Ali Akhtar, Pardo Jose M, Yun Dae-Jin
Department of Biomedical Science and Engineering, Konkuk University, Seoul, South Korea.
Instituto de Bioquímica Vegetal y Fotosíntesis, cicCartuja, CSIC-Universidad de Sevilla, Seville, Spain.
Front Plant Sci. 2020 Apr 22;11:379. doi: 10.3389/fpls.2020.00379. eCollection 2020.
Abscisic acid (ABA) is a key plant stress-signaling hormone that accumulates upon osmotic stresses such as drought and high salinity. Several proteins have been identified that constitute the ABA-signaling pathway. Among them ABA receptors (PYR/PYL/RCAR), co-receptor PP2Cs (protein phosphatases), SnRK2 kinases (SNF1-related protein kinases) and ABI5/ABFs (transcription factors) are the major components. Upon ABA signal, PYR/PYL receptors interact with and recruit PP2Cs, releasing SnRK2s kinases from sequestration with PP2Cs. This allows SnKR2s to promote the activation of downstream transcription factors of ABA pathway. However, apart from activation, ubiquitination and degradation of core proteins in the ABA pathway by the ubiquitin proteasome system is less explored. In this review we will focus on the recent findings about feedback regulation of ABA signaling core proteins through degradation, which is emerging as a critical step that modulates and eventually ceases the signal relay. Additionally, we also discuss the importance of the recently identified effector protein HOS15, which negatively regulate ABA-signaling through degradation of OST1.
脱落酸（ABA）是一种关键的植物胁迫信号激素，在干旱和高盐度等渗透胁迫下会积累。已经鉴定出几种构成ABA信号通路的蛋白质。其中，ABA受体（PYR/PYL/RCAR）、共受体PP2C（蛋白磷酸酶）、SnRK2激酶（SNF1相关蛋白激酶）和ABI5/ABFs（转录因子）是主要成分。在ABA信号作用下，PYR/PYL受体与PP2C相互作用并招募PP2C，使SnRK2激酶从与PP2C的结合中释放出来。这使得SnKR2能够促进ABA途径下游转录因子的激活。然而，除了激活之外，泛素蛋白酶体系统对ABA途径中核心蛋白的泛素化和降解研究较少。在这篇综述中，我们将重点关注通过降解对ABA信号核心蛋白进行反馈调节的最新发现，这一过程正成为调节并最终终止信号传递的关键步骤。此外，我们还讨论了最近鉴定出的效应蛋白HOS15的重要性，它通过降解OST1对ABA信号进行负调控。
