Evidence for RNA recombination between distinct isolates of Pepino mosaic virus.

Genetic recombination plays an important role in the evolution of virus genomes. In this study we analyzed publicly available genomic sequences of Pepino mosaic virus (PepMV) for recombination events using several bioinformatics tools. The genome-wide analyses not only confirm the presence of previously found recombination events in PepMV but also provide the first evidence for double recombinant origin of the US2 isolate

Detection and genetic variability of newly identified dasheen mosaic virus in Poland

Dasheen mosaic virus (DsMV) is one of the most important viral pathogens of aroids and can cause major economic losses for ornamental crops. Here, we present the detection and molecular characterisation of DsMV isolates originating from Monstera adansonii plants in Poland. Moreover, the genetic variability of DsMV isolates was analyzed based on the coat protein gene ( CP) of the Polish and other DsMV isolates described to date. The presence of DsMV was confirmed by transmission electron microscopy (TEM) and reverse transcription polymerase chain reaction (RT-PCR) with specific, diagnostic primers in three out of ten examined plants. To obtain full-length sequences of CP, two pairs of primers were designed and used in the RT-PCR. The specificity of obtained products was confirmed by Sanger sequencing. The obtained sequences of CP were compared with 44 other DsMV sequences retrieved from the GenBank. Analyses revealed that DsMV population is very diverse. The variability of DsMV isolates was confirmed by low sequence identity and pervasive recombination events. The phylogenetic analysis was performed based on 37 non-recombinant CP sequences. The maximum-likelihood reconstruction revealed that the Polish isolates are distinct and grouped separately from other DsMV isolates. Due to the high genetic diversity, detecting the virus could be difficult. Nonetheless disease management relies strongly on a fast and accurate identification of the causal agent. To our knowledge this is the first report of DsMV in Poland

Strain-dependent mutational effects for Pepino mosaic virus in a natural host

[EN] Pepino mosaic virus (PepMV) is an emerging plant pathogen that infects tomatoes worldwide. Understanding the factors that influence its evolutionary success is essential for developing new control strategies that may be more robust against the evolution of new viral strains. One of these evolutionary factors is the distribution of mutational fitness effect (DMFE), that is, the fraction of mutations that are lethal, deleterious, neutral, and beneficial on a given viral strain and host species. The goal of this study was to characterize the DMFE of introduced nonsynonymous mutations on a mild isolate of PepMV from the Chilean 2 strain (PepMV-P22). Additionally, we also explored whether the fitness effect of a given mutation depends on the gene where it appears or on epistatic interactions with the genetic background. To address this latter possibility, a subset of mutations were also introduced in a mild isolate of the European strain (PepMV-P11) and the fitness of the resulting clones measured.This study was financially supported by grant 2011/01/D/NZ9/00279, from the Poland National Science Center, to B.H.J and by grants BFU2015-65037-P, from Spain Ministry of Economy and Competitiveness-FEDER, and PROMETEOII/2014/021, from Generalitat Valenciana, to S.F.E.Minicka, J.; Elena Fito, SF.; Borodynko-Filas, N.; Rubis, B.; Hasiów-Jaroszewska, B. (2017). Strain-dependent mutational effects for Pepino mosaic virus in a natural host. BMC Evolutionary Biology. 17:1-11. https://doi.org/10.1186/s12862-017-0920-4S11117Steinhauer DA, Domingo E, Holland JJ. Lack of evidence for proofreading mechanisms associated with an RNA virus polymerase. Gene. 1992;122:281–8.Sanjuán R, Nebot MR, Chirico N, Mansky LM, Belshaw R. Viral mutation rates. J Virol. 2010;84:9733–48.Domingo E. Viruses at the edge of adaptation. 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Tridimensional model structure and patterns of molecular evolution of Pepino mosaic virus TGBp3 protein

<p>Abstract</p> <p>Background</p> <p><it>Pepino mosaic virus </it>(PepMV) is considered one of the most dangerous pathogens infecting tomatoes worldwide. The virus is highly diverse and four distinct genotypes, as well as inter-strain recombinants, have already been described. The isolates display a wide range on symptoms on infected plant species, ranging from mild mosaic to severe necrosis. However, little is known about the mechanisms and pattern of PepMV molecular evolution and about the role of individual proteins in host-pathogen interactions.</p> <p>Methods</p> <p>The nucleotide sequences of the triple gene block 3 (TGB3) from PepMV isolates varying in symptomatology and geographic origin have been analyzed. The modes and patterns of molecular evolution of the TGBp3 protein were investigated by evaluating the selective constraints to which particular amino acid residues have been subjected during the course of diversification. The tridimensional structure of TGBp3 protein has been modeled <it>de novo </it>using the Rosetta algorithm. The correlation between symptoms development and location of specific amino acids residues was analyzed.</p> <p>Results</p> <p>The results have shown that TGBp3 has been evolving mainly under the action of purifying selection operating on several amino acid sites, thus highlighting its functional role during PepMV infection. Interestingly, amino acid 67, which has been previously shown to be a necrosis determinant, was found to be under positive selection.</p> <p>Conclusions</p> <p>Identification of diverse selection events in TGB3p3 will help unraveling its biological functions and is essential to an understanding of the evolutionary constraints exerted on the <it>Potexvirus </it>genome. The estimated tridimensional structure of TGBp3 will serve as a platform for further sequence, structural and function analysis and will stimulate new experimental advances.</p

Pepino mosaic virus RNA-Dependent RNA Polymerase POL Domain Is a Hypersensitive Response-Like Elicitor Shared by Necrotic and Mild Isolate

[SPA] El virus del mosaico del pepino dulce (PepMV) es un patógeno emergente que representa una grave amenaza para la producción de tomate. Las enfermedades inducidas por PepMV se manifiestan con una amplia gama de síntomas, incluyendo la necrosis sistémica. Nuestros resultados muestran que la acumulación de PepMV depende tanto del aislado del virus, como de la variedad de tomate o las condiciones ambientales, asociado todo ello al desarrollo de la necrosis. La sustitución de una lisina por un ácido glutámico en la posición 67 del triple bloque de genes (TGB3), previamente descrita como un determinante de la necrosis, parece favorecer una mayor acumulación del virus pero no parece ser el elemento elicitor de la necrosis sistémica. La sobreexpresión tanto de TGB3 como del dominio polimerasa (POL) de la replicasa (RdRp) produjo necrosis, aunque sólo la expresión local de POL desencadenó síntomas caracteristos de HR. En conjunto, nuestros datos sugieren que el dominio RdRp-POL desempeña un papel importante en la inducción de necrosis de PepMV, dependiendo del nivel de acumulación del virus, que puede ser modulado por la naturaleza de TGB3, el genotipo del huesped y las condiciones ambientales. [ENG] Pepino mosaic virus (PepMV) is an emerging pathogen that represents a serious threat to tomato production worldwide. PepMV-induced diseases manifest with a wide range of symptoms, including systemic necrosis. Our results showed that PepMV accumulation depends on the virus isolate, tomato cultivar, and environmental conditions, and associates with the development of necrosis. Substitution of lysine for glutamic acid at position 67 in the triple gene block 3 (TGB3) protein, previously described as a necrosis determinant, led to increased virus accumulation and was necessary but not sufficient to induce systemic necrosis. Overexpression of both TGB3 and the polymerase domain (POL) of the RNA-dependent RNA polymerase (RdRp) resulted in necrosis, although only local expression of POL triggered HR-like symptoms. Altogether, our data suggest that the RdRp-POL domain plays an important role in PepMV necrosis induction, with necrosis development depending on the virus accumulation level, which can be modulated by the nature of TGB3, host genotype and environmental conditions.Agradecer la financiación del Ministerio de Economía y Competitividad (AGL2012-37390 ) y la fundación Séneca por la financiación de la Beca FPI

Host range and symptomatology of Pepino mosaic virus strains occurring in Europe

Pepino mosaic virus (PepMV) has caused great concern in the greenhouse tomato industry after it was found causing a new disease in tomato in 1999. The objective of this paper is to investigate alternative hosts and compare important biological characteristics of the three PepMV strains occurring in Europe when tested under different environmental conditions. To this end we compared the infectivity and symptom development of three, well characterized isolates belonging to three different PepMV strains, EU-tom, Ch2 and US1, by inoculating them on tomato, possible alternative host plants in the family Solanaceae and selected test plants. The inoculation experiments were done in 10 countries from south to north in Europe. The importance of alternative hosts among the solanaceous crops and the usefulness of test plants in the biological characterization of PepMV isolates are discussed. Our data for the three strains tested at 10 different European locations with both international and local cultivars showed that eggplant is an alternative host of PepMV. Sweet pepper is not an important host of PepMV, but potato can be infected when the right isolate is matched with a specific cultivar. Nicotiana occidentalis 37B is a useful indicator plant for PepMV studies, since it reacts with a different symptomatology to each one of the PepMV strains.Ravnikar, M.; Blystad, D.; Van Der Vlugt, R.; Alfaro Fernández, AO.; Del Carmen Cordoba, M.; Bese, G.; Hristova, D.... (2015). Host range and symptomatology of Pepino mosaic virus strains occurring in Europe. European Journal of Plant Pathology. 143(1):43-56. doi:10.1007/s10658-015-0664-1S43561431Alfaro-Fernández, A., Córdoba-Sellés, M. C., Herrera-Vásquez, J. A., Cebrián, M. C., & Jordá, C. (2009). Transmission of Pepino mosaic virus by the fungal vector Olpidium virulentus. Journal of Phytopathology, 158, 217–226.Charmichael, D. 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Molecular evolution of viral multifunctional proteins: the case of Potyvirus HC-Pro

[EN] Our knowledge on the mode of evolution of the multifunctional viral proteins remains incomplete. To tackle this problem, here, we have investigated the evolutionary dynamics of the potyvirus multifunctional protein HC-Pro, with particular focus on its functional domains. The protein was partitioned into the three previously described functional domains, and each domain was analyzed separately and assembled. We searched for signatures of adaptive evolution and evolutionary dependencies of amino acid sites within and between the three domains using the entire set of available potyvirus sequences in GenBank. Interestingly, we identified strongly significant patterns of co-occurrence of adaptive events along the phylogenetic tree in the three domains. These patterns suggest that Domain I, whose main function is to mediate aphid transmission, has likely been coevolving with the other two domains, which are involved in different functions but all requiring the capacity to bind RNA. By contrast, episodes of positive selection on Domains II and III did not correlate, reflecting a trade-off between their evolvability and their evolutionary dependency likely resulting from their functional overlap. Covariation analyses have identified several groups of amino acids with evidence of concerted variation within each domain, but interdomain significant covariations were only found for Domains II and III, further reflecting their functional overlappingThis work was supported by grants BFU2012-30805 (SFE) and BFU2012-36346 (MAF) from the Spanish Direccio´n General de Investigacio´n Cientı´fica y Te´cnica and by an EMBO Short-Term Fellowship and the Mentoring Program from the Foundation for Polish Science (BHJ).Hasiów-Jaroszewska, B.; Fares Riaño, MA.; Elena Fito, SF. (2014). Molecular evolution of viral multifunctional proteins: the case of Potyvirus HC-Pro. 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J Gen Virol 79:3119–3122Cantó T, López-Moya JJ, Serra-Yodi MT, Díaz-Ruiz JR, López-Abella D (1995) Different helper component mutations associated with lack of aphid transmissibility in two isolates of potato virus. Phytopathology 85:1519–1524Carrington JC, Freed DD, Sanders TC (1989) Autocatalytic processing of the potyvirus helper component proteinase in Escherichia coli and in vitro. J Virol 63:4459–4463Chung BY, Miller WA, Atkins JF, Firth AE (2008) An overlapping essential gene in the Potyviridae. Proc Natl Acad Sci USA 105:5897–5902Cronin S, Verchot J, Haldeman-Cahill R, Schaad MC, Carrington JC (1995) Long distance movement factor: a transport function of the potyvirus helper component-proteinase. Plant Cell 7:549–559Edgar RC (2004) MUSCLE: multiple sequence alignment with high accuracy and high throughput. Nucl Acids Res 32:1792–1797Elena SF, Rodrigo G (2012) Towards and integrated molecular model of plant-virus interactions. Curr Opin Virol 2:713–718Fares MA (2004) SWAPSC: sliding-window analysis procedure to detect selective constraints. Bioinformatics 20:2867–2868Fares MA, McNally D (2006) CAPS: coevolution analysis using protein sequences. Bioinformatics 22:2821–2822Fares MA, Travers AA (2006) A novel method for detecting intramolecular coevolution: adding a further dimension to selective constrains analyses. Genetics 173:9–23Fares MA, Elena SF, Ortiz J, Moya A, Barrio E (2002) A sliding window-based method to detect selective constraints in protein-coding genes and its application to RNA viruses. J Mol Evol 55:509–521Gibbs A, Ohshima K (2010) Potyviruses and the digital revolution. Annu Rev Phytopathol 48:205–223Guo D, Mertis A, Saarma M (1999) Self-association and mapping of interaction domains of helper component of Potato virus A potyvirus. J Gen Virol 80:1127–1131Guo B, Lin J, Ye K (2011) Structure of the autocatalytic cysteine protease domain of potyvirus helper-component proteinase. J Biol Chem 286:21937–21943Haikonen T, Rajamäki ML, Tian YP, Valkonen JPT (2013) Mutation of a short variable region in HC-Pro protein of Potato virus A affects interactions with microtubule-associated protein and induces necrotic responses in tobacco. Mol Plant Microbe Interact 26:721–733Hall TA (1999) BIOEDIT: a user-friendly biological sequence alignment editor and analysis program for Windows 95/98/NT. Nucl Acids Symp Ser 41:95–98Hughes AL (2009) Small effective population sizes and rare nonsynonymous variants in potyviruses. Virology 393:127–134Jones DT (1999) Protein secondary structure prediction based on position-specific scoring matrices. J Mol Biol 292:195–202Kasschau KD, Carrington JC (1995) Requirement for HC-Pro processing during genome amplification of Tobacco etch potyvirus. Virology 209:268–273Kasschau KD, Carrington JC (2001) Long-distance movement and replication maintenance functions correlate with silencing suppression activity of potyviral HC-Pro. Virology 285:71–81Kasschau KD, Cronin S, Carrington JC (1997) Genome amplification and long-distance movement functions associated with the central domain of Tobacco etch potyvirus helper component-proteinase. Virology 228:251–262Kosakovsky Pond SL, Frost SDW (2005a) DATAMONKEY: rapid detection of selective pressure on individual sites of codon alignments. Bioinformatics 21:2531–2533Kosakovsky Pond SL, Frost SDW (2005b) Not so different after all: a comparison of methods for detecting amino acid sites under selection. Mol Biol Evol 22:1208–1222Kosakovsky Pond SL, Posada D, Gravenor MB, Woelk CH, Frost SDW (2006) Automated phylogenetic detection of recombination using a genetic algorithm. Mol Biol Evol 23:1891–1901Lakatos L, Csorba T, Pantaleo V, Chapman EJ, Carrington JC, Liu YP, Dojla VV, Calvino LF, López-Moya JJ, Burgyan J (2006) Small RNA binding is a common strategy to suppress RNA silencing by several viral suppressors. 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Molecular evolution of Pepino mosaic virus during long-term passaging in different hosts and its impact on virus virulence

In this study the effect of host changes and multiple passages on Pepino mosaic virus (PepMV) evolution was analysed. A population of a mild isolate of PepMV was used to generate five independent evolution lineages on three tomato cultivars, which differ in rate of appearance of symptoms and their severity during viral infection (Beta Lux, Moneymaker and Malinowy Oarowski) and on Datura inoxia. Twenty serial passages were performed over a period of 217-220 days. Symptom severity was monitored along the entire experiment. After the last series of passages total RNAs from each lineage and host were isolated and the triple gene block 3 (TGB3) and coat protein (CP) were amplified, cloned and 10 clones for each gene sequenced. Among the 400 clones for both genes, 143 individual mutations (61 synonymous and 82 nonsynonymous) were identified, with the largest number of nonsynonymous mutations being observed for the tomato cultivars Malinowy Oarowski and Beta Lux. In two of the lineages evolving in the most susceptible variety of tomato (Beta Lux) necrotic changes in leaf blades appeared after 17 passages, leading to death of the plants. In these two lineages the mutation responsible for necrotic symptoms was K67E in TGB3. The appearance of this convergent mutation in independently evolving lineages may suggest that selection in this experimental set up favours more aggressive PepMV variants. We found a positive association between the severity of symptoms and the amount of genetic variability contained on viral populations. Indeed, the severity of symptoms turned out to be a good predictor for several indices of molecular variability. In addition, mapping all observed mutations in CP and TGB3 protein structures revealed that most were located on the surface, indicating a possible implication in viral-viral or viral-host interactions.This work was financially supported by project DEC-2011/01/D/NZ9/00279 from the National Science Center in Poland to B.H.J. Work in Valencia was supported by the Spanish Ministry of Economy and Competitiveness grant BFU2012-30805 to S. F. E.Minicka, J.; Rymelska, N.; Elena Fito, SF.; Czerwoniec, A.; Hasiów-Jaroszewska, B. (2015). Molecular evolution of Pepino mosaic virus during long-term passaging in different hosts and its impact on virus virulence. Annals of Applied Biology. 166(3):389-401. https://doi.org/10.1111/aab.12179S389401166