The concentration of transgene products (proteins and double-stranded RNA) in genetically modified (GM) crop tissues is measured to support food, feed, and environmental risk assessments. Measurement of transgene product concentrations in breeding stacks of previously assessed and approved GM events is required by many regulatory authorities to evaluate unexpected transgene interactions that might affect expression. Research was conducted to determine how well concentrations of transgene products in single GM events predict levels in breeding stacks composed of these events. The concentrations of transgene products were compared between GM maize, soybean, and cotton breeding stacks (MON-87427 × MON-89034 × DAS-Ø15Ø7-1 × MON-87411 × DAS-59122-7 × DAS-40278-9 corn, DAS-81419-2 × DAS-44406-6 soybean, and DAS-21023-5 × DAS-24236-5 × SYN-IR102-7 × MON-88913-8 × DAS-81910-7 cotton) and their component single events (MON-87427, MON-89034, DAS-Ø15Ø7-1, MON-87411, DAS-59122-7, and DAS-40278-9 corn, DAS-81419-2, and DAS-44406-6 soybean, and DAS-21023-5, DAS-24236-5, SYN-IR102-7, MON-88913-8, and DAS-81910-7 cotton). Comparisons were made within a crop and transgene product across plant tissue types and were also made across transgene products in each breeding stack for grain/seed. Scatter plots were generated comparing expression in the stacks to their component events, and the percent of variability accounted for by the line of identity (y = x) was calculated (coefficient of identity, I). Results support transgene concentrations in single events predicting similar concentrations in breeding stacks containing the single events. Therefore, food, feed, and environmental risk assessments based on concentrations of transgene products in single GM events are generally applicable to breeding stacks composed of these events.

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Endogenous allergenicity evaluation is a required part of the risk assessment for genetically engineered (GE) crops. Although maize is not considered a major allergenic food, a lipid transfer protein (Zea m 14) in maize grain has been identified as a potential IgE-mediated food allergen. Currently, the relationship between allergen exposure and risk of sensitization is not well understood. Hence, reliable quantitative methods are useful for determining the natural range and variability of allergen levels across multiple geographies and genetic backgrounds. A LC-MS/MS analytical method was developed and validated in our laboratory to quantify Zea m 14 in grain from 2 GE maize hybrids and 20 non-GE maize hybrids. The measured Zea m 14 levels in GE maize grain and conventional non-GE maize grain ranged from 146.87 to 574.93 ng/mg across 16 field sites located in the United States and Argentina. The method accurately quantified endogenous Zea m 14 from maize grain and results show Zea m 14 levels in the GE maize varieties were within the natural variation observed in traditionally bred non-GE maize.