MgAtg9 trafficking in Magnaporthe oryzae

Autophagy is a vacuolar/lysosomal cytoplasmic recycling system in eukaryotic cells. ScATG9 is indispensable for autophagy in Saccharomyces cerevisiae. Here, we deleted MgATG9, the orthologue of ScATG9, via targeted gene replacement in the phytopathogenic filamentous fungus Magnaporthe oryzae, and then analyzed the cellular distribution pattern of EGFP-MgAtg9 in the Mgatg9 Delta mutant. We detected an expression profile of multiple green dots in the conidial cell inoculated in rich media and in the appressoria differentiated from the conidia in H2O. Concurrent with the punctation, we found some fluorescent signals localized on the central vacuole of the submerged hyphae from the conidia cultured in rich media. Next, we introduced DsRed2-MgAtg8 into the Mgatg9 Delta mutant expressing EGFP-MgAtg9 and observed partial overlap at multiple sites in the conidial cell, reminiscent of that in the mammalian system. Our findings further led to the postulation that the multiple sites where the two fusions colocalized tend to merge as a central structure in the conidial cell. Finally, we tested the expression of EGFP-MgAtg9 in null mutants of MgATG1, 2, 13 and 18, respectively. We speculate that MgAtg1, 2 and 18, but not MgAtg13, is required for MgAtg9 cycling through the multiple colocalization sites to its storage pools in the conidial cell of M. oryzae, and fusion of these colocalization sites into a central structure could be governed through other unidentified mechanisms.