<p style="text-align: justify;">Maize line Bt11 was developed through a specific genetic modification to be resistant to attack by European corn borer (ECB; <i>Ostrinia nubilalis</i>), a major insect pest of maize in agriculture. The novel variety produced the insecticidal protein, Cry1Ab, derived from <i>Bacillus thuringiensis</i> subsp. kurstaki (B.t.k.) HD-1 strain. Delta-endotoxins, such as the Cry1Ab protein expressed in Bt11, act by selectively binding to specific sites localized on the brush border midgut epithelium of susceptible insect species. Following binding, cation-specific pores are formed that disrupt midgut ion flow and thereby cause paralysis and death. Cry1Ab is insecticidal only to lepidopteran insects, 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 <i>B. thuringiensis</i> on the surface of mammalian intestinal cells, therefore, livestock animals and humans are not susceptible to these proteins.</p>

<p style="text-align: justify;">Bt11 was also genetically modified to express the <i>pat</i> gene cloned from the common aerobic soil actinomycete, <i>Streptomyces viridochromogenes</i> strain Tu494, which encodes a phosphinothricin-N-acetyltransferase (PAT) enzyme. The PAT enzyme was used as a selectable marker enabling identification of transformed plant cells as well as a source of resistance to the herbicide phosphinothricin (also known as glufosinate ammonium, the active ingredient in the herbicides Basta, Rely, Finale, and Liberty). Glufosinate ammounium acts by inhibiting the plant enzyme glutamine synthetase, the only enzyme in plants that detoxifies ammonia by incorporating it into glutamine. Inhibition of this enzyme leads to an accumulation of ammonia in the plant tissues, which kills the plant within hours of application. PAT catalyses the acetylation of the herbicide phosphinothricin and thus detoxifies glufosinate ammonium into an inactive compound. The modified maize line is protected from ECB and permits farmers to use phosphinothricin-containing herbicides for weed control in the cultivation of maize.</p>
