Cyclic electron flow around photosystem I is essential for photosynthesis
Cyclic electron flow around photosystem I is essential for photosynthesis
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DOI：
10.1038/nature02598
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发表时间：
2004-06-03
期刊：
影响因子：
64.8
通讯作者：
Shikanai, T
中科院分区：
文献类型：
--
作者：
Munekaga, Y;Hashimoto, M;Shikanai, T
光合作用提供了至少两条途径，通过这些途径，光能可用于在叶绿体的类囊体膜上产生质子梯度，随后用于合成 ATP。第一条途径中，光系统 II (PSII) 中的水释放的电子最终通过光系统 I (PSI)(1) 转移到 NADP(+)。这种线性电子流是由两个串联的光化学反应驱动的。细胞色素 b(6)f 复合物介导两个光系统之间的电子传输并产生质子梯度 (DeltapH)。在仅由 PSI 驱动的第二条路线中，电子可以从还原的铁氧还蛋白或 NADPH 回收到质体醌，然后再循环到细胞色素 b(6)f 复合物(2-5)。这种循环流产生 DeltapH，从而产生 ATP，而不会积累还原物质。虽然从水到 NADP 1 的线性流通常用于解释光合作用的光依赖性反应的功能，但循环流的作用不太清楚。在高等植物中，循环流由两条部分冗余的路径组成。在这里，我们在拟南芥中构建了两个 PSI 循环途径均受损的突变体，并提供了循环流对于有效光合作用至关重要的证据。
Photosynthesis provides at least two routes through which light energy can be used to generate a proton gradient across the thylakoid membrane of chloroplasts, which is subsequently used to synthesize ATP. In the first route, electrons released from water in photosystem II (PSII) are eventually transferred to NADP(+) by way of photosystem I (PSI)(1). This linear electron flow is driven by two photochemical reactions that function in series. The cytochrome b(6)f complex mediates electron transport between the two photosystems and generates the proton gradient (DeltapH). In the second route, driven solely by PSI, electrons can be recycled from either reduced ferredoxin or NADPH to plastoquinone, and subsequently to the cytochrome b(6)f complex(2-5). Such cyclic flow generates DeltapH and thus ATP without the accumulation of reduced species. Whereas linear flow from water to NADP 1 is commonly used to explain the function of the light-dependent reactions of photosynthesis, the role of cyclic flow is less clear. In higher plants cyclic flow consists of two partially redundant pathways. Here we have constructed mutants in Arabidopsis thaliana in which both PSI cyclic pathways are impaired, and present evidence that cyclic flow is essential for efficient photosynthesis.