The involvement of hydrogen-producing and ATP-dependent NADPH-consuming pathways in setting the redox poise in the chloroplast of Chlamydomonas reinhardtii in anoxia.

Abstract

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 among such photosynthetic microorganisms recognized for its unusual wealth of fermentative pathways and the extensive remodeling of its metabolism upon the switch to anaerobic conditions. As regards the 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 relieved 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.

• Authors: Sophie Clowez, Damien Godaux, Pierre Cardol, Francis-André Wollman, Fabrice Rappaport
• Journal: The Journal of biological chemistry (J Biol Chem) Vol. 290 Issue 13 Pg. 8666-76 (Mar 27 2015) ISSN: 1083-351X [Electronic] United States
• PMID: 25691575 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

Chemical References

• Photosystem I Protein Complex
• NADP
• Hydrogen
• Adenosine Triphosphate
• Oxygen

Topics

• Adenosine Triphosphate (metabolism)
• Anaerobiosis
• Chlamydomonas reinhardtii (metabolism)
• Chloroplasts (metabolism)
• Hydrogen (metabolism)
• NADP (metabolism)
• Oxidation-Reduction
• Oxygen (metabolism)
• Photosystem I Protein Complex (metabolism)