Downstream nuclear events in brassinosteroid signalling

Nature. 2006 May 4;441(7089):96-100. doi: 10.1038/nature04681.


Brassinosteroids (BRs) are steroid hormones that control many aspects of plant growth and development. BRs bind to the plasma membrane receptor kinase BRI1, and act through a signalling pathway that involves a glycogen synthase kinase-3-like kinase (BIN2) and a serine/threonine phosphatase (BSU1). Previous models proposed that BIN2 negatively regulates BR signalling by controlling the stability and subcellular localization of the related transcription factors BES1 and BZR1 by phosphorylation, in a manner reminiscent of the canonical Wnt signalling pathway of metazoans. Here we present strong evidence for a different mode of regulation of BR signalling. We show that BES1 is localized constitutively to the nucleus, where its activity is modulated by nuclear-localized BIN2 kinase. BIN2-mediated phosphorylation of BES1 inhibits its DNA-binding activity on BR-responsive target promoters and its transcriptional activity through impaired multimerization. Our observations demonstrate that phosphorylation-dependent inhibition of DNA binding and trans-activation is the key primary mechanism of BES1 regulation.

Publication types

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

MeSH terms

  • Arabidopsis / cytology*
  • Arabidopsis / drug effects*
  • Arabidopsis / metabolism
  • Arabidopsis Proteins / metabolism*
  • Cell Nucleus / drug effects*
  • Cell Nucleus / metabolism*
  • DNA / metabolism
  • DNA-Binding Proteins
  • Glycogen Synthase Kinase 3 / metabolism
  • Nuclear Proteins / metabolism
  • Phosphorylation
  • Protein Kinases / metabolism*
  • Signal Transduction / drug effects*
  • Steroids / pharmacology*
  • Transcriptional Activation


  • Arabidopsis Proteins
  • BES1 protein, Arabidopsis
  • DNA-Binding Proteins
  • Nuclear Proteins
  • Steroids
  • DNA
  • Protein Kinases
  • BIN2 protein, Arabidopsis
  • Glycogen Synthase Kinase 3