In vivo interactions between photosynthesis, mitorespiration, and chlororespiration in Chlamydomonas reinhardtii.
Interactions between photosynthesis, mitochondrial respiration (mitorespiration), and chlororespiration have been investigated in the green alga Chlamydomonas reinhardtii using flash illumination and a bare platinum electrode. Depending on the physiological status of algae, flash illumination was found to induce either a fast (t(1/2) approximately 300 ms) or slow (t(1/2) approximately 3 s) transient inhibition of oxygen uptake. Based on the effects of the mitorespiratory inhibitors myxothiazol and salicyl hydroxamic acid (SHAM), and of propyl gallate, an inhibitor of the chlororespiratory oxidase, we conclude that the fast transient is due to the flash-induced inhibition of chlororespiration and that the slow transient is due to the flash-induced inhibition of mitorespiration. By measuring blue-green fluorescence changes, related to the redox status of the pyridine nucleotide pool, and chlorophyll fluorescence, related to the redox status of plastoquinones (PQs) in C. reinhardtii wild type and in a photosystem I-deficient mutant, we show that interactions between photosynthesis and chlororespiration are favored when PQ and pyridine nucleotide pools are reduced, whereas interactions between photosynthesis and mitorespiration are favored at more oxidized states. We conclude that the plastid oxidase, similar to the mitochondrial alternative oxidase, becomes significantly engaged when the PQ pool becomes highly reduced, and thereby prevents its over-reduction.
Département d'Ecophysiologie Végétale et de Microbiologie, Laboratoire d'Ecophysiologie de la Photosyntèse, UMR 163 CNRS CEA, Univ-Meéditerranée CEA 1000, Saint-Paul-lez-Durance, France. laurent.cournac@cea.fr
Laurent
L
Cournac
Gwendal
G
Latouche
Zoran
Z
Cerovic
Kevin
K
Redding
Jacques
J
Ravenel
Gilles
G
Peltier
D000818:Animals; D016825:Chlamydomonas reinhardtii / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D002734:Chlorophyll / Q000378:metabolism / Q000528:radiation effects; D003624:Darkness; D005453:Fluorescence; D008027:Light; D045342:Light-Harvesting Protein Complexes; D008689:Methacrylates; D010084:Oxidation-Reduction; D010101:Oxygen Consumption / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D010788:Photosynthesis / Q000502:physiology*; D045322:Photosynthetic Reaction Center Complex Proteins / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D045331:Photosystem I Protein Complex; D011435:Propyl Gallate / Q000494:pharmacology; D011742:Pyrimidine Nucleotides / Q000378:metabolism; D012457:Salicylamides / Q000494:pharmacology; D013844:Thiazoles / Q000494:pharmacology
D045342:Light-Harvesting Protein Complexes; D008689:Methacrylates; D045322:Photosynthetic Reaction Center Complex Proteins; D045331:Photosystem I Protein Complex; D011742:Pyrimidine Nucleotides; D012457:Salicylamides; D013844:Thiazoles; D002734:Chlorophyll; C030517:myxothiazol; D011435:Propyl Gallate; C005703:salicylhydroxamic acid