Cephalodia of the lichen Peltigera aphthosa (L.) Willd. Specific recognition of the compatible photobiont

A specific lectin was isolated from cephalodiate thallus lobes of the liche n Peltigera aphthosa and purified to homogeneity by two steps: Chromatograp hy on carboxymethyl-cellulose (CMC); and affinity chromatography on a lacto se agarose column. TEM immunogold labeling using antibodies raised against the lectin, revealed a clear gold labeling of fungal cell walls adjacent to the cephalodial Nostoc cells. We suggest that the lectin located on the fu ngal cell wall recognizes the compatible Nostoc at the initiation of cephal odia formation.