Ultrastructural localization of carbohydrate in cell walls of the entomogenous hyphomycete Nomuraea rileyi

Abstract

Several probes were used in this ultrastructural study to localize polysaccharides in cell walls on conidial germ tubes, hyphal bodies, and mycelia of the entomogenous hyphomycete Nomuraea rileyi. With the exception of galactose, labelling patterns did not vary from one morphological stage to another. Galactose, which was localized by using a monoclonal antibody to a galactose-specific lectin purified from insect larval hemolymph, was absent from cell walls of hyphal bodies and conidia but was present on germ-tube and mycelial surfaces. Chitin (N-acetylglucosamine), labelled with a wheat-germ agglutinin-ferritin conjugate, was present in the middle regions of lateral walls and septa, and β1-4 glucans were located in the middle and inner regions, as indicated by binding of a cellulase-gold conjugate. An anti-laminaribiose antibody was used to label β1-3 glucans present in the outer wall areas and inner regions near the plasmalemma. The location of mannose residues as indicated by concanavalin A - ferritin binding was similar to that of the β1-3 glucans; vesicle-like structures were also labelled. None of the probes labelled the outer conidial pellicle or exocellular sheath surrounding germ tubes, and labelling of mycelial sheath was inconsistent. The absence of galactose from Nomuraea hyphal body walls is discussed in terms of host-parasite interaction. Key words: Nomuraea rileyi, entomopathogenic fungi, glycoconjugates, lectins, monoclonal antibodies.