EvSec22, a SNARE Protein, Regulates Hyphal Growth, Stress Tolerance, and Nematicidal Pathogenicity in Esteya vermicola

<i>Bursaphelenchus xylophilus</i>, the causative agent of pine wilt disease (PWD), poses a severe global threat to coniferous forests. <i>Esteya vermicola</i>, an endoparasitic nematophagous fungus, exhibits promising biocontrol potential against this pinewood nematode. The vesicular transport system, evolutionarily conserved in eukaryotes, is essential for fungal pathogenicity. Based on our genome sequence of <i>E. vermicola</i> CBS115803, we identified <i>EvSec22</i>, a gene encoding a SNARE protein implicated in vesicular transport process. This study investigates the role of EvSec22 in <i>E. vermicola</i> during nematode infection, utilizing our optimized gene knockout methodology. Infection assays revealed that <i>EvSec22</i> deletion significantly impaired the pathogenicity of <i>E. vermicola</i> against <i>B. xylophilus</i>. Phenotypic analyses revealed that the <i>ΔEvSec22</i> mutant exhibited suppressed hyphal growth, reduced conidiation, and abnormal septal spacing. Furthermore, the mutant showed significantly diminished tolerance to osmotic stress (sorbitol) and oxidative stress (hydrogen peroxide). Overall, the <i>EvSec22</i> gene is associated with the virulence of <i>E. vermicola</i> CBS115803 against <i>B. xylophilus</i>, and its deletion also affects the normal growth of <i>E. vermicola</i> and its tolerance to abiotic stress. This study providing new insights into SNARE protein functions in fungal biocontrol agents.