Extracellular Vesicles Modulate Growth and Stress Adaptation in <i>Fusarium circinatum</i>

ABSTRACT The molecular mechanisms influencing Fusarium circinatum , an important pine tree pathogen, remain partially understood. We recently reported a biofilm‐mediated response in this fungus, which supports its adaptation to harsh conditions including heat stress. Here, we report that biofilm extracellular vesicles (EVs) play a key role in this adaptive response. The EVs were purified from planktonic and biofilm cells via differential ultracentrifugation and size exclusion chromatography. Their subsequent application to fungal cells revealed the capacity of biofilm‐derived EVs (bEVs) to promote conidial viability and germination. When bEV‐treated conidia were cultured in the presence of carbon sources (PM1), nitrogen sources (PM3B) and chemical sensitivity agents (PM21D), a delayed nutrient utilisation and adaptation to antimicrobial agents such as nystatin were observed. Furthermore, exogenous application of bEVs on mono‐ and polymicrobial biofilms significantly enhanced biomass and matrix production, with EVs derived from heat‐stressed biofilm (45°C, 1 h) showing more effectiveness at promoting biomass production and resistance to the antifungal agent, tebuconazole. This is consistent with the biofilm's heat resistance previously reported for F. circinatum biofilms. Taken together, our work provides novel insights into the EV‐mediated molecular interactions that modulate environmental responses in F. circinatum .