Cysteine biosynthesis acts as a regulatory hub for ABA-mediated stomatal closure

气孔关闭是植物对干旱相关胁迫（土壤干燥、强光和空气湿度降低）的最快和最关键的反应。植物激素脱落酸（阿坝）是气孔关闭的关键触发剂。全面的研究确定了保卫细胞中的阿坝受体复合物和阿坝信号转导级联。与此相反，知识的本地化和主要触发器的压力诱导阿坝合成才刚刚开始出现。我们发表的工作建立了木质部运输硫酸盐作为一种新的长距离信号，使气孔感知土壤水分状况。我们发现，在叶硫酸盐促进半胱氨酸的合成触发从头阿坝生产，原则上这一过程足以促进气孔关闭。此外，我们发现强光胁迫诱导的气孔关闭也依赖于半胱氨酸和阿坝的重新合成能力。在这里，我们将探讨这一机制的一般意义，通过筛选一系列的水分亏缺相关的压力，其依赖于硫酸盐/半胱氨酸触发气孔关闭。关于植物对干旱相关胁迫的生理反应，我们将研究硫酸盐是否、如何以及在哪些细胞类型中触发阿坝途径的两个限制步骤。已知氧化脂素OPDA的信号传导介导一组不同的胁迫反应，其中包括对土壤干燥的反应中的气孔关闭。然而，任何OPDA特异性受体和信号转导级联是未知的。OPDA与叶绿体基质中的伴侣CYP 20 -3结合，促进半胱氨酸合酶复合物的结合和活性。我们建议CYP 20 -3/pCSC中继功能作为OPDA的受体复合物，通过控制半胱氨酸的生物合成，刺激阿坝的生物合成，并将调查使用拟南芥突变体和应力conditions.If这些假设成立的组合这一功能，植物将能够协调不同的干旱相关的压力，这些不同的刺激纳入一个内源性信号：半胱氨酸诱导的阿坝生产。

Stomatal closure is the fastest and most critical response of plants towards the drought-associated stresses soil drying, high light, and decreased air humidity. The phyto¬hormone absicic acid (ABA) is the crucial trigger for stomatal closure. Comprehensive studies identified the ABA receptor complex and the ABA signal transduction cascade in guard cells. In contrast, the knowledge about the localization and the dominant triggers of stress-induced ABA synthesis is only beginning to emerge. Our published work established xylem-transported sulfate as a new long-distance signal that allows the stomata to perceive the soil water status. We showed that in the leaf sulfate promotes the synthesis of cysteine by triggering de novo ABA production and that in principle this process is sufficient to promote stomatal closure. In addition, we found that high light stress-induced stomatal closure also depends on the ability to synthesize cysteine and ABA de novo. Here we will investigate the general significance of this mechanism by screening a spectrum of water deficit related stresses for their dependence on sulfate/cysteine triggered stomatal closure. With respect to the physiological response of the plant to drought-related stresses we will investigate if, how and in which cell types the two limiting steps of the ABA pathway are triggered by sulfate. Signaling by the oxylipin OPDA is known to mediate a distinct set of stress responses, among them stomatal closure in reaction to soil drying. However, any OPDA-specific receptor and signal transduction cascade is unknown. OPDA binds to the chaperone CYP20-3 in the chloroplast stroma where is promotes association and activity of the cysteine synthase complex. We propose that the CYP20-3/pCSC relay functions as a receptor complex for OPDA that stimulates ABA biosynthesis by controlling cysteine biosynthesis and will investigate this function using combinations of Arabidopsis mutants and stress conditions.If these hypotheses hold, plants would be able to coordinate different drought-associated stresses by the inclusion of these diverse stimuli into one endogenous signal: cysteine-induced ABA production.