College of Horticulture, Shenyang Agricultural University, Shenyang, 110866, China; Key Laboratory of Protected Horticulture of Education Ministry and Liaoning Province, Shenyang, 110866, China; Collaborative Innovation Center of Protected Vegetable Surrounds Bohai Gulf Region, Shenyang, 110866, China.
Key Laboratory of Horticultural Crops Genetic Improvement (Ministry of Agriculture), Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing, 100081, China.
Plant Sci. 2020 Mar;292:110387. doi: 10.1016/j.plantsci.2019.110387. Epub 2019 Dec 24.
The cyclic electron flow (CEF) around photosystem I (PSI) plays a crucial role in photosynthesis and also functions in plant tolerance of abiotic environmental stress. However, the role of PGR5/PGRL1- and NDH-dependent CEF in tomato under hightemperature (HT) is poorly understood. Here, we assessed the photoprotective effect of these pathways in tomato leaves under HT by using antimycin A (AA) and rotenone (R), which are chemical inhibitors of PGR5/PGRL1- and NDH-dependent CEF, respectively. The results showed that AA treatment caused significantly greater inhibition of CEF under HT compared to R treatment. Moreover, AA treatment caused a greater decrease in maximal photochemistry efficiency (F/F) and increased damage to the donor and acceptor side of photosystem II (PSII); however, the limitation of the acceptor side in PSI [Y(NA)] was significantly increased. In addition, thylakoid membrane integrity was compromised and reactive oxygen species, proton gradient (ΔpH), antioxidant enzyme activity, and the expression of photosystem core subunit genes were significantly decreased under AA treatment. These findings indicate that PGR5/PGRL1-dependent CEF protects PSII and PSI from photooxidative damage through the formation of ΔpH while maintaining thylakoid membrane integrity and normal gene expression levels of core photosystem components. This study demonstrates that PGR5/PGRL1-dependent CEF plays a major role in HT response in tomato.
循环电子流（CEF）围绕光系统 I（PSI）发挥了至关重要的作用，在光合作用中，也在植物耐受非生物环境胁迫中发挥功能。然而，PGR5/PGRL1-NDH 依赖的 CEF 在番茄中应对高温（HT）的作用仍知之甚少。在这里，我们通过使用抗霉素 A（AA）和鱼藤酮（R）来评估这些途径在番茄叶片中的光保护作用，AA 和 R 分别是 PGR5/PGRL1-NDH 依赖的 CEF 的化学抑制剂。结果表明，与 R 处理相比，AA 处理在 HT 下对 CEF 的抑制作用更大。此外，AA 处理导致最大光化学效率（F/F）显著降低，并增加了对 PSII 供体和受体侧的损伤；然而，PSI 中受体侧的限制[Y（NA）]显著增加。此外，在 AA 处理下，类囊体膜完整性受损，活性氧、质子梯度（ΔpH）、抗氧化酶活性和光系统核心亚基基因的表达显著降低。这些发现表明，PGR5/PGRL1 依赖的 CEF 通过形成 ΔpH 来保护 PSII 和 PSI 免受光氧化损伤，同时保持类囊体膜完整性和核心光系统组件基因的正常表达水平。本研究表明，PGR5/PGRL1 依赖的 CEF 在番茄对 HT 的响应中起着重要作用。
