P1 Protein of Cocksfoot Mottle Virus is Indispensable for the Systemic Spread of the Virus

Meier, Merike; Paves, Heiti; Olspert, Allan; Tamm, Tiina; Truve, Erkki

doi:10.1007/s11262-005-6917-x

Cited by 25 publications

(22 citation statements)

References 26 publications

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“…3A), the CfMV icDNA (Meier et al, 2006) was linearized with Cfr42I, and the cohesive ends were filled by T4 DNA polymerase (Fermentas) treatment. RGMoV cDNA2 digested with Bsp68I and XmaJI was ligated into CfMV icDNA, cut by Cfr42I and XmaJI to create pT7CfMV:RGMoVrek2.…”

Section: Plasmidsmentioning

confidence: 99%

An attempt to identify recombinants between two sobemoviruses in doubly infected oat plants

Meier

Truve

2006

Environ. Biosafety Res.

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Recombination in RNA viruses is considered to play a major role as a driving force in virus variability to counterbalance loss in fitness that can be due to the accumulation of detrimental mutations. Studies on mixed infections are pertinent for understanding the role of recombination in virus evolution. They also provide important baseline information for studying the biosafety of plants expressing viral sequences. To investigate the possibility of RNA recombination occurrence between two sobemoviruses under little or no selection pressure, we co-infected test plants with Cocksfoot mottle virus (CfMV) and Ryegrass mottle virus (RGMoV). CfMV and RGMoV were selected because of their overlapping host range and geographical distribution. First, symptom development of both viruses in barley (Hordeum vulgare) and oat (Avena sativa) was examined. Both viruses generated quite strong infection symptoms in oat, but synergism was not detected. RGMoV was lethal for barley, whereas CfMV infection in barley was nearly symptomless. RT-PCR analysis revealed 100% infection with both viruses in oat but not in barley. Therefore, an RNA recombination study of CfMV and RGMoV was performed in oat. 105 plants were co-inoculated with both viruses and putative recombinational hot spot regions were screened for recombination events by RT-PCR analysis at a sensitivity level down to 0.1-100 pg of viral genomic RNA. No recombination events between the two sobemoviruses were detected.

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Section: Plasmidsmentioning

confidence: 99%

An attempt to identify recombinants between two sobemoviruses in doubly infected oat plants

Meier

Truve

2006

Environ. Biosafety Res.

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“…The 5¢-ends of genomes start with an untranslated region, followed by short ORF1, that code for 109-186 residue-long sobemovirus proteins with low similarity to each other [4]. The ORF1 coded proteins have been suggested to have a role in systemic infection [5] and in suppression of posttranscriptional gene silencing [6]. The 3¢-proximally located sobemovirus ORFs code for coat proteins (CP) with a comparably low sequence identity (16-31%).…”

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confidence: 99%

The Ryegrass mottle virus genome codes for a sobemovirus 3C-like serine protease and RNA-dependent RNA polymerase translated via −1 ribosomal frameshifting

2007

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In the course of sobemovirus gene cloning the complete genome of Ryegrass mottle virus (RGMoV) was sequenced. Sequence analysis revealed differences including missing and extraneous nucleotides in comparison to the previously published sequence (Zhang, Toriyama, Takanashi, J. Gen. Plant Pathol. 67, 63 (2001)). A gene coding for a typical sobemovirus 3C-like serine protease was identified in ORF2a after multiple sequence alignment analysis. The newly identified 57-amino-acid stretch in ORF2a showed similarities ranging from 38.5 to 50.9% among sequenced genes of sobemovirus proteases. ORF analysis of the RGMoV polyprotein coding sequence demonstrated the arrangement of ORF2b coding for RNA-dependent RNA polymerase (RdRP) in the -1 frame in regard to ORF2a. The localization of conserved among sobemoviruses slippery sequence (UUUAAAC) at the 3'-end of ORF2a suggests the translation of RdRP via a -1 ribosomal frameshifting mechanism, allowing to include the RGMoV in the sobemovirus group with a Cocksfoot mottle virus-like (CfMV-like) genome organization.

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“…It was previously reported that P1 of CfMV is indispensable for virus movement and accumulation in oats [19] and that it is a suppressor of RNA silencing [20]. However, it still remains unclear whether P1 facilitates virus spread as an RNA silencing suppressor or as a member of the movement RNP complex.…”

Section: Discussionmentioning

confidence: 99%

Cocksfoot mottle virus coat protein is dispensable for the systemic infection

Olspert

Kamsol

Sarmiento

et al. 2014

Virol J

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BackgroundThe Sobemovirus genome consists of polycistronic single-stranded positive-sense RNA. The first ORF encodes P1, a suppressor of RNA silencing required for virus movement. The coat protein (CP) is expressed from the 3′ proximal ORF3 via subgenomic RNA. In addition to its structural role, the CP of some sobemoviruses has been reported to be required for systemic movement and to interact with P1. The aim of this study was to analyse the role of Cocksfoot mottle virus (CfMV) CP in the suppression of RNA silencing and virus movement.MethodsAgrobacterium-mediated transient expression method was used for testing CfMV CP capacity to suppress RNA silencing. CP substitution and deletion mutants were generated to examine the role of this protein in CfMV infection, using three host plants (oat, barley and wheat). The viral movement was characterised with CfMV expressing EGFP fused to the C-terminus of CP.ResultsIn the current study we show that CfMV CP is an additional RNA silencing suppressor. Interestingly, we observed that all CP mutant viruses were able to infect the three tested host plants systemically, although usually with reduced accumulation. CfMV expressing EGFP was detected in epidermal and mesophyll cells of inoculated leaves. Although EGFP fluorescence was not detected in upper leaves, some plants displayed CfMV symptoms. Analysis of the upper leaves revealed that the viruses had lost the EGFP sequence and sometimes also most of the CP gene.ConclusionsThe present study demonstrates that CfMV CP suppresses RNA silencing but, surprisingly, is dispensable for systemic movement. Thus, CfMV does not move as virion in the tested host plants. The composition of the movement RNP complex remains to be elucidated.

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P1 Protein of Cocksfoot Mottle Virus is Indispensable for the Systemic Spread of the Virus

Cited by 25 publications

References 26 publications

An attempt to identify recombinants between two sobemoviruses in doubly infected oat plants

An attempt to identify recombinants between two sobemoviruses in doubly infected oat plants

The Ryegrass mottle virus genome codes for a sobemovirus 3C-like serine protease and RNA-dependent RNA polymerase translated via −1 ribosomal frameshifting

Cocksfoot mottle virus coat protein is dispensable for the systemic infection

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