A Combinatorial TIR1/AFB-Aux/IAA Co-Receptor System for Differential Sensing of Auxin

Nat Chem Biol. 2012 Apr 1;8(5):477-85. doi: 10.1038/nchembio.926.

Abstract

The plant hormone auxin regulates virtually every aspect of plant growth and development. Auxin acts by binding the F-box protein transport inhibitor response 1 (TIR1) and promotes the degradation of the AUXIN/INDOLE-3-ACETIC ACID (Aux/IAA) transcriptional repressors. Here we show that efficient auxin binding requires assembly of an auxin co-receptor complex consisting of TIR1 and an Aux/IAA protein. Heterologous experiments in yeast and quantitative IAA binding assays using purified proteins showed that different combinations of TIR1 and Aux/IAA proteins form co-receptor complexes with a wide range of auxin-binding affinities. Auxin affinity seems to be largely determined by the Aux/IAA. As there are 6 TIR1/AUXIN SIGNALING F-BOX proteins (AFBs) and 29 Aux/IAA proteins in Arabidopsis thaliana, combinatorial interactions may result in many co-receptors with distinct auxin-sensing properties. We also demonstrate that the AFB5-Aux/IAA co-receptor selectively binds the auxinic herbicide picloram. This co-receptor system broadens the effective concentration range of the hormone and may contribute to the complexity of auxin response.

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Arabidopsis Proteins / chemistry*
  • DNA-Binding Proteins / chemistry*
  • F-Box Proteins / chemistry*
  • Herbicides / chemistry
  • Indoleacetic Acids / chemistry*
  • Molecular Sequence Data
  • Nuclear Proteins / chemistry*
  • Picloram / chemistry
  • Receptors, Cell Surface / chemistry*

Substances

  • AFB5 protein, Arabidopsis
  • Arabidopsis Proteins
  • DNA-Binding Proteins
  • F-Box Proteins
  • Herbicides
  • IAA1 protein, Arabidopsis
  • Indoleacetic Acids
  • Nuclear Proteins
  • Receptors, Cell Surface
  • TIR1 protein, Arabidopsis
  • Picloram

Associated data

  • PubChem-Substance/134970358
  • PubChem-Substance/134970359
  • PubChem-Substance/134970360
  • PubChem-Substance/134970361