BRI1 is a critical component of a plasma-membrane receptor for plant steroids

Nature. 2001 Mar 15;410(6826):380-3. doi: 10.1038/35066597.


Most multicellular organisms use steroids as signalling molecules for physiological and developmental regulation. Two different modes of steroid action have been described in animal systems: the well-studied gene regulation response mediated by nuclear receptors, and the rapid non-genomic responses mediated by proposed membrane-bound receptors. Plant genomes do not seem to encode members of the nuclear receptor superfamily. However, a transmembrane receptor kinase, brassinosteroid-insensitive1 (BRI1), has been implicated in brassinosteroid responses. Here we show that BRI1 functions as a receptor of brassinolide, the most active brassinosteroid. The number of brassinolide-binding sites and the degree of response to brassinolide depend on the level of BRI1 protein. The brassinolide-binding activity co-immunoprecipitates with BRI1, and requires a functional BRI1 extracellular domain. Moreover, treatment of Arabidopsis seedlings with brassinolide induces autophosphorylation of BRI1, which, together with our binding studies, shows that BRI1 is a receptor kinase that transduces steroid signals across the plasma membrane.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Arabidopsis
  • Arabidopsis Proteins*
  • Brassinosteroids
  • Cholestanols / metabolism*
  • Enzyme Activation
  • Genes, Plant
  • Ligands
  • Mutation
  • Phosphorylation
  • Phytosterols / metabolism*
  • Protein Kinases / genetics
  • Protein Kinases / metabolism*
  • Protein Structure, Tertiary
  • Receptors, Steroid / metabolism*
  • Signal Transduction
  • Steroids, Heterocyclic / metabolism*


  • Arabidopsis Proteins
  • Brassinosteroids
  • Cholestanols
  • Ligands
  • Phytosterols
  • Receptors, Steroid
  • Steroids, Heterocyclic
  • Protein Kinases
  • BRI1 protein, Arabidopsis
  • brassinolide