title: Is kinase activity essential for biological functions of BRI1?
abstract: Brassinosteroids (BRs) are a major group of plant hormones that regulate plant growth and development. BRI1, a protein localized to the plasma membrane, functions as a BR receptor and it has been proposed that its kinase activity has an essential role in BR-regulated plant growth and development. Here we report the isolation and molecular characterization of a new allele of bri1, bri1-301, which shows moderate morphological phenotypes and a reduced response to BRs under normal growth conditions. Sequence analysis identified a two-base alteration from GG to AT, resulting in a conversion of 989G to 989I in the BRI1 kinase domain. An in vitro assay of kinase activity showed that bri1-301 has no detectable autophosphorylation activity or phosphorylation activity towards the BRI1 substrates TTL and BAK1. Furthermore, our results suggest that bri1-301, even with extremely impaired kinase activity, still retains partial function in regulating plant growth and development, which raises the question of whether BRI1 kinase activity is essential for BR-mediated growth and development in higher plants.
authors.affiliation: State Key Laboratory of Plant Genomics and National Center for Plant Gene Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: Weihui
authors.initials: W
authors.lastname: Xu
authors.forename: Juan
authors.initials: J
authors.lastname: Huang
authors.forename: Baohua
authors.initials: B
authors.lastname: Li
authors.forename: Jiayang
authors.initials: J
authors.lastname: Li
authors.forename: Yonghong
authors.initials: Y
authors.lastname: Wang
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D060406:Brassinosteroids; D002777:Cholestanols / Q000494:pharmacology; D018506:Gene Expression Regulation, Plant / Q000187:drug effects / Q000528:radiation effects; D008027:Light; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000302:isolation & purification / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D011494:Protein Kinases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D036226:Seedlings / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D013260:Steroids, Heterocyclic / Q000494:pharmacology
chemical_list: D029681:Arabidopsis Proteins; D060406:Brassinosteroids; D002777:Cholestanols; D050505:Mutant Proteins; D013260:Steroids, Heterocyclic; D011494:Protein Kinases; C108270:BRI1 protein, Arabidopsis; C023623:brassinolide