Recent Evidence Confirms Risks of Horizontal Gene Transfer S/R 30: Recent Evidence Confirms Risks of Horizontal Gene Transfer (Mae-Wan Ho)
Sexually reproducing organisms pass their DNA only “vertically,” from one generation to the next.
But bacteria and viruses exchange bits of DNA “horizontally,” from one organism to another.
What happens when artificially introduced genes get transferred horizontally?
The oft-repeated refrain that “transgenic DNA is just like ordinary DNA” is false.
Transgenic DNA is in many respects optimized for horizontal gene transfer.
It is designed to cross species barriers and to jump into genomes, and it has homologies to the DNA of many species and their genetic parasites (plasmids, transposons and viruses), thereby enhancing recombination with all of them.
Transgenic constructs contain
new combinations of genes that have never existed, and they also amplify gene products that have never been part of our food chain.
The health risks of horizontal gene transfer include:
- Antibiotic resistance genes spreading to pathogenic bacteria;
- Disease-associated genes spreading and recombining to create new viruses and bacteria that cause diseases;
- Transgenic DNA inserting into human cells, triggering cancer.
The risk of cancer is highlighted by the…report that gene therapy—genetic modification of human cells—claimed its first cancer victim.
The transgenic constructs used in genetic modification are basically the same whether it is of human cells or of other animals and plants.
An aggressive promoter from a virus is often used to boost the expression of the transgene—in animal and human cells from the cytomegalovirus that infects mammalian cells, and in plants the 35S promoter from the cauliflower mosaic virus (CaMV) that infects Cruciferae plants.
Unfortunately, although the CaMV virus is specific for plants, its 35S
promoter is active in species across the living world, human cells included, as we discovered in the scientific literature dating back to 1989.
Plant geneticists who have incorporated the promoter into practically all GM crops now grown commercially are apparently unaware of this crucial information.
Research results released early in 2002 by the Food Standards Agency indicate that transgenic DNA from GM soya flour, eaten in a single hamburger and milk shake meal, was found transferred to the bacteria in the gut contents from the colostomy bags of human volunteers. 
…although the CaMV virus is specific for plants, its 35S promoter is active in species across the living world…
The Agency dismissed the findings and downplayed the risks.
The comments, “it is extremely unlikely that genes from genetically modified (GM) food can end up in bacteria in the gut of people who eat them,” and “the findings had been assessed by several Government experts who had ruled that humans were not at risk,” are seriously misleading.
Second, there was no attempt to check for transgenic DNA in the blood and blood cells,
although scientific reports dating back to the early 1990s indicated transgenic DNA could pass through the intestine and the placenta, and become incorporated into the blood cells, liver and spleen cells and cells of the foetus and newborn.
Third, no attempt was made to address the limitations of the detection method and the scope of the investigation failed completely in assessing the real risks.
False assurances were made that “humans were not at risk.”
Another research project on horizontal gene transfer commissioned by the Ministry of Agriculture, Fisheries and Food (MAFF), the predecessor to the Food Standards Agency, concerns
Agrobacterium tumefaciens, the soil bacterium that causes crown gall disease, which has been developed as a major gene transfer vector for making transgenic plants.
Foreign genes are typically spliced into T-DNA—part of a plasmid called Ti (tumour-inducing)—that’s integrated into plant genome.bh.
It turns out that Agrobacterium injects T-DNA into plant cells in a process that strongly resembles conjugation, i.e., mating between bacterial cells, and all the necessary signals and genes involved are interchangeable with those for conjugation. That means transgenic plants created by the T-DNA vector system have a ready route for horizontal gene escape, via Agrobacterium, helped by the ordinary conjugative mechanisms of many other bacteria that cause diseases.
A report submitted to MAFF in 1997 had indeed raised the possibility that
Agrobacterium tumefaciens could be a vector for gene escape.
The researchers found that it was extremely difficult to get rid of the Agrobacterium.
High rates of gene transfer are known to be associated with the plant root system and the germinating seed.
Agrobacterium could multiply and transfer transgenic DNA to other bacteria, as well as to the next crop plant.
Agrobacterium was also found to transfer genes into several types of human cells, and in a manner similar to that which it uses to transform plant cells.
All the risks of horizontal gene transfer described above are real, and far outweigh any potential benefits that GM crops can offer.
There is no case for allowing any commercial release of GM crops and food products.
The following experiments and tests should be done to address the risks of horizontal gene transfer:
1. Feeding experiments similar to those carried out by Dr. Arpad Pusztai’s team should be done, using well-characterized transgenic soya and/or maize meal feed, with full, adequate monitoring for transgenic DNA in the faeces, blood and blood cells, and post-mortem histological examinations that include tracking transfer of transgenic DNA into the genome of cells. As an added control, nontransgenic DNA from the same GM feed sample should also be monitored.
2. Feeding trials on human volunteers should be carried out using well-characterized transgenic soya and/or maize meal feed, with full, adequate monitoring for transgenic DNA in the faeces, blood and blood cells. Also as an added control, nontransgenic DNA from the same GM feed sample should also be monitored.
** I think they should use US as human volunteers...WE would PROVE it ALL!!!
3. The stability of transgenic plants in successive generations should be systematically investigated, especially for those containing CaMV 35S promoter, using adequate quantitative molecular techniques.
4. Full molecular characterization of all transgenic lines must be carried out to establish uniformity and genetic stability of the insert(s).
5. All transgenic plants created by the
Agrobacterium T-DNA vector system should be tested for the persistence of the bacteria and vectors. The soil in which they have been grown should also be monitored for gene escape to soil bacteria. And the potential for horizontal gene transfer to the next crop via the germinating seed and root system should be carefully monitored.
**How come I have this strange feeling THIS will never happen?
Kat
August 9th, 2009, 11:38 PM
b they may be eating...
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