Photoinhibition of PSI and PSII in Nature and in the Laboratory: Ecological Approaches
Photoinhibition of PSI and PSII in Nature and in the Laboratory: Ecological Approaches
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自然界和实验室中 PSI 和 PSII 的光抑制：生态学方法
DOI：
10.1007/124_2022_67
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发表时间：
2023
期刊：
影响因子：
--
通讯作者：
Terashima Ichiro
中科院分区：
文献类型：
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作者：
Kono Masaru;Oguchi Riichi;Terashima Ichiro
光是植物进行有机物质光合作用所不可缺少的。地球上几乎所有的有机体，包括动物，最终都依赖于这种植物的功能来获得能量以及构成它们身体的材料。自相矛盾的是，光常常破坏光合作用装置。这种现象被称为光抑制，引起了许多光合作用研究人员的注意。尽管光抑制一词几乎被用来指光系统II的光抑制，但最近的研究表明，光抑制对光的波动很敏感。首先，我们比较了两种PSII光抑制假说：Mn/(两步)假说和过量-Y(NO)假说。前者认为放氧复合体(OEC)主要受损，而后者则认为PSII中过量的激发能量直接损害了D1的功能。两者都可以在实验室中诱导，并且可以在同一片叶片上平行发生。由于OEC受到紫外线(UV)或蓝光的破坏，叶表皮中的紫外线屏蔽物质起着至关重要的作用。研究还表明，在被Mn/(两步)机制破坏的PSII中，PSII的修复速度远慢于过量Y(NO)机制。因此，植物应该通过Mn/(两步)假说来避免PSII光抑制。比较了冷敏模式植物黄瓜和突变体PROTON GRIDENT 5中光系统I(PSI)的光抑制作用。文中还讨论了野外自然产生的脉动光对PSI光抑制的影响。这三种情况下的PSI光抑制可以用相似的情景来解释。当还原的P700向O2提供电子时，就会诱导氧化损伤。保护PSI免受光抑制的机制都有助于将P700氧化成安全的猝灭剂P700+。当叶片突然暴露在强光下时，激发能量从PSII溢出到PSI，保护PSII和PSI免受光抑制。在所有这些情况下，远红光在PSI保护中起着至关重要的作用。由于FR光不仅保护PSI，而且促进光合作用，特别是在波动光中的弱光阶段，FR光在光合作用中的作用应该得到充分的研究。文中还指出了今后应解决的其他重要生态问题。
Light is indispensable for plants to photosynthesize organic matters. Almost all the organisms including animals on our planet eventually rely on this plant function for their energy as well as the materials forming their bodies. Paradoxically, light often damages the photosynthetic apparatus. This phenomenon is called photoinhibition and has been attracting attention of many photosynthesis researchers. Although the term photoinhibition had been used almost synonymously to refer to photoinhibition of photosystem II (PSII), it was recently shown that PSI is susceptible to fluctuating light. First, we compare two PSII photoinhibition hypotheses: the Mn/(Two-step) hypothesis and Excess-Y(NO) hypothesis. The former claims that the oxygen-evolving complex (OEC) is primarily damaged, while the latter claims excess excitation energy in PSII directly damages D1 function. Both can be induced in the laboratory and may parallelly occur in the same leaf. Because OEC is damaged by ultraviolet (UV) or blue light, UV screening substances in the leaf epidermis plays a crucial role. It is also indicated that the rate of PSII repair in PSII damaged by the Mn/(Two-step) mechanism is much slower than that by the Excess-Y(NO) mechanism. It appears then plants should avoid PSII photoinhibition by the Mn/(Two-step) hypothesis. Photoinhibition of photosystem I (PSI) in cucumber, a model chilling sensitive plant, and that in the mutant ofPROTON GRADIENT 5are compared. The effects of fluctuating light, which naturally occurs in the field, on PSI photoinhibition are also discussed. The PSI photoinhibition in these three cases can be explained by similar scenarios. When reduced P700 donates electrons to O2, oxidative damage is induced. The mechanisms that protect PSI from photoinhibition all contribute to oxidation of P700 to P700+, a safe quencher. When a leaf is suddenly exposed to strong light, spillover of excitation energy from PSII to PSI protects both PSII and PSI from photoinhibition. In all these situations, far-red (FR) light plays essential roles in PSI protection. As FR light not only protects PSI but also enhances photosynthesis, especially in low light phases in the fluctuating light, the roles of FR light in photosynthesis should be fully examined. Other ecologically important problems that should be solved in the future are also pointed out.