Identification and characterization of a novel transcriptional factor Spt7 involved in conidia formation and mycelium development in Aspergillus niger

Abstract Background The conidia of filamentous fungi play a crucial role in the development and dissemination, which is precisely regulated by multiple genes and controlled by a central regulatory network. The novel transcription factor Spt7 serves as a core component of the global transcriptional coactivation complex SAGA (Spt-Ada-Gcn5-acetyltransferase), which regulates the majority of genes within the cell. Result In this study, the spt7 gene-deficient strain 42-Δspt7, derived from A. niger CGMCC 10142, exhibited slow growth, defective conidiation, and reduced antioxidant capacity. To elucidate the underlying global transcriptional mechanisms, a comparative transcriptome analysis was conducted between the 42-Δspt7 mutant and its wild-type progenitor. This analysis revealed that 1033 genes were downregulated, which were mapped to 66 distinct functional pathways involved in glycolysis (e.g., glucokinase, phosphoenolpyruvate carboxykinase), cell wall formation (e.g., feruloyl esterase A, glucan 1,3-beta-glucosidase A), mycelial growth (e.g., actin cytoskeleton-regulatory protein PAN1, glycerol-3-phosphate dehydrogenase [NAD(+)]), and conidiophore development (e.g., MYB family protein FlbD, regulatory protein BrlA, pigment biosynthesis protein Ayg1). Conclusions Most of these pathways were significantly downregulated, indicating that spt7 deletion disrupts SAGA complex integrity and impairs transcription of key genes, thus highlighting the critical role of Spt7 in regulating fungal development and metabolism.