CYTOCHEMICAL ANALYSIS OF INFECTION STRUCTURES OF COLLETOTRICHUM-LINDEMUTHIANUM USING FLUOROCHROME-LABELED LECTINS

The affinity of 13 rhodamine-conjugated lectins for infection structures of Colletotrichum lindemuthianum produced on the surface of glass slides or after penetration of plastic membranes was tested. Concanavalin A (ConA, wheatgerm agglutinin (WGA) and pokeweed mitogen (PWM) bound to conidia, conidial germ-tubes, immature hyaline appressoria and appressorial germ-tubes, but mature melanized appressoria were labelled weakly or not at all. Griffonia simplicifolia lectin 1 (GS-I) labelled all fungal structures except conidia and mature melanized appressoria. Bauhinia purpurea agglutinin (BPA) bound only to conidia. The remaining eight lectins did not bind to any fungal structures. Binding of ConA, WGA, GS-I and BPA appeared hapten-specific, being inhibited by appropriate sugars. PWM binding was only partially inhibited and may have been non-specific. Pretreatment of fungal structures with proteolytic enzymes abolished BPA binding but did not affect binding of other lectins. The data suggest: (a) walls of all fungal structures contain chitin and α-linked mannans; (b) all structures except conidia also contain terminal α-linked N-acetylgalactosamine residues; (c) these carbohydrates become inaccessible to lectins during maturation of appressoria; (d) a glycoprotein containing terminal galactose and/or N-acetylgalac tosamine residues is present on the surface of conidia. © 1991.