Abstract
Two novel double-stranded RNA (dsRNA) mycoviruses, termed Fusarium poae dsRNA virus 2 (FpV2) and Fusarium poae dsRNA virus 3 (FpV3), were isolated from the plant pathogenic fungus, Fusarium poae strain SX63, and molecularly characterized. FpV2 and FpV3, with respective genome sequences of 9518 and 9419 base pairs (bps), are both predicted to contain two discontinuous open reading frames (ORFs), ORF1 and ORF2. A hypothetical polypeptide (P1) and a RNA-dependent RNA polymerase (RdRp) are encoded by ORF1 and ORF2, respectively. Phytoreo_S7 domain (pfam07236) homologs were detected downstream of the RdRp domain (RdRp_4; pfam02123) of the ORF2-coded proteins of both FpV2 and FpV3. The same shifty heptamers (GGAAAAC) were both found immediately before the stop codon UAG of ORF1 in FpV2 and FpV3, which could mediate programmed –1 ribosomal frameshifting (–1 PRF). Phylogenetic analysis based on RdRp sequences clearly place FpV2 and FpV3 in a taxonomically unassigned dsRNA mycovirus group. Together, with a comparison of genome organization, a new taxonomic family termed Fusagraviridae is proposed to be created to include FpV2- and FpV3-related dsRNA mycoviruses, within which FpV2 and FpV3 would represent two distinct virus species.
Highlights
Mycoviruses, or fungal viruses, selectively infect fungi and are widespread in all major taxonomic fungal groups [1]
Several double-stranded RNA (dsRNA) species have been unassigned to any genus or family; for example, Botrytis cinerea RNA virus 1 (BcRV1), Fusarium graminearum dsRNA mycovirus-3 (FgV3), Fusarium virguliforme dsRNA mycovirus 1 and 2 (FvV1 and FvV2), Macrophomina phaseolina dsRNA virus 2 (MpRV2) and Sclerotinia sclerotiorum dsRNA mycovirus-L (SsNsV-L); these are large monopartite viruses representing an entirely different evolutionary lineage of dsRNA viruses [6,7,8,9]
We present the sequence and molecular characteristics of two novel relative dsRNA mycoviruses, termed Fusarium poae dsRNA virus 2 (FpV2) and Fusarium poae dsRNA virus 3 (FpV3), both isolated from identical Fusarium poae strain SX63
Summary
Mycoviruses, or fungal viruses, selectively infect fungi and are widespread in all major taxonomic fungal groups [1]. Most mycoviruses contain either double-stranded (ds) RNA or positive single-stranded (ss) RNA genomes, and one has an ssDNA genome, Sclerotinia sclerotiorum hypovirulence-associated DNA virus 1 (SsHADV-1) [2]. Six of these are composed of ssRNA genomes (Hypoviridae, Narnaviridae, Alphaflexiviridae, Gammaflexiviridae, Endornaviridae, and Barnaviridae), five consist of dsRNA genomes (Reoviridae, Partitiviridae, Chrysoviridae, Totiviridae, and Megabirnaviridae), and the other two families hold RNA reverse-transcribing genomes (Metaviridae and Pseudoviridae) [5]. Several dsRNA species have been unassigned to any genus or family; for example, Botrytis cinerea RNA virus 1 (BcRV1), Fusarium graminearum dsRNA mycovirus-3 (FgV3), Fusarium virguliforme dsRNA mycovirus 1 and 2 (FvV1 and FvV2), Macrophomina phaseolina dsRNA virus 2 (MpRV2) and Sclerotinia sclerotiorum dsRNA mycovirus-L (SsNsV-L); these are large monopartite viruses representing an entirely different evolutionary lineage of dsRNA viruses [6,7,8,9]
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