State Key Laboratory of Crop Genetics & Germplasm Enhancement and Utilization, College of Life Sciences, Nanjing Agricultural University, Nanjing, China.
Shandong Key Laboratory of Biophysics, Institute of Biophysics, Dezhou University, Dezhou, China.
Plant Cell Environ. 2024 Dec;47(12):5140-5157. doi: 10.1111/pce.15095. Epub 2024 Aug 21.
The mitogen-activated protein kinase (MAPK) cascade (MAPKKK-MAPKK-MAPK) plays a critical role in biotic and abiotic stress responses and abscisic acid (ABA) signalling. A previous study has shown that the ABA-activated MKK1-MPK1 cascade is essential in regulating ABA response and stress tolerance in rice. However, the specific MAPKKK upstream of the MKK1-MPK1 cascade in ABA signalling remains unknown. Here, we identified that MAPKKK28, a previously uncharacterized member of the rice MEKK family, is involved in regulating ABA responses, including seed germination, root growth, stomatal closure, and the tolerance to oxidative stress and osmotic stress. We found that MAPKKK28 directly interacts with and phosphorylates MKK1. Further analysis indicated that the activation of both MKK1 and MPK1 depends on MAPKKK28 in ABA signalling. Genetic analysis revealed that MAPKKK28 functions upstream of the MKK1-MPK1 cascade to positively regulate ABA responses and enhance tolerance to oxidative and osmotic stress. These results not only reveal a new complete MAPK cascade in plants but also uncover its importance in ABA signalling.
丝裂原活化蛋白激酶（MAPK）级联（MAPKKK-MAPKK-MAPK）在生物和非生物胁迫反应以及脱落酸（ABA）信号转导中发挥着关键作用。先前的研究表明，ABA 激活的 MKK1-MPK1 级联对于调节水稻中的 ABA 反应和应激耐受性至关重要。然而，ABA 信号转导中 MKK1-MPK1 级联上游的特定 MAPKKK 仍然未知。在这里，我们鉴定出 MAPKKK28，一种水稻 MEKK 家族中以前未被表征的成员，参与调节 ABA 反应，包括种子萌发、根生长、气孔关闭以及对氧化应激和渗透胁迫的耐受性。我们发现 MAPKKK28 直接与 MKK1 相互作用并磷酸化 MKK1。进一步的分析表明，MKK1 和 MPK1 的激活都依赖于 ABA 信号转导中的 MAPKKK28。遗传分析表明，MAPKKK28 在 MKK1-MPK1 级联的上游发挥作用，正向调节 ABA 反应并增强对氧化和渗透胁迫的耐受性。这些结果不仅揭示了植物中一个新的完整 MAPK 级联，也揭示了其在 ABA 信号转导中的重要性。
