Search Results (52)

Potyvirus genomes are expressed as a single large open reading frame, which is translated into a polyprotein that is post-translationally cleaved by three virus-encoded proteases into 10 functional proteins. Several of these potyviral proteins, including nuclear inclusion protein b (NIb), are multifunctional. Here, using the classic GFP silencing in Nicotiana benthamiana gfp-transgenic plants, we show that potato virus Y (PVY) NIb, in addition to its canonical role as the viral RNA-dependent RNA polymerase (RdRP), functions as a suppressor of RNA silencing. Mutational analyses reveal a previously unreported NIb nuclear localization signal (NLS) consisting of a triple-lysine motif. NIb suppression of RNA silencing activity was lost when the NLS was mutated, suggesting that nuclear localization is required for NIb suppression of RNA silencing activity. Analysis of sequenced GFP siRNAs revealed three reproducible hotspot regions at ≈175 nt, ≈320–330 nt, and a broader 3′-proximal region spanning ≈560–700 nt that contains multiple local maxima. These data show differences in the positional distribution of siRNAs between samples expressing NIb and those expressing NIb^Del3×2, the NIb null mutant that does not suppress RNA silencing. However, the positional distribution of GFP-derived small RNAs across the transgene differed modestly between NIb and NIb^Del3×2, while both treatments showed the same three reproducible hotspot regions. Furthermore, NIb was found to interact with four key RNA silencing pathway proteins—AGO4, HSP70, HSP90, and SGS3. Except for HSP90, each of these proteins showed degradation products that were absent in NIb mutants that did not suppress RNA silencing. These findings support a role for NIb in countering host defense during virus infection. Full article

GmSRC7 is a broad-spectrum antiviral R gene from soybean, but its downstream and functionally related genes remain unclear. Virus-induced gene silencing (VIGS) assays in Nicotiana benthamiana (Nb) showed that suppression of several gene families—WRKY transcription factors, chaperones, ethylene pathway components, MAPK cascade elements, salicylic acid (SA) signaling genes, calcium-dependent protein kinases, nuclear migration proteins, RNA replication-related genes, and immune regulators—consistently weakened GmSRC7-mediated resistance to Soybean Mosaic Virus (SMV) and Tobacco Mosaic Virus (TMV). Targeted silencing of four regulatory genes—NbEDS1, NbARF1, NbSGT1, and NbCOI1—markedly enhanced GmSRC7-mediated resistance to SMV and TMV in our experiments. Silencing the serine/threonine kinase gene NbPBS1 increased GmSRC7-conferred resistance to SMV but did not significantly alter its resistance to TMV. Transient expression assays showed that NbARF1, NbSGT1, and NbCOI1 antagonize GmSRC7-mediated defense against SMV and TMV, whereas NbPBS1 specifically suppresses anti-SMV activity without affecting TMV resistance. Transient overexpression of SA-degrading enzymes (AtS3H, AtS5H, and NahG) significantly reduced GmSRC7-conferred resistance to SMV, indicating that SA is essential for this R protein-mediated defense. Genes were also grouped by immune pathways and function: co-expression of chaperone family genes inhibited GmSRC7 activity against SMV and TMV, while co-expression of WRKY family genes enhanced anti-SMV activity of GmSRC7. Finally, transient silencing of soybean genes GmEDS1, GmSGT1-1, GmSGT1-2, GmJAR1, and GmSGS3 compromised GmSRC7-mediated resistance to SMV. Full article

Dendritic cells (DCs) are essential for antiviral immunity but are also susceptible to HIV-1 infection. Although sensing and restriction pathways in DCs are well described, the mechanisms underlying latent infection and its functional consequences remain unclear. In this study, we performed transcriptomic profiling of monocyte-derived DCs harboring transcriptionally active (Active-HIV) or latent HIV-1 (Latent-HIV) proviruses using a dual-reporter virus. Gene set enrichment analysis revealed suppression of metabolic and stress-modulatory programs in Active-HIV compared to unexposed DCs. In contrast, Latent-HIV showed broad downregulation of pathways, including interferon and innate responses and metabolic programs, indicating a hyporesponsive and dampened antiviral state despite the absence of differentially expressed genes (DEGs). DEG analysis of Active-HIV versus Latent-HIV showed that active transcription associates with cellular stress, cytoskeletal remodeling, and RNA processing. Functional analyses further demonstrated the activation of RNA processes, the suppression of antigen-presentation pathways, and altered membrane and cytoskeletal signaling in Active-HIV. These pathways suggest that transcriptionally active HIV-1 is linked to cellular programs supporting replication, coinciding with a metabolically strained yet immunologically engaged state that may impair antigen presentation. Conversely, latently infected DCs display a hyporesponsive state consistent with proviral silencing. This dichotomy reveals distinct mechanisms of DC dysfunction that may facilitate HIV-1 persistence and immune evasion. Full article

The Gretchen Hagen 3 (GH3) gene family, a key component of the early auxin-responsive gene family, plays a pivotal role in regulating plant growth, development, and stress responses. However, to date, a comprehensive genome-wide analysis of the GH3 gene family and its potential role in plant defense against viruses, such as tomato yellow leaf curl virus (TYLCV), has not been conducted in Nicotiana benthamiana. Here, the GH3 gene family was thoroughly examined in N. benthamiana using a comprehensive genome-wide bioinformatic approach. A total of 25 potential GH3 genes were discovered in N. benthamiana. Phylogenetic analysis classified these NbGH3s into three different clades. Chromosomal distribution and synteny analyses revealed that NbGH3s are unevenly distributed across 14 chromosomes, with 20 segmental and one tandem duplication pairs. Promoter analysis suggested their involvement in phytohormone signaling and stress responses. Quantitative PCR showed that several NbGH3s are transcriptionally responsive to TYLCV infection, with five of them significantly upregulated in infected leaves. Furthermore, virus-induced gene silencing revealed that the suppression of NbGH3-3 and NbGH3-9 markedly increased host susceptibility to TYLCV, underscoring their critical roles in plant antiviral defense mechanisms. This research establishes a framework for understanding the functions of NbGH3s in plant growth and their response to TYLCV infection. Full article

KSRP (KH-type splicing regulatory protein) has emerged as a pivotal regulator of gene expression at multiple levels, acting as a transcription and splicing factor in the nucleus, and mediating AU-rich element (ARE)-dependent mRNA decay, translational silencing, and microRNA (miRNA) maturation in the cytoplasm. We and others have shown that KSRP acts as a regulator of immune responses, e.g., by dampening the expression of proinflammatory cytokines such as TNF-α, IL-6, IL-8, but also of NOS2, and facilitating the maturation of regulatory miRNAs, including let-7a, miR-129, and miR-155. This review aims to present current knowledge on the regulation of KSRP activity as conferred by miRNAs, phosphorylation, ubiquitination, SUMOylation, and interactions with long non-coding RNAs to enable dynamic responses towards inflammatory stimuli, and the effects of KSRP on innate immune reactions. Here, KSRP acts as an inhibitor by attenuating RIG-I-mediated antiviral signaling, cytokine production, and phagocytosis. In vivo, KSRP deficiency reduced arthritis severity but heightened inflammatory responses in sepsis and enhanced pathogen clearance in invasive pulmonary aspergillosis. These findings position KSRP as a dual regulator that limits tissue damage while constraining antimicrobial immunity. As a perspective, modulation of KSRP activity by applying pharmacological inhibitors may provide strategies to either suppress hyperinflammation in autoimmunity and sepsis or enhance host defense in immunocompromised states. Full article

The potyvirus helper component proteinase (HcPro) is a multifunctional protein, with one of its most documented functions being host antiviral RNA silencing suppression. This study shows that the HcPro of potato virus Y (PVY), an important member of the potyvirus group, prevents the replication of a related competing secondary virus. This phenomenon, referred to as superinfection exclusion (SIE), is common in bacterial, human, and plant virus infections. We also report that HcPro’s induction of SIE is strain-specific and that this specificity is provided by the first four amino acid residues of the protein. Consistent with the mechanism of SIE, the study found that HcPro does not exclude a resident virus. Additionally, HcPro’s induction of SIE was observed to function independently of its ability to suppress antiviral RNA silencing. HcPro’s induction of SIE is relevant given the prevalence of multiple PVY strains that routinely co-infect the same cell and that may lead to recombination and emergence of new and more virulent strains. Furthermore, cross-protection or systemic acquired resistance (SAR) that is employed in plant virus disease management occurs when SIE moves from the cellular level and spreads systemically, emphasizing the importance of studying SIE. Full article

Ubiquitin-conjugating enzyme (UBC) plays a significant role in plant hormone signal transduction. In this study, we observed that TuMV infection markedly upregulates UBC mRNA expression, suggesting a close association between UBC and viral infection. Using Tobacco rattle virus (TRV)-based virus-induced gene silencing (VIGS) to downregulate UBC expression in Nicotiana benthamiana, we found that UBC-silenced plants exhibited enhanced susceptibility to TuMV compared with control plants. Conversely, transient overexpression of UBC protein suppressed viral propagation. Further analysis by reverse transcription quantitative PCR (RT-qPCR) revealed a substantial downregulation in the expression of SA and JA biosynthetic genes in UBC-silenced plants. Accordingly, liquid chromatography–tandem mass spectrometry (LC-MS/MS) confirmed a marked decrease in the accumulation of the corresponding hormones. Exogenous application of SA or JA partially restored antiviral resistance in UBC-silenced plants, indicating that hormonal deficiency contributes to enhanced viral susceptibility. Collectively, our results demonstrate that UBC positively regulates SA and JA biosynthesis. UBC silencing impairs both SA- and JA-mediated defense pathways, thereby facilitating viral infection in N. benthamiana. Full article

Chloroplasts, which are essential for plant defense and phytohormone signaling, contain ribosomal proteins that play key roles in viral infection processes. Plastid-specific ribosomal proteins (PSRPs), unique to chloroplasts, remain unexplored in their mechanistic roles during plant-virus interactions. In this study, we identified two PSRPs from non-heading Chinese cabbage (Brassica campestris ssp. chinensis) as interacting with turnip mosaic virus (TuMV, Potyvirus rapae). Subcellular localization revealed that BcPSRP2/4 is targeted to chloroplasts, while BiFC, Y2H, and LCAs confirmed their interaction with TuMV VPg (virus protein, genome-linked). Intriguingly, VPg altered the subcellular localization of BcPSRP2/4, suggesting an important role for BcPSRP2/4 in TuMV infection. Strikingly, overexpression of BcPSRP2/4 enhanced TuMV cell-to-cell movement, while psrp2 knockdown mutants in Arabidopsis exhibited a significant reduction in viral accumulation, highlighting their proviral roles. Furthermore, virus-induced gene silencing (VIGS)-mediated suppression of BcPSRP2/4 in non-heading Chinese cabbage resulted in milder symptoms upon TuMV infection without compromising plant growth: a distinct advantage over conventional resistance genes that incur fitness costs. These findings highlight PSRP2/4 as pivotal molecular hinges in chloroplast-virus interplay, offering novel targets for engineering sustainable antiviral strategies in cruciferous crops. Full article

Background: The ubiquitin–proteasome system plays a critical role in plant antiviral defense, with HECT-type E3 ubiquitin ligases serving as key regulators of protein turnover. To explore the potential involvement of the HECT gene family in host resistance against tomato yellow leaf curl virus (TYLCV), a comprehensive analysis was conducted in Nicotiana benthamiana. Methods: In this study, the HECT gene family in N. benthamiana was systematically investigated using a genome-wide bioinformatic analysis. The potential roles of these genes in the response to TYLCV infection were further examined using a virus-induced gene silencing (VIGS) technique. Results: Using a Hidden Markov Model approach, 18 NbHECT genes were identified that phylogenetically clustered into four subfamilies with distinct structural features. Chromosomal location and synteny analyses indicated that these genes were unevenly distributed across 11 chromosomes, with 10 instances of segmental duplication identified. Tissue-specific expression profiling demonstrated that 17 NbHECTs were constitutively expressed, with Group III members showing the highest expression in reproductive tissues. Following TYLCV infection, NbHECT6 was significantly downregulated while NbHECT13 was upregulated in both inoculated and systemic leaves. Functional validation through the VIGS approach revealed that suppression of NbHECT6 and NbHECT13 increased host susceptibility, as evidenced by exacerbated symptom severity and enhanced viral DNA accumulation compared to controls. Conclusions: These findings establish NbHECT6 and NbHECT13 as critical components of the plant antiviral response, providing new insights into ubiquitin-mediated defense mechanisms against geminiviruses. Full article

Cucumber mosaic virus (CMV) is a destructive viral pathogen of vegetables, fruits, grains, and ornamentals across the globe. This study investigated the comparative antiviral efficacy of chitosan–salicylic acid nanocomposite (Ch/SA NC) and salicylic acid (SA) against CMV in cucumber plants. Transmission electron microscopy (TEM) analyses revealed that Ch/SA NCs can aggregate on the viral coat protein surface, suggesting direct nanoparticle–virus interaction. Greenhouse trials showed that Ch/SA NC, particularly at 90 ppm applied 24 h before CMV inoculation, was the most effective treatment in reducing disease severity and viral load. SA at the same concentration also conferred significant protection when used prophylactically. An RT-PCR analysis confirmed suppression or complete silencing of CMV coat protein gene expression, especially Ch/SA NC-treated plants. Both treatments significantly enhanced the physiological condition of infected plants, including restoration of chlorophyll a, chlorophyll b, and carotenoids, and elevated levels of total phenolics, flavonoids carbohydrates, and proteins. In addition, they boosted the key antioxidant enzymes activities (POX, PPO, SOD) and improved vegetative growth indicators such as plant height, fruit fresh weight, and number of fruits per plant. These results indicate that Ch/SA NC and SA not only inhibit CMV replication but also stimulate host defense responses, improving overall plant health. The strong antiviral effect is likely due to the dual action of Ch/SA NC: direct virus binding and induction of systemic acquired resistance (SAR). Given their efficacy and eco-friendly nature, especially the Ch/SA NC, these treatments offer a promising strategy for integrated viral disease management. Future studies should investigate long-term environmental safety, molecular mechanisms, and field-level applicability. Full article

Porcine circovirus type 2 (PCV2) is a globally prevalent swine pathogen that induces immunosuppression, predisposing pigs to subclinical infections. In intensive farming systems, PCV2 persistently impairs growth performance and vaccine efficacy, leading to substantial economic losses in the swine industry. Emerging evidence suggests that certain viruses exploit Suppressor of Cytokine Signaling 3 (SOCS3), a key immune checkpoint protein, to subvert host innate immunity by suppressing cytokine signaling. While SOCS3 has been implicated in various viral infections, its regulatory role in PCV2 replication remains undefined. This study aims to elucidate the mechanisms underlying the interplay between SOCS3 and PCV2 during viral pathogenesis. Porcine SOCS3 was amplified using RT-PCR and stably overexpressed in PK-15 cells through lentiviral delivery. Bioinformatics analysis facilitated the design of three siRNA candidates targeting SOCS3. We systematically investigated the effects of SOCS3 overexpression and knockdown on PCV2 replication kinetics and host antiviral responses by quantifying the viral DNA load and the mRNA levels of cytokines. PCV2 infection upregulated SOCS3 expression at both transcriptional and translational levels in PK-15 cells. Functional studies revealed that SOCS3 overexpression markedly enhanced viral replication, whereas its knockdown suppressed viral proliferation. Intriguingly, SOCS3-mediated immune modulation exhibited a divergent regulation of antiviral cytokines: PCV2-infected SOCS3-overexpressing cells showed elevated IFN-β but suppressed TNF-α expressions, whereas SOCS3 silencing conversely downregulated IFN-β while amplifying TNF-α responses. This study unveils a dual role of SOCS3 during subclinical porcine circovirus type 2 (PCV2) infection: it functions as a host-derived pro-viral factor that facilitates viral replication while simultaneously reshaping the cytokine milieu to suppress overt inflammatory responses. These findings provide novel insights into the mechanisms underlying PCV2 immune evasion and persistence and establish a theoretical framework for the development of host-targeted control strategies. Although our results identify SOCS3 as a key host determinant of PCV2 persistence, the precise molecular pathways involved require rigorous experimental validation. Full article

Serine/arginine splicing factors (SRSFs) are critical regulators of gene expression that influence alternative splicing through RNA binding via the RNA recognition motif (RRM). Circular RNAs (circRNAs) are a subset of non-coding RNAs that exhibit differential expression in WSSV-infected Litopenaeus vannamei. This study investigates the role of LvSRSF2 in regulating circRNA expression in response to WSSV infection. LvSRSF2 was highly expressed in hemocytes and upregulated during WSSV infection. Silencing LvSRSF2 using dsRNA significantly upregulated the expression of circRNAs (circ-Alpha2, circ-Anillin, circ-Hemocytin, circ-Nephrin, and circ-Toll) in both WSSV-infected and uninfected shrimps at 72 h post-injection with dsRNAs. Knockdown of LvSRSF2 also significantly reduced WSSV copy numbers at 24 h post-infection and extended shrimp survival, with knockdown shrimp surviving up to 9 d compared to the control group. In addition, circ-Hemocytin, an SRSF2-related circRNA, was predicted to interact with six miRNAs targeting immune-related genes such as Toll, STAT, NF-κB, and Vago4. Following WSSV infection, circ-Hemocytin expression increased at 24 and 48 hpi, and the immune genes STAT and Vago4 were also upregulated, suggesting a potential circRNA–miRNA–mRNA regulatory axis in shrimp antiviral defense. Furthermore, targeted suppression of circ-Hemocytin expression using siRNAs significantly reduced its expression without affecting the corresponding linear transcript and resulted in a notable decrease in WSSV load in shrimp gills, highlighting its potential role in antiviral defense. Full article

Chilli veinal mottle virus (ChiVMV) severely compromises the quality and yield of solanaceous crops. The helper component protease (HCPro) of ChiVMV functions as a multifunctional RNA silencing suppressor that subverts host antiviral defenses through diverse strategies, However, the underlying mechanisms remain mechanistically unresolved. In this study, HCPro-overexpressing (HCPro-OX) and wild-type (WT) plants were inoculated with ChiVMV to monitor the physiological and molecular changes. Transcriptome analysis identified 11,815 differentially expressed genes (DEGs) under viral infection, among which 1115 genes were specifically regulated by HCPro. KEGG enrichment analysis revealed that the DEGs were significantly associated with plant hormone signal transduction pathways, indicating their crucial role in host–virus interactions. Furthermore, functional clustering of HCPro-regulated DEGs specifically identified key components in ethylene biosynthesis pathways. GO analysis of DEGs between virus-inoculated WT and HCPro-OX plants annotated ethylene biosynthesis-related genes NtACO and NtACS. qPCR validation confirmed that the expression of ethylene biosynthesis-related genes was suppressed by HCPro. Exogenous treatments with the ethylene precursor ACC demonstrated that ethylene suppressed viral accumulation, enhanced POD activity, and reduced the ROS accumulation induced by viral infection. In conclusion, our results demonstrate that HCPro promotes viral infection by suppressing ethylene biosynthesis, which in turn attenuates peroxidase activity, leading to ROS accumulation. Full article

MicroRNAs (miRNAs) are key regulators of gene expression, exerting post-translational control through mRNA silencing or degradation. These molecules play pivotal roles in host–pathogen interactions, particularly in modulating antiviral immune responses. The global public health threat posed by the H5N1 Highly Pathogenic Avian Influenza (HPAI) virus necessitates urgent exploration of novel therapeutic strategies. Our investigation revealed significant dysregulation of miR-18a-5p following influenza virus infection, observed consistently across both in vitro and in vivo models. Experimental evidence demonstrated that miR-18a-5p overexpression effectively inhibits H5N1 virus propagation through multiple mechanisms: (1) in vitro studies using A549 cells transfected with miR-18a-5p mimics showed a substantial reduction in viral replication; (2) animal models (mice and chickens) with elevated miR-18a-5p expression exhibited markedly suppressed AIV replication, reduced pathogenicity, and improved survival rates. The therapeutic potential of miR-18a-5p was particularly evident in its ability to significantly decrease mortality rates in H5N1-infected animals. Furthermore, this miRNA demonstrated robust protective effects against virus-induced lung damage, suggesting its dual role in both preventing and treating H5N1 infections. These findings position miR-18a-5p as a promising candidate for the development of broad-spectrum antiviral interventions, offering a novel strategic approach to combat this serious public health challenge. Full article

Long non-coding RNAs (lncRNAs) have been recognized for their crucial roles in the replication processes of various viruses. However, the specific functions and regulatory mechanisms of many lncRNAs in influenza A virus (IAV) pathogenesis remain poorly understood. In this study, we identified lncRNA THRIL and observed a significant reduction in its expression following IAV infection in A549 cells. The treatment of cells with the viral mimic poly (I:C), or with type I and type III interferons, resulted in a substantial decrease in THRIL expression. Furthermore, THRIL overexpression significantly enhanced IAV replication, while its silencing markedly reduced IAV replication. Additionally, IAV infection led to notable reductions in the expression levels of type I and type III interferons in cell lines overexpressing THRIL compared to control groups; conversely, cell lines with THRIL knockdown exhibited significantly higher interferon levels than control groups. Moreover, THRIL was found to inhibit the expression of several critical interferon-stimulated genes (ISGs), which are essential for an effective antiviral response. Notably, our findings demonstrated that THRIL impaired the activation of IRF3, a key transcription factor in the interferon signaling pathway, thereby suppressing host innate immunity. These results highlight THRIL’s potential as a therapeutic target for antiviral strategies. Full article