Involvement of the 90 kDa glycoprotein in adhesion of Nectria haematococca macroconidia

Previously we demonstrated that Nectria haemalococca macroconidia become adhesive within 5 min and adhere at the spore apices to substrata and to other spores. At the same time, the macroconidia produce mucilage at the spore tips which binds Concanavalin A (Con A), and produce a macroconidial-specific 90 kDa glycoprotein which binds Con A; Con A inhibits macroconidial adhesion. Here we demonstrate that snowdrop lectin, which specifically binds to alpha-mannose, also inhibits adhesion, and that polyclonal IgG prepared against the 90 kDa glycoprotein inhibits adhesion of both ungerminated and germinated macroconidia. Antiadhesive activity of the IgG is reduced by incubation of the antibodies with mannan; the mannan alone has no effect on adhesion. These data, and the fact that the anti-90 kDa IgG did not bind to the deglycosylated glycoprotein, suggest that mannose residues on the 90 kDa glycoprotein are involved in adhesion of N. haematococca macroconidia. We also demonstrate that the anti-90 kDa IgG primarily binds to the region with the spore tip mucilage, and that two transglutaminase inhibitors, iodoacetamide and cystamine, reduce adhesion, the macroconidial tip mucilage and the 90 kDa glycoprotein. Finally, consistent with compounds which become increasingly polymerized, we show that visualization of the macroconidial tip mucilage and the detection of the 90 kDa glycoprotein is transient over time. We postulate that a precursor of the 90 kDa glycoprotein in the spore tip mucilage is exocellularly cross-linked by a transglutaminase, and that the 90 kDa glycoprotein is a fungal glue. (C) 1997 Academic Press Limited.