@Article{IPB-1388, author = {Calderón Villalobos, L. I. A. and Lee, S. and De Oliveira, C. and Ivetac, A. and Brandt, W. and Armitage, L. and Sheard, L. B. and Tan, X. and Parry, G. and Mao, H. and Zheng, N. and Napier, R. and Kepinski, S. and Estelle, M.}, title = {{A combinatorial TIR1/AFB–Aux/IAA co-receptor system for differential sensing of auxin}}, year = {2012}, pages = {477-485}, journal = {Nat Chem Biol}, doi = {10.1038/nchembio.926}, url = {http://www.nature.com/nchembio/journal/vaop/ncurrent/full/nchembio.926.html}, volume = {8}, 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 AFB5Aux/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.} }