National Key Laboratory of Crop Genetic Improvement, Hubei Hongshan Laboratory, Huazhong Agricultural University, Wuhan 430070, China.
Plant Physiol. 2023 May 31;192(2):1603-1620. doi: 10.1093/plphys/kiad145.
Pectin methylesterification in guard cell (GC) walls plays an important role in stomatal development and stomatal response to external stimuli, and pectin methylesterase inhibitors (PMEIs) modulate pectin methylesterification by inhibition of pectin methylesterase (PME). However, the function of PMEIs has not been reported in stomata. Here, we report the role of Arabidopsis (Arabidopsis thaliana) PECTIN METHYLESTERASE INHIBITOR18 in stomatal dynamic responses to environmental changes. PMEI18 mutation increased pectin demethylesterification and reduced pectin degradation, resulting in increased stomatal pore size, impaired stomatal dynamics, and hypersensitivity to drought stresses. In contrast, overexpression of PMEI18 reduced pectin demethylesterification and increased pectin degradation, causing more rapid stomatal dynamics. PMEI18 interacted with PME31 in plants, and in vitro enzymatic assays demonstrated that PMEI18 directly inhibits the PME activity of PME31 on pectins. Genetic interaction analyses suggested that PMEI18 modulates stomatal dynamics mainly through inhibition of PME31 on pectin methylesterification in cell walls. Our results provide insight into the molecular mechanism of the PMEI18-PME31 module in stomatal dynamics and highlight the role of PMEI18 and PME31 in stomatal dynamics through modulation of pectin methylesterification and distribution in GC walls.
在保卫细胞（GC）壁中，果胶甲酯化在气孔发育和气孔对外界刺激的响应中起着重要作用，果胶甲酯酶抑制剂（PMEIs）通过抑制果胶甲酯酶（PME）来调节果胶甲酯化。然而，PMEIs 的功能在气孔中尚未报道。在这里，我们报告了拟南芥（Arabidopsis thaliana）Pectin Methylesterase Inhibitor18 在气孔对环境变化的动态响应中的作用。PMEI18 突变增加了果胶脱甲酯化和减少了果胶降解，导致气孔孔径增大，气孔动态受损，对干旱胁迫敏感。相比之下，PMEI18 的过表达减少了果胶脱甲酯化并增加了果胶降解，导致更快的气孔动态。PMEI18 在植物中与 PME31 相互作用，体外酶促测定表明 PMEI18 直接抑制 PME31 在果胶上的 PME 活性。遗传相互作用分析表明，PMEI18 通过抑制细胞壁中 PME31 对果胶甲酯化来调节气孔动态。我们的结果提供了对 PMEI18-PME31 模块在气孔动态中的分子机制的深入了解，并强调了 PMEI18 和 PME31 通过调节 GC 壁中果胶的甲酯化和分布在气孔动态中的作用。
