Multiple Mitochondrial Viruses in an Isolate of the Dutch Elm Disease FungusOphiostoma novo-ulmi

Hong, Yiguo; Dover, Sharon L; Cole, Thomas E.; Brasier, C. M.; Buck, K. W.

doi:10.1006/viro.1999.9691

Cited by 152 publications

(124 citation statements)

References 32 publications

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“…Co-infections by distantly related or congeneric mycoviruses have been described (Peever et al, 1997;Lakshman et al, 1998;Preisig et al, 1998;Hong et al, 1999;Ghabrial et al, 2002;Osaki et al, 2004;Park et al, 2005;Tuomivirta and Hantula, 2005;Vainio et al, 2012Vainio et al, , 2013a, and the overall similarity of the co-infecting viruses has been relatively low (30-53% at the aa level or o55% at the nt level). Sun et al (2006) have described that the transmission of Mycoreovirus 1 is enhanced by co-infection with Cryphonectria hypovirus 1 in C. parasitica.…”

Section: Discussionmentioning

confidence: 99%

Viruses accumulate in aging infection centers of a fungal forest pathogen

Vainio¹,

Müller²,

Korhonen³

et al. 2014

The ISME Journal

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Fungal viruses (mycoviruses) with RNA genomes are believed to lack extracellular infective particles. These viruses are transmitted laterally among fungal strains through mycelial anastomoses or vertically via their infected spores, but little is known regarding their prevalence and patterns of dispersal under natural conditions. Here, we examined, in detail, the spatial and temporal changes in a mycovirus community and its host fungus Heterobasidion parviporum, the most devastating fungal pathogen of conifers in the Boreal forest region. During the 7-year sampling period, viruses accumulated in clonal host individuals as a result of indigenous viruses spreading within and between clones as well as novel strains arriving via airborne spores. Viral community changes produced pockets of heterogeneity within large H. parviporum clones. The appearance of novel viral infections in aging clones indicated that transient cell-to-cell contacts between Heterobasidion strains are likely to occur more frequently than what was inferred from genotypic analyses. Intraspecific variation was low among the three partitivirus species at the study site, whereas the unassigned viral species HetRV6 was highly polymorphic. The accumulation of point mutations during persistent infections resulted in viral diversification, that is, the presence of nearly identical viral sequence variants within single clones. Our results also suggest that co-infections by distantly related viral species are more stable than those between conspecific strains, and mutual exclusion may play a role in determining mycoviral communities.

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Section: Discussionmentioning

confidence: 99%

Viruses accumulate in aging infection centers of a fungal forest pathogen

Vainio¹,

Müller²,

Korhonen³

et al. 2014

The ISME Journal

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“…An amino acid sequence alignment including sequences of HetMV1-an1 and related mitovirus species was generated using MAFFT version 7.017. The resulting alignment was examined by eye according to the conserved motifs of mitoviral polymerases (Hong et al, 1999), which were accurately aligned. Dendrogram construction was conducted with Bayesian clustering using the MrBayes program implemented in Geneious Pro 5.5.8 and neighbour-joining clustering using MEGA 5.…”

Section: Methodsmentioning

confidence: 99%

Diagnosis and discovery of fungal viruses using deep sequencing of small RNAs

Vainio¹,

Jurvansuu²,

Streng

et al. 2015

Journal of General Virology

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Analysis of virus-derived small RNAs with high-throughput sequencing has been successful for detecting novel viruses in plants and invertebrates. However, the applicability of this method has not been demonstrated in fungi, although fungi were among the first organisms reported to utilize RNA silencing. Here, we used virus-infected isolates of the fungal species complex Heterobasidion annosum sensu lato as a model system to test whether mycovirus genome segments can be detected with small RNA deep sequencing. Species of the genus Heterobasidion are some of the most devastating forest pathogens in boreal forests. These fungi cause wood decay and are commonly infected with species of the family Partitiviridae and the unassigned virus species Heterobasidion RNA virus 6. Small RNA deep sequencing allowed the simultaneous detection of all eight double-stranded RNA virus strains known to be present in the tested samples and one putative mitovirus species (family Narnaviridae) with a single-stranded RNA genome, designated here as Heterobasidion mitovirus 1. Prior to this study, no members of the family Narnaviridae had been described as infecting species of Heterobasidion. Quantification of viral double-and single-stranded RNA with quantitative PCR indicated that co-infecting viral species and viruses with segmented genomes can be detected with small RNA deep sequencing despite vast differences in the amount of RNA. This is the first study demonstrating the usefulness of this method for detecting fungal viruses. Moreover, the results suggest that viral genomes are processed into small RNAs by different species of Heterobasidion.

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“…p91 and p104 have consensus sequences for RNA-dependent RNA polymerases that are closely related to those of the replicases of RNA coliphages. Recently, several RNAs of viral origin have been isolated from plant pathogenic fungi (11,12). When the mitochondrial genetic code of fungi was applied, these RNAs showed only one open reading frame with consensus sequences for RNA-dependent RNA polymerases.…”

mentioning

confidence: 99%

Persistent Yeast Single-stranded RNA Viruses Exist in Vivo as Genomic RNA·RNA Polymerase Complexes in 1:1 Stoichiometry

Solórzano¹,

Rodríguez-Cousiño

Esteban

et al. 2000

Journal of Biological Chemistry

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Yeast narnavirus 20 S and 23 S RNAs encode RNA-dependent RNA polymerases p91 and p104, respectively, but do not encode coat proteins. Both RNAs form ribonucleoprotein complexes with their cognate polymerases. Here we show that these complexes are not localized in mitochondria, unlike the closely related mitoviruses, which reside in these organelles. Cytoplasmic localization of these polymerases was demonstrated by immunofluorescence and by fluorescence emitted from green fluorescent protein-fused polymerases. These fusion proteins were able to form ribonucleoprotein complexes as did the wild-type polymerases. Fluorescent observations and cell fractionation experiments suggested that the polymerases were stabilized by complex formation with their viral RNA genomes. Immunoprecipitation experiments with anti-green fluorescent protein antibodies demonstrated that a single polymerase molecule binds to a single viral RNA genome in the complex. Moreover, the majority (if not all) of 20 S and 23 S RNA molecules were found to form complexes with their cognate RNA polymerases. Since these viral RNAs were not encapsidated, ribonucleoprotein complex formation with their cognate RNA polymerases appears to be their strategy to survive in the host as persistent viruses.RNAs are involved in many fundamental biological processes and also serve as genetic entities. Although some RNAs have catalytic activities by themselves, most of their tasks are accomplished through interactions with proteins. Because of their versatility, RNA-protein interactions not only serve catalytic purposes, but can also affect the fate of the RNAs themselves. For example, the stability of mRNA is governed by complex interactions between cis-elements on the RNA and various proteins (1, 2). It is also well known that rRNAs, once assembled into ribosomal subunits, become extremely stable in vivo.(ϩ)-Single-stranded 20 S RNA (ScNV-20 S) and 23 S RNA (ScNV-23 S) viruses belong to the family Narnaviridae (3) and infect many Saccharomyces cerevisiae laboratory strains. Unlike other fungal viruses, they are not encapsidated in vivo into viral particles. Then, how can they survive stably without protective coats in the host cell as persistent viruses? This is one of the interesting questions to be answered. 20 S and 23 S RNA viruses have no extracellular transmission pathway and do not render any phenotypic changes in the host. They show 4ϩ:0 segregation in meiosis and can be efficiently transmitted during cytoduction using karyogamy-deficient mutants, thus suggesting their non-nuclear localization. 20 S and 23 S RNAs are induced under nitrogen starvation conditions, and their copy numbers reach up to 100,000 copies/ cell. They are stably maintained; and at present, there are no known procedures to eliminate these cryptic viruses from the host cell.The complete nucleotide sequences of 20 S and 23 S RNAs have been determined: 2514 bases for 20 S RNA and 2891 bases for 23 S RNA (4). These RNAs do not encode coat proteins, but do encode their RNA-dependent RNA poly...

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Multiple Mitochondrial Viruses in an Isolate of the Dutch Elm Disease FungusOphiostoma novo-ulmi

Cited by 152 publications

References 32 publications

Viruses accumulate in aging infection centers of a fungal forest pathogen

Viruses accumulate in aging infection centers of a fungal forest pathogen

Diagnosis and discovery of fungal viruses using deep sequencing of small RNAs

Persistent Yeast Single-stranded RNA Viruses Exist in Vivo as Genomic RNA·RNA Polymerase Complexes in 1:1 Stoichiometry

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