Introgression of OsAP47 by marker-assisted selection enhanced resistance against southern rice black-streaked dwarf virus disease.

Southern rice black-streaked dwarf virus disease (SRBSDVD) is the most destructive viral disease in rice. In order to breeding resistant cultivars, Insertion-Deletion (InDel) markers were developed linked to OsAP47, the first isolated major resistance gene against SRBSDVD. Marker-assisted selection (MAS) was conducted to introduce this gene into the commercial variety. A rice line carrying homozygous resistance allele of OsAP47 was selected and named Kanghei No. 201 (KH201). Evaluated by artificial inoculation, KH201 showed significantly higher resistance than the recurrent parent Suxiu No.867 (SX867). And no significant differences were detected for KH201 in the yield-related components, including spikelets per panicle (SPP), ripened grains per panicle (RGPP), 1000-grain weight (TGW) and panicles per square meter (PPSM), leading to stable theoretical yield. The results indicated that introgression of OsAP47 improved rice resistance and can avoid yield losses produced by SRBSDVD. KH201 was demonstrated as a resistance material that could be used in rice breeding.

Structure of orthoreovirus RNA chaperone σNS, a component of viral replication factories.

The mammalian orthoreovirus (reovirus) σNS protein is required for formation of replication compartments that support viral genome replication and capsid assembly. Despite its functional importance, a mechanistic understanding of σNS is lacking. We conducted structural and biochemical analyses of a σNS mutant that forms dimers instead of the higher-order oligomers formed by wildtype (WT) σNS. The crystal structure shows that dimers interact with each other using N-terminal arms to form a helical assembly resembling WT σNS filaments in complex with RNA observed using cryo-EM. The interior of the helical assembly is of appropriate diameter to bind RNA. The helical assembly is disrupted by bile acids, which bind to the same site as the N-terminal arm. This finding suggests that the N-terminal arm functions in conferring context-dependent oligomeric states of σNS, which is supported by the structure of σNS lacking an N-terminal arm. We further observed that σNS has RNA chaperone activity likely essential for presenting mRNA to the viral polymerase for genome replication. This activity is reduced by bile acids and abolished by N-terminal arm deletion, suggesting that the activity requires formation of σNS oligomers. Our studies provide structural and mechanistic insights into the function of σNS in reovirus replication.

Investigation and characterization of rice dwarfing epidemic caused by southern rice black-streaked dwarf virus in Jiangsu in 2023.

During the field surveys in Jiangsu Province, China, contiguous patches of rice plants with varying degrees of dwarfing, wax-white or dark brown enations at the base of stems, and abnormal heading symptoms were observed in the fields located in Jiangning District in Nanjing City, Jurong County in Zhenjiang City, and Zhangjiagang County in Suzhou City. Through molecular analyses, the presence of southern rice black-streaked dwarf virus was confirmed in symptomatic rice plants. The infections of other rice viruses that cause dwarfing were also ruled out. Additionally, Koch's postulates were fulfilled, further validating SRBSDV as the causal agent for the observed dwarfing disease epidemic. Furthermore, the phylogenetic analyses revealed that the SRBSDV prevalent in Jiangsu in 2023 may originate from multiple regions in Vietnam. Our study has documented the emergence of an SRBSDV epidemic in Jiangsu in 2023, marking the first incidence of southern rice black-streaked dwarf disease in this region.

Mammalian orthoreovirus can exit cells in extracellular vesicles.

Several egress pathways have been defined for many viruses. Among these pathways, extracellular vesicles (EVs) have been shown to function as vehicles of non-lytic viral egress. EVs are heterogenous populations of membrane-bound structures released from cells as a form of intercellular communication. EV-mediated viral egress may enable immune evasion and collective viral transport. Strains of nonenveloped mammalian orthoreovirus (reovirus) differ in cell lysis phenotypes, with T3D disrupting cell membranes more efficiently than T1L. However, mechanisms of reovirus egress and the influence of transport strategy on infection are only partially understood. To elucidate reovirus egress mechanisms, we infected murine fibroblasts (L cells) and non-polarized human colon epithelial (Caco-2) cells with T1L or T3D reovirus and enriched cell culture supernatants for large EVs, medium EVs, small EVs, and free reovirus. We found that both reovirus strains exit cells in association with large and medium EVs and as free virus particles, and that EV-enriched fractions are infectious. While reovirus visually associates with large and medium EVs, only medium EVs offer protection from antibody-mediated neutralization. EV-mediated protection from neutralization is virus strain- and cell type-specific, as medium EVs enriched from L cell supernatants protect T1L and T3D, while medium EVs enriched from Caco-2 cell supernatants largely fail to protect T3D and only protect T1L efficiently. Using genetically barcoded reovirus, we provide evidence that large and medium EVs can convey multiple particles to recipient cells. Finally, T1L or T3D infection increases the release of all EV sizes from L cells. Together, these findings suggest that in addition to exiting cells as free particles, reovirus promotes egress from distinct cell types in association with large and medium EVs during lytic or non-lytic infection, a mode of exit that can mediate multiparticle infection and, in some cases, protection from antibody neutralization.

Development and application of a multiplex PCR method for the simultaneous detection of goose parvovirus, waterfowl reovirus, and goose astrovirus in Muscovy ducks.

A multiplex polymerase chain reaction (PCR) method was developed to detect and distinguish goose parvovirus (GPV), waterfowl reovirus (WRV), and goose astrovirus (GAstV). Three pairs of primers were designed based on conserved regions in the genomic sequences of these enteric viruses and were used to specifically amplify targeted fragments of 493 bp from the viral protein 3 (VP3) gene of GPV, 300 bp from the sigma A-encoding gene of WRV, and 156 bp from the capsid protein-encoding gene of GAstV. The results showed that the primers can specifically amplify target fragments, without any cross-amplification with other viruses, indicating that the method had good specificity. A sensitivity test showed that the detection limit of the multiplex PCR method was 1 × 103 viral copies. A total of 102 field samples from Muscovy ducks with clinically suspected diseases were evaluated using the newly developed multiplex PCR method. The ratio of positive samples to total samples for GPV, WRV, and GAstV was 73.53% (75/102) for multiplex PCR and was 73.53% (75/102) for routine PCR. Seventy-five positive samples were detected by both methods, for a coincidence ratio of 100%. This multiplex PCR method can simultaneously detect GPV, WRV, and GAstV, which are associated with viral enteritis, thereby providing a specific, sensitive, efficient, and accurate new tool for clinical diagnosis and laboratory epidemiological investigations.

Dynamic gene expression of southern rice black-streaked dwarf virus during its infection in rice plants and vector insects.

In this century, a disease caused by southern rice black-streaked dwarf virus (SRBSDV) has resulted in significant loss in rice production in Asia. Aside from infecting rice plants, SRBSDV is transmitted by white-backed planthopper (WBPH) in a persistent propagative manner. Recent studies showed that SRBSDV can dynamically modulate the host cells throughout the infection progress. However, the expression dynamics of the SRBSDV genes during infection remain unclear. Here we established an absolute real-time quantitative PCR method to assess the dynamic of the SRBSDV genes expression in rice plants and planthoppers. Apart from displaying the expression levels of viral genes, we discovered that the expression level of viral genes in insects significantly surpasses that in plant cells. In addition, we identified two nonstructural proteins with unknown functions that exhibit the highest expression levels in plant and insect cells, respectively, which provide possible targets for restraining the disease outbreaks.

A novel chimeric RNA originating from BmCPV S4 and Bombyx mori HDAC11 transcripts regulates virus proliferation.

Polymerases encoded by segmented negative-strand RNA viruses cleave 5'-m7G-capped host transcripts to prime viral mRNA synthesis ("cap-snatching") to generate chimeric RNA, and trans-splicing occurs between viral and cellular transcripts. Bombyx mori cytoplasmic polyhedrosis virus (BmCPV), an RNA virus belonging to Reoviridae, is a major pathogen of silkworm (B. mori). The genome of BmCPV consists of 10 segmented double-stranded RNAs (S1-S10) from which viral RNAs encoding a protein are transcribed. In this study, chimeric silkworm-BmCPV RNAs, in which the sequence derived from the silkworm transcript could fuse with both the 5' end and the 3' end of viral RNA, were identified in the midgut of BmCPV-infected silkworms by RNA_seq and further confirmed by RT-PCR and Sanger sequencing. A novel chimeric RNA, HDAC11-S4 RNA 4, derived from silkworm histone deacetylase 11 (HDAC11) and the BmCPV S4 transcript encoding viral structural protein 4 (VP4), was selected for validation by in situ hybridization and Northern blotting. Interestingly, our results indicated that HDAC11-S4 RNA 4 was generated in a BmCPV RNA-dependent RNA polymerase (RdRp)-independent manner and could be translated into a truncated BmCPV VP4 with a silkworm HDAC11-derived N-terminal extension. Moreover, it was confirmed that HDAC11-S4 RNA 4 inhibited BmCPV proliferation, decreased the level of H3K9me3 and increased the level of H3K9ac. These results indicated that during infection with BmCPV, a novel mechanism, different from that described in previous reports, allows the genesis of chimeric silkworm-BmCPV RNAs with biological functions.

Characterization of the complete genome of oat sterile dwarf virus: a fijivirus occurring in the temperate climate zone of Europe.

Oat sterile dwarf virus (OSDV) is a fijivirus whose genome segments 7 to 10 were sequenced earlier. In the current study, the complete genome was sequenced. To confirm the genome ends, rapid amplification and sequencing of cDNA ends were performed. The complete OSDV genome consists of 10 double-stranded RNA (dsRNA) segments with a total size of 28,686 bp. The sense strand sequence of all segments has the terminal consensus sequence motif 5'-AACGA(5-7)… U(6-8)(A/U)GUC-3', in which the length of the stretches of A and U varies, being slightly shorter for segments 1-4 and longer for segments 5-10. The 3' end of segment 3 is …UGUC, not AGUC as in the other segments. Segments 5, 7, and 10 contain two small ORFs, while each of the other segments contains one long ORF. ORF7-2 and ORF9 are slightly longer than annotated before. Phylogenetic analysis based on amino acid sequences of the RNA-directed RNA polymerase (RdRP) placed OSDV between the plant fijiviruses and Nilaparvata lugens reovirus (NLRV), an insect fijivirus that does not replicate in plants. OSDV RdRP shares 48-49% sequence identity with other plant-infecting fijivirus RdRPs and 30% identity with that of NLRV. OSDV has earlier been reported in several Northern and Central European countries. The sequencing of the complete genome serves as a reference for identifying all segments in future high-throughput sequencing datasets, enabling the investigation of the molecular epidemiology and evolution of OSDV.

Reovirus genomic diversity confers plasticity for protease utility during adaptation to intracellular uncoating.

IMPORTANCE: Reoviruses infect many mammals and are widely studied as a model system for enteric viruses. However, most of our reovirus knowledge comes from laboratory strains maintained on immortalized L929 cells. Herein, we asked whether naturally circulating reoviruses possess the same genetic and phenotypic characteristics as laboratory strains. Naturally circulating reoviruses obtained from sewage were extremely diverse genetically. Moreover, sewage reoviruses exhibited poor fitness on L929 cells and relied heavily on gut proteases for viral uncoating and productive infection compared to laboratory strains. We then examined how naturally circulating reoviruses might adapt to cell culture conditions. Within three passages, virus isolates from the parental sewage population were selected, displaying improved fitness and intracellular uncoating in L929 cells. Remarkably, selected progeny clones were present at 0.01% of the parental population. Altogether, using reovirus as a model, our study demonstrates how the high genetic diversity of naturally circulating viruses results in rapid adaptation to new environments.

Isolation and genomic characterization of a cypovirus from Clanis bilineata.

Clanis bilineata Walker, soybean hawkmoth, belongs to the subfamily Ambulicinae (Sphingidae, Lepidoptera) and is an edible insect that usually grows on soybean leaves. In this study, we isolated a new cypovirus from naturally diseased Clanis bilineata larvae (named CbCPV), scanned its structure, sequenced its genome, and studied its phylogenetic relationship to other cypoviruses. Microscopy showed that CbCPV polyhedral occlusion bodies were about 1.878 µm on average and contained many virions in the ultrathin sections. The complete genome sequence of CbCPV is 22,812 bp comprising 10 segmented double-stranded RNAs. Apart from segment 1 containing one open reading frame (ORF) and one sub-ORF, the other nine segments all contain one open reading frame and encoded one putative protein. The non-coding regions contained conserved sequences at 5' termini (AGUCAAA) and 3' termini (AGC), except segment 4 containing a different 5' termini (AUGUUUA). The whole sequence of the polyhedrin gene in CbCPV contained 892 nucleotides, encoding a protein of 246 amino acids. Based on amino acid sequences of polyhedrin or RNA dependent RNA polymerase (RdRp), the phylogenetic analysis indicated that CbCPV was closely related to DnCPV-23. The putative function of all segments differed from each other, but the most closely related species of segments were DnCPV-23 with 98.2-99.8% nucleotide identity. Overall, the evidence of morphology, protein analysis and nucleic acids (genomic pattern) showed that CbCPV is a new isolate in the cypovirus-23 type and can be termed Clanis bilineata cypovirus type 23 (CbCPV-23).

Comparative transcriptional analysis between virulent isolate HN1307 and avirulent isolate GD1108 of grass carp reovirus genotype II.

As a widespread epidemic virus, genotype II of the grass carp reovirus poses a significant threat to the grass carp farming industry in China. Different genotype II isolates cause different degrees of virulence, although the underlying pathogenic mechanisms remain largely unknown. In this work, infections of grass carp with the virulent isolate grass carp reovirus (GCRV)-HN1307 and the avirulent isolate GCRV-GD1108 were performed to reveal a possible mutual transcriptional discrepancy. More differentially expressed genes (DEGs) were identified in the HN1307-infected group, which defined a grossly similar gene ontology (GO) pattern and different pathway landscape as the GD1108-infected group. Gene set enrichment analysis revealed that pathways related to innate immunity and metabolism were reciprocally activated and suppressed, respectively, following infection withHN1307, compared with GD1108. The trend analysis further indicated that immune-related pathways were involved in one of the four statistically significant profiles. Network analysis of transcription factor-gene interactions and protein-protein interactions on the immune-related profile suggested that among the core transcriptional factors (TFs) (UBTF, HCFC1, MAZ, MAX, and NRF1) and the hub proteins (Tlr3, Tlr7, Tlr9, Irf3, and Irf7), the latter were highly enriched in the toll-like receptor signaling pathway. Real-time quantitative PCR performed on the selected mRNAs validated the relative expression. This work will provide insights into the distinct transcriptional signatures from avirulent and virulent isolates of GCRV, which may contribute to the development of products for prevention.

Piscine Vitamin D Receptors Vdra/Vdrb in the Absence of Vitamin D Are Utilized by Grass Carp Reovirus for Promoting Viral Replication.

The vitamin D receptor (VDR) plays a pivotal role in the biological actions of vitamin D (VitD). However, little is known about the functions of VDR in the production of viral inclusion bodies (VIBs). Using a representative strain of grass carp reovirus (GCRV) genotype I, GCRV-873, we show that GCRV-873 recruits grass carp Vdrs for promoting the production of VIBs in the absence of VitD. Inhibition of cholesterol synthesis by lovastatin impairs the production of VIBs and blocks the effects of grass carp Vdrs in promoting the production of VIBs in the absence of VitD. Furthermore, grass carp Vdrs are found to form the Vdra-Vdrb heterodimer, which is vital for 3-hydroxy-3-methylglutaryl-coenzyme A reductase (hmgcr)-dependent cholesterol synthesis and GCRV replication. Intriguingly in the presence of VitD, grass carp Vdra but not Vdrb forms the heterodimer with the retinoid X receptor beta b (Rxrbb), which induces the transcription of those genes involved in the RIG-I-like receptor (RLR) antiviral signaling pathway for inhibiting GCRV infection. Furthermore, the VitD-activated Vdra-Vdrb heterodimer attenuates the transcription of the RLR antiviral signaling pathway induced by VitD. In the presence of VitD, a balance between the Vdra-Rxrbb heterodimers as coactivators and Vdra-Vdrb heterodimers as corepressors in affecting the transcriptional regulation of the RLR antiviral signaling pathway may eventually determine the outcome of GCRV infection. Transfection with VitD can abolish the effect of grass carp Vdrs in promoting GCRV replication in a dose-dependent manner. Taken together, these findings demonstrate that GCRV utilizes host Vdrs to increase hmgcr-dependent cholesterol synthesis for promoting its replication, which can be prevented by VitD treatment. IMPORTANCE Grass carp reovirus (GCRV) is the causative agent of grass carp hemorrhagic disease, which seriously harms freshwater fish. Although many positive or negative regulators of GCRV infection have been identified in teleosts, little is known about the molecular mechanisms by which GCRV utilizes host factors to generate its infectious compartments beneficial for viral replication and infection. Here, we show that in the absence of VitD, the GCRV-873 strain utilizes host vitamin D receptors Vdra/Vdrb to increase hmgcr-dependent cholesterol synthesis for promoting the production of VIBs, which are important functional sites for aquareovirus replication and assembly. The negative regulation of Vdrs during viral infection can be prevented by VitD treatment. Thus, this present work broadens understanding of the pivotal roles of Vdrs in the interaction between the host and GCRV in the absence or presence of VitD, which might provide a rational basis for developing novel anti-GCRV strategies.

[Variability of genes encoding nonstructural proteins of rotavirus А (Reoviridae: Rotavirus: Rotavirus A) genotype G9P[8] during the period of dominance in the territory of Nizhny Novgorod (central part of Russia) (2011-2020)].

INTRODUCTION: In Russia, rotavirus A is the main cause of severe viral gastroenteritis in young children. The molecular features that allow a rotavirus of a particular genotype to gain an evolutionary advantage remain unclear, therefore, the study of the genetic diversity of rotaviruses based on genes encoding nonstructural proteins (NSPs) responsible for the reproduction of the virus in the cell is an urgent task. OBJECTIVE: To study the genetic diversity of rotaviruses of genotype G9P[8], which dominated Nizhny Novgorod in 20112020, based on genes encoding nonstructural proteins. MATERIALS AND METHODS: Rotavirus-positive samples were subjected to PCR-genotyping and sequencing of NSP1 NSP5 genes. Phylogenetic analysis was carried out in the MEGA X program. RESULTS: In the period 20112020, G9P[8] rotaviruses with four variants of the NSP2 gene were co-circulating in Nizhny Novgorod. New alleles were noted in 2012 (N1-a-III), 2016 (N1-a-IV) and in 2019 (N1-a-II). The appearance of new variants of other genes occurred in 2014 (E1-3, NSP4), 2018 (T1-a3-III, NSP3) and in 2019 (A1-b-II, NSP1). NSP2 gene had the most variable amino acid sequence (16 substitutions), 2 to 7 substitutions were observed in NSP1, NSP3 and NSP4, NSP5 was conservative. DISCUSSION: The results obtained are consistent with the literature data and indicate the participation of NSP genes in maintaining the heterogeneity of the rotavirus population. CONCLUSION: Until 2018, the genetic diversity of rotaviruses in Nizhny Novgorod was determined by the circulation of strains carrying several alleles of the NSP2 gene and conservative genes NSP1, NSP3NSP5. By the end of the study period, new variants of the genotype G9P[8] were formed in the population, carrying previously unknown combinations of alleles of nonstructural genes.

Nonstructural protein NS17 of grass carp reovirus Honghu strain promotes virus infection by mediating cell-cell fusion and apoptosis.

Fusion-associated small transmembrane (FAST) proteins can promote cell fusion, alter membrane permeability and trigger apoptosis to promote virus proliferation in orthoreoviruses. However, it is unknown whether FAST proteins perform these functions in aquareoviruses (AqRVs). Non-structural protein 17 (NS17) carried by grass carp reovirus Honghu strain (GCRV-HH196) belongs to the FAST protein family, and we preliminarily explored its relevance to virus infection. NS17 has similar domains to FAST protein NS16 of GCRV-873, comprising a transmembrane domain, a polybasic cluster, a hydrophobic patch and a polyproline motif. It was observed in the cytoplasm and the cell membrane. Overexpression of NS17 enhanced the efficiency of cell-cell fusion induced by GCRV-HH196 and promoted virus replication. Overexpression of NS17 also led to DNA fragmentation and reactive oxygen species (ROS) accumulation, and it triggered apoptosis. The findings illuminate the functions of NS17 in GCRV infection, and provide a reference for the development of novel antiviral strategies.

A systematic review of southern rice black-streaked dwarf virus in the age of omics.

Southern rice black-streaked dwarf virus (SRBSDV) is one of the most damaging rice viruses. The virus decreases rice quality and yield, and poses a serious threat to food security. From this perspective, this review performed a survey of published studies in recent years to understand the current status of SRBSDV and white-backed planthopper (WBPH, Sogatella furcifera) transmission processes in rice. Recent studies have shown that the interactions between viral virulence proteins and rice susceptibility factors shape the transmission of SRBSDV. Moreover, the transmission of SRBSDV is influenced by the interactions between viral virulence proteins and S. furcifera susceptibility factors. This review focused on the molecular mechanisms of key genes or proteins associated with SRBSDV infection in rice via the S. furcifera vector, and the host defense response mechanisms against viral infection. A sustainable control strategy using RNAi was summarized to address this pest. Finally, we also present a model for screening anti-SRBSDV inhibitors using viral proteins as targets. © 2023 Society of Chemical Industry.

An Aquareovirus Exploits Membrane-Anchored HSP70 To Promote Viral Entry.

Temperature dependency of viral diseases in ectotherms has been an important scientific issue for decades, while the molecular mechanism behind this phenomenon remains largely mysterious. In this study, deploying infection with grass carp reovirus (GCRV), a double-stranded RNA aquareovirus, as a model system, we demonstrated that the cross talk between HSP70 and outer capsid protein VP7 of GCRV determines temperature-dependent viral entry. Multitranscriptomic analysis identified HSP70 as a key player in the temperature-dependent pathogenesis of GCRV infection. Further biochemical, small interfering RNA (siRNA) knockdown, pharmacological inhibition, and microscopic approaches revealed that the primary plasma membrane-anchored HSP70 interacts with VP7 to facilitate viral entry during the early phase of GCRV infection. Moreover, VP7 functions as a key coordinator protein to interact with multiple housekeeping proteins and regulate receptor gene expression, concomitantly facilitating viral entry. This work illuminates a previously unidentified immune evasion mechanism by which an aquatic virus hijacks heat shock response-related proteins to enhance viral entry, pinpointing targeted preventives and therapeutics for aquatic viral diseases. IMPORTANCE The seasonality of viral diseases in ectotherms is a prevailing phenomenon in the aquatic environment, which causes huge economic losses every year worldwide and hinders sustainable development of the aquaculture industry. Nevertheless, our understanding of the molecular mechanism of how temperature determines the pathogenesis of aquatic viruses remains largely unexplored. In this study, by deploying grass carp reovirus (GCRV) infection as a model system, we demonstrated that temperature-dependent, primarily membrane-localized HSP70 interacts with major outer capsid protein VP7 of GCRV to bridge the virus-host interaction, reshape the host's behaviors, and concomitantly facilitate viral entry. Our work unveils a central role of HSP70 in the temperature-dependent pathogenesis of aquatic viruses and provides a theoretical basis for the formulation of prevention and control strategies for aquatic viral diseases.

BmCPV replication is suppressed by the activation of the NF-κB/autophagy pathway through the interaction of vsp21 translated by vcircRNA_000048 with ubiquitin carboxyl-terminal hydrolase.

Bombyx mori cypovirus (BmCPV), a typical double-stranded RNA virus, was demonstrated to generate a viral circRNA, vcircRNA_000048, which encodes a vsp21 with 21 amino acid residues to suppress viral replication. However, the regulatory mechanism of vsp21 on virus infection remained unclear. This study discovered that vsp21 induces reactive oxygen species (ROS) generation, activates autophagy, and attenuates virus replication by inducing autophagy. Then we confirmed that the effect of vsp21-induced autophagy on viral replication was attributed to the activation of the NF-κB signaling pathway. Furthermore, we clarified that vsp21 interacted with ubiquitin carboxyl-terminal hydrolase (UCH) and that ubiquitination and degradation of phospho-IκB-α were enhanced by vsp21 via competitive binding to UCH. Finally, we validated that vsp21 activates the NF-κB/autophagy pathway to suppress viral replication by interacting with UCH. These findings provided new insights into regulating viral multiplication and reovirus-host interaction.

The structure of a 12-segmented dsRNA reovirus: New insights into capsid stabilization and organization.

Infecting a wide range of hosts, members of Reovirales (formerly Reoviridae) consist of a genome with different numbers of segmented double stranded RNAs (dsRNA) encapsulated by a proteinaceous shell and carry out genome replication and transcription inside the virion. Several cryo-electron microscopy (cryo-EM) structures of reoviruses with 9, 10 or 11 segmented dsRNA genomes have revealed insights into genome arrangement and transcription. However, the structure and genome arrangement of 12-segmented Reovirales members remain poorly understood. Using cryo-EM, we determined the structure of mud crab reovirus (MCRV), a 12-segmented dsRNA virus that is a putative member of Reovirales in the non-turreted Sedoreoviridae family, to near-atomic resolutions with icosahedral symmetry (3.1 Å) and without imposing icosahedral symmetry (3.4 Å). These structures revealed the organization of the major capsid proteins in two layers: an outer T = 13 layer consisting of VP12 trimers and unique VP11 clamps, and an inner T = 1 layer consisting of VP3 dimers. Additionally, ten RNA dependent RNA polymerases (RdRp) were well resolved just below the VP3 layer but were offset from the 5-fold axes and arranged with D5 symmetry, which has not previously been seen in other members of Reovirales. The N-termini of VP3 were shown to adopt four unique conformations; two of which anchor the RdRps, while the other two conformations are likely involved in genome organization and capsid stability. Taken together, these structures provide a new level of understanding for capsid stabilization and genome organization of segmented dsRNA viruses.

A Rice Receptor-like Protein Negatively Regulates Rice Resistance to Southern Rice Black-Streaked Dwarf Virus Infection.

Plants rely on various receptor-like proteins and receptor-like kinases to recognize and defend against invading pathogens. However, research on the role of receptor-like proteins in plant antiviral defense, particularly in rice-virus interactions, is limited. In this study, we identified a receptor-like gene, OsBAP1, which was significantly induced upon infection with southern rice black-streaked dwarf virus (SRBSDV) infection. A viral inoculation assay showed that the OsBAP1 knockout mutant exhibited enhanced resistance to SRBSDV infection, indicating that OsBAP1 plays a negatively regulated role in rice resistance to viral infection. Transcriptome analysis revealed that the genes involved in plant-pathogen interactions, plant hormone signal transduction, oxidation-reduction reactions, and protein phosphorylation pathways were significantly enriched in OsBAP1 mutant plants (osbap1-cas). Quantitative real-time PCR (RT-qPCR) analysis further demonstrated that some defense-related genes were significantly induced during SRBSDV infection in osbap1-cas mutants. Our findings provide new insights into the role of receptor-like proteins in plant immune signaling pathways, and demonstrate that OsBAP1 negatively regulates rice resistance to SRBSDV infection.

Oncolytic Reoviruses: Can These Emerging Zoonotic Reoviruses Be Tamed and Utilized?

Orthoreovirus is a nonenveloped double-stranded RNA virus under the Reoviridae family. This group of viruses, especially mammalian orthoreovirus (MRV), are reported with great therapeutic values due to their oncolytic effects. In this review, the life cycle and oncolytic effect of MRV and a few emerging reoviruses were summarized. This article also highlights the challenges and strategies of utilizing MRV and the emerging reoviruses, avian orthoreovirus (ARV) and pteropine orthoreovirus (PRV), as oncolytic viruses (OVs). Besides, the emergence of potential ARV and PRV as OVs were discussed in comparison to MRV. Finally, the risk of reovirus as zoonosis or reverse zoonosis (zooanthroponosis) were debated, and concerns were raised in this article, which warrant continue surveillance of reovirus (MRV, ARV, and PRV) in animals, humans, and the environment.