Duan Penggen, Rao Yuchun, Zeng Dali, Yang Yaolong, Xu Ran, Zhang Baolan, Dong Guojun, Qian Qian, Li Yunhai
State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, 100101, China; University of Chinese Academy of Sciences, Beijing, 100039, China.
Plant J. 2014 Feb;77(4):547-57. doi: 10.1111/tpj.12405. Epub 2014 Jan 7.
Although grain size is one of the most important components of grain yield, little information is known about the mechanisms that determine final grain size in crops. Here we characterize rice small grain1 (smg1) mutants, which exhibit small and light grains, dense and erect panicles and comparatively slightly shorter plants. The short grain and panicle phenotypes of smg1 mutants are caused by a defect in cell proliferation. The smg1 mutations were identified, using a map-based cloning approach, in mitogen-activated protein kinase kinase 4 (OsMKK4). Relatively higher expression of OsMKK4/SMG1 was detected in younger organs than in older ones, consistent with its role in cell proliferation. Green fluorescent protein (GFP)-OsMKK4/SMG1 fusion proteins appear to be distributed ubiquitously in plant cells. Further results revealed that OsMKK4 influenced brassinosteroid (BR) responses and the expression of BR-related genes. Thus, our findings have identified OsMKK4 as a factor for grain size, and suggest a possible link between the MAPK pathways and BRs in grain growth.
尽管粒重是作物产量最重要的组成部分之一，但对于决定作物最终粒重的机制却知之甚少。在此，我们对水稻小粒1（smg1）突变体进行了表征，该突变体表现出籽粒小且轻、穗密集直立以及植株相对略矮的特征。smg1突变体的短粒和短穗表型是由细胞增殖缺陷所致。利用图位克隆方法，在促分裂原活化蛋白激酶激酶4（OsMKK4）中鉴定出了smg1突变。与OsMKK4在细胞增殖中的作用一致，在较幼嫩的器官中检测到的OsMKK4/SMG1表达相对高于较老的器官。绿色荧光蛋白（GFP）-OsMKK4/SMG1融合蛋白似乎在植物细胞中普遍分布。进一步的结果表明，OsMKK4影响油菜素内酯（BR）反应以及BR相关基因的表达。因此，我们的研究结果确定了OsMKK4是粒重的一个影响因素，并提示了丝裂原活化蛋白激酶（MAPK）途径与BR在籽粒生长过程中的可能联系。
