HOG-MAPK pathway core cascade proteins AoSsk2, AoPbs2 and AoHog1 regulate hyphal development, conidiation, stress...

The high-osmolarity glycerol mitogen-activated protein kinase (HOG-MAPK) pathway is highly conserved in fungi, yet its biological functions in the nematode-trapping fungus Arthrobotrys oligospora remain largely uncharacterized. Here, we identified three core components of the HOG-MAPK pathway (AoSsk2, AoPbs2, AoHog1) in A. oligospora, and constructed their gene deletion mutants via homologous recombination. Phenotypic analyses showed that disruption of these genes markedly ‌diminished mycelial growth, conidiation, and tolerance to multiple abiotic stressors. The mycelial growth of the mutant strain was significantly impaired, and both the length of mycelial cells and the number of nuclei were markedly reduced. Importantly, the mutant strain has almost completely lost its ability to produce conidia. In contrast, the mutants produced more traps after nematode induction, with no notable change in nematode mortality. Transcriptomic, cytological and metabolomic assays further revealed that these genes regulate lipid metabolism, autophagy, and secondary metabolism, notably arthrobotrisin biosynthesis in A. oligospora. Collectively, these results demonstrate that AoSsk2, AoPbs2 and AoHog1 are essential players in multiple biological processes of A. oligospora, which provides the foundation for future studies on the role of HOG-MAPK in the regulation of vegetative growth and trap development in NT fungi.