The regulatory network of transcription factor Skn7 collaborates with bHLH1 during fungal-fungal interactions.

Fungal-fungal interactions have attracted increasing attention due to alterations in physiological and developmental patterns and the upregulation of secondary metabolites. However, the molecular mechanisms underlying this phenomenon remain poorly understood. Previously, we reported that intracellular reactive oxygen species (ROS) function as signal molecules to induce defense responses in a basidiomycete fungus, , against a Mucoromycete fungus w5, concomitant with the upregulation of Skn7, a regulator participating in oxidative stress response. In this study, gene silencing and overexpression experiments demonstrated the involvement of Skn7 in mycelial growth and antioxidation in during cocultivation. According to the transcriptomic data, Skn7 was associated with the expression profiles of intracellular antioxidative enzymes, laccases, and secondary metabolite biosynthesis genes, including and . Chromatin immunoprecipitation followed by massively parallel sequencing analysis, along with electrophoretic mobility shift assay experiments, further confirmed the direct binding of Skn7 to these gene promoters. Another transcription factor, bHLH1, was identified to directly interact with Skn7 in regulating antioxidative defense mechanisms without influencing the expression of genes involved in secondary metabolite biosynthesis. Our work demonstrates Skn7 as a crucial transcription factor that orchestrates the regulatory network and targets downstream genes, thereby protecting against extracellular oxidative stress and elevated intracellular ROS levels during fungal-fungal interactions. Furthermore, we reveal the collaborative role of bHLH1 and Skn7 in fungal antagonism defense.IMPORTANCEFungal-fungal interactions are widespread and play a significant role in the function and stability of ecosystems. This study reveals the molecular mechanisms by which employs the transcription factors Skn7 and bHLH1 to coordinately regulate antioxidant defense mechanisms during its antagonistic interaction with w5. Skn7 not only directly regulates the expression of intracellular antioxidative enzymes and laccases but also regulates secondary metabolite biosynthesis genes. The two transcription factors collaborate to protect against oxidative stress. These findings deepen our understanding of signal transduction and defense mechanisms during fungal interactions, as well as provide new insights into the regulation of secondary metabolites in fungi.