RNAi-mediated combinatorial silencing of StUGPase and StVInv genes effectively mitigates cold-induced sweetening in...

RNAi mediated combinatorial silencing of StUGPase and StVInv genes in potato demonstrated significant reduction of sucrose and reducing sugar accumulation after cold storage with improved chipping quality. Potato (Solanum tuberosum L.) is stored in cold conditions after harvest to maintain year-round availability by preserving its physiological vigour and preventing rotting. However, cold storage of potato leads to cold-induced sweetening, an undesirable physiological pathway of breakdown of starch into reducing sugars (RS), primarily glucose and fructose. These RS react with free amino acids at high temperature, producing dark, bitter-tasting products due to non-enzymatic Maillard reaction, rendering the tubers unsuitable for processing. UDP-glucose pyrophosphorylase (StUGPase) and vacuolar acid invertase (StVInv) are the two key enzymes that play central roles in the CIS pathway. To mitigate CIS, a combinatorial RNA interference (RNAi) approach was adopted to simultaneously silence both genes. A hairpin RNA (hpRNA) construct, CISCOM, was designed by fusing cDNA fragments of StUGPase and StVInv in sense and antisense orientations, separated by the potato GBSS intron. CISCOM transgenics of two Indian cultivars of processing quality, Kufri Chipsona-1 (KC1) and Kufri Chipsona-3 (KC3), demonstrated significantly low sucrose and RS accumulation following one month of cold storage at 4 °C due to many folds reduction at the transcript level and activities of both the enzymes. Chips produced from cold-stored RNAi potato tubers were lighter in colour, as acceptable by processing standards, compared to those from non-transgenic controls, which were unacceptably dark brown in colour. The study highlights the potential of combinatorial RNAi as an effective strategy to ameliorate cold-induced sweetening and much needed boost to the potato processing sector.