| The starch with properties of lower-gelatinization temperature and better-stability of freeze thawing has many applications in food and chemical industries. But the starch from most wildly cultivated potato cultivars hardly own these better properties. In the present research, antisense-RNA technique was employed to regulate the expression of key genes involved in the biosynthesis potato starch to change the structure and components of starch granule, and further to develop processing potato lines with properties of lower-gelatinization temperature and better-stability of freeze thawing. The following are the main work we did:1. Complete sequence of SSⅡcDNA and partial sequence of SSⅢcDNA, from 1940～3899 bp, were cloned. And sequence analysis indicated that the cloned sequence of SSⅡwas a 2320 bp fragment and shared a 96.80% homology with the reported CDS. The SSⅢfragment was a 1959 bp long fragment and shared a 93.81% homology with the reported sequence from 1940 to 3899 bp.2. The 5'flanking region of GBSS gene was sub-cloned from plasmid LS-9, and sequence analysis indicated it was a 599 bp fragment. The tuber-specific- promoter Patatin was also sub-cloned from plasmid LS-9, and sequence analysis indicated it was a 968 bp fragment.3. After analysing sequence homology of the three desired genes with DNAStar, each fragment with 500～600 nucleotides from every gene of GBSS, SSⅡand SSⅢwas choosen and the 3-choosen fragments shared little homology with each other. The fusion gene GS2S3 containing that three fragments from GBSS, SSII and SSIII irrespectively was constructed by TP-PCR.4. The pBIGSG, the expression vector of GS2S3 gene driven by GBSS gene 5'flanking sequence, and pBIGSP ,the expression vector of GS2S3 gene driven by Patatin promoter had been constructed and transformed into LBA4404.5. Some parameters of Agrobaterium tumefaciens mediated transformation system of potato was gotten by detailed study of the preincubate time, tincture time, co-culture time and Kan concentration.
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