Abstract
The endogenous auxin Indole-3-butyric acid (IBA) has been assumed to act via Indole-3-acetic acid (IAA) pathway to regulate the plant development. However, recent results suggest that cellular transport of IBA does not require either auxin influx carrier AUX1 or efflux carrier PIN2. In addition, IBA has been shown to effect the hypocotyl elongation and lateral root development differentially than of IAA, suggesting that IBA signaling and transport are possibly mediated by yet unidentified novel pathways. In the present work, by using available auxin signaling and transport mutants, we tried to elucidate the intracellular machinery that regulates the IBA response in Arabidopsis root. Our results suggest that IBA and IAA use a common response pathway in regulating the root meristem development, as all these auxin signaling and transport mutants showed resistance to both IAA or IBA induced root growth inhibition. In contrast, IBA but not IAA selectively increased the lateral root in all these mutants suggesting that IBA regulates the lateral root development through yet unidentified response pathway that works in parallel to known IAA pathway.
