Eisosomal proteins are essential for plant–fungal interaction of Neurospora crassa and the sweetgrass Brachypodium distachyon

Plant fungal associations encompass a continuum from pathogenic to mutualistic interactions that have profoundly shaped terrestrial ecosystems. The ability of fungi to colonize living plant tissues typically depends on tightly coordinated signaling and membrane organizations processes. Recently, we described a previously unrecognized endophytic interaction between the filamentous model fungus Neurospora crassa and the sweetgrass Brachypodium distachyon. Contrary to its long-standing classification as a strictly saprotrophic species, N. crassa was observed to invade root epidermal and cortical cells and to colonize the vascular bundles without inducing disease symptoms, indicating a stable nonpathogenic association. To identify functional elements in this interaction, we systematically screened N. crassa mutants lacking key signaling and membrane-associated components. Disruption of certain signaling pathways including MAP kinase and NADPH oxidase mutants did not impair plant colonization. However, deletion of ncw-6 or div-23, two proteins associated with and localized to eisosomes, completely disrupted plant root colonization of N. crassa. Eisosomes are plasma membrane microdomains in fungi that contain transporters and integral membrane proteins. These findings suggest an integral function of eisosomes in plant-fungal interaction of N. crassa and possibly other fungi as well.