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Sugar metabolism, chip color, invertase activity, and gene expression during long-term cold storage of potato (Solanum tuberosum) tubers from wild-type and vacuolar invertase silencing lines of Katahdin

Wiberley-Bradford, Amy E., Busse, James S., Jiang, Jiming, Bethke, Paul C.
BMC Research Notes 2014 v.7 no.801 pp. 1-10
RNA interference, Solanum tuberosum, beta-fructofuranosidase, carbohydrate composition, carbohydrate metabolism, cold storage, color, enzyme activity, fructose, frying, gene expression, genes, genetically modified foods, glucose, messenger RNA, postharvest physiology, potato chips, potatoes, reducing sugars, starch, storage temperature, storage time, sucrose, transgenic plants, tubers
Storing potato tubers at low temperatures helps to minimize losses from sprouting and disease but often leads to an accumulation of reducing sugars in a process called cold-induced sweetening. When tubers with increased amounts of reducing sugars are processed at high temperatures, as by frying, they produce dark-colored, bitter-tasting products that contain elevated amounts of acrylamide, a neurotoxin and possible carcinogen. Transgenic potato tubers with decreased levels of vacuolar invertase (VInv), which converts sucrose from starch breakdown to the reducing sugars glucose and fructose, accumulate fewer reducing sugars during cold-induced sweetening than tubers with higher VInv levels. In this study, the characteristics of tubers in which the vacuolar invertase gene VInv was silenced using RNA-interference were investigated with regard to temperature-dependent sucrose and reducing sugar accumulation, chip color and expression of temperature-responsive genes during long-term cold storage. VInv transcript accumulation and enzyme activity in transgenic tubers were lower than those in control tubers at 3-9°C, but transcript accumulation of other sugar-metabolism genes was largely unaffected by invertase silencing. Chips made from transgenic tubers were paler in color than those from untransformed tubers, and transgenic tubers had lower reducing sugar contents. Tuber sucrose contents were higher in transformed lines than in controls. Responses of sugar contents and transcript levels to tuber storage temperature, time in storage and invertase expression shed light on the regulation of sugar metabolism in stored potato tubers.