EVIDENCE FOR VIRAL AND NAKED DOUBLE-STRANDED RNAS IN THE BASIDIOMYCETE AGROCYBE-AEGERITA

Double-stranded (ds) RNAs were purified from the vegetative mycelium of the commercial basidiomycete Agrocybe aegerita, by gel-filtration chromatography, and their dsRNA nature was demonstrated. They were shown to be distributed in two different RNase-resistant complexes which were separated by sucrose density gradient ultracentrifugation: the first complex is the encapsidated genome (6200 bp) of an isometric mycovirus; the second consists of three naked dsRNA molecules (1900-1800-1700 bp respectively) associated with large vesicles or mitochondria. This is the first report of the presence of naked dsRNA, unencapsidated, viral genome fragments which have co-evolved with their host, or else represent new replicating genetic elements (dsRNA "plasmids") of unknown function, in a non pathogenic higher fungus. © 1990 Springer-Verlag.