7500 Olson Memorial HighwayGolden Valley
|Country||Environment||Food and/or Feed||Food||Feed||Marketing|
|Taiwan||Approval valid until April 20, 2014.|
|vip3Aa20||vegetative insecticidal protein (Bacillus thuringiensis strain AB88)||IR||ZmUbiInt (Zea mayspolyubiquitin gene promoter and first intron).||CaMV 35S 3′ polyadenylation signal||1||native|
|pmi||mannose-6-phosphate isomerase (Escherichia coli)||SM||ZmUbiInt (Zea mayspoly-ubiquitin gene promoter and first intron)||A. tumefaciensnopaline synthase (nos) 3′-untranslated region||1|
|Center of Origin||Reproduction||Toxins||Allergenicity|
|Mesoamerican region, now Mexico and Central America||Cross-pollination via wind-borne pollen is limited, pollen viability is about 30 minutes. Hybridization reported with teosinte species and rarely with members of the genus Tripsacum.||No endogenous toxins or significant levels of antinutritional factors.||Although some reported cases of maize allergy, protein(s) responsible have not been identified.|
|Bacillus thuringiensisstrain AB88||vip3A||While target lepidopteran insects are susceptible to oral doses of VIP proteins, there is no evidence of toxic effects in laboratory mammals, in birds, and in non-target arthropods, including beneficial insects.|
Southern blot analyses and nucleotide sequencing demonstrated that MIR162 maize contains a single intact T-DNA insert in the nuclear maize genome. Southern blot analyses further demonstrated that the T-DNA insert contains: i) single copies of a vip3Aa gene and a pmigene; ii) two copies of the ZmUbiInt promoter; iii) one copy of the NOS terminator; and iv) no backbone sequences from transformation plasmid pNOV1300. Nucleotide sequencing of the T-DNA insert in MIR162 maize revealed two codon changes within the vip3Aa coding sequence relative to the intended vip3Aa sequence; one of these was a silent mutation and the other codon change resulted in an amino acid substitution. The vip3Aa gene variant present in MIR162 maize has been designated vip3Aa20. Nucleotide sequencing additionally determined that the MIR162 maize T-DNA insert did not locate within any known Z. mays gene. Further, no novel open reading frames were created that spanned either the 5? or 3? junctions between the T-DNA and Z. mays genomic sequences. These genetic characterization data demonstrate that, apart from the well-characterized change that resulted in a single altered amino acid in the vip3Aa coding sequence, there were no unintended changes in the MIR162 maize genome as a result of the T-DNA insertion. Observations of vip3Aa20 and pmisegregation ratios over several generations of MIR162 maize were consistent with the genes being linked at a single locus in the maize genome, and indicate stable inheritance of the transgenes. These data also indicated that no novel proteins, other than Vip3Aa20 and PMI, would be produced in MIR162 maize.
The levels of expression of the Vip3Aa20 and PMI proteins in maize plants derived from event MIR162 were determined in several plant tissues and whole plants at four growth stages (V9-V12, anthesis, kernel maturity and senescence) in two field maize hybrids that were hemizygous for both transgenes. Kernels from MIR162 maize are the most likely tissue to comprise foodstuffs, either as grain or grain by-products. The average Vip3Aa20 concentration measured in kernels from MIR162 maize (43.56 ? Vip3Aa20/g dry weight at senescence) represents less than 0.004% of the total protein. The average PMI concentration measured in kernels from MIR162 maize (1.93 ? PMI/g dry weight at senescence) represents less than 0.0002% of the total protein (these calculations are based on maize grain or kernels containing 10% total protein by weight). Given the low levels of Vip3Aa20 and PMI in MIR162 kernels, dietary exposure potential can be considered minimal. Since no health hazards were identified for either the Vip3Aa20 or PMI proteins (summarized below), specific dietary exposure estimates are not necessary to support a conclusion regarding the safety of MIR162 maize.
The genetic modification resulting in transgenic maize event MIR162 was not intended to affect a specific agronomic or phenotypic characteristic except to confer resistance to certain lepidopteran insect pests. Grain yield and agronomic performance of MIR162 maize (field corn) hybrids were evaluated in a series of trials across a total of 16 locations over two years. In addition to inspections for disease and insect damage, qualitative and quantitative comparisons for a number of morphological and agronomic traits were made between MIR162 hybrids and non-transgenic control hybrids. The traits chosen for agronomic comparison were those typically observed by professional maize breeders and agronomists, covering a broad range of characteristics that encompass the entire life cycle of the maize plant. The agronomic performance and phenotypic data generated for MIR162-derived hybrids and their corresponding near isogenic non-transgenic control hybrids suggest that the genetic modification resulting in event MIR162 did not have any unintended effect on plant growth habit and general morphology, lifespan, vegetative vigour, flowering and pollination, grain yield, or disease susceptibility.
Maize has lost the ability to survive in the wild due to its long process of domestication, and needs human intervention to disseminate its seed. Although maize from the previous crop year can over-winter and germinate the following year, it cannot persist as a weed. In contrast to weedy plants, maize has a pistillate inflorescence (ear) with a cob enclosed with husks. Consequently seed dispersal of individual kernels does not occur naturally. The phenotypic comparison of event MIR162-derived hybrids and non-transgenic hybrids did not reveal any consistent biologically meaningful differences in vegetative vigour, time to maturity and seed production. These data support the conclusion that event MIR162-derived hybrids are unlikely to form feral persistent populations, or to be more invasive or weedy than conventional maize hybrids.
The intended effects of expression of the Vip3Aa20 and PMI proteins are unrelated to plant pest potential, and maize itself is not a plant pest in the United States or Canada. In addition, agronomic characteristics of MIR162-derived hybrids were not consistently significantly different than near-isogenic non-transgenic hybrids and indicated that growth habit of maize had not been unintentionally altered as a result of the genetic modification. Field observations did not indicate modifications to disease and pest susceptibilities.
An assessment of risk for nontarget organisms and endangered species that might be exposed to the Vip3Aa20 protein in MIR162 maize was performed. Extensive nontarget organism studies were performed with 12 different species representative of wild birds, wild mammals, pollinators, above ground arthropods, soil-swelling arthropods, aquatic organisms and farmed fish. No adverse effects were observed in any study that exposed representative nontarget organisms to Vip3Aa proteins. The concentration of Vip3Aa tested in the studies was sufficient to achieve margins of exposure of ? 1 for all but one species based on realistic expected environmental concentrations.
There is a weight of evidence that at concentrations in MIR162 maize, the toxicity of Vip3Aa20 will be limited to certain species of Lepidoptera. Its receptor-mediated mechanism of action and absence of activity in bioassays with multiple species outside of the order Lepidoptera support this conclusion. The comparison of hazard and exposure data corroborate the hypothesis that Vip3Aa20 is not harmful to nontarget organisms at concentrations likely to result from cultivation of MIR162, and provide a weight of evidence that Vip3Aa20 in MIR162 maize will have no harmful effects on populations of potentially exposed nontarget organisms.
The only endangered lepidopteran with potential for exposure to insecticidal proteins in maize is the Karner blue butterfly (Lycaeides melissa samuelis), which is listed as extirpated (a wildlife species that no longer exists in the wild in Canada, but exists elsewhere in the wild) in Schedule 1 of the Species at Risk Act. Even should Karner blue butterfly populations be recovered in the wild in Canada, exposure to maize pollen from MIR162 would be minimal because of the large separation between populations of its food plant (wild lupine; Lupinus perennis) and cultivated maize, and because maize anthesis usually occurs after the Karner blue has finished feeding.
Potential Impact on Biodiversity
Event MIR162 has no novel phenotypic characteristics which would extend its use beyond the current geographic range of maize production in the United States and Canada. Since maize does not out cross to wild relatives in the United States or Canada, there will be no transfer of novel traits to unmanaged environments. MIR162 maize provides excellent protection against feeding damage caused by A. ipsilon, H. zea, S. albicosta, and S. frugiperda. For this reason, its introduction will impact current maize insect control practices in a very positive way, having the potential to displace conventional insecticide applications for control of these pests. Therefore, the potential impact on biodiversity of MIR162 is equivalent to its unmodified counterparts.
Maize event MIR162 will be grown for the same uses as maize varieties currently commercially available in the United States. While maize grown in the United States is predominantly (roughly 60 percent) used to feed domestic animals, either as grain or silage, maize grain is also processed by wet or dry milling to yield food products such as high fructose corn syrup, starch, oil, grits, and flour. Non-food/feed purposes for grain include use for fuel ethanol production; however, the by-products of such industrial distilling processes may also be used in animal feeds. Maize event MIR162 is suitable for the same uses as conventional maize.
Key nutritional components in maize grain and forage derived from event MIR162 and near-isogenic non-transgenic control plants were compared. Replicate trials of transgenic and corresponding near-isogenic non-transgenic control hybrids were planted in multiple locations selected to be representative of the range of environmental conditions under which the hybrid varieties would typically be grown. Samples of grain and forage were harvested from six of these trial locations and compositional data for the MIR162 and control hybrids were subjected to analysis of variance across all locations and compared to compositional analysis data for grain and forage published in the literature and in compositional analysis databases.Among the numerous compositional analyses that were carried out, most showed no consistent statistically significant differences. Statistically significant differences were noted for levels of the proximates ash, NDF and starch; the minerals calcium, iron and phosphorus; vitamins A (b-carotene), B6 and E (a-tocopherol); linoleic and linolenic fatty acids; the secondary metabolites ferulic acid and p-coumeric acid; and the phytosterol, b-sitosterol. However, the magnitudes of the differences were small and in every case the average values (when quantifiable) were all within the ranges of natural variation as reported in the literature. Overall, no consistent patterns emerged to suggest that biologically significant changes in composition or nutritive value of the grain or forage had occurred as an unintended result of the transformation process or expression of the Vip3Aa20 or PMI proteins.The conclusion based on these data was that grain and forage from MIR162 maize were substantially equivalent in composition to both the non-transgenic control hybrid included in this study, and to other commercial maize hybrids.
The potential toxicity and allergenicity of the Vip3Aa20 and PMI proteins expressed in event MIR162 maize was evaluated by acute oral toxicity testing, digestive fate, and heat stability studies. In addition, amino acid sequence homology searches were performed against known toxins and allergens. Neither the Vip3Aa20 protein nor the PMI protein produced any adverse effects in laboratory mice challenged with a single oral dose corresponding to 1250 mg/kg body weight or 3080 mg/kg body weight, respectively. Both the Vip3Aa20 and PMI proteins were rapidly degraded following exposure to pepsincontaining simulated gastric fluid, indicating that any Vip3Aa20 or PMI protein in the diet would be readily digested as conventional dietary protein. In addition, the Vip3Aa20 and PMI proteins were both shown to lose biological (Vip3Aa20) or enzymatic (PMI) activity following incubation at 65ºC for 30 minutes. Neither the Vip3Aa20 protein nor the PMI protein shows significant amino acid sequence similarity to known or putative mammalian toxins or to allergenic protein sequences that are biologically relevant or have implications for allergenic potential. Based on this weight-of-evidence approach, it was concluded that the Vip3Aa20 and PMI proteins expressed in event MIR162 were extremely unlikely to exhibit mammalian toxicity or allergenicity.
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