Aflatoxins, toxic secondary metabolites produced by some Aspergillus species, are a universal agricultural economic problem and a critical health issue. Despite decades of control efforts, aflatoxin contamination is responsible for a global loss of millions of tons of crops each year. 

Researchers from University of Arizona (Usa) showed that host-induced gene silencing is an effective method for eliminating this toxin in transgenic maize; the results were published in ScienceAdvances journal. They transformed maize plants with a kernel-specific RNA interference (RNAi) gene cassette targeting the aflC gene, which encodes an enzyme in the Aspergillus aflatoxin biosynthetic pathway. After pathogen infection, aflatoxin could not be detected in kernels from these RNAi transgenic maize plants, while toxin loads reached thousands of parts per billion in nontransgenic control kernels. A comparison of transcripts in developing aflatoxin-free transgenic kernels with those from nontransgenic kernels showed no significant differences between these two groups. These results demonstrate that small interfering RNA molecules can be used to silence aflatoxin biosynthesis in maize, providing an attractive and precise engineering strategy that could also be extended to other crops to improve food security.

These corn cobs show the sites where they were infected with Aspergillus fungus. Although non-transgenic and transgenic kernels showed evidence of equal infection, the transgenics accumulated no toxin. Red dots mark the kernels harvested by the researchers to then determine toxin levels. (Photo: Monica Schmidt)