POTATO GENETICS, CYTOGENETICS, DISEASE RESISTANCE, AND PRE-BREEDING UTILIZING WILD AND CULTIVATED SPECIES
Location: Vegetable Crops Research Unit
Title: Suppression of the vacuolar invertase gene prevents cold-induced sweetening in potato
Submitted to: Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 17, 2010
Publication Date: August 24, 2010
Citation: Bhaskar, P.B., Wu, L., Bethke, P.C., Vaillancourt, B., Jansky, S.H., Busse, J.S., Buell, R., Hamernik, A.J., Jiang, J. 2010. Suppression of the vacuolar invertase gene prevents cold-induced sweetening in potato. Plant Physiology. Available: http://www.plantphysiol.org/content/154/2/939.
Interpretive Summary: Potato chips are a popular snack food and consumers prefer light colored chips. Potatoes used for potato chip production are stored in temperature-controlled facilities for up to nine months, and cool storage temperatures are highly beneficial in that they reduce waste caused by spoilage. Unfortunately, chips made from potatoes stored at low temperatures are often dark colored and bitter tasting. Recent reports have shown that carbohydrate-rich fried foods such as potato chips contain acrylamide, a compound that raises food safety concerns. Darker colored chips are more likely to contain greater amounts of acrylamide than lighter colored chips. Using a recently developed molecular technology, we have shown that decreasing the activity of one key enzyme is sufficient to allow for cold storage of potatoes without compromising the appearance, taste and safety of potato chips. This result provides guidance for the development of new potato varieties, either through conventional breeding or though molecular techniques, that perform well for the potato industry and which meet consumer needs.
Storing potato (Solanum tuberosum) tubers at cold temperatures prevents sprouting and minimizes losses due to disease. Unfortunately, cold storage triggers an accumulation of reducing sugars, a phenomenon referred to as cold-induced sweetening (CIS). High-temperature processing of potato tubers with elevated amounts of reducing sugars results in dark-colored, bitter-tasting products that are unacceptable to consumers. These products also have elevated amounts of acrylamide, and acrylamide has become a major food safety concern. We set out to control both problems by silencing the potato gene encoding vacuolar invertase (VInv). Vacuolar invertase hydrolyzes sucrose to form the reducing sugars glucose and fructose and this activity is the final step in a metabolic pathway in which starch breakdown leads to reducing sugar accumulation during CIS. Potato chips made from tubers derived from RNAi-based VInv gene silencing lines had acceptable, light color after cold storage for up to six months. Chip color was directly correlated with the amount of VInv transcript among RNAi lines. In addition, acrylamide content was reduced up to 15-fold in chips processed from VInv gene silencing lines compared to controls. Plant growth characteristics, yield, and specific gravity for most RNAi lines were not different from untransformed controls. The data demonstrate that the VInv gene plays a critical role in CIS. Suppressing this gene can be employed to effectively solve both processing quality and acrylamide problems in potato. The relationship between VInv gene expression and chip color can be used to establish a benchmark for use in developing new potato varieties that produce light-colored chips with low acrylamide after low temperature storage.