title: Genome-wide study of KNOX regulatory network reveals brassinosteroid catabolic genes important for shoot meristem function in rice.
abstract: In flowering plants, knotted1-like homeobox (KNOX) transcription factors play crucial roles in establishment and maintenance of the shoot apical meristem (SAM), from which aerial organs such as leaves, stems, and flowers initiate. We report that a rice (Oryza sativa) KNOX gene Oryza sativa homeobox1 (OSH1) represses the brassinosteroid (BR) phytohormone pathway through activation of BR catabolism genes. Inducible overexpression of OSH1 caused BR insensitivity, whereas loss of function showed a BR-overproduction phenotype. Genome-wide identification of loci bound and regulated by OSH1 revealed hormonal and transcriptional regulation as the major function of OSH1. Among these targets, BR catabolism genes CYP734A2, CYP734A4, and CYP734A6 were rapidly upregulated by OSH1 induction. Furthermore, RNA interference knockdown plants of CYP734A genes arrested growth of the SAM and mimicked some osh1 phenotypes. Thus, we suggest that local control of BR levels by KNOX genes is a key regulatory step in SAM function.
authors.affiliation: Plant Gene Expression Center, U.S. Department of Agriculture-Agricultural Research Service, Plant and Microbial Biology Department, University of California at Berkeley, Berkeley, California 94720.
authors.forename: Katsutoshi
authors.initials: K
authors.lastname: Tsuda
authors.affiliation: Plant Genetics Laboratory, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan Department of Genetics, School of Life Science, Graduate University for Advanced Studies, Mishima, Shizuoka 411-8540, Japan.
authors.forename: Nori
authors.initials: N
authors.lastname: Kurata
authors.affiliation: Plant Genetics Laboratory, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan Tsukuba Divison, Mitsubishi Space Software Co., Tsukuba, Ibaraki 305-0032, Japan.
authors.forename: Hajime
authors.initials: H
authors.lastname: Ohyanagi
authors.affiliation: Plant Gene Expression Center, U.S. Department of Agriculture-Agricultural Research Service, Plant and Microbial Biology Department, University of California at Berkeley, Berkeley, California 94720 hake@berkeley.edu.
authors.forename: Sarah
authors.initials: S
authors.lastname: Hake
mesh_terms: D060406:Brassinosteroids / Q000378:metabolism* / Q000494:pharmacology; D047369:Chromatin Immunoprecipitation; D017124:Conserved Sequence; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D055785:Gene Knockdown Techniques; D053263:Gene Regulatory Networks; D017343:Genes, Plant; D018519:Meristem / Q000187:drug effects / Q000235:genetics*; D009154:Mutation / Q000235:genetics; D012275:Oryza / Q000187:drug effects / Q000235:genetics*; D010641:Phenotype; D018515:Plant Leaves / Q000187:drug effects / Q000235:genetics; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D060406:Brassinosteroids; D010940:Plant Proteins