Evaluating the mode of Antifungal action of Heat-Stable Antifungal Factor (HSAF) in Neurospora crassa

Heat-stable antifungal factor (HSAF) isolated from Lysobacter enzymogenes has shown a broad-spectrum of antifungal activities. However, little is known about its mode of action. In this study, we used the model filamentous fungus Neurospora crassa to investigate the antifungal mechanism of HSAF. We first used HSAF to treat N. crassa strain for different time points. Spore germination, growth phenotype and differential gene expression analysis were conducted by utilizing global transcriptional profiling combined with genetic and physiological analyses. Our data showed that HSAF could significantly inhibit the germination and aerial hyphae growth of N.crassa. RNA-seq analysis showed a group of genes associated with cell wall formation and remodeling were highly activated. Screening of N. crassa gene deletion mutants combined with scanning electron microscopic observation revealed 3 fungal cell wall integrity related genes played important role in the interaction between N. crassa and L. enzymogens. In addition, WGCNA analysis, accompany with confocal microscopy observation revealed that HSAF could trigger autophagy mediated degradation and eventually result in cell death in N. crassa. The findings of this work provided new insights into the interactions between the predatory Lysobacter and its fungal prey. Transcriptome of Neurospora crassa mycelia after treatment with 40 μM HSAF for different time points (0, 5, 30 and 60min).