Characterization of auxin-induced ARRO-1 expression in the primary root of Malus domestica.

ARRO-1, a novel 2-oxoacid-dependent dioxygenase (2-ODD) is up-regulated during IBA-induced adventitious root formation in stem discs of Malus domestica. Analysis of ARRO-1's expression profile in the primary root of apple seedlings indicates that it is also highly up-regulated in the root in response to both IAA and IBA, but not 2, 4-D. Auxin-derived evolution of ethylene can be discounted as the source of ARRO-1 induction as ARRO-1 is not induced in the root following treatment with the ethylene precursor ACC. Constitutive expression in the primary root further suggests that ARRO-1's role may be linked to the regulation of natural auxin levels within plant tissues. Significantly, orthologues of ARRO-1 have been identified in Arabidopsis thaliana by means of DNA database analysis which will enable the further molecular characterization of this class of 2-ODD.