Abstract
The dynamic remodeling of the fungal cell wall depends on a balance between chitin synthesis and degradation. Chitinases are critical for nutrient acquisition, cell wall remodeling, and defense; yet, the upstream regulatory mechanisms controlling chitinase gene expression remain poorly understood. Here, Tandem Affinity Purification-Mass Spectrometry (TAP-MS) with the Penicillium oxalicum Snf1 kinase (PoSnf1) as bait identified the zinc finger transcription factor (TF) PoCon7 as a putative target of the Snf1 kinase complex. This complex comprises the catalytic α subunit Snf1, one of three alternative β subunits Gal83, and the γ subunit Snf4. Although PoCon7 does not directly bind PoSnf1 or PoSnf4, it specifically interacts with PoGal83. Phylogenetic analysis indicates that PoCon7 is a conserved, nuclear-localized C2H2-type TF in filamentous fungi. PoCon7 is likely essential for fungal viability, as only a truncated mutant (con7-B) could be generated, while full deletion was lethal. The con7-B mutant displayed delayed hyphal extension, reduced conidiation, downregulation of developmental genes, and upregulation of cell wall-degrading enzyme (CWDE) genes. DNA Affinity Purification Sequencing (DAP-seq) revealed that PoCon7 binds target gene promoters via the motif 5'-TATTWTTAT-3'. ChIP-qPCR confirmed PoCon7 enrichment at specific sites within the chitinase genes chi18A and chi18C, and the disruption of PoCon7 markedly reduced their expression. Thus, PoCon7 represents the first TF shown to directly regulate chitinase gene expression in filamentous fungi.