<p style="text-align: justify;">The T14 and T25 lines were derived by chemically mediated transformation of cultured protoplasts obtained from a yellow dent corn line with purified DNA containing the <i>pat</i> gene isolated from <i>S. viridochromogenes</i>. Transformed cell colonies were selected and regenerated on medium containing glufosinate ammonium. The primary transformants, T14 and T25, were then backcrossed with both commercial public inbred lines and proprietary inbred lines of the yellow dent corn type.</p>

<p style="text-align: justify;">The <i>pat</i> gene introduced in the transformants T14 and T25 was modified to optimize its expression in plants without altering the amino acid sequence of the PAT enzyme.</p>

<p style="text-align: justify;">The transformed lines T14 and T25 also contained the beta lactamase (<i>bla</i>) gene included as a selectable marker to identify transformed bacterial cell colonies during the initial stages of cloning the recombinant <i>pat</i> gene. The <i>bla</i> gene codes for a beta-lactamase enzyme that confers resistance to some beta-lactam antibiotics, including the moderate-spectrum penicillin and ampicillin antibiotics. The <i>bla</i> gene is not functional in the modified maize lines, as its promoter is only active in bacteria.</p>
