A novel mycovirus isolated from the plant-pathogenic fungus Alternaria dianthicola.

Here, we describe the molecular characterization of a novel mycovirus isolated from a phytopathogenic fungus, Alternaria dianthicola, which we have named "Alternaria dianthicola dsRNA virus 1" (AdRV1). AdRV1 has a genome of 3,014 bp that contains two non-overlapping open reading frames (ORF1 and 2) coding for a hypothetical protein and an RNA-dependent RNA polymerase (RdRp), respectively. Based on the RdRp, AdRV1 is phylogenetically related to some unclassified dsRNA mycoviruses, including Alternaria longipes dsRNA virus 1, and shows a distant relationship to members of the family Partitiviridae. To the best of our knowledge, this is the first report of mycovirus infecting A. dianthicola.

Molecular characterization of a putative gammapartitivirus in the phytopathogenic fungus Nigrospora oryzae.

We report the molecular attributes of a novel bisegmented double-stranded RNA (dsRNA) virus, designated "Nigrospora oryzae partitivirus 1" (NoPV1), from a phytopathogenic fungus Nigrospora oryzae. The genome of NoPV1 contains two dsRNA segments (dsRNA1 and 2), 1875 bp and 1601 bp in length, respectively. dsRNA1 and -2 both have a single open reading frame encoding the RNA-dependent RNA polymerase and coat protein, respectively. NoPV1 has a high degree of sequence identity to members of genus Gammapartitivirus in the family Partitiviridae. This is the first report of a mycovirus in the family Partitiviridae that infects N. oryzae.

A mitovirus isolated from the phytopathogenic fungus Alternaria brassicicola.

Alternaria brassicicola is one of the causal agents of alternaria blackspot in rapeseed. In this study, a dsRNA segment was isolated and sequenced from the fungus. The complete nucleotide sequence of the dsRNA was 2506 bp in length and, using the fungal mitochondrial genetic code, was predicted to contain a single large open reading frame (ORF) in the positive strand. This ORF was predicted to encode a protein with 719 amino acids that contains characteristic conserved motifs of the RNA-dependent RNA polymerase (RdRp). BLAST analysis revealed that this protein had significant sequence similarity to the RdRp from viruses of the genus Mitovirus. These results indicated that the dsRNA segment represents the replicative form of a mitovirus, which is tentatively designated "Alternaria brassicicola mitovirus 1" (AbMV1) and is a new member of the genus Mitovirus in the family Narnaviridae.

A novel fusarivirus isolated from the phytopathogenic fungus Nigrospora oryzae.

In this study, we report the discovery and molecular characterization of a novel mycovirus, Nigrospora oryzae fusarivirus 1 (NoFV1) isolated from the rice-infecting fungus Nigrospora oryzae. Excluding a poly (A) tail, the genome of the virus is 7004 nucleotide (nt) long containing three putative nonoverlapping open reading frames (ORF1, ORF2, and ORF3). The large ORF1 encodes a polypeptide with a conserved RNA-dependent RNA polymerase (RdRp) domain and a helicase domain that functions for RNA replication. Each of the smaller ORF2 and the smallest ORF3 encodes a putative protein with an unknown function. Amino acid (aa) sequence similarities between the NoFV1-ORF1- and ORF2-encoded proteins and the homologous sequences from other mycoviruses were found. Phylogenetic analysis on the basis of the RdRp and helicase domains showed that NoFV1 is phylogenetically related to viruses in the newly proposed family Fusariviridae. Thus, we suggest that NoFV1 might be a novel member of family Fusariviridae.

Molecular identification of a novel victorivirus from the phytopathogenic fungus Nigrospora oryzae.

Nigrospora oryzae is a worldwide phytopathogenic fungus that can infect many plant host species. In this study, complete sequence of a novel mycovirus from N. oryzae was reported. The viral genome is 5100 base pairs in length and possesses two overlapping open reading frames (ORFs). The two ORFs potentially encode proteins that showed significant similarity to the capsid protein and RNA-dependent RNA polymerase, in the family Totiviridae, respectively. Phylogenetic tree showed that this novel mycovirus is a new member of the genus Victorivirus in the family Totiviridae. We here designated the virus as Nigrospora oryzae victorivirus 1 (NoRV1), the first putative victorivirus identified in N. oryzae.

A novel nonsegmented double-stranded RNA mycovirus identified in the phytopathogenic fungus Nigrospora oryzae shows similarity to partitivirus-like viruses.

Nigrospora oryzae is a pathogen that can infect plants of various species. Here, we report the isolation of a novel mycovirus from N. oryzae infecting rice, as well as the complete genome sequence and genomic organization of this virus, which we have named "Nigrospora oryzae nonsegmented RNA virus 1" (NoNRV1). The genome of NoNRV1 contained two non-overlapping open reading frames (ORF1 and ORF2) potentially encoding a protein with an unknown function in ORF1 and a putative RNA-dependent RNA polymerase (RdRp) in ORF2. Homology and phylogenetic analysis revealed that NoNRV1 was most similar to the Ustilaginoidea virens nonsegmented virus 1 (UvNV-1) and distantly related to members of the virus family Partitiviridae. It is proposed that NoNRV1, together with UvNV-1 and other related viruses, might represent a novel virus taxon of mycoviruses belonging to a partitivirus-like lineage.

Detection and characterization of a novel Gammapartitivirus in the phytopathogenic fungus Colletotrichum acutatum strain HNZJ001.

Spherical virus-like particles about 40nm in diameter were observed under transmission electron microscope (TEM) and two dsRNA bands (dsRNA-1 and dsRNA-2) were detected on agarose gel after extraction from the mycelial preparation of a Colletotrichum acutatum strain HNZJ001 that isolated from an anthracnose lesion on immature pepper fruit. The complete nucleotide sequences of the dsRNAs were determined. DsRNA-1 (1762 nt) and dsRNA-2 (1381 nt) each contained a single open reading frame and potentially encoded 62 kDa and 40 kDa proteins, respectively. The 62 kDa protein showed similarity to the RNA-dependent RNA polymerase (RdRp) of partitiviruses, while the 40 kDa product had no significant similarity to any published capsid protein throughout all databases, besides of low homology with the hypothetical "capsid" protein of a few partitiviruses in fungus Ustilaginoidea virens. Genome comparison and phylogenetic analysis indicated that the virus is closely related to the mycovirus in the family Partitiviridae. The results suggested a novel two-segment dsRNA virus be detected. We name it Colletotrichum acutatum partitivirus 1 (CaPV1). RT-PCR detection, using a primer pair based on the RdRp of the dsRNA-1 showed very high efficiency of CaPV1 transmission into the progenies of the fungus. Virus curing and fungal phenotype observation for evaluation of the impact of CaPV1 in host fungus were also carried out.