Plant hormones such as ethylene (ET) and salicylic acid (SA) have an elementary role in the regulation of ER stress and unfolded protein response (UPR) in plants via modulating defence responses or inducing oxidative stress. Chloroplasts can be sources and targets of reactive oxygen species (ROS) that affect photosynthetic efficiency, which has not been investigated under tunicamycin (Tm)-induced ER stress. In this study, the direct and indirect effects of Tm on chloroplastic ROS production were first investigated in leaves of wild-type tomato ( L.) plants. Secondly changes in activities of photosystem II and I were analysed under Tm exposure and after application of the chemical chaperone 4-phenylbutyrate (PBA) in different genotypes, focusing on the regulatory role of SA and ET Tm treatments significantly but indirectly induced ROS production in tomato leaves and in parallel it decreased the effective quantum yield of PSII [Y(II)] and PSI [Y(I)], as well as the photochemical quenching coefficient (qP) and the quantum yield of non-photochemical energy dissipation in PSI due to acceptor-side limitation [Y(NA)]. At the same time, Tm increased non-photochemical quenching (NPQ) and cyclic electron flow (CEF) in tomato leaves after 24 h. However, the photosynthetic activity of the SA hydroxylase-overexpressing NahG tomato plants was more severely affected by Tm as compared to wild-type and ET-insensitive () plants. These results suggest the protective role of SA in the regulation of photosynthetic activity contributing to UPR and the survival of plants under ER stress. Interestingly, the activation of photoprotective mechanisms by NPQ was independent of SA but dependent on active ET signalling under ER stress, whereas CEF was reduced by ET due to its higher ratio in plants.

中文翻译：

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内质网应激诱导剂衣霉素对番茄植株光合光反应的水杨酸和乙烯依赖性影响

乙烯 (ET) 和水杨酸 (SA) 等植物激素通过调节防御反应或诱导氧化应激，在调节植物内质网应激和未折叠蛋白反应 (UPR) 方面发挥着基本作用。叶绿体可以是影响光合效率的活性氧 (ROS) 的来源和目标，但尚未在衣霉素 (Tm) 诱导的 ER 胁迫下进行研究。在本研究中，首先在野生型番茄 (L.) 植物的叶子中研究了 Tm 对叶绿体 ROS 产生的直接和间接影响。其次，分析了不同基因型在 Tm 暴露下和应用化学伴侣 4-苯基丁酸酯（PBA）后光系统 II 和 I 活性的变化，重点关注 SA 和 ET Tm 处理显着但间接诱导番茄 ROS 产生的调节作用同时，它降低了 PSII [Y(II)] 和 PSI [Y(I)] 的有效量子产率，以及光化学猝灭系数 (qP) 和 PSI 中非光化学能量耗散的量子产率到受体侧限制[Y(NA)]。同时，24小时后，Tm增加了番茄叶片的非光化学猝灭（NPQ）和循环电子流（CEF）。然而，与野生型和 ET 不敏感植物相比，SA 羟化酶过表达 NahG 番茄植物的光合活性受 Tm 的影响更严重。这些结果表明 SA 在调节光合活性中的保护作用，有助于 UPR 和 ER 胁迫下植物的生存。有趣的是，NPQ 激活光保护机制与 SA 无关，但依赖于 ER 胁迫下活跃的 ET 信号传导，而 CEF 由于 ET 在植物中的比例较高而被 ET 降低。