Although morphology and grain size are important to rice growth and yield, the identity of abundant natural allelic variations that determine agronomically important differences in crops is unknown. Here, we characterized the function of mitogen-activated protein kinase 3 from Oryza officinalis Wall. ex Watt encoded by OrMKK3. Different alternative splicing variants occurred in OrMKK3. Green fluorescent protein (GFP)–OrMKK3 fusion proteins localized to the cell membrane and nuclei of rice protoplasts. Overexpression of OrMKK3 influenced the expression levels of the grain size-related genes SMG1, GW8, GL3, GW2, and DEP3. Phylogenetic analysis showed that OrMKK3 is well conserved in plants while showing large amounts of variation between indica, japonica, and wild rice. In addition, OrMKK3 slightly influenced brassinosteroid (BR) responses and the expression levels of BR-related genes. Our findings thus identify a new gene, OrMKK3, influencing morphology and grain size and that represents a possible link between mitogen-activated protein kinase and BR response pathways in grain growth.

尽管形态和籽粒大小对水稻生长和产量很重要，但决定作物农艺学重要差异的丰富天然等位基因变异的身份尚不清楚。在这里，我们表征了来自Oryza officinalis Wall的丝裂原激活蛋白激酶 3 的功能。ex 瓦特由OrMKK3编码。OrMKK3中出现了不同的选择性剪接变体。绿色荧光蛋白 (GFP) – OrMKK3融合蛋白定位于水稻原生质体的细胞膜和细胞核。OrMKK3的过表达影响晶粒大小相关基因SMG1、GW8、GL3、GW2和DEP3 的表达水平。系统发育分析表明，OrMKK3在植物中高度保守，而在籼稻、粳稻和野生稻之间表现出大量变异。此外，OrMKK3轻微影响油菜素类固醇 (BR) 反应和 BR 相关基因的表达水平。因此，我们的研究结果确定了一个新基因OrMKK3，它影响形态和籽粒大小，并且代表了丝裂原激活蛋白激酶和籽粒生长中 BR 反应途径之间可能的联系。