<p style="text-align: justify;">Maize line DLL25 was produced by biolistic transformation of maize gentoype A188xB73, a cross between two publicly available inbred lines. The original transformant was then crossed with elite inbred lines. The constitutive expression of the <i>bar</i> gene was regulated using the cauliflower mosaic virus (CaMV) 35S promoter. The <i>bar</i> gene introduced in the transformant DLL25 was modified to optimize its expression in plants without altering the amino acid sequence it encodes.</p>

<p style="text-align: justify;">The plasmid used for transformation contained the beta-lactamase encoding <i>bla</i> gene, which was included as a selectable marker to screen for bacterial colonies that had been transformed with the recombinant plasmid. The bacterial expression of beta-lactamase confers resistance to some beta-lactam antibiotics, including the moderate-spectrum penicillin and ampicillin. The <i>bla</i> gene was driven by a bacterial promoter and was therefore not functional in plants.</p>
