CLONING, ANTISENSE RNA INHIBITION, AND THE COORDINATED EXPRESSION OF UDP-GLUCOSE PYROPHOSPHORYLASE WITH STARCH BIOSYNTHETIC GENES IN POTATO-TUBERS

A UDP-glucose pyrophosphorylase (UDPG-PPase, E.C. 2.7.7.9) cDNA from potato (Solanum tuberosum L.) tuber was cloned and sequenced. RNA analysis revealed expression in all tissues of the developing potato plant and that UDPG-PPase RNA could be induced by high sucrose treatments to exised leaves. In tubers, a coordinated expression of UDPG-PPase RNA with the RNA levels of several additional enzymes involved in the conversion of sucrose to starch was observed at harvest. Tubers of potato plants transformed with a patatin promoter-antisense-UDPG-PPase cDNA fusion were stored for 0, 1, 3 and 6 weeks at 4 degrees C and 12 degrees C. The tubers expressed various levels of antisense and sense UDPG-PPase RNA. The maximum antisense-mediated inhibition of UDPG-PPase enzyme activity was 30%, and this inhibition was maintained throughout the six weeks of storage at both 4 degrees C and 12 degrees C. No significant changes could consistently be found in Glc-1-P, Glc-6-P, Fru-6-P, UDP-Glc, glucose or fructose content in the transgenic tubers compared to wild type tubers. However, a statistically significant decrease in sucrose content was associated with the transgenic reduction of UDPG-PPase activity after 3 and 6 weeks of storage.