T-DNA integration patterns in transgenic maize lines mediated by Agrobacterium tumefaciens

To explore transfer deoxyribonucleic acid (T-DNA) integration patterns in the maize genome, we improved the protocol of thermal asymmetric interlaced polymerase chain reaction (TAIL-PCR), and amplified the flanking sequences around T-DNA integration sites from 70 independent transgenic maize lines mediated by Agrobacterium tumefaciens. Out of 64 specific amplified fragments, 32 and 9 are homologous to the sequences of the maize genome and the expression plasmid, respectively. For 26 of them, a filler sequence was found flanking the cleavage sites. These results demonstrate that cleavage occurs not only during the T-DNA borders but also inside or outside the borders. The border sequences and some inside sequences can be deleted, and filler sequences can be inserted. Illegitimate recombination is a major pattern of T-DNA integration, while some hot spots and preference are present on maize chromosomes.Key words: Agrobacterium tumefaciens, maize, thermal asymmetric interlaced PCR, transfer DNA,transgenics