<p style="text-align: justify;">These transgenic maize lines were produced using a microparticle bombardment (biolistic) technique to introduce the genes of interest, followed by plant regeneration in tissue culture on glufosinate-containing medium to select transformed plants. The plasmid DNA, PHP6710, used in the transformation contained three genes: (1) DNA adenine methylase encoding <i>dam</i> gene; (2) the <i>pat</i> gene from <i>S. viridochromogenes</i>; and the beta-lactamase encoding <i>bla</i> gene, which conferred resistance to the antibiotic ampicillin and was used to select bacterial colonies transformed with plasmid DNA.</p>

<p style="text-align: justify;">Tissue-specific expression of the <i>dam</i> gene was accomplished by including sequences from the maize anther-specific 512del promoter, and constitutive expression of the <i>pat</i> gene was regulated using the cauliflower mosaic virus (CaMV) 35S promoter.</p>

<p style="text-align: justify;">Prior to biolistic transformation, PHP6710 plasmid DNA was subjected to restriction enzyme digestion to isolate a 4.5 kb DNA fragment containing the <i>dam</i> and <i>pat</i> genes, but not the <i>bla</i> gene. It was this DNA fragment, not the entire plasmid, that was used for the transformation procedure.</p>
