title: Chemical genetics reveal the novel transmembrane protein BIL4, which mediates plant cell elongation in brassinosteroid signaling.
abstract: Steroid hormones are conserved between animals and plants as signaling molecules to control growth and development. Plant steroid hormones, brassinosteroids (BRs), appear to play an important role in plant cell elongation. BRs bind to leucine-rich repeat kinase BRASSINOSTEROID-INSENSITIVE 1 (BRI1) localized to the plasma membrane, activate transcription factors in collaboration with cytosolic kinases and phosphatases, and regulate BR-responsive gene expression, but the details regarding the BR signaling pathway from perception to nuclear events remain unknown. In this study we used chemical genetics to identify an evolutionarily conserved transmembrane protein, Brz-insensitive-long hypocotyls 4 (BIL4), and demonstrated its role as a critical component of plant cell elongation occurring upon BR signaling. A dominant mutation, bil4-1D, showed cell elongation in the presence of the BR-specific inhibitor Brz. Brz suppresses expression of the BIL4 gene in wild-type plants, and overexpression of BIL4 in bil4-1D suppresses the BR deficiency caused by Brz. Our results indicate that BIL4 mediates cell elongation on BR signaling.
authors.affiliation: Plant Chemical Biology Research Unit, RIKEN Advanced Science Institute, Wako, Saitama, Japan.
authors.forename: Ayumi
authors.initials: A
authors.lastname: Yamagami
authors.forename: Miki
authors.initials: M
authors.lastname: Nakazawa
authors.forename: Minami
authors.initials: M
authors.lastname: Matsui
authors.forename: Masafumi
authors.initials: M
authors.lastname: Tujimoto
authors.forename: Masaaki
authors.initials: M
authors.lastname: Sakuta
authors.forename: Tadao
authors.initials: T
authors.lastname: Asami
authors.forename: Takeshi
authors.initials: T
authors.lastname: Nakano
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000166:cytology* / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D049108:Cell Enlargement / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D010937:Plant Growth Regulators / Q000737:chemistry / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D015398:Signal Transduction; D013256:Steroids / Q000737:chemistry / Q000378:metabolism*; D014230:Triazoles / Q000737:chemistry / Q000494:pharmacology
chemical_list: D029681:Arabidopsis Proteins; C539779:BIL4 protein, Arabidopsis; D008565:Membrane Proteins; D010937:Plant Growth Regulators; D012333:RNA, Messenger; D013256:Steroids; D014230:Triazoles