The transgenic maize line MON801 was genetically engineered to resist ECB by producing its own insecticide. This line was developed by introducing the cry1Ab gene, isolated from the common soil bacterium Bacillus thuringiensis (Bt), into the maize cultivar Hi-II by particle acceleration (biolistic) transformation. The cry1Ab gene produces the insect control protein Cry1Ab, a delta-endotoxin.

The insecticidally active portion of the Cry1Ab protein produced by the Bt maize is identical to that found in nature and in commercial Bt spray formulations. Cry proteins, of which Cry1Ab 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. Cry1Ab is insecticidal 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 delta-endotoxins of B. thuringiensis on the surface of mammalian intestinal cells, therefore, livestock animals and humans are not susceptible to these proteins.

The nptII gene was isolated from transposon Tn5 in Klebsiella pneumonia. The nptII protein, neomycin phosphotransferase II, confers resistance to some aminoglycoside antibiotics including neomycin and kanamycin, and was used as a selectable marker for transformed plant cells.