Laboratory of Plant Molecular Physiology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo, 113-8657, Japan.
Gene Discovery Research Group, RIKEN Center for Sustainable Resource Science, Tsukuba, Ibaraki, 305-0074, Japan.
Nat Commun. 2020 Mar 13;11(1):1373. doi: 10.1038/s41467-020-15239-3.
SNF1-related protein kinases 2 (SnRK2s) are key regulators governing the plant adaptive responses to osmotic stresses, such as drought and high salinity. Subclass III SnRK2s function as central regulators of abscisic acid (ABA) signalling and orchestrate ABA-regulated adaptive responses to osmotic stresses. Seed plants have acquired other types of osmotic stress-activated but ABA-unresponsive subclass I SnRK2s that regulate mRNA decay and promote plant growth under osmotic stresses. In contrast to subclass III SnRK2s, the regulatory mechanisms underlying the rapid activation of subclass I SnRK2s in response to osmotic stress remain elusive. Here, we report that three B4 Raf-like MAP kinase kinase kinases (MAPKKKs) phosphorylate and activate subclass I SnRK2s under osmotic stress. Transcriptome analyses reveal that genes downstream of these MAPKKKs largely overlap with subclass I SnRK2-regulated genes under osmotic stress, which indicates that these MAPKKKs are upstream factors of subclass I SnRK2 and are directly activated by osmotic stress.
SNF1 相关蛋白激酶 2（SnRK2s）是调控植物适应渗透胁迫（如干旱和高盐）的关键调节剂。第三类 SnRK2s 作为脱落酸（ABA）信号的中央调节剂，协调 ABA 调控的适应渗透胁迫的反应。种子植物获得了其他类型的渗透胁迫激活但 ABA 不响应的第一类 SnRK2s，它们调节 mRNA 衰减并促进渗透胁迫下的植物生长。与第三类 SnRK2s 不同，快速激活渗透胁迫下第一类 SnRK2s 的调节机制仍然难以捉摸。在这里，我们报告说，三种 B4 Raf 样 MAP 激酶激酶激酶（MAPKKKs）在渗透胁迫下磷酸化并激活第一类 SnRK2s。转录组分析显示，这些 MAPKKKs 下游的基因与渗透胁迫下第一类 SnRK2 调控的基因大部分重叠，这表明这些 MAPKKKs 是第一类 SnRK2 的上游因子，并且直接被渗透胁迫激活。
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