Virulensome: a transient organelle mediating fungal virulence

Fungal pathogens utilize specialized cellular systems to overcome host defenses, yet no dedicated pathogenic organelles have been previously defined in fungi. Here, we describe a transient, membrane-bound vesicle (100–250 nm in diameter) that forms specifically within the infection structures of a nematode-trapping fungus Dactylellina haptotyla, which we term the virulensome. Density-gradient isolation yielded virulensome-enriched fractions that killed 81.6% of Caenorhabditis elegans larvae within 24 h and perforated the nematode cuticle. Quantitative proteomics revealed 486 core components, including 31 peptidases and 23 glycoside hydrolases. Knockout of each of three representative proteins—an α-mannosidase (DHGH1), a metalloendopeptidase (DHMEPE1), and a WSC-domain protein-reduced virulensome abundance by up to 80% and lowered nematode mortality by 4-fold. Conversely, recombinant DHGH1 or DHMEPE1 killed >90% of nematodes in vitro. Live-cell super-resolution imaging showed virulensomes polarizing toward the host interface, disintegrating within infection bulbs, and releasing toxic effector cargos into the nematode body. These findings define the virulensome that packages and delivers destructive enzymes in a targeted manner, revealing a previously unrecognized mechanism of pathogenesis.