Distinct contribution of two cyclic electron transport pathways to P700 oxidation
Distinct contribution of two cyclic electron transport pathways to P700 oxidation
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DOI：
10.1093/plphys/kiac557
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发表时间：
2022-12-08
期刊：
影响因子：
7.4
通讯作者：
Shikanai, Toshiharu
中科院分区：
文献类型：
--
作者：
Zhou, Qi;Yamamoto, Hiroshi;Shikanai, Toshiharu
光系统I （PSI）周围的循环电子传递（CET）使类囊体腔酸化，并下调细胞色素b(6)f复合物的电子传递。这种光合作用控制对PSI的特殊对叶绿素（P700）的氧化是PSI光保护所必需的。此外，依赖于质子梯度调节5 （PGR5）蛋白的CET通过将电子池从PSI的受体侧移动到质体醌池来氧化P700。该受体侧调控模型是基于表达衣藻（Chlamydomonas reinhardtii）质体末端氧化酶（CrPTOX2）的拟南芥（Arabidopsis thaliana） pgr5-1突变体的表型而提出的。在这项研究中，我们扩展了研究，包括拟南芥氯呼吸还原2-2 （crr2-2）突变体在另一个依赖于叶绿体NADH脱氢酶样（NDH）复合物的CET途径中存在缺陷。虽然CrPTOX2的引入并没有弥补PGR5受体侧调控的缺陷，但NDH复合物的功能除了在诱导光合作用过程中发生逆反应外，得到了补充。我们评估了野生型、pgr5-1和crr2-2背景下CrPTOX2在波动光强下的影响。在高光期，PGR5依赖性和ndh依赖性的CET都参与了光合调控的诱导，而PGR5依赖性的CET则优先参与受体侧调控。相反，NDH复合物可能在弱光期参与受体侧调控，而在强光期不参与。我们评估了PSI对波动光的敏感性，并阐明了受体侧调节是通过在强光下氧化P700来实现PSI光保护的必要条件。
Cyclic electron transport (CET) around Photosystem I (PSI) acidifies the thylakoid lumen and downregulates electron transport at the cytochrome b(6)f complex. This photosynthetic control is essential for oxidizing special pair chlorophylls (P700) of PSI for PSI photoprotection. In addition, CET depending on the PROTON GRADIENT REGULATION 5 (PGR5) protein oxidizes P700 by moving a pool of electrons from the acceptor side of PSI to the plastoquinone pool. This model of the acceptor-side regulation was proposed on the basis of the phenotype of the Arabidopsis (Arabidopsis thaliana) pgr5-1 mutant expressing Chlamydomonas (Chlamydomonas reinhardtii) plastid terminal oxidase (CrPTOX2). In this study, we extended the research including the Arabidopsis chlororespiratory reduction 2-2 (crr2-2) mutant defective in another CET pathway depending on the chloroplast NADH dehydrogenase-like (NDH) complex. Although the introduction of CrPTOX2 did not complement the defect in the acceptor-side regulation by PGR5, the function of the NDH complex was complemented except for its reverse reaction during the induction of photosynthesis. We evaluated the impact of CrPTOX2 under fluctuating light intensity in the wild-type, pgr5-1 and crr2-2 backgrounds. In the high-light period, both PGR5- and NDH-dependent CET were involved in the induction of photosynthetic control, whereas PGR5-dependent CET preferentially contributed to the acceptor-side regulation. On the contrary, the NDH complex probably contributed to the acceptor-side regulation in the low-light period but not in the high-light period. We evaluated the sensitivity of PSI to fluctuating light and clarified that acceptor-side regulation was necessary for PSI photoprotection by oxidizing P700 under high light.