Novel food information: Glufosinate tolerant rice event LLRICE62

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 Bayer CropScience that it has no objection to the food use of glufosinate tolerant rice lines containing event LLRICE62. The Department conducted a comprehensive assessment of this rice 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 Bayer CropScience and the evaluation by Heath Canada and contains no confidential business information.

Introduction

Bayer CropScience has developed rice (O. sativa) lines based upon transformation event LibertyLink^® rice 62 (LLRICE62). Rice varieties containing this event express the bar gene which confers tolerance to glufosinate-ammonium herbicides (trade name, Liberty^®). Health Canada has previously indicated no objection to the sale of glufosinate tolerant corn (DLL25 and DBT418) and cotton (LLCotton25) lines for human food applications in Canada. Like rice event LLRICE62, these lines express the bar gene which confers tolerance to glufosinate ammonium.

The safety assessment performed by Food Directorate evaluators was conducted according to Health Canada's Guidelines for the Safety Assessment of Novel Foods. The assessment considered: how rice event LLRICE62 was developed; how the composition and nutritional quality of grain derived from rice varieties containing this event compare to grain of non-modified rice varieties; and what the potential is for grain derived from lines containing this event to be toxic or cause allergic reactions.

The Food Directorate has a legislated responsibility for 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 rice lines containing event LLRICE62 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

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

Development of the modified plant

The transformation of callus tissue from O. sativa cultivar 'Bengal' was performed by particle bombardment using a purified plasmid fragment containing the bar gene and the regulatory components necessary for expression. The plasmid pB5/35Sbar was digested with restriction enzymes PvuI and HindIII and a 1501 bp fragment containing the bar gene cassette (P35S-bar-T35S) was purified and used in the transformation. The genetic elements of this cassette include the Cauliflower mosaic virus (CaMV) 35S promoter, the Streptomyces hygroscopicus bar gene, and the CaMV T35S terminator.

Characterization of the modified plant

Southern blot and PCR analysis of LLRICE62 demonstrated the insertion of one copy of the bar cassette at one locus in the rice genome. Southern blot analysis also demonstrated the integrity of the bar gene and regulatory elements, as well as the absence of plasmid backbone sequences. In addition, the sequence of the plant genome flanking DNA was determined at the transgene locus which identified the site integration on chromosome six.

Stability of the inserted bar gene cassette was evaluated in different rice genetic backgrounds over four generations of conventional breeding at various growing locations. The results of Southern blot analysis demonstrated the stability of the LLRICE62 event at the genomic level in different environments.

Product information

Rice event LLRICE62 differs from its traditional counterpart by the addition of the novel bar gene sequence into the genome, and the expression of the PAT protein. The protein encoded by this gene is expressed at different levels throughout the plant tissue and throughout the life of the plant. The level of the PAT protein produced by the bar gene in LLRICE62 was determined by a PAT specific enzyme-linked immunosorbent assay (ELISA). The PAT protein was found in roots, stems and leaves of LLRICE62. Average levels of PAT were12 µg/g fresh weight in roots, 30 µg/g fresh weight in stems and 90 µg/g fresh weight in leaves. PAT protein comprises an average of 0.23, 0.19 and 0.13% of the total crude protein in roots, stems and leaves respectively. In studies involving grain, the PAT protein was found to comprise 0.02% of the total extractable protein.

Dietary exposure

Rice grain containing LLRICE62 is expected to be used by the food industry in applications similar to grain from conventional rice varieties. Rice grain is consumed by humans as either whole grain food or as an ingredient in processed food.

Nutrition

Studies for the safety and nutritional content of LLRICE62 were based on grain and processed rice samples generated from 14 different trial sites in the United States over two years. In most of the studies the non-transgenic 'Bengal' control was compared with a non-sprayed and sprayed transgenic rice variety carrying the LLRICE62 event. Samples were analysed for proximates, amino acids, minerals, vitamins, fatty acids and anti-nutritional components. The results of compositional analyses for the rice grain from transgenic (sprayed and non-sprayed) and non-transgenic samples were comparable.

Chemistry/toxicology

No toxic effects were seen in mice receiving 7.8 g/kg bw/day of PAT protein in their diet for 14 days. Since proteins that are toxins exert their effects in the nanogram to milligram per kilogram body weight range, this result suggests that the PAT protein is not a toxin. Because of the rapid digestion (<1 minute) of PAT in gastric fluids, there is little likelihood of exposure to the intact protein. The rapid digestibility of PAT is also in contrast to known food allergens, which are generally resistant to digestion. Further, in contrast to the relatively high content of known food allergens in foods, PAT constitutes less than 0.02% of the total protein in the transformed rice. The PAT protein has no amino acid sequence homology with any known toxins or allergens. Therefore, the weight of evidence suggests that the novel PAT protein is unlikely to have toxic or allergenic properties.

The insertion of the bar gene did not result in an increase in the levels of endogenous anti-nutrients or allergens in rice. There was no detected change in the proportion of endogenous rice 14-16 kDa allergenic proteins to total extractable protein content when LLRICE62 was compared to conventional commercial rice. In addition, protein extracts from LLRICE62 did not increase the allergenic response in the sera of patients with known rice allergies relative to those from conventional rice.

Conclusion

Health Canada's review of the information presented by Bayer CropScience in support of the food use of glufosinate tolerant rice lines containing event LLRICE62 concluded that the food use of grain from rice lines containing this event does not raise concerns related to safety. Health Canada is of the opinion that grain from rice lines containing event LLRICE62 is as safe and nutritious as grain from current commercial rice varieties.

Health Canada's opinion deals only with the food use of glufosinate tolerant rice lines containing event LLRICE62. 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