Crops all over the world are susceptible to infection by fungi of various Aspergillus species, a fungus that produces secondary metabolites known as aflatoxins. These compounds have been implicated in stunting children’s growth, increasing the risk for liver cancer, and making people more susceptible to diseases such as HIV and malaria.
“Aflatoxin is one of the most potent toxins on the planet,” Schmidt said. “Usually it won’t kill a person outright, but it can make you very sick.”
Schmidt and her team set out to study whether a naturally occurring biological mechanism called RNA interference could be used as a weapon against the Aspergillus toxin.
The modified corn plants carry a genetic blueprint for small RNA molecules, each only about 20 base pairs long, only in the edible kernels, not the whole plant.
“The corn is constantly producing that RNA during the entire development of the kernel,” Schmidt explained. “When the kernels come in contact with the fungus, the RNA moves over into the fungus.”
Once inside the fungal cells, the hairpin-shaped RNA molecules pair up with corresponding target sequences of the fungus’ own RNA that code for an enzyme needed for toxin production, in a process called RNA interference. This causes the toxin production to shut down, but does not in any other way impact the fungus, which continues to grow and live on the corn, albeit harmlessly.