Biotechnology of Food, FDA and New Tomato

Biotechnology of Food

Biotechnology refers to the techniques that allow scientists to modify DNA, the genetic material of living things.

New plant varieties have been developed using biotechnology, and on May 18, 1994, the Food and Drug Administration announced it had determined that a new tomato developed through biotechnology is as safe as tomatoes bred by conventional means. This was the first time FDA had evaluated a whole for food produced by biotechnology, by which plant improvements can be made more precisely than through traditional cross-breeding.

The tomato was developed by means of genetic engineering by Calgene, Inc., of Davis Calif. Calgene claims that the fresh market tomato, called FLAV SAVRTM, many remain on the vine longer to ripen to full flavor before harvest. (In order to make the trip to market without being crushed, other tomato varieties must be harvested while they are green and firm before reaching full flavor. After shipment, processors induce ripening by treating the tomatoes with ethylene gas, the natural ripening agent in tomatoes).

FLAVR SAVRTM stays firm after harvest because, through gene manipulation, the formation of polygalacturonase (PG), an enzyme that occurs naturally in tomatoes, is suppressed. PG breaks down pectin, found in the cell walls, and causes ripe tomatoes to soften. PG is suppressed by introducing into the plant a reverse copy-called an antisense gene-of the tomato DNA that produces the PG enzyme. Thus, FLAVR SAVRTM tomatoes, with lower levels of PG than other varieties, can be allowed to remain on the vine longer before they are picked because they soften more slowly and will still be firm in the supermarket.

FDA has worked with Calgene for several years. In August 1991, Calgene requested and advisory opinion from FDA asking if FLAVR SAVRTM tomatoes would be subject to the same regulation as other tomato varieties.

Earlier, in November 1990, Calgene has requested an advisory opinion asking whether the kanr gene, a gene that makes a plant cell resistant to the antibiotic kanamycin, could be used as a marker in production of genetically engineered tomatoes, cotton, and rapeseed oil (canola) plants. The kanr gene functions as a marker when it is linked to the antisense gene. The kanr gene contains information to allow tomato cells to produce the protein APH(3′)II (aminoglycoside-3′ -phosphotransferase II), which inactivates the antibiotic kanamycin. Therefore, only plant cells that have taken up the kanr gene will survive when grown in the presence of kanamycin. This allows developers to select plants that have taken up the antisense PG gene.

FDA’s review of FLAVR SAVRTM was conducted consistent with a policy it published in the May 29, 1992, Federal Register, showing how the agency interprets the Federal Food, Drug, and Cosmetic Act with respect to foods derived from new plant varieties.

The 1992 policy is based on existing food law, and requires that genetically engineered foods meet the same rigorous safety standards as is required of all other foods. The law places a responsibility on producers and sellers to offer only safe products to consumers, and provides FDA with the legal tools for enforcement.

Food law requires pre-market approval for food additives, whether or not they are the products of biotechnology. Therefore, FDA’s biotechnology policy treats substances intentionally added to food through genetic engineering as food additives if they are significantly different in structure, function, or amount than substances currently found in food. Many of the food crops currently being developed using biotechnology do not contain substances that are significantly different from those already in the diet and thus do not require pre-market approval.

The 1992 policy statement contains detailed scientific guidancefor developers of new plant varieties so that they understand the issues FDA considers important. For example, safety assessments of foods derived from new plant varieties include evaluations of:

  • the purpose or the intended technical effect of the genetic modification
  • the source, function and stable incorporation of introduced genetic material
  • analytical studies to determine whether the genetic modification had any effects on the composition of the food (such as the levels of important nutrients and naturally occurring toxicants)
  • the safety of new or modified substances (for example, proteins, carbohydrates, fats, or oils) in the food.

In keeping with the policy statement, FDA’s Center for Food Safety and Applied Nutrition (CFSAN) considered Calgene’s request as a consultation rather than as an advisory opinion. Then, on July 16, 1993, FDA announced that Calgene had filed a food additive petition to allow the use of APH(3′)II in its new plant varieties.

CFSAN’s scientists reviewed all the data submitted by Calgene. The data provided by the firm indicate that:

    • The intended effect of the altered RNA of the new PG gene that suppresses the breakdown of pectin in FLAVR SAVRTM tomatoes does not raise safety questions. Pectin is a part of many fruits and vegetables, and is a generally recognized as safe (GRAS) substance that is directly added to many foods as a gelling agent (as in jelly) and as a stabilizer (as in ice cream). In addition, the prevention of pectin degradation in FLAVR SAVRTM tomatoes occurs without adversely affecting other characteristics of the tomato, such as nutrients and toxicant levels.
    • The DNA used to transfer the kanr gene and PG gene to FLAVR SAVRTM tomatoes does not contain other genes that would produce any protein known to be toxic.
    • Calgene has established that the DNA inserted into the plants (to transfer the genes) is stable in FLAVR SAVRTM tomatoes and will remain unchanged from one generation of plants to the next. The firm has tested the plants for five generations.
    • The levels of vitamins A and C are comparable to the levels of those same nutrients in other varieties of tomatoes.

  • Tomatine, a naturally occurring toxicant in all tomatoes, is distributed throughout the tomato plant, but is most concentrated in leaves and in opening flowers. The tomatine concentration in tomatoes depends on the degree of ripeness, and declines as green fruit ripens to red. Tomatine levels in the ripe FLAVR SAVRTM are comparable to tomatine levels in commercial tomato varieties.

FDA also evaluated Calgene’s food additive petition for the use of APH(3′)II in the development of new varieties of tomatoes, rapeseed oil, and cotton. FDA’s evaluation included food safety and environmental consideration associated with the use of APH(3′)II and the kanr gene. Calgene provided data and information showing that APH(3′)II does not exhibit characteristics of substances known to be food allergens-for example, APH(3′)II does not contain sugar molecules attached to the protein and is rapidly degraded in simulated gastric conditions.

Calgene also provided data and information to support the conclusion that APH(3′)II would not interfere with te effectiveness of the orally administered antibiotics kanamycin and neomycin. For example, APH(3′)II requires the presence of the substance adenosine-5′ -triphosphate (ATP) in order to inactivate the antibiotics kanamycin and neomycin, and foods do not contain enough ATP to allow the inactivation reaction to proceed. In addition, as already mentioned, APH(3′) is rapidly degraded under normal gastric conditions.

Calgene also provided data and information to support the conclusion that the kanr gene is unlikely to be transferred to microorganisms that nat reside in the human gut or in soil. Therefore, use of the gene does not pose a safety concern with respect to a potential increase in the population of antibiotic-resistant pathogenic microorganisms.

After evaluating all data submitted by Calgene for the use of APH(3′)II in tomatoes, rapeseed oil, and cotton is safe. FDA also concluded that the safety assessment conducted by the firm for FLAVR SAVRTM is consistent with the principles that are appropriate for evaluating a whole food. FDA determined that the data indicate that the FLAVR SAVRTM tomato has not been significantly altered when compared to other varieties of tomatoes. In other words, the new product is as safe as other commonly consumed tomatoes.

FDA’s approach to evaluating the safety of FLAVR SAVRTM was discussed in April 1994 by its Food Advisory Committee, a panel of experts from outside the agency. Members of the panel concurred with FDA’s preliminary assessment that all relevant safety questions about the new tomato had been resolved.

FDA did not find it necessary to require special labeling for FLAVR SAVRTM since it maintains the essential characteristics of other tomatoes. However, Calgene plans to provide point-of-sale information for consumers about the development of FLAVR SAVRTM through genetic engineering.

The finding that the biotechnology-derived tomato is as safe as its traditional counterparts followed FDA approval in 1990 of the first biotechnology food ingredient processing aid, chymosin, an agent that helps milk clot in making cheese.


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