Identification of glycoproteins specific to biotrophic intracellular hyphae formed in the Colletotrichum lindemuthianum-bean interaction.

Abstract

Monoclonal antibodies (MAbs) specific for intracellular for hyphae (IH, i.e. infection vesicles and primary hyphae). Appressoria/germ tubes and conidia of Colletotrichum lindemuthianum (Sace, & Magn.) Briosi & Cav. isolated from infected leaves of Phaseolus vulgoria L. were obtained using a co-immunization procedure. One of the MAhs; UB25, bound specifically to IH in immunofluorescence immunogold and Western blot assays: it showed no affinity for conidia, conidial germ tubes, appressoria or appressorial germ tubes growing in vitro, of for any plant components. Immunogold labeling of infected tissue prepared by high pressure freezing, freeze-substitution and low temperature embedding showed that the UB25 antigen was present in the interfacial matri surrounding IH and in the fungal wall. The antigen was confined to infection vesicles and primary hyphae in contact with host protoplast and could not be detected in primary hyphae growing in intercellular spaces. UB25 recognizes a protein epitope present in a set of N-linked glycoproteins. These glycoproteins are expressed at an early stage of intracellular development, suggesting a possible role in biotrophy or recognition.