Balancing the two photosystems: photosynthetic electron transfer governs transcription of reaction centre genes in chloroplasts
Balancing the two photosystems: photosynthetic electron transfer governs transcription of reaction centre genes in chloroplasts
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DOI：
10.1098/rstb.2000.0697
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发表时间：
2000-10-29
影响因子：
6.3
通讯作者：
Pfannschmidt, T
中科院分区：
文献类型：
--
作者：
Allen, JF;Pfannschmidt, T
叶绿体是细胞质细胞器，其主要功能是光合作用，但也包含小型，特化和准自治的遗传系统。在光合作用中，两个能量转换光系统以电化学方式串联连接。连接的电子载体被光系统I（PS I）氧化并被光系统II（PS II）还原。最近的研究表明，氧化还原状态的一个连接电子载体，质体醌，控制转录的叶绿体基因的反应中心蛋白的两个光系统。控制抵消电子传递的不平衡，导致它：氧化plastoquinone诱导PS II和抑制PS I;减少plastoquinone诱导PS I和抑制PS II。这种互补性在体内，使用有利于一个或其他光系统，并在体外，当位点特异性电子传递抑制剂被添加到转录和光合活性叶绿体观察。因此，有一个转录水平的控制，具有类似于纯粹的翻译后“状态转换”的调节功能，其中吸收的激发能在光系统之间的重新分配是由类囊体膜蛋白磷酸化介导的。甚至在相应的状态转换完成之前，就可以检测到体内光谱变化诱导的转录速率变化，这表明氧化还原信号转导的分支途径的运作。这些研究结果表明，光系统化学计量的调整机制，其中初始事件涉及的plastoquinone的氧化还原状态的传感器，因此可能是相同的初始事件的状态转换。叶绿体转录的氧化还原控制也与电子传递和基因表达之间的直接调控偶联决定叶绿体核外遗传系统的功能和组成的提议一致。
Chloroplasts are cytoplasmic organelles whose primary function is photosynthesis, but which also contain small, specialized and quasi-autonomous genetic systems. In photosynthesis, two energy converting photosystems are connected, electrochemically, in series. The connecting electron carriers are oxidized by photosystem I (PS I) and reduced by photosystem II (PS II). It has recently been shown that the oxidation-reduction state of one connecting electron carrier, plastoquinone, controls transcription of chloroplast genes for reaction centre proteins of the two photosystems. The control counteracts the imbalance in electron transport that causes it: oxidized plastoquinone induces PS II and represses PS I; reduced plastoquinone induces PS I and represses PS II. This complementarity is observed both in vivo, using light favouring one or other photosystem, and in vitro, when site-specific electron transport inhibitors are added to transcriptionally and photosynthetically active chloroplasts. There is thus a transcriptional level of control that has a regulatory function similar to that of purely post-translational 'state transitions' in which the redistribution of absorbed excitation energy between photosystems is mediated by thylakoid membrane protein phosphorylation. The changes in rates of transcription that are induced by spectral changes in vivo can be detected even before the corresponding state transitions are complete, suggesting the operation of a branched pathway of redox signal transduction. These findings suggest a mechanism for adjustment of photosystem stoichiometry in which initial events involve a sensor of the redox state of plastoquinone, and may thus be the same as the initial events of state transitions. Redox control of chloroplast transcription is also consistent with the proposal that a direct regulatory coupling between electron transport and gene expression determines the function and composition of the chloroplast's extra-nuclear genetic system.