RESUMO
Bunyaviruses are enveloped negative or ambisense single-stranded RNA viruses with a genome divided into several segments. The canonical view depicts each viral particle packaging one copy of each genomic segment in one polarity named the viral strand. Several opposing observations revealed nonequal ratios of the segments, uneven number of segments per virion, and even packaging of viral complementary strands. Unfortunately, these observations result from studies often addressing other questions, on distinct viral species, and not using accurate quantitative methods. Hence, what RNA segments and strands are packaged as the genome of any bunyavirus remains largely ambiguous. We addressed this issue by first investigating the virion size distribution and RNA content in populations of the tomato spotted wilt virus (TSWV) using microscopy and tomography. These revealed heterogeneity in viral particle volume and amount of RNA content, with a surprising lack of correlation between the two. Then, the ratios of all genomic segments and strands were established using RNA sequencing and qRT-PCR. Within virions, both plus and minus strands (but no mRNA) are packaged for each of the three L, M, and S segments, in reproducible nonequimolar proportions determined by those in total cell extracts. These results show that virions differ in their genomic content but together build up a highly reproducible genetic composition of the viral population. This resembles the genome formula described for multipartite viruses, with which some species of the order Bunyavirales may share some aspects of the way of life, particularly emerging properties at a supravirion scale.
Assuntos
Orthobunyavirus , Tospovirus , Orthobunyavirus/genética , RNA Viral/genética , Tospovirus/genética , Genoma Viral/genética , Vírion/genéticaRESUMO
Two members of the family Betaflexiviridae associated with yam (Dioscorea spp.) have been described so far: yam latent virus (YLV) and yam virus Y (YVY). However, their geographical distribution and molecular diversity remain poorly documented. Using a nested RT-PCR assay, we detected YVY in D. alata, D. bulbifera, D. cayenensis, D. rotundata, and D. trifida in Guadeloupe, and in D. rotundata in Côte d'Ivoire, thus extending the known host range of this virus and geographical distribution. Using amplicon sequencing, we determined that the molecular diversity of YVY in the yam samples analyzed in this work ranged between 0.0 and 29.1% and that this diversity is partially geographically structured. We also identified three isolates of banana mild mosaic virus (BanMMV) infecting D. alata in Guadeloupe, providing the first evidence for BanMMV infection in yam.
Assuntos
Carlavirus , Dioscorea , Flexiviridae , Vírus do Mosaico , MusaRESUMO
Sugarcane streak mosaic virus (SCSMV), now assigned to the genus Poacevirus of the family Potyviridae, was reported for the first time in 1932 in Louisiana and was believed to be strain F of sugarcane mosaic virus (SCMV) for more than six decades. SCMV-F was renamed SCSMV in 1998 after partial sequencing of its genome and phylogenetic investigations. Following the development of specific molecular diagnostic methods in the 2000s, SCSMV was recurrently found in sugarcane exhibiting streak mosaic symptoms in numerous Asian countries, but not in the Western hemisphere or in Africa. In this review, we give an overview of the current knowledge on this disease and the progression in research on SCSMV. This includes symptoms, geographical distribution and incidence, diagnosis and genetic diversity of the virus, epidemiology, as well as control. Finally, we highlight future challenges as sugarcane streak mosaic has recently been found in Africa where this disease represents a new threat to sugarcane production.
RESUMO
Cordyline virus 1 (CoV1) is a velarivirus that has so far only been reported in ornamental Ti plants (Cordyline fruticosa). Using high-throughput sequencing, we identified CoV1 infection in yam accessions from Vanuatu. Using a specific RT-PCR assay, we found that CoV1 is also present and highly prevalent in Dioscorea alata, D. cayenensis, and D. trifida in Guadeloupe. Phylogenetic analysis showed that CoV1 isolates infecting yam in Guadeloupe display a low level of molecular diversity. These data provide insights into the transmission of CoV1 in yam in Guadeloupe.
Assuntos
Closteroviridae , Cordyline , Dioscorea , Variação Genética , FilogeniaRESUMO
We report the complete genome sequence of a novel member of the genus Vitivirus (family Betaflexiviridae, subfamily Trivirinae) infecting pineapple. The complete genome sequence of this virus was obtained from total RNA extracted from pineapple leaf samples collected in Reunion Island, using a combination of high-throughput sequencing technologies. The viral genome is 6,757 nt long, excluding the poly(A) tail, and shares all the hallmarks of vitiviruses. Phylogenetic analysis performed on the replication-associated protein and capsid protein gene sequences unambiguously place this new virus, for which we propose the name "pineapple virus A", in the genus Vitivirus.
Assuntos
Ananas , Flexiviridae , Proteínas do Capsídeo/genética , Flexiviridae/genética , Genoma Viral , Sequenciamento de Nucleotídeos em Larga Escala , Fases de Leitura Aberta , Filogenia , Doenças das Plantas , RNA , RNA Mensageiro , RNA Viral/genética , ReuniãoRESUMO
Pearl millet (Pennisetum glaucum (L.) R. Br.) is a staple food that is widely cultivated in sub-Saharan Africa. In August 2018, a survey was conducted in the main producing regions of Burkina Faso, and leaf samples were analyzed using virion-associated nucleic acid (VANA)-based metagenomic approach and Illumina sequencing. A new virus, tentatively named "Pennisetum glaucum marafivirus" (PGMV), was detected, and its complete nucleotide sequence of 6364 nucleotides was determined. The sequence contains a large open reading frame (ORF) encoding a polyprotein of 224.2 kDa with five domains (methyltransferase, papain-like protease, helicase, RNA-dependent RNA polymerase, and coat proteins), typical of marafiviruses. Additionally, a characteristic conserved marafibox domain was detected in the genome. The nucleotide sequence of the complete PGMV genome shares 68.5% identity with that of sorghum bicolor marafivirus, and its coat protein shares 58.5% identity with that of oat blue dwarf virus. Phylogenetic analysis confirmed that the pearl millet virus is unambiguously grouped with members of the genus Marafivirus in the family Tymoviridae. This is the first report on the occurrence of a marafivirus in pearl millet.
Assuntos
Pennisetum , Tymoviridae , Burkina Faso , Genoma Viral , Sequenciamento de Nucleotídeos em Larga Escala , Filogenia , RNA Viral/genética , Tymoviridae/genéticaRESUMO
Dioscorea mosaic associated virus (DMaV) is a member of the genus Sadwavirus, family Secoviridae, that is associated with mosaic symptoms in Dioscorea rotundata in Brazil. The genome of a DMaV isolate detected in D. trifida in Guadeloupe was sequenced by high-throughput sequencing. Using an RT-PCR-based detection assay, we found that DMaV infects D. alata, D. bulbifera, D. cayenensis-rotundata, D. esculenta, and D. trifida accessions conserved in Guadeloupe and Côte d'Ivoire and displays a very high level of molecular diversity in a relatively small region of the genome targeted by the assay. We also provide evidence that DMaV is also present in D. rotundata in Benin and in D. alata in Nigeria.
Assuntos
Dioscorea , Especificidade de Hospedeiro , Secoviridae , Dioscorea/virologia , Variação Genética , Filogenia , Secoviridae/classificaçãoRESUMO
Over the last decade, viral metagenomic studies have resulted in the discovery of thousands of previously unknown viruses. These studies are likely to play a pivotal role in obtaining an accurate and robust understanding of how viruses affect the stability and productivity of ecosystems. Among the metagenomics-based approaches that have been developed since the beginning of the 21st century, shotgun metagenomics applied specifically to virion-associated nucleic acids (VANA) has been used to disentangle the diversity of the viral world. We summarize herein the results of 24 VANA-based studies, focusing on plant and insect samples conducted over the last decade (2010 to 2020). Collectively, viruses from 85 different families were reliably detected in these studies, including capsidless RNA viruses that replicate in fungi, oomycetes, and plants. Finally, strengths and weaknesses of the VANA approach are summarized and perspectives of applications in detection, epidemiological surveillance, environmental monitoring, and ecology of plant viruses are provided. [Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.
Assuntos
Ácidos Nucleicos , Vírus de Plantas , Metagenômica/métodos , Ecossistema , Doenças das Plantas , Vírus de Plantas/genética , Vírion/genética , PlantasRESUMO
A novel geminivirus was identified in France and Spain in asymptomatic plants of white clover (Trifolium repens) and shrub medick (Medicago arborea). Its genome has the hallmarks of a capulavirus, and its relationship to other capulaviruses was confirmed by phylogenetic analysis. White clover isolates formed a tight cluster in the phylogenetic tree, while shrub medick isolates formed two distinct, more divergent groups with sequence identity values close to the species cutoff. These three groups have likely participated in recombination events involving alfalfa leaf curl virus and French bean severe leaf curl virus. The name "trifolium virus 1" (TrV1) is proposed for this new Capulavirus. Three TrV1 genotypes (TrV1-A, TrV1-B, and TrV1-C) were clearly distinguished.
Assuntos
Filogenia , Trifolium/virologia , Vírus não Classificados/classificação , Vírus não Classificados/genética , Vírus não Classificados/isolamento & purificação , Sequência de Aminoácidos , Biodiversidade , Vírus de DNA/genética , Fabaceae/virologia , Geminiviridae/classificação , Geminiviridae/genética , Geminiviridae/isolamento & purificação , Genótipo , Fases de Leitura Aberta , Doenças das Plantas/virologia , Análise de Sequência de DNARESUMO
Plant virus ecology began to be explored at the end of the 19th century. Since then, major advances have revealed complex virus-host-vector interactions in a variety of environments. These advances have been accelerated by development of new technologies for virus detection and characterization, the latest of which being high-throughput sequencing (HTS). HTS technologies have proved to be effective for non-targeted characterization of all or nearly all viruses present in a sample without requiring prior information about virus identity, as would be needed for virus-targeted tests. Phytoviromic studies have thus made important advances, including characterization of the complex interactions between phytovirus dynamics and the structure of multi-species host communities, and documentation of the effects of anthropogenic ecosystem simplification on plant virus emergence and diversity. However, such studies must overcome challenges at every stage, from plant sampling to bioinformatics analysis. This review summarizes major advances in plant virus ecology, in association with technological developments, and presents key considerations for use of HTS in the study of the ecology of phytovirus communities.
Assuntos
Ecossistema , Vírus de Plantas , Vírus de DNA , Ecologia , Nucleotídeos , Vírus de Plantas/genéticaRESUMO
The Honghe Hani rice terraces system (HHRTS) is a traditional rice cultivation system where Hani people cultivate remarkably diverse rice varieties. Recent introductions of modern rice varieties to the HHRTS have significantly increased the severity of rice diseases within the terraces. Here, we determine the impacts of these recent introductions on the composition of the rice-associated microbial communities. We confirm that the HHRTS contains a range of both traditional HHRTS landraces and introduced modern rice varieties and find differences between the microbial communities of these two groups. However, this introduction of modern rice varieties has not strongly impacted the overall diversity of the HHRTS rice microbial community. Furthermore, we find that the rice varieties (i.e. groups of closely related genotypes) have significantly structured the rice microbial community composition (accounting for 15%-22% of the variance) and that the core microbial community of HHRTS rice plants represents less than 3.3% of all the microbial taxa identified. Collectively, our study suggests a highly diverse HHRTS rice holobiont (host with its associated microbes) where the diversity of rice hosts mirrors the diversity of their microbial communities. Further studies will be needed to better determine how such changes might impact the sustainability of the HHRTS.
Assuntos
Biodiversidade , Microbiota/genética , Oryza/microbiologia , Agricultura/métodos , China , Humanos , Doenças das Plantas/microbiologiaRESUMO
Nine complete nucleotide sequences of geminialphasatellites (subfamily Geminialphasatellitinae, family Alphasatellitidae) recovered from the wild Poaceae Sorghum arundinaceum collected in Reunion are described and analyzed. While the helper geminivirus was identified as an isolate of maize streak virus (genus Mastrevirus, family Geminiviridae), the geminialphasatellite genomes were most closely related to, and shared ~63% identity with, clecrusatellites. Even though the geminialphasatellite molecules lack an adenine rich-region, they have the typical size of geminialphasatellites, encode a replication-associated protein in the virion sense, and have probable stem-loop structures at their virion-strand origins of replication. According to the proposed geminialphasatellite species and genus demarcation thresholds (88% and 70% nucleotide identity, respectively), the genomes identified here represent a new species (within a new genus) for which we propose the name "Sorghum mastrevirus-associated alphasatellite" (genus "Sorgasalphasatellite").
Assuntos
Geminiviridae/genética , Vírus do Listrado do Milho/genética , Poaceae/virologia , Sorghum/virologia , Genoma Viral/genética , Filogenia , Doenças das Plantas/virologia , Reunião , Análise de Sequência de DNA/métodos , Zea mays/virologiaRESUMO
A novel virus infecting yams (Dioscorea spp.), tentatively named "yam asymptomatic virus 1" (YaV1), was characterized and sequenced from an asymptomatic D. alata plant from Vanuatu. Sequence comparisons and phylogenetic analysis showed that YaV1 is a novel ampelovirus and has the smallest genome among "subgroup 1" members. RT-PCR-based screening of a yam germplasm collection conserved in Guadeloupe showed that YaV1 is prevalent in D. alata, D. bulbifera, D. cayennensis subsp. rotundata, D. esculenta and D. trifida accessions but causes no apparent symptoms. Additional phylogenetic analysis revealed a low variability of YaV1 in Guadeloupe in a limited part of the genome, and suggested the occurrence of plant-to-plant transmission.
Assuntos
Closteroviridae/classificação , Dioscorea/virologia , Filogenia , Doenças das Plantas/virologia , Closteroviridae/isolamento & purificação , Closteroviridae/patogenicidade , Variação Genética , Genoma Viral , Guadalupe , Prevalência , Reação em Cadeia da Polimerase em Tempo RealRESUMO
Genomoviruses (family Genomoviridae) are circular single-stranded DNA viruses that have been mainly identified through metagenomics studies in a wide variety of samples from various environments. Here, we describe 98 genomes of genomoviruses found associated with members of 19 plant families from Australia, Brazil, France, South Africa and the USA. These 98 genomoviruses represent 29 species, 26 of which are new, in the genera Gemykolovirus (n = 37), Gemyduguivirus (n = 9), Gemygorvirus (n = 8), Gemykroznavirus (n = 6), Gemycircularvirus (n = 21) and Gemykibivirus (n = 17).
Assuntos
Infecções por Vírus de DNA/virologia , Vírus de DNA/isolamento & purificação , Genoma Viral , Plantas/virologia , Austrália , Brasil , Vírus de DNA/classificação , França , Metagenômica , Filogenia , África do Sul , Estados UnidosRESUMO
Advances in molecular techniques used in viral metagenomics coupled with high throughput sequencing is rapidly expanding our knowledge of plant-associated virus diversity. Applying such approaches, we have identified five novel circular replication-associated protein (Rep)-encoding single-stranded (CRESS) DNA viruses from Poaceae and Apiaceae plant from South Africa and New Zealand. These viruses have a simple genomic organization, including two open reading frames that likely encode a Rep and a capsid protein (CP), a conserved nonanucleotide motif on the apex of a putative stem loop structure, and conserved rolling-circle replication and helicase motifs within their likely Rep: all suggesting that they replicate through rolling-circle replication. The Reps and the CPs putatively encoded by these five novel viruses share low to moderate degrees of similarity (22.1 - 44.6%) with other CRESS DNA viruses.
Assuntos
Apiaceae/virologia , Vírus de DNA/isolamento & purificação , DNA Circular , Vírus de Plantas/genética , Poaceae/virologia , Motivos de Aminoácidos , Nova Zelândia , África do SulRESUMO
Using high-throughput sequencing of small interfering RNAs (siRNAs), virion-associated nucleic acid (VANA), and double stranded RNAs (dsRNAs), we have determined the complete genome sequences of Comorian isolates of two ipomoviruses, cassava brown streak virus (CBSV) and a divergent isolate of Ugandan cassava brown streak virus (UCBSV-KM) representing a new strain of this virus. While the large ORF of CBSV shares the highest nucleotide sequence identity (95.9%) with a Tanzanian isolate of CBSV, the large UCBSV-KM ORF shares the highest nucleotide sequence identity (77.5%) with a Malawian isolate of UCBSV. This low value is near the species demarcation threshold for the family Potyviridae (<76%). Phylogenetic analysis confirms that UCBSV-KM represents a new lineage that is genetically distinct from the currently described UCBSV strains.
Assuntos
Potyviridae/genética , Sequência de Bases/genética , Comores , Sequenciamento de Nucleotídeos em Larga Escala/métodos , Manihot/virologia , Filogenia , Doenças das Plantas/virologia , RNA Viral/genética , Análise de Sequência de DNA/métodosRESUMO
Nanoviruses are multi-component plant-infecting single-stranded DNA viruses. Using a viral metagenomics-informed approach, a new nanovirus and two associated alphasatellite molecules have been identified in an uncultivated asymptomatic Vicia cracca plant in the Rhône region of France. This novel nanovirus genome includes eight genomic components (named DNA-R, DNA-S, DNA-M, DNA-C, DNA-N, DNA-U1, DNA-U2 and DNA-U4) and, across all components, shares < 66% pairwise sequence identity with other nanovirus genomes. The two associated alphasatellites share 62% identity with each other and < 81% identity will all other nanovirus-associated alphasatellites.
Assuntos
DNA Viral/genética , Genoma Viral , Nanovirus/genética , Doenças das Plantas/virologia , Vírus Reordenados/genética , Vicia/virologia , Alphavirus/classificação , Alphavirus/genética , Alphavirus/isolamento & purificação , Sequência de Bases , DNA de Cadeia Simples/genética , França , Nanovirus/classificação , Nanovirus/isolamento & purificação , Filogenia , Filogeografia , Vírus Reordenados/classificação , Vírus Reordenados/isolamento & purificação , Homologia de Sequência do Ácido NucleicoRESUMO
BACKGROUND: In Africa and Asia, sugarcane is the host of at least seven different virus species in the genus Mastrevirus of the family Geminiviridae. However, with the exception of Sugarcane white streak virus in Barbados, no other sugarcane-infecting mastrevirus has been reported in the New World. Conservation and exchange of sugarcane germplasm using stalk cuttings facilitates the spread of sugarcane-infecting viruses. METHODS: A virion-associated nucleic acids (VANA)-based metagenomics approach was used to detect mastrevirus sequences in 717 sugarcane samples from Florida (USA), Guadeloupe (French West Indies), and Réunion (Mascarene Islands). Contig assembly was performed using CAP3 and sequence searches using BLASTn and BLASTx. Mastrevirus full genomes were enriched from total DNA by rolling circle amplification, cloned and sequenced. Nucleotide and amino acid sequence identities were determined using SDT v1.2. Phylogenetic analyses were conducted using MEGA6 and PHYML3. RESULTS: We identified a new sugarcane-infecting mastrevirus in six plants sampled from germplasm collections in Florida and Guadeloupe. Full genome sequences were determined and analyzed for three virus isolates from Florida, and three from Guadeloupe. These six genomes share >88% genome-wide pairwise identity with one another and between 89 and 97% identity with a recently identified mastrevirus (KR150789) from a sugarcane plant sampled in China. Sequences similar to these were also identified in sugarcane plants in Réunion. CONCLUSIONS: As these virus isolates share <64% genome-wide identity with all other known mastreviruses, we propose classifying them within a new mastrevirus species named Sugarcane striate virus. This is the first report of sugarcane striate virus (SCStV) in the Western Hemisphere, a virus that most likely originated in Asia. The distribution, vector, and impact of SCStV on sugarcane production remains to be determined.
Assuntos
Geminiviridae/classificação , Geminiviridae/isolamento & purificação , Saccharum/virologia , Clonagem Molecular , Análise por Conglomerados , DNA Viral/química , DNA Viral/genética , DNA Viral/isolamento & purificação , Florida , Guadalupe , Filogenia , Reunião , Análise de Sequência de DNA , Homologia de Sequência , Sequenciamento Completo do GenomaRESUMO
The discovery and full-genome sequences of two isolates of a fourth capulavirus species are reported. The viruses were discovered during a viral metagenomics survey of uncultivated Plantago lanceolata plants in the Åland archipelago of south western Finland. The newly discovered viruses apparently produce no symptoms in P. lanceolata. They have a genome organization that is very similar to that of the three known capulavirus species and additionally share between 62.9 and 67.1% genome-wide sequence identity with the isolates of these species. It is therefore proposed that these viruses be assigned to a new capulavirus species named "Plantago lanceolata latent virus".
Assuntos
Geminiviridae/classificação , Doenças das Plantas/virologia , Plantago/virologia , Finlândia , Geminiviridae/genética , Geminiviridae/isolamento & purificação , MetagenômicaRESUMO
The full-length genome sequences of two novel poleroviruses found infecting cowpea plants, cowpea polerovirus 1 (CPPV1) and cowpea polerovirus 2 (CPPV2), were determined using overlapping RT-PCR and RACE-PCR. Whereas the 5845-nt CPPV1 genome was most similar to chickpea chlorotic stunt virus (73% identity), the 5945-nt CPPV2 genome was most similar to phasey bean mild yellow virus (86% identity). The CPPV1 and CPPV2 genomes both have a typical polerovirus genome organization. Phylogenetic analysis of the inferred P1-P2 and P3 amino acid sequences confirmed that CPPV1 and CPPV2 are indeed poleroviruses. Four apparently unique recombination events were detected within a dataset of 12 full polerovirus genome sequences, including two events in the CPPV2 genome. Based on the current species demarcation criteria for the family Luteoviridae, we tentatively propose that CPPV1 and CPPV2 should be considered members of novel polerovirus species.