Scientists in Arizona say they've found a way to genetically modify corn to beat back a costly and potentially deadly toxin using a technique that could be adapted to fight other blights.
Aflatoxin is a byproduct of a fungus that can grow on crops like corn, rice, and nuts when they're stored in warm, humid spaces. But by altering a form of the biochemical messenger RNA in the corn, researchers from the University of Arizona and the US Department of Agriculture say they kept the toxin from taking root.
"Retarding fungal growth is very difficult," said University of Arizona geneticist Monica Schmidt, co-author of a newly published study detailing the work. Attempts to breed fungus-resistant crops have had little success, "So we thought, 'How can we just go after the toxin?'"
To do that, Schmidt and her colleagues modified a corn gene to produce a strand of the biochemical messenger RNA — which helps cells build proteins — that would spoof the fungus. It latches onto the cells of the fungus and blocks the production of a similar RNA that would give rise to the toxin.
"No RNA, no protein, no toxin," she said.
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Aflatoxin can cause fatal liver damage at high doses, and the United Nations
blames chronic low doses for up to 155,000 cases of liver cancer a year, mostly in Africa and Asia. It can also stunt the growth of children.
Acute aflatoxin poisoning is rare in Western countries, but a 2004 outbreak in Kenya killed 125 people and sickened nearly 200 more. Farmers throw out up to 16 million tons of tainted corn a year to prevent its spread. More than 100 countries now set standards to prevent contamination.
The Arizona team grew three lines of their genetically modified corn and dosed them with the fungus that produces aflatoxin. None of the kernels sampled afterward contained the poison, while unmodified control plants were badly affected.
The findings were
published Friday in the research journal Science Advances. Previous attempts by other researchers produced only limited reductions in aflatoxin while yielding stunted plants, the authors reported.
These corn cobs show the sites where they were infected with aflatoxin. Although non-transgenic and transgenic kernels showed evidence of equal infection, the transgenics accumulated no toxin. Credit: Monica Schmidt/University of Arizona
Though the National Academies of Science found no safety issues with genetically modified food in a sweeping 2016 report, the issue remains controversial among the public. Schmidt said the technique can be transferred to other crops — but there's still a lot of testing to be done before regulators would allow it to come to market.
"With any GM crops, the first question is, 'Did your inserted trait cause other things you didn't intend?' " she said. Tests of corn kernels the team modified show no other RNA molecules that differed from kernels of non-modified plants, but more study would be needed to make sure it produced no side effects in the rest of the plant — or in any animals that consumed it.
"This is extremely preliminary," Schmidt said. But if the technique passes future tests, it can be used to attack not only the fungus that produces aflatoxin but other harmful fungi as well.
"There are many other fungal toxins, but aflatoxin's the biggie," she said.
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