The ROP2-RIC7 pathway negatively regulates light-induced stomatal opening by inhibiting exocyst subunit Exo70B1 in Arabidopsis
The ROP2-RIC7 pathway negatively regulates light-induced stomatal opening by inhibiting exocyst subunit Exo70B1 in Arabidopsis
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DOI：
10.1111/nph.13625
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发表时间：
2016-01-01
期刊：
影响因子：
9.4
通讯作者：
Lee, Youngsook
中科院分区：
文献类型：
--
作者：
Hong, Daewoong;Jeon, Byeong Wook;Lee, Youngsook
气孔是植物表面的微小阀门，调节植物与环境之间的气体交换。气孔开度需要严格控制，以促进二氧化碳的吸收，防止过量水分流失。植物Rho-type(ROP)GTPase 2(ROP2)是光诱导气孔开放负调控系统中的一个分子成分。此前，ROP相互作用的CDC42和RAC相互作用的结合基序包含蛋白7(RIC7)被认为在ROP2下游发挥作用。为了了解RIC7调控光诱导气孔开放的分子机制，我们分析了RIC7突变体植株的气孔反应，并通过酵母双杂交筛选鉴定了RIC7的目的蛋白。RIC7基因敲除促进了光诱导的气孔开放，而RIC7过表达则抑制了RIC7的开放，表明RIC7负调控拟南芥的气孔开放。RIC7与囊泡运输机制的一个组成部分Exo70家族蛋白B1(Exo70B1)相互作用。RIC7和Exo70B1在光或成分活性ROP2条件下定位于质膜区域。Exo70B1和ric7/exo70b1的敲除突变体表现出抑制光诱导气孔开放的作用。我们的结果表明，ROP2和RIC7通过抑制Exo70B1来抑制过度的气孔开放，而Exo70B1很可能参与了光诱导气孔开放所需的小泡运输。
Stomata are the tiny valves on the plant surface that mediate gas exchange between the plant and its environment. Stomatal opening needs to be tightly regulated to facilitate CO2 uptake and prevent excess water loss. Plant Rho-type (ROP) GTPase 2 (ROP2) is a molecular component of the system that negatively regulates light-induced stomatal opening. Previously, ROP-interactive Cdc42- and Rac-interactive binding motif-containing protein 7 (RIC7) was suggested to function downstream of ROP2. However, the underlying molecular mechanism remains unknown.To understand the mechanism by which RIC7 regulates light-induced stomatal opening, we analyzed the stomatal responses of ric7 mutant Arabidopsis plants and identified the target protein of RIC7 using a yeast two-hybrid screen.Light-induced stomatal opening was promoted by ric7 knockout, whereas it was inhibited by RIC7 overexpression, indicating that RIC7 negatively regulates stomatal opening in Arabidopsis. RIC7 interacted with exocyst subunit Exo70 family protein B1 (Exo70B1), a component of the vesicle trafficking machinery. RIC7 and Exo70B1 localized to the plasma membrane region under light or constitutively active ROP2 conditions. The knockout mutant of Exo70B1 and ric7/exo70b1 exhibited retarded light-induced stomatal opening.Our results suggest that ROP2 and RIC7 suppress excess stomatal opening by inhibiting Exo70B1, which most likely participates in the vesicle trafficking required for light-induced stomatal opening.