Cloning of Granule-Bound Starch Synthase Gene and Construction of Its RNAi Vector in Potato Tuber

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There is about 17% starch in potato(Solanum tuberosum L.) tubers.Potato starch granules are composed of two polysaccharides,unbranched amylose(approximately 20% to 25%) and branched amylopectin(approximately 75% to 80%).To develop transgenic potato with high-amylopectin in tubers,we got a cDNA sequence of the potato GBSSI from the total RNA of potato tubers by RT-PCR using specific primers of conserved domain of GenBank Accession Number X58453 sequence.The GBSSI cDNA sequence shared 99.78% similarity with the GBSSI gene in GenBank(accession No.X58453).The full-length of cDNA was 1 824 bp,which contained 607 amino acids,three conserved domains and many important functional sites.The 3D structure of GBSSI was highly similar to that of the glycogen synthase,indicating that GBSSI has a function of starch synthesis.GBSSI similar gene obtained here was granule-bound starch synthase,and its sequence was submitted to GenBank,with the accession number of EU403426.On the basis of a 542 bp RNAi target region from the CDS of GBSSI,the sense and antisense fragments were amplified and separated by a 237 bp intron to construct the RNA interference expression vector pBI121g-PgABI containing "sense gbssA-VP1-ABI3-like protein intron-antisense gbss B" regulated by Patatin promoter,which will lay a solid foundation for the study on synthesis of starch and breeding of transgenic potato with high amylopectin content or pure amylopectin.