Figure 7.

Model for auxin response. In this model, TIR1 functions in an SCF ubiquitin ligase that targets one or more negative regulators of the auxin response pathway for ubiquitination and degradation. SCF^TIR1 activity requires the RUB modification of AtCUL1 via the AXR1–ECR1 pathway. The ubiquitin–mediated degradation of the repressor(s) derepresses the response pathway resulting in the activation of the early auxin response genes (AUX/IAA genes) that may control downstream events resulting in auxin-regulated growth and development. E1, ubiquitin-activating enzyme; E2, ubiquitin-conjugating enzyme; E2R, RUB-conjugating enzyme.