<p style="text-align: justify;">The Bt-maize Event 176 (tradenames NaturGard&trade; KnockOut&trade;) 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. These novel plants produce a truncated version of the insecticidal protein, Cry1Ab, derived from <i>Bacillus thuringiensis</i> subp. kurstaki strain HD-1. Event 176 is also genetically modified to express the <i>bar</i> gene cloned from the soil bacterium <i>Streptomyces hygroscopicus</i>, which encodes a phosphinothricin-N-acetyltransferase (PAT) enzyme. The PAT enzyme is useful 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 ). PAT catalyses the acetylation of phosphinothricin, and thus detoxifies phosphinothricin, eliminating its herbicidal activity. Delta-endotoxins, such as the Cry1Ab protein expressed in Event 176, 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>
