Abstract

A Comparison of Protein and Phenolic Compounds in Seed from GMO and Non-GMO Soybean

Savithiry S Natarajan, Farooq H Khan, Davanand L Luthria, Mark L Tucker, QijianSong and Wesley M Garrett

Soybean protein is a valuable and important component in human and animal diets. Approximately 94% of the soybean planted in the US is genetically modified (GM) to enhance quality and productivity. Since value-added traits are continuously being developed by genetic modification, it is important to determine if any unintended changes occur in GM soybean seeds. In this investigation, we have selected three different transgenic lines, denoted event 1,2 and 3 with a single Agrobacterium tumefaciens T-DNA insert that included genes for a herbicide-resistance selectable gene (bar) and a β-glucuronidase (GUS) reporter gene expressed using a double 35S Cauliflower Mosaic Virus (CaMV) promoter and a soybean polygalacturonase (Glyma12g01480) promoter, respectively. The transgenic lines and nontransgenic progenitor isoline (control) were used for both proteomic and phenolic compound analysis. Seed proteins were separated by two-dimensional polyacrylamide gel electrophoresis (2D-PAGE). Out of approximately 1300 protein spots detected per protein extract, 30 spots were selected for further analysis based on software-determined differences (ANOVA) in their relative abundance in the protein gels for the control and three events. Subsequent statistical analysis after Bonferroni correction indicated that the abundance of only two of the thirty protein spots were significantly different at the 1% probability level. Two protein spots, an isoflavone reductase and a quinine oxidoreductase-like protein, in event 2 were significantly different from the control and the other two transgenic events. All thirty protein spots were analyzed and identified by mass spectrometry (MS) followed by a search of the NCBI databases using the Mascot search engine. In addition to protein, two classes of phenolic compounds, isoflavonoids and phenolic acids, were analyzed by LC-MS. The results indicated no systematic differences in the amount or profile for either class of phenolic compounds in the control or three transgenic events.