Figure 1.

A simple model of the nuclear auxin signaling pathway of plants. Auxin binds to the TIR1/AFB auxin receptors, which are part of Skp1-Cullin-F-box (SCF) ubiquitin ligase complexes and have a weak basal affinity for Aux/IAA proteins that is greatly enhanced in the presence of auxin. This auxin-mediated interaction with the SCF^TIR1/AFB ubiquitin ligase complex promotes Aux/IAA ubiquitination and proteasomal degradation. Aux/IAA degradation relieves repression of class A auxin response factors (ARFs), which then activate transcription of auxin-inducible genes containing Auxin-responsive cis-regulatory elements (AuxREs).