GM Crop Database

Database Product Description

FLAVR SAVR (CGN-89564-2)
Host Organism
Solanum lycopersicum (Tomato)
Trait
Delayed softening through suppression of polygalacturonase (PG) enzyme activity.
Trait Introduction
Agrobacterium tumefaciens-mediated plant transformation.
Proposed Use

Production for human consumption.

Product Developer
Calgene Inc.

Summary of Regulatory Approvals

Country Food Feed Environment Notes
Canada 1995 View
Japan 1997 1996
Mexico 1995 1995 1995
United States 1994 1994 1992

Introduction Expand

FLAVR SAVR™ tomatoes were developed using recombinant DNA techniques to express the trait of delayed softening of tomato fruit. The novel variety was developed by insertion of an additional copy of the polygalacturonase (PG) encoding gene in the “antisense” orientation, resulting in reduced translation of the endogenous PG messenger RNA (mRNA). The antisense PG gene is essentially a reverse copy of part of the native tomato PG gene that suppresses the expression of endogenous PG enzyme prior to the onset of fruit ripening. 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. Reduced PG expression decreases the breakdown of pectin and leads to fruit with slowed cell wall breakdown, better viscosity characteristics and delayed softening. FLAVR SAVR™ tomatoes have improved harvest and processing properties that allow the transgenic tomatoes to remain longer on the vine to develop their natural flavour, maintain firmness for shipping and produce a thicker consistency in processing.

An antibiotic resistance marker gene (neo) encoding the enzyme neomycin phosphotransferase II (NPTII), which inactivates aminoglycoside antibiotics such as kanamycin and neomycin, was also introduced into the genome of this transgenic tomato. This gene was derived from a bacterial transposon (Tn5 transposable element from Escherichia coli) and was included as a selectable marker to identify transformed plants during tissue culture regeneration and multiplication. The expression of the neo gene in these plants has no agronomic significance and the safety of the NPTII enzyme as a food additive was evaluated by the United States Food and Drug Administration in 1994 (US FDA, 1994).

Summary of Introduced Genetic Elements Expand

Code Name Type Promoter, other Terminator Copies Form
PG polygalacturonase DR CaMV 35S tml gene and the transcript 7gene from the octopine-type Ti plasmid pTiA6 Native, anti-sense orientation
nptII neomycin phosphotransferase II SM mannopine synthase from A. tumefaciens mannopine synthase from A. tumefaciens Native

Characteristics of Solanum lycopersicum (Tomato) Expand

Center of Origin Reproduction Toxins Allergenicity

The regions of Ecuador, Peru, and the Galapagos Islands.

Almost exclusively self-pollinating; hybridization with related Solanum species (e.g., S. lycopersicoides) requires human intervention.

Glycoalkaloids, primarily alpha-tomatine, but also solanine and chaconine. Also, lectins and oxalate.

Although not a major cause of allergic reactions, several glycoproteins from tomatoes are known to be allergenic.

Modification Method Expand

This bioengineered tomato was produced by Agrobacterium-mediated transformation of tomato (Solanum lycopersicum) in which the transfer-DNA (T-DNA) region of the bacterial tumour inducing (Ti) plasmid was modified to contain DNA sequences encoding an “antisense” PG gene construct and the NPTII encoding neo gene from E. coli K12. During transformation, the T-DNA portion of the plasmid was transferred into the plant cells and stably integrated into the plant's genome.

The antisense PG gene was under the regulatory control of a single copy of the 35S promoter from the cauliflower mosaic virus (CaMV), or two tandem copies of the 35S promoter. The terminator sequences were from the tml gene and the transcript 7 gene from the octopine-type Ti plasmid pTiA6 from A. tumefaciens. Expression of the neo gene was under the control of the 5' promoter and 3' terminator sequences from the mannopine synthase gene derived from A. tumefaciens.

Characteristics of the Modification Expand

The Inserted DNA

Southern blot analyses of genomic DNA from FLAVR SAVR™ tomato line CR3-613 demonstrated insertion of the complete T-DNA region containing sequences encoding the antisense PG gene construct and NPTII. There was no incorporation of plasmid DNA sequences outside of the T-DNA region.

Genetic Stability of the Introduced Trait

FLAVR SAVR™ tomatoes were tested for five generations, establishing that the T-DNA inserted into the plants was stable and remained unchanged from one generation of plants to the next.

Expressed Material

The only novel protein expressed in FLAVR SAVR™ tomatoes was the enzyme NPTII. The antisense PG gene did not encode any polypeptide products and was introduced to suppress endogenous PG activity. The measured level of endogenous PG activity in transgenic FLAVR SAVR™ tomato was found to be less than 1% of PG activity found in the unmodified parental line.

Environmental Safety Considerations Expand

Field Testing

FLAVR SAVR™ tomatoes were field tested in the United States from 1988 to 1992. Field trials demonstrated that the variation in agronomic characteristics among the FLAVR SAVR™ tomato lines did not differ significantly from the natural variation found in commercial cultivars of tomato. These reports determined that FLAVR SAVR™ tomatoes did not exhibit weedy characteristics, and have no effect on nontarget organisms or the general environment.

Outcrossing

Cultivated tomatoes are self-fertile, and almost exclusively self-pollinating. Their unique flower and anther morphology makes tomato an essentially cleistogamous plant (self-pollination and fertilization occur within an unopened flower). A low crossing rate between tomato varieties was demonstrated and attributed to limited availability of pollen and poor foraging activity of insect pollinators.

Several related species are found as weeds in tomato fields, however tomato is generally sexually incompatible with all these weedy relatives. Two Solanum species, S. lycopersicoides and S. rickii, can be crossed with commercial tomato under specific, controlled conditions, but they do not naturally cross with S. lycopersicum and require the intervention of man. Neither Solanum species is a weed pest in the United States.

The cherry tomato, S. lycopersicum var. cerasiforme can be crossed with tomato, S. lycopersicum. However, it would be very unlikely for traits from FLAVR SAVR™ tomato to naturally introgress into cherry tomatoes (var. cerasiforme) in the United States since the rate of outcrossing in tomatoes is low and cherry tomatoes are not common in areas devoted to large-scale cultivation of tomatoes.

It was concluded that the chance of genetic exchange both among tomato crops and with other species, was remote. In the event that an outcrossing event involving pollen from a FLAVR SAVR™ tomato did occur, it was unlikely the antisense modification to delay fruit softening could affect seed persistence or weediness potential in progeny. Field testing determined that the expression of the antisense PG gene did not change any morphological or physiological characteristics which might affect pollination. It was determined that there was no likelihood that these modified tomato lines would gain a selective advantage that would enable FLAVR SAVR™ tomatoes to become weeds or increase the weedy potential of another plant.

Weediness Potential

FLAVR SAVR™ tomato has little potential to become a weed. There were no morphological, physiological, or disease resistance characteristics of the FLAVR SAVR™ tomato that differed significantly from the agricultural practices used normally for the propagation of tomatoes, with the exception of having the potential to be left longer in the field to ripen. Although having an increased field ripening period, FLAVR SAVR™ tomatoes eventually decay into components, which are presumably identical to the decay components of nontransgenic tomatoes. FLAVR SAVR™ tomato differed with respect to having an increased resistance to certain fungal pathogens, likely due to the increased integrity of the cell walls.

Tomatoes are not considered a weed pest. Tomato volunteers are not uncommon, but are easily controlled using herbicides or by mechanical means. Seed dispersal by birds or mammals is insignificant. Furthermore, due to its tropical origin, tomato is very sensitive to temperatures below 10ºC and winter cold will kill the majority of volunteer seedlings following harvest. Tomatoes are not persistent in undisturbed environments without human intervention.

Secondary and Non-Target Adverse Effects

It was concluded that the genes inserted into FLAVR SAVR™ tomatoes would not result in any deleterious effects or significant impacts on nontarget organisms, including those that are recognized as beneficial to agriculture and those that are recognized as threatened or endangered in the United States. Since the antisense PG gene construct did not result in the production of any new protein(s), there is unlikely to be any associated toxicity. Field testing determined that there were no significant differences in the susceptibility of modified and non-modified crops to pests and diseases. Analysis of biochemical components of FLAVR SAVR™ tomatoes were compared to nontransgenic tomatoes and no toxic components were identified in concentrations that differed significantly from the concentrations found in nontransgenic tomatoes. Furthermore, FLAVR SAVR™ tomatoes have neither direct pathogenic properties nor any hypothetical mechanisms for pathogenesis.

Impact on Biodiversity

FLAVR SAVR™ tomatoes have no novel phenotypic characteristics that would extend their use beyond the current geographic range of tomato production. Since the risk of gene transfer to wild relatives in the United States is very remote, it was determined that the risk of transferring genetic traits of FLAVR SAVR™ tomatoes to species in unmanaged environments was not significant.

Food and/or Feed Safety Considerations Expand

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 these novel tomatoes will not result in any change in the consumption pattern for fresh or processed tomato products. The transgenic FLAVR SAVR™ lines are 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.

Nutritional Data

The analysis of nutrients from the novel FLAVR SAVR™ tomatoes 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 food supply in Canada and the United States.

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 alpha-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 alpha-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. Alpha-tomatine was detected (at a limit of detection of 2.5 ppm) in only one out of 38 red ripe FLAVR SAVR™ fruits and four out of 60 red ripe commercial tomato fruits. Other than reduced polygalacturonase activity, the disease, pest and other agronomic characteristics of the FLAVR SAVR™ tomato were comparable to unmodified varieties.

Toxicity and Allergenicity

The reduced synthesis of native PG was not judged to have any potential for human toxicity or allergenicity. Analysis of biochemical components of FLAVR SAVR™ tomatoes were compared to nontransgenic tomatoes and no toxic components were identified in concentrations that differed significantly from the concentrations in nontransgenic tomatoes. The antisense PG gene did not encode for any new protein products and therefore, should not have any toxic properties. The novel protein NPTII expressed by the neo gene is widespread in nature and no toxic or allergenic effects have ever been reported.

Additional data from three 28-day rat feeding trials demonstrated no biologically significant changes in body weight, organ weight, food consumption, hematologic parameters, and clinical chemistry findings. There was disparity among the three studies regarding the incidence of rats with gastric erosions. Although no definitive conclusions could be drawn regarding the etiology(ies) of these erosions, it was determined that they were also present in rats fed non-transgenic tomatoes and that, where they occurred, they were no more severe in rats fed FLAVR SAVR™ tomatoes than in rats fed non-transgenic tomatoes.

Abstract Collapse

The tomato is a vine-like herb of the nightshade family (Solanaceae) that also includes potatoes, peppers and eggplants. Botanically this vegetable is a fruit (a berry), which although being a perennial plant in the tropics, is grown as an annual plant in northern climates. The tomato is a native of the Peru, Bolivia, and Ecuador area of the Andes Mountains. Its antiquity is uncertain in regard to cultivation but it was being cultivated when Europeans discovered America. However, it was not generally cultivated in the United States until 1835 because, until then, it was widely believed to be poisonous.

Tomatoes are propagated from seeds. In temperate regions seeds are generally started in greenhouses, hotbeds, or cold frames; the plants are set out in the fields when danger of frost is past. Fresh tomatoes are harvested by hand, while those destined for canning or for processing into soups, sauces and ketchups are harvested by machine. The numerous varieties differ greatly in plant form and fruit type, the latter ranging from a small currant size through cherry, plum, and pear forms to the large, nearly round fruits, 10 cm (4 in) or more in diameter, which are the most widely grown. All forms include red- and yellow-fruited varieties.

Tomatoes are a valuable source of food minerals and vitamins, and are low in calories. One medium-sized tomato provides 57% of the recommended daily allotment (RDA) of vitamin C, 25% RDA vitamin A, and 8% RDA iron, yet it has only 35 calories. Tomatoes are also rich in the anti-oxidant lycopene, a carotenoid that has been found to protect cells from oxidants that have been linked to cancer. In laboratory tests, lycopene was found to be twice as powerful as beta-carotene in neutralizing free radicals. Lycopene has been linked to risk reduction for a number of types of cancers, including prostate, lung and stomach, pancreatic, cervical, colorectal, oral and esophageal cancers.

In the fresh market industry the tomato fruit is often picked at the mature green or breaker stages for long-distance shipping, and is then subsequently ripened by treatment with ethylene (12 to 18 h at 20ºC). For processing tomatoes the ethylene-producing compound, ethephon or Ethrel, is applied prior to harvest when only 10% of the fruit is ripe; this accelerates and concentrates fruit-ripening and facilitates once-over machine harvest.

Pectin is a building block in plant cell walls and is what gives tomatoes their firmness. Fruit softening during ripening is due to the breakdown of cell wall pectin by an enzyme called polygalacturonase (PG). The FLAVR SAVR™ tomato line was genetically engineered to express delayed softening 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 antisense PG gene is essentially a reverse copy of part of the native tomato PG gene that suppresses the expression of endogenous PG enzyme prior to the onset of fruit ripening. 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. Reduced PG expression decreases the breakdown of pectin and leads to fruit with slowed cell wall breakdown, better viscosity characteristics and delayed softening. FLAVR SAVR™ tomatoes have improved harvest and processing properties that allow the transgenic tomatoes to remain longer on the vine to develop their natural flavour, maintain firmness for shipping and produce a thicker consistency in processing. The measured level of endogenous PG activity in transgenic FLAVR SAVR tomato was found to be less than 1% of PG activity found in the unmodified parental line.

FLAVR SAVR™ tomatoes were field tested in the United States from 1988 to 1992. Field trials demonstrated that the variation in agronomic characteristics among the FLAVR SAVR™ tomato lines did not differ significantly from the natural variation found in commercial cultivars of tomato. These reports indicated that FLAVR SAVR™ tomatoes did not exhibit weedy characteristics, and had no observable effect on nontarget organisms or the general environment. The transformed tomato line was not expected to impact on threatened or endangered species.

Cultivated tomatoes are self-fertile, and almost exclusively self-pollinating. Their unique flower and anther morphology makes tomato an essentially cleistogamous plant, in which self-pollination and fertilization occur within an unopened flower. A low crossing rate between tomato varieties was demonstrated and attributed to the limited availability of pollen and poor foraging activity of insect pollinators.

Several related species are found as weeds in tomato fields, however, commercial tomato is generally sexually incompatible with these weedy relatives. Two Solanum species, S. lycopersicoides and S. rickii, neither of which is a weed pest in the United States, can be crossed with commercial tomato only under specific, controlled conditions requiring human intervention. The cherry tomato, S. lycopersicum var. cerasiforme can be crossed with tomato. However, it would be very unlikely for the FLAVR SAVR™ tomato line to hybridize with cherry tomatoes in the United States since the rate of outcrossing in tomatoes is low and cherry tomatoes are not common in areas devoted to the large-scale cultivation of tomatoes. It was concluded that the chance of genetic exchange among tomato crops was small and outcrossing to other species, even more remote. In the event that an outcrossing event involving pollen from the transgenic FLAVR SAVR™ tomato line did occur, it was unlikely that the delayed-ripening trait would increase the plant’s weediness or probability of survival.

Tomatoes are consumed in both fresh (whole and sliced or diced in a variety of foods) and processed (soups, ketchup, paste, prepared sauces) forms, and the genetic modification introduced into the transgenic tomato line was not expected to result in any changes in consumption patterns. FLAVR SAVR™ tomatoes were expected to provide an alternate or additional choice to consumers and food manufacturers.

The analysis of nutrients from FLAVR SAVR™ tomatoes and non-transgenic control lines did not reveal any significant differences in the levels of macro- and micronutrients, pH, total acidity, total solids, or sugars. Levels of glycoalkaloids (alpha-tomatine) present in mature tomatoes from the transgenic tomato line were within the range reported for conventional tomato varieties.

As the antisense PG gene did not encode for any new protein there was no expectation of toxic or allergenic potential related to the genetic modification. Additional data from three 28-day rat feeding trials comparing transgenic and non-transgenic tomatoes demonstrated no biologically significant changes in body weight, organ weight, food consumption, hematologic parameters, and clinical chemistry findings that were specific to the transgenic line.

Links to Further Information Expand

European Commission Scientific Committee on Food Office of Food Biotechnology, Health Canada U.S. Department of Agriculture, Animal and Plant Health Inspection Service US Food and Drug Administration USDA-APHIS Environmental Assessment

This record was last modified on Wednesday, May 20, 2015