<i>Plum Pox Virus</i>
            6K1 Protein Is Required for Viral Replication and Targets the Viral Replication Complex at the Early Stage of Infection

Cui, Hongguang; Wang, Aiming

doi:10.1128/jvi.00024-16

Cited by 81 publications

(86 citation statements)

References 55 publications

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“…Another interesting case is the nonsynonymous mutation 6K1/T1126M (OEOEOEOE). The 6K1 small peptide is required for viral replication and colocalizes with chloroplast-bound viral replicase elements 6K2 and NIb at early stages of infection (38). The fitness effects resulting from the interaction between this particular mutation at 6K1 and all four other mutations were always host dependent.…”

Section: Resultsmentioning

confidence: 90%

Effect of Host Species on Topography of the Fitness Landscape for a Plant RNA Virus

Cervera

Lalić

Elena

2016

J Virol

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Adaptive fitness landscapes are a fundamental concept in evolutionary biology that relate the genotypes of individuals to their fitness. In the end, the evolutionary fate of evolving populations depends on the topography of the landscape, that is, the numbers of accessible mutational pathways and possible fitness peaks (i.e., adaptive solutions). For a long time, fitness landscapes were only theoretical constructions due to a lack of precise information on the mapping between genotypes and phenotypes. In recent years, however, efforts have been devoted to characterizing the properties of empirical fitness landscapes for individual proteins or for microbes adapting to artificial environments. In a previous study, we characterized the properties of the empirical fitness landscape defined by the first five mutations fixed during adaptation of tobacco etch potyvirus (TEV) to a new experimental host, Arabidopsis thaliana. Here we evaluate the topography of this landscape in the ancestral host Nicotiana tabacum. By comparing the topographies of the landscapes for the two hosts, we found that some features remained similar, such as the existence of fitness holes and the prevalence of epistasis, including cases of sign and reciprocal sign epistasis that created rugged, uncorrelated, and highly random topographies. However, we also observed significant differences in the fine-grained details between the two landscapes due to changes in the fitness and epistatic interactions of some genotypes. Our results support the idea that not only fitness tradeoffs between hosts but also topographical incongruences among fitness landscapes in alternative hosts may contribute to virus specialization. IMPORTANCEDespite its importance for understanding virus evolutionary dynamics, very little is known about the topography of virus adaptive fitness landscapes, and even less is known about the effects that different host species and environmental conditions may have on this topography. To bridge this gap, we evaluated the topography of a small fitness landscape formed by all genotypes that result from every possible combination of the first five mutations fixed during adaptation of TEV to the novel host A. thaliana. To assess the effect that host species may have on this topography, we evaluated the fitness of every genotype in both the ancestral and novel hosts. We found that both landscapes share some macroscopic properties, such as the existence of holes and being highly rugged and uncorrelated, yet they differ in microscopic details due to changes in the magnitude and sign of fitness and epistatic effects. T he effects of mutations can be influenced by their interactions with other mutations, with the environment, or both. Epistatic interactions among genetic loci determine the ruggedness of fitness landscapes. In the absence of epistasis, landscapes are single peaked and smooth (1). For such simple landscapes, predicting the result of evolution is an easy task. In contrast, epistatic interactions create curvature in the lands...

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Section: Resultsmentioning

confidence: 90%

Effect of Host Species on Topography of the Fitness Landscape for a Plant RNA Virus

Cervera

Lalić

Elena

2016

J Virol

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“…A TuMV infectious clone TuMV6K2‐mCherry//GFP‐HDEL that contains a separate expression of cassette for expression of GFP fused with an ER retention signal HDEL was coinfiltrated with either an NbEXPA1 expression vector or an empty vector (mock) into the fully expanded leaves of N. benthamiana plants at the 6‐ to 7‐leaf stage. As potyviral intercellular movement takes place usually at 96 hpi (Cui and Wang, ), viral replication may be assessed by analysis of the viral RNA level in primarily infected cells by sampling inoculated leaf tissues at 72 hpi or an earlier time point. In this study, the inoculated leaves were collected from mock‐infected and TuMV‐infected plants at 54 hpi and TuMV genomic RNA levels were determined by qRT‐PCR using the GFP transcripts as an internal control.…”

Section: Resultsmentioning

confidence: 99%

“…When this clone is introduced into a compatible host plant, primarily infected cells would emit green and red fluorescence, and secondarily infected cells would emit green fluorescence only. N. benthamiana leaves were agroinfiltrated with NbEXPA1 and pVPH‐GFP//mCherry‐HDEL and the agroinfiltrated leaf tissues were collected at 54 hpi to assess viral RNA replication in the primarily infected cells (Cui and Wang, ). qRT‐PCR was conducted using mCherry transcripts as an internal control to determine PPV RNA accumulation.…”

Section: Resultsmentioning

confidence: 99%

“…Potyviral 6K2 protein plays a central role in the remodeling of the endoplasmic reticulum (ER) and formation of the membrane‐associated viral replication complex (VRC) (Wei and Wang, ; Wei et al ., 2010a; Grangeon et al ., ). The VRC contains viral RNA, viral proteins (6K1, 6K2, P3, CI, VPg, NIa‐Pro, and NIb) and host proteins (Beauchemin and Laliberté, ; Beauchemin et al ., ; Dufresne et al ., ; Thivierge et al ., ; Cotton et al ., ; Cui et al ., ; Huang et al ., ; Wei et al ., ; Xiong and Wang, ; Wan et al ., ; Cui and Wang, ; Li et al ., 2016b).…”

Section: Introductionmentioning

confidence: 99%

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NbEXPA1, an α‐expansin, is plasmodesmata‐specific and a novel host factor for potyviral infection

Park

Renaud

et al. 2017

The Plant Journal

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Plasmodesmata (PD), unique to the plant kingdom, are structurally complex microchannels that cross the cell wall to establish symplastic communication between neighbouring cells. Viral intercellular movement occurs through PD. To better understand the involvement of PD in viral infection, we conducted a quantitative proteomic study on the PD-enriched fraction from Nicotiana benthamiana leaves in response to infection by Turnip mosaic virus (TuMV). We report the identification of a total of 1070 PD protein candidates, of which 100 (≥2-fold increase) and 48 (≥2-fold reduction) are significantly differentially accumulated in the PD-enriched fraction, when compared with protein levels in the corresponding healthy control. Among the differentially accumulated PD protein candidates, we show that an α-expansin designated NbEXPA1, a cell wall loosening protein, is PD-specific. TuMV infection downregulates NbEXPA1 mRNA expression and protein accumulation. We further demonstrate that NbEXPA1 is recruited to the viral replication complex via the interaction with NIb, the only RNA-dependent RNA polymerase of TuMV. Silencing of NbEXPA1 inhibits plant growth and TuMV infection, whereas overexpression of NbEXPA1 promotes viral replication and intercellular movement. These data suggest that NbEXPA1 is a host factor for potyviral infection. This study not only generates a PD-proteome dataset that is useful in future studies to expound PD biology and PD-mediated virus-host interactions but also characterizes NbEXPA1 as the first PD-specific cell wall loosening protein and its essential role in potyviral infection.

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“…First-strand cDNA synthesis was carried out with an oligo(dT) 12-18 primer using Superscript III reverse transcriptase (Invitrogen). RT-PCR and real-time qRT-PCR were performed essentially as described previously (89). For qRT-PCR to determine viral RNA accumulation and SGS3 transcript levels, a 20-l volume containing 4 l of 10-fold-diluted cDNA, 5 M each primer, and 1ϫ SYBR green PCR mix (Bio-Rad) was used.…”

Section: Methodsmentioning

confidence: 99%

The Potyvirus Silencing Suppressor Protein VPg Mediates Degradation of SGS3 via Ubiquitination and Autophagy Pathways

Cheng

Wang

2017

J Virol

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RNA silencing is an innate antiviral immunity response of plants and animals. To counteract this host immune response, viruses have evolved an effective strategy to protect themselves by the expression of viral suppressors of RNA silencing (VSRs). Most potyviruses encode two VSRs, helper component-proteinase (HCPro) and viral genome-linked protein (VPg). The molecular biology of the former has been well characterized, whereas how VPg exerts its function in the suppression of RNA silencing is yet to be understood. In this study, we show that infection by Turnip mosaic virus (TuMV) causes reduced levels of suppressor of gene silencing 3 (SGS3), a key component of the RNA silencing pathway that functions in doublestranded RNA synthesis for virus-derived small interfering RNA (vsiRNA) production. We also demonstrate that among 11 TuMV-encoded viral proteins, VPg is the only one that interacts with SGS3. We furthermore present evidence that the expression of VPg alone, independent of viral infection, is sufficient to induce the degradation of SGS3 and its intimate partner RNA-dependent RNA polymerase 6 (RDR6). Moreover, we discover that the VPg-mediated degradation of SGS3 occurs via both the 20S ubiquitin-proteasome and autophagy pathways. Taken together, our data suggest a role for VPg-mediated degradation of SGS3 in suppression of silencing by VPg.IMPORTANCE Potyviruses represent the largest group of known plant viruses and cause significant losses of many agriculturally important crops in the world. In order to establish infection, potyviruses must overcome the host antiviral silencing response. A viral protein called VPg has been shown to play a role in this process, but how it works is unclear. In this paper, we found that the VPg protein of Turnip mosaic virus (TuMV), which is a potyvirus, interacts with a host protein named SGS3, a key protein in the RNA silencing pathway. Moreover, this interaction leads to the degradation of SGS3 and its interacting and functional partner RDR6, which is another essential component of the RNA silencing pathway. We also identified the cellular pathways that are recruited for the VPg-mediated degradation of SGS3. Therefore, this work reveals a possible mechanism by which VPg sabotages host antiviral RNA silencing to promote virus infection. KEYWORDS RDR6, RNA silencing, SGS3, VPg, VSR, autophagy, potyvirus, ubiquitination T o establish systemic infection, an invading virus must remodel and recruit host elements and overcome resistance responses through complex molecular virushost interactions (1-3). One such essential antiviral response is RNA silencing (4-6), a cellular mechanism conserved from lower eukaryotes to mammals to regulate endogenous gene expression at the transcriptional and posttranscriptional levels (7, 8). To activate antiviral RNA silencing, the viral double-stranded RNAs (dsRNAs), which may

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Plum Pox Virus 6K1 Protein Is Required for Viral Replication and Targets the Viral Replication Complex at the Early Stage of Infection

Cited by 81 publications

References 55 publications

Effect of Host Species on Topography of the Fitness Landscape for a Plant RNA Virus

Effect of Host Species on Topography of the Fitness Landscape for a Plant RNA Virus

NbEXPA1, an α‐expansin, is plasmodesmata‐specific and a novel host factor for potyviral infection

The Potyvirus Silencing Suppressor Protein VPg Mediates Degradation of SGS3 via Ubiquitination and Autophagy Pathways

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