| 18781324 |
Shao N, Beck CF, Lemaire SD, Krieger-Liszkay A: Photosynthetic electron flow affects H2O2 signaling by inactivation of catalase in Chlamydomonas reinhardtii. Planta. 2008 Nov;228(6):1055-66. Epub 2008 Sep 10.
A specific signaling role for H (2) O (2) in Chlamydomonas reinhardtii was demonstrated by the definition of a promoter that specifically responded to this ROS. Expression of a nuclear-encoded reporter gene driven by this promoter was shown to depend not only on the level of exogenously added H (2) O (2) but also on light. In the dark, the induction of the reporter gene by H (2) O (2) was much lower than in the light. This lower induction was correlated with an accelerated disappearance of H (2) O (2) from the culture medium in the dark. Due to a light-induced reduction in catalase activity, H (2) O (2) levels in the light remained higher. Photosynthetic electron transport mediated the light-controlled down-regulation of the catalase activity since it was prevented by 3-(3'4'-dichlorophenyl)-1,1-dimethylurea (DCMU), an inhibitor of photosystem II. In the presence of light and DCMU, expression of the reporter gene was low while the addition of aminotriazole, a catalase inhibitor, led to a higher induction of the reporter gene by H (2) O (2) in the dark. The role of photosynthetic electron transport and thioredoxin in this regulation was investigated by using mutants deficient in photosynthetic electron flow and by studying the correlation between NADP-malate dehydrogenase and catalase activities. It is proposed that, contrary to expectations, a controlled down-regulation of catalase activity occurs upon a shift of cells from dark to light. This down-regulation apparently is necessary to maintain a certain level of H (2) O (2) required to activate H (2) O (2)-dependent signaling pathways. |
1(0,0,0,1) |