Location: Vegetable Crops ResearchTitle: Regulation of sugar metabolism in wild-type and low-invertase transgenic chipping potatoes during and after cooling for low-temperature storage
Submitted to: American Journal of Potato Research
Publication Type: Proceedings
Publication Acceptance Date: 3/10/2015
Publication Date: 7/19/2015
Citation: Wiberley-Bradford, A.E., Busse, J.S., Bethke, P.C. 2015. Regulation of sugar metabolism in wild-type and low-invertase transgenic chipping potatoes during and after cooling for low-temperature storage. American Journal of Potato Research. Paper No. G36.
Technical Abstract: Regulation of sugar metabolism in cold-stored potato tubers has significant ramifications for potato chip and French fry producers and consumers. Though low-temperature storage reduces losses due to sprouting and disease, it induces accumulation of the reducing sugars glucose and fructose. These react with free amino acids during frying to produce dark-colored and bitter-tasting products that have elevated levels of acrylamide, a suspected carcinogen. Elevated amounts of tuber glucose and fructose are produced when vacuolar acid invertase (VInv) hydrolyses sucrose derived from starch degradation. In this study, wild-type tubers and tubers in which VInv expression was reduced by RNA interference were used to study the regulation of sugar metabolism during and after cooling of tubers for low temperature storage. It was found that transcriptional control of genes central to carbohydrate metabolism occurred in three overlapping phases. First, soon after cooling began, increases in VInv and ß-amylase expression occurred. Next, in the later stages of cooling, large decreases in AGPase and GBSS expression were observed. Finally, when tubers reached 3-5oC, large increases in ß-amylase expression and tuber sucrose contents were observed, as were large increases in glucose and fructose contents in tubers with high VInv expression. These data support a model in which reducing sugar accumulation is controlled both by temperature-regulated changes in sucrose accumulation, resulting from increased starch degradation by ß-amylase and decreased starch resynthesis by AGPase and GBSS, and by differences in VInv activity that persist throughout storage.