Gene transfer and cauliflower mosaic virus promoter 35S activity in mammalian cells

The cauliflower mosaic virus 35S promoter (CaMV35s) is extensively used in genetically modified crops for human and animal consumption. Horizontal gene transfer is attracting particular attention, in light of experimental reports, showing the presence of dietary DNA into animal tissues. Health implications may derive from possible activities of the heterologous promoter in mammalian cells after integration in the host genome. To evaluate this hypothesis, in vivo and in vitro experiments were performed using GFP as reporter gene. Recombinant plasmid DNA was fed to Balb/c mice and searched in several tissues by PCR amplification. The activity of the plant virus promoter was assessed by RT-PCR and fluorescence microscopy after liposome-mediated transfection of murine gonadic cells. Obtained data did not highlight evidences of dietary DNA transfer in mice. No CaMV35s transcriptional activity was detected in this experimental model. These findings emphasize the need for further studies and standardized methods.