title: The involvement of hydrogen-producing and ATP-dependent NADPH-consuming pathways in setting the redox poise in the chloroplast of Chlamydomonas reinhardtii in anoxia.
abstract: Photosynthetic microalgae are exposed to changing environmental conditions. In particular, microbes found in ponds or soils often face hypoxia or even anoxia, and this severely impacts their physiology. Chlamydomonas reinhardtii is one among such photosynthetic microorganisms recognized for its unusual wealth of fermentative pathways and the extensive remodeling of its metabolism upon the switch to anaerobic conditions. As regards the photosynthetic electron transfer, this remodeling encompasses a strong limitation of the electron flow downstream of photosystem I. Here, we further characterize the origin of this limitation. We show that it stems from the strong reducing pressure that builds up upon the onset of anoxia, and this pressure can be relieved either by the light-induced synthesis of ATP, which promotes the consumption of reducing equivalents, or by the progressive activation of the hydrogenase pathway, which provides an electron transfer pathway alternative to the CO2 fixation cycle.
authors.affiliation: From the Institut de Biologie Physico-Chimique, UMR 7141 CNRS-UPMC, 13 Rue P et M Curie, 75005 Paris, France, and.
authors.forename: Sophie
authors.initials: S
authors.lastname: Clowez
authors.affiliation: the Laboratoire de Génétique et Physiologie des Microalgues, Phytosystems, Department of Life Sciences, Institute of Botany, 27 Bld. du Rectorat, University of Liège, B-4000 Liège, Belgium.
authors.forename: Damien
authors.initials: D
authors.lastname: Godaux
authors.affiliation: the Laboratoire de Génétique et Physiologie des Microalgues, Phytosystems, Department of Life Sciences, Institute of Botany, 27 Bld. du Rectorat, University of Liège, B-4000 Liège, Belgium.
authors.forename: Pierre
authors.initials: P
authors.lastname: Cardol
authors.affiliation: From the Institut de Biologie Physico-Chimique, UMR 7141 CNRS-UPMC, 13 Rue P et M Curie, 75005 Paris, France, and.
authors.forename: Francis-André
authors.initials: FA
authors.lastname: Wollman
authors.affiliation: From the Institut de Biologie Physico-Chimique, UMR 7141 CNRS-UPMC, 13 Rue P et M Curie, 75005 Paris, France, and Fabrice.Rappaport@ibpc.fr.
authors.forename: Fabrice
authors.initials: F
authors.lastname: Rappaport
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000693:Anaerobiosis; D016825:Chlamydomonas reinhardtii / Q000378:metabolism*; D002736:Chloroplasts / Q000378:metabolism*; D006859:Hydrogen / Q000378:metabolism*; D009249:NADP / Q000378:metabolism*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism*; D045331:Photosystem I Protein Complex / Q000378:metabolism
chemical_list: D045331:Photosystem I Protein Complex; D009249:NADP; D006859:Hydrogen; D000255:Adenosine Triphosphate; D010100:Oxygen
keywords: Anaerobic Glycolysis; Chlamydomonas; Electron Transfer; Hydrogenase; Oxidation-Reduction (Redox); Photosynthesis