Auxin response factors: Structure and Regulation

In plants, most developmental mechanisms implicate a family of transcription factors (TFs), the Auxin Response Factors (ARFs), that regulate transcriptional reprogramming in response to the hormone, auxin (1). One fundamental question is to understand how ARFs contribute to the multiplicity of transcriptional responses initiated by this one developmental signal, auxin. ARFs are divided into three functional classes (A, B, C) and exhibit distinct binding preferences for pairs of cis-elements known as AuxREs (Auxin Responsive Elements), which can be arranged in three configurations: IR (inverted repeats), ER (everted repeats), and DR (direct repeats). the molecular basis of ARF binding specificity remains largely unknown. In particular, it is unclear why ARFs, which all recognize the same DNA element as monomers, show distinct specificities when acting as dimers or higher-order complexes.