The non-template functions of helper virus RNAs create optimal replication conditions to enhance the proliferation of satellite RNAs.

As a type of parasitic agent, satellite RNAs (satRNAs) rely on cognate helper viruses to achieve their replication and transmission. During the infection of satRNAs, helper virus RNAs serve as templates for synthesizing viral proteins, including the replication proteins essential for satRNA replication. However, the role of non-template functions of helper virus RNAs in satRNA replication remains unexploited.

Identification of Host Factors Interacting with a γ-Shaped RNA Element from a Plant Virus-Associated Satellite RNA.

Previously, we identified a highly conserved, γ-shaped RNA element (γRE) from satellite RNAs of cucumber mosaic virus (CMV), and we determined γRE to be structurally required for satRNA survival and the inhibition of CMV replication. It remains unknown how γRE biologically functions. In this work, pull-down assays were used to screen candidates of host factors from plants using biotin-labeled γRE as bait.

Molecular Interaction of Nonsense-Mediated mRNA Decay with Viruses.

The virus-host interaction is dynamic and evolutionary. Viruses have to fight with hosts to establish successful infection. Eukaryotic hosts are equipped with multiple defenses against incoming viruses.

Movement Protein Mediates Systemic Necrosis in Tomato Plants with Infection of Tomato Mosaic Virus.

The necrogenic strain N5 of tomato mosaic virus (ToMV-N5) causes systemic necrosis in tomato cultivar Hezuo903. In this work, we mapped the viral determinant responsible for the induction of systemic necrosis. By exchanging viral genes between N5 and a non-necrogenic strain S1, we found that movement protein (MP) was the determinant for the differential symptoms caused by both strains.

Infection of Has Important Biological Impacts on a Fungal Host.

(NoNRV1) has been reported previously in the fungus , but its biological effects on its host are unknown. In this work, we isolated a strain 9-1 of from a chrysanthemum leaf and identified NoNRV1 infection in the isolated strain. The genome sequence of NoNRV1 identified here is highly homologous to that of the isolate HN-21 of NoNRV1 previously reported; thus, we tentatively designated the newly identified NoNRV1 as NoNRV1-ZJ.

The Weak Small RNA-Binding Activity of the 2b Proteins of Subgroup II Cucumber Mosaic Virus Strains Is Insufficient for RNA Silencing Suppression.

The 2b proteins encoded by cucumber mosaic virus (CMV) subgroup I strains suppress RNA silencing primarily by competitively binding small RNAs (sRNAs) in the host cell cytoplasm. Interestingly, 2b proteins encoded by CMV subgroup II strains accumulate predominantly in nuclei. Here we determined that whereas the 2b protein (Fny2b) of subgroup IA strain Fny-CMV is highly effective in suppressing both sense RNA-induced and inverted repeat-induced posttranscriptional gene silencing, the 2b protein (LS2b) of the subgroup II strain LS-CMV was not as effective.

Infection of Arabidopsis by cucumber mosaic virus triggers jasmonate-dependent resistance to aphids that relies partly on the pattern-triggered immunity factor BAK1.

Many aphid-vectored viruses are transmitted nonpersistently via transient attachment of virus particles to aphid mouthparts and are most effectively acquired or transmitted during brief stylet punctures of epidermal cells. In Arabidopsis thaliana, the aphid-transmitted virus cucumber mosaic virus (CMV) induces feeding deterrence against the polyphagous aphid Myzus persicae. This form of resistance inhibits prolonged phloem feeding but promotes virus acquisition by aphids because it encourages probing of plant epidermal cells.

Has an Xrn-Resistant, Translated Subgenomic RNA and a BTE 3' CITE.

(OPMV) is a recently discovered umbravirus in the family OPMV has a plus-sense genomic RNA (gRNA) of 4,241 nucleotides (nt) from which replication protein p35 and p35 extension product p98, the RNA-dependent RNA polymerase (RdRp), are expressed. Movement proteins p27 (long distance) and p28 (cell to cell) are expressed from a 1,440-nt subgenomic RNA (sgRNA2). A highly conserved structure was identified just upstream from the sgRNA2 transcription start site in all umbraviruses, which includes a carmovirus consensus sequence, denoting generation by an RdRp-mediated mechanism.

Viral Perturbation of Alternative Splicing of a Host Transcript Benefits Infection.

Pathogens disturb alternative splicing patterns of infected eukaryotic hosts. However, in plants it is unknown if this is incidental to infection or represents a pathogen-induced remodeling of host gene expression needed to support infection. Here, we compared changes in transcription and protein accumulation with changes in transcript splicing patterns in maize () infected with the globally important pathogen sugarcane mosaic virus (SCMV).

A conserved RNA structure is essential for a satellite RNA-mediated inhibition of helper virus accumulation.

As a class of parasitic, non-coding RNAs, satellite RNAs (satRNAs) have to compete with their helper virus for limited amounts of viral and/or host resources for efficient replication, by which they usually reduce viral accumulation and symptom expression. Here, we report a cucumber mosaic virus (CMV)-associated satRNA (sat-T1) that ameliorated CMV-induced symptoms, accompanied with a significant reduction in the accumulation of viral genomic RNAs 1 and 2, which encode components of the viral replicase. Intrans replication assays suggest that the reduced accumulation is the outcome of replication competition.

Heterologous Replicase from Cucumoviruses can Replicate Viral RNAs, but is Defective in Transcribing Subgenomic RNA4A or Facilitating Viral Movement.

Interspecific exchange of RNA1 or RNA2 between the cucumoviruses (CMV) and (TAV) was reported to be non-viable in plants previously. Here we investigated viability of the reassortants between CMV and TAV in plants by -mediated viral inoculation. The reassortants were composed of CMV RNA1 and TAV RNA2 plus RNA3 replicated in the inoculated leaves, while they were defective in viral systemic movement at the early stage of infection.

Concerted action of two 3' cap-independent translation enhancers increases the competitive strength of translated viral genomes.

Several families of plant viruses evolved cap-independent translation enhancers (3'CITE) in the 3' untranslated regions of their genomic (g)RNAs to compete with ongoing cap-dependent translation of cellular mRNAs. Umbravirus Pea enation mosaic virus (PEMV)2 is the only example where three 3'CITEs enhance translation: the eIF4E-binding Panicum mosaic virus-like translational enhancer (PTE) and ribosome-binding 3' T-shaped structure (TSS) have been found in viruses of different genera, while the ribosome-binding kl-TSS that provides a long-distance interaction with the 5' end is unique. We report that the PTE is the key translation promoting element, but inhibits translation in cis and in trans in the absence of the kl-TSS by sequestering initiation factor eIF4G.

The interaction between endogenous 30S ribosomal subunit protein S11 and Cucumber mosaic virus LS2b protein affects viral replication, infection and gene silencing suppressor activity.

Cucumber mosaic virus (CMV) is a model virus for plant-virus protein interaction and mechanism research because of its wide distribution, high-level of replication and simple genome structure. The 2b protein is a multifunctional protein encoded by CMV that suppresses RNA silencing-based antiviral defense and contributes to CMV virulence in host plants. In this report, 12 host proteins were identified as CMV LS2b binding partners using the yeast two-hybrid screen system from the Arabidopsis thaliana cDNA library.

An improved cucumber mosaic virus-based vector for efficient decoying of plant microRNAs.

We previously devised a cucumber mosaic virus (CMV)-based vector system carrying microRNA target mimic sequences for analysis of microRNA function in Arabidopsis thaliana. We describe an improved version in which target mimic cloning is achieved by annealing two partly-overlapping complementary DNA oligonucleotides for insertion into an infectious clone of CMV RNA3 (LS strain) fused to the cauliflower mosaic virus-derived 35S promoter. LS-CMV variants carrying mimic sequences were generated by co-infiltrating plants with Agrobacterium tumefaciens cells harboring engineered RNA3 with cells carrying RNA1 and RNA2 infectious clones.

Using a viral vector to reveal the role of microRNA159 in disease symptom induction by a severe strain of Cucumber mosaic virus.

In transgenic Arabidopsis (Arabidopsis thaliana), expression of the Cucumber mosaic virus (CMV) 2b silencing suppressor protein from the severe subgroup IA strain Fny disrupted microRNA (miRNA)-regulated development but orthologs from mild subgroup II strains (Q and LS) did not, explaining strain-specific differences in symptom severity. However, it is unknown which miRNAs affected by Fny2b critically affect viral symptoms. Observations that Fny2b-transgenic plants phenocopy microRNA159ab (mir159ab) mutant plants and that Fny2b altered miR159ab-regulated transcript levels suggested a role for miR159ab in elicitation of severe symptoms by Fny-CMV.

A trio of viral proteins tunes aphid-plant interactions in Arabidopsis thaliana.

Background: Virus-induced deterrence to aphid feeding is believed to promote plant virus transmission by encouraging migration of virus-bearing insects away from infected plants. We investigated the effects of infection by an aphid-transmitted virus, cucumber mosaic virus (CMV), on the interaction of Arabidopsis thaliana, one of the natural hosts for CMV, with Myzus persicae (common names: 'peach-potato aphid', 'green peach aphid').

Methodology/principal Findings: Infection of Arabidopsis (ecotype Col-0) with CMV strain Fny (Fny-CMV) induced biosynthesis of the aphid feeding-deterrent 4-methoxy-indol-3-yl-methylglucosinolate (4MI3M).

Self-interaction of the cucumber mosaic virus 2b protein plays a vital role in the suppression of RNA silencing and the induction of viral symptoms.

The cucumber mosaic virus (CMV) 2b protein is an RNA silencing suppressor protein that can also play direct and indirect roles in symptom induction. Previous work has shown that a hybrid virus, FRad35(2b) -CMV (renamed here as CMV-FRad2b-Pro), generated by replacement of the 2b gene of strain Fny-CMV with that from Rad35-CMV, displays markedly lower pathogenicity than Fny-CMV on Nicotiana species. However, the replacement of proline with leucine at position 55 of the 2b protein of CMV-FRad2b-Pro (protein Rad2b-Pro) created a virus (CMV-FRad2b-Leu) that induced severe symptoms.

Analysis of tomato microRNAs expression profile induced by Cucumovirus and Tobamovirus infections.

MicroRNAs (miRNAs) are a class of small RNAs that affect the morphological and physiological development of plants. In recent years, there is accumulating evidence that miRNAs are involved in defense mechanism of host plants. Therefore, investigating the alteration of miRNAs expression profiles after virus infection will provide new insights for understanding the sophisticated virus-host plant interaction.

A novel double-stranded RNA virus detected in Primula malacoides is a plant-isolated partitivirus closely related to partitivirus infecting fungal species.

A novel virus was detected in ornamental plants of Primula malacoides Franch exhibiting typical yellow-edge symptoms. Two double-stranded RNA (dsRNA) segments, of 2390 bp and 2344 bp, respectively, were extracted from plant tissues, and these same dsRNAs were detected from purified virions of about 35 nm in diameter. The two dsRNAs, putatively encoding partitivirus-related RNA-dependent RNA polymerase and capsid protein, were sequenced.

The 2b protein and the C-terminus of the 2a protein of cucumber mosaic virus subgroup I strains both play a role in viral RNA accumulation and induction of symptoms.

Two chimeras of cucumber mosaic virus (CMV), FCb7(2b)-CMV and FRad35(2b)-CMV, with the 2b genes of strains Cb7-CMV and Rad35-CMV, respectively, in an Fny-CMV background, gave different responses on Nicotiana glutinosa: FCb7(2b)-CMV induced systemic necrosis while FRad35(2b)-CMV caused only mild mosaic. This differential virulence was attributable to the nature of amino acid 55 of their 2b proteins. However, sequence analysis revealed that Leu(55) of the 2b protein was necessary but not sufficient for FCb7(2b)-CMV to induce systemic necrosis.