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[PMID]:27815694
[Au] Autor:Yahaya A; Dangora DB; Alegbejo MD; Kumar PL; Alabi OJ
[Ad] Endereço:Department of Biological Sciences, Ahmadu Bello University, Zaria, Kaduna State, Nigeria.
[Ti] Título:Identification and molecular characterization of a novel sugarcane streak mastrevirus and an isolate of the A-strain of maize streak virus from sugarcane in Nigeria.
[So] Source:Arch Virol;162(2):597-602, 2017 Feb.
[Is] ISSN:1432-8798
[Cp] País de publicação:Austria
[La] Idioma:eng
[Ab] Resumo:Sugarcane and maize plants showing symptoms typical of those described for the so-called "African streak viruses" (AfSVs) were encountered during field surveys conducted from February to July 2015 to document viruses infecting both crops across the northern Guinea savannah region of Nigeria. As part of this study, two categories of complete mastrevirus-like genome sequences were obtained from nine samples (maize = 2; sugarcane = 7). In pairwise comparisons, the full-length genomes of the first sequence category (2,687 nt each; maize = 2; sugarcane = 2) shared 96 to 99% identity with global isolates of the A-strain of maize streak virus (MSV-A), indicating that sugarcane may also serve as a reservoir host to MSV-A. Analysis of the complete genomes belonging to the second sequence category (2,757 nt each; sugarcane = 5) showed that they shared 42 to 67% identity with their closest AfSV relatives, thus indicating that they represent sequences of a novel mastrevirus. Both sequence categories shared 61-62% sequence identity with each other. Further analysis revealed that the novel sugarcane-infecting virus, tentatively named as sugarcane chlorotic streak virus (SCSV), arose from a putative interspecific recombination event involving two grass-infecting mastreviruses, eragrostis streak virus and urochloa streak virus, as putative parental sequences. The results of this study add to the repertoire of diverse AfSVs present in cereal and sugarcane mixed cropping landscapes in the northern Guinea savannah region of Nigeria, with implications for disease epidemiology.
[Mh] Termos MeSH primário: DNA Viral/genética
Genoma Viral
Vírus do Listrado do Milho/genética
Filogenia
Saccharum/virologia
Zea mays/virologia
[Mh] Termos MeSH secundário: Sequência de Bases
Vírus do Listrado do Milho/classificação
Vírus do Listrado do Milho/isolamento & purificação
Nigéria
Doenças das Plantas/virologia
Recombinação Genética
Alinhamento de Sequência
Homologia de Sequência do Ácido Nucleico
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Nm] Nome de substância:
0 (DNA, Viral)
[Em] Mês de entrada:1702
[Cu] Atualização por classe:170214
[Lr] Data última revisão:
170214
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:161106
[St] Status:MEDLINE
[do] DOI:10.1007/s00705-016-3148-5


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[PMID]:26081946
[Au] Autor:Nair SK; Babu R; Magorokosho C; Mahuku G; Semagn K; Beyene Y; Das B; Makumbi D; Lava Kumar P; Olsen M; Boddupalli PM
[Ad] Endereço:International Maize and Wheat Improvement Center (CIMMYT), ICRISAT Campus, Patancheru, Greater Hyderabad, 502324, India, Sudha.nair@cgiar.org.
[Ti] Título:Fine mapping of Msv1, a major QTL for resistance to Maize Streak Virus leads to development of production markers for breeding pipelines.
[So] Source:Theor Appl Genet;128(9):1839-54, 2015 Sep.
[Is] ISSN:1432-2242
[Cp] País de publicação:Germany
[La] Idioma:eng
[Ab] Resumo:Msv1 , the major QTL for MSV resistance was delimited to an interval of 0.87 cM on chromosome 1 at 87 Mb and production markers with high prediction accuracy were developed. Maize streak virus (MSV) disease is a devastating disease in the Sub-Saharan Africa (SSA), which causes significant yield loss in maize. Resistance to MSV has previously been mapped to a major QTL (Msv1) on chromosome 1 that is germplasm and environment independent and to several minor loci elsewhere in the genome. In this study, Msv1 was fine-mapped through QTL isogenic recombinant strategy using a large F 2 population of CML206 × CML312 to an interval of 0.87 cM on chromosome 1. Genome-wide association study was conducted in the DTMA (Drought Tolerant Maize for Africa)-Association mapping panel with 278 tropical/sub-tropical breeding lines from CIMMYT using the high-density genotyping-by-sequencing (GBS) markers. This study identified 19 SNPs in the region between 82 and 93 Mb on chromosome 1(B73 RefGen_V2) at a P < 1.00E-04, which coincided with the fine-mapped region of Msv1. Haplotype trend regression identified a haplotype block significantly associated with response to MSV. Three SNPs in this haplotype block at 87 Mb on chromosome 1 had an accuracy of 0.94 in predicting the disease reaction in a collection of breeding lines with known responses to MSV infection. In two biparental populations, selection for resistant Msv1 haplotype demonstrated a reduction of 1.03-1.39 units on a rating scale of 1-5, compared to the susceptible haplotype. High-throughput KASP assays have been developed for these three SNPs to enable routine marker screening in the breeding pipeline for MSV resistance.
[Mh] Termos MeSH primário: Mapeamento Cromossômico
Resistência à Doença/genética
Vírus do Listrado do Milho
Doenças das Plantas/genética
Locos de Características Quantitativas
Zea mays/genética
[Mh] Termos MeSH secundário: Cromossomos de Plantas
Marcadores Genéticos
Haplótipos
Fenótipo
Melhoramento Vegetal
Polimorfismo de Nucleotídeo Único
Zea mays/virologia
[Pt] Tipo de publicação:JOURNAL ARTICLE; RESEARCH SUPPORT, NON-U.S. GOV'T
[Nm] Nome de substância:
0 (Genetic Markers)
[Em] Mês de entrada:1512
[Cu] Atualização por classe:170917
[Lr] Data última revisão:
170917
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:150618
[St] Status:MEDLINE
[do] DOI:10.1007/s00122-015-2551-8


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[PMID]:25344899
[Au] Autor:Oppong A; Offei SK; Ofori K; Adu-Dapaah H; Lamptey JN; Kurenbach B; Walters M; Shepherd DN; Martin DP; Varsani A
[Ad] Endereço:CSIR-Crops Research Institute, P.O. Box 3785, Kumasi, Ghana, alnopp@yahoo.co.uk.
[Ti] Título:Mapping the distribution of maize streak virus genotypes across the forest and transition zones of Ghana.
[So] Source:Arch Virol;160(2):483-92, 2015 Feb.
[Is] ISSN:1432-8798
[Cp] País de publicação:Austria
[La] Idioma:eng
[Ab] Resumo:Throughout sub-Saharan Africa, maize streak virus strain A (MSV-A), the causal agent of maize streak disease (MSD), is an important biological constraint on maize production. In November/December 2010, an MSD survey was carried out in the forest and transition zones of Ghana in order to obtain MSV-A virulence sources for the development of MSD-resistant maize genotypes with agronomic properties suitable for these regions. In 79 well-distributed maize fields, the mean MSD incidence was 18.544 % and the symptom severity score was 2.956 (1 = no symptoms and 5 = extremely severe). We detected no correlation between these two variables. Phylogenetic analysis of cloned MSV-A isolates that were fully sequenced from samples collected in 51 of these fields, together with those sampled from various other parts of Africa, indicated that all of the Ghanaian isolates occurred within a broader cluster of West African isolates, all belonging to the highly virulent MSV-A1 subtype. Besides being the first report of a systematic MSV survey in Ghana, this study is the first to characterize the full-genome sequences of Ghanaian MSV isolates. The 51 genome sequences determined here will additionally be a valuable resource for the rational selection of representative MSV-A variant panels for MSD resistance screening.
[Mh] Termos MeSH primário: Genoma Viral/genética
Vírus do Listrado do Milho/classificação
Vírus do Listrado do Milho/genética
Doenças das Plantas/virologia
Zea mays/virologia
[Mh] Termos MeSH secundário: Sequência de Bases
DNA Circular/genética
DNA Viral/genética
Florestas
Genótipo
Gana
Vírus do Listrado do Milho/isolamento & purificação
Dados de Sequência Molecular
Filogeografia
Folhas de Planta/virologia
Análise de Sequência de DNA
[Pt] Tipo de publicação:JOURNAL ARTICLE; RESEARCH SUPPORT, NON-U.S. GOV'T
[Nm] Nome de substância:
0 (DNA, Circular); 0 (DNA, Viral)
[Em] Mês de entrada:1509
[Cu] Atualização por classe:150203
[Lr] Data última revisão:
150203
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:141027
[St] Status:MEDLINE
[do] DOI:10.1007/s00705-014-2260-7


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[PMID]:25166274
[Au] Autor:Shepherd DN; Dugdale B; Martin DP; Varsani A; Lakay FM; Bezuidenhout ME; Monjane AL; Thomson JA; Dale J; Rybicki EP
[Ad] Endereço:Department of Molecular and Cell Biology, University of Cape Town, Rondebosch, Cape Town, South Africa.
[Ti] Título:Inducible resistance to maize streak virus.
[So] Source:PLoS One;9(8):e105932, 2014.
[Is] ISSN:1932-6203
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:Maize streak virus (MSV), which causes maize streak disease (MSD), is the major viral pathogenic constraint on maize production in Africa. Type member of the Mastrevirus genus in the family Geminiviridae, MSV has a 2.7 kb, single-stranded circular DNA genome encoding a coat protein, movement protein, and the two replication-associated proteins Rep and RepA. While we have previously developed MSV-resistant transgenic maize lines constitutively expressing "dominant negative mutant" versions of the MSV Rep, the only transgenes we could use were those that caused no developmental defects during the regeneration of plants in tissue culture. A better transgene expression system would be an inducible one, where resistance-conferring transgenes are expressed only in MSV-infected cells. However, most known inducible transgene expression systems are hampered by background or "leaky" expression in the absence of the inducer. Here we describe an adaptation of the recently developed INPACT system to express MSV-derived resistance genes in cell culture. Split gene cassette constructs (SGCs) were developed containing three different transgenes in combination with three different promoter sequences. In each SGC, the transgene was split such that it would be translatable only in the presence of an infecting MSV's replication associated protein. We used a quantitative real-time PCR assay to show that one of these SGCs (pSPLITrepIII-Rb-Ubi) inducibly inhibits MSV replication as efficiently as does a constitutively expressed transgene that has previously proven effective in protecting transgenic maize from MSV. In addition, in our cell-culture based assay pSPLITrepIII-Rb-Ubi inhibited replication of diverse MSV strains, and even, albeit to a lesser extent, of a different mastrevirus species. The application of this new technology to MSV resistance in maize could allow a better, more acceptable product.
[Mh] Termos MeSH primário: Resistência à Doença
Vírus do Listrado do Milho/genética
Plantas Geneticamente Modificadas/virologia
Zea mays/genética
Zea mays/imunologia
[Mh] Termos MeSH secundário: Técnicas de Cultura de Células
Genoma Viral
Vírus do Listrado do Milho/imunologia
Plantas Geneticamente Modificadas/imunologia
Regiões Promotoras Genéticas
Transgenes
Proteínas Virais/genética
Proteínas Virais/imunologia
Replicação Viral
Zea mays/virologia
[Pt] Tipo de publicação:JOURNAL ARTICLE; RESEARCH SUPPORT, NON-U.S. GOV'T
[Nm] Nome de substância:
0 (Viral Proteins)
[Em] Mês de entrada:1511
[Cu] Atualização por classe:170220
[Lr] Data última revisão:
170220
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:140829
[St] Status:MEDLINE
[do] DOI:10.1371/journal.pone.0105932


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[PMID]:24796552
[Au] Autor:Oluwafemi S; Kraberger S; Shepherd DN; Martin DP; Varsani A
[Ad] Endereço:Department of Crop Production, Soil and Environmental Management, Bowen University, P.M.B. 284, Iwo, Osun State, Nigeria.
[Ti] Título:A high degree of African streak virus diversity within Nigerian maize fields includes a new mastrevirus from Axonopus compressus.
[So] Source:Arch Virol;159(10):2765-70, 2014 Oct.
[Is] ISSN:1432-8798
[Cp] País de publicação:Austria
[La] Idioma:eng
[Ab] Resumo:The A-strain of maize streak virus (MSV-A; genus Mastrevirus, family Geminiviridae), the causal agent of maize streak disease, places a major constraint on maize production throughout sub-Saharan Africa. In West-African countries such as Nigeria, where maize is not cultivated year-round, this MSV strain is forced to overwinter in non-maize hosts. In order to both identify uncultivated grasses that might harbour MSV-A during the winter season and further characterise the diversity of related maize-associated streak viruses, we collected maize and grass samples displaying streak symptoms in a number of Nigerian maize fields. From these we isolated and cloned 18 full mastrevirus genomes (seven from maize and 11 from various wild grass species). Although only MSV-A isolates were obtained from maize, both MSV-A and MSV-F isolates were obtained from Digitaria ciliaris. Four non-MSV African streak viruses were also sampled, including sugarcane streak Reunion virus and Urochloa streak virus (USV) from Eleusine coacana, USV from Urochloa sp., maize streak Reunion virus (MSRV) from both Setaria barbata and Rottboellia sp., and a novel highly divergent mastrevirus from Axonopus compressus, which we have tentatively named Axonopus compressus streak virus (ACSV). Besides the discovery of this new mastrevirus species and expanding the known geographical and host ranges of MSRV, we have added D. ciliaris to the list of uncultivated species within which Nigerian MSV-A isolates are possibly able to overwinter.
[Mh] Termos MeSH primário: Vírus do Listrado do Milho/classificação
Vírus do Listrado do Milho/genética
Zea mays/virologia
[Mh] Termos MeSH secundário: DNA Viral
Digitaria/virologia
Eleusine/virologia
Genoma Viral/genética
Nigéria
Doenças das Plantas/virologia
Setaria (Planta)/virologia
[Pt] Tipo de publicação:JOURNAL ARTICLE; RESEARCH SUPPORT, NON-U.S. GOV'T
[Nm] Nome de substância:
0 (DNA, Viral)
[Em] Mês de entrada:1411
[Cu] Atualização por classe:140924
[Lr] Data última revisão:
140924
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:140507
[St] Status:MEDLINE
[do] DOI:10.1007/s00705-014-2090-7


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[PMID]:24789787
[Au] Autor:Monjane AL; Martin DP; Lakay F; Muhire BM; Pande D; Varsani A; Harkins G; Shepherd DN; Rybicki EP
[Ad] Endereço:Molecular and Cell Biology Department, University of Cape Town, Cape Town, South Africa Institute of Infectious Diseases and Molecular Medicine, University of Cape Town, Cape Town, South Africa.
[Ti] Título:Extensive recombination-induced disruption of genetic interactions is highly deleterious but can be partially reversed by small numbers of secondary recombination events.
[So] Source:J Virol;88(14):7843-51, 2014 Jul.
[Is] ISSN:1098-5514
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:Although homologous recombination can potentially provide viruses with vastly more evolutionary options than are available through mutation alone, there are considerable limits on the adaptive potential of this important evolutionary process. Primary among these is the disruption of favorable coevolved genetic interactions that can occur following the transfer of foreign genetic material into a genome. Although the fitness costs of such disruptions can be severe, in some cases they can be rapidly recouped by either compensatory mutations or secondary recombination events. Here, we used a maize streak virus (MSV) experimental model to explore both the extremes of recombination-induced genetic disruption and the capacity of secondary recombination to adaptively reverse almost lethal recombination events. Starting with two naturally occurring parental viruses, we synthesized two of the most extreme conceivable MSV chimeras, each effectively carrying 182 recombination breakpoints and containing thorough reciprocal mixtures of parental polymorphisms. Although both chimeras were severely defective and apparently noninfectious, neither had individual movement-, encapsidation-, or replication-associated genome regions that were on their own "lethally recombinant." Surprisingly, mixed inoculations of the chimeras yielded symptomatic infections with viruses with secondary recombination events. These recombinants had only 2 to 6 breakpoints, had predominantly inherited the least defective of the chimeric parental genome fragments, and were obviously far more fit than their synthetic parents. It is clearly evident, therefore, that even when recombinationally disrupted virus genomes have extremely low fitness and there are no easily accessible routes to full recovery, small numbers of secondary recombination events can still yield tremendous fitness gains. Importance: Recombination between viruses can generate strains with enhanced pathological properties but also runs the risk of producing hybrid genomes with decreased fitness due to the disruption of favorable genetic interactions. Using two synthetic maize streak virus genome chimeras containing alternating genome segments derived from two natural viral strains, we examined both the fitness costs of extreme degrees of recombination (both chimeras had 182 recombination breakpoints) and the capacity of secondary recombination events to recoup these costs. After the severely defective chimeras were introduced together into a suitable host, viruses with between 1 and 3 secondary recombination events arose, which had greatly increased replication and infective capacities. This indicates that even in extreme cases where recombination-induced genetic disruptions are almost lethal, and 91 consecutive secondary recombination events would be required to reconstitute either one of the parental viruses, moderate degrees of fitness recovery can be achieved through relatively small numbers of secondary recombination events.
[Mh] Termos MeSH primário: Adaptação Biológica
Recombinação Homóloga
Vírus do Listrado do Milho/genética
Viabilidade Microbiana
[Mh] Termos MeSH secundário: DNA Viral/química
DNA Viral/genética
Evolução Molecular
Vírus do Listrado do Milho/fisiologia
Doenças das Plantas/virologia
Análise de Sequência de DNA
Zea mays/virologia
[Pt] Tipo de publicação:JOURNAL ARTICLE; RESEARCH SUPPORT, NON-U.S. GOV'T
[Nm] Nome de substância:
0 (DNA, Viral)
[Em] Mês de entrada:1408
[Cu] Atualização por classe:170220
[Lr] Data última revisão:
170220
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:140503
[St] Status:MEDLINE
[do] DOI:10.1128/JVI.00709-14


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[PMID]:24524215
[Au] Autor:Cassone BJ; Wijeratne S; Michel AP; Stewart LR; Chen Y; Yan P; Redinbaugh MG
[Ti] Título:Virus-independent and common transcriptome responses of leafhopper vectors feeding on maize infected with semi-persistently and persistent propagatively transmitted viruses.
[So] Source:BMC Genomics;15:133, 2014 Feb 14.
[Is] ISSN:1471-2164
[Cp] País de publicação:England
[La] Idioma:eng
[Ab] Resumo:BACKGROUND: Insects are the most important epidemiological factors for plant virus disease spread, with >75% of viruses being dependent on insects for transmission to new hosts. The black-faced leafhopper (Graminella nigrifrons Forbes) transmits two viruses that use different strategies for transmission: Maize chlorotic dwarf virus (MCDV) which is semi-persistently transmitted and Maize fine streak virus (MFSV) which is persistently and propagatively transmitted. To date, little is known regarding the molecular and cellular mechanisms in insects that regulate the process and efficiency of transmission, or how these mechanisms differ based on virus transmission strategy. RESULTS: RNA-Seq was used to examine transcript changes in leafhoppers after feeding on MCDV-infected, MFSV-infected and healthy maize for 4 h and 7 d. After sequencing cDNA libraries constructed from whole individuals using Illumina next generation sequencing, the Rnnotator pipeline in Galaxy was used to reassemble the G. nigrifrons transcriptome. Using differential expression analyses, we identified significant changes in transcript abundance in G. nigrifrons. In particular, transcripts implicated in the innate immune response and energy production were more highly expressed in insects fed on virus-infected maize. Leafhoppers fed on MFSV-infected maize also showed an induction of transcripts involved in hemocoel and cell-membrane linked immune responses within four hours of feeding. Patterns of transcript expression were validated for a subset of transcripts by quantitative real-time reverse transcription polymerase chain reaction using RNA samples collected from insects fed on healthy or virus-infected maize for between a 4 h and seven week period. CONCLUSIONS: We expected, and found, changes in transcript expression in G. nigrifrons feeding of maize infected with a virus (MFSV) that also infects the leafhopper, including induction of immune responses in the hemocoel and at the cell membrane. The significant induction of the innate immune system in G. nigrifrons fed on a foregut-borne virus (MCDV) that does not infect leafhoppers was less expected. The changes in transcript accumulation that occur independent of the mode of pathogen transmission could be key for identifying insect factors that disrupt vector-mediated plant virus transmission.
[Mh] Termos MeSH primário: Hemípteros/genética
Hemípteros/virologia
Vírus do Listrado do Milho/fisiologia
Transcriptoma
Waikavirus/fisiologia
Zea mays/virologia
[Mh] Termos MeSH secundário: Animais
Metabolismo Energético/genética
Biblioteca Gênica
Sequenciamento de Nucleotídeos em Larga Escala
Imunidade Inata/genética
Insetos Vetores/genética
Fatores de Tempo
Regulação para Cima
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Em] Mês de entrada:1408
[Cu] Atualização por classe:170220
[Lr] Data última revisão:
170220
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:140215
[St] Status:MEDLINE
[do] DOI:10.1186/1471-2164-15-133


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[PMID]:23679984
[Au] Autor:Ruschhaupt M; Martin DP; Lakay F; Bezuidenhout M; Rybicki EP; Jeske H; Shepherd DN
[Ad] Endereço:Department of Molecular Biology and Plant Virology, Institute of Biology, University of Stuttgart, Pfaffenwaldring 57, Stuttgart, Germany.
[Ti] Título:Replication modes of Maize streak virus mutants lacking RepA or the RepA-pRBR interaction motif.
[So] Source:Virology;442(2):173-9, 2013 Aug 01.
[Is] ISSN:1096-0341
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:The plant-infecting mastreviruses (family Geminiviridae) express two distinct replication-initiator proteins, Rep and RepA. Although RepA is essential for systemic infectivity, little is known about its precise function. We therefore investigated its role in replication using 2D-gel electrophoresis to discriminate the replicative forms of Maize streak virus (MSV) mutants that either fail to express RepA (RepA(-)), or express RepA that is unable to bind the plant retinoblastoma related protein, pRBR. Whereas amounts of viral DNA were reduced in two pRBR-binding deficient RepA mutants, their repertoires of replicative forms changed only slightly. While a complete lack of RepA expression was also associated with reduced viral DNA titres, the only traces of replicative intermediates of RepA(-) viruses were those indicative of recombination-dependent replication. We conclude that in MSV, RepA, but not RepA-pRBR binding, is necessary for single-stranded DNA production and efficient rolling circle replication.
[Mh] Termos MeSH primário: DNA Helicases/metabolismo
Vírus do Listrado do Milho/fisiologia
Transativadores/metabolismo
Proteínas Virais/metabolismo
Replicação Viral
[Mh] Termos MeSH secundário: Células Cultivadas
DNA Helicases/genética
Eletroforese em Gel Bidimensional
Vírus do Listrado do Milho/genética
Deleção de Sequência
Transativadores/genética
Carga Viral
Proteínas Virais/genética
Zea mays/virologia
[Pt] Tipo de publicação:JOURNAL ARTICLE; RESEARCH SUPPORT, NON-U.S. GOV'T
[Nm] Nome de substância:
0 (Trans-Activators); 0 (Viral Proteins); 0 (replication initiator protein); EC 3.6.4.- (DNA Helicases)
[Em] Mês de entrada:1308
[Cu] Atualização por classe:131121
[Lr] Data última revisão:
131121
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:130518
[St] Status:MEDLINE


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[PMID]:23268599
[Au] Autor:Monjane AL; Pande D; Lakay F; Shepherd DN; van der Walt E; Lefeuvre P; Lett JM; Varsani A; Rybicki EP; Martin DP
[Ad] Endereço:Department of Molecular and Cell Biology, University of Cape Town, Rondebosch, Cape Town 7701, South Africa.
[Ti] Título:Adaptive evolution by recombination is not associated with increased mutation rates in Maize streak virus.
[So] Source:BMC Evol Biol;12:252, 2012 Dec 27.
[Is] ISSN:1471-2148
[Cp] País de publicação:England
[La] Idioma:eng
[Ab] Resumo:BACKGROUND: Single-stranded (ss) DNA viruses in the family Geminiviridae are proving to be very useful in real-time evolution studies. The high mutation rate of geminiviruses and other ssDNA viruses is somewhat mysterious in that their DNA genomes are replicated in host nuclei by high fidelity host polymerases. Although strand specific mutation biases observed in virus species from the geminivirus genus Mastrevirus indicate that the high mutation rates in viruses in this genus may be due to mutational processes that operate specifically on ssDNA, it is currently unknown whether viruses from other genera display similar strand specific mutation biases. Also, geminivirus genomes frequently recombine with one another and an alternative cause of their high mutation rates could be that the recombination process is either directly mutagenic or produces a selective environment in which the survival of mutants is favoured. To investigate whether there is an association between recombination and increased basal mutation rates or increased degrees of selection favoring the survival of mutations, we compared the mutation dynamics of the MSV-MatA and MSV-VW field isolates of Maize streak virus (MSV; Mastrevirus), with both a laboratory constructed MSV recombinant, and MSV recombinants closely resembling MSV-MatA. To determine whether strand specific mutation biases are a general characteristic of geminivirus evolution we compared mutation spectra arising during these MSV experiments with those arising during similar experiments involving the geminivirus Tomato yellow leaf curl virus (Begomovirus genus). RESULTS: Although both the genomic distribution of mutations and the occurrence of various convergent mutations at specific genomic sites indicated that either mutation hotspots or selection for adaptive mutations might elevate observed mutation rates in MSV, we found no association between recombination and mutation rates. Importantly, when comparing the mutation spectra of MSV and TYLCV we observed similar strand specific mutation biases arising predominantly from imbalances in the complementary mutations G → T: C → A. CONCLUSIONS: While our results suggest that recombination does not strongly influence mutation rates in MSV, they indicate that high geminivirus mutation rates are at least partially attributable to increased susceptibility of all geminivirus genomes to oxidative damage while in a single stranded state.
[Mh] Termos MeSH primário: Evolução Molecular
Vírus do Listrado do Milho/genética
Taxa de Mutação
Recombinação Genética
[Mh] Termos MeSH secundário: Adaptação Fisiológica/genética
Sequência de Bases
Geminiviridae/classificação
Geminiviridae/genética
Genoma Viral/genética
Genótipo
Dados de Sequência Molecular
Mutação
Doenças das Plantas/virologia
Seleção Genética
Homologia de Sequência do Ácido Nucleico
Especificidade da Espécie
Zea mays/virologia
[Pt] Tipo de publicação:JOURNAL ARTICLE; RESEARCH SUPPORT, NON-U.S. GOV'T
[Em] Mês de entrada:1306
[Cu] Atualização por classe:170220
[Lr] Data última revisão:
170220
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:121228
[St] Status:MEDLINE
[do] DOI:10.1186/1471-2148-12-252


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[PMID]:22136133
[Au] Autor:Monjane AL; van der Walt E; Varsani A; Rybicki EP; Martin DP
[Ad] Endereço:Department of Molecular and Cell Biology, University of Cape Town, Rondebosch, 7701, Cape Town, South Africa.
[Ti] Título:Recombination hotspots and host susceptibility modulate the adaptive value of recombination during maize streak virus evolution.
[So] Source:BMC Evol Biol;11:350, 2011 Dec 02.
[Is] ISSN:1471-2148
[Cp] País de publicação:England
[La] Idioma:eng
[Ab] Resumo:BACKGROUND: Maize streak virus -strain A (MSV-A; Genus Mastrevirus, Family Geminiviridae), the maize-adapted strain of MSV that causes maize streak disease throughout sub-Saharan Africa, probably arose between 100 and 200 years ago via homologous recombination between two MSV strains adapted to wild grasses. MSV recombination experiments and analyses of natural MSV recombination patterns have revealed that this recombination event entailed the exchange of the movement protein - coat protein gene cassette, bounded by the two genomic regions most prone to recombination in mastrevirus genomes; the first surrounding the virion-strand origin of replication, and the second around the interface between the coat protein gene and the short intergenic region. Therefore, aside from the likely adaptive advantages presented by a modular exchange of this cassette, these specific breakpoints may have been largely predetermined by the underlying mechanisms of mastrevirus recombination. To investigate this hypothesis, we constructed artificial, low-fitness, reciprocal chimaeric MSV genomes using alternating genomic segments from two MSV strains; a grass-adapted MSV-B, and a maize-adapted MSV-A. Between them, each pair of reciprocal chimaeric genomes represented all of the genetic material required to reconstruct - via recombination - the highly maize-adapted MSV-A genotype, MSV-MatA. We then co-infected a selection of differentially MSV-resistant maize genotypes with pairs of reciprocal chimaeras to determine the efficiency with which recombination would give rise to high-fitness progeny genomes resembling MSV-MatA. RESULTS: Recombinants resembling MSV-MatA invariably arose in all of our experiments. However, the accuracy and efficiency with which the MSV-MatA genotype was recovered across all replicates of each experiment depended on the MSV susceptibility of the maize genotypes used and the precise positions - in relation to known recombination hotspots - of the breakpoints required to re-create MSV-MatA. Although the MSV-sensitive maize genotype gave rise to the greatest variety of recombinants, the measured fitness of each of these recombinants correlated with their similarity to MSV-MatA. CONCLUSIONS: The mechanistic predispositions of different MSV genomic regions to recombination can strongly influence the accessibility of high-fitness MSV recombinants. The frequency with which the fittest recombinant MSV genomes arise also correlates directly with the escalating selection pressures imposed by increasingly MSV-resistant maize hosts.
[Mh] Termos MeSH primário: Evolução Molecular
Genoma Viral
Vírus do Listrado do Milho/genética
Recombinação Genética
Zea mays/virologia
[Mh] Termos MeSH secundário: Adaptação Biológica/genética
DNA Viral/genética
Resistência à Doença/genética
Aptidão Genética
Genótipo
Doenças das Plantas/genética
Doenças das Plantas/virologia
Zea mays/genética
[Pt] Tipo de publicação:JOURNAL ARTICLE; RESEARCH SUPPORT, NON-U.S. GOV'T
[Nm] Nome de substância:
0 (DNA, Viral)
[Em] Mês de entrada:1204
[Cu] Atualização por classe:170220
[Lr] Data última revisão:
170220
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:111206
[St] Status:MEDLINE
[do] DOI:10.1186/1471-2148-11-350



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