The putative forkhead transcription factor FhpA is necessary for development, aflatoxin production, and stress response in Aspergillus flavus

Authors: Lohmar, Jessica; Gross, Stephanie; Carter Wientjes, Carol; Mack, Brian; Wei, Qijian; Lebar, Matthew; Cary, Jeffrey

Submitted to: Toxins
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/30/2024
Publication Date: 3/3/2025
Citation: Lohmar, J.M., Gross, S.R., Carter Wientjes, C.H., Mack, B.M., Wei, Q., Lebar, M.D., Cary, J.W. 2025. The putative forkhead transcription factor FhpA is necessary for development, aflatoxin production, and stress response in Aspergillus flavus. Toxins. Article 114902. https://doi.org/10.1371/journal.pone.0315766.
DOI: https://doi.org/10.1371/journal.pone.0315766

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 the fungus, Aspergillus (A.) flavus. Aflatoxins are toxic and carcinogenic compounds often produced by A. 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 or sell them at a reduced value due to strict domestic and international regulatory guidelines with regards to aflatoxin contamination. We have succeeded identifying a gene, designated fhpA, from A. flavus that when inactivated stops the fungus from making structures known as sclerotia that help the fungus to spread and survive in the field under adverse conditions leading to increased opportunity for the fungus to infect and contaminate crops with aflatoxins. While inactivation of the fhpA gene did not significantly reduce aflatoxin production, it did cause a reduction in a group of toxic compounds known as indole diterpenes that are most often found as compounds in sclerotia. Identification of fhpA will add to our knowledge of regulation of growth 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: Forkhead transcription factors are known to be regulators of several important biological processes in many eukaryotic species including fungi. Bioinformatic analysis of the Aspergillus flavus genome revealed four putative forkhead transcription factor genes. Genetic disruption of three of the four identified putative forkhead transcription factor genes revealed little to no significant alterations in morphological phenotype when compared to the wild-type control strain. Disruption of (AFLA_005634 /F9C07_7177, homolog of the Aspergillus nidulans fhpA gene (AN4521), caused increases in conidial production and a complete abolishment of sclerotial production revealing that the fhpA gene is necessary for regulating normal morphological development in A. flavus. Additional experimental results confirmed that the loss of the fphA gene did not change the ability of A. flavus to respond to the cell wall perturbing agent SDS and that fhpA is dispensable for tolerance to various osmotic stress agents. Furthermore, secondary metabolite analysis of the wild-type and fhpA mutant strains revealed that fhpA regulates the production of several secondary metabolite compounds in A. flavus including aflatoxins, aflatrem, and CPA. Overall, these results suggest that fhpA is an important regulator of morphological and chemical development in A. flavus.