Preliminary investigations of extracellular vesicles from the wheat pathogen Zymoseptoria tritici

The fungal wheat pathogen Zymoseptoria tritici resides exclusively in the apoplast during the extended latent phase of the foliar infection. Consequently, the apoplast is likely the site of significant molecular events mediating interactions between pathogen and host. The mechanisms used by Z. tritici to secrete disease-associated molecules into the harsh apoplastic environment and/or deliver them to host cells is currently unknown and represents a critical gap in our understanding of pathogen infections. While many molecules are likely secreted by classical pathways, non-classical mechanisms may also be used. Extracellular vesicles (EVs) have emerged as a potential mechanism of secretion and cross-kingdom transport. We hypothesise that EVs may play a role in pathogen-host communication during Z. tritici infection of wheat. We have made preliminary investigations of putative Z. tritici EVs isolated from in vitro culture filtrates. Ultracentrifugation-based techniques, transmission electron microscopy and single-particle analysis were used to purify and characterise putative EVs; these have been optimised to allow for proteomic profiling to begin dissecting vesicle cargoes. The establishment of these techniques in vitro will allow us to expand our investigation to in planta contexts and examine if Z. tritici EVs are deployed during infection of wheat. We anticipate this study will begin to address unanswered questions about how fungal pathogens communicate with their hosts.