Figure 3.

Plants use the circadian system to regulate auxin response. Circadian regulation has been observed at every level of the auxin pathway. In continuous conditions, expression of genes involved in biosynthesis, transport, conjugation, and transcriptional repression peaks during subjective day or dusk. Conversely, receptor gene expression and the auxin transcriptional response peaks during subjective night or dawn. Thus, transcriptional and growth effects show peak sensitivity to exogenous auxin treatment during subjective night.