The Involvement of Hydrogen-producing and ATP-dependent NADPH Consuming Pathways in Setting the Redox Poise in the Chloroplast of Chlamydomonas reinhardtii in Anoxia. [Plant Biology]

February 17th, 2015 by Clowez, S., Godaux, D., Cardol, P., Wollman, F.-A., Rappaport, F.

Photosynthetic microalgae are exposed to changing environmental conditions. In particular, microbes found in ponds or soils often face hypoxia or even anoxia and this severely impacts their physiology. Chlamydomonas reinhardtii is one amongst such photosynthetic microorganisms recognized for its unusual wealth of fermentative pathways and the extensive remodeling of its metabolism upon switch to anaerobic conditions. As regard to photosynthetic electron transfer, this remodeling encompasses a strong limitation of the electron flow downstream of Photosystem I. Here, we further characterize the origin of this limitation. We show that it stems from the strong reducing pressure that builds up upon the onset of anoxia and this pressure can be relieve either by the light-induced synthesis of ATP which promotes the consumption of reducing equivalents, or by the progressive activation of the hydrogenase pathway which provides an electron transfer pathway alternative to the CO2 fixation cycle.
  • Posted in Journal of Biological Chemistry, Publications
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