XVI International Botanical Congess

Many fungi produce large quantities of surface proteinaceous fibrils which strongly resemble bacterial fimbriae or pili. These fungal fimbriae have been most studied in the basidiomycete Ustilago violacea (= Microbotryum violaceum). In this species they are 7 ?m in diameter and vary greatly in length sometimes reaching over 20 ?m. The fibrils are produced over the entire surface of the hyphae and sporidia of both mating types. Defimbriated cells (mechanical or heat treatment) extrude fimbriae at the rate of ca 1 ?m/h. The fimbriae consist of a 74 kDa glycoprotein containing an aglycone of 47 kDa that is collagenous in nature coupled with a mannose dominated glycosylated moiety, and also short (30 bases) ssRNA molecules. Fimbriae of similar appearance but unknown structure have been detected on many other fungi and in some algae. Given the unique ribonucleoprotein structure of these fimbriae, the collagenous nature of the protein (previously unknown outside Animalia) and their ability to extend for great distances into host plants, their functions and properties are of great interest in studies of both animal and plant pathogenicity. We summarize the current state of our knowledge of these structures and their possible functions in processes as diverse as conjugation, flocculation and pathogenicity.