Lipid mobilization and acid phosphatase activity in lytic compartments during conidium dormancy and appressorium formation of Colletotrichum graminicola

Colletotrichum graminicola, a pathogen of sorghum and corn, was investigated prior and during germination as to certain aspects of acid phosphatase activity and lipid mobilization. Ungerminated conidia cytoplasm was filled with lipid deposits, which were mobilized during the germination process. Cytochemical ultrastructural examination showed that conidia vacuoles exhibit acid phosphatase activity, which is suggestive of lytic activity. Lipid bodies, stored in the ungerminated conidia cytoplasm, were internalized by vacuoles in a process analogous to microautophagy and were apparently digested inside them. The lipid bodies disappeared and vacuoles became enlarged in conidial cells during germination. Appressoria also showed acid phosphatase activity in multiple heterogeneous vesicles which were, in most cases, juxtaposed with lipid bodies. These results suggest that the vacuolar system plays an important role during C. graminicola germination and that the initial stages of lipid metabolization are taking place inside the vacuoles.