<p style="text-align: justify;">Canola (<i>Brassica napus</i>) line GT73 (synonym RT73) was developed to allow the use of glyphosate, the active ingredient in the herbicide Roundup&reg;, as a weed control option in canola crops. Two novel genes were introduced into canola line GT73, which in combination provide field level tolerance to glyphosate. 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 biosynthesis 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 a modified version of glyphosate oxidase, a bacterial enzyme from <i>Ochrobactrum anthropi</i> strain LBAA. The gene was modified to improve the affinity of the enzyme for glyphosate and is referred to as the <i>gox</i> variant (<i>goxv247</i>). Glyphosate oxidase (GOX) accelerates the normal degradation of the herbicide 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>

<p style="text-align: justify;">These two enzymes, CP4 EPSPS and glyphosate oxidase, allow GT73 canola to be protected against herbicide damage when glyphosate is used for weed control in the cultivation of canola.</p>
