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ARS Home » Pacific West Area » Albany, California » Western Regional Research Center » Crop Improvement and Genetics Research » Research » Publications at this Location » Publication #307261

Research Project: Host-Specific Molecular Genetic Tools for Development of Disease-Resistant Crops

Location: Crop Improvement and Genetics Research

Title: Impacts on the metabolome of down-regulating polyphenol oxidase in transgenic potato tubers

Author
item SHEPHERD, LOUISE - The James Hutton Institute
item ALEXANDER, COLIN - Biomathematics And Statistics Scotland (BIOSS)
item HACKETT, CHRISTINE - Biomathematics And Statistics Scotland (BIOSS)
item MCRAE, DIANE - The James Hutton Institute
item SUNGURTAS, JULIA - The James Hutton Institute
item VERRALL, SUSAN - The James Hutton Institute
item MORRIS, JENNIFER - The James Hutton Institute
item HEDLEY, PETER - The James Hutton Institute
item Belknap, William
item Rockhold, David
item DAVIES, HOWARD - The James Hutton Institute

Submitted to: Transgenic Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/12/2014
Publication Date: 6/15/2015
Citation: Shepherd, L.V., Alexander, C.J., Hackett, C.A., Mcrae, D., Sungurtas, J.A., Verrall, S.R., Morris, J.A., Hedley, P.E., Belknap, W.R., Rockhold, D.R., Davies, H.V. 2015. Impacts on the metabolome of down-regulating polyphenol oxidase in transgenic potato tubers. Transgenic Research. 24:447-461.

Interpretive Summary: Public perceptions of transgenic foods have played an important part in limiting the commercial introduction of commodities improved using genetic engineering. One of the major concerns is the possibility that introducing DNA into a chromosome of the target plant could have unintended effects on the properties of the plant and foods derived from it. This study was designed to evaluate transgenic potatoes that were engineered to resist bruising by reducing the levels of the enzyme Polyphenol Oxidase (PPO) and to detect unexpected changes in them. The biochemicals in transformed and untransformed (control) tubers were inventoried utilizing Liquid Chromatography coupled with Mass Spectrometry. This very sensitive technique allows general evaluation of metabolism in the tubers by measuring the levels of a wide variety of compounds (in this case 134 different metabolites). As it is known that wounding of potato tubers (control and transgenic) induces marked metabolic changes, both wounded and un-wounded tubers were evaluated. Very few differences were consistently observed between the non-transgenic control lines and the transgenic low-PPO lines. There was no discernable pattern in the metabolites that were different; they were components of various biochemical pathways. Overall, mechanical damage (slicing) to tubers had a considerably greater impact on the metabolite profile than the genetic engineering process or reductions in PPO gene expression. These results show that low-PPO potatoes can be made by genetic transformation without unintended effects on their biochemical constituents.

Technical Abstract: Tubers of potato (Solanum tuberosum L. cv. Estima) genetically modified (GM) to reduce polyphenol oxidase (PPO) activity and enzymatic discolouration were assessed for changes in the metabolome using Liquid Chromatography-Mass Spectrometry (LC-MS) and Gas Chromatography (GC)-MS. Metabolome changes induced over a 48 h period by tuber wounding (sliced transverse sections) were also assessed using two PPO antisense lines (-PPO) and a wild-type (WT) control. Data were analysed using Principal Components Analysis (PCA) and ANalysis Of VAriance (ANOVA) to assess differences between genotypes and temporal changes post-tuber wounding (by slicing). The levels of 15 metabolites (out of a total of 134 that were detected) differed between the WT and -PPO lines in mature tubers at harvest. A considerably higher number (63) of these metabolites changed significantly over a 48 hour period following tuber wounding. For individual metabolites the magnitude of the differences between the WT and -PPO lines at harvest were small compared with the impacts of tuber wounding on metabolite levels. Some of the observed metabolite changes are explicable in terms of pathways known to be affected by wound responses. Whilst some statistically significant interactions (11 metabolites) were observed between line and time after wounding, very few profiles were consistent when comparing the WT with both -PPO lines, and the underlying metabolites appeared to be random in terms of the pathways they occupy. Overall, mechanical damage to tubers has a considerably greater impact on the metabolite profile than any potential unintended effects resulting from the down-regulation of PPO gene expression.