RESUMEN
This work reports the complete genome sequence, production of a polyclonal antiserum, and host range of a Brazilian strain of johnsongrass mosaic virus (JGMV) found infecting Panicum maximum in the state of São Paulo, Brazil. The complete genome sequence of this potyvirus, comprising 9874 nucleotides, showed 82 % amino acid sequence identity in the polyprotein to that of an isolate of JGMV from Australia. The experimental host range of this virus included mainly fodder species. Cultivated species such as rice, oats, sugarcane, rye, corn and wheat were not infected, suggesting that current isolates of this potyvirus do not represent a threat to these crops in Brazil.
Asunto(s)
Genoma Viral/genética , Potyvirus/genética , Secuencia de Aminoácidos , Secuencia de Bases , Brasil , Ensayo de Inmunoadsorción Enzimática , Datos de Secuencia Molecular , Panicum/virología , Poaceae/virología , Potyvirus/aislamiento & purificación , Potyvirus/patogenicidadRESUMEN
BACKGROUND: Viruses that have spent most of their evolutionary time associated with a single host lineage should have sequences that reflect codivergence of virus and host. Several examples for RNA viruses of host-virus tree congruence are being challenged. DNA viruses, such as mastreviruses, are more likely than RNA viruses to have maintained a record of host lineage association. RESULTS: The full genomes of 28 isolates of Wheat dwarf virus (WDV), a member of the Mastrevirus genus, from different regions of China were sequenced. The analysis of these 28 entire genomes and 18 entire genome sequences of cereal mastreviruses from other countries support the designation of wheat, barley and oat mastrevirus isolates as separate species. They revealed that relative divergence times for the viruses WDV, Barley dwarf virus (BDV), Oat dwarf virus (ODV) and Maize streak virus (MSV) are proportional to divergence times of their hosts, suggesting codivergence. Considerable diversity among Chinese isolates was found and was concentrated in hot spots in the Rep A, SIR, LIR, and intron regions in WDV genomes. Two probable recombination events were detected in Chinese WDV isolates. Analysis including further Mastrevirus genomes concentrated on coding regions to avoid difficulties due to recombination and hyperdiversity. The analysis demonstrated congruence of trees in two branches of the genus, but not in the third. Assuming codivergence, an evolutionary rate of 10-8 substitutions per site per year was calculated. The low rate implies stronger constraints against change than are obtained by other methods of estimating the rate. CONCLUSION: We report tests of the hypothesis that mastreviruses have codiverged with their monocotyledonous hosts over 50 million years of evolution. The tests support the hypothesis for WDV, BDV and ODV, but not for MSV and other African streak viruses.
Asunto(s)
Evolución Molecular , Geminiviridae/genética , Interacciones Huésped-Patógeno , Enfermedades de las Plantas/virología , Poaceae/virología , Geminiviridae/clasificación , Geminiviridae/aislamiento & purificación , Datos de Secuencia Molecular , Filogenia , Recombinación Genética , Alineación de Secuencia , Análisis de Secuencia de ADNRESUMEN
This work focused on the assessment of plant virus occurrence among primitive and higher plants in the Antarctic region. Sampling occurred during two seasons (2004/5 and 2005/6) at the Ukrainian Antarctic Station 'Academician Vernadskiy' positioned on Argentina Islands. Collected plant samples of four moss genera (Polytrichum, Plagiatecium, Sanionia and Barbilophozia) and one higher monocot plant species, Deschampsia antarctica, were further subjected to enzyme-linked immunosorbent assay to test for the presence of common plant viruses. Surprisingly, samples of Barbilophozia and Polytrichum mosses were found to contain antigens of viruses from the genus Tobamovirus, Tobacco mosaic virus and Cucumber green mottle mosaic virus, which normally parasitize angiosperms. By contrast, samples of the monocot Deschampsia antarctica were positive for viruses typically infecting dicots: Cucumber green mottle mosaic virus, Cucumber mosaic virus and Tomato spotted wilt virus. Serological data for Deschampsia antarctica were supported in part by transmission electron microscopy observations and bioassay results. The results demonstrate comparatively high diversity of plant viruses detected in Antarctica; the results also raise questions of virus specificity and host susceptibility, as the detected viruses normally infect dicotyledonous plants. However, the means of plant virus emergence in the region remain elusive and are discussed.
Asunto(s)
Briófitas/virología , Virus de Plantas/aislamiento & purificación , Poaceae/virología , Virus ARN/aislamiento & purificación , Regiones Antárticas , Cucumis sativus/virología , Cucumovirus/aislamiento & purificación , Cucumovirus/patogenicidad , Ensayo de Inmunoadsorción Enzimática , Microscopía Electrónica de Transmisión , Enfermedades de las Plantas/virología , Hojas de la Planta/virología , Virus de Plantas/clasificación , Virus de Plantas/patogenicidad , Virus ARN/clasificación , Virus ARN/patogenicidad , Nicotiana/virología , Virus del Mosaico del Tabaco/aislamiento & purificación , Virus del Mosaico del Tabaco/patogenicidad , Tobamovirus/aislamiento & purificación , Tospovirus/aislamiento & purificaciónRESUMEN
We have analyzed the genotypic diversity of sugarcane yellow leaf virus (SCYLV) collected from North, South, and Central America by fingerprinting assays and selective cDNA cloning and sequencing. One group of isolates from Colombia, designated the C-population, has been identified as residing at the root node between a separable superpopulation structure of SCYLV and other members of the family Luteoviridae, indicating that the progenitor viruses of the North, South, and Central American isolates of the SCYLV superpopulation most likely arose from a C-population structure. From a model of intrafamilial evolution (F. Moonan et al., Virology 269:156-171, 2000), a prediction could be made that within the SCYLV species, the capacity of genomic sequence divergence would range from lowest in the capsid protein open reading frame 3 (ORF 3) to highest in a region spanning across the carboxy-terminal end of the RNA-dependent RNA polymerase ORF. We have demonstrated the validity and applicability of this intrafamilial model for the prediction of intraspecies SCYLV diversity. Analysis of spatial phylogenetic variation (SPV) within the SCYLV isolates could not be assessed by application of a "partial likelihoods assessed through optimization" (PLATO)-derived intraspecies model alone. However, application of a PLATO-derived intrafamilial model with the intraspecies-derived model allowed distinction of three forms of SPV. Two of the SPV forms identified correspond to the extremes in a continuum of sequence evolution displayed in a SCYLV superpopulation structure, and the third form was diagnostic of a C-population structure. The application of these types of models has value in terms of predicting the types of SCYLV intraspecies diversity that may exist worldwide, and in general, may be useful in application for more informed design of transgenes for use in the elicitation of homology-dependent virus resistance mechanisms in transgenic plants.
Asunto(s)
Evolución Molecular , Variación Genética , Luteovirus/genética , Poaceae/virología , América Central , Colombia , Dermatoglifia del ADN/métodos , Genotipo , Luteovirus/clasificación , Luteovirus/aislamiento & purificación , América del Norte , Filogenia , Análisis de Secuencia de ADN/métodos , América del SurRESUMEN
A previously uncharacterized virus was reported in southeast Brazil causing a yellowing leaf disease in sugarcane. The virus, termed sugarcane yellow leaf virus (ScYLV), shares features typical of the luteoviruses. To start the molecular characterization of ScYLV, the nucleotide sequence of the coat protein (CP), 17 kDa protein and C-terminus of the RNA-dependent RNA polymerase coding regions was determined from an RT-PCR amplification product. Comparisons showed that the deduced amino acid sequences share a considerable degree of identity and similarity with corresponding sequences of known luteoviruses, thus clearly establishing ScYLV as a member of the family Luteoviridae. The authenticity of the CP open reading frame was confirmed by its expression in Escherichia coli. The recombinant CP positively reacted in immunoblot assays with polyclonal antibodies raised against native ScYLV. Furthermore, phylogenetic analyses also suggest that the 5' and 3' coding blocks of the ScYLV genome possess different taxonomic affinities within the Luteoviridae family, as does also the genome of soybean dwarf virus.
Asunto(s)
Luteovirus/clasificación , Luteovirus/genética , Secuencia de Aminoácidos , Secuencia de Bases , Brasil , Cápside/genética , Clonación Molecular , Cartilla de ADN/genética , ADN Complementario/genética , Luteovirus/aislamiento & purificación , Datos de Secuencia Molecular , Sistemas de Lectura Abierta , Filogenia , Plantas Comestibles/virología , Poaceae/virología , ARN Viral/genética , ARN Viral/aislamiento & purificación , Homología de Secuencia de AminoácidoRESUMEN
Four cDNA clones were generated from the genomic dsRNA of an Australian isolate of pangola stunt Fijivirus (PaSV). Each clone hybridized with nucleic acid extracts from PaSV infected plants but not healthy plants. Further, each clone hybridized with more than one segment of the PaSV dsRNA genome. One clone was used to demonstrate that homology existed between the Australian isolate of PaSV and a South American isolate of PaSV although the isolates differed in the sizes of the genomic dsRNAs and in the vector species. The clone also hybridized with some segments of the maize rough dwarf Fijivirus genome.