PARENT SESSION
Posters P1A Proton coupled electron transport and ATPase. Abstracts (172-180)

Contribution of cyclic electron flow around PSI to CO₂ fixation in Arabidopsis. Yuri Munekage^*,1, Dominique Rumeau¹, Stephan Cuiné¹, Toshiharu Shikanai², Bernard Genty¹, Gilles Peltier¹, ¹ CEA Cadarache DSV DEVM Laboratoire d’Ecophysiologie de la Photosynthese UMR 6191 CNRS-CEA, Aix-Marseille II, Saint-Paul-lez-Durance, France² Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma, Nara, Japan

ABSTRACT- Cyclic electron flow around photosystem (PS) I has been extensively investigated in vitro and in vivo, however, its contribution to C3 photosynthesis is still matter of debate especially in vivo. We isolated an Arabidopsis pgr5 as non-photochemical quenching (NPQ) deficient mutant, in which ferredoxin dependent cyclic activity is affected. In recent work, we have produced double mutants crossed between pgr5 and crr2,3,4, in which both PGR5 and NDH dependent cyclic activity are impaired. Although single mutants, pgr5 and crr2,3,4, did not show any effects on growth, double mutants showed a drastic effect on growth even at low light intensity. This work suggested that cyclic electron flow around PSI is essential for plant growth. Here, we measured gas exchange together with chlorophyll fluorescence and PSI-dependent absorbance change at 820 nm in pgr5 and in crr4pgr5 mutant. We will discuss our results regarding the contribution of both PGR5 and NDH dependent cyclic pathways to CO₂ fixation. Data on the localization of PGR5 protein in the thylakoid membrane will be shown.

KEY WORDS: CO2 fixation, cyclic electron flow, Arabidopsis, chlorophyll fluorescence