Fig. 2
From: Q&A: Auxin: the plant molecule that influences almost anything
The nuclear auxin pathway (NAP) is the machinery that controls auxin gene expression. Without auxin (a), the transcriptional functions of the auxin response factors (ARF, in blue) are inhibited by the Aux/IAA proteins (in red) through heterodimerization. When auxin enters the nucleus (b), it allows binding between Aux/IAAs and the SCF (TIR/AFBs) complex (in green). These co-receptors will subsequently be degraded, allowing the ARF to modulate auxin-related gene expression