Beyond the debate

A leading opponent of transgenic crops in Britain recants. But Australian scientists developing GM crops to help feed the world aren’t waiting for local anti-GM campaigners to see the scientific light.

The earth beneath the meadows and crop fields of Europe moved perceptibly early in January when British journalist, author and environmental activist Mark Lynas renounced his opposition to genetically modified crops in a frank address to the Oxford Farming Conference.

Lynas’s conversion to the GM cause was not entirely unexpected: he had shown signs of wavering in an article in New Statesman in 2010, titled ‘Why We Greens Keep Getting it Wrong’. Early in 2012, he published an article advocating the use of nuclear power to reduce carbon emissions and climate change, and in September published another saying that, without nuclear power, the battle against global warming was as good as lost.

In his Oxford address, Lynas apologised for his involvement in vandalising field trials of GM crops and criticised organisations with which he had previously been associated, including Greenpeace and the organic farming lobby group, the UK Soil Association. He admitted that before 2008 he had never read a peer-reviewed paper on biotechnology or plant science.

He explained that anti-science environmentalism had become increasingly inconsistent with his pro-science environmentalism on the issue of climate change. With uncanny prescience, given the recent meteoric blast in Russia, he said: “You are more likely to get hit by an asteroid than to get hurt by GM food.”

Lynas was as formidable an opponent of GM agriculture as is his durable Australian counterpart, expatriate New Zealander Bob Phelps. Phelps, director of Gene Ethics, has been an environmental activist since the mid-1970s, and an implacable opponent of genetically modified organisms since the early 1980s.

What chance that Phelps, or his Western Australian ally Julie Newman, of the Network of Concerned Farmers, will renounce their opposition GMOs? Keith Alcock, retired director of agricultural research in the Department of Agriculture and Food Western Australia under the anti-GM Labor Government of Geoff Gallop, doubts it. “We were conscious that there would be challenges in getting the GM crops message across,” he Alcock. “Clearly, the general public would find it hard or even impossible to comprehend the science, or it just didn’t want to know and hoped it would go away.

“People prefer not to have pesticides on their food but, given that this is impossible, they simply prefer not to know about it. Few understand what a huge challenge it is to feed the world, and that it’s going to become harder and harder each decade as the global population increases, even as the area of arable land declines through salinity, desertification or urban sprawl.

“We knew the best answer was a GM trait that had consumer benefits that could be sold to the public, but the trouble was we didn’t have any at the time. But what we had were insect-resistance traits that massively decreased the need for insecticide spraying in Australian cotton and herbicide-tolerant canolas that could greatly reduce herbicide use.”

The Liberal Government of Colin Barnett eventually ended WA’s ban on GM crops in 2006, and the state is now Australia’s largest producer of GM herbicide-tolerant canola. A common criticism of GM crops is that they provide no benefit to consumers, only risk. But the argument did not prevent Greenpeace activists making a nocturnal raid on trial plots of a GM wheat with modified starch for improved nutrition at CSIRO’s experiment farm near Canberra, in July 2011.

Low GI starch

Developed by CSIRO’s Plant Industry researchers, the wheat is engineered to produce low glycaemic index starch, with potential benefits for bowel health and reducing the risk of type 2 diabetes. CSIRO is also close to commercialising oilseed crops engineered to produce high levels of omega-3 polyunsaturated fatty acids (PUFAs) in their seeds. Currently, omega-3 PUFAs are extracted from marine fish, a shrinking global resource. Omega-3 PUFAs are essential for human health, playing crucial roles in the development of the brain and visual system in the embryo and in maintaining cognitive function and optimal metabolism through life.

While such developments offer direct benefits to consumers, Australian plant biotechnology research institutions are well advanced on developing GM crops that will defend themselves against fungal pathogens and parasites. If they provide less obvious benefits to consumers, they promise tangible benefits to farmers and to global food production, as the planet’s human population careers towards a peak of 9 billion-plus by 2050.

Root-lesion nematodes (Pratylenchus spp) are part of a $120 billion problem for global agriculture caused by nematodes that attack a wide range of horticultural crops and field crops like cereals, legumes, beets and canola. Mike Jones, Professor of Agricultural Biotechnology at Perth’s Murdoch University, says root-lesion nematodes are an increasing problem for grain farmers who have adopted zero-till systems.

Jones has exploited the discovery of RNA-induced gene silencing in the nematode Caenorhabditis elegans by US Nobel laureates Andy Fire and Craig Mello, to develop prototype crops that are resistant to root lesion nematodes. In 1997 Mello and Fire observed that small molecules of RNA could suppress the activity of target genes in C. elegans via the phenomenon now known as RNA interference. By injecting the nematode with single-stranded RNAs complementary to the messenger RNAs of a target gene, they were able to silence the target gene. The interference effect eventually diffused from the original cell through the nematode’s body, silencing the target gene in all of its 959 cells.

“We’ve been doing deep sequencing of the transcriptomes of root-lesion nematodes and comparing them with the transcriptome of C. elegans, looking for genes we can knock down with RNA interference,” Jones says. “Plant nematodes have been very much a neglected subject in crop research. But fortunately, science chose C. elegans as the model multicellular organism for the first genome project, and around 700 laboratories in 33 countries have worked on it, so it’s the best annotated and understood genome of any multicellular organism, and a fantastic resource for comparative genomics research on plant nematodes.

“We’ve been able to identify a variety of target genes that, when silenced by RNA interference, prevent root-lesion nematodes completing their life cycle. By modifying plants to express small RNA molecules that target these genes, we can make them resistant to the nematodes.”

According to Jones, there are various ways to make crops resistant, such as locking the nematode out of the host plant’s roots or producing small interfering RNAs in the cytoplasm of the cell that will be ingested when the nematode feeds on the plant’s roots.

This use of RNA interference to protect crops against root lesion nematodes is a world first. Other Australian and overseas researchers are attempting to develop RNA-interference systems that will protect crops against insect pests, including aphids, which also spread plant viruses that can severely reduce the productivity of plants. The sap-sucking habits of aphids that make them such effective transmitters of plant viruses, also make them highly vulnerable to gene-silencing RNAs expressed in sap.

“It seemed to me that this was one area that was going to be commercially viable for transgenic plants. It would not be a primary trait, but would be ‘stacked’ with transgenes for other important traits, including resistance to viruses.”

Stacked traits

The attraction of ‘stacking’ traits mediated by RNA interference is that it exploits a natural mechanism that operates in all plants, and in all higher life forms. The fact that RNA interference is a natural mechanism that switches off gene expression should make transgenic crops exploiting the technology more acceptable to regulators and less targeted by anti-GM activists. Much of the opposition to transgenic crops has centred around the supposed health risks associated with ‘contamination’ by transgenic proteins, like the Bt proteins used to confer resistance to chewing insects in crops like cotton and maize, and herbicide-resistant proteins in canola and soybean.

The GM-shy nations of the European Union have introduced laws specifying that ‘contamination’ of conventional produce by transgenic proteins must not exceed 0.9%. The choice of a 1% threshold was entirely arbitrary and not indicative of any scientifically verifiable risk. For EU nations that provide large subsidies to farmers, it serves as a non-tariff barrier to imports from nations that grow GM crops. Anti-GM activists in the EU regard any level of ‘contamination’ as unacceptable and continue to lobby for a zero-tolerance policy.

At Melbourne’s La Trobe University, Professor Marilyn Anderson is leading Hexima’s research into natural anti-fungal proteins in plants to develop transgenic maize varieties that will be resistant to a variety of economically important fungal pathogens. Hexima is a biotechnology that developed from basic research conducted in biochemistry at La Trobe University and botany at the University of Melbourne.

Maize is still a minor crop in Australia, but has overtaken wheat and rice as the world’s most important cereal crop. At least 10% of global production is lost to fungus diseases. “Maize is such a huge crop that, if we are successful at reducing disease, even a 5% increase in productivity will significantly benefit global food and biofuel production,” Anderson says.

Maize breeding is a big industry in its own right in the US, and seed companies invest heavily in developing varieties with new or improved traits. Maize varieties with Bt genes that protect against European corn borer and maize root worm were among the first transgenic crops grown in the world, and transgenic varieties so dominate the modern industry that anti-GM activists in North America ignore them.

All these factors make it attractive for Australian plant molecular geneticists to develop transgenic maize with traits that could benefit the US-dominated global maize industry. Maize can act as a test-bed for new types of transgenes, like genes that could one day be repatriated to Australia to protect local staples like wheat and canola against fungus attack.

America’s largest producer of hybrid crop seeds, Dupont Pioneer - formerly Pioneer Hi-Bred, is a major partner of Hexima’s research. Hexima has built a biosecure greenhouse and tissue-culture facility on the La Trobe University campus to generate, grow on and evaluate maize lines containing anti-fungal transgenes. Early on, Anderson’s group focused on the natural antibiotics in plant floral tissues which protect the valuable sexual tissues from damage by fungal pathogens; even in susceptible crop plants, fungi often do not infect reproductive tissues.

The La Trobe team had to learn how to make transgenic maize, using Pioneer’s high-efficiency protocols. “In less than three years we attained the same level of efficiency as Pioneer, which has been making transgenic maize lines for years,” she says. “It’s plant transformation on a scale far beyond anything that you would see in a typical research setting. We had to build a tissue-culture factory, as well as the greenhouse, and start pumping genes through. We created our 10,000th transgenic maize line last August.”

Without giving away proprietary secrets, Anderson says her team has widened its search for anti-fungal compounds, and most transgenic lines contain pairings of different transgenes, because ‘stacking’ compounds yields synergies resulting in levels of protection that would not have been predicted from the simple additive effects of two compounds.

The reduced fungal infections due to such synergies yield a double benefit: increases in yield, at reduced cost, and greatly reduced levels of potentially carcinogenic compounds such as aflatoxins, which are a major cause of deaths from liver cancer from grain stored in crude village silos in Africa. Anti-GM activists would face a moral dilemma if they sought to argue against transgenic proteins that actually protect humans against long-term damage to their health, by warding off diseases that contaminate dietary staples in developing nations against potent liver toxins.

The debate over the safety and efficacy of GM crops will likely long outlive the scientific research that settles their safety and efficacy. However, the more individuals, such as Lynas, who can be encouraged to engage with the science, the greater the awareness of the true costs and benefits of GMOs. And despite the public resistance from some quarters - and some governments - the science will continue to develop new crops with improved characteristics and nutrition profiles.