ARCHIVED - Suppressed Polygalacturonase Activity Flavr Savr™ Tomato
Novel Food Information - Food Biotechnology
Health Canada has notified Calgene Inc. that it has no objection to the food use of the transgenic FLAVR SAVR™ tomato which has been developed to exhibit reduced pectin degradation through a suppression of polygalacturonase activity. The Department conducted a comprehensive assessment of the FLAVR SAVR™ tomato 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 derived from genetically modified organisms.
The following provides a summary regarding the Calgene Inc. notification to Health Canada and contains no confidential business information.
The FLAVR SAVR™ tomato (Lycopersicon esculentum) was developed through a specific genetic modification to exhibit decreased polygalacturonase (PG) activity. The novel variety was developed by insertion of an additional copy of the PG encoding gene in the "antisense" orientation, resulting in reduced translation of the endogenous PG messenger RNA (mRNA). The PG enzyme is the chief mechanism of pectin degradation in tomato fruit leading to fruit softening. The transgenic variety ripens normally but experiences less pectin breakdown and, therefore, has increased thickness and consistency that benefits all stages of harvesting and processing.
2. Development of the Modified Plant
The FLAVR SAVR™ tomato was created by Agrobacterium-mediated transformation in which the transfer-DNA (T-DNA) contained a copy of the tomato PG encoding gene in the antisense orientation. In addition, the T-DNA contained sequences encoding the enzyme neomycin phosphotransferase II (NPTII). The expression of NPTII activity was used as a selectable trait to screen transformed plants for the presence of the antisense-PG gene. Transcription of the antisense-PG gene did not result in the expression of any novel protein. There was no incorporation of translatable plasmid DNA sequences outside of the T-DNA region.
3. Product Information
The mechanism of decreased PG activity in FLAVR SAVR™ tomato is likely linked to the hybridization of antisense and sense mRNA transcripts, resulting in a decreased amount of free positive sense mRNA available for protein translation. The measured level of PG activity in transgenic FLAVR SAVR™ tomato was found to be less than 1% of PG activity found in the unmodified parental line. The presence of NPTII protein has been judged to be insignificant with respect to any human health risk due to exposure. Alpha-tomatine is the principal naturally occurring glycoalkaloid in tomato, and the level of a-tomatine decreases as the fruit matures so that the amounts in vine-ripened red tomatoes are negligible. Solanine and chaconine, which are the main glycoalkaloids occurring in potato, have been found in tomato in lesser amounts. A comparison of the amounts of a-tomatine in transgenic and non-transgenic tomatoes did not reveal any statistically significant difference and the levels were within the normal range reported for tomatoes. Other than reduced polygalacturonase activity, the disease, pest and other agronomic characteristics of the FLAVR SAVR™ tomato were comparable to unmodified varieties.
4. Dietary Exposure
The human consumption of the FLAVR SAVR™ tomato will be as both fresh and processed tomato products. Fresh market tomatoes are eaten whole and sliced or diced in a variety of foods. Processed tomatoes are consumed in the form of soups, preserves, ketchup, paste and prepared sauces. The genetic modification of this novel variety will not result in any change in the consumption pattern for fresh or processed tomato products. The transgenic FLAVR SAVR™ line is expected to replace other tomato cultivars currently in use due to improved quality and handling characteristics. Hence, it will provide an alternate or additional choice to consumers and food manufacturers.
The analysis of nutrients from the novel FLAVR SAVR™ line and non-transgenic control lines did not reveal any significant differences in the levels of macro- and micronutrients, pH, total acidity, total solids, and sugars. The consumption of this product will, therefore, have no significant impact on the nutritional quality of the Canadian food supply.
The reduced synthesis of native PG arising as a result of the suppression of PG mRNA translation by introduction of an antisense-PG gene sequence is not judged to have any potential for additional human toxicity or allergenicity.
Health Canada's review of the information presented in support of the food use of reduced polygalacturonase activity FLAVR SAVR™ tomato concluded that this novel variety does not raise concerns related to human food safety. Health Canada is of the opinion that the products from the FLAVR SAVR™ tomato are as safe and nutritious as those available from current commercial tomato cultivars.
Health Canada's opinion pertains only to the food use of the FLAVR SAVR™ tomato. Issues related to growing the FLAVR SAVR™ tomato in Canada and its use as animal feed are 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 Protection 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:
Office of Food Biotechnology
Health Protection Branch
Ottawa, Ontario K1A 0L2
Facsimile: (613) 952-6400
Telephone: (613) 952-5137
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