Abstract：The plant expression vector pBdENP was constructed on the basis of pBI121, which contains the neomycin phosphotransferase gene (nptⅡ) espression cassette and the β-glucuronidase (gus) gene driven by a recombinant pumpkin ( Cucurbita moschata ) phloem-specific promoter (dENP ). Potato (Solanum tuberosum ) leaf discs from aseptically cultured cv. Favorita plants were transformed with pBdENP and pBI121 mediated by Agrobacterium tumefaciens, respectively．And one hundred and six independent transformants of kanamycin resistant potato plants were regenerated. PCR and Southern blotting analyses confirmed that the gus gene had been integrated into the plant genome in 65 out of all independently transformed potato plants. Integration of the transgene varied from one to over two estimated copies in the analyzed plants. Gus expression in the transgenic plants was either constitutive or in a tissue specific manner, depending on the nature of the promoter used. Results from histochemical staining confirmed that the GUS activity was localized specificly in phloem tissue of the transgenic plants if the gus gene is driven by dENP promoter. The average GUS activity in pBdENP transgenic plants had no significant difference compared with that driven by CaMV35S promoter. These results indicate that the recombinant dENP promoter can achieve a highly efficient and phloem-specific expression of a foreign gene, and can be practically useful in developing transgenic potato plants for improvement of aphid-resistence or disease-resistence.
