<p style="text-align: justify;">Sugar beet line T120-7 was developed using recombinant DNA techniques to allow for the use of glufosinate ammonium, the active ingredient in phosphinothricin herbicides (Basta&reg;, Ignite&reg;, Rely&reg;, Liberty&reg;, Harvest&reg;, and Finale&reg;) as a weed control option. This line was genetically engineered to express a new enzyme, phosphinothricin-N-acetyltransferase (PAT), derived from the common aerobic soil actinomycete, <i>Streptomyces viridochromogenes</i>.</p>

<p style="text-align: justify;">Glufosinate is a short name for the ammonium salt, glufosinate-ammonium. It is a broad-spectrum contact herbicide and is used to control a wide range of weeds after the crop emerges or for total vegetation control on land not used for cultivation. Glufosinate is a natural compound isolated from two species of Streptomyces fungi. It inhibits the activity of an enzyme, glutamine synthetase, which is necessary for the production of glutamine and for ammonia detoxification. The application of glufosinate leads to reduced glutamine and increased ammonia levels in the plant tissues. This causes photosynthesis to stop and the plant dies within a few days. Glufosinate also inhibits the same enzyme in animals. It is highly biodegradable, has no residual activity, and very low toxicity for humans and wild fauna.</p>

<p style="text-align: justify;">The PAT enzyme detoxifies phosphinothricin via acetylation into an inactive compound. An antibiotic resistance marker gene (<i>neo</i>) encoding the enzyme neomycin phosphotransferase II (NPTII), which inactivates aminoglycoside antibiotics such as kanamycin and neomycin, was also introduced into the genome of line T120-7. This gene was derived from a bacterial transposon (Tn5 transposable element from <i>Escherichia coli</i>) and was included as a selectable marker to identify transformed plants during tissue culture regeneration and multiplication. The expression of the <i>neo</i> gene in these plants has no agronomic significance and the safety of the NPTII enzyme as a food additive was evaluated by the United States Food and Drug Administration in 1994 (US FDA, 1994).</p>
