title: Control of hydrogen photoproduction by the proton gradient generated by cyclic electron flow in Chlamydomonas reinhardtii.
abstract: Hydrogen photoproduction by eukaryotic microalgae results from a connection between the photosynthetic electron transport chain and a plastidial hydrogenase. Algal H₂ production is a transitory phenomenon under most natural conditions, often viewed as a safety valve protecting the photosynthetic electron transport chain from overreduction. From the colony screening of an insertion mutant library of the unicellular green alga Chlamydomonas reinhardtii based on the analysis of dark-light chlorophyll fluorescence transients, we isolated a mutant impaired in cyclic electron flow around photosystem I (CEF) due to a defect in the Proton Gradient Regulation Like1 (PGRL1) protein. Under aerobiosis, nonphotochemical quenching of fluorescence (NPQ) is strongly decreased in pgrl1. Under anaerobiosis, H₂ photoproduction is strongly enhanced in the pgrl1 mutant, both during short-term and long-term measurements (in conditions of sulfur deprivation). Based on the light dependence of NPQ and hydrogen production, as well as on the enhanced hydrogen production observed in the wild-type strain in the presence of the uncoupling agent carbonyl cyanide p-trifluoromethoxyphenylhydrazone, we conclude that the proton gradient generated by CEF provokes a strong inhibition of electron supply to the hydrogenase in the wild-type strain, which is released in the pgrl1 mutant. Regulation of the trans-thylakoidal proton gradient by monitoring pgrl1 expression opens new perspectives toward reprogramming the cellular metabolism of microalgae for enhanced H₂ production.
authors.affiliation: Commissariat à l'Energie Atomique et aux Energies Alternatives, Direction des Sciences du Vivant, Institut de Biologie Environementale et de Biotechnologie, Laboratoire de Bioénergétique et Biotechnologie des Bactéries et Microalgues, Commissariat à l'Energie Atomique Cadarache, 13108 Saint-Paul-lez-Durance, France.
authors.forename: Dimitri
authors.initials: D
authors.lastname: Tolleter
authors.forename: Bart
authors.initials: B
authors.lastname: Ghysels
authors.forename: Jean
authors.initials: J
authors.lastname: Alric
authors.forename: Dimitris
authors.initials: D
authors.lastname: Petroutsos
authors.forename: Irina
authors.initials: I
authors.lastname: Tolstygina
authors.forename: Danuta
authors.initials: D
authors.lastname: Krawietz
authors.forename: Thomas
authors.initials: T
authors.lastname: Happe
authors.forename: Pascaline
authors.initials: P
authors.lastname: Auroy
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Adriano
authors.forename: Audrey
authors.initials: A
authors.lastname: Beyly
authors.forename: Stéphan
authors.initials: S
authors.lastname: Cuiné
authors.forename: Julie
authors.initials: J
authors.lastname: Plet
authors.forename: Ilja M
authors.initials: IM
authors.lastname: Reiter
authors.forename: Bernard
authors.initials: B
authors.lastname: Genty
authors.forename: Laurent
authors.initials: L
authors.lastname: Cournac
authors.forename: Michael
authors.initials: M
authors.lastname: Hippler
authors.forename: Gilles
authors.initials: G
authors.lastname: Peltier
mesh_terms: D000332:Aerobiosis; D000693:Anaerobiosis; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D016825:Chlamydomonas reinhardtii / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D004579:Electron Transport / Q000187:drug effects / Q000502:physiology; D004583:Electrons; D005816:Genetic Complementation Test; D006859:Hydrogen / Q000378:metabolism*; D006864:Hydrogenase / Q000378:metabolism; D008027:Light; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism; D010788:Photosynthesis / Q000187:drug effects / Q000502:physiology*; D045331:Photosystem I Protein Complex / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified; D061209:Proton Ionophores / Q000494:pharmacology; D011522:Protons; D013455:Sulfur / Q000378:metabolism
chemical_list: D008565:Membrane Proteins; D045331:Photosystem I Protein Complex; D010940:Plant Proteins; D061209:Proton Ionophores; D011522:Protons; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D013455:Sulfur; D006859:Hydrogen; D006864:Hydrogenase; D010100:Oxygen