Investigating photosynthesis by proton motive force modulations via ATP synthase and cytochrome b6f complex

通过 ATP 合酶和细胞色素 b6f 复合物研究质子基序力调节的光合作用

• 批准号: 461765884
• 负责人: Dr. Felix Buchert
• 金额: --
• 依托单位: Arbeitsgruppe Plant Biochemistry and Biotechnology
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/461765884?language=en
• 关键词: Investigating; photosynthesis; proton; motive; force

Photosynthesis converts light energy to chemical energy. Tightly regulated processes enable light harvesting by two photosystems which is associated with linear electron transfer from water to CO2, and the generation of a proton motive force (pmf) that fuels the ATP synthase. Both photosystems are functionally coupled by mobile electron carriers and the cytochrome b6f complex, which is also part of a cyclic electron flow pathway around photosystem I in ATP-deprived conditions. The pmf has two components, an electric membrane potential (delta.psi) and an osmotic gradient of H+ ions (delta.pH). The delta.pH is crucial on two photoprotective levels: It triggers the onset of nonphotochemical chlorophyll fluorescence quenching to protect photosystem II, and it induces the slowdown of electron flow at the cytochrome b6f complex to protect photosystem I. On the other hand, an excessive delta.pH and delta.psi destabilise photosystem II. Therefore, the pmf is subject to qualitative and quantitative control for efficient photosynthesis. In this context, ion channels and antiporters but also the major proton-conductive modulator, the ATP synthase, are important.The ATP synthase is regulated on multiple levels and its ATP hydrolysis activity is elevating the pmf in darkness in the green alga Chlamydomonas reinhardtii. In contrast, the ATP synthase in the vascular plants shows very low ATPase activity in the dark. We have indications that this difference is linked to structural variations in a rotor subunit which will be tested in domain swapping mutants of Chlamydomonas and Arabidopsis thaliana. In this gain- vs. loss-of-function approach, we will examine and compare how the photosynthetic apparatus that is adapted to algal- and plant-specific photoprotection mechanisms is affected by the non-native ATP synthase behaviour. Moreover, we will explore an algal ATP synthase mutant that fails to throttle its activity in response to altered metabolic conditions, and plan to compare the phenotype to the situation in Arabidopsis. Since electron transfer via the cytochrome b6f complex is subjected to ATP synthase performance, we will use a b6f mutant which is hypersensitive to the lumen acidification. Thereby, we plan to obtain more insights into the established pmf quality in the context of regulatory ATP synthase adjustments. Furthermore, we explore the possibility of delta.psi sensing in the algal cytochrome b6f complex as a measure to keep the complex functional. Finally, we plan to investigate if a hybrid ATP synthase with a non-native rotor ring allows Chlamydomonas to grow at different light conditions by harbouring a modified pmf-to-ATP conversion efficiency.

光合作用将光能转化为化学能。严格调控的过程使两个光系统能够捕获光，这两个光系统与从水到二氧化碳的线性电子转移有关，并产生质子动力（pmf），为ATP合成酶提供燃料。两个光系统都由移动电子载体和细胞色素b6f复合物在功能上偶联，这也是atp剥夺条件下光系统I周围循环电子流途径的一部分。pmf有两个组成部分，电膜电位（delta.psi）和H+离子的渗透梯度（delta.pH）。奥卡万戈三角洲。pH在两个光保护水平上是至关重要的：它触发非光化学叶绿素荧光猝灭以保护光系统II，并诱导细胞色素b6f复合物的电子流减慢以保护光系统i。另一方面，过量的δ。pH和。psi破坏光系统II。因此，pmf受到有效光合作用的定性和定量控制。在这种情况下，离子通道和反转运体以及主要的质子传导调节剂ATP合酶都很重要。绿藻衣藻（Chlamydomonas reinhardtii）的ATP合成酶在多个水平上受到调控，其ATP水解活性提高了黑暗中的pmf。相比之下，维管植物的ATP合成酶在黑暗中表现出非常低的ATP酶活性。我们有迹象表明这种差异与转子亚基的结构变化有关，该亚基将在衣藻和拟南芥的结构域交换突变体中进行测试。在这种获得与失去功能的方法中，我们将检查和比较适应藻类和植物特异性光保护机制的光合装置如何受到非天然ATP合酶行为的影响。此外，我们将探索一种藻类ATP合酶突变体，该突变体在代谢条件改变的情况下无法抑制其活性，并计划将其表型与拟南芥的情况进行比较。由于通过细胞色素b6f复合物的电子转移受到ATP合酶性能的影响，我们将使用对管腔酸化敏感的b6f突变体。因此，我们计划在调节ATP合酶调节的背景下获得更多关于已建立的pmf质量的见解。此外，我们还探讨了delta的可能性。海藻细胞色素b6f复合体中的Psi感应是维持复合体功能的一种措施。最后，我们计划研究具有非天然转子环的杂交ATP合酶是否允许衣藻在不同的光照条件下生长，从而具有改良的pmf到ATP的转化效率。