Diversity and specificity: auxin perception and signaling through the TIR1/AFB pathway

• The TIR1/AFB-Aux/IAA-ARF module has a key role in auxin signaling.
• Combinatorial protein interactions contribute to the specificity of auxin signaling.
• Multimerization of Aux/IAAs and ARFs mediates transcriptional regulation by auxin.

Auxin is a versatile plant hormone that plays an essential role in most aspects of plant growth and development. Auxin regulates various growth processes by modulating gene transcription through a SCFTIR1/AFB-Aux/IAA-ARF nuclear signaling module. Recent work has generated clues as to how multiple layers of regulation of the auxin signaling components may result in diverse and specific response outputs. In particular, interaction and structural studies of key auxin signaling proteins have produced novel insights into the molecular basis of auxin-regulated transcription and may lead to a refined auxin signaling model.