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Volume 94,
Issue 8,
2013
Volume 94, Issue 8, 2013
- Insect
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Ultrastructural and genomic characterization of a second banchine polydnavirus confirms the existence of shared features within this ichnovirus lineage
More LessPolydnaviruses (PDVs) are symbiotic viruses carried by endoparasitic wasps and transmitted to caterpillar hosts during parasitization. Although they share several features, including a segmented dsDNA genome, a unique life cycle where replication is restricted to the wasp host, and immunodepressive/developmental effects on the caterpillar host, PDVs carried by ichneumonid and braconid wasps (referred to as ichnoviruses and bracoviruses, respectively) have different evolutionary origins. In addition, ichnoviruses (IVs) form two distinct lineages, with viral entities found in wasps belonging to the subfamilies Campopleginae and Banchinae displaying strikingly different virion morphologies and genomic features. However, the current description for banchine IVs is based on the characterization of a single species, namely that of the Glypta fumiferanae IV (GfIV). Here we provide an ultrastructural and genomic analysis of a second banchine IV isolated from the wasp Apophua simplicipes, and we show that this virus shares many features with GfIV, including a multi-nucleocapsid virion, an aggregate genome size of ~300 kb, genome segments <5 kb, an impressively high degree of genome segmentation and a very similar gene content (same gene families in both viruses). Altogether, the data presented here confirm the existence of shared characteristics within this banchine IV lineage.
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- Plant
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A recombinant begomovirus resulting from exchange of the C4 gene
A begomovirus isolated from Malvastrum coromandelianum and tomato originating from Yunnan province (China) was shown to be representative of a new begomovirus species, for which the name tomato leaf curl Yunnan virus (TLCYnV) is proposed. TLCYnV has high levels of sequence identity to tomato yellow leaf curl China virus (TYLCCNV) across the whole genome, except for sequences encompassing the C4 gene. Agrobacterium-mediated inoculation showed TLCYnV to be highly infectious to a range of plant species but poorly infectious to M. coromandelianum. In contrast to TYLCCNV, TLCYnV was shown to infect tomato in the absence of a betasatellite. In field-collected samples, TLCYnV was identified most frequently in tomato in which it was not associated with a betasatellite. Transgenic expression in Nicotiana benthamiana showed that the C4 protein of TYLCCNV did not induce developmental abnormalities, whereas the C4 of TLCYnV induced severe developmental abnormalities, reminiscent of virus symptoms. The genome of TLCYnV was shown to be significantly less methylated in plants than that of TYLCCNV and the C4 protein of TLCYnV was shown to suppress post-transcriptional gene silencing and transcriptional gene silencing more effectively than the C4 of TYLCCNV. The results indicate that TLCYnV evolved from TYLCCNV by recombination, acquiring a more virulent C4, allowing it to dispense with the requirement for a betasatellite. The implications of these findings in relation to the evolution of monopartite begomoviruses are discussed.
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Non-structural protein P6 encoded by rice black-streaked dwarf virus is recruited to viral inclusion bodies by binding to the viroplasm matrix protein P9-1
More LessLike other members of the family Reoviridae, rice black-streaked dwarf virus (RBSDV, genus Fijivirus) is thought to replicate and assemble within cytoplasmic viral inclusion bodies, commonly called viroplasms. RBSDV P9-1 is the key protein for the formation of viroplasms, but little is known about the other proteins of the viroplasm or the molecular interactions amongst its components. RBSDV non-structural proteins were screened for their association with P9-1 using a co-immunoprecipitation assay. Only P6 was found to directly interact with P9-1, an interaction that was confirmed by bimolecular fluorescence complementation assay in Spodoptera frugiperda (Sf9) cells. Immunoelectron microscopy showed that P6 and P9-1 co-localized in electron-dense inclusion bodies, indicating that P6 is a constituent of the viroplasm. In addition, non-structural protein P5 also localized to viroplasms and interacted with P6. In Sf9 cells, P6 was diffusely distributed throughout the cytoplasm when expressed alone, but localized to inclusions when co-expressed with P9-1, suggesting that P6 is recruited to viral inclusion bodies by binding to P9-1. P5 localized to the inclusions formed by P9-1 when co-expressed with P6 but did not when P6 was absent, suggesting that P5 is recruited to viroplasms by binding to P6. This study provides a model by which viral non-structural proteins are recruited to RBSDV viroplasms.
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Genetic characterization of novel putative rhabdovirus and dsRNA virus from Japanese persimmon
More LessDeep-sequencing analysis of nucleic acids from leaf tissue of Japanese persimmon trees exhibiting fruit apex disorder in some fruits detected two molecules that were graft transmitted to healthy seedlings. One of the complete genomes consisted of 13 467 nt and encoded six genes similar to those of plant rhabdoviruses. The virus formed a distinct cluster in the genus Cytorhabdovirus with lettuce necrotic yellows virus, lettuce yellow mottle virus and strawberry crinkle virus in a phylogenetic tree based on the L protein (RNA-dependent RNA polymerase, RdRp). The other consisted of 7475 nt and shared a genome organization similar to those of some insect and fungal viruses having dsRNA genomes. In a phylogenetic tree using the RdRp sequence of several unassigned dsRNA viruses, the virus formed a possible new genus cluster with two insect viruses, Circulifer tenellus virus 1 and Spissistilus festinus virus 1, and one plant virus, cucurbit yellows-associated virus.
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- Other viruses
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Characterization of an unusual transmissible spongiform encephalopathy in goat by transmission in knock-in transgenic mice
More LessBovine spongiform encephalopathy (BSE) is a fatal neurodegenerative disorder of cattle, and its transmission to humans through contaminated food is thought to be the cause of the variant form of Creutzfeldt–Jakob disease. BSE is believed to have spread from the recycling in cattle of ruminant tissue in meat and bone meal (MBM). However, during this time, sheep and goats were also exposed to BSE-contaminated MBM. Both sheep and goats are experimentally susceptible to BSE, and while there have been no reported natural BSE cases in sheep, two goat BSE field cases have been documented. While cases of BSE are rare in small ruminants, the existence of scrapie in both sheep and goats is well established. In the UK, during 2006–2007, a serious outbreak of clinical scrapie was detected in a large dairy goat herd. Subsequently, 200 goats were selected for post-mortem examination, one of which showed biochemical and immunohistochemical features of the disease-associated prion protein (PrPTSE) which differed from all other infected goats. In the present study, we investigated this unusual case by performing transmission bioassays into a panel of mouse lines. Following characterization, we found that strain properties such as the ability to transmit to different mouse lines, lesion profile pattern, degree of PrP deposition in the brain and biochemical features of this unusual goat case were neither consistent with goat BSE nor with a goat scrapie herdmate control. However, our results suggest that this unusual case has BSE-like properties and highlights the need for continued surveillance.
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Volumes and issues
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Volume 104 (2023)
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Volume 2 (1968)
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Volume 1 (1967)
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