MgAtg9 trafficking inMagnaporthe oryzae

Abstract

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 Mgatg9Delta 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 H(2)O. 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 Mgatg9Delta 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.

Autophagy vitalizes the pathogenicity of pathogenic fungi

“…However, such a central structure is not detected in proximity of the vacuoles of moatg13Δ and moatg17Δ mutants. 63 These findings are not consistent with observations in yeast. 64,65 It can be speculated that MoAtg13 and/or MoAtg17 has lost its function in autophagy in M. oryzae and therefore the Atg1-Atg13 complex might not be preserved across all fungi during evolution.…”

“…By contrast, the expression pattern of the same fusion proteins is not changed in a moatg13Δ mutant. 63 It was concluded that cycling of MgAtg9 through multiple sites (as indicated by colocalization studies) to its storage pools in the cytosol of M. oryzae depends on MoATG1, MoATG2, and MoATG18, but not MoATG13. Loss of MoATG1, MoATG2 and MoATG18 might prevent MoATG9 from leaving the PASlike structures in M. oryzae.…”

“…86 localizes to the PAS as reported previously. 63 When a DsRed2-MoAtg8 fusion protein is expressed in an moatg5Δ mutant also expressing GFP-MoAtg5, then the DsRed2-MoAtg8 protein colocalizes with GFP-MoAtg5 puncta. The GFP-MoAtg5 and DsRed2-MoAtg8 fusion proteins are colocalized in the perivacuolar region in M. oryzae (unpublished data) consistent with at least transient localization to the PAS.…”

Linkage of autophagy to fungal development, lipid storage and virulence inMetarhizium robertsii

“…1D), which is consistent with studies in mammals that show the constitutive occurrence of autophagy. 21 Similar to the pattern of Atg protein localization in yeast and Magnaporthe cells, [22][23][24] punctate localization of MrAtg8 was observed in conidia, germlings, appressoria and hyphal bodies (fungal cells harvested from the hemolymph of infected insect) by N-terminal fusion with the red fluorescent protein (RFP) ( Fig. 2A-D).…”

The autophagy gene BbATG5, involved in the formation of the autophagosome, contributes to cell differentiation and growth but is dispensable for pathogenesis in the entomopathogenic fungus Beauveria bassiana

“…In the rice blast fungus M. grisea (oryzae), deletion mutants of Mgatg1, Mgatg4, Mgatg5, Mgatg8 and Mgatg9 result in an inability to form the infection structure and loss of the ability of the fungus to infect its plant host (Veneault-Fourrey et al, 2006;Liu et al, 2010Liu et al, , 2007Dong et al, 2009;Lu et al, 2009). In the basidiomycete plant-pathogenic fungus Ustilago maydis, deletion of atg1 or atg8 also blocks autophagy and affects morphogenesis, but the Datg1 strain is only slightly less pathogenic than the wild-type (WT), whereas the Datg8 strain is significantly reduced in fungal pathogenicity (Nadal & Gold, 2010).…”