The mechanical properties of guard cell (GC) walls are important for stomatal development and stomatal response to external stimuli. However, the molecular mechanisms of pectin synthesis and pectin composition controlling stomatal development and dynamics remain poorly explored. Here, we characterized the role of two Arabidopsis (Arabidopsis thaliana) galacturonosyltransferases, GAUT10 and GAUT11, in plant growth, stomatal development, and stomatal dynamics. GAUT10 and GAUT11 double mutations reduced pectin synthesis and promoted homogalacturonan (HG) demethylesterification and demethylesterified HG degradation, resulting in larger stomatal complexes and smaller pore areas, increased stomatal dynamics, and enhanced drought tolerance of plants. In contrast, increased GAUT10 or GAUT11 expression impaired stomatal dynamics and drought sensitivity. Genetic interaction analyses together with immunolabeling analyses suggest that the methylesterified HG level is important in stomatal dynamics, and pectin abundance with the demethylesterified HG level controls stomatal dimension and stomatal size. Our results provide insight into the molecular mechanism of GC wall properties in stomatal dynamics, and highlight the role of GAUT10 and GAUT11 in stomatal dimension and dynamics through modulation of pectin biosynthesis and distribution in GC walls.

中文翻译：

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两种半乳糖醛酸转移酶在植物生长、气孔发育和动力学中起作用

保卫细胞 (GC) 壁的机械性能对于气孔发育和气孔对外部刺激的反应很重要。然而，果胶合成的分子机制和控制气孔发育和动力学的果胶组成仍然很少被探索。在这里，我们描述了两种拟南芥 (Arabidopsis thaliana) 半乳糖醛酸转移酶 GAUT10 和 GAUT11 在植物生长、气孔发育和气孔动力学中的作用。GAUT10和GAUT11双突变减少了果胶合成，促进了同型半乳糖醛酸（HG）去甲基酯化和去甲基酯化HG降解，导致气孔复合体更大、孔面积更小，气孔动力学增加，植物的耐旱性增强。相反，增加的 GAUT10 或 GAUT11 表达损害了气孔动力学和干旱敏感性。遗传相互作用分析和免疫标记分析表明，甲基酯化 HG 水平在气孔动力学中很重要，而去甲基化 HG 水平的果胶丰度控制着气孔尺寸和气孔大小。我们的研究结果提供了对气孔动力学中 GC 壁特性的分子机制的深入了解，并通过调节 GC 壁中果胶的生物合成和分布突出了 GAUT10 和 GAUT11 在气孔尺寸和动力学中的作用。