Abstract: Binary vectors were constructed by fusing 0.4, 0.8, 1.6, and 2.9 kb 5' flanking regions of GBSS gene with GUS (β-glucuronidase). Transient GUS expression was observed in in vitro tuber slices bombarded with 0.8 kb GBSS-GUS construct. These constructs were then transferred into potato ( Solanum tuberosum L. cv. Desiree) via Agrobacterium tumefaciens transformation. Transgenic potato plants were confmned by X-Gluc staining and PCR. Using in vitro tuberization system, GUS expressions were assayed with fluorescence, it was shown that 0.8, 1.6 and 2.9 kb GBSS-GUS expressions were higher than 0.4 kb GBSS-GUS. 1.6 and 2.9 kb GBSS-GUS expressions were about 2 to 10-folds higher in tubers than in stems. In cultured shoots, GBSS-GUS expression could be induced by increased sucrose concentration but inhibited by light.

Key words: Gene regulation, Granule-bound starch synthase, Tuber-specific expression, in vitro tuberization, Solanum tuberosum