The sugar beet line T120-7 was genetically engineered to express
tolerance to glufosinate ammonium, the active ingredient in
phosphinothricin herbicides (Basta®, Rely®, Finale®, and Liberty®).
Glufosinate ammonium 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. Phosphinothricin herbicides applied at
rates recommended for effective weed control are toxic to
conventional sugar beet varieties. The modified T120-7 line permits
growers to use phosphinothricin-containing herbicides for weed
control in the cultivation of sugar beet.
Glufosinate tolerance in T120-7 sugar beet is the result of the
introduction of the pat gene into the beet genome via
Agrobacterium-mediated transformation. The pat gene was isolated
from the common soil fungus, Streptomyces viridochromogenes, and
encodes the enzyme phosphinothricin-N-acetyltransferase (PAT). PAT
catalyses the acetylation of phosphinothricin which detoxifies it
into an inactive compound.