title: Redox and ATP control of photosynthetic cyclic electron flow in Chlamydomonas reinhardtii (I) aerobic conditions.
abstract: Assimilation of atmospheric CO2 by photosynthetic organisms such as plants, cyanobacteria and green algae, requires the production of ATP and NADPH in a ratio of 3:2. The oxygenic photosynthetic chain can function following two different modes: the linear electron flow which produces reducing power and ATP, and the cyclic electron flow which only produces ATP. Some regulation between the linear and cyclic flows is required for adjusting the stoichiometric production of high-energy bonds and reducing power. Here we explore, in the green alga Chlamydomonas reinhardtii, the onset of the cyclic electron flow during a continuous illumination under aerobic conditions. In mutants devoid of Rubisco or ATPase, where the reducing power cannot be used for carbon fixation, we observed a stimulation of the cyclic electron flow. The present data show that the cyclic electron flow can operate under aerobic conditions and support a simple competition model where the excess reducing power is recycled to match the demand for ATP.
authors: UMR 7141, CNRS et Université Pierre et Marie Curie (Paris VI), Institut de Biologie Physico-Chimique, 13 Rue Pierre et Marie Curie 75005 Paris, France. jean.alric@ibpc.fr
authors: Jean
authors: J
authors: Alric
authors: Jérôme
authors: J
authors: Lavergne
authors: Fabrice
authors: F
authors: Rappaport
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000332:Aerobiosis; D000818:Animals; D002245:Carbon Dioxide / Q000378:metabolism; D016825:Chlamydomonas reinhardtii / Q000254:growth & development / Q000378:metabolism*; D000460:Chlorophyta / Q000378:metabolism; D002736:Chloroplasts / Q000378:metabolism; D000458:Cyanobacteria / Q000378:metabolism; D004237:Diuron / Q000494:pharmacology; D004579:Electron Transport; D007700:Kinetics; D008027:Light; D010084:Oxidation-Reduction; D010788:Photosynthesis / Q000187:drug effects / Q000502:physiology*; D010944:Plants / Q000378:metabolism; D013053:Spectrophotometry
chemical_list: D002245:Carbon Dioxide; D000255:Adenosine Triphosphate; D004237:Diuron