Enzymatic degradation is an effective means to reduce aflatoxin contamination in maize

Authors: SCHMIDT, MONICA - University Of Arizona; MAO, YIZHOU - University Of Arizona; Opoku, Joseph; Mehl, Hillary

Submitted to: BMC Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/30/2021
Publication Date: 12/17/2021
Citation: Schmidt, M., Mao, Y., Opoku, J., Mehl, H.L. 2021. Enzymatic degradation is an effective means to reduce aflatoxin contamination in maize. BioMed Central (BMC)Biotechnology. 21. Article 70. https://doi.org/10.1186/s12896-021-00730-6.
DOI: https://doi.org/10.1186/s12896-021-00730-6

Interpretive Summary: Crop contamination with toxic, carcinogenic fungal compounds called aflatoxins impacts human and animal health and the value of agricultural commodities worldwide. Several approaches including host resistance and biological control are used to minimize crop aflatoxin contamination, but control of aflatoxins is inconsistent and additional tactics are needed. Biotechnology has great potential as a way to improve aflatoxin control, and in this study lines of transgenic maize expressing an aflatoxin-degrading enzyme isolated from an edible mushroom were developed and evaluated. Following inoculation with an aflatoxin-producing isolate of the fungus Aspergillus flavus, grains from transgenic lines of maize had significantly reduced aflatoxin compared to grains from the non-transgenic control plants. This demonstrates the feasibility of expressing an aflatoxin-degrading enzyme in maize kernels as a strategy to reduce aflatoxin concentrations in a major staple crop.

Technical Abstract: Aflatoxins are carcinogenic compounds produced by certain species of Aspergillus fungi. The consumption of crops contaminated with this toxin cause serious detrimental health effects, including death, in both livestock and humans. As a consequence, both the detection and quantification of this toxin in food/feed items is tightly regulated with crops exceeding the allowed limits eliminated from food chains. Globally, this toxin causes massive agricultural and economic losses each year. In this paper we investigate the feasibility of using an aflatoxin-degrading enzyme strategy to reduce/eliminate aflatoxin loads in developing maize kernels. We used an endoplasmic reticulum (ER) targeted sub-cellular compartmentalization stabilizing strategy to accumulate an aflatoxin-degrading enzyme isolated from the edible ringless honey mushroom Armillariella tabescens and expressed it in embryo tissue in developing maize kernels. Three transgenic maize lines that were determined to be expressing the aflatoxin-degrading enzyme, both at the RNA and protein level, were challenged with the aflatoxin-producing strain Aspergillus flavus AF13. The transgenic maize lines had non-detectable levels of aflatoxin at 14-days post-infection and significantly reduced levels of aflatoxin at 30-days post-infection compared to nontransgenic controls. The expression of an aflatoxin-degrading enzyme in developing maize kernels was shown to be an effective means to control aflatoxin in maize in pre-harvest conditions. This aflatoxin-degradation strategy could play a significant role in the enhancement of both US and global food security and sustainability.