Horizontal gene transfer in plants, a biohazard? Outcome of a literature review

Abstract

Presented here is an assessment on the putative biohazard of spontaneous horizontal gene transfer (HGT) in plants. Suggestions for spontaneous HGT between sexually incompatible plant species and between plants and microorganisms are numerous. The novel argument is sequence homology, but this argument is known to be invalid or at least inadequate. Only one case was found for HGT from a bacterium to a plant. This most probably took place in the evolutionary past. None of the supposed HGT cases brought forward up to the end of 1992 include the description of a mechanism by which a DNA fragment is detached from one genome, passed at least one membrane, and is inserted into another plant genome. Spontaneous HGT to plants with subsequent vertical (trans) gene transfer through normal seed set cannot be totally excluded, however, the literature up to 1993 does not provide any scientifically valid indication that such an HGT should be considered as a realistic biohazard.