The hyphae-specific C₂H₂ transcription factor HscA regulates development, stress response, and mycotoxin production...

The zinc cluster family is the largest group of transcription factors involved in regulating fungal growth, morphology, and differentiation in Aspergillus species. In this study, we investigated hyphae-specific zinc cluster transcription factors and characterized a novel hyphae-specific Cys₂His₂ zinc finger transcription factor, designated HscA, in the model fungus Aspergillus nidulans and the toxigenic fungus Aspergillus flavus. Phenotypic analyses demonstrated that HscA is essential for normal asexual and sexual development in A. nidulans and A. flavus. Deletion of hscA resulted in elevated sensitivity to cell wall stress agents and an ion depletion stressor. Moreover, the hscA null mutant exhibited decreased production of sterigmatocystin in A. nidulans and aflatoxin B1 in A. flavus. Conidial production in the kernel was decreased in the ΔhscA strain compared to the control in A. flavus. Overall, these results suggest that HscA plays a pivotal role in fungal development, stress tolerance, and mycotoxin production in Aspergillus species.

Fungal growth and development are closely regulated by a variety of transcription factors. This study identified and characterized a hyphae-specific Cys₂His₂ zinc finger transcription factor in two Aspergillus species. HscA contains a Cys₂His₂ zinc finger domain and plays a crucial role in appropriate fungal development in A. nidulans and A. flavus. Particularly, HscA is involved in stress tolerance in both hyphal and conidial stages. We further demonstrated that HscA acts as a positive regulator of sterigmatocystin production in A. nidulans and is essential for proper aflatoxin B1 production in A. flavus. Additionally, our findings indicate that HscA is crucial for conidial formation in kernel assays, implying that HscA may function as a virulence factor. Overall, these findings enhance our understanding of mycotoxin production and fungal pathogenicity in Aspergillus species.