<p style="text-align: justify;">Canola (<i>Brassica napus</i>) line HCN92 (synonyms: Topas19/2, Innovator) was developed through a specific genetic modification to allow the use of glufosinate ammonium, the active ingredient in phosphinothricin herbicides such as Liberty&reg;. The <i>pat</i> gene, which encodes the enzyme phosphinothricin-N-acetyltransferase (PAT) and confers tolerance to glufosinate ammonium, was isolated from the common aerobic soil actinomycete, <i>Streptomyces viridochromogenes</i> strain T&uuml; 494 and introduced into the parent canola line.</p>

<p style="text-align: justify;">The PAT enzyme was used as a selectable marker enabling identification of transformed plant cells as well as a source of field tolerance to phosphinothricin containing herbicides. Glufosinate ammounium acts by inhibiting the plant enzyme glutamine synthetase, a key enzyme 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 phosphinothricin detoxifying it into an inactive compound. The modified canola permits farmers to use phosphinothricin-containing herbicides for weed control in the cultivation of canola.</p>
