Study on the mechanism of regulation of PSI/PSII stoichiometry

在含氧光合作用中，光能转换是由PSI和PSII共同作用驱动的。因此，能量转换的效率严格取决于两个光反应之间的平衡。我们发现通过控制类囊体ETS状态诱导的PSI合成来调节PSI/PSII的化学计量，从而维持这种平衡。我们进一步的研究集中在(i) ETS状态与PSI合成调控之间的关系，（ii） PSI合成过程中被控制的位点。对于问题(1)，在驯化前后通过火焰诱导类囊体成分的氧化还原来检测ETS状态。对于（ii），在不同的光合条件下研究了Chl a的合成和psaA/B多肽的合成。结果表明：(1)hqno敏感的Cyt b_6氧化被监测到；(2)该反应的较大尺寸引起PSI合成的刺激；(3)PSI合成的控制至少发生在Chl a合成的末端步骤。psaA/B的转录调控似乎不参与这种控制。在此基础上，提出了PSI形成的调控机制、信号、信号转导和PSI合成的控制位点的工作模型。

Light-energy conversion in oxygenic photosynthesis is driven by cooperative actions of PSI and PSII. Thus, the efficiency of energy conversion depends strictly on the balance between the two photoreactions. We have found that the balance is maintained by regulation of PSI/PSII stoichiometry through the control of PSI synthesis induced by the state of thylakoid ETS. Our further study has focused on (i) the relationship between the state of ETS and regulation of PSI synthesis, (ii) the site controlled in the process of PSI synthesis. For the problems (1), examination of ETS state has been done by flah-induced oxidation-reduction of thylakoid components before and after acclimation. For (ii), Chl a synthesis and synthesis of psaA/B polypeptides have been examined under various photosynthetic conditions. Results have indicated that (1) HQNO-sensitive Cyt b_6 oxidation is monitored, (2) greater size of this reaction causes stimulation of PSI synthesis, (3) control of PSI synthesis occurs at least at the terminal step (s) of Chl a synthesis. Regulation of transcription of psaA/B seems not to be involved in this control. Based on these results, a work model for the mechanism of regulation of PSI formation, the signal, the signal transduction and the control site of PSI synthesis, has been proposed.