title: Arabidopsis thaliana PGR7 encodes a conserved chloroplast protein that is necessary for efficient photosynthetic electron transport.
abstract: A significant fraction of a plant's nuclear genome encodes chloroplast-targeted proteins, many of which are devoted to the assembly and function of the photosynthetic apparatus. Using digital video imaging of chlorophyll fluorescence, we isolated proton gradient regulation 7 (pgr7) as an Arabidopsis thaliana mutant with low nonphotochemical quenching of chlorophyll fluorescence (NPQ). In pgr7, the xanthophyll cycle and the PSBS gene product, previously identified NPQ factors, were still functional, but the efficiency of photosynthetic electron transport was lower than in the wild type. The pgr7 mutant was also smaller in size and had lower chlorophyll content than the wild type in optimal growth conditions. Positional cloning located the pgr7 mutation in the At3g21200 (PGR7) gene, which was predicted to encode a chloroplast protein of unknown function. Chloroplast targeting of PGR7 was confirmed by transient expression of a GFP fusion protein and by stable expression and subcellular localization of an epitope-tagged version of PGR7. Bioinformatic analyses revealed that the PGR7 protein has two domains that are conserved in plants, algae, and bacteria, and the N-terminal domain is predicted to bind a cofactor such as FMN. Thus, we identified PGR7 as a novel, conserved nuclear gene that is necessary for efficient photosynthetic electron transport in chloroplasts of Arabidopsis.
authors.affiliation: Department of Plant and Microbial Biology, University of California, Berkeley, California, United States of America.
authors.forename: Hou-Sung
authors.initials: HS
authors.lastname: Jung
authors.forename: Yuki
authors.initials: Y
authors.lastname: Okegawa
authors.forename: Patrick M
authors.initials: PM
authors.lastname: Shih
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Kellogg
authors.forename: Salah E
authors.initials: SE
authors.lastname: Abdel-Ghany
authors.forename: Marinus
authors.initials: M
authors.lastname: Pilon
authors.forename: Kimmen
authors.initials: K
authors.lastname: Sjölander
authors.forename: Toshiharu
authors.initials: T
authors.lastname: Shikanai
authors.forename: Krishna K
authors.initials: KK
authors.lastname: Niyogi
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002734:Chlorophyll / Q000378:metabolism; D019295:Computational Biology; D004579:Electron Transport / Q000235:genetics / Q000502:physiology*; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism*; D015151:Immunoblotting; D010641:Phenotype; D010788:Photosynthesis / Q000235:genetics / Q000502:physiology*; D010802:Phylogeny; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D002734:Chlorophyll; D049452:Green Fluorescent Proteins