Ultrastructure of virus-like particles in <i>Plasmopara halstedii</i>

Gulya, T. J.; Freeman, Thomas; Mayhew, D. E.

doi:10.1139/b92-044

Cited by 8 publications

(5 citation statements)

References 10 publications

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“…Similar virions or other VLPs were never observed in sunflower cells of either infected or healthy plants. These results were in accordance with those reported for the North American race 2 isolates of P. halstedii (Gulya et al ., 1992), which corresponds to pathotype 300 (Gulya, 2007).…”

Section: Resultssupporting

confidence: 93%

“…As far as yet determined, but regardless of their host's pathotype, geographical origin and fungicide sensitivity, all viral characteristics of different P. halstedii isolates were identical to one another. Also in agreement with the result of this study were the morphological and biochemical characters which have been previously reported for virions occurring in a single North American pathotype (Gulya et al ., 1992; Mayhew et al ., 1992). In contrast to S. macrospora , in which two isometric viruses showed clear differences in many characters (Honkura et al ., 1983; Shirako and Ehara, 1985; Yokoi et al ., 1999, 2003), the results of our study suggested the presence of a single virus in P. halstedii.…”

Section: Resultssupporting

confidence: 93%

“…(1990) described isometric virions which were found in a single North American pathotype of P. halstedii . The putative coat protein was determined to consist of a 37.5 kDa‐polypeptide and RNA was determined to encode the viral genome (Gulya et al ., 1992; Mayhew et al ., 1992). P. halstedii is distributed world‐wide and shows a broad spectrum of pathotypes (physiological races) as reported by Gulya (2007).…”

Section: Introductionmentioning

confidence: 99%

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Different pathotypes of the sunflower downy mildew pathogen Plasmopara halstedii all contain isometric virions†

Heller-Dohmen

Göpfert

Hammerschmidt

et al. 2008

Molecular Plant Pathology

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Eight pathotypes of Plasmopara halstedii were screened to investigate the occurrence of virions and the potential viral influence on the pathogenicity of the sunflower downy mildew pathogen. In 23 of 26 P. halstedii isolates derived from eight countries in Europe, North America and South America, virions were detected by transmission electron microscopy. By contrast, there were no ultrastructural indications of virus-like particles in eight other related Oomycetes. The virions of representative P. halstedii isolates were morphologically and biochemically characterized and compared among each other. Regardless of their host's pathotypes, the geographical origin of the isolate and the sensitivity towards the fungicide metalaxyl, the viral characters obtained were uniform. The virions were isometric and measured approximately 37 nm in diameter. One polypeptide of c. 36 kDa and two segments of single-stranded RNA (3.0 and 1.6 kb) were detected. Both viral RNA segments were detected by capillary electrophoresis in the three remaining P. halstedii isolates where virions were undetectable by transmission electron microscopy. Virus-specific primers for the 1.6 kb-segment were synthesized and used to determine and compare a partial sequence of the viral coat protein among virions of different P. halstedii pathotypes. In all tested isolates, fragments of 0.7 kb were amplified which were directly sequenced. Sequence variation was insignificant. As both less aggressive and more aggressive P. halstedii isolates contained virions, the presence or absence of virions could not explain the diverse aggressiveness of the downy mildew pathogen towards sunflower. Moreover, the results indicated that pathogenicity of P. halstedii was not related to variation in morphological or biochemical characters of the virions.

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Section: Resultssupporting

confidence: 93%

Section: Resultssupporting

confidence: 93%

Section: Introductionmentioning

confidence: 99%

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Different pathotypes of the sunflower downy mildew pathogen Plasmopara halstedii all contain isometric virions†

Heller-Dohmen

Göpfert

Hammerschmidt

et al. 2008

Molecular Plant Pathology

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“…A molecular mass of the CP of ca. 37.5 kDa [ 8 ] to 36 kDa [ 1 ] was estimated previously by SDS-PAGE analysis. This was in discrepancy with the molecular mass of 40 kDa calculated for the 375 amino acids deduced from the nucleotide sequence of ORF2.…”

Section: Resultsmentioning

confidence: 99%

“…Almost 20 years ago, isometric virions were found in a single North American pathotype of P. halstedii [ 7 ]. The CP was determined to consist of a 37.5 kDa polypeptide and RNA was determined to encode the viral genome [ 8 , 9 ]. A more recent screening of P. halstedii isolates from different countries showed the occurrence of morphologically and biochemically indistinguishable virions in all samples independent of their host's origin or pathotype or fungicide tolerance [ 1 ].…”

Section: Introductionmentioning

confidence: 99%

The nucleotide sequence and genome organization of Plasmopara halstedii virus

Heller-Dohmen

Göpfert

Pfannstiel

et al. 2011

Virol J

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BackgroundOnly very few viruses of Oomycetes have been studied in detail. Isometric virions were found in different isolates of the oomycete Plasmopara halstedii, the downy mildew pathogen of sunflower. However, complete nucleotide sequences and data on the genome organization were lacking.MethodsViral RNA of different P. halstedii isolates was subjected to nucleotide sequencing and analysis of the viral genome. The N-terminal sequence of the viral coat protein was determined using Top-Down MALDI-TOF analysis.ResultsThe complete nucleotide sequences of both single-stranded RNA segments (RNA1 and RNA2) were established. RNA1 consisted of 2793 nucleotides (nt) exclusive its 3' poly(A) tract and a single open-reading frame (ORF1) of 2745 nt. ORF1 was framed by a 5' untranslated region (5' UTR) of 18 nt and a 3' untranslated region (3' UTR) of 30 nt. ORF1 contained motifs of RNA-dependent RNA polymerases (RdRp) and showed similarities to RdRp of Scleropthora macrospora virus A (SmV A) and viruses within the Nodaviridae family. RNA2 consisted of 1526 nt exclusive its 3' poly(A) tract and a second ORF (ORF2) of 1128 nt. ORF2 coded for the single viral coat protein (CP) and was framed by a 5' UTR of 164 nt and a 3' UTR of 234 nt. The deduced amino acid sequence of ORF2 was verified by nano-LC-ESI-MS/MS experiments. Top-Down MALDI-TOF analysis revealed the N-terminal sequence of the CP. The N-terminal sequence represented a region within ORF2 suggesting a proteolytic processing of the CP in vivo. The CP showed similarities to CP of SmV A and viruses within the Tombusviridae family. Fragments of RNA1 (ca. 1.9 kb) and RNA2 (ca. 1.4 kb) were used to analyze the nucleotide sequence variation of virions in different P. halstedii isolates. Viral sequence variation was 0.3% or less regardless of their host's pathotypes, the geographical origin and the sensitivity towards the fungicide metalaxyl.ConclusionsThe results showed the presence of a single and new virus type in different P. halstedii isolates. Insignificant viral sequence variation indicated that the virus did not account for differences in pathogenicity of the oomycete P. halstedii.

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ssRNA viruses from biotrophic Oomycetes form a new phylogenetic group between Nodaviridae and Tombusviridae

Grasse

Spring

2017

Arch Virol

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Plasmopara halstedii virus (PhV) is one of the few characterized oomycete viruses. Although it is fully sequenced and well-studied in its genetic diversity, the exact classification and phylogenetic relationships of PhV remain uncertain. The only known virus with characteristics similar to PhV is the Sclerophthora macrospora Virus A (SmV-A). Both viruses infect obligate biotrophic oomycetes. While RNA-dependent RNA polymerases (RdRp) of oomycetes viruses have high similarity to the corresponding enzymes from viruses classified in the family Nodaviridae, the coat proteins (CP) seem to be completely different from those of other viruses of this family. In contrast, the coat proteins of PhV and SmV-A have high similarity to viruses classified in the Tombusviridae, Circoviridae and a new group of hybrid DNA-RNA viruses (so-called chimeric viruses or cruciviruses). Because phylogenetic analyses based on the sequences of either RdRp or CP result in different affinities, an alternative, genome-based approach combining the sequences of both proteins was used. This analysis placed the two oomycete viruses together with Tombunodavirus UC1 in a new, independent group between families Nodaviridae and Tombusviridae.

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Ultrastructure of virus-like particles in Plasmopara halstedii

Cited by 8 publications

References 10 publications

Different pathotypes of the sunflower downy mildew pathogen Plasmopara halstedii all contain isometric virions†

Different pathotypes of the sunflower downy mildew pathogen Plasmopara halstedii all contain isometric virions†

The nucleotide sequence and genome organization of Plasmopara halstedii virus

ssRNA viruses from biotrophic Oomycetes form a new phylogenetic group between Nodaviridae and Tombusviridae

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