P-167 - Three newly characterized Neofusicoccum parvum small secreted proteins differentially affect defense responses in Nicotiana benthamiana and Vitis vinifera

Botryosphaeria dieback (BD) is a major Grapevine Trunk Disease causing significant economic losses worldwide. Since the early 2000s ban on sodium arsenite, efficient treatments have been lacking. Neofusicoccum parvum is among the most aggressive xylem-inhabiting Botryosphaeriaceae fungi. However, the molecular mechanisms of host-microbe interactions remain unclear. This study focuses on three cysteine-rich small secreted proteins (SCPs) of N. parvum, selected for their As(III) affinity and secretion in woody tissues during infection. They belong to the cerato-platanin and major allergen Alt a1 families. Structural analysis reveals similarities with effectors from wilting pathogens infecting woody plants. Quantification in infected wood shows early SCP expression during colonization. Transient expression of SCPs in Nicotiana benthamiana and Vitis vinifera leaves via agroinfiltration enables screening of 17 stress- and pathogen-responsive genes. A differential effect on gene expression is observed between host and non-host plants, with downregulation of genes related to ROS- and ethylene-mediated pathways, potentially involved in signaling and tyloses synthesis, suggesting a role in wood colonization. Additionally, stilbene synthase overexpression matches with stilbene accumulation in infected plants. These SCPs likely play key roles in grapevine infection, and their As(III) affinity suggests sodium arsenite may inhibit fungal effectors beyond its direct antifungal action.