Complete genome sequence of a highly divergent carrot torradovirus 1 strain from Apium graveolens.

A new virus was identified in a celery plant showing chlorotic rings, mosaic and strong yellowing symptoms, and its complete genome sequence was determined. The genomic organization of this novel virus is analogous to that of known members of the genus Torradovirus, consisting of two single-stranded RNAs of 6,823 (RNA1) and 4,263 nucleotides (RNA2), excluding the poly(A) tails. BLAST searches against the nucleotide and protein databases showed that this virus is closely related to but different from carrot torradovirus 1 (CaTV1). Comparisons between the two viruses demonstrated relatively low levels of nucleotide and amino acid similarity in different parts of their genomes, as well as considerable differences in the sizes of their two genomic RNAs. However, the protease-polymerase (Pro-Pol) and capsid protein (CP) regions of this virus share >80% amino acid identity with the corresponding regions of CaTV1. Therefore, based on the current ICTV species demarcation criteria for the family Secoviridae, the virus from celery is a divergent strain of CaTV1, named "CaTV1-celery". Nevertheless, differences between CaTV1 and CaTV1-celery in genome size, as well as in biological and epidemiological features, may warrant their separation into two distinct species in the future.

Complete genome sequence and construction of an infectious full-length cDNA clone of celery latent virus - an unusual member of a putative new genus within the Potyviridae.

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'.

Complete genome sequence and construction of an infectious full-length cDNA clone of a German isolate of celery mosaic virus.

The complete genome sequence of a German isolate of celery mosaic virus (CeMV, a potyvirus) from Quedlinburg (DSMZ PV-1003) was determined (MF962880). This represents the second fully sequenced genome of this virus, along with a Californian isolate (HQ676607.1). The positive-sense single-stranded RNA is 10,000 nucleotides in length and shows the typical organization of potyviruses but has a shorter PIPO than CeMV California. In comparison to CeMV isolates from different origins, CeMV-Quedlinburg and isolates from the Netherlands (AF203531.1) and Aschersleben, Germany (AJ271087.1) show a NAG instead of DAG in the region of the coat protein responsible for aphid transmission. In this study the first infectious full-length clone of celery mosaic virus was obtained and the infectivity confirmed by Rhizobium radiobacter infiltration of Apium species.

Efficacy of Combination Treatment with Sodium Metasilicate and Sodium Hypochlorite for Inactivation of Norovirus on Fresh Vegetables.

In recent years, fresh vegetables have frequently been associated with the foodborne transmission of enteric viruses, such as human norovirus (NoV). Therefore, several studies have focused on developing methods to inactivate foodborne viruses for preventing outbreaks of foodborne illnesses. Sodium hypochlorite (NaOCl) is commonly used as a disinfectant, but results in undesirable effects on the appearance and taste of foods and can generate toxic byproducts when it exceeds the allowable concentration. Here, we evaluated the efficacy of a range of NaOCl concentrations (50-1000 ppm) for reducing the amounts of human NoV (NoV GII.4) on lettuce (Lactuca sativa), celery (Apium graveolens L.), and white cabbage (Brassica oleracea ssp. capitata). In addition, the combination treatment of NaOCl and sodium metasilicate (SMS, 0.1-0.5%) pentahydrate was evaluated for its ability to decrease the populations of NoV GII.4 in the three food samples. An immunomagnetic separation procedure combined with reverse transcription quantitative polymerase chain reaction was used for virus detection. For lettuce, celery, and cabbage, the NoV GII.4 recovery rates were 57.3% ± 6.5%, 52.5% ± 1.7%, and 60.3% ± 3.9%, respectively, using a glycine/NaCl elution buffer (0.25 M glycine/0.14 M NaCl, pH 9.5). The reductions of NoV GII.4 were 3.17, 3.06, and 3.27 log10 genomic copies/µL for lettuce, celery, and cabbage, respectively, at 1000 ppm NaOCl, while a reduction of ∼3 log10 genomic copies/µL was obtained when the samples were treated with a combination of 100 ppm NaOCl and 0.4% SMS pentahydrate. Taken together, these results demonstrated that combined treatment with NaOCl and SMS pentahydrate was an efficient strategy to reduce the concentration of NaOCl for control of NoV GII.4 contamination in fresh vegetables.

Application of next generation sequencing toward sensitive detection of enteric viruses isolated from celery samples as an example of produce.

Next generation sequencing (NGS) holds promise as a single application for both detection and sequence identification of foodborne viruses; however, technical challenges remain due to anticipated low quantities of virus in contaminated food. In this study, with a focus on data analysis using several bioinformatics tools, we applied NGS toward amplification-independent detection and identification of norovirus at low copy (<103 copies) or within multiple strains from produce. Celery samples were inoculated with human norovirus (stool suspension) either as a single norovirus strain, a mixture of strains (GII.4 and GII.6), or a mixture of different species (hepatitis A virus and norovirus). Viral RNA isolation and recovery was confirmed by RT-qPCR, and optimized for library generation and sequencing without amplification using the Illumina MiSeq platform. Extracts containing either a single virus or a two-virus mixture were analyzed using two different analytic approaches to achieve virus detection and identification. First an overall assessment of viral genome coverage for samples varying in copy numbers (1.1×103 to 1.7×107) and genomic content (single or multiple strains in various ratios) was completed by reference-guided mapping. Not unexpectedly, this targeted approach to identification was successful in correctly mapping reads, thus identifying each virus contained in the inoculums even at low copy (estimated at 12 copies). For the second (metagenomic) approach, samples were treated as "unknowns" for data analyses using (i) a sequence-based alignment with a local database, (ii) an "in-house" k-mer tool, (iii) a commercially available metagenomics bioinformatic analysis platform cosmosID, and (iv) an open-source program Kraken. Of the four metagenomics tools applied in this study, only the local database alignment and in-house k-mer tool were successful in detecting norovirus (as well as HAV) at low copy (down to <103 copies) and within a mixture of virus strains or species. The results of this investigation provide support for continued investigation into the development and integration of these analytical tools for identification and detection of foodborne viruses.

Complete genome sequence of Celery mosaic virus and its relationship to other members of the genus Potyvirus.

The complete genomic sequence of Celery mosaic virus (CeMV) was found to be 9999 nucleotides in length, excluding the 3' poly(A) tail. The genome contains a single large open reading frame encoding a polyprotein of 3181 amino acids. Its genomic organization is typical of potyviruses and contains conserved motifs found in members of the genus Potyvirus. Pairwise comparison of the polyprotein sequences shows that CeMV shares 39.0-71.9% sequence identity with other members of the genus Potyvirus. Phylogenetic analysis based on the polyprotein sequences indicates that CeMV is most closely related to Apium virus Y, and together with Panax virus Y, the three viruses form a distinct clade.

Biological characterization and complete genomic sequence of Apium virus Y infecting celery.

A celery isolate of Apium virus Y (ApVY-Ce) from diseased plants in a commercial field in California was characterized. The experimental host range of the virus included 13 plant species in the families Apiaceae, Chenopodiaceae and Solanaceae. Almost all infected plant species showed foliar chlorosis and distortion or severe stunting and systemic chlorosis. ApVY-Ce was transmitted to all 10 host species in the Apiaceae by green peach aphids. It reacted with the potyvirus group antibody and Celery mosaic virus (CeMV) antiserum. The complete genomic sequence of ApVY-Ce was determined to be 9917 nucleotides, excluding the 3' poly(A) tail, and it comprises a large open reading frame encoding a polyprotein of 3184 amino acid residues. Its genomic organization is typical of potyviruses, and contains conserved motifs found in the genus Potyvirus. Comparisons with available genomic sequences of other potyviruses indicate that ApVY-Ce shares 26.1-52.9% identities with species of the existing genera and unassigned viruses in the Potyviridae at the polyprotein sequence level. Extensive phylogenetic analysis based on the 3'-partial sequences confirms that ApVY-Ce is most closely related to CeMV and is a distinct species of the genus Potyvirus.

Binding of virus-like particles of Norwalk virus to romaine lettuce veins.

Noroviruses (NoV) annually cause millions of cases of gastrointestinal disease in the United States. NoV are associated with raw shellfish outbreaks, particularly oysters, which are thought to bioaccumulate NoV particles during the filter-feeding process. NoV outbreaks, however, have also been known to occur from other common-source food-borne vehicles, such as lettuce, frozen raspberries, and salad. In this study, we evaluated romaine lettuce as a potential vehicle for NoV transmission by testing the binding and distribution of NoV to the surface of romaine. Recombinant Norwalk virus-like particles (rNVLP) applied to the surface of romaine lettuce localized as large clusters primarily on the leaf veins. An extract of romaine lettuce leaves in phosphate-buffered saline (PBS) (romaine extract [RE]) bound rNVLP in a dose-dependent manner. RE did not bind rNVLP by histo-blood group antigens (HBGA), nor was RE competitive with rNVLP binding to porcine gastric mucin. These results suggested that non-HBGA molecules in RE bind rNVLP by a binding site(s) that is different from the defined binding pocket on the virion. Extracts of cilantro, iceberg lettuce, spinach, and celery also bound rNVLP. Samples of each of the vegetables spiked with rNVLP and tested with anti-NVLP antibody revealed by confocal microscopy the presence of rNVLP not only on the veins of cilantro but also throughout the surface of iceberg lettuce.

Occurrence and distribution of Potato virus Y strain N (PVY(N)) on celery in Iran.

Celery (Apium graveolens) is an important crop grown in many countries. Different types of diseases present a major constraint to Celery production and can lead to significant reductions in yield Potato Virus Y, the type member of the genus Potyvirus(family Potyviridae) is one of the causal agents of viral diseases in crops. In the present study, PVY occurring in celery fields was determined as the causal agent of mosaic disease of celery (Apium graveolens). The virus is naturally transmitted by aphids in a non-persistent manner. During growing seasons 2006-2007 celery fields were visited through Tehran Province and a total 332 sample based on selection of plants expressing symptoms like mosaic, vein clearing and mottling were collected. By using serological method (DAS-ELIZA) with specific antiserum of PVY (DSMZ-AS-0137.403) 17.64% of the samples were infected with PVY .The reaction of PVY infected samples were positive in TAS-ELIZA with specific monoclonal antibody (MAbs) of PVYN strain (DSMZ-AS-403.1). PVY N strain isolated from celery was reported for the first time in Iran and in the world in this survey.