Journal
PLANT CELL
Volume 23, Issue 7, Pages 2619-2630Publisher
OXFORD UNIV PRESS INC
DOI: 10.1105/tpc.111.086876
Keywords
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Funding
- European FP6 program (SOLAR-H Project) [STRP516510]
- FP7 program (SOLAR-H2 Project) [RTD212508]
- FP5 program (Stress Imaging Project) [RTN2-2001-00190]
- French Agence Nationale pour la Recherche
- Deutsche Forschungsgemeinshaft
- Bundesministerium fur Bildung und Forschung [BMBF 0315265]
- FP7-funded Sunbiopath project [GA245070]
- European Union
- Region Provence Alpes Cote d'Azur
- French Ministry of Research
- Commissariat a l'Energie Atomique et aux Energies Alternatives
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Hydrogen photoproduction by eukaryotic microalgae results from a connection between the photosynthetic electron transport chain and a plastidial hydrogenase. Algal H-2 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, H-2 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 H-2 production.
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