INVOLVEMENT OF FIMBRIAE IN FUNGAL HOST MYCOPARASITE INTERACTION

Germ tubes of the biotrophic haustorial mycoparasite, Piptocephalis virginiana, show directed growth towards hyphae of the mucoraceous fungi Mortierella pusilla, Phascolomyces articulosus and M. candelabrum. The mycoparasite will subsequently attach to cell walls of both the susceptible, M. pusilla, and resistant, P. articulosus, hosts but not to the non-host M. candelabrum. Fimbriae were observed by electron microscopy on the surfaces of the host and non-host species but not the mycoparasite. Polyclonal antiserum prepared against the fimbrial protein of Ustilago violacea crossreacted with 64 kDa proteins from both M. pusilla and P. articulosus and 60 and 57 kDa proteins from M. candelabrum. These proteins were electroeluted from polyacrylamide gels and were shown subsequently to form fibrils with the same diameter as the cell surface fimbriae. To ascertain the role of fimbriae in host-mycoparasite interactions, the antiserum was incubated with P. virginiana and M. pusilla, and with P. virginiana and P. articulosus. Contacts between mycoparasite and host were blocked significantly by the antiserum. This inhibition was not due to any effect of the antiserum on the linear growth rate of mycoparasite germ tubes. Thus, it was proposed that the recognition of fimbriae by the mycoparasite leads to directed growth and contact between mycoparasite germ tubes and the hyphae of a potential host. © 1992.