Liberator™ canola

The rapeseed line pHoe6/Ac was genetically engineered to express tolerance to glufosinate ammonium, the active ingredient in phosphinothricin herbicides (Basta®, Rely®, Finale®, and Liberty®).

Glufosinate tolerance in pHoe6/Ac rapeseed is the result of introducing a synthetic copy of the 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.

pHoe6/Ac

Canola with tolerance to the herbicide phosphinothricin (Glufosinate ammonium) conferred through insertion of a copy of the phosphinothricin acetyltransferase (pat) gene from the aerobic actinomycete Streptomyces viridochromogenes. Since the native pat gene has a high G:C content, which is atypical for plants, a modified nucleotide sequence was synthesised using codons preferred by plants. The amino acid sequence remains unchanged.

DNA-based methods:
DNA-based methods available include PCR and Southern-Blot methodology. They allow detection and identification of the event Liberator pHoe6/Ac through detection of nucleotide sequences that are specific to these events.
Protein-based methods:
Protein-based methods available include quantitative methods (e.g. specific PAT protein ELISA test) or qualitative methods (e.g. Trait LL Leaf Test kit) based on the specific interaction between antibodies and the PAT protein produced by the introduced gene. They allow detection and identification of glufosinate-ammonium herbicide tolerance trait through detection of the PAT protein in the product. Protein-based methodology offers an easier-to-use alternative to DNA-based methodology.

In addition to these methods, control samples of the product genetic material are available.

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.