Molecular aspects of gene transfer and foreign DNA acquisition in prokaryotes with regard to safety issues

Abstract

Horizontal gene transfer (HGT) is part of prokaryotic life style and a major factor in evolution. In principle, any combinations of genetic information can be explored via HGT for effects on prokaryotic fitness. HGT mechanisms including transformation, conjugation, transduction, and variations of these plus the role of mobile genetic elements are summarized with emphasis on their potential to translocate foreign DNA. Complementarily, we discuss how foreign DNA can be integrated in recipient cells through homologous recombination (HR), illegitimate recombination (IR), and combinations of both, site-specific recombination, and the reconstitution of plasmids. Integration of foreign DNA by IR is very low, and combinations of IR with HR provide intermediate levels compared to the high frequency of homologous integration. A survey of studies on potential HGT from various transgenic plants indicates very rare transfer of foreign DNA. At the same time, in prokaryotic habitats, genes introduced into transgenic plants are abundant, and natural HGT frequencies are relatively high providing a greater chance for direct transfer instead of via transgenic plants. It is concluded that potential HGT from transgenic plants to prokaryotes is not expected to influence prokaryotic evolution and to have negative effects on human or animal health and the environment.

Scientific Opinion on applications (EFSA-GMO-UK-2008-57 and EFSA-GMO-RX-MON15985) for the placing on the market of insect-resistant genetically modified cotton MON 15985 for food and feed uses, import and processing, and for the renewal of authorisation o

“…The contribution of HGT of the recombinant nptII gene to the development and proliferation of antibiotic-resistant bacteria should be seen in the context of the naturally ongoing resistance gene transfer between bacteria, which is several orders of magnitude more frequent (Brigulla and Wackernagel, 2010). The contribution of the frequency of HGT of the recombinant nptII gene must likewise be regarded relative to the natural distribution and prevalence of nptII genes on mobile genetic elements in bacteria.…”

Mutagenicity, antioxidant activity and nutritional content of long-life tomato

“…Moreover, studies carried out by Ho and Steinbrecher (1998);Brigulla et al, (2010);ElNahas et al, (2011) andOraby et al, (2015) showed that there are health risks related to the ingestion of diets containing genetically modified components, both by classic genetic engineering and transgenesis.…”

Explanatory note on DNA sequence similarity searches in the context of the assessment of horizontal gene transfer from plants to microorganisms

“…Illegitimate recombination (IR) processes in bacteria (homology-facilitated or not) have also been shown only in laboratory studies (de Vries and Wackernagel, 2002;Brigulla and Wackernagel 2010). In IR, at the most, one stretch of sequence identity intervenes (homology-facilitated IR).…”

“…Otherwise, these recombination events occur mostly within short stretches of sequence identity (microhomologies of 3-12 nucleotides). Transformation rates for IR are considered to be 10 3 (for homology-facilitated IR with about 1 kb sequence identity at one stretch of the sequence) to 10 10 -fold lower than for HR (de Vries and Wackernagel, 2002;Hülter and Wackernagel, 2008;EFSA, 2009;Brigulla and Wackernagel 2010). IR processes involving DNA from plant sources must be extremely rare, if occurring at all, and are therefore not considered to significantly increase the likelihood of HGT compared to non-GM DNA sequences from plants.…”