Novel Food Information - Imidazolinone Herbicide Tolerant Soybean CV127

Health Canada has notified BASF Canada that it has no objection to the sale of food derived from herbicide tolerant soybean CV127. The Department conducted a comprehensive assessment of this soybean event according to its Guidelines for the Safety Assessment of Novel Foods. These Guidelines are based upon internationally accepted principles for establishing the safety of foods with novel traits.

Background:

The following provides a summary of the notification from BASF Canada and the evaluation by Heath Canada and contains no confidential business information.

1. Introduction

BASF Canada has developed soybean event CV127 using recombinant DNA techniques in order to introduce the coding sequence for the gene csr1-2 which confers tolerance to the imidazolinone herbicides through the expression of the AtAHASL protein. The expression of this recombinant protein allows for the plant to continue branched chain amino acid synthesis in the presence of imidazolinone herbicides, which are used as a broad weed killer.

The assessment considered: how CV127 soybean was developed; how the composition and nutritional quality of CV127 soybean compared to non-modified soybean varieties; and what the potential is for CV127 soybean to be toxic or cause allergic reactions. BASF has provided data which demonstrates that CV127 soybean is as safe as traditional soybean varieties used as food in Canada.

The Food Directorate has a legislated responsibility for the pre-market assessment of novel foods and novel food ingredients, as detailed in Division 28 of Part B of the Food and Drug Regulations (Novel Foods). Foods derived from soybean CV127 are considered novel foods 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

(i) the plant, animal or microorganism exhibits characteristics that were not previously observed in that plant, animal or microorganism

2. Development of the Modified Plant

The petitioner has provided information describing the methods used to develop CV127 soybean and data that characterize the genetic modification that confers tolerance to the imidazolinone herbicides through the expression of the AtAHASL protein. CV127 soybean was produced via microparticle bombardment of embryogenic axis tissue of the commercial ‘Conquista’ variety of soybean with vector pAC321. The transforming plasmid contains one transfer DNA (T-DNA) consisting of the csr1-2 gene coding sequence from Arabidopsis thaliana and its associated regulatory elements and the AtSEC61 coding sequence.

The petitioner has provided data for three generations of CV127 soybean that demonstrated that the trait is stable at the genomic level and is inherited in the expected Mendelian manner.

3. Characterization of the Modified Plant

Southern blot analysis was used to determine the number of insertion sites and copies of the integrated T-DNA as well as the presence or absence of plasmid backbone sequence. This analysis demonstrated the T-DNA inserted at a single site and at a single locus of the soybean genome, and a single functional copy of the T-DNA was integrated. This analysis also demonstrated the presence of a single copy of the coding sequence for the AtSEC61? subunit protein, a small transport protein of the endoplasmic reticulum, on the 5' end of the csr1-2 gene. CV127 soybean genomic DNA probed for backbone sequences showed no detectable hybridization bands, thus CV127 soybean does not contain backbone sequences from the transformation vector pAC321.

The petitioner has provided data for three generations of CV127 soybean that demonstrated that the trait is stable at the genomic level and is inherited in the expected Mendelian manner.

4. Product Information

Soybean event CV127 differs from conventional soybean by the insertion of two novel genes; csr1-2 and AtSEC61 and their associated regulatory elements. The insertion of these genes results in the expression of two novel proteins in CV127; AtAHASL and AtSEC61. The expression of AtAHASL confers tolerance to imidazolinone herbicides. The expression of AtSEC61 was shown to be negligible and has no effect on the characteristics of the soybean line. The SEC61 subunit protein is common to many crop plants with a history of safe use. Also, the SEC61 subunit protein is known to be ubiquitous in all eukaryotes. Endogenous levels are at such a low level that even with the presence of the recombinant AtSEC61 protein in the sample there is still no detectable expression.

The petitioner has provided data to demonstrate the level of expression of the AtAHASL in CV127 soybean. The expression levels of the AtAHAS protein in various tissues of soybean CV127 was shown to be highest in leaves and whole plants in the V2 growth stage, at which the need for branched chain amino acids is greatest. All grain samples had AtAHAS levels below the limit of quantification of the ELISA assay (13 ng/g); however these low expression levels were sufficient to provide imidazolinone herbicide tolerance to soybean CV127.

5. Dietary Exposure

The genetic modification of CV127 soybean is not intended to alter any of its nutritional aspects. Therefore, the use of CV127 soybean and products derived from it will be similar to traditional soybean varieties. The introduction of CV127 soybean will only replace a fraction of current soybean varieties and is not anticipated to result in a change in the dietary intake of soybean and soybean-derived products.

6. Nutrition

Compositional and nutritional assessment of CV127 soybean was conducted by comparing to the control (non-transgenic, isoline soybean variety lacking the csr1-2 gene) and two conventional soybean varieties (Monsoy 8001 and Coodetec 217). Three studies were conducted to establish the nutritional safety of soybean CV127 which included data on nutrient composition of grain, composition of processed grain fractions, and a feeding study with broiler chickens.

Nutrient composition analyses included all nutritional and compositional parameters in soybean matrices for food use as suggested in the OECD document (ENV/JM/MONO(2001)15) on soybean. All analyses were performed using approved scientific and appropriate statistical methods. Based on the data provided, the genetically modified imidazolinone herbicide tolerant soybean is similar to the control and conventional commercial varieties of soybean.

7. Chemistry/Toxicology

The novel genes in CV127 soybean were isolated from Arabidopsis thaliana, which is not known to produce any toxins or allergens.

The calculated level of exposure to AtAHASL is considered to be very low. Additionally, this calculation is based on very conservative assumptions and thus the actual exposure to the protein should be significantly lower than the estimate. For example, infants consuming soybean-based formula have the greatest potential exposure to CV127 soybeans. However, soybean-based infant formula undergoes extensive food processing and it is expected that AtAHASL would be denatured in the final food product. Given that, in general, a proteins shape is related to its function, the toxicity associated with a denatured protein is likely to be negligible.

The results of the in vitro simulated gastric fluid and simulated intestinal fluid assays demonstrate that the CV127 soybean-derived AtAHASL protein and microbial-derived AtSEC61? protein were quickly digested under experimental conditions. These results suggest that when AtAHASL and AtSEC61? proteins are ingested, they are unlikely to gain access to the general circulatory system and therefore unlikely to cause systemic toxicity.

AtAHASL and AtSEC61? proteins did not show significant sequence homology with any known toxins. This finding is consistent with a protein with a low toxic potential. It was noted that AtAHASL and AtSEC61? are naturally found in plants, and humans have a history of exposure to these proteins through their normal diets, with no associated toxicities.

Soybeans are known to produce dietary allergens and anti-nutrients. A proteomic analysis was performed to quantify several known allergens in both the Conquista and the CV127 soybean grains. The results demonstrate that there is no significant difference in the allergen content between the modified and unmodified soybean lines. The levels and distribution of all antinutrients were comparable in the parent and transgenic plants.

Unlike allergenic proteins which can constitute 1-80% of total protein content, AtAHASL constitutes a negligible amount of the total protein content in CV127 soybeans. Further, no significant homology was found between the amino acid sequences of AtAHASL and AtSEC61? to those of known allergens. Both proteins are rapidly digested in simulated gastric and intestinal fluids in vitro, suggesting that AtAHASL and AtSEC61? proteins would be readily digested in the gastrointestinal tract.

Taken together, CV127 soybean would not be associated with any greater allergenic or toxic risk to consumer health than conventional soybean currently available in the Canadian market.

Conclusion:

Health Canada's review of the information presented in support of the food use of CV127 soybean concluded that derived food products do not raise concerns related to safety. Health Canada is of the opinion that CV127 soybean is as safe and nutritious as food from current commercial soybean varieties.

Health Canada's opinion deals only with the human food use of soybean event CV127. Issues related to the environmental safety of CV127 in Canada and its use as livestock feed have been addressed separately through existing regulatory processes in the Canadian Food Inspection Agency (CFIA). From their assessment, the CFIA concluded that there are no concerns from an environmental and feed safety perspective. This perspective is applicable to the food and feed products derived from imidazolinone tolerant soybean CV127 destined for commercial sale.

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.

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
novelfoods-alimentsnouveaux@hc-sc.gc.ca