Electron Cryo-Microscopy Studies of Helminthosporium victoriae Virus 190S.

The parasitic nature of viruses is a source of intense interest owing to the wide variety of potential hosts, which include humans, livestock, fungi, agricultural crops, as well as many others [1]. Viruses are differentiated by variations in properties such as size, capsid morphology, genomic composition, replication strategy, and host target [1, 2]. The family Totiviridae of dsRNA viruses is characterized by virions with a non-segmented dsRNA genome that infect yeast, smut, filamentous fungi, protozoa and shrimp [2-4]. The subject of this study, Helminthosporium victoriae virus 190S (HvV190S) was discovered in 1978 in the filamentous fungus Helminthosporium victoriae (H. victoriae) [2,4]. Virions have a capsid with a smooth outer surface and a maximum diameter of ~400 Å. The single dsRNA genome segment codes for two viral proteins: coat protein (CP, 81 kDa) and RNA dependent RNA polymerase (RdRp, 92 kDa) [2-4].