<p style="text-align: justify;">Maize line MON802 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 MON802, 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 gut paralysis and eventual death due to bacterial sepsis. 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;">In addition, two novel genes were introduced into maize line MON802, which in combination provide field level tolerance to glyphosate the active ingredient in Roundup&reg; herbicide. The novel plants express a glyphosate tolerant version of the enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) encoding gene isolated from <i>Agrobacterium tumefaciens</i> strain CP4 (CP4 EPSPS). Glyphosate specifically binds to and inactivates EPSPS, which is involved in the biosythesis of the aromatic amino acids tyrosine, phenylalanine and tryptophan. The EPSPS enzyme is present in all plants, bacteria and fungi, but not in animals, which do not synthesize their own aromatic amino acids. The modified enzyme (CP4 EPSPS) has a reduced binding affinity for glyphosate and allows the plant to function normally in the presence of the herbicide.</p>

<p style="text-align: justify;">The second gene codes for glyphosate oxidase (<i>gox</i> gene), a bacterial enzyme from <i>Ochrobactrum anthropi</i> and is ubiquitous in nature. Glyphosate oxidase (GOX) accelerates the normal degradation of glyphosate into aminomethylphosphonic acid (AMPA) and glyoxylate. AMPA is the principal metabolite of glyphosate and is degraded by several microorganisms while glyoxylate is commonly found in plant cells and is broken down by the glyoxylic pathway for lipid metabolism.</p>
