title: BRS1, a serine carboxypeptidase, regulates BRI1 signaling in Arabidopsis thaliana.
abstract: Brassinosteroid-insensitive 1 (BRI1) of Arabidopsis thaliana encodes a cell surface receptor for brassinosteroids. Mutations in BRI1 severely affect plant growth and development. Activation tagging of a weak bri1 allele (bri1-5) resulted in the identification of a new locus, brs1-1D. BRS1 is predicted to encode a secreted carboxypeptidase. Whereas a brs1 loss-of-function allele has no obvious mutant phenotype, overexpression of BRS1 can suppress bri1 extracellular domain mutants. Genetic analyses showed that brassinosteroids and a functional BRI1 protein kinase domain are required for suppression. In addition, overexpressed BRS1 missense mutants, predicted to abolish BRS1 protease activity, failed to suppress bri1-5. Finally, the effects of BRS1 are selective: overexpression in either wild-type or two other receptor kinase mutants resulted in no phenotypic alterations. These results strongly suggest that BRS1 processes a protein involved in an early event in the BRI1 signaling.
authors.affiliation: Division of Biological Sciences, University of Missouri, Columbia, MO 65211, USA.
authors.forename: J
authors.initials: J
authors.lastname: Li
authors.forename: K A
authors.initials: KA
authors.lastname: Lease
authors.forename: F E
authors.initials: FE
authors.lastname: Tax
authors.forename: J C
authors.initials: JC
authors.lastname: Walker
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology / Q000378:metabolism*; D029681:Arabidopsis Proteins; D001483:Base Sequence; D002268:Carboxypeptidases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002874:Chromosome Mapping; D018076:DNA, Complementary; D008969:Molecular Sequence Data; D010641:Phenotype; D011494:Protein Kinases / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D029681:Arabidopsis Proteins; D018076:DNA, Complementary; D011494:Protein Kinases; C108270:BRI1 protein, Arabidopsis; D002268:Carboxypeptidases; C022633:serine carboxypeptidase; C499281:BRS1 protein, Arabidopsis