Aflatoxin is a well-known global health threat. This poison, produced by the Aspergillus fungus, is common in corn, wheat, rice and many other crops. Hot climates and inadequate storage practices augment the spread of the fungus and its accompanying toxin.It has also proved extremely difficult to eliminate or even reduce. A new gene-based approach could change that.
Countries in the developing world cannot afford to either test for aflatoxin or discard crops containing it. Corn riddled with aflatoxin may still be eaten or fermented to make alcoholic beverages.
Scientists at the University of Arizona may have a solution to the aflatoxin problem: shut off the gene in the fungus that triggers its production.To force the Aspergillus fungus to stop making aflatoxin, Monica Schmidt and colleagues at the Arizona Genomics Institute used a technique called host-induced gene silencing, a branch of a broader approach to genetics known as RNA interference. They create a genetic sequence containing the desired fungal trait—that is, an absence of aflatoxin production—and insert that sequence into the corn. That sequence is then transferred to the infecting fungal cell, overriding the genetic code linked to aflatoxin production.
Schmidt and her team grew corn plants with and without the introduced RNA sequence and then injected aflatoxin-producing Aspergillus into all the plants. When they harvested the kernels and measured their aflatoxin levels, they found no aflatoxin in the experimental plants. Corn without the newly introduced RNA sequences had aflatoxin levels of up to 225,000 parts per billion. Schmidt is now studying the feasibility of stopping the growth of the Aspergillus fungus, not just the toxin it produces, by interfering with corn RNA.
