Database Product Description
- Host Organism
- Glycine max (Soybean)
- Phosphinothricin (PPT) herbicide tolerance, specifically glufosinate ammonium.
- Trait Introduction
- Microparticle bombardment of plant cells or tissue
- Proposed Use
Production for human consumption.
- Product Developer
- Bayer CropScience (Aventis CropScience(AgrEvo))
Summary of Regulatory Approvals
Summary of Introduced Genetic Elements Expand
Characteristics of Glycine max (Soybean) Expand
Donor Organism Characteristics Expand
Modification Method Expand
Environmental Safety Considerations Expand
Food and/or Feed Safety Considerations Expand
Soybean (Glycine max) is grown primarily for its seed, which has many uses in the food and industrial sectors, and represents one of the major sources of edible vegetable oil and of proteins for livestock feed use. The major producers of soybeans were the United States, Brazil, Argentina, China, India, Paraguay and Canada.
A major food use of soybean in North America and Europe is as purified oil, used in margarines, shortenings, and cooking and salad oils. It is also a major ingredient in food products such as tofu, tempeh, soya sauce, simulated milk and meat products, and is a minor ingredient in many processed foods. Soybean meal is used as a supplement in feed rations for livestock.
Weeds are a major production problem in soybean cultivation. Typically, weeds are managed using a combination of cultural (e.g., seed bed preparation, using clean seed, variety selection, and planting date) and chemical controls. Depending on the production area and the prevalent weed species, herbicides may be applied before planting (e.g., pendimethalin, trifluralin, metribuzin), after planting but before emergence (e.g., pendimethalin, linuron, imazethapyr), and/or after emergence (e.g., bentazon, acifluorfen, fomesafen). Commonly, several different herbicides are required to adequately control weeds in soybean fields.
The soybean lines W62 and W98 were genetically engineered to express tolerance to glufosinate ammonium, the active ingredient in phosphinothricin herbicides (Basta®, Rely®, Finale®, and Liberty®). Glufosinate chemically resembles the amino acid glutamate and acts to inhibit an enzyme, called glutamine synthetase, which is involved in the synthesis of glutamine. Essentially, glufosinate acts enough like glutamate, the molecule used by glutamine synthetase to make glutamine, that it blocks the enzyme's usual activity. Glutamine synthetase is also involved in ammonia detoxification. The action of glufosinate results in reduced glutamine levels and a corresponding increase in concentrations of ammonia in plant tissues, leading to cell membrane disruption and cessation of photosynthesis resulting in plant withering and death.
Glufosinate tolerance in W62 and W98 soybean lines is the result of introducing a gene encoding the enzyme phosphinothricin-N-acetyltransferase (PAT) isolated from the common aerobic soil actinomycete, Streptomyces hygroscopicus, the same organism from which glufosinate was originally isolated. The PAT enzyme catalyzes the acetylation of phosphinothricin, detoxifying it into an inactive compound. The PAT enzyme is not known to have any toxic properties. The PAT encoding gene (bar) was introduced into the soybean genome by micro-particle acceleration (biolistic) transformation, and the resulting soybean lines displayed field tolerance to phosphinothricin-containing herbicides, thereby permitting farmers to use this herbicide for weed control in soybean cultivation.
The soybean lines W62 and W98 were field tested in the United States from 1990-1993, and field trial reports indicated that these lines did not exhibit weedy characteristics, and had no effect on non-target organisms or the general environment. Soybean does not have any weedy relatives with which it can crossbreed in the continental United States or Canada. Additionally, soybean plants are almost completely self-pollinated, and the reproductive and growth characteristics of these transgenic lines were unchanged by the genetic modification resulting in glufosinate-tolerance. It was therefore concluded that the potential for transfer of the glufosinate-tolerance trait from W62 and W68 lines to soybean relatives through gene flow (outcrossing) was negligible in managed ecosystems, and that there was no potential for transfer to wild species in Canada or the continental United States.
The food and livestock feed safety of glufosinate-tolerant soybean lines W62 and W98 was established based on the lack of toxicity or allergenicity of the PAT enzyme and by direct laboratory analyses. The nutritional equivalence and wholesomeness of these soybeans compared to conventional (non-transgenic) soybeans was demonstrated by the analysis of key nutrients, including proximates (e.g., moisture, crude protein, crude fat, ash, acid detergent fibre, neutral detergent fibre, carbohydrate), fatty acid analysis, amino acid analysis, and analyses of minerals (calcium, phosphorous, and potassium). The values for each of these parameters were found to be within the normal range of expression found in unmodified soybean varieties.
Samples of seed from the transgenic lines were analyzed to determine concentrations of known antinutrients found in soybean (e.g., trypsin inhibitors, lectins, stachyose, raffinose, and phytic acid), as well as concentrations of phytoestrogens. The levels of these substances were found to be within the normal range of expression of currently cultivated varieties of soybean.
The low potential toxicity and allergenicity of the PAT protein expressed in the transgenic soybean lines W62 and W98 was supported by previous studies demonstrating a lack of amino acid sequence homology between the PAT protein and known protein allergens and toxins, and through examination of the protein’s physiochemical characteristics (e.g., susceptibility to pepsin degradation in simulated gastric fluids, heat instability).
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This record was last modified on Friday, March 26, 2010