Abscisic acid sensor RCAR7/PYL13, specific regulator of protein phosphatase coreceptors
Abscisic acid sensor RCAR7/PYL13, specific regulator of protein phosphatase coreceptors
复制标题
DOI：
10.1073/pnas.1322085111
复制
发表时间：
2014-04-15
影响因子：
11.1
通讯作者：
Grill, Erwin
中科院分区：
文献类型：
--
作者：
Fuchs, Stefan;Tischer, Stefanie V.;Grill, Erwin
植物激素脱落酸（阿坝）既是一种发育信号，也是干旱和寒冷等环境信号的整合者。阿坝感受募集ABA结合调节组分[阿坝受体的调节组分（RCAR）/PYR 1/PYL]和相关的蛋白磷酸酶2C（PP 2C）。植物激素结合使辅助受体的磷酸酶活性失活，允许阿坝信号通过下游蛋白激酶的磷酸化传递。RCAR和PP 2C共受体分别由拟南芥中包含14个和9个成员的小蛋白质家族代表。RCAR-PP 2C相互作用的特异性和有助于特定组合的限制条件知之甚少。在这篇文章中，我们分析了RCAR 7/PYL 13，其特征在于保守的ABA结合口袋中的三个变体氨基酸残基。RCAR 7在体外以纳摩尔阿坝水平调节PP 2Cs ABI 1、ABI 2和PP 2CA的磷酸酶活性;然而，它不能调节结构相关的对阿坝1（HAB 1）的超敏反应。HAB 1的定点突变建立了RCAR 7的ABA依赖性调节。将RCAR 7的非规范氨基酸残基转化为共有ABA结合口袋并没有明显改变受体功能。拟南芥中RCAR 7的异位表达导致阿坝超敏性影响基因调控、种子萌发和气孔关闭。RCAR 7功能丧失突变体显示阿坝响应没有变化，类似于RCAR 9敲除系，而RCAR 7和RCAR 9的组合缺陷导致ABA不敏感的种子萌发。该研究显示了RCAR 7在早期植物发育中的作用，证明了其阿坝受体功能，并确定了RCAR 7-PP 2C相互作用的结构限制。
The plant hormone abscisic acid (ABA) acts both as a developmental signal and as an integrator of environmental cues such as drought and cold. ABA perception recruits an ABA-binding regulatory component [regulatory component of ABA receptor (RCAR)/PYR1/PYL] and an associated protein phosphatase 2C (PP2C). Phytohormone binding inactivates the phosphatase activity of the co-receptor, permitting phosphorelay of the ABA signal via downstream protein kinases. RCARs and PP2C coreceptors are represented by small protein families comprising 14 and 9 members in Arabidopsis, respectively. The specificity of the RCAR-PP2C interaction and the constraints contributing to specific combinations are poorly understood. In this contribution, we analyzed RCAR7/PYL13, which is characterized by three variant amino acid residues in the conserved ABA-binding pocket. RCAR7 regulated the phosphatase activity of the PP2Cs ABI1, ABI2, and PP2CA in vitro at nanomolar ABA levels; however, it was unable to regulate the structurally related hypersensitive to ABA 1 (HAB1). Site-directed mutagenesis of HAB1 established ABA-dependent regulation by RCAR7. Conversion of the noncanonical amino acid residues of RCAR7 into the consensus ABA-binding pocket did not perceptibly change receptor function. Ectopic expression of RCAR7 in Arabidopsis resulted in ABA hypersensitivity affecting gene regulation, seed germination, and stomatal closure. The RCAR7 loss-of-function mutant revealed no changes in ABA responses, similar to the RCAR9 knockout line, whereas the combined deficiency of RCAR7 and RCAR9 resulted in ABA-insensitive seed germination. The study shows a role of RCAR7 in early plant development, proves its ABA receptor function, and identifies structural constraints of RCAR7-PP2C interaction.