Molecular characterization of a novel single-stranded RNA mycovirus infecting the plant pathogenic fungus Ustilaginoidea virens

Abstract

Abstract Mycovirus is a kind of virus that infects fungi and oomycetes and can replicate in them, which widespread in all major groups of plant-pathogenic fungi and oomycetes. To date, no positive-sense single-stranded RNA (+ ssRNA) virus has been reported to be associated with Ustilaginoidea virens, the notorious causal agent of rice false smut (RFS). Here, we report the molecular characterization of a novel + ssRNA mycovirus, Ustilaginoidea virens narnavirus 1 (UvNV1), isolated from U. virens strain Uv418. UvNV1 has a genome of 3,131 nt and possesses an open reading frame (ORF) predicted to encode an RNA-dependent RNA polymerase (RdRP) of 1,017 amino acids (aa) with a molecular mass of 116.6 kDa. BLASTp analysis revealed that the RdRP showed 50.34% aa similarity to that of the previously described Zhangzhou Narna tick virus 1. Phylogenetic analyses indicated that UvNV1 is highly similar to viruses taxonomically classified in the genus Narnavirus, family Narnaviridae. Taken together, these results clearly demonstrate that UvNV1 is the first + ssRNA virus known to infect U. virens.