Abstract
To explore the genetic factors affecting postembryonic root formation, we screened Arabidopsis mutants with irregular adventitious and lateral root formation. The ar-C22 mutation showed retarded growth of primary roots, no production of lateral root, and adventitious root formation. Although the primary roots and hypocotyls in ar-C22 mutant showed a vascular system with fewer cells, adventitious roots showed normal vascular system and branched secondary roots. The hypocotyls of ar-C22 showed auxin accumulation in vascular system. Application of auxin induced the lateral root formation in the primary root of ar-C22 mutant. Gene analysis revealed that ar-C22 is a new ahk4/cre1/wol allele known as cytokinin receptor. All AHK genes, AHK2∼4, are ubiquitously expressed in vascular system of hypocotyl and the ahk2ahk3ahk4 triple mutant showed similar root morphology to ar-C22 mutant. These results suggest that retarded vascular system of ar-C22 hypocotyls leads the accumulation of auxin resulting in the adventitious root formation.
