Volume 89, Issue 2, February (2003), pp. 159-166 © The Author 2003
doi:10.1079/BJN2002764

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Fate of genetically modified maize DNA in the oral cavity and rumen of sheep

Paula S. Duggan¹, Philip A. Chambers¹, John Heritage¹ and J. Michael Forbes^2*
1Division of Microbiology, School of Biochemistry and Molecular Biology, University of Leeds, LS2 9JT, UK
²Centre for Animal Sciences, School of Biology, University of Leeds, Leeds LS2 9JT, UK

 (Received 17 December 2001–Revised 12 August 2002–Accepted 22 September 2002)

The polymerase chain reaction (PCR) technique was used to investigate the fate of a transgene in the rumen of sheep fed silage and maize grains from an insect-resistant maize line. A 1914-bp DNA fragment containing the entire coding region of the synthetic cryIA(b) gene was still amplifiable from rumen fluid sampled 5 h after feeding maize grains. The same target sequence, however, could not be amplified from rumen fluid sampled from sheep fed silage prepared from the genetically modified maize line. PCR amplification of a shorter (211-bp), yet still highly specific, target sequence was possible with rumen fluid sampled up to 3 and 24 h after feeding silage and maize grains, respectively. These findings indicate that intact transgenes from silage are unlikely to survive significantly in the rumen since a DNA sequence 211-bp long is very unlikely to transmit genetic information. By contrast, DNA in maize grains persists for a significant time and may, therefore, provide a source of transforming DNA in the rumen. In addition, we have examined the biological activity of plasmid DNA that had previously been exposed to the ovine oral cavity. Plasmid extracted from saliva sampled after incubation for 8 min was still capable of transforming competent Escherichia coli to kanamycin resistance, implying that DNA released from the diet within the mouth may retain sufficient biological activity for the transformation of competent oral bacteria.

Keywords:
Horizontal gene transfer: DNA survival: Insect-resistant maize: Antibiotic resistance: Transformation efficiency