Maize line DBT418 was genetically modified to contain two novel genes, cry1Ac and bar, for insect and herbicide tolerance respectively. Both genes were introduced into a maize line by particle acceleration (biolistic) transformation.

The transgenic maize line DBT418 was developed to resist ECB by producing its own insecticide. This event was genetically engineered by introducing the cry1Ac gene, isolated from the common soil bacterium Bacillus thuringiensis (Bt), into the maize line AT824. The cry1Ac gene produces the insect control protein Cry1Ac, a delta-endotoxin. Cry proteins, of which Cry1Ac 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. Cry1Ac is lethal only when eaten by the larvae of lepidopteran insects (moths and butterflies), 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.

In addition to the cry1Ac gene, DBT418 was developed to allow for the use of glufosinate ammonium, the active ingredient in phosphinothricin herbicides (Basta®, Rely®, Liberty®, and Finale®), as a weed control option, and as a breeding tool for selecting plants containing the cry1Ac gene. DBT418 contains the bar gene isolated from a common soil actinomycete, Streptomyces hygroscopicus. This gene allows for the production of the enzyme phosphinothricin N-acetyltransferase (PAT) which confers tolerance to glufosinate.

The PAT enzyme in maize line DBT418 converts L-phosphinothricin (PPT), the active ingredient in glufosinate ammonium, to an inactive form, thereby conferring resistance to the herbicide. In the absence of PAT, application of glufosinate leads to reduced production of the amino acid glutamine and increased ammonia levels in the plant tissues, resulting in the death of the plant. The PAT enzyme is not known to have any toxic properties.

Expression of the Cry1Ac protein and PAT occurred in most, but not all, tissues of the maize plant with levels highest in leaves, and lower levels in roots, prop roots, stalk, tassel, cob, husk, and kernels. No Cry1Ac or PAT proteins were detected in silk or pollen.