Identification and localisation of glycoproteins in the extracellular matices around germ-tubes and appressoria of Colletotrichum species

A monoclonal antibody (MAb), UB31, is described that binds to the extracellular matrix (ECM) surrounding germ-tubes and appressoria, but not conidia, of the bean anthracnose fungus, Colletotrichum lindemuthianum. Comparative localisation studies with MAb UB26, which has the same cell type specificity, suggest that the ECM is heterogeneous in composition. Immunofluorescence showed that UB31 labelled appressoria more intensely than germ-tubes, whereas UB26 labelled these structures to a similar extent. Immunofluorescence and TEM-immunogold labelling showed that UB31 antigens were located close to the appressorial wall, while UB26 antigens extended further away from the wall. MAb UB31 bound to the ECMs of all six Colletotrichum species tested. Western blotting and ELISA indicated that the antibody recognises a high M-r glycoprotein (> 200000) that may be linked to melanin. The glycoprotein recognised by UB31 was not removed from substrata by ultrasonication, suggesting it may contribute to germling adhesion.