Identification and Characterization of Pathogenicity-Related Transcription Factor in Aspergillus flavus

Aspergillus flavus is a major pathogenic fungus of seed crops such as peanuts and maize. It is the major aflatoxin producer, which is one of the most carcinogenic mycotoxins. Upon contaminating host crops via conidia, A. flavus undergoes hyphal growth, invasion, and aflatoxin production. These processes are tightly regulated by numerous transcription factors (TFs) that orchestrate gene expression during fungal development and pathogenicity. To identify pathogenicity-related TFs, we conducted transcriptomic analyses using multiple infection models, including maize and soybean. Based on the results, we selected ten candidate TFs, and further phenotypic analyses were carried out. We found one Zn2Cys6 transcription factor that was hyphae-specific and highly expressed at early stages of infection, which we named hptA (hyphae-specific pathogenicity-related transcription factor A). The hptA deletion mutant was generated, and disruption of hptA resulted in impaired fungal development. Also, the ∆hptA strain exhibited a significant defect in aflatoxin production compared to the control. Lastly, a kernel bioassay was carried out against maize and soybean. The ∆hptA strain showed reduced conidial colonization and aflatoxin production in both infection models. Taken together, these results indicate that hptA is a hyphae-specific pathogenicity-related transcription factor that is required for proper fungal development, pathogenicity, and toxigenicity in A. flavus.