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Rothamsted Institute in Hertfordshire, UK, has begun an open-air GM wheat trial that is re-energising the country's debate on genetically modified (GM) crops. The crop has been engineered to produce an aphid 'alarm' pheromone that aims to repel the aphid pests from the crop and/or attract aphid predators.
Despite the media hype, there has been no critical analysis of the scientific or political rationale behind the project. The huge PR campaign headed by the lobby group Sense About Science has successfully confused the public and obscured the facts. Meanwhile, Rothamsted is pressing for debates with GM sceptics in an attempt to convince the public that the GM technology is based on environmental principles, and is needed to feed a starving world. But evidence of the technology's effectiveness, safety and potential non-private beneficiaries is conspicuously lacking. The inclusion of a herbicide tolerance (see below) trait in the crop - not disclosed to the public - also discredits the institute's claims of being "environmentalists" with aims to promote sustainable agricultural practices and reduce chemical use.
What is the GM wheat?
According to Rothamsted, these new GM crops are "designed to 'emulate' a plant's natural defence system" and have been shrewdly dubbed "second generation" GM crops, distinguishing them from the herbicide-tolerant crops that currently dominate the market [1]. Herbicide-tolerant crops promote the use of chemical herbicides, as GM plants made tolerant to them will not die after application. The scientists claim that their new strategy will reduce pesticide use, as aphids will be deterred from the crop, and the pheromone may also attract aphid predators to the plant.
The GM spring wheat allegedly contains a modified version of an 'alarm' pheromone normally produced by aphids to alert them of danger. Currently, there is no published data on this GM crop, so there is little scientific information on the genetic modification or the GM plants themselves to justify the project. What little information there is has come from press releases and from the institute's application for consent to release the GM crop available on the internet [2].
The pheromone (E)-β-farnesene (EBF) is produced by some plants such as peppermint as a natural defence against aphids. The experiment will test two different varieties of pheromone-producing wheat. One expresses the alarm pheromone alone, and the second expresses the pheromone and an additional enzyme that increases the levels of pheromone substrate, and therefore levels of the pheromone itself.
The DNA sequences put into the wheat include chimeric versions of the peppermint gene encoding EBF synthase, expressed under the maize ubiquitin promoter 1. EBF synthase converts substrates including farnesyl diphosphate (FPP) into EBF. The Ubiquitin promoter is expected to express the enzyme everywhere in the plant. The second GM wheat produces in addition FPP synthase, the enzyme that makes FPP. The theory is that more substrate will be available to increase pheromone production. The first line carries 4 copies of the EBF synthase transgene, while the second line contains one copy of both the EPF synthase and FPP synthase transgenes. As stated in Rothamsted's application [2], "the nucleotide sequences of these genes are synthetic and chimeric and not found naturally". They have not analysed the genome of the GM wheat to determine the structure or location of the inserted DNA. The transgenes were judged to be stably inherited according to the PCR experiments. But without thorough molecular genetic characterization, transgene instability cannot be ruled out, and this is a notorious limitation of genetic modification of crop plants (see [3] Transgenic Lines Proven Unstable, SiS 20).
Apart from the pheromone-related genes, there are extra DNA elements including neomycin and kanamycin antibiotic resistance, and both DNA constructs also contain a gene conferring resistance to glufosinate ammonium herbicides. These can be used as selectable markers for transgenic plants [4] but are surplus to requirement in protecting plants against aphid attack; and should have been removed from the transgenic plants to prevent the genes from spreading to other crops and indeed to bacterial pathogens in the environment.
Kanamycin is still in clinical use and also cross reacts with other new antibiotics (see [5] Kanamycin Still Used and Cross-Reacts with New Antibiotics, ISIS report).
The only information published by Rothamsted on any aphid-repelling GM crops refers to kanamycin resistance for selection, so the herbicide resistance trait is not even used. But there is a clear intention to benefit from this trait once the crop is commercialised. As stated in their application, "these plants possess the ability to tolerate glufosinate-based herbicides which would increase their survivability in environments where these herbicides were the only ones used".
It also transpires that Bayer, the major producer of glufosinate and glufosinate-tolerant crops including canola, soybean, cotton and corn, is a partner of Rothamsted. The fact that glufosinate herbicides have been banned in the EU since 2009 due to their high toxicity in mammals (including reproductive problems) raises the question - is this product really aimed for the UK market? The fact that the wheat is also the spring and not winter variety adds further weight to this question, as the overwhelming majority grown in the UK is of the winter variety.
With regards to general plant health, no physiological or morphological analyses of the plants were performed on the grounds that [2] "no other changes to the plant morphology or development are apparent".
Previous experiments with alarm pheromone
There have been no publications on the new GM wheat. The institute, did however, publish results of a flowering plant, A. thaliana also expressing the pheromone [4]. The study looked at acute effects on aphid behaviour but did not test any long-term impacts on aphids or beneficial insects. Aphids were exposed to the pheromone either in droplet form or through exposure to air space above the plants for 1 minute or 15 minutes. They recorded a near 80 % behavioural response to EBF-containing droplets after one minute that was reduced to around 40 % after 15 minutes. Exposure to air space above the transgenic plants elicited a near 15 % response after 1 minute that was also reduced to below 10 % after 15 minutes. The length of time the predator species D. rapae spent on the GM plants was also increased from 10 to 15 minutes.
The trend for a reduction of aphid response from 1 to 15 minutes exposes a limitation in the technology that has been highlighted in other studies - the potential habituation of aphids to the pheromone. Ordinarily, aphids release these signals in acute pulses, which differ significantly to the continual expression in GM crops.
A follow up study performed in Germany using the same GM A. thaliana plants made by Rothamsed, found that the aphids no longer responded at all in the long term [6]. An experiment allowing aphids to choose between GM and control non-GM plants over a period of 2 weeks found no significant difference. They also analysed the numbers of winged morph offspring that were produced. EBF is thought to increase the numbers of winged aphids that can then escape potential danger. There were no differences in the total numbers of offspring or the percentage of winged offspring produced.
Another study, again using Rothamsted's GM A. thaliana found habituation to the pheromone with no significant difference in response to GM versus non-GM plants after only 3 generations [7]. There was a fitness cost to the habituation, with more being predated after 24 hours of co-habitation with beetles. It would have been interesting to see the effects on predators over a longer period of time. The rapid habituation to the pheromone suggests that the GM wheat will not have any long-lasting effects, and simple laboratory experiments prior to field release would have provided answers to these basic questions.
Risks of genetic contamination
The researchers are claiming risks of genetic contamination to be negligible, although possible. However, genetic contamination of wheat has been documented in the past, and widespread contamination by other GM crops including corn and canola has been well documented.
Wheat is predominantly self-pollinating, but can also cross-pollinate, the level depending on many factors including weather conditions, wild-life, and size and densities of both GM fields and donor plant fields. Insect pollination can also occur in hot conditions during seed set. As stated in the application [2] "Dispersal of seed prior to harvest by wind is unlikely, but possible by wildlife". They also admit that: "Under certain growing conditions individual genotypes may have out-crossing rates of up to 4-5%". Further, the trial report does not deal with seed transfer by birds and small four-footed animals both in faeces and by sticking to feet and feathers or coats. It is very difficult to prevent small animals from spreading wheat grains. The sucking nature of aphid feeding can also enable the transfer of transgenic DNA to other plants.
The grain obtained will be disposed of in a deep landfill using an approved contractor, however there is no discussion of the predictable spread of seed along roadways from truck wheel, wells etc. This has already led to the contamination of seed stocks, roadsides and rail tracks with herbicide-resistant rapeseed (called canola in the US) in Japan and Canada that has all but decimated Western Canada's organic trade of the crop (see [8]Transgenic Contamination of Certified Seed Stocks, SiS19). Coincidentally, Maurice Maloney, current director of Rothamsted Institute, had developed glyphosate-tolerant rapeseed.
Herbicide-tolerant GM wheat has already contaminated non-GM seed stocks in wheat samples obtained from certified seed producers in Colorado, USA [9]. GM wheat trials with a 200 metre buffer zone of pollen receptor plots did not prevent pollen-mediated genetic outflow in Switzerland [10]. The buffer zone proposed by Rothamsted Institute, is for cereals not to be grown at less than 80 metres surrounding the trial field.
Additional concerns
Horizontal gene transfer is an alternative form of genetic contamination whereby transgenic DNA can be taken up by unrelated species such as microorganisms in the soil or on the plant surface. Horizontal gene transfer and recombination is the main route for generating new pathogens and spreading antibiotic and drug resistance, and genetic engineering is nothing if not greatly facilitated horizontal gene transfer and recombination. Transgenic DNA is different from natural DNA; not only does it contain new combinations of genes, but also new synthetic genes that have never existed in billions of years of evolution: new coding sequences, promoters and other non-coding regulatory sequences that boost gene expression to abnormally high levels (see [11] Horizontal Gene Transfer Does Happen, SiS 38, [12] Scientists Discover New Route for GM-gene 'Escape', SiS 50).
The use of the bacterial vector Agrobacterium tumefaciens which is capable of infecting bacterial cells that exist in the soil and gut, as well as human cells can cause DNA mutations and possible cancer development. The application states [2]: "The plasmid backbone sequences, nptI gene [antibiotic resistance], origins of replication, border sequences etc. come originally from E. coli and Agrobacterium tumefaciens, two common gut and soil bacteria respectively and these sequences are already widespread in the soil metagenome". They further state that "These elements may increase the rates of horizontal gene transfer and establishment in soil bacteria because they provide a theoretical mechanism for homologous recombination and selection." Despite this admission, risks during the trial are estimated "negligible", and such elements are already "common" in bacterial species anyway.
Other research at Rothamsted
Much of the media attention surrounding the Institute has aimed to distinguish it from the private corporations that have commercialised most GM crops. Although Rothamsted is a public institution with research money awarded by the government's BBSRC (Biotechnology and Biological Sciences Research Council), it has a long history of chemical agriculture and has commercialised herbicides in the past, including 2,4-D which is a component of the notorious Agent Orange pesticide used in the Vietnam war. They also invented pyrethroid insecticides, which are the most common insecticides today. Indeed, the Institute was founded in 1843 by John Bennett Lawes, who a year earlier had opened up a chemical fertilizer company that marked the beginnings of the chemical fertilizer industry. Rothamsted was set up to investigate the differences between inorganic and organic farming. Their links to chemical agriculture is not new or unusual. A recent publication supporting the use of paraquat herbicides for sustainable agriculture was timed with the EU-wide re-introduction in 2003 after individual nations had banned it due to health concerns. In 2007, an EU-wide ban was put in place with links to Parkinson's disease amongst the major concerns.
That is not all.
Rothamsted's links to corporate agribusiness
As proudly stated on Rothamsted Institute's website:
"Our portfolio of industrial partners includes global agri-biotech companies such as Syngenta, Dow Agrosciences, Bayer Agriculture, BASF and Monsanto and multinational organisations such as British Sugar and Novozymes Biologicals Inc. Examples of collaboration with Small and Medium-Size Enterprises include work done with VSN International, BioForsk and ADAS. We also have projects funded by industrial organisations such as the National Farmers Union and the British Beet Research Organisation. The quality and impact of our input is such that we have been very successful in building long-term relationships with our partners."
Can one still believe Rothamsted's GM wheat is a mere experiment with no commercial objectives in mind? Should taxpayer's money be hijacked to support GM development for corporate agribusiness without regard for potential damage to health and environment?
References
- Rothamsted Research Institute, 11th June 2012 http://www.rothamsted.ac.uk/Content.php?Section=AphidWheat
- APPLICATION FOR CONSENT TO RELEASE A GMO - HIGHER PLANTS. Study of aphid, predator and parasitoid behaviour in wheat producing aphid alarm pheromone. Defra.gov.uk. http://archive.defra.gov.uk/environment/quality/gm/regulation/documents/11-r8-01-app-a.pdf
- Ho MW. Transgenic lines proven unstable. Science in Society 20, 35, 2003
- Beale MH, Birkett MA, Bruce TJ, Chamberlain K, Field LM, Huttly AK, Martin JL, Parker R, Phillips AL, Pickett JA, Prosser IM, Shewry PR, Smart LE, Wadhams LJ, Woodcock CM, Zhang Y. Proc Natl Acad Sci U S A 2006, 103, 10509-13.
- Cummins J. Kanamycin still used and cross-reacts with new antibiotics. ISIS report, 27 May 2001, http://www.i-sis.org.uk/kanomycin.php
- Kunert G, Reinhold C, Gershenzon J. Constitutive emission of the aphid alarm pheromone, (E)-β-farnesene, from plants does not serve as a direct defense against aphids. BMC Ecology 2010, 10, 23-35.
- de Vos M, Cheng WY, Summers HE, Raguso RA, Jander G. Alarm pheromone habituation in Myzus persicae has fitness consequences and causes extensive gene expression changes. Proc Natl Acad Sci U S A 2010, 107, 14673-8.
- Cummins J. Transgenic Contamination of Certified Seed Stocks. Science in Society 19, 48, 2003
- Gaines T, Preston C, Byrne P, WB Henry, Westra P. Adventitious Presence of Herbicide Resistant Wheat in Certified and Farm-Saved Seed Lots.
- Foetzki A, Quijano CD, Moullet O, Fammartino A, Kneubuehler Y, Mascher F, Sautter C, Bigler F. Surveying of pollen-mediated crop-to-crop gene flow from a wheat field trial as a biosafety measure. GM Crops Food 2012, 3 [Epub ahead of print]
- Ho MW and Cummins J. Horizontal gene transfer from GMOs does happen.Science in Society 38, 22-24, 2008
- Ho MW. Scientists discover new route for GM-gene 'escape'.Science in Society 50, 14-16, 2011.
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