title: Phosphorylation of the Light-Harvesting Complex II Isoform Lhcb2 Is Central to State Transitions.
abstract: Light-harvesting complex II (LHCII) is a crucial component of the photosynthetic machinery, with central roles in light capture and acclimation to changing light. The association of an LHCII trimer with PSI in the PSI-LHCII supercomplex is strictly dependent on LHCII phosphorylation mediated by the kinase STATE TRANSITION7, and is directly related to the light acclimation process called state transitions. In Arabidopsis (Arabidopsis thaliana), the LHCII trimers contain isoforms that belong to three classes: Lhcb1, Lhcb2, and Lhcb3. Only Lhcb1 and Lhcb2 can be phosphorylated in the N-terminal region. Here, we present an improved Phos-tag-based method to determine the absolute extent of phosphorylation of Lhcb1 and Lhcb2. Both classes show very similar phosphorylation kinetics during state transition. Nevertheless, only Lhcb2 is extensively phosphorylated (>98%) in PSI-LHCII, whereas phosphorylated Lhcb1 is largely excluded from this supercomplex. Both isoforms are phosphorylated to different extents in other photosystem supercomplexes and in different domains of the thylakoid membranes. The data imply that, despite their high sequence similarity, differential phosphorylation of Lhcb1 and Lhcb2 plays contrasting roles in light acclimation of photosynthesis.
authors.affiliation: Department of Botany and Plant Biology (P.L., D.D., F.C., G.F., M.G.-C.) and iGE3, Institute of Genetics and Genomics of Geneva (M.G.-C.), University of Geneva, 1211 Geneva 4, Switzerland.
authors.forename: Paolo
authors.identifier: http://orcid.org/0000-0003-0587-7621
authors.initials: P
authors.lastname: Longoni
authors.affiliation: Department of Botany and Plant Biology (P.L., D.D., F.C., G.F., M.G.-C.) and iGE3, Institute of Genetics and Genomics of Geneva (M.G.-C.), University of Geneva, 1211 Geneva 4, Switzerland.
authors.forename: Damien
authors.identifier: http://orcid.org/0000-0002-6155-9153
authors.initials: D
authors.lastname: Douchi
authors.affiliation: Department of Botany and Plant Biology (P.L., D.D., F.C., G.F., M.G.-C.) and iGE3, Institute of Genetics and Genomics of Geneva (M.G.-C.), University of Geneva, 1211 Geneva 4, Switzerland.
authors.forename: Federica
authors.initials: F
authors.lastname: Cariti
authors.affiliation: Department of Botany and Plant Biology (P.L., D.D., F.C., G.F., M.G.-C.) and iGE3, Institute of Genetics and Genomics of Geneva (M.G.-C.), University of Geneva, 1211 Geneva 4, Switzerland.
authors.forename: Geoffrey
authors.initials: G
authors.lastname: Fucile
authors.affiliation: Department of Botany and Plant Biology (P.L., D.D., F.C., G.F., M.G.-C.) and iGE3, Institute of Genetics and Genomics of Geneva (M.G.-C.), University of Geneva, 1211 Geneva 4, Switzerland michel.goldschmidt-clermont@unige.ch.
authors.forename: Michel
authors.initials: M
authors.lastname: Goldschmidt-Clermont
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D015151:Immunoblotting; D007700:Kinetics; D008027:Light; D045342:Light-Harvesting Protein Complexes / Q000235:genetics / Q000378:metabolism*; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D010766:Phosphorylation / Q000528:radiation effects; D010788:Photosynthesis / Q000235:genetics / Q000528:radiation effects; D045331:Photosystem I Protein Complex / Q000235:genetics / Q000378:metabolism*; D020524:Thylakoids / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; C423618:CAB2 protein, Arabidopsis; C000602509:Lhcb2 protein, Arabidopsis; D045342:Light-Harvesting Protein Complexes; D046912:Multiprotein Complexes; D045331:Photosystem I Protein Complex