioaak@ug.edu.pl [Department of Plant Physiology, University of Gdansk, Al. Marszalka Pilsudskiego 46, 81-378 Gdynia (Poland); Shutova, Tatiana; Samuelsson, Goeran [Umea Plant Science Centre, Department of Plant Physiology, Umea University, SE 90187 Umea (Sweden); Tukaj, Zbigniew [Department of Plant Physiology, University of Gdansk, Al. Marszalka Pilsudskiego 46, 81-378 Gdynia (Poland)

    2011-08-15

    Intact cells of Chlamydomonas reinhardtii as well as isolated thylakoid membranes and photosystem II complexes were used to examine a possible mechanism of anthracene (ANT) interaction with the photosynthetic apparatus. Since ANT concentrations above 1 mM were required to significantly inhibit the rate of oxygen evolution in PS II membrane fragments it may indicate that the toxicant did not directly interact with this photosystem. On the other hand, stimulation of oxygen uptake by ANT-treated thylakoids suggested that ANT could either act as an artificial electron acceptor in the photosynthetic electron transport chain or function as an uncoupler. Electron transfer from excited chlorophyll to ANT is impossible due to the very low reduction potential of ANT and therefore we propose that toxic concentrations of ANT increase the thylakoid membrane permeability and thereby function as an uncoupler, enhancing electron transport in vitro. Hence, its unspecific interference with photosynthetic membranes in vitro suggests that the inhibitory effect observed on intact cell photosynthesis is caused by uncoupling of phosphorylation.

  12. The RNA Structure of cis-acting Translational Elements of the Chloroplast psbC mRNA in Chlamydomonas reinhardtii

    Science.gov (United States)

    Rahim, Mir Munir A.; Vigneault, Frederic; Zerges, William

    2016-01-01

    Photosystem II is the first of two light-driven oxidoreductase complexes in oxygenic photosynthesis. The biogenesis of photosystem II requires the synthesis of polypeptide subunits encoded by the genomes in the chloroplast and the nucleus. In the chloroplast of the green alga Chlamydomonas reinhardtii, the synthesis of each subunit requires interactions between the 5′ UTR of the mRNA encoding it and gene-specific translation factors. Here, we analyze the sequences and structures in the 5′ UTR of the psbC mRNA, which are known to be required to promote translation and genetic interaction with TBC1, a nuclear gene required specifically for psbC translation. Results of enzymatic probing in vitro and chemical probing in vivo and in vitro support three secondary structures and reveal that one participates in a pseudoknot structure. Analyses of the effects of mutations affecting pseudoknot sequences, by structural mapping and thermal gradient gel electrophoresis, reveal that flexibility at the base of the major stem-loop is required for translation and higher order RNA conformation, and suggest that this conformation is stabilized by TBC1. This RNA pseudoknot tertiary structure is analogous to the internal ribosome entry sites that promote translation of certain viruses and cellular mRNAs in the nuclear-cytoplasmic systems of eukaryotes. PMID:27379123

  13. The mechanism of anthracene interaction with photosynthetic apparatus: A study using intact cells, thylakoid membranes and PS II complexes isolated from Chlamydomonas reinhardtii

    International Nuclear Information System (INIS)

    Intact cells of Chlamydomonas reinhardtii as well as isolated thylakoid membranes and photosystem II complexes were used to examine a possible mechanism of anthracene (ANT) interaction with the photosynthetic apparatus. Since ANT concentrations above 1 mM were required to significantly inhibit the rate of oxygen evolution in PS II membrane fragments it may indicate that the toxicant did not directly interact with this photosystem. On the other hand, stimulation of oxygen uptake by ANT-treated thylakoids suggested that ANT could either act as an artificial electron acceptor in the photosynthetic electron transport chain or function as an uncoupler. Electron transfer from excited chlorophyll to ANT is impossible due to the very low reduction potential of ANT and therefore we propose that toxic concentrations of ANT increase the thylakoid membrane permeability and thereby function as an uncoupler, enhancing electron transport in vitro. Hence, its unspecific interference with photosynthetic membranes in vitro suggests that the inhibitory effect observed on intact cell photosynthesis is caused by uncoupling of phosphorylation.

  14. The RNA Structure of cis-acting Translational Elements of the Chloroplast psbC mRNA in Chlamydomonas reinhardtii.

    Science.gov (United States)

    Rahim, Mir Munir A; Vigneault, Frederic; Zerges, William

    2016-01-01

    Photosystem II is the first of two light-driven oxidoreductase complexes in oxygenic photosynthesis. The biogenesis of photosystem II requires the synthesis of polypeptide subunits encoded by the genomes in the chloroplast and the nucleus. In the chloroplast of the green alga Chlamydomonas reinhardtii, the synthesis of each subunit requires interactions between the 5' UTR of the mRNA encoding it and gene-specific translation factors. Here, we analyze the sequences and structures in the 5' UTR of the psbC mRNA, which are known to be required to promote translation and genetic interaction with TBC1, a nuclear gene required specifically for psbC translation. Results of enzymatic probing in vitro and chemical probing in vivo and in vitro support three secondary structures and reveal that one participates in a pseudoknot structure. Analyses of the effects of mutations affecting pseudoknot sequences, by structural mapping and thermal gradient gel electrophoresis, reveal that flexibility at the base of the major stem-loop is required for translation and higher order RNA conformation, and suggest that this conformation is stabilized by TBC1. This RNA pseudoknot tertiary structure is analogous to the internal ribosome entry sites that promote translation of certain viruses and cellular mRNAs in the nuclear-cytoplasmic systems of eukaryotes. PMID:27379123

  15. Combined Increases in Mitochondrial Cooperation and Oxygen Photoreduction Compensate for Deficiency in Cyclic Electron Flow in Chlamydomonas reinhardtii[W][OPEN

    Science.gov (United States)

    Dang, Kieu-Van; Plet, Julie; Tolleter, Dimitri; Jokel, Martina; Cuiné, Stéphan; Carrier, Patrick; Auroy, Pascaline; Richaud, Pierre; Johnson, Xenie; Alric, Jean; Allahverdiyeva, Yagut; Peltier, Gilles

    2014-01-01

    During oxygenic photosynthesis, metabolic reactions of CO2 fixation require more ATP than is supplied by the linear electron flow operating from photosystem II to photosystem I (PSI). Different mechanisms, such as cyclic electron flow (CEF) around PSI, have been proposed to participate in reequilibrating the ATP/NADPH balance. To determine the contribution of CEF to microalgal biomass productivity, here, we studied photosynthesis and growth performances of a knockout Chlamydomonas reinhardtii mutant (pgrl1) deficient in PROTON GRADIENT REGULATION LIKE1 (PGRL1)–mediated CEF. Steady state biomass productivity of the pgrl1 mutant, measured in photobioreactors operated as turbidostats, was similar to its wild-type progenitor under a wide range of illumination and CO2 concentrations. Several changes were observed in pgrl1, including higher sensitivity of photosynthesis to mitochondrial inhibitors, increased light-dependent O2 uptake, and increased amounts of flavodiiron (FLV) proteins. We conclude that a combination of mitochondrial cooperation and oxygen photoreduction downstream of PSI (Mehler reactions) supplies extra ATP for photosynthesis in the pgrl1 mutant, resulting in normal biomass productivity under steady state conditions. The lower biomass productivity observed in the pgrl1 mutant in fluctuating light is attributed to an inability of compensation mechanisms to respond to a rapid increase in ATP demand. PMID:24989042

  16. Induction of Photosynthetic Carbon Fixation in Anoxia Relies on Hydrogenase Activity and Proton-Gradient Regulation-Like1-Mediated Cyclic Electron Flow in Chlamydomonas reinhardtii1

    Science.gov (United States)

    Bailleul, Benjamin; Berne, Nicolas

    2015-01-01

    The model green microalga Chlamydomonas reinhardtii is frequently subject to periods of dark and anoxia in its natural environment. Here, by resorting to mutants defective in the maturation of the chloroplastic oxygen-sensitive hydrogenases or in Proton-Gradient Regulation-Like1 (PGRL1)-dependent cyclic electron flow around photosystem I (PSI-CEF), we demonstrate the sequential contribution of these alternative electron flows (AEFs) in the reactivation of photosynthetic carbon fixation during a shift from dark anoxia to light. At light onset, hydrogenase activity sustains a linear electron flow from photosystem II, which is followed by a transient PSI-CEF in the wild type. By promoting ATP synthesis without net generation of photosynthetic reductants, the two AEF are critical for restoration of the capacity for carbon dioxide fixation in the light. Our data also suggest that the decrease in hydrogen evolution with time of illumination might be due to competition for reduced ferredoxins between ferredoxin-NADP+ oxidoreductase and hydrogenases, rather than due to the sensitivity of hydrogenase activity to oxygen. Finally, the absence of the two alternative pathways in a double mutant pgrl1 hydrogenase maturation factor G-2 is detrimental for photosynthesis and growth and cannot be compensated by any other AEF or anoxic metabolic responses. This highlights the role of hydrogenase activity and PSI-CEF in the ecological success of microalgae in low-oxygen environments. PMID:25931521

  17. Induction of Photosynthetic Carbon Fixation in Anoxia Relies on Hydrogenase Activity and Proton-Gradient Regulation-Like1-Mediated Cyclic Electron Flow in Chlamydomonas reinhardtii.

    Science.gov (United States)

    Godaux, Damien; Bailleul, Benjamin; Berne, Nicolas; Cardol, Pierre

    2015-06-01

    The model green microalga Chlamydomonas reinhardtii is frequently subject to periods of dark and anoxia in its natural environment. Here, by resorting to mutants defective in the maturation of the chloroplastic oxygen-sensitive hydrogenases or in Proton-Gradient Regulation-Like1 (PGRL1)-dependent cyclic electron flow around photosystem I (PSI-CEF), we demonstrate the sequential contribution of these alternative electron flows (AEFs) in the reactivation of photosynthetic carbon fixation during a shift from dark anoxia to light. At light onset, hydrogenase activity sustains a linear electron flow from photosystem II, which is followed by a transient PSI-CEF in the wild type. By promoting ATP synthesis without net generation of photosynthetic reductants, the two AEF are critical for restoration of the capacity for carbon dioxide fixation in the light. Our data also suggest that the decrease in hydrogen evolution with time of illumination might be due to competition for reduced ferredoxins between ferredoxin-NADP(+) oxidoreductase and hydrogenases, rather than due to the sensitivity of hydrogenase activity to oxygen. Finally, the absence of the two alternative pathways in a double mutant pgrl1 hydrogenase maturation factor G-2 is detrimental for photosynthesis and growth and cannot be compensated by any other AEF or anoxic metabolic responses. This highlights the role of hydrogenase activity and PSI-CEF in the ecological success of microalgae in low-oxygen environments. PMID:25931521

  18. Organisation on Photosystem I and Photosystem II in red alga Cyanidium caldarium: encounter of cyanobacterial and higher plant concepts

    Czech Academy of Sciences Publication Activity Database

    Gardian, Zdenko; Bumba, Ladislav; Schrofel, A.; Herbstová, Miroslava; Nebesářová, Jana; Vácha, František

    2007-01-01

    Roč. 1767, č. 6 (2007), s. 725-731. ISSN 0005-2728 R&D Projects: GA AV ČR IAA608170603; GA ČR GP310/07/P115; GA ČR GA206/06/0364 Institutional research plan: CEZ:AV0Z50510513; CEZ:AV0Z60220518 Keywords : Photosystem I * Photosystem II Subject RIV: BO - Biophysics Impact factor: 3.835, year: 2007

  19. On the ultrafast kinetics of the energy and electron transfer reactions in photosystem I

    Energy Technology Data Exchange (ETDEWEB)

    Slavov, Chavdar Lyubomirov

    2009-07-09

    The subject of the current work is one of the main participants in the light-dependent phase of oxygenic photosynthesis, Photosystem I (PS I). This complex carries an immense number of cofactors: chlorophylls (Chl), carotenoids, quinones, etc, which together with the protein entity exhibit several exceptional properties. First, PS I has an ultrafast light energy trapping kinetics with a nearly 100% quantum efficiency. Secondly, both of the electron transfer branches in the reaction center are suggested to be active. Thirdly, there are some so called 'red' Chls in the antenna system of PS I, absorbing light with longer wavelengths than the reaction center. These 'red' Chls significantly modify the trapping kinetics of PS I. The purpose of this thesis is to obtain better understanding of the above-mentioned, specific features of PS I. This will not merely cast more light on the mechanisms of energy and electron transfer in the complex, but also will contribute to the future developments of optimized artificial light-harvesting systems. In the current work, a number of PS I complexes isolated from different organisms (Thermosynechococcus elongatus, Chlamydomonas reinhardtii, Arabidopsis thaliana) and possessing distinctive features (different macroorganisation, monomers, trimers, monomers with a semibelt of peripheral antenna attached; presence of 'red' Chls) is investigated. The studies are primarily focused on the electron transfer kinetics in each of the cofactor branches in the PS I reaction center, as well as on the effect of the antenna size and the presence of 'red' Chls on the trapping kinetics of PS I. These aspects are explored with the help of several ultrafast optical spectroscopy methods: (i) time-resolved fluorescence ? single photon counting and synchroscan streak camera; and (ii) ultrafast transient absorption. Physically meaningful information about the molecular mechanisms of the energy trapping in PS I is

  20. Heat shock induced change in protein ubiquitination in Chlamydomonas

    International Nuclear Information System (INIS)

    Ubiquitin was purified from pea (Pisum sativum L.) and its antibody was produced. Western blot analysis showed that the antibody cross-reacted with ubiquitins from a green alga Chlamydomonas reinhardtii, a brown alga Laminaria angustata and a red alga Porphyridium cruentum but not with ubiquitin from a blue-green alga Synechococcus sp. In Chlamydomonas, the antibody also reacted with some ubiquitinated proteins including 28- and 31-kDa polypeptides. The isoelectric points of Chlamydomonas ubiquitin and the 28- and 31-kDa ubiquitinated proteins were 8.0, 8.9 and 10.3, respectively. The ubiquitinated proteins, including the 28- and 31-kDa polypeptides were detected after in vitro ATP-dependent ubiquitination of Chlamydomonas cell extract with l25I-labeled bovine ubiquitin. Heat treatment of Chlamydomonas cells (>40°C) caused drastic increase of ubiquitinated proteins with high mol wt (>60kDa), and coordinated redistribution or decrease of other ubiquitinated proteins and free ubiquitin. Quantitative analysis revealed that the 28- and 31-kDa ubiquitinated proteins showed different responses against heat stress, i.e. the former being more sensitive than the latter. (author)

  1. Novel structural aspect of the diatom thylakoid membrane: lateral segregation of photosystem I under red-enhanced illumination.

    Science.gov (United States)

    Bína, David; Herbstová, Miroslava; Gardian, Zdenko; Vácha, František; Litvín, Radek

    2016-01-01

    Spatial segregation of photosystems in the thylakoid membrane (lateral heterogeneity) observed in plants and in the green algae is usually considered to be absent in photoautotrophs possessing secondary plastids, such as diatoms. Contrary to this assumption, here we show that thylakoid membranes in the chloroplast of a marine diatom, Phaeodactylum tricornutum, contain large areas occupied exclusively by a supercomplex of photosystem I (PSI) and its associated Lhcr antenna. These membrane areas, hundreds of nanometers in size, comprise hundreds of tightly packed PSI-antenna complexes while lacking other components of the photosynthetic electron transport chain. Analyses of the spatial distribution of the PSI-Lhcr complexes have indicated elliptical particles, each 14 × 17 nm in diameter. On larger scales, the red-enhanced illumination exerts a significant effect on the ultrastructure of chloroplasts, creating superstacks of tens of thylakoid membranes. PMID:27149693

  2. High-Level Accumulation of Triacylglycerol and Starch in Photoautotrophically Grown Chlamydomonas debaryana NIES-2212.

    Science.gov (United States)

    Toyoshima, Masakazu; Sato, Naoki

    2015-12-01

    Microalgae have the potential to produce triacylglycerol (TAG) and starch, which provide alternative sources of biofuel. A problem in using Chlamydomonas reinhardtii as a model for TAG production has been that this alga lacks phosphatidylcholine (PC), which is thought to be important for TAG synthesis in plants. We found that C. debaryana is one of the rare species of Chlamydomonas having PC. Here we show that this strain, grown under complete photoautotrophic conditions, accumulated TAG and starch up to 20 and 250 pg per cell, respectively, during the stationary phase without nutrient deprivation. Addition of nutrients in this state did not cause loss of TAG, which was found in dilution with fresh medium. The photosynthetically produced TAG contained a high level of monounsaturated fatty acids, which is a preferred property as a material for biodiesel. The oil bodies were present in the cytoplasm, either between the cytoplasmic membrane and the chloroplast or between the chloroplast and the nucleus, whereas the starch granules were present within the chloroplast. Oil bodies were also deposited as a broad layer in the peripheral space of the cytoplasm outside the chloroplast, and might be easily released from the cells by genetic, chemical or mechanical manipulation. These results suggest that C. debaryana is a promising seed organism for developing a good biofuel producer. PMID:26542110

  3. The involvement of carbohydrate reserves in hydrogen photoproduction by the green alga Chlamydomonas reinhardtii

    International Nuclear Information System (INIS)

    The unicellular green alga Chlamydomonas reinhardtii is able to produce hydrogen, using water as an electron donor, and sunlight as an energy source. Although this property offers interesting biotechnological perspectives, a major limitation is related to the sensitivity of hydrogenase to oxygen which is produced by photosynthesis. It had been previously shown that in conditions of sulfur deprivation, C. reinhardtii is able to produce hydrogen during several days (Melis et an. 2000). During this process, two pathways, one direct depending on photosystem II (PSII) activity and the other involving only the PSI, are involved, starch reserves being supposed to play a role in both of these pathways. The purpose of this phD thesis was to elucidate the mechanisms linking starch catabolism to the hydrogen photoproduction process. Firstly, the analysis of mutants affected in starch biosynthesis (sta6 and sta7) showed that if starch reserves are essential to the functioning of the indirect pathway, they are not involved in the direct one. Secondly, in order to identify metabolic steps and regulatory processes involved in starch breakdown, we developed a genetic approach based on the search of mutants affected in starch reserves mobilization. Eight mutant (std1 to std8) diversely affected in their ability to degrade starch after an accumulation phase have been isolated from an insertional mutant library of 15,000 clones. One of these mutants, std1, is affected in a kinase related to the DYRK family (dual-specificity tyrosine regulated serine threonine kinase). Although the targets of this putative kinase remain to be identified, the analysis of the granule bound proteome displayed profound alterations in the expression profile of starch phosphorylases, potentially involved in starch breakdown. STD1 represents the first starch catabolism regulator identified to date in plants. (author)

  4. Hydrogen production by Chlamydomonas reinhardtii: an elaborate interplay of electron sources and sinks

    International Nuclear Information System (INIS)

    The unicellular green alga Chlamydomonas reinhardtii possesses a [FeFe]-hydrogenase HydA1 (EC 1.12.7.2), which is coupled to the photosynthetic electron transport chain. Large amounts of H2 are produced in a light-dependent reaction for several days when C. reinhardtii cells are deprived of sulfur. Under these conditions, the cells drastically change their physiology from aerobic photosynthetic growth to an anaerobic resting state. The understanding of the underlying physiological processes is not only important for getting further insights into the adaptability of photosynthesis, but will help to optimize the biotechnological application of algae as H2 producers. Two of the still most disputed questions regarding H2 generation by C. reinhardtii concern the electron source for H2 evolution and the competition of the hydrogenase with alternative electron sinks. We analyzed the H2 metabolism of S-depleted C. reinhardtii cultures utilizing a special mass spectrometer setup and investigated the influence of photosystem II (PSII)- or ribulose-bisphosphate-carboxylase/oxygenase (Rubisco)-deficiency. We show that electrons for H2-production are provided both by PSII activity and by a non-photochemical plastoquinone reduction pathway, which is dependent on previous PSII activity. In a Rubisco-deficient strain, which produces H2 also in the presence of sulfur, H2 generation seems to be the only significant electron sink for PSII activity and rescues this strain at least partially from a light-sensitive phenotype.The latter indicates that the down-regulation of assimilatory pathways in S-deprived C. reinhardtii cells is one of the important prerequisites for a sustained H2 evolution. (authors)

  5. Towards functional proteomics of membrane protein complexes: analysis of thylakoid membranes from Chlamydomonas reinhardtii.

    Science.gov (United States)

    Hippler, M; Klein, J; Fink, A; Allinger, T; Hoerth, P

    2001-12-01

    Functional proteomics of membrane proteins is an important tool for the understanding of protein networks in biological membranes but structural studies on this part of the proteome are limited. In this study we undertook such an approach to analyse photosynthetic thylakoid membranes isolated from wild-type and mutant strains of Chlamydomonas reinhardtii. Thylakoid membrane proteins were separated by high-resolution two-dimensional gel electrophoresis (2-DE) and analysed by immuno-blotting and mass spectrometry for the presence of membrane-spanning proteins. Our data show that light-harvesting complex proteins (LHCP), that cross the membrane with three transmembrane domains, can be separated using this method. We have identified more than 30 different LHCP spots on our gels. Mass spectrometric analysis of 2-DE separated Lhcb1 indicates that this major LHCII protein can associate with the thylakoid membrane with part of its putative transit sequence. Separation of isolated photosystem I (PSI) complexes by 2-DE revealed the presence of 18 LHCI protein spots. The use of two peptide-specific antibodies directed against LHCI subunits supports the interpretation that some of these spots represent products arising from differential processing and post-translational modifications. In addition our data indicate that the reaction centre subunit of PSI, PsaA, that possesses 11 transmembrane domains, can be separated by 2-DE. Comparison between 2-DE maps from thylakoid membrane proteins isolated from a PSI-deficient (Deltaycf4) and a crd1 mutant, which is conditionally reduced in PSI and LHCI under copper-deficiency, showed the presence of most of the LHCI spots in the former but their absence in the latter. Our data demonstrate that (i) hydrophobic membrane proteins like the LHCPs can be faithfully separated by 2-DE, and (ii) that high-resolution 2-DE facilitates the comparative analysis of membrane protein complexes in wild-type and mutants cells. PMID:11849598

  6. Spectral hole burning studies of photosystem II

    Energy Technology Data Exchange (ETDEWEB)

    Chang, H.C.

    1995-11-01

    Low temperature absorption and hole burning spectroscopies were applied to the D1-D2-cyt b{sub 559} and the CP47 and CP43 antenna protein complexes of Photosystem H from higher plants. Low temperature transient and persistent hole-burning data and theoretical calculations on the kinetics and temperature dependence of the P680 hole profile are presented and provide convincing support for the linker model. Implicit in the linker model is that the 684-nm-absorbing Chl a serve to shuttle energy from the proximal antenna complex to reaction center. The stoichiometry of isolated Photosystem H Reaction Center (PSII RC) in several different preparations is also discussed. The additional Chl a are due to 684-nm-absorbing Chl a, some contamination by the CP47 complex, and non-native Chl a absorbing near 670 nm. In the CP47 protein complex, attention is focused on the lower energy chlorophyll a Q{sub y}-states. High pressure hole-burning studies of PSII RC revealed for the first time a strong pressure effect on the primary electron transfer dynamics. The 4.2 K lifetime of P680*, the primary donor state, increases from 2.0 ps to 7.0 ps as pressure increases from 0.1 to 267 MPa. Importantly, this effect is irreversible (plastic) while the pressure induced effect on the low temperature absorption and non-line narrowed P680 hole spectra are reversible (elastic). Nonadiabatic rate expressions, which take into account the distribution of energy gap values, are used to estimate the linear pressure shift of the acceptor state energy for both the superexchange and two-step mechanisms for primary charge separation. It was found that the pressure dependence could be explained with a linear pressure shift of {approximately} 1 cm{sup -1}/MPa in magnitude for the acceptor state. The results point to the marriage of hole burning and high pressures as having considerable potential for the study of primary transport dynamics in reaction centers and antenna complexes.

  7. Swimming of Chlamydomonas reinhardtii in weakly elastic fluids

    Science.gov (United States)

    Yang, Jing; Gollub, Jerry; Arratia, Paulo

    2012-11-01

    The swimming behavior of the algae Chlamydomonas reinhardtii in weakly elastic fluids is investigated in experiments using microscopy and tracking methods. The effects of fluid viscosity and elasticity on the swimming speed, flagellar shape, beating frequency, and efficiency are examined. Here, the fluid viscosity is varied using water and sucrose solutions, while fluid elasticity is introduced by adding flexible polymer CMC (carboxymethyl cellulose) to the buffer solution. Swimming experiments are performed in a thin-film apparatus equipped with a microscope and high-speed camera. We find that even small amounts of fluid elasticity can have a significant effect on the swimming kinematics and dynamics of Chlamydomonas because of the relatively high beating frequency of its flagella (50-60 Hz). For example, the Chlamydomonas swimming speed is hindered by fluid elasticity compared to Newtonian fluids. In addition, the algae swimming speed decreases as the fluid elasticity is increased. This research is supported by the NSF through grant DMR-1104705.

  8. Real-time monitoring of genetically modified Chlamydomonas reinhardtii during the Foton M3 space mission and ground irradiation experiment

    Science.gov (United States)

    Lambreva, Maya; Rea, Giuseppina; Antonacci, Amina; Serafini, Agnese; Damasso, Mario; Margonelli, Andrea; Johanningmeier, Udo; Bertalan, Ivo; Pezzotti, Gianni; Giardi, Maria Teresa

    Long-term space exploration, colonization or habitation requires biological life support systems capable to cope with the deleterious space environment. The use of oxygenic photosynthetic microrganisms is an intriguing possibility mainly for food, O2 and nutraceutical compounds production. The critical points of utilizing plantsor algae-based life support systems are the microgravity and the ionizing radiation, which can influence the performance of these organisms. The aim of the present study was to assess the effects of space environment on the photosynthetic activity of various microrganisms and to select space stress-tolerant strains. Site-directed and random mutants of the unicellular green alga Chlamydomonas reinhardtii of Photosystem II D1 protein were used as a model system to test and select the amino acid substitutions capable to account for space stress tolerance. We focussed our studies also on the accumulation of the Photosystem II photoprotective carotenoids (the xantophylls violaxanthin, anteraxanthin and zeaxanthin), powerful antioxidants that epidemiological studies demonstrated to be human vision protectors. Metabolite profiling by quantitative HPLC methods revealed the organisms and the stress conditions capable to accumulate the highest pigment levels. In order to develop a project for a rationale metabolic engineering of algal secondary metabolites overproduction, we are performing expression analyses on the carotenoid biosynthetic pathway under physiological and mimicked space conditions. To identify the consequences of the space environment on the photosynthetic apparatus the changes in the Photosystem II efficiency were monitored in real time during the ESA-Russian Foton-M3 mission in September 2007. For the space flight a high-tech, multicell fluorescence biosensor, Photo-II, was designed and built by the Centre for Advanced Research in Space Optics in collaboration with Kayser-Italy, Biosensor and DAS. Photo-II is an automatic device

  9. High quality metabolomic data for Chlamydomonas reinhardtii

    Directory of Open Access Journals (Sweden)

    Fiehn Oliver

    2008-04-01

    Full Text Available Abstract The green eukaryote alga Chlamydomonas reinhardtii is a unicellular model to study control of metabolism in a photosynthetic organism. We here present method improvements for metabolite profiling based on GC-TOF mass spectrometry focusing on three parameters: quenching and cell disruption, extract solvent composition and metabolite annotation. These improvements facilitate using smaller cell numbers and hence, smaller culture volumes which enable faster and more precise sampling techniques that eventually lead to a higher number of samples that can be processed, e.g. for time course experiments. Quenching of metabolism was achieved by mixing 1 ml of culture to 1 ml of -70°C cold 70% methanol. After centrifugation, cells were lyophilized and disrupted by milling using 2-6E6 lyophilized cells, around 500-fold less than previously reported. Glass beads were compared to metal balls for milling, and five different extraction solvents were tested. Additionally, all peaks were annotated in an automated way using the GC-TOF database BinBase instead of manual investigation of a single reference chromatogram. Median precision of analysis was used to decide for the eventual procedure which was applied to a proof-of-principle study of time dependent changes of metabolism under standard conditions.

  10. Patching Holes in the Chlamydomonas Genome.

    Science.gov (United States)

    Tulin, Frej; Cross, Frederick R

    2016-01-01

    The Chlamydomonas genome has been sequenced, assembled, and annotated to produce a rich resource for genetics and molecular biology in this well-studied model organism. However, the current reference genome contains ∼1000 blocks of unknown sequence ('N-islands'), which are frequently placed in introns of annotated gene models. We developed a strategy to search for previously unknown exons hidden within such blocks, and determine the sequence, and exon/intron boundaries, of such exons. These methods are based on assembly and alignment of short cDNA and genomic DNA reads, completely independent of prior reference assembly or annotation. Our evidence indicates that a substantial proportion of the annotated intronic N-islands contain hidden exons. For most of these, our algorithm recovers full exonic sequence with associated splice junctions and exon-adjacent intronic sequence. These new exons represent de novo sequence generally present nowhere in the assembled genome, and the added sequence improves evolutionary conservation of the predicted encoded peptides. PMID:27175017

  11. Testing directed evolution strategies for space exploration: genetic modification of photosystem II to increase stress tolerance under space conditions

    Science.gov (United States)

    Bertalan, I.; Giardi, M. T.; Johanningmeier, U.

    Plants and many microorganisms are able to convert and store solar energy in chemical bonds by a process called photosynthesis They remove CO 2 from the atmosphere fix it as carbohydrate and simultaneously evolve oxygen Oxygen evolution is of supreme relevance for all higher life forms and results from the splitting of water molecules This process is catalyzed by the so called photosystem II PSII complex and represents the very beginning of biomass production PS II is also a central point of regulation being responsive to various physical and physiological parameters Complex space radiation is damaging PS II and reduces photosynthetic efficiency Thus bioregenerative life-support systems are severely disturbed at this point Genetic manipulation of photosynthesis checkpoints offer the possibility to adjust biomass and oxygen production to changing environmental conditions As the photosynthetic apparatus has adapted to terrestrial and not to space conditions we are trying to adapt a central and particularly stress-susceptible element of the photosynthesis apparatus - the D1 subunit of PS II - to space radiation by a strategy of directed evolution The D1 subunit together with its sister subunit D2 form the reaction centre of PS II D1 presents a central weak point for radiation energy that hits the chloroplast We have constructed a mutant of the green alga Chlamydomonas reinhardtii with a defect D1 protein This mutant is easily transformable with D1-encoding PCR fragments without purification and cloning steps 1 When

  12. Misunderstood or lacking legitimacy?

    OpenAIRE

    Cohen, G.; Sims, D

    2007-01-01

    In spite of the rising interest in marketing within professional service firms in the last twenty years, past research has identified a reluctant acceptance and application of marketing within these organisations. The present paper will debate whether this is due to lack of understanding of the role of marketing, lack of acceptance as a valid management discipline suitable for professional services or lack of legitimacy as a profession in its own right. A brief overview of the role of marketi...

  13. Photoinduced changes in photosystem II pigments

    Energy Technology Data Exchange (ETDEWEB)

    Andreeva, Atanaska S; Busheva, Mira C; Stoitchkova, Katerina V; Tzonova, Iren K, E-mail: katys@phys.uni-sofia.b

    2010-11-01

    The photosynthetic apparatus in higher plants performs two seemingly opposing tasks: efficient harvest of sunlight, but also rapid and harmless dissipation of excess light energy as heat to avoid deleterious photodamage. In order to study this process in pigment-protein supercomplexes of photosystem II (PSII), 77 K fluorescence and room temperature resonance Raman (RR) spectroscopy were applied to investigate the changes in structure and spectral properties of the pigments in spinach PSII membranes. The high-light treatment results in a strong quenching of the fluorescence (being largest when the excitation is absorbed by carotenoids) and a red-shift of the main maximum. Decomposition of the fluorescence spectra into four bands revealed intensive quenching of F685 and F695 bands, possible bleaching of chlorophyll a, enhanced extent of light harvesting complexes (LHCII) aggregation and increased energy transfer to aggregated LHCII. The analysis of RR spectra revealed the predominant contribution of ss-carotene (ss-Car) upon 457.8 and 488 nm excitations and lutein (Lut) at 514.5 nm. During prolonged exposure to strong light no significant bleaching of ss-Car and weak photobleaching of Lut is observed. The results will contribute to the efforts to produce more efficient and robust solar cells when exposed to fluctuations in light intensity.

  14. Photoinduced changes in photosystem II pigments

    International Nuclear Information System (INIS)

    The photosynthetic apparatus in higher plants performs two seemingly opposing tasks: efficient harvest of sunlight, but also rapid and harmless dissipation of excess light energy as heat to avoid deleterious photodamage. In order to study this process in pigment-protein supercomplexes of photosystem II (PSII), 77 K fluorescence and room temperature resonance Raman (RR) spectroscopy were applied to investigate the changes in structure and spectral properties of the pigments in spinach PSII membranes. The high-light treatment results in a strong quenching of the fluorescence (being largest when the excitation is absorbed by carotenoids) and a red-shift of the main maximum. Decomposition of the fluorescence spectra into four bands revealed intensive quenching of F685 and F695 bands, possible bleaching of chlorophyll a, enhanced extent of light harvesting complexes (LHCII) aggregation and increased energy transfer to aggregated LHCII. The analysis of RR spectra revealed the predominant contribution of ss-carotene (ss-Car) upon 457.8 and 488 nm excitations and lutein (Lut) at 514.5 nm. During prolonged exposure to strong light no significant bleaching of ss-Car and weak photobleaching of Lut is observed. The results will contribute to the efforts to produce more efficient and robust solar cells when exposed to fluctuations in light intensity.

  15. Multistep organic synthesis of modular photosystems

    Science.gov (United States)

    2012-01-01

    Summary Quite extensive synthetic achievements vanish in the online supporting information of publications on functional systems. Underappreciated, their value is recognized by experts only. As an example, we here focus in on the recent synthesis of multicomponent photosystems with antiparallel charge-transfer cascades in co-axial hole- and electron-transporting channels. The synthetic steps are described one-by-one, starting with commercial starting materials and moving on to key intermediates, such as asparagusic acid, an intriguing natural product, as well as diphosphonate “feet”, and panchromatic naphthalenediimides (NDIs), to finally reach the target molecules. These products are initiators and propagators for self-organizing surface-initiated polymerization (SOSIP), a new method introduced to secure facile access to complex architectures. Chemoorthogonal to the ring-opening disulfide exchange used for SOSIP, hydrazone exchange is then introduced to achieve stack exchange, which is a “switching” technology invented to drill giant holes into SOSIP architectures and fill them with functional π-stacks of free choice. PMID:23015840

  16. Analysis of Axonemal Assembly During Ciliary Regeneration in Chlamydomonas.

    Science.gov (United States)

    Hunter, Emily L; Sale, Winfield S; Alford, Lea M

    2016-01-01

    Chlamydomonas reinhardtii is an outstanding model genetic organism for study of assembly of cilia. Here, methods are described for synchronization of ciliary regeneration in Chlamydomonas to analyze the sequence in which ciliary proteins assemble. In addition, the methods described allow analysis of the mechanisms involved in regulation of ciliary length, the proteins required for ciliary assembly, and the temporal expression of genes encoding ciliary proteins. Ultimately, these methods can contribute to discovery of conserved genes that when defective lead to abnormal ciliary assembly and human disease. PMID:27514926

  17. Origin of pronounced differences in 77 K fluorescence of the green alga Chlamydomonas reinhardtii in state 1 and 2.

    Science.gov (United States)

    Ünlü, Caner; Polukhina, Iryna; van Amerongen, Herbert

    2016-04-01

    In response to changes in the reduction state of the plastoquinone pool in its thylakoid membrane, the green alga Chlamydomonas reinhardtti is performing state transitions: remodelling of its thylakoid membrane leads to a redistribution of excitations over photosystems I and II (PSI and PSII). These transitions are accompanied by marked changes in the 77 K fluorescence spectrum, which form the accepted signature of state transitions. The changes are generally thought to reflect a redistribution of light-harvesting complexes (LHCs) over PSII (fluorescing below 700 nm) and PSI (fluorescing above 700 nm). Here we studied the picosecond fluorescence properties of C. reinhardtti over a broad range of wavelengths with very low excitation intensities (0.2 nJ per laser pulse). Cells were directly used for time-resolved fluorescence measurements at 77 K without further treatment, such as medium exchange with glycerol. It is observed that upon going from state 1 (relatively more fluorescence below 700 nm) to state 2 (relatively more fluorescence above 700 nm), a large part of the fluorescence of LHC/PSII becomes substantially quenched in concurrence with LHC detachment from PSII, whereas the absolute amount of PSI fluorescence hardly changes. These results are in agreement with the recent proposal that the amount of LHC moving from PSII to PSI upon going from state 1 to state 2 is rather limited (Unlu et al. Proc Natl Acad Sci USA 111 (9):3460-3465, 2014). PMID:26518693

  18. Relationships between H{sub 2} photoproduction and different electron transport pathways in sulfur-deprived Chlamydomonas reinhardtii

    Energy Technology Data Exchange (ETDEWEB)

    Antal, Taras K.; Volgusheva, Alena A.; Kukarskih, Galina P.; Krendeleva, Tatyana E.; Rubin, Andrej B. [Faculty of Biology, Moscow State University, Vorobyevi Gory 119992, Moscow (Russian Federation)

    2009-11-15

    In this study the relationships between photosystem (PS) II dependent and independent pathways of H{sub 2} photoproduction, cyclic electron transport around PS I, chloro- and mitorespiration, and transmembrane {delta}pH were examined by inhibitor analysis in S deprived Chlamydomonas reinhardtii. The rate of non-photochemical reduction of plastoquinones in photosynthetic membranes was significantly diminished under starvation which may explain the minor contribution of the PS II independent pathway of H{sub 2} photoproduction in starved cells. The suppressive effect of the herbicide 3-(3,4-dichlorophenyl)-1,1-dimethylurea on the long-term H{sub 2} photoproduction was shown to be entirely attributed to the inhibition of electron transport in PS II, whereas non-specific interactions did not take place. Ferredoxin-quinone reductase - dependent cyclic electron transport around PS I slowed down H{sub 2} photoproduction more than two fold. This result was related to the competition between ferredoxin-quinone reductase and hydrogenase for the reduced ferredoxin and to the decrease in transmembrane {delta}pH induced by the cyclic electron flow. The {delta}pH gradient was shown to down regulate the PS II independent pathway of H{sub 2} photoproduction in starved cells. (author)

  19. Control of Hydrogen Photoproduction by the Proton Gradient Generated by Cyclic Electron Flow in Chlamydomonas reinhardtii[W

    Science.gov (United States)

    Tolleter, Dimitri; Ghysels, Bart; Alric, Jean; Petroutsos, Dimitris; Tolstygina, Irina; Krawietz, Danuta; Happe, Thomas; Auroy, Pascaline; Adriano, Jean-Marc; Beyly, Audrey; Cuiné, Stéphan; Plet, Julie; Reiter, Ilja M.; Genty, Bernard; Cournac, Laurent; Hippler, Michael; Peltier, Gilles

    2011-01-01

    Hydrogen photoproduction by eukaryotic microalgae results from a connection between the photosynthetic electron transport chain and a plastidial hydrogenase. Algal H2 production is a transitory phenomenon under most natural conditions, often viewed as a safety valve protecting the photosynthetic electron transport chain from overreduction. From the colony screening of an insertion mutant library of the unicellular green alga Chlamydomonas reinhardtii based on the analysis of dark-light chlorophyll fluorescence transients, we isolated a mutant impaired in cyclic electron flow around photosystem I (CEF) due to a defect in the Proton Gradient Regulation Like1 (PGRL1) protein. Under aerobiosis, nonphotochemical quenching of fluorescence (NPQ) is strongly decreased in pgrl1. Under anaerobiosis, H2 photoproduction is strongly enhanced in the pgrl1 mutant, both during short-term and long-term measurements (in conditions of sulfur deprivation). Based on the light dependence of NPQ and hydrogen production, as well as on the enhanced hydrogen production observed in the wild-type strain in the presence of the uncoupling agent carbonyl cyanide p-trifluoromethoxyphenylhydrazone, we conclude that the proton gradient generated by CEF provokes a strong inhibition of electron supply to the hydrogenase in the wild-type strain, which is released in the pgrl1 mutant. Regulation of the trans-thylakoidal proton gradient by monitoring pgrl1 expression opens new perspectives toward reprogramming the cellular metabolism of microalgae for enhanced H2 production. PMID:21764992

  20. Representative Pathways of Excitation Migration in Photosystem I

    CERN Document Server

    Park, S; Lu, D; Schulten, K; Park, Sanghyun; Sener, Melih K.; Lu, Deyu; Schulten, Klaus

    2002-01-01

    Photosystem I is a protein-pigment complex that performs photosynthesis in plants, green algae, and cyanobacteria. It contains an aggregate of chlorophylls that absorbs light and delivers the resulting electronic excitation to the special pair of chlorophylls where the excitation energy is used for producing charge separation across the cell membrane. The seemingly random arrangement of chlorophylls in photosystem I poses the question which pathways excitation migration follows towards the special pair after absorption of light at any of its chlorophylls. We employ a master equation to describe the process of excitation migration in photosystem I, and find representative paths of excitation migration based on the mean first-passage time from each chlorophyll to the special pair. The resulting paths, beginning at each of the chlorophylls and ending at the special pair, provide a complete yet distilled picture of the excitation migration towards the special pair.

  1. Observation of Coherence in the Photosystem II Reaction Center

    CERN Document Server

    Fuller, Franklin D; Senlik, S Seckin; Wilcox, Daniel E; Ogilvie, Jennifer P

    2013-01-01

    Photosynthesis powers life on our planet. The basic photosynthetic architecture comprises antenna complexes to harvest solar energy and reaction centers to convert the energy into a stable charge separated state. In oxygenic photosynthesis, the initial charge separation event occurs in the photosystem II reaction center; the only known natural enzyme that uses solar energy to split water. Energy transfer and charge separation in photosynthesis are rapid and have high quantum efficiencies. Recently, nonlinear spectroscopic experiments have suggested that electronic coherence may play a role in energy transfer efficiency in antenna complexes. Here we report the observation of coherence in the photosystem II reaction center by two dimensional electronic spectroscopy. The frequencies of the observed coherences match exciton difference frequencies and/or known vibrational modes of the photosystem II reaction center. These observations raise questions about the possible role of electronic and/or vibrational coheren...

  2. Estudio del metabolismo del glicolato en celulas de Chlamydomonas reinhardtii

    OpenAIRE

    Borrero Rubio, José Antonio

    1994-01-01

    En este trabajo pretendemos contribuir a los actuales conocimientos sobre el metabolismo del glicolato en Chlamydomonas reinhardtii desde tres aproximaciones:1. Por una parte , analizar las actividades enzimáticas implicadas en la biosíntesis y oxidación

  3. Dissecting the molecular mechanisms of intraflagellar transport in Chlamydomonas

    DEFF Research Database (Denmark)

    Pedersen, L. B.; Geimer, S.; Rosenbaum, J. L.

    2006-01-01

    the IFT system have been identified and characterized, but the mechanisms by which these different components are coordinated and regulated at the flagellar base and tip are unclear. Results Using a variety of Chlamydomonas mutants, we confirm that cDynein1b requires kinesin-2 for transport toward the...

  4. Manganese encrustation of zygospores of a chlamydomonas (chlorophyta: volvocales).

    Science.gov (United States)

    Schulz-Baldes, M; Lewin, R A

    1975-06-13

    In media containing normal trace-element supplements, but not in manganese-deficient media, zygospores of a new species of Chlamydomonas (isolated from soil) become encrusted with a dark brown mineral coating. Staining with benzidine indicates that the encrustation is rich in manganese. This has been confirmed by x-ray analysis in combination with a scanning electron microscope. PMID:17798436

  5. Model of carbon dioxide assimilation in Chlamydomonas reinhardii

    Energy Technology Data Exchange (ETDEWEB)

    Spalding, M.H.; Portis, A.R. Jr.

    1985-01-01

    A simple model of photosynthetic CO/sub 2/ assimilation in Chlamydomonas has been developed in order to evaluate whether a CO/sub 2/-concentrating system could explain the photosynthetic characteristics of this alga (high apparent affinity for CO/sub 2/, low photorespiration, little O/sub 2/ inhibition of photosynthesis, and low CO/sub 2/ compensation concentration). Similarly, the model was developed to evaluate whether the proposed defects in the CO/sub 2/-concentrating system of two Chlamydomonas mutants were consistent with their observed photosynthetic characteristics. The model treats a Chlamydomonas cell as a single compartment with two carbon inputs: passive diffusion of CO/sub 2/, and active transport of HCO/sub 3//sup -/. Internal inorganic carbon was considered to have two potential fates: assimilation to fixed carbon via ribulose 1,5-bisphosphate carboxylase-oxygenase or exiting the cell by either passive CO/sub 2/ diffusion or reversal of HCO/sub 3//sup -/ transport. Published values for kinetic parameters were used where possible. The model accurately reproduced the CO/sub 2/-response curves of photosynthesis for wild-type Chlamydomonas, the two mutants defective in the CO/sub 2/-concentrating system, and a double mutant constructed by crossing these two mutants. The model also predicts steady-state internal inorganic-carbon concentrations in reasonable agreement with measured values in all four cases. Carbon dioxide compensation concentrations for wild-type Chlamydomonas were accurately predicted by the model and those predicted for the mutants were in qualitative agreement with measured values. The model also allowed calculation of approximate energy costs of the CO/sub 2/-concentrating system. These calculations indicate that the system may be no more energy-costly than CO/sub 4/ photosynthesis. 38 references, 4 figures, 4 tables.

  6. Developing molecular tools for Chlamydomonas reinhardtii

    Science.gov (United States)

    Noor-Mohammadi, Samaneh

    Microalgae have garnered increasing interest over the years for their ability to produce compounds ranging from biofuels to neutraceuticals. A main focus of researchers has been to use microalgae as a natural bioreactor for the production of valuable and complex compounds. Recombinant protein expression in the chloroplasts of green algae has recently become more routine; however, the heterologous expression of multiple proteins or complete biosynthetic pathways remains a significant challenge. To take full advantage of these organisms' natural abilities, sophisticated molecular tools are needed to be able to introduce and functionally express multiple gene biosynthetic pathways in its genome. To achieve the above objective, we have sought to establish a method to construct, integrate and express multigene operons in the chloroplast and nuclear genome of the model microalgae Chlamydomonas reinhardtii. Here we show that a modified DNA Assembler approach can be used to rapidly assemble multiple-gene biosynthetic pathways in yeast and then integrate these assembled pathways at a site-specific location in the chloroplast, or by random integration in the nuclear genome of C. reinhardtii. As a proof of concept, this method was used to successfully integrate and functionally express up to three reporter proteins (AphA6, AadA, and GFP) in the chloroplast of C. reinhardtii and up to three reporter proteins (Ble, AphVIII, and GFP) in its nuclear genome. An analysis of the relative gene expression of the engineered strains showed significant differences in the mRNA expression levels of the reporter genes and thus highlights the importance of proper promoter/untranslated-region selection when constructing a target pathway. In addition, this work focuses on expressing the cofactor regeneration enzyme phosphite dehydrogenase (PTDH) in the chloroplast and nuclear genomes of C. reinhardtii. The PTDH enzyme converts phosphite into phosphate and NAD(P)+ into NAD(P)H. The reduced

  7. Force field development on pigments of photosystem 2 reaction centre

    Czech Academy of Sciences Publication Activity Database

    Palenčár, Peter

    2005-01-01

    Roč. 43, č. 3 (2005), s. 417-420. ISSN 0044-5231 R&D Projects: GA ČR GP206/02/D177 Institutional research plan: CEZ:AV0Z50510513; CEZ:AV0Z60870520 Keywords : photosystem 2 Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 0.750, year: 2005

  8. Force field development on pigments of photosystem 2 reaction centre

    Czech Academy of Sciences Publication Activity Database

    Palenčár, P.; Vácha, František; Kutý, Michal

    2005-01-01

    Roč. 43, - (2005), 417-420. ISSN 0300-3604 R&D Projects: GA ČR GP206/02/D177 Institutional research plan: CEZ:AV0Z50510513; CEZ:AV0Z60870520 Keywords : photosystem 2 Subject RIV: BO - Biophysics Impact factor: 0.810, year: 2005

  9. Photoinhibition of Photosystems I and II Using Chlorophyll Fluorescence Measurements

    Science.gov (United States)

    Quiles, Maria Jose

    2005-01-01

    In this study the photoinhibition of photosystems (PS) I and II caused by exposure to high intensity light in oat ("Avena sativa," var Prevision) is measured by the emission of chlorophyll fluorescence in intact leaves adapted to darkness. The maximal quantum yield of PS II was lower in plants grown under high light intensity than in plants grown…

  10. Photochemical and photoelectrochemical quenching of chlorophyll fluorescence in photosystem II

    Czech Academy of Sciences Publication Activity Database

    Vredenberg, W.; Durchan, M.; Prášil, Ondřej

    2009-01-01

    Roč. 1787, č. 12 (2009), s. 1468-1478. ISSN 0005-2728 R&D Projects: GA ČR GA206/08/1683 Institutional research plan: CEZ:AV0Z50200510 Keywords : Chlorophyll a fluorescence * Photosystem II * Heterogeneity Subject RIV: EE - Microbiology, Virology Impact factor: 3.688, year: 2009

  11. Photosystem I from the unusual cyanobacterium Gloeobacter violaceus

    NARCIS (Netherlands)

    Mangels, D.; Kruip, J.; Berry, S.; Rögner, M.; Boekema, E.J.; Koenig, F.

    2002-01-01

    Photosystem I (PS I) from the primitive cyanobacterium Gloeobacter violaceus has been purified and characterised. Despite the fact that the isolated complexes have the same subunit composition as complexes from other cyanobacteria, the amplitude of flash-induced absorption difference spectra indicat

  12. D1-protein dynamics in photosystem II: the lingering enigma

    Science.gov (United States)

    The D1/D2 heterodimer core dominates the photosystem II reaction center. A characteristic feature of this heterodimer is the differentially rapid, light-dependent degradation of the D1 protein. The D1 protein is possibly the most researched photosynthetic polypeptide, with aspects of structure–funct...

  13. Rigid-rod push–pull naphthalenediimide photosystems

    OpenAIRE

    Sakai, Naomi; Sisson, Adam L.; Bhosale, Sheshanath; Fürstenberg, Alexandre; Banerji, Natalie Renuka; Vauthey, Eric; Matile, Stefan

    2007-01-01

    Design, synthesis and evaluation of advanced rigid-rod pi-stack photosystems with asymmetric scaffolds are reported. The influence of push-pull rods on self-organization, photoinduced charge separation and photosynthetic activity is investigated and turns out to be surprisingly small overall.

  14. How energy funnels from the phycoerythrin antenna complex to photosystem I and photosystem II in cryptophyte Rhodomonas CS24 cells.

    Science.gov (United States)

    van der Weij-De Wit, Chantal D; Doust, Alexander B; van Stokkum, Ivo H M; Dekker, Jan P; Wilk, Krystyna E; Curmi, Paul M G; Scholes, Gregory D; van Grondelle, Rienk

    2006-12-14

    We report an investigation of energy migration dynamics in intact cells of the photosynthetic cryptophyte Rhodomonas CS24 using analyses of steady-state and time-resolved fluorescence anisotropy measurements. By fitting a specific model to the fluorescence data, we obtain three time scales (17, 58, and 113 ps) by which the energy is transferred from phycoerythrin 545 (PE545) to the membrane-associated chlorophylls (Chls). We propose that these time scales reflect both an angular distribution of PE545 around the photosystems and the relative orientations of the donor dihydrobiliverdin (DBV) bilin and the acceptor Chl. Contrary to investigations of the isolated antenna complex, it is demonstrated that energy transfer from PE545 does not occur from a single-emitting bilin, but rather both the peripheral dihydrobiliverdin (DBV) chromophores in PE545 appear to be viable donors of excitation energy to the membrane-bound proteins. The model shows an almost equal distribution of excitation energy from PE545 to both photosystem I (PSI) and photosystem II (PSII), whose trap times correspond well to those obtained from experiments on isolated photosystems. PMID:17149931

  15. Fluorescence changes accompanying short-term light adaptations in photosystem I and photosystem II of the cyanobacterium Synechocystis sp. PCC 6803 and phycobiliprotein-impaired mutants: State 1/State 2 transitions and carotenoid-induced quenching of phycobilisomes.

    Science.gov (United States)

    Stadnichuk, Igor N; Lukashev, Evgeny P; Elanskaya, Irina V

    2009-03-01

    The features of the two types of short-term light-adaptations of photosynthetic apparatus, State 1/State 2 transitions, and non-photochemical fluorescence quenching of phycobilisomes (PBS) by orange carotene-protein (OCP) were compared in the cyanobacterium Synechocystis sp. PCC 6803 wild type, CK pigment mutant lacking phycocyanin, and PAL mutant totally devoid of phycobiliproteins. The permanent presence of PBS-specific peaks in the in situ action spectra of photosystem I (PSI) and photosystem II (PSII), as well as in the 77 K fluorescence excitation spectra for chlorophyll emission at 690 nm (PSII) and 725 nm (PSI) showed that PBS are constitutive antenna complexes of both photosystems. The mutant strains compensated the lack of phycobiliproteins by higher PSII content and by intensification of photosynthetic linear electron transfer. The detectable changes of energy migration from PBS to the PSI and PSII in the Synechocystis wild type and the CK mutant in State 1 and State 2 according to the fluorescence excitation spectra measurements were not registered. The constant level of fluorescence emission of PSI during State 1/State 2 transitions and simultaneous increase of chlorophyll fluorescence emission of PSII in State 1 in Synechocystis PAL mutant allowed to propose that spillover is an unlikely mechanism of state transitions. Blue-green light absorbed by OCP diminished the rout of energy from PBS to PSI while energy migration from PBS to PSII was less influenced. Therefore, the main role of OCP-induced quenching of PBS is the limitation of PSI activity and cyclic electron transport under relatively high light conditions. PMID:19169839

  16. The Chlamydomonas cell wall: characterization of the wall framework

    OpenAIRE

    1985-01-01

    The cell wall of the biflagellate alga Chlamydomonas reinhardtii is a multilayered, extracellular matrix composed of carbohydrates and 20-25 polypeptides. To learn more about the forces responsible for the integrity of this cellulose-deficient cell wall, we have begun studies to identify and characterize the framework of the wall and to determine the effects of the cell wall-degrading enzyme, lysin, on framework structure and protein composition. In these studies we used walls released into t...

  17. Lipidomic Analysis of Chlamydomonas reinhardtii under Nitrogen and Sulfur Deprivation

    OpenAIRE

    Dawei Yang; Donghui Song; Tobias Kind; Yan Ma; Jens Hoefkens; Oliver Fiehn

    2015-01-01

    Chlamydomonas reinhardtii accumulates lipids under complete nutrient starvation conditions while overall growth in biomass stops. In order to better understand biochemical changes under nutrient deprivation that maintain production of algal biomass, we used a lipidomic assay for analyzing the temporal regulation of the composition of complex lipids in C. reinhardtii in response to nitrogen and sulfur deprivation. Using a chip-based nanoelectrospray direct infusion into an ion trap mass spectr...

  18. High-efficiency transformation of Chlamydomonas reinhardtii by electroporation.

    OpenAIRE

    Shimogawara, K; Fujiwara, S.; Grossman, A; Usuda, H

    1998-01-01

    We have established a high-efficiency method for transforming the unicellular, green alga Chlamydomonas reinhardtii by electroporation. Electroporation of strains CC3395 and CC425, cell wall-less mutants devoid of argininosuccinate lyase (encoded by ARG7), in the presence of the plasmid pJD67 (which contains ARG7) was used to optimize conditions for the introduction of exogenous DNA. The conditions that were varied included osmolarity, temperature, concentration of exogenous DNA, voltage and ...

  19. Green algae Chlamydomonas reinhardtii possess endogenous sialylated N-glycans

    OpenAIRE

    Mamedov, Tarlan; Yusibov, Vidadi

    2011-01-01

    Green algae have a great potential as biofactories for the production of proteins. Chlamydomonas reinhardtii, a representative of eukaryotic microalgae, has been extensively used as a model organism to study light-induced gene expression, chloroplast biogenesis, photosynthesis, light perception, cell–cell recognition, and cell cycle control. However, little is known about the glycosylation machinery and N-linked glycan structures of green algae. In this study, we performed mass spectrometry a...

  20. TETX: a novel nuclear selection marker for Chlamydomonas reinhardtii transformation

    OpenAIRE

    Garcia-Echauri, Sergio A; Cardineau, Guy A.

    2015-01-01

    Background Transformation of microalgae to obtain recombinant proteins, lipids or metabolites of economic value is of growing interest due to low costs associated with culture growth and scaling up. At present there are only three stable nuclear selection markers for the transformation of Chlamydomonas reinhardtii, which is the most commonly transformed microalgae, specifically: the aminoglycoside phosphotransferaseses aph7and aphVIII and the phleomycin resistance ble gene. As several microal...

  1. Transformace ptDNA \\kur{Chlamydomonas reinhardtii}

    OpenAIRE

    Husáková, Jana

    2011-01-01

    The aim of this master thesis was to test and compare two available methods of genetic transformation (biolistics, electroporation) of the plastid genome of green algae Chlamydomonas reinhardtii. For biolistic transformation a wide range of experimental parameters which generally influence ptDNA transformation efficiency was optimized: physiological condition of acceptor cells, type and size of microparticles, pressure of propulsion gas (helium), length of projectile trajectory, transformatio...

  2. An optimized, chemically regulated gene expression system for Chlamydomonas.

    Directory of Open Access Journals (Sweden)

    Paola Ferrante

    Full Text Available BACKGROUND: Chlamydomonas reinhardtii is a model system for algal and cell biology and is used for biotechnological applications, such as molecular farming or biological hydrogen production. The Chlamydomonas metal-responsive CYC6 promoter is repressed by copper and induced by nickel ions. However, induction by nickel is weak in some strains, poorly reversible by chelating agents like EDTA, and causes, at high concentrations, toxicity side effects on Chlamydomonas growth. Removal of these bottlenecks will encourage the wide use of this promoter as a chemically regulated gene expression system. METHODOLOGY: Using a codon-optimized Renilla luciferase as a reporter gene, we explored several strategies to improve the strength and reversibility of CYC6 promoter induction. Use of the first intron of the RBCS2 gene or of a modified TAP medium increases the strength of CYC6 induction up to 20-fold. In the modified medium, induction is also obtained after addition of specific copper chelators, like TETA. At low concentrations (up to 10 microM TETA is a more efficient inducer than Ni, which becomes a very efficient inducer at higher concentrations (50 microM. Neither TETA nor Ni show toxicity effects at the concentrations used. Unlike induction by Ni, induction by TETA is completely reversible by micromolar copper concentrations, thus resulting in a transient "wave" in luciferase activity, which can be repeated in subsequent growth cycles. CONCLUSIONS: We have worked out a chemically regulated gene expression system that can be finely tuned to produce temporally controlled "waves" in gene expression. The use of cassettes containing the CYC6 promoter, and of modified growth media, is a reliable and economically sustainable system for the temporally controlled expression of foreign genes in Chlamydomonas.

  3. Relevance of nutrient media composition for hydrogen production in Chlamydomonas.

    Science.gov (United States)

    Gonzalez-Ballester, David; Jurado-Oller, Jose Luis; Fernandez, Emilio

    2015-09-01

    Microalgae are capable of biological H2 photoproduction from water, solar energy, and a variety of organic substrates. Acclimation responses to different nutrient regimes finely control photosynthetic activity and can influence H2 production. Hence, nutrient stresses are an interesting scenario to study H2 production in photosynthetic organisms. In this review, we mainly focus on the H2-production mechanisms in Chlamydomonas reinhardtii and the physiological relevance of the nutrient media composition when producing H2. PMID:25952745

  4. Characterizing the Anaerobic Response of Chlamydomonas reinhardtii by Quantitative Proteomics

    OpenAIRE

    Terashima, Mia; Specht, Michael; Naumann, Bianca; Hippler, Michael

    2010-01-01

    The versatile metabolism of the green alga Chlamydomonas reinhardtii is reflected in its complex response to anaerobic conditions. The anaerobic response is also remarkable in the context of renewable energy because C. reinhardtii is able to produce hydrogen under anaerobic conditions. To identify proteins involved during anaerobic acclimation as well as to localize proteins and pathways to the powerhouses of the cell, chloroplasts and mitochondria from C. reinhardtii in aerobic and anaerobic...

  5. Molecular Map of the Chlamydomonas reinhardtii Nuclear Genome

    OpenAIRE

    Kathir, Pushpa; LaVoie, Matthew; Brazelton, William J.; Haas, Nancy A.; Lefebvre, Paul A.; Silflow, Carolyn D.

    2003-01-01

    We have prepared a molecular map of the Chlamydomonas reinhardtii genome anchored to the genetic map. The map consists of 264 markers, including sequence-tagged sites (STS), scored by use of PCR and agarose gel electrophoresis, and restriction fragment length polymorphism markers, scored by use of Southern blot hybridization. All molecular markers tested map to one of the 17 known linkage groups of C. reinhardtii. The map covers approximately 1,000 centimorgans (cM). Any position on the C. re...

  6. New thioredoxin targets in the unicellular photosynthetic eukaryote Chlamydomonas reinhardtii

    OpenAIRE

    Lemaire, Stéphane D.; Guillon, Blanche; Le Maréchal, Pierre; Keryer, Eliane; Miginiac-Maslow, Myroslawa; Decottignies, Paulette

    2004-01-01

    Proteomics were used to identify the proteins from the eukaryotic unicellular green alga Chlamydomonas reinhardtii that can be reduced by thioredoxin. These proteins were retained specifically on a thioredoxin affinity column made of a monocysteinic thioredoxin mutant able to form mixed disulfides with its targets. Of a total of 55 identified targets, 29 had been found previously in higher plants or Synechocystis, but 26 were new targets. Biochemical tests were performed on three of them, sho...

  7. D-lactate metabolism in the alga, Chlamydomonas Reinhardtii

    International Nuclear Information System (INIS)

    [14C]D-lactate rapidly accumulates in Chlamydomonas cells under anaerobic conditions from the sugar-phosphate pools which are labeled during photosynthesis with 14CO2. A soluble D-lactate dehydrogenase (30 μmol NADH oxidized/h/mg Chl), which functions only in the direction of pyruvate reduction, has been partially purified and characterized. The D-lactate is reoxidized in Chlamydomonas by a mitochondrial membrane-bound dehydrogenase. This enzyme is known in the plant literature as glycolate dehydrogenase, an enzyme of the oxidative photosynthetic carbon (C2) cycle. This dehydrogenase may be linked to the mitochondrial electron transport chain, although the direct electron acceptor is unknown. Therefore, D-lactate accumulation may be, in part, due to the shut down of electron transport during anaerobiosis. In vivo chase experiments have shown that the D-lactate turns over rapidly when algal cells, which have been grown with air levels of CO2 (0.04%), are returned to aerobic conditions in the light. Such turnover is not observed in cells which had been grown with 1 to 5% CO2. Cells grown with high CO2 have lower levels of glycolate dehydrogenase activity. They are currently using mutants of Chlamydomonas deficient in mitochondrial respiration to study the role of D-lactate oxidation in these algae

  8. Characterization of new radioresistant strains of Chlamydomonas reinhardtii

    International Nuclear Information System (INIS)

    The purpose of this work is to investigate 4 new mutant strains of Chlamydomonas reinhardtii induced in respect to their radioresistance at different levels: cellular, molecular and biochemical. A comparison between radioresistance of the strains, DNA-ssb repair activity and pigment contents (chl 'a', chl 'b' and carotenoids) is made. Strain 137C(+) and mutant strains GK-1(+), GK-2(+), GK-3(+), and AKK-9-9(-) are used. The radioresistance has been assessed according to colony forming ability of the strains after irradiation with gamma rays (60C0, I=12.4 rads-1 doses 10, 50, 100, 150, 200 and 250 Gy). The data obtained reveal that there is a relationship between radioresistance, DNA-ssb repair efficiency and plastid pigment content in the tested Chlamydomonas reinhardtii strains. This relationship is most pronounced in strain AK-9-9 which displays the highest level of radioresistance. On the basis of data obtained the authors propose mutant strain AK-9-9 to be included in the existing collection of mutant strains of Chlamydomonas reinhardtii

  9. Activation of Autophagy by Metals in Chlamydomonas reinhardtii.

    Science.gov (United States)

    Pérez-Martín, Marta; Blaby-Haas, Crysten E; Pérez-Pérez, María Esther; Andrés-Garrido, Ascensión; Blaby, Ian K; Merchant, Sabeeha S; Crespo, José L

    2015-09-01

    Autophagy is an intracellular self-degradation pathway by which eukaryotic cells recycle their own material in response to specific stress conditions. Exposure to high concentrations of metals causes cell damage, although the effect of metal stress on autophagy has not been explored in photosynthetic organisms. In this study, we investigated the effect of metal excess on autophagy in the model unicellular green alga Chlamydomonas reinhardtii. We show in cells treated with nickel an upregulation of ATG8 that is independent of CRR1, a global regulator of copper signaling in Chlamydomonas. A similar effect on ATG8 was observed with copper and cobalt but not with cadmium or mercury ions. Transcriptome sequencing data revealed an increase in the abundance of the protein degradation machinery, including that responsible for autophagy, and a substantial overlap of that increased abundance with the hydrogen peroxide response in cells treated with nickel ions. Thus, our results indicate that metal stress triggers autophagy in Chlamydomonas and suggest that excess nickel may cause oxidative damage, which in turn activates degradative pathways, including autophagy, to clear impaired components and recover cellular homeostasis. PMID:26163317

  10. Nucleated assembly of Chlamydomonas and Volvox cell walls.

    Science.gov (United States)

    Adair, W S; Steinmetz, S A; Mattson, D M; Goodenough, U W; Heuser, J E

    1987-11-01

    The Chlamydomonas reinhardtii cell wall is made up of hydroxyproline-rich glycoproteins, arranged in five distinct layers. The W6 (crystalline) layer contains three major glycoproteins (GP1, GP2, GP3), selectively extractable with chaotropic agents, that self-assemble into crystals in vitro. A system to study W6 assembly in a quantitative fashion was developed that employs perchlorate-extracted Chlamydomonas cells as nucleating agents. Wall reconstitution by biotinylated W6 monomers was monitored by FITC-streptavidin fluorescence and quick-freeze/deep-etch electron microscopy. Optimal reconstitution was obtained at monomer concentrations (0.2-0.3 mg/ml) well below those required for nonnucleated assembly. Assembly occurred from multiple nucleation sites, and faithfully reflected the structure of the intact W6 layer. Specificity of nucleated assembly was demonstrated using two cell-wall mutants (cw-2 and cw-15); neither served as a substrate for assembly of wild-type monomers. In addition, W6 sublayers were assembled from purified components: GP2 and GP3 coassembled to form the inner (W6A) sublayer; this then served as a substrate for self-assembly of GP1 into the outer (W6B) sublayer. Finally, evolutionary relationships between C. reinhardtii and two additional members of the Volvocales (Chlamydomonas eugametos and Volvox carteri) were explored by performing interspecific reconstitutions. Hybrid walls were obtained between C. reinhardtii and Volvox but not with C. eugametos, confirming taxonomic assignments based on structural criteria. PMID:3680387

  11. Actin is required for IFT regulation in Chlamydomonas reinhardtii.

    Science.gov (United States)

    Avasthi, Prachee; Onishi, Masayuki; Karpiak, Joel; Yamamoto, Ryosuke; Mackinder, Luke; Jonikas, Martin C; Sale, Winfield S; Shoichet, Brian; Pringle, John R; Marshall, Wallace F

    2014-09-01

    Assembly of cilia and flagella requires intraflagellar transport (IFT), a highly regulated kinesin-based transport system that moves cargo from the basal body to the tip of flagella [1]. The recruitment of IFT components to basal bodies is a function of flagellar length, with increased recruitment in rapidly growing short flagella [2]. The molecular pathways regulating IFT are largely a mystery. Because actin network disruption leads to changes in ciliary length and number, actin has been proposed to have a role in ciliary assembly. However, the mechanisms involved are unknown. In Chlamydomonas reinhardtii, conventional actin is found in both the cell body and the inner dynein arm complexes within flagella [3, 4]. Previous work showed that treating Chlamydomonas cells with the actin-depolymerizing compound cytochalasin D resulted in reversible flagellar shortening [5], but how actin is related to flagellar length or assembly remains unknown. Here we utilize small-molecule inhibitors and genetic mutants to analyze the role of actin dynamics in flagellar assembly in Chlamydomonas reinhardtii. We demonstrate that actin plays a role in IFT recruitment to basal bodies during flagellar elongation and that when actin is perturbed, the normal dependence of IFT recruitment on flagellar length is lost. We also find that actin is required for sufficient entry of IFT material into flagella during assembly. These same effects are recapitulated with a myosin inhibitor, suggesting that actin may act via myosin in a pathway by which flagellar assembly is regulated by flagellar length. PMID:25155506

  12. Energy brands lack vitality

    International Nuclear Information System (INIS)

    The three Dutch energy companies (Nuon, Essent and Eneco Energie) have relatively little brand strength. The brands are not perceived to be sufficiently different from one another and are not valued by consumers. With liberalisation imminent, this is hardly a strong starting point. How can you win over consumers if it is not clear what is on offer? In the business market, decision-makers are better placed to distinguish between brands. However, the brands lack vitality in this sector of the market too. The only consolation is that the situation is by no means exclusive to the Netherlands

  13. Plastidial Expression of Type II NAD(P)H Dehydrogenase Increases the Reducing State of Plastoquinones and Hydrogen Photoproduction Rate by the Indirect Pathway in Chlamydomonas reinhardtii1.

    Science.gov (United States)

    Baltz, Anthony; Dang, Kieu-Van; Beyly, Audrey; Auroy, Pascaline; Richaud, Pierre; Cournac, Laurent; Peltier, Gilles

    2014-05-12

    Biological conversion of solar energy into hydrogen is naturally realized by some microalgae species due to a coupling between the photosynthetic electron transport chain and a plastidial hydrogenase. While promising for the production of clean and sustainable hydrogen, this process requires improvement to be economically viable. Two pathways, called direct and indirect photoproduction, lead to sustained hydrogen production in sulfur-deprived Chlamydomonas reinhardtii cultures. The indirect pathway allows an efficient time-based separation of O2 and H2 production, thus overcoming the O2 sensitivity of the hydrogenase, but its activity is low. With the aim of identifying the limiting step of hydrogen production, we succeeded in overexpressing the plastidial type II NAD(P)H dehydrogenase (NDA2). We report that transplastomic strains overexpressing NDA2 show an increased activity of nonphotochemical reduction of plastoquinones (PQs). While hydrogen production by the direct pathway, involving the linear electron flow from photosystem II to photosystem I, was not affected by NDA2 overexpression, the rate of hydrogen production by the indirect pathway was increased in conditions, such as nutrient limitation, where soluble electron donors are not limiting. An increased intracellular starch was observed in response to nutrient deprivation in strains overexpressing NDA2. It is concluded that activity of the indirect pathway is limited by the nonphotochemical reduction of PQs, either by the pool size of soluble electron donors or by the PQ-reducing activity of NDA2 in nutrient-limited conditions. We discuss these data in relation to limitations and biotechnological improvement of hydrogen photoproduction in microalgae. PMID:24820024

  14. All-trans retinal constitutes the functional chromophore in Chlamydomonas rhodopsin

    OpenAIRE

    Hegemann, P.; Gärtner, W; R. Uhl

    1991-01-01

    Orientation of the green alga Chlamydomonas in light (phototaxis and stop responses) is controlled by a visual system with a rhodopsin as the functional photoreceptor. Here, we present evidence that in Chlamydomonas wild-type cells all-trans retinal is the predominant isomer and that it is present in amounts similar to that of the rhodopsin itself.

  15. The NIT1 Promoter Allows Inducible and Reversible Silencing of Centrin in Chlamydomonas reinhardtii

    OpenAIRE

    Koblenz, Bettina; Lechtreck, Karl-Ferdinand

    2005-01-01

    An inverted repeat corresponding to parts of the centrin gene of Chlamydomonas reinhardtii was placed downstream of the NIT1 promoter, which is induced by ammonium starvation. After induction, transformants developed centrin deficiency as assayed by immunofluorescence, Western blotting, and Northern blotting. The effect was reversible, demonstrating that the NIT1 promoter allowed controlled RNA interference in Chlamydomonas reinhardtii.

  16. The involvement of carbohydrate reserves in hydrogen photoproduction by the green alga Chlamydomonas reinhardtii; L'implication des reserves carbonees dans la photoproduction d'hydrogene chez l'algue verte Chlamydomonas reinhardtii

    Energy Technology Data Exchange (ETDEWEB)

    Chochois, V.

    2009-09-15

    The unicellular green alga Chlamydomonas reinhardtii is able to produce hydrogen, using water as an electron donor, and sunlight as an energy source. Although this property offers interesting biotechnological perspectives, a major limitation is related to the sensitivity of hydrogenase to oxygen which is produced by photosynthesis. It had been previously shown that in conditions of sulfur deprivation, C. reinhardtii is able to produce hydrogen during several days (Melis et an. 2000). During this process, two pathways, one direct depending on photosystem II (PSII) activity and the other involving only the PSI, are involved, starch reserves being supposed to play a role in both of these pathways. The purpose of this phD thesis was to elucidate the mechanisms linking starch catabolism to the hydrogen photoproduction process. Firstly, the analysis of mutants affected in starch biosynthesis (sta6 and sta7) showed that if starch reserves are essential to the functioning of the indirect pathway, they are not involved in the direct one. Secondly, in order to identify metabolic steps and regulatory processes involved in starch breakdown, we developed a genetic approach based on the search of mutants affected in starch reserves mobilization. Eight mutant (std1 to std8) diversely affected in their ability to degrade starch after an accumulation phase have been isolated from an insertional mutant library of 15,000 clones. One of these mutants, std1, is affected in a kinase related to the DYRK family (dual-specificity tyrosine regulated serine threonine kinase). Although the targets of this putative kinase remain to be identified, the analysis of the granule bound proteome displayed profound alterations in the expression profile of starch phosphorylases, potentially involved in starch breakdown. STD1 represents the first starch catabolism regulator identified to date in plants. (author)

  17. Phytotoxicity of Four Photosystem II Herbicides to Tropical Seagrasses

    OpenAIRE

    Flores, Florita; Catherine J Collier; Mercurio, Philip; Negri, Andrew P.

    2013-01-01

    Coastal waters of the Great Barrier Reef (GBR) are contaminated with agricultural pesticides, including the photosystem II (PSII) herbicides which are the most frequently detected at the highest concentrations. Designed to control weeds, these herbicides are equally potent towards non-target marine species, and the close proximity of seagrass meadows to flood plumes has raised concerns that seagrasses may be the species most threatened by herbicides from runoff. While previous work has identi...

  18. Observation of Coherence in the Photosystem II Reaction Center

    OpenAIRE

    Fuller, Franklin D; Pan, Jie; Senlik, S. Seckin; Wilcox, Daniel E.; Ogilvie, Jennifer P.

    2013-01-01

    Photosynthesis powers life on our planet. The basic photosynthetic architecture comprises antenna complexes to harvest solar energy and reaction centers to convert the energy into a stable charge separated state. In oxygenic photosynthesis, the initial charge separation event occurs in the photosystem II reaction center; the only known natural enzyme that uses solar energy to split water. Energy transfer and charge separation in photosynthesis are rapid and have high quantum efficiencies. Rec...

  19. Detection of hydrogen peroxide in Photosystem II (PSII using catalytic amperometric biosensor

    Directory of Open Access Journals (Sweden)

    Ankush ePrasad

    2015-10-01

    Full Text Available Hydrogen peroxide (H2O2 is known to be generated in Photosystem II (PSII via enzymatic and non-enzymatic pathways. Hydrogen peroxide (H2O2 is known to be generated in Photosystem II (PSII via enzymatic and non-enzymatic pathways. Detection of H2O2 by different spectroscopic techniques has been explored, however its sensitive detection has always been a challenge in photosynthetic research. During the recent past, fluorescence probes such as Amplex Red has been used but is known to either lack specificity or limitation with respect to the minimum detection limit of H2O2. We have employed an electrochemical biosensor for real time monitoring of H2O2 generation at the level of sub-cellular organelles. The electrochemical biosensor comprises of counter electrode and working electrodes. The counter electrode is a platinum plate, while the working electrode is a mediator based catalytic amperometric biosensor device developed by the coating of a carbon electrode with osmium-horseradish peroxidase which acts as H2O2 detection sensor. In the current study, generation and kinetic behaviour of H2O2 in PSII membranes have been studied under light illumination. Electrochemical detection of H2O2 using the catalytic amperometric biosensor device is claimed to serve as a promising technique for detection of H2O2 in photosynthetic cells and subcellular structures including PSII or thylakoid membranes. It can also provide a precise information on qualitative determination of H2O2 and thus can be widely used in photosynthetic research.

  20. Multiple-endpoint assay provides a detailed mechanistic view of responses to herbicide exposure in Chlamydomonas reinhardtii

    Energy Technology Data Exchange (ETDEWEB)

    Nestler, Holger [Eawag, Swiss Federal Institute of Aquatic Science and Technology, Ueberlandstrasse 133, 8600 Duebendorf (Switzerland); ETH Zurich, Swiss Federal Institute of Technology, Institute of Biogeochemistry and Pollutant Dynamics, Universitaetstrasse 16, 8092 Zurich (Switzerland); Groh, Ksenia J.; Schoenenberger, Rene; Behra, Renata [Eawag, Swiss Federal Institute of Aquatic Science and Technology, Ueberlandstrasse 133, 8600 Duebendorf (Switzerland); Schirmer, Kristin [Eawag, Swiss Federal Institute of Aquatic Science and Technology, Ueberlandstrasse 133, 8600 Duebendorf (Switzerland); ETH Zurich, Swiss Federal Institute of Technology, Institute of Biogeochemistry and Pollutant Dynamics, Universitaetstrasse 16, 8092 Zurich (Switzerland); EPF Lausanne, School of Architecture, Civil and Environmental Engineering, 1015 Lausanne (Switzerland); Eggen, Rik I.L. [Eawag, Swiss Federal Institute of Aquatic Science and Technology, Ueberlandstrasse 133, 8600 Duebendorf (Switzerland); ETH Zurich, Swiss Federal Institute of Technology, Institute of Biogeochemistry and Pollutant Dynamics, Universitaetstrasse 16, 8092 Zurich (Switzerland); Suter, Marc J.-F., E-mail: suter@eawag.ch [Eawag, Swiss Federal Institute of Aquatic Science and Technology, Ueberlandstrasse 133, 8600 Duebendorf (Switzerland); ETH Zurich, Swiss Federal Institute of Technology, Institute of Biogeochemistry and Pollutant Dynamics, Universitaetstrasse 16, 8092 Zurich (Switzerland)

    2012-04-15

    The release of herbicides into the aquatic environment raises concerns about potential detrimental effects on ecologically important non-target species, such as unicellular algae, necessitating ecotoxicological risk assessment. Algal toxicity tests based on growth, a commonly assessed endpoint, are integrative, and hence do not provide information about underlying toxic mechanisms and effects. This limitation may be overcome by measuring more specific biochemical and physiological endpoints. In the present work, we developed and applied a novel multiple-endpoint assay, and analyzed the effects of the herbicides paraquat, diuron and norflurazon, each representing a specific mechanism of toxic action, on the single celled green alga Chlamydomonas reinhardtii. The endpoints added to assessment of growth were pigment content, maximum and effective photosystem II quantum yield, ATP content, esterase and oxidative activity. All parameters were measured at 2, 6 and 24 h of exposure, except for growth and pigment content, which were determined after 6 and 24 h only. Effective concentrations causing 50% of response (EC50s) and lowest observable effect concentrations (LOECs) were determined for all endpoints and exposure durations where possible. The assay provided a detailed picture of the concentration- and time-dependent development of effects elicited by the analyzed herbicides, thus improving the understanding of the underlying toxic mechanisms. Furthermore, the response patterns were unique to the respective herbicide and reflected the different mechanisms of toxicity. The comparison of the endpoint responses and sensitivities revealed that several physiological and biochemical parameters reacted earlier or stronger to disturbances than growth. Overall, the presented multiple-endpoint assay constitutes a promising basis for investigating stressor and toxicant effects in green algae.

  1. Multiple-endpoint assay provides a detailed mechanistic view of responses to herbicide exposure in Chlamydomonas reinhardtii

    International Nuclear Information System (INIS)

    The release of herbicides into the aquatic environment raises concerns about potential detrimental effects on ecologically important non-target species, such as unicellular algae, necessitating ecotoxicological risk assessment. Algal toxicity tests based on growth, a commonly assessed endpoint, are integrative, and hence do not provide information about underlying toxic mechanisms and effects. This limitation may be overcome by measuring more specific biochemical and physiological endpoints. In the present work, we developed and applied a novel multiple-endpoint assay, and analyzed the effects of the herbicides paraquat, diuron and norflurazon, each representing a specific mechanism of toxic action, on the single celled green alga Chlamydomonas reinhardtii. The endpoints added to assessment of growth were pigment content, maximum and effective photosystem II quantum yield, ATP content, esterase and oxidative activity. All parameters were measured at 2, 6 and 24 h of exposure, except for growth and pigment content, which were determined after 6 and 24 h only. Effective concentrations causing 50% of response (EC50s) and lowest observable effect concentrations (LOECs) were determined for all endpoints and exposure durations where possible. The assay provided a detailed picture of the concentration- and time-dependent development of effects elicited by the analyzed herbicides, thus improving the understanding of the underlying toxic mechanisms. Furthermore, the response patterns were unique to the respective herbicide and reflected the different mechanisms of toxicity. The comparison of the endpoint responses and sensitivities revealed that several physiological and biochemical parameters reacted earlier or stronger to disturbances than growth. Overall, the presented multiple-endpoint assay constitutes a promising basis for investigating stressor and toxicant effects in green algae.

  2. High light-induced hydrogen peroxide production in Chlamydomonas reinhardtii is increased by high CO2 availability.

    Science.gov (United States)

    Roach, Thomas; Na, Chae Sun; Krieger-Liszkay, Anja

    2015-03-01

    The production of reactive oxygen species (ROS) is an unavoidable part of photosynthesis. Stress that accompanies high light levels and low CO2 availability putatively includes enhanced ROS production in the so-called Mehler reaction. Such conditions are thought to encourage O2 to become an electron acceptor at photosystem I, producing the ROS superoxide anion radical (O2·-) and hydrogen peroxide (H2 O2 ). In contrast, here it is shown in Chlamydomonas reinhardtii that CO2 depletion under high light levels lowered cellular H2 O2 production, and that elevated CO2 levels increased H2 O2 production. Using various photosynthetic and mitochondrial mutants of C. reinhardtii, the chloroplast was identified as the main source of elevated H2 O2 production under high CO2 availability. High light levels under low CO2 availability induced photoprotective mechanisms called non-photochemical quenching, or NPQ, including state transitions (qT) and high energy state quenching (qE). The qE-deficient mutant npq4 produced more H2 O2 than wild-type cells under high light levels, although less so under high CO2 availability, whereas it demonstrated equal or greater enzymatic H2 O2 -degrading capacity. The qT-deficient mutant stt7-9 produced the same H2 O2 as wild-type cells under high CO2 availability. Physiological levels of H2 O2 were able to hinder qT and the induction of state 2, providing an explanation for why under high light levels and high CO2 availability wild-type cells behaved like stt7-9 cells stuck in state 1. PMID:25619314

  3. Mutagenesis and phenotypic selection as a strategy toward domestication of Chlamydomonas reinhardtii strains for improved performance in photobioreactors.

    Science.gov (United States)

    Bonente, Giulia; Formighieri, Cinzia; Mantelli, Manuela; Catalanotti, Claudia; Giuliano, Giovanni; Morosinotto, Tomas; Bassi, Roberto

    2011-09-01

    Microalgae have a valuable potential for biofuels production. As a matter of fact, algae can produce different molecules with high energy content, including molecular hydrogen (H(2)) by the activity of a chloroplastic hydrogenase fueled by reducing power derived from water and light energy. The efficiency of this reaction, however, is limited and depends from an intricate relationships between oxygenic photosynthesis and mitochondrial respiration. The way toward obtaining algal strains with high productivity in photobioreactors requires engineering of their metabolism at multiple levels in a process comparable to domestication of crops that were derived from their wild ancestors through accumulation of genetic traits providing improved productivity under conditions of intensive cultivation as well as improved nutritional/industrial properties. This holds true for the production of any biofuels from algae: there is the need to isolate multiple traits to be combined and produce organisms with increased performances. Among the different limitations in H(2) productivity, we identified three with a major relevance, namely: (i) the light distribution through the mass culture; (ii) the strong sensitivity of the hydrogenase to even very low oxygen concentrations; and (iii) the presence of alternative pathways, such as the cyclic electron transport, competing for reducing equivalents with hydrogenase and H(2) production. In order to identify potentially favorable mutations, we generated a collection of random mutants in Chlamydomonas reinhardtii which were selected through phenotype analysis for: (i) a reduced photosynthetic antenna size, and thus a lower culture optical density; (ii) an altered photosystem II activity as a tool to manipulate the oxygen concentration within the culture; and (iii) State 1-State 2 transition mutants, for a reduced cyclic electron flow and maximized electrons flow toward the hydrogenase. Such a broad approach has been possible thanks to the

  4. Activities of photosystem I and photosystem II of chloroplasts isolated from different plants under the ionizing radiation

    International Nuclear Information System (INIS)

    Oil and oil products are the most common and harmful environmental factors, which cause significant changes in the functioning of the plants. In the present study of Phragmites australis, Zygophyllum fabago and Argusia Sibirica plants spread on the polluted with oil area of the former iodine production plant located in Ramani district of Azerbaijan, were used as subjects of investigation. Chloroplasts were isolated from plants collected under 250 μR/hr background radiation and natural conditions. The quantum yield of (PS) II and the photochemical activity of photosystem (PS) II (based on evolution oxygen) and photosystem (PS) I (based on absorption of oxygen) was analyzed. The potential quantum yields of PS II took low values under the influence of ionizing radiation

  5. Association of chlorophyll a/c(2) complexes to photosystem I and photosystem II in the cryptophyte Rhodomonas CS24

    OpenAIRE

    Kereihe, Sami; Kouril, Roman; Oostergetel, Gert T.; Fusetti, Fabrizia; Boekema, Egbert J.; Doust, Alexander B.; van der Weij-de Wit, Chantal D.; Dekker, Jan P; Kereïche, Sami; Kouřil, Roman

    2008-01-01

    Photosynthetic supercomplexes from the cryptophyte Rhodomonas CS24 were isolated by a short detergent treatment of membranes from the cryptophyte Rhodomonas CS24 and studied by electron microscopy and low-temperature absorption and fluorescence spectroscopy. At least three different types of supercomplexes of photosystem I (PSI) monomers and peripheral Chl a/c(2) proteins were found. The most common complexes have Chl a/c(2) complexes at both sides of the PSI core monomer and have dimensions ...

  6. The stoichiometry of the two photosystems in higher plants revisited.

    Science.gov (United States)

    Fan, Da-Yong; Hope, Alexander B; Smith, Paul J; Jia, Husen; Pace, Ronald J; Anderson, Jan M; Chow, Wah Soon

    2007-08-01

    The stoichiometry of Photosystem II (PSII) to Photosystem I (PSI) reaction centres in spinach leaf segments was determined by two methods, each capable of being applied to monitor the presence of both photosystems in a given sample. One method was based on a fast electrochromic (EC) signal, which in the millisecond time scale represents a change in the delocalized electric potential difference across the thylakoid membrane resulting from charge separation in both photosystems. This method was applied to leaf segments, thus avoiding any potential artefacts associated with the isolation of thylakoid membranes. Two variations of this method, suppressing PSII activity by prior photoinactivation (in spinach and poplar leaf segments) or suppressing PSI by photo-oxidation of P700 (the chlorophyll dimer in PSI) with background far-red light (in spinach, poplar and cucumber leaf segments), each gave the separate contribution of each photosystem to the fast EC signal; the PSII/PSI stoichiometry obtained by this method was in the range 1.5-1.9 for the three plant species, and 1.5-1.8 for spinach in particular. A second method, based on electron paramagnetic resonance (EPR), gave values in a comparable range of 1.7-2.1 for spinach. A third method, which consisted of separately determining the content of functional PSII in leaf segments by the oxygen yield per single turnover-flash and that of PSI by photo-oxidation of P700 in thylakoids isolated from the corresponding leaves, gave a PSII/PSI stoichiometry (1.5-1.7) that was consistent with the above values. It is concluded that the ratio of PSII to PSI reaction centres is considerably higher than unity in typical higher plants, in contrast to a surprisingly low PSII/PSI ratio of 0.88, determined by EPR, that was reported for spinach grown in a cabinet under far-red-deficient light in Sweden [Danielsson et al. (2004) Biochim. Biophys. Acta 1608: 53-61]. We suggest that the low PSII/PSI ratio in the Swedish spinach, grown in far

  7. Subunit composition of CP43-less photosystem II complexes of Synechocystis sp. PCC 6803: implications for the assembly and repair of photosystem II.

    Science.gov (United States)

    Boehm, M; Yu, J; Reisinger, V; Beckova, M; Eichacker, L A; Schlodder, E; Komenda, J; Nixon, P J

    2012-12-19

    Photosystem II (PSII) mutants are useful experimental tools to trap potential intermediates involved in the assembly of the oxygen-evolving PSII complex. Here, we focus on the subunit composition of the RC47 assembly complex that accumulates in a psbC null mutant of the cyanobacterium Synechocystis sp. PCC 6803 unable to make the CP43 apopolypeptide. By using native gel electrophoresis, we showed that RC47 is heterogeneous and mainly found as a monomer of 220 kDa. RC47 complexes co-purify with small Cab-like proteins (ScpC and/or ScpD) and with Psb28 and its homologue Psb28-2. Analysis of isolated His-tagged RC47 indicated the presence of D1, D2, the CP47 apopolypeptide, plus nine of the 13 low-molecular-mass (LMM) subunits found in the PSII holoenzyme, including PsbL, PsbM and PsbT, which lie at the interface between the two momomers in the dimeric holoenzyme. Not detected were the LMM subunits (PsbK, PsbZ, Psb30 and PsbJ) located in the vicinity of CP43 in the holoenzyme. The photochemical activity of isolated RC47-His complexes, including the rate of reduction of P680(+), was similar to that of PSII complexes lacking the Mn(4)CaO(5) cluster. The implications of our results for the assembly and repair of PSII in vivo are discussed. PMID:23148271

  8. Microoxic Niches within the Thylakoid Stroma of Air-Grown Chlamydomonas reinhardtii Protect [FeFe]-Hydrogenase and Support Hydrogen Production under Fully Aerobic Environment.

    Science.gov (United States)

    Liran, Oded; Semyatich, Rinat; Milrad, Yuval; Eilenberg, Haviva; Weiner, Iddo; Yacoby, Iftach

    2016-09-01

    Photosynthetic hydrogen production in the microalga Chlamydomonas reinhardtii is catalyzed by two [FeFe]-hydrogenase isoforms, HydA1 and HydA2, both irreversibly inactivated upon a few seconds exposure to atmospheric oxygen. Until recently, it was thought that hydrogenase is not active in air-grown microalgal cells. In contrast, we show that the entire pool of cellular [FeFe]-hydrogenase remains active in air-grown cells due to efficient scavenging of oxygen. Using membrane inlet mass spectrometry, (18)O2 isotope, and various inhibitors, we were able to dissect the various oxygen uptake mechanisms. We found that both chlororespiration, catalyzed by plastid terminal oxidase, and Mehler reactions, catalyzed by photosystem I and Flavodiiron proteins, significantly contribute to oxygen uptake rate. This rate is considerably enhanced with increasing light, thus forming local anaerobic niches at the proximity of the stromal face of the thylakoid membrane. Furthermore, we found that in transition to high light, the hydrogen production rate is significantly enhanced for a short duration (100 s), thus indicating that [FeFe]-hydrogenase functions as an immediate sink for surplus electrons in aerobic as well as in anaerobic environments. In summary, we show that an anaerobic locality in the chloroplast preserves [FeFe]-hydrogenase activity and supports continuous hydrogen production in air-grown microalgal cells. PMID:27443604

  9. The microalga Chlamydomonas reinhardtii CW-15 as a solar cell for hydrogen peroxide photoproduction. Comparison between free and immobilized cells and thylakoids for energy conversion efficiency

    Energy Technology Data Exchange (ETDEWEB)

    Scholz, W.; Galvan, F.; Rosa, F.F. de la [Instituto de Bioquimica Vegetal y Fotosintesis, Universidad de Sevilla y CSIC, Sevilla (Spain)

    1995-11-28

    Immobilized cells and thylakoid vesicles of the microalga Chlamydomonas reinhardtii CW-15 have been developed as a solar cell because of their capabilities of producing hydrogen peroxide. This compound is an efficient and clean fuel used for rocket propulsion, motors and for heating. Hydrogen peroxide is produced by the photosystem in a catalyst cycle in which a redox mediator (methyl viologen) is reduced by electrons obtained from water by the photosynthetic apparatus of the microalga and it is re-oxidized by the oxygen dissolved in the solution. The photoproduction has been investigated using a discontinuous system with whole cells, or thylakoid vesicles, free or immobilized on alginate. The stimulation by azide as an inhibitor of catalase has also been analyzed. Under determined optimum conditions, the photoproduction by Ca-alginate entrapped cells, with a rate of 33 {mu}mol H{sub 2}O{sub 2}/mg Chl.h, was maintained for several hours with an energy conversion efficiency of 0.25%

  10. Effective viscosity of non-gravitactic Chlamydomonas Reinhardtii microswimmer suspensions

    Science.gov (United States)

    Mussler, Matthias; Rafaï, Salima; Peyla, Philippe; Wagner, Christian

    2013-03-01

    Active microswimmers are known to affect the macroscopic viscosity of suspensions in a more complex manner than passive particles. For puller-like microswimmers an increase in the viscosity has been observed. It has been suggested that the persistence of the orientation of the microswimmers hinders the rotation that is normally caused by the vorticity. It was previously shown that some sorts of algae are bottom-heavy swimmers, i.e., their centre of mass is not located in the centre of the body. In this way, the algae affect the vorticity of the flow when they are perpendicularly oriented to the axis of gravity. This orientation of gravity to vorticity is given in a rheometer that is equipped with a cone-plate geometry. Here we present measurements of the viscosity both in a cone-plate and a Taylor-Couette cell. The two set-ups yielded the same increase in viscosity although the axis of gravitation in the Taylor-Couette cell is parallel to the direction of vorticity. In a complementary experiment we tested the orientation of the direction of swimming through microscopic observation of single Chlamydomonas reinhardtii and could not identify a preferred orientation, i.e., our specific strain of Chlamydomonas reinhardtii are not bottom-heavy swimmers. We thus conclude that bottom heaviness is not a prerequisite for the increase of viscosity and that the effect of gravity on the rheology of our strain of Chlamydomonas reinhardtii is negligible. This finding reopens the question of whether the origin of persistence in the orientation of cells is actually responsible for the increased viscosity of the suspension.

  11. Synthesizing and salvaging NAD: lessons learned from Chlamydomonas reinhardtii.

    Directory of Open Access Journals (Sweden)

    Huawen Lin

    2010-09-01

    Full Text Available The essential coenzyme nicotinamide adenine dinucleotide (NAD+ plays important roles in metabolic reactions and cell regulation in all organisms. Bacteria, fungi, plants, and animals use different pathways to synthesize NAD+. Our molecular and genetic data demonstrate that in the unicellular green alga Chlamydomonas NAD+ is synthesized from aspartate (de novo synthesis, as in plants, or nicotinamide, as in mammals (salvage synthesis. The de novo pathway requires five different enzymes: L-aspartate oxidase (ASO, quinolinate synthetase (QS, quinolate phosphoribosyltransferase (QPT, nicotinate/nicotinamide mononucleotide adenylyltransferase (NMNAT, and NAD+ synthetase (NS. Sequence similarity searches, gene isolation and sequencing of mutant loci indicate that mutations in each enzyme result in a nicotinamide-requiring mutant phenotype in the previously isolated nic mutants. We rescued the mutant phenotype by the introduction of BAC DNA (nic2-1 and nic13-1 or plasmids with cloned genes (nic1-1 and nic15-1 into the mutants. NMNAT, which is also in the de novo pathway, and nicotinamide phosphoribosyltransferase (NAMPT constitute the nicotinamide-dependent salvage pathway. A mutation in NAMPT (npt1-1 has no obvious growth defect and is not nicotinamide-dependent. However, double mutant strains with the npt1-1 mutation and any of the nic mutations are inviable. When the de novo pathway is inactive, the salvage pathway is essential to Chlamydomonas for the synthesis of NAD+. A homolog of the human SIRT6-like gene, SRT2, is upregulated in the NS mutant, which shows a longer vegetative life span than wild-type cells. Our results suggest that Chlamydomonas is an excellent model system to study NAD+ metabolism and cell longevity.

  12. Genetic Analysis of Mating Locus Linked Mutations in CHLAMYDOMONAS REINHARDII

    OpenAIRE

    Galloway, R. E.; Goodenough, U. W.

    1985-01-01

    The mating-type (mt) locus of Chlamydomonas reinhardii has been analyzed using four mutant strains (imp-1, imp-10, imp-11 and imp-12). All have been shown, or are shown here, to carry mutations linked to either the plus (mt+) or the minus (mt-) locus, and their behavior in complementation tests has allowed us to define several distinct functions for each locus. Specifically, we propose that the mt+ locus contains the following genes or regulatory elements: a locus designated sfu, which is n...

  13. Flagellar force production during regeneration in Chlamydomonas reinhardtii

    Science.gov (United States)

    Yukich, John N.; Clodfelter, Catherine; Bernd, Karen K.

    2009-11-01

    Several respiratory, digestive, and reproductive disorders originate with motional dysfunction of cilia and flagella. The usefulness of cilia and flagella is understood, but the internal mechanism for creating their breast stroke-like motion is not. This study reports on standardization of calibration, trapping and cell movement recording methods. Our techniques permit us to measure the flagellar swimming force of Chlamydomonas during flagella regeneration. We find that as flagella length increases, the flagellar force is maximized after 50% of full length is achieved except for a significant dip at 75% of full length. These results raise many questions regarding the flagella infrastructure.

  14. Chlamydomonas reinhardtii selenocysteine tRNA[Ser]Sec

    OpenAIRE

    RAO, MAHADEV; CARLSON, Bradley A.; Novoselov, Sergey V.; Weeks, Donald P.; Vadim N Gladyshev; Dolph L Hatfield

    2003-01-01

    Eukaryotic selenocysteine (Sec) protein insertion machinery was thought to be restricted to animals, but the occurrence of both Sec-containing proteins and the Sec insertion system was recently found in Chlamydomonas reinhardtii, a member of the plant kingdom. Herein, we used RT-PCR to determine the sequence of C. reinhardtii Sec tRNA[Ser]Sec, the first non-animal eukaryotic Sec tRNA[Ser]Sec sequence. Like its animal counterpart, it is 90 nucleotides in length, is aminoacylated with serine by...

  15. The vacuum ultraviolet irradiation of green inicellular alga chlamydomonas reinbardtii

    International Nuclear Information System (INIS)

    The action of vacuum ultraviolet (Ar, 120-130 nm) irradiation of green alga Chlamydomonas reinhardtii was investigated. The high frequency discharge in Ar as a source of vacuum ultraviolet radiation was used. The registration of cell destruction by microscopic observation and photography was realized. The dependence of cells survival rate was compared with those by UV-B and UV-C irradiation. It was shown that most efficiency of cell's destruction by vacuum ultraviolet irradiation was realized. This work was carring out according with project proposed for vacuum ultraviolet support. 21 refs., 6 figs.,

  16. Reverse genetics in Chlamydomonas: a platform for isolating insertional mutants

    Directory of Open Access Journals (Sweden)

    de Montaigu Amaury

    2011-07-01

    Full Text Available Abstract A method was developed to identify insertional mutants of Chlamydomonas reinhardtii disrupted for selected target genes. The approach relies on the generation of thousands of transformants followed by PCR-based screenings that allow for identification of strains harboring the introduced marker gene within specific genes of interest. Our results highlight the strengths and limitations of two independent screens that differed in the nature of the marker DNA used (PCR-amplified fragment containing the plasmid-free marker versus entire linearized plasmid with the marker and in the strategies used to maintain and store transformants.

  17. Genome-wide analysis of alternative splicing in Chlamydomonas reinhardtii

    Directory of Open Access Journals (Sweden)

    Thomas Julie

    2010-02-01

    Full Text Available Abstract Background Genome-wide computational analysis of alternative splicing (AS in several flowering plants has revealed that pre-mRNAs from about 30% of genes undergo AS. Chlamydomonas, a simple unicellular green alga, is part of the lineage that includes land plants. However, it diverged from land plants about one billion years ago. Hence, it serves as a good model system to study alternative splicing in early photosynthetic eukaryotes, to obtain insights into the evolution of this process in plants, and to compare splicing in simple unicellular photosynthetic and non-photosynthetic eukaryotes. We performed a global analysis of alternative splicing in Chlamydomonas reinhardtii using its recently completed genome sequence and all available ESTs and cDNAs. Results Our analysis of AS using BLAT and a modified version of the Sircah tool revealed AS of 498 transcriptional units with 611 events, representing about 3% of the total number of genes. As in land plants, intron retention is the most prevalent form of AS. Retained introns and skipped exons tend to be shorter than their counterparts in constitutively spliced genes. The splice site signals in all types of AS events are weaker than those in constitutively spliced genes. Furthermore, in alternatively spliced genes, the prevalent splice form has a stronger splice site signal than the non-prevalent form. Analysis of constitutively spliced introns revealed an over-abundance of motifs with simple repetitive elements in comparison to introns involved in intron retention. In almost all cases, AS results in a truncated ORF, leading to a coding sequence that is around 50% shorter than the prevalent splice form. Using RT-PCR we verified AS of two genes and show that they produce more isoforms than indicated by EST data. All cDNA/EST alignments and splice graphs are provided in a website at http://combi.cs.colostate.edu/as/chlamy. Conclusions The extent of AS in Chlamydomonas that we observed is much

  18. Electron microcopy in structural studies of photosystem I from the red alga Cyanidium caldarium

    Czech Academy of Sciences Publication Activity Database

    Gardian, Zdenko; Bumba, Ladislav; Vácha, František

    Moscow: NIA-Priroda, 2006, s. 180. [International Meeting "Photosynthesis in the Post-Genomic Era: Structure and Function of Photosystems". Pushchino (RU), 20.08.2006-26.08.2006] Institutional research plan: CEZ:AV0Z50510513 Keywords : photosystem I * Cyanidium caldarium Subject RIV: BO - Biophysics

  19. Effects of Chlorophyll Availability on Fluorescence Components of Photosystems in the ORF469-Deletion Mutant of Cyanobacterium

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    PCR-amplified ORF469 fragment from Synechocystis sp.PCC 6803 was cloned into pUC118 and a construct was made in which part of ORF469 was deleted and replaced by erythromycin resistance cassette.Transformation of wild type strain of Synechocystis sp.PCC 6803 with this construct yielded a mutant in which ORF469 was deleted.In the resulting mutant, the light-independent pathway of chlorophyll biosynthesis was inactivated and availability of chlorophyll was fully dependent on light.When propagated the mutant in dark, the chlorophyll was non-detectable and protochlorophyllide with 645 nm fluorescence emission peak was accumulated.Meanwhile, the fluorescence emission peaks (excited at 435 nm) of thylakoids at 685 nm, 695 nm and 725 nm, which represented relative chlorophyll-binding proteins, disappeared.Upon return of dark-grown ORF469 mutant to the light, greening occurred and chlorophyll was synthesized to assembly fluorescence emission components in photosystems.Newly synthesized chlorophyll combined the fluorescence component of 685 nm at first, then 725 nm and 695 nm at last, which indicates a pecking order for biogenesis of chlorophyll-binding proteins when availability of chlorophyll is limited.The mutant lacking ORF469 in Synechocystis sp.PCC 6803 was suggested as an excellent cyanobacterial system for studies on the interactions between chlorophyll and chlorophyll-binding proteins in photosystems.

  20. Posttranslational modifications in the CP43 subunit of photosystem II

    OpenAIRE

    Anderson, Lorraine B.; Maderia, Melissa; Ouellette, Anthony J. A.; Putnam-Evans, Cindy; Higgins, LeeAnn; Krick, Thomas; MacCoss, Michael J; Lim, Hanjo; Yates, John R.; Barry, Bridgette A.

    2002-01-01

    Photosystem II (PSII) catalyzes the light-driven oxidation of water and the reduction of plastoquinone; the oxidation of water occurs at a cluster of four manganese. The PSII CP43 subunit functions in light harvesting, and mutations in the fifth luminal loop (E) of CP43 have established its importance in PSII structure and/or assembly [Kuhn, M. G. & Vermaas, V. F. J. (1993) Plant Mol. Biol. 23, 123–133]. The sequence A350PWLEPLR357 in luminal loop E is conserved in CP43 genes from 50 organism...

  1. Cell response of Chlamydomonas actinochloris culture to repeated microwave irradiation

    Directory of Open Access Journals (Sweden)

    OLESIA O. GRYGORIEVA

    2015-05-01

    Full Text Available Abstract. Grygorieva OO, Berezovsjka MA, Dacenko OI. 2015. Cell response of Chlamydomonas actinochloris culture to repeated microwave irradiation. Nusantara Bioscience 7: 38-42. Two cultures of Chlamydomonas actinochloris Deason et Bold in the lag-phase were exposed to the microwave irradiation. One of them (culture 1 was not treated beforehand, whereas the other (culture 2 was irradiated by microwaves 2 years earlier. The measurement of cell quantity as well as measurement of change of intensities and spectra of cultures photoluminescence (PL in the range of chlorophyll a emission was regularly conducted during the cell cultures development. Cell concentration of culture 1 exposed to the microwave irradiation for the first time has quickly restored while cell concentration of culture 2 which was irradiated repeatedly has fallen significantly. The following increasing of cell concentration of culture 2 is negligible. Cell concentration reaches the steady-state level that is about a half of the cell concentration of control culture. Initially the PL efficiency of cells of both cultures decreases noticeable as a result of irradiation. Then there is the monotonic increase to the values which are significantly higher than the corresponding values in the control cultures. The ratio of the intensities at the maxima of the main emission bands of chlorophyll for control samples of both cultures remained approximately at the same level. At the same time effect of irradiation on the cell PL spectrum appears as a temporary reduction of this magnitude.

  2. Bioenergetics of growth and lipid production in Chlamydomonas reinhardtii

    International Nuclear Information System (INIS)

    The study of thermodynamic aspects of the lipid, e.g., raw material for biodiesel, production in microalgae is important, as the non-lipid producing biological activities of the algal cultivation consume part of the solar energy captured during photosynthesis in expense of the exergetic efficiency of the lipid production process. The cultivation of Chlamydomonas reinhardtii (a unicellular biflagellate fresh-water microalga) is modeled as a three-step chemical mechanism representing growth, respiration, and lipid production. Further, the comprehensive thermodynamic analysis of these mechanisms is presented. The cumulative degree of perfection of the cellular proliferation, after excluding the lipid synthesis, fluctuates with no trend around 0.52 ± 0.19. The exergy analysis has indicated that C. reinhardtii prefers to maximize the lipid production when it is difficult to generate new cells. Under batch production of algal biomass, the highest heat and exergy loss per unit biomass production are accountable under the most favorable biological growth conditions, whereas the highest exergetic efficiency of the lipid production accounted under the least favorable growth conditions, which is in line with the previous studies. - Highlights: • Biomass, lipid production and respiration modeled as three-step chemical reaction. • CDP (cumulative degree of perfection) is calculated based on the model. • The CDP of the algae, after excluding the lipids, is about 0.52 ± 0.19. • Chlamydomonas reinhardtii maximized lipid production when it was difficult to grow

  3. Glucose respiration in the intact chloroplast of Chlamydomonas reinhardtii

    International Nuclear Information System (INIS)

    Chloroplastic respiration was monitored by measuring 14CO2 from 14C glucose in the darkened Chlamydomonas reinhardtii F-60 chloroplast, The patterns of 14CO2 evolution from labeled glucose in the absence and presence of the inhibitors iodoacetamide, glycolate-2-phosphate, and phosphoenolypyruvate were those expected from the oxidative pentose phosphate cycle and glycolysis. The Km for glucose was 56 micromolar and for MgATP was 200 micromolar. Release of 14CO2 was inhibited by phloretin and inorganic phosphate. Comparing the inhibition of CO2 evolution generated by pH 7.5 with respect to pH 8.2 (optimum) in chloroplasts given C-1, C-2, and C-6 labeled glucose indicated that a suboptimum pH affects the recycling of the pentose phosphate intermediates to a greater extent than CO2 evolution from C-1 of glucose. Respiratory inhibition by pH 7.5 in the darkened chloroplast was alleviated by NH4Cl and KCl (stromal alkalating agents), iodoacetamide (an inhibitor of glyceraldehyde 3-phosphate dehydrogenase), or phosphoenolypyruvate (an inhibitor of phosphofructokinase). It is concluded that the site which primarily mediates respiration in the darkened Chlamydomonas chloroplast is the fructose-1,6-bisphosphatase/phosphofructokinase junction. The respiratory pathways described here can account for the total oxidation of a hexose to Co2 and for interactions between carbohydrate metabolism and the oxyhydrogen reaction in algal cells adapted to a hydrogen metabolism

  4. A role for the membrane in regulating Chlamydomonas flagellar length.

    Directory of Open Access Journals (Sweden)

    William Dentler

    Full Text Available Flagellar assembly requires coordination between the assembly of axonemal proteins and the assembly of the flagellar membrane and membrane proteins. Fully grown steady-state Chlamydomonas flagella release flagellar vesicles from their tips and failure to resupply membrane should affect flagellar length. To study vesicle release, plasma and flagellar membrane surface proteins were vectorially pulse-labeled and flagella and vesicles were analyzed for biotinylated proteins. Based on the quantity of biotinylated proteins in purified vesicles, steady-state flagella appeared to shed a minimum of 16% of their surface membrane per hour, equivalent to a complete flagellar membrane being released every 6 hrs or less. Brefeldin-A destroyed Chlamydomonas Golgi, inhibited the secretory pathway, inhibited flagellar regeneration, and induced full-length flagella to disassemble within 6 hrs, consistent with flagellar disassembly being induced by a failure to resupply membrane. In contrast to membrane lipids, a pool of biotinylatable membrane proteins was identified that was sufficient to resupply flagella as they released vesicles for 6 hrs in the absence of protein synthesis and to support one and nearly two regenerations of flagella following amputation. These studies reveal the importance of the secretory pathway to assemble and maintain full-length flagella.

  5. Metabolism of acyl-lipids in Chlamydomonas reinhardtii.

    Science.gov (United States)

    Li-Beisson, Yonghua; Beisson, Fred; Riekhof, Wayne

    2015-05-01

    Microalgae are emerging platforms for production of a suite of compounds targeting several markets, including food, nutraceuticals, green chemicals, and biofuels. Many of these products, such as biodiesel or polyunsaturated fatty acids (PUFAs), derive from lipid metabolism. A general picture of lipid metabolism in microalgae has been deduced from well characterized pathways of fungi and land plants, but recent advances in molecular and genetic analyses of microalgae have uncovered unique features, pointing out the necessity to study lipid metabolism in microalgae themselves. In the past 10 years, in addition to its traditional role as a model for photosynthetic and flagellar motility processes, Chlamydomonas reinhardtii has emerged as a model organism to study lipid metabolism in green microalgae. Here, after summarizing data on total fatty acid composition, distribution of acyl-lipid classes, and major acyl-lipid molecular species found in C. reinhardtii, we review the current knowledge on the known or putative steps for fatty acid synthesis, glycerolipid desaturation and assembly, membrane lipid turnover, and oil remobilization. A list of characterized or putative enzymes for the major steps of acyl-lipid metabolism in C. reinhardtii is included, and subcellular localizations and phenotypes of associated mutants are discussed. Biogenesis and composition of Chlamydomonas lipid droplets and the potential importance of lipolytic processes in increasing cellular oil content are also highlighted. PMID:25660108

  6. Photosystem II Repair and Plant Immunity: Lessons Learned from Arabidopsis Mutant Lacking the THYLAKOID LUMEN PROTEIN 18.3

    OpenAIRE

    Järvi, Sari; Isojärvi, Janne; Kangasjärvi, Säijaliisa; Salojärvi, Jarkko; Mamedov, Fikret; Suorsa, Marjaana; Aro, Eva-Mari

    2016-01-01

    Chloroplasts play an important role in the cellular sensing of abiotic and biotic stress. Signals originating from photosynthetic light reactions, in the form of redox and pH changes, accumulation of reactive oxygen and electrophile species or stromal metabolites are of key importance in chloroplast retrograde signaling. These signals initiate plant acclimation responses to both abiotic and biotic stresses. To reveal the molecular responses activated by rapid fluctuations in growth light inte...

  7. Prospects of using unicellular algae protein in biological life-support systems. [Chlorella, Chlamydomonas, Spirulina, Euglena

    Energy Technology Data Exchange (ETDEWEB)

    Antonyan, A.A.; Abakumova, I.A.; Meleshko, G.I.; Vlasova, T.F.

    The concentration, amino acid composition and biological value of proteins of unicellular algae belonging to various taxonomic groups (Chlorella, Chlamydomonas, Spirulina, Euglena) were investigated. With respect to their characteristics, these algae hold promise as components of biological life-support systems (BLSS). Indices characterizing the protein and biomass quality and biological value were calculated. Such indices as A/E (where A is an essential amino acid and E is the sum total of amino acids), anti-E/T (where anti-E is nitrogen of essential amino acids and T is its sum total), amino acid number, factor of digestibility in vitro were high enough and close to the respective parameters of the reference protein. Animal experiments showed high biological value of the algal biomass and the lack of its toxic or other adverse effects. It is suggested that the differences in the protein composition associated with various algal forms and cultivation conditions can be used to produce balanced diets by varying the portion of each form of the photoautotropic component of BLSS.

  8. Chlamydomonas fla mutants reveal a link between deflagellation and intraflagellar transport

    Directory of Open Access Journals (Sweden)

    Quarmby Lynne

    2003-08-01

    Full Text Available Abstract Background Cilia and flagella are often lost in anticipation of mitosis or in response to stress. There are two ways that a cell can lose its flagella: resorption or deflagellation. Deflagellation involves active severing of the axoneme at the base of the flagellum; this process is defective in Chlamydomonas fa mutants. In contrast, resorption has been thought to occur as a consequence of constitutive disassembly at the tip in the absence of continued assembly, which requires intraflagellar transport (IFT. Chlamydomonas fla mutants are unable to build and maintain flagella due to defects in IFT. Results fla10 cells, which are defective in kinesin-II, the anterograde IFT motor, resorb their flagella at the restrictive temperature (33°C, as previously reported. We find that in standard media containing ~300 microM calcium, fla10 cells lose flagella by deflagellation at 33°C. This temperature-induced deflagellation of a fla mutant is not predicted by the IFT-based model for flagellar length control. Other fla mutants behave similarly, losing their flagella by deflagellation instead of resorption, if adequate calcium is available. These data suggest a new model whereby flagellar resorption involves active disassembly at the base of the flagellum via a mechanism with components in common with the severing machinery of deflagellation. As predicted by this model, we discovered that deflagellation stimuli induce resorption if deflagellation is blocked either by mutation in a FA gene or by lack of calcium. Further support for this model comes from our discovery that fla10-fa double mutants resorb their flagella more slowly than fla10 mutants. Conclusions Deflagellation of the fla10 mutant at the restrictive temperature is indicative of an active disassembly signal, which can manifest as either resorption or deflagellation. We propose that when IFT is halted by either an inactivating mutation or a cellular signal, active flagellar disassembly

  9. Robust expression of a bioactive mammalian protein in chlamydomonas chloroplast

    Science.gov (United States)

    Mayfield, Stephen P.

    2010-03-16

    Methods and compositions are disclosed to engineer chloroplast comprising heterologous mammalian genes via a direct replacement of chloroplast Photosystem II (PSII) reaction center protein coding regions to achieve expression of recombinant protein above 5% of total protein. When algae is used, algal expressed protein is produced predominantly as a soluble protein where the functional activity of the peptide is intact. As the host algae is edible, production of biologics in this organism for oral delivery or proteins/peptides, especially gut active proteins, without purification is disclosed.

  10. Robust expression of a bioactive mammalian protein in Chlamydomonas chloroplast

    Energy Technology Data Exchange (ETDEWEB)

    Mayfield, Stephen P

    2015-01-13

    Methods and compositions are disclosed to engineer chloroplast comprising heterologous mammalian genes via a direct replacement of chloroplast Photosystem II (PSII) reaction center protein coding regions to achieve expression of recombinant protein above 5% of total protein. When algae is used, algal expressed protein is produced predominantly as a soluble protein where the functional activity of the peptide is intact. As the host algae is edible, production of biologics in this organism for oral delivery of proteins/peptides, especially gut active proteins, without purification is disclosed.

  11. Evidences of oxidative stress during hydrogen photoproduction in sulfur-deprived cultures of Chlamydomonas reinhardtii

    Czech Academy of Sciences Publication Activity Database

    Sáens, M. E.; Bišová, Kateřina; Touloupakis, E.; Faraloni, C.; Dario Di Marzio, W.; Torzillo, G.

    2015-01-01

    Roč. 40, č. 30 (2015), s. 10410-10417. ISSN 0360-3199 Institutional support: RVO:61388971 Keywords : Oxidative stress * Chlamydomonas reinhardtii * H-2 production Subject RIV: EE - Microbiology, Virology Impact factor: 3.313, year: 2014

  12. The Chlamydomonas genome reveals the evolution of key animal and plant functions

    Czech Academy of Sciences Publication Activity Database

    Merchant, S.S.; Prochnik, S. E.; Bišová, Kateřina

    2007-01-01

    Roč. 318, - (2007), s. 245-251. ISSN 0036-8075 Institutional research plan: CEZ:AV0Z50200510 Keywords : chlamydomonas reinhardtii * alga * eukaryotic cell Subject RIV: EE - Microbiology, Virology Impact factor: 26.372, year: 2007

  13. Structure and energy transfer in photosystems of oxygenic photosynthesis.

    Science.gov (United States)

    Nelson, Nathan; Junge, Wolfgang

    2015-01-01

    Oxygenic photosynthesis is the principal converter of sunlight into chemical energy on Earth. Cyanobacteria and plants provide the oxygen, food, fuel, fibers, and platform chemicals for life on Earth. The conversion of solar energy into chemical energy is catalyzed by two multisubunit membrane protein complexes, photosystem I (PSI) and photosystem II (PSII). Light is absorbed by the pigment cofactors, and excitation energy is transferred among the antennae pigments and converted into chemical energy at very high efficiency. Oxygenic photosynthesis has existed for more than three billion years, during which its molecular machinery was perfected to minimize wasteful reactions. Light excitation transfer and singlet trapping won over fluorescence, radiation-less decay, and triplet formation. Photosynthetic reaction centers operate in organisms ranging from bacteria to higher plants. They are all evolutionarily linked. The crystal structure determination of photosynthetic protein complexes sheds light on the various partial reactions and explains how they are protected against wasteful pathways and why their function is robust. This review discusses the efficiency of photosynthetic solar energy conversion. PMID:25747397

  14. Switchable photosystem-II designer algae for photobiological hydrogen production

    Science.gov (United States)

    Lee, James Weifu

    2010-01-05

    A switchable photosystem-II designer algae for photobiological hydrogen production. The designer transgenic algae includes at least two transgenes for enhanced photobiological H.sub.2 production wherein a first transgene serves as a genetic switch that can controls photosystem II (PSII) oxygen evolution and a second transgene encodes for creation of free proton channels in the algal photosynthetic membrane. In one embodiment, the algae includes a DNA construct having polymerase chain reaction forward primer (302), a inducible promoter (304), a PSII-iRNA sequence (306), a terminator (308), and a PCR reverse primer (310). In other embodiments, the PSII-iRNA sequence (306) is replaced with a CF.sub.1-iRNA sequence (312), a streptomycin-production gene (314), a targeting sequence (316) followed by a proton-channel producing gene (318), or a PSII-producing gene (320). In one embodiment, a photo-bioreactor and gas-product separation and utilization system produce photobiological H.sub.2 from the switchable PSII designer alga.

  15. Is the cell division cycle gated by a circadian clock? The case of Chlamydomonas reinhardtii

    OpenAIRE

    1995-01-01

    Circadian oscillators are known to regulate the timing of cell division in many organisms. In the case of Chlamydomonas reinhardtii, however, this conclusion has been challenged by several investigators. We have reexamined this issue and find that the division behavior of Chlamydomonas meets all the criteria for circadian rhythmicity: persistence of a cell division rhythm (a) with a period of approximately 24 h under free-running conditions, (b) that is temperature compensated, and (c) which ...

  16. The Chlamydomonas Genome Reveals the Evolution of Key Animal and Plant Functions

    OpenAIRE

    Merchant, Sabeeha S; Prochnik, Simon E; Vallon, Olivier; Harris, Elizabeth H.; Karpowicz, Steven J.; Witman, George B.; Terry, Astrid; Salamov, Asaf; Fritz-Laylin, Lillian K.; Maréchal-Drouard, Laurence; Marshall, Wallace F.; Qu, Liang-Hu; Nelson, David R.; Sanderfoot, Anton A.; Spalding, Martin H

    2007-01-01

    Chlamydomonas reinhardtii is a unicellular green alga whose lineage diverged from land plants over 1 billion years ago. It is a model system for studying chloroplast-based photosynthesis, as well as the structure, assembly, and function of eukaryotic flagella (cilia), which were inherited from the common ancestor of plants and animals, but lost in land plants. We sequenced the ∼120-megabase nuclear genome of Chlamydomonas and performed comparative phylogenomic analyses, identifying genes enco...

  17. Distinct Mechanisms Regulating Gene Expression Coexist within the Fermentative Pathways in Chlamydomonas reinhardtii

    OpenAIRE

    Larisa Angela Swirsky Whitney; Giacomo Novi; Pierdomenico Perata; Elena Loreti

    2012-01-01

    Under dark anoxia, the unicellular green algae Chlamydomonas reinhardtii may produce hydrogen by means of its hydrogenase enzymes, in particular HYD1, using reductants derived from the degradation of intercellular carbon stores. Other enzymes belonging to the fermentative pathways compete for the same reductants. A complete understanding of the mechanisms determining the activation of one pathway rather than another will help us engineer Chlamydomonas for fermentative metabolite production, ...

  18. Azolla filiculoides Nitrogenase Activity Decrease Induced by Inoculation with Chlamydomonas sp. †

    OpenAIRE

    Habte, Mitiku

    1986-01-01

    Experiments were conducted to determine the influence of Chlamydomonas sp. on nitrogen fixation (C2H2 → C2H4) in Azolla filiculoides and on the nitrogen fixation and growth of free-living Anabaena azollae 2B organisms. Inoculation of azolla medium with Chlamydomonas sp. was associated with decreased nitrogenase activity in A. filiculoides and with increases in the density of a fungal population identified as Acremonium sp. Subsequent inoculation of azolla medium with this fungus was also acco...

  19. Development of a forward genetic screen to isolate oil mutants in the green microalga Chlamydomonas reinhardtii

    OpenAIRE

    Cagnon, Caroline; Mirabella, Boris; Nguyen, Hoa Mai; Beyly-Adriano, Audrey; Bouvet, Séverine; Cuiné, Stéphan; Beisson, Fred; Peltier, Gilles; Li-Beisson, Yonghua

    2013-01-01

    Background Oils produced by microalgae are precursors to biodiesel. To achieve a profitable production of biodiesel from microalgae, identification of factors governing oil synthesis and turnover is desirable. The green microalga Chlamydomonas reinhardtii is amenable to genetic analyses and has recently emerged as a model to study oil metabolism. However, a detailed method to isolate various types of oil mutants that is adapted to Chlamydomonas has not been reported. Results We describe here ...

  20. Chloroplast lipid transfer processes in Chlamydomonas reinhardtii involving a TRIGALACTOSYLDIACYLGLYCEROL 2 (TGD2) orthologue.

    Science.gov (United States)

    Warakanont, Jaruswan; Tsai, Chia-Hong; Michel, Elena J S; Murphy, George R; Hsueh, Peter Y; Roston, Rebecca L; Sears, Barbara B; Benning, Christoph

    2015-12-01

    In plants, lipids of the photosynthetic membrane are synthesized by parallel pathways associated with the endoplasmic reticulum (ER) and the chloroplast envelope membranes. Lipids derived from the two pathways are distinguished by their acyl-constituents. Following this plant paradigm, the prevalent acyl composition of chloroplast lipids suggests that Chlamydomonas reinhardtii (Chlamydomonas) does not use the ER pathway; however, the Chlamydomonas genome encodes presumed plant orthologues of a chloroplast lipid transporter consisting of TGD (TRIGALACTOSYLDIACYLGLYCEROL) proteins that are required for ER-to-chloroplast lipid trafficking in plants. To resolve this conundrum, we identified a mutant of Chlamydomonas deleted in the TGD2 gene and characterized the respective protein, CrTGD2. Notably, the viability of the mutant was reduced, showing the importance of CrTGD2. Galactoglycerolipid metabolism was altered in the tgd2 mutant with monogalactosyldiacylglycerol (MGDG) synthase activity being strongly stimulated. We hypothesize this to be a result of phosphatidic acid accumulation in the chloroplast outer envelope membrane, the location of MGDG synthase in Chlamydomonas. Concomitantly, increased conversion of MGDG into triacylglycerol (TAG) was observed. This TAG accumulated in lipid droplets in the tgd2 mutant under normal growth conditions. Labeling kinetics indicate that Chlamydomonas can import lipid precursors from the ER, a process that is impaired in the tgd2 mutant. PMID:26496373

  1. Biofiksasi CO2 Oleh Mikroalga Chlamydomonas sp dalam Photobioreaktor Tubular

    Directory of Open Access Journals (Sweden)

    Hadiyanto Hadiyanto

    2014-05-01

    Full Text Available Mikroalga memiliki potensi dalam membiofiksasi CO2 dan dapat dimanfaatkan untuk mengurangi kadar CO2 dalam gas pencemar. Pertumbuhan mikroalga sangat dipengaruhi oleh konsentrasi gas CO2 di dalam gas pencemar. Tujuan penelitian ini adalah untuk mengeetahui kemampuan mikroalga Chlamydomonas sp yang dikultivasi dalam photobioreaktor tubular dalam penyerapan gas CO2 serta untuk mengetahui konsentrasi maksimum gas CO2 dalam umpan untuk memproduksi biomasa mikroalga yang optimal. Percobaan dilakukan dnegan memvariasi laju alir dari 0.03 -0.071 L/menit dan konsentrasi CO2 dalam umpan 10-30%. Hasil penelitian menunjukkan bahwa biomasa mikroalga dapat diproduksi dengan maksimal dengan konsentrasi gas CO2 20% dengan laju alir 0.07 L/min. Semakin tinggi laju alir maka produksi biomasa alga semakin besar. Kecepatan pertumbuhan alga maksimum terjadi pada 0.31 /hari. Pada konsentrasi gas CO2 30%, terjadi substrate inhibition yang disebabkan carbon dalam bentuk ion bicarbonate tidak dapat dikonsumsi lagi di dalam kultur alga. Kata kunci : Mikroalga, chlamydomonas sp, biofiksasi CO2, biogas Abstract Microalgae have a potential for CO2 biofixation and therefore can be used to reduce the CO2 concentration in the gas pollutants. Moreover, microalgae growth is strongly affected by the concentration of CO2 in the exhaust gas pollutants. The objective of this research was to investigate the ability of microalgae Chlamydomonas sp which was cultivated in a tubular photobioreactor for CO2 absorption as well as to determine the maximum concentration of CO2 in the feed gas to obtain optimum microalgae biomass. The experiments were performed by varying the gas flow rate of 0.03 -0.071 L / min and the concentration of CO2 in the feed of 10-30%. The results showed that the maximum biomass of microalgae can be produced with CO2 concentration of 20% vol with a flow rate of 0.07 L / min. The result also showed that increasing the gas flow rate, the greater of the production of

  2. When Lack of Evidence Is Evidence of Lack.

    Science.gov (United States)

    Pickering, Neil

    2015-12-01

    In their recent article "A Gentle Ethical Defence of Homeopathy," Levy, Gadd, Kerridge, and Komesaroff use the claim that "lack of evidence is not equivalent to evidence of lack" as a component of their ethical defence of homeopathy. In response, this article argues that they cannot use this claim to shore up their ethical arguments. This is because it is false. PMID:26631232

  3. Effect of mutagen combined action on Chlamydomonas reinhardtii cells. II

    International Nuclear Information System (INIS)

    The effect of UV radiation and UV radiation combined with alkylnitrosourea derivatives (N-methyl-N-nitrosourea and N-ethyl-N-nitrosourea) was observed on survival of cells of the algae Chlamydomonas reinhardtii. In particular, single parts were evaluated of the overall lethal effect - dying of cells before division and dying of cells after division. It was found that the combined action of low doses of UV radiation and alkylnitrosoureas result in a pronounced protective effect which manifests itself by a higher frequency of surviving cells than was that effected by the action of alkylnitrosoureas alone. As a result of combined action with higher doses of UV radiation this effect is lost, and the resultant values will come close to the theoretically anticipated values. This gradual transition from a protective to an additive effect mainly manifests itself by changes in the proportion of cells dying before division. (author)

  4. Effect of mutagen combined action on Chlamydomonas Reinhardtii cells. I

    International Nuclear Information System (INIS)

    The effect was investigated of single and combined actions of alkylnitrosourea derivatives (N-methyl-N-nitrosourea and N-ethyl-N-nitrosourea) and UV-radiation on the survival of cells of Chlamydomonas reinhardtii algae in dependence on the sequence of application of mutagens and on the given conditions of cultivation following mutagen activity. In particular, the single phases were investigated of the total lethal effect, i.e., the death of cells before division and their death after division. The most pronounced changes in dependence on the sequence of application of mutagens and on the given conditions of cultivation were noted in cell death before division. In dependence on the sequence of application of mutagens, the effect of the combined action on the survival of cells changed from an additive (alkylnitrosourea + UV-radiation) to a protective effect (UV-radiation + alkylnitrosourea). (author)

  5. Antiphase Synchronization in a Flagellar-Dominance Mutant of Chlamydomonas

    Science.gov (United States)

    Leptos, Kyriacos C.; Wan, Kirsty Y.; Polin, Marco; Tuval, Idan; Pesci, Adriana I.; Goldstein, Raymond E.

    2013-10-01

    Groups of beating flagella or cilia often synchronize so that neighboring filaments have identical frequencies and phases. A prime example is provided by the unicellular biflagellate Chlamydomonas reinhardtii, which typically displays synchronous in-phase beating in a low-Reynolds number version of breaststroke swimming. We report the discovery that ptx1, a flagellar-dominance mutant of C. reinhardtii, can exhibit synchronization in precise antiphase, as in the freestyle swimming stroke. High-speed imaging shows that ptx1 flagella switch stochastically between in-phase and antiphase states, and that the latter has a distinct waveform and significantly higher frequency, both of which are strikingly similar to those found during phase slips that stochastically interrupt in-phase beating of the wild-type. Possible mechanisms underlying these observations are discussed.

  6. Antiphase Synchronization in a Flagellar-Dominance Mutant of Chlamydomonas

    CERN Document Server

    Leptos, Kyriacos C; Polin, Marco; Tuval, Idan; Pesci, Adriana I; Goldstein, Raymond E

    2013-01-01

    Groups of beating flagella or cilia often synchronize so that neighboring filaments have identical frequencies and phases. A prime example is provided by the unicellular biflagellate Chlamydomonas reinhardtii, which typically displays synchronous in-phase beating in a low-Reynolds number version of breaststroke swimming. We report here the discovery that ptx1, a flagellar dominance mutant of C. reinhardtii, can exhibit synchronization in precise antiphase, as in the freestyle swimming stroke. Long-duration high-speed imaging shows that ptx1 flagella switch stochastically between in-phase and antiphase states, and that the latter has a distinct waveform and significantly higher frequency, both of which are strikingly similar to those found during phase slips that stochastically interrupt in-phase beating of the wildtype. Possible mechanisms underlying these observations are discussed.

  7. Cilia and ciliopathies:From Chlamydomonas and beyond

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The biological function of motile cilia/flagella has long been recognized. The non-motile primary cilium, once regarded as a vestigial organelle, however, has been found recently to play unexpected roles in mammalian physiology and development. Defects in cilia have profound impact on human health. Diseases related to cilia, collectively called ciliopathies include male infertility, primary cilia dyskinesia, renal cyst formation, blindness, polydactyly, obesity, hypertension, and even mental retardation. Our current understanding of cilia and ciliopathies has been fueled by basic research employing various model organisms including Chlamydomonas, a unicellular green alga. This review article provides a general introduction to the cell biology of cilia and an overview of various cilia-related diseases.

  8. Effect of selenate on growth and photosynthesis of Chlamydomonas reinhardtii

    International Nuclear Information System (INIS)

    Algal communities play a crucial role in aquatic food webs by facilitating the transfer of dissolved inorganic selenium (both an essential trace element and a toxic compound for a wide variety of organisms) to higher trophic levels. The dominant inorganic chemical species of selenium in freshwaters are selenite (SeO32-) and selenate (SeO42-). At environmental concentrations, selenite is not likely to have direct toxic effects on phytoplankton growth [Morlon, H., Fortin, C., Floriani, M., Adam, C., Garnier-Laplace, J., Boudou, A., 2005a. Toxicity of selenite in the unicellular green alga Chlamydomonas reinharditii: comparison between effects at the population and sub-cellular level. Aquat. Toxicol. 73(1), 65-78]. The effects of selenate, on the other hand, are poorly documented. We studied the effects of selenate on Chlamydomonas reinhardtii growth (a common parameter in phytotoxicity tests). Growth inhibition (96-h IC50) was observed at 4.5 ± 0.2 μM selenate (p < 0.001), an effective concentration which is low compared to environmental concentrations. Growth inhibition at high selenium concentrations may result from impaired photosynthesis. This is why we also studied the effects of selenate on the photosynthetic process (not previously assessed in this species to our knowledge) as well as selenate's effects on cell ultrastructure. The observed ultrastructural damage (chloroplast alterations, loss of appressed domains) confirmed that chloroplasts are important targets in the mechanism of selenium toxicity. Furthermore, the inhibition of photosynthetic electron transport evaluated by chlorophyll fluorescence induction confirmed this hypothesis and demonstrated that selenate disrupts the photosynthetic electron chain. Compared to the classical 'growth inhibition' parameter used in phytotoxicity tests, cell diameter and operational photosynthetic yield were more sensitive and may be convenient tools for selenate toxicity assessment in non-target plants

  9. 紫外诱变筛选耐氧性Chlamydomonas moewusii产氢藻株%Screening of Oxygen-Tolerance Phenotypes in Hydrogen-Producing Strains of Chlamydomonas moewusii with Ultraviolet Radiation

    Institute of Scientific and Technical Information of China (English)

    张彦婷; 范晓蕾; 李潇萍; 郭荣波

    2011-01-01

    In order to reduce the sensitivity of hydrogenases in green algae to 02, four mutants of Chlamydomonas moewusii trains with improved oxygen-tolerance and hydrogen-evolving activities, namely Mu-l, Mu-2, Mu-3 and Mu-4, were generated via ultraviolet mutagenesis and were screened following an exposure to metronidazole and applied oxygen. Then, the screened strains were characterized by the hydrogenases activity in vivo, the respiration activity and the photosystem Ⅱ activity of algal cells. The results show that the hydrogenase activities in vivo of the four mutants are respectively 1.69, 2. 86, 1.06 and 1.80 times that of the wild type, that the residual activities of the mutants after a treatment with 1% O2 ( volume fraction) increase respectively from the original ( 20. 00 ± 2. 47)% to (34. 40 ±.4. 88)%, (32. 50 +2. 85)%, (55.60 +3.30)% and (43. 10 +8. 73)%, and that, there are no obvious differences in photosynthesis and respiration during the growth of Mu-l, Mu-2 and the wild type.%为解决绿藻中氢化酶对O2极为敏感的问题,以具高产氢催化活性的绿藻Chlamydomonas moewusii野生株作为出发藻株,通过紫外辐射,结合甲硝唑及外加氧法进行耐氧性产氢突变株的诱变和筛选,得到4株耐氧性及产氢活性均显著提高的突变藻株Mu-1、Mu-2、Mu-3、Mu-4,并进行了相应的氢化酶体内活性、呼吸活性与光系统Ⅱ光化学活性分析.结果表明,4株突变藻株的氢化酶体内活性约为野生株氢化酶体内活性的1.69、2.86、1.06和1.80倍,突变株经1%(体积分数)O2处理后,残留活性分别从野生株的(20.00±2.47)%提高到(34.40±4.88)%、(32.50±2.85)%、(55.60±3.30)%和(43.10±8.73)%,而Mu-1和Mu-2两株藻在生长过程中的的光合作用与呼吸作用均未发现明显变化.

  10. Inactivation of the clpC1 gene encoding a chloroplast Hsp100 molecular chaperone causes growth retardation, leaf chlorosis, lower photosynthetic activity, and a specific reduction in photosystem content.

    Science.gov (United States)

    Sjögren, Lars L E; MacDonald, Tara M; Sutinen, Sirkka; Clarke, Adrian K

    2004-12-01

    ClpC is a molecular chaperone of the Hsp100 family. In higher plants there are two chloroplast-localized paralogs (ClpC1 and ClpC2) that are approximately 93% similar in primary sequence. In this study, we have characterized two independent Arabidopsis (Arabidopsis thaliana) clpC1 T-DNA insertion mutants lacking on average 65% of total ClpC content. Both mutants display a retarded-growth phenotype, leaves with a homogenous chlorotic appearance throughout all developmental stages, and more perpendicular secondary influorescences. Photosynthetic performance was also impaired in both knockout lines, with relatively fewer photosystem I and photosystem II complexes, but no changes in ATPase and Rubisco content. However, despite the specific drop in photosystem I and photosystem II content, no changes in leaf cell anatomy or chloroplast ultrastructure were observed in the mutants compared to the wild type. Previously proposed functions for envelope-associated ClpC in chloroplast protein import and degradation of mistargeted precursors were examined and shown not to be significantly impaired in the clpC1 mutants. In the stroma, where the majority of ClpC protein is localized, marked increases of all ClpP paralogs were observed in the clpC1 mutants but less variation for the ClpR paralogs and a corresponding decrease in the other chloroplast-localized Hsp100 protein, ClpD. Increased amounts of other stromal molecular chaperones (Cpn60, Hsp70, and Hsp90) and several RNA-binding proteins were also observed. Our data suggest that overall ClpC as a stromal molecular chaperone plays a vital role in chloroplast function and leaf development and is likely involved in photosystem biogenesis. PMID:15563614

  11. Robustness and Optimality of Light Harvesting in Cyanobacterial Photosystem I

    CERN Document Server

    Sener, M K; Ritz, T; Park, S; Fromme, P; Schulten, K; Sener, Melih K.; Lu, Deyu; Ritz, Thorsten; Park, Sanghyun; Fromme, Petra; Schulten, Klaus

    2002-01-01

    As most biological species, photosynthetic lifeforms have evolved to function optimally, despite thermal disorder and with fault tolerance. It remains a challenge to understand how this is achieved. To address this challenge the function of the protein-pigment complex photosystem I (PSI) of the cyanobacterium Synechococcus elongatus is investigated theoretically. The recently obtained high resolution structure of this complex exhibits an aggregate of 96 chlorophylls that are electronically coupled to function as a light-harvesting antenna complex. This paper constructs an effective Hamiltonian for the chlorophyll aggregate to describe excitation transfer dynamics and spectral properties of PSI. For this purpose, a new kinetic expansion method, the sojourn expansion, is introduced. Our study shows that at room temperature fluctuations of site energies have little effect on the calculated excitation lifetime and quantum yield, which compare favorably with experimental results. The efficiency of the system is fo...

  12. Mechanisms of light harvesting by photosystem II in plants

    CERN Document Server

    Amarnath, Kapil; Schneider, Anna R; Fleming, Graham R

    2015-01-01

    Light harvesting by photosystem II (PSII) in plants is highly efficient and acclimates to rapid changes in the intensity of sunlight. However, the mechanisms of PSII light harvesting have remained experimentally inaccessible. Using a structure-based model of excitation energy flow in 200 nanometer (nm) x 200 nm patches of the grana membrane, where PSII is located, we accurately simulated chlorophyll fluorescence decay data with no free parameters. Excitation movement through the light harvesting antenna is diffusive, but becomes subdiffusive in the presence of charge separation at reaction centers. The influence of membrane morphology on light harvesting efficiency is determined by the excitation diffusion length of 50 nm in the antenna. Our model provides the basis for understanding how nonphotochemical quenching mechanisms affect PSII light harvesting in grana membranes.

  13. Polarization-dependent single-molecule spectroscopy on photosystem I

    Science.gov (United States)

    Skandary, S.; Konrad, A.; Hussels, M.; Meixner, A. J.; Brecht, M.

    2015-08-01

    Single-molecule spectroscopy (SMS) at low temperature was used to study the spectral properties, heterogeneities and spectral dynamics of the chlorophyll a (Chl a) molecules responsible for the fluorescence emission of photosystem I (PS I). The fluorescence spectra of single PS I complexes are dominated by several red-shifted Chl a molecules categorized into red pools called C708 and C719. By polarization dependent measurements we demonstrate spectrally separate emissions corresponding to C708 and C719 in single PS I monomers and trimers. Moreover, we compared the results of SMS polarization dependent between monomeric and trimeric PS I complexes and give an estimation for the orientation between these red pools. As a consequence, we get new insight into the energy transfer towards and between the red Chl a molecules in PS I complexes.

  14. Phytotoxicity of four photosystem II herbicides to tropical seagrasses.

    Directory of Open Access Journals (Sweden)

    Florita Flores

    Full Text Available Coastal waters of the Great Barrier Reef (GBR are contaminated with agricultural pesticides, including the photosystem II (PSII herbicides which are the most frequently detected at the highest concentrations. Designed to control weeds, these herbicides are equally potent towards non-target marine species, and the close proximity of seagrass meadows to flood plumes has raised concerns that seagrasses may be the species most threatened by herbicides from runoff. While previous work has identified effects of PSII herbicides on the photophysiology, growth and mortality in seagrass, there is little comparative quantitative toxicity data for seagrass. Here we applied standard ecotoxicology protocols to quantify the concentrations of four priority PSII herbicides that inhibit photochemistry by 10, 20 and 50% (IC10, IC20 and IC50 over 72 h in two common seagrass species from the GBR lagoon. The photosystems of seagrasses Zosteramuelleri and Haloduleuninervis were shown to be generally more sensitive to the PSII herbicides Diuron, Atrazine, Hexazinone and Tebuthiuron than corals and tropical microalgae. The herbicides caused rapid inhibition of effective quantum yield (∆F/F m ', indicating reduced photosynthesis and maximum effective yields (Fv/Fm corresponding to chronic damage to PSII. The PSII herbicide concentrations which affected photosynthesis have been exceeded in the GBR lagoon and all of the herbicides inhibited photosynthesis at concentrations lower than current marine park guidelines. There is a strong likelihood that the impacts of light limitation from flood plumes and reduced photosynthesis from PSII herbicides exported in the same waters would combine to affect seagrass productivity. Given that PSII herbicides have been demonstrated to affect seagrass at environmental concentrations, we suggest that revision of environmental guidelines and further efforts to reduce PSII herbicide concentrations in floodwaters may both help protect

  15. The cry-DASH cryptochrome encoded by the sll1629 gene in the cyanobacterium Synechocystis PCC 6803 is required for Photosystem II repair.

    Science.gov (United States)

    Vass, István-Zoltán; Kós, Péter B; Knoppová, Jana; Komenda, Josef; Vass, Imre

    2014-01-01

    The role of the Syn-CRY cryptochrome from the cyanobacterium Synechocystis sp. PCC 6803 has been a subject of research for more than a decade. Recently we have shown that photolyase, showing strong homology with Syn-CRY is required for Photosystem II repair by preventing accumulation of DNA lesions under UV-B (Vass et al. 2013). Here we investigated if Syn-CRY is also involved in PSII repair, either via removal of DNA lesions or other mechanism? The Δsll1629 mutant lacking Syn-CRY lost faster the PSII activity and D1 protein during UV-B or PAR than the WT. However, no detectable damages in the genomic DNA were observed. The transcript levels of the UV-B and light stress indicator gene psbA3, encoding D1, are comparable in the two strains showing that Δsll1629 cells are not defective at the transcriptional level. Nevertheless 2D protein analysis in combination with mass spectrometry showed a decreased accumulation of several, mostly cytoplasmic, proteins including PilA1 and bicarbonate transporter SbtA. Δsll1629 cells exposed to high light also showed a limitation in de novo assembly of PSII. It is concluded that Syn-CRY is required for efficient restoration of Photosystem II activity following UV-B and PAR induced photodamage. This effect is not caused by retardation of DNA repair, instead the synthesis of new D1 (and D2) subunit(s) and/or the assembly of the Photosystem II reaction center complex is likely affected due to the lack of intracellular CO2, or via a so far unidentified pathway that possibly includes the PilA1 protein. PMID:24389045

  16. Keeping the green world alive. The repair cycle of Photosystem II

    Czech Academy of Sciences Publication Activity Database

    Komenda, Josef; Michoux, F.; Nixon, P. J.

    Boca Raton: CRC Press; Taylor and Francis Group, 2012 - (Amendola, V.; Meneghetti, M.), s. 3-22 ISBN 978-1-4398-5473-0 Institutional support: RVO:61388971 Keywords : Photosystem II * alga * plant Subject RIV: EE - Microbiology, Virology

  17. Assembly of photo-bioelectrochemical cells using photosystem I-functionalized electrodes

    Science.gov (United States)

    Efrati, Ariel; Lu, Chun-Hua; Michaeli, Dorit; Nechushtai, Rachel; Alsaoub, Sabine; Schuhmann, Wolfgang; Willner, Itamar

    2016-02-01

    The design of photo-bioelectrochemical cells based on native photosynthetic reaction centres is attracting substantial recent interest as a means for the conversion of solar light energy into electrical power. In the natural photosynthetic apparatus, the photosynthetic reaction centres are coupled to biocatalytic transformations leading to CO2 fixation and O2 evolution. Although significant progress in the integration of native photosystems with electrodes for light-to-electrical energy conversion has been achieved, the conjugation of the photosystems to enzymes to yield photo-bioelectrocatalytic solar cells remains a challenge. Here we demonstrate the assembly of integrated photosystem I/glucose oxidase or glucose dehydrogenase photo-bioelectrochemical electrodes. We highlight the photonic wiring of the biocatalysts by means of photosystem I using glucose as fuel. Our results provide a general approach to assemble photo-bioelectrochemical solar cells with wide implications for solar energy conversion, bioelectrocatalysis and sensing.

  18. Composition and structure of photosystem I in the moss Physcomitrella patens

    DEFF Research Database (Denmark)

    Busch, Andreas; Petersen, Jørgen; Webber-Birungi, Miriam T.; Powikrowska, Marta; Lassen, Lærke Marie Münter; Naumann-Busch, Bianca; Nielsen, Agnieszka Janina Zygadlo; Ye, Juanying; Boekema, Egbert J.; Jensen, Ole Nørregaard; Lunde, Christina; Jensen, Poul Erik

    2013-01-01

    intact photosystem I (PSI) with its associated light-harvesting complex (LHCI) from the moss Physcomitrella patens and characterized its structure, polypeptide composition, and light-harvesting function using electron microscopy, mass spectrometry, biochemical, and physiological methods. It became...

  19. Reversible room temperature photooxidation of the peripheral chlorophyll of Photosystem II reaction centre

    Czech Academy of Sciences Publication Activity Database

    Litvín, R.; Bína, D.; Vácha, František

    Brno: Masaryk University Brno, 2005. s. 29. [Central-European Conference "Photosynthesis and Stress". 05.09.15-05.09.16, Brno] Institutional research plan: CEZ:AV0Z50510513 Keywords : Photosystem II Subject RIV: CE - Biochemistry

  20. Electron microcopy in structural studies of photosystem I from the red alga Cyanidium caldarium

    Czech Academy of Sciences Publication Activity Database

    Gardian, Zdenko; Bumba, Ladislav; Vácha, František

    Pau: Pau University, 2006, s. 189. [12th International Symposium on Phototrophic Prokaryotes. Pau (FR), 27.08.2006-01.09.2006] Institutional research plan: CEZ:AV0Z50510513 Keywords : photosystem I Subject RIV: BO - Biophysics

  1. Excited state dynamics in photosystem I: effects of detergent and excitation wavelength.

    OpenAIRE

    Hastings, G; Reed, L J; S. Lin; Blankenship, R. E.

    1995-01-01

    Femtosecond transient absorption spectroscopy has been used to investigate the energy transfer and trapping processes in both intact membranes and purified detergent-isolated particles from a photosystem II deletion mutant of the cyanobacterium Synechocystis sp. PCC 6803, which contains only the photosystem I reaction center. Processes with similar lifetimes and spectra are observed in both the membrane fragments and the detergent-isolated particles, suggesting little disruption of the core a...

  2. Photosystem 0, a proposed ancestral photosystem without reducing power that synthesizes ATP during light-dark cycling

    CERN Document Server

    Muller, A W J

    2005-01-01

    Photosystem 0 is a proposed membrane-based mechanism for free energy gain as ATP from fluctuating light. The PS0 reaction centers have no reducing power: charge transport is only temporary. Light induces within the reaction centers metastable dipoles that generate a membrane potential that drives ATP synthesis while protons move through the ATPsynthase enzyme. After the decay of the dipole potential in the dark, the protons either (1) return across the membrane by conduction or (2) are pumped back by ATPsynthase, backwards active as ATPase at a higher H+/ATP ratio. PS0 constitutes a link to previously proposed free energy sources for early evolution that work on thermal cycling. Several contemporary photosynthetic phenomena may be relics of PS0.

  3. Plastidial Expression of Type II NAD(P)H Dehydrogenase Increases the Reducing State of Plastoquinones and Hydrogen Photoproduction Rate by the Indirect Pathway in Chlamydomonas reinhardtii1[W][OPEN

    Science.gov (United States)

    Baltz, Anthony; Dang, Kieu-Van; Beyly, Audrey; Auroy, Pascaline; Richaud, Pierre; Cournac, Laurent; Peltier, Gilles

    2014-01-01

    Biological conversion of solar energy into hydrogen is naturally realized by some microalgae species due to a coupling between the photosynthetic electron transport chain and a plastidial hydrogenase. While promising for the production of clean and sustainable hydrogen, this process requires improvement to be economically viable. Two pathways, called direct and indirect photoproduction, lead to sustained hydrogen production in sulfur-deprived Chlamydomonas reinhardtii cultures. The indirect pathway allows an efficient time-based separation of O2 and H2 production, thus overcoming the O2 sensitivity of the hydrogenase, but its activity is low. With the aim of identifying the limiting step of hydrogen production, we succeeded in overexpressing the plastidial type II NAD(P)H dehydrogenase (NDA2). We report that transplastomic strains overexpressing NDA2 show an increased activity of nonphotochemical reduction of plastoquinones (PQs). While hydrogen production by the direct pathway, involving the linear electron flow from photosystem II to photosystem I, was not affected by NDA2 overexpression, the rate of hydrogen production by the indirect pathway was increased in conditions, such as nutrient limitation, where soluble electron donors are not limiting. An increased intracellular starch was observed in response to nutrient deprivation in strains overexpressing NDA2. It is concluded that activity of the indirect pathway is limited by the nonphotochemical reduction of PQs, either by the pool size of soluble electron donors or by the PQ-reducing activity of NDA2 in nutrient-limited conditions. We discuss these data in relation to limitations and biotechnological improvement of hydrogen photoproduction in microalgae. PMID:24820024

  4. Effects of light, food availability and temperature stress on the function of photosystem II and photosystem I of coral symbionts.

    Directory of Open Access Journals (Sweden)

    Mia O Hoogenboom

    Full Text Available BACKGROUND: Reef corals are heterotrophic coelenterates that achieve high productivity through their photosynthetic dinoflagellate symbionts. Excessive seawater temperature destabilises this symbiosis and causes corals to "bleach," lowering their photosynthetic capacity. Bleaching poses a serious threat to the persistence of coral reefs on a global scale. Despite expanding research on the causes of bleaching, the mechanisms remain a subject of debate. METHODOLOGY/PRINCIPAL FINDINGS: This study determined how light and food availability modulate the effects of temperature stress on photosynthesis in two reef coral species. We quantified the activities of Photosystem II, Photosystem I and whole chain electron transport under combinations of normal and stressful growth temperatures, moderate and high light levels and the presence or absence of feeding of the coral hosts. Our results show that PS1 function is comparatively robust against temperature stress in both species, whereas PS2 and whole chain electron transport are susceptible to temperature stress. In the symbiotic dinoflagellates of Stylophora pistillata the contents of chlorophyll and major photosynthetic complexes were primarily affected by food availability. In Turbinaria reniformis growth temperature was the dominant influence on the contents of the photosynthetic complexes. In both species feeding the host significantly protected photosynthetic function from high temperature stress. CONCLUSIONS/SIGNIFICANCE: Our findings support the photoinhibition model of coral bleaching and demonstrate that PS1 is not a major site for thermal damage during bleaching events. Feeding mitigates bleaching in two scleractinian corals, so that reef responses to temperature stresses will likely be influenced by the coinciding availabilities of prey for the host.

  5. The Henrietta Lacks legacy grows

    OpenAIRE

    Greely, Henry T.; Cho, Mildred K.

    2013-01-01

    Now that the NIH has reached an agreement with Henrietta Lacks's family concerning the use of the HeLa cell line, what lessons can we learn about informed consent and the unforeseen use of biological samples?

  6. Metabolism of D-lactate and structurally related organic acids in Chlamydomonas reinhardtii

    International Nuclear Information System (INIS)

    During the initial minutes of anaerobiosis, 14C-labeled D-lactate, derived from the photosynthetic sugar phosphate pool, accumulated in the unicellular green alga, Chlamydomonas reinhardtii. The production of the D-isomer of lactate by algae is in contrast to plant and mammalian cells in which L-lactate is formed. After initial lactate formation, Chlamydomonas exhibits a mixed-acid type fermentation, thereby avoiding lactate accumulation and enabling the cells to tolerate extended periods of anaerobiosis. A pyruvate reductase which catalyzes the formation of D-lactate in Chlamydomonas was partially purified and characterized. Lactate produced anaerobically was metabolized only when Chlamydomonas cells were returned to aerobic conditions, and reoxidation of the D-lactate was apparently catalyzed by a mitochondrial membrane-bound dehydrogenase, rather than by the soluble pyruvate reductase. Mutants of Chlamydomonas, deficient in mitochondrial respiration, were used to demonstrate that lactate metabolism was linked to the mitochondrial electron transport chain. In addition, the oxidation of glycolate, a structural analog of lactate, was also linked to mitochondrial electron transport in vivo

  7. Activation of a chloroplast type of fructose bisphosphatase from Chlamydomonas reinhardtii by light-mediated agents

    Science.gov (United States)

    Huppe, H. C.; Buchanan, B. B.

    1989-01-01

    A chloroplast type of fructose-1,6-bisphosphatase, a central regulatory enzyme of photosynthetic carbon metabolism, has been partially purified from Chlamydomonas reinhardtii. Unlike its counterpart from spinach chloroplasts, the algal FBPase showed a strict requirement for a dithiol reductant irrespective of Mg2+ concentration. The enzymes from the two sources resembled each other immunologically, in subunit molecular mass and response to pH. In the presence of dithiothreitol, the pH optimum for both the algal and spinach enzymes shifted from 8.5 to a more physiologic value of 8.0 as the Mg2+ concentration was increased from 1 to 16 mM. At 1 mM Mg2+, a concentration estimated to be close to physiological, the Chlamydomonas FBPase was active only in the presence of reduced thioredoxin and was most active with Chlamydomonas thioredoxin f. Under these conditions, the enzyme showed a pH optimum of 8.0. The data suggest that the Chlamydomonas enzyme resembles its spinach counterpart in most respects, but it has a stricter requirement for reduction and less strict reductant specificity. A comparison of the properties of the FBPases from Chlamydomonas and spinach will be helpful for elucidating the mechanism of the reductive activation of this enzyme.

  8. Energy transfer between photosystem II units in a connected package model of the photochemical apparatus of photosynthesis

    OpenAIRE

    Butler, Warren L.

    1980-01-01

    A model of the photochemical apparatus of photosynthesis, presented previously in a tripartite format, is used in a bipartite format to analyze energy transfer between photosystem II units. The model is used to develop analytical expressions for the photochemical properties of chloroplasts that include a term for the probability for energy transfer between photosystem II units. In particular, a normalized plot of the fluorescence of variable yield as a function of the closure of photosystem I...

  9. Intragenic enhancers and suppressors of phytoene desaturase mutations in Chlamydomonas reinhardtii.

    Directory of Open Access Journals (Sweden)

    Phoi T Tran

    Full Text Available Photosynthetic organisms synthesize carotenoids for harvesting light energy, photoprotection, and maintaining the structure and function of photosynthetic membranes. A light-sensitive, phytoene-accumulating mutant, pds1-1, was isolated in Chlamydomonas reinhardtii and found to be genetically linked to the phytoene desaturase (PDS gene. PDS catalyzes the second step in carotenoid biosynthesis--the conversion of phytoene to ζ-carotene. Decreased accumulation of downstream colored carotenoids suggested that the pds1-1 mutant is leaky for PDS activity. A screen for enhancers of the pds1-1 mutation yielded the pds1-2 allele, which completely lacks PDS activity. A second independent null mutant (pds1-3 was identified using DNA insertional mutagenesis. Both null mutants accumulate only phytoene and no other carotenoids. All three phytoene-accumulating mutants exhibited slower growth rates and reduced plating efficiency compared to wild-type cells and white phytoene synthase mutants. Insight into amino acid residues important for PDS activity was obtained through the characterization of intragenic suppressors of pds1-2. The suppressor mutants fell into three classes: revertants of the pds1-1 point mutation, mutations that changed PDS amino acid residue Pro64 to Phe, and mutations that converted PDS residue Lys90 to Met. Characterization of pds1-2 intragenic suppressors coupled with computational structure prediction of PDS suggest that amino acids at positions 90 and 143 are in close contact in the active PDS enzyme and have important roles in its structural stability and/or activity.

  10. Environmental pH and the Requirement for the Extrinsic Proteins of Photosystem II in the Function of Cyanobacterial Photosynthesis.

    Science.gov (United States)

    Morris, Jaz N; Eaton-Rye, Julian J; Summerfield, Tina C

    2016-01-01

    In one of the final stages of cyanobacterial Photosystem II (PS II) assembly, binding of up to four extrinsic proteins to PS II stabilizes the oxygen-evolving complex (OEC). Growth of cyanobacterial mutants deficient in certain combinations of these thylakoid-lumen-associated polypeptides is sensitive to changes in environmental pH, despite the physical separation of the membrane-embedded PS II complex from the external environment. In this perspective we discuss the effect of environmental pH on OEC function and photoautotrophic growth in cyanobacteria with reference to pH-sensitive PS II mutants lacking extrinsic proteins. We consider the possibilities that, compared to pH 10.0, pH 7.5 increases susceptibility to PS II-generated reactive oxygen species (ROS) causing photoinhibition and reducing PS II assembly in some mutants, and that perturbations to channels in the lumenal regions of PS II might alter the accessibility of water to the active site as well as egress of oxygen and protons to the thylakoid lumen. Reduced levels of PS II in these mutants, and reduced OEC activity arising from the disruption of substrate/product channels, could reduce the trans-thylakoid pH gradient (ΔpH), leading to the impairment of photosynthesis. Growth of some PS II mutants at pH 7.5 can be rescued by elevating CO2 levels, suggesting that the pH-sensitive phenotype might primarily be an indirect result of back-pressure in the electron transport chain that results in heightened production of ROS by the impaired photosystem. PMID:27555848

  11. Environmental pH and the Requirement for the Extrinsic Proteins of Photosystem II in the Function of Cyanobacterial Photosynthesis

    Science.gov (United States)

    Morris, Jaz N.; Eaton-Rye, Julian J.; Summerfield, Tina C.

    2016-01-01

    In one of the final stages of cyanobacterial Photosystem II (PS II) assembly, binding of up to four extrinsic proteins to PS II stabilizes the oxygen-evolving complex (OEC). Growth of cyanobacterial mutants deficient in certain combinations of these thylakoid-lumen-associated polypeptides is sensitive to changes in environmental pH, despite the physical separation of the membrane-embedded PS II complex from the external environment. In this perspective we discuss the effect of environmental pH on OEC function and photoautotrophic growth in cyanobacteria with reference to pH-sensitive PS II mutants lacking extrinsic proteins. We consider the possibilities that, compared to pH 10.0, pH 7.5 increases susceptibility to PS II-generated reactive oxygen species (ROS) causing photoinhibition and reducing PS II assembly in some mutants, and that perturbations to channels in the lumenal regions of PS II might alter the accessibility of water to the active site as well as egress of oxygen and protons to the thylakoid lumen. Reduced levels of PS II in these mutants, and reduced OEC activity arising from the disruption of substrate/product channels, could reduce the trans-thylakoid pH gradient (ΔpH), leading to the impairment of photosynthesis. Growth of some PS II mutants at pH 7.5 can be rescued by elevating CO2 levels, suggesting that the pH-sensitive phenotype might primarily be an indirect result of back-pressure in the electron transport chain that results in heightened production of ROS by the impaired photosystem.

  12. Effect of Photon Fluence Rate on Oxygen Evolution and Uptake by Chlamydomonas reinhardtii Suspensions Grown in Ambient and CO(2)-Enriched Air.

    Science.gov (United States)

    Sueltemeyer, D F; Klug, K; Fock, H P

    1986-06-01

    A closed system consisting of an assimilation chamber furnished with a membrane inlet from the liquid phase connected to a mass spectrometer was used to measure O(2) evolution and uptake by Chlamydomonas reinhardtii cells grown in ambient (0.034% CO(2)) or CO(2)-enriched (5% CO(2)) air. At pH = 6.9, 28 degrees C and concentrations of dissolved inorganic carbon (DIC) saturating for photosynthesis, O(2) uptake in the light (U(o)) equaled O(2) production (E(o)) at the light compensation point (15 micromoles photons per square meter per second). E(o) and U(o) increased with increasing photon fluence rate (PFR) but were not rate saturated at 600 micromoles photons per square meter per second, while net O(2) exchange reached a saturation level near 500 micromoles photons per square meter per second which was nearly the same for both, CO(2)-grown and air-grown cells. Comparison of the U(o)/E(o) ratios between air-grown and CO(2)-grown C. reinhardtii showed higher values for air-grown cells at light intensities higher than light compensation. For both, air-grown and CO(2)-grown algae the rates of mitochondrial O(2) uptake in the dark measured immediately before and 5 minutes after illumination were much lower than U(o) at PFR saturating for net photosynthesis. We conclude that noncyclic electron flow from water to NADP(+) and pseudocyclic electron flow via photosystem I to O(2) both significantly contribute to O(2) exchange in the light. In contrast, mitochondrial respiration and photosynthetic carbon oxidation cycle are regarded as minor O(2) consuming reactions in the light in both, air-grown and CO(2)-grown cells. It is suggested that the "extra" O(2) uptake by air-grown algae provides ATP required for the energy dependent CO(2)/HCO(3) (-) concentrating mechanism known to be present in these cells. PMID:16664823

  13. Negative impact on growth and photosynthesis in the green alga Chlamydomonas reinhardtii in the presence of the estrogen 17α-ethynylestradiol.

    Directory of Open Access Journals (Sweden)

    Tessa Pocock

    Full Text Available It is well known that estrogenic compounds affect development of fertilized eggs of many species of birds, fish and amphibians through disrupted activity of carbonic anhydrase (CA. The most potent activity comes from the most commonly occurring synthetic sterol, 17α-Ethynylestradiol (EE2. Less is known about the responses of aquatic phytoplankton to these compounds. Here we show for the first time that, in comparision to the control, the addition of 7 µM EE2 reduced the growth rate of the green alga Chlamydomonas reinhardtii by 68% for cells grown at high CO2. When cells were grown in ambient air (low Ci with a fully activated carbon concentrating mechanism through the induction of CA activity, the growth rates were reduced by as much as 119%. A reduced growth rate could be observed at EE2 concentrations as low as 10 pM. This was accompanied by a reduced maximum capacity for electron transport in photosystem II as determined by a lower FV/FM for low Ci-grown cells, which indicates the involvement of CAH3, a CA specifically located in the thylakoid lumen involved in proton pumping across the thylakoid membranes. These results were in agreement with an observed reduction in the chloroplastic affinity for Ci as shown by a strong increase in the Michaelis-Menten K0.5 for HCO3-. In itself, a lowering of the growth rate of a green alga by addition of the sterol EE2 warrants further investigation into the potential environmental impact by the release of treated waste water.

  14. The Type II NADPH Dehydrogenase Facilitates Cyclic Electron Flow, Energy-Dependent Quenching, and Chlororespiratory Metabolism during Acclimation of Chlamydomonas reinhardtii to Nitrogen Deprivation.

    Science.gov (United States)

    Saroussi, Shai I; Wittkopp, Tyler M; Grossman, Arthur R

    2016-04-01

    When photosynthetic organisms are deprived of nitrogen (N), the capacity to grow and assimilate carbon becomes limited, causing a decrease in the productive use of absorbed light energy and likely a rise in the cellular reduction state. Although there is a scarcity of N in many terrestrial and aquatic environments, a mechanistic understanding of how photosynthesis adjusts to low-N conditions and the enzymes/activities integral to these adjustments have not been described. In this work, we use biochemical and biophysical analyses of photoautotrophically grown wild-type and mutant strains of Chlamydomonas reinhardtii to determine the integration of electron transport pathways critical for maintaining active photosynthetic complexes even after exposure of cells to N deprivation for 3 d. Key to acclimation is the type II NADPH dehydrogenase, NDA2, which drives cyclic electron flow (CEF), chlororespiration, and the generation of an H(+) gradient across the thylakoid membranes. N deprivation elicited a doubling of the rate of NDA2-dependent CEF, with little contribution from PGR5/PGRL1-dependent CEF The H(+) gradient generated by CEF is essential to sustain nonphotochemical quenching, while an increase in the level of reduced plastoquinone would promote a state transition; both are necessary to down-regulate photosystem II activity. Moreover, stimulation of NDA2-dependent chlororespiration affords additional relief from the elevated reduction state associated with N deprivation through plastid terminal oxidase-dependent water synthesis. Overall, rerouting electrons through the NDA2 catalytic hub in response to photoautotrophic N deprivation sustains cell viability while promoting the dissipation of excess excitation energy through quenching and chlororespiratory processes. PMID:26858365

  15. Phase-dependent forcing and synchronization in the three-sphere model of Chlamydomonas

    Science.gov (United States)

    Bennett, Rachel R.; Golestanian, Ramin

    2013-07-01

    The green alga Chlamydomonas swims with synchronized beating of its two flagella, and is experimentally observed to exhibit run-and-tumble behaviour similar to bacteria. Recently, we studied a simple hydrodynamic three-sphere model of Chlamydomonas with a phase-dependent driving force that can produce run-and-tumble behaviour when intrinsic noise is added, due to the nonlinear mechanics of the system. Here, we consider the noiseless case and explore numerically the parameter space in the driving force profiles, which determine whether or not the synchronized state evolves from a given initial condition, as well as the stability of the synchronized state. We find that phase-dependent forcing, or a beat pattern, is necessary for stable synchronization in the geometry we work with. The phase-dependent forcing allows this simple model of Chlamydomonas to produce a rich variety of behaviours.

  16. The Chlamydomonas Genome Reveals the Evolution of Key Animal and Plant Functions

    Energy Technology Data Exchange (ETDEWEB)

    Merchant, Sabeeha S

    2007-04-09

    Chlamydomonas reinhardtii is a unicellular green alga whose lineage diverged from land plants over 1 billion years ago. It is a model system for studying chloroplast-based photosynthesis, as well as the structure, assembly, and function of eukaryotic flagella (cilia), which were inherited from the common ancestor of plants and animals, but lost in land plants. We sequenced the 120-megabase nuclear genome of Chlamydomonas and performed comparative phylogenomic analyses, identifying genes encoding uncharacterized proteins that are likely associated with the function and biogenesis of chloroplasts or eukaryotic flagella. Analyses of the Chlamydomonas genome advance our understanding of the ancestral eukaryotic cell, reveal previously unknown genes associated with photosynthetic and flagellar functions, and establish links between ciliopathy and the composition and function of flagella.

  17. Isolation, growth, ultrastructure, and metal tolerance of the green alga, Chlamydomonas acidophila (Chlorophyta).

    Science.gov (United States)

    Nishikawa, K; Tominaga, N

    2001-12-01

    An acidophilic volvocine flagellate, Chlamydomonas acidophila (Volvocales) that was isolated from an acid lake, Katanuma, in Miyagi prefecture, Japan was studied for growth, ultrastructural characterization, and metal tolerance. Chlamydomonas acidophila is obligately photoautotrophic, and did not grow in the cultures containing acetate or citrate even in the light. The optimum pH for growth was 3.5-4.5. To characterize metal tolerance, the toxic effects of Cd, Co, Cu, and Zn on this alga were also studied. Effective metal concentrations, which limited the growth by 50%, EC50 were measured, after 72 h of static exposure. EC50s were 14.4 microM Cd2+, 81.3 microM Co2+, 141 microM Cu2+, and 1.16 mM Zn2+ for 72 h of exposure. Thus, this alga had stronger tolerance to these metals than other species in the genus Chlamydomonas. PMID:11826960

  18. Phase-dependent forcing and synchronization in the three-sphere model of Chlamydomonas

    International Nuclear Information System (INIS)

    The green alga Chlamydomonas swims with synchronized beating of its two flagella, and is experimentally observed to exhibit run-and-tumble behaviour similar to bacteria. Recently, we studied a simple hydrodynamic three-sphere model of Chlamydomonas with a phase-dependent driving force that can produce run-and-tumble behaviour when intrinsic noise is added, due to the nonlinear mechanics of the system. Here, we consider the noiseless case and explore numerically the parameter space in the driving force profiles, which determine whether or not the synchronized state evolves from a given initial condition, as well as the stability of the synchronized state. We find that phase-dependent forcing, or a beat pattern, is necessary for stable synchronization in the geometry we work with. The phase-dependent forcing allows this simple model of Chlamydomonas to produce a rich variety of behaviours. (paper)

  19. Site-specific basal body duplication in Chlamydomonas.

    Science.gov (United States)

    O'Toole, Eileen T; Dutcher, Susan K

    2014-02-01

    Correct centriole/basal body positioning is required for numerous biological processes, yet how the cell establishes this positioning is poorly understood. Analysis of centriolar/basal body duplication provides a key to understanding basal body positioning and function. Chlamydomonas basal bodies contain structural features that enable specific triplet microtubules to be specified. Electron tomography of cultures enriched in mitotic cells allowed us to follow basal body duplication and identify a specific triplet at which duplication occurs. Probasal bodies elongate in prophase, assemble transitional fibers (TF) and are segregated with a mature basal body near the poles of the mitotic spindle. A ring of nine-singlet microtubules is initiated at metaphase, orthogonal to triplet eight. At telophase/cytokinesis, triplet microtubule blades assemble first at the distal end, rather than at the proximal cartwheel. The cartwheel undergoes significant changes in length during duplication, which provides further support for its scaffolding role. The uni1-1 mutant contains short basal bodies with reduced or absent TF and defective transition zones, suggesting that the UNI1 gene product is important for coordinated probasal body elongation and maturation. We suggest that this site-specific basal body duplication ensures the correct positioning of the basal body to generate landmarks for intracellular patterning in the next generation. PMID:24166861

  20. Isolation and characterization of glutamine synthetase genes in Chlamydomonas reinhardtii.

    Science.gov (United States)

    Chen, Q; Silflow, C D

    1996-11-01

    To elucidate the role of glutamine synthetase (GS) in nitrogen assimilation in the green alga Chlamydomonas reinhardtii we used maize GS1 (the cytosolic form) and GS2 (the chloroplastic form) cDNAs as hybridization probes to isolate C. reinhardtii cDNA clones. The amino acid sequences derived from the C. reinhardtii clones have extensive homology with GS enzymes from higher plants. A putative amino-terminal transit peptide encoded by the GS2 cDNA suggests that the protein localizes to the chloroplast. Genomic DNA blot analysis indicated that GS1 is encoded by a single gene, whereas two genomic fragments hybridized to the GS2 cDNA probe. All GS2 cDNA clones corresponded to only one of the two GS2 genomic sequences. We provide evidence that ammonium, nitrate, and light regulate GS transcript accumulation in green algae. Our results indicate that the level of GS1 transcripts is repressed by ammonium but induced by nitrate. The level of GS2 transcripts is not affected by ammonium or nitrate. Expression of both GS1 and GS2 genes is regulated by light, but perhaps through different mechanisms. Unlike in higher plants, no decreased level of GS2 transcripts was detected when cells were grown under conditions that repress photorespiration. Analysis of GS transcript levels in mutants with defects in the nitrate assimilation pathway show that nitrate assimilation and ammonium assimilation are regulated independently. PMID:8938407

  1. Histones of Chlamydomonas reinhardtii. Synthesis, acetylation, and methylation

    International Nuclear Information System (INIS)

    Histones of the green alga Chlamydomonas reinhardtii were prepared by a new method and fractionated by reversed-phase high-performance liquid chromatography. Acid-urea-Triton gel analysis and tritiated acetate labeling demonstrated high levels of steady-state acetylation for the single histone H3 protein, in contrast to low levels on histones H4 and H2B. Twenty percent of histone H3 is subject to dynamic acetylation with, on average, three acetylated lysine residues per protein molecule. Histone synthesis in light-dark-synchronized cultures was biphasic with pattern differences between two histone H1 variants, between two H2A variants, and between H2B and ubiquitinated H2B. Automated protein sequence analysis of histone H3 demonstrated a site-specific pattern of steady-state acetylation between 7 and 17% at five of the six amino-terminal lysines and of monomethylation between 5 and 81% at five of the eight amino-terminal lysines in a pattern that may limit dynamic acetylation. An algal histone H3 sequence was confirmed by protein sequencing with a since threonine as residue 28 instead of the serine(28)-alanine(29) sequence, present in all other known plant and animal H3 histones

  2. Response of Chlamydomonas reinhardtii to naphthenic acid exposure

    International Nuclear Information System (INIS)

    This study examined the feasibility of using a model organism for the algal bioremediation of oil sands process water (OSPW), a highly toxic mixture of sediments, bitumen, ions, and organic and inorganic compounds. Naphthenic acids (NAs) are a contaminant class of particular concern. Bioremediation techniques may mitigate toxicity of OSPW in general, and NAs in particular. Although most studies on the biodegradation of NAs focus on the role of bacteria, fungi, and emergent macrophytes, studies have indicated that algae may also play a key role through direct degradation, biosequestration, or photosynthetic aeration of waters to promote other biological reactions. Chlamydomonas frigida is of particular interest, but no cultures are currently available. Therefore, this study used C. reinhardtii, a well-characterized model organism, to begin analysis of potential algal bioremediation of OSPW. Cultures of C. reinhardtii were grown heterotrophically in nutrient media spiked with a dilution series of NAs. Culture densities were measured to compile growth curves over time, changes in rate of growth, and survivability. Negative ion electrospray mass spectrometry was used to determine the concentration of NAs in solution in relation to growth rate and culture density. The study determined the tolerance of C. reinhardtii to NAs. A mechanism for this tolerance was then proposed.

  3. Transport and metabolism of glycolic acid by Chlamydomonas reinhardtii

    International Nuclear Information System (INIS)

    In order to understand the excretion of glycolate from Chlamydomonas reinhardtii, the conditions affecting glycolate synthesis and metabolism were investigated. Although glycolate is synthesized only in the light, the metabolism occurs in the light and dark with greater metabolism in the light due to refixation of photorespiratory CO2. The amount of internal glycolate will affect the metabolism of externally added glycolate. When glycolate synthesis exceeds the metabolic capacity, glycolate is excreted from the cell. The transport of glycolate into the cells occurs very rapidly. Equilibrium is achieved at 40C within the time cells are pelleted by the silicone oil centrifugation technique through a layer of [14C] glycolate. Glycolate uptake does not show the same time, temperature and pH dependencies as diffusion of benzoate. Uptake can be inhibited by treatment of cells with N-ethylmaleimide and stimulated in the presence of valino-mycin/KCl. Acetate and lactate are taken up as quickly as glycolate. The hypothesis was made that glycolate is transported by a protein carrier that transports monocarboxylic acids. The equilibrium concentration of glycolate is dependent on the cell density, implying that there may be a large number of transporter sites and that uptake is limited by substrate availability

  4. Singlet oxygen production in Chlamydomonas reinhardtii under heat stress.

    Science.gov (United States)

    Prasad, Ankush; Ferretti, Ursula; Sedlářová, Michaela; Pospíšil, Pavel

    2016-01-01

    In the current study, singlet oxygen formation by lipid peroxidation induced by heat stress (40 °C) was studied in vivo in unicellular green alga Chlamydomonas reinhardtii. Primary and secondary oxidation products of lipid peroxidation, hydroperoxide and malondialdehyde, were generated under heat stress as detected using swallow-tailed perylene derivative fluorescence monitored by confocal laser scanning microscopy and high performance liquid chromatography, respectively. Lipid peroxidation was initiated by enzymatic reaction as inhibition of lipoxygenase by catechol and caffeic acid prevented hydroperoxide formation. Ultra-weak photon emission showed formation of electronically excited species such as triplet excited carbonyl, which, upon transfer of excitation energy, leads to the formation of either singlet excited chlorophyll or singlet oxygen. Alternatively, singlet oxygen is formed by direct decomposition of hydroperoxide via Russell mechanisms. Formation of singlet oxygen was evidenced by the nitroxyl radical 2,2,6,6-tetramethylpiperidine-1-oxyl detected by electron paramagnetic resonance spin-trapping spectroscopy and the imaging of green fluorescence of singlet oxygen sensor green detected by confocal laser scanning microscopy. Suppression of singlet oxygen formation by lipoxygenase inhibitors indicates that singlet oxygen may be formed via enzymatic lipid peroxidation initiated by lipoxygenase. PMID:26831215

  5. Identification of the Elusive Pyruvate Reductase of Chlamydomonas reinhardtii Chloroplasts.

    Science.gov (United States)

    Burgess, Steven J; Taha, Hussein; Yeoman, Justin A; Iamshanova, Oksana; Chan, Kher Xing; Boehm, Marko; Behrends, Volker; Bundy, Jacob G; Bialek, Wojciech; Murray, James W; Nixon, Peter J

    2016-01-01

    Under anoxic conditions the green alga Chlamydomonas reinhardtii activates various fermentation pathways leading to the creation of formate, acetate, ethanol and small amounts of other metabolites including d-lactate and hydrogen. Progress has been made in identifying the enzymes involved in these pathways and their subcellular locations; however, the identity of the enzyme involved in reducing pyruvate to d-lactate has remained unclear. Based on sequence comparisons, enzyme activity measurements, X-ray crystallography, biochemical fractionation and analysis of knock-down mutants, we conclude that pyruvate reduction in the chloroplast is catalyzed by a tetrameric NAD(+)-dependent d-lactate dehydrogenase encoded by Cre07.g324550. Its expression during aerobic growth supports a possible function as a 'lactate valve' for the export of lactate to the mitochondrion for oxidation by cytochrome-dependent d-lactate dehydrogenases and by glycolate dehydrogenase. We also present a revised spatial model of fermentation based on our immunochemical detection of the likely pyruvate decarboxylase, PDC3, in the cytoplasm. PMID:26574578

  6. Characterizing the anaerobic response of Chlamydomonas reinhardtii by quantitative proteomics.

    Science.gov (United States)

    Terashima, Mia; Specht, Michael; Naumann, Bianca; Hippler, Michael

    2010-07-01

    The versatile metabolism of the green alga Chlamydomonas reinhardtii is reflected in its complex response to anaerobic conditions. The anaerobic response is also remarkable in the context of renewable energy because C. reinhardtii is able to produce hydrogen under anaerobic conditions. To identify proteins involved during anaerobic acclimation as well as to localize proteins and pathways to the powerhouses of the cell, chloroplasts and mitochondria from C. reinhardtii in aerobic and anaerobic (induced by 8 h of argon bubbling) conditions were isolated and analyzed using comparative proteomics. A total of 2315 proteins were identified. Further analysis based on spectral counting clearly localized 606 of these proteins to the chloroplast, including many proteins of the fermentative metabolism. Comparative quantitative analyses were performed with the chloroplast-localized proteins using stable isotopic labeling of amino acids ([(13)C(6)]arginine/[(12)C(6)]arginine in an arginine auxotrophic strain). The quantitative data confirmed proteins previously characterized as induced at the transcript level as well as identified several new proteins of unknown function induced under anaerobic conditions. These proteins of unknown function provide new candidates for further investigation, which could bring insights for the engineering of hydrogen-producing alga strains. PMID:20190198

  7. Lipidomic Analysis of Chlamydomonas reinhardtii under Nitrogen and Sulfur Deprivation.

    Directory of Open Access Journals (Sweden)

    Dawei Yang

    Full Text Available Chlamydomonas reinhardtii accumulates lipids under complete nutrient starvation conditions while overall growth in biomass stops. In order to better understand biochemical changes under nutrient deprivation that maintain production of algal biomass, we used a lipidomic assay for analyzing the temporal regulation of the composition of complex lipids in C. reinhardtii in response to nitrogen and sulfur deprivation. Using a chip-based nanoelectrospray direct infusion into an ion trap mass spectrometer, we measured a diversity of lipid species reported for C. reinhardtii, including PG phosphatidylglycerols, PI Phosphatidylinositols, MGDG monogalactosyldiacylglycerols, DGDG digalactosyldiacylglycerols, SQDG sulfoquinovosyldiacylglycerols, DGTS homoserine ether lipids and TAG triacylglycerols. Individual lipid species were annotated by matching mass precursors and MS/MS fragmentations to the in-house LipidBlast mass spectral database and MS2Analyzer. Multivariate statistics showed a clear impact on overall lipidomic phenotypes on both the temporal and the nutrition stress level. Homoserine-lipids were found up-regulated at late growth time points and higher cell density, while triacyclglycerols showed opposite regulation of unsaturated and saturated fatty acyl chains under nutritional deprivation.

  8. Calcium titration of Chlamydomonas reinhardtii centrin and its structural changes

    Science.gov (United States)

    Ocaña, Wanda; Pastrana-Ríos, Belinda

    2014-07-01

    Chlamydomonas reinhardtii centrin is a highly conserved calcium binding protein belonging to the EF-hand superfamily. Centrin, like other calcium binding proteins, changes conformation upon calcium binding. In addition, the calcium binding sites are comprised mainly of aspartates and glutamates which would serve as probes for a calcium binding event. 2D IR correlation spectroscopy has proven to be a valuable technique to determine the differences in the molecular behavior of the EF-hand domains within centrin. Moreover, the differences in affinity for calcium displayed by these domains were correlated to differences in the molecular behavior of these EF-hand domains when compared with each other and the full-length protein. We were able to confirm the nature of the two independent domains within centrin. Furthermore, we established the mechanism of aggregation was self-association due to adsorption of centrin to the ZnSe ATR crystal and estimated the extent of aggregation of the full-length protein.

  9. Expression of human soluble TRAIL in Chlamydomonas reinhardtii chloroplast

    Institute of Scientific and Technical Information of China (English)

    YANG Zongqi; LI yinü; CHEN Feng; LI Dong; ZHANG Zhifang; LIU Yanxin; ZHENG Dexian; WANG Yong; SHEN Guifang

    2006-01-01

    Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) induces selectively apoptosis in various tumor cells and virus-infected cells, but rarely in normal cells. A chloroplast expression vector, p64TRAIL, containing the cDNA coding for the soluble TRAIL (sTRAIL), was constructed with clpP-trnL-petB-chlL-rpl23-rpl2 as Chlamydomonas reinhardtii plastid homologous recombinant fragments and spectinomycin-resistant aadA gene as a select marker. The plasmid p64TRAIL was transferred into the chloroplast genome of C. reinhardtii by the biolistic method. Three independently transformed lines were obtained by 100 mg/L spectinomycin selection. PCR amplification, Southern blot analysis of the sTRAIL coding region DNA and cultivation cells in the dark all showed that the exogenous DNA had been integrated into chloroplast genome of C. reinhardtii. Western blot analysis showed that human soluble TRAIL was expressed in C. reinhardtii chloroplast. The densitometric analysis of Western blot indicated that the expressed human sTRAIL protein in the chloroplasts of C. reinhardtii accounted for about 0.43%-0.67% of the total soluble proteins.These experimental results demonstrated the possibility of using transgenic chloroplasts of green alga as bioreactors for production of biopharmaceuticals.

  10. LET dependence of survival curve shape in chlamydomonas

    International Nuclear Information System (INIS)

    Chlamydomonas reinhardi, a haploid eukaryotic alga, was grown synchronously. A tandem Van de Graaff accelerator was used to produce protons and deuterons with LET's of 13 to 26 MeV-cm/sup 2//g and /sup 3/He and /sup 4/He nuclei at 71 to 87 MeV-cm/sup 2//g. Low-LET electrons were supplied by a 1.5 MeV electron Van de Graaff machine. The survival curves were fitted to the linear quadratic formula: S = exp(-αD + βD/sup 2/). In contrast to the response of mammalian cells, the first-power coefficient, α, remained at zero, or slightly less than zero, for all LET values up to 26 MeV-cm/sup 2//g. At the higher values it became positive; however, even at the highest stopping power, the curve had an obvious shoulder. The second-power coefficient, β, increased gradually with increasing LET up to 71 MeV-cm/sup 2//g, and rapidly between 71 and 87 MeV-cm/sup 2//g. This suggests that intra-track interactions may be largely responsible for ''sublesions''

  11. The pH tolerance of Chlamydomonas applanata (Volvocales, Chlorophyta).

    Science.gov (United States)

    Visviki, I; Santikul, D

    2000-02-01

    The effects of hydrogen ions on the growth and ultrastructure of Chlamydomonas applanata Pringsheim were examined. This species exhibits wide tolerance growing at pH values ranging from 3.4 to 8.4, with optimum growth obtained at 7.4. Growth is noticeably depressed at pH 4.4 and 3.4. At the ultrastructural level, exposure to pH 4.4 results in a 10% decrease in cell volume of single vegetative cells, an increase in pyrenoidal volume, and reduction of starch reserves. Palmelloid colonies also appear. pH 3.4 induces excessive production of mucilage and leads to the preponderance of palmelloid colonies. Cell death of both colony and single cells is seen, as well as loss of motility and abnormal cell division. Surviving single cells are significantly larger than controls, with thicker cell walls, smaller chloroplasts, and larger vacuome. Such cells entering dormancy ensure the survival of the species in times of stress. PMID:10629274

  12. Stimulation of growth and photosynthetic carbon metabolism in Chlamydomonas reinhardtii with triacontanol

    International Nuclear Information System (INIS)

    Treatment of Chlamydomonas reinhardtii Dangeard cells (-, strain N. 90), cultured at 5% CO2, with 1 to 1000 μg/L triacontanol (TRIA) resulted in a 21% to 35% increase in cell density, 7% to 31% increase in total chlorophyll, and 20% to 100% increase in photosynthetic CO2 assimilation. Chlamydomonas cells responded to a broad range of TRIA concentrations that were at least 10-fold above the optimum concentration for higher plants. Octacosanol inhibited the effect of TRIA on photosynthetic CO2 assimilation. TRIA did not alter glycolate excretion, the CO2 compensation point or sensitivity of photosynthetic CO2 assimilation to O2 in Chlamydomonas. Kinetic analysis of TRIA-treated cells showed that the increase in photosynthetic CO2 assimilation was a result of an increase in the whole-cell apparent Vmax. The activity of RuBP carboxylase/oxygenase was significantly higher in cell lysates from TRIA-treated cells than those from control cells. However, quantification of RuBP carboxylase/oxygenase levels by 14CABP binding did not show increased enzyme levels in TRIA-treated cells. Therefore, there was an increase in the specific activity of RuBP carboxylase/oxygenase extracted from Chlamydomonas cells treated with TRIA. TRIA alone had no effect in vitro on the activity of RuBPcarboxylase/oxygenase purified from spinach (Spinacia oleracea) leaves or from cell lysates of Chlamydomonas. RuBP levels were significantly higher in TRIA-treated cells at high and low CO2. Increased RuBP levels in TRIA-treated Chlamydomonas cells were also observed in the absence of CO2 with atmospheres of N2 and 21% O2

  13. Picosecond time-resolved fluorescence studies on excitation energy transfer in a histidine 117 mutant of the D2 protein of photosystem II in Synechocystis 6803.

    Science.gov (United States)

    Vasil'ev, S; Bruce, D

    2000-11-21

    The role of the peripheral reaction center chlorophyll a molecule associated with His117 of the D2 polypeptide in photosystem II was investigated in Synechocystis sp. PCC 6803 using a combination of steady state, pump-probe, and picosecond time-resolved fluorescence spectroscopy. Data were obtained from intact cells and isolated thylakoid membranes of a control mutant and a D2-H117T mutant, both of which lacked photosystem I. Excitation energy transfer and trapping were investigated by analyzing the data with a kinetic model that used an exact numerical solution of the Pauli master equation, taking into account available photosystem II spectral and structural information. The results of our kinetic analysis revealed the observed difference in excited-state dynamics between the H117T mutant and the control to be consistent with a retardation of the rate of excitation energy transfer from the peripheral chlorophyll of D2 (Chl at His117) to the electron-transfer pigments and an increase of the rate constant for charge recombination in the H117T mutant. The kinetic model was able to account for the experimentally observed changes in absorption cross section and fluorescence decay kinetics between the control and mutant by invoking changes in only these two rate constants. The results rule out quenching of excitation by a chlorophyll cation radical as a mechanism responsible for the lower efficiency of excitation energy utilization in the H117T mutant. Our work also demonstrates the importance of the chlorophyll associated with His117 of the D2 protein for excitation energy transfer to the PSII electron-transfer pigments and for the effective stabilization of the primary radical pair. PMID:11087370

  14. Isolation and Characterization of Photosystem Ⅱ of Porphyra yezoensis Ueda

    Institute of Scientific and Technical Information of China (English)

    Zheng-Quan GAO; Guang-Ce WANG; Cheng-Kui TSENG

    2004-01-01

    The thylakoid membranes were isolated and purified from gametophyte ofPorphyra yezoensis Ueda (P. yezoensis) by sucrose density gradient ultracentrifugation. After P.yezoensis gametophyte thylakoid membranes were solubilized with SDS, the photosystem Ⅱ (PSII) particles were isolated and purified. The activity of PSII particles was determined with DCIP (2,6-dichloroindophenol) photoreduction reaction. The composition of purified PSII particles was detected by SDS-PAGE. As a result, seven proteins including 55 kD protein, 47 kD protein, 43 kD protein, 33 kD protein, 31 kD protein, 29 kD protein, and 18 kD protein were found. Compared with PSII particles of higher plants and other algae, they were identified as D1/D2 complex, CP47, CP43, 33 kD protein, D1, D2 and cyt c-550 respectively. Besides, other three new proteins of 20 kD, 16 kD and 14 kD respectively were found. Among these extrinsic proteins, the 16 kD and 14 kD proteins had not been reported previously, and the 20 kD protein was found for the first time in multicellular red algae.

  15. Photosystem II repair in marine diatoms with contrasting photophysiologies.

    Science.gov (United States)

    Lavaud, Johann; Six, Christophe; Campbell, Douglas A

    2016-02-01

    Skeletonema costatum and Phaeodactylum tricornutum are model marine diatoms with differing strategies for non-photochemical dissipation of excess excitation energy within photosystem II (PSII). We showed that S. costatum, with connectivity across the pigment bed serving PSII, and limited capacity for induction of sustained non-photochemical quenching (NPQ), maintained a large ratio of [PSII(Total)]/[PSII(Active)] to buffer against fluctuations in light intensity. In contrast, P. tricornutum, with a larger capacity to induce sustained NPQ, could maintain a lower [PSII(Total)]/[PSII(Active)]. Induction of NPQ was correlated with an active PSII repair cycle in both species, and inhibition of chloroplastic protein synthesis with lincomycin leads to run away over-excitation of remaining PSII(Active), particularly in S. costatum. We discuss these distinctions in relation to the differing capacities, induction and relaxation rates for NPQ, and as strain adaptations to the differential light regimes of their originating habitats. The present work further confirms the important role for the light-dependent fast regulation of photochemistry by NPQ interacting with PSII repair cycle capacity in the ecophysiology of both pennate and centric diatoms. PMID:26156125

  16. Ultraviolet-B induced damage to photosystem II in intact filaments of Spirulina platensis

    International Nuclear Information System (INIS)

    When Spirulina platensis filaments were exposed to 0.75 mW x m-2 x s-1 of ultraviolet-B radiation (the ultraviolet-B radiation under clear sky condition is ∝1.0 mW x m-2 x s-1), an inhibition in photosystem II activity was observed, the inhibition being 90% after 90 min exposure. Upon exposure to ultraviolet-B, the room temperature emission characteristics of Spirulina cells were altered when excited with light primarily absorbed by chlorophyll a or phycobilisomes. When the cells were exposed for 3 h the emission at 685 nm (F685), when excited at 440 nm (primarily chlorophyll a absorption), was enhanced compared to 715 nm (F715) band of photosystem I suggesting a decrease in energy transfer from photosystem II to photosystem I. Similarly, when the cells were excited at 580 nm (primarily the phycobilisomes), the ratio of emission intensity at 685 nm (F685) to that of 655 nm (F655) was decreased in the exposed cells. This change in emission characteristics seems to be linked with the uncoupling of the energy transfer from all phycocyanin to chlorophyll a of photosystem II. A small shift in emission peak positions was also indicated when excited either at 440 nm or 580 nm. (orig./AJ)

  17. Ultraviolet-B induced damage to photosystem II in intact filaments of Spirulina platensis

    Energy Technology Data Exchange (ETDEWEB)

    Kolli, B.K.; Tiwari, S.; Mohanty, P. [Jawaharlal Nehru Univ., New Delhi (India). Schoof of Life Sciences

    1998-05-01

    When Spirulina platensis filaments were exposed to 0.75 mW x m{sup -2} x s{sup -1} of ultraviolet-B radiation (the ultraviolet-B radiation under clear sky condition is {proportional_to}1.0 mW x m{sup -2} x s{sup -1}), an inhibition in photosystem II activity was observed, the inhibition being 90% after 90 min exposure. Upon exposure to ultraviolet-B, the room temperature emission characteristics of Spirulina cells were altered when excited with light primarily absorbed by chlorophyll a or phycobilisomes. When the cells were exposed for 3 h the emission at 685 nm (F{sub 685}), when excited at 440 nm (primarily chlorophyll a absorption), was enhanced compared to 715 nm (F{sub 715}) band of photosystem I suggesting a decrease in energy transfer from photosystem II to photosystem I. Similarly, when the cells were excited at 580 nm (primarily the phycobilisomes), the ratio of emission intensity at 685 nm (F{sub 685}) to that of 655 nm (F{sub 655}) was decreased in the exposed cells. This change in emission characteristics seems to be linked with the uncoupling of the energy transfer from all phycocyanin to chlorophyll a of photosystem II. A small shift in emission peak positions was also indicated when excited either at 440 nm or 580 nm. (orig./AJ)

  18. Ultraviolet modification of Chlamydomonas reinhardtii for carbon capture

    Directory of Open Access Journals (Sweden)

    Gopal NS

    2016-04-01

    Full Text Available Nikhil S Gopal,1 K Sudhakar2 1The Lawrenceville School, Lawrenceville, NJ, USA; 2Bioenergy Laboratory, Malauna Azad National Institute of Technology, Bhopal, India Purpose: Carbon dioxide (CO2 levels have been rising rapidly. Algae are single-cell organisms with highly efficient CO2 uptake mechanisms. Algae yield two to ten times more biomass versus terrestrial plants and can grow nearly anywhere. Large scale CO2 sequestration is not yet sustainable due to high amounts of nitrogen (N and phosphate (P needed to grow algae in media. Methods: Mutant strains of Chlamydomonas reinhardtii were created using ultraviolet light (2.2–3 K J/m2 and natural selection using media with 20%–80% lower N and P compared to standard Sueoka's high salt medium. Strains were selected based upon growth in media concentrations varying from 20% to 80% less N/P compared to control. Biomass was compared to wild-type control (CC-125 using direct counts, optical density dry weight, and mean doubling time. Results: Mean doubling time was 20 and 25 hours in the low N and N/P strains, respectively (vs 66 hours in control. Using direct counts, growth rates of mutant strains of low N and N/P cultures were not statistically different from control (P=0.37 and 0.70, respectively. Conclusion: Two new strains of algae, as well as wild-type control, were able to grow while using 20%–40% less N and P. Ultraviolet light-based modification of algae is an inexpensive and alternative option to genetic engineering techniques. This technique might make larger scale biosequestration possible. Keywords: biosequestration, ultraviolet, carbon sequestration, carbon capture, algae

  19. Chloroplast genetics of chlamydomonas. II. Mapping by cosegregation frequency analysis

    International Nuclear Information System (INIS)

    This paper presents segregation and cosegregation data for a set of 15 chloroplast genes of Chlamydomonas, and uses these data to generate a linear map of the chloroplast genome. The data were derived from pedigree analysis of a total of 1596 zoospore clones resulting from 12 crosses in each of which 4 to 7 pairs of chloroplast alleles were segregating. The crosses are a subset of those previously described. By means of pedigree analysis, Type III segregations (nonreciprocal conversion-like events) were distinguished from Type III segregations (reciprocal events). The average frequency of Type II segregation was found to be the same for all 15 genes, indicating randomness of this event with respect to map location. Type III segregations occurred with a different and characteristic frequency for each gene, and were interpreted as a measure of the distance of each gene from the postulated centromere-like attachment point. Cosegregations, involving two or more genes, occurred with frequencies characteristic of the particular genes and much lower than expected for the product of single-gene events, indicating strong positive interference. Pairwise cosegregation frequencies provided unambiguous data for the gene order, confirmed by cosegregation runs of three or more genes. Apparent lengths of cosegregation runs, as fractions of the total map, indicate much longer stretches of gene conversion-like events than have been reported for other genetic systems. Comparisons of cosegregation frequencies in cross 20 after 15'', 30'', and 15'' uv irradiation of the mt+ before mating, indicate little if any consistent effect of this irradiation on segregation events

  20. Three-dimensional structure of photosystem II from Thermosynechococcus elongates in complex with terbutryn

    International Nuclear Information System (INIS)

    Photosystem II is a key component of the photosynthetic pathway producing oxygen at the thylakoid membrane of cyanobacteria, green algae, and plants. The three-dimensional structure of photosystem II from the cyanobacterium Thermosynechococcus elongates in a complex with herbicide terbutryn (a photosynthesis inhibitor) was determined for the first time by X-ray diffraction and refined at 3.2 Å resolution (Rfactor = 26.9%, Rfree = 29.9%, rmsd for bond lengths is 0.013 Å, and rmsd for bond angles is 2.2°). The terbutryn molecule was located in the binding pocket of the mobile plastoquinone. The atomic coordinates of the refined structure of photosystem II in a complex with terbutryn were deposited in the Protein Data Bank.

  1. Consequences of Decreased Light Harvesting Capability on Photosystem II Function in Synechocystis sp. PCC 6803

    Directory of Open Access Journals (Sweden)

    Aparna Nagarajan

    2014-12-01

    Full Text Available Cyanobacteria use large pigment-protein complexes called phycobilisomes to harvest light energy primarily for photosystem II (PSII. We used a series of mutants with partial to complete reduction of phycobilisomes to examine the effects of antenna truncation on photosystem function in Synechocystis sp. PCC 6803. The antenna mutants CB, CK, and PAL expressed increasing levels of functional PSII centers to compensate for the loss of phycobilisomes, with a concomitant decrease in photosystem I (PSI. This increased PSII titer led to progressively higher oxygen evolution rates on a per chlorophyll basis. The mutants also exhibited impaired S-state transition profiles for oxygen evolution. Additionally, P700+ re-reduction rates were impacted by antenna reduction. Thus, a decrease in antenna size resulted in overall physiological changes in light harvesting and delivery to PSII as well as changes in downstream electron transfer to PSI.

  2. Kinetics of phyllosemiquinone oxidation in the Photosystem I reaction centre of Acaryochloris marina.

    Science.gov (United States)

    Santabarbara, Stefano; Bailleul, Benjamin; Redding, Kevin; Barber, James; Rappaport, Fabrice; Telfer, Alison

    2012-02-01

    Light-induced electron transfer reactions in the chlorophyll a/d-binding Photosystem I reaction centre of Acaryochloris marina were investigated in whole cells by pump-probe optical spectroscopy with a temporal resolution of ~5ns at room temperature. It is shown that phyllosemiquinone, the secondary electron transfer acceptor anion, is oxidised with bi-phasic kinetics characterised by lifetimes of 88±6ns and 345±10ns. These lifetimes, particularly the former, are significantly slower than those reported for chlorophyll a-binding Photosystem I, which typically range in the 5-30ns and 200-300ns intervals. The possible mechanism of electron transfer reactions in the chlorophyll a/d-binding Photosystem I and the slower oxidation kinetics of the secondary acceptors are discussed. PMID:22037394

  3. Electrophoretic analysis, labeling and isolation of Chlamydomonas reinhardtii flagellum membrane proteins

    OpenAIRE

    Aleksander F. Sikorski

    2015-01-01

    SDS-polyacrylamide electrophoretic patterns of Chlamydomonas flagellum membrane proteins displayad 6 fractions, 3 PAS-positive among them. The surface radiolabeling of the flagellum membrane suggested an outer surface exposure of fraction '5', and internal localization of fractions '4' and '6'. Application of SDS-polyacrylamide gel electrophoresis and radiolabeled membranes allowed to isolate individual membrane polypeptides.

  4. Similar relative mutation rates in the three genetic compartments of Mesostigma and Chlamydomonas.

    Science.gov (United States)

    Hua, Jimeng; Smith, David Roy; Borza, Tudor; Lee, Robert W

    2012-01-01

    Levels of nucleotide substitution at silent sites in organelle versus nuclear DNAs have been used to estimate relative mutation rates among these compartments and explain lineage-specific features of genome evolution. Synonymous substitution divergence values in animals suggest that the rate of mutation in the mitochondrial DNA is 10-50 times higher than that of the nuclear DNA, whereas overall data for most seed plants support relative mutation rates in mitochondrial, plastid, and nuclear DNAs of 1:3:10. Little is known about relative mutation rates in green algae, as substitution rate data is limited to only the mitochondrial and nuclear genomes of the chlorophyte Chlamydomonas. Here, we measure silent-site substitution rates in the plastid DNA of Chlamydomonas and the three genetic compartments of the streptophyte green alga Mesostigma. In contrast to the situation in animals and land plants, our results support similar relative mutation rates among the three genetic compartments of both Chlamydomonas and Mesostigma. These data are discussed in relation to published intra-species genetic diversity data for the three genetic compartments of Chlamydomonas and are ultimately used to address contemporary hypotheses on the organelle genome evolution. To guide future work, we describe evolutionary divergence data of all publically available Mesostigma viride strains and identify, for the first time, three distinct lineages of Mesostigma. PMID:21621456

  5. Nonthermal effect of microwave irradiation on nitrite uptake in Chlamydomonas reinhardtii

    International Nuclear Information System (INIS)

    When cells of the unicellular green alga Chlamydomonas reinhardtii were subjected to microwave irradiation at 2.45 GHz, nitrite uptake kinetics still obeyed the Michaelis-Menten equation, the Km of the process remaining constant, whereas V max increased, which indicates an enhanced nonthermal permeability in irradiated cells. (author)

  6. In Vitro Evolution and Preliminary Characterization of a Cadmium-Resistant Population of Chlamydomonas reinhardtii

    OpenAIRE

    Nagel, Klaus; Voigt, Jürgen

    1989-01-01

    A cadmium-tolerant population of Chlamydomonas reinhardtii was derived from a Cd-sensitive cell wall-deficient strain by long-term selection in liquid culture. A comparison of Cd-sensitive and Cd-tolerant cells revealed that Cd tolerance was due to genetically determined alterations of metabolism rather than to increased efficiency of a detoxification system.

  7. Modifying effect of caffeine on lethality and mutability of Chlamydomonas reinhardii cells following UV irradiation

    International Nuclear Information System (INIS)

    The modifying effect of caffeine was studied using two standard and two UV-sensitive strains of Chlamydomonas reinhardii Dang. Cell survival and mutation frequency was microscopically evaluated on media without caffeine and on media with 1.5 mM of caffeine. The obtained results were indicative of the stimulating effect of caffeine upon survival in all strains. (author)

  8. Electrophoretic analysis, labeling and isolation of Chlamydomonas reinhardtii flagellum membrane proteins

    Directory of Open Access Journals (Sweden)

    Aleksander F. Sikorski

    2015-05-01

    Full Text Available SDS-polyacrylamide electrophoretic patterns of Chlamydomonas flagellum membrane proteins displayad 6 fractions, 3 PAS-positive among them. The surface radiolabeling of the flagellum membrane suggested an outer surface exposure of fraction '5', and internal localization of fractions '4' and '6'. Application of SDS-polyacrylamide gel electrophoresis and radiolabeled membranes allowed to isolate individual membrane polypeptides.

  9. Rapid induction of lipid droplets in Chlamydomonas reinhardtii and Chlorella vulgaris by Brefeldin A.

    Directory of Open Access Journals (Sweden)

    Sangwoo Kim

    Full Text Available Algal lipids are the focus of intensive research because they are potential sources of biodiesel. However, most algae produce neutral lipids only under stress conditions. Here, we report that treatment with Brefeldin A (BFA, a chemical inducer of ER stress, rapidly triggers lipid droplet (LD formation in two different microalgal species, Chlamydomonas reinhardtii and Chlorella vulgaris. LD staining using Nile red revealed that BFA-treated algal cells exhibited many more fluorescent bodies than control cells. Lipid analyses based on thin layer chromatography and gas chromatography revealed that the additional lipids formed upon BFA treatment were mainly triacylglycerols (TAGs. The increase in TAG accumulation was accompanied by a decrease in the betaine lipid diacylglyceryl N,N,N-trimethylhomoserine (DGTS, a major component of the extraplastidic membrane lipids in Chlamydomonas, suggesting that at least some of the TAGs were assembled from the degradation products of membrane lipids. Interestingly, BFA induced TAG accumulation in the Chlamydomonas cells regardless of the presence or absence of an acetate or nitrogen source in the medium. This effect of BFA in Chlamydomonas cells seems to be due to BFA-induced ER stress, as supported by the induction of three homologs of ER stress marker genes by the drug. Together, these results suggest that ER stress rapidly triggers TAG accumulation in two green microalgae, C. reinhardtii and C. vulgaris. A further investigation of the link between ER stress and TAG synthesis may yield an efficient means of producing biofuel from algae.

  10. The cell cycle of Chlamydomonas reinhardtii: the role of the commitment point

    Czech Academy of Sciences Publication Activity Database

    Oldenhof, H.; Zachleder, Vilém; van den Ende, H.

    2007-01-01

    Roč. 52, č. 1 (2007), s. 53-60. ISSN 0015-5632 Institutional research plan: CEZ:AV0Z50200510 Keywords : chlamydomonas reinhardtii * cell cycle * commitment point Subject RIV: EE - Microbiology, Virology Impact factor: 0.989, year: 2007

  11. Azolla filiculoides Nitrogenase Activity Decrease Induced by Inoculation with Chlamydomonas sp. †

    Science.gov (United States)

    Habte, Mitiku

    1986-01-01

    Experiments were conducted to determine the influence of Chlamydomonas sp. on nitrogen fixation (C2H2 → C2H4) in Azolla filiculoides and on the nitrogen fixation and growth of free-living Anabaena azollae 2B organisms. Inoculation of azolla medium with Chlamydomonas sp. was associated with decreased nitrogenase activity in A. filiculoides and with increases in the density of a fungal population identified as Acremonium sp. Subsequent inoculation of azolla medium with this fungus was also accompanied by a significant decrease in nitrogenase activity of A. filiculoides. However, the extent of depression of nitrogenase activity was significantly higher when azolla medium was inoculated with Chlamydomonas sp. than when it was inoculated with Acremonium sp. Inoculation of nitrogen-free Stanier medium with either Acremonium sp. or Chlamydomonas sp. did not adversely affect the growth or nitrogenase activity of free-living A. azollae. Decreased nitrogenase activity in A. filiculoides is apparently related to the adverse influence of the green alga and the fungus on the macrosymbiont. The mechanisms that might be involved are discussed. PMID:16347211

  12. Manipulating the chloroplast genome of Chlamydomonas: Present realities and future prospects

    Energy Technology Data Exchange (ETDEWEB)

    Boynton, J.; Gillham, N.; Hauser, C.; Heifetz, P.; Lers, A.; Newman, S.; Osmond, B.

    1992-12-31

    Biotechnology is being applied in vitro modification and stable reintroduction of chloroplast genes in Chlamydomonas reinhardtii and Nicotiana tabacum by homologous recombination. We are attempting the function analyses of plastid encoded proteins involved in photosynthesis, characterization of sequences which regulate expression of plastid genes at the transcriptional and translational levels, targeted disruption of chloroplast genes and molecular analysis of processes involved in chloroplast recombination.

  13. A mutation in the centriole-associated protein centrin causes genomic instability via increased chromosome loss in Chlamydomonas reinhardtii

    Directory of Open Access Journals (Sweden)

    Marshall Wallace F

    2005-05-01

    Full Text Available Abstract Background The role of centrioles in mitotic spindle function remains unclear. One approach to investigate mitotic centriole function is to ask whether mutation of centriole-associated proteins can cause genomic instability. Results We addressed the role of the centriole-associated EF-hand protein centrin in genomic stability using a Chlamydomonas reinhardtii centrin mutant that forms acentriolar bipolar spindles and lacks the centrin-based rhizoplast structures that join centrioles to the nucleus. Using a genetic assay for loss of heterozygosity, we found that this centrin mutant showed increased genomic instability compared to wild-type cells, and we determined that the increase in genomic instability was due to a 100-fold increase in chromosome loss rates compared to wild type. Live cell imaging reveals an increased rate in cell death during G1 in haploid cells that is consistent with an elevated rate of chromosome loss, and analysis of cell death versus centriole copy number argues against a role for multipolar spindles in this process. Conclusion The increased chromosome loss rates observed in a centrin mutant that forms acentriolar spindles suggests a role for centrin protein, and possibly centrioles, in mitotic fidelity.

  14. PSR1 Is a Global Transcriptional Regulator of Phosphorus Deficiency Responses and Carbon Storage Metabolism in Chlamydomonas reinhardtii.

    Science.gov (United States)

    Bajhaiya, Amit K; Dean, Andrew P; Zeef, Leo A H; Webster, Rachel E; Pittman, Jon K

    2016-03-01

    Many eukaryotic microalgae modify their metabolism in response to nutrient stresses such as phosphorus (P) starvation, which substantially induces storage metabolite biosynthesis, but the genetic mechanisms regulating this response are poorly understood. Here, we show that P starvation-induced lipid and starch accumulation is inhibited in a Chlamydomonas reinhardtii mutant lacking the transcription factor Pi Starvation Response1 (PSR1). Transcriptomic analysis identified specific metabolism transcripts that are induced by P starvation but misregulated in the psr1 mutant. These include transcripts for starch and triacylglycerol synthesis but also transcripts for photosynthesis-, redox-, and stress signaling-related proteins. To further examine the role of PSR1 in regulating lipid and starch metabolism, PSR1 complementation lines in the psr1 strain and PSR1 overexpression lines in a cell wall-deficient strain were generated. PSR1 expression in the psr1 lines was shown to be functional due to rescue of the psr1 phenotype. PSR1 overexpression lines exhibited increased starch content and number of starch granules per cell, which correlated with a higher expression of specific starch metabolism genes but reduced neutral lipid content. Furthermore, this phenotype was consistent in the presence and absence of acetate. Together, these results identify a key transcriptional regulator in global metabolism and demonstrate transcriptional engineering in microalgae to modulate starch biosynthesis. PMID:26704642

  15. Characterization and differential expression of microRNAs elicited by sulfur deprivation in Chlamydomonas reinhardtii

    Directory of Open Access Journals (Sweden)

    Shu Longfei

    2012-03-01

    Full Text Available Abstract Background microRNAs (miRNAs have been found to play an essential role in the modulation of numerous biological processes in eukaryotes. Chlamydomonas reinhardtii is an ideal model organism for the study of many metabolic processes including responses to sulfur-deprivation. We used a deep sequencing platform to extensively profile and identify changes in the miRNAs expression that occurred under sulfur-replete and sulfur-deprived conditions. The aim of our research was to characterize the differential expression of Chlamydomonas miRNAs under sulfur-deprived conditions, and subsequently, the target genes of miRNA involved in sulfur-deprivation were further predicted and analyzed. Results By using high-throughput sequencing, we characterized the microRNA transcriptomes under sulphur-replete and sulfur-deprived conditions in Chlamydomonas reinhardtii. We predicted a total of 310 miRNAs which included 85 known miRNAs and 225 novel miRNAs. 13 miRNAs were the specific to the sulfur-deprived conditions. 47 miRNAs showed significantly differential expressions responding to sulfur-deprivation, and most were up-regulated in the small RNA libraries with sulfur-deprivation. Using a web-based integrated system (Web MicroRNAs Designer 3 and combing the former information from a transcriptome of Chlamydomonas reinhardtii, 22 miRNAs and their targets involved in metabolism regulation with sulfur-deprivation were verified. Conclusions Our results indicate that sulfur-deprivation may have a significant influence on small RNA expression patterns, and the differential expressions of miRNAs and interactions between miRNA and its targets might further reveal the molecular mechanism responding to sulfur-deprivation in Chlamydomonas reinhardtii.

  16. Thermal bleaching induced changes in photosystem II function not reflected by changes in photosystem II protein content of Stylophora pistillata

    Science.gov (United States)

    Jeans, J.; Szabó, M.; Campbell, D. A.; Larkum, A. W. D.; Ralph, P. J.; Hill, R.

    2014-03-01

    Scleractinian corals exist in a symbiosis with marine dinoflagellates of the genus Symbiodinium that is easily disrupted by changes in the external environment. Increasing seawater temperatures cause loss of pigments and expulsion of the symbionts from the host in a process known as coral bleaching; though, the exact mechanism and trigger of this process has yet to be elucidated. We exposed nubbins of the coral Stylophora pistillata to bleaching temperatures over a period of 14 daylight hours. Fifty-nine percent of the symbiont population was expelled over the course of this short-term treatment. Maximum quantum yield ( F V/ F M) of photosystem (PS) II for the in hospite symbiont population did not change significantly over the treatment period, but there was a significant decline in the quantity of PSII core proteins (PsbA and PsbD) at the onset of the experimental increase in temperature. F V/ F M from populations of expelled symbionts dropped sharply over the first 6 h of temperature treatment, and then toward the end of the experiment, it increased to an F V/ F M value similar to that of the in hospite population. This suggests that the symbionts were likely damaged prior to expulsion from the host, and the most damaged symbionts were expelled earlier in the bleaching. The quantity of PSII core proteins, PsbA and PsbD, per cell was significantly higher in the expelled symbionts than in the remaining in hospite population over 6-10 h of temperature treatment. We attribute this to a buildup of inactive PSII reaction centers, likely caused by a breakdown in the PSII repair cycle. Thus, thermal bleaching of the coral S. pistillata induces changes in PSII content that do not follow the pattern that would be expected based on the results of PSII function.

  17. Carbon allocation and element composition in four Chlamydomonas mutants defective in genes related to the CO2 concentrating mechanism

    Czech Academy of Sciences Publication Activity Database

    Memmola, F.; Mukherjee, B.; Moroney, James V.; Giordano, Mario

    2014-01-01

    Roč. 121, 2-3 (2014), s. 201-211. ISSN 0166-8595 Institutional support: RVO:61388971 Keywords : Chlamydomonas mutants * carbon * carbon dioxide * elemental stoichiometry Subject RIV: EE - Microbiology, Virology Impact factor: 3.502, year: 2014

  18. High-Throughput Genetics Strategies for Identifying New Components of Lipid Metabolism in the Green Alga Chlamydomonas reinhardtii.

    Science.gov (United States)

    Li, Xiaobo; Jonikas, Martin C

    2016-01-01

    Microalgal lipid metabolism is of broad interest because microalgae accumulate large amounts of triacylglycerols (TAGs) that can be used for biodiesel production (Durrett et al Plant J 54(4):593-607, 2008; Hu et al Plant J 54(4):621-639, 2008). Additionally, green algae are close relatives of land plants and serve as models to understand conserved lipid metabolism pathways in the green lineage. The green alga Chlamydomonas reinhardtii (Chlamydomonas hereafter) is a powerful model organism for understanding algal lipid metabolism. Various methods have been used to screen Chlamydomonas mutants for lipid amount or composition, and for identification of the mutated loci in mutants of interest. In this chapter, we summarize the advantages and caveats for each of these methods with a focus on screens for mutants with perturbed TAG content. We also discuss technical opportunities and new tools that are becoming available for screens of mutants altered in TAG content or perturbed in other processes in Chlamydomonas. PMID:27023238

  19. The conserved plant sterility gene HAP2 functions after attachment of fusogenic membranes in Chlamydomonas and Plasmodium gametes

    OpenAIRE

    Liu, Yanjie; Tewari, Rita; Ning, Jue; Blagborough, Andrew M; Garbom, Sara; Pei, Jimin; Grishin, Nick V.; Steele, Robert E.; Sinden, Robert E.; Snell, William J.; Billker, Oliver

    2008-01-01

    The cellular and molecular mechanisms that underlie species-specific membrane fusion between male and female gametes remain largely unknown. Here, by use of gene discovery methods in the green alga Chlamydomonas, gene disruption in the rodent malaria parasite Plasmodium berghei, and distinctive features of fertilization in both organisms, we report discovery of a mechanism that accounts for a conserved protein required for gamete fusion. A screen for fusion mutants in Chlamydomonas identified...

  20. The effects of light-induced reduction of the photosystem II reaction center

    Czech Academy of Sciences Publication Activity Database

    Kutý, Michal

    2009-01-01

    Roč. 8, č. 15 (2009), s. 923-933. ISSN 1610-2940 R&D Projects: GA MŠk(CZ) LC06010 Institutional research plan: CEZ:AV0Z60870520 Keywords : Photosystem II * Reaction center * Pheophytin Subject RIV: CE - Biochemistry Impact factor: 2.336, year: 2009

  1. Phosphatidylglycerol requirement for the assembly and function of photosystem I and II reaction centers

    Czech Academy of Sciences Publication Activity Database

    Komenda, Josef; Komura, M.; Ughy, B.; Domonkos, I.; Sallai, A.; Fukushim, Y.; Bogos, B.; Wada, H.; Gombos, Z.; Itoh, S.

    Tsukuba: Verlag, 2006, s85. [Annual Meeting of the Japanese Society of Plant Physiologists /47./. Tsukuba (JP), 19.05.2006-21.05.2006] Institutional research plan: CEZ:AV0Z50200510 Keywords : photosystem II * Phosphatidylglycerol Subject RIV: EE - Microbiology, Virology

  2. Supermolecular organization of photosystem II and its associated light-harvesting antenna in Arabidopsis thaliana

    NARCIS (Netherlands)

    Yakushevska, AE; Jensen, PE; Keegstra, W; van Roon, H; Scheller, HV; Boekema, EJ; Dekker, JP; Yakushevska, Alevtyna E.; Jensen, Poul E.; Scheller, Henrik V.; Dekker, Jan P.

    2001-01-01

    The organization of Arabidopsis thaliana photosystem II (PSII) and its associated light-harvesting antenna (LHCII) was studied in isolated PSII-LHCII supercomplexes and native membrane-bound crystals by transmission electron microscopy and image analysis. Over 4000 single-particle projections of PSI

  3. Studying the Effect of Light Quality on the Size of the Photosystem II Light Harvesting Complex

    Science.gov (United States)

    Muhoz, Romualdo; Quiles, Maria J.

    2003-01-01

    In this article the effect of light quality on the size of the photosystem II (PSII) light harvesting complex (LHCII) is studied by measuring the chlorophyll fluorescence emitted by leaf sections of oat ("Avena sativa," var. Prevision) plants previously treated with either white light or with light filtered through blue, green, red or farred…

  4. Recent advances in understanding the assembly and repair of photosystem II

    Czech Academy of Sciences Publication Activity Database

    Nixon, P. J.; Michoux, F.; Yu, J.; Boehm, M.; Komenda, Josef

    2010-01-01

    Roč. 106, č. 1 (2010), s. 1-16. ISSN 0305-7364 R&D Projects: GA AV ČR IAA400200801 Institutional research plan: CEZ:AV0Z50200510 Keywords : Photosynthesis * photoinhibition * Photosystem II Subject RIV: EE - Microbiology, Virology Impact factor: 3.388, year: 2010

  5. Continuum probe two-dimensional electronic spectroscopy of the photosystem II reaction center

    Directory of Open Access Journals (Sweden)

    Ogilvie J. P.

    2013-03-01

    Full Text Available We report two-dimensional electronic spectroscopy of the photosystem II reaction center, collected in the pump-probe geometry employing a continuum probe. This enables observation of ion bands that report on intermediates in the charge separation process.

  6. Manganese Loading and Photosystem II Stability are Key Components of Manganese Efficiency in Plants

    DEFF Research Database (Denmark)

    Schmidt, Sidsel Birkelund

    Manganese (Mn) deficiency constitutes a major plant nutritional problem in commercial crop production of winter cereals. In plants, Mn has an indispensable role in the oxygen evolving complex (OEC) of photosystem II (PSII). Hence, the consequences of Mn deficiency are reduced plant growth, and...

  7. Reversible room temperature photooxidation of the peripheral chlorophyll of Photosystem II reaction centre

    Czech Academy of Sciences Publication Activity Database

    Litvín, R.; Vácha, František

    Coimbra: BES/ISE, 2005. s. 22. [International Symposium on Bioelectrochemistry /18./ and Spring Meeting Bioelectrochemistry /3./. 05.06.19 - 05.06.25, Coimbra] Institutional research plan: CEZ:AV0Z50510513 Keywords : Photosystem II Subject RIV: CE - Biochemistry

  8. Towards crystallization of the photosystem II reaction center from Pisum sativum

    Czech Academy of Sciences Publication Activity Database

    Kutá-Smatanová, Ivana; Šáchová, Marie; Vácha, František

    Heraklion : FESPP, 2002. s. 449. [13th Congress of the Federation of European Societies of Plant Physiology. 02.09.2002-06.09.2002, Hersonissos] R&D Projects: GA MŠk LN00A141; GA ČR GA206/00/D007 Keywords : photosystem II * Pisum sativum Subject RIV: ED - Physiology

  9. Changes in Thermostability of Photosystem Ⅱ and Leaf Lipid Composition of Rice Mutant with Deficiency of Light-harvesting Chlorophyll Protein Complexes

    Institute of Scientific and Technical Information of China (English)

    Yunlai Tang; Mei Chen; Yinong Xu; Tingyun Kuang

    2007-01-01

    We studied the difference in thermostability of photosystem Ⅱ (PSⅡ) and leaf lipid composition between a T-DNA insertion mutant rice (Oryza sativa L.) VG28 and its wild type Zhonghua11. Native green gel and SDS-PAGE electrophoreses revealed that the mutant VG28 lacked all light-harvesting chlorophyll a/b protein complexes. Both the mutant and wild type were sensitive to high temperatures, and the maximal efficiency of PSⅡ photochemistry (Fv/Fm) and oxygen-evolving activity of PSⅡ in leaves significantly decreased with increasing temperature. However, the PSⅡ activity of the mutant was markedly more sensitive to high temperatures than that of the wild type. Lipid composition analysis showed that the mutant had less phosphatidylglycerol and sulfoquinovosyl diacylglycerol compared with the wild type. Fatty acid analysis revealed that the mutant had an obvious decrease in the content of unsaturation of membrane lipids on the thermostability of PSll are discussed.

  10. Effect of supplementary VB radiation on chlorophyll synthesis and accumulation of photosystems during chloroplast development in Spirodela oligorrhiza

    International Nuclear Information System (INIS)

    Although the effects of ultraviolet B (UVB, 290-320 nm) radiation have been studied in plants extensively, little is known about the potential impacts on maturation of chloroplasts. To address this problem, the effects of supplementary UVB on chloroplast development were examined in the aquatic higher plant Spirodela oligorrhiza. Dark-grown Spirodela-containing proplastids were exposed to photosynthetically active radiation (PAR) and ultraviolet A (UVA, 320-400 nm), plus supplementary UVB equivalent to 1% of PAR on a photon basis. The biosynthesis and assembly of chlorophyll (Chl) into reaction centers was followed for 4 days in situ by low temperature (77 K) Chl fluorescence. Impacts on chloroplast development were detected after only 1 h incubation in light with supplementary UVB. Fluorescence emission signals from Chl associated with the photosystem (PS) II antenna, PSII reaction centers and PSI reaction centers were detected at the same time with or without UVB, but the magnitude of PS fluorescence was diminished up to 60% in plants incubated in UVB. The Chl content was also lower in UVB-treated plants, but to a lesser degree than anticipated by low temperature fluorescence, suggesting lack of organization and/or association of Chl with PS. Electron transport, measured with room temperature fluorescence induction, was not consistently different in plants exposed to UVB. These results suggest that with UVB, fewer and/or smaller PS form during chloroplast development, but there is not a large inhibition of Chl synthesis or PSII activity. (Author)

  11. MPH1 is a thylakoid membrane protein involved in protecting photosystem II from photodamage in land plants.

    Science.gov (United States)

    Liu, Jun; Last, Robert L

    2015-01-01

    Photosystem II (PSII) is highly susceptible to photoinhibition caused by environmental stimuli such as high light; therefore plants have evolved multifaceted mechanisms to efficiently protect PSII from photodamage. We previously published data suggesting that Maintenance of PSII under High light 1 (MPH1, encoded by AT5G07020), a PSII-associated proline-rich protein found in land plants, participates in the maintenance of normal PSII activity under photoinhibitory stress. Here we provide additional evidence for the role of MPH1 in protecting PSII against photooxidative damage. Two Arabidopsis thaliana mutants lacking a functional MPH1 gene suffer from severe photoinhibition relative to the wild-type plants under high irradiance light. The mph1 mutants exhibit significantly decreased PSII quantum yield and electron transport rate after exposure to photoinhibitory light. The mutants also display drastically elevated photodamage to PSII reaction center proteins after high-light treatment. These data add further evidence that MPH1 is involved in PSII photoprotection in Arabidopsis. MPH1 homologs are found across phylogenetically diverse land plants but are not detected in algae or prokaryotes. Taken together, these results suggest that MPH1 protein began to play a role in protecting PSII against excess light following the transition from aquatic to terrestrial conditions. PMID:26337456

  12. Self-consistent QM/MM methodologies for structural refinement of photosystem II and other macromolecules of biological interest

    Energy Technology Data Exchange (ETDEWEB)

    Batista, Enrique R [Los Alamos National Laboratory; Sproviero, Eduardo M [YALE UNIV; Newcomer, Michael [YALE UNIV; Gascon, Jose A [YALE UNIV; Batista, Victor S [YALE UNIV

    2008-01-01

    The combination of quantum mechanics and molecular mechanics (QM/MM) is one of the most promising approaches to study the structure, function, and properties of proteins and nucleic acids. However, there some instances in which the limitations of either the MM (lack of a proper electronic description) or QM (limited to a few number of atoms) methods prevent a proper description of the system. To address this issue, we review here our approach to fine-tune the structure of biological systems using post-QM/MM refinements. These protocols are based on spectroscopy data, and/or partitioning of the system to extend the QM description to a larger region of a protein. We illustrate these methodologies through applications to several biomolecules, which were pre-optimized at the QM/MM level and then further refined using postQM/MM refinement methodologies: mod(QM/MM), which refines the atomic charges of the residues included in the MM region accounting for polarization effects; mod(QM/MM)-opt that partition the MM region in smaller parts and optimizes each part in an iterative. self-consistent way, and the Polarized-Extended X-Ray Absorption Fine Structure (P-EXAFS) fitting procedure, which fine-tune the atomic coordinates to reproduce experimental polarized EXAFS spectra. The first two techniques were applied to the guanine quadruplex. while the P-EXAFS refinement was applied to the oxygen evolving complex of photosystem II.

  13. Spatial location of photosystem pigment-protein complexes in thylakoid membranes of chloroplasts of Pisum sativum studied by chlorophyll fluorescence

    International Nuclear Information System (INIS)

    Ultrastructure of plant chloroplasts was studied by a single-molecule spectroscopy setup at a temperature of 77 K exploring spatial location of photosystems. Two chloroplast thylakoid membrane regions were visualized by fluorescence microscopy and detected at different wavelengths. The size of these regions and the spatial resolution of the microscope allowed us to measure their chlorophyll fluorescence emission spectra of these membrane domains. While the grana regions are characterized by a predominant presence of Photosystem II pigment-protein complexes emitting at 685 nm, Photosystem I complexes are localized in stroma regions and emit at 730 nm

  14. Spatial location of photosystem pigment-protein complexes in thylakoid membranes of chloroplasts of Pisum sativum studied by chlorophyll fluorescence

    Energy Technology Data Exchange (ETDEWEB)

    Vacha, F. [Institute of Physical Biology, University of South Bohemia, Branisovska 31, 370 05 Ceske Budejovice (Czech Republic) and Biological centre, Academy of Sciences of the Czech Republic, UMBR, Branisovska 31, 370 05 Ceske Budejovice (Czech Republic)]. E-mail: vacha@jcu.cz; Adamec, F. [Institute of Physical Biology, University of South Bohemia, Branisovska 31, 370 05 Ceske Budejovice (Czech Republic); Biological centre, Academy of Sciences of the Czech Republic, UMBR, Branisovska 31, 370 05 Ceske Budejovice (Czech Republic); Valenta, J. [Institute of Physical Biology, University of South Bohemia, Branisovska 31, 370 05 Ceske Budejovice (Czech Republic); Department of Chemical Physics and Optics, Faculty of Mathematics and Physics, Charles University, Ke Karlovu 3, 121 16 Prague 2 (Czech Republic); Vacha, M. [Department of Organic and Polymeric Materials, Tokyo Institute of Technology, Ookayama 2-12-1-S8, Meguro-ku, Tokyo, 152-8552 (Japan)

    2007-01-15

    Ultrastructure of plant chloroplasts was studied by a single-molecule spectroscopy setup at a temperature of 77 K exploring spatial location of photosystems. Two chloroplast thylakoid membrane regions were visualized by fluorescence microscopy and detected at different wavelengths. The size of these regions and the spatial resolution of the microscope allowed us to measure their chlorophyll fluorescence emission spectra of these membrane domains. While the grana regions are characterized by a predominant presence of Photosystem II pigment-protein complexes emitting at 685 nm, Photosystem I complexes are localized in stroma regions and emit at 730 nm.

  15. The energy balance of the biomass generation of Chlamydomonas acidophila under acidic and neutral conditions and Chlamydomonas reinhardtii; Die Energiebilanz der Biomasseneubildung von Chlamydomonas acidophila unter sauren und neutralen Bedingungen und von Chlamydomonas reinhardtii

    Energy Technology Data Exchange (ETDEWEB)

    Langner, Uwe

    2009-01-16

    In this study the influence of pH < 3 as an extreme environment has been investigated for the eukaryotic green alga Chlamydomonas (C.) acidophila. The limited number of trophic levels, consisting of bacteria, phytoplankton, zooplankton and macrophytes, is a special characteristic of extreme acidic water bodies. C. acidophila was isolated from an extreme acidic mining lake (RL 111) (Bissinger et al. 2000). A special feature of the examined algal species is its wide tolerance range of external pH values from 2 to 7 (Cassin 1874, Gerloff-Elias et al. 2005a). C. acidophila is a dominant species in the acidic mining lakes, it can grow up to chlorophyll maxima of 500 {mu}g L{sup -1} during the summer time (Nixdorf et al. 1998, 2003). The alga can be found elsewhere in extreme acidic water bodies around the world. The hydrochemistry of the acidic mining lakes in the central regions of Germany and Lusatia show clear differences compared to neutral water bodies. Some of the characteristics of acidic mining lakes are high metal and heavy metal (aluminum) concentrations, high ion concentrations, which lead to high conductivity, as well as low phosphate concentrations, ammonium as the only nitrogen source and CO{sub 2} as the only inorganic carbon source. Many eukaryotic microalgae in acidic water bodies including C. acidophila show a neutral cytosolic pH. This is provided by special adaptations of the organisms. Thus, organisms in extreme acidic environments have a positive cell surface charge, a very efficient H{sup +}-ATPase and high internal buffer capacities. These mechanisms work contrary to the proton influx and the acidification of the cytosol and are therefore proof for the physiological impact of osmoregulation by microalgae in extreme acidic environments (Sekler et al.1991, Weiss et al. 1999). Hence, these mechanisms also complicate the access to nutrients for the algal cell. The passive influx of positively charged ions such as potassium or ammonium is reduced by

  16. The microalga Chlamydomonas reinhardtii as a platform for the production of human protein therapeutics

    OpenAIRE

    Rasala, Beth A.; Mayfield, Stephen P.

    2011-01-01

    Microalgae are a diverse group of eukaryotic photosynthetic microorganisms. While microalgae play a crucial role in global carbon fixation and oxygen evolution, these organisms have recently gained much attention for their potential role in biotechnological and industrial applications, such as the production of biofuels. We investigated the potential of the microalga Chlamydomonas reinhardtii to be a platform for the production of human therapeutic proteins. C. reinhardtii is a unicellular fr...

  17. Isolation and genetic analysis of Chlamydomonas reinhardtii strains resistant to cadmium.

    OpenAIRE

    Collard, J. M.; Matagne, R. F.

    1990-01-01

    In Chlamydomonas reinhardtii, cadmium induces reduction of growth, reduction of chlorophyll content, and lethality. The toxicity was higher in a cell wall-deficient strain than in the wild type. By growing the cells on agar medium containing cadmium at concentrations inducing high lethality, stable resistant clones were isolated. The resistance was due to a nuclear mutation (cadAR) which probably preexisted in the wild-type cell population, as suggested by the fluctuation test. A double mutan...

  18. Protocol: methodology for chromatin immunoprecipitation (ChIP) in Chlamydomonas reinhardtii

    OpenAIRE

    Strenkert Daniela; Schmollinger Stefan; Schroda Michael

    2011-01-01

    Abstract We report on a detailed chromatin immunoprecipitation (ChIP) protocol for the unicellular green alga Chlamydomonas reinhardtii. The protocol is suitable for the analysis of nucleosome occupancy, histone modifications and transcription factor binding sites at the level of mononucleosomes for targeted and genome-wide studies. We describe the optimization of conditions for crosslinking, chromatin fragmentation and antibody titer determination and provide recommendations and an example f...

  19. Characterization of Chlamydomonas reinhardtii phosphatidylglycerophosphate synthase in Synechocystis sp. PCC 6803

    OpenAIRE

    Hung, Chun-Hsien; Endo, Kaichiro; Kobayashi, Koichi; Nakamura, Yuki; Wada, Hajime

    2015-01-01

    Phosphatidylglycerol (PG) is an indispensable phospholipid class with photosynthetic function in plants and cyanobacteria. However, its biosynthesis in eukaryotic green microalgae is poorly studied. Here, we report the isolation and characterization of two homologs (CrPGP1 and CrPGP2) of phosphatidylglycerophosphate synthase (PGPS), the rate-limiting enzyme in PG biosynthesis, in Chlamydomonas reinhardtii. Heterologous complementation of Synechocystis sp. PCC 6803 pgsA mutant by CrPGP1 and Cr...

  20. Regulation by Light of Chemotaxis to Nitrite during the Sexual Life Cycle in Chlamydomonas reinhardtii

    OpenAIRE

    Elena Ermilova; Zhanneta Zalutskaya

    2014-01-01

    Nitrite plays an important role in the nitrogen metabolism of most cells, including Chlamydomonas reinhardtii. We have shown that vegetative cells of C. reinhardtii are attracted by nitrite. The Nia1nit2 mutant with defects in genes encoding the nitrate reductase and regulatory protein NIT2 respectively was found to exhibit normal chemotaxis to nitrite. The data suggest that chemotaxis events appear to be specific and independent of those involved in nitrate assimilation. Unlike vegetative ce...

  1. Predicting the physiological role of circadian metabolic regulation in the green alga Chlamydomonas reinhardtii.

    Directory of Open Access Journals (Sweden)

    Sascha Schäuble

    Full Text Available Although the number of reconstructed metabolic networks is steadily growing, experimental data integration into these networks is still challenging. Based on elementary flux mode analysis, we combine sequence information with metabolic pathway analysis and include, as a novel aspect, circadian regulation. While minimizing the need of assumptions, we are able to predict changes in the metabolic state and can hypothesise on the physiological role of circadian control in nitrogen metabolism of the green alga Chlamydomonas reinhardtii.

  2. ChlamyCyc: an integrative systems biology database and web-portal for Chlamydomonas reinhardtii

    OpenAIRE

    Kempa Stefan; Christian Jan-Ole; May Patrick; Walther Dirk

    2009-01-01

    Abstract Background The unicellular green alga Chlamydomonas reinhardtii is an important eukaryotic model organism for the study of photosynthesis and plant growth. In the era of modern high-throughput technologies there is an imperative need to integrate large-scale data sets from high-throughput experimental techniques using computational methods and database resources to provide comprehensive information about the molecular and cellular organization of a single organism. Results In the fra...

  3. A forward genetic approach in Chlamydomonas reinhardtii as a strategy for exploring starch catabolism

    OpenAIRE

    Hande Tunçay; Justin Findinier; Thierry Duchêne; Virginie Cogez; Charlotte Cousin; Gilles Peltier; Ball, Steven G; David Dauvillée

    2013-01-01

    A screen was recently developed to study the mobilization of starch in the unicellular green alga Chlamydomonas reinhardtii. This screen relies on starch synthesis accumulation during nitrogen starvation followed by the supply of nitrogen and the switch to darkness. Hence multiple regulatory networks including those of nutrient starvation, cell cycle control and light to dark transitions are likely to impact the recovery of mutant candidates. In this paper we monitor the specificity of this m...

  4. Rapid Induction of Lipid Droplets in Chlamydomonas reinhardtii and Chlorella vulgaris by Brefeldin A

    OpenAIRE

    Sangwoo Kim; Hanul Kim; Donghwi Ko; Yasuyo Yamaoka; Masumi Otsuru; Maki Kawai-Yamada; Toshiki Ishikawa; Hee-Mock Oh; Ikuo Nishida; Yonghua Li-Beisson; Youngsook Lee

    2013-01-01

    Algal lipids are the focus of intensive research because they are potential sources of biodiesel. However, most algae produce neutral lipids only under stress conditions. Here, we report that treatment with Brefeldin A (BFA), a chemical inducer of ER stress, rapidly triggers lipid droplet (LD) formation in two different microalgal species, Chlamydomonas reinhardtii and Chlorella vulgaris. LD staining using Nile red revealed that BFA-treated algal cells exhibited many more fluorescent bodies t...

  5. UREA TRANSPORT DURING GAMETOGENESIS OF THE UNICELLULAR GREEN ALGA CHLAMYDOMONAS REINHARDTII

    OpenAIRE

    Zalutskaya, Zhanneta; Lapina, Tatyana; Von, Wiren; Ermilova, Elena

    2009-01-01

    Direct urea transport mechanisms are present in Chlamydomonas reinhardtii. Urea uptake system(s) are repressed by ammonium and they can be induced by urea or acetamide in ammonium-starved vegetative cells. Urea transport ability of the alga is altered during gametogenesis. Unlike vegetative cells, mature gametes showed a low urea uptake. Incubation of gametes with urea or acetamide resulted in the increasing of urea uptake ability and the regaining of chemotactic activity. The data suggest a ...

  6. Biochemische und funktionelle Charakterisierung eines anaerob induzierten Ferredoxins aus Chlamydomonas reinhardtii

    OpenAIRE

    Jacobs, Jessica

    2009-01-01

    Im Genom der einzelligen Grünalge Chlamydomonas reinhardtii konnten sechs Gene identifiziert werden, die für (putative) Ferredoxine kodieren. Semiquantitative RT-PCR-Analysen zeigten, dass unter anaeroben Bedingungen nur das Transkript des FDX5-Gens signifikant akkumuliert. Da dies eine vitale Funktion des FDX5-Genproduktes im veränderten Metabolismus anaerober C. reinhardtii Zellen, der durch einen komplexen bakterienartigen Gärungsstoffwechsel und die Produktion von Wasserstoff ...

  7. The Involvement of hybrid cluster protein 4, HCP4, in Anaerobic Metabolism in Chlamydomonas reinhardtii

    OpenAIRE

    Olson, Adam C.; Carter, Clay J

    2016-01-01

    The unicellular green algae Chlamydomonas reinhardtii has long been studied for its unique fermentation pathways and has been evaluated as a candidate organism for biofuel production. Fermentation in C. reinhardtii is facilitated by a network of three predominant pathways producing four major byproducts: formate, ethanol, acetate and hydrogen. Previous microarray studies identified many genes as being highly up-regulated during anaerobiosis. For example, hybrid cluster protein 4 (HCP4) was fo...

  8. Phytotoxicity Evaluation of Type B Trichothecenes Using a Chlamydomonas reinhardtii Model System

    OpenAIRE

    Suzuki, Tadahiro; Iwahashi, Yumiko

    2014-01-01

    Type B trichothecenes, which consist of deoxynivalenol (DON) and nivalenol (NIV) as the major end products, are produced by phytotoxic fungi, such as the Fusarium species, and pollute arable fields across the world. The DON toxicity has been investigated using various types of cell systems or animal bioassays. The evaluation of NIV toxicity, however, has been relatively restricted because of its lower level compared with DON. In this study, the Chlamydomonas reinhardtii testing system, which ...

  9. СHEMOTAXIS OF CHLAMYDOMONAS REINHARDTII TO NITRATE IS CHANGED DURING GAMETOGENESIS

    OpenAIRE

    Ermilova, Elena; Zalutskaya, Zhanneta; Lapina, Tatyana

    2009-01-01

    During sexual differentiation Chlamydomonas reinhardtii changes its chemotactic behavior to nitrate. Unlike vegetative cells and noncompetent pregametes, mature gametes did not show chemotaxis to nitrate. Loss of chemotaxis to nitrate in matingcompetent cells is controlled by gamete-specific genes that are common for both mating-type gametes. Just like gamete formation, the change in chemotaxis mode is controlled by the sequential action of two environmental cues, removal of nitrogen from the...

  10. Successful Transient Expression of Cas9 and Single Guide RNA Genes in Chlamydomonas reinhardtii

    OpenAIRE

    Jiang, Wenzhi; Brueggeman, Andrew J.; Horken, Kempton M.; Plucinak, Thomas M.; Weeks, Donald P.

    2014-01-01

    The clustered regularly interspaced short palindromic repeat (CRISPR)/Cas9 system has become a powerful and precise tool for targeted gene modification (e.g., gene knockout and gene replacement) in numerous eukaryotic organisms. Initial attempts to apply this technology to a model, the single-cell alga, Chlamydomonas reinhardtii, failed to yield cells containing edited genes. To determine if the Cas9 and single guide RNA (sgRNA) genes were functional in C. reinhardtii, we tested the ability o...

  11. Light-Induced Production of An Antibody Fragment and Malaria Vaccine Antigen from Chlamydomonas reinhardtii

    OpenAIRE

    Neera Munjal; Andrea Juliana Garzon-Sanabria; Katelyn Wilson Quinones; James Gregory; Zivko L. Nikolov

    2014-01-01

    The eukaryotic green alga, Chlamydomonas reinhardtii, is a unique expression platform that can efficiently express complex therapeutic proteins. However, demonstrating that therapeutic molecules can be produced in quantifiable levels is essential to establish the potential of the C. reinhardtii expression system. Thus, the objective of this investigation was to determine the process conditions that could maximize C. reinhardtii biomass accumulation and induced-production of the two recombinan...

  12. Sustainability Evaluation of Biodiesel Produced from Microalgae Chlamydomonas sp Grown in Brewery Wastewater

    OpenAIRE

    Mata, Teresa M.; Santos, Janaína; Mendes, Adélio M; Caetano, Nídia S.; Martins, António A.

    2014-01-01

    This study performs a sustainability evaluation of biodiesel from microalga Chlamydomonas sp. grown in 20 % (v/v) of brewery’s wastewater, blended with pentose sugars (xylose, arabinose or ribose resulting from the hydrolysis of brewer’s spent grains (BSG). The life cycle steps considered for the study are: microalgae cultivation, biomass processing and lipids extraction at the brewery site, and its conversion to biodiesel at a dedicated external biofuel’s plant. Three sustainabil...

  13. Chlamydomonas reinhardtii: duration of its cell cycle and phases at growth rates affected by light intensity

    Czech Academy of Sciences Publication Activity Database

    Vítová, Milada; Bišová, Kateřina; Umysová, Dáša; Hlavová, Monika; Kawano, S.; Zachleder, Vilém; Čížková, Mária

    2011-01-01

    Roč. 233, č. 1 (2011), s. 75-86. ISSN 0032-0935 R&D Projects: GA AV ČR IAA500200614; GA ČR GA525/09/0102; GA ČR GA204/09/0111 Institutional research plan: CEZ:AV0Z50200510 Keywords : Cell division timing * Cell cycle phases * Chlamydomonas Subject RIV: EE - Microbiology, Virology Impact factor: 3.000, year: 2011

  14. Relation between hydrogen production and photosynthesis in the green algae Chlamydomonas reinhardtii

    OpenAIRE

    Basu, Alex

    2015-01-01

    The modernized world is over-consuming low-cost energy sources that strongly contributes to pollution and environmental stress. As a consequence, the interest for environmentally friendly alternatives has increased immensely. One such alternative is the use of solar energy and water as a raw material to produce biohydrogen through the process of photosynthetic water splitting. In this work, the relation between H2-production and photosynthesis in the green algae Chlamydomonas reinhardtii was ...

  15. Low oxygen levels contribute to improve photohydrogen production in mixotrophic non-stressed Chlamydomonas cultures

    OpenAIRE

    Jurado-Oller, Jose Luis; Dubini, Alexandra; Galván, Aurora; Fernández, Emilio; González-Ballester, David

    2015-01-01

    Background Currently, hydrogen fuel is derived mainly from fossil fuels, but there is an increasing interest in clean and sustainable technologies for hydrogen production. In this context, the ability of some photosynthetic microorganisms, particularly cyanobacteria and microalgae, to produce hydrogen is a promising alternative for renewable, clean-energy production. Among a diverse array of photosynthetic microorganisms able to produce hydrogen, the green algae Chlamydomonas reinhardtii is t...

  16. The Metabolome of Chlamydomonas reinhardtii following Induction of Anaerobic H2 Production by Sulfur Depletion*

    OpenAIRE

    Timmins, Matthew; Zhou, Wenxu; Rupprecht, Jens; Lim, Lysha; Thomas-Hall, Skye R.; Doebbe, Anja; Kruse, Olaf; Hankamer, Ben; Marx, Ute C.; Smith, Steven M.; Schenk, Peer M.

    2009-01-01

    The metabolome of the model species Chlamydomonas reinhardtii has been analyzed during 120 h of sulfur depletion to induce anaerobic hydrogen (H2) production, using NMR spectroscopy, gas chromatography coupled to mass spectrometry, and TLC. The results indicate that these unicellular green algae consume freshly supplied acetate in the medium to accumulate energy reserves during the first 24 h of sulfur depletion. In addition to the previously reported accumulation of starch, large amounts of ...

  17. CRISPR/Cas9-induced knockout and knock-in mutations in Chlamydomonas reinhardtii

    OpenAIRE

    Sung-Eun Shin; Jong-Min Lim; Hyun Gi Koh; Eun Kyung Kim; Nam Kyu Kang; Seungjib Jeon; Sohee Kwon; Won-Sub Shin; Bongsoo Lee; Kwon Hwangbo; Jungeun Kim; Sung Hyeok Ye; Jae-Young Yun; Hogyun Seo; Hee-Mock Oh

    2016-01-01

    Genome editing is crucial for genetic engineering of organisms for improved traits, particularly in microalgae due to the urgent necessity for the next generation biofuel production. The most advanced CRISPR/Cas9 system is simple, efficient and accurate in some organisms; however, it has proven extremely difficult in microalgae including the model alga Chlamydomonas. We solved this problem by delivering Cas9 ribonucleoproteins (RNPs) comprising the Cas9 protein and sgRNAs to avoid cytotoxicit...

  18. Stress induces the assembly of RNA granules in the chloroplast of Chlamydomonas reinhardtii

    OpenAIRE

    Uniacke, James; Zerges, William

    2008-01-01

    Eukaryotic cells under stress repress translation and localize these messenger RNAs (mRNAs) to cytoplasmic RNA granules. We show that specific stress stimuli induce the assembly of RNA granules in an organelle with bacterial ancestry, the chloroplast of Chlamydomonas reinhardtii. These chloroplast stress granules (cpSGs) form during oxidative stress and disassemble during recovery from stress. Like mammalian stress granules, cpSGs contain poly(A)-binding protein and the small, but not the lar...

  19. Time-Course Global Expression Profiles of Chlamydomonas reinhardtii during Photo-Biological H2 Production

    OpenAIRE

    Anh Vu Nguyen; Joerg Toepel; Steven Burgess; Andreas Uhmeyer; Olga Blifernez; Anja Doebbe; Ben Hankamer; Peter Nixon; Lutz Wobbe; Olaf Kruse

    2011-01-01

    We used a microarray study in order to compare the time course expression profiles of two Chlamydomonas reinhardtii strains, namely the high H₂ producing mutant stm6glc4 and its parental WT strain during H₂ production induced by sulfur starvation. Major cellular reorganizations in photosynthetic apparatus, sulfur and carbon metabolism upon H₂ production were confirmed as common to both strains. More importantly, our results pointed out factors which lead to the higher H₂ production in the mut...

  20. Plectin-like proteins are present in cells of Chlamydomonas eugametos (Volvocales).

    Science.gov (United States)

    Hendrychová, J; Vítová, M; Bisová, K; Wiche, G; Zachleder, V

    2002-01-01

    Using both monoclonal and polyclonal antibodies against mammalian plectin (multifunctional protein cross-linking cytoskeletal structures, mainly intermediate filaments, in mammalian cells), several putative isoforms of plectin-like proteins were found in protein extracts from the green alga Chlamydomonas eugametos (Volvocales). Immunofluorescence and immunoblotting revealed that some of the plectin-like proteins were present in perinuclear region or localized near the cell wall, probably being attached to the cytoplasmic membrane. PMID:12503400

  1. Plectin-like Proteins Are Present in Cells of Chlamydomonas eugametos (Volvocales)

    Czech Academy of Sciences Publication Activity Database

    Hendrychová, Jana; Vítová, Milada; Bišová, Kateřina; Wiche, G.; Zachleder, Vilém

    2002-01-01

    Roč. 47, č. 5 (2002), s. 535-539. ISSN 0015-5632 R&D Projects: GA ČR GA204/97/0576; GA ČR GA204/99/1235; GA ČR GA204/02/1438; GA AV ČR IAC5020012 Institutional research plan: CEZ:AV0Z5020903 Keywords : chlamydomonas eugametos * immunofluorescence Subject RIV: EE - Microbiology, Virology Impact factor: 0.979, year: 2002

  2. Chlamydomonas reinhardtii telomere repeats form unstable structures involving guanine-guanine base pairs.

    OpenAIRE

    Petracek, M E; Berman, J.

    1992-01-01

    Unusual DNA structures involving four guanines in a planar formation (guanine tetrads) are formed by guanine-rich (G-rich) telomere DNA and other G-rich sequences (reviewed in (1)) and may be important in the structure and function of telomeres. These structures result from intrastrand and/or interstrand Hoogsteen base pairs between the guanines. We used the telomeric repeat of Chlamydomonas reinhardtii, TTTTAGGG, which contains 3 guanines and has a long interguanine A + T tract, to determine...

  3. Plastid terminal oxidase 2 (PTOX2) is the major oxidase involved in chlororespiration in Chlamydomonas

    OpenAIRE

    Houille-Vernes, Laura; Rappaport, Fabrice; Wollman, Francis-André; Alric, Jean; Johnson, Xenie

    2011-01-01

    By homology with the unique plastid terminal oxidase (PTOX) found in plants, two genes encoding oxidases have been found in the Chlamydomonas genome, PTOX1 and PTOX2. Here we report the identification of a knockout mutant of PTOX2. Its molecular and functional characterization demonstrates that it encodes the oxidase most predominantly involved in chlororespiration in this algal species. In this mutant, the plastoquinone pool is constitutively reduced under dark-aerobic conditions, resulting ...

  4. Cell adhesion-dependent inactivation of a soluble protein kinase during fertilization in Chlamydomonas.

    OpenAIRE

    Zhang, Y.; Luo, Y.; Emmett, K; Snell, W J

    1996-01-01

    Within seconds after the flagella of mt+ and mt- Chlamydomonas gametes adhere during fertilization, their flagellar adenylyl cyclase is activated several fold and preparation for cell fusion is initiated. Our previous studies indicated that early events in this pathway, including control of adenylyl cyclase, are regulated by phosphorylation and dephosphorylation. Here, we describe a soluble, flagellar protein kinase activity that is regulated by flagellar adhesion. A 48-kDa, soluble flagellar...

  5. Expression and molecular analysis of phbB gene in Chlamydomonas reinhardtii

    Institute of Scientific and Technical Information of China (English)

    WANG Chaogang; HU Zhangli; HU Wei; LEI Anping

    2004-01-01

    The expression vector containing phbB and ble genes was constructed and transformed into cell-walldeficient strain Chlamydomonas reinhardtii CC-849 by the glass-bead method. The transgenic alga was selected and maintained in the TAP agar plates containing 10 μg/mL Zeomycin. Transgenic alga, which could express phbB at the transcriptional level, was obtained and further confirmed with PCR, Southern blot and RT-PCR-DNA hybridization analysis.

  6. Identification and molecular characterization of a novel Chlamydomonas reinhardtii mutant defective in chlorophyll biosynthesis

    Science.gov (United States)

    Mitra, Mautusi

    2013-01-01

    The green micro-alga Chlamydomonas reinhardtii is an elegant model organism to study all aspects of oxygenic photosynthesis. Chlorophyll (Chl) and heme are major tetrapyrroles that play an essential role in energy metabolism in photosynthetic organisms and are synthesized via a common branched tetrapyrrole biosynthetic pathway. One of the enzymes in the pathway is Mg chelatase (MgChel) which inserts Mg 2+ into protoporphyrin IX (PPIX, proto) to form magnesium-protoporphyrin IX (MgPPIX, Mgproto), the first biosynthetic intermediate in the Chl branch. MgChel is a multimeric enzyme that consists of three subunits designated CHLD, CHLI and CHLH. Plants have two isozymes of CHLI (CHLI1 and CHLI2) which are 70%-81% identical in protein sequences. Although the functional role of CHLI1 is well characterized, that of CHLI2 is not. We have isolated a non-photosynthetic light sensitive mutant 5A7 by random DNA insertional mutagenesis that is devoid of any detectable Chl. PCR based analyses show that 5A7 is missing the CHLI1 gene and at least eight additional functionally uncharacterized genes. 5A7 has an intact CHLI2 gene. Complementation with a functional copy of the CHLI1 gene restored Chl biosynthesis, photo-autotrophic growth and light tolerance in 5A7. We have identified the first chli1 (chli1-1) mutant of Chlamydomonas reinhardtii and in green algae. Our results show that in the wild type Chlamydomonas CHLI2 protein amount is lower than that of CHLI1 and the chli1-1 mutant has a drastic reduction in CHLI2 protein levels although it possesses the CHLI2 gene. Our chli1-1 mutant opens up new avenues to explore the functional roles of CHLI1 and CHLI2 in Chl biosynthesis in Chlamydomonas, which has never been studied before. PMID:24555064

  7. Characterization of trimeric Photosystem I particles from the prochlorophyte Prochlorothrix hollandica by electron microscopy and image analysis

    NARCIS (Netherlands)

    Staay, Georg W.M. van der; Boekema, Egbert J.; Dekker, Jan P.; Matthijs, Hans C.P.

    1993-01-01

    Photosystem I particles from Prochlorothrix hollandica were isolated from dodecylmaltoside solubilized thylakoid membranes on sucrose gradients in the presence of dodecylmaltoside. The particles were characterized by electron microscopy and image reconstruction techniques. The lowest, major green ba

  8. Recharacterization of Chlamydomonas reinhardtii and its relatives with new isolates from Japan.

    Science.gov (United States)

    Nakada, Takashi; Shinkawa, Haruka; Ito, Takuro; Tomita, Masaru

    2010-01-01

    Chlamydomonas reinhardtii P. A. Dang. (Volvocales, Chlorophyceae) is one of the most intensely studied algae, and its whole genome was sequenced. Although this species was originally described based on materials from France and is often referred to as a cosmopolitan species, all culture strains available today have been isolated from eastern North America. The distinctions with similar and/or closely related species, such as Chlamydomonas globosa J. Snow and Chlamydomonas orbicularis E. G. Pringsh., are also contentious. In this study, new strains of C. reinhardtii and C. globosa were isolated from Japan and compared with several strains similar to C. reinhardtii. Based on the morphological, genealogical, phylogenetical, and mating studies including the new Japanese strains, the circumscription of C. reinhardtii was clarified. C. reinhardtii was most closely related to C. globosa, and they were shown to be different species. Although C. reinhardtii was similar to C. orbicularis, the authentic strain of C. orbicularis was morphologically distinguishable and phylogenetically distant from C. reinhardtii. Discovery of the Japanese strains of C. reinhardtii supports the cosmopolitan distribution of this species. Based on Japanese strains and/or strains from other countries, emended descriptions of C. reinhardtii, C. globosa, and C. orbicularis are given. PMID:19882207

  9. ChlamyCyc: an integrative systems biology database and web-portal for Chlamydomonas reinhardtii

    Directory of Open Access Journals (Sweden)

    Kempa Stefan

    2009-05-01

    Full Text Available Abstract Background The unicellular green alga Chlamydomonas reinhardtii is an important eukaryotic model organism for the study of photosynthesis and plant growth. In the era of modern high-throughput technologies there is an imperative need to integrate large-scale data sets from high-throughput experimental techniques using computational methods and database resources to provide comprehensive information about the molecular and cellular organization of a single organism. Results In the framework of the German Systems Biology initiative GoFORSYS, a pathway database and web-portal for Chlamydomonas (ChlamyCyc was established, which currently features about 250 metabolic pathways with associated genes, enzymes, and compound information. ChlamyCyc was assembled using an integrative approach combining the recently published genome sequence, bioinformatics methods, and experimental data from metabolomics and proteomics experiments. We analyzed and integrated a combination of primary and secondary database resources, such as existing genome annotations from JGI, EST collections, orthology information, and MapMan classification. Conclusion ChlamyCyc provides a curated and integrated systems biology repository that will enable and assist in systematic studies of fundamental cellular processes in Chlamydomonas. The ChlamyCyc database and web-portal is freely available under http://chlamycyc.mpimp-golm.mpg.de.

  10. Distinct Mechanisms Regulating Gene Expression Coexist within the Fermentative Pathways in Chlamydomonas reinhardtii

    Directory of Open Access Journals (Sweden)

    Larisa Angela Swirsky Whitney

    2012-01-01

    Full Text Available Under dark anoxia, the unicellular green algae Chlamydomonas reinhardtii may produce hydrogen by means of its hydrogenase enzymes, in particular HYD1, using reductants derived from the degradation of intercellular carbon stores. Other enzymes belonging to the fermentative pathways compete for the same reductants. A complete understanding of the mechanisms determining the activation of one pathway rather than another will help us engineer Chlamydomonas for fermentative metabolite production, including hydrogen. We examined the expression pattern of the fermentative genes PDC3, LDH1, ADH2, PFL1, and PFR1 in response to day-night cycles, continuous light, continuous darkness, and low or high oxygen availability, which are all conditions that vary on a regular basis in Chlamydomonas' natural environment. We found that all genes except PFL1 show daily fluctuations in expression, and that PFR1 differentiated itself from the others in that it is clearly responsive to low oxygen, where as PDC3, LDH1, and ADH2 are primarily under diurnal regulation. Our results provide evidence that there exist at least three different regulatory mechanisms within the fermentative pathways and suggest that the fermentative pathways are not redundant but rather that availability of a variety of pathways allows for a differential metabolic response to different environmental conditions.

  11. Survival of Human Metallothionein-2 Transplastomic Chlamydomonas reinhardtii to Ultraviolet B Exposure

    Institute of Scientific and Technical Information of China (English)

    Yu-Kun ZHANG; Gui-Fang SHEN; Bing-Gen RU

    2006-01-01

    Solar ultraviolet (UV) radiation has a great influence on green organisms, especially plankton like Chlamydomonas. A human metallothionein-2 gene, which is generally considered to have an anti-radiation function by its coding product, was transferred into the chloroplast genome of Chlamydomonas reinhardtii.To dynamically measure the UV effects on Chlamydomonas cells grown in liquid tris-acetate-phosphate medium, a new method was developed based on the relationship between the chlorophyll content of an algal culture and its absorbance at 570 nm after the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. In this experiment, both the wild-type and the transplastomic C. reinhardtii cells were cultivated in 96-well microplates containing liquid tris-acetate-phosphate medium in the absence or presence of zinc, copper,cadmium and cysteine. The transgenic C. reinhardtii showed a higher resistance than wild-type to UV-B exposure under all the examined conditions. Metals in the medium had positive impacts on both types of cells,but had significant influence only on the transplastomic cells. However, the high cell viability of the transgenic alga at the end of the 8 h UV-B treatment disappeared after a 20-h recovery culture. Cysteine did not protect cells from UV-B damage, but clearly enhanced the growth of both wild-type and transgenic C.reinhardtii.

  12. Construction and evaluation of a whole genome microarray of Chlamydomonas reinhardtii

    Directory of Open Access Journals (Sweden)

    Toepel Jörg

    2011-11-01

    Full Text Available Abstract Background Chlamydomonas reinhardtii is widely accepted as a model organism regarding photosynthesis, circadian rhythm, cell mobility, phototaxis, and biotechnology. The complete annotation of the genome allows transcriptomic studies, however a new microarray platform was needed. Based on the completed annotation of Chlamydomonas reinhardtii a new microarray on an Agilent platform was designed using an extended JGI 3.1 genome data set which included 15000 transcript models. Results In total 44000 probes were determined (3 independent probes per transcript model covering 93% of the transcriptome. Alignment studies with the recently published AUGUSTUS 10.2 annotation confirmed 11000 transcript models resulting in a very good coverage of 70% of the transcriptome (17000. Following the estimation of 10000 predicted genes in Chlamydomonas reinhardtii our new microarray, nevertheless, covers the expected genome by 90-95%. Conclusions To demonstrate the capabilities of the new microarray, we analyzed transcript levels for cultures grown under nitrogen as well as sulfate limitation, and compared the results with recently published microarray and RNA-seq data. We could thereby confirm previous results derived from data on nutrient-starvation induced gene expression of a group of genes related to protein transport and adaptation of the metabolism as well as genes related to efficient light harvesting, light energy distribution and photosynthetic electron transport.

  13. Detection and characterization of phosphatidylcholine in various strains of the genus Chlamydomonas (Volvocales, Chlorophyceae).

    Science.gov (United States)

    Sakurai, Kenta; Mori, Natsumi; Sato, Naoki

    2014-09-01

    The laboratory strains of Chlamydomonas reinhardtii have been reported to contain no phosphatidylcholine (PC), which is considered to be replaced by another zwitterionic lipid, diacylglyceryl-N,N,N-trimethylhomoserine (DGTS). According to the recently published classification, the strains belonged to the subgroup Reinhardtinia. Screening for PC in 13 selected strains of Chlamydomonas in the NIES Algal Collection, which are different in habitats and belong to different phylogenetic subgroups in the genus, revealed the presence of PC in four strains: a strain in the subgroup Polytominia, and three strains in Reinhardtinia. PC was not detected in three other strains of Reinhardtinia analyzed. The presence/absence of PC was not related to the phylogenetic relationship based on 18S rRNA. DGTS was detected in all the strains analyzed. The rare isomer of linolenic acid, 18:3(5,9,12), which has been found in the DGTS of C. reinhardtii, was found in the PC of the two strains and in the DGTS of the five strains. The occurrence of this fatty acid seems limited to a branch of Reinhardtinia. Acquisition and loss of PC in various strains of Chlamydomonas are discussed from the viewpoint of evolution of PC biosynthetic pathway. PMID:24947506

  14. The cyanobacterium Synechococcus resists UV-B by exchanging photosystem II reaction-center D1 proteins

    International Nuclear Information System (INIS)

    Current ambient UV-B levels can significantly depress productivity in aquatic habitats, largely because UV-B inhibits several steps of photosynthesis, including the photooxidation of water catalyzed by photosystem II. We show that upon UV-B exposure the cyanobacterium Synechococcus sp. PCC 7942 rapidly changes the expression of a family of three psbA genes encoding photosystem II D1 proteins. In wild-type cells the psbAI gene is expressed constitutively, but strong accumulations of psbAII and psbAIII transcripts are induced within 15 min of moderate UV-B exposure (0.4 W/m2). This transcriptional response causes an exchange of two distinct photosystem II D1 proteins. D1:1 is encoded by psbAI, but on UV-B exposure, it is largely replaced by the alternate D1:2 form, encoded by both psbAII and psbAIII. The total content of D1 and other photosystem II reaction center protein, D2, remained unchanged throughout the UV exposure, as did the content and composition of the phycobilisome. Wild-type cells suffered only slight transient inhibition of photosystem II function under UV-B exposure. In marked contrast, under the same UV-B treatment, a mutant strain expressing only psbAI suffered severe (40%) and sustained inhibition of photosystem II function. Another mutant strain with constitutive expression of psbAII and psbAIII was almost completely resistant to the UV-B treatment, showing no inhibition of photosystem II function and only a slight drop in electron transport. In Synechococcus the rapid exchange of alternate D1 forms, therefore, accounts for much of the cellular resistance to UV-B inhibition of photosystem II activity and photosynthetic electron transport. This molecular plasticity may be an important element in community-level responses to UV-B, where susceptibility to UV-B inhibition of photosynthesis changes diurnally

  15. Radiation characteristics of Chlamydomonas reinhardtii CC125 and its truncated chlorophyll antenna transformants tla1, tlaX and tla1-CW{sup +}

    Energy Technology Data Exchange (ETDEWEB)

    Berberoglu, Halil; Pilon, Laurent [Mechanical and Aerospace Engineering Department, Henry Samueli School of Engineering and Applied Science, University of California, Los Angeles, CA 90095 (United States); Melis, Anastasios [Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720 (United States)

    2008-11-15

    This experimental study reports, for the first time, the radiation characteristics of the unicellular green algae Chlamydomonas reinhardtii strain CC125 and its truncated chlorophyll antenna transformants tla1, tlaX and tla1-CW{sup +}. Photobiological hydrogen production is a sustainable alternative to thermo-chemical and electrolytic technologies with the possible advantage of carbon dioxide mitigation. However, scale-up of photobioreactors from bench top to industrial scale is made difficult by excessive absorption and waste of light energy as heat and fluorescence. This results in limited light penetration into the photobioreactor and low solar to hydrogen energy conversion efficiency. To overcome these challenges, the algae C. reinhardtii have been genetically engineered with reduced pigment concentrations in their photosystems. This can improve the performance of photobioreactors by increasing the saturation irradiance of algae and quantum efficiency of photobiological hydrogen production. The extinction and absorption coefficients of all strains studied are obtained from normal-normal and normal-hemispherical transmittance measurements over the spectral range from 300 to 1300 nm. Moreover, a polar nephelometer is used to measure the scattering phase function of the microorganisms at 632.8 nm. It is established that the wild strain C. reinhardtii CC125 has major absorption peaks at 435 and 676 nm, corresponding to the in vivo absorption peaks of chlorophyll a, and at 475 and 650 nm corresponding to those of chlorophyll b. The genetically engineered strains have less chlorophyll pigments than the wild strain and thus have smaller absorption cross-sections. In particular, the mutant tlaX features a significant reduction in chlorophyll b concentration. For all mutants, however, the reduction in the absorption cross-section is accompanied by an increase in scattering cross-section. Although scattering becomes the dominant phenomenon contributing to the overall

  16. Subunit composition of CP43-less photosystem II complexes of Synechocystis sp. PCC 6803: implications for the assembly and repair of photosystem II

    OpenAIRE

    Boehm, M.; Yu, J.; Reisinger, V.; Beckova, M.; Eichacker, L.A.; Schlodder, E.; Komenda, J. (Jan); Nixon, P J

    2012-01-01

    Photosystem II (PSII) mutants are useful experimental tools to trap potential intermediates involved in the assembly of the oxygen-evolving PSII complex. Here, we focus on the subunit composition of the RC47 assembly complex that accumulates in a psbC null mutant of the cyanobacterium Synechocystis sp. PCC 6803 unable to make the CP43 apopolypeptide. By using native gel electrophoresis, we showed that RC47 is heterogeneous and mainly found as a monomer of 220 kDa. RC47 complexes co-purify wit...

  17. Excitation energy distribution between two photosystems in Porphyra yezoensis and its sig-nificance in photosynthesisevolution

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Comparative investigation on energy distribution between twophotosystems were carried out in the sporo- phytes and gametophytes of Porphyra yezoensis. By perfor- ming 77 K fluorescence spectra, we suggested that there probably existed a pathway for energy transfer from PSⅡ to PSⅠ to redistribute the absorbed energy in gametophytes, while no such a way or at minor level in sporophytes. Electron transfer inhibitor DCMU blocked the energy transfer from PSⅡ to PSⅠ in gametophytes, but no obvious effects on sporophytes. These indicated that excitation energy dis-tribution between two photosystems in gametophytes was more cooperative than that in sporophytes. These data in ontogenesis reflected the evolution process of photosynthetic organisms and supported the hypothesis of independent evolution of each photosystem.

  18. Variation in sulfide tolerance of photosystem II in phylogenetically diverse cyanobacteria from sulfidic habitats

    Science.gov (United States)

    Miller, Scott R.; Bebout, Brad M.

    2004-01-01

    Physiological and molecular phylogenetic approaches were used to investigate variation among 12 cyanobacterial strains in their tolerance of sulfide, an inhibitor of oxygenic photosynthesis. Cyanobacteria from sulfidic habitats were found to be phylogenetically diverse and exhibited an approximately 50-fold variation in photosystem II performance in the presence of sulfide. Whereas the degree of tolerance was positively correlated with sulfide levels in the environment, a strain's phenotype could not be predicted from the tolerance of its closest relatives. These observations suggest that sulfide tolerance is a dynamic trait primarily shaped by environmental variation. Despite differences in absolute tolerance, similarities among strains in the effects of sulfide on chlorophyll fluorescence induction indicated a common mode of toxicity. Based on similarities with treatments known to disrupt the oxygen-evolving complex, it was concluded that sulfide toxicity resulted from inhibition of the donor side of photosystem II.

  19. Evidence that an internal carbonic anhydrase is present in 5% CO2-grown and air-grown Chlamydomonas

    International Nuclear Information System (INIS)

    Inorganic carbon (C/sub i/) uptake was measured in wild-type cells of Chlamydomonas reinhardtii, and in cia-3, a mutant strain of C. reinhardtii that cannot grow with air levels of CO2. Both air-grown cells, that have a CO2 concentrating system, and 5% CO2-grown cells that do not have this system, were used. When the external pH was 5.1 or 7.3, air-grown, wild-type cells accumulated inorganic carbon (C/sub i/) and this accumulation was enhanced when the permeant carbonic anhydrase inhibitor, ethoxyzolamide, was added. When the external pH was 5.1, 5% CO2-grown cells also accumulated some C/sub i/, although not as much as air-grown cells and this accumulation was stimulated by the addition of ethoxyzolamide. At the same time, ethoxyzolamide inhibited CO2 fixation by high CO2-grown, wild-type cells at both pH 5.1 and 7.3. These observations imply that 5% CO2-grown, wild-type cells, have a physiologically important internal carbonic anhydrase, although the major carbonic anhydrase located in the periplasmic space is only present in air-grown cells. Inorganic carbon uptake by cia-3 cells supported this conclusion. This mutant strain, which is thought to lack an internal carbonic anhydrase, was unaffected by ethoxyzolamide at pH 5.1. Other physiological characteristics of cia-3 resemble those of wild-type cells that have been treated with ethoxyzolamide. It is concluded that an internal carbonic anhydrase is under different regulatory control than the periplasmic carbonic anhydrase

  20. Multiple stressor effects in Chlamydomonas reinhardtii – Toward understanding mechanisms of interaction between effects of ultraviolet radiation and chemical pollutants

    International Nuclear Information System (INIS)

    Highlights: • Systematic study of multiple stressor effects of UVR and chemicals in C. reinhardtii. • UVR and chemicals did not act independently on algal photosynthesis and reproduction. • Multiple stressor effects of UVR and chemicals depended on chemical MOA. • Synergistic effect interactions not limited to oxidative stress inducing chemicals. • Multiple MOAs of UVR may limit applicability of current prediction models. - Abstract: The effects of chemical pollutants and environmental stressors, such as ultraviolet radiation (UVR), can interact when organisms are simultaneously exposed, resulting in higher (synergistic) or lower (antagonistic) multiple stressor effects than expected based on the effects of single stressors. Current understanding of interactive effects is limited due to a lack of mechanism-based multiple stressor studies. It has been hypothesized that effect interactions may generally occur if chemical and non-chemical stressors cause similar physiological effects in the organism. To test this hypothesis, we exposed the model green alga Chlamydomonas reinhardtii to combinations of UVR and single chemicals displaying modes of action (MOA) similar or dissimilar to the impact of UVR on photosynthesis. Stressor interactions were analyzed based on the independent action model. Effect interactions were found to depend on the MOA of the chemicals, and also on their concentrations, the exposure time and the measured endpoint. Indeed, only chemicals assumed to cause effects on photosynthesis similar to UVR showed interactions with UVR on photosynthetic yield: synergistic in case of Cd(II) and paraquat and antagonistic in case of diuron. No interaction on photosynthesis was observed for S-metolachlor, which acts dissimilarly to UVR. However, combined effects of S-metolachlor and UVR on algal reproduction were synergistic, highlighting the importance of considering additional MOA of UVR. Possible mechanisms of stressor effect interactions are

  1. New tools for chloroplast genetic engineering allow the synthesis of human growth hormone in the green alga Chlamydomonas reinhardtii.

    Science.gov (United States)

    Wannathong, Thanyanan; Waterhouse, Janet C; Young, Rosanna E B; Economou, Chloe K; Purton, Saul

    2016-06-01

    In recent years, there has been an increasing interest in the exploitation of microalgae in industrial biotechnology. Potentially, these phototrophic eukaryotes could be used for the low-cost synthesis of valuable recombinant products such as bioactive metabolites and therapeutic proteins. The algal chloroplast in particular represents an attractive target for such genetic engineering, both because it houses major metabolic pathways and because foreign genes can be targeted to specific loci within the chloroplast genome, resulting in high-level, stable expression. However, routine methods for chloroplast genetic engineering are currently available only for one species-Chlamydomonas reinhardtii-and even here, there are limitations to the existing technology, including the need for an expensive biolistic device for DNA delivery, the lack of robust expression vectors, and the undesirable use of antibiotic resistance markers. Here, we describe a new strain and vectors for targeted insertion of transgenes into a neutral chloroplast locus that (i) allow scar-less fusion of a transgenic coding sequence to the promoter/5'UTR element of the highly expressed endogenous genes psaA or atpA, (ii) employ the endogenous gene psbH as an effective but benign selectable marker, and (iii) ensure the successful integration of the transgene construct in all transformant lines. Transformation is achieved by a simple and cheap method of agitation of a DNA/cell suspension with glass beads, with selection based on the phototrophic rescue of a cell wall-deficient ΔpsbH strain. We demonstrate the utility of these tools in the creation of a transgenic line that produces high levels of functional human growth hormone. PMID:26887319

  2. Multiple stressor effects in Chlamydomonas reinhardtii – Toward understanding mechanisms of interaction between effects of ultraviolet radiation and chemical pollutants

    Energy Technology Data Exchange (ETDEWEB)

    Korkaric, Muris [Eawag, Swiss Federal Institute of Aquatic Science and Technology, Department of Environmental Toxicology, 8600, Duebendorf (Switzerland); ETH Zürich, Institute of Biogeochemistry and Pollutant Dynamics, 8092 Zürich (Switzerland); Behra, Renata; Fischer, Beat B. [Eawag, Swiss Federal Institute of Aquatic Science and Technology, Department of Environmental Toxicology, 8600, Duebendorf (Switzerland); Junghans, Marion [Swiss Center for Applied Ecotoxicology Eawag-EPFL, 8600, Duebendorf (Switzerland); Eggen, Rik I.L., E-mail: rik.eggen@eawag.ch [Eawag, Swiss Federal Institute of Aquatic Science and Technology, Department of Environmental Toxicology, 8600, Duebendorf (Switzerland); ETH Zürich, Institute of Biogeochemistry and Pollutant Dynamics, 8092 Zürich (Switzerland)

    2015-05-15

    Highlights: • Systematic study of multiple stressor effects of UVR and chemicals in C. reinhardtii. • UVR and chemicals did not act independently on algal photosynthesis and reproduction. • Multiple stressor effects of UVR and chemicals depended on chemical MOA. • Synergistic effect interactions not limited to oxidative stress inducing chemicals. • Multiple MOAs of UVR may limit applicability of current prediction models. - Abstract: The effects of chemical pollutants and environmental stressors, such as ultraviolet radiation (UVR), can interact when organisms are simultaneously exposed, resulting in higher (synergistic) or lower (antagonistic) multiple stressor effects than expected based on the effects of single stressors. Current understanding of interactive effects is limited due to a lack of mechanism-based multiple stressor studies. It has been hypothesized that effect interactions may generally occur if chemical and non-chemical stressors cause similar physiological effects in the organism. To test this hypothesis, we exposed the model green alga Chlamydomonas reinhardtii to combinations of UVR and single chemicals displaying modes of action (MOA) similar or dissimilar to the impact of UVR on photosynthesis. Stressor interactions were analyzed based on the independent action model. Effect interactions were found to depend on the MOA of the chemicals, and also on their concentrations, the exposure time and the measured endpoint. Indeed, only chemicals assumed to cause effects on photosynthesis similar to UVR showed interactions with UVR on photosynthetic yield: synergistic in case of Cd(II) and paraquat and antagonistic in case of diuron. No interaction on photosynthesis was observed for S-metolachlor, which acts dissimilarly to UVR. However, combined effects of S-metolachlor and UVR on algal reproduction were synergistic, highlighting the importance of considering additional MOA of UVR. Possible mechanisms of stressor effect interactions are

  3. Efficient Heterologous Transformation of Chlamydomonas reinhardtii npq2 Mutant with the Zeaxanthin Epoxidase Gene Isolated and Characterized from Chlorella zofingiensis

    Directory of Open Access Journals (Sweden)

    Herminia Rodríguez

    2012-09-01

    Full Text Available In the violaxanthin cycle, the violaxanthin de-epoxidase and zeaxanthin epoxidase catalyze the inter-conversion between violaxanthin and zeaxanthin in both plants and green algae. The zeaxanthin epoxidase gene from the green microalga Chlorella zofingiensis (Czzep has been isolated. This gene encodes a polypeptide of 596 amino acids. A single copy of Czzep has been found in the C. zofingiensis genome by Southern blot analysis. qPCR analysis has shown that transcript levels of Czzep were increased after zeaxanthin formation under high light conditions. The functionality of Czzep gene by heterologous genetic complementation in the Chlamydomonas mutant npq2, which lacks zeaxanthin epoxidase (ZEP activity and accumulates zeaxanthin in all conditions, was analyzed. The Czzep gene was adequately inserted in the pSI105 vector and expressed in npq2. The positive transformants were able to efficiently convert zeaxanthin into violaxanthin, as well as to restore their maximum quantum efficiency of the PSII (Fv/Fm. These results show that Chlamydomonas can be an efficient tool for heterologous expression and metabolic engineering for biotechnological applications.

  4. Photosystem II electron flow as a measure for phytoplankton gross primary production.

    OpenAIRE

    Geel, C.

    1997-01-01

    Saturating pulse fluorescence measurements, well known from studies of higher plants for determination of photosystem II (PS II) characteristics, were applied to cultures of the green alga Dunaliella teitiolecta (Chapter 2). The actual efficiency of PS II (φ PS II ), the maximal efficiency of PS II (F v /F m ), and both photochemical and non- photochemical fluorescence quenching were determined for cultures of D. tertiolecta growing under varying light intensities. The rate of PS II electron ...

  5. Cyanobacterial Light-Harvesting Phycobilisomes Uncouple From Photosystem I During Dark-To-Light Transitions

    OpenAIRE

    Volha Chukhutsina; Luca Bersanini; Eva-Mari Aro; Herbert van Amerongen

    2015-01-01

    Photosynthetic organisms cope with changes in light quality by balancing the excitation energy flow between photosystems I (PSI) and II (PSII) through a process called state transitions. Energy redistribution has been suggested to be achieved by movement of the light-harvesting phycobilisome between PSI and PSII, or by nanometre scale rearrangements of the recently discovered PBSPSII- PSI megacomplexes. The alternative ‘spillover’ model, on the other hand, states that energy redistribution is...

  6. Assembling and maintaining the Photosystem II complex in chloroplasts and cyanobacteria

    Czech Academy of Sciences Publication Activity Database

    Komenda, Josef; Sobotka, Roman; Nixon, P. J.

    2012-01-01

    Roč. 15, č. 3 (2012), s. 245-2051. ISSN 1369-5266 R&D Projects: GA ČR GAP501/10/1000; GA ČR(CZ) GAP501/11/0377; GA MŠk(CZ) ED2.1.00/03.0110; GA AV ČR IAA400200801 Institutional support: RVO:61388971 Keywords : alga * cyanobacteria * Photosystem II Subject RIV: EE - Microbiology, Virology Impact factor: 8.455, year: 2012

  7. Backbone assignment and secondary structure of the PsbQ protein from Photosystem II

    Czech Academy of Sciences Publication Activity Database

    Horničáková, M.; Kohoutová, Jaroslava; Schlagnitweit, J.; Wohlschlager, Ch.; Ettrich, Rüdiger; Fiala, R.; Schoefberger, W.; Müller, N.

    2011-01-01

    Roč. 5, č. 2 (2011), s. 169-175. ISSN 1874-2718 R&D Projects: GA MŠk(CZ) LC06010 Institutional research plan: CEZ:AV0Z60870520 Keywords : Photosystem II * PsbQ * Missing link * NMR resonance assignment * Protein-protein interaction Subject RIV: BO - Biophysics Impact factor: 0.720, year: 2011 http://www.springerlink.com/content/3n38075w5h1l1082/fulltext.pdf

  8. Persistent spectral hole burning in oxygen-evolving photosystem II cores from cyanobacteria and higher plants

    International Nuclear Information System (INIS)

    Persistent spectral hole burning was performed on active photosystem II (PSII) cores from spinach and synechocystis 6803, each containing ∼32 chlorophyll a molecules per core. Hole-burning action spectra are presented. The data appear inconsistent with a mechanism involving non-photochemical hole burning, as has previously been observed in isolated PSII protein-pigment fragments. A photochemical hole-burning mechanism involving charge separation in P680 accounts for the features of the spectra presented

  9. Differential responses of photosystems I and II to seasonal drought in two Ficus species

    Science.gov (United States)

    Zhang, Shubin; Huang, Wei; Zhang, Jiaolin; Cao, Kunfang

    2016-05-01

    Hemiepiphytic Ficus species exhibit more conservative water use strategy and are more drought-tolerant compared with their non-hemiepiphytic congeners, but a difference in the response of photosystem I (PSI) and photosystem II (PSII) to drought stress has not been documented to date. The enhancement of non-photochemical quenching (NPQ) and cyclic electron flow (CEF) have been identified as important mechanisms that protect the photosystems under drought conditions. Using the hemiepiphytic Ficus tinctoria and the non-hemiepiphytic Ficus racemosa, we studied the water status and the electron fluxes through PSI and PSII under seasonal water stress. Our results clearly indicated that the decline in the leaf predawn water potential (ψpd), the maximum photosynthetic rate (Amax) and the predawn maximum quantum yield of PSII (Fv/Fm) were more pronounced in F. racemosa than in F. tinctoria at peak drought. The Fv/Fm of F. racemosa was reduced to 0.69, indicating net photoinhibition of PSII. Concomitantly, the maximal photo-oxidizable P700 (Pm) decreased significantly in F. racemosa but remained stable in F. tinctoria. The fraction of non-photochemical quenching [Y(NPQ)] and the ratio of effective quantum yield of PSI to PSII [Y(I)/Y(II)] increased for both Ficus species at peak drought, with a stronger increase in F. racemosa. These results indicated that the enhancement of NPQ and the activation of CEF contributed to the photoprotection of PSI and PSII for both Ficus species under seasonal drought, particularly for F. racemosa.

  10. Light-harvesting features revealed by the structure of plant Photosystem I

    CERN Document Server

    Ben-Shem, A; Nelson, N; 10.1023/B:PRES.0000036881.23512.42

    2004-01-01

    Oxygenic photosynthesis is driven by two multi-subunit membrane protein complexes, Photosystem I and Photosystem II. In plants and green algae, both complexes are composed of two moieties: a reaction center (RC), where light-induced charge translocation occurs, and a peripheral antenna that absorbs light and funnels its energy to the reaction center. The peripheral antenna of PS I (LHC I) is composed of four gene products (Lhca 1-4) that are unique among the chlorophyll a/b binding proteins in their pronounced long-wavelength absorbance and in their assembly into dimers. The recently determined structure of plant Photosystem I provides the first relatively high- resolution structural model of a super-complex containing a reaction center and its peripheral antenna. We describe some of the structural features responsible for the unique properties of LHC I and discuss the advantages of the particular LHC I dimerization mode over monomeric or trimeric forms. In addition, we delineate some of the interactions betw...

  11. Probing the connection of PBSs to the photosystems in Spirulina platensis by artificially induced fluorescence fluctuations

    International Nuclear Information System (INIS)

    The molecular architecture and the structural connections of phycobilisomes (PBSs) to the photosystems in the intact cells of Spirulina platensis were studied by taking advantage of glycerol- and betaine-induced fluorescence fluctuations. Generally, with a selective excitation of C-phycocyanin (C-PC), glycerol could induce not only decoupling of PBSs from the photosystems but also of C-PC rods from allophycocyanin (APC) cores, while betaine could strengthen the connection of PBSs to the thylakoid membrane but induce a partial dissociation of PBS. On the other hand, glycerol did not exert an influence on the fluorescence spectra of the photosystems in isolated thylakoid membrane. Therefore, it was deduced that glycerol could provide a molecular environment to weaken the hydrophobic interactions of not only the LCM with the membrane but also the linker polypeptides to the water-soluble phycobiliproteins (C-PC and APC), while the betaine could strengthen the hydrophobic interaction of LCM with the membrane but weaken the electrostatic interaction of linker polypeptides to C-PC and/or APC

  12. Probing the connection of PBSs to the photosystems in Spirulina platensis by artificially induced fluorescence fluctuations

    Energy Technology Data Exchange (ETDEWEB)

    Li Heng [Key Laboratory of Photochemistry, Center for Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080 (China); Yang Shuzhen [Key Laboratory of Photochemistry, Center for Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080 (China); Xie Jie [Key Laboratory of Photochemistry, Center for Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080 (China); Zhao Jingquan [Key Laboratory of Photochemistry, Center for Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080 (China)]. E-mail: zhaojq@iccas.ac.cn

    2007-01-15

    The molecular architecture and the structural connections of phycobilisomes (PBSs) to the photosystems in the intact cells of Spirulina platensis were studied by taking advantage of glycerol- and betaine-induced fluorescence fluctuations. Generally, with a selective excitation of C-phycocyanin (C-PC), glycerol could induce not only decoupling of PBSs from the photosystems but also of C-PC rods from allophycocyanin (APC) cores, while betaine could strengthen the connection of PBSs to the thylakoid membrane but induce a partial dissociation of PBS. On the other hand, glycerol did not exert an influence on the fluorescence spectra of the photosystems in isolated thylakoid membrane. Therefore, it was deduced that glycerol could provide a molecular environment to weaken the hydrophobic interactions of not only the L{sub CM} with the membrane but also the linker polypeptides to the water-soluble phycobiliproteins (C-PC and APC), while the betaine could strengthen the hydrophobic interaction of L{sub CM} with the membrane but weaken the electrostatic interaction of linker polypeptides to C-PC and/or APC.

  13. Characteristics of Photosystem II Behavior in Cotton (Gossypium hirsutum L.) Bract and Capsule Wall

    Institute of Scientific and Technical Information of China (English)

    ZHANG Ya-li; LUO Hong-hai; HU Yuan-yuan; Reto J. Strasser; ZHANG Wang-feng

    2013-01-01

    Though bract and capsule wall of boll in cotton (Gossypium hirsutum L.) have different photosynthetic capacities, the features of photosystem II (PS II) in these organs are scarce. In this paper, chlorophyll a lfuorescence emission was measured to investigate the difference in the photosynthetic apparatus of dark-acclimated (JIP-test) and light-acclimated (light-saturation pulse method) bract and capsule wall. Compared with leaves, the oxygen evolving system of non-foliar organs had lower efifciency. The pool size of PS II electron acceptor of non-foliar organs was small, and the photochemical activity of leaves was higher than that of the bract and capsule wall. In regard to the photosystem I (PS I) electron acceptor side, the pool size of end electron acceptors of leaves was larger, and the quantum yield of electron transport from QA (PS II primary plastoquinone acceptor) further than the PS I electron acceptors of leaves was higher than that of bract and capsule wall. In all green organs, the actual quantum yield of photochemistry decreased with light. The thermal dissipation fraction of light absorbed by the PS II antennae was the highest in bract and the lowest in capsule wall relative to leaves. Compared with leaves, capsule wall was characterized by less constitutive thermal dissipation and via dissipation as lfuorescence emission. These results suggested that lower PS II photochemical activity in non-foliar organs may be result from limitations at the donor side of PS II and the acceptor sides of both photosystems.

  14. Substrate-water exchange in photosystem II is arrested before dioxygen formation

    Science.gov (United States)

    Nilsson, Håkan; Rappaport, Fabrice; Boussac, Alain; Messinger, Johannes

    2014-07-01

    Light-driven oxidation of water into dioxygen, catalysed by the oxygen-evolving complex (OEC) in photosystem II, is essential for life on Earth and provides the blueprint for devices for producing fuel from sunlight. Although the structure of the OEC is known at atomic level for its dark-stable state, the mechanism by which water is oxidized remains unsettled. Important mechanistic information was gained in the past two decades by mass spectrometric studies of the H218O/H216O substrate-water exchange in the four (semi) stable redox states of the OEC. However, until now such data were not attainable in the transient states formed immediately before the O-O bond formation. Using modified photosystem II complexes displaying up to 40-fold slower O2 production rates, we show here that in the transient state the substrate-water exchange is dramatically slowed as compared with the earlier S states. This further constrains the possible sites for substrate-water binding in photosystem II.

  15. HYPERSENSITIVE TO HIGH LIGHT1 interacts with LOW QUANTUM YIELD OF PHOTOSYSTEM II1 and functions in protection of photosystem II from photodamage in Arabidopsis.

    Science.gov (United States)

    Jin, Honglei; Liu, Bing; Luo, Lujun; Feng, Dongru; Wang, Peng; Liu, Jun; Da, Qingen; He, Yanming; Qi, Kangbiao; Wang, Jinfa; Wang, Hong-Bin

    2014-03-01

    Under high-irradiance conditions, plants must efficiently protect photosystem II (PSII) from damage. In this study, we demonstrate that the chloroplast protein HYPERSENSITIVE TO HIGH LIGHT1 (HHL1) is expressed in response to high light and functions in protecting PSII against photodamage. Arabidopsis thaliana hhl1 mutants show hypersensitivity to high light, drastically decreased PSII photosynthetic activity, higher nonphotochemical quenching activity, a faster xanthophyll cycle, and increased accumulation of reactive oxygen species following high-light exposure. Moreover, HHL1 deficiency accelerated the degradation of PSII core subunits under high light, decreasing the accumulation of PSII core subunits and PSII-light-harvesting complex II supercomplex. HHL1 primarily localizes in the stroma-exposed thylakoid membranes and associates with the PSII core monomer complex through direct interaction with PSII core proteins CP43 and CP47. Interestingly, HHL1 also directly interacts, in vivo and in vitro, with LOW QUANTUM YIELD OF PHOTOSYSTEM II1 (LQY1), which functions in the repair and reassembly of PSII. Furthermore, the hhl1 lqy1 double mutants show increased photosensitivity compared with single mutants. Taken together, these results suggest that HHL1 forms a complex with LQY1 and participates in photodamage repair of PSII under high light. PMID:24632535

  16. A Dual Strategy to Cope with High Light in Chlamydomonas reinhardtii.

    OpenAIRE

    Allorent, G; Tokutsu, R; Roach, T; Peers, G; Cardol, Pierre; Girard-Bascou, J; Seigneurin-Berny, P; KUNTZ, M; Breyton, C; Franck, Fabrice; Wollman, F-A; Niyogi, K; Krieger-Liszkay, A; Minagawa, J.; Finazzi, G

    2013-01-01

    International audience Absorption of light in excess of the capacity for photosynthetic electron transport is damaging to photosynthetic organisms. Several mechanisms exist to avoid photodamage, which are collectively referred to as nonphotochemical quenching. This term comprises at least two major processes. State transitions (qT) represent changes in the relative antenna sizes of photosystems II and I. High energy quenching (qE) is the increased thermal dissipation of light energy trigge...

  17. Ultrafast Primary Reactions in the Photosystems of Oxygen-Evolving Organisms

    Science.gov (United States)

    Holzwarth, A. R.

    In oxygen-evolving photosynthetic organisms (plants, green algae, cyanobacteria), the primary steps of photosynthesis occur in two membrane-bound protein supercomplexes, Photosystem I (PS I) and Photosystem II (PS II), located in the thylakoid membrane (c.f. Fig. 7.1) along with two other important protein complexes, the cytochrome b6/f complex and the ATP-synthase [1]. Each of the photosystems consists of a reaction center (RC) where the photoinduced early electron transfer processes occur, of a so-called core antenna consisting of chlorophyll (Chl) protein complexes responsible for light absorption and ultrafast energy transfer to the RC pigments, and additional peripheral antenna complexes of various kinds that increase the absorption cross-section. The peripheral complexes are Chl a/b-protein complexes in higher plants and green algae (LHC I or LHC II for PS I or PS II, respectively) and so-called phycobilisomes in cyanobacteria and red algae [2-4]. The structures and light-harvesting functions of these antenna systems have been extensively reviewed [2, 5-9]. Recently, X-ray structures of both PS I and PS II antenna/RC complexes have been determined, some to atomic resolution. Although many details of the pigment content and organization of the RCs and antenna systems of PS I and PS II have been known before, the high resolution structures of the integral complexes allow us for the first time to try to understand structure/function relationships in detail. This article covers our present understanding of the ultrafast energy transfer and early electron transfer processes occurring in the photosystems of oxygen-evolving organisms. The main emphasis will be on the electron transfer processes. However, in both photosystems the kinetics of the energy transfer processes in the core antennae is intimately interwoven with the kinetics of the electron transfer steps. Since both types of processes occur on a similar time scale, their kinetics cannot be considered

  18. Crystal structure of the Psb28 accessory factor of Thermosynechococcus elongatus photosystem II at 2.3 Å.

    Science.gov (United States)

    Bialek, Wojciech; Wen, Songjia; Michoux, Franck; Beckova, Martina; Komenda, Josef; Murray, James W; Nixon, Peter J

    2013-11-01

    Members of the Psb28 family of proteins are accessory factors implicated in the assembly and repair of the photosystem II complex. We present here the crystal structure of the Psb28 protein (Tlr0493) found in the thermophilic cyanobacterium Thermosynechococcus elongatus at a resolution of 2.3 Å. Overall the crystal structure of the Psb28 monomer is similar to the solution structures of C-terminally His-tagged Psb28-1 from Synechocystis sp. PCC 6803 obtained previously by nuclear magnetic resonance spectroscopy. One new aspect is that Escherichia coli-expressed T. elongatus Psb28 is able to form dimers in solution and packs as a dimer of dimers in the crystal. Analysis of wild type and mutant strains of Synechocystis 6803 by blue native-polyacrylamide gel electrophoresis suggests that Psb28-1, the closest homologue to T. elongatus Psb28 in this organism, also exists as an oligomer in vivo, most likely a dimer. In line with the prediction based on the crystal structure of T. elongatus Psb28, the addition of a 3× Flag-tag to the C-terminus of Synechocystis 6803 Psb28-1 interferes with the accumulation of the Psb28-1 oligomer in vivo. In contrast, the more distantly related Psb28-2 protein found in Synechocystis 6803 lacks the residues that stabilize dimer formation in the T. elongatus Psb28 crystal and is detected as a monomer in vivo. Overall our data suggest that the dimer interface in the Psb28 crystal might be physiologically relevant. PMID:24126792

  19. Acclimation of Antarctic Chlamydomonas to the sea-ice environment: a transcriptomic analysis.

    Science.gov (United States)

    Liu, Chenlin; Wang, Xiuliang; Wang, Xingna; Sun, Chengjun

    2016-07-01

    The Antarctic green alga Chlamydomonas sp. ICE-L was isolated from sea ice. As a psychrophilic microalga, it can tolerate the environmental stress in the sea-ice brine, such as freezing temperature and high salinity. We performed a transcriptome analysis to identify freezing stress responding genes and explore the extreme environmental acclimation-related strategies. Here, we show that many genes in ICE-L transcriptome that encoding PUFA synthesis enzymes, molecular chaperon proteins, and cell membrane transport proteins have high similarity to the gens from Antarctic bacteria. These ICE-L genes are supposed to be acquired through horizontal gene transfer from its symbiotic microbes in the sea-ice brine. The presence of these genes in both sea-ice microalgae and bacteria indicated the biological processes they involved in are possibly contributing to ICE-L success in sea ice. In addition, the biological pathways were compared between ICE-L and its closely related sister species, Chlamydomonas reinhardtii and Volvox carteri. In ICE-L transcripome, many sequences homologous to the plant or bacteria proteins in the post-transcriptional, post-translational modification, and signal-transduction KEGG pathways, are absent in the nonpsychrophilic green algae. These complex structural components might imply enhanced stress adaptation capacity. At last, differential gene expression analysis at the transcriptome level of ICE-L indicated that genes that associated with post-translational modification, lipid metabolism, and nitrogen metabolism are responding to the freezing treatment. In conclusion, the transcriptome of Chlamydomonas sp. ICE-L is very useful for exploring the mutualistic interaction between microalgae and bacteria in sea ice; and discovering the specific genes and metabolism pathways responding to the freezing acclimation in psychrophilic microalgae. PMID:27161450

  20. Trophic transfer of gold nanoparticles from Euglena gracilis or Chlamydomonas reinhardtii to Daphnia magna

    International Nuclear Information System (INIS)

    Understanding the trophic transfer of nanoparticles (NPs) is important because NPs are small enough to easily penetrate into organisms. In this study, we evaluated the trophic transfer of gold NPs (AuNPs) within the aquatic food chain. We observed AuNPs transfer from 2 species of primary producers (Chlamydomonas reinhardtii or Euglena gracilis) to the primary consumer (Daphnia magna). Also, bioaccumulation of AuNPs in E. gracilis was higher than that in C. reinhardtii. The reasons for the difference in Au accumulation may be the physical structure of these organisms, and the surface area that is available for interaction with NPs. C. reinhardtii has a cell wall that may act as a barrier to the penetration of NPs. The size of E. gracilis is larger than that of C. reinhardtii. This study demonstrates the trophic transfer of AuNPs from a general producer to a consumer in an aquatic environment. - Highlights: • This study evaluated the trophic transfer of AuNPs in an aquatic food chain. • Chlamydomonas reinhardtii and Euglena gracilis were selected as the primary producers. • Daphnia magna was used as the primary consumer. • The bioaccumulation of AuNPs in E. gracilis was higher than that in C. reinhardtii. • AuNPs were transferred from C. reinhardtii and E. gracilis to D. magna. - Gold nanoparticles can transfer from primary producers (Chlamydomonas reinhardtii or Euglena gracilis) to the primary consumer (Daphnia magna) in an aquatic environment

  1. Engineering the chloroplast targeted malarial vaccine antigens in Chlamydomonas starch granules.

    Directory of Open Access Journals (Sweden)

    David Dauvillée

    Full Text Available BACKGROUND: Malaria, an Anopheles-borne parasitic disease, remains a major global health problem causing illness and death that disproportionately affects developing countries. Despite the incidence of malaria, which remains one of the most severe infections of human populations, there is no licensed vaccine against this life-threatening disease. In this context, we decided to explore the expression of Plasmodium vaccine antigens fused to the granule bound starch synthase (GBSS, the major protein associated to the starch matrix in all starch-accumulating plants and algae such as Chlamydomonas reinhardtii. METHODS AND FINDINGS: We describe the development of genetically engineered starch granules containing plasmodial vaccine candidate antigens produced in the unicellular green algae Chlamydomonas reinhardtii. We show that the C-terminal domains of proteins from the rodent Plasmodium species, Plasmodium berghei Apical Major Antigen AMA1, or Major Surface Protein MSP1 fused to the algal granule bound starch synthase (GBSS are efficiently expressed and bound to the polysaccharide matrix. Mice were either immunized intraperitoneally with the engineered starch particles and Freund adjuvant, or fed with the engineered particles co-delivered with the mucosal adjuvant, and challenged intraperitoneally with a lethal inoculum of P. Berghei. Both experimental strategies led to a significantly reduced parasitemia with an extension of life span including complete cure for intraperitoneal delivery as assessed by negative blood thin smears. In the case of the starch bound P. falciparum GBSS-MSP1 fusion protein, the immune sera or purified immunoglobulin G of mice immunized with the corresponding starch strongly inhibited in vitro the intra-erythrocytic asexual development of the most human deadly plasmodial species. CONCLUSION: This novel system paves the way for the production of clinically relevant plasmodial antigens as algal starch-based particles

  2. A transposon with an unusual arrangement of long terminal repeats in the green alga Chlamydomonas reinhardtii.

    OpenAIRE

    Day, A; Schirmer-Rahire, M; Kuchka, M R; Mayfield, S P; Rochaix, J D

    1988-01-01

    We have isolated a 5.7-kbp dispersed moderately repeated DNA sequence (TOC1) from the mutant OEE1 gene of the Chlamydomonas reinhardtii strain FUD44. The copy number (2 to over 30) and genomic locations of TOC1 elements vary widely in different C. reinhardtii strains. Our standard laboratory photosynthetic strain exhibits a high degree of TOC1 instability during short periods of mitotic growth. TOC1 appears to be a retrotransposon: it contains LTRs and an oligonucleotide stretch that correspo...

  3. Molecular studies of linkage group XIX of Chlamydomonas reinhardtii: evidence against a basal body location

    OpenAIRE

    1991-01-01

    Linkage group XIX (also known as the UNI linkage group) in the green alga, Chlamydomonas reinhardtii, exhibits a number of unusual properties that have lead to the suggestion that it represents a basal body-associated chromosome. To begin a molecular analysis of this linkage group, we have identified DNA sequences from it and used them to determine the copy number of linkage group XIX within the cell. We find that linkage group XIX is present in the same copy number per cell as nuclear linkag...

  4. Effect of temperature and light intensity on growth and photosynthetic activity of Chlamydomonas Reinhardtii

    International Nuclear Information System (INIS)

    The effect of five temperatures (15, 20, 25, 30 and 350C) and two levels of illumination on growth and photosynthetic activity of Chlamydomonas reinhardtii has been studied. The growth of the cultures was evaluated by optical density. Photosynthetic activity has been carried out studying either the assimilation rate of CO2 labelled with C 14 or the oxygen evolution by means of polarographic measurements. The maximum photosynthetic rate has been obtained at 250C for the lower lavel of illumination (2400 lux) and at 350C for the higher one (13200 lux). These results suggest an interacton of temperature and illumination on photosynthetic activity. (author)

  5. Multiple facets of anoxic metabolism and hydrogen production in the unicellular green alga Chlamydomonas reinhardtii.

    Science.gov (United States)

    Grossman, Arthur R; Catalanotti, Claudia; Yang, Wenqiang; Dubini, Alexandra; Magneschi, Leonardo; Subramanian, Venkataramanan; Posewitz, Matthew C; Seibert, Michael

    2011-04-01

    Many microbes in the soil environment experience micro-oxic or anoxic conditions for much of the late afternoon and night, which inhibit or prevent respiratory metabolism. To sustain the production of energy and maintain vital cellular processes during the night, organisms have developed numerous pathways for fermentative metabolism. This review discusses fermentation pathways identified for the soil-dwelling model alga Chlamydomonas reinhardtii, its ability to produce molecular hydrogen under anoxic conditions through the activity of hydrogenases, and the molecular flexibility associated with fermentative metabolism that has only recently been revealed through the analysis of specific mutant strains. PMID:21563367

  6. Ciliary kinematics of Chlamydomonas reinhardtii in Complex Fluids: Role of viscosity

    Science.gov (United States)

    Gopinath, Arvind; Qin, Boyang; Arratia, Paulo

    2014-11-01

    The motility behavior of microorganisms can be significantly affected by the rheology of their fluidic environment. Guided by our experiments on the swimming gait of Chlamydomonas reinhardtii in viscoelastic fluids, we focus on ciliary waveforms in Newtonian fluids and systematically study the effect of increasing viscosity. We find that the beat frequency as well as the wave speed are both strongly influenced by fluid viscosity. Interestingly, ciliary waveforms at low viscosity show a larger influence of the cell body than waveforms at higher viscosity. We use slender body theory and principal component analysis to elucidate the role of fluid viscosity in regulating the kinematics of the swimming process.

  7. Protocol: methodology for chromatin immunoprecipitation (ChIP in Chlamydomonas reinhardtii

    Directory of Open Access Journals (Sweden)

    Strenkert Daniela

    2011-11-01

    Full Text Available Abstract We report on a detailed chromatin immunoprecipitation (ChIP protocol for the unicellular green alga Chlamydomonas reinhardtii. The protocol is suitable for the analysis of nucleosome occupancy, histone modifications and transcription factor binding sites at the level of mononucleosomes for targeted and genome-wide studies. We describe the optimization of conditions for crosslinking, chromatin fragmentation and antibody titer determination and provide recommendations and an example for the normalization of ChIP results as determined by real-time PCR.

  8. Emergent Run-and-Tumble Behavior in a Simple Model of Chlamydomonas with Intrinsic Noise

    Science.gov (United States)

    Bennett, Rachel R.; Golestanian, Ramin

    2013-04-01

    Recent experiments on the green alga Chlamydomonas that swims using synchronized beating of a pair of flagella have revealed that it exhibits a run-and-tumble behavior similar to that of bacteria such as E. coli. Using a simple purely hydrodynamic model that incorporates a stroke cycle and an intrinsic Gaussian white noise, we show that a stochastic run-and-tumble behavior could emerge due to the nonlinearity of the combined synchronization-rotation-translation dynamics. Our study suggests that nonlinear mechanics could be a significant contributing factor to how the trajectories of the microorganism are selected.

  9. Emergent run-and-tumble behavior in a simple model of Chlamydomonas with intrinsic noise.

    Science.gov (United States)

    Bennett, Rachel R; Golestanian, Ramin

    2013-04-01

    Recent experiments on the green alga Chlamydomonas that swims using synchronized beating of a pair of flagella have revealed that it exhibits a run-and-tumble behavior similar to that of bacteria such as E. coli. Using a simple purely hydrodynamic model that incorporates a stroke cycle and an intrinsic Gaussian white noise, we show that a stochastic run-and-tumble behavior could emerge due to the nonlinearity of the combined synchronization-rotation-translation dynamics. Our study suggests that nonlinear mechanics could be a significant contributing factor to how the trajectories of the microorganism are selected. PMID:25167039

  10. Population Dynamics of Chlamydomonas sajao and Its Influence on Soil Aggregate Stabilization in the Field

    OpenAIRE

    Metting, Blaine

    1986-01-01

    Chlamydomonas sajao, a single-celled, eucaryotic microalga, was inoculated onto replicated field plots cropped to corn at two rates (5 × 1011 and 5 × 107 log-phase cells ha−1) to assess colonization, reproduction, and persistence, changes in soil carbohydrate content, and wet stability of 0.92- to 1.68-mm-sized aggregates from the surface 2- to 3-mm soil veneer. The most-probable-number technique and extraction and fluorometric quantification of chlorophyll were used as indices of microalgal ...

  11. Effect of O2:CO2 Ratio on the Primary Metabolism of Chlamydomonas reinhardtii

    OpenAIRE

    Kliphuis, A.M.J.; Martens, D. E.; Janssen, M.G.J.; Wijffels, R.H.

    2011-01-01

    High oxygen:carbon dioxide ratios may have a negative effect on growth and productivity of microalgae. To investigate the effect of O2 and CO2 concentrations and the ratio between these on the metabolism of Chlamydomonas reinhardtii we performed turbidostat experiments at different O2:CO2 ratios. These experiments showed that elevated O2 concentrations and the corresponding increase in the ratio of O2:CO2 common in photobioreactors led to a reduction of growth and biomass yield on light with ...

  12. Characterization of a Synechococcus sp. strain PCC 7002 spontaneous mutant strain defective in accumulation of photosystem II core chlorophyll-protein complexes.

    OpenAIRE

    Webb, R.; Punnett, T

    1989-01-01

    Two photosystem II-associated chlorophyll-protein complexes of Synechococcus sp. strain PCC 7002 were identified. Their polypeptide compositions were similar to those of chlorophyll-containing antenna complexes of other cyanobacteria. Strain GT8B did not possess the complex responsible for 695-nm fluorescence and was unable to grow photoautotrophically; hence, this complex is necessary for photosystem II function in vivo.

  13. Lack of Set Theory Relevant Prerequisite Knowledge

    Science.gov (United States)

    Dogan-Dunlap, Hamide

    2006-01-01

    Many students struggle with college mathematics topics due to a lack of mastery of prerequisite knowledge. Set theory language is one such prerequisite for linear algebra courses. Many students' mistakes on linear algebra questions reveal a lack of mastery of set theory knowledge. This paper reports the findings of a qualitative analysis of a…

  14. Light-induced gradual activation of photosystem II in dark-grown Norway spruce seedlings.

    Science.gov (United States)

    Pavlovič, Andrej; Stolárik, Tibor; Nosek, Lukáš; Kouřil, Roman; Ilík, Petr

    2016-06-01

    Gymnosperms, unlike angiosperms, are able to synthesize chlorophyll and form photosystems in complete darkness. Photosystem I (PSI) formed under such conditions is fully active, but photosystem II (PSII) is present in its latent form with inactive oxygen evolving complex (OEC). In this work we have studied light-induced gradual changes in PSII function in dark-grown cotyledons of Norway spruce (Picea abies) via the measurement of chlorophyll a fluorescence rise, absorption changes at 830nm, thermoluminescence glow curves (TL) and protein analysis. The results indicate that in dark-grown cotyledons, alternative reductants were able to act as electron donors to PSII with inactive OEC. Illumination of cotyledons for 5min led to partial activation of PSII, which was accompanied by detectable oxygen evolution, but still a substantial number of PSII centers remained in the so called PSII-QB-non-reducing form. Interestingly, even 24h long illumination was not sufficient for the full activation of PSII centers. This was evidenced by a weak attachment of PsbP protein and the absence of PsbQ protein in PSII particles, the absence of PSII supercomplexes, the suboptimal maximum yield of PSII photochemistry, the presence of C band in TL curve and also the presence of up-shifted Q band in TL in DCMU-treated cotyledons. This slow light-induced activation of PSII in dark-grown cotyledons could contribute to the prevention of PSII overexcitation before the light-induced increase in PSI/PSII ratio allows effective operation of linear electron flow. PMID:26901522

  15. Stable expression of a bifunctional diterpene synthase in the chloroplast of Chlamydomonas reinhardtii

    DEFF Research Database (Denmark)

    Zedler, Julie A Z; Gangl, Doris; Hamberger, Björn Robert;

    2015-01-01

    Chlamydomonas reinhardtii has been shown to hold significant promise as a production platform for recombinant proteins, but transformation of the nuclear genome is still a non-trivial process due to random gene insertion and frequent silencing. Insertion of transgenes into the chloroplasts is an...

  16. Chloroplast genetics of chlamydomonas. I. Allelic segregation ratios

    International Nuclear Information System (INIS)

    This paper presents allelic segregation data from a series of 16 crosses segregated for nuclear and chloroplast genes. By means of pedigree analysis, segregants of chloroplast genes. By means of pedigree analysis, segregants of chloroplast markers occurring in the zygote have been distinguished from those occurring in zoospore clones. The genes ac1, ac2, and tm1 showed little if any deviation from 1:1 either in zygotic segregation or in zoospore clones. The genes sm2, ery, and spc showed a significant excess of the allele from the mt+ parent in zygotes. However, in zoospores, mt+ excess was seen only when the allele was the mutant (resistant) form but not when it was wild type (sensitive). These results show that the extent of preferential segregation differs in zygotes and in zoospores, and that preferential segregation is influenced by map location and by allele specificity. A comparison of progeny from zygotes mated after 0, 15'', 30'', and 50'' uv irradiation of the mt+ gametes demonstrated the lack of an effect of uv upon allelic segregation ratios. In total, these results exclude the multi-copy model of chloroplast genome segregation suggested by Gillham. Boynton and Lee (1974) and support the diploid model we have previously proposed

  17. Chloroplast genetics of chlamydomonas. I. Allelic segregation ratios. [UV radiation

    Energy Technology Data Exchange (ETDEWEB)

    Sager, R.; Ramanis, Z.

    1976-06-01

    This paper presents allelic segregation data from a series of 16 crosses segregated for nuclear and chloroplast genes. By means of pedigree analysis, segregants of chloroplast genes. By means of pedigree analysis, segregants of chloroplast markers occurring in the zygote have been distinguished from those occurring in zoospore clones. The genes ac1, ac2, and tm1 showed little if any deviation from 1:1 either in zygotic segregation or in zoospore clones. The genes sm2, ery, and spc showed a significant excess of the allele from the mt+ parent in zygotes. However, in zoospores, mt+ excess was seen only when the allele was the mutant (resistant) form but not when it was wild type (sensitive). These results show that the extent of preferential segregation differs in zygotes and in zoospores, and that preferential segregation is influenced by map location and by allele specificity. A comparison of progeny from zygotes mated after 0, 15'', 30'', and 50'' uv irradiation of the mt+ gametes demonstrated the lack of an effect of uv upon allelic segregation ratios. In total, these results exclude the multi-copy model of chloroplast genome segregation suggested by Gillham. Boynton and Lee (1974) and support the diploid model we have previously proposed.

  18. Enhanced methane production of Chlorella vulgaris and Chlamydomonas reinhardtii by hydrolytic enzymes addition

    International Nuclear Information System (INIS)

    Highlights: • Methane production of microalgae biomass is hampered by their cell wall. • Pretreatment should be designed in accordance to the microalgae specie. • Fresh Chlamydomonas reinhardtii exhibited high anaerobic biodegradability. • Chlorella vulgaris anaerobic biodegradability was enhanced by 50% using protease pretreatment. - Abstract: The effect of enzymatic hydrolysis on microalgae organic matter solubilisation and methane production was investigated in this study. Even though both biomasses, Chlamydomonas reinhardtii and Chlorella vulgaris, exhibited similar macromolecular distribution, their cell wall composition provided different behaviors. The addition of carbohydrolase (Viscozyme) and protease (Alcalase) resulted in high carbohydrates and protein solubilisation on both biomasses (86–96%). Despite the high carbohydrate solubilisation with the carbohydrolase, methane production was enhanced by 14% for C. vulgaris, while hydrolyzed C. reinhardtii did not show any improvement. The addition of protease to C. reinhardtii increased methane production by 1.17-fold. The low enhancement achieved together with the inherent high biodegradability of this biomass would not justify the cost associated to the enzyme addition. On the other hand, C. vulgaris hydrolyzed with the protease resulted in 86% anaerobic biodegradability compared to 54% of the raw biomass. Therefore, the application of protease prior anaerobic digestion of C. vulgaris could be a promising approach to decrease the energetic input required for cell wall disruption

  19. Experimental Genome-Wide Determination of RNA Polyadenylation in Chlamydomonas reinhardtii.

    Directory of Open Access Journals (Sweden)

    Stephen A Bell

    Full Text Available The polyadenylation of RNA is a near-universal feature of RNA metabolism in eukaryotes. This process has been studied in the model alga Chlamydomonas reinhardtii using low-throughput (gene-by-gene and high-throughput (transcriptome sequencing approaches that recovered poly(A-containing sequence tags which revealed interesting features of this critical process in Chlamydomonas. In this study, RNA polyadenylation has been studied using the so-called Poly(A Tag Sequencing (PAT-Seq approach. Specifically, PAT-Seq was used to study poly(A site choice in cultures grown in four different media types-Tris-Phosphate (TP, Tris-Phosphate-Acetate (TAP, High-Salt (HS, and High-Salt-Acetate (HAS. The results indicate that: 1. As reported before, the motif UGUAA is the primary, and perhaps sole, cis-element that guides mRNA polyadenylation in the nucleus; 2. The scope of alternative polyadenylation events with the potential to change the coding sequences of mRNAs is limited; 3. Changes in poly(A site choice in cultures grown in the different media types are very few in number and do not affect protein-coding potential; 4. Organellar polyadenylation is considerable and affects primarily ribosomal RNAs in the chloroplast and mitochondria; and 5. Organellar RNA polyadenylation is a dynamic process that is affected by the different media types used for cell growth.

  20. Measurement of Lipid Droplet Accumulation Kinetics in Chlamydomonas reinhardtii Using Seoul-Fluor

    Directory of Open Access Journals (Sweden)

    Noo Li Jeon

    2013-10-01

    Full Text Available Alternative energy resources have become an important issue due to the limited stocks of petroleum-based fuel. Microalgae, a source of renewable biodiesel, use solar light to convert CO2 into lipid droplets (LDs. Quantification of LDs in microalgae is required for developing and optimizing algal bioprocess engineering. However, conventional quantification methods are both time and labor-intensive and difficult to apply in high-throughput screening systems. LDs in plant and mammalian cells can be visualized by staining with various fluorescence probes such as the Nile Red, BODIPY, and Seoul-Fluor (SF series. This report describes the optimization of LD staining in Chlamydomonas reinhardtii with SF probes via systematic variations of dye concentration, staining time, temperature, and pH. A protocol for quantitative measurement of accumulation kinetics of LDs in C. reinhardtii was developed using a spectrofluorimeter and the accuracy of LD size measurement was confirmed by transmission electron microscopy (TEM. Our results indicate that our spectrofluorimeter-based measurement approach can monitor kinetics of intracellular LDs (in control and nitrogen-source-starved Chlamydomonas reinhardtii accumulation that has not been possible in the case of conventional imaging-based methods. Our results presented here confirmed that an SF44 can be a powerful tool for in situ monitoring and tracking of intracellular LDs formation.

  1. Biofixation of Carbon dioxide by Chlamydomonas sp. in a Tubular Photobioreactor

    Directory of Open Access Journals (Sweden)

    H Hadiyanto

    2012-02-01

    Full Text Available The biogas production from anaerobic digestion is a potential fuel for power generators application, if biogas can be upgraded to the same standards as fossil natural gas by CO2, H2S, and other non-combustible component removal. Microalgae Chlamydomonas sp. has potency to biofix the carbon dioxide and can be used as an additional food ingredient. The variations of flow rate and carbon dioxide concentration in the process resulting different value of biomass production and carbon dioxide biofixation. Biomass production at 40% carbon dioxide concentration obtained 5.685 gr/dm3 at 10% carbon dioxide concentration obtained 4.892 gr/dm3. The greatest value of carbon dioxide absorption occurs at a 40% concentration amounting to 12.09%. The rate of growth and productivity of microalgae tend to rise in 10% and 20% (%v carbon dioxide concentration, but began started a constant at 30% and 40% (%v carbon dioxide concentration. Biomass production tends to increase in light conditions while a constant in dark conditions. This study used Chlamydomonas sp. as media culture and performed on bubble column and tubular reactor with 6 litres of culture medium at a temperature of 28oC and atmospheric pressure.

  2. Characterization of DNA repair deficient strains of Chlamydomonas reinhardtii generated by insertional mutagenesis.

    Directory of Open Access Journals (Sweden)

    Andrea Plecenikova

    Full Text Available While the mechanisms governing DNA damage response and repair are fundamentally conserved, cross-kingdom comparisons indicate that they differ in many aspects due to differences in life-styles and developmental strategies. In photosynthetic organisms these differences have not been fully explored because gene-discovery approaches are mainly based on homology searches with known DDR/DNA repair proteins. Here we performed a forward genetic screen in the green algae Chlamydomonas reinhardtii to identify genes deficient in DDR/DNA repair. We isolated five insertional mutants that were sensitive to various genotoxic insults and two of them exhibited altered efficiency of transgene integration. To identify genomic regions disrupted in these mutants, we established a novel adaptor-ligation strategy for the efficient recovery of the insertion flanking sites. Four mutants harbored deletions that involved known DNA repair factors, DNA Pol zeta, DNA Pol theta, SAE2/COM1, and two neighbouring genes encoding ERCC1 and RAD17. Deletion in the last mutant spanned two Chlamydomonas-specific genes with unknown function, demonstrating the utility of this approach for discovering novel factors involved in genome maintenance.

  3. Characterization of Hydrocortisone Biometabolites and 18S rRNA Gene in Chlamydomonas reinhardtii Cultures

    Directory of Open Access Journals (Sweden)

    Seyed Bagher Mosavi-Azam

    2008-10-01

    Full Text Available A unicellular microalga, Chlamydomonas reinhardtii, was isolated from rice paddy-field soil and water samples and used in the biotransformation of hydrocortisone (1. This strain has not been previously tested for steroid bioconversion. Fermentation was carried out in BG-11 medium supplemented with 0.05% substrate at 25ºC for 14 days of incubation. The products obtained were chromatographically purified and characterized using spectroscopic methods. 11b,17b-Dihydroxyandrost-4-en-3-one (2, 11b-hydroxyandrost-4-en-3,17-dione (3, 11b,17a,20b,21-tetrahydroxypregn-4-en-3-one (4 and prednisolone (5 were the main products of the bioconversion. The observed bioreaction features were the side chain degradation of the substrate to give compounds 2 and 3 and the 20-ketone reduction and 1,2-dehydrogenation affording compounds 4 and 5, respectively. A time course study showed the accumulation of product 2 from the second day of the fermentation and of compounds 3, 4 and 5 from the third day. All the metabolites reached their maximum concentration in seven days. Microalgal 18S rRNA gene was also amplified by PCR. PCR products were sequenced to confirm their authenticity as 18S rRNA gene of microalgae. The result of PCR blasted with other sequenced microalgae in NCBI showed 100% homology to the 18S small subunit rRNA of two Chlamydomonas reinhardtii spp.

  4. Overexpression of Ferredoxin, PETF, Enhances Tolerance to Heat Stress in Chlamydomonas reinhardtii

    Directory of Open Access Journals (Sweden)

    Li-Fen Huang

    2013-10-01

    Full Text Available Reactive oxygen species (ROS produced by plants in adverse environments can cause damage to organelles and trigger cell death. Removal of excess ROS can be achieved through the ascorbate scavenger pathway to prevent plant cell death. The amount of this scavenger can be regulated by ferredoxin (FDX. Chloroplastic FDXs are electron transfer proteins that perform in distributing photosynthetic reducing power. In this study, we demonstrate that overexpression of the endogenous photosynthetic FDX gene, PETF, in Chlamydomonas reinhardtii could raise the level of reduced ascorbate and diminish H2O2 levels under normal growth conditions. Furthermore, the overexpressing PETF transgenic Chlamydomonas lines produced low levels of H2O2 and exhibited protective effects that were observed through decreased chlorophyll degradation and increased cell survival under heat-stress conditions. The findings of this study suggest that overexpression of PETF can increase the efficiency of ROS scavenging in chloroplasts to confer heat tolerance. The roles of PETF in the downregulation of the ROS level offer a method for potentially improving the tolerance of crops against heat stress.

  5. Proteomic Alterations of Antarctic Ice Microalga Chlamydomonas sp. Under Low-Temperature Stress

    Institute of Scientific and Technical Information of China (English)

    Guang-Feng Kan; Jin-Lai Miao; Cui-Juan Shi; Guang-You Li

    2006-01-01

    Antarctic ice microalga can survive and thrive in cold channels or pores in the Antarctic ice layer. In order to understand the adaptive mechanisms to low temperature, in the present study we compared two-dimensional polyacrylamide gel electrophoresis (2-DE) profiles of normal and low temperature-stressed Antarctic ice microalga Chlamydomonas sp. cells. In addition, new protein spots induced by low temperature were identified with peptide mass fingerprinting based on matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and database searching. Well-resolved and reproducible 2-DE patterns of both normal and low temperature-stressed cells were acquired. A total of 626 spots was detected in control cells and 652 spots were detected in the corresponding low temperature-stressed cells. A total of 598 spots was matched between normal and stressed cells. Two newly synthesized proteins (a and b) in low temperature-stressed cells were characterized. Protein spot A (53 kDa, pI 6.0) was similar to isopropylmalate/homocitrate/citramalate synthases, which act in the transport and metabolism of amino acids. Protein spot b (25 kDa, pI 8.0) was related to glutathione S-transferase, which functions as a scavenger of active oxygen, free radicals, and noxious metabolites. The present study is valuable for the application of ice microalgae, establishing an ice microalga Chlamydomonas sp. proteome database, and screening molecular biomarkers for further studies.

  6. CRISPR/Cas9-induced knockout and knock-in mutations in Chlamydomonas reinhardtii.

    Science.gov (United States)

    Shin, Sung-Eun; Lim, Jong-Min; Koh, Hyun Gi; Kim, Eun Kyung; Kang, Nam Kyu; Jeon, Seungjib; Kwon, Sohee; Shin, Won-Sub; Lee, Bongsoo; Hwangbo, Kwon; Kim, Jungeun; Ye, Sung Hyeok; Yun, Jae-Young; Seo, Hogyun; Oh, Hee-Mock; Kim, Kyung-Jin; Kim, Jin-Soo; Jeong, Won-Joong; Chang, Yong Keun; Jeong, Byeong-Ryool

    2016-01-01

    Genome editing is crucial for genetic engineering of organisms for improved traits, particularly in microalgae due to the urgent necessity for the next generation biofuel production. The most advanced CRISPR/Cas9 system is simple, efficient and accurate in some organisms; however, it has proven extremely difficult in microalgae including the model alga Chlamydomonas. We solved this problem by delivering Cas9 ribonucleoproteins (RNPs) comprising the Cas9 protein and sgRNAs to avoid cytotoxicity and off-targeting associated with vector-driven expression of Cas9. We obtained CRISPR/Cas9-induced mutations at three loci including MAA7, CpSRP43 and ChlM, and targeted mutagenic efficiency was improved up to 100 fold compared to the first report of transgenic Cas9-induced mutagenesis. Interestingly, we found that unrelated vectors used for the selection purpose were predominantly integrated at the Cas9 cut site, indicative of NHEJ-mediated knock-in events. As expected with Cas9 RNPs, no off-targeting was found in one of the mutagenic screens. In conclusion, we improved the knockout efficiency by using Cas9 RNPs, which opens great opportunities not only for biological research but also industrial applications in Chlamydomonas and other microalgae. Findings of the NHEJ-mediated knock-in events will allow applications of the CRISPR/Cas9 system in microalgae, including "safe harboring" techniques shown in other organisms. PMID:27291619

  7. Spontaneous mutations in the ammonium transport gene AMT4 of Chlamydomonas reinhardtii.

    Science.gov (United States)

    Kim, Kwang-Seo; Feild, Eithne; King, Natalie; Yaoi, Takuro; Kustu, Sydney; Inwood, William

    2005-06-01

    Evidence in several microorganisms indicates that Amt proteins are gas channels for NH(3) and CH(3)NH(2), and this has been confirmed structurally. Chlamydomonas reinhardtii has at least four AMT genes, the most reported for a microorganism. Under nitrogen-limiting conditions all AMT genes are transcribed and Chlamydomonas is sensitive to methylammonium toxicity. All 16 spontaneous methylammonium-resistant mutants that we analyzed had defects in accumulation of [(14)C]methylammonium. Genetic crosses indicated that 12 had lesions in a single locus, whereas two each had lesions in other loci. Lesions in different loci were correlated with different degrees of defect in [(14)C]methylammonium uptake. One mutant in the largest class had an insert in the AMT4 gene, and the insert cosegregated with methylammonium resistance in genetic crosses. The other 11 strains in this class also had amt4 lesions, which we characterized at the molecular level. Properties of the amt4 mutants were clearly different from those of rh1 RNAi lines. They indicated that the physiological substrates for Amt and Rh proteins, the only two members of their protein superfamily, are NH(3) and CO(2), respectively. PMID:15802504

  8. Biofixation of Carbon dioxide by Chlamydomonas sp. in a Tubular Photobioreactor

    Directory of Open Access Journals (Sweden)

    H Hadiyanto

    2012-04-01

    Full Text Available The biogas production from anaerobic digestion is a potential fuel for power generators application, if biogas can be upgraded to the same standards as fossil natural gas by CO2, H2S, and other non-combustible component removal. Microalgae Chlamydomonas sp. has potency to biofix the carbon dioxide and can be used as an additional food ingredient. The variations of flow rate and carbon dioxide concentration in the process resulting different value of biomass production and carbon dioxide biofixation. Biomass production at 40% carbon dioxide concentration obtained 5.685 gr/dm3 at 10% carbon dioxide concentration obtained 4.892 gr/dm3. The greatest value of carbon dioxide absorption occurs at a 40% concentration amounting to 12.09%. The rate of growth and productivity of microalgae tend to rise in 10% and 20% (%v carbon dioxide concentration, but began started a constant at 30% and 40% (%v carbon dioxide concentration. Biomass production tends to increase in light conditions while a constant in dark conditions. This study used Chlamydomonas sp. as media culture and performed on bubble column and tubular reactor with 6 litres of culture medium at a temperature of 28oC and atmospheric pressure.

  9. CRISPR/Cas9-induced knockout and knock-in mutations in Chlamydomonas reinhardtii

    Science.gov (United States)

    Shin, Sung-Eun; Lim, Jong-Min; Koh, Hyun Gi; Kim, Eun Kyung; Kang, Nam Kyu; Jeon, Seungjib; Kwon, Sohee; Shin, Won-Sub; Lee, Bongsoo; Hwangbo, Kwon; Kim, Jungeun; Ye, Sung Hyeok; Yun, Jae-Young; Seo, Hogyun; Oh, Hee-Mock; Kim, Kyung-Jin; Kim, Jin-Soo; Jeong, Won-Joong; Chang, Yong Keun; Jeong, Byeong-ryool

    2016-01-01

    Genome editing is crucial for genetic engineering of organisms for improved traits, particularly in microalgae due to the urgent necessity for the next generation biofuel production. The most advanced CRISPR/Cas9 system is simple, efficient and accurate in some organisms; however, it has proven extremely difficult in microalgae including the model alga Chlamydomonas. We solved this problem by delivering Cas9 ribonucleoproteins (RNPs) comprising the Cas9 protein and sgRNAs to avoid cytotoxicity and off-targeting associated with vector-driven expression of Cas9. We obtained CRISPR/Cas9-induced mutations at three loci including MAA7, CpSRP43 and ChlM, and targeted mutagenic efficiency was improved up to 100 fold compared to the first report of transgenic Cas9-induced mutagenesis. Interestingly, we found that unrelated vectors used for the selection purpose were predominantly integrated at the Cas9 cut site, indicative of NHEJ-mediated knock-in events. As expected with Cas9 RNPs, no off-targeting was found in one of the mutagenic screens. In conclusion, we improved the knockout efficiency by using Cas9 RNPs, which opens great opportunities not only for biological research but also industrial applications in Chlamydomonas and other microalgae. Findings of the NHEJ-mediated knock-in events will allow applications of the CRISPR/Cas9 system in microalgae, including “safe harboring” techniques shown in other organisms. PMID:27291619

  10. Light and Heat Induced Denaturation of Photosystem Ⅱ Core Antenna Complex CP47

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    Light and heat induced denaturation of CP47, the core antenna complex of photosystem Ⅱ purified from spinach, were investigated using absorption and circular dichroism spectra.Light caused the destruction of chlorophyll a and excitonic interaction of chlorophyll a in CP47, while the protein secondary structure was not apparently changed.Heat induced the destruction of protein secondary structure and excitonic interaction of chlorophyll a, but the chlorophyll a molecule was not damaged.The results suggest that both the chlorophyll a molecular structure and the protein native conformation are necessary for excitonic interaction of chlorophyll a and the energy transfer function of the chlorophyll a binding protein.

  11. Molecular dynamics studies of pathways of water movement in cyanobacterial photosystem II

    Energy Technology Data Exchange (ETDEWEB)

    Gabdulkhakov, A. G., E-mail: azat@vega.protres.ru; Kljashtorny, V. G.; Dontsova, M. V. [Russian Academy of Sciences, Institute of Protein Research (Russian Federation)

    2015-01-15

    Photosystem II (PSII) catalyzes the light-induced generation of oxygen from water. The oxygen-evolving complex is buried deep in the protein on the lumenal side of PSII, and water molecules need to pass through protein subunits to reach the active site—the manganese cluster. Previous studies on the elucidation of water channels in PSII were based on an analysis of the cavities in the static PSII structure determined by X-ray diffraction. In the present study, we perform molecular dynamics simulations of the water movement in the transport system of PSII.

  12. X-Ray Powder Diffraction from Sub-Micron Crystals of Photosystem-1 Membrane Protein

    OpenAIRE

    Shapiro, D. A.; DePonte, D.; Doak, R. B.; Fromme, P.; Hembree, G.; Hunter, M; Marchesini, S.; Schmidt, K.; Starodub, D.; Weierstall, U.; Chapman, H.; Spence, J

    2008-01-01

    We demonstrate that powder diffraction data can be collected from sub-micron crystals of a mbrane protein with nearly two orders of magnitude more atoms than the molecules commonly used for powder diffraction. The crystals of photosystem-1 protein were size-selected using a 500 nm pore- size filter and delivered to a soft x-ray beam with a photon energy of 1.5 keV using a dynamically focused micro-jet developed for the serial crystallography experiment at beamline 9.0.1. The 10-micron jet pla...

  13. The thermostability of photosystem II photochemistry is related to maintenance of thylakoid membranes organization

    Czech Academy of Sciences Publication Activity Database

    Karlický, Václav; Kurasová, I.; Špunda, Vladimír

    Brno: Global Change Research Centre, The Czech Academy of Sciences, v. v. i., 2015 - (Urban, O.; Šprtová, M.; Klem, K.), s. 142-145 ISBN 978-80-87902-10-3. [Global Change: A Complex Challenge /4th/. Brno (CZ), 23.03.2015-24.03.2015] R&D Projects: GA MŠk(CZ) LO1415; GA MŠk(CZ) ED1.1.00/02.0073; GA ČR GA13-28093S Institutional support: RVO:67179843 Keywords : membrane * photosystem * photochemistry Subject RIV: EH - Ecology, Behaviour

  14. Structural changes in the S3 state of the oxygen evolving complex in photosystem II

    Science.gov (United States)

    Hatakeyama, Makoto; Ogata, Koji; Fujii, Katsushi; Yachandra, Vittal K.; Yano, Junko; Nakamura, Shinichiro

    2016-05-01

    The S3 state of the Mn4CaO5-cluster in photosystem II was investigated by DFT calculations and compared with EXAFS data. Considering previously proposed mechanism; a water molecule is inserted into an open coordination site of Mn upon S2 to S3 transition that becomes a substrate water, we examined if the water insertion is essential for the S3 formation, or if one cannot eliminate other possible routes that do not require a water insertion at the S3 stage. The novel S3 state structure consisting of only short 2.7-2.8 Å Mnsbnd Mn distances was discussed.

  15. Hydrogen ions directly regulating the oligomerization state of Photosystem I in intact Spirulina platensis cells

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    H+ concentration induced-monomerization or trimerization of photosystem I (PSI) in cyanobacteria has never been directly observed. In this work, taking characteristic spectra for the trimers and monomers as the indicators, it was experimentally demonstrated that H+ could induce the oligomeric changes of PSI reaction centers in the intact Spirulina ,platensis cells and also in the isolated thylakoid membrane complexes. Especially, the higher concentration of H+ would induce the monomerization while the lower the trimerization, suggesting the electrostatic interaction should be mainly responsible forchanges in the oligomeric state of PSI in Spirulina platensis.

  16. Molecular dynamics studies of pathways of water movement in cyanobacterial photosystem II

    International Nuclear Information System (INIS)

    Photosystem II (PSII) catalyzes the light-induced generation of oxygen from water. The oxygen-evolving complex is buried deep in the protein on the lumenal side of PSII, and water molecules need to pass through protein subunits to reach the active site—the manganese cluster. Previous studies on the elucidation of water channels in PSII were based on an analysis of the cavities in the static PSII structure determined by X-ray diffraction. In the present study, we perform molecular dynamics simulations of the water movement in the transport system of PSII

  17. Identification of pH-sensing Sites in the Light Harvesting Complex Stress-related 3 Protein Essential for Triggering Non-photochemical Quenching in Chlamydomonas reinhardtii.

    Science.gov (United States)

    Ballottari, Matteo; Truong, Thuy B; De Re, Eleonora; Erickson, Erika; Stella, Giulio R; Fleming, Graham R; Bassi, Roberto; Niyogi, Krishna K

    2016-04-01

    Light harvesting complex stress-related 3 (LHCSR3) is the protein essential for photoprotective excess energy dissipation (non-photochemical quenching, NPQ) in the model green algaChlamydomonas reinhardtii Activation of NPQ requires low pH in the thylakoid lumen, which is induced in excess light conditions and sensed by lumen-exposed acidic residues. In this work we have used site-specific mutagenesisin vivoandin vitrofor identification of the residues in LHCSR3 that are responsible for sensing lumen pH. Lumen-exposed protonatable residues, aspartate and glutamate, were mutated to asparagine and glutamine, respectively. By expression in a mutant lacking all LHCSR isoforms, residues Asp(117), Glu(221), and Glu(224)were shown to be essential for LHCSR3-dependent NPQ induction inC. reinhardtii Analysis of recombinant proteins carrying the same mutations refoldedin vitrowith pigments showed that the capacity of responding to low pH by decreasing the fluorescence lifetime, present in the wild-type protein, was lost. Consistent with a role in pH sensing, the mutations led to a substantial reduction in binding the NPQ inhibitor dicyclohexylcarbodiimide. PMID:26817847

  18. Identification, expression and characterization of archaeal-type opsins of Chlamydomonas reinhardtii

    OpenAIRE

    Kateriya, Suneel

    2005-01-01

    Phototaxis and photophobic responses of green algae are mediated by rhodopsin-based photoreceptors that use microbial-type chromophores (all-trans retinal). Analysis of stimuli-response curves of the C. reinhardtii photoreceptor current led to the suggestion that they are based on two photosystems, one of which is more active at low flash intensities, whereas the other dominates at high flash energies. Two cDNA sequences were identified in the EST database of the C.reinhardtii that encoded mi...

  19. Function of the chloroplast hydrogenase in the microalga Chlamydomonas: the role of hydrogenase and state transitions during photosynthetic activation in anaerobiosis.

    Directory of Open Access Journals (Sweden)

    Bart Ghysels

    Full Text Available Like a majority of photosynthetic microorganisms, the green unicellular alga Chlamydomonas reinhardtii may encounter O2 deprived conditions on a regular basis. In response to anaerobiosis or in a respiration defective context, the photosynthetic electron transport chain of Chlamydomonas is remodeled by a state transition process to a conformation that favours the photoproduction of ATP at the expense of reductant synthesis. In some unicellular green algae including Chlamydomonas, anoxia also triggers the induction of a chloroplast-located, oxygen sensitive hydrogenase, which accepts electrons from reduced ferredoxin to convert protons into molecular hydrogen. Although microalgal hydrogen evolution has received much interest for its biotechnological potential, its physiological role remains unclear. By using specific Chlamydomonas mutants, we demonstrate that the state transition ability and the hydrogenase function are both critical for induction of photosynthesis in anoxia. These two processes are thus important for survival of the cells when they are transiently placed in an anaerobic environment.

  20. Function of the chloroplast hydrogenase in the microalga Chlamydomonas: the role of hydrogenase and state transitions during photosynthetic activation in anaerobiosis.

    Science.gov (United States)

    Ghysels, Bart; Godaux, Damien; Matagne, René F; Cardol, Pierre; Franck, Fabrice

    2013-01-01

    Like a majority of photosynthetic microorganisms, the green unicellular alga Chlamydomonas reinhardtii may encounter O2 deprived conditions on a regular basis. In response to anaerobiosis or in a respiration defective context, the photosynthetic electron transport chain of Chlamydomonas is remodeled by a state transition process to a conformation that favours the photoproduction of ATP at the expense of reductant synthesis. In some unicellular green algae including Chlamydomonas, anoxia also triggers the induction of a chloroplast-located, oxygen sensitive hydrogenase, which accepts electrons from reduced ferredoxin to convert protons into molecular hydrogen. Although microalgal hydrogen evolution has received much interest for its biotechnological potential, its physiological role remains unclear. By using specific Chlamydomonas mutants, we demonstrate that the state transition ability and the hydrogenase function are both critical for induction of photosynthesis in anoxia. These two processes are thus important for survival of the cells when they are transiently placed in an anaerobic environment. PMID:23717558

  1. System-level network analysis of nitrogen starvation and recovery in Chlamydomonas reinhardtii reveals potential new targets for increased lipid accumulation

    Czech Academy of Sciences Publication Activity Database

    Valledor, Luis; Furuhashi, T.; Recuenco-Muňoz, L.; Wienkoop, S.; Weckwerth, W.

    2014-01-01

    Roč. 7, č. 171 (2014), s. 1-17. ISSN 1754-6834 Institutional support: RVO:67179843 Keywords : chlamydomonas reinhardtii * lipid accumulation * nitrogen Subject RIV: EI - Biotechnology ; Bionics Impact factor: 6.044, year: 2014

  2. Simulations of the polarisation-dependent Raman intensity of β-carotene in photosystem II crystals

    International Nuclear Information System (INIS)

    Highlights: • First polarisation-dependent Raman spectroscopy on photosystem II crystals. • Orientation-dependent Raman intensity simulations for di- and monomeric crystals. • Simulations account for all β-carotenes (β-Car) in the unit cell for the first time. • Prediction for identificationy of the β-Car cation in side-path electron transport. - Abstract: In order to clarify possibilities to identify the β-carotene (β-Car) radicals in secondary electron transfer (ET) reactions in the photosystem II core complex (PSIIcc), Raman intensities of all 96 β-Car cofactors in the unit cell of PSIIcc-dimer crystals as a function of polarisation and crystal orientation were simulated based on the 2.9 Å resolution structure. The Raman-active symmetry Ag in the C2h group is assigned to the β-Car modes ν66 and ν67. Simulations are in agreement with experiment for off-resonant excitation at 1064 nm. Resonant measurements at 476 and 532 nm excitation can not be explained, which is attributed to mode mixing in the excited state and the existence of different spectral pools. The identity of the β-Car oxidised in secondary ET can not be resolved by Raman measurements on PSIIcc-dimer crystals. Additional simulations show that similar measurements on PSIIcc-monomer crystals could provide a possible route to solve this issue

  3. Photochemical reactions of chlorophyll in dehydrated photosystem II: two chlorophyll forms (680 and 700 nm).

    Science.gov (United States)

    Heber, Ulrich; Shuvalov, Vladimir A

    2005-06-01

    Lichens and phototolerant poikilohydric mosses differ from spinach leaves, fern fronds or photosensitive mosses in that they show strongly decreased Fo chlorophyll fluorescence after drying. This desiccation-induced fluorescence loss is rapidly reversible under rehydration. Fluorescence emission from Photosystem II at 685 nm was decreased more strongly by dehydration than 720 nm emission. Reaction centers of Photosystem II lose activity on dehydration and regain it on hydration. Heating of desiccated lichens increased Fo chlorophyll fluorescence. The activation energy for the reversible part of the temperature-dependent fluorescence increase was 0.045 eV, which corresponds to the energy difference between the 680 and 697 nm absorption bands. In desiccated chlorolichens such as Parmelia sulcata, heating induces the appearance of positive variable fluorescence related to the reversible reduction of QA due to overcoming the energy barrier. This is interpreted to provide information on the mechanism of photoprotection: energy is dissipated by changing Chl680 or P680 into a chlorophyll form, which absorbs at 700 nm and emits light at 720 nm (Chl-720 or P680(700)) with a low quantum yield. Dissipation of light energy in this trap is activated by desiccation. PMID:16049759

  4. Co-assembly of photosystem II/reduced graphene oxide multilayered biohybrid films for enhanced photocurrent

    Science.gov (United States)

    Cai, Peng; Feng, Xiyun; Fei, Jinbo; Li, Guangle; Li, Jiao; Huang, Jianguo; Li, Junbai

    2015-06-01

    A new type of biohybrid photo-electrochemical cell was fabricated by layer-by-layer assembly of photosystem II and reduced graphene oxide. We demonstrate that the photocurrent in the direct electron transfer is enhanced about two fold with improved stability. The assembly strategy without any cross-linker or additional electron mediators makes the cell fabrication and operation much simpler as compared to previous approaches. This work may open new routes for the construction of solar energy conversion systems based on photoactive proteins and graphene materials.A new type of biohybrid photo-electrochemical cell was fabricated by layer-by-layer assembly of photosystem II and reduced graphene oxide. We demonstrate that the photocurrent in the direct electron transfer is enhanced about two fold with improved stability. The assembly strategy without any cross-linker or additional electron mediators makes the cell fabrication and operation much simpler as compared to previous approaches. This work may open new routes for the construction of solar energy conversion systems based on photoactive proteins and graphene materials. Electronic supplementary information (ESI) available: Detailed experimental procedures, XRD patterns, UV-vis spectra, XPS spectra, SDS-PAGE patterns, AFM images and SEM images. See DOI: 10.1039/c5nr02322j

  5. Time and spectral resolved phosphorescence of singlet oxygen and pigments in photosystem II particles

    International Nuclear Information System (INIS)

    Singlet oxygen generated via chlorophyll triplets in photosynthetic systems can destroy basic components of photosynthetic apparatus. In order to study this process a sensitive spectroscopic experimental set-up was built to detect both weak infrared (IR) chlorophyll phosphorescence (between 900 and 1000 nm) and singlet oxygen phosphorescence (at 1270 nm). The spectral and time resolution of the used monochromator and photon counting multiscaler are sufficient to provide two-dimensional matrix of temporally and spectrally resolved IR luminescence data. We have studied IR emission of photosystem II particles in D2O and H2O buffer including the effect of the sodium dodecyl sulphate (SDS) detergent. Both sub-microsecond lifetime of chlorophyll triplet states and microsecond lifetime of singlet oxygen were determined. The singlet oxygen lifetime in D2O (of 18 μs) was approximately five times longer than that in H2O. Quantum efficiency of singlet oxygen generation in photosystem II particles was significantly lower than that in chlorophyll a in acetone, however, it could be substantially increased by addition of SDS

  6. Modification of Herbicide Binding to Photosystem II in Two Biotypes of Senecio vulgaris L

    Science.gov (United States)

    Pfister, Klaus; Radosevich, Steven R.; Arntzen, Charles J.

    1979-01-01

    The present study compares the binding and inhibitory activity of two photosystem II inhibitors: 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron [DCMU]) and 2-chloro-4-(ethylamine)-6-(isopropyl amine)-S-triazene (atrazine). Chloroplasts isolated from naturally occurring triazine-susceptible and triazine-resistant biotypes of common groundsel (Senecio vulgaris L.) showed the following characteristics. (a) Diuron strongly inhibited photosynthetic electron transport from H2O to 2,6-dichlorophenolindophenol in both biotypes. Strong inhibition by atrazine was observed only with the susceptible chloroplasts. (b) Hill plots of electron transport inhibition data indicate a noncooperative binding of one inhibitor molecule at the site of action for both diuron and atrazine. (c) Susceptible chloroplasts show a strong diuron and atrazine binding (14C-radiolabel assays) with binding constants (K) of 1.4 × 10−8 molar and 4 × 10−8 molar, respectively. In the resistant chloroplasts the diuron binding was slightly decreased (K = 5 × 10−8 molar), whereas no specific atrazine binding was detected. (d) In susceptible chloroplasts, competitive binding between radioactively labeled diuron and non-labeled atrazine was observed. This competition was absent in the resistant chloroplasts. We conclude that triazine resistance of both intact plants and isolated chloroplasts of Senecio vulgaris L. is based upon a minor modification of the protein in the photosystem II complex which is responsible for herbicide binding. This change results in a specific loss of atrazine (triazine)-binding capacity. PMID:16661120

  7. Simulations of the polarisation-dependent Raman intensity of β-carotene in photosystem II crystals

    Energy Technology Data Exchange (ETDEWEB)

    Brose, K., E-mail: katharina.brose@gmx.net [Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstraße 36, 10623 Berlin (Germany); Zouni, A. [Institut für Chemie, Max-Volmer-Laboratorium, Technische Universität Berlin, Straße des 17. Juni 135, 10623 Berlin (Germany); Müh, F. [Institut für Theoretische Physik, Johannes Kepler Universität Linz, Altenberger Straße 69, 4040 Linz (Austria); Mroginski, M.A. [Institut für Chemie, Max-Volmer-Laboratorium, Technische Universität Berlin, Straße des 17. Juni 135, 10623 Berlin (Germany); Maultzsch, J. [Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstraße 36, 10623 Berlin (Germany)

    2013-06-03

    Highlights: • First polarisation-dependent Raman spectroscopy on photosystem II crystals. • Orientation-dependent Raman intensity simulations for di- and monomeric crystals. • Simulations account for all β-carotenes (β-Car) in the unit cell for the first time. • Prediction for identificationy of the β-Car cation in side-path electron transport. - Abstract: In order to clarify possibilities to identify the β-carotene (β-Car) radicals in secondary electron transfer (ET) reactions in the photosystem II core complex (PSIIcc), Raman intensities of all 96 β-Car cofactors in the unit cell of PSIIcc-dimer crystals as a function of polarisation and crystal orientation were simulated based on the 2.9 Å resolution structure. The Raman-active symmetry A{sub g} in the C{sub 2h} group is assigned to the β-Car modes ν{sub 66} and ν{sub 67}. Simulations are in agreement with experiment for off-resonant excitation at 1064 nm. Resonant measurements at 476 and 532 nm excitation can not be explained, which is attributed to mode mixing in the excited state and the existence of different spectral pools. The identity of the β-Car oxidised in secondary ET can not be resolved by Raman measurements on PSIIcc-dimer crystals. Additional simulations show that similar measurements on PSIIcc-monomer crystals could provide a possible route to solve this issue.

  8. Sulphate, more than a nutrient, protects the microalga Chlamydomonas moewusii from cadmium toxicity

    Energy Technology Data Exchange (ETDEWEB)

    Mera, Roi; Torres, Enrique, E-mail: torres@udc.es; Abalde, Julio

    2014-03-01

    Highlights: • Sulphate effect on cadmium toxicity in the microalga Chlamydomonas moewusii Gerloff. • Cadmium increases the sulphur requirements in Chlamydomonas moewusii. • Kinetic coefficients for sulphate utilization and cadmium effect on them. • Sulphate and cadmium influence on the biosynthesis of low-molecular mass thiols. • Cadmium toxicity reduction by sulphate due to higher biosynthesis of thiols. - Abstract: Sulphur is an essential macroelement that plays important roles in living organisms. The thiol rich sulphur compounds, such as cysteine, γ-Glu–Cys, glutathione and phytochelatins participate in the tolerance mechanisms against cadmium toxicity. Plants, algae, yeasts and most prokaryotes cover their demand for reduced sulphur by reduction of inorganic sulphate. The aim of this study was to investigate, using a bifactorial experimental design, the effect of different sulphate concentrations in the nutrient solution on cadmium toxicity in the freshwater microalga Chlamydomonas moewusii. Cell growth, kinetic parameters of sulphate utilization and intracellular concentrations of low-molecular mass thiol compounds were determined. A mathematical model to describe the growth of this microalga based on the effects of sulphate and cadmium was obtained. An ANOVA revealed an interaction between them, 16% of the effect sizes was explained by this interaction. A higher amount of sulphate in the culture medium allowed a higher cadmium tolerance due to an increase in the thiol compound biosynthesis. The amount of low-molecular mass thiol compounds, mainly phytochelatins, synthesized by this microalga was significantly dependent on the sulphate and cadmium concentrations; the higher phytochelatin content was obtained in cultures with 4 mg Cd/L and 1 mM sulphate. The maximum EC{sub 50} value (based on nominal cadmium concentration) reached for this microalga was 4.46 ± 0.42 mg Cd/L when the sulphate concentration added to the culture medium was also 1 m

  9. Degradation and Movement in Soil of the Herbicide Isoproturon Analyzed by a Photosystem II-Based Biosensor

    Czech Academy of Sciences Publication Activity Database

    Malý, Jan; Klem, K.; Lukavská, Alena; Masojídek, Jiří

    2005-01-01

    Roč. 34, - (2005), s. 1780-1788. ISSN 0047-2425 R&D Projects: GA ČR GA522/03/0659; GA MPO FT-TA/089 Institutional research plan: CEZ:AV0Z50200510 Keywords : Photosystem II * Herbicide-detection Subject RIV: EE - Microbiology, Virology Impact factor: 2.121, year: 2005

  10. Heat stress and recovery of photosystem II efficiency in wheat (Triticum aestivum L.) cultivars acclimated to different growth temperatures

    DEFF Research Database (Denmark)

    Haque, Sabibul; Kjær, Katrine Heinsvig; Rosenqvist, Eva; Sharma, Dew Kumari; Ottosen, Carl-Otto

    2014-01-01

    The effect of heat stress on photosystem II (PS II) efficiency and post-stress recovery was studied in four wheat cultivars using chlorophyll fluorescence. The main aim was to examine the cultivar differences in relation to inhibition and recovery of PSII functionality after heat stress at differ...

  11. Monolayers of photosystem II on gold electrodes with enhanced sensor response-effect of porosity and protein layer arrangement

    Czech Academy of Sciences Publication Activity Database

    Malý, J.; Krejčí, J.; Ilie, M.; Jakubka, L.; Masojídek, Jiří; Pilloton, R.; Sameh, K.; Steffan, P.; Stryhal, Z.; Sugiura, M.

    2005-01-01

    Roč. 381, - (2005), s. 1558-1567. ISSN 1618-2642 R&D Projects: GA ČR GA522/03/0659; GA MPO FT-TA/089 Institutional research plan: CEZ:AV0Z50200510 Keywords : protein monolayer * photosystem II * nanostructured electrodes Subject RIV: EE - Microbiology, Virology Impact factor: 2.695, year: 2005

  12. Photosystem II-inhibitors play a limited role in sweet corn response to 4-hydroxyphenyl pyruvate dioxygenase-inhibiting herbicides

    Science.gov (United States)

    Postemergence (POST) application of 4-hydroxyphenyl pyruvate dioxygenase (HPPD) inhibitors in combination with a photosystem II (PSII) inhibitor, such as atrazine, is common practice in sweet corn production. Given the sensitivity of sweet corn to HPPD-inhibiting herbicides, the objective of this wo...

  13. Perioxidases play important roles in abscisic acid (ABA)-simulating photosystem II (PSII) thermostabilty of apple tree rootstock leaves

    Czech Academy of Sciences Publication Activity Database

    Brestic, M.; Shao, H. B.; Ferus, P.; Malbeck, Jiří

    2011-01-01

    Roč. 10, č. 71 (2011), s. 15891-15900. ISSN 1684-5315 Institutional research plan: CEZ:AV0Z50380511 Keywords : Photosystem II thermostability * antioxidant activity * phytohormones Subject RIV: EF - Botanics Impact factor: 0.573, year: 2010

  14. Membrane-Associated Polypeptides Induced in Chlamydomonas by Limiting CO(2) Concentrations.

    Science.gov (United States)

    Spalding, M H; Jeffrey, M

    1989-01-01

    Chlamydomonas reinhardtii and other unicellular green algae have a high apparent affinity for CO(2), little O(2) inhibition of photosynthesis, and reduced photorespiration. These characteristics result from operation of a CO(2)-concentrating system. The CO(2)-concentrating system involves active inorganic carbon transport and is under environmental control. Cells grown at limiting CO(2) concentrations have inorganic carbon transport activity, but cells grown at 5% CO(2) do not. Four membrane-associated polypeptides (M(r) 19, 21, 35, and 36 kilodaltons) have been identified which either appear or increase in abundance during adaptation to limiting CO(2) concentrations. The appearance of two of the polypeptides occurs over roughly the same time course as the appearance of the CO(2)-concentrating system activity in response to CO(2) limitation. PMID:16666503

  15. Some observations on the carbon dioxide burst in chlorella and chlamydomonas.

    Science.gov (United States)

    Bunt, J S

    1970-02-01

    In the course of mass spectrometer studies with the algae Chlorella and Chlamydomonas, data were obtained which indicate that the CO(2) burst and gulp are sensitive to oxygen. Furthermore, the CO(2) burst was found to be strongly suppressed when wave lengths shorter than 460 nanometers were blocked at intensities adequate to saturate photosynthesis. Under appropriate conditions at 30 degrees , the CO(2) burst was interrupted by a brief CO(2) gulp and the post illumination gulp by a brief burst of CO(2). The post illumination gulp of CO(2) could be induced during illumination by interposition of a filter blocking wave lengths shorter than 460 nanometers. These data are discussed in relation to earlier reports of the phenomenon and briefly as they affect the detection of photorespiration. PMID:16657291

  16. Membrane-associated polypeptides induced in Chlamydomonas by limiting CO sub 2 concentrations

    Energy Technology Data Exchange (ETDEWEB)

    Spalding, M.H.; Jeffrey, M. (Iowa State Univ., Ames (USA))

    1989-01-01

    Chlamydomonas reinhardtii and other unicellular green algae have a high apparent affinity for CO{sub 2}, little O{sub 2} inhibition of photosynthesis, and reduced photorespiration. These characteristics result from operation of a CO{sub 2}-concentrating system. The CO{sub 2}-concentrating system involves active inorganic carbon transport and is under environmental control. Cells grown at limiting CO{sub 2} concentrations have inorganic carbon transport activity, but cells grown at 5% CO{sub 2} do not. Four membrane-associated polypeptides (M{sub r}, 19, 21, 35, and 36 kilodaltons) have been identified which either appear or increase in abundance during adaptation to limiting CO{sub 2} concentrations. The appearance of two of the polypeptides occurs over roughly the same time course as the appearance of the CO{sub 2}-concentrating system activity in response to CO{sub 2} limitation.

  17. Influence of sulphate on the reduction of cadmium toxicity in the microalga Chlamydomonas moewusii.

    Science.gov (United States)

    Mera, Roi; Torres, Enrique; Abalde, Julio

    2016-06-01

    Cadmium is considered as one of the most hazardous metals for living organism and ecosystems. Environmental factors play an important role since they alter the toxicity of metals by varying the bioavailability of these elements for the organisms. The aim of the present study was to investigate, using the freshwater microalga Chlamydomonas moewusii, the existence of an interaction between cadmium and sulphate as a factor that varied the toxicity of this metal. Different cell parameters such as cell growth, content of chlorophylls and biosynthesis of phytochelatins (PCs) were determined. A two-way ANOVA showed that the interaction had a significant effect size of 21% (pcadmium on the growth and on the content of chlorophylls was observed. In addition, the increase of sulphate concentration allowed the biosynthesis of a higher amount of PCs and/or PCs with higher chain length. This higher biosynthesis was responsible for the reduction of the toxic effect of cadmium and explained the interaction. PMID:26963118

  18. A forward genetic approach in Chlamydomonas reinhardtii as a strategy for exploring starch catabolism.

    Directory of Open Access Journals (Sweden)

    Hande Tunçay

    Full Text Available A screen was recently developed to study the mobilization of starch in the unicellular green alga Chlamydomonas reinhardtii. This screen relies on starch synthesis accumulation during nitrogen starvation followed by the supply of nitrogen and the switch to darkness. Hence multiple regulatory networks including those of nutrient starvation, cell cycle control and light to dark transitions are likely to impact the recovery of mutant candidates. In this paper we monitor the specificity of this mutant screen by characterizing the nature of the genes disrupted in the selected mutants. We show that one third of the mutants consisted of strains mutated in genes previously reported to be of paramount importance in starch catabolism such as those encoding β-amylases, the maltose export protein, and branching enzyme I. The other mutants were defective for previously uncharacterized functions some of which are likely to define novel proteins affecting starch mobilization in green algae.

  19. Measurement of swimming force generation during flagella regeneration in Chlamydomonas reinhardtii

    Science.gov (United States)

    Yukich, John N.; Shaban, Mona; Clodfelter, Catherine; Bernd, Karen

    2007-11-01

    The green alga Chlamydomonas reinhardtii has been at the forefront of many studies investigating the establishment and function of flagella in facilitating cellular motility. Previously we reported an intriguing pattern during flagella regeneration in which increases in force do not always correspond with increase in flagella length. That work made direct measurement of maximum flagellar swimming force by measuring the cell's ability to escape from an optical trap (optical tweezers). Here, we report on optimization and automation of the force measurement using power spectral density calibration of the trap and distance of periodic displacement from the trap center. This process yields an average value for the swimming force. The intriguing pattern described for maximum swimming force is also evident in the average swimming force data, suggesting that the phenomenon reflects a change in flagella functionality during regeneration.

  20. Effect of Temperature and light intensity on growth and Photosynthetic Activity of Chlamydomonas reinhard II

    International Nuclear Information System (INIS)

    The effect of five temperatures (15,20,25,30 and 35 degree centigree) and two levels of illumination on growth and photosynthetic activity of Chlamydomonas reinhard II has been studied. The growth of the cultures was evaluated by optical density. Photosynthetic activity has been carried out studying either the assimilation rate of C02 labelled with C-14 or the oxygen evolution by means of polarographic measurements. The maximum photosynthetic rate has been obtained at 25 degree centigree for the lower level of illumination (2400 lux) and at 35 degree centigree for the higher one (13200 lux) and at 35 degree centigree for the higher ono (13200 lux). These results suggest an interaction of temperature and illumination on photosynthetic activity. (Author) 37 refs

  1. A chloroplast pathway for the de novo biosynthesis of triacylglycerol in Chlamydomonas reinhardtii

    Energy Technology Data Exchange (ETDEWEB)

    Fan, J.; Xu, C.; Andre, C.

    2011-06-23

    Neutral lipid metabolism has been extensively studied in yeast, plants and mammals. In contrast, little information is available regarding the biochemical pathway, enzymes and regulatory factors involved in the biosynthesis of triacylglycerol (TAG) in microalgae. In the conventional TAG biosynthetic pathway widely accepted for yeast, plants and mammals, TAG is assembled in the endoplasmic reticulum (ER) from its immediate precursor diacylglycerol (DAG) made by ER-specific acyltransferases, and is deposited exclusively in lipid droplets in the cytosol. Here, we demonstrated that the unicellular microalga Chlamydomonas reinhardtii employs a distinct pathway that uses DAG derived almost exclusively from the chloroplast to produce TAG. This unique TAG biosynthesis pathway is largely dependent on de novo fatty acid synthesis, and the TAG formed in this pathway is stored in lipid droplets in both the chloroplast and the cytosol. These findings have wide implications for understanding TAG biosynthesis and storage and other areas of lipid metabolism in microalgae and other organisms.

  2. Efficient expression of green fluorescent protein (GFP) mediated by a chimeric promoter in Chlamydomonas reinhardtii

    Science.gov (United States)

    Wu, Jinxia; Hu, Zhangli; Wang, Chaogang; Li, Shuangfei; Lei, Anping

    2008-08-01

    To improve the expression efficiency of exogenous genes in Chlamydomonas reinhardtii, a high efficient expression vector was constructed. Green fluorescent protein (GFP) was expressed in C. reinhardtii under the control of promoters: RBCS2 and HSP70A-RBCS2. Efficiency of transformation and expression were compared between two transgenic algae: RBCS2 mediated strain Tran-I and HSP70A-RBCS2 mediated strain Tran-II. Results show that HSP70A-RBCS2 could improve greatly the transformation efficiency by approximately eightfold of RBCS2, and the expression efficiency of GFP in Tran-II was at least double of that in Tran-I. In addition, a threefold increase of GFP in Tran-II was induced by heat shock at 40°C. All of the results demonstrated that HSP70A-RBCS2 was more efficient than RBCS2 in expressing exogenous gene in C. reinhardtii.

  3. ATP Production in Chlamydomonas reinhardtii Flagella by Glycolytic Enzymes

    DEFF Research Database (Denmark)

    Mitchell, Beth F; Pedersen, Lotte B; Feely, Michael;

    2005-01-01

    Eukaryotic cilia and flagella are long, thin organelles, and diffusion from the cytoplasm may not be able to support the high ATP concentrations needed for dynein motor activity. We discovered enzyme activities in the Chlamydomonas reinhardtii flagellum that catalyze three steps of the lower half...... of glycolysis (phosphoglycerate mutase, enolase, and pyruvate kinase). These enzymes can generate one ATP molecule for every substrate molecule consumed. Flagellar fractionation shows that enolase is at least partially associated with the axoneme, whereas phosphoglycerate mutase and pyruvate kinase...... primarily reside in the detergent-soluble (membrane + matrix) compartments. We further show that axonemal enolase is a subunit of the CPC1 central pair complex and that reduced flagellar enolase levels in the cpc1 mutant correlate with the reduced flagellar ATP concentrations and reduced in vivo beat...

  4. Investigating the link between fermentative metabolism and hydrogen production in the unicellular green alga Chlamydomonas reinhardtii

    Energy Technology Data Exchange (ETDEWEB)

    Burgess, S.J.; Nixon, P.J. [Imperial College London (United Kingdom)

    2010-07-01

    In the model green alga Chlamydomonas reinhardtii, the electrons required for hydrogen production can come from both the biophotolysis of water and from the fermentation of carbohydrate reserves. Anoxia leads to the activation of several fermentative pathways, which produce a number of end products including formic, malic and acetic acid along with ethanol, carbon dioxide and hydrogen. It has been proposed that by switching off competing fermentative pathways hydrogen production can be increased. Therefore the aim of this study was to devise an experimental strategy to down-regulate the expression of enzymes thought to control C. reinhardtii's fermentative metabolism. We demonstrate here that it is possible to use artificial microRNA (amiRNA) technology to generate knock-down mutants with reduced expression of pyruvate formate lyase (PFL1), a key fermentative enzyme in C. reinhardtii. This work opens up new possibilities to improve hydrogen yields through metabolic engineering. (orig.)

  5. Structural Insight into the Complex of Ferredoxin and [FeFe] Hydrogenase from Chlamydomonas reinhardtii.

    Science.gov (United States)

    Rumpel, Sigrun; Siebel, Judith F; Diallo, Mamou; Farès, Christophe; Reijerse, Edward J; Lubitz, Wolfgang

    2015-07-27

    The transfer of photosynthetic electrons by the ferredoxin PetF to the [FeFe] hydrogenase HydA1 in the microalga Chlamydomonas reinhardtii is a key step in hydrogen production. Electron delivery requires a specific interaction between PetF and HydA1. However, because of the transient nature of the electron-transfer complex, a crystal structure remains elusive. Therefore, we performed protein-protein docking based on new experimental data from a solution NMR spectroscopy investigation of native and gallium-substituted PetF. This provides valuable information about residues crucial for complex formation and electron transfer. The derived complex model might help to pinpoint residue substitution targets for improved hydrogen production. PMID:26010059

  6. Dynamic curvature regulation accounts for the symmetric and asymmetric beats of Chlamydomonas flagella

    CERN Document Server

    Sartori, Pablo; Scholich, Andre; Jülicher, Frank; Howard, Jonathon

    2015-01-01

    Axonemal dyneins are the molecular motors responsible for the beating of cilia and flagella. These motors generate sliding forces between adjacent microtubule doublets within the axoneme, the motile cytoskeletal structure inside the flagellum. To create regular, oscillatory beating patterns, the activities of the axonemal dyneins must be coordinated both spatially and temporally. It is thought that coordination is mediated by stresses or strains that build up within the moving axoneme, but it is not known which components of stress or strain are involved, nor how they feed back on the dyneins. To answer this question, we used isolated, reactivate axonemes of the unicellular alga Chlamydomonas as a model system. We derived a theory for beat regulation in a two-dimensional model of the axoneme. We then tested the theory by measuring the beat waveforms of wild type axonemes, which have asymmetric beats, and mutant axonemes, in which the beat is nearly symmetric, using high-precision spatial and temporal imaging....

  7. Recombinant Reconstitution and Purification of the IFT-B Core Complex from Chlamydomonas reinhardtii.

    Science.gov (United States)

    Taschner, Michael; Lorentzen, Esben

    2016-01-01

    Eukaryotic cilia and flagella are assembled and maintained by intraflagellar transport (IFT), the bidirectional transport of proteins between the ciliary base and tip. IFT is mediated by the multi-subunit IFT complex, which simultaneously binds cargo proteins and the ciliary motors. So far 22 subunits of the IFT complex have been identified, but insights into the biochemical architecture and especially the three-dimensional structure of this machinery are only starting to emerge because of difficulties in obtaining homogeneous material suitable for structural analysis. Here, we describe a protocol for the purification and reconstitution of a complex containing nine Chlamydomonas reinhardtii IFT proteins, commonly known as the IFT-B core complex. In our hands, this protocol routinely yields several milligrams of pure complex suitable for structural analysis by X-ray crystallography and single-particle cryo-electron microscopy. PMID:27514916

  8. DNA-free two-gene knockout in Chlamydomonas reinhardtii via CRISPR-Cas9 ribonucleoproteins.

    Science.gov (United States)

    Baek, Kwangryul; Kim, Duk Hyoung; Jeong, Jooyeon; Sim, Sang Jun; Melis, Anastasios; Kim, Jin-Soo; Jin, EonSeon; Bae, Sangsu

    2016-01-01

    Microalgae are versatile organisms capable of converting CO2, H2O, and sunlight into fuel and chemicals for domestic and industrial consumption. Thus, genetic modifications of microalgae for enhancing photosynthetic productivity, and biomass and bio-products generation are crucial for both academic and industrial applications. However, targeted mutagenesis in microalgae with CRISPR-Cas9 is limited. Here we report, a one-step transformation of Chlamydomonas reinhardtii by the DNA-free CRISPR-Cas9 method rather than plasmids that encode Cas9 and guide RNAs. Outcome was the sequential CpFTSY and ZEP two-gene knockout and the generation of a strain constitutively producing zeaxanthin and showing improved photosynthetic productivity. PMID:27466170

  9. Trichloroacetate affects the EPR SignalⅡslow and SignalⅠin the thylakoid of Chlamydomonas reinhardtii

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    One electron paramagnetic resonance (EPR) signal, named SignalⅡslow, originates from the oxidized Tyrosine 160 (YDo) of D2 polypeptide of photosystemⅡ reaction center. After adding high concentration trichloroacetate (TCA) to the Chlamydomonas reinhardtii thylakoid suspension, this signal was abolished in a minute. Treatment of TCA also removes a few of polypeptides, including three extrinsic polypeptides of oxygen-evolving complex, from the thylakoid membrane. Based upon the analysis of the microenvironment around YD with a three-dimensional model, it is indicated that relatively high hydrophobicity of this microenvironment may be the essential prerequisite for TCA to affect YD. It has been observed that TCA treatment also retards the decay of the SignalⅠ, produced by the oxidized reaction center chlorophyll dimer (P700+) of photosys- temⅠ.

  10. Identification and Characterization of a cis-Regulatory Element for Zygotic Gene Expression in Chlamydomonas reinhardtii.

    Science.gov (United States)

    Hamaji, Takashi; Lopez, David; Pellegrini, Matteo; Umen, James

    2016-01-01

    Upon fertilization Chlamydomonas reinhardtii zygotes undergo a program of differentiation into a diploid zygospore that is accompanied by transcription of hundreds of zygote-specific genes. We identified a distinct sequence motif we term a zygotic response element (ZYRE) that is highly enriched in promoter regions of C reinhardtii early zygotic genes. A luciferase reporter assay was used to show that native ZYRE motifs within the promoter of zygotic gene ZYS3 or intron of zygotic gene DMT4 are necessary for zygotic induction. A synthetic luciferase reporter with a minimal promoter was used to show that ZYRE motifs introduced upstream are sufficient to confer zygotic upregulation, and that ZYRE-controlled zygotic transcription is dependent on the homeodomain transcription factor GSP1. We predict that ZYRE motifs will correspond to binding sites for the homeodomain proteins GSP1-GSM1 that heterodimerize and activate zygotic gene expression in early zygotes. PMID:27172209

  11. Cell types and their status in Chlamydomonas-like algae (Chlorophyceae on agar medium culture

    Directory of Open Access Journals (Sweden)

    M.М. Pavlovska

    2014-04-01

    Full Text Available The classification of cell types under agar culture was proposed. Six cell morphotypes were allocated. The statuses were identified depending on the reduction of monade attributes of cells. The variants of transition from one cell morphotype to another under dissolving mucilage were shown. The monade, cocciod, palmeloid and gloeocysta morphotypes approximately equally represented in all clades. The asterococcus and mucogleocysta morphotypes presented only in Reinhardtinia аnd Oogamochlamydinia clades. Any morphotype isn’t typical for all clades of Chlamydomonas-like algae at once. The most of morphotypes numbers (5 from 6 are presented in Reinhardtinia clade. This demonstrates the diversity of the Reinhardtinia clade species. There are only one morphotype presented in Polytominia and Monadinia clades. There are four morphotypes presented in Oogamochlamydinia clade, three – in Moewusinia, two morphotypes – in Chloromonadinia.

  12. Growth of the green algae Chlamydomonas reinhardtii under red and blue lasers

    Science.gov (United States)

    Kuwahara, Sara S.; Cuello, Joel L.; Myhre, Graham; Pau, Stanley

    2011-03-01

    Red and blue lasers, holding promise as an electric light source for photosynthetic systems on account of being true monochromatic, high-power, and having high electrical-conversion efficiency, were employed in growing a green alga, Chlamydomonas reinhardtii. The laser treatments tested included: 655-nm Red; 680-nm Red; 655-nm Red+474-nm Blue and 680-nm Red+474-nm Blue. A white cold cathode lamp with spectral output similar to that of white fluorescent lamp served as control. C. reinhardtii successfully grew and divided under the 655 and 680-nm red lasers as well as under the white-light control. Supplementing either red with blue laser, however, resulted in increased algae cell count that significantly exceeded those under both red lasers and the white-light control on average by 241%.

  13. Efficient expression of green fluorescent protein (GFP) mediated by a chimeric promoter in Chlamydomonas reinhardtii

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    To improve the expression efficiency of exogenous genes in Chlamydomonas reinhardtii, a high efficient expression vector was constructed. Green fluorescent protein (GFP) was expressed in C. Reinhardtii under the control of promoters: RBCS2 and HSP70A-RBCS2. Efficiency of transformation and expression were compared between two transgenic algae: RBCS2 mediated strain Tran-I and HSP70A-RBCS2 mediated strain Tran-II. Results show that HSP70A-RBCS2 could improve greatly the transformation efficiency by approximately eightfold of RBCS2, and the expression efficiency of GFP in Tran-II was at least double of that in Tran-I. In addition, a threefold increase of GFP in Tran-II was induced by heat shock at 40°C. All of the results demonstrated that HSP70A-RBCS2 was more efficient than RBCS2 in expressing exogenous gene in C. Reinhardtii.

  14. Successful expression of heterologous egfp gene in the mitochondria of a photosynthetic eukaryote Chlamydomonas reinhardtii.

    Science.gov (United States)

    Hu, Zhangli; Zhao, Zhonglin; Wu, Zhihua; Fan, Zhun; Chen, Jun; Wu, Jinxia; Li, Jiancheng

    2011-09-01

    The efficient expression of exogenous gene in mitochondria of photosynthetic organism has been an insurmountable problem. In this study, the pBsLPNCG was constructed by inserting the egfp gene into a site between TERMINVREP-Left repeats and the cob gene in a fragment of mitochondrial DNA of Chlamydomonas reinhardtii CC-124 and introduced into the mitochondria of respiratory deficient dum-1 mutation of C. reinhardtii CC-2654. Sequencing and DNA Southern analyses revealed that egfp gene had been integrated into the mitochondrial genome of transgenic algae as expected and no other copy of egfp existed in their nucleic genome. Both the fluorescence detection and Western blot analysis confirmed the presence of eGFP protein in the transgenic algae; it indicated that the egfp gene was successfully expressed in the mitochondria of C. reinhardtii. PMID:21664493

  15. DNA-free two-gene knockout in Chlamydomonas reinhardtii via CRISPR-Cas9 ribonucleoproteins

    Science.gov (United States)

    Baek, Kwangryul; Kim, Duk Hyoung; Jeong, Jooyeon; Sim, Sang Jun; Melis, Anastasios; Kim, Jin-Soo; Jin, EonSeon; Bae, Sangsu

    2016-01-01

    Microalgae are versatile organisms capable of converting CO2, H2O, and sunlight into fuel and chemicals for domestic and industrial consumption. Thus, genetic modifications of microalgae for enhancing photosynthetic productivity, and biomass and bio-products generation are crucial for both academic and industrial applications. However, targeted mutagenesis in microalgae with CRISPR-Cas9 is limited. Here we report, a one-step transformation of Chlamydomonas reinhardtii by the DNA-free CRISPR-Cas9 method rather than plasmids that encode Cas9 and guide RNAs. Outcome was the sequential CpFTSY and ZEP two-gene knockout and the generation of a strain constitutively producing zeaxanthin and showing improved photosynthetic productivity. PMID:27466170

  16. Inhomogeneous distribution of Chlamydomonas in a cylindrical container with a bubble plume

    Directory of Open Access Journals (Sweden)

    Yuki Nonaka

    2016-02-01

    Full Text Available Swimming microalgae show various taxes, such as phototaxis and gravitaxis, which sometimes result in the formation of a cell-rich layer or a patch in a suspension. Despite intensive studies on the effects of shear flow and turbulence on the inhomogeneous distribution of microalgae, the effect of a bubble plume has remained unclear. In this study, we used Chlamydomonas as model microalgae, and investigated the spatial distribution of cells in a cylindrical container with a bubble plume. The results illustrate that cells become inhomogeneously distributed in the suspension due to their motility and photo-responses. A vortical ring distribution was observed below the free surface when the bubble flow rate was sufficiently small. We performed a scaling analysis on the length scale of the vortical ring, which captured the main features of the experimental results. These findings are important in understanding transport phenomena in a microalgae suspension with a bubble plume.

  17. Inhomogeneous distribution of Chlamydomonas in a cylindrical container with a bubble plume

    Science.gov (United States)

    Nonaka, Yuki; Kikuchi, Kenji; Numayama-Tsuruta, Keiko; Kage, Azusa; Ueno, Hironori; Ishikawa, Takuji

    2016-01-01

    ABSTRACT Swimming microalgae show various taxes, such as phototaxis and gravitaxis, which sometimes result in the formation of a cell-rich layer or a patch in a suspension. Despite intensive studies on the effects of shear flow and turbulence on the inhomogeneous distribution of microalgae, the effect of a bubble plume has remained unclear. In this study, we used Chlamydomonas as model microalgae, and investigated the spatial distribution of cells in a cylindrical container with a bubble plume. The results illustrate that cells become inhomogeneously distributed in the suspension due to their motility and photo-responses. A vortical ring distribution was observed below the free surface when the bubble flow rate was sufficiently small. We performed a scaling analysis on the length scale of the vortical ring, which captured the main features of the experimental results. These findings are important in understanding transport phenomena in a microalgae suspension with a bubble plume. PMID:26787679

  18. Critical role of Chlamydomonas reinhardtii ferredoxin-5 in maintaining membrane structure and dark metabolism.

    Science.gov (United States)

    Yang, Wenqiang; Wittkopp, Tyler M; Li, Xiaobo; Warakanont, Jaruswan; Dubini, Alexandra; Catalanotti, Claudia; Kim, Rick G; Nowack, Eva C M; Mackinder, Luke C M; Aksoy, Munevver; Page, Mark Dudley; D'Adamo, Sarah; Saroussi, Shai; Heinnickel, Mark; Johnson, Xenie; Richaud, Pierre; Alric, Jean; Boehm, Marko; Jonikas, Martin C; Benning, Christoph; Merchant, Sabeeha S; Posewitz, Matthew C; Grossman, Arthur R

    2015-12-01

    Photosynthetic microorganisms typically have multiple isoforms of the electron transfer protein ferredoxin, although we know little about their exact functions. Surprisingly, a Chlamydomonas reinhardtii mutant null for the ferredoxin-5 gene (FDX5) completely ceased growth in the dark, with both photosynthetic and respiratory functions severely compromised; growth in the light was unaffected. Thylakoid membranes in dark-maintained fdx5 mutant cells became severely disorganized concomitant with a marked decrease in the ratio of monogalactosyldiacylglycerol to digalactosyldiacylglycerol, major lipids in photosynthetic membranes, and the accumulation of triacylglycerol. Furthermore, FDX5 was shown to physically interact with the fatty acid desaturases CrΔ4FAD and CrFAD6, likely donating electrons for the desaturation of fatty acids that stabilize monogalactosyldiacylglycerol. Our results suggest that in photosynthetic organisms, specific redox reactions sustain dark metabolism, with little impact on daytime growth, likely reflecting the tailoring of electron carriers to unique intracellular metabolic circuits under these two very distinct redox conditions. PMID:26627249

  19. Separate origins of ice-binding proteins in antarctic chlamydomonas species.

    Directory of Open Access Journals (Sweden)

    James A Raymond

    Full Text Available The green alga Chlamydomonas raudensis is an important primary producer in a number of ice-covered lakes and ponds in Antarctica. A C. raudensis isolate (UWO241 from Lake Bonney in the McMurdo Dry Valleys, like many other Antarctic algae, was found to secrete ice-binding proteins (IBPs, which appear to be essential for survival in icy environments. The IBPs of several Antarctic algae (diatoms, a prymesiophyte, and a prasinophyte are similar to each other (here designated as type I IBPs and have been proposed to have bacterial origins. Other IBPs (type II IBPs that bear no resemblance to type I IBPs, have been found in the Antarctic Chlamydomonas sp. CCMP681, a putative snow alga, raising the possibility that chlamydomonad IBPs developed separately from the IBPs of other algae. To test this idea, we obtained the IBP sequences of C. raudensis UWO241 by sequencing the transcriptome. A large number of transcripts revealed no sequences resembling type II IBPs. Instead, many isoforms resembling type I IBPs were found, and these most closely matched a hypothetical protein from the bacterium Stigmatella aurantiaca. The sequences were confirmed to encode IBPs by the activity of a recombinant protein and by the matching of predicted and observed isoelectric points and molecular weights. Furthermore, a mesophilic sister species, C. raudensis SAG49.72, showed no ice-binding activity or PCR products from UWO241 IBP primers. These results confirm that algal IBPs are required for survival in icy habitats and demonstrate that they have diverse origins that are unrelated to the taxonomic positions of the algae. Last, we show that the C. raudensis UWO241 IBPs can change the structure of ice in a way that could increase the survivability of cells trapped in the ice.

  20. Separate origins of ice-binding proteins in antarctic chlamydomonas species.

    Science.gov (United States)

    Raymond, James A; Morgan-Kiss, Rachael

    2013-01-01

    The green alga Chlamydomonas raudensis is an important primary producer in a number of ice-covered lakes and ponds in Antarctica. A C. raudensis isolate (UWO241) from Lake Bonney in the McMurdo Dry Valleys, like many other Antarctic algae, was found to secrete ice-binding proteins (IBPs), which appear to be essential for survival in icy environments. The IBPs of several Antarctic algae (diatoms, a prymesiophyte, and a prasinophyte) are similar to each other (here designated as type I IBPs) and have been proposed to have bacterial origins. Other IBPs (type II IBPs) that bear no resemblance to type I IBPs, have been found in the Antarctic Chlamydomonas sp. CCMP681, a putative snow alga, raising the possibility that chlamydomonad IBPs developed separately from the IBPs of other algae. To test this idea, we obtained the IBP sequences of C. raudensis UWO241 by sequencing the transcriptome. A large number of transcripts revealed no sequences resembling type II IBPs. Instead, many isoforms resembling type I IBPs were found, and these most closely matched a hypothetical protein from the bacterium Stigmatella aurantiaca. The sequences were confirmed to encode IBPs by the activity of a recombinant protein and by the matching of predicted and observed isoelectric points and molecular weights. Furthermore, a mesophilic sister species, C. raudensis SAG49.72, showed no ice-binding activity or PCR products from UWO241 IBP primers. These results confirm that algal IBPs are required for survival in icy habitats and demonstrate that they have diverse origins that are unrelated to the taxonomic positions of the algae. Last, we show that the C. raudensis UWO241 IBPs can change the structure of ice in a way that could increase the survivability of cells trapped in the ice. PMID:23536869

  1. O(2) uptake in the light in chlamydomonas: evidence for persistent mitochondrial respiration.

    Science.gov (United States)

    Peltier, G; Thibault, P

    1985-09-01

    The nature of the process responsible for the stationary O(2) uptake occurring in the light under saturating CO(2) concentration in Chlamydomonas reinhardii has been investigated. For this purpose, a mass spectrometer with a membrane inlet system was used to measure O(2) uptake and evolution in the algal suspension. First, we observed that the O(2) uptake rate was constant (about 0.5 micromoles of O(2) per milligram chlorophyll per minute) during a light to dark transition and was not affected by 3-(3,4-dichlorophenyl)-1,1-dimethylurea. Salicylhydroxamic acid had no effect on O(2) uptake in the dark or in the light, but was found to have the same inhibitory effect either in the dark or in the light when added to cyanide-treated algae. The stimulation of the O(2) uptake rate due to the uncoupling effect of carbonyl cyanide m-chlorophenylhydrazone was about the same in the dark or in the light. From these results, we conclude that mitochondrial respiration is maintained during illumination and therefore is not inhibited by high ATP levels. Another conclusion is that in conditions where photorespiration is absent, no other light-dependent O(2) uptake process occurs. If Mehler reactions are involved, in Chlamydomonas, under conditions where both photosynthetic carbon oxidation and reduction cycles cannot operate (as in cyanide-treated algae), their occurrence in photosynthesizing algae either under saturating CO(2) concentration or at the CO(2) compensation point appears very unlikely. The comparison with the situation previously reported in Scenedesmus (R. J. Radmer and B. Kok 1976 Plant Physiol 58: 336-340) suggests that different O(2) uptake processes might be present in these two algal species. PMID:16664375

  2. A Chlamydomonas-derived Human Papillomavirus 16 E7 vaccine induces specific tumor protection.

    Directory of Open Access Journals (Sweden)

    Olivia C Demurtas

    Full Text Available BACKGROUND: The E7 protein of the Human Papillomavirus (HPV type 16, being involved in malignant cellular transformation, represents a key antigen for developing therapeutic vaccines against HPV-related lesions and cancers. Recombinant production of this vaccine antigen in an active form and in compliance with good manufacturing practices (GMP plays a crucial role for developing effective vaccines. E7-based therapeutic vaccines produced in plants have been shown to be active in tumor regression and protection in pre-clinical models. However, some drawbacks of in whole-plant vaccine production encouraged us to explore the production of the E7-based therapeutic vaccine in Chlamydomonas reinhardtii, an organism easy to grow and transform and fully amenable to GMP guidelines. METHODOLOGY/PRINCIPAL FINDINGS: An expression cassette encoding E7GGG, a mutated, attenuated form of the E7 oncoprotein, alone or as a fusion with affinity tags (His6 or FLAG, under the control of the C. reinhardtii chloroplast psbD 5' UTR and the psbA 3' UTR, was introduced into the C. reinhardtii chloroplast genome by homologous recombination. The protein was mostly soluble and reached 0.12% of total soluble proteins. Affinity purification was optimized and performed for both tagged forms. Induction of specific anti-E7 IgGs and E7-specific T-cell proliferation were detected in C57BL/6 mice vaccinated with total Chlamydomonas extract and with affinity-purified protein. High levels of tumor protection were achieved after challenge with a tumor cell line expressing the E7 protein. CONCLUSIONS: The C. reinhardtii chloroplast is a suitable expression system for the production of the E7GGG protein, in a soluble, immunogenic form. The production in contained and sterile conditions highlights the potential of microalgae as alternative platforms for the production of vaccines for human uses.

  3. Survival and proliferation characteristics of the microalga Chlamydomonas sp. ICE-L after hypergravitational stress pretreatment

    Science.gov (United States)

    Gao, Zhengquan; Li, Demao; Meng, Chunxiao; Xu, Dong; Zhang, Xiaowen; Ye, Naihao

    2013-09-01

    Seeking extraterrestrial life, transferring between planets, even migrating to other planets attracts more and more attention of public and scientists. However, to make it clear for the ability to survive the forces studies is prerequisite to enable the speculations by natural means. Gravity is a critical force involved in all the life on Earth and, possibly, others planets. Organisms have been grown in microgravity habitats and in centrifuges to characterize the biological response to a range of gravitational forces and radiation levels in space and on Earth. However, little is known about the profiles of eukaryotic life under conditions of hyperacceleration attributable to extreme gravities. In this study, a eukaryotic extremophile, the Antarctic green microalga Chlamydomonas sp. ICE-L, showed amazing proliferation capacity during and after hypergravitational stress for 30 min to 48 h at 110,200, 423,400, and 670,800g. These extreme gravities also had profound effects on viability, reproduction rate, photosynthesis efficiency, and gene transcriptional expression of this microalga. Most notably, all three supergravities efficiently stimulated algal cell division, but the greater the centrifugal force and the longer the duration of treatment, the lower the viable rate and breeding potential of samples in the following incubation. These results illustrated Chlamydomonas sp. ICE-L is a useful eukaryotic model system candidate for space research. Further studies could provide new insight into the physical limits of life and its evolution and enhance the possibility for interstellar space travel and the quest for extraterrestrial life according to panspermia theory. Also, it indicated that life come from the outer space is not always prokaryotes but may be eukaryotes.

  4. Temperature dependence of photosynthesis and thylakoid lipid composition in the red snow alga Chlamydomonas cf. nivalis (Chlorophyceae).

    Science.gov (United States)

    Lukeš, Martin; Procházková, Lenka; Shmidt, Volha; Nedbalová, Linda; Kaftan, David

    2014-08-01

    Here, we report an effect of short acclimation to a wide span of temperatures on photosynthetic electron transfer, lipid and fatty acid composition in the snow alga Chlamydomonas cf. nivalis. The growth and oxygen evolution capacity were low at 2 °C yet progressively enhanced at 10 °C and were significantly higher at temperatures from 5 to 15 °C in comparison with the mesophilic control Chlamydomonas reinhardtii. In search of the molecular mechanisms responsible for the adaptation of photosynthesis to low temperatures, we have found unprecedented high rates of QA to QB electron transfer. The thermodynamics of the process revealed the existence of an increased structural flexibility that we explain with the amino acid changes in the D1 protein combined with the physico-chemical characteristics of the thylakoid membrane composed of > 80% negatively charged phosphatidylglycerol. PMID:24698015

  5. Photoregulation of fructose and glucose respiration in the intact chloroplasts of Chlamydomonas reinhardtii F-60 and spinach

    International Nuclear Information System (INIS)

    The photoregulation of chloroplastic respiration was studied by monitoring in darkness and in light the release of 14CO2 from whole chloroplasts of Chlamydomonas reinhardtii F-60 and spinach (Spinacia oleracea L.) supplied externally with [14C]glucose and [14C]fructose, respectively. CO2 release was inhibited more than 90% in both chloroplasts by a light intensity of 4 W m-2. Oxidants, oxaloacetate in Chlamydomonas, nitrite in spinach, and phenazine methosulfate in both chloroplasts, reversed the inhibition. The onset of the photoinhibitory effect on CO2 release was relatively rapid compared to the restoration of CO2 release following illumination. In both darkened chloroplasts, dithiothreitol inhibited release. Of the four enzymes (fructokinase, phosphoglucose isomerase, glucose-6-P dehydrogenase, and gluconate-6-P dehydrogenase) in the pathway catalyzing the release of CO2 from fructose, only glucose-6-P dehydrogenase was deactivated by light and by dithiothreitol. 33 refs., 3 figs., 4 tabs

  6. Effect of Phosphatidylcholine on the Steady State Fluorescence of Chlorophyll in Photosystem Ⅱ Particles

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    Phosphatidylcholine (PC) accounts for less than 1% of the total lipids in plant photosystem II (PSII) particles.In this experiment, PSII particles were reconstituted with PC to construct PSII-PC vesicles.The effect of PC on the steady state fluorescence of chlorophyll (Chl) in PSII particles was studied.The results show that PC significantly affected the fluorescence intensity, but did not obviously affect the fluorescence emission band peak position.PC also did not obviously affect the absorbance at 436 nm or the amide I band peak position in FT-IR spectroscopy of PSII particles.The results suggest that PC may affect the light energy transfer from the antenna chlorophyll molecules to the reaction center chlorophyll molecule (P680).

  7. Methodology of Pulsed Photoacoustics and Its Application to Probe Photosystems and Receptors

    Directory of Open Access Journals (Sweden)

    Harvey J.M. Hou

    2010-06-01

    Full Text Available We review recent advances in the methodology of pulsed time-resolved photoacoustics and its application to studies of photosynthetic reaction centers and membrane receptors such as the G protein-coupled receptor rhodopsin. The experimental parameters accessible to photoacoustics include molecular volume change and photoreaction enthalpy change. Light-driven volume change secondary to protein conformational changes or electrostriction is directly related to the photoreaction and thus can be a useful measurement of activity and function. The enthalpy changes of the photochemical reactions observed can be measured directly by photoacoustics. With the measurement of enthalpy change, the reaction entropy can also be calculated when free energy is known. Dissecting the free energy of a photoreaction into enthalpic and entropic components may provide critical information about photoactivation mechanisms of photosystems and photoreceptors. The potential limitations and future applications of time-resolved photoacoustics are also discussed.

  8. Solar Photo Catalytic Hydrogen Production from water using a dual bed photosystem

    Energy Technology Data Exchange (ETDEWEB)

    Florida Solar Energy Center

    2003-03-30

    A body of work was performed in which the feasibility of photocatalytically decomposing water into its constituent elements using a dual bed, or modular photosystem, under solar radiation was investigated. The system envisioned consists of two modules, each consisting of a shallow, flat, sealed container, in which microscopic photocatalytic particles are immobilized. The photocatalysts absorb light, generating free electrons and lattice vacancy holes, which are capable of performing reductive and oxidative chemistry, respectively. The photocatalysts would be chosen as to whether they specifically promote H{sub 2} or O{sub 2} evolution in their respective containers. An aqueous solution containing a redox mediator is pumped between the two chambers in order to transfer electron equivalents from one reaction to the other.

  9. Ammonia triggers photodamage of photosystem II in the cyanobacterium Synechocystis sp. strain PCC 6803.

    Science.gov (United States)

    Drath, Miriam; Kloft, Nicole; Batschauer, Alfred; Marin, Kay; Novak, Jens; Forchhammer, Karl

    2008-05-01

    Ammonia has long been known to be toxic for many photosynthetic organisms; however, the target for its toxicity remains elusive. Here, we show that in the cyanobacterium Synechocystis sp. strain PCC 6803, ammonia triggers a rapid photodamage of photosystem II (PSII). Whereas wild-type cells can cope with this damage by turning on the FtsH2-dependent PSII repair cycle, the FtsH2-deficient mutant is highly sensitive and loses PSII activity at millimolar concentration of ammonia. Ammonia-triggered PSII destruction is light dependent and occurs already at low photon fluence rates. Experiments with monochromatic light showed that ammonia-promoted PSII photoinhibition is executed by wavebands known to directly destroy the manganese cluster in the PSII oxygen-evolving complex, suggesting that the oxygen-evolving complex may be a direct target for ammonia toxicity. PMID:18322144

  10. Ammonia Triggers Photodamage of Photosystem II in the Cyanobacterium Synechocystis sp. Strain PCC 68031[OA

    Science.gov (United States)

    Drath, Miriam; Kloft, Nicole; Batschauer, Alfred; Marin, Kay; Novak, Jens; Forchhammer, Karl

    2008-01-01

    Ammonia has long been known to be toxic for many photosynthetic organisms; however, the target for its toxicity remains elusive. Here, we show that in the cyanobacterium Synechocystis sp. strain PCC 6803, ammonia triggers a rapid photodamage of photosystem II (PSII). Whereas wild-type cells can cope with this damage by turning on the FtsH2-dependent PSII repair cycle, the FtsH2-deficient mutant is highly sensitive and loses PSII activity at millimolar concentration of ammonia. Ammonia-triggered PSII destruction is light dependent and occurs already at low photon fluence rates. Experiments with monochromatic light showed that ammonia-promoted PSII photoinhibition is executed by wavebands known to directly destroy the manganese cluster in the PSII oxygen-evolving complex, suggesting that the oxygen-evolving complex may be a direct target for ammonia toxicity. PMID:18322144

  11. Quantification of cyclic electron flow around Photosystem I in spinach leaves during photosynthetic induction.

    Science.gov (United States)

    Fan, Da-Yong; Nie, Qin; Hope, Alexander B; Hillier, Warwick; Pogson, Barry J; Chow, Wah Soon

    2007-01-01

    The variation of the rate of cyclic electron transport around Photosystem I (PS I) during photosynthetic induction was investigated by illuminating dark-adapted spinach leaf discs with red + far-red actinic light for a varied duration, followed by abruptly turning off the light. The post-illumination re-reduction kinetics of P700+, the oxidized form of the photoactive chlorophyll of the reaction centre of PS I (normalized to the total P700 content), was well described by the sum of three negative exponential terms. The analysis gave a light-induced total electron flux from which the linear electron flux through PS II and PS I could be subtracted, yielding a cyclic electron flux. Our results show that the cyclic electron flux was small in the very early phase of photosynthetic induction, rose to a maximum at about 30 s of illumination, and declined subsequently to leaves by a relatively straightforward method. PMID:17211579

  12. Simultaneous Femtosecond X-ray Spectroscopy and Diffraction of Photosystem II at Room Temperature

    Science.gov (United States)

    Kern, Jan; Alonso-Mori, Roberto; Tran, Rosalie; Hattne, Johan; Gildea, Richard J.; Echols, Nathaniel; Glöckner, Carina; Hellmich, Julia; Laksmono, Hartawan; Sierra, Raymond G.; Lassalle-Kaiser, Benedikt; Koroidov, Sergey; Lampe, Alyssa; Han, Guangye; Gul, Sheraz; DiFiore, Dörte; Milathianaki, Despina; Fry, Alan R.; Miahnahri, Alan; Schafer, Donald W.; Messerschmidt, Marc; Seibert, M. Marvin; Koglin, Jason E.; Sokaras, Dimosthenis; Weng, Tsu-Chien; Sellberg, Jonas; Latimer, Matthew J.; Grosse-Kunstleve, Ralf W.; Zwart, Petrus H.; White, William E.; Glatzel, Pieter; Adams, Paul D.; Bogan, Michael J.; Williams, Garth J.; Boutet, Sébastien; Messinger, Johannes; Zouni, Athina; Sauter, Nicholas K.; Yachandra, Vittal K.; Bergmann, Uwe; Yano, Junko

    2013-01-01

    Intense femtosecond X-ray pulses produced at the Linac Coherent Light Source (LCLS) were used for simultaneous X-ray diffraction (XRD) and X-ray emission spectroscopy (XES) of microcrystals of Photosystem II (PS II) at room temperature. This method probes the overall protein structure and the electronic structure of the Mn4CaO5 cluster in the oxygen-evolving complex of PS II. XRD data are presented from both the dark state (S1) and the first illuminated state (S2) of PS II. Our simultaneous XRD/XES study shows that the PS II crystals are intact during our measurements at the LCLS, not only with respect to the structure of PS II, but also with regard to the electronic structure of the highly radiation sensitive Mn4CaO5 cluster, opening new directions for future dynamics studies. PMID:23413188

  13. Filling the Green Gap of a Megadalton Photosystem I Complex by Conjugation of Organic Dyes.

    Science.gov (United States)

    Gordiichuk, Pavlo I; Rimmerman, Dolev; Paul, Avishek; Gautier, Daniel A; Gruszka, Agnieszka; Saller, Manfred; de Vries, Jan Willem; Wetzelaer, Gert-Jan A H; Manca, Marianna; Gomulya, Widianta; Matmor, Maayan; Gloukhikh, Ekaterina; Loznik, Mark; Ashkenasy, Nurit; Blom, Paul W M; Rögner, Matthias; Loi, Maria Antonietta; Richter, Shachar; Herrmann, Andreas

    2016-01-20

    Photosynthesis is Nature's major process for converting solar into chemical energy. One of the key players in this process is the multiprotein complex photosystem I (PSI) that through absorption of incident photons enables electron transfer, which makes this protein attractive for applications in bioinspired photoactive hybrid materials. However, the efficiency of PSI is still limited by its poor absorption in the green part of the solar spectrum. Inspired by the existence of natural phycobilisome light-harvesting antennae, we have widened the absorption spectrum of PSI by covalent attachment of synthetic dyes to the protein backbone. Steady-state and time-resolved photoluminescence reveal that energy transfer occurs from these dyes to PSI. It is shown by oxygen-consumption measurements that subsequent charge generation is substantially enhanced under broad and narrow band excitation. Ultimately, surface photovoltage (SPV) experiments prove the enhanced activity of dye-modified PSI even in the solid state. PMID:26619248

  14. Effects of CeCl3 on Energy Transfer and Oxygen Evolution in Spinach Photosystem

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Due to 4f electron characteristics and alternation valence, cerium involved in an oxidation-reduction reaction in plant, closely relating to photosynthesis. Our studies proved that cerium could promote photosynthesis and greatly improve spinach growth. However, the mechanism of promoting energy transfer and conversion by cerium remains unclear. Here we reported that the effects of Ce3+ on energy transfer and oxygen evolution in photosystem Ⅱ(PSⅡ) isolated from spinach, which was related to 4f electron characteristics and alternation valence in Ce molecule. The methods of absorption spectrum, fluorescence spectrum were used in the research. Results showed that Ce3+ treatment at low concentration could suitably change PSⅡ microenvironment, increase the absorbance of visible light, improve the energy transfer among amino acids within PSⅡ protein-pigment complex, and accelerate energy transport from tyrosine residue to chlorophyll a. In summary, the photochemical activity of PSⅡ(fluorescence quantum yield) and its oxygen evolving rate were enhanced by Ce3+.

  15. Effect of Mn cluster on the formation of superoxide radicals in photoinhibition of photosystem

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    To further realize the action of superoxide radicals (O-2) in photoinhibition of photosystem Ⅱ (PS Ⅱ),we employed 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as a spin trap, associated with EPR spectroscopy, to study the effect of illumination time on O-*2 formation during high light photoinhibition in PS Ⅱ membranes and Mn-depleted PS Ⅱ membranes. Results indicated that the removal of Mn cluster from PSⅡmembranes has a strong influence on the dynamnics of superoxide formation.The relative mechanism was also discussed.These novel findings may further promote the studies of the structure and function of PSⅡand the mechanism of photoinhibition.

  16. Effect of phosphatidylglycerol on conformation and micro-environment of tyrosyl residue in photosystem

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The structural aspects in the interaction of phosphatidylglycerol (PG) with photosystem II (PSII),mainly the effect of PG on conformation and microenvironment of tyrosine residues of PSII proteins were studied by Fourier transform infrared (FTIR) spectroscopy.It was found that the binding of PG to PSII particle induces changes in the conformation and micropolarity of phenol ring in the tyrosine residues.In other words,the PG effect on the PSII results in blue shift of the stretch vibrational band in the phenol ring from 1620 to 1500 cm-1 with the enhancement of the absorbance intensity.Additionally,a new spectrum of hydrogen bond was also observed.The results imply that the hydrogen-bond formation between the OH group of phenol and one of PG might cause changes in the structures of tyrosine residues in PSII proteins.

  17. The Daughter Four-Membered Microtubule Rootlet Determines Anterior-Posterior Positioning of the Eyespot in Chlamydomonas reinhardtii

    OpenAIRE

    Boyd, Joseph S; Gray, Miranda M.; Thompson, Mark D.; Horst, Cynthia J.; Dieckmann, Carol L.

    2011-01-01

    The characteristic geometry of the unicellular chlorophyte Chlamydomonas reinhardtii has contributed to its adoption as a model system for cellular asymmetry and organelle positioning. The eyespot, a photosensitive organelle, is localized asymmetrically in the cell at a precisely-defined position relative to the flagella and cytoskeletal microtubule rootlets. We have isolated a mutant, named pey1 for posterior eyespot, with variable microtubule rootlet lengths. The length of the acetylated da...

  18. Photostimulation of H2 production in the green alga Chlamydomonas reinhardtii upon photoinhibition of its O2-evolving system

    International Nuclear Information System (INIS)

    A brief exposure (15-30 min) of green alga Chlamydomonas reinhardtii cells to high intensity light (100 W·m-2) was accompanied by rapid suppression of photosynthetic O2 evolution. The decline in the rate of O2 evolution was accompanied by stimulation of H2 production. The effect was dependent on cell suspension density, culture age, and light intensity. It appears that photoinhibition of photosynthetic O2 evolution led to anaerobiosis that is favorable for H2 production. (author)

  19. Functional Characterization of the Chlamydomonas reinhardtii ERG3 Ortholog, a Gene Involved in the Biosynthesis of Ergosterol

    OpenAIRE

    Brumfield, Kristy M.; Moroney, James V.; Moore, Thomas S.; Simms, Tiffany A.; David Donze

    2010-01-01

    BACKGROUND: The predominant sterol in the membranes of the alga Chlamydomonas reinhardtii is ergosterol, which is commonly found in the membranes of fungi, but is rarely found in higher plants. Higher plants and fungi synthesize sterols by different pathways, with plants producing cycloartenol as a precursor to end-product sterols, while non-photosynthesizing organisms like yeast and humans produce lanosterol as a precursor. Analysis of the C. reinhardtii genome sequence reveals that this alg...

  20. Manipulation of oil synthesis in Nannochloropsis strain NIES-2145 with a phosphorus starvation–inducible promoter from Chlamydomonas reinhardtii

    OpenAIRE

    Iwai, Masako; Hori, Koichi; Sasaki-Sekimoto, Yuko; Shimojima, Mie; Ohta, Hiroyuki

    2015-01-01

    Microalgae accumulate triacylglycerols (TAGs) under conditions of nutrient stress. Phosphorus (P) starvation induces the accumulation of TAGs, and the cells under P starvation maintain growth through photosynthesis. We recently reported that P starvation–dependent overexpression of type-2 diacylglycerol acyl-CoA acyltransferase (CrDGTT4) from Chlamydomonas reinhardtii using a sulfoquinovosyldiacylglycerol synthase 2 (SQD2) promoter, which has increased activity during P starvation, enhances T...

  1. 3D Ultrastructural Organization of Whole Chlamydomonas reinhardtii Cells Studied by Nanoscale Soft X-Ray Tomography

    OpenAIRE

    Hummel, Eric; Guttmann, Peter; Werner, Stephan; Tarek, Basel; SCHNEIDER, Gerd; Kunz, Michael; Frangakis, Achilleas S.; Westermann, Benedikt

    2012-01-01

    The complex architecture of their structural elements and compartments is a hallmark of eukaryotic cells. The creation of high resolution models of whole cells has been limited by the relatively low resolution of conventional light microscopes and the requirement for ultrathin sections in transmission electron microscopy. We used soft x-ray tomography to study the 3D ultrastructural organization of whole cells of the unicellular green alga Chlamydomonas reinhardtii at unprecedented spatial re...

  2. 3D ultrastructural organization of whole Chlamydomonas reinhardtii cells studied by nanoscale soft x-ray tomography

    OpenAIRE

    Hummel, Eric; Guttmann, Peter; Werner, Stephan; Tarek, Basel; SCHNEIDER, Gerd; Kunz, Michael; Frangakis, Achilleas S.; Westermann, Benedikt

    2012-01-01

    The complex architecture of their structural elements and compartments is a hallmark of eukaryotic cells. The creation of high resolution models of whole cells has been limited by the relatively low resolution of conventional light microscopes and the requirement for ultrathin sections in transmission electron microscopy. We used soft x-ray tomography to study the 3D ultrastructural organization of whole cells of the unicellular green alga Chlamydomonas reinhardtii at unprecedented spatial re...

  3. Cell-to-Cell Diversity in a Synchronized Chlamydomonas Culture As Revealed by Single-Cell Analyses

    OpenAIRE

    Garz, Andreas; Sandmann, Michael; Rading, Michael; Ramm, Sascha; Menzel, Ralf; Steup, Martin

    2012-01-01

    In a synchronized photoautotrophic culture of Chlamydomonas reinhardtii, cell size, cell number, and the averaged starch content were determined throughout the light-dark cycle. For single-cell analyses, the relative cellular starch was quantified by measuring the second harmonic generation (SHG). In destained cells, amylopectin essentially represents the only biophotonic structure. As revealed by various validation procedures, SHG signal intensities are a reliable relative measure of the cel...

  4. Identification of astaxanthin diglucoside diesters from snow alga Chlamydomonas nivalis by liquid chromatography – atmospheric pressure chemical ionization mass spectrometry

    Czech Academy of Sciences Publication Activity Database

    Řezanka, Tomáš; Nedbalová, Linda; Sigler, Karel; Cepák, Vladislav

    2008-01-01

    Roč. 69, č. 2 (2008), s. 479-490. ISSN 0031-9422 R&D Projects: GA MŠk 1M0571; GA AV ČR(CZ) KJB601110509 Institutional research plan: CEZ:AV0Z50200510; CEZ:AV0Z60050516 Keywords : chlamydomonas nivalis * snow alga * astaxanthin diglucoside diesters Subject RIV: EE - Microbiology, Virology Impact factor: 2.946, year: 2008

  5. Carotenoid triplet states in photosystem II: coupling with low-energy states of the core complex.

    Science.gov (United States)

    Santabarbara, Stefano; Agostini, Alessandro; Casazza, Anna Paola; Zucchelli, Giuseppe; Carbonera, Donatella

    2015-02-01

    The photo-excited triplet states of carotenoids, sensitised by triplet-triplet energy transfer from the chlorophyll triplet states, have been investigated in the isolated Photosystem II (PSII) core complex and PSII-LHCII (Light Harvesting Complex II) supercomplex by Optically Detected Magnetic Resonance techniques, using both fluorescence (FDMR) and absorption (ADMR) detection. The absence of Photosystem I allows us to reach the full assignment of the carotenoid triplet states populated in PSII under steady state illumination at low temperature. Five carotenoid triplet ((3)Car) populations were identified in PSII-LHCII, and four in the PSII core complex. Thus, four (3)Car populations are attributed to β-carotene molecules bound to the core complex. All of them show associated fluorescence emission maxima which are relatively red-shifted with respect to the bulk emission of both the PSII-LHCII and the isolated core complexes. In particular the two populations characterised by Zero Field Splitting parameters |D|=0.0370-0.0373 cm(-1)/|E|=0.00373-0.00375 cm(-1) and |D|=0.0381-0.0385 cm(-1)/|E|=0.00393-0.00389 cm(-1), are coupled by singlet energy transfer with chlorophylls which have a red-shifted emission peaking at 705 nm. This observation supports previous suggestions that pointed towards the presence of long-wavelength chlorophyll spectral forms in the PSII core complex. The fifth (3)Car component is observed only in the PSII-LHCII supercomplex and is then assigned to the peripheral light harvesting system. PMID:25481107

  6. A miniature bioassay for testing the acute phytotoxicity of photosystem II herbicides on seagrass.

    Directory of Open Access Journals (Sweden)

    Adam D Wilkinson

    Full Text Available Photosystem II (PSII herbicides have been detected in nearshore tropical waters such as those of the Great Barrier Reef and may add to the pressure posed by runoff containing sediments and nutrients to threatened seagrass habitats. There is a growing number of studies into the potential effects of herbicides on seagrass, generally using large experimental setups with potted plants. Here we describe the successful development of an acute 12-well plate phytotoxicity assay for the PSII herbicide Diuron using isolated Halophila ovalis leaves. Fluorescence images demonstrated Diuron affected the entire leaf surface evenly and responses were not influenced by isolating leaves from the plant. The optimum exposure duration was 24 h, by which time the inhibition of effective quantum yield of PSII (∆F/F(m' was highest and no deterioration of photosystems was evident in control leaves. The inhibition of ∆F/F(m' by Diuron in isolated H. ovalis leaves was identical to both potted and hydroponically grown plants (with leaves remaining attached to rhizomes, indicating similar reductions in photosynthetic activity in these acute well-plate assays. The sensitivity of the assay was not influenced by irradiance (range tested 40 to 400 μmol photons m(-2 s(-1. High irradiance, however, caused photo-oxidative stress in H. ovalis and this generally impacted in an additive or sub-additive way with Diuron to damage PSII. The bioassay using isolated leaves is more rapid, uses far less biological material and does not rely on specialised aquarium facilities in comparison with assays using potted plants. The development and validation of this sensitive bioassay will be useful to reliably screen and monitor the phytotoxicity of existing and emerging PSII herbicides and contribute to risk assessments and water quality guideline development in the future.

  7. The Lack of Successors in Family Farms

    OpenAIRE

    Alessandro Corsi

    2005-01-01

    The traditional process of farm transmission within the family is threatened by the increasing age of operators and by their children’s preference for other activi-ties. After describing the national patterns of agricultural labour ageing, this es-say aims at quantifying the proportion of those family farms that will probably have no successors and analysing their characteristics, using a random sample of individual farm data from Piedmont drawn from the 2000 Agricultural Census. The lack of ...

  8. In vivo photosystem I reduction in thermophilic and mesophilic cyanobacteria: The thermal resistance of the process is limited by factors other than the unfolding of the partners

    International Nuclear Information System (INIS)

    Photosystem I reduction by plastocyanin and cytochrome c 6 in cyanobacteria has been extensively studied in vitro, but much less information is provided on this process inside the cell. Here, we report an analysis of the electron transfer from both plastocyanin and cytochrome c 6 to photosystem I in intact cells of several cyanobacterial species, including a comparative study of the temperature effect in mesophilic and thermophilic organisms. Our data show that cytochrome c 6 reduces photosystem I by following a reaction mechanism involving complex formation, whereas the copper-protein follows a simpler collisional mechanism. These results contrast with previous kinetic studies in vitro. The effect of temperature on photosystem I reduction leads us to conclude that the thermal resistance of this process is determined by factors other than the proper stability of the protein partners

  9. The ferredoxin-thioredoxin system of a green alga, Chlamydomonas reinhardtii: identification and characterization of thioredoxins and ferredoxin-thioredoxin reductase components

    Science.gov (United States)

    Huppe, H. C.; de Lamotte-Guery, F.; Buchanan, B. B.

    1990-01-01

    The components of the ferredoxin-thioredoxin (FT) system of Chlamydomonas reinhardtii have been purified and characterized. The system resembled that of higher plants in consisting of a ferredoxin-thioredoxin reductase (FTR) and two types of thioredoxin, a single f and two m species, m1 and m2. The Chlamydomonas m and f thioredoxins were antigenically similar to their higher-plant counterparts, but not to one another. The m thioredoxins were recognized by antibodies to both higher plant m and bacterial thioredoxins, whereas the thioredoxin f was not. Chlamydomonas thioredoxin f reacted, although weakly, with the antibody to spinach thioredoxin f. The algal thioredoxin f differed from thioredoxins studied previously in behaving as a basic protein on ion-exchange columns. Purification revealed that the algal thioredoxins had molecular masses (Mrs) typical of thioredoxins from other sources, m1 and m2 being 10700 and f 11500. Chlamydomonas FTR had two dissimilar subunits, a feature common to all FTRs studied thus far. One, the 13-kDa ("similar") subunit, resembled its counterpart from other sources in both size and antigenicity. The other, 10-kDa ("variable") subunit was not recognized by antibodies to any FTR tested. When combined with spinach, (Spinacia oleracea L.) thylakoid membranes, the components of the FT system functioned in the light activation of the standard target enzymes from chloroplasts, corn (Zea mays L.) NADP-malate dehydrogenase (EC 1.1.1.82) and spinach fructose 1,6-bisphosphatase (EC 3.1.3.11) as well as the chloroplast-type fructose 1,6-bisphosphatase from Chlamydomonas. Activity was greatest if ferredoxin and other components of the FT system were from Chlamydomonas. The capacity of the Chlamydomonas FT system to activate autologous FBPase indicates that light regulates the photosynthetic carbon metabolism of green algae as in other oxygenic photosynthetic organisms.

  10. Alternative acetate production pathways in Chlamydomonas reinhardtii during dark anoxia and the dominant role of chloroplasts in fermentative acetate production.

    Science.gov (United States)

    Yang, Wenqiang; Catalanotti, Claudia; D'Adamo, Sarah; Wittkopp, Tyler M; Ingram-Smith, Cheryl J; Mackinder, Luke; Miller, Tarryn E; Heuberger, Adam L; Peers, Graham; Smith, Kerry S; Jonikas, Martin C; Grossman, Arthur R; Posewitz, Matthew C

    2014-11-01

    Chlamydomonas reinhardtii insertion mutants disrupted for genes encoding acetate kinases (EC 2.7.2.1) (ACK1 and ACK2) and a phosphate acetyltransferase (EC 2.3.1.8) (PAT2, but not PAT1) were isolated to characterize fermentative acetate production. ACK1 and PAT2 were localized to chloroplasts, while ACK2 and PAT1 were shown to be in mitochondria. Characterization of the mutants showed that PAT2 and ACK1 activity in chloroplasts plays a dominant role (relative to ACK2 and PAT1 in mitochondria) in producing acetate under dark, anoxic conditions and, surprisingly, also suggested that Chlamydomonas has other pathways that generate acetate in the absence of ACK activity. We identified a number of proteins associated with alternative pathways for acetate production that are encoded on the Chlamydomonas genome. Furthermore, we observed that only modest alterations in the accumulation of fermentative products occurred in the ack1, ack2, and ack1 ack2 mutants, which contrasts with the substantial metabolite alterations described in strains devoid of other key fermentation enzymes. PMID:25381350

  11. Time sequence of the damage to the acceptor and donor sides of photosystem II by UV-B radiation as evaluated by chlorophyll a fluorescence

    OpenAIRE

    Rensen, van, J.J.S.; Vredenberg, W J; Rodrigues, G.C.

    2007-01-01

    The effects of ultraviolet-B (UV-B) radiation on photosystem II (PS II) were studied in leaves of Chenopodium album. After the treatment with UV-B the damage was estimated using chlorophyll a fluorescence techniques. Measurements of modulated fluorescence using a pulse amplitude modulated fluorometer revealed that the efficiency of photosystem II decreased both with increasing time of UV-B radiation and with increasing intensity of the UV-B. Fluorescence induction rise curves were analyzed us...

  12. Effect of photosystem I inactivation on chlorophyll a fluorescence induction in wheat leaves: Does activity of photosystem I play any role in OJIP rise?

    Science.gov (United States)

    Zivcak, Marek; Brestic, Marian; Kunderlikova, Kristyna; Olsovska, Katarina; Allakhverdiev, Suleyman I

    2015-11-01

    Interpretation of the fast chlorophyll a fluorescence induction is still a subject of continuing discussion. One of the contentious issues is the influence of photosystem I (PSI) activity on the kinetics of the thermal JIP-phase of OJIP rise. To demonstrate this influence, we realized a series of measurements in wheat leaves subjected to PSI photoinactivation by the sequence of red saturation pulses (15,000 μmol photons m(-2) s(-1) for 0.3 s, every 10 s) applied in darkness. Such a treatment led to a moderate decrease of maximum quantum efficiency of PSII (by ~8%), but a strong decrease of the number of oxidizable PSI (by ~55%), which considerably limited linear electron transport and CO2 assimilation. Surprisingly, the PSI photoinactivation had low effects on OJIP kinetics of variable fluorescence. In particular, the amplitude of variable fluorescence of IP-step (ΔVIP), which has been considered to be a measure of PSI content, was not decreased, despite the low content of photooxidizable PSI. On the other hand, the slower relaxation of chlorophyll fluorescence after saturation pulse as well as the results of the double-hit method suggest that PSI inactivation treatment led to an increase of the fraction of QB-nonreducing PSII reaction centers. Our results somewhat challenge the mainstream interpretations of JIP-thermal phase, and at least suggest that the IP amplitude cannot serve to estimate reliably the PSI content or the PSI to PSII ratio. Moreover, these results recommend the use of the novel method of PSI inactivation, which might help clarify some important issues needed for the correct understanding of the OJIP fluorescence rise. PMID:26388470

  13. Accidents in radiotherapy: Lack of quality assurance?

    International Nuclear Information System (INIS)

    About 150 radiological accidents, involving more than 3000 patients with adverse effects, 15 patient's fatalities and about 5000 staff and public exposures have been collected and analysed. Out of 67 analysed accidents in external beam therapy 22% has been caused by wrong calculation of the exposure time or monitor units, 13% by inadequate review of patient's chart, 12% by mistakes in the anatomical area to be treated. The remaining 35% can be attributed to 17 different causes. The most common mistakes in brachytherapy were wrong activities of sources used for treatment (20%), inadequate procedures for placement of sources applicators (14%), mistakes in calculating the treatment time (12%), etc. The direct and contributing causes of radiological accidents have been deduced from each event, when it was possible and categorized into 9 categories: mistakes in procedures (30%), professional mistakes (17%), communication mistakes (15%), lack of training (8.5%), interpretation mistakes (7%), lack of supervision (6%), mistakes in judgement (6%), hardware failures (5%), software and other mistakes (5.5%). Three types of direct and contributing causes responsible for almost 62% of all accidents are directly connected to the quality assurance of treatment. The lessons learnt from the accidents are related to frequencies of direct and contributing factors and show that most of the accident are caused by lack, non-application of quality assurance (QA) procedures or by underestimating of QA procedures. The international system for collection of accidents and dissemination of lessons learnt from the different accidents, proposed by IAEA, can contribute to better practice in many radiotherapy departments. Most of the accidents could have been avoided, had a comprehensive QA programme been established and properly applied in all radiotherapy departments, whatever the size. (author)

  14. Why does Colombia lack agricultural commodity futures?

    Directory of Open Access Journals (Sweden)

    Pablo Moreno-Alemay

    2015-11-01

    Full Text Available This article explores the reasons why futures contracts are not traded as an alternative to price hedging for agricultural goods in Colombia. Based on surveys, interviews and statistical analysis, this study identified that conceptual gaps in contract negotiation, lack of consensus in the agricultural sector regarding the use of financial mechanisms and the sector’s infrequent contact with Colombia’s financial institutions, are the main reasons why a futures contracts market has not emerged.

  15. A lacking term in the proton spin

    International Nuclear Information System (INIS)

    The spin structure of an elementary particle shows that the center of mass and center of charge of the particle are two different points. Dirac's spin operator is the angular momentum of the particle with respect to the center of charge. This implies that the addition of the three Dirac spin operators of the three quarks cannot produce the spin of the proton. It is necessary to add at least, the angular momenta of the three quarks with respect to their corresponding center of mass. This lacking term, which is related to the separation between both points has a clear relationship with Dirac's electric dipole term.

  16. Oil accumulation in the model green alga Chlamydomonas reinhardtii: characterization, variability between common laboratory strains and relationship with starch reserves

    Directory of Open Access Journals (Sweden)

    Carrier Patrick

    2011-01-01

    Full Text Available Abstract Background When cultivated under stress conditions, many microalgae species accumulate both starch and oil (triacylglycerols. The model green microalga Chlamydomonas reinhardtii has recently emerged as a model to test genetic engineering or cultivation strategies aiming at increasing lipid yields for biodiesel production. Blocking starch synthesis has been suggested as a way to boost oil accumulation. Here, we characterize the triacylglycerol (TAG accumulation process in Chlamydomonas and quantify TAGs in various wild-type and starchless strains. Results In response to nitrogen deficiency, Chlamydomonas reinhardtii produced TAGs enriched in palmitic, oleic and linoleic acids that accumulated in oil-bodies. Oil synthesis was maximal between 2 and 3 days following nitrogen depletion and reached a plateau around day 5. In the first 48 hours of oil deposition, a ~80% reduction in the major plastidial membrane lipids occurred. Upon nitrogen re-supply, mobilization of TAGs started after starch degradation but was completed within 24 hours. Comparison of oil content in five common laboratory strains (CC124, CC125, cw15, CC1690 and 11-32A revealed a high variability, from 2 μg TAG per million cell in CC124 to 11 μg in 11-32A. Quantification of TAGs on a cell basis in three mutants affected in starch synthesis (cw15sta1-2, cw15sta6 and cw15sta7-1 showed that blocking starch synthesis did not result in TAG over-accumulation compared to their direct progenitor, the arginine auxotroph strain 330. Moreover, no significant correlation was found between cellular oil and starch levels among the twenty wild-type, mutants and complemented strains tested. By contrast, cellular oil content was found to increase steeply with salt concentration in the growth medium. At 100 mM NaCl, oil level similar to nitrogen depletion conditions could be reached in CC124 strain. Conclusion A reference basis for future genetic studies of oil metabolism in Chlamydomonas

  17. Delayed flowering is associated with lack of photosynthetic acclimation in Pigeon pea (Cajanus cajan L.) grown under elevated CO₂.

    Science.gov (United States)

    Sreeharsha, Rachapudi Venkata; Sekhar, Kalva Madhana; Reddy, Attipalli Ramachandra

    2015-02-01

    In the present study, we investigated the likely consequences of future atmospheric CO2 concentrations [CO2] on growth, physiology and reproductive phenology of Pigeonpea. A short duration Pigeonpea cultivar (ICPL 15011) was grown without N fertilizer from emergence to final harvest in CO2 enriched atmosphere (open top chambers; 550μmolmol(-1)) for two seasons. CO2 enrichment improved both net photosynthetic rates (Asat) and foliar carbohydrate content by 36 and 43%, respectively, which further reflected in dry biomass after harvest, showing an increment of 29% over the control plants. Greater carboxylation rates of Rubisco (Vcmax) and photosynthetic electron transport rates (Jmax) in elevated CO2 grown plants measured during different growth periods, clearly demonstrated lack of photosynthetic acclimation. Further, chlorophyll a fluorescence measurements as indicated by Fv/Fm and ΔF/Fm' ratios justified enhanced photosystem II efficiency. Mass and number of root nodules were significantly high in elevated CO2 grown plants showing 58% increase in nodule mass ratio (NMR) which directly correlated with Pn. Growth under high CO2 showed significant ontogenic changes including delayed flowering. In conclusion, our data demonstrate that the lack of photosynthetic acclimation and increased carbohydrate-nitrogen reserves modulate the vegetative and reproductive growth patterns in Pigeonpea grown under elevated CO2. PMID:25575994

  18. Light acclimation in the lycophyte Selaginella martensii depends on changes in the amount of photosystems and on the flexibility of the light-harvesting complex II antenna association with both photosystems.

    Science.gov (United States)

    Ferroni, Lorenzo; Suorsa, Marjaana; Aro, Eva-Mari; Baldisserotto, Costanza; Pancaldi, Simonetta

    2016-07-01

    Vascular plants have evolved a long-term light acclimation strategy primarily relying on the regulation of the relative amounts of light-harvesting complex II (LHCII) and of the two photosystems, photosystem I (PSI) and photosystem II (PSII). We investigated whether such a model is also valid in Selaginella martensii, a species belonging to the early diverging group of lycophytes. Selaginella martensii plants were acclimated to three natural light regimes (extremely low light (L), medium light (M) and full sunlight (H)) and thylakoid organization was characterized combining ultrastructural, biochemical and functional methods. From L to H plants, thylakoid architecture was rearranged from (pseudo)lamellar to predominantly granal, the PSII : PSI ratio changed in favour of PSI, and the photochemical capacity increased. However, regulation of light harvesting did not occur through variations in the amount of free LHCII, but rather resulted from the flexibility of the association of free LHCII with PSII and PSI. In lycophytes, the free interspersed LHCII serves a fixed proportion of reaction centres, either PSII or PSI, and the regulation of PSI-LHCII(-PSII) megacomplexes is an integral part of long-term acclimation. Free LHCII ensures photoprotection of PSII, allows regulated use of PSI as an energy quencher, and can also quench endangered PSI. PMID:27058989

  19. A quantitative structure–function relationship for the Photosystem II reaction center: Supermolecular behavior in natural photosynthesis

    OpenAIRE

    Barter, Laura M. C.; Durrant, James R; Klug, David R.

    2003-01-01

    Light-induced charge separation is the primary photochemical event of photosynthesis. Efficient charge separation in photosynthetic reaction centers requires the balancing of electron and excitation energy transfer processes, and in Photosystem II (PSII), these processes are particularly closely entangled. Calculations that treat the cofactors of the PSII reaction center as a supermolecular complex allow energy and electron transfer reactions to be described in a unified way. This calculation...

  20. Subunit Organization of a Synechocystis Hetero-Oligomeric Thylakoid FtsH Complex Involved in Photosystem II Repair

    Czech Academy of Sciences Publication Activity Database

    Boehm, M.; Yu, J.; Krynická, Vendula; Barker, M.; Tichý, Martin; Komenda, Josef; Nixon, P. J.; Nield, J.

    2012-01-01

    Roč. 24, č. 9 (2012), s. 3669-3683. ISSN 1040-4651 R&D Projects: GA MŠk(CZ) ED2.1.00/03.0110; GA ČR GBP501/12/G055 Institutional support: RVO:61388971 Keywords : photosystem II * FtsH metalloproteases * subunit Subject RIV: EE - Microbiology, Virology Impact factor: 9.251, year: 2012