Detection of autophagy-related structures in fruiting bodies of edible mushroom, Pleurotus ostreatus

Autophagy is involved in various fungal morphogenetic processes. However, there are limited reports regarding the role of autophagy in mushroom fruiting body formation. The purpose of this study was to reveal the autophagy-related structures in mushroom-forming fungi. The edible mushroom Pleurotus ostreatus was used in this study. Transmission electron microscopy revealed double-membrane bounded structures containing cytoplasmic components in the fruiting bodies of this fungus. Some of these double-membrane structures were observed to interact with the vacuoles. Additionally, curved flat cisternae of various lengths were detected in the cytoplasm. The shape, size and thickness of the limiting membrane of the double-membrane structures and the flat cisternae corresponded well with those of the autophagosomes and the isolation membranes, respectively. Regarding autophagosome formation, a membrane-bound specific zone was detected near the isolation membrane, which appeared to expand along the novel membrane. This is the first detailed report showing autophagy-related structures in P. ostreatus and provides a possible model for autophagosome formation in these filamentous fungi.