Fungal extracellular vesicles mediate cross-kingdom trafficking of virulence effectors into plant cells to promote infection.

Abstract

Extracellular vesicles (EVs) mediate cross-kingdom communication by delivering bioactive molecules between cells. While the role of fungal EVs in cross-kingdom RNA trafficking has been well established, whether and how they deliver pathogen-derived virulence effectors into host plants to facilitate infection remains largely unclear. Here, we report that the fungal pathogen Rhizoctonia solani secretes vesicles enriched in an EV-positive marker, RsTsp2, and two effectors, RsNP8 and RsSerp. These proteins are upregulated during the infection and are critical for the virulence of the fungus. Intriguingly, our observations reveal that clathrin-coated vesicles (CCVs) accumulate at the fungal infection sites, with the RsTsp2, RsSerp and RsNP8 detected in these vesicles, suggesting these EV-associated proteins enter plant cells via clathrin-mediated endocytosis (CME). RsNP8 was further observed in the chloroplast, where it interacts with NP8-Interacting Chloroplast Protein 1 (NICP1) in Arabidopsis. NICP1 plays a role in plant immunity by mediating the reactive oxygen species (ROS) burst during the infection, while RsNP8 suppresses this immune response. Furthermore, the silencing of RsTsp2, RsSerp, and RsNP8 in R. solani reduces sheath blight disease progression in rice plants. This work reveals that fungal EVs facilitate effectors cross-kingdom trafficking into plants, providing a novel mechanism by which eukaryotic pathogens invade their hosts.