Phospholipid acylhydrolases trigger membrane degradation during fungal sporogenesis

Abstract: Armillaria ostoyae is a phytopathogen infecting coniferous trees. Fruiting bodies of this basidiomycete contain high phospholipase A1 (PLA1) activity. In this paper, the role of phospholipid-deacylating activity, which was also detected in fruiting bodies of other basidiomycetes, in the fungal lipid metabolism is elucidated. For A. ostoyae the occurrence of PLA1 activity is shown to be restricted to the late reproductive phase, correlating with the release of mature spores. Specific expression in the spore-producing tissue provides evidence for the involvement of PLA1 in spore formation. Based on lipid analysis, the degradation of membrane phospholipids in this tissue can be ascribed mainly to PLA1 activity because other enzymes such as phospholipases C and D, triglyceride lipase and phosphatidic acid phosphatase had only low activities. A concomitant increase in the concentration of fatty acids and their anabolites (di- and triglycerides), which are used as storage lipids in the developing fungal spore cells, was observed. Therefore, PLA1 contributes to the formation of spores by providing membrane constituents as a source of fatty acids. [Copyright &y& Elsevier]