Heterogeneous flavonoid glucosyltransferases in purple derivatives from a controlling element-suppressed bronze mutant in maize.

The Ds(Dissociation)-suppressed bronze mutant bz-m2(DI), which is extremely stable in the absence of the regulatory element Ac (Activator), becomes both somatically and germinally unstable when Ac is present. Instability in the germ line may result in the generation of stable (Ac-nonresponding), colored Bz' derivatives. The characterization of several properties of the Bz-controlled enzyme UDPglucose: flavonoid 3-O-glucosyltransferase from mature kernel endosperms of 15 such Bz' derivatives has revealed two distinct groups. The enzyme in group I Bz' derivatives does not differ from the normal enzyme in the Bz progenitor allele of bz-m2(DI). Group II Bz' derivatives, on the other hand, make altered, labile UDPglucose:flavonoid glucosytransferases different from the normal enzyme and probably different from each other. The significance of these two classes of derivatives and possible mechanisms involved in their origin are discussed.