A comprehensive analysis of the WRKY family in soybean and functional analysis of GmWRKY164-GmGSL7c in resistance to soybean mosaic virus.

BACKGROUND: Soybean mosaic disease caused by soybean mosaic virus (SMV) is one of the most devastating and widespread diseases in soybean producing areas worldwide. The WRKY transcription factors (TFs) are widely involved in plant development and stress responses. However, the roles of the GmWRKY TFs in resistance to SMV are largely unclear. RESULTS: Here, 185 GmWRKYs were characterized in soybean (Glycine max), among which 60 GmWRKY genes were differentially expressed during SMV infection according to the transcriptome data. The transcriptome data and RT-qPCR results showed that the expression of GmWRKY164 decreased after imidazole treatment and had higher expression levels in the incompatible combination between soybean cultivar variety Jidou 7 and SMV strain N3. Remarkably, the silencing of GmWRKY164 reduced callose deposition and enhanced virus spread during SMV infection. In addition, the transcript levels of the GmGSL7c were dramatically lower upon the silencing of GmWRKY164. Furthermore, EMSA and ChIP-qPCR revealed that GmWRKY164 can directly bind to the promoter of GmGSL7c, which contains the W-box element. CONCLUSION: Our findings suggest that GmWRKY164 plays a positive role in resistance to SMV infection by regulating the expression of GmGSL7c, resulting in the deposition of callose and the inhibition of viral movement, which provides guidance for future studies in understanding virus-resistance mechanisms in soybean.

Identification of soybean mosaic virus strain SC7 resistance loci and candidate genes in soybean [Glycine max (L.) Merr.].

Soybean [Glycine max (L.) Merr.] is an important legume crop worldwide, which provides abundant plant protein and oil for human beings. Soybean mosaic virus (SMV) can cause serious damage to the yield and quality of soybean, but it is difficult to control SMV with chemicals, breeding SMV-resistant varieties has become the most effective way to control the disease. Therefore, it is important to identify SMV resistance genes from soybean resources and apply them to soybean breeding. In this study, the disease rates (DRs) of 219 soybean accessions to SMV strain SC7 in two environments were investigated. A high-density NJAU 355 K SoySNP array was used for genome-wide association study (GWAS) of DR. A 274 kb region on chromosome 15 (1,110,567 bp to 1,384,173 bp) was repeatedly detected in two environments. Six new significant single nucleotide polymorphisms (SNPs) on chromosome 15 were identified. Four of these six SNPs were located within two candidate genes, Glyma.15G015700 and Glyma.15G015800. The elite haplotype Glyma.15G015700Hap I with low DR exhibited strong resistance to SC7. The expression of Glyma.15G015700 in the SMV-resistant accession increased significantly after inoculation with SC7. Furthermore, most of the proteins predicted to interact with Glyma.15G015700 are heat shock proteins, which have been shown to be related to disease resistance. In summary, new SMV resistance loci and a new candidate gene, Glyma.15G015700, were identified and might be utilized in further soybean disease resistance breeding.

Transgenic expression of artificial microRNA targeting soybean mosaic virus P1 gene confers virus resistance in plant.

RNA silencing is an innate immune mechanism of plants against invasion by viral pathogens. Artificial microRNA (amiRNA) can be engineered to specifically induce RNA silencing against viruses in transgenic plants and has great potential for disease control. Here, we describe the development and application of amiRNA-based technology to induce resistance to soybean mosaic virus (SMV), a plant virus with a positive-sense single-stranded RNA genome. We have shown that the amiRNA targeting the SMV P1 coding region has the highest antiviral activity than those targeting other SMV genes in a transient amiRNA expression assay. We transformed the gene encoding the P1-targeting amiRNA and obtained stable transgenic Nicotiana benthamiana lines (amiR-P1-3-1-2-1 and amiR-P1-4-1-2-1). Our results have demonstrated the efficient suppression of SMV infection in the P1-targeting amiRNA transgenic plants in an expression level-dependent manner. In particular, the amiR-P1-3-1-2-1 transgenic plant showed high expression of amiR-P1 and low SMV accumulation after being challenged with SMV. Thus, a transgenic approach utilizing the amiRNA technology appears to be effective in generating resistance to SMV.

Replacement of P1 of soybean mosaic virus with P1 of clover yellow vein virus has no impact on virus viability and host specificity.

Potyvirus genomes are expressed as polyproteins that are autocatalytically cleaved to produce 10 to 12 multifunctional proteins, among which P1 is the most variable. It has long been hypothesized that P1 plays role(s) in host adaptation and host specificity. We tested this hypothesis using two phylogenetically distinct potyviruses: soybean mosaic virus (SMV), with a narrow host range, and clover yellow vein virus (ClYVV), with a broader host range. When the full-length P1 cistron of SMV-N was replaced with P1 from ClYVV-No.30, the chimera systemically infected only SMV-N-permissive hosts. Hence, there were no changes in the host range or host specificity of the chimeric viruses. Despite sharing only 20.3% amino acid sequence identity, predicted molecular models of P1 proteins from SMV-N and ClYVV-No.30 showed analogous topologies. These observations suggest that P1 of ClYVV-No.30 can functionally replace P1 of SMV-N. However, the P1 proteins of these two potyviruses are not determinants of host specificity and host range.

Genome-Wide Analysis and Expression Profiling of Soybean RbcS Family in Response to Plant Hormones and Functional Identification of GmRbcS8 in Soybean Mosaic Virus.

Rubisco small subunit (RbcS), a core component with crucial effects on the structure and kinetic properties of the Rubisco enzyme, plays an important role in response to plant growth, development, and various stresses. Although Rbcs genes have been characterized in many plants, their muti-functions in soybeans remain elusive. In this study, a total of 11 GmRbcS genes were identified and subsequently divided into three subgroups based on a phylogenetic relationship. The evolutionary analysis revealed that whole-genome duplication has a profound effect on GmRbcSs. The cis-acting elements responsive to plant hormones, development, and stress-related were widely found in the promoter region. Expression patterns based on the RT-qPCR assay exhibited that GmRbcS genes are expressed in multiple tissues, and notably Glyma.19G046600 (GmRbcS8) exhibited the highest expression level compared to other members, especially in leaves. Moreover, differential expressions of GmRbcS genes were found to be significantly regulated by exogenous plant hormones, demonstrating their potential functions in diverse biology processes. Finally, the function of GmRbcS8 in enhancing soybean resistance to soybean mosaic virus (SMV) was further determined through the virus-induced gene silencing (VIGS) assay. All these findings establish a strong basis for further elucidating the biological functions of RbcS genes in soybeans.

A cluster of atypical resistance genes in soybean confers broad-spectrum antiviral activity.

Soybean mosaic virus (SMV) is a severe soybean (Glycine max) pathogen. Here we characterize a soybean SMV resistance cluster (SRC) that comprises five resistance (R) genes. SRC1 encodes a Toll/interleukin-1 receptor and nucleotide-binding site (TIR-NBS [TN]) protein, SRC4 and SRC6 encode TIR proteins with a short EF-hand domain, while SRC7 and SRC8 encode TNX proteins with a noncanonical basic secretory protein (BSP) domain at their C-termini. We mainly studied SRC7, which contains a noncanonical BSP domain and gave full resistance to SMV. SRC7 possessed broad-spectrum antiviral activity toward several plant viruses including SMV, plum pox virus, potato virus Y, and tobacco mosaic virus. The TIR domain alone was both necessary and sufficient for SRC7 immune signaling, while the NBS domain enhanced its activity. Nuclear oligomerization via the interactions of both TIR and NBS domains was essential for SRC7 function. SRC7 expression was transcriptionally inducible by SMV infection and salicylic acid (SA) treatment, and SA was required for SRC7 triggered virus resistance. SRC7 expression was posttranscriptionally regulated by miR1510a and miR2109, and the SRC7-miR1510a/miR2109 regulatory network appeared to contribute to SMV-soybean interactions in both resistant and susceptible soybean cultivars. In summary, we report a soybean R gene cluster centered by SRC7 that is regulated at both transcriptional and posttranscriptional levels, possesses a yet uncharacterized BSP domain, and has broad-spectrum antiviral activities. The SRC cluster is special as it harbors several functional R genes encoding atypical TIR-NBS-LRR (TNL) type R proteins, highlighting its importance in SMV-soybean interaction and plant immunity.

Silencing GmATG7 Leads to Accelerated Senescence and Enhanced Disease Resistance in Soybean.

Autophagy plays a critical role in nutrient recycling/re-utilizing under nutrient deprivation conditions. However, the role of autophagy in soybeans has not been intensively investigated. In this study, the Autophay-related gene 7 (ATG7) gene in soybeans (referred to as GmATG7) was silenced using a virus-induced gene silencing approach mediated by Bean pod mottle virus (BPMV). Our results showed that ATG8 proteins were highly accumulated in the dark-treated leaves of the GmATG7-silenced plants relative to the vector control leaves (BPMV-0), which is indicative of an impaired autophagy pathway. Consistent with the impaired autophagy, the dark-treated GmATG7-silenced leaves displayed an accelerated senescence phenotype, which was not seen on the dark-treated BPMV-0 leaves. In addition, the accumulation levels of both H2O2 and salicylic acid (SA) were significantly induced in the GmATG7-silenced plants compared with the BPMV-0 plants, indicating an activated immunity. Consistently, the GmATG7-silenced plants were more resistant against both Pseudomonas syringae pv. glycinea (Psg) and Soybean mosaic virus (SMV) compared with the BPMV-0 plants. However, the activated immunity in the GmATG7-silenced plant was not dependent upon the activation of MPK3/MPK6. Collectively, our results demonstrated that the function of GmATG7 is indispensable for autophagy in soybeans, and the activated immunity in the GmATG7-silenced plant is a result of impaired autophagy.

Tobacco Necrosis Virus-AC Single Coat Protein Amino Acid Substitutions Determine Host-Specific Systemic Infections of Nicotiana benthamiana and Soybean.

Plant viruses often infect several distinct host species. Sometimes, viruses can systemically infect a specific host whereas, in other cases, only local infections occur in other species. How viral and host factors interact to determine systemic infections among different hosts is largely unknown, particularly for icosahedral positive-stranded RNA viruses. The Tobacco necrosis virus-A Chinese isolate belongs to the genus Alphanecrovirus in the family Tombusviridae. In this study, we investigated variations in systemic infections of tobacco necrosis virus-AC (TNV-AC) in Nicotiana benthamiana and Glycine max (soybean) by alanine-scanning mutagenesis of the viral coat protein (CP), which is essential for systemic movement of TNV-AC. We found that three amino acids, R169, K177, and Q233, are key residues that mediate varying degrees of systemic infections of N. benthamiana and soybean. Further analysis revealed that variations in systemic trafficking of TNV-AC CP mutants in N. benthamiana and soybean are associated with virion assembly and stability. The CP amino acids K177 and Q233 are highly conserved among all TNV-A isolates and are replaced by Q and K in the TNV-D isolates. We demonstrated that systemic infectivity of either TNV-AC K177A and Q233A or K177Q and Q233K mutants are correlated with the binding affinity of the mutated CPs to the host-specific Hsc70-2 protein. These results expand our understanding of host-dependent long-distance movement of icosahedral viruses in plants.[Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Development of a Csy4-processed guide RNA delivery system with soybean-infecting virus ALSV for genome editing.

BACKGROUND: A key issue for implementation of CRISPR-Cas9 genome editing for plant trait improvement and gene function analysis is to efficiently deliver the components, including guide RNAs (gRNAs) and Cas9, into plants. Plant virus-based gRNA delivery strategy has proven to be an important tool for genome editing. However, its application in soybean which is an important crop has not been reported yet. ALSV (apple latent spherical virus) is highly infectious virus and could be explored for delivering elements for genome editing. RESULTS: To develop a ALSV-based gRNA delivery system, the Cas9-based Csy4-processed ALSV Carry (CCAC) system was developed. In this system, we engineered the soybean-infecting ALSV to carry and deliver gRNA(s). The endoribonuclease Csy4 effectively releases gRNAs that function efficiently in Cas9-mediated genome editing. Genome editing of endogenous phytoene desaturase (PDS) loci and exogenous 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) sequence in Nicotiana. benthamiana (N. benthamiana) through CCAC was confirmed using Sanger sequencing. Furthermore, CCAC-induced mutagenesis in two soybean endogenous GW2 paralogs was detected. CONCLUSIONS: With the aid of the CCAC system, the target-specific gRNA(s) can be easily manipulated and efficiently delivered into soybean plant cells by viral infection. This is the first virus-based gRNA delivery system for soybean for genome editing and can be used for gene function study and trait improvement.

GmST1, which encodes a sulfotransferase, confers resistance to soybean mosaic virus strains G2 and G3.

Soybean mosaic virus (SMV) is one of the most widespread and devastating viral diseases worldwide. The genetic architecture of qualitative resistance to SMV in soybean remains unclear. Here, the Rsvg2 locus was identified as underlying soybean resistance to SMV by genome-wide association and linkage analyses. Fine mapping results showed that soybean resistance to SMV strains G2 and G3 was controlled by a single dominant gene, GmST1, on chromosome 13, encoding a sulfotransferase (SOT). A key variation at position 506 in the coding region of GmST1 associated with the structure of the encoded SOT and changed SOT activity levels between RSVG2-S and RSVG2-R alleles. In RSVG2-S allele carrier "Hefeng25", the overexpression of GmST1 carrying the RSVG2-R allele from the SMV-resistant line "Dongnong93-046" conferred resistance to SMV strains G2 and G3. Compared to Hefeng25, the accumulation of SMV was decreased in transgenic plants carrying the RSVG2-R allele. SMV infection differentiated both the accumulation of jasmonates and expression patterns of genes involved in jasmonic acid (JA) signalling, biosynthesis and catabolism in RSVG2-R and RSVG2-S allele carriers. This characterization of GmST1 suggests a new scenario explaining soybean resistance to SMV.

A bean common mosaic virus-resistance gene in the soybean variant V94-5152 was mapped to the Rsv4 locus conferring resistance to soybean mosaic virus.

KEY MESSAGE: In the soybean variant V94-5152, a BCMV-resistance gene was mapped near to the region of SMV-resistance Rsv4 locus, raising a possibility that V94-5152 may rely on Rsv4 locus to resist against both SMV and BCMV. Both Soybean mosaic virus (SMV) and Bean common mosaic virus (BCMV) can induce soybean mosaic diseases, but few studies have explored soybean resistance against BCMV so far. In this study, V94-5152, a soybean variant resistant to BCMV and SMV, was crossed with a susceptible cultivar, Williams 82 to map the resistance gene. By inoculating 292 F2 individuals with a BCMV isolate HZZB011, a segregation ratio of 3 resistant: 1 susceptible was observed, suggesting that V94-5152 possesses a single-dominant resistance gene against BCMV-HZZB011. Bulk segregation analysis (BSA) then revealed that the resistance gene is closely linked to BARCSOYSSR_02_0617, a simple sequence repeat (SSR) marker on chromosome 2. Genotyping neighboring SSR markers among the 292 F2 individuals enabled us to draw a genetic linkage map, which indicated that the BCMV-resistance gene is located 0.2 cM downstream of BARCSOYSSR_02_0617. Amplification and sequencing ten candidate genes (Glyma02g121300 to Glyma02g122200) around this marker then revealed four genes containing nonsynonymous changes or indels. Also, this location is near to the recently cloned SMV-resistance Rsv4 locus from the cultivar Peking. By obtaining ten more sequences of Rsv4 locus from cultivated and wild soybean materials, we further investigated the variation and evolutionary patterns of this virus-resistance locus. It was evident that positive selections had been acting on this locus, with one critical amino acid change (R55P) shared by all resistance soybeans tested.

Mosaic genome evolution and phylogenetics of Chrysodeixis includens nucleopolyhedrovirus (ChinNPV) and virulence of seven new isolates from the Brazilian states of Minas Gerais and Mato Grosso.

In a comparative analysis of genome sequences from isolates of the baculovirus Chrysodeixis includens nucleopolyhedrovirus (ChinNPV) from Brazil and Guatemala, we identified a subset of isolates possessing chimeric genomes. We identified six distinct phylogenetically incongruous regions (PIRs) dispersed in the genomes, of between 279 and 3345 bp in length. The individual PIRs possessed high sequence similarity among the affected ChinNPV isolates but varied in coverage in some instances. The donor for four of the PIRs implicated in horizontal gene transfer (HGT) was identified as Trichoplusia ni single nucleopolyhedrovirus (TnSNPV), an alphabaculovirus closely related to ChinNPV, or another unknown but closely related virus. BLAST searches of the other two PIRs returned only ChinNPV sequences, but HGT from an unknown donor baculovirus cannot be excluded. Although Chrysodeixis includens and Trichoplusia ni are frequently co-collected from soybean fields in Brazil, pathogenicity data suggest that natural coinfection of C. includens larvae with ChinNPV and TnSNPV is probably uncommon. Additionally, since the chimeric ChinNPV genomes with tracts of TnSNPV sequence were restricted to a single monophyletic lineage of closely related isolates, a model of progressive restoration of the native DNA sequence by recombination with ChinNPV possessing a fully or partially non-chimeric genome is reasonable. However, multiple independent HGT from TnSNPV to ChinNPV during the evolution of these isolates cannot be excluded. Mortality data suggest that the ChinNPV isolates with chimeric genomes are not significantly different in pathogenicity towards C. includens when compared to most other ChinNPV isolates. Exclusion of the PIRs prior to phylogenetic analysis had a large impact on the topology of part of the maximum-likelihood tree, revealing a homogenous clade of three isolates (IB, IC and ID) from Paraná state in Brazil collected in 2006, together with an isolate from Guatemala collected in 1972 (IA), comprising the lineage uniquely affected by HGT from TnSNPV. The other 10 Brazilian ChinNPV isolates from Paraná, Mato Grosso, and Minas Gerais states showed higher variability, where only three isolates from Paraná state formed a monophyletic group correlating with geographical origin.

Complete nucleotide sequence of soybean leaf rugose mosaic virus, an atypical member of the genus Bymovirus.

The host range of previously reported bymoviruses is restricted to plants belonging to the family Poaceae. Soybean leaf rugose mosaic virus (SbLRMV) from non-Poaceae plants is related to bymoviruses based on a partial genome sequence. However, unlike bymoviruses, this virus infects plants of at least four dicotyledonous families, including Fabaceae, and causes disease in soybean. Complete nucleotide sequences of two variants of SbLRMV were determined, and its taxonomic position was clarified. RNA1 is 7109 nucleotides (nt) long with one large open reading frame (ORF), possibly encoding a polyprotein of 257 kDa. This polyprotein is likely processed into eight mature proteins. The entire RNA1 ORF shares 52%-55% nucleotide sequence identity and 27%-43% amino acid sequence identity, and the coat protein shares 49%-54% nucleotide sequence identity and 30%-34% amino acid sequence identity to other bymoviruses. The similarity to other viruses in the family Potyviridae is generally lower. RNA2 is 3413 or 3415 nt long and putatively encodes a polyprotein of 108 kDa. This protein is probably cleaved into two mature proteins. The sequences of these two RNAs are very similar to those of bymoviruses. Phylogenetic analysis of members of the family Potyviridae showed that RNA1 and RNA2 of SbLRMV formed a basal clade with known bymoviruses. Inoculation tests using leaf samples suggested that SbLRMV RNA1 can systemically infect and cause disease in soybean without the presence of RNA2. In conclusion, SbLRMV is an atypical member of the genus Bymovirus that infects soybean (Fabaceae) and other dicots rather than gramineous hosts.

Biological and molecular characterization of bean bushy stunt virus, a novel bipartite begomovirus infecting common bean in northwestern Argentina.

Common bean plants (Phaseolus vulgaris L.) showing different virus-like symptoms were collected in northwestern Argentina. Dot-blot hybridization tests showed that the begomoviruses bean golden mosaic virus and tomato yellow vein streak virus were the most prevalent, but they also revealed the presence of unknown begomoviruses. The complete genome sequence of one of these unknown begomoviruses was determined. Sequence analysis showed that the virus is a typical New World begomovirus, for which the name "bean bushy stunt virus" (BBSV) is proposed. Biological assays based on biolistic inoculations showed that BBSV induced leaf roll and stunting symptoms similar to those observed in the field-collected common bean sample.

Silencing Autophagy-Related Gene 2 (ATG2) Results in Accelerated Senescence and Enhanced Immunity in Soybean.

Autophagy plays a critical role in nutrient recycling and stress adaptations. However, the role of autophagy has not been extensively investigated in crop plants. In this study, soybean autophagy-related gene 2 (GmATG2) was silenced, using virus-induced silencing (VIGS) mediated by Bean pod mottle virus (BPMV). An accelerated senescence phenotype was exclusively observed for the GmATG2-silenced plants under dark conditions. In addition, significantly increased accumulation of both ROS and SA as well as a significantly induced expression of the pathogenesis-related gene 1 (PR1) were also observed on the leaves of the GmATG2-silenced plants, indicating an activated immune response. Consistent with this, GmATG2-silenced plants exhibited a significantly enhanced resistance to Pseudomonas syringae pv. glycinea (Psg) relative to empty vector control plants (BPMV-0). Notably, the activated immunity of the GmATG2-silenced plants was independent of the MAPK signaling pathway. The fact that the accumulation levels of ATG8 protein and poly-ubiquitinated proteins were significantly increased in the dark-treated GmATG2-silenced plants relative to the BPMV-0 plants indicated that the autophagic degradation is compromised in the GmATG2-silenced plants. Together, our results indicated that silencing GmATG2 compromises the autophagy pathway, and the autophagy pathway is conserved in different plant species.

Two TGA Transcription Factor Members from Hyper-Susceptible Soybean Exhibiting Significant Basal Resistance to Soybean mosaic virus.

TGA transcription factors (TFs) exhibit basal resistance in Arabidopsis, but susceptibility to a pathogen attack in tomatoes; however, their roles in soybean (Glycine max) to Soybean mosaic virus (SMV) are unknown. In this study, 27 TGA genes were isolated from a SMV hyper-susceptible soybean NN1138-2, designated GmTGA1~GmTGA27, which were clustered into seven phylogenetic groups. The expression profiles of GmTGAs showed that the highly expressed genes were mainly in Groups I, II, and VII under non-induction conditions, while out of the 27 GmTGAs, 19 responded to SMV-induction. Interestingly, in further transient N. benthamiana-SMV pathosystem assay, all the 19 GmTGAs overexpressed did not promote SMV infection in inoculated leaves, but they exhibited basal resistance except one without function. Among the 18 functional ones, GmTGA8 and GmTGA19, with similar motif distribution, nuclear localization sequence and interaction proteins, showed a rapid response to SMV infection and performed better than the others in inhibiting SMV multiplication. This finding suggested that GmTGA TFs may support basal resistance to SMV even from a hyper-susceptible source. What the mechanism of the genes (GmTGA8, GmTGA19, etc.) with basal resistance to SMV is and what their potential for the future improvement of resistance to SMV in soybeans is, are to be explored.

Optimizing the PBS1 Decoy System to Confer Resistance to Potyvirus Infection in Arabidopsis and Soybean.

The Arabidopsis resistance protein RPS5 is activated by proteolytic cleavage of the protein kinase PBS1 by the Pseudomonas syringae effector protease AvrPphB. We have previously shown that replacing seven amino acids at the cleavage site of PBS1 with a motif cleaved by the NIa protease of turnip mosaic virus (TuMV) enables RPS5 activation upon TuMV infection. However, this engineered resistance conferred a trailing necrosis phenotype indicative of a cell-death response too slow to contain the virus. We theorized this could result from a positional mismatch within the cell between PBS1TuMV, RPS5, and the NIa protease. To test this, we relocalized PBS1TuMV and RPS5 to cellular sites of NIa accumulation. These experiments revealed that relocation of RPS5 away from the plasma membrane compromised RPS5-dependent cell death in Nicotiana benthamiana, even though PBS1 was efficiently cleaved. As an alternative approach, we tested whether overexpression of plasma membrane-localized PBS1TuMV could enhance RPS5 activation by TuMV. Significantly, overexpressing the PBS1TuMV decoy protein conferred complete resistance to TuMV when delivered by either agrobacterium or by aphid transmission, showing that RPS5-mediated defense responses are effective against bacterial and viral pathogens. Lastly, we have now extended this PBS1 decoy approach to soybean by modifying a soybean PBS1 ortholog to be cleaved by the NIa protease of soybean mosaic virus (SMV). Transgenic overexpression of this soybean PBS1 decoy conferred immunity to SMV, demonstrating that we can use endogenous PBS1 proteins in crop plants to engineer economically relevant disease resistant traits.

Transmission blockage of an orthotospovirus using synthetic peptides.

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.

Soybean vein necrosis orthotospovirus can move systemically in soybean in the presence of bean pod mottle virus.

Soybean vein necrosis virus (SVNV), the causal agent of the homonymous disease, is a ubiquitous virus in North America. The widespread presence of the virus has led to the hypothesis that mixed infections with other viruses could alter disease symptoms, localization in the plant and even epidemiology. The potential interaction between bean pod mottle virus (BPMV), soybean mosaic virus (SMV), the most economically important soybean viruses in the U.S., and SVNV was assessed in the work presented here. Results revealed that soybean, a local lesion host for SVNV, becomes permissive in the presence of BPMV; whereas there where no obvious interactions observed in mixed infections with SMV.

Precise Exchange of the Helper-Component Proteinase Cistron Between Soybean mosaic virus and Clover yellow vein virus: Impact on Virus Viability and Host Range Specificity.

Soybean mosaic virus and Clover yellow vein virus are two definite species of the genus Potyvirus within the family Potyviridae. Soybean mosaic virus-N (SMV-N) is well adapted to cultivated soybean (Glycine max) genotypes and wild soybean (G. soja), whereas it remains undetectable in inoculated broad bean (Vicia faba). In contrast, clover yellow vein virus No. 30 (ClYVV-No. 30) is capable of systemic infection in broad bean and wild soybean; however, it infects cultivated soybean genotypes only locally. In this study, SMV-N was shown to also infect broad bean locally; hence, broad bean is a host for SMV-N. Based on these observations, it was hypothesized that lack of systemic infection by SMV-N in broad bean and by ClYVV-No. 30 in cultivated soybean is attributable to the incompatibility of multifunctional helper-component proteinase (HC-Pro) in these hosts. The logic of selecting the HC-Pro cistron as a target is based on its established function in systemic movement and being a relevant factor in host range specificity of potyviruses. To test this hypothesis, chimeras were constructed with precise exchanges of HC-Pro cistrons between SMV-N and ClYVV-No. 30. Upon inoculation, both chimeras were viable in infection, but host range specificity of the recombinant viruses did not differ from those of the parental viruses. These observations suggest that (i) HC-Pro cistrons from SMV-N and ClYVV-No. 30 are functionally compatible in infection despite 55.6 and 48.9% nucleotide and amino acid sequence identity, respectively, and (ii) HC-Pro cistrons from SMV-N and ClYVV-No. 30 are not the determinants of host specificity on cultivated soybean or broad beans, respectively.