State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, The Innovative Academy of Seed Design, Chinese Academy of Sciences, 100101 Beijing, China.
College of Advanced Agricultural Sciences, University of Chinese Academy of Sciences, 100049 Beijing, China.
Proc Natl Acad Sci U S A. 2020 Nov 3;117(44):27694-27702. doi: 10.1073/pnas.2007366117. Epub 2020 Oct 19.
Abscisic acid (ABA) is the key phytohormone in plant drought tolerance and stress adaptation. The clade A protein phosphatase 2Cs (PP2Cs) like ABI1 (ABA-INSENSITIVE 1) work as coreceptors of ABA and regulate multiple ABA responses. Ubiquitination of ABI1 has been proven to play important regulatory roles in ABA signaling. However, the specific ubiquitin conjugating enzyme (E2) involved is unknown. Here, we report that UBC27 is an active E2 that positively regulates ABA signaling and drought tolerance. UBC27 forms the E2-E3 pair with the drought regulator RING E3 ligase AIRP3. Both UBC27 and AIRP3 interact with ABI1 and affect the ubiquitination and degradation of ABI1. ABA activates the expression of , inhibits the proteasome degradation of UBC27, and enhances the interaction between UBC27 and ABI1 to increase its activity. These findings uncover a regulatory mechanism in ABA signaling and drought response and provide a further understanding of the plant ubiquitination system and ABA signaling pathway.
脱落酸 (ABA) 是植物耐旱性和应激适应的关键植物激素。类 A 蛋白磷酸酶 2C（PP2C），如 ABI1（ABA 不敏感 1），作为 ABA 的核心受体，调节多种 ABA 反应。ABI1 的泛素化已被证明在 ABA 信号转导中发挥重要的调节作用。然而，具体涉及的泛素连接酶 (E2) 尚不清楚。在这里，我们报告 UBC27 是一种积极的 E2，可正向调节 ABA 信号和耐旱性。UBC27 与干旱调节剂 RING E3 连接酶 AIRP3 形成 E2-E3 对。UBC27 和 AIRP3 均与 ABI1 相互作用，并影响 ABI1 的泛素化和降解。ABA 激活的表达，抑制蛋白酶体降解 UBC27，并增强 UBC27 与 ABI1 的相互作用，以提高其活性。这些发现揭示了 ABA 信号和干旱反应的调控机制，为植物泛素化系统和 ABA 信号通路提供了进一步的认识。
