Crop plants have also been genetically engineered for resistance to the broad spectrum herbicide, Liberty. The story is similar to Roundup Ready. A bacterial gene was discovered that encoded a protein called phosphinothricin acetyl transferase (PAT). PAT is an enzyme that controls resistance by detoxifying the Liberty herbicide molecule (glufosinate-ammonium).
Genetically engineered plants can make the PAT enzyme and breakdown Liberty before it can bind to the enzyme glutamine synthetase. This enzyme allows plants to make certain amino acids and recycle ammonium. Therefore, Liberty resistance comes from a transgene that provides an additional enzymatic function rather than a backup enzyme as with Roundup Ready. The 35S promoter has also been used in the Liberty Link transgene. Therefore, plants with this gene will have resistance to Liberty all season long in all cells.