title: Brassinosteroid regulates cell elongation by modulating gibberellin metabolism in rice.
abstract: Brassinosteroid (BR) and gibberellin (GA) are two predominant hormones regulating plant cell elongation. A defect in either of these leads to reduced plant growth and dwarfism. However, their relationship remains unknown in rice (Oryza sativa). Here, we demonstrated that BR regulates cell elongation by modulating GA metabolism in rice. Under physiological conditions, BR promotes GA accumulation by regulating the expression of GA metabolic genes to stimulate cell elongation. BR greatly induces the expression of D18/GA3ox-2, one of the GA biosynthetic genes, leading to increased GA1 levels, the bioactive GA in rice seedlings. Consequently, both d18 and loss-of-function GA-signaling mutants have decreased BR sensitivity. When excessive active BR is applied, the hormone mostly induces GA inactivation through upregulation of the GA inactivation gene GA2ox-3 and also represses BR biosynthesis, resulting in decreased hormone levels and growth inhibition. As a feedback mechanism, GA extensively inhibits BR biosynthesis and the BR response. GA treatment decreases the enlarged leaf angles in plants with enhanced BR biosynthesis or signaling. Our results revealed a previously unknown mechanism underlying BR and GA crosstalk depending on tissues and hormone levels, which greatly advances our understanding of hormone actions in crop plants and appears much different from that in Arabidopsis thaliana.
authors.affiliation: State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: Hongning
authors.initials: H
authors.lastname: Tong
authors.affiliation: State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: Yunhua
authors.initials: Y
authors.lastname: Xiao
authors.affiliation: State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: Dapu
authors.initials: D
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: Shaopei
authors.initials: S
authors.lastname: Gao
authors.affiliation: State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: Linchuan
authors.initials: L
authors.lastname: Liu
authors.affiliation: Department of Genetics, Development, and Cell Biology, Iowa State University, Ames, Iowa 50011.
authors.forename: Yanhai
authors.initials: Y
authors.lastname: Yin
authors.affiliation: Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: Yun
authors.initials: Y
authors.lastname: Jin
authors.affiliation: State Key Laboratory of Rice Biology, China National Rice Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou 310006, China.
authors.forename: Qian
authors.initials: Q
authors.lastname: Qian
authors.affiliation: State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China ccchu@genetics.ac.cn.
authors.forename: Chengcai
authors.initials: C
authors.lastname: Chu
mesh_terms: D060406:Brassinosteroids / Q000494:pharmacology*; D049108:Cell Enlargement / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects*; D005875:Gibberellins / Q000032:analysis / Q000378:metabolism*; D008954:Models, Biological; D009154:Mutation; D012275:Oryza / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D010937:Plant Growth Regulators / Q000378:metabolism*; D018515:Plant Leaves / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D036226:Seedlings / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D060406:Brassinosteroids; D005875:Gibberellins; D010937:Plant Growth Regulators; D010940:Plant Proteins