title: OsMAPK6, a mitogen-activated protein kinase, influences rice grain size and biomass production.
abstract: Grain size is an important agronomic trait in determining grain yield. However, the molecular mechanisms that determine the final grain size are not well understood. Here, we report the functional analysis of a rice (Oryza sativa L.) mutant, dwarf and small grain1 (dsg1), which displays pleiotropic phenotypes, including small grains, dwarfism and erect leaves. Cytological observations revealed that the small grain and dwarfism of dsg1 were mainly caused by the inhibition of cell proliferation. Map-based cloning revealed that DSG1 encoded a mitogen-activated protein kinase (MAPK), OsMAPK6. OsMAPK6 was mainly located in the nucleus and cytoplasm, and was ubiquitously distributed in various organs, predominately in spikelets and spikelet hulls, consistent with its role in grain size and biomass production. As a functional kinase, OsMAPK6 interacts strongly with OsMKK4, indicating that OsMKK4 is likely to be the upstream MAPK kinase of OsMAPK6 in rice. In addition, hormone sensitivity tests indicated that the dsg1 mutant was less sensitive to brassinosteroids (BRs). The endogenous BR levels were reduced in dsg1, and the expression of several BR signaling pathway genes and feedback-inhibited genes was altered in the dsg1 mutant, with or without exogenous BRs, indicating that OsMAPK6 may contribute to influence BR homeostasis and signaling. Thus, OsMAPK6, a MAPK, plays a pivotal role in grain size in rice, via cell proliferation, and BR signaling and homeostasis.
authors.affiliation: National Centre for Plant Gene Research, State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, 100101, China.
authors.forename: Shuying
authors.initials: S
authors.lastname: Liu
authors.affiliation: National Centre for Plant Gene Research, State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, 100101, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Hua
authors.affiliation: National Centre for Plant Gene Research, State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, 100101, China.
authors.forename: Sujun
authors.initials: S
authors.lastname: Dong
authors.affiliation: State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou, 310006, China.
authors.forename: Hongqi
authors.initials: H
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou, 310006, China.
authors.forename: Xudong
authors.initials: X
authors.lastname: Zhu
authors.affiliation: National Centre for Plant Gene Research, State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, 100101, China.
authors.forename: Jun'e
authors.initials: J
authors.lastname: Jiang
authors.affiliation: National Centre for Plant Gene Research, State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, 100101, China.
authors.forename: Fang
authors.initials: F
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, 100101, China.
authors.forename: Yunhai
authors.initials: Y
authors.lastname: Li
authors.affiliation: National Centre for Plant Gene Research, State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, 100101, China.
authors.forename: Xiaohua
authors.initials: X
authors.lastname: Fang
authors.affiliation: National Centre for Plant Gene Research, State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, 100101, China.
authors.forename: Fan
authors.initials: F
authors.lastname: Chen
mesh_terms: D000595:Amino Acid Sequence; D018533:Biomass; D060406:Brassinosteroids / Q000494:pharmacology; D049109:Cell Proliferation / Q000187:drug effects / Q000235:genetics; D002523:Edible Grain / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D048053:Mitogen-Activated Protein Kinase 6 / Q000235:genetics / Q000378:metabolism*; D020929:Mitogen-Activated Protein Kinase Kinases / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D012275:Oryza / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D010937:Plant Growth Regulators / Q000494:pharmacology; D018515:Plant Leaves / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified; D011485:Protein Binding; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid
chemical_list: D060406:Brassinosteroids; D010937:Plant Growth Regulators; D010940:Plant Proteins; D049452:Green Fluorescent Proteins; D048053:Mitogen-Activated Protein Kinase 6; D020929:Mitogen-Activated Protein Kinase Kinases
keywords: Oryza sativa L; OsMAPK6; brassinosteroid; cell proliferation; dwarf; grain size