Complete genome sequence of a novel mitovirus identified in the phytopathogenic fungus Alternaria tenuissima

Abstract

In this study, a novel positive-sense single-stranded RNA (+ ssRNA) mycovirus, Alternaria tenuissima mitovirus 1 (AtMV1), was identified in Alternaria tenuissima strain YQ-2-1, a phytopathogenic fungus causing leaf blight on muskmelon. The genome of AtMV1 is a single RNA molecule that is 3013 nt in length with an A + U content of 66.58% and contains a single open reading frame (ORF) using the fungal mitochondrial genetic code. The ORF was predicted to encode a 313-amino-acid RNA-dependent RNA polymerase (RdRp) with a molecular mass of 35.48 kDa, which contains six conserved motifs with the highly conserved GDD tripeptide in motif IV. The 5ʹ and 3ʹ untranslated regions were predicted to fold into stem-loop and panhandle secondary structures. The results of a BLASTp search revealed that the amino acid (aa) sequence of RdRp of AtMV1 shared the highest sequence similarity (51.04% identity) with that of Sichuan mito-like virus 30, a member of the genus Duamitovirus within the family Mitoviridae. Phylogenetic analysis based on the aa sequence of the RdRp suggested that AtMV1 is a novel member of the genus Duamitovirus. To our knowledge, this is the first report of the complete genome sequence of a new mitovirus infecting A. tenuissima.