Figure 1.

Schematic representation of the AFB-Aux/IAA-ARF system and feedback relationships with polar auxin transport (PAT) and auxin metabolism (A) ARF, Aux/IAA, and TIR1/AFB domain organization. (B) ARFs and Aux/IAAs can interact within their families through domain III and IV to form homo- and hetero-dimers (left) and interaction between families can also occur involving ARFs and Aux/IAAs (top right), and Aux/IAAs and TIR1/AFBs (bottom right). (C) The complexity of feedback regulation in auxin response. Lines ending in bars indicate inhibition, whereas lines ending in arrowheads indicate activation. Possible mechanisms of action are indicated by dashed lines.