Abstract
To elucidate the molecular mechanisms of auxin-regulated lateral root formation, we are studying solitary-root (slr) mutants, which have gain-of-function mutations in IAA14, a member of Aux/IAA family in Arabidopsis (Fukaki et al., Plant J. 2002). The slr mutants have no lateral roots, few root hairs, and reduced gravitropism in roots and hypocotyls. To identify genes that genetically interact with SLR/IAA14 in lateral root formation, we isolated the extragenic suppressor mutants of slr-1 from EMS-mutagenized slr-1 seedlings. The ssl2 (suppressor of slr 2) is a single recessive mutation, and we have four ssl2 alleles (ssl2-1~ssl2-4). The ssl2 slr-1 double mutants produce lateral roots but still have few root hairs and reduced gravitropism, indicating that the ssl2 mutations specifically suppress the slr-1 defect in lateral root formation. These results indicate that the slr phenotype in lateral root formation is partially dependent on SSL2. Positional cloning of SSL2 gene will be presented.
