Search Results (67)

Saffron (Crocus sativus L.) is a high-value crop vulnerable to potyvirus infections threatening its yield and quality. In this study, we combined Oxford Nanopore long-read sequencing with exploratory transcriptomic profiling to characterize the saffron virome and to describe expression profiles associated with two distinct infection histories: (i) saffron plants experimentally inoculated with cucumber mosaic virus (CMV; Cucumovirus CMV) and turnip mosaic virus (TuMV; Potyvirus rapae) under controlled greenhouse conditions, and (ii) saffron plants naturally infected by diverse viruses. We identified six plant-infecting viral families in both conditions, including Potyviridae, Geminiviridae, Caulimoviridae, Tymoviridae, Aspiviridae, and Partitiviridae. Transcriptomic profiling revealed distinct expression profiles associated with each infection background. Given the limitations of the experimental design, gene expression differences are interpreted descriptively. We describe pathway enrichments associated with antiviral responses. Naturally infected plants exhibited a broad-spectrum, tolerance-based response characterized by the upregulation of photosynthesis-related genes, calcium-mediated signaling components, and stress-responsive transcription factors. In contrast, virus-inoculated plants activated a targeted antiviral program involving RNA silencing, autophagy, ubiquitin-mediated proteolysis, and hormonal regulation. Both GO and KEGG enrichment analyses supported these findings, highlighting photosynthesis and metabolic flexibility in naturally infected plants versus hypersensitive response, RNA surveillance, and lignin biosynthesis in virus-inoculated plants. This work provides a comprehensive view of the saffron virome and offers a hypothesis-generating overview of transcriptional responses associated with natural versus experimental virus infections. These findings advance the understanding of the saffron virome and provide a valuable resource for breeding virus-resistant cultivars. Full article

Passion fruit (Passiflora edulis Sims) is an important economic fruit crop in Rwanda grown for both domestic consumption and export markets. However, viral diseases pose a significant threat to passion fruit production. Among these, passion fruit woodiness disease (PWD) is the most destructive, causing yield losses of up to 100%. A survey was carried out to assess the distribution of Ugandan passiflora virus (UPV; Potyvirus passiflorafricanse) in major passion fruit growing areas. UPV is one of the major viruses known to cause PWD. The incidence of viral symptoms observed in the field did not differ significantly among districts, ranging from 81% in Rusizi to 100% in Rwamagana. However, mean symptom severity scores varied significantly between districts, with the highest severity recorded in Kayonza (3.1) and the lowest in Rulindo (1.9). Serological analysis detected potyviruses in 44% of the total samples (n = 216), including 43% of symptomatic (n = 144) and 47% of asymptomatic (n = 72) leaf samples collected from passion fruit fields. Further analysis using Reverse-Transcription Polymerase Chain Reaction (RT-PCR) detected UPV in 56% of symptomatic (n = 126) and 53% of asymptomatic (n = 60) samples, corresponding to 55% of the total samples tested (n = 186). The virus was present in all surveyed districts, with UPV infection prevalence of 89% in Rusizi, 75% in Rwamagana, 74% in Karongi, 59% in Nyamagabe, 44% in Nyaruguru, 38% in Kayonza, and 30% in both Gakenke and Rulindo. Fifteen partial coat-protein gene sequences for the Rwandan isolates were obtained. The newly described Rwandan isolates shared 97–99% nucleotide (nt) identity with one another, 89–94% with previously reported Rwandan isolates, 81–97% with Ugandan isolates, and 80–82% with Kenyan UPV isolates, suggesting that the Rwandan virus population is relatively homogenous. Genetic distances among the 15 new UPV isolates and previously reported Rwandan, Ugandan, and Kenyan isolates were very short (0.01–0.03), indicating high sequence similarity. All Rwandan isolates clustered into a single major clade, together with some Ugandan and Kenyan isolates. This close genetic relationship suggests a common ancestry and the regional spread of a single dominant UPV lineage. These findings highlight the need to reinforce seed and planting-material certification systems, as well as the need to enhance farmer capacity through targeted training on viral disease identification and management practices. This is vital to limiting the spread of viral diseases that threaten income security among smallholder passion fruit farmers. Full article

CRISPR-Cas9 technology has opened new perspectives in genome editing of clonally, asexually propagated and polyploid plants by enabling multiple allelic gene edits. Traditional Agrobacterium- and particle bombardment-mediated transformations, which rely on integration of gene-editing transgene cassettes, have been efficiently applied to several plants; however, concerns about the acceptability of resultant edited transgenic genotypes make these methods less attractive for vegetatively propagated crops. We leveraged and optimized the CRISPR-Cas9/sgRNA-RNPs system for delivery into protoplasts of the hexaploid sweetpotato cultivar PI-318846, targeting eukaryotic translation initiation factor isoform 4E genes to enhance resistance to SPFMV potyviruses. To evaluate the efficiency of pre-assembled Cas9/sgRNA-RNP in sweetpotato transfection, single guide RNAs were designed to target putative host susceptibility genes: IbeIF4E, IbeIF(iso)4E, and IbCBP. Freshly isolated leaf protoplasts were subjected to CRISPR-CAS9-RNP PEG-mediated transfection under different parameters. Sweetpotato regenerants screened using PCR-RE-T7 assay, sequencing, and Inference CRISPR Edit analyses of target-site amplicons revealed the most efficient editing conditions utilizing 25% PEG with a 3:1 (15 µg:45 µg) ratio of Cas9/sgRNA-RNP for 25 min and 48 h incubation period. Different allelic InDels were obtained with editing efficiencies of 10–20% in regenerated plantlets, demonstrating that PEG-mediated CRISPR-RNP transfection system is key for advancing DNA-free editing tools in polyploid and vegetatively propagated crops. Full article

The soybean mosaic virus (SMV), a significant viral pathogen impacting soybean cultivation, leads to substantial yield losses and diminishes seed quality. In a prior study, we developed a targeted silencing vector using RNA interference (RNAi) technology targeting the CP gene, which codes for the viral coat proteins in the SMV genome. This vector was delivered into soybean plants through Agrobacterium-mediated transformation. In our current research, we utilized ongoing molecular characterization and resistance screening to identify four genetically pure lines that display moderate to high resistance to SMV. Additionally, the transgenic plants exhibited resistance to three other potyviruses: the bean common mosaic virus, the recombinant soybean mosaic virus, and the watermelon mosaic virus. Greenhouse and field trials conducted with these lines demonstrated that RNAi-mediated silencing of the CP gene significantly enhanced disease resistance. It is noteworthy that, in comparison to the receptor plants, the transgenic plants exhibited no significant differences in maturity, plant height, branching number, node number, pod number, or 100-seed weight. These results offer valuable genetic resources and theoretical support for molecular breeding strategies aimed at combating SMV in soybeans, as well as for RNAi-based methods to control plant viral infections. Full article

Cassava (Manihot esculenta) is a staple crop in sub-Saharan Africa threatened by several viral diseases. Here, we describe the genome sequence of a novel bipartite cheravirus (family Secoviridae) infecting cassava in the Democratic Republic of Congo and Tanzania. We designate the new virus “cassava Congo cheravirus”. Each RNA segment encodes a single polyprotein (P1 and P2 for RNA1 and RNA2, respectively), embedded with various putative cleavage sites (six and three in P1 and P2, respectively), consistent with members of the genus Cheravirus. We note two new features in the P1: (i) the presence of two domains, X1 and X2, upstream of the putative helicase region, which we also predict in other cheraviruses and (ii) the presence of a Maf/HAM1-like inosine triphosphatase (ITPase) domain, a rare motif among viruses only previously detected in three potyviruses and a torradovirus, all of which infect plants from the Euphorbia family. Phylogenetic analyses placed the virus firmly within the genus Cheravirus, with amino acid identities in the Pro-Pol and coat protein regions well below existing ICTV species thresholds, supporting its classification as a virus belonging to a new species in the Cheravirus genus. Spatially distinct isolates from Bas-Congo, South-Kivu, and Tanzania form three genetic clusters, with evidence of recombination in both RNA segments. These results expand the known diversity of cassava viruses and suggest possible adaptation to the cassava host via ITPase acquisition. Full article

Cowpea (Vigna unguiculata) is a crop of significant socioeconomic importance, particularly in the semi-arid regions of Africa and America. However, its productivity has been adversely affected by viral diseases, including the cowpea aphid-borne mosaic virus (CABMV), a single-stranded RNA virus. It is known that the VPg protein interacts with the host’s translation initiation factor (eIF4E), promoting viral replication. This study aimed to investigate the relationship between mutations in the cowpea eIF4E gene and resistance to CABMV. Twenty-seven cultivars were screened by PCR and bioassays for presence/absence of mutations associated with resistance or susceptibility to Potyviruses. Of the cultivars with mutations previously associated with susceptibility, 88.24% exhibited viral symptoms, while 62.5% associated with resistance remained asymptomatic. The in silico analyses revealed that non-synonymous mutations (Pro68Arg, Gly109Arg) alter the structure of the eIF4E protein, reducing its affinity to VPg. Molecular dynamics simulations also pointed to an enhanced structural stability of eIF4E in resistant cultivars and reinforced, for the first time, key mutations and the functional role of the eIF4E gene in resistance to CABMV in cowpea. Our results offer valuable insights for virus disease management and for genetic improvement programs for this important crop. Full article

Potyviruses (family Potyviridae, genus Potyvirus), including emerging ones, pose a growing threat to cucurbit production. This study presents the first virome analysis of severely symptomatic cucurbits in continental Croatia, combining high-throughput sequencing (HTS) and RT-PCR diagnostics. Zucchini, cucumber, and butternut squash plants with severe virus-like symptoms sampled in 2021–2022 were found to consistently host a complex of potyviruses, including watermelon mosaic virus (WMV), zucchini yellow mosaic virus (ZYMV), and Moroccan watermelon mosaic virus (MWMV)—the latter being newly reported in Croatia and representing likely its northernmost detection in Europe. Phylogenetic analysis classified WMV isolates as emerging strains of subgroup EM3 and ZYMV as subgroup A1, consistent with European lineages. Croatian MWMV isolates formed a distinct subclade within the Mediterranean group, raising questions about its diversification trajectory. The findings highlight the expanding range of MWMV and underscore the value of HTS for early detection of emerging threats. These results have critical implications for cucurbit disease management, indicating the need to re-evaluate resistance claims in commercial cultivars and implement stricter phytosanitary surveillance in Croatia. The potential role of climate change in facilitating virus spread via aphid vectors is discussed, warranting further risk assessment and international monitoring efforts. Full article

Our knowledge of the molecular data on viruses infecting potato (Solanum tuberosum) and its weeds in Indonesia still needs to be expanded. Thirteen potato leaves, together with one carrot (Daucus carota subsp. sativus) and one Oxalis latifolia leaves grew adjacent to potato fields were sampled in West, Central, and East Java Provinces of Indonesia to be tested using RT-PCR with universal primers to monitor the presence of potyviruses, carlaviruses, and begomoviruses in the surveyed regions. According to the test results and BLAST nucleotide analysis, four potato samples were found to be infected by potato virus Y (PVY, Potyvirus). All samples tested negative for carlaviruses and begomoviruses. Both phylogenetic trees constructed by MEGA11 software based on partial coat protein and partial coat protein + 3′-UTR sequences demonstrated that the four new PVY isolates belong to strain N. Nucleotide and amino acid homology analysis determined that all four new and 12 other strain N isolates registered in NBCI GenBank were identical at the observed genome region, suggested the same origin of Indonesian isolates. This study improved our understanding of the variation in PVY isolates in Indonesia and highlighted the need for tight surveillance since the country imports most of its tubers used as planting material. Full article

In the mid-1970s, it was revealed that the 5′ end of the RNA genome of poliovirus (PV) was covalently linked to a peptide called VPg (viral protein, genome-linked). Subsequently, VPgs have been found attached to many other viruses and even phages. This review summarizes the patterns of physicochemical properties that are conserved within the VPgs of plus-strand RNA viruses where short-peptide VPgs have been identified. Mutagenesis and structural data indicate the importance of a 5 aa conserved motif at the N-termini of picornaviral VPgs (around the tyrosine 3 residue, which forms a covalent bond to UMP and the RNA). Hidden Markov models have been used to find motifs and VPgs in additional genera of picornaviruses, as well as dicistroviruses in insects and comoviruses in plants. These latter VPgs are bound to the RNA termina through linkages to serine or threonine. The role of free VPg and VPgpU needs clarification, especially in light of multiple genome copies in many of the viruses. Lysine and other positively charged side chains are hallmarks of VPgs. These may contribute to interactions with the viral RNA, polymerase, membranes and cellular proteins. The larger protein VPgs from potyviruses and noroviruses/caliciviruses may also show some areas of similar properties to these small peptides. Full article

Potyviruses, a major group of plant viruses, utilize HC-Pro, a multifunctional protein, to suppress RNA silencing, a crucial plant defense mechanism. While HC-Pro’s role in RNA silencing suppression has been studied in several potyviruses, the specific mechanisms and interactions of HC-Pro from bean yellow mosaic virus (BYMV), a potyvirus with a broad host range, remain poorly understood. To address this knowledge gap, this study aimed to investigate the role of P1 and HC-Pro from BYMV in enhancing gene expression and suppressing RNA silencing in Nicotiana benthamiana. The findings revealed that BYMV HC-Pro significantly enhanced reporter transgene expression, likely through the suppression of RNA silencing pathways. This effect was further amplified by the presence of the P1 protein, another viral component. Analysis of HC-Pro mutants revealed that the conserved FRNK box within HC-Pro is crucial for its suppression activity and its ability to enhance gene expression. Furthermore, HC-Pro significantly downregulated the expression of key RNA silencing-related genes, including DCL2, DCL4, RDR6, AGO1-1, AGO1-2, and AGO2. These findings demonstrate that the BYMV P1::HC-Pro complex serves as a potent suppressor of RNA silencing and a promising tool for enhancing gene expression in plants. The results have significant implications for developing novel strategies in plant biotechnology, particularly for the production of high-value recombinant proteins. Full article

Viruses are a major pathogen challenging the sustainable production of cucurbits worldwide. Pumpkin and winter squash showed severe virus-like symptoms during the fall of 2022 and 2023 in Georgia, USA. Symptomatic leaves were collected from the field and processed for small RNA sequencing for virus identification using high-throughput sequencing (HTS). HTS analysis revealed the presence of two aphid-transmitted viruses (ATVs), zucchini yellow mosaic virus (ZYMV) and papaya ringspot virus (PRSV), along with three whitefly-transmitted viruses, cucurbit chlorotic yellows virus, cucurbit yellow stunting disorder virus, and cucurbit leaf crumple virus. The results of our study suggest a significant shift in ATV’s abundance in these two crops between 2022 and 2023. According to the qPCR data in the fall of 2022, pumpkins experience an incidence of 56.25% and 31.25% of PRSV and ZYMV, respectively. Similarly, winter squash shows an incidence of 50% and 32.14% of PRSV and ZYMV, respectively. Mixed infection of both viruses was also observed in these two crops. In 2023, we observed a predominance of ZYMV in pumpkin and winter squash (61.25% and 42.50%, respectively). However, PRSV was not detected in pumpkins, and it was detected at a negligible level (0.62%) in winter squash using qPCR. Phylogenetic analysis of ZYMV-encoded coat protein (CP) and helper component-protease (HC-Pro) from Georgia suggests a close relationship with the European isolates. Conversely, PRSV-encoded CP and NIa-VPg show a more diverse evolutionary history. Overall, this research will provide valuable insights into the dynamics of ZYMV and PRSV in pumpkin and winter squash crops within the southeastern United States. Full article

Over the past two decades, plant viral vectors have emerged as a powerful tool for the production of recombinant proteins in plants. Among the different plant viruses engineered to carry foreign genes of interest in their genomes, potyviruses have gained attention due to their polyprotein expression strategy and broad host range. To date, at least eleven different species belonging to the genus Potyvirus have been used for heterologous gene expression in both their natural and experimental hosts. This review article provides an overview of the current state of potyvirus-based plant viral vectors, discussing the advantages and limitations of these systems. We also discuss the future challenges and potential applications of potyvirus-based expression vectors, including the production of vaccines, nanoparticles, therapeutics, and metabolic engineering. Overall, we highlight the potential of potyvirus-based vectors as a versatile tool for recombinant protein production in plants. Full article

Wisteria vein mosaic virus (WVMV, Potyvirus wisteriae), a virus belonging to the genus Potyvirus, is responsible for Wisteria vein mosaic disease (WMD), a severe disease that affects Wisteria, a genus of garden plants acclaimed worldwide. Although probably originating in the Far East, WVMV infection was first reported in the US, and subsequently in numerous countries. Following the first molecular detection of an Italian isolate, WVMV Bari, its full-length genome was achieved using NGS barcoding technology. A PhyML phylogenetic analysis, supported by clustering algorithm validation, identified a clear separation between two phylogroups. One major clade comprised WVMV strains isolated from Wisteria spp. A second clade grouped three highly divergent strains, at the borderline species threshold, all found in non-wisteria hosts. Relying on a Relative Time Dated Tips (RTDT) molecular clock, the first emergence of WVMV clades has been traced back to around the 17th century. A network inference analysis confirmed the sharp separation between the two host-related phylogroups, also highlighting the presence of potential intermediate variants. Inter-population genetic parameters revealed a very high genetic differentiation in both populations, which was made reliable by statistically significant permutation tests. The migrant number (Nm) and fixation index (F_ST) evidenced a restricted gene flow and strong population structures. According to the dN/dS ratio and negative neutrality tests, it was derived that purifying selection at the expense of non-silent variants is underway within WVMV populations. Targeting WVMV evolutionary traits, the present effort raised interesting questions about the underestimated potential of this culpably neglected species to spread in economically relevant crops. The main intention of our study is, therefore, to propose an evolution-based analysis approach that serves as a case study to investigate how other potyviruses or newly emerging viruses may spread. Full article

In agriculture, new and sustainable strategies are increasingly demanded to integrate the traditional management of viral diseases based on the use of virus-free propagation materials and resistant or tolerant cultivars and on the control of insect vectors. Among the possible Integrated Pest Management (IPM) approaches, organic biostimulants have shown promising results in enhancing plant tolerance to virus infections by improving plant fitness and productivity and modulating metabolic functions. In this study, the combination of two organic biostimulants, Alert D-Max and Resil EVO Q, composed of seaweed and alfalfa extracts, enzymatic hydrolysates, and micronized zeolite, was applied on the leaves and roots of zucchini squashes, both healthy and infected by zucchini yellow mosaic virus (ZYMV). Four applications were scheduled based on ZYMV inoculation timing, and plant vegetative and reproductive parameters were recorded along with the virus titre and symptom severity. The modulation of the expression of specific genes potentially involved in pattern-triggered immunity (PTI), systemic acquired resistance (SAR), and oxidative stress defence pathways was also investigated. Besides increasing the general fitness of the healthy plants, the biostimulants significantly improved the production of flowers and fruits of the infected plants, with a potential positive impact on their productivity. The repeated biostimulant applications also led to a one-tenth reduction in ZYMV titre over time and induced a progressive slowdown of symptom severity. Genes associated with SAR and PTI were up-regulated after biostimulant applications, suggesting the biostimulant-based priming of plant defence mechanisms. Due to the observed beneficial effects, the tested biostimulant mix can be an effective component of the IPM of cucurbit crops, acting as a sustainable practice for enhancing plant fitness and tolerance to potyviruses. Full article

Potyvirus diseases are one of the main challenges facing the production of yam (Dioscorea spp.). The objective of this study was to identify the potyviruses present in the Dioscorea spp. germplasm collection at Instituto de Investigaciones de Viandas Tropicales (INIVIT) to establish methodologies for the characterization of the associated diseases. For this purpose, immunochemical and molecular methods were used to identify the potyviruses present. The symptomatology of Dioscorea spp. at INIVIT’s germplasm collection was described. In addition, the severity and incidence in the germplasm collection and production areas were evaluated. As a result, the first report of yam mosaic virus (Potyvirus yamtesselati) and yam mild mosaic virus (Potyvirus yamplacidum) in Cuba is presented. The existence of resistant, tolerant, and susceptible cultivars to potyvirus-associated diseases in the germplasm collection was detected, and the incidence of these diseases was higher than 64% in the production areas evaluated. This study represents a step forward in the establishment of certification programs for propagating material of Dioscorea spp. in Cuba. Full article