Fig. 3.

The Ubiquitin-mediated proteolysis of Aux/IAA proteins regulates auxin response. In the absence of an auxin stimulus, Aux/ IAA proteins inhibit ARF transcriptional activity by forming heterodimers. Auxin perception (by an unknown receptor) targets the Aux/IAA proteins to the SCFTIR1 complex, resulting in their ubiquitination and degradation, thereby derepressing the ARF transcription factors. Among the ARF targets are the Aux/IAA genes themselves, which produce nascent Aux/IAA proteins that restore repression upon the pathway in a negative feedback loop