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.
State transitions in Chlamydomonas reinhardtii. The role of the Mehler reaction in state 2-to-state 1 transition / G. Forti, G. Caldiroli. - In: PLANT PHYSIOLOGY. - ISSN 0032-0889. - 137:2(2005), pp. 492-499.
State transitions in Chlamydomonas reinhardtii. The role of the Mehler reaction in state 2-to-state 1 transition
G. FortiPrimo
;
2005
Abstract
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.Pubblicazioni consigliate
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