GM Crops and the Global Divide

Jennifer Thomson

• Publisher: CSIRO PUBLISHING
• Year: 2021
• ISBN:
  9781486312672
• Topic: Technik & Maschinenbau
• Subtopic: Agronomie

Attitudes to GM crops continue to generate tension, even though they have been grown commercially for over 20 years. Negative sentiment towards their development limits their adoption in Western countries, despite there being no evidence of harm to human health. These unfounded concerns about genetically modified crops have also inhibited uptake in many countries throughout Africa and Asia, having a major impact on agricultural productivity and preventing the widespread cultivation of potentially life-saving crops.

GM Crops and the Global Divide traces the historical importance that European attitudes to past colonial influences, aid, trade and educational involvement have had on African leaders and their people. The detrimental impact that these attitudes have on agricultural productivity and food security continues to be of growing importance, especially in light of climate change, drought and the potential rise in sea levels – the effects of which could be mitigated by the cultivation of GM and gene-edited crops.

Following on from her previous books Genes for Africa, GM Crops: The Impact and the Potential and Food for Africa, Jennifer Thomson unravels the reasons behind these negative attitudes towards GM crop production. By addressing the detrimental effects that anti-GM opinions have on nutrition security in developing countries and providing a clear account of the science to counter these attitudes, she hopes to highlight and ultimately bridge this global divide.

1

Genetically modified organisms make their entrance

I first became aware of the scientific advances that would allow researchers to genetically modify organisms in August 1974 while on honeymoon in Sweden. My PhD supervisor, David Woods, who was on sabbatical leave in Norway, had, together with his family, joined my husband and me while we were staying on an island off the coast of Stockholm. ‘This could change the way we microbiologists carry out our research’, he told me. ‘It could also revolutionise medical research with life-saving drugs being made in micro-organisms such as bacteria and yeast.’

As a result, I was not totally ignorant of this new field of research when I arrived at Harvard Medical School in Boston in September 1974 to begin my postdoctoral fellowship. The Department of Microbiology and Immunology was abuzz with the new recombinant DNA research technology that enabled scientists to cut and splice together DNA from different organisms, recombining the DNA in totally novel ways and giving them new characteristics or traits. Researchers could also use this technology to insert a gene they were interested in learning about into a bacterium to study its properties and functions.

For instance, Nagata et al. (1980) cloned a fragment of DNA from interferon-producing human white blood cells and showed that it had biological interferon activity. The word ‘clone’ simply means making an identical copy of something. In this case a fragment of DNA was inserted into a plasmid vector and introduced into the bacterium Escherichia coli. The researchers were then able to study interferon activity in E. coli, an organism much easier to work with than human white blood cells. The head of the laboratory responsible for this and further work on interferon, Charles Weismann, had already by this time, cofounded the biotechnology company, Biogen.

Another example came from the laboratory of Roy Curtiss (of whom more later). They were interested in the bacterium Streptococcus mutans, the main cause of dental caries and thus likely to be one of the most ubiquitous infectious agents worldwide. At the time, S. mutans was difficult to analyse genetically by classical methods and thus, by cloning several its genes into E. coli, the protein products could be analysed. In this way it was possible to determine the genes that are responsible for the ability of S. mutans to colonise the oral cavity and cause tooth decay (Curtiss et al. 1983).

Another early example was the cloning and characterisation of the vitellogenin structural gene of Xenopus laevis, the African clawed frog, widely used in research as a model system for humans. The most famous use of the frog was as a test for pregnancy developed by scientists at the University of Cape Town in South Africa. The test was done by injecting a frog with a woman’s urine and was widely used from the 1930s until the 1960s (Shapiro and Zwarenstein 1934). The vitellogenin protein is the main egg storage protein precursor and is important in the development of many animals that give rise to their offspring via eggs.

A further example enabled scientists to determine that the mouse gene coding for dihydrofolate reductase rendered the E. coli host cells, into which it was cloned, resistant to the drug trimethoprim, which is used mainly for the treatment of bladder infections (Chang et al. 1978). The scientist in whose Stanford University laboratory this work was carried out was Stanley Cohen, who later teamed up with Herb Boyer to form the first biotechnology company, Genentech. As with Biogen, this will be discussed later in this chapter.

And then, of course, came the cloning of genes for pharmaceutical purposes, such as human growth hormone (Goeddel et al. 1979a), human insulin (Goeddel et al. 1979b), urokinase, used to treat blood clots (Ratzkin et al. 1981), and somatostatin, which regulates several human hormones (Itakura et al. 1977). However, those applications will be dealt with in detail further in this chapter.

In retrospect, however, genetically modified organisms (GMOs) appeared on the scene in a rather dramatic way. Paul Berg, a biochemist at Stanford, was one of the first scientists to develop recombinant DNA technology, or rDNA as it soon became known. Berg’s research applied knowledge and techniques developed in the 1950s and 60s by earlier scientists. In particular, his work relied on the use of restriction enzymes, which Werner Arber had discovered in bacteria in the 1960s (Arber 1974). These enzymes provide the bacteria with a defence mechanism against invading viruses. Once the virus has injected its DNA into the bacterium, the enzymes recognise the viral DNA as foreign and cut it up in a process called restriction digestion, as it restricts the invading virus from developing. The bacteria’s own DNA is immune to this digestion because it is modified for its own protection. Restriction enzymes cut DNA, using specific recognition sequences, leaving overhanging single strands, enabling them to ‘stick together’. Hence these became known as ‘sticky ends’.

These techniques were so fundamentally important for rDNA technology that Werner Arber and Paul Berg both won Nobel Prizes for their work: Arber received the Nobel Prize in Physiology or Medicine in 1978, together with Hamilton Smith and David Nathan, and Paul Berg shared the 1980 Nobel Prize in Chemistry with Walter Gilbert and Frederick Sanger.

What Paul Berg did that was so innovative was to use a specific restriction enzyme to cut the SV40 DNA into pieces and then use the same restriction enzyme to cut DNA from a bacterial virus, or bacteriophage, (from the Greek phago, meaning eating or devouring) called lambda, resulting in the lambda carrying various pieces of SV40 DNA. The final step involved placing the mutant genetic material into a laboratory strain of the E. coli bacterium. Because the bacteriophage transfers the inserted DNA into another bacterium, it is called a ‘vector’, which is the agent used to introduce genes into another organism. This last step, however, was not completed in the original experiment due to the pleas of several fellow investigators who feared the biohazards associated with it.

The SV40 virus is known to cause cancer tumours in mice. Additionally, the E. coli bacterium (although not the strain used by Berg) inhabits the human intestinal tract. For these reasons, the other investigators feared that the final step would create cloned SV40 DNA that might escape into the environment and infect laboratory workers, who might then become cancer victims. These concerns led several leading scientists to send a letter to the President of the National Academy of Sciences (NAS) in which they requested the appointment of an ad hoc committee to study the biosafety implications of this new technology. This committee held a meeting late in 1974 that resolved that scientists should halt experiments involving rDNA until a conference was held to debate these issues.

After this meeting, members sent a letter to Science, which became famous as the ‘Berg Letter’ (Berg et al. 1974). In it they wrote:

There is a serious concern that some of these artificial recombinant DNA molecules could prove biologically hazardous … First, and most important, that until the potential hazards of such recombinant DNA molecules have been better evaluated or until adequate methods are developed for preventing their spread, scientists throughout the world join with the members of this committee in voluntarily deferring the following types of experiments.

They then went on to list these types of experiments, including the introduction of antibiotic resistance or toxin formation, as well as linkage with any potentially oncogenic viruses. They followed this with the caveat:

The above recommendations are made with the realization that our concern is based on judgments of potential rather than demonstrated risk since there are few available experimental data on the hazards of such DNA molecules.

As requested by the NAS committee, the Asilomar Conference on Recombinant DNA was duly convened in February 1975 with the aim of discussing the potential biohazards and regulation of this technology. About 140 professionals, including biologists, lawyers and physicians, participated and drew up a voluntary set of guidelines to ensure the safety of rDNA. The conference also placed scientific research more into the public domain and saw the first application of the precautionary principle to this technology. This heralded a turning point, both for good and bad, of biotechnology, the effects of which are felt to this day.

The precautionary principle defines actions on issues considered to be uncertain. The principle is used by policy makers to justify discretionary decisions in situations where there is the possibility of harm from making a certain decision when extensive scientific knowledge on the matter is lacking. The principle implies that there is a social responsibility to protect the public from exposure to harm, when scientific investigation has found a plausible risk.

During the conference, the principles guiding the recommendations for how to conduct experiments using this technology safely were established. The first principle was that physical and biological containment should be made an essential consideration in the experimental design. However, the second principle, which has been largely overlooked in many cases, was that the effectiveness of the containment should match the estimated risk as closely as possible.

In a paper entitled ‘Personal reflections on the origins and emergence of recombinant DNA technology’ (Berg and Mertz 2010), Paul Berg reflects on the guidelines implemented as an outcome of the Asilomar conference:

In the summer of 1976, the National Institutes of Health issued its first set of Guidelines for Research Involving Recombinant DNA. These guidelines and analogous ones from other international jurisdictions along with their updates have been adhered to throughout the world. In the over three decades since adoption of these various regulations for conducting recombinant DNA research, many millions of experiments have been performed without reported incident. No documented hazard to public health has ever been attributable to the applications of recombinant DNA technology. Moreover, the concern that moving DNA among species would breach customary breeding barriers with profound effects on natural evolutionary processes has substantially diminished as research has revealed such exchanges occur in nature as well.

The National Institutes of Health (NIH) guidelines, initially for research funded by the NIH but subsequently extended to cover any research supported by federal funds in the USA, required that different levels of containment be used according to the estimated level of danger. The containment was of two types. The first was biological containment, which depends on the use of weakened strains of the host organisms so that if they were to escape the laboratory they would have difficulty surviving. The second is physical containment, which involves the establishment of four levels of security, including laboratory procedures and, in the case of levels 3 and 4, specialised construction requirements.

Unfortunately, the Asilomar conference and the subsequent NIH guidelines, far from reassuring the public regarding this new technology, resulted in an overwhelming fear of its potential dangers. The media were full of stories of evil-intentioned scientists creating toxin-producing ‘superbugs’ that could escape from the laboratories in the dead of night, invade the city’s drinking water and kill the unsuspecting citizens. In April 1977, Time magazine highlighted the issue as its cover story, with a picture showing an evil-looking scientist peering ominously into a test tube containing a pink fluid. This was meant to show that the DNA in the test tube had been mixed with phenol, which is used to extract DNA from bacterial cells. Unfortunately for Time, phenol is only pink when it carries impurities that result in the disintegration of DNA. The experiment depicted in this picture would not have worked!

To try to counter these negative attitudes, many of Harvard’s senior scientists took to the weekly Saturday marketplace in the town square with models of DNA trying to explain the benefits of rDNA. But the mayor of Cambridge, where the main Harvard campus is located, Alfred Vellucci, banned all work on rDNA in his city, which led to several scientists leaving Harvard to work at universities where such restrictions did not exist.

One of the major concerns expressed by the public, and reflected in the media at the time, was that genetically engineered bacteria could infect humans and cause illness or even death. To counter these fears, some scientists set about determining the fitness of bacteria carrying foreign genes. Many were of the opinion that, as the genomes of bacteria are small, and their genes appeared to be efficiently compact, extra DNA could prove to be a burden and decrease the competitiveness of such bacteria outside the laboratory. As mentioned earlier, if an E. coli bacterium expressing a toxin gene from a snake or a scorpion were released into the environment, could it replicate and kill any humans who encountered or swallowed it?

One such scientist was Mark Richmond, Professor of Bacteriology at the University of Bristol, who worked on antibiotic resistance. In an article published with colleagues in Nature in 1976 (Hartley et al. 1976), he wrote, ‘Escherichia coli K12 is frequently used in genetic engineering experiments. In order to a...