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News | Photosynthesis
The rate of oxygen reduction by photosynthetic electron transport is significant in the presence of high concentrations of CO2 and not under CO2 limitation.
Different pathways of photosynthetic electron transport take place in the chloroplast. The main pathway is the linear electron transport leading to the generation of NADPH and the formation of a proton gradient required for ATP synthesis. The two minor pathways, cyclic flow and pseudocyclic flow to O2, lead also to the formation of a proton gradient without generating NADPH. The partition between these three pathways is not well understood. It is generally assumed that the pseudocyclic way is only induced when the final electron acceptor CO2 is limiting. Chlamydomonas reinhardtii does not generate H2O2 by photorespiration and is thus an ideal organism to study the dependence of pseudocyclic flow on acceptor limitation. In contrast to expectation, it was shown by varying CO2 availability that pseudocyclic flow occurred in parallel to linear flow and that it was not more active under CO2 limitation. Under CO2 limitation, electron transport is very efficiently down regulated and the reduction of O2 is suppressed as demonstrated by using several mutants affected in certain regulation mechanisms. This study allows reconsidering the role of pseudocyclic flow also for other organisms like higher plants.
Roach T, Na CS, Krieger-Liszkay A. High light-induced hydrogen peroxide production in Chlamydomonas reinhardtii is increased by high CO2 availability.Plant J. 2015; 81(5):759-66. http://dx.doi.org/10.1111/tpj.12768
CEA is a French government-funded technological research organisation in four main areas: low-carbon energies, defense and security, information technologies and health technologies. A prominent player in the European Research Area, it is involved in setting up collaborative projects with many partners around the world.