Department of Plant Biology, Institute of Biology, Faculty of Science and Informatics, University of Szeged, Közép Fasor 52, H-6726, Szeged, Hungary.
Department of Plant Biology, Institute of Biology, Faculty of Science and Informatics, University of Szeged, Közép Fasor 52, H-6726, Szeged, Hungary; Doctoral School of Biology, University of Szeged, Közép Fasor 52, H-6726, Szeged, Hungary.
J Plant Physiol. 2024 Apr;295:154222. doi: 10.1016/j.jplph.2024.154222. Epub 2024 Mar 11.
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 (Solanum lycopersicum 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 Never ripe (Nr) 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 Nr plants.
植物激素，如乙烯（ET）和水杨酸（SA），通过调节防御反应或诱导氧化应激，在植物内质网应激和未折叠蛋白反应（UPR）的调节中起着基本作用。叶绿体可以是活性氧（ROS）的来源和靶点，影响光合作用效率，而在衣霉素（Tm）诱导的内质网应激下，这一点尚未得到研究。在这项研究中，首先在野生型番茄（Solanum lycopersicum L.）叶片中研究了 Tm 对叶绿体 ROS 产生的直接和间接影响。其次，在不同基因型下，分析了 Tm 暴露后和应用化学伴侣 4-苯基丁酸（PBA）后光系统 II 和 I 的活性变化，重点研究了 SA 和 ET 的调节作用。Tm 处理显著但间接诱导了番茄叶片中的 ROS 产生，同时降低了 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 中由于受体侧限制导致的非光化学能量耗散的量子产率 [Y(NA)]。同时，Tm 在 24 小时后增加了番茄叶片中的非光化学猝灭（NPQ）和循环电子流（CEF）。然而，与野生型和 ET 不敏感的 Never ripe（Nr）植物相比，SA 羟化酶过表达的 NahG 番茄植物的光合作用活性受到 Tm 的影响更为严重。这些结果表明，SA 在调节光合作用活性中的保护作用有助于 UPR 和植物在 ER 应激下的存活。有趣的是，NPQ 激活光保护机制独立于 SA，但依赖于 ER 应激下活跃的 ET 信号，而 CEF 由于 Nr 植物中 ET 的比例较高而降低。
