Immunogold labeling of extracellular vesicles from the fungal pathogen Fusarium graminearum reveals the presence of the protein marker Sur7

Fusarium head blight, caused by Fusarium graminearum, is one of the most threatening fungal diseases of cereals worldwide. Current practices for control of F. graminearum are not always efficient, as epidemics still occur and there is low resistance in wheat varieties. Therefore, novel antifungal targets must be discovered by analyzing the molecular interaction between F. graminearum and its host. Fungal extracellular vesicles (EVs) are small membrane-bound compartments (30-1000 nm) that carry macromolecules and support fungal virulence, hence the disruption of EV production could lead to reduced fungal pathogenicity. However, EV study is limited by the lack of surface protein markers to aid in their characterization. Therefore, the aim of this report was to target a surface protein marker with an antibody, to unlock advanced EV characterization techniques. Using the list of potential EV markers for Candida albicans, we selected the tetraspanin-like Sur7 to perform immunogold microscopy, revealing that this protein is a surface marker of F. graminearum EVs. SUR7 is present on the surface of some but not all vesicles. EVs carrying SUR7 were larger than those without the marker, suggesting that there are subtypes of fungal EVs. The epitope recognized by the anti-Sur7 antibody is conserved in other Fusarium pathogens, making Sur7 a potential pan-Fusarium EV marker. Our results unlock techniques, such as immunoaffinity chromatography and antibody labeling, to track fungal EVs and understand their biogenesis, which may lead to the development of novel antifungals.