Herbicide Tolerant Canola

Canola  modified for glufosinate tolerance with the insertion of the phosphinothricin acetyltransferase (pat) gene from Streptomyces viridochromogenes, conferring tolerance to phosphinothricin (Glufosinate ammonium) herbicide.

pHoe4/Ac

The pat gene is a synthetic version of the gene isolated from Streptomyces viridochromogenes, strain Tü 494. The nucleotide sequence has been modified to provide codons preferred by plants without changing the amino acid sequence of the enzyme.

Southern blot analysis indicated that a single copy of the transformation cassette was integrated into the host genome with no integration of any portions of the vector backbone.

The canola line T45 was genetically engineered to express tolerance to glufosinate ammonium, the active ingredient in phosphinothricin herbicides (Basta®, Rely®, Finale®, and Liberty®). Glufosinate chemically resembles the amino acid glutamate and acts to inhibit an enzyme, called glutamine synthetase, which is involved in the synthesis of glutamine. Essentially, glufosinate acts enough like glutamate, the molecule used by glutamine synthetase to make glutamine, that it blocks the enzyme's usual activity. Glutamine synthetase is also involved in ammonia detoxification. The action of glufosinate results in reduced glutamine levels and a corresponding increase in concentrations of ammonia in plant tissues, leading to cell membrane disruption and cessation of photosynthesis resulting in plant withering and death.

Glufosinate tolerance in T45 is the result of introducing a gene encoding the enzyme phosphinothricin-N-acetyltransferase (PAT) isolated from the common aerobic soil actinomycete, Streptomyces viridochromogenes, the same organism from which glufosinate was originally isolated. The PAT enzyme catalyzes the acetylation of phosphinothricin, detoxifying it into an inactive compound. The PAT enzyme is not known to have any toxic properties. Line HCN28 was derived from T45.