Wang Kai, He Junna, Zhao Yang, Wu Ting, Zhou Xiaofeng, Ding Yanglin, Kong Lingyao, Wang Xiaoji, Wang Yu, Li Jigang, Song Chun-Peng, Wang Baoshan, Yang Shuhua, Zhu Jian-Kang, Gong Zhizhong
State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China.
College of Horticulture, China Agricultural University, Beijing 100193, China.
Plant Cell. 2018 Apr;30(4):815-834. doi: 10.1105/tpc.17.00875. Epub 2018 Apr 4.
The reversible phosphorylation of proteins by kinases and phosphatases is an antagonistic process that modulates many cellular functions. Protein phosphatases are usually negatively regulated by inhibitor proteins. During abscisic acid (ABA) signaling, these inhibitor proteins comprise PYR1/PYL/RCAR ABA receptors, which inhibit the core negative regulators, the clade A type 2C protein phosphatases (PP2Cs). However, it is not known whether these PP2Cs are positively regulated by other proteins. Here, we identified an () mutant that exhibits pleiotropic ABA-hypersensitive phenotypes. encodes an uncharacterized protein that is conserved in both monocots and dicots. EAR1 interacts with the N-terminal inhibition domains of all six PP2Cs, ABA INSENSITIVE1 (ABI1), ABI2, HYPERSENSITIVE TO ABA1 (HAB1), HAB2, ABA-HYPERSENSITIVE GERMINATION1 (AHG1), and AHG3, during ABA signaling and enhances the activity of PP2Cs both in vitro and in vivo. ABA treatment caused EAR1 to accumulate in the nucleus. These results indicate that EAR1 is a negative regulator of ABA signaling that enhances the activity of PP2Cs by interacting with and releasing the N-terminal autoinhibition of these proteins.
激酶和磷酸酶对蛋白质进行的可逆磷酸化是一个调节多种细胞功能的拮抗过程。蛋白磷酸酶通常受抑制蛋白的负调控。在脱落酸（ABA）信号传导过程中，这些抑制蛋白包括PYR1/PYL/RCAR ABA受体，它们抑制核心负调控因子——A类2C型蛋白磷酸酶（PP2C）。然而，尚不清楚这些PP2C是否受其他蛋白的正调控。在此，我们鉴定出一个表现出多效性ABA超敏表型的（）突变体。（该基因）编码一种在单子叶植物和双子叶植物中均保守的未知蛋白。在ABA信号传导过程中，EAR1与所有六种PP2C（ABA不敏感蛋白1（ABI1）、ABI2、对ABA敏感1（HAB1）、HAB2、ABA超敏萌发1（AHG1）和AHG3）的N端抑制结构域相互作用，并在体外和体内增强PP2C的活性。ABA处理导致EAR1在细胞核中积累。这些结果表明，EAR1是ABA信号传导的负调控因子，它通过与这些蛋白的N端自抑制结构域相互作用并解除其抑制来增强PP2C的活性。
