title: Redox modulation of cyclic electron flow around photosystem I in C3 plants.
abstract: We have investigated the occurrence of cyclic electron flow in intact spinach leaves. In particular, we have tested the hypothesis that cyclic flow requires the presence of supercomplexes in the thylakoid membrane or other strong associations between proteins. Using biochemical approaches, we found no evidence of the presence of supercomplexes related to cyclic electron flow, making previous structural explanations for the modulation of cyclic flow rather unlikely. On the other hand, we found that the fraction of photosystem I complexes engaged in cyclic flow could be modulated by changes in the redox state of the chloroplast stroma. Our findings support therefore a dynamic model for the occurrence of linear and cyclic electron flow in C3 plants, based on the competition between cytochrome b(6)f and FNR for electrons carried by ferredoxin. This would be ultimately regulated by the balance between the redox state of PSI acceptors and donors during photosynthesis, in a diffusing system.
authors.affiliation: UMR-7099, CNRS-Université Paris-7, Institut de Biologie Physico-Chimique, Paris, France.
authors.forename: Cécile
authors.initials: C
authors.lastname: Breyton
authors.forename: Beena
authors.initials: B
authors.lastname: Nandha
authors.forename: Giles N
authors.initials: GN
authors.lastname: Johnson
authors.forename: Pierre
authors.initials: P
authors.lastname: Joliot
authors.forename: Giovanni
authors.initials: G
authors.lastname: Finazzi
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D002734:Chlorophyll / Q000378:metabolism; D045346:Cytochrome b6f Complex / Q000032:analysis; D004579:Electron Transport; D010084:Oxidation-Reduction; D045331:Photosystem I Protein Complex / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism; D018724:Spinacia oleracea / Q000378:metabolism*; D020524:Thylakoids / Q000737:chemistry
chemical_list: D045331:Photosystem I Protein Complex; D002734:Chlorophyll; C001785:chlorophyll P 700; D045346:Cytochrome b6f Complex