Aegerolysin proteins from the fungal genus Pleurotus have been recently found to interact with ceramide phosphoethanolamine (CPE), a membrane sphingolipid that is specific to invertebrates. Upon binding to lipid membranes, Pleurotus aegerolysins recruit pleurotlysin B (PlyB) to form multimeric bi-component, A2B-type, transmembrane cytolytic complexes.
As some of bacterial aegerolysin-based heteromeric complexes have already been reported to have selective insecticidal properties, and have been successfully introduced into plants via genetic transformation, our aim was to investigate whether similar complexes deriving from Pleurotus spp. have the same potential.
We isolated and characterized three recombinant Pleurotus aegerolysins, namely ostreolysin A6 (OlyA6), pleurotolysin A2 (PlyA2) and erylysin A (EryA), and their MACPF-protein partner PlyB. The insecticidal properties of these aegerolysins, either alone or in combination with PlyB, were studied on Colorado potato beetle (CPB) larvae, Western corn rootworm (WCR) larvae, spotted wing drosophila, mealworm, grain aphid and greater wax moth.
These aegerolysins bind to insect cells and artificial lipid membranes with physiologically relevant CPE concentrations. Moreover, aegerolysins permeabilize these membranes when combined with PlyB. OlyA6/PlyB, PlyA2/PlyB and EryA/PlyB complexes have shown a selective toxic effect on CPB larvae and WCR, and not to other tested insect pests. Exposure of CPB larvae to leaf disks treated with protein mixtures caused significant larval mortalities on day 5 after initiation of the experiment, and exposure of WCR larvae to artificial food mixed with OlyA6/PlyB and PlyA2/PlyB resulted in significant mortalities on day 5 after the initiation of the experiment. The ability of aegerolysins from the fungal genus Pleurotus to target CPE, and to form transmembrane pores with PlyB, suggest their possible use as biopesticides for controlling CPB larvae and WCR.