The 14-3-3 protein homolog ArtA regulates development and secondary metabolism in the opportunistic plant pathogen Aspergillus flavus

Authors: IBARRA, BEATRIZ - Northern Illinois University; LOHMAR, JESSICA - Northern Illinois University; SATTERLEE, TIMOTHY - Northern Illinois University; MCDONALD, TAYLOR - Northern Illinois University; Cary, Jeffrey; CALVO, ANA - Northern Illinois University

Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/6/2017
Publication Date: 3/1/2018
Citation: Ibarra, B.A., Lohmar, J.M., Satterlee, T., McDonald, T., Cary, J.W., Calvo, A.M. 2018. The 14-3-3 protein homolog ArtA regulates development and secondary metabolism in the opportunistic plant pathogen Aspergillus flavus. Applied and Environmental Microbiology. 84(5):e02241-17. https://doi.org/10.1128/AEM.02241-17.
DOI: https://doi.org/10.1128/AEM.02241-17

Interpretive Summary: This work describes experiments that have been conducted in an effort to better understand the genetic mechanisms that control aflatoxin production and growth and development in Aspergillus flavus. Aflatoxins are toxic and carcinogenic compounds often produced by the fungi, Aspergillus flavus during growth on crops such as corn, peanuts, cottonseed, and treenuts. Because of the potential health risks, aflatoxin contamination of food and feed crops is also of great economic importance to farmers who cannot sell their crops due to strict domestic and international regulatory guidelines with regards to aflatoxin contamination. We have succeeded identifying a gene, designated artA, from A. flavus that when inactivated significantly reduces the ability of the fungus to produce conidia and sclerotia that help the fungus to spread and survive in the field under adverse conditions. In addition, this study showed that artA controls the production of aflatoxins and other secondary metabolites produced by A. flavus. Identification of artA will add to our knowledge of regulation of development and toxin production in A. flavus and this in turn will help in devising strategies for eliminating fungal toxin contamination of food and feed crops.

Technical Abstract: The opportunistic plant pathogenic fungus Aspergillus flavus produces carcinogenic mycotoxins denominated aflatoxins (AFs). Aflatoxin contamination of agriculturally important crops such as maize, peanut, sorghum and tree nuts is responsible for serious adverse health and economic impacts worldwide. In order to identify possible genetic targets to reduce AF contamination, we have characterized the artA gene, encoding a putative 14-3-3 homolog in A. flavus. The artA deletion mutant presents a slight decrease in vegetative growth and alterations in morphological development and secondary metabolism. Specifically, artA affects conidiation, and this effect is influenced by the type of substrate and culture condition. In addition, normal levels of artA are required for sclerotial development. Importantly, artA negatively regulates AF production as well as the concomitant expression of genes in the AF gene cluster. Furthermore, the expression of other A. flavus secondary metabolite genes is also artA-dependent, including genes in the cyclopiazonic acid (CPA) and ustiloxin gene clusters. Interestingly, protein interaction studies indicated that ArtA interacts with the epigenetic regulator RtfA in this agriculturally important fungus.