Arabidopsis cysteine-rich receptor-like protein kinase <i>CRK33</i> affects stomatal density and drought tolerance

Cysteine-rich receptor-like protein kinases (CRKs) are transmembrane proteins containing two domains of unknown function 26 (DUF26) RLKs in their ectodomain. Despite that CRKs control important aspects of plant development, only few proteins have functionally been characterized. In this work, we analyzed the function of CRK33 by characterizing two insertional lines. The stomatal density and stomatal index were decreased in <i>crk33-2</i> and <i>crk33-3</i> plants in comparison to wild-type plants, correlating with a decreased transpiration in transgenic plants and a higher drought tolerance. Furthermore, photosynthesis and stomatal conductance changed. Finally, all four stomata cell fate genes were upregulated, especially the expression of <i>TMM</i> and <i>SPCH</i> in the mutant background, suggesting a role for CRK33 in stomatal spacing.富含半胱氨酸的类受体蛋白激酶（Cysteine-rich receptor-like protein kinases, CRKs）是一类跨膜蛋白，其胞外域包含两个功能未知结构域26（Domain of Unknown Function 26, DUF26）。尽管CRKs可调控植物发育的诸多关键过程，但目前仅对该家族中少数蛋白的功能完成了鉴定。本研究通过对两个插入突变株系进行功能表征，解析了CRK33的生物学功能。与野生型植株相比，crk33-2与crk33-3突变体植株的气孔密度及气孔指数均显著降低，这与突变体植株的蒸腾速率下降及更强的耐旱性呈显著相关。此外，突变体的光合速率与气孔导度亦发生显著改变。最后，所有4个气孔细胞命运相关基因均出现表达上调，其中突变体背景下TMM与SPCH的表达上调尤为显著，这表明CRK33在气孔间距调控中发挥关键作用。