Database Product Description
- Host Organism
- Zea mays (Maize)
- Trade Name
- Glufosinate ammonium herbicide tolerance and male sterility
- Trait Introduction
- Electroporation of immature embryos.
- Proposed Use
Production for human consumption and livestock feed.
- Product Developer
- Bayer CropScience (Aventis CropScience(AgrEvo))
Summary of Regulatory Approvals
Summary of Introduced Genetic Elements Expand
Characteristics of Zea mays (Maize) Expand
Donor Organism Characteristics Expand
Modification Method Expand
Maize (Zea mays L.) 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 the production of ethanol. 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 maize line MS6 was genetically engineered to express male sterility and 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 this maize line is the result of introducing a gene encoding the enzyme phosphinothricin-N-acetyltransferase (PAT) isolated from the common aerobic soil actinomycete, Streptomyces hygroscopicus. 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 male-sterile trait was introduced by inserting the barnase gene, isolated from Bacillus amyloliquefaciens, a common soil bacterium that is frequently used as a source for industrial enzymes. The barnase gene encodes for a ribonuclease enzyme (RNAse) that is expressed only in the tapetum cells of the pollen sac during anther development. The RNAse affects RNA production, disrupting normal cell functioning and arresting early anther development, thus leading to male sterility. The PAT enzyme was used as a selectable marker enabling identification of transformed plants during tissue culture regeneration, and as a field selection method to identify the male-sterile lines prior to flowering. Under field conditions, plants that were not male-sterile could be eliminated by application of the herbicide glufosinate ammonium. The novel hybrid system provided an efficient and effective way to identify male-sterile plants for use in hybrid seed production.
In the United States, the male-sterile line MS3 was designated as the antecedent organism for MS6 for the purposes of conducting the environmental safety assessment. Maize lines MS3 and MS6 were genetically modified using the same transformation technique and the same genetic elements. Based on the similarity between MS6 and the antecedent organism MS3, and on an analysis of scientific data and field tests of MS6, the maize line MS6 was judged not to have any characteristics that would pose a greater impact on the environment or on non-target organisms.
For additional information related to either the environmental or food safety assessment of the antecedent organism, MS3, the reader is referred to the description for that product.
Links to Further Information Expand
This record was last modified on Friday, March 26, 2010