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1.
J Gen Virol ; 105(5)2024 May.
Article in English | MEDLINE | ID: mdl-38717918

ABSTRACT

The tomato spotted wilt virus (TSWV) is a member of the Tospoviridae family and has an negative/ambisense single-stranded RNA genome. Frankliniella occidentalis and F. intonsa are known to be dominant pests in Capsicum annuum (hot pepper) and can cause damage to the plant either directly by feeding, or indirectly by transmitting TSWV in a persistent and propagative manner, resulting in serious economic damage. This study compared the immune responses of two different thrips species against TSWV infection by transcriptome analysis, which then allowed the assessment of antiviral responses using RNA interference (RNAi). Both adult thrips shared about 90 % of the transcripts in non-viruliferous conditions. Most signal components of the immune pathways were shared by these two thrips species, and their expression levels fluctuated differentially in response to TSWV infection at early immature stages. The functional assays using RNAi treatments indicated that the Toll and JAK/STAT pathways were associated with the antiviral responses, but the IMD pathway was not. The upregulation of dorsal switch protein one supported its physiological role in recognizing TSWV infection and triggering the eicosanoid biosynthetic pathway, which mediates melanization and apoptosis in thrips. In addition, the signal components of the RNAi pathways fluctuated highly after TSWV infection. Individual RNAi treatments specific to the antiviral signalling and response components led to significant increases in the TSWV amount in the thrips, causing virus-induced mortality. These findings suggest that immune signalling pathways leading to antiviral responses are operating in the thrips to regulate TSWV litres to prevent a fatal viral overload. This study also indicates the differential antiviral responses between the TSWV-transmitting F. occidentalis and F. intonsa.


Subject(s)
Plant Diseases , Thysanoptera , Tospovirus , Tospovirus/immunology , Tospovirus/physiology , Tospovirus/genetics , Animals , Thysanoptera/virology , Thysanoptera/immunology , Plant Diseases/virology , Plant Diseases/immunology , Capsicum/virology , Capsicum/immunology , Virus Replication , RNA Interference , Insect Vectors/virology , Insect Vectors/immunology , Gene Expression Profiling , Signal Transduction
2.
Virus Res ; 344: 199362, 2024 06.
Article in English | MEDLINE | ID: mdl-38508402

ABSTRACT

We report the characterization of a novel tri-segmented RNA virus infecting Mercurialis annua, a common crop weed and model species in plant science. The virus, named "Mercurialis latent virus" (MeLaV) was first identified in a mixed infection with the recently described Mercurialis orthotospovirus 1 (MerV1) on symptomatic plants grown in glasshouses in Lausanne (Switzerland). Both viruses were found to be transmitted by Thrips tabaci, which presumably help the inoculation of infected pollen in the case of MeLaV. Complete genome sequencing of the latter revealed a typical ilarviral architecture and close phylogenetic relationship with members of the Ilarvirus subgroup 1. Surprisingly, a short portion of MeLaV replicase was found to be identical to the partial sequence of grapevine angular mosaic virus (GAMV) reported in Greece in the early 1990s. However, we have compiled data that challenge the involvement of GAMV in angular mosaic of grapevine, and we propose alternative causal agents for this disorder. In parallel, three highly-conserved MeLaV isolates were identified in symptomatic leaf samples in The Netherlands, including a herbarium sample collected in 1991. The virus was also traced in diverse RNA sequencing datasets from 2013 to 2020, corresponding to transcriptomic analyses of M. annua and other plant species from five European countries, as well as metaviromics analyses of bees in Belgium. Additional hosts are thus expected for MeLaV, yet we argue that infected pollen grains have likely contaminated several sequencing datasets and may have caused the initial characterization of MeLaV as GAMV.


Subject(s)
Genome, Viral , Ilarvirus , Phylogeny , Plant Diseases , Pollen , Vitis , Vitis/virology , Plant Diseases/virology , Pollen/virology , Ilarvirus/genetics , Ilarvirus/isolation & purification , Ilarvirus/classification , Animals , RNA, Viral/genetics , Whole Genome Sequencing , Thysanoptera/virology
3.
J Virol ; 95(21): e0059721, 2021 10 13.
Article in English | MEDLINE | ID: mdl-34232724

ABSTRACT

Frankliniella occidentalis (western flower thrips [WFT]) and Thrips tabaci (onion thrips [OT]) are insect species that greatly impact horticultural crops through direct damage and their efficient vectoring of tomato spotted wilt virus and iris yellow spot virus. In this study, we collected thrips of these species from 12 field populations in various regions in Italy. We also included one field population of Neohydatothrips variabilis (soybean thrips [ST]) from the United States. Total RNA data from high-throughput sequencing (HTS) were used to assemble the virome, and then we assigned putative viral contigs to each thrips sample by real-time reverse transcription-quantitative PCR (qRT-PCR). Excluding plant and fungal viruses, we were able to identify 61 viral segments, corresponding to 41 viruses: 14 were assigned to WFT, 17 to OT, and 1 to ST; 9 viruses could not be assigned to any species based on our stringent criteria. All these viruses are putative representative of new species (with only the exception of a sobemo-like virus that is 100% identical to a virus recently characterized in ST) and some belong to new higher-ranking taxa. These additions to the viral phylogeny suggest previously undescribed evolutionary niches. Most of Baltimore's classes of RNA viruses were present (positive- and minus-strand and double-stranded RNA viruses), but only one DNA virus was identified in our collection. Repeated sampling in a subset of locations in 2019 and 2020 and further virus characterization in a subset of four thrips populations maintained in the laboratory allowed us to provide evidence of a locally persistent thrips core virome that characterizes each population. IMPORTANCE Harnessing the insect microbiome can result in new approaches to contain their populations or the damage they cause vectoring viruses of medical, veterinary, or agricultural importance. Persistent insect viruses are a neglected component of their microbiota. In this study, for the first time, we characterize the virome associated with the two model systems for tospovirus-transmitting thrips species, of utmost importance for the direct and indirect damage they cause to a number of different crops. The thrips virome characterized includes several novel viruses, which in some cases reveal previously undescribed clades. More importantly, some of the viruses we describe are part of a core virome that is specific and consistently present in distinct geographical locations monitored over the years, hinting at a possible mutualistic symbiotic relationship with their host.


Subject(s)
Insect Vectors/virology , Thysanoptera/virology , Tospovirus/classification , Tospovirus/genetics , Virome , Animals , Computational Biology/methods , Genome, Viral , High-Throughput Nucleotide Sequencing , Phylogeny , Plant Diseases/virology , RNA Viruses/classification , RNA Viruses/genetics , RNA, Viral , Reverse Transcriptase Polymerase Chain Reaction , Species Specificity
4.
Arch Virol ; 166(6): 1711-1722, 2021 Jun.
Article in English | MEDLINE | ID: mdl-33866416

ABSTRACT

Viruses are widespread in alfalfa (Medicago sativa L.), representing a key limitation to the production of this important forage plant. Understanding the diversity of plant viruses in alfalfa and their potential vectors will play an important role in management to minimize the emergence, transmission, and impact of viruses. Next-generation sequencing (NGS) targeting the transcriptome was applied to monitor the virus communities in alfalfa and its two main pests, thrips (Odontothrips loti Haliday and Frankliniella intonsa Trybom) and aphids (Acyrthosiphon pisum Mordvilko and Therioaphis trifolii Monell). A comparison of transcriptome datasets with reference databases revealed the presence of eight candidate viruses. Five out of the eight viruses, alfalfa mosaic virus (AMV), Medicago sativa alphapartitivirus 1 (MsAPV1), Medicago sativa deltapartitivirus 1 (MsDPV1), Medicago sativa amalgavirus 1 (MsAV1), and bean yellow mosaic virus (BYMV), were confirmed by RT-PCR. We identified and determined the presence of four RNA viruses from alfalfa samples, two viruses (AMV and MsAPV1) from thrips samples, and one virus (BYMV) from T. trifolii. All sequences isolated from the insect samples were more than 95% identical to the sequences from the alfalfa samples or to sequences from the National Center for Biotechnology Information (NCBI) reference database. The RNA-seq results of this study suggest that AMV and MsAPV1 are the predominant RNA plant viruses infecting alfalfa and that they are carried by the major pests. This lays the foundation for future research on the vectors and transmission of these viruses. In addition, the sequence data have enabled the assembly of the first complete genome sequence of MsDPV1 from alfalfa.


Subject(s)
Aphids/virology , Medicago sativa/virology , Plant Viruses/isolation & purification , RNA-Seq , Thysanoptera/virology , Animals , China , Plant Viruses/classification , Plant Viruses/genetics , RNA, Viral/genetics
5.
Cells ; 10(2)2021 02 14.
Article in English | MEDLINE | ID: mdl-33672941

ABSTRACT

Thrips are important pests of agricultural, horticultural, and forest crops worldwide. In addition to direct damages caused by feeding, several thrips species can transmit diverse tospoviruses. The present understanding of thrips-tospovirus relationships is largely based on studies of tomato spotted wilt virus (TSWV) and Western flower thrips (Frankliniella occidentalis). Little is known about other predominant tospoviruses and their thrips vectors. In this study, we report the progression of watermelon bud necrosis virus (WBNV) infection in its vector, melon thrips (Thrips palmi). Virus infection was visualized in different life stages of thrips using WBNV-nucleocapsid protein antibodies detected with FITC-conjugated secondary antibodies. The anterior midgut was the first to be infected with WBNV in the first instar larvae. The midgut of T. palmi was connected to the principal salivary glands (PSG) via ligaments and the tubular salivary glands (TSG). The infection progressed to the PSG primarily through the connecting ligaments during early larval instars. The TSG may also have an ancillary role in disseminating WBNV from the midgut to PSG in older instars of T. palmi. Infection of WBNV was also spread to the Malpighian tubules, hindgut, and posterior portion of the foregut during the adult stage. Maximum virus-specific fluorescence in the anterior midgut and PSG indicated the primary sites for WBNV replication. These findings will help to better understand the thrips-tospovirus molecular relationships and identify novel potential targets for their management. To our knowledge, this is the first report of the WBNV dissemination path in its vector, T. palmi.


Subject(s)
Citrullus/virology , Necrosis/virology , Plant Diseases/virology , Virus Diseases/virology , Animals , Larva/virology , Nucleocapsid Proteins/metabolism , Salivary Glands/virology , Thysanoptera/metabolism , Thysanoptera/virology , Tospovirus/metabolism
6.
PLoS One ; 16(3): e0247500, 2021.
Article in English | MEDLINE | ID: mdl-33657150

ABSTRACT

Thrips and thrips-transmitted tospoviruses cause significant losses in crop yields worldwide. The melon thrips (Thrips palmi) is not only a pest of cucurbit crops, but also a vector that transmits tospoviruses, such as the watermelon silver mottle virus (WSMoV). Vector transmission of tospoviruses has been well studied in the tomato spotted wilt virus (TSWV)-Frankliniella occidentalis model system; however, until now the transmission mode of WSMoV by T. palmi has not been sufficiently examined. The results of the transmission assays suggest that T. palmi transmits WSMoV in a persistent manner, and that the virus is mainly transmitted by adults, having been ingested at the first-instar larval stage. Complementary RNAs corresponding to the NSm and NSs genes of WSMoV were detected in viruliferous thrips by reverse transcription-polymerase chain reaction; NSs protein was also detected in viruliferous thrips by western blotting, verifying the replication of WSMoV in T. palmi. Furthermore, we demonstrated that in thrips infected with WSMoV at the first-instar larval stage, the virus eventually infected various tissues of the adult thrips, including the primary salivary glands. Taken together, these results suggest that T. palmi transmits WSMoV in a persistent-propagative mode. The results of this study make a significant contribution to the understanding of the transmission biology of tospoviruses in general.


Subject(s)
Citrullus/virology , Plant Diseases/virology , Thysanoptera/virology , Tospovirus/genetics , Animals , Female , Larva/virology , Male , RNA, Viral/genetics , Reverse Transcriptase Polymerase Chain Reaction , Salivary Glands/virology , Virus Replication
7.
Sci Rep ; 10(1): 15797, 2020 09 25.
Article in English | MEDLINE | ID: mdl-32978446

ABSTRACT

Tomato spotted wilt virus (TSWV) is a generalist pathogen with one of the broadest known host ranges among RNA viruses. To understand how TSWV adapts to different hosts, we experimentally passaged viral populations between two alternate hosts, Emilia sochifolia and Datura stramonium, and an obligate vector in which it also replicates, western flower thrips (Frankliniella occidentalis). Deep sequencing viral populations at multiple time points allowed us to track the evolutionary dynamics of viral populations within and between hosts. High levels of viral genetic diversity were maintained in both plants and thrips between transmission events. Rapid fluctuations in the frequency of amino acid variants indicated strong host-specific selection pressures on proteins involved in viral movement (NSm) and replication (RdRp). While several genetic variants showed opposing fitness effects in different hosts, fitness effects were generally positively correlated between hosts indicating that positive rather than antagonistic pleiotropy is pervasive. These results suggest that high levels of genetic diversity together with the positive pleiotropic effects of mutations have allowed TSWV to rapidly adapt to new hosts and expand its host range.


Subject(s)
Biodiversity , Biological Evolution , Datura stramonium/virology , Host Specificity/genetics , Plant Diseases/virology , Thysanoptera/virology , Tospovirus/genetics , Animals , Flowers/virology , Insect Vectors/virology , Plant Diseases/genetics , Tospovirus/isolation & purification
8.
PLoS One ; 15(6): e0233722, 2020.
Article in English | MEDLINE | ID: mdl-32479526

ABSTRACT

Melon yellow spot orthotospovirus (MYSV), a member of the genus Orthotospovirus, is an important virus in cucurbits. Thrips palmi is considered the most serious pest of cucurbits because it directly damages and indirectly transmits MYSV to the plant. The effects of MYSV-infected plants on the development time, fecundity, and preference of the thrips were analyzed in this study. Our results showed that the development time of male and female thrips did not differ significantly between MYSV-infected and non-infected cucumbers. The survival rate of thrips in non-infected and MYSV-infected cucumbers were not significantly different. In a non-choice assay, T. palmi adults were released on non-infected and MYSV-infected cucumbers and allowed to lay eggs. The number of hatched larvae did not significantly differ between non-infected and MYSV-infected cucumbers. In a choice assay, MYSV had no detectable effect on the number of adult thrips and preceding hatched larvae. In a pull assay, the settling rate of thrips on the released plant did not differ significantly when the adult thrips were released to non-infected or MYSV infected cucumbers for any cucumber cultivar. Based on our results, we propose that the effects of MYSV-infected cucumbers on the development time, fecundity, or preference of T. palmi may not be an important factor in MYSV spread between cucumbers.


Subject(s)
Cucumis sativus/parasitology , Orthobunyavirus/pathogenicity , Thysanoptera/physiology , Animals , Female , Fertility , Host Specificity , Male , Thysanoptera/growth & development , Thysanoptera/pathogenicity , Thysanoptera/virology
9.
Virus Res ; 284: 197979, 2020 07 15.
Article in English | MEDLINE | ID: mdl-32335149

ABSTRACT

Tobacco streak virus incidence in the cotton field, cv.CO14 at Department of Cotton, Tamil Nadu Agricultural University (TNAU), Coimbatore, India was nearly 36.50 %. Cotton plants infected with TSV exhibits different types of symptoms, including necrotic spots, lesions, mosaic, purplish necrotic rings, square drying, veinal necrosis and drying of terminal shoots. The highly prevalent thrips species in this cotton ecosystem was established as Thrips palmi (60.00 %) by morphological (ESEM) and molecular methods (RT-PCR using mtCOI primers). The density of the alternate weed host, Parthenium hysterophorus, was 15.05 plants per m2 in these fields. Association of Thrips palmi with Parthenium was confirmed, when observed under environmental scanning electron microscope (ESEM), Parthenium pollen grains (i.e., average size @ 15000X =12.94 µm) were found adhering to its body. Molecular studies through RT-PCR confirmed the presence of TSV in the leaves and pollen grains of symptomatic and symptom-free Parthenium plants collected from the cotton field (cv. CO14). Therefore, the combined role of Thrips palmi and the Parthenium pollen grains in the transmission of TSV was examined; acquiring of TSV and its presence in the body of Thrips palmi instars and adults after 72 h of AAP was convincingly demonstrated using RT-PCR, NASH and qPCR. However virus acquired thrips could not transmit the virus. Pollen from TSV infected Parthenium plants when dusted on cotton (ANKUR 2110) seedlings along with virus acquired or non-acquired thrips led to symptom development 22 days after sowing. From the study it is evident that thrips only facilitate the movement of TSV borne pollen grains, and thereby contributing to active spread of the virus.


Subject(s)
Asteraceae/virology , Ecosystem , Gossypium/virology , Ilarvirus/physiology , Plant Leaves/virology , Pollen/virology , Thysanoptera/virology , Animals , Ilarvirus/genetics , Ilarvirus/isolation & purification , Virus Diseases/transmission
10.
BMC Genomics ; 21(1): 170, 2020 Feb 18.
Article in English | MEDLINE | ID: mdl-32070289

ABSTRACT

BACKGROUND: To date, four thrips vectors have been reported to transmit five different tospoviruses in India. Their identification at an early stage is crucial in formulating appropriate pest management strategies. Since morphometric key-based thrips identification based on the adult stage is time-consuming, there is a need to develop diagnostic tools which are rapid, accurate, and independent of developmental stages. Here, we report a multiplex PCR assay to identify four major thrips vectors viz. Thrips palmi, T. tabaci, Scirtothrips dorsalis, and Frankliniella schultzei present in India. RESULTS: Cytochrome oxidase subunit III and internal transcribed spacer region 2 were utilized to design species-specific primers. Of 38 pairs of primers tested, primer pairs AG35F-AG36R, AG47F-AG48R, AG87F-AG88R, and AG79F-AG80R amplified 568 bp, 713 bp, 388 bp, and 200 bp products from the DNA templates of T. palmi, S. dorsalis, T. tabaci, and F. schultzei, respectively at same PCR conditions. The specificity of the primer pairs was validated with a large number of known specimens and no cross-reactivity was observed with other thrips species. The multiplex PCR assay with a cocktail of all the four primer pairs detected four thrips vectors efficiently and could discriminate all of them concurrently in a single reaction. CONCLUSION: The multiplex PCR reported in this study could identify the major thrips vectors reported in India. The assay will be useful in ascertaining distribution profile of major thrips vectors, disease epidemiology, screening large samples, and quarantine.


Subject(s)
Disease Vectors/classification , Multiplex Polymerase Chain Reaction , Thysanoptera/classification , Thysanoptera/genetics , Tospovirus , Animals , Electron Transport Complex IV/genetics , India , Reproducibility of Results , Thysanoptera/virology
11.
Insect Sci ; 27(4): 626-645, 2020 Aug.
Article in English | MEDLINE | ID: mdl-31453663

ABSTRACT

Western flower thrip, Frankliniella occidentalis (Pergande), is among the most economically important agricultural pests globally, attacking a wide range of vegetable and horticultural crops. In addition to causing extensive crop damage, the species is notorious for vectoring destructive plant viruses, mainly belonging to the genera Orthotospovirus, Ilarvirus, Alphacarmovirus and Machlomovirus. Once infected by orthotospoviruses, thrips can remain virulent throughout their lifespan and continue transmitting viruses to host plants when and wherever they feed. These irruptive viral outbreaks in crops will permanently disrupt functional integrated pest management systems, and typically require a remedial treatment involving insecticides, contributing to further development of insecticide resistance. To mitigate against this continuing cycle, the most effective management is early and comprehensive surveillance of the pest species and recognition of plant viruses in the field. This review provides information on the pest status of F. occidentalis, discusses the current global status of the viruses vectored by this thrip species, examines the mechanisms involved in transmitting virus-induced diseases by thrips, and reviews different management strategies, highlighting the potential management tactics developed for various cropping systems. The early surveillance and the utilization of potential methods for control of both F. occidentalis and viruses are proposed.


Subject(s)
Insect Control , Insecticides/therapeutic use , Plant Diseases/virology , Plant Viruses/physiology , Thysanoptera/physiology , Animal Distribution , Animals , Introduced Species , Thysanoptera/virology
12.
J Gen Virol ; 101(1): 112-121, 2020 01.
Article in English | MEDLINE | ID: mdl-31724933

ABSTRACT

Orthotospoviruses are acquired by thrips during feeding on infected tissue. Virions travel through the foregut and enter midgut epithelial cells through the interaction between the viral glycoproteins and cellular receptors. Glycoprotein RGD motifs and N-linked glycosylation sites have been predicted to mediate receptor binding or play important roles in virus entry into host cells, yet their function needs to be validated. In this study, peptides derived from the soybean vein necrosis virus N glycoprotein were utilized to identify critical regions in virus-vector interactions. Transmission mediated by single Neohydatothrips variabilis dropped by more than 2/3 when thrips were fed on peptide NASIAAAHEVSQE or the combination of NASIRGDHEVSQE and RLTGECNITKVSLTN when compared to the controls; indicating that this strategy could significantly reduce transmission efficiency, opening new avenues in the control of diseases caused by orthotospoviruses.


Subject(s)
Peptides/genetics , Tospovirus/genetics , Animals , Glycoproteins/genetics , Insect Vectors/genetics , Plant Diseases/virology , Glycine max/virology , Thysanoptera/virology , Virion/genetics
13.
Sci Rep ; 9(1): 17157, 2019 11 20.
Article in English | MEDLINE | ID: mdl-31748622

ABSTRACT

There is increasing evidence that acylsugars deter insect pests and plant virus vectors, including the western flower thrips (WFT), Frankliniella occidentalis (Pergande), vector of tomato spotted wilt virus (TSWV). Acylsugars are sugar-polyesters composed of saturated, un-saturated, and variously branched short and long chain fatty acids (FAs) esterified to a glucose (acylglucose) or sucrose (acylsucrose) moiety. We sought to understand how acylsucrose amount and composition of associated FA profiles interacted to mediate resistance to WFT oviposition and TSWV inoculation on tomato leaves. Towards this goal, we examined WFT oviposition and TSWV inoculation behavior on tomato lines bred to exude varying amounts of acylsucrose in association with diverse FA profiles. Our data show that as acylsucrose amounts increased, WFT egg-laying (oviposition) decreased and TSWV inoculation was suppressed. Western flower thrips also responded to FA profiles that included iC4, iC11, nC12 and nC10 FA. These findings support improving acylsugar-mediated resistance against WFT by breeding tomatoes exuding greater amounts of acylsucrose associated with specific FA profiles. We show that increasing acylsucrose amount output by type IV trichomes and selecting for particular FA profiles through advanced breeding profoundly affects WFT behavior in ways that benefit management of WFT as direct pests and as TSWV vectors.


Subject(s)
Flowers/virology , Insect Vectors/virology , Oviposition/physiology , Plant Leaves/virology , Solanum lycopersicum/virology , Thysanoptera/virology , Tospovirus/pathogenicity , Animals , Fatty Acids/metabolism , Female , Flowers/metabolism , Insecta/virology , Solanum lycopersicum/metabolism , Plant Diseases/virology , Plant Leaves/metabolism , Sucrose/metabolism , Trichomes/virology
14.
Viruses ; 11(10)2019 10 12.
Article in English | MEDLINE | ID: mdl-31614704

ABSTRACT

The XIth International Symposium on Thysanoptera and Tospoviruses co-hosted by the Yunnan Academy of Agricultural Sciences, and Nanjing Agricultural University was held from September 21-25 in Kunming, China (Figure 1) [...].


Subject(s)
Thysanoptera , Tospovirus , Animals , China , Host Microbial Interactions , Pest Control, Biological , Thysanoptera/classification , Thysanoptera/physiology , Thysanoptera/virology , Tospovirus/classification , Tospovirus/genetics , Tospovirus/pathogenicity
16.
Arch Virol ; 164(11): 2799-2804, 2019 Nov.
Article in English | MEDLINE | ID: mdl-31440810

ABSTRACT

Thrips palmi transmits the tospoviruses watermelon bud necrosis (WBNV) and groundnut bud necrosis virus (GBNV) in persistent propagative way. Little is known about the T. palmi-WBNV and -GBNV relationship. In this study, we report the effects of WBNV and GBNV infection on the life history traits of T. palmi. Both WBNV and GBNV had some negative effects on the adult life span, fecundity and survival of T. palmi as compared to non-exposed T. palmi. Tospovirus exposure favoured a female-biased ratio in the experimental population.


Subject(s)
Insect Vectors/virology , Plant Diseases/virology , Thysanoptera/virology , Tospovirus/growth & development , Animals , Female , Male , Plants/virology , Tospovirus/genetics
17.
J Insect Sci ; 19(3)2019 May 01.
Article in English | MEDLINE | ID: mdl-31127944

ABSTRACT

Iris yellow spot virus (IYSV) from the genus Tospovirus, family Peribunyaviridae, reduces yield in several crops, especially Allium spp. IYSV is primarily transmitted by onion thrips (Thrips tabaci), but little is known about how IYSV impacts the biology of its principal vector. In a controlled experiment, the effect of IYSV on the lifespan and fecundity of onion thrips was examined. Larvae were reared on IYSV-infected onions until pupation. Individual pupae were confined until adults eclosed, and the lifespan and total progeny produced per adult were monitored daily. Thrips were tested for the virus in reverse-transcriptase polymerase chain reaction using specific primers to confirm the presence of IYSV. Results indicated that 114 and 35 out of 149 eclosing adults tested positive (viruliferous) and negative (nonviruliferous) for IYSV, respectively. The viruliferous adults lived 1.1-6.1 d longer (average of 3.6 d) than nonviruliferous adults. Fecundity of viruliferous and nonviruliferous onion thrips was similar with 2.0 ± 0.1 and 2.3 ± 0.3 offspring produced per female per day, respectively. Fecundity for both viruliferous and nonviruliferous thrips also was significantly positively correlated with lifespan. These findings suggest that the longer lifespan of viruliferous onion thrips adults may allow this primary vector of IYSV to infect more plants, thereby exacerbating IYSV epidemics.


Subject(s)
Thysanoptera/virology , Tospovirus/physiology , Animals , Female , Fertility , Insect Vectors/virology , Longevity , Onions/virology , Plant Diseases/virology , Thysanoptera/physiology
18.
Viruses ; 11(2)2019 02 22.
Article in English | MEDLINE | ID: mdl-30813271

ABSTRACT

Tomato chlorotic spot virus (TCSV) and groundnut ringspot virus (GRSV) share several genetic and biological traits. Both of them belong to the genus Tospovirus (family Peribunyaviridae), which is composed by viruses with tripartite RNA genome that infect plants and are transmitted by thrips (order Thysanoptera). Previous studies have suggested several reassortment events between these two viruses, and some speculated that they may share one of their genomic segments. To better understand the intimate evolutionary history of these two viruses, we sequenced the genomes of the first TCSV and GRSV isolates ever reported. Our analyses show that TCSV and GRSV isolates indeed share one of their genomic segments, suggesting that one of those viruses may have emerged upon a reassortment event. Based on a series of phylogenetic and nucleotide diversity analyses, we conclude that the parental genotype of the M segment of TCSV was either eliminated due to a reassortment with GRSV or it still remains to be identified.


Subject(s)
Genome, Viral , Reassortant Viruses , Solanum lycopersicum/virology , Tospovirus/genetics , Animals , Evolution, Molecular , Genetic Variation , High-Throughput Nucleotide Sequencing , Phylogeny , RNA, Viral/genetics , Thysanoptera/virology
19.
Arch Virol ; 164(1): 117-126, 2019 Jan.
Article in English | MEDLINE | ID: mdl-30288607

ABSTRACT

An orthotospovirus distinct from all other orthotospoviruses was isolated from naturally infected alstroemeria plants. Disease symptoms caused by this virus mainly consisted of yellow spots on the leaves based on which the name alstroemeria yellow spot virus (AYSV) was coined. A host range analysis was performed and a polyclonal antiserum was produced against purified AYSV ribonucleoproteins which only reacted with the homologous antigen and not with any other (established or tentative) orthotospovirus from a selection of American and Asian species. Upon thrips transmission assays the virus was successfully transmitted by a population of Thrips tabaci. The entire nucleotide sequence of the M and S RNA segments was elucidated by a conventional cloning and sequencing strategy, and contained 4797 respectively 2734 nucleotides (nt). Simultaneously, a next generation sequencing (NGS) approach (RNAseq) was employed and generated contigs covering the entire viral tripartite RNA genome. In addition to the M and S RNA nucleotide sequences, the L RNA (8865 nt) was obtained. The nucleocapsid (N) gene encoded by the S RNA of this virus consisted of 819 nucleotides with a deduced N protein of 272 amino acids and by comparative sequence alignments to other established orthotospovirus species showed highest homology (69.5% identity) to the N protein of polygonum ringspot virus. The data altogether support the proposal of AYSV as a new orthotospovirus species within a growing clade of orthotospoviruses that seem to share the Middle East basin as a region of origin.


Subject(s)
Alstroemeria/virology , Plant Diseases/virology , Plant Viruses/genetics , Plant Viruses/isolation & purification , Animals , Insect Vectors/virology , Phylogeny , RNA, Viral/genetics , RNA, Viral/isolation & purification , Thysanoptera/virology , Nicotiana/virology
20.
PLoS One ; 13(12): e0208538, 2018.
Article in English | MEDLINE | ID: mdl-30532222

ABSTRACT

Thrips palmi is a widely distributed major agricultural pest in the tropics and subtropics, causing significant losses in cucurbit and solanaceous crops through feeding damage and transmission of tospoviruses. Thrips palmi is a vector of capsicum chlorosis virus (CaCV) in Australia. The present understanding of transmission biology and potential effects of CaCV on T. palmi is limited. To gain insights into molecular responses to CaCV infection, we performed RNA-Seq to identify thrips transcripts that are differentially-abundant during virus infection of adults. De-novo assembly of the transcriptome generated from whole bodies of T. palmi adults generated 166,445 contigs, of which ~24% contained a predicted open reading frame. We identified 1,389 differentially-expressed (DE) transcripts, with comparable numbers up- (708) and down-regulated (681) in virus-exposed thrips compared to non-exposed thrips. Approximately 59% of these DE transcripts had significant matches to NCBI non-redundant proteins (Blastx) and Blast2GO identified provisional functional categories among the up-regulated transcripts in virus-exposed thrips including innate immune response-related genes, salivary gland and/or gut-associated genes and vitellogenin genes. The majority of the immune-related proteins are known to serve functions in lysosome activity and melanisation in insects. Most of the up-regulated oral and extra-oral digestion-associated genes appear to be involved in digestion of proteins, lipids and plant cell wall components which may indirectly enhance the likelihood or frequency of virus transmission or may be involved in the regulation of host defence responses. Most of the down-regulated transcripts fell into the gene ontology functional category of 'structural constituent of cuticle'. Comparison to DE genes responsive to tomato spotted wilt virus in Frankliniella occidentalis indicates conservation of some thrips molecular responses to infection by different tospoviruses. This study assembled the first transcriptome in the genus Thrips and provides important data to broaden our understanding of networks of molecular interactions between thrips and tospoviruses.


Subject(s)
Gene Expression Profiling , Thysanoptera/genetics , Thysanoptera/virology , Tospovirus/physiology , Animals , Molecular Sequence Annotation , RNA, Messenger/genetics , Species Specificity
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