<p style="text-align: justify;">Corn line 98140 was genetically engineered to express the GAT4621 (glyphosate acetyltransferase) and ZM-HRA (modified version of a maize acetolactate synthase) proteins. The GAT4621 protein, encoded by the <i>gat4621</i> gene, confers tolerance to glyphosate-containing herbicides by acetylating glyphosate and thereby rendering it non-phytotoxic. The ZM-HRA protein, encoded by the <i>zm-hra</i> gene, confers tolerance to the ALS-inhibiting class of herbicides.</p>

<p style="text-align: justify;">The <i>gat4621</i> gene is based on the sequences of three <i>gat</i> genes from the common soil bacterium <i>Bacillus licheniformis</i>. <i>B. licheniformis</i> is widespread in the environment; therefore, animals and humans are regularly exposed without adverse consequences to this organism and its components, such as the glyphosate acetyltransferase (GAT) protein. GAT proteins are members of the GCN 5-related family of N-acetyltransferases (also known as the GNAT family). The GNAT superfamily is one of the largest enzyme superfamilies recognized to date with over 10,000 representatives from plants, animals and microbes. The GAT4621 protein is 75-78% identical and 90-91% similar at the amino acid level to each of the three native GAT enzymes from which it was derived. In 98140 corn, the expression of the <i>gat4621</i> gene is driven by the maize ubiquitin promoter.</p>

<p style="text-align: justify;">The ZM-HRA protein is a modified version of the maize acetolactate synthase (ALS) enzyme, which is involved in branched chain amino acid (leucine, isoleucine and valine) biosynthesis in the plastid. The herbicide tolerant <i>zm-hra</i> gene was made by isolating the herbicide sensitive maize <i>als</i> gene and introducing two specific amino acid changes known to confer herbicide tolerance to tobacco ALS. In 98140 corn, the expression of the <i>zm-hra</i> gene is driven by the maize ALS promoter.</p>

<p style="text-align: justify;">The dual herbicide tolerance of 98140 corn will enable growers to choose an optimal combination of these herbicides to best manage their individual weed populations. The availability of 98140 corn will enable growers to proactively manage weed populations while delaying adverse population shifts of troublesome weeds or the development of resistance. Herbicide tolerant 98140 corn will be marketed in the U.S. under the brand name Optimum&trade; GAT&trade;.</p>
