title: A new class of transcription factors mediates brassinosteroid-regulated gene expression in Arabidopsis.
abstract: Brassinosteroids (BRs) signal through a plasma membrane-localized receptor kinase to regulate plant growth and development. We showed previously that a novel protein, BES1, accumulates in the nucleus in response to BRs, where it plays a role in BR-regulated gene expression; however, the mechanism by which BES1 regulates gene expression is unknown. In this study, we dissect BES1 subdomains and establish that BES1 is a transcription factor that binds to and activates BR target gene promoters both in vitro and in vivo. BES1 interacts with a basic helix-loop-helix protein, BIM1, to synergistically bind to E box (CANNTG) sequences present in many BR-induced promoters. Loss-of-function and gain-of-function mutants of BIM1 and its close family members display BR response phenotypes. Thus, BES1 defines a new class of plant-specific transcription factors that cooperate with transcription factors such as BIM1 to regulate BR-induced genes.
authors.affiliation: Howard Hughes Medical Institute and Plant Biology Laboratory, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA.
authors.forename: Yanhai
authors.initials: Y
authors.lastname: Yin
authors.forename: Dionne
authors.initials: D
authors.lastname: Vafeados
authors.forename: Yi
authors.initials: Y
authors.lastname: Tao
authors.forename: Shigeo
authors.initials: S
authors.lastname: Yoshida
authors.forename: Tadao
authors.initials: T
authors.lastname: Asami
authors.forename: Joanne
authors.initials: J
authors.lastname: Chory
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism; D004268:DNA-Binding Proteins; D018506:Gene Expression Regulation, Plant / Q000502:physiology*; D018257:Helix-Loop-Helix Motifs / Q000502:physiology; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism; D010840:Phytosterols / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; C456160:BES1 protein, Arabidopsis; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D010840:Phytosterols; D014157:Transcription Factors