Transcriptome Analysis Reveals That a Gti1/Pac2 Family Gene, CpSge1, Regulates Fungal Growth, Stress Response, and Virulence in Cryphonectria parasitica

The Gti1/Pac2 family comprises crucial transcription factors widely distributed in fungi with generally two members, Gti1 (also known as Wor1, Ryp1, or Sge1), and Pac2, where the Gti1 homologues play significant roles in the growth, spore production, and pathogenicity of various pathogenic fungi. Despite its recognized significance, the roles of this family in Cryphonectria parasitica, the pathogen responsible for chestnut blight (a globally significant forest disease), remain unexplored. In this study, CpSge1 was identified in C. parasitica and then knocked out to explore its functions. The results showed that CpSge1 significantly affected the vegetative growth, conidiation, hydrophobicity, and stress tolerance of C. parasitica. Notably, the CpSge1 deletion mutants were significantly less pathogenic compared with the wild type. Transcriptomic analysis of the wild type and the CpSge1 deletion mutant during the vegetative growth and infection stages revealed that CpSge1 regulated a number of pathogenicity-related genes in C. parasitica. A yeast one-hybrid assay verified the direct binding of CpSge1 to the promoter regions of genes encoding pectin lyase CpPL1 and major facilitator superfamily transporter CpMF1. In summary, these data suggest that CpSge1 is the core regulator of fungal growth, stress tolerance, gene expression, and virulence in C. parasitica, which may improve our understanding of the molecular pathogenesis of C. parasitica and help us to develop effective control strategies.