Database Product Description
- Host Organism
- Zea mays L. (Maize)
- Resistance to corn root worm (Coleopteran, Diabrotica sp.)
- 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 L. (Maize) Expand
Donor Organism Characteristics Expand
Modification Method Expand
Characteristics of the Modification Expand
Environmental Safety Considerations Expand
Food and/or Feed Safety Considerations Expand
Maize is used as a raw material for the manufacture of starch, the majority of which is converted by a complex refining process into sweeteners, syrups and fermentation products, including ethanol. Maize oil is extracted from the germ of the maize kernel. In the United States and Canada, only a small proportion of the whole kernel is consumed by humans, while 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 proportion is now being used for the production of ethanol. The entire maize plant, 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 maize acreage, and is a major ruminant feedstuff. Livestock that feed on maize include cattle, pigs, poultry, sheep and goats, fish and companion animals.
Industrial uses for maize products include recycled paper, paints, cosmetics and car parts. Refined maize products are also used in bioproducts such as antibiotics.
Diabrotica virgifera, western corn root worm (Family Coleoptera), is a major pest of maize in the US maize-growing belt. The larvae feed on maize roots, the damage from which causes nutrient and water depletion and ultimately lodging, making harvesting difficult. In the year 2000, over 14 million acres of United States maize was treated with chemical insecticides for this major pest. The corn root worm is estimated to cost the maize industry in the United States one billion dollars per year due to pesticide costs and crop damage.
Maize line MON 863 was produced using recombinant-DNA techniques to express the cry3Bb1 gene encoding a Coleopteran-specific insecticidal protein from Bacillus thuringiensis (subsp. kumamotoensis) in order to control infestation with corn root worm. This gene was introduced into the publicly available inbred line, A634, by particle acceleration (biolistic) transformation.
The cry3Bb1 gene encodes the insect control protein Cry3Bb1, a delta-endotoxin. Cry proteins, of which Cry3Bb1 is only one, act by selectively binding to specific sites localized on the lining of the midgut of susceptible insect species. Following binding, pores are formed that disrupt midgut ion flow, causing gut paralysis and eventual death due to bacterial sepsis. Cry3Bb1 is lethal only when eaten by Coleopteran species, including corn root worm, and its specificity of action is directly attributable to the presence of specific binding sites in the target insects. There are no binding sites for the delta-endotoxins of B. thuringiensis on the surface of mammalian intestinal cells, therefore, livestock animals and humans are not susceptible to these proteins.
MON 863 was tested in field trials in the United States. Data collected from these trials indicated that MON 863 was not different from other maize varieties in terms of agronomic characteristics, aside from resistance to corn root worm
Maize does not have any closely related species growing in the wild in continental United States and Canada. Cultivated maize can naturally cross with annual teosinte (Zea mays ssp. mexicana) when grown in close proximity, however, these wild maize relatives are native to Central America and are not naturalized in Canada or the United States. Additionally, reproductive characteristics such as pollen production, viability, and dispersal were unchanged in MON 863. Gene exchange between MON 863 and maize relatives was determined to be negligible in managed ecosystems, with no potential for transfer to wild species in Canada and the United States.
MON 863 lines expressing the Cry3Bb1 protein were compared to their non-transformed counterpart for relative abundance of beneficial arthropods. Field studies demonstrated that Cry3Bb1 had neither a direct nor an indirect effect on the beneficial arthropod populations. In summary, it was determined that when compared with currently commercialized maize varieties, MON 863 maize did not present an increased risk to or impact on interacting organisms, including humans, with the exception of specific coleopteran insect species.
The authorization for environmental release and livestock feed approval in Canada was granted for 1 year only. Renewal of the authorization was contingent on the submission of a new beneficial insect study as the original study on green lacewings was not considered of an optimal design. The new information was submitted in 2004 and the authorization renewed.
Regulatory authorities in Canada and United States have mandatory requirements for developers of Bt maize to implement specific Insect Resistant Management (IRM) Programs. As for other Bt maize varieties, farmers growing MON 863 are required to plant 20% of their acreage to non-Bt varieties.
Nutritional and anti-nutritional factors in MON 863 were examined and found to be within the normal range of unmodified maize varieties, though there were some differences from the parental line. The Cry3Bb1 protein was found in oral gavage studies to have a No Observed Adverse Effect Level (NOAEL) over 3200 mg/kg which exceeds the expected dietary exposure for humans by approximately 58000X. This level exceeded the livestock dietary exposure by 1000X.
Cry3Bb1 did not exhibit amino acid sequence homology or protein structure homology to known toxins or allergens. In addition, it was found that the Cry3Bb1 protein expressed by MON 863 maize lines digests rapidly in simulated gastric environments, was easily inactivated by heat and was not glycosylated. All these indicated that the Cry3Bb1 protein did not have potential for being an allergen or toxin.
Links to Further Information Expand
This record was last modified on Thursday, February 26, 2015