title: PGR5 is involved in cyclic electron flow around photosystem I and is essential for photoprotection in Arabidopsis.
abstract: During photosynthesis, plants must control the utilization of light energy in order to avoid photoinhibition. We isolated an Arabidopsis mutant, pgr5 (proton gradient regulation), in which downregulation of photosystem II photochemistry in response to intense light was impaired. PGR5 encodes a novel thylakoid membrane protein that is involved in the transfer of electrons from ferredoxin to plastoquinone. This alternative electron transfer pathway, whose molecular identity has long been unclear, is known to function in vivo in cyclic electron flow around photosystem I. We propose that the PGR5 pathway contributes to the generation of a Delta(pH) that induces thermal dissipation when Calvin cycle activity is reduced. Under these conditions, the PGR5 pathway also functions to limit the overreduction of the acceptor side of photosystem I, thus preventing photosystem I photoinhibition.
authors.affiliation: Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma, Japan.
authors.forename: Yuri
authors.initials: Y
authors.lastname: Munekage
authors.forename: Masaya
authors.initials: M
authors.lastname: Hojo
authors.forename: Jörg
authors.initials: J
authors.lastname: Meurer
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Endo
authors.forename: Masao
authors.initials: M
authors.lastname: Tasaka
authors.forename: Toshiharu
authors.initials: T
authors.lastname: Shikanai
mesh_terms: D000595:Amino Acid Sequence / Q000235:genetics; D017360:Arabidopsis / Q000166:cytology / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000302:isolation & purification* / Q000528:radiation effects; D001483:Base Sequence / Q000235:genetics; D002245:Carbon Dioxide / Q000378:metabolism; D019069:Cell Respiration / Q000235:genetics / Q000528:radiation effects; D002734:Chlorophyll / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D004579:Electron Transport / Q000235:genetics* / Q000528:radiation effects; D018506:Gene Expression Regulation, Plant / Q000502:physiology* / Q000528:radiation effects; D008027:Light / Q000009:adverse effects; D045342:Light-Harvesting Protein Complexes; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics / Q000528:radiation effects; D009249:NADP / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D010084:Oxidation-Reduction / Q000528:radiation effects; D010100:Oxygen / Q000378:metabolism; D010775:Photic Stimulation / Q000009:adverse effects; D010788:Photosynthesis / Q000235:genetics* / Q000528:radiation effects; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics* / Q000302:isolation & purification* / Q000378:metabolism / Q000528:radiation effects; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D020524:Thylakoids / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects
chemical_list: D029681:Arabidopsis Proteins; D045342:Light-Harvesting Protein Complexes; D046911:Macromolecular Substances; C465062:PGR5 protein, Arabidopsis; D045322:Photosynthetic Reaction Center Complex Proteins; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D002734:Chlorophyll; D002245:Carbon Dioxide; D009249:NADP; C001785:chlorophyll P 700; D010100:Oxygen