A type II NAD(P)H dehydrogenase in Chlamydomonas chloroplasts

Gilles Peltier1, Carine Desplats1, Florence Mus1, Stéphan Cuine1, Laurent Cournac1, Bart Ghysels1,2, Frédéric Jans2,3, Emmanuel Mignolet2, Pierre-Alain Houyoux2, Pierre Cardol2,3, Fabrice Franck2 and Claire Remacle3

1CEA Cadarache, DSV, Institut de Biologie Environnementale et de Biotechnologie, Laboratoire de Bioénergétique et Biotechnologie des Bactéries et Microalgues, UMR 6191 CNRS/CEA/Université d'Aix-Marseille, Saint-Paul-lez-Durance, F-13108 France 2Laboratory of Plant Biochemistry and Photobiology and 3Laboratory of Genetics of Microorganisms, Department of Life Sciences, Institute of Plant Biology, B22, University of Liège, 27 Boulevard du Rectorat, 4000-Liège, Belgium

Chlororespiration and hydrogen photoproduction have been widely studied in Chlamydomonas. Although these phenomena partly rely on non-photochemical reduction of plastoquinones (PQs), the enzyme catalyzing this reaction has not been identified yet in Chlamydomonas. With the aim to elucidate the nature of the PQ reducing enzyme, one of the type II NAD(P)H dehydrogenases identified in the Chlamydomonas genome (Nda2) was produced as a recombinant protein in E. coli and further characterized. Using specific antibodies, we show that Nda2 is localized in thylakoid membranes. When added to thylakoids, recombinant Nda2 is shown to reduce PQs from exogenous NAD(P)H. Moreover, RNAi lines expressing low Nda2 levels are strongly affected in non-photochemical reduction of PQ and hydrogen photoproduction. We conclude that Nda2, the first type II NAD(P)H dehydrogenase described so far in chloroplasts, is involved in non-photochemical reduction of PQs and participates to chlororespiration and hydrogen photoproduction.

e-mail address of presenting author: gilles.peltier@cea.fr