Poisonous carcinogens called Aflatoxins can be produced when food crops are infected by certain species of the fungus Aspergillus. Consumers in the developed world are largely protected from exposure to these dangerous natural compounds through pest control and product screening. Unfortunately, in the developing world, aflatoxins are frequent contaminants in staple foodstuffs such as maize and groundnuts (peanuts).
There is new hope for a solution to this vexing health issue based on a recent collaboration between groups of scientists in the US and in India. They have developed peanut cultivars that are nearly immune to aflatoxin contamination. This breakthrough was achieved by combining the effects of plant “defensins” to limit infections by the fungus, and “host induced gene silencing” using inhibitory RNAs that interfere with toxin production by any of the fungus that does manage to infect. These peanut lines can now be cultivated and crossed with the existing varieties to extend this protection, particularly in the areas of sub-Saharan Africa and Southeast Asia where peanuts are a key part of the locally grown food supply.
This breakthrough is described in [an October 2017] paper published in the Plant Biotechnology Journal. The twelve authors represent three teams of researchers from the USDA Southern Regional Research Center in Louisiana, the Donald Danforth Plant Science Center in Missouri, and the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) in India.
I spoke with Dr. Dilip Shah of the Danforth Center whose group contributed the “defensin” genes. Most plants have genes to make these small proteins (or peptides), but the defensins in peanut are not able to stop infections by Aspergillus when the developing, underground seedpods are injured through drought and other stress. Shah found different defensin peptides in alfalfa and Mediterranean clover that are effective against Aspergillus. The genes for those peptides were transferred into the improved peanut lines. This class of peptides is already a common part of our diet, and there are no reports of these proteins being allergens.
The additional strategy of using small RNAs to specifically shut down the pathogen’s ability to make the toxin is an approach that has also recently been demonstrated to be effective in corn. Once again, small RNAs like this are common in foods.
By combining two tactics, these researchers have developed a solution that is both more effective and likely more robust. A similar approach could be taken for other crops like corn and tree nuts that can be contaminated with aflatoxins.
This potential public health breakthrough has been made possible because of the tools and knowledge-base of modern molecular genetics. The next steps beyond this “genetic engineering” phase of the project will require some funding of conventional breeding to move the trait into varieties that are well suited to the specific needs of the mostly small-holder farmers who produce groundnuts. There will also need to be time and funding to navigate the testing and approvals processes for a “GMO” crop. Hopefully those and other barriers can be minimized so that millions of people can soon be freed from the well-documented risks that come from consuming aflatoxin-contaminated food. Now that the technical breakthrough is complete, this becomes both a logistical and a social justice challenge.
Steve Savage is an agricultural scientist (plant pathology) who has worked for Colorado State University, DuPont (fungicide development), Mycogen (biocontrol development), and for the past 13 years as an independent consultant. His blog is Applied Mythology. Follow him on Twitter @grapedoc
This article originally appeared at Forbes as “Collaboration Provides Hope In The Battle Against Mycotoxin-Induced Cancer In The Developing World” and has been republished here with permission.