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Sent: 19 June 2002 09:59
To: '[email protected]'
Subject: 57: Re: Evolutionary risks of transgenes
Professor Muir again, in response to Wayne Knibb (message 51, June 18) and in support of Glenn Ashton (message 55, June 17).
Glenn is quite correct to question if Knibb's comments are serious or facetious. Wayne would have us believe that if risks of a technology are no greater than those found in nature we should allow those risks. This argument is flawed at several levels. At the most base level, for example, it is the fact that natural phenomenon, such as radon (a radioactive gas released from some rocky materials upon which some houses are built), causes cancer and kills thousands of people each year. Should we then allow manufacture of household products with radioactive materials in them as long as the risk of dying from those products is no greater than those found in nature, i.e. kills no more than a few thousand a year? This notion is clearly unacceptable.
Taking this analogy to ecological harm, it is true that natural mutations do occur which result in evolutionary divergence, the formation of new species, and elimination of others. This is a fact of evolution and is how it works. It also requires evolutionary time in millions of years for other species to adapt to these changes (disruptions) and that these disruptions do not occur too frequently, i.e. are rare. However, the creation of new mutations by man (transgenes) that result in formation of new species and elimination of others is clearly unacceptable, we do not have evolutionary time to adjust to the changes that we can bring upon ourselves through such actions. We can also bring about more changes too rapidly for any ecosystem to adapt to.
Secondly, extrapolation of natural mutation rates with associated environmental harms to engineered mutations and possible associated harms is not scientifically valid for a number of reasons. Firstly, natural mutations are primarily the result of single base changes and explore only a small subset of possibilities around a local fitness surface, they are entirely random, and the vast majority are lethal or reduce fitness. Engineered mutations, on the other hand, are the result of directed evolution by supposed intelligent beings, not at random, and the purpose of the engineered gene is to confer some advantage, or it would not have been developed or commercialized. For example, ask yourself, how long would it take for a natural mutation to occur for spider silk production in goats milk? [this reference is to the ongoing project of developing commercial quantities of spider silk from transgenic goats - see e.g. Alan Dove. "Milking the genome for profit", Nature Biotechnology (2000), 18, 1045-1048...Moderator]. This may not be a speciation event, but it is clearly an event impossible with natural mutations.
Secondly, with gene breeding (random exon shuffling) entire chromosome segments across species can be recombined in ways not possible with natural mutations. In this way, the global fitness surface can be explored with engineered mutations. The result could be an organism that is shifted to a new higher fitness peak thus initiating a speciation event, an event with unpredictable harm and one we should not be allowed to do. See Muir and Howard (2001) for more detailed criticisms on these and other issues raised by Knibb (1997). [An exon is a segment of a eukaryotic gene that is transcribed as part of the primary transcript and is retained, after processing, with other exons to form a functional mRNA molecule. Many eukaryotic genes are composed of a mosaic of exons and introns...Moderator].
Professor of Genetics
Department of Animal Sciences
W. Lafayette, IN 47907-1151
e-mail: bmuir (at) purdue.edu
Muir, W.M. and R.D. Howard. 2001. Methods to Assess Ecological Risks of Transgenic Fish Releases. In Genetically Engineered Organisms: Assessing Environmental and Human Health Effects Eds. D.K. Letourneau and B. E. Burrows. CRC Press p 355-38
Sent: 19 June 2002 11:55
To: '[email protected]'
Subject: 58: Re: Evolutionary risks of transgenes
This is from Andrzej Aniol. I have a PhD in plant physiology and am Department Head, Plant Biochemistry and Physiology of Plant Breeding Institute, Radzikow, Poland, working on physiology and genetics of cereal plant response to abiotic stress, particularly aluminum toxicity/tolerance mechanism in cereals. During the last years, I have been involved in negotiations of the Cartagena Protocol, member of the Intergovernmental Committee for the Cartagena Protocol on Biosafety (ICCP) Bureau from Central and Eastern Europe (CEE) countries.
In response to Glenn Ashton's comments (massage 55, June 18):
The difference between introduced crop genetic characters "for profit" and "altered traits through natural selection" is nothing new and is not linked only to genetic engineering (GE). Since neolitic times, genetic characters were incorporated into plants "for profit", transforming them into cultivars during the process called domestication. Most characters introduced through artificial selection, and maintained by plant husbandry, were (and are) disadvantageous from the biological (and evolutionary) point of view. For illustration, just take a look at the cultivated corn (maize) plant, which is a biological "cripple", completely lacking seed dispersal mechanism, just to mention one character.
The characters introduced through GE methods, like those introduced during plant domestication "for profit", were not and are not "intentionally advantageous for survival" as Glenn Ashton claims. On the contrary, those traits must be advantageous for production of yield under artificial crop production systems in agriculture. Into the majority of cultivars, so many inadaptable characters were accumulated that when left unattended outside of the agrosystem they are not able to survive. Thus, dangers connected with trangene "escape" into wild flora, emergence of "super-weeds", genetic "contamination" are greatly exaggerated - at least as presently-used GM crops are concerned. It might change in the case of other transgenes - therefore "case by case" risk assessment is necessary.
To summarise, agriculture and plant husbandry were and are working since the beginning outside the bonus of natural selection and GE technology changes nothing in this respect. The most important change connected with GE technology is the increased possibility for utilization of genes, theoretically from all living organisms, and this implies much more work on evaluation and selection of products resulting from GE methods.
The statement by Glenn Ashton that "We cannot in good conscience interfere in the evolutionary process for profit" is not as self-evident as he claims. Why not? Actually we are interfering in this process since the beginning of our civilization - look not only at plants but also at dogs and horses, for example. Taking this statement seriously means that the opposition to GE technology is only one aspect of general anti-technological thinking. The last sentence of Glenn Ashton's message referring to "corporate capitalist system" seems to confirm that not a scientific argument is important in this dispute but ideological and political convictions. If so the dispute should take place in another forum and another place.
a.aniol (at) ihar.edu.pl
Sent: 19 June 2002 16:30
To: '[email protected]'
Subject: 59: Illegitimate vs. homologous recombination
I am Bruno Tinland, a scientist working for Monsanto Company in Brussels.
I would like to comment on Joe Cummins's statements (message 56, June 18). The statement in question is: "In reply to Prof. Burke's question, the evidence is clear and unequivocal. All of the transgenic plants now commercialised or being tested, originated from genetic transformation based on illegitimate (non-homologous) recombination, while all of the traits selected and manipulated in traditional breeding originated from homologous (legitimate) recombination. Plant genetic engineering has not yet achieved a genetic transformation that is based on homologous recombination. In a sense it is correct to say that transgenic plants are genetic "bastards"". [endquote]
As someone who has produced scientific research and publications in this area, I am concerned to read such a definite statement from Prof. Cummins. Homologous recombination is one of the mechanisms used in producing new traits in crops, but this is certainly not the only one. Studies performed on resistance genes families have shown that illegitimate events like transposition took place as well (Ronald (1998), Current Opinion Plant Biology 1: 294-298; Michelmore and Meyers (1998). Genome Research, 1113-1130).
More importantly, I would like to stress now that illegitimate recombination is a basic process (and not a "bastard" one) participating to the life of higher eucaryotic cells (among them plant cells). This process, which is used during DNA repair, occurs in somatic cells several orders of magnitude more frequently than homologous recombination. Also, it contributed to genome evolution. Transposition is a first example that everyone is aware of. As a second example, I would like to cite the presence in the Arabidopsis genome of mitochondrial DNA, which could be uptaken by the plant only following such a process (Lin et al. (1999), Nature 402: 761-768). As a third example, I would like to mention that some Nicotiana species, which are distributed over several world areas contain, in their nuclear genome, genes which have been naturally transferred by Agrobacterium (bacterial genes, integrated through illegitimate recombination) and might have contributed to their evolution (Aoki et al. (1994), Molecular and General Genetics 243: 706-710; Frundt et al. (1998), Molecular and General Genetics 259: 559-568).
The claim that GM plants are genetic "bastards" because illegitimate recombination took place, reflects a polemical attitude and not a scientific one. As has been noted by others in this conference, scientists have a personal responsibility to report their science fairly and objectively. Over-statement and imprecise use of language do little more than confuse the reader and misrepresent the current state of knowledge.
Bruno Tinland, Ph.D.
e-mail: bruno.tinland (at) monsanto.com
[Some definitions may be useful at this stage. Recombination is defined as an exchange of nucleotide sequences between two nucleic acid molecules. Recombination results in heritable, permanent changes. The crossing over and exchange of chromosome fragments during meiosis is a classical example of recombination. Recombination is generally categorized as either homologous or nonhomologous. In homologous recombination, also referred to as legitimate or precise recombination, crossovers occur between two related DNA molecules at sites precisely matched. Sequence similarity between the two nucleic acids is required for homologous recombination to take place. Nonhomologous or illegitimate recombination occurs between two unrelated molecules at non-corresponding sites with no requirement for sequence homology. These above definitions are from Laurent Farinelli and Pia MalnoŽ (1996) http://www.bats.ch/data/english/k5titel.htm. Transposition is the process whereby a transposon or insertion sequence inserts itself into a new site on the same or another DNA molecule. The exact mechanism is not fully understood and different transposons may transpose by different mechanisms....Moderator]