The Arabidopsis transthyretin-like protein is a potential substrate of BRASSINOSTEROID-INSENSITIVE 1

Plant Cell. 2004 Sep;16(9):2406-17. doi: 10.1105/tpc.104.023903. Epub 2004 Aug 19.


BRASSINOSTEROID-INSENSITIVE 1 (BRI1) is a Leu-rich-repeat (LRR) receptor kinase that functions as a critical component of a transmembrane brassinosteroid (BR) receptor. It is believed that BRI1 becomes activated through heterodimerization with BAK1, a similar LRR receptor kinase, in response to BR signal. A yeast two-hybrid screen using the kinase domain of BRI1 identified an Arabidopsis thaliana Transthyretin-Like protein (TTL) as a potential BRI1 substrate. TTL interacts with BRI1 in a kinase-dependent manner in yeast and is phosphorylated by BRI1 in vitro. TTL displays a similar expression pattern with BRI1 and is associated with the plasma membrane. Overexpression of the TTL gene results in a phenotype that was observed in weak bri1 mutants and null bak1 mutants. By contrast, two T-DNA insertional mutations in the TTL gene promote plant growth and enhance BR sensitivity. We hypothesized that TTL might directly regulate certain biochemical activities near the plasma membrane to control plant growth.

Publication types

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

MeSH terms

  • Amino Acid Sequence / genetics
  • Arabidopsis / genetics*
  • Arabidopsis / metabolism*
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / isolation & purification
  • Arabidopsis Proteins / metabolism*
  • Base Sequence / genetics
  • DNA, Complementary / analysis
  • DNA, Complementary / genetics
  • Gene Expression Regulation, Plant / genetics
  • Growth Inhibitors / metabolism
  • Growth Substances / genetics
  • Growth Substances / metabolism
  • Membrane Proteins / genetics
  • Membrane Proteins / isolation & purification
  • Membrane Proteins / metabolism*
  • Molecular Sequence Data
  • Mutation / genetics
  • Prealbumin / metabolism
  • Protein Kinases / genetics
  • Protein Kinases / metabolism*
  • Up-Regulation / genetics


  • Arabidopsis Proteins
  • DNA, Complementary
  • Growth Inhibitors
  • Growth Substances
  • Membrane Proteins
  • Prealbumin
  • TTL protein, Arabidopsis
  • Protein Kinases
  • BRI1 protein, Arabidopsis