Identification and biochemical characterization of an Arabidopsis indole-3-acetic acid glucosyltransferase

Biochemical characterization of recombinant gene products following a phylo genetic analysis of the UDP-glucosyltransferase (UGT) multigene family of A rabidopsis has identified one enzyme (UGT84B1) with high activity toward th e plant hormone indole-3-acetic acid (IAA) and three related enzymes (UGT84 B2, UGT75B1, and UGT75B2) with trace activities. The identity of the IAA co njugate has been confirmed to be 1-O-indole acetyl glucose ester. A sequenc e annotated as a UDP-glucose:IAA glucosyltransferase (IAA-UGT) in the Arabi dopsis genome and expressed sequence tag data bases given its similarity to the maize iaglu gene sequence showed no activity toward IAA This study des cribes the first biochemical analysis of a recombinant IAA-UGT and provides the foundation for future genetic approaches to understand the role of 1-O -indole acetyl glucose ester in Arabidopsis.