Partitioning of the proton motive force into delta phi and delta pH and its role in light regulation of photosynthesis

光合作用是由光能转化为化学能驱动的。总的质子动力（pmf =跨膜电势（δ phi）和pH梯度（δ pH）的总和）与光合电子传递一起在类囊体膜上建立，代表ATP合成的驱动力。然而，对于其他过程，如能量耗散和玉米黄质合成，δ phi的重要性在很大程度上尚未得到充分研究，这些过程受管腔pH（因此也受pH梯度）的调节。通过测量电致变色吸收变化，可以很容易地在植物体内条件下研究pmf分为两个组分，即phi和pH，这是跨膜电场的直接测量。我们的初步数据表明，pmf的分配动力学与体内条件下ph调节的能量耗散动力学不太一致，支持了跨膜电场可能有助于这种光保护机制的假设。计划项目的目标是阐明跨膜电场（delta phi）在光激活，光驯化和光合作用调节中的作用。为此，我们希望采用光谱学方法(i)对不同光照条件下pmf分配的动态进行详细表征，并与pH调节的光合过程有关；（ii）研究人工修改δ phi和δ pH对总体pmf的相对贡献对pH调节过程的影响。

Photosynthesis is driven by the conversion of light energy into chemical energy. The overall proton motive force (pmf = the sum of the transmembrane electric potential (delta phi) and pH gradient (delta pH)) which is built up across the thylakoid membrane along with photosynthetic electron transport represents the driving force for ATP synthesis. However, the importance of delta phi for other processes, that are regulated by the lumen pH (and hence also by the pH gradient), such as energy dissipation and zeaxanthin synthesis, is largely understudied. The partitioning of the pmf into its two components, delta phi and delta pH, can easily be studied in plants under in vivo conditions by measuring electrochromic absorption changes which are a direct measure for the transmembrane electric field. Our preliminary data indicated that the dynamics of the partitioning of the pmf do not correspond well with the dynamics of pH-regulated energy dissipation under in vivo conditions, supporting the hypothesis that also the transmembrane electric field may contribute to this photoprotective mechanism. The goal of the planned project is to elucidate the role of the transmembrane electric field (delta phi) in light activation, light acclimation, and regulation of photosynthesis. To this end we want to follow a spectroscopic approach (i) to perform a detailed characterization of the dynamics of pmf partitioning in response to different light conditions and in relation to pH-regulated photosynthetic processes and (ii) to study the impact of the artificial modification of the relative contributions of delta phi and delta pH to the overall pmf on pH-regulated processes.