P-310 - Cross-kingdom RNA communication in the Hordeum vulgare–Blumeria hordei Interaction

The establishment of host-microbe interactions involves molecular communication between both partners, potentially mediated by extracellular vesicles (EVs) that facilitate the transfer of small RNAs and proteins for intra- and inter-organismal exchange. Profiling of H. vulgare EVs during B. hordei infection revealed a polydisperse EV population with an associated repertoire of biomolecules. Site-specific profiling of sRNAs discovered an enrichment of H. vulgare rRNA fragments in EVs and infected epidermis, as well as particular B. hordei tRNA fragments in haustoria. This research explores the emerging biological function of selected sRNAs along with rRNA and tRNA in the course of the Hv–Bh interaction. Furthermore,the association of the RALPH effector with crude EVs and its interaction with total H. vulgare RNA suggest that it binds to Hv sRNAs involved in ckRNAi and blocking their function by preventing binding to the target mRNA. Therefore, we aim to characterize RNA-binding proteins to gain insights into their roles in transport and functional activity of transferred sRNAs. Proteomic analyses have revealed an enrichment of biotic stress response proteins associated with EVs. The H. vulgare t-SNARE protein Ror2, a A. thaliana PEN1 ortholog and EV marker, accumulates in EVs during infection and might serve as a potential EV marker. In conclusion, the EV-mediated transfer of sRNAs provides insights into the underlying molecular mechanisms governing host-pathogen interactions.