Graduate School of Bio-Applications and Systems Engineering, Tokyo University of Agriculture and Technology, Koganei, 184-8588, Tokyo, Japan.
School of Agriculture, Meiji University, Kawasaki, 214-8571, Kanagawa, Japan.
Plant J. 2024 Jun;118(6):1747-1759. doi: 10.1111/tpj.16706. Epub 2024 Mar 13.
Abscisic acid (ABA) is a phytohormone that promotes leaf senescence in response to environmental stress. We previously identified methyl CpG-binding domain 10 (MBD10) as a phosphoprotein that becomes differentially phosphorylated after ABA treatment in Arabidopsis. ABA-induced leaf senescence was delayed in mbd10 knockout plants but accelerated in MBD10-overexpressing plants, suggesting that MBD10 positively regulates ABA-induced leaf senescence. ABA-induced phosphorylation of MBD10 occurs in planta on Thr-89, and our results demonstrated that Thr-89 phosphorylation is essential for MBD10's function in leaf senescence. The in vivo phosphorylation of Thr-89 in MBD10 was significantly downregulated in a quadruple mutant of group C MAPKs (mpk1/2/7/14), and group C MAPKs directly phosphorylated MBD10 in vitro. Furthermore, mpk1/2/7/14 showed a similar phenotype as seen in mbd10 for ABA-induced leaf senescence, suggesting that group C MAPKs are the cognate kinases of MBD10 for Thr-89. Because group C MAPKs have been reported to function downstream of SnRK2s, our results indicate that group C MAPKs and MBD10 constitute a regulatory pathway for ABA-induced leaf senescence.
脱落酸（ABA）是一种植物激素，可促进植物在应对环境胁迫时叶片衰老。我们之前鉴定了甲基化 CpG 结合域蛋白 10（MBD10）是一种在拟南芥经 ABA 处理后发生差异磷酸化的磷酸蛋白。mbd10 敲除植株中的 ABA 诱导的叶片衰老被延迟，但 MBD10 过表达植株中的衰老加速，表明 MBD10 正向调控 ABA 诱导的叶片衰老。ABA 诱导的 MBD10 磷酸化在体内发生于 Thr-89，我们的结果表明 Thr-89 磷酸化对于 MBD10 在叶片衰老中的功能是必需的。在 C 组 MAPK 的四重突变体（mpk1/2/7/14）中，MBD10 中 Thr-89 的体内磷酸化显著下调，C 组 MAPK 可在体外直接磷酸化 MBD10。此外，mpk1/2/7/14 在 ABA 诱导的叶片衰老中表现出与 mbd10 相似的表型，表明 C 组 MAPK 是 MBD10 的 Thr-89 的同源激酶。由于 C 组 MAPK 已被报道作为 SnRK2 的下游因子发挥作用，我们的结果表明 C 组 MAPK 和 MBD10 构成了 ABA 诱导的叶片衰老的调控途径。
