UK body warns against marker genes in transgenic plants

by Chakravarthi Raghavan


Geneva, 27 July -- The UK official body looking after issues of food safety and standards appears to have questioned the use of antibiotic resistant marker genes in genetic engineering for transgenic plants and seeds.

The UK doubts and warning are in a letter from N. Tomlinson of the UK Joint Food Safety and Standards Group in the UK government's Ministry of Agriculture, Food and Fisheries (MAFF) in commenting on the United States Food and Drug Administration's (FDA) draft document, "Guidance for Industry: Use of Antibiotic Resistance Marker Genes in Transgenic Plants."

The Tomlinson letter dated 4 December 1998, citing new findings from the Leeds University, has been made public in a press release of the UK-based 'Institute of Science in Society'

The Tomlinson letter to the US FDA warns about the risks involved in the use of marker-genes (commonly used in so-called genetic engineering), due to

* Exposure of farm workers and food processors to transgenic DNA in dust and pollen;

* Transfer of antibiotic resistant marker genes to (intestinal) gut microorganisms;

* Transfer of antibiotic marker genes to environmental organisms;

* Transfer of transgenic DNA into mammalian cells; and

* Ampicillin resistance marker gene compromising treatment for meningitis.

The MAFF letter cites new findings from the University of Leeds showing "the relative difficulty with which plant DNA is degraded during processing."

The letter also mentions other new research showing that bacteria in the mouth can take up foreign DNA and express the gene(s); and transformable bacteria are also present in the respiratory tract.

MAFF warns that "there is a case to be concerned about the problem of gene transfer to environmental organisms" and that bacteria that have taken up the antibiotic resistance genes "could also act as a gene pool that may interact with human pathogens."

"The widespread use of transgenics carrying antibiotic resistance marker genes will involve a massive amplification of these genes in the biosphere. Whether or not these genes are expressed, amplification on the scale that will occur when transgenic crops are planted in large fields means that arguments about the rarity of possible transfer events will become less significant," says the MAFF letter.

MAFF cites recent publications showing that transgenic DNA may gain access into mammalian cells by being carried in pathogenic bacteria that invade cells.

The ampicillin-resistance marker gene encodes a beta-lactamase which inactivates penicillin and other penicillin-like antibiotics. This gene is highly mutable, and hence capable of extending its spectrum of resistance to many other similar antibiotics.

"Human respiratory flora contains notable potential pathogens including Neisseria meningitides and Streptococcus pneumonia. These bacteria do not currently exhibit high-level, beta- lactamase mediated resistance to penicillin."

Dr. Mae-Wan Ho, a molecular biologist and professor at the Open University of UK, is one of the scientists who have been warning of these possibilities of horizontal gene transfer to unrelated species for several years.

Commenting on the Tomlinson letter, Dr. Mae-Wan Ho says, "it is irresponsible for the Government (of UK) to continue with the massive farm-scale field trials in view of the evidence its own scientists are taking into account."

She points out that transgenic pollen can travel for miles. Not only farm workers and food processors, but the general public will also be exposed to transgenic DNA, while bees will certainly take it up and contaminate the honey. There is no provision to monitor for horizontal gene transfer or impacts on health in the current farm-scale trials.

The current farm-scale field trials involve herbicide-tolerant transgenic maize and canola. The transgenic maize carries a 'disrupted' ampicillin-resistance gene, which is not expressed. However, given the mutability of that gene, it may become re- activated in bacteria, she says. (SUNS4486)

The above article first appeared in the South-North Development Monitor (SUNS) of which Chakravarthi Raghavan is the Chief Editor.

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