Database Product Description
- Host Organism
- Zea mays (Maize)
- Glyphosate herbicide tolerance.
- Trait Introduction
- Microparticle bombardment of plant cells or tissue
- Proposed Use
Production for human consumption and livestock feed.
- Product Developer
- Monsanto Company
Summary of Regulatory Approvals
Summary of Introduced Genetic Elements Expand
Characteristics of Zea mays (Maize) Expand
Donor Organism Characteristics Expand
Modification Method Expand
Characteristics of the Modification Expand
Food and/or Feed Safety Considerations Expand
Maize (Zea mays L.), or corn, is grown primarily for its kernel, which is largely refined into products used in a wide range of food, medical, and industrial goods.
Only a small amount of whole maize kernel is consumed by humans. Maize oil is extracted from the germ of the maize kernel and maize is also a raw material in the manufacture of starch. A complex refining process converts the majority of this starch into sweeteners, syrups and fermentation products, including ethanol. Refined maize products, sweeteners, starch, and oil are abundant in processed foods such as breakfast cereals, dairy goods, and chewing gum.
In the United States and Canada maize is typically used as animal feed, with roughly 70% of the crop fed to livestock, although an increasing amount is being used for ethanol production. The entire maize plant, the kernels, and several refined products such as glutens and steep liquor, are used in animal feeds. Silage made from the whole maize plant makes up 10-12% of the annual corn acreage, and is a major ruminant feedstuff. Livestock that feed on maize include cattle, pigs, poultry, sheep, goats, fish and companion animals.
Industrial uses for maize products include recycled paper, paints, cosmetics, pharmaceuticals and car parts.
The MON832 line of maize was developed to allow the use of glyphosate, the active ingredient in the herbicide Roundup®, as a weed control option. In order to obtain field tolerance to glyphosate herbicide, two novel genes, EPSPS and goxv247, were introduced maize by particle acceleration (biolistic) transformation.
The EPSPS gene codes for the enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) that is present in all plants, bacteria and fungi. The EPSPS gene put into MON832 was isolated from strain CP4 of the common soil bacterium Agrobacterium tumefaciens and is a glyphosate tolerant form of EPSPS. The EPSPS enzyme is part of an important biochemical pathway in plants called the shikimate pathway that is involved in the production of aromatic amino acids and other aromatic compounds. When conventional maize plants are treated with glyphosate, they cannot produce the aromatic amino acids needed to grow and survive. EPSPS is not present in mammals, birds or aquatic life forms, which do not synthesize their own aromatic amino acids. For this reason, glyphosate has little toxicity to these organisms. The EPSPS enzyme is naturally present in foods derived from plant and microbial sources.
MON832 contains a second gene that codes for a modified version of glyphosate oxidase (GOX) enzyme that is ubiquitous in nature. The goxv247 gene inserted into MON832 was isolated from strain LBAA of the bacterium Ochrobactrum anthropi. The GOX enzyme accelerates the normal breakdown of the herbicide glyphosate into two non-toxic compounds, aminomethylphosphonic acid (AMPA) and glyoxylate. AMPA is the principal breakdown product of glyphosate and is degraded by several microorganisms, while glyoxylate is commonly found in plant cells and is broken down by the glyoxylic pathway for lipid metabolism.
The major components of grain and forage from MON832 maize were analyzed in order to determine their safety for use as food and as livestock feed. Proximate analysis determined that MON832 grain was comparable to that of the non-transgenic control line in its protein, fat, ash, carbohydrate, fibre, moisture and caloric content. Additionally, the amino acid and fatty acid composition of MON832 grain was comparable to that of a non-transgenic line. Based on this data, it was concluded that there was no significant difference between the forage from MON832 maize and the control line.
The low potential for toxicity of the transgenic maize line MON832 was demonstrated by examining the amino acid sequence homology and protein characterization of the line. The CP4 EPSPS and GOX proteins did not show meaningful amino acid sequence homology with known allergens or protein toxins. Further assessment of the allergenic potential of these proteins consisted of digestibility studies and an acute oral toxicity study involving mice. Results of the digestibility studies indicated that, unlike known protein allergens, the CP4 EPSPS and GOX proteins are rapidly degraded and their enzymatic activity lost under conditions that simulate mammalian digestion. The mouse toxicity study indicated that there were no toxic effects caused by consumption of the CP4 EPSPS or GOX proteins, as measured by the absence of treatment-related adverse effects in the mice. It was therefore concluded that the CP4 EPSPS and GOX proteins are not likely to pose any toxicity or allergenicity concerns.
Links to Further Information Expand
This record was last modified on Monday, March 28, 2016