Aflatoxin-free transgenic maize using host-induced gene silencing

Authors: THAKARE, DHIRAJ - University Of Arizona; ZHANG, JIANWEI - University Of Arizona; WING, ROD - University Of Arizona; Cotty, Peter; SCHMIDT, MONICA - University Of Arizona

Submitted to: Science Advances
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/2016
Publication Date: 3/1/2017
Citation: Thakare, D., Zhang, J., Wing, R.A., Cotty, P.J., Schmidt, M.A. 2017. Aflatoxin-free transgenic maize using host-induced gene silencing. Science Advances. 3(3):e1602382.

Interpretive Summary: Aflatoxins are toxic fungal metabolites that frequently contaminate crops. These toxins can inhibit human development, cause cancer, suppress the immune system and cause death from liver failure. Aflatoxin contamination is very difficult to manage in corn. Development of host resistance to contamination has been difficult but would be useful to the industry as a tool to pair with the largely successful biocontrols. In recent years, genetic engineering technology has been developed that allows development of plants that can turn off pathogen genes. This technology, called Host-Induced Gene Silencing (HIGS), was used in the current work to develop corn plants that turn off the ability of fungi to produce aflatoxins. The genetically engineered plants were highly resistant to aflatoxins demonstrating the ability of HIGS to prevent aflatoxin production in corn and providing an attractive engineering strategy to improve food security.

Technical Abstract: Aflatoxins are potent carcinogenic anti-nutritionals that suppress immune systems and contaminate staple foods in warm regions across the globe as the result of crop infection by certain Aspergillus species. Despite decades of control efforts, millions of tons of crops are produced annually that exceed maximum permissible aflatoxin concentrations. Here we demonstrate host-induced gene silencing is an effective tool for preventing aflatoxins in crops. Transgenic maize plants were produced that express a kernel-specific RNAi cassette targeted to silence expression of a gene encoding an enzyme required for aflatoxin biosynthesis. Pathogen challenged, kernels from these RNAi transgenic maize plants developed undetectable quantities of aflatoxins compared to thousands of parts per billion in similarly infected nontransgenic kernels. No substantial differences were detected between transcripts in developing kernels from aflatoxin-free transgenic kernels and those from nontransgenic kernels. These results demonstrate that short interfering RNA molecules can be used to silence aflatoxin biosynthesis, providing an attractive engineering strategy to improve food security.