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
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 line GU262 was 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 GU262 soybean is the result of introducing a gene encoding the enzyme phosphinothricin-N-acetyltransferase (PAT) isolated from the common aerobic soil actinomycete, Streptomyces viridochromogenes, 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 gene was introduced into the soybean genome by micro-particle acceleration (biolistic) transformation, and the resulting soybean line, GU262, displayed field tolerance to phosphinothricin-containing herbicides, thereby permitting farmers to use this herbicide for weed control in soybean cultivation.
The transgenic soybean line GU262 was field tested in the United States from 1996 to 1998, and field trial reports indicated that this line did not exhibit weedy characteristics, and had no effect on non-target organisms or the general environment. In the United States, the transgenic soybean lines A2704-12, A2704-21, and A5547-35 were designated as the antecedent organisms to GU262 for the purposes of conducting an environmental safety assessment. The soybean line GU262 and its progeny were similar to the antecedent organisms as they were genetically engineered to express the same pat gene, and they all exhibited similar agronomic characteristics. Based on the similarity between GU262 and the antecedent organisms A2704-12, A2704-21, and A5547-35, and on an analysis of scientific data and field tests, the soybean line GU262 was judged not to have any characteristics that would have a significant impact on any beneficial organisms in the environment or on any threatened or endangered species.
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 GU262 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 the transgenic line 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.