To prevent gene flow from transgenic plants, an issue that raises environmental and regulatory concerns, Moon et al. [1] have proposed the use of site-specific recombinases and zinc finger nucleases (ZFNs) for transgene excision from pollen. According to their suggestion, a transgenic construct is flanked with the recognition sites of a site-specific recombinase, and this transgenic cassette is excised upon pollen-specific expression of the recombinase. Likewise, ZFNs can be employed to delete transgenes by making two concurrent double-strand breaks (DSBs) at the 5' and 3' ends of the cassette. Although successful transgene removal using recombinases has been reported in many systems [2,3], ZFN-mediated transgene excision is an intriguing new idea. Here, we wish to emphasize the possibility of using ZFNs as new tools for DNA excision in plants and to discuss other applications of the technology.
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