Viruses in the family
have a mono-, bi- or tripartite positive-sense RNA genome of 13-19 kb, and non-enveloped, filamentous particles 650-2200 nm long and 12 nm in diameter. They infect plants, ...mainly dicots, many of which are fruit crops. This is a summary of the ICTV Report on the family
, which is available at ictv.global/report/closteroviridae.
Virus discovery based on high-throughput sequencing relies on enrichment for virus sequences prior to library preparation to achieve a sufficient number of viral reads. In general, preparations of ...double-stranded RNA or total RNA preparations treated to remove rRNA are used for sequence enrichment. We used virus-specific antibodies to immunocapture virions from plant sap to conduct cDNA synthesis, followed by library preparation and HTS. For the four potato viruses PLRV, PVY, PVA and PYV, template preparation by virion immunocapture provided a simpler and less expensive method than the enrichment of total RNA by ribosomal depletion. Specific enrichment of viral sequences without an intermediate amplification step was achieved, and this high coverage of sequences across the viral genomes was important to identify rare sequence variations. Using this approach, the first complete genome sequence of a potato yellowing virus isolate (PYV, DSMZ PV-0706) was determined in this study. PYV can be confidently assigned as a distinct species in the genus Ilarvirus.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The family
includes viruses with flexuous filamentous virions that are 470-800 nm in length and 12-13 nm in diameter. Alphaflexiviruses have a single-stranded, positive-sense RNA genome of 5.5-9 kb. ...They infect plants and plant-infecting fungi. They share a distinct lineage of alphavirus-like replication proteins that is unusual in lacking any recognized protease domain. With a single exception, cell-to-cell and long-distance movement is facilitated by triple gene block proteins in plant-infecting genera. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the family
which is available at www.ictv.global/report/alphaflexiviridae.
Celery latent virus (CeLV) is an incompletely described plant virus known to be sap and seed transmissible and to possess flexuous filamentous particles measuring about 900 nm in length, suggesting ...it as a possible member of the family Potyviridae. Here, an Italian isolate of CeLV was transmitted by sap to a number of host plants and shown to have a single-stranded and monopartite RNA genome being 11 519 nucleotides (nts) in size and possessing some unusual features. The RNA contains a large open reading frame (ORF) that is flanked by a short 5' untranslated region (UTR) of 13 nt and a 3' UTR consisting of 586 nt that is not polyadenylated. CeLV RNA shares nt sequence identity of only about 40 % with other members of the Potyviridae (potyvirids). The CeLV polyprotein is notable in that it starts with a signal peptide, has a putative P3N-PIPO ORF and shares low aa sequence identity (about 18 %) with other potyvirids. Although potential cleavage sites were not identified for the N-terminal two-thirds of the polyprotein, the latter possesses a number of sequence motifs, the identity and position of which are characteristic of other potyvirids. Attempts at constructing an infectious full-length cDNA clone of CeLV were successful following Rhizobium radiobacter infiltration of Nicotiana benthamiana and Apium graveolens. CeLV appears to have the largest genome of all known potyvirids and some unique genome features that may warrant the creation of a new genus, for which we propose the name 'celavirus'.
Clematis vitalba L. is a climbing shrub and a pioneer plant in abandoned orchards or vineyards that are widespread in temperate climate zones. In past years, several viruses infecting the Clematis ...species have been identified, including different ilarviruses. Prunus virus I (PrVI) is a recently described ilarvirus, which has been shown to infect sweet cherries and peaches in Greece. Moreover, its presence has been detected in ornamental Clematis in Russia. In the present work, we analyzed the virome of wildly growing C. vitalba plants from Hungary, Slovakia and Croatia showing different kinds of symptoms using high-throughput sequencing (HTS) of small RNAs or ribodepleted RNAs. Applying HTS enabled us to identify the presence of PrVI in C. vitalba, and the bioinformatic analyses were further validated with RT-PCR using PrVI-specific primers and Sanger dideoxy sequencing. Nearly full genome sequences of all three viral RNAs of one Hungarian, two Slovak and one Croatian isolate were determined. Their phylogenetic analysis showed high similarity to each other and to other PrVI isolates described from Central Europe. As the sampled plants were co-infected with other viruses, it is not possible to determine a direct correlation between the infection with PrVI and the observed symptoms. Analyses of different Prunus species in stock collection showed infection of several peach and sweet cherry varieties in Hungary. Our results expand the knowledge on the natural host range of PrVI and highlight the necessity to evaluate alternative plant hosts (even non-Prunus) of PrVI and the role of the virus in the etiology of the potential diseases.
Etiological studies of a recently emerged bushy top disease of tobacco in Ethiopia indicated that a ~4.5-kb dsRNA from infected plants represents an umbravirus, whereas a smaller band (~0.5 kb) is ...that of a new satellite RNA. Potato leafroll virus was also consistently associated with the disease. The three agents, whose experimental host ranges are restricted to members of the family Solanaceae, always occurred together in field samples and are transmitted together by the aphid Myzus persicae nicotianae. The umbravirus, which represents a new species, is most closely related to groundnut rosette virus, and the name Ethiopian tobacco bushy top virus is proposed.
The associations between pathogens and their hosts are complex and can result from any combination of evolutionary events such as codivergence, switching, and duplication of the pathogen. Mycoviruses ...are RNA viruses which infect fungi and for which natural vectors are so far unknown. Thus, lateral transfer might be improbable and codivergence their dominant mode of evolution. Accordingly, mycoviruses are a suitable target for statistical tests of virus-host codivergence, but inference of mycovirus phylogenies might be difficult because of low sequence similarity even within families.
We analyzed here the evolutionary dynamics of all mycovirus families by comparing virus and host phylogenies. Additionally, we assessed the sensitivity of the co-phylogenetic tests to the settings for inferring virus trees from their genome sequences and approximate, taxonomy-based host trees.
While sequence alignment filtering modes affected branch support, the overall results of the co-phylogenetic tests were significantly influenced only by the number of viruses sampled per family. The trees of the two largest families, Partitiviridae and Totiviridae, were significantly more similar to those of their hosts than expected by chance, and most individual host-virus links had a significant positive impact on the global fit, indicating that codivergence is the dominant mode of virus diversification. However, in this regard mycoviruses did not differ from closely related viruses sampled from non-fungus hosts. The remaining virus families were either dominated by other evolutionary modes or lacked an apparent overall pattern. As this negative result might be caused by insufficient taxon sampling, the most parsimonious hypothesis still is that host-parasite evolution is basically the same in all mycovirus families. This is the first study of mycovirus-host codivergence, and the results shed light not only on how mycovirus biology affects their co-phylogenetic relationships, but also on their presumable host range itself.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Leaf samples from Thailand of Sauropus androgynus (L.) Merr. plants presenting leaf yellowing symptoms were screened by reverse transcription polymerase chain reaction for the presence of polerovirus ...infection. In five of eight samples, a polerovirus was detected, and in four of these five polerovirus‐positive samples, a begomovirus infection had been detected in a previous study. The complete polerovirus genome sequence was determined from the sample which was not also infected with a begomovirus. Analysis of the sequence revealed the typical genome organization of a polerovirus. The highest nucleotide sequence identity to any other polerovirus species sequence in GenBank was 49% to pepper yellow leaf curl virus (PYLCV), and the highest amino acid sequence identity of all deduced protein sequences was 70% with the coat protein of PYLCV. Based on these findings, we propose this novel polerovirus species be named Sauropus yellowing virus (SaYV).
Three field experiments were conducted to assess the effect of planting date on the incidence of viral diseases and the severity and the susceptibility of the cultivars. Two cultivars of cucumber ...(Hybrid Tokyo F1 and Poinsett) and one local variety of zucchini (Bolle) were used for the evaluation in May-July 2014, September-November 2014, and February-April 2015. A randomized complete block design with three replications was used for the experiments. Data were collected on disease incidence, severity, and time until first symptoms occurred. Area under severity index progress curve (AUSIPC) and area under disease progress curve (AUDPC) were calculated respectively for disease severity as well as the incidence on each cultivar. The results demonstrate the susceptibility of all cultivars to the tested viral diseases. The effect of planting dates on cultivars was significantly different (P<0.05) at the different growing stages whereas there was no significant difference (P>0.05) in planting date-variety interaction.
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