The light intensity-dependent transition to state 1 of dark-adapted anaerobic state 2 Chlamydomonas reinhardtii cells is stimulated by oxygen and by other electron acceptors for photosystem I, such as oxaloacetate and methylviologen. This suggests that the transition to state 1 requires the oxidation of the intersystem chain by photosystem I photochemistry. On the other hand, the mere oxidation in the dark of the chain - by addition of O 2 - leads only to a slow and incomplete transition. The light-driven stimulation by O2 of the state 1 transition is saturated at an O 2 concentration of 15 to 20 μM, definitely higher than that of respiration. We suggest that this may represent the affinity for oxygen of the Mehler reaction, a conclusion that is confirmed by the observations that mitochondrial respiration is apparently not involved in modulating state 2-to-state 1 transition. The catalysis of the state 2-to-state 1 transition upon illumination of anaerobically adapted algae might represent, therefore, a relevant physiological role of this process in C. reinhardtii.
|Titolo:||State transitions in Chlamydomonas reinhardtii. The role of the Mehler reaction in state 2-to-state 1 transition|
FORTI, GIORGIO (Primo)
|Parole Chiave:||Chlamydomonas reinhardtii; electron transport; light; metabolism; oxygen consumption; photosynthesis;|
|Settore Scientifico Disciplinare:||Settore BIO/04 - Fisiologia Vegetale|
|Data di pubblicazione:||2005|
|Digital Object Identifier (DOI):||10.1104/pp.104.048256|
|Appare nelle tipologie:||01 - Articolo su periodico|