Abstract
Lateral root (LR) formation is initiated from the asymmetric cell division of the pericycle cells adjacent to xylem poles in the primary root in Arabidopsis thaliana. It has been shown that the auxin signaling mediated by the auxin response factors ARF7, ARF19, their repressor protein SLR/IAA14, and the direct targets of ARF7/19 including LBD16/ASL18, promotes LR formation in Arabidopsis. ARF7/19 are mainly expressed in root stele tissues including xylem-pole pericycle cells. However, it is unknown exactly when and where ARF7/19-dependent auxin response is required for LR formation. In this study, we analyzed the transgenic Arabidopsis plants expressing ARF7/19 in the spatio-temporal specific manner. 1) We examined the timing when ARF7/19 activity is required for LR formation by using ARF7/19-inducible lines. 2) We also examined whether targeted expression of ARF7/19 or LBD16 in the protoxylem pericycle restores LR formation in the arf7 arf19 mutant background. Based on these results, we will discuss the spatio-temporal regulation of ARF7/19-dependent auxin response in LR formation.
