|SHEPHERD, LOUISE - The James Hutton Institute
|HACKETT, CHRISTINE - Biomathematics And Statistics Scotland (BIOSS)
|ALEXANDER, COLIN - The James Hutton Institute
|MCNICOL, JAMES - The James Hutton Institute
|SUNGURTAS, JULIA - The James Hutton Institute
|MCRAE, DIANE - The James Hutton Institute
|DAVIES, HOWARD - The James Hutton Institute
Submitted to: Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/31/2015
Publication Date: 6/1/2016
Citation: Shepherd, L., Hackett, C., Alexander, C., Mcnicol, J., Sungurtas, J., Mcrae, D., Mc Cue, K.F., Belknap, W.R., Davies, H. 2016. Impact of light-exposure on the metabolite balance of transgenic potato tubers with modified glycoalkaloid biosynthesis. Food Chemistry. 200:263-373.
Interpretive Summary: Glycoalkaloids are naturally occurring, but undesirable, secondary metabolites found in potatoes and other crops in the Solanaceae family. The levels of glycoalkaloids in potatoes fluctuate in response to environmental stress and are known to be increased by exposure to light. In this study, the effects of light exposure on metabolite composition were measured in the inner flesh and outer peel layers of potatoes genetically engineered (GE) to have reduced levels of solanine, one of the glycoalkaloids. Only 19 identified metabolites differed significantly between the low-solanine GE line and the control. These differences were, for the most part, explicable in terms of the modification to the glycoalkaloid pathway due to down regulation of the solanine biosynthesis gene. The levels of another glycoalkaloid, a-chaconine, were higher in the low-solanine potato than in the control after exposure to light, probably due to increased flow of the metabolic pathway to this branchpoint when synthesis of solanine was blocked. Although differences were also found in a few non-targeted metabolites, none of these pose new food safety concerns for human or animal consumption of these potatoes. Overall, the results suggest that the low-solanine GE potatoes are not any more or any less safe foods than conventional potatoes exposed to light.
Technical Abstract: Metabolite profiling has been used to assess the impact of light exposure on the composition of potato (Solanum tuberosum L. cv. Desirée) tubers genetically modified (GM) to reduce glycoalkaloid (specifically a-solanine) content via the down-regulation of the SGT1 gene. Using a combination of liquid chromatography-mass spectrometry (LC-MS) and gas chromatography (GC)-MS, the response to light (four and 11 days exposure) of GM line sgt9-2 was compared with its control (BIN+14-3; transformed with an empty vector) for both the outer peel and inner flesh tuber tissues. Metabolomic data were analyzed using principal component analysis and analysis of variance. The sgt9-2 line (unlike BIN+14-3) exhibited an almost complete knock-out of a-solanine, and exposing tubers of this line to light had little impact on this metabolite’s levels. However, levels of a-chaconine increased significantly in the peel of both lines when exposed to light, and by significantly more in sgt9-2 cf. BIN+14-3. Profiling analyses revealed that the major differences in other metabolite levels significant for a main effect were those driven by differential distributions within tuber tissue types (peel and flesh), and from exposure of tubers to light, and not (in this case) from differences arising from the transgenic event itself. Many of the observed metabolite changes in the light-exposed samples are explicable in terms of pathways known to be affected by stress responses. Only 19 identified metabolites differed significantly between the two lines, and these were, for the most part, explicable in terms of the modification to the glycoalkaloid pathway following down regulation of the SGT1 gene. The fewest number of metabolites observed for a main effect related to temporal differences in light exposure treatment.