The dominant patent holder in agrobacterium transformation, the most widely-used means of plant gene-transfer, is Monsanto, a big agricultural firm.

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Gene transfer is an age-old concern of farmers, who've learned how to prevent pollen cross-contamination when necessary for commercial reasons.

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"This discovery represents a significant advance because it avoids the need for cross-kingdom gene transfer, " he said, noting that many other scientists are working towards the total removal of selection markers.

BBC: NEWS | Science/Nature | Scientists hope to ease GM fears

They used a modified version of the HIV virus to transfer a gene for neprilysin to neurons of genetically modified mice which produced human beta-amyloid.

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