title: SMALL GRAIN 1, which encodes a mitogen-activated protein kinase kinase 4, influences grain size in rice.
abstract: 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.
authors: 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.
authors: Penggen
authors: P
authors: Duan
authors: Yuchun
authors: Y
authors: Rao
authors: Dali
authors: D
authors: Zeng
authors: Yaolong
authors: Y
authors: Yang
authors: Ran
authors: R
authors: Xu
authors: Baolan
authors: B
authors: Zhang
authors: Guojun
authors: G
authors: Dong
authors: Qian
authors: Q
authors: Qian
authors: Yunhai
authors: Y
authors: Li
mesh_terms: D060406:Brassinosteroids / Q000378:metabolism; D049109:Cell Proliferation; D002874:Chromosome Mapping; D032461:Chromosomes, Plant / Q000235:genetics*; D002523:Edible Grain / Q000166:cytology / Q000201:enzymology / Q000235:genetics / Q000254:growth & development; D035264:Flowers / Q000166:cytology / Q000201:enzymology / Q000235:genetics / Q000254:growth & development; D018506:Gene Expression Regulation, Plant; D017930:Genes, Reporter; D048670:MAP Kinase Kinase 4 / Q000235:genetics* / Q000378:metabolism; D018519:Meristem / Q000166:cytology / Q000201:enzymology / Q000235:genetics / Q000254:growth & development; D009154:Mutation; D012275:Oryza / Q000166:cytology / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D010641:Phenotype; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D018520:Plant Shoots / Q000166:cytology / Q000201:enzymology / Q000235:genetics / Q000254:growth & development; D030821:Plants, Genetically Modified; D011993:Recombinant Fusion Proteins; D036226:Seedlings / Q000166:cytology / Q000201:enzymology / Q000235:genetics / Q000254:growth & development; D015398:Signal Transduction
chemical_list: D060406:Brassinosteroids; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; D048670:MAP Kinase Kinase 4
keywords: SMG1/OsMKK4; cell proliferation; grain size; panicle size; rice