Novel food information: Herbicide tolerant 98140 corn (OptimumTM GATTM corn)

On this page

• Background
• Introduction
• Development of the modified plant
• Characterization of the modified plant
• Product information
• Dietary exposure
• Nutrition
• Chemistry/toxicology
• Conclusion

Background

Health Canada has notified Pioneer Hi-Bred Production Ltd. that it has no objection to the food use of Herbicide Tolerant 98140 Corn event DP-Ø9814Ø-6 (trade name Optimum^TM GAT^TM corn). The Department conducted a comprehensive assessment of this corn event according to its Guidelines for the Safety Assessment of Novel Foods (September 1994). These guidelines are based upon internationally accepted principles for establishing the safety of foods with novel traits.

The following provides a summary of the notification from Pioneer Hi-Bred Production Ltd. and the evaluation by Health Canada (and contains no confidential business information).

Introduction

Optimum^TM GAT^TM corn was developed to be tolerant to ALS-inhibiting herbicides and herbicides containing glyphosate. The herbicide tolerance was achieved through the transformation of conventional corn line/variety PHWVZ. The transgenic expression cassette encodes the novel proteins GAT4621 (glyphosate acetyltransferase) and ZM-HRA (Zea mays - acetolactate synthase protein).

The assessment conducted by Food Directorate evaluators determined: how Optimum^TM GAT^TM corn was developed; how the composition and nutritional quality of Optimum^TM GAT^TM corn compared to non-modified varieties; and what the potential is for Optimum^TM GAT^TM corn to be toxic or cause allergic reactions. Pioneer has provided data which demonstrates that Optimum GAT corn is as safe and of the same nutritional quality as traditional corn varieties used as food in Canada.

The Food Program has a legislated responsibility for the pre-market assessment of novel foods and novel food ingredients as detailed in the Food and Drug Regulations (Division 28). Food use of Optimum^TM GAT^TM corn is considered novel under the following part of the definition of novel foods:

" c) a food that is derived from a plant, animal or microorganism that has been genetically modified such that

1. the plant, animal or microorganism exhibits characteristics that were not previously observed in that plant, animal or microorganism."

Development of the modified plant

Optimum^TM GAT^TM corn was genetically modified using Agrobacterium tumefaciens mediated transformation of commercial corn variety PHWVZ. The transforming plasmid PHP24279 carried the transferred DNA (T-DNA) sequence comprised of an expression cassette containing the gat4621 and zm-hra genes and their associated regulatory elements.

Characterization of the modified plant

Southern blot analysis of Optimum^TM GAT^TM corn demonstrated the insertion of a single intact copy of the gat4621 and zm-hra gene cassettes in the PHWVZ corn genome at a single locus. Southern blot analysis also demonstrated the integrity of both the gat4621 and zm-hra genes and their regulatory elements. As expected, Southern blot analysis also confirmed the absence of plasmid backbone DNA in Optimum^TM GAT^TM corn.

The stability of the inserted cassettes was evaluated in several generations of Optimum^TM GAT^TM corn. The results of the Southern blot analysis and segregation data demonstrated the stability of 98140 corn at the genomic level. Also, the segregation data clearly demonstrated the traits to be stable phenotypically and inherited in the expected Mendelian manner.

Confirmation of the identities of GAT4621 and ZM-HRA proteins was generated using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), supported by N-terminal amino acid sequence analysis, as well as immunological staining properties. Protein expression levels were determined by an enzyme-linked immunosorbent assay (ELISA) and performed on corn grain from the R6 developmental stage which is directly pre-harvest.

Product information

Optimum GAT corn differs from its traditional counterpart by the addition of both the gat4621 gene and zm-hra gene and their associated regulatory elements into the genome. This results in the expression of both the GAT4621 protein and ZM-HRA protein. These proteins impart tolerance to ALS-inhibiting herbicides and herbicides containing glyphosate. The proteins encoded by the inserted gene sequences are expressed at different levels in the plant tissue.

Dietary exposure

Optimum^TM GAT^TM corn 98140 is expected to be used in similar applications as traditional corn varieties by the food industry. The most common use of yellow dent corn in food is the production of starch and sweetener products through wet milling. Dry milling is also used to produce corn grits, flour, and meal although the greatest food product from dry milling is used in brewing.

Nutrition

The nutrient data pertaining to Optimum^TM GAT^TM corn was obtained from six samples of test 98140 corn compared to control corn (PHWVZ) grown at 4 US and 2 Canadian sites. The data was collected using an appropriate study design and accepted analytical methods.

Grain samples were analysed for key components including fatty acid profile, proximates, amino acids, minerals (copper, iron, magnesium, manganese, potassium, sodium, zinc), vitamins (beta-carotene, pantothenic acid, vitamin B1, vitamin B2, vitamin B3, vitamin B6, folic acid, vitamin E (alpha-tocopherol isomer), anti-nutrients, and secondary metabolites. The nutritional composition of the corn from transgenic and non-transgenic samples was comparable. For the few comparisons where the differences were statistically significant, Pioneer provided evidence that the differences were small and that the levels were within the ranges of commercial unmodified corn lines currently sold. The presence of five acetylated amino acids (N-acetyl-L-aspartate (NAA), N-acetyl-L-glutamate (NAG), N-acetyl serine (NAS), N-acetyl threonine (NAT), and N-acetyl glycine (NAGly)) were identified by Pioneer. The levels of NAA and NAG were statistically significantly higher in 98140 corn compared to the control corn. There were no differences found between the control and 98140 corn in the levels of the other three acetylated amino acids. Pioneer provided evidence that NAA and NAG and other acetylated amino acids are present in a wide variety of foods. The information provided by Pioneer demonstrated that the nutritional composition of Optimum^TM GAT^TM corn is equivalent to conventional corn.

Chemistry/toxicology

The novel genes present in Optimum^TM GAT^TM corn were not isolated from a known pathogen. The novel genes generate proteins that are not considered likely to be toxins, based on acute toxicity studies in mice administered the proteins at levels orders of magnitude greater than the hypothetical level of intake of the proteins from this crop in the human diet. In addition, the novel proteins bear no biologically significant homology to any known toxin.

The novel proteins are not considered likely to be allergens since they do not share the characteristics of proteins that are food allergens. The gat4621 novel gene is derived from genes of B. licheniformis optimized for glyphosate acetylation activity by a gene shuffling process. B. licheniformis is not a known allergen source. For the ZM-HRA protein, the donor organism (corn) is not a known allergen source and ALS is not a known food allergen. The amino acid sequences of the novel proteins are not homologous to those of known allergens and contain no linear epitopes matching those of known allergens.

The creation of the novel metabolite N-acetyl glyphosate (NAG) and the acetylation of unintended substrates were examined. Pioneer provided results of a 90-day feeding study in which rats were fed NAG. No adverse effects were observed. The results of this study and other information indicated that most of the NAG is excreted unaltered in the urine and does not bioaccumulate. Also, acetylated glutamine, cystine, threonine, and methionine have been shown to substitute for their non-acetylated counterparts in animal feeding studies. Pioneer provided evidence that deacetylase enzymes are widely distributed in the tissues (including brain, kidney, liver, intestine) of humans and other animals.

Conclusion

Health Canada's review of the information presented in support of the food use of Optimum^TM GAT^TM corn 98140 does not raise concerns related to food safety. Health Canada is of the opinion that food derived from Optimum^TM GAT^TM corn 98140 is as safe and nutritious as food from current commercial corn varieties.

Health Canada's opinion deals only with the food use of Optimum^TM GAT^TM corn 98140. Issues related to its use as animal feed have been addressed separately through existing regulatory processes in the Canadian Food Inspection Agency.

This Novel Food Information document has been prepared to summarize the opinion regarding the subject product provided by the Food Directorate, Health Products and Food Branch, Health Canada. This opinion is based upon the comprehensive review of information submitted by the petitioner according to the Guidelines for the Safety Assessment of Novel Foods (September 1994).

For further information, please contact:

Novel Foods Section
Food Directorate
Health Products and Food Branch
Health Canada, PL2204A1
251 Frederick Banting Driveway
Ottawa, Ontario K1A 0K9
bmh-bdm@hc-sc.gc.ca