GM-free Scotland

 

A. The extent
B. The potential
C. The mechanisms
D. Antibiotic resistance genes
E. References

A. Horizontal gene transfer: the EXTENT
A computer search of scientific journals between 1993-6 came up with 67 papers giving direct or indirect evidence of horizontal gene transfers. Transfers have been identified between very different bacteria, between fungi, between bacteria and protozoa (single-cell organisms), between bacteria and higher plants and animals, between fungi and between insects (1).

The recent sequencing of the entire genome of E. coli 0157 revealed that 1,387 genes (out of a total of about 5000) had been acquired by horizontal gene transfer (2). While this magnitude of foreign DNA 'absorption' may be rare, it warns us that there exist strains of microbes which possess elevated potential to incorporate foreign DNA. In the case of E. coli 0157, this potential has led to its extreme toxicity.

B. Horizontal gene transfer: the POTENTIAL
An expert court witness asked to advise on the state of our knowledge on the subject of horizontal gene transfer in July 1999 said ''Horizontal transfer of genes is now an indisputable fact'' and pointed out that many natural habitats exist which have a high potential for DNA movement, for example plant root tubers and within animal intestines (3). It has been clearly demonstrated that DNA can survive intact in the soi1 (4), during animal feed processing (5), and in the digestive system from where it can enter animal tissues (6).

C. Horizontal gene transfer: the MECHANISM
It was also stated in court evidence that ''The occurrence and mechanisms for horizontal transfer of genes have been remarkably little studied'' although many possible DNA uptake mechanisms involving both free DNA and a variety of vectors, such as viruses, were described (3).

Viruses have a proven ability to acquire genes from their hosts and to swap parts with other viruses. Aware of this, and the known similarities between viral strains, one professor of plant genetics has outlined a cascade of DNA transfers triggered by the viral DNA which is now being used almost ubiquitously to transform organisms for food production. He envisaged that the engineered viral DNA, being in an unusual and unstable form, would recombine with related viruses, such as Hepatitis B or Human Immunodifficiency Virus, to ultimately create a supervirus propagated in plants, insects and humans. In such circumstances, human survival would be marginal(7).

D. Antibiotic resistance genes
Regulatory and public attention has, so far, centred only on the genes engineered for antibiotic resistance. The UK Advisory Committee for Novel Foods and Processes has presented a rigorous argument that these genes should not be in the food chain because of the threat they pose to our ability to treat infectious disease (8).

E. References

Ho M.W., Department of Biology, UK Open University, Excerpt from a talk given at The National Council of Women of Great Britain Symposium on Food: Facts, Fallacies an; Fears, 22 March 1996, Darlington

Perna N.T. et al. (2001) Genome sequence of enterohaemorrhagic Escherichia coll 0157:H7 Nature 409 25 January 529-33

Traavik T, Professor and Scientific Director at the Norwegian Institute of Gene Ecology, Department of Virology, University of Trompe, Norway, Evidence given at the trial of 28 Greenpeace activists against AgrEvo (92 references cited), April 2000

Gebhard F. and Smalla K. (1999) Monitoring field releases of genetically modified sugar beets for persistence of transgenic plant DNA and horizontal gene transfer, FEMS Microbiology Ecology, 28(3) May 261-72

Forbes J.M. et al (1998) Effect of feed processing conditions on DNA fragmentation Final report on CS0116 to the ACNFP

Doerfler W. and Schubbert R. (1998) Uptake of foreign DNA from the environment: the gastrointestinal tract and the placenta as portals of entry. Vien Klin. Wochenschr. 110(2) 40-4

Professor Joe Cummins, Department of Plant Sciences, University of Western Ontario, London, Ontario

ACNFP Annual Report 1998, Appendix XI

This briefing paper was produced by Genetic Engineering Network Scotland using as much scientific literature as could be accessed and read. It is not exhaustive, and will be subject to on-going amendments.
The text was prepared with the non-scientific of our community in mind, and, to that purpose, our comments are intended to clarify the mplications of the scientific observations described; scientists should be able to read the literature for themselves.

We welcome comments.