Abstract
We analyzed two dominant mutants of Arabidopsis, crane-1 (cra-1) and cra-2, which are defective in lateral root formation. Although these mutants were isolated independently, they share several common phenotypes such as up-curled true leaves and dwarfism. We found out a missense mutation in domain II of IAA18 gene (At1g51950), a member of Aux/IAA transcriptional regulator family, in the genome of both cra-1 and cra-2, strongly suggesting that CRA encodes IAA18. These mutations are thought to stabilize IAA18 protein in crane mutants. Real-time RT-PCR analysis revealed that IAA18 is expressed in most organs including seedling roots. In yeast two-hybrid experiments, IAA18 protein has the ability to interact with ARF7 and ARF19, which are previously reported as key transcriptional factors required for lateral root formation. These results suggest that CRA/IAA18 is a novel regulator of lateral root formation in Arabidopsis.
