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A combinatorial TIR1/AFB-Aux/IAA co-receptor system for differential sensing of auxin.


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.

Pubmed ID: 22466420


  • Calderón Villalobos LI
  • Lee S
  • De Oliveira C
  • Ivetac A
  • Brandt W
  • Armitage L
  • Sheard LB
  • Tan X
  • Parry G
  • Mao H
  • Zheng N
  • Napier R
  • Kepinski S
  • Estelle M


Nature chemical biology

Publication Data

May 20, 2012

Associated Grants

  • Agency: Biotechnology and Biological Sciences Research Council, Id: BB/F007418/1
  • Agency: Biotechnology and Biological Sciences Research Council, Id: BB/F013981/1
  • Agency: Biotechnology and Biological Sciences Research Council, Id: BB/F014651/1
  • Agency: NCI NIH HHS, Id: R01 CA107134
  • Agency: NCI NIH HHS, Id: R01 CA107134
  • Agency: NIGMS NIH HHS, Id: R01 GM043644
  • Agency: NIGMS NIH HHS, Id: R01 GM043644-25
  • Agency: NIGMS NIH HHS, Id: T32 GM07270
  • Agency: Howard Hughes Medical Institute, Id:

Mesh Terms

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