Fate of transgenic plant DNA in the environment

Abstract

This review addresses the possible ecological effects of transgenic plants on micro-organisms in the field, hence, in the phytosphere and in the soil matrix. The important steps involved in the interaction between plant DNA and bacteria and the factors that influence the horizontal gene transfer (HGT) process will be discussed. HGT is a process in which two partners are involved, even if indirectly. In the first section, aspects concerning bacteria, such as their physico-chemical, biological and genetic characteristics, are described. Parameters affecting transgenic DNA fate in the environment are described in the second section. Subsequently, terrestrial habitats are evaluated in terms of their capacity to favor horizontal gene transfer. Finally, we focused on several studies in order to evaluate possible perturbations of soil bacterial community composition due to cultivation of transgenic plants in the field.

Risks from GMOs due to Horizontal Gene Transfer

“…Although cultivation-based selection systems underestimate the HGT frequencies (Rizzi et al, 2008), experimental and laboratory studies also suggest limited circumstances that support the transfer and persistence of DNA from plants to bacteria . The only genes from GM plants that are likely to be successfully transferred to bacteria are other bacterial genes, including antibiotic resistance genes used in the transformation process (Pontiroli et al, 2007).…”

“…More recently, concerns have been raised that HGT from genetically modified organisms (GMOs) could have adverse effects (Pontiroli et al, 2007). HGT of an introduced gene in a GMO may confer a novel trait in another organism, which could be a source of potential harm to the health of people or the environment.…”

Soil persistence of DNA from transgenic poplar

“…Recombinant DNA released by genetically modified (GM) plants in the soil environment could enhance the frequency of horizontal gene transfer (HGT) from plants to soil microorganisms, causing the undesired spread of transgenes Pontiroli et al, 2007). In recent work, HGT events involving bulk and rhizosphere soil bacteria exposed to recombinant DNA were detected at extremely low frequency (Keese, 2008) while the absence of transformable bacteria in rhizosphere-and soilassociated communities suggests that natural transformation represents a rare event (Richter and Smalla, 2007;Van Overbeek et al, 2007).…”

“…To date, most of the studies concerning DNA persistence in soil have been carried out using GM annual plants (Pontiroli et al, 2007). Notwithstanding the fact that the exposure of soil-borne microorganisms to the GM material is also dependent on the life-span of the plant, information on forest tree species on this topic is still scanty.…”

“…Finally, it is worth noting that information concerning the fate of recombinant DNA in soil can be acquired on different scales, and microcosms that mimic the conditions of agricultural soils have been used to monitor DNA persistence and degradation (Lilley et al, 2003;Pontiroli et al, 2007). In the present work, microcosm experiments were carried out with loamy sand in order to investigate the effect of DNA purity and temperature on the fate of the 35SCaMV-bar, 35SCaMV-StSy and NosP-nptII sequences.…”