title: The chloroplast calcium sensor CAS is required for photoacclimation in Chlamydomonas reinhardtii.
abstract: The plant-specific calcium binding protein CAS (calcium sensor) has been localized in chloroplast thylakoid membranes of vascular plants and green algae. To elucidate the function of CAS in Chlamydomonas reinhardtii, we generated and analyzed eight independent CAS knockdown C. reinhardtii lines (cas-kd). Upon transfer to high-light (HL) growth conditions, cas-kd lines were unable to properly induce the expression of LHCSR3 protein that is crucial for nonphotochemical quenching. Prolonged exposure to HL revealed a severe light sensitivity of cas-kd lines and caused diminished activity and recovery of photosystem II (PSII). Remarkably, the induction of LHCSR3, the growth of cas-kd lines under HL, and the performance of PSII were fully rescued by increasing the calcium concentration in the growth media. Moreover, perturbing cellular Ca(2+) homeostasis by application of the calmodulin antagonist W7 or the G-protein activator mastoparan impaired the induction of LHCSR3 expression in a concentration-dependent manner. Our findings demonstrate that CAS and Ca(2+) are critically involved in the regulation of the HL response and particularly in the control of LHCSR3 expression.
authors.affiliation: Institute of Plant Biology and Biotechnology, University of Münster, 48143 Muenster, Germany.
authors.forename: Dimitris
authors.initials: D
authors.lastname: Petroutsos
authors.forename: Andreas
authors.initials: A
authors.lastname: Busch
authors.forename: Ingrid
authors.initials: I
authors.lastname: Janssen
authors.forename: Kerstin
authors.initials: K
authors.lastname: Trompelt
authors.forename: Sonja Verena
authors.initials: SV
authors.lastname: Bergner
authors.forename: Stefan
authors.initials: S
authors.lastname: Weinl
authors.forename: Michael
authors.initials: M
authors.lastname: Holtkamp
authors.forename: Uwe
authors.initials: U
authors.lastname: Karst
authors.forename: Jörg
authors.initials: J
authors.lastname: Kudla
authors.forename: Michael
authors.initials: M
authors.lastname: Hippler
mesh_terms: D000222:Adaptation, Physiological / Q000528:radiation effects*; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology*; D002147:Calmodulin / Q000037:antagonists & inhibitors; D016825:Chlamydomonas reinhardtii / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects; D002734:Chlorophyll / Q000378:metabolism / Q000528:radiation effects; D002736:Chloroplasts / Q000378:metabolism* / Q000528:radiation effects; D015536:Down-Regulation / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018506:Gene Expression Regulation, Plant / Q000502:physiology / Q000528:radiation effects; D036341:Intercellular Signaling Peptides and Proteins; D008027:Light; D045342:Light-Harvesting Protein Complexes / Q000235:genetics / Q000378:metabolism; D010455:Peptides / Q000494:pharmacology; D010641:Phenotype; D010788:Photosynthesis / Q000502:physiology / Q000528:radiation effects; D045332:Photosystem II Protein Complex / Q000378:metabolism / Q000528:radiation effects; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D040901:Proteomics; D017384:Sequence Deletion; D015398:Signal Transduction / Q000502:physiology / Q000528:radiation effects; D013449:Sulfonamides / Q000494:pharmacology; D020524:Thylakoids / Q000378:metabolism / Q000528:radiation effects; D014862:Wasp Venoms / Q000494:pharmacology
chemical_list: D002147:Calmodulin; D004791:Enzyme Inhibitors; D036341:Intercellular Signaling Peptides and Proteins; D045342:Light-Harvesting Protein Complexes; D010455:Peptides; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D013449:Sulfonamides; D014862:Wasp Venoms; D002734:Chlorophyll; C017967:W 7; C037500:mastoparan; D002118:Calcium