Department of Biology, University of Fribourg, 1700 Fribourg, Switzerland.
Plant Physiol. 2013 Aug;162(4):1815-21. doi: 10.1104/pp.113.218156. Epub 2013 Jun 11.
Salicylic acid (SA) is central for the defense of plants to pathogens and abiotic stress. SA is synthesized in chloroplasts from chorismic acid by an isochorismate synthase (ICS1); SA biosynthesis is negatively regulated by autoinhibitory feedback at ICS1. Genetic studies indicated that the multidrug and toxin extrusion transporter ENHANCED DISEASE SUSCEPTIBILITY5 (EDS5) of Arabidopsis (Arabidopsis thaliana) is necessary for SA accumulation after biotic and abiotic stress, but so far it is not understood how EDS5 controls the biosynthesis of SA. Here, we show that EDS5 colocalizes with a marker of the chloroplast envelope and that EDS5 functions as a multidrug and toxin extrusion-like transporter in the export of SA from the chloroplast to the cytoplasm in Arabidopsis, where it controls the innate immune response. The location at the chloroplast envelope supports a model of the effect of EDS5 on SA biosynthesis: in the eds5 mutant, stress-induced SA is trapped in the chloroplast and inhibits its own accumulation by autoinhibitory feedback.
水杨酸（SA）是植物防御病原体和非生物胁迫的核心物质。SA 由叶绿体中的色氨酸合成酶（ICS1）从支链氨基酸合成；SA 的生物合成受到 ICS1 的自动抑制反馈负调控。遗传研究表明，拟南芥（Arabidopsis thaliana）的多药和毒素外排转运蛋白增强病害易感性 5（EDS5）对于生物和非生物胁迫后 SA 的积累是必需的，但迄今为止，还不清楚 EDS5 如何控制 SA 的生物合成。在这里，我们表明 EDS5 与叶绿体被膜的标记物共定位，并且 EDS5 在拟南芥中将 SA 从叶绿体输出到细胞质中作为一种多药和毒素外排样转运蛋白发挥作用，在那里它控制先天免疫反应。在叶绿体被膜上的位置支持了 EDS5 对 SA 生物合成影响的模型：在 eds5 突变体中，应激诱导的 SA 被困在叶绿体中，并通过自动抑制反馈抑制自身积累。
