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12 recordsLinked to original sources
PubMed2026

Hybridization capture increases on-target nanopore sequencing of plant RNA tobamovirus- derived cDNA libraries.

High-throughput sequencing (HTS) can support plant virus surveillance, but host nucleic acids often reduce on-target read recovery. We evaluated a targeted hybridization-capture workflow in which barcoded double-stranded cDNA (ds-cDNA) libraries generated from plant RNA extracts spiked with lyophilized tobamovirus-positive controls were enriched before Oxford Nanopore sequencing. Biotinylated probes targeted conserved regions of cucumber green mottle mosaic virus (CGMMV), species Tobamovirus viridimaculae; pepper mild mottle virus (PMMoV), species Tobamovirus capsici; and tobacco mosaic virus (TMV), species Tobamovirus tabaci. Across four pairs per virus, relative target-read abundance increased after capture from 0.76 ± 0.33% to 37.62 ± 15.72% for CGMMV, 8.16 ± 3.86% to 24.68 ± 12.34% for PMMoV, and 15.62 ± 10.40% to 36.83 ± 30.33% for TMV. Exact two-sided Wilcoxon signed-rank tests yielded P = 0.125 for each virus; with four nonzero differences in a common direction, this was the minimum attainable two-sided P value. Genome-coverage breadth was maintained. Retrospective duplex qPCR supported an increased virus-to-18S ratio for CGMMV, showed a variable PMMoV response, and showed a decreased virus-to-18S ratio for TMV because the 18S signal shifted earlier by as much as or more than the TMV signal. The findings provide proof-of-concept evidence for target-dependent library enrichment but do not establish analytical sensitivity, diagnostic performance, or field validity. Validation with naturally infected, low-titer, and mixed-infection samples and comparison with simpler targeted workflows are required.

biosecurity↗
PubMed2026

Tobamoviruses: Advances in Molecular Biology, Host Interactions and Integrated Disease Management.

Tobamoviruses (viruses in the genus Tobamovirus, family Virgaviridae) lead to major yield losses in economically important crops around the world. In this review, we go beyond the canonical gene expression framework by integrating recent discoveries of reverse open reading frames (rORFs) on the negative-strand RNA. These rORFs have only been experimentally validated in cucumber green mottle mosaic virus (CGMMV), with predicted sequence-conserved homologs across a subset of the genus, including TMV, ToBRFV, and PMMoV. However, they are not universally present in all tobamoviruses. We systematically dissect the infection cycle-from disassembly and replication to cell-to-cell and systemic movement-with an emphasis on the host factors hijacked at each stage. We synthesize current understanding of plant antiviral immunity, focusing on RNA silencing and NLR receptor-mediated resistance as two pillars of defense, along with the transcription factors and microRNAs that orchestrate these responses. We critically evaluate the experimental evidence for both plant defenses and viral counter-strategies, noting that many mechanistic models derive from limited model systems. We further characterize host genetic resistance and susceptibility factors applicable to crop breeding. These resources include dominant NLR and non-NLR resistance, as well as recessive resistance derived from modified host susceptibility genes. We address how viral mutations, recombination and fitness trade-offs undermine resistance durability. We then evaluate their practical deployment through conventional breeding, the exploitation of quantitative resistance, and genome editing, and outline associated agronomic drawbacks and regulatory constraints. Using ToBRFV as a case study, we analyze its epidemiological traits and assess the current arsenal of surveillance tools, from field diagnostics to remote sensing. Finally, we survey management strategies across a spectrum of maturity. Some approaches, including sanitation protocols and conventionally bred resistant cultivars, have proven effective under field conditions. The first dsRNA-based biopesticide has recently been registered in China, while other biological control agents and low-risk chemical approaches remain largely at the experimental stage. We also discuss the bottlenecks that impede lab-to-field transition and highlight promising solutions such as precision breeding and evolution-oriented cultivar deployment. By bridging molecular virology, epidemiology, and integrated disease management, this review provides a critical, bench-to-field framework for the sustainable control of tobamoviruses.

TMV↗
PubMed1977

Particles produced during a mixed infection by two tobamoviruses contain coat proteins of both viruses.

Particles from plants mixedly infected with two tobamoviruses, whose particles differ in density, were all of a single, intermediate density, suggesting that they contain both coat proteins and that the proteins occur in the same proportion in all particles. Plants inoculated with the genome-containing particles of one of the tobamoviruses together with the noninfective, short, coat protein messenger-containing particles of the other yielded only particles with the density of the first;.there was no evidence of complementation.

Mosaic Viruses↗
PubMed1976

In vitro translation of polyribosome-associated RNAs from tobamovirus-infected plants.

RNAs associated with polyribosomes in plants infected with the U2 strain of tobacco mosaic virus (TMV) or with sunnhemp mosaic virus have been isolated. Most are about 0.35 X 10(6) daltons in weight. They translate efficiently in vitro to produce their respective coat proteins which were identified by their serological behavior and peptide composition. They also reassemble in vitro with coat protein. The coat protein of sunnhemp mosaic virus reassembles more quickly than that of TMV U2.

Cell-Free System↗
PubMed1976

Translation in vitro of artificially produced fragments of a tobamovirus genome.

Particles of the U2 strain of tobacco mosaic virus (TMV) were partly disassembled by SDS, treated with RNases and then phenol, and yielded RNA molecules one quarter to half the size of the intact virus genome. These molecules, when translated in vitro, produced the coat protein of the virus. Reassembly experiments indicated that the active messenger molecules were those that most rapidly reassembled with coat protein; the rate of reassembly was greatly diminished by treatment with spleen phosphodiesterase. Particles of sunnhemp mosaic virus (the bean strain of TMV) resist disassembly by detergent much more than those of the U2 strain of TMV.

Cell-Free System↗
PubMed1976

On the nature of the difference in the densities of the particles of two tobamoviruses.

Particles of sunnhemp mosaic virus (SHMV) are denser than those of the U2 strain of tobacco mosaic virus (T2MV) when their densities are estimated by equilibrium centrifugation in gradients of either cesium chloride or Metrizamide; in cesium chloride the densities are 1.318 and 1.307 g/ml, and in Metrizamide they are 1.249 and 1.240 g/ml. Experiments with particles reassembled from homologous or heterologous mixtures of the RNAs and coat proteins of the viruses show that the difference in their densities is determined by their coat proteins. The disassembled coat proteins of the two viruses have the same density, but polymerized SHMV protein is less dense than polymerized T2MV protein. Particles reassembled from homologous or heterologous mixtures of the RNAs and coat proteins of the viruses have the density of the nucleoprotein particles used as the source of protein. The density difference of the two virus nucleoproteins therefore reflects the different behavior of the two proteins on assembly with RNA.

Centrifugation, Density Gradient↗
PubMed1976

Mixed infection with two tobamoviruses: the formation of particles containing the coat protein messenger RNAs of either virus.

Plants mixedly infected with the U2 strain of tobacco mosaic virus (T2MV) and sunnhemp mosaic virus (SHMV) and grown at 35 degrees, yield particles of the same modal lengths (300 and 40 nm) as those found in plants singly infected with SHMV, but not in plants infected with T2MV, which yield only the long particles. At least some of the particles produced in mixedly infected plants contain coat proteins of both viruses. When RNAs from these particles are translated in vitro the coat proteins of both viruses are produced, although when a mixture of RNAs from particles of SHMV and T2MV, grown separately, are translated in vitro only SHMV protein is produced. These and other results suggest that the short particles produced in mixedly infected plants contain both coat protein messengers.

Antigens, Viral↗
PubMed2026

The durable resistance gene Tm-22 remains partially resistant to tomato brown rugose fruit virus.

The tomato Tm-22 gene is a highly effective, and durable resistance gene in agriculture that has protected tomato production against viruses of the Tobamovirus genus, such as tomato mosaic virus (ToMV) and tobacco mosaic virus (TMV) for over 60 years. This dominant R gene, originally sourced from wild tomato species (Solanum peruvianum), acts by recognizing the viral movement protein (MP) and triggering an immune response, often resulting in extreme resistance (ER). However, this durable protection is challenged by a recently emerged new tobamovirus named tomato brown rugose fruit virus (ToBRFV, Tobamovirus fructirugosum). ToBRFV-encoded MP is responsible for ER breakdown. Here, we present evidence that while ToBRFV can evade Tm-22-mediated ER, Nicotiana benthamiana and tomato plants carrying Tm-22 still remain partially resistant to ToBRFV. We show that ToBRFV MP is recognized by and interacts with Tm-22 to trigger an attenuated hypersensitive response. Moreover, we discover that overexpression of Tm-22 can enhance resistance to ToBRFV. These findings demonstrate the practical value of Tm-22 in ongoing resistance breeding programs and open a potential avenue to restore Tm-22 immunity through upregulation of Tm-22 expression.

Solanum lycopersicum↗
PubMed2026

Strain Diversity and Resistance to Cucumber Green Mottle Mosaic Virus (CGMMV) in Cucumber.

Cucumber green mottle mosaic virus (CGMMV) is a tobamovirus that causes disease in cucumber crops worldwide, leading to significant economic losses. To study the variability of CGMMV in southeastern Spain, partial genome sequences were obtained from isolates collected in 2017 and 2020 from cucumber crops. Phylogenetic analyses revealed that isolates clustered into two major groups, Asian (AS)-like and European (EU)-like CGMMV isolates. These two groups coexisted in the same area, crops, and even individual plants, although the AS type predominated. The accumulation and symptom expression of molecularly cloned isolates from these two groups were assessed in two cucumber cultivars (resistant and susceptible) under both summer and winter conditions. An in planta antagonistic interaction was detected between the AS and EU isolates, in which the accumulation of CGMMV-EU was suppressed during mixed infections. A multivariate analysis did not identify statistically significant differences because of variations in environmental conditions. Unlike CGMMV-EU, CGMMV-AS did not show significant differences in accumulation based on the plant genotype. To further investigate this, the response to CGMMV-AS infection was analyzed in additional susceptible and resistant cultivars. All cultivars appeared to be similarly susceptible to CGMMV-AS, in contrast to CGMMV-EU, which accumulated to a much lower extent in resistant compared with susceptible plants. These results reinforce the need to continue epidemiological surveillance, identify new sources of resistance, and implement strict control of infected seed trade, given the growing threat that CGMMV-AS isolates pose to cucumber cultivation.

agroinfectious clone↗
PubMed2026

Infectious Clone Development of Zucchini Green Mottle Mosaic Virus Infecting Medicinal Plant Trichosanthes kirilowii and Establishment of a Serological Assay System.

Trichosanthes kirilowii has long been cultivated for application in traditional Chinese medicine. In this study, we identified two isolates of zucchini green mottle mosaic virus (ZGMMV; species Tobamovirus cucurbitae) from T. kirilowii plants. We determined the complete genome sequences of the ZGMMV isolates named ZGMMV-GL-1 and ZGMMV-GL-2. Each ZGMMV genome was 6,517 nucleotides in length, with only a single nucleotide variation detected between two sequences. Sequence analysis revealed that the ZGMMV isolates from this study shared 88.07 to 91.62% nucleotide identity with five other ZGMMV isolates deposited in GenBank. Phylogenetic analysis indicated that ZGMMV isolates can be clustered into two distinct groups; our two isolates shared the highest sequence similarity with the ZGMMV isolate from Nanning (GenBank accession number MF066176) and clustered within Group II. The coat protein (CP) gene was cloned from ZGMMV-infected T. kirilowii samples, and the CPZGMMV was expressed using the pET28(a) vector. Specific polyclonal antiserum CPZGMMV was generated by immunizing rabbits with the purified protein, and its sensitivity was determined to be satisfactory. Leveraging the high accuracy and sensitivity of the CPZGMMV antiserum, we developed a rapid, precise, and scalable diagnostic method for ZGMMV. We then constructed the full-length cDNA clones (ZGMMV-GL-1 and ZGMMV-GL-2). Additionally, the ZGMMV cDNA infectious clones from T. kirilowii were also able to infect Nicotiana benthamiana and Cucumis sativus systemically, inducing rough-textured and curled leaves in N. benthamiana and mosaic symptoms in C. sativus and T. kirilowii. In this study, we produced an antiserum against the ZGMMV CP and developed a sensitive, rapid, and reliable diagnostic assay, which lays a technical foundation for the detection and monitoring of ZGMMV. Therefore, the establishment of the ZGMMV infectious clone facilitates further research on viral protein functions, plant-pathogen interactions, and the formulation of effective ZGMMV management strategies.

Nicotiana benthamiana↗
PubMed2025

Tm-1 back in business: an allele from Solanum pennellii accessions plays a major role in ToBRFV resistance.

The Tm-1 allele from Solanum pennellii accessions together with an additional, likely recessive, locus are required for complete ToBRFV resistance. The Tobamovirus Tomato Brown Rugose Fruit Virus (ToBRFV) poses a significant threat to global tomato production. ToBRFV is a mechanically transmitted virus containing a single-stranded positive sense RNA genome. Disease symptoms include brown, rough patches on fruit surfaces, leaf mosaicism and shape abnormalities, and, in advanced stages, total collapse of infected plants. ToBRFV was first detected in the Middle East in 2014 and has rapidly spread to multiple countries across Asia, Europe, and America. In recent years, numerous studies have focused on the identification of ToBRFV resistance traits that are suitable for tomato breeding programs. In this study, we identified five ToBRFV-resistant accessions of Solanum pennellii, a wild relative of cultivated tomato. We confirmed that the major gene controlling this resistance trait is the S. pennellii allele of Tm-1. Tm-1 was previously identified in S. habrochaites as a semidominant Tomato Mosaic Virus (ToMV) resistance gene. Our results show that full resistance to ToBRFV disease requires an additional undescribed locus. These results show the potential of S. pennellii as a novel source of resistance against ToBRFV.

Disease Resistance↗