title: Functional Accumulation of Antenna Proteins in Chlorophyll b-Less Mutants of Chlamydomonas reinhardtii.
abstract: The green alga Chlamydomonas reinhardtii contains several light-harvesting chlorophyll a/b complexes (LHC): four major LHCIIs, two minor LHCIIs, and nine LHCIs. We characterized three chlorophyll b-less mutants to assess the effect of chlorophyll b deficiency on the function, assembly, and stability of these chlorophyll a/b binding proteins. We identified point mutations in two mutants that inactivate the CAO gene responsible for chlorophyll a to chlorophyll b conversion. All LHCIIs accumulated to wild-type levels in a CAO mutant but their light-harvesting function for photosystem II was impaired. In contrast, most LHCIs accumulated to wild-type levels in the mutant and their light-harvesting capability for photosystem I remained unaltered. Unexpectedly, LHCI accumulation and the photosystem I functional antenna size increased in the mutant compared with in the wild type when grown in dim light. When the CAO mutation was placed in a yellow-in-the-dark background (yid-BF3), in which chlorophyll a synthesis remains limited in dim light, accumulation of the major LHCIIs and of most LHCIs was markedly reduced, indicating that sustained synthesis of chlorophyll a is required to preserve the proteolytic resistance of antenna proteins. Indeed, after crossing yid-BF3 with a mutant defective for the thylakoid FtsH protease activity, yid-BF3-ftsh1 restored wild-type levels of LHCI, which defines LHCI as a new substrate for the FtsH protease.
authors.affiliation: Institut de Biologie Physico-Chimique, UMR7141 CNRS-UPMC, Paris 75005, France.
authors.forename: Sandrine
authors.initials: S
authors.lastname: Bujaldon
authors.affiliation: Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan; JST-CREST, Okayama University, Okayama 700-8530, Japan.
authors.forename: Natsumi
authors.initials: N
authors.lastname: Kodama
authors.affiliation: Institut de Biologie Physico-Chimique, UMR7141 CNRS-UPMC, Paris 75005, France.
authors.forename: Fabrice
authors.initials: F
authors.lastname: Rappaport
authors.affiliation: Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad 500046, India.
authors.forename: Rajagopal
authors.initials: R
authors.lastname: Subramanyam
authors.affiliation: Institut de Biologie Physico-Chimique, UMR7141 CNRS-UPMC, Paris 75005, France.
authors.forename: Catherine
authors.initials: C
authors.lastname: de Vitry
authors.affiliation: Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan; JST-CREST, Okayama University, Okayama 700-8530, Japan. Electronic address: taka@cc.okayama-u.ac.jp.
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Takahashi
authors.affiliation: Institut de Biologie Physico-Chimique, UMR7141 CNRS-UPMC, Paris 75005, France. Electronic address: wollman@ibpc.fr.
authors.forename: Francis-André
authors.initials: FA
authors.lastname: Wollman
mesh_terms: D000483:Alleles; D016825:Chlamydomonas reinhardtii / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D002734:Chlorophyll / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D061146:Chlorophyll Binding Proteins / Q000235:genetics / Q000378:metabolism*; D008027:Light; D010105:Oxygenases / Q000378:metabolism; D017354:Point Mutation; D060431:Thylakoid Membrane Proteins / Q000378:metabolism
chemical_list: D061146:Chlorophyll Binding Proteins; D060431:Thylakoid Membrane Proteins; D002734:Chlorophyll; C037184:chlorophyll b; D010105:Oxygenases; C115272:chlorophyll a oxygenase
keywords: CAO gene; Chlamydomonas reinhardtii; antenna protein; chlorophyll b-less mutant