Khan Irfan Ullah, Ali Akhtar, Zareen Shah, Khan Haris Ali, Lim Chae Jin, Park Junghoon, Pardo Jose M, Yun Dae-Jin
Department of Biomedical Science & Engineering, Konkuk University, Seoul 05029, Korea.
Institute of Glocal Disease Control, Konkuk University, Seoul 05029, Korea.
Plants (Basel). 2022 Mar 18;11(6):815. doi: 10.3390/plants11060815.
The plant hormone, abscisic acid (ABA), is not only important for promoting abiotic stress responses but also plays a versatile and crucial role in plant immunity. The pathogen infection-induced dynamic accumulation of ABA mediates the degradation of non-expresser of PR genes 1 (NPR1) through the CUL3 proteasome pathway. However, the functional significance of NPR1 degradation by other E3 ligases in response to ABA remains unclear. Here, we report that NPR1 is induced transcriptionally by ABA and that mutation results in ABA insensitivity during seed germination and seedling growth. Mutants lacking downregulate the expression of ABA-responsive transcription factors ABA INSENSITIVE4 (ABI4) and ABA INSENSITIVE5 (ABI5), and that of their downstream targets , , , and . The mutation also affects the transcriptional activity of WRKY18, which activates in the presence of ABA. Furthermore, NPR1 directly interacts with and is degraded by HOS15, a substrate receptor for the DDB1-CUL4 ubiquitin E3 ligase complex. Collectively, our findings demonstrate that NPR1 acts as a positive regulator of ABA-responsive genes, whereas HOS15 promotes NPR1 degradation in a proteasome-dependent manner.
植物激素脱落酸（ABA）不仅对促进非生物胁迫反应很重要，而且在植物免疫中也发挥着多方面的关键作用。病原体感染诱导的ABA动态积累通过CUL3蛋白酶体途径介导病程相关基因非表达子1（NPR1）的降解。然而，其他E3连接酶响应ABA对NPR1进行降解的功能意义仍不清楚。在此，我们报道NPR1受ABA转录诱导，其突变导致种子萌发和幼苗生长期间对ABA不敏感。缺失的突变体下调ABA响应转录因子ABA不敏感4（ABI4）和ABA不敏感5（ABI5）及其下游靶标、、、和的表达。突变还影响WRKY18的转录活性，WRKY18在ABA存在时激活。此外，NPR1直接与DDB1-CUL4泛素E3连接酶复合物的底物受体HOS15相互作用并被其降解。总的来说，我们的研究结果表明NPR1作为ABA响应基因的正调控因子，而HOS15以蛋白酶体依赖的方式促进NPR1降解。
