title: Transcription factor HAT1 is phosphorylated by BIN2 kinase and mediates brassinosteroid repressed gene expression in Arabidopsis.
abstract: Plant steroid hormones, brassinosteroids (BRs), play essential roles in modulating cell elongation, vascular differentiation, senescence and stress responses. BRs signal through plasma membrane-localized receptor and other components to modulate the BES1/BZR1 (BRI1-EMS SUPPRESSOR 1/BRASSINAZOLE RESISTANT 1) family of transcription factors that modulate thousands of target genes. Arabodopsis thaliana homeodomain-leucine zipper protein 1 (HAT1), which encodes a homeodomain-leucine zipper (HD-Zip) class II transcription factor, was identified through chromatin immunoprecipitation (ChIP) experiments as a direct target gene of BES1. Loss-of-function and gain-of-function mutants of HAT1 display altered BR responses. HAT1 and its close homolog HAT3 act redundantly, as the double mutant hat1 hat3 displayed a reduced BR response that is stronger than the single mutants alone. Moreover, hat1 hat3 enhanced the phenotype of a weak allele of the BR receptor mutant bri1 and suppressed the phenotype of constitutive BR response mutant bes1-D. These results suggest that HAT1 and HAT3 function to activate BR-mediated growth. Expression levels of several BR-repressed genes are increased in hat1 hat3 and reduced in HAT1OX, suggesting that HAT1 functions to repress the expression of a subset of BR target genes. HAT1 and BES1 bind to a conserved homeodomain binding (HB) site and BR response element (BRRE) respectively, in the promoters of some BR-repressed genes. BES1 and HAT1 interact with each other and cooperate to inhibit BR-repressed gene expression. Furthermore, HAT1 can be phosphorylated and stabilized by GSK3 (GLYCOGEN SYNTHASE KINASE 3)-like kinase BIN2 (BRASSINOSTEROID-INSENSITIVE 2), a well established negative regulator of the BR pathway. Our results thus revealed a previously unknown mechanism by which BR signaling modulates BR-repressed gene expression and coordinates plant growth.
authors.affiliation: College of Life Science, Ministry of Education Key Laboratory for Bio-Resource and Eco-Environment, State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu, 610064, China; Department of Genetics, Development and Cell Biology, Iowa State University, Ames, IA, 50011, USA.
authors.forename: Dawei
authors.initials: D
authors.lastname: Zhang
authors.forename: Huaxun
authors.initials: H
authors.lastname: Ye
authors.forename: Hongqing
authors.initials: H
authors.lastname: Guo
authors.forename: Abbagail
authors.initials: A
authors.lastname: Johnson
authors.forename: Meishan
authors.initials: M
authors.lastname: Zhang
authors.forename: Honghui
authors.initials: H
authors.lastname: Lin
authors.forename: Yanhai
authors.initials: Y
authors.lastname: Yin
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000201:enzymology / Q000235:genetics* / Q000502:physiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D060406:Brassinosteroids / Q000378:metabolism*; D004268:DNA-Binding Proteins; D015870:Gene Expression; D018506:Gene Expression Regulation, Plant; D017930:Genes, Reporter; D051548:Histone Acetyltransferases; D018546:Hypocotyl / Q000166:cytology / Q000201:enzymology / Q000235:genetics / Q000502:physiology; D008969:Molecular Sequence Data; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010641:Phenotype; D010766:Phosphorylation; D010937:Plant Growth Regulators / Q000378:metabolism; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic / Q000235:genetics; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D036226:Seedlings / Q000166:cytology / Q000201:enzymology / Q000235:genetics / Q000502:physiology; D015398:Signal Transduction; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D060406:Brassinosteroids; D004268:DNA-Binding Proteins; D051548:Histone Acetyltransferases; D009687:Nuclear Proteins; D010937:Plant Growth Regulators; D011494:Protein Kinases; D014157:Transcription Factors; C456160:BES1 protein, Arabidopsis; C000593713:HAC1 protein, Arabidopsis; C448985:At4g18710 protein, Arabidopsis
keywords: Arabidopsis thaliana; BES1; BIN2; HAT1; HAT3; brassinosteroids; phosphorylation; transcription repression