Phospholipid signaling and multivesicular endolysosomes modulate membrane dynamics at the biotrophic interface in Rice Blast

Magnaporthe oryzae, the rice blast pathogen, secretes an arsenal of apoplastic and cytoplasmic effector proteins to suppress host immunity during the biotrophy phase. The proposed non-conventional secretion of cytoplasmic effectors into the Biotrophic Interfacial Complex (BIC), remains uncharted except for the involvement of the exocyst complex therein. Recently, the plant endocytic machinery has been implicated in translocation of cytoplasmic effectors to the host. Here, we used live cell imaging and mutant analyses to provide new insight into late endolysosomal mediators as conduits for establishment of the BIC and/or unconventional secretion across the host interface. Rerouting of the late endocytic GTPase Rab7 occurs at the BIC; and the dominant negative Rab7T22N led to significant defects in focal interface formation. FYVE biosensor and pharmacological interventions revealed that Rab7 membrane trafficking and establishment/integrity of the biotrophy interface requires the PI3 kinase Vps34 and phosphoinositide PI3(P) function. Additional pharmacological evidence supports endolysosomal trafficking to the host interface follows a distinct non-conventional secretion route too. Finally, we show that the Multi-Vesicular Bodies and lysosomal membranes act as downstream modules of the Rab7 function in precise sorting and specialised traffic of cytoplasmic effectors across the Magnaporthe-Rice interface during blast disease.