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Two novel mitoviruses from a Canadian isolate of the Dutch elm pathogen Ophiostoma novo-ulmi (93-1224).

Hintz WE, Carneiro JS, Kassatenko I, Varga A, James D - Virol. J. (2013)

Bottom Line: Numerous mitigation strategies have been tried to eradicate this pathogen, but success has thus far been limited.An alternative approach might utilize double-stranded RNA (dsRNA) mycoviruses which have been reported to induce hypovirulence in other fungi.Naïve fungal hosts could be infected with both the engineered molecule and a helper mitovirus encoding an RdRp which would provide replication capacity for both molecules.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biology, University of Victoria, P.O. Box 3020 STN CSC, Victoria, BC V8W 3N5, Canada. whintz@uvic.ca

ABSTRACT

Background: Ophiostoma novo-ulmi is the causative agent of Dutch elm disease (DED). It is an ascomycetous filamentous fungus that ranks as the third most devastating fungal pathogen in Canada. The disease front has spread eastward and westward from the epicentre in Ontario and Quebec and is threatening elm populations across the country. Numerous mitigation strategies have been tried to eradicate this pathogen, but success has thus far been limited. An alternative approach might utilize double-stranded RNA (dsRNA) mycoviruses which have been reported to induce hypovirulence in other fungi.

Methods: Using a modified single primer amplification technique (SPAT) in combination with chromosomal walking, we have determined the genome sequence of two RdRp encoding dsRNA viruses from an O. novo-ulmi isolate (93-1224) collected from the disease front in Winnipeg.

Results: We propose that these viruses, which we have named OnuMV1c and OnuMV7 based on sequence similarity to other Ophiostoma mitoviruses, are two new members of the genus Mitovirus in the family Narnaviridae.

Conclusions: The discovery of such dsRNA elements raises the potential for engineering these viruses to include other genetic elements, such as anti-sense or interfering RNAs, to create novel and highly specific biological controls. Naïve fungal hosts could be infected with both the engineered molecule and a helper mitovirus encoding an RdRp which would provide replication capacity for both molecules.

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Alignment of the RdRp conserved amino acid motifs of O. novo-ulmi encoded by mitochondrial viruses. Virus notations and labelling of the motifs follow Hong et al. [18]. Symbols shown below the alignment indicate identical amino acids (*), as well as higher (:) and lower (.) chemically-similar residues, respectively, as defined in the CLUSTAL W program. Analysis of the amino acid sequence of OnuMV1c showed at least three common motifs (shaded) that are typically conserved in the sequences of all polymerases showing RNA template specificity. Numbers in parentheses represent the number of amino acid residues between motifs.
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Figure 4: Alignment of the RdRp conserved amino acid motifs of O. novo-ulmi encoded by mitochondrial viruses. Virus notations and labelling of the motifs follow Hong et al. [18]. Symbols shown below the alignment indicate identical amino acids (*), as well as higher (:) and lower (.) chemically-similar residues, respectively, as defined in the CLUSTAL W program. Analysis of the amino acid sequence of OnuMV1c showed at least three common motifs (shaded) that are typically conserved in the sequences of all polymerases showing RNA template specificity. Numbers in parentheses represent the number of amino acid residues between motifs.

Mentions: Alignment of the RdRp encoded by OnuMV1c and 7 with accordant regions of all other Ophiostoma mitoviruses (OnuMV1a, 1b, 3a, 3b, 4, 5, and 6) revealed three well-conserved motifs (labeled as Motifs II, III and IV in Figure 4) and three less conserved motifs[17] (labeled as Motifs I, V and VI). Also recognized were conserved amino acids D in Motif II, G in Motif III, DD in Motif IV that are common to all other RNA virus genomes[18]. Within Motif I of the Ophiostoma mitoviruses there were seven positions showing identical amino acids and an additional fifteen positions having chemically similar amino acids. Core conserved features of Motif II consisted of DLS-A/S-ATDR-F/L/M-P. Motif III consisted of GQ-P/G-MG-AC-Y/L/Q/F-S/T-SW and each of Motifs IV and VI consisted of L/I-GDD and E-F/I-AK/R respectively (Figure 4). For this group of mitoviruses most of the variability in these motifs was found in OnuMV7 which was the least conserved mitovirus species overall. Part of conserved Motif IV (GDD) also corresponded to the conserved region VI in an alignment of viruses of the family Partitiviridae[19].


Two novel mitoviruses from a Canadian isolate of the Dutch elm pathogen Ophiostoma novo-ulmi (93-1224).

Hintz WE, Carneiro JS, Kassatenko I, Varga A, James D - Virol. J. (2013)

Alignment of the RdRp conserved amino acid motifs of O. novo-ulmi encoded by mitochondrial viruses. Virus notations and labelling of the motifs follow Hong et al. [18]. Symbols shown below the alignment indicate identical amino acids (*), as well as higher (:) and lower (.) chemically-similar residues, respectively, as defined in the CLUSTAL W program. Analysis of the amino acid sequence of OnuMV1c showed at least three common motifs (shaded) that are typically conserved in the sequences of all polymerases showing RNA template specificity. Numbers in parentheses represent the number of amino acid residues between motifs.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3750502&req=5

Figure 4: Alignment of the RdRp conserved amino acid motifs of O. novo-ulmi encoded by mitochondrial viruses. Virus notations and labelling of the motifs follow Hong et al. [18]. Symbols shown below the alignment indicate identical amino acids (*), as well as higher (:) and lower (.) chemically-similar residues, respectively, as defined in the CLUSTAL W program. Analysis of the amino acid sequence of OnuMV1c showed at least three common motifs (shaded) that are typically conserved in the sequences of all polymerases showing RNA template specificity. Numbers in parentheses represent the number of amino acid residues between motifs.
Mentions: Alignment of the RdRp encoded by OnuMV1c and 7 with accordant regions of all other Ophiostoma mitoviruses (OnuMV1a, 1b, 3a, 3b, 4, 5, and 6) revealed three well-conserved motifs (labeled as Motifs II, III and IV in Figure 4) and three less conserved motifs[17] (labeled as Motifs I, V and VI). Also recognized were conserved amino acids D in Motif II, G in Motif III, DD in Motif IV that are common to all other RNA virus genomes[18]. Within Motif I of the Ophiostoma mitoviruses there were seven positions showing identical amino acids and an additional fifteen positions having chemically similar amino acids. Core conserved features of Motif II consisted of DLS-A/S-ATDR-F/L/M-P. Motif III consisted of GQ-P/G-MG-AC-Y/L/Q/F-S/T-SW and each of Motifs IV and VI consisted of L/I-GDD and E-F/I-AK/R respectively (Figure 4). For this group of mitoviruses most of the variability in these motifs was found in OnuMV7 which was the least conserved mitovirus species overall. Part of conserved Motif IV (GDD) also corresponded to the conserved region VI in an alignment of viruses of the family Partitiviridae[19].

Bottom Line: Numerous mitigation strategies have been tried to eradicate this pathogen, but success has thus far been limited.An alternative approach might utilize double-stranded RNA (dsRNA) mycoviruses which have been reported to induce hypovirulence in other fungi.Naïve fungal hosts could be infected with both the engineered molecule and a helper mitovirus encoding an RdRp which would provide replication capacity for both molecules.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biology, University of Victoria, P.O. Box 3020 STN CSC, Victoria, BC V8W 3N5, Canada. whintz@uvic.ca

ABSTRACT

Background: Ophiostoma novo-ulmi is the causative agent of Dutch elm disease (DED). It is an ascomycetous filamentous fungus that ranks as the third most devastating fungal pathogen in Canada. The disease front has spread eastward and westward from the epicentre in Ontario and Quebec and is threatening elm populations across the country. Numerous mitigation strategies have been tried to eradicate this pathogen, but success has thus far been limited. An alternative approach might utilize double-stranded RNA (dsRNA) mycoviruses which have been reported to induce hypovirulence in other fungi.

Methods: Using a modified single primer amplification technique (SPAT) in combination with chromosomal walking, we have determined the genome sequence of two RdRp encoding dsRNA viruses from an O. novo-ulmi isolate (93-1224) collected from the disease front in Winnipeg.

Results: We propose that these viruses, which we have named OnuMV1c and OnuMV7 based on sequence similarity to other Ophiostoma mitoviruses, are two new members of the genus Mitovirus in the family Narnaviridae.

Conclusions: The discovery of such dsRNA elements raises the potential for engineering these viruses to include other genetic elements, such as anti-sense or interfering RNAs, to create novel and highly specific biological controls. Naïve fungal hosts could be infected with both the engineered molecule and a helper mitovirus encoding an RdRp which would provide replication capacity for both molecules.

Show MeSH
Related in: MedlinePlus