ANALYSIS OF THE EXPRESSION OF POTATO URIDINEDIPHOSPHATE-GLUCOSE PYROPHOSPHORYLASE AND ITS INHIBITION BY ANTISENSE RNA

The expression of the enzyme UDP-glucose pyrophosphorylase (UGPase; EC 2.7.7.9) from potato (Solanum tuberosum L.) was analysed with respect to sink-source interactions and potato tuber storage. The highest lev el of expression was found in developing tubers, the strongest sink ti ssue. Storage of mature tubers at low temperatures led to an increase of the steady-state level of UGPase mRNA, implicating a role of this e nzyme in the process of ''cold-sweetening''. Transgenic plants were cr eated expressing UGPase antisensee RNA under the control of the 35S pr omoter of the Cauliflower Mosaic Virus with the polyadenylation signal of the octopine-synthase gene. Regenerated plants were tested for red uction of UGPase at the RNA, protein and activity levels. Plants with a 95%-96% reduction of UGPase activity in growing tubers showed no cha nge in growth and development. Also, carbohydrate metabolism in tubers of these plants was not substantially affected, indicating that only 4% of the wild-type UGPase activity is sufficient for the enzyme to fu nction in plant growth and development.