Application Of RNAi Technology In Potato Starch Metabolic

Starch is the second most aboudent carbohydrate after the cellulose. The content of starch is 8-34% in potato (Solanum tuberosum L.) tubers. Potato is a ideal crop to produce starch which is used as one of the most important raw materials in both food and industrial applications. In the most applications, the potato starch is required to possess the properties of lower-gelatinization temperature and faintish retrogradation. The characteristic of starch is related to the ratio of amylose and amylopectin, and the key enzymes in starch biosynthesis pathway such as adenosine 5'diphosphate glucose pyrophosphorylase, starch synthase, starch-branching enzyme and starch debranching enzyme. The enzyme associated with the amylose synthesis is just particle-bound starch synthase (GBSS).RNA interference (RNAi) is mediated by endogenous or exogenous specific double-stranded RNA. The double-stranded RNAs are processed into siRNAs by Dicer proteins. siRNAs regulate gene expression at different levels, such as transcriptional gene silencing (induced by siRNA-mediated DNA methylation to suppress gene transcription) and post-transcriptional gene silencing (siRNA-mediated cleavage of mRNA).In order to inhibit the expression of GBSS I (Granule-bound starch synthase I) gene encoding the key enzyme in amylose synthesis pathway and to produce a new potato cultivar free of amylose, plant binary expression vectors were constructed to silence GBSS I at transcriptional and post-transcriptional levels according to the principle of RNA interference.In addition, as an important food and cash crop, potatoes need to be supplied year round and storage in low temperature is a common way to avoid germination. However, the browning caused by cold-induced sweetening seriously affects the quality of potato tubers. Therefore, spontaneous suppression of amylose formation and cold-induced sweetening may create a novel type of potato for production and application. RNA interference technology is an acceptable strategy for this.In this study, a binary expression vector is constructed to silence both vacuolar acid invertase gene (VInv) and GBSS, aiming to minimize amylose formation and reduce cold-induced sweetening.