Institut des Sciences du Végétal, Centre National de la Recherche Scientifique, Unité Propre de Recherche 2355, 1 Avenue de la Terrasse, Bâtiment 23, 91198 Gif-sur-Yvette, France.
Sci Signal. 2011 Nov 29;4(201):re4. doi: 10.1126/scisignal.2002164.
The soluble receptors of abscisic acid (ABA) have been identified in Arabidopsis thaliana. The 14 proteins in this family, bearing the double name of PYRABACTIN RESISTANCE/PYRABACTIN-LIKE (PYR/PYL) or REGULATORY COMPONENTS OF ABA RECEPTOR (RCAR) (collectively referred to as PYR/PYL/RCAR), contain between 150 and 200 amino acids with homology to the steroidogenic acute regulatory-related lipid transfer (START) protein. Structural studies of these receptors have provided rich insights into the early mechanisms of ABA signaling. The binding of ABA to PYR/PYL/RCAR triggers the pathway by inducing structural changes in the receptors that allows them to sequester members of the clade A negative regulating protein phosphatase 2Cs (PP2Cs). This liberates the class III ABA-activated Snf1-related kinases (SnRK2s) to phosphorylate various targets. In guard cells, a specific SnRK2, OPEN STOMATA 1 (OST), stimulates H(2)O(2) production by NADPH oxidase respiratory burst oxidase protein F and inhibits potassium ion influx by the inward-rectifying channel KAT1. OST1, the kinase CPK23, the calcium-dependent kinase CPK21, and the counteracting PP2Cs modulate the slow anion channel SLAC1, a pathway that contributes to stomatal responses to diverse stimuli, including ABA and carbon dioxide. A minimal ABA response pathway that leads to activation of the SLAC1 homolog, SLAH3, and presumably stomatal closure has been reconstituted in vitro. The identification of the soluble receptors and core components of the ABA signaling pathway provides promising targets for crop design with higher resilience to water deficit while maintaining biomass.
脱落酸（ABA）的可溶性受体已在拟南芥中被鉴定出来。该家族的 14 种蛋白，具有吡咯啉-5-羧酸/吡咯啉-5-羧酸样（PYR/PYL）或 ABA 受体调节成分（RCAR）的双重名称（统称为 PYR/PYL/RCAR），包含 150 到 200 个氨基酸，与甾体生成急性调节蛋白相关脂质转移（START）蛋白具有同源性。这些受体的结构研究为 ABA 信号转导的早期机制提供了丰富的见解。ABA 与 PYR/PYL/RCAR 的结合通过诱导受体的结构变化触发途径，使它们能够隔离 A 族负调节蛋白磷酸酶 2C（PP2C）的成员。这释放了第三类 ABA 激活的 Snf1 相关激酶（SnRK2s）来磷酸化各种靶标。在保卫细胞中，一种特定的 SnRK2，即开放气孔 1（OST），通过 NADPH 氧化酶呼吸爆发氧化酶蛋白 F 刺激 H2O2 的产生，并通过内向整流通道 KAT1 抑制钾离子内流。激酶 CPK23、钙依赖性激酶 CPK21 和拮抗的 PP2C 调节慢阴离子通道 SLAC1，该途径有助于气孔对包括 ABA 和二氧化碳在内的各种刺激的反应。一个导致 SLAC1 同源物 SLAH3 激活的最小 ABA 反应途径，以及可能导致气孔关闭的途径，已经在体外重建。可溶性受体和 ABA 信号转导途径的核心成分的鉴定为设计具有更高抗旱性而又保持生物质的作物提供了有希望的靶点。
