GM Crop Database

Database Product Description

W62, W98 (ACS-GMØØ1-8, ACS-GMØØ2-9)
Host Organism
Glycine max (Soybean)
Trait
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

Country Food Feed Environment Notes
United States 1998 1998 1996

Introduction Expand

Soybean lines W62 and W98 were developed through a specific genetic modification to allow the use of glufosinate ammonium, the active ingredient in phosphinothricin herbicides (Basta , Ignite , Rely , Liberty , Harvest , and Finale ) as a weed control option in soybean crops. The bar gene, conferring tolerance to glufosinate ammonium, was cloned from the common aerobic soil actinomycete, Streptomyces hygroscopicus, and encodes the enzyme phosphinothricin-N-acetyltransferase (PAT).

Glufosinate is a short name for the ammonium salt, glufosinate-ammonium. It is a broad-spectrum contact herbicide and is used to control a wide range of weeds after the crop emerges or for total vegetation control on land not used for cultivation. Glufosinate is a natural compound isolated from two species of Streptomyces fungi. It inhibits the activity of an enzyme, glutamine synthetase, which is necessary for the production of glutamine and for ammonia detoxification. The application of glufosinate leads to reduced glutamine and increased ammonia levels in the plant tissues. This causes photosynthesis to stop and the plant dies within a few days. Glufosinate also inhibits the same enzyme in animals. It is highly biodegradable, has no residual activity, and very low toxicity for humans and wild fauna. The PAT enzyme detoxifies phosphinothricin by acetylation into an inactive compound.

These herbicide tolerant soybean lines also expressed a reporter gene encoding the enzyme beta-D-glucuronidase (GUS), which was used during the development process to select for transformed plants during tissue culture regeneration and multiplication.

Summary of Introduced Genetic Elements Expand

Code Name Type Promoter, other Terminator Copies Form
bar phosphinothricin N-acetyltransferase HT CaMV 35S
gus beta-D-glucuronidase SM

Characteristics of Glycine max (Soybean) Expand

Center of Origin Reproduction Toxins Allergenicity

Southeast Asia; wild soybean species endemic in China, Korea, Japan, Taiwan.

Self-polinated; rarely displays any dormancy characteristics; does not compete well with other cultivated plants.

Raw soybeans contain trypsin inhibitors, which are toxin when eaten.

Soy allergies are common, and eating soy products can cause rashes and swelling of the skin in sensitive individuals.

Donor Organism Characteristics Expand

Latin Name Gene Pathogenicity
Streptomyces hygroscopicus bar S. hygroscopicus is ubiquitous in the soil and there have been no reports of adverse affects on humans, animals, or plants.

Modification Method Expand

Lines W62 and W98 were produced via biolistic transformation of soybean with a pUC19 based plasmid containing a modified form the bar gene under the control of promoter sequences derived from the 35S transcript from cauliflower mosaic virus (CaMV).

Environmental Safety Considerations Expand

Field Testing

Transgenic soybean lines W62 and W98 were field tested in the United States from 1990-1993 and field trial reports from these tests demonstrated that the transformed lines did not exhibit weedy characteristics, and had no effect on nontarget organisms or the general environment.

Outcrossing

Gene introgression from transformed soybean lines W62 and W98 was extremely unlikely as there are no relatives of cultivated soybean in the continental United States and Canada, and soybean plants are almost completely self-pollinated. Furthermore, the reproductive characteristics such as pollen production and viability were unchanged by the genetic modification resulting in W62 and W98.

Cultivated soybean, Glycine max, naturally hybridizes with the wild annual species G. soja. Although G. soja is native to China, Korea, Japan, Taiwan and the former USSR it is not naturalized in North America, although it may possibly be grown in research plots. It was concluded that the potential for transfer of the herbicide tolerant trait from the transgenic lines to soybean relatives through gene flow was negligible in managed ecosystems, and that there was no potential for transfer to wild species in Canada and continental United States.

Weediness Potential

No competitive advantage was conferred to lines W62 and W98 other than that conferred by tolerance to glufosinate ammonium. Resistance to glufosinate ammonium will not, in itself, render soybean weedy or invasive of natural habitats since none of the reproductive or growth characteristics were modified. In the unlikely event of the formation of a herbicide tolerant hybrid, there would be no competitive advantage conferred on any hybrid progeny in the absence of sustained glufosinate ammonium use. The glufosinate ammonium tolerant plant would easily be controlled by mechanical means or by using alternative herbicides. Cultivated soybean is highly unlikely to establish in non-cropped habitats and there have been no reports of soybean surviving as a weed or exhibiting weed-like characteristics. It was concluded that soybean lines W62 and W98, had no altered weed of invasiveness potential compared to commercial soybean varieties.

Secondary and Non-Target Adverse Effects

Field observations of soybean lines W62 and W98 did not have a significant adverse impact on organisms beneficial to plants or agriculture, nontarget organisms, these events were not expected to impact on threatened or endangered species The PAT enzyme responsible for glufosinate ammonium tolerance that confers glufosinate resistance in transgenic soybean lines is normally not present in soybeans and is not known to have any toxic property. The lack of known toxicity for this enzyme suggests no potential for deleterious effects on beneficial organisms. The high specificity of the enzyme for its substrates makes it unlikely that the introduced enzyme would metabolize endogenous substrates to produce compounds toxic to beneficial organisms.

Impact on Biodiversity

Soybean lines W62 and W98 have no novel phenotypic characteristics that would extend their use beyond the current geographic range of soybean production. Since there are no wild relatives of soybean in Canada and continental United States and since soybean is not an invasive species, the novel trait will not be transferred to species in unmanaged environments.

Food and/or Feed Safety Considerations Expand

Nutritional Data

Samples of hay, forage, seed, hulls, and toasted and non-toasted defatted soy meal from transgenic soybean were subjected to proximate analyses (moisture, crude protein, crude fat, ash, acid detergent fibre, neutral detergent fibre, carbohydrate). As well, seed samples were subjected to fatty acid analysis, amino acid analysis, and analyses of minerals (calcium, phosphorous, and potassium). The values for each of these parameters was found to be within the normal range reported by the USDA for soybean.

Toxicology

Samples of seed were analyzed for stachyose, raffinose, and phytic acid, and additionally for trypsin inhibitor and lectins in seed. The concentrations of phytoestrogens, such as daidzein, genistein, and glycitein, were determined for samples of seed, and toasted and non-toasted soy meal. The levels of these compounds were not statistically different between samples from non-transgenic and transgenic soybeans.

Allergenicity

The low potential for allergenicity of the PAT protein has previously been established through amino acid sequence comparisons with known protein allergens and digestability studies using simulated gastric and intestinal fluids.

Abstract Collapse

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).

Links to Further Information Expand


This record was last modified on Friday, March 26, 2010