Dr. Mae-Wan Ho
I obtained my B.Sc. Biology (1964) and Ph. D. Biochemistry (1967) from Hong Kong University, and was Postdoctoral Fellow in Biochemical Genetics, University of California San Diego, from 1968 to 1972. An award of a Fellowship of the US National Genetics Foundation took me to London University in the United Kingdom, where I became Senior Research Fellow in Queen Elizabeth College. I then became Lecturer in Genetics (from 1976) and Reader in Biology (from 1985) in the Open University, and since retiring in June 2000, Visiting Reader in Biology at the Open University and Visiting Professor of Biophysics in Catania University, Sicily. My career so far spanned more than 30 years in research and teaching in biochemistry, evolution, molecular genetics and biophysics, with over 200 publications including 10 books. Since 1994, I have been scientific advisor and spokesperson for the Third World Network on biotechnology, biosafety and related issues, and have produced many reports and papers on the subject for policy-makers and the general public, as well as articles for peer-reviewed scientific journals.
In 1999, I co-founded the Institute of Science in Society (ISIS) of which I am Director. I-SIS is a not-for-profit organisation promoting socially and ecologically accountable science and the integration of science in society. I-SIS also represent a group of scientists around the world (currently 364 from some 40 countries) who have co-signed a World Scientists Statement and Open Letter to All Governments, calling for a moratorium on environmental releases of GMOs on grounds that they are unsafe, and to revoke and ban patents on life-forms and living processes, on grounds that they are unethical (1).
I reiterate ISIS' written objections to placing Chardon LL on the National List which have been submitted,
Today, I want to explain why GMOs are different, how they are made, why they are inherently unreliable and unsafe, and how current regulatory processes fail to protect health and biodiversity, using Chardon LL as a case study.
One of the major shortcomings of current regulatory systems is their fragmented state, reflecting the fragmented state of the science. Those busy exploiting the technology for biomedicine are unaware of what is happening in agriculture and vice versa. Many applications are not regulated because they fall between the scopes of different directives and regulatory bodies (2,3). Regulators pay lip service to the precautionary principle which is enshrined in the International Biosafety Protocol under the UN Convention on Biological Diversity negotiated in Montreal in January 2000, and to which the UK Government is a party. In practice, however, they have been adopting the anti-precautionary approach, and confusion abounds over how scientific evidence is to be interpreted and used (4).
The creation of genetically modified organisms (GMOs) is a new departure from conventional selective breeding and introduces new hazards. This view is shared by many scientists, including those advising the United States and United Kingdom Governments (1). The techniques and the nature of artificial constructs (GM constructs) made are the same in all applications of GMOs, whether in agriculture or in biomedicine, and so are the hazards involved.
Conventional selective breeding is restricted to crossing varieties within a species or between closely related species with similar genetic makeup. That is because genetic barriers prevent reproduction between unrelated species and limit the exchange of genetic material between them.
GMOs are created in the laboratory by genetic engineering, techniques that modify the genetic material directly. The genetic material is deoxyribonucleic acid or DNA. DNA is made up of long strings of four different units, A, T, C, G repeated apparently at random for millions or billions of times. The exact sequences matter, as they code for specific proteins and enzymes that make up intricate structures of the organism and enable the organism to transform material and energy to grow, develop and do all the things that constitute being alive. The totality of all the genetic material of an organism is its genome, which is organized in a specific way typical of a species, and represented in every cell of the organism.
In making GMOs, genetic material from different sources are cut and recombined to make artificial GM-constructs that are transferred into the genomes of organisms. So, genes can be combined from widely disparate sources, and transferred between species that would never interbreed in nature. In other words, the GM-constructs are designed to overcome species barriers and to invade genomes. There is thus no limit to the new genes and new combinations of genes that can be made in the laboratory, nor to the GMOs created, all of which may never have existed in billions of years of evolution.
Most of the genes used in GM constructs originate from a wide variety of bacteria and viruses that cause diseases and other genetic parasites which spread drug and antibiotic resistance genes. A gene is never used by itself. It needs a start and a stop signal, a promoter and a terminator. The promoter-gene-terminator together form a unit GM-construct known as an 'expression cassette' which looks like this:
| promoter | gene | terminator |
Very often, the three parts of the expression cassette originate from different sources. The promoter is usually from a virus, which makes the gene over-express at very high rates continuously, to make lots of the protein or gene product. This is something that never happens in a healthy organism, and effectively puts the gene outside the normal metabolic regulation of the GM organism. The most common promoter used in plants is from the cauliflower mosaic virus (CaMV), a plant pathogen. The CaMV 35S promoter is in practically all GM crops already commercialized or undergoing field trials. The gene pat coding for resistance to the herbicide glufosinate in Chardon LL is derived from the soil bacterium, Streptomyces viridochromogenes, joined to the CaMV 35S promoter and terminator.
Apart from the expression cassette containing the gene of interest, it is necessary to have at least one other cassette containing an antibiotic resistance gene with its own promoter and terminator. This enables the genetic engineer to select for cells that have taken up the GM construct with the antibiotic, which kills off all other cells. Two or more expression cassettes are linked or stacked in series in a typical GM construct. Chardon LL has an expression cassette for AmpR, a gene coding for resistance to ampicillin, belonging to the gut bacterium, Escherichia coli, although the gene is not actively expressed in the GM plant.
For ease of handling and bulking up GM constructs, and for transferring them into genomes, genetic engineers make a large variety of artificial gene carrier or vectors (5) by combining parts of the most aggressive natural vectors, viruses, plasmids and transposons.
A virus consists of genetic material wrapped in a protein coat. It sheds its overcoat on entering a cell and can either hi-jack the cell to make many more copies of itself, or it can jump directly into the cell's genome. Plasmids are pieces of 'free', usually circular, genetic material that can be indefinitely maintained in the cell separately from the cell's genome, and replicates with the cell. Transposons, or 'jumping genes', are blocks of genetic material which have the ability to jump in and out of genomes, with or without multiplying themselves in the process. Genes hitch-hiking in genetic parasites therefore, have a greater probability of being successfully transferred into cells and genomes. Genetic parasites are vectors for gene transfer.
Natural genetic parasites are restricted by species barriers, so for example, pig viruses will infect pigs, but not human beings, and cabbage virus will not attack tomatoes. It is the protein coat of the virus that determines host specificity, which is why naked viral genomes (the genetic material stripped of the coat) have generally been found to have a wider host range than the intact virus. Similarly, the signals for propagating different plasmids (such as the 'origin of replication') and transposons are usually specific to a limited range of host species, although there are exceptions.
Artificial vectors, however, are especially designed to overcome species barriers and to invade genomes, so a vector can transfer, say, GM constructs containing human genes spliced into it, to the genomes of all other mammals, or of plants. Artificial vectors greatly enhance horizontal gene transfer, or gene transfer across species barriers.
In making GMOs, the GM construct is generally spliced into an artificial vector and vector sequences often end up in the resultant GMO, even parts of the vector that are not intended to do so. This gives rise to uncharacterized, unknown sequences that may not be safe.
Chardon LL was made by splicing the pat gene expression cassette into the artificial vector pUC18, which already contains the AmpR gene. The pUC18 vector is derived from a naturally occurring plasmid, ColE1 of E. coli, joined with a part of a transposon that contains the AmpR gene. It is maintained in high numbers of copies in the E. coli cell on account of a very active origin of replication, and hence offers a convenient way to bulk up the GM construct. Chardon LL therefore contains almost all of the pUC18 plasmid vector sequence as well as the pat gene expression cassette.
The genetic engineer cannot control or target where and in what form the GM construct becomes integrated into the genome. Each GM line is the result of one or more 'transformational' events in a single plant cell, in which the GM construct integrates into the cell's genome. An entire plant is grown from that cell, the progeny of which constitutes the GM line. Because transformation is random, each transformed cell, and hence the GM line derived from it, will be distinct, despite the fact that the same GM-construct(s) and plant cells are used.
GM constructs are also structurally unstable, and are frequently rearranged (scrambled up), deleted or repeated in part or in whole when they are integrated into the host genome. The resultant GMOs, likewise, are unstable and do not breed true, as significant genetic and epigenetic changes may occur in subsequent generations (6-8), multiplying the unpredictable risks to health and biodiversity.
Thus, unless there are good molecular genetic data documenting the genetic stability of the GM line, it is impossible to guarantee that it is stable or uniform to begin with, or that it will not change further in subsequent generations, especially with regard to properties that affect safety.
Unfortunately, regulators in Europe, Canada and the United States all appear to be unaware of this. They have not required industry to submit molecular genetic data in sufficient detail to document genetic stability, or to allow identification of the GM line unambiguously (9). Instead, they are effectively granting blanket approval for GMOs from multiple transformation events plus all progeny arising from them, variously backcrossed to non GM varieties.
Thus, the product approved under the entity, Chardon LL(Aventis - T25), is stated as 'Seeds of maize line HE/80 transformation event 25 and any progeny derived from crosses of event T25 with traditional corn varieties.' But no molecular genetic data documenting the stability or homogeneity of the seeds have been provided.
European Commission legislation actually requires that new plant varieties be tested for Distinctness, Uniformity and Stability (DUS) prior to being placed on the National List of a Member State, and prior to marketing. There is no evidence that any GM line, let alone Chardon LL, has passed this test, which requires the molecular genetic data mentioned above. Incidentally, this also invalidates patents on transgenic lines and organisms.
The GM insert in Chardon LL has almost the entire pUC18 sequence plus the pat gene cassette, but the AmpR gene had been disrupted in its promoter region. This is a sign of structural instability. Most worrying, the GM insert includes the origin of replication for the pUC18 plasmid used as a vector, which introduces its own risks (see below).
There are four special safety concerns arising from GMOs (10):
The exotic genes introduced into GM crops are mainly from bacteria and non-food species. Furthermore, the expression of these genes is often greatly amplified by strong viral promoters. In practice, that means all species interacting with the GM plants - from decomposers and earthworms in the soil to insects, small mammals, birds and human beings - will be exposed to large quantities of proteins new to their physiology. Adverse reactions may occur in all species, including immune or allergic responses. For example, Bt toxins from the soil bacterium Bacillus thuringiensis, engineered into GM crops to kill insect pests, are found to harm beneficial insects such as lacewings, and endangered species such as monarch butterflies and the black swallowtail (1). One of them, the Cry9C in Aventis' Starlink GM maize intended for animal feed, is a potential allergen for human beings, and is behind the recent massive recall of contaminated taco shells in the United States (11).
How safe is the pat gene product in Chardon LL? It originates from a soil bacterium, Streptomyces viridochromogene, which has never been part of our food chain, nor animal feed. The Streptomyces genus includes plant (12) as well as human and animal pathogens (13). One feeding trial was conducted in rats for 14 days on the extracted protein, obtained, not from Chardon LL, but from GM oil seed rape. Rats are monogastrics and have a completely different digestive system from ruminants, which have four stomachs and keep the plant material longer. Furthermore, the feeding experiment was never completed, and no histological data on the state of internal organs were ever presented. As has been argued by Dr. Arpad Pusztai and others, feeding studies must be done on young animals, as the young are more susceptible to adverse effects, and histological examinations are crucial.
The random, uncontrollable insertion of GM constructs into the host genome and interaction of exotic genes with host genes is well known to give many developmental failures and gross abnormalities in animals. In microorganisms and plants, unexpected toxins and allergens have been found. The most notorious case involved a genetically engineered batch of tryptophan that killed 37 and made 1500 seriously ill in 1989 (1).
There were no attempts to characterise Chardon LL for unintended toxins and allergens, because industry is not required to do so. The characterisations that were carried out were undiscriminating. Nevertheless, significant differences were often found between GM and non GM counterparts, but were explained away by appealing to variations in other varieties of the species under the principle of 'substantial equivalence'. In other words, Chardon LL could have the worst characteristics of all the varieties within a species, and still be considered substantially equivalent.
No feeding studies were done with GM plant material of Chardon LL, and hence its safety is unknown and unproven. Ewen and Pusztai carried out feeding studies with GM potatoes, from which they concluded that significant effects may be due to the transformation process or the GM construct, and not just the gene product itself (14). As yet, our Government have made no attempts to repeat those investigations. In the case of Chardon LL, they seem to be avoiding the issue altogether by accepting feeding data on the novel protein alone.
Safety concerns have indeed been raised over the 35S promoter from the cauliflower mosaic virus (CaMV) that is in the GM-constructs of practically all GM crops already commercialized or undergoing field trials. In a series of scientific papers (15-18), my colleagues and I point out that
These findings suggest that CaMV 35S promoter has the potential to reactivate dormant viruses, which have now been found in all genomes, plants and animals included, and to recombine with other viruses, dormant or otherwise, to create new viruses. In addition, the fact that the promoter is active in animal and human cells means that, if transferred into their genomes, it may result in over-expression of genes that are associated with cancer. There is a strong case for recalling all GM crops containing the CaMV 35S promoter from environmental release on grounds of safety.
Chardon LL does have a CaMV 35S promoter and is hence subject to all the potential hazards that it brings. In addition, it has an origin of replication for the pUC plasmid vector, plus further stretches of uncharacterized, unidenfied sequences of unknown function and safety belonging to the plasmid, as mentioned in ISIS' written objection (19). The origin of replication, claimed not to be active in plant cells, will be active in bacteria to which the GM construct is transferred. This signal enables the GM construct linked to it to be maintained in the bacteria as an independently replicating plasmid, hence enabling the GM construct to be multiplied and spread widely by horizontal gene transfer.
GM constructs can spread by ordinary cross-pollination to non GM plants of the same species or related species. The most obvious effects of cross-pollination already identified are in creating herbicide-tolerant weeds and superweeds (1). Another consequence is the spread of the novel genes and GM-constructs for over-expression, as well as the antibiotic resistance marker genes. This will multiply the unpredictable physiological impacts on the organisms to which the genes and gene-constructs are transferred, and hence on the ecosystem.
By far, the most serious consequences are from the horizontal transfer of GM constructs to unrelated species, in principle, to all species interacting with the released GMO (20) microorganisms, earthworms and arthropods in the soil, insects, birds, mammals, human beings. This is not just a theoretical possibility. There is already evidence that GM genes from GM plant material can transfer to soil bacteria and fungi. Recent experiments in 'gene therapy' have also amply documented that GM constructs, of the same form as those used in GM crops can readily invade cells and genomes of animals and human beings (21). One of the routes of 'gene therapy' is oral administration, ie, swallowing.
What is the probability of horizontal gene transfer in the gut? An important factor is whether the GM genetic material is sufficiently broken down in processed food and animal feed. The UK Government's own commissioned research has repeatedly shown that most commercial processing either left the genetic material intact or in large fragments (22, 23). The scientists advised against using GM material in animal feed (22).
In fact, government scientists have pointed out that the possibility of horizontal gene transfer starts in the mouth, which contains dangerous bacteria that can take up antibiotic resistance genes (24) and similar bacteria are present in the respiratory tract. They warn of dangers to farm workers and food processors from GM pollen and dust (25). But, of course, such dangers would apply to the general public as well. Several months ago, Prof. Hans-Hinrich Kaatz from the University of Jena in Germany, reported that GM genes have transferred via GM pollen to bacteria and yeast living in the gut of bee larvae (26). This raises the issue of the safety of GM honey.
Chardon LL's ampicillin resistance gene is reported to be non-functional because its promoter is lost. However, this gene is notorious for its ability to mutate and extend the ability of the enzyme encoded to break down new generations of b-lactam antibiotics (penicillin and chemically similar derivatives). It may regain function through mutation or recombination on being transferred horizontally, as was also pointed out by the Government's own scientific advisors (25). There is an entire class of transposons in bacteria called integrons that can take up an antibiotic resistance gene and provide it with a ready-made promoters (see ISIS' written objection, ref.19, and reviewed in ref. 27). It should also be noted that a rearrangement of the GM construct, which brings the CaMV 35S promoter next to the inactive ampicillin-resistance gene will restore gene expression. The CaMV 35S promoter is functional in bacteria.
The hazards from horizontal transfer of GM constructs such as that in Chardon LL are summarised as follows,
• New viruses that cause diseases due to recombination between viral genes and viruses in the environment. Recombinant infectious viruses have been recovered in many GM plants containing GM viral genes that are supposed to make the plants resistant to viral infections (reviewed in ref.17).
• New bacteria that cause diseases due to recombination between bacterial genes and bacteria in the environment. The existence of uncharacterized sequences from the bacterial plasmid vector in Chardon LL is particularly relevant here.
• Spread of drug and antibiotic resistance genes to bacteria, making infections much more difficult to treat. The transfer of antibiotic resistance genes from GM plant material to soil bacteria and fungi has been found both in the laboratory and in the field (20), and there is no reason to expect that Chardon LL's ampicillin resistance gene will not be transferred.
• Harmful effects, including cancer, as the result of random insertion of GM constructs into cells. This possibility is amply demonstrated in 'gene therapy' experiments where similar constructs are introduced into cells in tissue culture (21).
• Dormant viruses reactivated by the CaMV and other viral promoters. Recombinant replicating viruses routinely arise when gene therapy vectors are 'packaged' in cultured cells that contain dormant viruses (21).
• Multiplication of ecological impacts due to all the above.
There is now overwhelming evidence that horizontal gene transfer and recombination are responsible for the resurgence of drug and antibiotic resistant infectious diseases worldwide within the past 25 years (27). We have reviewed the evidence extensively and questioned whether genetic engineering, in enhancing horizontal gene transfer and recombination, may have contributed, and will continue to do so if unchecked.
The current regulatory systems do not take horizontal gene transfer into account (2,3). There is no requirement for industry to monitor and report on horizontal gene transfer. On the contrary, dangerous vectors, GM constructs and GM genetic material are either being released directly into the environment, or are being recycled as food, feed, fertilizer and landfills (2). We have repeatedly drawn attention to the dangers of horizontal gene transfer to no avail. Our Government as well as the biotech companies have been acting in violation of the precautionary principle as well as sound science (4). Governments as much as the biotech companies may well be held legally responsible for any harm from GMOs.
The version of the precautionary principle most relevant for GMOs is one stating that when there is reasonable suspicion of serious irreversible harm, lack of scientific certainty or consensus must not be used to postpone preventative action. I hold that the precautionary principle is part and parcel of sound science because science, as opposed to fundamentalist religion, is an active knowledge system. Scientific evidence is always uncertain and incomplete, and the proper role of scientific evidence, therefore is to set precaution. Dr. Peter Saunders, Professor of Applied Mathematics and co-Founder of ISIS, shows how the precautionary principle is just codified common sense that people have accepted in courts of law as much as statisticians have accepted in setting the burden of proof (4).
Society accepts with the law that a person is assumed innocent until proven guilty beyond reasonable doubt, because, so the saying goes: 'It is better that a hundred guilty men should go free than that one innocent man should be convicted.' If we seriously want to protect health and the environment, then we must acknowledge that there is already reasonable suspicion that GM technology is hazardous, and that the effects are uncontrollable and irreversible. The burden of proof, therefore, should be on industry to establish it is safe beyond reasonable doubt, particularly as there is no evidence of benefit or need (see below). Unfortunately, our regulatory systems have operated the other way round. The burden of proof is on civil society to establish it is harmful before it can be rejected.
Statisticians have actually been practising precaution by setting a 5% probability as the 'level of significance'. It means that to justify introducing something new, one should assume a 'null hypothesis' that there is no difference between the new and the old, unless the improvement observed is such that there is only a 1 in 20 chance for getting observed difference. The same goes for safety testing. One starts with the null hypothesis that there is no difference between GM and non GM. However, the failure to show that GM is significantly harmful does not mean it proves GM is safe. Many factors can contribute to this failure, including insufficient number of experiments and experiments badly designed and executed. Unfortunately, such failures have all too often been taken as evidence that GM is safe.
The scientific evidence of actual and suspected hazards arising from GM technology is sufficiently compelling for hundreds of scientists around the world to call for an immediate moratorium on further environmental releases in accordance with the precautionary principle as well as sound science (1). The scientists also demand a ban on patents on life-forms and living processes, on grounds that they amount to corporate ownership of life that destroy livelihoods, compromise food security, violate basic human rights and dignity and are contrary to public good.
Supporters of GM agriculture are still speaking of potential benefits after more than 20 years, because there has been none so far. Evidence is emerging that GM crops are agronomically as well as ecologically unsustainable. Transgene instability due to gene silencing, rearrangement and loss of GM constructs give rise to inconsistent performance in the field, yield drag and other failures (1). There is no evidence that Chardon LL will be different.
Global market for GM crops has collapsed as people all over the world are rejecting them and opting for organic sustainable agriculture. Agroecological approaches since the 1980s, which combine local farming knowledge and techniques with contemporary western scientific knowledge, have led to improved yields, as well as social, economic, health and environmental benefits for tens of millions in the developing as well as the developed world.
We should reject not only Chardon LL but the entire genetic modification approach based on a discredited, mechanistic paradigm at odds both with the scientific findings of the new genetics and with our aspiration for a safe, healthy, just and compassionate world (28).
Article first published 24/10/00
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