title: Chlamydomonas reinhardtii PsbS Protein Is Functional and Accumulates Rapidly and Transiently under High Light.
abstract: 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.
authors.affiliation: Aix Marseille Université (AMU), Commissariat à l'Energie Atomique (CEA), Centre National de la Recherche Scientifique (CNRS), UMR 7265 Biologie Végétale et Microbiologie Environnementales, Bioscience and Biotechnology Institute of Aix-Marseille (BIAM), Laboratoire de Génétique et Biophysique des Plantes, 13009 Marseille, France (T.T., S.C.); and Aix Marseille Université (AMU), Commissariat à l'Energie Atomique (CEA), Centre National de la Recherche Scientifique (CNRS), UMR 7265 Biologie Végétale et Microbiologie Environnementales, Bioscience and Biotechnology Institute of Aix-Marseille (BIAM), Laboratoire de Bioénergétique et Biotechnologie des Bactéries et Microalgues, 13108 St. Paul Les Durance, France (P.A., G.P.).
authors.forename: Tania
authors.initials: T
authors.lastname: Tibiletti
authors.affiliation: Aix Marseille Université (AMU), Commissariat à l'Energie Atomique (CEA), Centre National de la Recherche Scientifique (CNRS), UMR 7265 Biologie Végétale et Microbiologie Environnementales, Bioscience and Biotechnology Institute of Aix-Marseille (BIAM), Laboratoire de Génétique et Biophysique des Plantes, 13009 Marseille, France (T.T., S.C.); and Aix Marseille Université (AMU), Commissariat à l'Energie Atomique (CEA), Centre National de la Recherche Scientifique (CNRS), UMR 7265 Biologie Végétale et Microbiologie Environnementales, Bioscience and Biotechnology Institute of Aix-Marseille (BIAM), Laboratoire de Bioénergétique et Biotechnologie des Bactéries et Microalgues, 13108 St. Paul Les Durance, France (P.A., G.P.).
authors.forename: Pascaline
authors.initials: P
authors.lastname: Auroy
authors.affiliation: Aix Marseille Université (AMU), Commissariat à l'Energie Atomique (CEA), Centre National de la Recherche Scientifique (CNRS), UMR 7265 Biologie Végétale et Microbiologie Environnementales, Bioscience and Biotechnology Institute of Aix-Marseille (BIAM), Laboratoire de Génétique et Biophysique des Plantes, 13009 Marseille, France (T.T., S.C.); and Aix Marseille Université (AMU), Commissariat à l'Energie Atomique (CEA), Centre National de la Recherche Scientifique (CNRS), UMR 7265 Biologie Végétale et Microbiologie Environnementales, Bioscience and Biotechnology Institute of Aix-Marseille (BIAM), Laboratoire de Bioénergétique et Biotechnologie des Bactéries et Microalgues, 13108 St. Paul Les Durance, France (P.A., G.P.).
authors.forename: Gilles
authors.initials: G
authors.lastname: Peltier
authors.affiliation: Aix Marseille Université (AMU), Commissariat à l'Energie Atomique (CEA), Centre National de la Recherche Scientifique (CNRS), UMR 7265 Biologie Végétale et Microbiologie Environnementales, Bioscience and Biotechnology Institute of Aix-Marseille (BIAM), Laboratoire de Génétique et Biophysique des Plantes, 13009 Marseille, France (T.T., S.C.); and Aix Marseille Université (AMU), Commissariat à l'Energie Atomique (CEA), Centre National de la Recherche Scientifique (CNRS), UMR 7265 Biologie Végétale et Microbiologie Environnementales, Bioscience and Biotechnology Institute of Aix-Marseille (BIAM), Laboratoire de Bioénergétique et Biotechnologie des Bactéries et Microalgues, 13108 St. Paul Les Durance, France (P.A., G.P.) stefano.caffarri@univ-amu.fr.
authors.forename: Stefano
authors.initials: S
authors.lastname: Caffarri
mesh_terms: D020418:Algal Proteins / Q000378:metabolism*; D016825:Chlamydomonas reinhardtii / Q000235:genetics / Q000254:growth & development / Q000378:metabolism* / Q000528:radiation effects; D002734:Chlorophyll / Q000378:metabolism; D003470:Culture Media; D005453:Fluorescence; D005786:Gene Expression Regulation / Q000528:radiation effects; D007700:Kinetics; D008027:Light; D045342:Light-Harvesting Protein Complexes / Q000235:genetics / Q000378:metabolism*; D009584:Nitrogen / Q000172:deficiency; D010641:Phenotype; D045332:Photosystem II Protein Complex / Q000378:metabolism; D013312:Stress, Physiological / Q000235:genetics / Q000528:radiation effects
chemical_list: D020418:Algal Proteins; D003470:Culture Media; D045342:Light-Harvesting Protein Complexes; D045332:Photosystem II Protein Complex; D002734:Chlorophyll; D009584:Nitrogen