Fig. 1

Model of auxin transduction pathway and schematic representation of the ARF and Aux/IAA structures as found in Arabidopsis thaliana. a Activation and repression activities depend on ARF middle domain amino-acid composition. DBD indicates the DNA binding domain found usptream of auxin-inducible genes. In absence of auxin, AuxIAA are dimerised with the ARF, preventing them to exert their activating or repressing activity. When auxin is present, it targets the Aux/IAA to the proteasome leaving the ARF free to dimerise and exert their regulating activity. Source: adapted from [22]. b DBD: DNA binding domain; I: Aux/IAA specific putative homo-dimerisation domain; AD: Activation domain; RD: Repression domain; II: Aux/IAA specific degradation domain; III & IV: protein dimerisation domains. Arrowed lines indicate the extent of each inhibiting ARF structure. Source: adapted from [2, 23] with the notable difference that we found domains III and IV when aligning full length protein sequences for ARF13