Dissection of respiratory and cyclic electron transport in Synechocystis sp. PCC 6803
Dissection of respiratory and cyclic electron transport in Synechocystis sp. PCC 6803
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DOI：
10.1007/s10265-022-01401-z
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发表时间：
2022-06
影响因子：
2.8
通讯作者：
Shoko Kusama;C. Miyake;Shuji Nakanishi;Ginga Shimakawa
中科院分区：
文献类型：
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作者：
Shoko Kusama;C. Miyake;Shuji Nakanishi;Ginga Shimakawa
循环电子传递（CET）是一个很有吸引力的假说，用于调节光合电子传递和产生额外的ATP。CET的概念是在过去几十年中建立的，并且被提出在产氧光合作用的祖先蓝藻中起作用。CET的体内活性经常从光系统（PS）I中的反应中心叶绿素（P700）的氧化还原状态（在不存在PSII活性的情况下）或通过分别通过P700氧化还原状态和叶绿素荧光比较PSI和PSII活性来评估。然而，CET活性的评估是复杂的，特别是在蓝藻中，其中CET共享系统间链，包括质体醌，细胞色素b 6/f复合物，质体蓝蛋白，和细胞色素c 6，光合线性电子传递（LET）和呼吸电子传递（RET）。在这里，我们试图区分在RET和CET在蓝藻Synechocystissp体内电子传递速率。PCC 6803。当PSII被抑制时，氧化的P700（P700+）的还原率下降到小于10%，表明PSII是PSI的主要电子源，但P700+也被来自其他来源的电子还原。氧化戊糖磷酸（pentose phosphate，RET）途径是RET的主要电子源，它被乙醇醛（glycolaldehyde，GA）抑制。在GA和KCN抑制P700 ~+途径和呼吸末端氧化酶的条件下，P700 ~+还原率小于未加任何抑制剂时的1%。本研究表明，在集胞藻中，PSII受到抑制时，电子向PSI的传递主要来自于电子传递途径。PCC 6803。
Cyclic electron transport (CET) is an attractive hypothesis for regulating photosynthetic electron transport and producing the additional ATP in oxygenic phototrophs. The concept of CET has been established in the last decades, and it is proposed to function in the progenitor of oxygenic photosynthesis, cyanobacteria. The in vivo activity of CET is frequently evaluated either from the redox state of the reaction center chlorophyll in photosystem (PS) I, P700, in the absence of PSII activity or by comparing PSI and PSII activities through the P700 redox state and chlorophyll fluorescence, respectively. The evaluation of CET activity, however, is complicated especially in cyanobacteria, where CET shares the intersystem chain, including plastoquinone, cytochromeb6/fcomplex, plastocyanin, and cytochromec6, with photosynthetic linear electron transport (LET) and respiratory electron transport (RET). Here we sought to distinguish the in vivo electron transport rates in RET and CET in the cyanobacteriumSynechocystissp. PCC 6803. The reduction rate of oxidized P700 (P700+) decreased to less than 10% when PSII was inhibited, indicating that PSII is the dominant electron source to PSI but P700+is also reduced by electrons derived from other sources. The oxidative pentose phosphate (OPP) pathway functions as the dominant electron source for RET, which was found to be inhibited by glycolaldehyde (GA). In the condition where the OPP pathway and respiratory terminal oxidases were inhibited by GA and KCN, the P700+reduction rate was less than 1% of that without any inhibitors. This study indicate that the electron transport to PSI when PSII is inhibited is dominantly derived from the OPP pathway inSynechocystissp. PCC 6803.