CHARACTERIZATION OF TRANSGENIC POTATO (SOLANUM-TUBEROSUM) TUBERS WITHINCREASED ADPGLUCOSE PYROPHOSPHORYLASE

The aim of the work described in this paper was to characterize the tu bers of potato (Solanum tuberosum var. Prairie) plants that had been t ransformed with the Escherichia call ADPglucose pyrophosphorylase (EC 2.7.7.27) gene, glgC-16, under the control of a patatin promoter. Over 30 lines of transformed plants with increased ADPglucose pyrophosphor ylase activity were obtained. The tubers of six of these lines were co mpared with those of control plants expressing the gene for beta-glucu ronidase. The average increase in pyrophosphorylase activity was 200%, and the highest was 400%. Western immunoblotting of tuber extracts sh owed that the amounts of glgC-16 protein were linearly related to the extractable activity of the ADPglucose pyrophosphorylase. Cell fractio nation studies showed that the increased activity of the pyrophosphory lase in the glgC-16 tubers had a similar intracellular location, the a myloplast fraction, to that found in the control tubers. No pleiotropi c changes in the maximum catalytic activities of the following enzymes could be detected in the glgC-16 tubers: sucrose synthase, fructokina se, UDPglucose pyrophosphorylase, phosphofructokinase, soluble starch synthase, starch branching enzyme, phosphoglucomutase and alkaline ino rganic pyrophosphatase. The glgC-16 tubers are held to be suitable for the study of the role of ADPglucose pyrophosphorylase in the control of starch synthesis.