Abstract：
Plasma membrane (PM)-associated abscisic acid (ABA) signal transduction is an important component of ABA signaling. The C2-domain ABA-related (CAR) proteins have been reported to play a crucial role in recruiting ABA receptor PYR1/PYL/RCAR (PYLs) to the PM. However, the molecular details of the involvement of CAR proteins in membrane-delimited ABA signal transduction remain unclear. For instance, where this response process takes place and whether any additional members besides PYL are taking part in this signaling process. Here, the GUS-tagged materials for all Arabidopsis CAR members were used to comprehensively visualize the extensive expression patterns of the CAR family genes. Based on the representativeness of CAR1 in response to ABA, we determined to use it as a target to study the function of CAR proteins in PM-associated ABA signaling. Single-particle tracking showed that ABA affected the spatiotemporal dynamics of CAR1. The presence of ABA prolonged the dwell time of CAR1 on the membrane and showed faster lateral mobility. Surprisingly, we verified that CAR1 could directly recruit hypersensitive to ABA1 (HAB1) and SNF1-related protein kinase 2.2 (SnRK2.2) to the PM at both the bulk and single-molecule levels. Furthermore, PM localization of CAR1 was demonstrated to be related to membrane microdomains. Collectively, our study revealed that CARs recruited the three main components of ABA signaling to the PM to respond positively to ABA. This study deepens our understanding of ABA signal transduction.
摘要：
质膜（PM）相关脱落酸（ABA）信号转导是ABA信号的重要组成部分。已报道C2结构域ABA相关（CAR）蛋白在将ABA受体PYR1/PYL/RCAR（PYL）募集到PM中起关键作用。然而,CAR蛋白参与膜界定的ABA信号转导的分子细节仍不清楚.例如,此响应过程发生的位置，以及PYL以外的任何其他成员是否参与此信令过程。这里,所有拟南芥CAR成员的GUS标记材料用于全面可视化CAR家族基因的广泛表达模式。基于CAR1响应ABA的代表性，我们决定将其作为目标来研究CAR蛋白在PM相关ABA信号传导中的功能。单粒子示踪表明ABA影响CAR1的时空动力学。ABA的存在延长了CAR1在膜上的停留时间，并显示出更快的横向迁移率。令人惊讶的是,我们验证了CAR1可以在整体和单分子水平上直接招募对ABA1（HAB1）和SNF1相关蛋白激酶2.2（SnRK2.2）过敏的PM。此外，CAR1的PM定位被证明与膜微结构域有关。总的来说，我们的研究表明，CAR将ABA信号的三个主要成分招募到PM，以对ABA做出积极反应。本研究加深了我们对ABA信号转导的理解。
