title: A Light Switch Based on Protein S-Nitrosylation Fine-Tunes Photosynthetic Light Harvesting in Chlamydomonas.
abstract: 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.
authors.affiliation: Bielefeld University, Faculty of Biology, Center for Biotechnology (CeBiTec), 33615 Bielefeld, Germany (H.B., L.W., O.K.); andSorbonne Universités, UPMC University of Paris 6, Centre National de la Recherche Scientifique, UMR8226, Laboratoire de Biologie Moléculaire et Cellulaire des Eucaryotes, Institut de Biologie Physico-Chimique, 75005 Paris, France (M.D.M., S.M., C.H.M., S.D.L.).
authors.forename: Hanna
authors.initials: H
authors.lastname: Berger
authors.affiliation: Bielefeld University, Faculty of Biology, Center for Biotechnology (CeBiTec), 33615 Bielefeld, Germany (H.B., L.W., O.K.); andSorbonne Universités, UPMC University of Paris 6, Centre National de la Recherche Scientifique, UMR8226, Laboratoire de Biologie Moléculaire et Cellulaire des Eucaryotes, Institut de Biologie Physico-Chimique, 75005 Paris, France (M.D.M., S.M., C.H.M., S.D.L.).
authors.forename: Marcello
authors.initials: M
authors.lastname: De Mia
authors.affiliation: Bielefeld University, Faculty of Biology, Center for Biotechnology (CeBiTec), 33615 Bielefeld, Germany (H.B., L.W., O.K.); andSorbonne Universités, UPMC University of Paris 6, Centre National de la Recherche Scientifique, UMR8226, Laboratoire de Biologie Moléculaire et Cellulaire des Eucaryotes, Institut de Biologie Physico-Chimique, 75005 Paris, France (M.D.M., S.M., C.H.M., S.D.L.).
authors.forename: Samuel
authors.identifier: 0000-0002-9214-7792
authors.initials: S
authors.lastname: Morisse
authors.affiliation: Bielefeld University, Faculty of Biology, Center for Biotechnology (CeBiTec), 33615 Bielefeld, Germany (H.B., L.W., O.K.); andSorbonne Universités, UPMC University of Paris 6, Centre National de la Recherche Scientifique, UMR8226, Laboratoire de Biologie Moléculaire et Cellulaire des Eucaryotes, Institut de Biologie Physico-Chimique, 75005 Paris, France (M.D.M., S.M., C.H.M., S.D.L.).
authors.forename: Christophe H
authors.identifier: 0000-0002-0729-3841
authors.initials: CH
authors.lastname: Marchand
authors.affiliation: Bielefeld University, Faculty of Biology, Center for Biotechnology (CeBiTec), 33615 Bielefeld, Germany (H.B., L.W., O.K.); andSorbonne Universités, UPMC University of Paris 6, Centre National de la Recherche Scientifique, UMR8226, Laboratoire de Biologie Moléculaire et Cellulaire des Eucaryotes, Institut de Biologie Physico-Chimique, 75005 Paris, France (M.D.M., S.M., C.H.M., S.D.L.).
authors.forename: Stéphane D
authors.initials: SD
authors.lastname: Lemaire
authors.affiliation: Bielefeld University, Faculty of Biology, Center for Biotechnology (CeBiTec), 33615 Bielefeld, Germany (H.B., L.W., O.K.); andSorbonne Universités, UPMC University of Paris 6, Centre National de la Recherche Scientifique, UMR8226, Laboratoire de Biologie Moléculaire et Cellulaire des Eucaryotes, Institut de Biologie Physico-Chimique, 75005 Paris, France (M.D.M., S.M., C.H.M., S.D.L.).
authors.forename: Lutz
authors.initials: L
authors.lastname: Wobbe
authors.affiliation: Bielefeld University, Faculty of Biology, Center for Biotechnology (CeBiTec), 33615 Bielefeld, Germany (H.B., L.W., O.K.); andSorbonne Universités, UPMC University of Paris 6, Centre National de la Recherche Scientifique, UMR8226, Laboratoire de Biologie Moléculaire et Cellulaire des Eucaryotes, Institut de Biologie Physico-Chimique, 75005 Paris, France (M.D.M., S.M., C.H.M., S.D.L.) olaf.kruse@uni-bielefeld.de.
authors.forename: Olaf
authors.initials: O
authors.lastname: Kruse
mesh_terms: D020418:Algal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism; D002696:Chlamydomonas / Q000502:physiology* / Q000528:radiation effects; D003545:Cysteine / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D008027:Light; D045342:Light-Harvesting Protein Complexes / Q000378:metabolism* / Q000528:radiation effects; D008958:Models, Molecular; D010084:Oxidation-Reduction; D010788:Photosynthesis / Q000502:physiology* / Q000528:radiation effects; D045332:Photosystem II Protein Complex / Q000378:metabolism* / Q000528:radiation effects; D012333:RNA, Messenger / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D013879:Thioredoxins / Q000378:metabolism; D020524:Thylakoids / Q000378:metabolism
chemical_list: D020418:Algal Proteins; D045342:Light-Harvesting Protein Complexes; D045332:Photosystem II Protein Complex; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D013879:Thioredoxins; D003545:Cysteine