AUTHOR=Ren Yaoyao , Jin Jing , Zheng Mumin , Yang Qingli , Xing Fuguo 

TITLE=Ethanol Inhibits Aflatoxin B1 Biosynthesis in Aspergillus flavus by Up-Regulating Oxidative Stress-Related Genes

JOURNAL=Frontiers in Microbiology

VOLUME=10

YEAR=2020

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2019.02946

DOI=10.3389/fmicb.2019.02946

ISSN=1664-302X

ABSTRACT=<p>As the most carcinogenic, toxic, and economically costly mycotoxins, aflatoxin B<sub>1</sub> (AFB<sub>1</sub>) is primarily biosynthesized by <italic>Aspergillus flavus</italic> and <italic>Aspergillus parasiticus</italic>. Aflatoxin biosynthesis is related to oxidative stress and functions as a second line of defense from excessive reactive oxygen species. Here, we find that ethanol can inhibit fungal growth and AFB<sub>1</sub> production by <italic>A. flavus</italic> in a dose-dependent manner. Then, the ethanol’s molecular mechanism of action on AFB<sub>1</sub> biosynthesis was revealed using a comparative transcriptomic analysis. RNA-Seq data indicated that all the genes except for <italic>aflC</italic> in the aflatoxin gene cluster were down-regulated by 3.5% ethanol. The drastic repression of aflatoxin structural genes including the complete inhibition of <italic>aflK</italic> and <italic>aflLa</italic> may be correlated with the down-regulation of the transcription regulator genes <italic>aflR</italic> and <italic>aflS</italic> in the cluster. This may be due to the repression of several global regulator genes and the subsequent overexpression of some oxidative stress-related genes. The suppression of several key aflatoxin genes including <italic>aflR</italic>, <italic>aflD</italic>, <italic>aflM</italic>, and <italic>aflP</italic> may also be associated with the decreased expression of the global regulator gene <italic>veA</italic>. In particular, ethanol exposure caused the decreased expression of stress response transcription factor <italic>srrA</italic> and the overexpression of bZIP transcription factor <italic>ap-1</italic>, C<sub>2</sub>H<sub>2</sub> transcription factors <italic>msnA</italic> and <italic>mtfA</italic>, together with the enhanced levels of anti-oxidant enzymatic genes including <italic>Cat</italic>, <italic>Cat1</italic>, <italic>Cat2</italic>, <italic>CatA</italic>, and Cu, Zn superoxide dismutase gene <italic>sod1</italic>. Taken together, these RNA-Seq data strongly suggest that ethanol inhibits AFB<sub>1</sub> biosynthesis by <italic>A. flavus</italic> via enhancing fungal oxidative stress response. In conclusion, this study served to reveal the anti-aflatoxigenic mechanisms of ethanol in <italic>A. flavus</italic> and to provide solid evidence for its use in controlling AFB<sub>1</sub> contamination.</p>