Soybean RNA interference lines silenced for eIF4E show broad potyvirus resistance

Soybean mosaic virus (SMV), a potyvirus, is the most prevalent and destructive viral pathogen in soybean-planting regions of China. Moreover, other potyviruses, including bean common mosaic virus (BCMV) and watermelon mosaic virus (WMV), also threaten soybean farming. The eukaryotic translation initiation factor 4E (eIF4E) plays a critical role in controlling resistance/susceptibility to potyviruses in plants. In the present study, much higher SMV-induced eIF4E1 expression levels were detected in a susceptible soybean cultivar when compared with a resistant cultivar, suggesting the involvement of eIF4E1 in the response to SMV by the susceptible cultivar. Yeast two-hybrid and bimolecular fluorescence complementation assays showed that soybean eIF4E1 interacted with SMV VPg in the nucleus and with SMV NIa-Pro/NIb in the cytoplasm, revealing the involvement of VPg, NIa-Pro, and NIb in SMV infection and multiplication. Furthermore, transgenic soybeans silenced for eIF4E were produced using an RNA interference approach. Through monitoring for viral symptoms and viral titers, robust and broad-spectrum resistance was confirmed against five SMV strains (SC3/7/15/18 and SMV-R), BCMV, and WMV in the transgenic plants. Our findings represent fresh insights for investigating the mechanism underlying eIF4E-mediated resistance in soybean and also suggest an effective alternative for breeding soybean with broad-spectrum viral resistance.     

The P2 of Wheat yellow mosaic virus rearranges the endoplasmic reticulum and recruits other viral proteins into replication‐associated inclusion bodies

Viruses commonly modify host endomembranes to facilitate biological processes in the viral life cycle. Infection by viruses belonging to the genus Bymovirus (family Potyviridae) has long been known to induce the formation of large membranous inclusion bodies in host cells, but their assembly and biological roles are still unclear. Immunoelectron microscopy of cells infected with the bymovirus Wheat yellow mosaic virus (WYMV) showed that P1, P2 and P3 are the major viral protein constituents of the membranous inclusions, whereas NIa‐Pro (nuclear inclusion‐a protease) and VPg (viral protein genome‐linked) are probable minor components. P1, P2 and P3 associated with the endoplasmic reticulum (ER), but only P2 was able to rearrange ER and form large aggregate structures. Bioinformatic analyses and chemical experiments showed that P2 is an integral membrane protein and depends on the active secretory pathway to form aggregates of ER membranes. In planta and in vitro assays demonstrated that P2 interacts with P1, P3, NIa‐Pro or VPg and recruits these proteins into the aggregates. In vivo RNA labelling using WYMV‐infected wheat protoplasts showed that the synthesis of viral RNAs occurs in the P2‐associated inclusions. Our results suggest that P2 plays a major role in the formation of membranous compartments that house the genomic replication of WYMV.     

Association between flower stalk elongation,an Arabidopsis developmental trait,and the subcellular location and movement dynamics of the nonstructural protein P3 of Turnip mosaic virus

Virus infections affect plant developmental traits but this aspect of the interaction has not been extensively studied so far. Two strains of Turnip mosaic virus differentially affect Arabidopsis development, especially flower stalk elongation, which allowed phenotypical, cellular, and molecular characterization of the viral determinant, the P3 protein. Transiently expressed wild-type green fluorescent protein-tagged P3 proteins of both strains and selected mutants of them revealed important differences in their behaviour as endoplasmic reticulum (ER)-associated peripheral proteins flowing along the reticulum, forming punctate accumulations. Three-dimensional (3D) model structures of all expressed P3 proteins were computationally constructed through I-TASSER protein structure predictions, which were used to compute protein surfaces and map electrostatic potentials to characterize the effect of amino acid changes on features related to protein interactions and to phenotypical and subcellular results. The amino acid at position 279 was the main determinant affecting stalk development. It also determined the speed of ER-flow of the expressed proteins and their final location. A marked change in the protein surface electrostatic potential correlated with changes in subcellular location. One single amino acid in the P3 viral protein determines all the analysed differential characteristics between strains differentially affecting flower stalk development. A model proposing a role of the protein in the intracellular movement of the viral replication complex, in association with the viral 6K2 protein, is proposed. The type of association between both viral proteins could differ between the strains.     

Mitogen‐activated protein kinase phosphatase 1 reduces the replication efficiency of Bamboo mosaic virus in Nicotiana benthamiana

In plants, the mitogen‐activated protein kinase (MAPK) cascades are the central signaling pathways of the complicated defense network triggered by the perception of pathogen‐associated molecular patterns to repel pathogens. The Arabidopsis thaliana MAPK phosphatase 1 (AtMKP1) negatively regulates the activation of MAPKs. Recently, the AtMKP1 homolog of Nicotiana benthamiana (NbMKP1) was found in association with the Bamboo mosaic virus (BaMV) replication complex. This study aimed to investigate the role of NbMKP1 in BaMV multiplication in N. benthamiana. Silencing of NbMKP1 increased accumulations of the BaMV‐encoded proteins and the viral genomic RNA, although the same condition reduced the infectivity of Pseudomonas syringae pv. tomato DC3000 in N. benthamiana. On the other hand, overexpression of NbMKP1 decreased the BaMV coat protein accumulation in a phosphatase activity‐dependent manner in protoplasts. NbMKP1 also negatively affected the in vitro RNA polymerase activity of the BaMV replication complex. Collectively, the activity of NbMKP1 seems to reduce BaMV multiplication, inconsistent with the negatively regulatory role of MKP1 in MAPK cascades in terms of warding off fungal and bacterial invasion. In addition, silencing of NbMKP1 increased the accumulation of Foxtail mosaic virus but decreased Potato virus X. The discrepant effects exerted by NbMKP1 on different pathogens foresee the difficulty to develop plants with broad‐spectrum resistance through genetically manipulating a single player in MAPK cascades.     

Translationally controlled tumour protein (TCTP) from tomato and Nicotiana benthamiana is necessary for successful infection by a potyvirus

Translationally controlled tumour protein (TCTP) is a ubiquitously distributed protein in eukaryotes, involved in the regulation of several processes, including cell cycle progression, cell growth, stress protection, apoptosis and maintenance of genomic integrity. Its expression is induced during the early stages of tomato (Solanum lycopersicum) infection by the potyvirus Pepper yellow mosaic virus (PepYMV, a close relative of Potato virus Y). Tomato TCTP is a protein of 168 amino acids, which contains all the conserved domains of the TCTP family. To study the effects of TCTP silencing in PepYMV infection, Nicotiana benthamiana plants were silenced by virus‐induced gene silencing (VIGS) and transgenic tomato plants silenced for TCTP were obtained. In the early stages of infection, both tomato and N. benthamiana silenced plants accumulated less virus than control plants. Transgenic tomato plants showed a drastic reduction in symptoms and no viral accumulation at 14 days post‐inoculation. Subcellular localization of TCTP was determined in healthy and systemically infected N. benthamiana leaves. TCTP was observed in both the nuclei and cytoplasm of non‐infected cells, but only in the cytoplasm of infected cells. Our results indicate that TCTP is a growth regulator necessary for successful PepYMV infection and that its localization is altered by the virus, probably to favour the establishment of virus infection. A network with putative interactions that may occur between TCTP and Arabidopsis thaliana proteins was built. This network brings together experimental data of interactions that occur in other eukaryotes and helps us to discuss the possibilities of TCTP involvement in viral infection.     

Differential Roles of Hsp70 and Hsp90 in the Assembly of the Replicase Complex of a Positive-Strand RNA Plant Virus

Assembly of viral replicase complexes of eukaryotic positive-strand RNA viruses is a regulated process: multiple viral and host components must be assembled on intracellular membranes and ordered into quaternary complexes capable of synthesizing viral RNAs. However, the molecular mechanisms underlying this process are poorly understood. In this study, we used a model virus, Red clover necrotic mosaic virus (RCNMV), whose replicase complex can be detected readily as the 480-kDa functional protein complex. We found that host heat shock proteins Hsp70 and Hsp90 are required for RCNMV RNA replication and that they interact with p27, a virus-encoded component of the 480-kDa replicase complex, on the endoplasmic reticulum membrane. Using a cell-free viral translation/replication system in combination with specific inhibitors of Hsp70 and Hsp90, we found that inhibition of p27-Hsp70 interaction inhibits the formation of the 480-kDa complex but instead induces the accumulation of large complexes that are nonfunctional in viral RNA synthesis. In contrast, inhibition of p27-Hsp90 interaction did not induce such large complexes but rendered p27 incapable of binding to a specific viral RNA element, which is a critical step for the assembly of the 480-kDa replicase complex and viral RNA replication. Together, our results suggest that Hsp70 and Hsp90 regulate different steps in the assembly of the RCNMV replicase complex.     

Mutations in the Capsid Protein of Brome Mosaic Virus Affecting Encapsidation Eliminate Vesicle Induction In Planta: Implications for Virus Cell-to-Cell Spread

Positive-strand RNA viruses are known to rearrange the endomembrane network to make it more conducive for replication, maturation, or egress. Our previous transmission electron microscopic (TEM) analysis showed that ectopic expression of wild-type (wt) capsid protein (CP) of Brome mosaic virus (BMV) has an intrinsic property of modifying the endoplasmic reticulum (ER) to induce vesicles similar to those present in wt BMV infection. In this study, we evaluated the functional significance of CP-mediated vesicle induction to the BMV infection cycle in planta. Consequently, the cytopathologic changes induced by wt CP or its mutants defective in virion assembly due to mutations engineered in either N- or C-proximal domains were comparatively analyzed by TEM in two susceptible (Nicotiana benthamiana and Chenopodium quinoa) and one nonhost (N. clevelandii) plant species. The results showed that in susceptible hosts, CP-mediated ER-derived vesicle induction is contingent on the expression of encapsidation-competent CP. In contrast, unlike in N. benthamiana and C. quinoa, transient expression of wt CP in nonhost N. clevelandii plants eliminated vesicle induction. Additionally, comparative source-to-sink analysis of virus spread in leaves of N. benthamiana and N. clevelandii coexpressing wt BMV and Cucumber mosaic virus (CMV) showed that despite trans-encapsidation, CMV failed to complement the defective cell-to-cell movement of BMV. The significance and relation of CP-mediated vesicle induction to virus cell-to-cell movement are discussed.     

The serine/threonine/tyrosine kinase STY46 defends against hordeivirus infection by phosphorylating γb protein

Protein phosphorylation is a common post-translational modification that frequently occurs during plant–virus interaction. Host protein kinases often regulate virus infectivity and pathogenicity by phosphorylating viral proteins. The Barley stripe mosaic virus (BSMV) γb protein plays versatile roles in virus infection and the coevolutionary arms race between plant defense and viral counter-defense. Here, we identified that the autophosphorylated cytosolic serine/threonine/tyrosine (STY) protein kinase 46 of Nicotiana benthamiana (NbSTY46) phosphorylates and directly interacts with the basic motif domain (aa 19–47) of γb in vitro and in vivo. Overexpression of wild-type NbSTY46, either transiently or transgenically, suppresses BSMV replication and ameliorates viral symptoms, whereas silencing of NbSTY46 leads to increased viral replication and exacerbated symptom. Moreover, the antiviral role of NbSTY46 requires its kinase activity, as the NbSTY46_T436A mutant, lacking kinase activity, not only loses the ability to phosphorylate and interact with γb but also fails to impair BSMV infection when expressed in plants. NbSTY46 could also inhibit the replication of Lychnis ringspot virus, another chloroplast-replicating hordeivirus. In summary, we report a function of the cytosolic kinase STY46 in defending against plant viral infection by phosphorylating a viral protein in addition to its basal function in plant growth, development, and abiotic stress responses.

The cytosolic serine/threonine/tyrosine kinase STY46 negatively regulates Barley stripe mosaic virus replication by phosphorylating and interacting with cb protein.     

Antisense RNA approach targeting Rep gene of Mungbean yellow mosaic India virus to develop resistance in soybean

The Yellow mosaic disease is caused by Mungbean yellow mosaic India virus (MYMIV) and Mungbean yellow mosaic virus (MYMV) belonging to the genus Begomovirus of the family Geminiviridae. Yellow mosaic disease (YMD) is a major constraint to the production of soybean in South-East Asia. In India, yield losses of 10–88% had been reported due to YMD of soybean. An effort has been made to generate resistant soybean plants, by a construct targeting replication initiation protein (Rep) gene sequences of MYMIV. A construct containing the sequences of Rep gene (566?bp) in antisense orientation was used to transform cotyledonary node explants of three soybean cultivars (JS 335, JS 95-60 and NRC 37). Transformation efficiencies of 0.2, 0.21 and 0.24% were obtained with three soybean cultivars, JS 335, JS 95-60 and NRC 37, respectively. The presence of transgene in T₁ plants was confirmed by polymerase chain reaction (PCR) and sequence analysis. The level of resistance was observed by challenge inoculation with the virus in T₁ lines. The inheritance of transgene showed classical Mendelian pattern in six transgenic lines.     

High overexpression of CERES,a plant regulator of translation,induces different phenotypical defence responses during TuMV infection

Mutations in the eukaryotic translation initiation factors eIF4E and eIF(iso)4E confer potyvirus resistance in a range of plant hosts. This supports the notion that, in addition to their role in translation of cellular mRNAs, eIF4E isoforms are also essential for the potyvirus cycle. CERES is a plant eIF4E- and eIF(iso)4E-binding protein that, through its binding to the eIF4Es, modulates translation initiation; however, its possible role in potyvirus resistance is unknown. In this article, we analyse if the ectopic expression of AtCERES is able to interfere with turnip mosaic virus replication in plants. Our results demonstrate that, during infection, the ectopic expression of CERES in Nicotiana benthamiana promotes the development of a mosaic phenotype when it is accumulated to moderate levels, but induces veinal necrosis when it is accumulated to higher levels. This necrotic process resembles a hypersensitive response (HR)-like response that occurs with different HR hallmarks. Remarkably, Arabidopsis plants inoculated with a virus clone that promotes high expression of CERES do not show signs of infection. These final phenotypical outcomes are independent of the capacity of CERES to bind to eIF4E. All these data suggest that CERES, most likely due to its leucine-rich repeat nature, could act as a resistance protein, able to promote a range of different defence responses when it is highly overexpressed from viral constructs.     

Alarming increase in the incidence of Cucumber mosaic virus in cowpea (Vigna unguiculata (L.) Walp.) in northern Nigeria

Cowpea plays a key nutritional role in the diet of the Nigerian people. Viral diseases are a major limitation to cowpea production worldwide, and thus, constant viral surveillance is crucial for monitoring and management purposes. In this study, cowpea leaf samples from fields in three northern Nigeria states, Kano, Kaduna and Niger, were tested to determine the status of six common viruses previously reported in these cowpea-producing states following the release of virus-resistant varieties. Cowpea aphid-borne mosaic virus (CABMV), Blackeye cowpea mosaic virus (BICMV), Cowpea mottle virus, Southern bean mosaic virus and Cucumber mosaic virus (CMV) were detected. Cowpea yellow mosaic virus, which was previously reported in all three states, was not detected in any of the samples tested, while CMV that was previously regarded as unimportant to cowpea production in Nigeria had the highest incidence in all three states, and the overall highest incidence of 58.8%, while CABMV had the lowest incidence (7.5%). CMV was also present in seven of the ten mixed infection combinations detected. Dual infection of CMV and BICMV, which often results in cowpea stunt, the most devastating cowpea disease in the USA, was the most frequently detected mixed infection (28.1%) and was detected in all three states. This observed elevation in CMV infection in cowpea must be closely monitored and swiftly managed to avert possible devastating crop yield losses.     

RSC3K of soybean cv. Kefeng No.1 confers resistance to soybean mosaic virus by interacting with the viral protein P3

Soybean mosaic virus (SMV) is one of the most devastating viral pathogens of soybean (Glycine max (L.) Merr). In total, 22 Chinese SMV strains (SC1–SC22) have been classified based on the responses of 10 soybean cultivars to these pathogens. However, although several SMV-resistance loci in soybean have been identified, no gene conferring SMV resistance in the resistant soybean cultivar (cv.) Kefeng No.1 has been cloned and verified. Here, using F₂-derived F₃ (F_2:3) and recombinant inbred line (RIL) populations from a cross between Kefeng No.1 and susceptible soybean cv. Nannong 1138-2, we localized the gene in Kefeng No.1 that mediated resistance to SMV-SC3 strain to a 90-kb interval on chromosome 2. To study the functions of candidate genes in this interval, we performed Bean pod mottle virus (BPMV)-induced gene silencing (VIGS). We identified a recombinant gene (which we named R_SC3K) harboring an internal deletion of a genomic DNA fragment partially flanking the LOC100526921 and LOC100812666 reference genes as the SMV-SC3 resistance gene. By shuffling genes between infectious SMV DNA clones based on the avirulent isolate SC3 and virulent isolate 1129, we determined that the viral protein P3 is the avirulence determinant mediating SMV-SC3 resistance on Kefeng No.1. P3 interacts with RNase proteins encoded by R_SC3K, LOC100526921, and LOC100812666. The recombinant R_SC3K conveys much higher anti-SMV activity than LOC100526921 and LOC100812666, although those two genes also encode proteins that inhibit SMV accumulation, as revealed by gene silencing in a susceptible cultivar and by overexpression in Nicotiana benthamiana. These findings demonstrate that R_SC3K mediates the resistance of Kefeng No.1 to SMV-SC3 and that SMV resistance of soybean is determined by the antiviral activity of RNase proteins.     

Characterization of Synergy between Cucumber mosaic virus and Tobacco necrosis virus in Nicotiana benthamiana

Mixed infections of Nicotiana benthamiana plants by Cucumber mosaic virus (CMV) and Tobacco necrosis virus (TNV) exhibit a synergistic interaction and result in symptom enhancement. Accumulation of CMV(+) RNA as well as capsid protein (CP) in mixed infection was considerably higher than that of singly‐infected plants. There was also a slight increase in TNV(+) RNA and CP levels in doubly infected plants. Synergistic infection by CMV‐ and TNV‐induced higher increase in the levels of malonyldialdehyde, hydrogen peroxide (H₂O₂) and more decline in the activities of catalase than singly infected ones. Both peroxidase and superoxide dismutase activities increased rapidly for the first 10 days post inoculation (dpi) in doubly‐infected plants and then declined, whereas the enzyme activities continued to increase after 10 dpi in singly infected plants and had higher enzyme activities in the late stages than that of co‐infected plants. These results suggest that synergistic infection by CMV and TNV produced severes oxidative stress in N. benthamiana plants and the synergy between the two viruses was mutual.     

The conserved aromatic residue W122 is a determinant of potyviral coat protein stability,replication, and cell-to-cell movement in plants

Coat proteins (CPs) play critical roles in potyvirus cell-to-cell movement. However, the underlying mechanism controlling them remains unclear. Here, we show that substitutions of alanine, glutamic acid, or lysine for the conserved residue tryptophan at position 122 (W¹²²) in tobacco vein banding mosaic virus (TVBMV) CP abolished virus cell-to-cell movement in Nicotiana benthamiana plants. In agroinfiltrated N. benthamiana leaf patches, both the CP and RNA accumulation levels of three W¹²² mutant viruses were significantly reduced compared with those of wild-type TVBMV, and CP accumulated to a low level similar to that of a replication-deficient mutant. The results of polyprotein transient expression experiments indicated that CP instability was responsible for the significantly low CP accumulation levels of the three W¹²² mutant viruses. The substitution of W¹²² did not affect CP plasmodesmata localization or virus particle formation; however, the substitution significantly reduced the number of virus particles. The wild-type TVBMV CP could complement the reduced replication and abolished cell-to-cell movement of the mutant viruses. When the codon for W¹²² was mutated to that for a different aromatic residue, phenylalanine or tyrosine, the resultant mutant viruses moved systemically and accumulated up to 80% of the wild-type TVBMV level. Similar results were obtained for the corresponding amino acids of W¹²² in the watermelon mosaic virus and potato virus Y CPs. Therefore, we conclude that the aromatic ring in W¹²² in the core domain of the potyviral CP is critical for cell-to-cell movement through the effects on CP stability and viral replication.     

Effect of mitochondria-targeted antioxidant SkQ1 on programmed cell death induced by viral proteins in tobacco plants

Programmed cell death (PCD) is the main defense mechanism in plants to fight various pathogens including viruses. The best-studied example of virus-induced PCD in plants is Tobacco mosaic virus (TMV)-elicited hypersensitive response in tobacco plants containing the N resistance gene. It was previously reported that the animal mitochondrial protein Bcl-xL, which lacks a homolog in plants, effectively suppresses plant PCD induced by TMV p50 — the elicitor of hyper-sensitive response in Nicotiana tabacum carrying the N gene. Our studies show that the mitochondria-targeted antioxidant SkQ1 effectively suppresses p50-induced PCD in tobacco plants. On the other hand, SkQ1 did not affect Poa semilatent virus TGB3-induced endoplasmic reticulum stress, which is followed by PCD, in Nicotiana benthamiana epidermal cells. These data suggest that mitochondria-targeted antioxidant SkQ1 can be used to study molecular mechanisms of PCD suppression in plants.     

GAPDH-A Recruits a Plant Virus Movement Protein to Cortical Virus Replication Complexes to Facilitate Viral Cell-to-Cell Movement

The formation of virus movement protein (MP)-containing punctate structures on the cortical endoplasmic reticulum is required for efficient intercellular movement of Red clover necrotic mosaic virus (RCNMV), a bipartite positive-strand RNA plant virus. We found that these cortical punctate structures constitute a viral replication complex (VRC) in addition to the previously reported aggregate structures that formed adjacent to the nucleus. We identified host proteins that interacted with RCNMV MP in virus-infected Nicotiana benthamiana leaves using a tandem affinity purification method followed by mass spectrometry. One of these host proteins was glyceraldehyde 3-phosphate dehydrogenase-A (NbGAPDH-A), which is a component of the Calvin-Benson cycle in chloroplasts. Virus-induced gene silencing of NbGAPDH-A reduced RCNMV multiplication in the inoculated leaves, but not in the single cells, thereby suggesting that GAPDH-A plays a positive role in cell-to-cell movement of RCNMV. The fusion protein of NbGAPDH-A and green fluorescent protein localized exclusively to the chloroplasts. In the presence of RCNMV RNA1, however, the protein localized to the cortical VRC as well as the chloroplasts. Bimolecular fluorescence complementation assay and GST pulldown assay confirmed in vivo and in vitro interactions, respectively, between the MP and NbGAPDH-A. Furthermore, gene silencing of NbGAPDH-A inhibited MP localization to the cortical VRC. We discuss the possible roles of NbGAPDH-A in the RCNMV movement process.     

NbEXPA1, an α‐expansin,is plasmodesmata‐specific and a novel host factor for potyviral infection

Plasmodesmata (PD), unique to the plant kingdom, are structurally complex microchannels that cross the cell wall to establish symplastic communication between neighbouring cells. Viral intercellular movement occurs through PD. To better understand the involvement of PD in viral infection, we conducted a quantitative proteomic study on the PD‐enriched fraction from Nicotiana benthamiana leaves in response to infection by Turnip mosaic virus (TuMV). We report the identification of a total of 1070 PD protein candidates, of which 100 (≥2‐fold increase) and 48 (≥2‐fold reduction) are significantly differentially accumulated in the PD‐enriched fraction, when compared with protein levels in the corresponding healthy control. Among the differentially accumulated PD protein candidates, we show that an α‐expansin designated NbEXPA1, a cell wall loosening protein, is PD‐specific. TuMV infection downregulates NbEXPA1 mRNA expression and protein accumulation. We further demonstrate that NbEXPA1 is recruited to the viral replication complex via the interaction with NIb, the only RNA‐dependent RNA polymerase of TuMV. Silencing of NbEXPA1 inhibits plant growth and TuMV infection, whereas overexpression of NbEXPA1 promotes viral replication and intercellular movement. These data suggest that NbEXPA1 is a host factor for potyviral infection. This study not only generates a PD‐proteome dataset that is useful in future studies to expound PD biology and PD‐mediated virus–host interactions but also characterizes NbEXPA1 as the first PD‐specific cell wall loosening protein and its essential role in potyviral infection.     

Translationally controlled tumour protein: A protein necessary for potyvirus intracellular multiplication that supports plant infection by unrelated viruses

The multifunctional protein translationally controlled tumour protein (TCTP) was previously identified as necessary for infection by the potyvirus pepper yellow mosaic virus. Using turnip mosaic virus (TuMV) as a model to study potyvirus biology, we confirmed that TCTP has a positive effect on virus infection. Living cell confocal microscopy demonstrated that TCTP colocalises with 6K2-tagged replication vesicles and with a perinuclear globular structure typically observed during potyvirus infection. Also, TCTP silenced protoplasts showed reduced virus accumulation, quantified by qRT-PCR, which suggests an effect on virus replication, translation or other intracellular process. Finally, TCTP silencing in plants reduced the accumulation of two species belonging to Orthotospovirus and a Begomovirus genus, which are not closely related to potyviruses. The results suggest that TCTP is a general susceptibility factor to several unrelated viruses.