So far no evidence under natural conditions
When genetic material from one organism is passed on to another directly, outside the sexual reproduction route, this process is called horizontal gene transfer . Can transgenes from genetically modified plants be absorbed by micro-organisms and spread in this way? And if so, what are the consequences?
Since the first release of transgenic petunias in Germany at the start of the 1990s, safety research projects have been dealing with this topic. Under optimised conditions in the laboratory, horizontal transfer was demonstrated for the first time in 1998, but no evidence of it has so far been found under natural conditions.
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Research projects: results at a glanceTopic: What is the risk of horizontal gene transfer between transgenic apple trees and bacteria living in the plant? Result: No horizontal gene transfer of transgenic DNA from apple trees to bacteria living in the plant (endophytic bacteria) was detected.
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Topic: A special soil bacterium, Agrobacterium tumefaciens, is used as a ‘gene ferry’ to insert new genes into plant cells. The desired foreign gene is inserted into the bacterium’s plasmid. Is it possible that the genetically modified Agrobacteria transfer their genetic information to the bacteria living in the plant (endophytic bacteria) as well as to the plant itself? Result: Horizontal gene transfer of the plasmid DNA from Agrobacteria to endophytic bacteria was detected only in vitro and even then only when the gene transfer had been triggered specifically by an external plasmid from the bacterial community.
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Topic: Does gene transfer from rapeseed pollen to micro-organisms take place in the digestive tract of bees? Result: No transfer of herbicide- (glufosinate ) resistance genes from the pollen of GM oilseed rape to intestinal bacteria was found in field conditions, making it a very improbable event. More than a third of all intestinal bacteria were naturally resistant to glufosinate in any case.
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Topic: When cattle are fed on Bt maize, can transgenic DNA transfer to micro-organisms in the cow's digestive tract? Result: No horizontal gene transfer was detected between plant DNA and bacteria in the cow.
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Topic: Trees live in mutual symbiosis with soil fungi. Research has been conducted to investigate whether transgenic DNA can transfer from transgenic poplars to rhizosphere fungi. Result (1): No evidence was found of any transfer of the herbicide-resistance gene from poplars to their fungal partners in field conditions. A total of 100,000 ectomycorrhizas were investigated for possible horizontal gene transfer. Result (2): No gene transfer was observed between aspen and the mycorrhizal fungus A.muscaria under optimised laboratory conditions.
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Topic: The biological safety research project into T4 lysozyme potatoes, which produce an antibacterial substance, also looked at the possibility of horizontal gene transfer from transgenic DNA to soil bacteria. Result: Gene transfer was detected under optimised conditions in the laboratory. Specially constructed recipient bacteria were able to take up and integrate the transgenic DNA. Naturally occurring bacteria, however, were not able to do this.
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Topic: Release of DNA from transgenic sugar beet and horizontal gene transfer in the soil Result (1): Transgene DNA was Result (2): Gene transfer was demonstrated for the first time under optimised conditions in the laboratory.
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Topic: In the nineties, genetically modified bacteria, in this case nodule bacteria (rhizobia), were field tested for the first time in Germany. Can gene transfer occur between different rhizobial strains or between rhizobia and other bacteria? Result (1): No transfer of genes to the rhizobia was detected. Result (2): Gene transfer between strains within the root nodules was detected only when the foreign gene was on a plasmid rather than in the chromosome Result (3): Whether or not gene transfer from a plasmid was possible depended on the strain within the species. There was no gene transfer to bacteria of other genera.
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Topic: The first trials to investigate horizontal gene transfer took place in the early nineties. What is the probability of gene transfer taking place between transgenic plants and soil bacteria or fungi under natural conditions? This investigation focussed in particular on the antibiotic resistance genes used as a marker gene. Result (1): No gene transfer was observed under optimised laboratory conditions. Result (2): Horizontal gene transfer to a soil fungus was initially suspected but no firm evidence was found. |
More from GMO Safety
- Do bacteria absorb plant genes: current knowledge.
- Antibiotic-resistance markers: Once necessary, now undesirable
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