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ARS Home » Southeast Area » New Orleans, Louisiana » Southern Regional Research Center » Food and Feed Safety Research » Research » Publications at this Location » Publication #430493
Research Project: Aflatoxin Control through Identification of Intrinsic and Extrinsic Factors Governing the Aspergillus Flavus-Corn Interaction

Location: Food and Feed Safety Research

Title: Role of the osaA transcription factor gene in development, secondary metabolism, and virulence in the mycotoxigenic fungus Aspergillus flavus

Author
item EHETASUM HOSSAIN, FARZANA - Northern Illinois University
item DABHOLKAR, APOORVA - Northern Illinois University
item Lohmar, Jessica
item Lebar, Matthew
item Mack, Brian
item CALVO, ANA - Northern Illinois University

Submitted to: Toxins
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/22/2025
Publication Date: 12/30/2025
Citation: Ehetasum Hossain, F., Dabholkar, A., Lohmar, J.M., Lebar, M.D., Mack, B.M., Calvo, A.M. 2025. Role of the osaA transcription factor gene in development, secondary metabolism, and virulence in the mycotoxigenic fungus Aspergillus flavus. Toxins. 18(1) Article 23. https://doi.org/10.3390/toxins18010023.
DOI: https://doi.org/10.3390/toxins18010023

Interpretive Summary: Aspergillus flavus is a plant pathogen that infects crops like peanuts, corn, and cotton, contaminating them with toxins such as aflatoxins (AFs) and cyclopiazonic acid (CPA). AFs can suppress the immune system, cause birth defects, and lead to cancer, while CPA disrupts calcium regulation in cells. Because of these health risks, crops contaminated with AFs cannot be sold, resulting in major economic losses for U.S. farmers. Current control methods—fungicides, biological control, and resistant crop varieties—are often unreliable due to environmental factors and evolving fungal populations.This study identified a gene called osaA as a key regulator of fungal development, toxin production, and corn infection. Deleting osaA prevented A. flavus from producing sclerotia and txoins, and also weakened its cell wall and stress response, reducing its ability to infect corn. These findings suggest that osaA is a promising genetic target for new strategies to control A. flavus and reduce toxin contamination in crops.

Technical Abstract: Aspergillus flavus colonizes oil-seed crops contaminating them with aflatoxins, highly carcinogenic mycotoxins that cause severe health and economic losses. Genetic studies may reveal new targets for effective control strategies. Here we characterized a putative WOPR transcription factor gene, osaA, in A. flavus. Our results revealed that osaA regulates conidiation and sclerotial formation. Importantly, deletion of osaA reduces aflatoxin B1 production, while, unexpectedly, transcriptome analysis indicated upregulation of aflatoxin biosynthetic genes, suggesting post-transcriptional or cofactor-mediated regulation. Cyclopiazonic acid production also decreased in absence of osaA. In addition, the osaA mutant exhibited upregulation of genes in the imizoquin and aspirochlorine clusters. Moreover, osaA is indispensable for normal seed colonization; deletion of osaA significantly reduced fungal burden in corn kernels. Aflatoxin content in seeds also decreased in the absence of osaA. Furthermore, deletion of osaA caused a reduction in cell-wall chitin content, as well as alterations in oxidative stress sensitivity, which could in part contribute to the observed reduction in pathogenicity. Additionally, promoter analysis of osaA-dependent genes indicated potential interactions with stress-responsive regulators, indicated by an enrichment in Sko1 and Cst6 binding motifs. Understanding the osaA regulatory scope provides insight into fungal biology and identifies potential targets for controlling aflatoxin contamination and pathogenicity