Tomato Spotted Wilt Tospovirus Research Articles

Registration of ‘TifJumbo’ peanut

Abstract‘TifJumbo’ (Reg. no. CV‐157, PI 701814) is a virginia‐type peanut (Arachis hypogaea L. subsp. hypogaea var. hypogaea) cultivar released by the USDA–ARS and the Georgia Agricultural Experiment Station in 2021. TifJumbo was developed at the University of Georgia Coastal Plain Experiment Station, Tifton, GA. Our research objective was to develop a high oleic acid, virginia market‐type cultivar that also has resistance to the peanut root‐knot nematode [Meloidogyne arenaria (Neal) Chitwood race 1] and resistance to spotted wilt caused by Tomato spotted wilt tospovirus (TSWV). Breeding populations were developed by hybridizing C1805‐2‐9‐16 × N08082olJCT. C1805‐2‐9‐16 is a breeding line selected from the cross of Tifguard × ‘Florida‐07’. N08082olJCT is a ‘Bailey’‐derived, high‐oleic breeding line. Marker assisted selection was used in the development of TifJumbo to select for nematode resistance and the high oleic to linoleic (O/L) characteristic. TifJumbo has a high level of resistance to both the peanut root‐knot nematode and TSWV and has a high O/L ratio. When tested in fields without nematode pressure, TifJumbo exhibited yields that were at least similar to other currently grown peanut cultivars. When tested in fields with nematode pressure, TifJumbo exhibited significantly higher yields in comparison to Bailey, a widely grown, nematode‐susceptible, virginia‐type cultivar. Grade variables for TifJumbo were similar to other common virginia‐type peanut cultivars. Seed size and size distribution were similar to other virginia‐type cultivars.

Registration of ‘TifNV‐HG’ peanut

Abstract‘TifNV‐HG’ (Reg. no. CV‐153, PI 702637) is a runner‐type peanut (Arachis hypogaea L. subsp. hypogaea var. hypogaea) cultivar released by the USDA‐ARS and the Georgia Agricultural Experiment Station in 2021. TifNV‐HG was developed at the University of Georgia Coastal Plain Experiment Station, Tifton, GA. TifNV‐HG is a high oleic acid, runner market‐type cultivar that also has resistance to the peanut root‐knot nematode [Meloidogyne arenaria (Neal) Chitwood race 1] and resistance to spotted wilt caused by Tomato spotted wilt tospovirus (TSWV). Breeding populations were developed by hybridizing C1805‐617‐2 × ‘Georgia‐06G’. C1805‐617‐2 is a breeding line selected from the cross of ‘Tifguard’ × ‘Florida‐07’. Marker‐assisted selection was used in the development of TifNV‐HG to select for nematode resistance and the high oleic to linoleic (O/L) characteristic. TifNV‐HG has a high level of resistance to both the peanut root‐knot nematode and TSWV and has a high ratio of oleic acid to linoleic acid. When tested in fields without nematode pressure, TifNV‐HG exhibited yields that were at least similar to other currently grown peanut cultivars. When tested in fields with nematode pressure, TifNV‐HG exhibited yield that was at least equivalent to the nematode‐resistant cultivars TifNV‐High O/L and Georgia‐14N and significantly higher than the susceptible check cultivar Georgia‐06G. TifNV‐HG exhibited higher grade in comparison to TifNV‐High O/L.

Distribution and identification of main Viruses Infecting Pepper in Qinghai.

From 2019 to 2021, pepper viruses were investigated in pepper planting areas and collected a total of 333 samples were in Qinghai (The central district, Datong, Huangzhong in Xining; Ledu district, Pingan, Huzhu, Minhe in Haidong, and Jianzha in Huangnan). RT-PCR and molecular cloning were conducted for virus detection in 333 suspected viral samples, the results revealed that viruses infecting pepper mainly included 11 capsicum viruses. Tomato spotted wilt tospovirus （TSWV）has the highest detection rate (36%) in Datong County, and Pepper cryptic virus 1 (PCV1) has the highest detection rate (57%) in Huangzhong County. In the Haidong, 86.3% of the peppers were Broad bean wilt virus 2（BBWV2）, virus-infected Pepper cryptic virus 2 (PCV2), TSWV and Cucumber mosaic virus （CMV） were detected in Xunhua, among which PCV1 and CMV had the highest detection rate (30.4%); PCV1, TSWV, and PCV2 were detected in Ledu and PCV2 had the highest detection rate (50%). There were 17 kinds of co-infection and the co-infection of two viruses occurred often. There were only 5 kinds of co-infection of three. Combined infection contained PCV1 and TMV was the most common. The distribution and species of pepper viruses from the pepper planting areas were clarified and it laid the foundation for preventing and controlling pepper viruses across Qinghai province.

Updating viral agents in tomato seeds with new generation diagnostic technologies

The aim of this study is to identify and update the list of viral pathogens in tomato seeds, which plays an important role for our country's economy, and to control, on behalf of our country, viral factors like TYLCV and PepMV, which were thought not to be existing in the past but were determined by new and sensitive methods in the recent years. It is also the aim, if viral pathogens like TYLCV and PepMV are found, to share this findings with the necessary institutions and to update the viral factors which needs to be tested, and the quarantine lists. Two hundred and thirty-eight seed samples were used in this study. Serological and molecular methods were used in order to identify the viral pathogens in the seed samples. Two hundred and thirty-eight seed samples of different tomato varieties were tested in order to prove the possible existence of Tobacco mosaic tobamovirus (TMV), Tomato mosaic tobamovirus (ToMV), Cucumber mosaic cucumovirus (CMV), Tomato yellow leaf curl geminivirus (TYLCV), Tomato spotted wilt tospovirus (TSWV), Pepino mosaic potexvirus (PepMV), Pepper mild mottle tobamovirus (PMMoV), and Tomato brown rugose fruit tobamovirus (ToBRFV) and as a result 12% of the seeds were founded to be infected with TMV, 23% with ToMV and 8% with CMV. Within the scope of this study it was seen that some seed samples have mixed infections. Sixty-seven seeds of the 238 seeds has been found to be infected in this study. This is a rate of 28% were the seeds are infected at least with one viral pathogen.

Genome-Wide Identification and Functions against Tomato Spotted Wilt Tospovirus of PR-10 in Solanum lycopersicum.

Tomato spotted wilt virus impacts negatively on a wide range of economically important plants, especially tomatoes. When plants facing any pathogen attack or infection, increase the transcription level of plant genes that are produced pathogenesis-related (PR) proteins. The aim of this study is a genome-wide identification of PR-10 superfamily and comparative analysis of PR-10 and Sw-5b gene functions against tomato responses to biotic stress (TSWV) to systemic resistance in tomato. Forty-five candidate genes were identified, with a length of 64–210 amino acid residues and a molecular weight of 7.6–24.4 kDa. The PR-10 gene was found on ten of the twelve chromosomes, and it was determined through a genetic ontology that they were involved in six biological processes and molecular activities, and nine cellular components. Analysis of the transcription level of PR-10 family members showed that the PR-10 gene (Solyc09g090980) has high expression levels in some parts of the tomato plant. PR-10 and Sw-5b gene transcription and activity in tomato leaves were strongly induced by TSWV infection, whereas H8 plants having the highest significantly upregulated expression of PR-10 and Sw-5b gene after the inoculation of TSWV, and TSWV inoculated in M82 plants showed significantly upregulated expression of PR-10 gene comparatively lower than H8 plants. There was no significant expression of Sw-5b gene of TSWV inoculated in M82 plants and then showed highly significant correlations between PR-10 and Sw-5b genes at different time points in H8 plants showed significant correlations compared to M82 plants after the inoculation of TSWV; a heat map showed that these two genes may also participate in regulating the defense response after the inoculation of TSWV in tomato.

Antalya İli Kumluca İlçesindeki Biber Yetiştirilen Seralarda Domates Lekeli Solgunluk Virüsü (Tomato spotted wilt tospovirus-TSWV)’ nün Yaygınlığı ve Konukçu Yabancı Ot Türlerinin Belirlenmesi

There are many viruses that infect pepper and limit its production. Among these viruses, Tomato spotted wilt tospovirus (TSWV) infects crops in 35 plant families that are economically important, including pepper. In the present study; totaly 156 leaf samples were collected, including 57 from pepper plants showing virus-like symptoms and 99 from weeds and/or plants other than peppers in and around the greenhouse, through surveys carried out in pepper greenhouses in Kumluca district of Antalya province, from September to December 2020. Then, the plant leaf samples were tested to determine TSWV infections by the Double Antibody Sandwich Enzyme-linked Immunosorbent Assay (DAS-ELISA) method. According to result of the tests, it was determined that 55.76% of the tested leaf samples were infected with TSWV, while this rate was determined as 96.49% for pepper samples and 32.32% for other plant samples. During the survey studies, it was revealed that the leaf samples of 13 out of 31 weed and different plant species except pepper were infected with at least one of the viruses. In addition, pepper plants showing symptoms TSWV-like symptoms in pepper greenhouses were counted during the survey, and the prevalence of this virus disease was calculated on the basis of Kumluca district and neighborhoods. As a result of these calculations, the prevalences of TSWV; for Kumluca, Mavikent, Beykonak, Salur, Hacıveliler, Adrasan, Merkez, and Kavakköy were determined as 26.93%, 26.92%, 32.27%, 20.66%, 21.13%, 17.66%, 13%, and 25%, respectively.

Different Methods for Detection and Diagnosis of Tomato Spotted Wilt Tospovirus Infection of some Cucurbit Host Plants and its Main Vector of Thrips Species in Field and Greenhouse in Egypt

The study recorded for the first time in Egypt the presence of tomato spotted wilt virus (TSWV) on cucurbits, which was confirmed using several serological tests, like double antibody sandwich ELISA (DAS-ELISA); Dot-blot ELISA assay and Immuno capture polymerase chain reaction (IC-PCR). By using Dot blot immunoassay test reaction against TSWV antisera, the ability of thrips species Thrips tabaci (Lind), Thrips palmi (Karny), and Frankliniella occidentalis (​Pergande), on the transmission of the (TSWV) were asserted. In the greenhouse, eleven plant species were determined as the host range of virus and field samples showed the similar symptoms. The mechanical transmission of TSWV showed a positive reaction bearing symptoms on the leaves of Cucumber, zucchini, smoke, datura and tomato plants 15-20 days after inoculation with transmission rates of 46.5, 40, 46.5, 46.5 and 86.5%, respectively. DAS-ELISA using antisera of TSWV showed that the greenhouse leaves samples were infected; otherwise, an amplification of IC-PCR products of 500 bp was detected by agarose electrophoresis of total RNA isolated from infected leaves.

The Tomato spotted wilt virus (TSWV) Genome is Differentially Targeted in TSWV-Infected Tomato (Solanum lycopersicum) with or without Sw-5 Gene.

Tospoviruses cause significant losses to a wide range of agronomic and horticultural crops worldwide. The type member, Tomato spotted wilt tospovirus (TSWV), causes systemic infection in susceptible tomato cultivars, whereas its infection is localized in cultivars carrying the Sw-5 resistance gene. The response to TSWV infection in tomato cultivars with or without Sw-5 was determined at the virus small RNA level in the locally infected leaf. Predicted reads were aligned to TSWV reference sequences. The TSWV genome was found to be differentially processed among each of the three-viral genomic RNAs—Large (L), Medium (M) and Small (S)—in the Sw-5(+) compared to Sw-5(−) genotypes. In the Sw-5(+) cultivar, the L RNA had the highest number of viral small-interfering RNAs (vsiRNAs), whereas in the Sw-5(−) cultivar the number was higher in the S RNA. Among the three-viral genomic RNAs, the distribution of hotspots showed a higher number of reads per million reads of vsiRNAs of 21 and 22 nt class at the 5′ and 3′ ends of the L and the S RNAs, with less coverage in the M RNA. In the Sw-5(−) cultivar, the nature of the 5′ nucleotide-end in the siRNAs varied significantly; reads with 5′-adenine-end were most abundant in the mock control, whereas cytosine and uracil were more abundant in the infected plants. No such differences were seen in case of the resistant genotype. Findings provided insights into the response of tomato cultivars to TSWV infection.

Virusi biljaka familije štitonoša

The Apiaceae are a large plant family consisting of approximately 250 genera and over 3,000 species grown worldwide. Its representative vegetables are carrot, parsley, parsnip and celery, as well as some wellknown spice plants such as fennel, anise, caraway, dill, and coriander. Their production is imperiled by numerous pathogens, among which viruses are of great importance. Globally more than 30 viruses are known to affect carrot and other plant species belonging to family Apiaceae. The principal viruses are: Celery mosaic virus (CeMV), Parsnip yellow fleck virus, (PYFV), Carrot red leaf virus (CtRLV) and Carrot mottle virus (CMoV). In Serbia, three viruses are present on carrot and celery: CeMV, Cucumber mosaic virus (CMV) and Tomato spotted wilt tospovirus (TSWV). The economic importance of viruses infecting umbelliferous has long been recognised due to the foliar symptoms and viral dieback of seedlings. These viruses affect carrot crops only sporadically, but when they do occur they can be devastating. Other umbelliferous viruses are known to occur worlwide, however, their effects are not clear.

A convenient in vivo cap donor delivery system to investigate the cap snatching of plant bunyaviruses

Like their animal-infecting counterparts, plant bunyaviruses use capped RNA leaders cleaved from host cellular mRNAs to prime viral genome transcription in a process called cap-snatching, but in vivo systems to investigate the details of this process are lacking for them. Here, we report that Rice stripe tenuivirus (RSV) and Tomato spotted wilt tospovirus (TSWV) cleave capped RNA leaders from mRNAs transiently expressed by agroinfiltration, which makes it possible to artificially deliver defined cap donors to the two plant bunyaviruses with unprecedented convenience. With this system, some ideas regarding how plant bunyaviruses select and use capped RNA leaders can be tested easily. We were also able to obtain clear evidence that the capped RNA leaders selected by TSWV are generally longer than those by RSV. TSWV frequently uses the prime-and-realign mechanism in transcription primed by capped RNA leaders shorter than a certain length, like that has been demonstrated recently for RSV.

Studies on the interaction between tomato spotted wilt tospovirus and thrips

Tomato spotted wilt tospovirus (TSWV), a type species of the genus Orthotospovirus, which belongs to the family Tospoviridae, causes necrotic yellow and necrosis diseases of vegetables including tomatoes and green peppers, and to flowers such as chrysanthemum and dahlia, and causes economic damage, yield loss, and loss of quality. TSWV has a spherical enveloped virion that contains three species of singlestrand RNA segments (L, M, and S). The genome encodes fives genes; a putative cell-to-cell movement protein (NSm), a non-structural protein (NSs), a nucleocapsid protein (N), an RNA-dependent RNA polymerase, and a precursor of surface glycoproteins (GN/GC). TSWV is transmitted in a circulative and propagative manner by thrips such as western flower thrips (Frankliniella occidentalis) and onion thrips (Thrips tabaci). TSWV has been controlled using the virus resistance genes of the cultivars and by controlling the vector using insecticides. However, the emergence of TSWV that can no longer be controlled using the resistance gene of the cultivars and the development of resistance to insecticides by thrips is a serious problem worldwide. Hence, the interactions among TSWV, western flower thrips, and Arabisopsis thaliana were analysed to develop a novel way to control TSWV on the basis of the interaction mechanism.

Studies of the interaction between tomato spotted wilt tospovirus and thrips

Studies of the interaction between tomato spotted wilt tospovirus and thrips

Putative Auxin and Light Responsive Promoter Elements From the Tomato spotted wilt tospovirus Genome, When Expressed as cDNA, Are Functional in Arabidopsis

Members of the virus order Bunyavirales cause serious diseases in animals, humans and plants. Family Tospoviridae in this order contains only one genus Orthotospovirus, and members in this genus exclusively infect plants. Tomato spotted wilt tospovirus (TSWV) is considered one of the most economically important plants viruses. Little is known about the regulatory elements in the TSWV genome. Here we show that, when in the cDNA form, the 5′-upstream region of the TSWV-coded GN/GC gene (pGN/GC) possesses putative cis-regulatory elements, including an auxin responsive element (AuxRE) for binding of auxin response factors (ARFs), as well as a circadian clock-associated 1 (CCA1) protein binding site (CBS). Due to the lack of a reverse genetics system, we verified the functionality of these elements in Arabidopsis. pGN/GC showed light-suppressive promoter activity in transgenic Arabidopsis, and mutation in the CBS was sufficient to switch the activity to light inducible. Additionally, exogenous auxin treatments repressed the promoter activity of both wild type and CBS-mutated pGN/GC. Mutation in AuxRE in both promoters abolished their sensitivity to auxin. As transcriptional repressors, both CCA1 and ARF2 were able to bind to pGN/GC directly. To our knowledge, this is the first report that a 5′-terminal sequence of an RNA virus has light-and hormone-responsive promoter activities when expressed as cDNA in host plant’s nuclear background. Our findings suggest new clues on the possible origin, evolution and function of the TSWV genomic sequence and its non-coding regions.

Comprehensive transcriptome analysis and functional characterization of PR-5 for its involvement in tomato Sw-7 resistance to tomato spotted wilt tospovirus

Tomato spotted wilt tospovirus (TSWV), one of the most important plant viruses, causes yield losses to many crops including tomato. The current disease management for TSWV is based mainly on breeding tomato cultivars containing the Sw-5 locus. Unfortunately, several Sw-5 resistance-breaking strains of TSWV have been identified. Sw-7 is an alternative locus conferring resistance to a broad range of TSWV strains. In an effort to uncover gene networks that are associated with the Sw-7 resistance, we performed a comparative transcriptome profiling and gene expression analysis between a nearly-isogenic Sw-7 line and its susceptible recurrent parent (Fla. 8059) upon infection by TSWV. A total of 1,244 differentially expressed genes were identified throughout a disease progression process involving networks of host resistance genes, RNA silencing/antiviral defense genes, and crucial transcriptional and translational regulators. Notable induced genes in Sw-7 include those involved in callose accumulation, lignin deposition, proteolysis process, transcriptional activation/repression, and phosphorylation. Finally, we investigated potential involvement of PR-5 in the Sw-7 resistance. Interestingly, PR-5 overexpressed plants conferred enhanced resistance, resulting in delay in virus accumulation and symptom expression. These findings will facilitate breeding and genetic engineering efforts to incorporate this new source of resistance in tomato for protection against TSWV.

Registration of ‘TifNV‐High O/L’ Peanut

‘TifNV‐High O/L’ (Reg. No. CV‐132, PI 680611) is a runner‐type peanut (Arachis hypogaea L. subsp. hypogaea var. hypogaea) cultivar released by the USDA‐ARS and the Georgia Agricultural Experiment Station in 2014. TifNV‐High O/L was developed at the University of Georgia Coastal Plain Experiment Station, Tifton, GA. Our research objective was to combine resistance to the peanut root‐knot nematode and resistance to spotted wilt caused by Tomato spotted wilt tospovirus (TSWV) with the high oleic acid characteristic. Breeding populations were developed by hybridizing the nematode‐resistant cultivar Tifguard with the high oleic cultivar Florida‐07. Marker assisted selection was used to select for nematode resistance and the high oleic to linoleic fatty acid ratio (O/L) characteristic. TifNV‐High O/L has a high level of resistance to both the peanut root‐knot nematode and TSWV, and it has a high ratio of oleic acid to linoleic acid. When tested in fields without nematode pressure, TifNV‐High O/L exhibited yields that were similar to other currently grown peanut cultivars. When tested in fields with nematode pressure, TifNV‐High O/L exhibited significantly higher yields in comparison to Georgia‐06G, a widely grown susceptible cultivar. Grade variables for TifNV‐High O/L were similar to other common peanut cultivars. Seed size and size distribution were similar to other large‐seeded runner‐type cultivars.

Plant Population and Replant Method Effects on Peanut Seeded in Single Rows

ABSTRACT The University of Georgia Extension recommendation for optimum plant stand in peanut (Arachis hypogaea L.) is 13.1 plants/m, although previous work has shown that yield potential can be maintained at lower plant stands. The unpredictable and often extreme weather and the ubiquity of pathogens in the region often contribute to poor emergence and poor plant stands. When plant stand is adversely affected, replanting the field may be a practical option. The objectives of this study were to determine i) the effect of plant stand on yield, grade and disease incidence, ii) at what plant stand peanut gains an advantage from replanting and iii) the best method for replanting peanut when an adequate stand is not achieved. Field trials took place in Plains, GA in 2011, 2012, and 2013; and Tifton, GA in 2012 and 2013 to evaluate peanut production at six plant stands (3.3, 4.9, 6.6, 8.2, 9.8, and 11.5 plants/m, in addition to a 13.1 plants/m control) in combination with three replant practices; i) no replant, ii) destroy the original stand and replant at a full seeding rate, and iii) add a reduced rate of seed to supplement the original stand) in a randomized complete block design. A positive linear trend for yield and a negative linear trend for tomato spotted wilt Tospovirus incidence were discovered as plant stand increased. Yield advantages from replanting occurred via supplemental seed addition to initial stands of 3.3 and 8.2 plants/m. Destroying the initial stand and completely replanting was never beneficial when compared to the other two replant practices. Replanting is warranted via supplemental seed addition at plant stands equal-to or below 8.2 plants/m.

A multilayered regulatory mechanism for the autoinhibition and activation of a plant CC-NB-LRR resistance protein with an extra N-terminal domain.

The tomato resistance protein Sw-5b differs from the classical coiled-coil nucleotide-binding leucine-rich repeat (CC-NB-LRR) resistance proteins by having an extra N-terminal domain (NTD). To understand how NTD, CC and NB-LRR regulate autoinhibition and activation of Sw-5b, we dissected the function(s) of each domain. When viral elicitor was absent, Sw-5b LRR suppressed the central NB-ARC to maintain autoinhibition of the NB-LRR segment. The CC and NTD domains independently and additively enhanced the autoinhibition of NB-LRR. When viral elicitor was present, the NB-LRR segment of Sw-5b was specifically activated to trigger a hypersensitive response. Surprisingly, Sw-5b CC suppressed the activation of NB-LRR, whereas the extra NTD of Sw-5b became a positive regulator and fully activated the resistance protein, probably by relieving the inhibitory effects of the CC. In infection assays of transgenic plants, the NB-LRR segment alone was insufficient to confer resistance against Tomato spotted wilt tospovirus; the layers of NTD and CC regulation on NB-LRR were required for Sw-5b to confer resistance. Based on these findings, we propose that, to counter the negative regulation of the CC on NB-LRR, Sw-5b evolved an extra NTD to coordinate with the CC, thus developing a multilayered regulatory mechanism to control autoinhibition and activation.

Plasmodesmata targeting and intercellular trafficking of Tomato spotted wilt tospovirus movement protein NSm is independent of its function in HR induction.

The movement protein NSm of Tomato spotted wilt tospovirus (TSWV) plays pivotal roles in viral intercellular trafficking. Recently, the TSWV NSm was also identified as an avirulence (Avr) determinant during the Sw-5b-mediated hypersensitive response (HR). However, whether the cell-to-cell movement of NSm is coupled to its function in HR induction remains obscure. Here, we showed that the NSm mutants defective in targeting plasmodesmata and cell-to-cell movement were still capable of inducing Sw-5b-mediated HR. In addition, introduction of a single amino-acid substitution, C118Y or T120N, identified previously from TSWV resistance-breaking isolates, into the movement-defective NSm mutants resulted in the failure of HR induction. Collectively, our results showed that the intercellular trafficking of NSm is uncoupled from its function in HR induction. These findings shed light on the evolutionary mechanism of R-Avr recognition and may be used to explain why this uncoupled phenomenon can be observed in many different viruses.

The ER-Membrane Transport System Is Critical for Intercellular Trafficking of the NSm Movement Protein and Tomato Spotted Wilt Tospovirus

Plant viruses move through plasmodesmata to infect new cells. The plant endoplasmic reticulum (ER) is interconnected among cells via the ER desmotubule in the plasmodesma across the cell wall, forming a continuous ER network throughout the entire plant. This ER continuity is unique to plants and has been postulated to serve as a platform for the intercellular trafficking of macromolecules. In the present study, the contribution of the plant ER membrane transport system to the intercellular trafficking of the NSm movement protein and Tomato spotted wilt tospovirus (TSWV) is investigated. We showed that TSWV NSm is physically associated with the ER membrane in Nicotiana benthamiana plants. An NSm-GFP fusion protein transiently expressed in single leaf cells was trafficked into neighboring cells. Mutations in NSm that impaired its association with the ER or caused its mis-localization to other subcellular sites inhibited cell-to-cell trafficking. Pharmacological disruption of the ER network severely inhibited NSm-GFP trafficking but not GFP diffusion. In the Arabidopsis thaliana mutant rhd3 with an impaired ER network, NSm-GFP trafficking was significantly reduced, whereas GFP diffusion was not affected. We also showed that the ER-to-Golgi secretion pathway and the cytoskeleton transport systems were not involved in the intercellular trafficking of TSWV NSm. Importantly, TSWV cell-to-cell spread was delayed in the ER-defective rhd3 mutant, and this reduced viral infection was not due to reduced replication. On the basis of robust biochemical, cellular and genetic analysis, we established that the ER membrane transport system serves as an important direct route for intercellular trafficking of NSm and TSWV.

Phorate‐induced Host Defence Responses Condition Acquired Resistance to Tomato Spotted Wilt in Cultivated Peanut (Arachis hypogaea L.)

AbstractPhorate is an acetylcholinesterase‐inhibiting organophosphate pesticide used for the control of insects, mites and nematodes. In cultivated peanut (Arachis hypogaea L.), phorate is often used as an in‐furrow, systemic insecticide to reduce thrips populations which vector tomato spotted wilt tospovirus (TSWV). However, phorate‐induced suppression of disease incidence and severity is not solely due to thrips control because other pesticides control thrips but not TSWV. The present research was focused on understanding the biochemical and molecular components of the phorate‐induced host responses that may condition acquired resistance to TSWV in peanut. Phorate treatments adversely affected maximal quantum yield of the light reactions (Fv/Fm). A dose‐dependent increase in ascorbic acid content and in activities of the oxidative stress‐related enzymes, catalase and superoxide dismutase was evident following phorate treatment, whereas the level of glutathione reductase was not affected. An RT‐PCR differential display screen identified 35 expressed sequence tags (ESTs) responsive to phorate treatment in peanut leaves. Functional annotations revealed transcriptional regulation of ESTs implicated in primary and secondary metabolism including photosynthesis‐related genes, mitigation of oxidative stress, signalling pathways and pathogenesis‐ and defence‐related proteins. Two ESTs encoding membrane trafficking functions were downregulated, which may reflect reduced internalization and/or subsequent replication of viral particles in phorate‐treated leaves. Time‐course quantitative RT‐PCR analyses further verified fidelity and sensitivity of the mRNA differential display screen and corroborated that systemic spread of TSWV in field‐grown plants is reduced following phorate application. The mélange of differentially regulated gene functions is consistent with a model in which a phorate‐induced breach of redox control culminates in hypersensitive cell death and subsequent induction of systemic acquired resistance.