More and more evidence of 'horizontal gene transfer'
It is not the first time that researchers find bacterial, fungal or viral DNA in the genome of plants or animals. High throughput genome analyses in recent years find more and more examples of possible "horizontal gene transfers." In a horizontal gene transfer there is exchange of genes between different species -- in contrast to normal gene transfer from parents to progeny which occurs within one species.
Finding similar sequences is not a full proof that they are the result of horizontal gene transfer, but in the case of sweet potato there are strong indications that this has happened. Indeed, Agrobacterium is specialized to transfer a part of its own DNA, the so-called T-DNA, to plants. And it is this T-DNA that has been found in sweet potato.
Natural GMO's
The mechanism that Agrobacterium uses to incorporate its own T-DNA in the genetic material of plants forms the basis of the GMO technology. While Agrobacterium traditionally introduces its T-DNA only in a few plant cells, biotechnologist have succeeded to regenerate plants from these cells. The finding of T-DNAs in sweet potato now reveals that this extra step has also occurred in nature thousands of years ago. Prof. Lieve Gheysen, one of the researchers involved: "The natural presence of Agrobacterium T-DNA in sweet potato and its stable inheritance during evolution is a beautiful example of the possibility of DNA exchange across species barriers. It demonstrates that genetic modification also happens in nature. In comparison to "natural" GMOs, that are beyond our control, human-made GMOs have the advantage that we know exactly which characteristic we add to the plant."
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