Abstract
The members of Auxin Reponse Factor (ARF) regulate auxin-mediated gene expression during plant development. arf7 arf19 double mutants exhibit strong auxin-related phenotypes including severely impaired lateral root formation, which not seen in single mutants. These results indicate that lateral root formation is redundantly regulated by ARF7 and ARF19. Global gene expression analysis revealed that auxin-regulated gene expression, including genes encoding Lateral Organ Boundaries (LOB) -domain (LBD) proteins, is severely impaired in arf7 arf19 double mutant (Okushima et al., in press). Several LBD genes are specifically expressed in roots and they contain AuxREs in their promoter regions. We found that overexpression of one of these LBD genes rescues the lateral root phenotype of arf7 arf19 double mutant. These observations strongly suggest that ARF7 and ARF19 promote lateral root formation through the activation of auxin-responsive LBD expression.
