CLONING AND EXPRESSION OF SOLANIDINE UDP-GLUCOSE GLUCOSYLTRANSFERASE FROM POTATO

A cDNA encoding solanidine glucosyltransferase (SGT) was isolated from potato. The cDNA was selected from a yeast expression library using a positive selection based on the higher toxicity of steroidal alkaloid aglycons relative to their associated glycosylated forms. The cDNA co ntained an open reading frame encoding a 56 kDa polypeptide with regio ns of similarity to previously characterized UDP-glucosyltransferases. The enzyme activity and reaction products of recombinant SGT in yeast were consistent with those observed for the endogenous enzyme from po tato. SGT mRNA and protein accumulated in tubers in response to woundi ng. The time course for SGT mRNA accumulation paralleled that of 3-hyd roxy-3-methylglutaryl-coenzymeA isoform 1 (hmg1) mRNA. Steady-state SG T mRNA levels also increased transiently upon wounding of leaves.