The pat gene introduced is a was synthetic version which was modified to optimize its expression in plants without altering the amino acid sequence of the PAT enzyme.

Inserted DNA sequences
The pat gene is derived from the microorganism Streptomyces viridochromogenes strain Tu494, and encodes for the enzyme phosphinothricin acetyl transferase (PAT). This modifies and inactivates the herbicide glufosinate ammonium, and its presence thus confers to the plant tolerance to this herbicide. The pat gene was modified at the DNA sequence level to increase its level of expression in the plant. The modification to the DNA sequence of the gene did not result in any changes to the amino acid sequence of the PAT protein. Corn T25 contains the 35S promoter and terminator sequences derived from cauliflower mosaic virus (CaMV).  The relevant promoter sequences are form pos. 6808 -7437 and the relevant terminator sequences are from pos. 7429 -7632 of the CaMV genome sequence (Franck et al., Cell21. (1980). pp. 285-294). The 35S promoter directs high level constitutive expression and is widely used as a promoter for high expression of genes.

DNA cassette:

bla (0.86) | Ori-pUC (2.63) | P-35S (0.52) >> space (0.029) >> pat (0.53) >> space  (0.019) >> T-35S( 0.2)

Note: the symbols >> and << indicate the sense and anti-sense direction of transcription, respectively, between different elements (typically, promoter - coding sequence - terminator). If present, the symbol | indicates elements that may be cloned adjacently in a cassette but that presumably are not transcribed together. The numbers in parenthesis indicate the approximate length in Kb of each genetic element.

Information on the vector
The vector used for the production of the recombinant maize T25 is plasmid pUC/AC. To construct the plasmid, the synthetic pat gene was cloned into the Sal1, between the CaMV derived 35S gene promoter and terminator sequences of the pUC derived plasmid. The chimeric pat gene cassette (35S promoter: pat:.35S terminator) can be isolated as a 1.3 kb EcoR1 fragment.  The construct contains no other plant expressible genes. The pUC sequences include an ampicillin resistance (ampR) gene and a bacterial origin of replication.  The ampR gene has regulatory signals recognized in bacteria but not functional in transgenic corn cells.