Glucosyltransferase that catalyzes the formation of 1-O-beta-D-glucose esters with hydroxybenzoic acids as preferred glucosyl acceptors. Has the highest activity with 3,4-dihydroxybenzoate, vanillate and gallate in vitro. Gallate is the predicted native substrate of the enzyme, which thus catalyzes the formation of 1-O-galloyl-beta-D-glucose, the first committed step of gallotannin biosynthesis. 3,4,5-trihydroxybenzoate + UDP-alpha-D-glucose = 1-O-galloyl-beta-D-glucose + UDP UDP-alpha-D-glucose + vanillate = 1-O-(4-hydroxy-3-methoxybenzoyl)-beta-D-glucose + UDP 3,4-dihydroxybenzoate + UDP-alpha-D-glucose = 1-O-(3,4-dihydroxy-benzoyl)-beta-D-glucose + UDP Expressed in swelling buds and young leaves. Belongs to the UDP-glycosyltransferase family.