Reduced non-photochemical quenching and enhanced hydrogen production in a PGRL1 Chlamydomonas knock-out mutant affected in cyclic electron flow around photosystem I
Dimitri Tolleter1, Bart Ghysels1, Jean Alric2, Pascaline Auroy1, Jean-Marc Adriano1, Audrey Beyly1, Stéphan Cuiné1, Ilya Reiter1, Bernard Genty1, Laurent Cournac1, and Gilles Peltier1
1) CEA Cadarache, Institut de Biologie Environnementale et de Biotechnologie, UMR 6191 CNRS/CEA/Université d'Aix-Marseille, Saint-Paul-lez-Durance, 13108 France
2) CNRS, Unité Mixte de Recherche 7141/Université Pierre et Marie Curie, Institut de Biologie Physico-Chimique, Paris 75005, France
Some microalgal species such as Chlamydomonas reinhardtii harbour a hydrogenase enzyme connected to the photosynthetic electron transport chain, enabling these organisms to produce hydrogen using sunlight and water as main resources. With the aim to identify regulatory mechanisms of photosynthesis in C. reinhardtii and explore novel strategies to improve H2 production, we have set-up a mutant screening based on the analysis of chlorophyll fluorescence profiles under photoautotrophic conditions. Among 15 mutants affected in chlorophyll fluorescence parameters that were isolated, a PGRL1 knock-out mutant was identified. PGRL1 was recently identified in Arabidopsis as an essential component of cyclic electron flow (CEF) around photosystem I (PSI) in interaction with PGR5 (dalCorso et al. 2008 Cell 132, 273). The pgrL1 mutant, which is affected in non-photochemical quenching during the induction phase of photosynthesis, shows normal photosynthetic electron transport rates under a wide range of irradiances and a lower CEF activity around PSI when compared to the wild-type. When placed under anaerobiosis, the pgrL1 mutant displays an increased capacity to produce hydrogen photoproduction either during short-term or during long-term experiments, the later being carried out in conditions of sulphur deficiency. We conclude that the proton gradient generated by CEF around PSI strongly limits electron transport reactions involved in hydrogen production in wild-type Chlamydomonas strains.
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