Rapid and reversible root growth inhibition by TIR1 auxin signalling (Nature Plants)

Auxin mediates many of its effects through transcriptional changes via the well-known interaction between its co-receptors and transcriptional regulators (TIR1/AFB – Aux/IAA), but some auxin responses happen too quickly to be explained by transcriptional changes. Fendrych et al. demonstrate that root growth rate slows within 30 seconds of auxin application, and accelerates within 2 minutes of auxin removal. They show that these rapid responses depend on the auxin influx carrier AUX1, suggesting that the growth response is mediated by intracellular auxin. Through inhibitor, mutant and artificial ligand studies, they show that the growth effect is mediated by interaction between auxin and TIR1, which “implies that this canonical signalling pathway regulates root growth via an unknown, non-transcriptional signalling branch.” (Summary by Mary Williams) Nature Plants 10.1038/s41477-018-0190-1