Novel food information: Insect resistant cotton event 281-24-236

Background

Health Canada has notified Dow AgroSciences Canada Inc. that it has no objection to the food use of cotton lines containing event 281-24-236. The Department conducted a comprehensive assessment of this product 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 Dow AgroSciences Canada Inc., and the evaluation by Heath Canada and contains no confidential business information.

Introduction

Dow AgroSciences Canada has developed cotton (Gossypium hirsutum L..) lines based upon transformation event 281-24-236. Cotton varieties containing this event express the cry1F gene which confers resistance to certain lepidopteran pests. Lines containing this event also express the pat gene which confers tolerance to glufosinate ammonium. Health Canada has previously indicated no objection to the sale of corn line 1507 containing the Cry1F for human food applications. No objection has also been taken to the sale of sugarbeet (event T120-7) soybean (A5547-127, A2704-12), corn (DLL25) and canola (HCN92, event T45) containing the PAT protein for human food use.

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 cotton event 281-24-236 was developed; how the composition and nutritional quality of cotton oil derived from cotton varieties containing this event compare to the oil of non-modified cotton varieties; and what the potential is for oil 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 cotton lines containing event 281-24-236 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

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

Development of the modified plant

The petitioner has provided information describing the methods used to develop Cry1F insect resistant cotton and molecular biology data that characterizes the genetic changes which confers insect resistance and tolerance to glufosinate ammonium. The transgenic cotton events were developed by means of Agrobacterium tumefaciens transformation.Plasmid pAGM281 was used to develop cotton event 281-24-236 containing the cry1F gene and a copy of the pat gene and contained the following elements: the Zea mays promoter plus Zea mays exon 1 and intron 1 (Ubi Zm 1), a synthetic optimized copy of the cry 1F gene [cry1F(synpro)], a bidirectional terminator from Agrobacterium pTi15955 (ORF25 polyA), a synthetic optimized copy of the pat gene based on the sequence from Streptomyces viridochromogenes (Pat) and the Mannopine synthase promoter from pTi15955 including four copies of the octopine synthase enhancer from pTiAch5 [(4OCS))mas 2'].

Characterization of the modified plant

Southern blot analysis of cotton event 281-24-236 demonstrated the insertion at a single locus of a single copy of the cry1F(synpro) gene. The Southern blot analysis also confirmed the presence of the a full copy of the pat gene and an additional hybridizing fragment of the pat gene and its promoter Ubi Zm 1. Southern analysis of this cotton event also confirmed the absence of any plasmid derived sequences outside the T-DNA region, such as the erythromycin resistance gene found in the plasmid backbone.

Sequence analysis confirmed the expected sequence of the cry1F(synpro) transgene except for two nucleotide changes within the UbiZm1 promoter region. This two nucleotide change in the promoter region does not alter the Cry1F protein produced or the expression of this protein. Sequencing also confirmed the presence of an additional pat fragment containing 231 contiguous base pairs (bp) of pat plus 24 bp from an adjacent region, constituting a 255 bp open reading frame (ORF). This truncated pat coding region represents approximately 50% of a full length pat gene. Further analysis using RT-PCR indicated that the truncated PAT showed a 16 fold lower transcription level than that of the full length pat gene. Western Blot analysis of cotton event 281-24-236 using the PAT specific polyclonal antibody showed no detectable truncated PAT protein in any plant tissues, indicating that while the truncated PAT RNA transcript is detected, it is expressed at a much lower level than the full length transcript and is not translated into protein at detectable levels in the cotton tissue.

Southern blot analysis was used to demonstrate the stability of inheritance of the cry1F gene and the pat gene within segregating generations of cotton event 281-24-236. Data presented demonstrated that the integrations in both cotton events are stable and that the genes segregated according to Mendelian inheritance over seven generations.

Product information

Cotton event 281-24-236 differs from its traditional counterpart by the addition of the cry1F gene and the pat gene sequences into the genome. The introduction of these genes results in the expression of the Cry1F and PAT proteins. The proteins encoded by these genes are expressed at different levels throughout the plant tissue and throughout the life of the plant.

Dietary exposure

Typically, cotton by-products occur as blended items and are a minor component of daily dietary intake. Humans may consume cotton products as a food (cottonseed oil) or as food ingredients (cottonseed fatty acids, cooked and partially de-fatted cottonseed flour and decorticated ground cottonseed kernels). Cottonseed products besides the oil can be used as human food, however this is not common and will not contribute significantly to human dietary exposure.

Cottonseed oil derived from cotton lines containing event 281-24-236 is expected to be used by the food industry in applications similar to cottonseed oil derived from other cotton varieties. Food grade cottonseed oil is a common vegetable oil ingredient in many processed human foods.

A study published by the FAO tracking cottonseed consumption percentage of the total human diet throughout the world showed that Canada is a minor not major consumer. As a result, any dietary exposure to the Canadian population will likely be negligible.

Nutrition

Samples of delinted cottonseed were analysed for proximates, minerals, amino acids, vitamins, fatty acids, tocopherols, gossypol, aflatoxins and cyclopropenoid fatty acids. Results of this study showed that proximate values were within literature ranges and no significant differences were observed between control and the cry1F product. The cottonseed samples were also analysed for eleven minerals, eighteen amino acids, twenty-two fatty acids, eight vitamins and five anti-nutrients. Most comparisons showed no statistically significant difference between test and control treatments. For analytes which showed significant differences, the values were within the literature range and were found to be biologically insignificant.

The cottonseed oil samples were analysed for twenty-two fatty acids, four anti-nutrients and tocopherols (total, alpha, beta, gamma and delta). Most of the comparison showed no statistically significant differences between test and control treatments. For analytes for which significant differences were observed, the absolute differences between test and control varieties was small and had no nutritional relevance.

Chemistry/Toxicology

There is no apparent health concern with cottonseed oil derived from this novel plant. Dietary exposure to Cry 1F and PAT proteins are below the limit of detection and therefore the respective exposures would be no more the 0.08 and 0.16 ng/kg bw/day. These levels of exposure are more than 100 million times less than those doses used in acute oral toxicity studies in mice, which failed to demonstrate any toxicity. The safety was further assured by the comparison of the amino acid sequences of all these novel proteins to sequences of know toxins which showed no significant homology. As well, an in vitro model system suggests that all these proteins would likely be rapidly digested after ingestion and thus the novel proteins in this plant do not pose toxicological concern.

Concentrations of the endogenous anti-nutrients, gossypol and cyclopropenoid fatty acids were shown to be essentially the same in cottonseed oil derived from this novel cotton plant and from a conventional cotton plant, and therefore this novel food posed no greater risk than food made from a conventional variety.

The cottonseed oil derived from this novel cotton plant is very unlikely to pose an allergenic concern. Food allergens are generally proteins which may be pepsin resistant. Because of processing methods cottonseed oil has no detectable proteins and therefore the likelihood that these novel proteins would pose an allergenic concern is very remote. Further these novel proteins are easily digested under conditions of similar to the human stomach and therefore ingested novel proteins would not have access to the circulatory system. The novel proteins do not have any structural similarity to know allergens. The totality of evidence suggests that it is unlikely that they would be an allergen.

Conclusion

Health Canada's review of the information presented in support of the food use of Insect Resistant Cotton Event 281-24-236 concluded that the food use of cotton lines containing this event does not raise concerns related to safety. Health Canada is of the opinion that cotton lines containing event 281-24-236 is as safe and nutritious as current commercial cotton varieties.

Health Canada's opinion deals only with the food use of Insect Resistant Cotton Event 281-24-236 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 and Nutrition Directorate
Health Products and Food Branch
Health Canada, PL2204A1
251 Frederick Banting Driveway
Ottawa, Ontario K1A 0K9
bmh-bdm@hc-sc.gc.ca

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Date modified:: 2024-10-22

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