Receptor-like kinases (RLKs) are important for plant growth, development and defense responses. The S-receptor protein kinases (SRKs), which represent an RLK subfamily, control the self- incompatibility among Brassica species. However, little information is available regarding SRK functions in rice. We identified a gene OsSRK1 encoding an atypical SRK. The transcript of OsSRK1 was induced by abscisic acid (ABA), salt and polyethylene glycol. OsSRK1 localized to the plasma membrane and cytoplasm. Leaf width was increased in OsSRK1-overexpression (OsSRK1-OX) transgenic rice plants, likely because of an increase in cell number per leaf. Furthermore, the expression levels of OsCYCA3-1 and OsCYCD2-1, which encode positive regulators of cell division, were up-regulated in leaf primordium of OsSRK1-OX rice plants relative to those in wild type. Meanwhile, the expression level of OsKRP1, which encodes cell cycle inhibitor, was down-regulated in the OsSRK1-OX plants. Therefore, it is deduced that OsSRK1 regulates leaf width by promoting cell division in the leaf primordium. Additionally, OsSRK1-OX plants exhibited enhanced ABA sensitivity and salt tolerance compared with wild type. These results suggest that OsSRK1 plays important roles in leaf development and salt responses in rice.

受体样激酶（RLK）对于植物生长，发育和防御反应非常重要。代表RLK亚科的S受体蛋白激酶（SRK）控制芸苔属之间的自交不亲和性。但是，关于稻米中SRK功能的信息很少。我们鉴定出一个编码非典型SRK的基因OsSRK1。OsSRK1的转录本由脱落酸（ABA），盐和聚乙二醇诱导。OsSRK1定位于质膜和细胞质。OsSRK1-过表达（OsSRK1- OX）转基因水稻植株的叶宽增加，可能是由于每片叶的细胞数增加。此外，OsCYCA3-1的表达水平与野生型相比，OsSRK1- OX水稻叶片原基中的编码细胞分裂的正调控子的OsCYCD2-1和OsCYCD2-1上调。同时，的表达水平OsKRP1，其编码细胞周期抑制剂，是在下调OsSRK1 -OX植物。因此，推测OsSRK1通过促进叶片原基中的细胞分裂来调节叶片宽度。另外，与野生型相比，Os SRK1- OX植物表现出增强的ABA敏感性和耐盐性。这些结果表明，OsSRK1在水稻叶片发育和盐分响应中起着重要作用。