Complex auxin responses are mediated by the interaction
of two different protein families, Aux/IAA proteins (transcriptional
repressors) and the auxin response factors
(ARFs) that relay auxin signaling at the transcriptional
level by inducing primarily three groups of genes: Aux/IAA,
GH3 and small auxin-up RNA (SAUR) [62,63]. Several
transcription factors, such as members of the HD-Zip
family, AP2-type, AS2-like (LBD), MYB-like, zinc fingerlike
and many others, are also genes that depend on auxin
signaling [62,63]. On auxin perception by the TIR1 auxin
receptor, TIR1 degrades the Aux/IAA proteins, which are
negative regulators of auxin signaling that bind and inhibit
ARF transcription factors.