Wang Xinyong, Lin Guanquan, Wang Hongliang, Zhang Zhen, Wang Yubei, Lang Zhaobo, Zhu Jian-Kang, Wei Pengcheng, Wang Pengcheng
Institute of Advanced Biotechnology and School of Medicine, Southern University of Science and Technology, Shenzhen 518055, China; Shanghai Center for Plant Stress Biology, CAS Center for Excellence in Molecular Plant Sciences, Chinese Academy of Sciences, Shanghai 200032, China.
Institute of Advanced Biotechnology and School of Medicine, Southern University of Science and Technology, Shenzhen 518055, China.
Cell Rep. 2025 Jul 22;44(7):115894. doi: 10.1016/j.celrep.2025.115894. Epub 2025 Jun 21.
Protein kinases in the mitogen-activated protein kinase kinase kinase (MAPKKK) superfamily are known to be central actors in orchestrating cell differentiation, growth, and responses to extracellular stimuli in eukaryotes. However, the rice (Oryza sativa L.) MAPKKKs, especially the rapidly accelerated fibrosarcoma (RAF) subgroup ones, have rarely been studied yet. In this study, we generate high-order mutants of B1, B2, and B3 RAF subgroup MAPKKKs. The resulting raf-b2, raf-b3q, and raf-b2/3q mutants are hyposensitive to abscisic acid (ABA) but show dramatic sensitivity to various osmotic stresses. The rice B2 and B3 RAFs can phosphorylate stress-activated protein kinases (SAPKs), and in the rice raf-b2/3q, the ABA-triggered activation of SAPKs is largely impaired, and the expression of stress-response genes is decreased compared to that in the wild type. Our study reveals a crucial role of B2 and B3 subgroup RAFs in ABA signaling and osmotic stresses and sheds light on the functional divergence of the RAF-SAPK cascade in different plant species.
已知丝裂原活化蛋白激酶激酶激酶（MAPKKK）超家族中的蛋白激酶在真核生物中协调细胞分化、生长以及对细胞外刺激的反应方面起着核心作用。然而，水稻（Oryza sativa L.）中的MAPKKKs，尤其是快速加速纤维肉瘤（RAF）亚组的成员，尚未得到充分研究。在本研究中，我们构建了B1、B2和B3 RAF亚组MAPKKKs的高阶突变体。产生的raf-b2、raf-b3q和raf-b2/3q突变体对脱落酸（ABA）不敏感，但对各种渗透胁迫表现出显著的敏感性。水稻B2和B3 RAFs能够磷酸化胁迫激活蛋白激酶（SAPKs），在水稻raf-b2/3q中，ABA触发的SAPKs激活受到很大损害，与野生型相比，胁迫响应基因的表达降低。我们的研究揭示了B2和B3亚组RAFs在ABA信号传导和渗透胁迫中的关键作用，并阐明了不同植物物种中RAF-SAPK级联的功能差异。
