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: over-expression 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.
|Original language||English (US)|
|Number of pages||6|
|Journal||Proceedings of the National Academy of Sciences of the United States of America|
|State||Published - May 8 2001|
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