U.K . BODY WARNS AGAINST MARKER GENES IN TRANSGENIC PLANTS

The UK Joint Food Safety and Standards Group, which comes under the UK Government's Ministry of Agriculture, Food and Fisheries, has warned of the risks involved in the use of antibiotic-resistant marker genes in transgenic plants and seeds in genetic engineering.

By Chakravarthi Raghavan

August 1999

Geneva: The UK official body looking after issues of food safety and standards appears to have questioned the use of antibiotic-resistant marker genes [a marker gene is a gene that is used to track the presence or absence or other genes on the same piece of DNA transferred into a cell] 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 (FDA)'s 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-resistant 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.

The 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.

The 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 high 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 the 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 Ho says, 'It is irresponsible for the Government (of the 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 reactivated in bacteria, she says. - Third World Network Features

About the writer: Chakravarthi Raghavan is Chief Editor of SUNS (South-North Development Monitor), a daily bulletin, and Third World Network's representative in Geneva.

1933/99