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two novel dnas that enhance symptoms and overcome cmd2 resistance to cassava mosaic disease.cassava mosaic begomoviruses (cmbs) cause cassava mosaic disease (cmd) across africa and the indian subcontinent. like all members of the geminivirus family, cmbs have small, circular single-stranded dna genomes. we report here the discovery of two novel dna sequences, designated segs-1 and segs-2 (forsequencesenhancinggeminivirussymptoms), that enhance symptoms and break resistance to cmd. the segs are characterized by gc-rich regions and the absence of long open reading frames. both segs enhan ...201626865712
divergent evolutionary and epidemiological dynamics of cassava mosaic geminiviruses in madagascar.cassava mosaic disease (cmd) in madagascar is caused by a complex of at least six african cassava mosaic geminivirus (cmg) species. this provides a rare opportunity for a comparative study of the evolutionary and epidemiological dynamics of distinct pathogenic crop-infecting viral species that coexist within the same environment. the genetic and spatial structure of cmg populations in madagascar was studied and bayesian phylogeographic modelling was applied to infer the origins of madagascan cmg ...201627600545
a single-tube duplex and multiplex pcr for simultaneous detection of four cassava mosaic begomovirus species in cassava plants.a single-tube duplex and multiplex pcr was developed for the simultaneous detection of african cassava mosaic virus (acmv), east african cassava mosaic cameroon virus (eacmcv), east african cassava mosaic malawi virus (eacmmv) and east african cassava mosaic zanzibar virus (eacmzv), four cassava mosaic begomoviruses (cmbs) affecting cassava in sub-saharan africa. co-occurrence of the cmbs in cassava synergistically enhances disease symptoms and complicates their detection and diagnostics. four p ...201323174160
complete genome sequencing of two causative viruses of cassava mosaic disease in ghana.cassava mosaic disease (cmv), caused by one or a combination of cassava mosaic geminiviruses, is ranked among the most important constraints to profitable and efficient production of cassava. effective control measures require in-depth knowledge of the viral causative agent. using rolling-circle amplification and unique enzymes, the full genome of two species of cassava mosaic geminivirus isolated from infected cassava plants in ghana were cloned into pcambia 1300 and pet-28b. the sequences of t ...201223237086
multiplex rt-pcr assays for the simultaneous detection of both rna and dna viruses infecting cassava and the common occurrence of mixed infections by two cassava brown streak viruses in east africa.uniplex and multiplex reverse transcription-polymerase chain reaction (rt-pcr) protocols were developed for the detection of cassava brown streak viruses (cbsvs) in single and mixed infections with cassava mosaic begomoviruses (cmbs) in a tropical crop plant, cassava (manihot esculenta). cmbs contain ssdna as their genome (genus begomovirus, family geminiviridae) while cbsvs are made up of positive sense ssrna (genus ipomovirus, family potyviridae), and they cause the economically important cass ...201222080852
east african cassava mosaic-like viruses from africa to indian ocean islands: molecular diversity, evolutionary history and geographical dissemination of a bipartite begomovirus.cassava (manihot esculenta) is a major food source for over 200 million sub-saharan africans. unfortunately, its cultivation is severely hampered by cassava mosaic disease (cmd). caused by a complex of bipartite cassava mosaic geminiviruses (cmg) species (family: geminivirideae; genus: begomovirus) cmd has been widely described throughout africa and it is apparent that cmg's are expanding their geographical distribution. determining where and when cmg movements have occurred could help curtail i ...201223186303
molecular interaction between two cassava geminiviruses exhibiting cross-protection.there are increasing reports of geminivirus mixed infections of field plant hosts. these mixed infections have been suggested to result in recombinations, emergence of new viruses and new disease epidemics. we previously reported the occurrence of mixed infection between african cassava mosaic virus (acmv) and east african cassava mosaic cameroon virus (eacmcv) resulting in severe symptoms in cassava fields in cameroon. here, we show that reassortment of dna-a and dna-b components of acmv and ea ...201121925553
a common set of developmental mirnas are upregulated in nicotiana benthamiana by diverse begomoviruses.begomoviruses are single-stranded dna viruses that cause economically important diseases of many crops throughout the world and induce symptoms in plants, including enations, leaf curling and stunting, that resemble developmental abnormalities. micrornas (mirnas) are small endogenous rnas that are involved in a variety of activities, including plant development, signal transduction and protein degradation, as well as response to environmental stress, and pathogen invasion.201121447165
comparison of phenotypes produced in response to transient expression of genes encoded by four distinct begomoviruses in nicotiana benthamiana and their correlation with the levels of developmental mirnas.abstract: background: whitefly-transmitted geminiviruses (begomoviruses) are a major limiting factor for the production of numerous dicotyledonous crops throughout the world. begomoviruses differ in the number of components that make up their genomes and association with satellites, and yet they cause strikingly similar phenotypes, such as leaf curling, chlorosis and stunted plant growth. micrornas (mirnas) are small endogenous rnas that regulate plant growth and development. the study described ...201121592402
biotechnological approaches to determine the impact of viruses in the energy crop plant jatropha curcas.abstract: background: geminiviruses infect a wide range of plant species including jatropha and cassava both belonging to family euphorbiaceae. cassava is traditionally an important food crop in sub - saharan countries, while jatropha is considered as valuable biofuel plant with great perspectives in the future. results: a total of 127 jatropha samples from ethiopia and kenya and 124 cassava samples from kenya were tested by enzyme-linked immunosorbent assay (elisa) for rna virus and polymerase ...201121812981
influence of retinoblastoma-related gene silencing on the initiation of dna replication by african cassava mosaic virus rep in cells of mature leaves in nicotiana benthamiana plants.abstract: background: geminiviruses mainly infect terminally differentiated tissues and cells in plants. they need to re-programme host cellular machinery for dna replication. this process is thought to be mediated by inactivation of cell-cycle repressor proteins and by induction of host dna synthesis protein expression through actions of the geminviral replication initiator protein (rep). findings: exploiting a nicotiana benthamiana pori2 line, which is transformed with a transgene consisting ...201122204717
a geminivirus-satellite complex is associated with leaf deformity of mentha (mint) plants in punjab.a widespread leaf deformity disease of mentha (mint), accompanied by whiteflies, the vectors of begomoviruses, was observed in punjab in the last few years. the presence of begomovirus was indicated by dna dot-blot analysis using the conserved coat protein and replication-associated protein genes of another begomovirus, sri lankan cassava mosaic virus (slcmv). a dna fragment (2.0 kb), representing a partial genomic dna of a begomovirus, amplified from the symptomatic mentha leaves was used to de ...201123637488
genetic variability of east african cassava mosaic cameroon virus under field and controlled environment conditions.cassava geminiviruses occur in all cassava growing areas of africa and are considered to be the most damaging vector-borne plant pathogens. at least seven species of these viruses have been identified. we investigated genetic variation in east african cassava mosaic cassava cameroon virus (eacmcv) from naturally infected cassava and from experimentally infected nicotiana benthamiana. results showed that the populations of eacmcv in cassava and in n. benthamiana were genetically heterogeneous. mu ...201121429548
top 10 plant viruses in molecular plant pathology.many scientists, if not all, feel that their particular plant virus should appear in any list of the most important plant viruses. however, to our knowledge, no such list exists. the aim of this review was to survey all plant virologists with an association with molecular plant pathology and ask them to nominate which plant viruses they would place in a 'top 10' based on scientific/economic importance. the survey generated more than 250 votes from the international community, and allowed the gen ...201122017770
a new strain of indian cassava mosaic virus causes a mosaic disease in the biodiesel crop jatropha curcas.jatropha curcas mosaic disease is a newly emerging disease that challenges the productivity of a prospective biofuel crop, j. curcas. the aetiology of this disease has not been resolved. here, we report the complete nucleotide sequences of a jatropha virus isolated from dharwad, southern india. phylogenetic analysis of the virus genome suggests it is a new strain of indian cassava mosaic virus. agroinfiltration of the two cloned viral dna components produced systemic infection and typical mosaic ...201020224893
differential interaction between cassava mosaic geminiviruses and geminivirus satellites.geminiviruses are often associated with subviral agents called dna satellites that require proteins encoded by the helper virus for their replication, movement and encapsidation. hitherto, most of the single-stranded dna satellites reported to be associated with members of the family geminiviridae have been associated with monopartite begomoviruses. cassava mosaic disease is known to be caused by viruses belonging to nine different begomovirus species in the african continent and the indian subc ...201020335493
plant geminivirus rep protein induces rereplication in fission yeast.the replication-associated protein (rep) of geminiviruses, single-stranded dna viruses of higher plants, is essential for virus replication. since these viruses do not encode their own polymerases, rep induces differentiated plant cells to reenter the cell cycle by interacting with the plant homologues of retinoblastoma proteins in order to activate the host dna synthesis machinery. we have used fission yeast (schizosaccharomyces pombe) as a model organism to analyze the impact of ectopically ex ...200919369323
characterization of the cassava geminivirus transcription activation protein putative nuclear localization signal.the geminivirus transcription activation protein (trap) localizes to the nucleus and contains a putative nuclear localization signal (nls) ((28)prrrr(32)) on the n-terminus. the role of individual residues of this putative nls on nuclear localization and symptom induction was investigated using trap of east african cassava mosaic cameroon virus (eacmcv). subcellular localization was conducted using the green fluorescent protein (gfp). results showed that the proline residue at position 28 (pro-2 ...200919665038
validation of high rates of nucleotide substitution in geminiviruses: phylogenetic evidence from east african cassava mosaic viruses.whitefly-transmitted geminiviruses are major pathogens of the important crop cassava in africa. the intensive sampling and sequencing of cassava mosaic disease-causing viruses that occurred in the wake of a severe outbreak in central africa (1997-2002) allowed us to estimate the rate of evolution of this virus. east african cassava mosaic virus and related species are obligately bipartite (dna-a and dna-b segments), and these two genome segments have different evolutionary histories. despite the ...200919264617
dose-dependent rnai-mediated geminivirus resistance in the tropical root crop cassava.cassava mosaic disease is a major constraint for cassava production in africa, resulting in significant economic losses. we have engineered transgenic cassava with resistance to african cassava mosaic virus (acmv), by expressing acmv ac1-homologous hairpin double-strand rnas. transgenic cassava lines with high levels of ac1-homologous small rnas have acmv immunity with increasing viral load and different inoculation methods. we report a correlation between the expression of the ac1-homologous sm ...200919300911
multiplex pcr for the detection of african cassava mosaic virus and east african cassava mosaic cameroon virus in cassava.a multiplex pcr was developed for simultaneous detection of african cassava mosaic virus (acmv) and east african cassava mosaic cameroon virus (eacmcv) in cassava affected with cassava mosaic disease (cmd). one set of three primers consisting of an upstream primer common for both viruses and two down stream virus-specific primers were designed for simultaneous amplification of 368 base pair (bp) and 650 bp dna fragments specific to the replicase gene of acmv and eacmcv, respectively. similarly, ...200818789974
phenotypes and functional effects caused by various viral rna silencing suppressors in transgenic nicotiana benthamiana and n. tabacum.rna silencing suppressor genes derived from six virus genera were transformed into nicotiana benthamiana and n. tabacum plants. these suppressors were p1 of rice yellow mottle virus (rymv), p1 of cocksfoot mottle virus, p19 of tomato bushy stunt virus, p25 of potato virus x, hcpro of potato virus y (strain n), 2b of cucumber mosaic virus (strain kin), and ac2 of african cassava mosaic virus (acmv). hcpro caused the most severe phenotypes in both nicotiana spp. ac2 also produced severe effects in ...200818184062
role of a geminivirus av2 protein putative protein kinase c motif on subcellular localization and pathogenicity.virus-derived genes or genome fragments are increasingly being used to generate transgenic plants with resistance to plant viruses. there is need to rapidly investigate these genes in plants using transient expression prior to using them as transgenes since they may be pathogenic to plants. in this study, we investigated the av2 protein encoded by east african cassava mosaic cameroon virus, a virus associated with a cassava disease epidemic in western africa. for subcellular localization, av2 wa ...200818405995
disassembly of african cassava mosaic virus.the plant-infecting geminiviruses encapsidate their single-stranded dna genome in characteristic twinned particles that are unique among viruses. these particles are formed by joining two incomplete t=1 icosahedra. african cassava mosaic virions were purified by density-gradient centrifugation from infected nicotiana benthamiana plants and analysed for their stability with respect to ph changes and heat treatment by using electron microscopy. negative staining and rotary shadowing revealed stabl ...200818632975
a single amino acid change in a geminiviral rep protein differentiates between triggering a plant defence response and initiating viral dna replication.we have devised an in planta system for functional analysis of the replication-associated protein (rep) of african cassava mosaic virus (acmv). using this assay and pcr-based random mutagenesis, we have identified an acmv rep mutant that failed to trigger the hypersensitive response (hr), but had an enhanced ability to initiate dna replication. the mutant rep-green fluorescent protein (gfp) fusion protein was localized to the nucleus. sequence analysis showed that the mutated rep gene had three ...200818796734
the role of biotechnology for agricultural sustainability in africa.sub-saharan africa could have a shortfall of nearly 90mt of cereals by the year 2025 if current agricultural practices are maintained. biotechnology is one of the ways to improve agricultural production. insect-resistant varieties of maize and cotton suitable for the subcontinent have been identified as already having a significant impact. virus-resistant crops are under development. these include maize resistant to the african endemic maize streak virus and cassava resistant to african cassava ...200817761472
diversity of begomoviruses associated with mosaic disease of cultivated cassava (manihot esculenta crantz) and its wild relative (manihot glaziovii mull. arg.) in uganda.cassava (manihot esculenta) growing in uganda during 2001-2002 has been screened for the presence of begomoviruses using pcr-rflp, cloning full-length genomic components and nucleotide sequence analysis. in contrast with a recent survey in neighbouring kenya, which identified three distinct strains of east african cassava mosaic virus (eacmv, eacmv-ug and eacmv-ke2) as well as east african cassava mosaic zanzibar virus and the new species east african cassava mosaic kenya virus, only eacmv-ug an ...200818559947
alternate hosts of african cassava mosaic virus and east african cassava mosaic cameroon virus in nigeria.cassava mosaic disease (cmd) caused by african cassava mosaic virus (acmv) and east african cassava mosaic cameroon virus (eacmcv) is the major constraint to cassava production in nigeria. sequences of the dna-a component of acmv and eacmcv isolates from leguminous plant species (senna occidentalis, leucana leucocephala and glycine max), castor oil plant (ricinus communis), a weed host (combretum confertum) and a wild species of cassava (manihot glaziovii) were determined. all acmv isolates from ...200818661095
agroinfection of cloned sri lankan cassava mosaic virus dna to arabidopsis thaliana, nicotiana tabacum and cassava.sri lankan cassava mosaic virus (slcmv) is a bipartite begomovirus infecting cassava in india and sri lanka. we have used agrobacterium-mediated inoculation (agroinoculation) of cloned slcmv dna to inoculate additional hosts, nicotiana tabacum and arabidopsis. although slcmv infection in these hosts caused stunting, leaf deformation and developmental abnormalities, accumulation levels of viral dna in the infected plants suggested that this virus was poorly adapted to them. in the natural host, c ...200818982246
infectivity, pseudorecombination and mutagenesis of kenyan cassava mosaic begomoviruses.cloned dna-a and dna-b components of kenyan isolates of east african cassava mosaic virus (eacmv, eacmv-ug and eacmv-ke2), east african cassava mosaic kenya virus (eacmkv) and east african cassava mosaic zanzibar virus (eacmzv) are shown to be infectious in cassava. eacmv and eacmkv genomic components have the same iteron sequence (ggggg) and can form viable pseudorecombinants, while eacmzv components have a different sequence (ggaga) and are incompatible with eacmv and eacmkv. mutagenesis of ea ...200717412996
deletion and recombination events between the dna-a and dna-b components of indian cassava-infecting geminiviruses generate defective molecules in nicotiana benthamiana.cloned dna-b components, belonging to the bipartite begomoviruses indian cassava mosaic virus (icmv) and sri lankan cassava mosaic virus (slcmv), family geminiviridae, when co-inoculated along with previously cloned dna-a components of the respective viruses onto the experimental host nicotiana benthamiana, generated defective dnas (def-dna) ranging in size from 549 to 1555 nucleotides. all the cloned def-dnas contained the common region (cr) as well as portions of either dna-a or dna-b and, in ...200717109983
tissue and cell tropism of indian cassava mosaic virus (icmv) and its av2 (precoat) gene product.in order to establish defined viruses for challenging plants in resistance breeding programmes, indian cassava mosaic virus (icmv; family geminiviridae) dna clones were modified to monitor viral spread in plants by replacing the coat protein gene with the green fluorescent protein (gfp) reporter gene. comparative in situ hybridization experiments showed that icmv was restricted to the phloem in cassava and tobacco. gfp-tagged virus spread similarly, resulting in homogeneous fluorescence within n ...200717049959
the consensus n-myristoylation motif of a geminivirus ac4 protein is required for membrane binding and pathogenicity.some geminiviruses encode a small protein, ac4, whose role in pathogenesis has only recently attracted attention. a few studies have shown that this protein is involved in pathogenesis and suppresses rna silencing. here, using nicotiana benthamiana, we show that east african cassava mosaic cameroon virus (eacmcv) ac4 is a pathogenicity determinant and that it suppresses the systemic phase of rna silencing. furthermore, confocal imaging analyses show that it binds preferentially to the plasma mem ...200717427808
transgenic cassava resistance to african cassava mosaic virus is enhanced by viral dna-a bidirectional promoter-derived sirnas.expression of double-stranded rna (dsrna) homologous to virus sequences can effectively interfere with rna virus infection in plant cells by triggering rna silencing. here we applied this approach against a dna virus, african cassava mosaic virus (acmv), in its natural host cassava. transgenic cassava plants were developed to express small interfering rnas (sirna) from a camv 35s promoter-controlled, intron-containing dsrna cognate to the common region-containing bidirectional promoter of acmv d ...200717492253
cassava mosaic virus disease in east and central africa: epidemiology and management of a regional pandemic. 200617027685
biodiversity and recombination of cassava-infecting begomoviruses from southern india.cassava mosaic disease (cmd) is caused by various begomoviruses of the family geminiviridae leading to considerable crop losses in africa and asia. recombination between their genomic components has generated new pathotypes with enhanced virulence in africa. here, we report about a survey on the biodiversity of begomoviruses in cassava from southern india (tamil nadu and kerala states) performed in 2001 and 2002. viral dna a components from stem cuttings were analysed using polymerase chain reac ...200616132175
genetic diversity and phylogeography of cassava mosaic viruses in kenya.cassava is a major factor in food security across sub-saharan africa. however, the crop is susceptible to losses due to biotic stresses, in particular to viruses of the genus begomovirus (family geminiviridae) that cause cassava mosaic disease (cmd). during the 1990s, an epidemic of cmd severely hindered cassava production across eastern and central africa. a significant influence on the appearance of virus epidemics is virus diversity. here, a survey of the genetic diversity of cmd-associated b ...200616963765
the oligomeric rep protein of mungbean yellow mosaic india virus (mymiv) is a likely replicative helicase.geminiviruses replicate by rolling circle mode of replication (rcr) and the viral rep protein initiates rcr by the site-specific nicking at a conserved nonamer (taatatt downward arrow ac) sequence. the mechanism of subsequent steps of the replication process, e.g. helicase activity to drive fork-elongation, etc. has largely remained obscure. here we show that rep of a geminivirus, namely, mungbean yellow mosaic india virus (mymiv), acts as a replicative helicase. the rep-helicase, requiring > or ...200617142233
the use of biolistic inoculation of cassava mosaic begomoviruses in screening cassava for resistance to cassava mosaic disease.inoculation of cassava with infectious clones of cassava mosaic geminiviruses (geminiviridae: begomovirus) and total dna extracts from plants infected with well-characterised viruses was evaluated using the bio-rad helios gene gun system. total dna extracts from infected plants and cloned viruses were produced for coating gold particles and bombardment onto new cassava genotypes, 96/1089a, 96/1039, 96/0160, 96/0304 and three local landraces tme 117, tme 3 and tme 4. cloned dna of a kenyan isolat ...200616839615
both indian cassava mosaic virus and sri lankan cassava mosaic virus are found in india and exhibit high variability as assessed by pcr-rflp.the biodiversity of geminiviruses associated with the cassava mosaic disease (cmd) in india was investigated using pcr to specifically amplify the dna of indian cassava mosaic virus (icmv) or sri lankan cassava mosaic virus (slcmv) and also by using pcr to amplify specific viral genes, followed by digestion with different restriction endonucleases to obtain polymorphic patterns (pcr-rflp). results showed that both icmv and slcmv were present in mosaic-affected cassava; icmv was geographically re ...200515503225
microrna-binding viral protein interferes with arabidopsis development.micrornas (mirnas) are small (approximately 21 nt), noncoding rnas that negatively regulate target mrnas at the posttranscriptional level that are involved in development. in plants, virus-induced disease symptoms often result in developmental abnormalities resembling perturbation of mirna-mediated function. here, we report that expression in transgenic plants of a geminivirus-encoded ac4 protein from african cassava mosaic virus cameroon strain (acmv), a suppressor of posttranscriptional gene s ...200516006510
molecular biodiversity of cassava begomoviruses in tanzania: evolution of cassava geminiviruses in africa and evidence for east africa being a center of diversity of cassava geminiviruses.cassava is infected by numerous geminiviruses in africa and india that cause devastating losses to poor farmers. we here describe the molecular diversity of seven representative cassava mosaic geminiviruses (cmgs) infecting cassava from multiple locations in tanzania. we report for the first time the presence of two isolates in east africa: (eacmcv-[tz1] and eacmcv-[tz7]) of the species east african cassava mosaic cameroon virus, originally described in west africa. the complete nucleotide seque ...200515784145
biolistic infection of cassava using cloned components of indian cassava mosaic virus.cassava mosaic disease (cmd) is a major constraint to cassava production in africa and asia. of the two begomoviruses associated with cmd on the indian subcontinent, indian cassava mosaic virus (icmv) and sri lankan cassava mosaic virus, only the latter has been successfully reintroduced into cassava to resolve the aetiology of the disease. here, we report the complete nucleotide sequence of an icmv isolate from maharashtra (icmv-[mah2]), central india. biolistic inoculation of the cloned compon ...200515824887
identification of a second begomovirus, sri lankan cassava mosaic virus, causing cassava mosaic disease in india.the dna a and dna b components of a begomovirus associated with cassava mosaic disease (cmd) originating from kerala, india, were cloned. biolistically inoculated clones induced symptoms typical of cmd in cassava. sequence comparisons showed the virus to be an isolate of sri lankan cassava mosaic virus (slcmv). this is the first time this begomovirus species has been identified in india and only the second species shown to cause cmd in the country. the implication of these findings on our unders ...200515986172
resistance to cassava mosaic disease in transgenic cassava expressing antisense rnas targeting virus replication genes.african cassava mosaic virus (acmv) is a major contributor to cassava mosaic disease (cmd), the economically most important and devastating disease of cassava in africa. we have developed transgenic cassava plants with increased acmv resistance using improved antisense rna technology by targeting the viral mrnas of rep (ac1), trap (ac2) and ren (ac3). viral dna replication assays in detached leaves demonstrated that replication of two acmv isolates was strongly reduced or inhibited in most trans ...200517173627
broad spectrum resistance to ssdna viruses associated with transgene-induced gene silencing in cassava.geminiviruses are ssdna viruses that infect a range of economically important crop species. we have developed a pathogen-derived transgenic approach to generate high levels of resistance against these pathogens in a susceptible cultivar of cassava (manihot esculenta). integration of the ac1 gene (which encodes the replication-associated protein) from african cassava mosaic virus imparted resistance against the homologous virus and provided strong cross-protection against two heterologous species ...200415630623
short interfering rna accumulation correlates with host recovery in dna virus-infected hosts, and gene silencing targets specific viral sequences.viruses are both inducers and targets of posttranscriptional gene silencing (ptgs), a natural defense mechanism in plants. here we report molecular evidence of the ability of single-stranded dna (ssdna) viruses to induce ptgs in infected plants irrespective of the severity of or recovery from the symptoms. our results reveal that five distinct species of cassava-infecting geminiviruses were capable of triggering ptgs by producing two classes of virus-specific short interfering rnas (sirnas) of 2 ...200415220420
differential roles of ac2 and ac4 of cassava geminiviruses in mediating synergism and suppression of posttranscriptional gene silencing.posttranscriptional gene silencing (ptgs) in plants is a natural defense mechanism against virus infection. in mixed infections, virus synergism is proposed to result from suppression of the host defense mechanism by the viruses. synergistic severe mosaic disease caused by simultaneous infection with isolates of the cameroon strain of african cassava mosaic virus (acmv-[cm]) and east african cassava mosaic cameroon virus (eacmcv) in cassava and tobacco is characterized by a dramatic increase in ...200415308741
east african cassava mosaic zanzibar virus - a recombinant begomovirus species with a mild phenotype.cassava plants exhibiting mild symptoms of cassava mosaic disease (cmd) were collected from unguja island, zanzibar. cuttings grown from these plants in the glasshouse produced similar symptoms, which were milder than those caused by other known cassava mosaic geminiviruses (cmgs). the whitefly vector, bemisia tabaci (gennadius), transmitted the putative virus to 27.7% (n = 18) of target plants. total dna extracted from diseased leaves did not yield diagnostic pcr-bands using virus-specific prim ...200415375675
short deletions in nuclear targeting sequences of african cassava mosaic virus coat protein prevent geminivirus twinned particle formation.coat proteins (cps) of geminiviruses are multifunctional proteins. using transient expression experiments, we have recently identified putative sequence motifs of african cassava mosaic virus (acmv) cp involved in nuclear import (nls) and export (nes) (virology 286 (2001) 373). here, we report on the effect of corresponding deletion mutants in the context of infecting viruses. since nls and nes may overlap with dna binding and multimerisation domains, we have investigated their effect on viral i ...200414972538
begomoviruses from mungbeans in pakistan: epitope profiles, dna a sequences and phylogenetic relationships.monoclonal antibodies raised against particles of african cassava mosaic virus, indian cassava mosaic virus or okra leaf curl virus were used to test samples collected in pakistan from begomovirus-infected plants. epitope profiles obtained from cucurbits resembled those previously reported for pakistani begomoviruses. in contrast, epitope profiles obtained from legumes showed little diversity and were quite distinct from these. dna with nucleotide sequences typical of begomovirus dna a component ...200415045567
a geminivirus-induced gene silencing system for gene function validation in cassava.we have constructed an african cassava mosaic virus (acmv) based gene-silencing vector as a reverse genetics tool for gene function analysis in cassava. the vector carrying a fragment from the nicotiana tabacum sulfur gene (su), encoding one unit of the chloroplast enzyme magnesium chelatase, was used to induce the silencing of the cassava orthologous gene resulting in yellow-white spots characteristic of the inhibition of su expression. this result suggests that well developed sequence database ...200415630624
geminate structures of african cassava mosaic virus.two types of geminate structures were purified from african cassava mosaic geminivirus (acmv)-infected nicotiana benthamiana plants and analyzed by electron cryomicroscopy and image reconstruction. after cesium sulfate density gradient centrifugation, they were separated into lighter top (t) and heavier bottom (b) components. t particles comigrated with host proteins, whereas b particles were concentrated in a cesium density typical for complete virions. both particles were composed of two incom ...200415194750
novel system for the simultaneous analysis of geminivirus dna replication and plant interactions in nicotiana benthamiana.the origin of replication of african cassava mosaic virus (acmv) and a gene expression vector based on potato virus x were exploited to devise an in planta system for functional analysis of the geminivirus replication-associated protein (rep) in transgenic nicotiana benthamiana line pori-2. this line contains an integrated copy of a tandem repeat of the acmv origin of replication flanking nonviral sequences that can be mobilized and replicated by rep as an episomal replicon. a rep-gfp fusion pro ...200314645587
short interfering rna-mediated interference of gene expression and viral dna accumulation in cultured plant cells.gene silencing mediated by double-stranded rna is a sequence-specific rna degradation mechanism highly conserved in eukaryotes that serves as an antiviral defense pathway in both plants and drosophila. short interfering rnas (sirnas), the 21- to 23-nt double-stranded intermediates of this natural defense mechanism, are becoming powerful tools for reducing gene expression and countering viral infection in a variety of mammalian cells. here we report the use of sirnas to target reporter gene expre ...200312886005
bemisia tabaci (homoptera: aleyrodidae) biotypes in india.host plant performance, esterase, and virus transmission tests revealed cassava-strain and sweetpotato-strain populations of whitefly bemisia tabaci (gennadius) biotypes in india. individuals from the sweetpotato-reared population did not breed on cassava, manihot esculenta crantz, and the cassava-strain-reared individuals failed to develop on sweetpotato, ipomoea batatus (l.) lam. eggplant, solanum melongena l., and tobacco, nicotiana tabacum l., were common hosts for both biotypes. the cassava ...200314994796
efficient replication of cloned african cassava mosaic virus in cassava leaf disks.a transient viral replication assay for cloned african cassava mosaic virus (acmv) was developed using cassava leaf disks. tms60444 leaf disks were transfected using biolistic-mediated inoculation with acmv clones pkacmva and pkacmvb, which originate from west kenya acmv isolate 844 (acmv-ke). viral dna synthesized de novo was monitored by southern hybridization with an av1 dna probe. by using the methylation-sensitive restriction enzymes dpni and mboi, it was possible to distinguish between the ...200312606075
characterisation of sri lankan cassava mosaic virus and indian cassava mosaic virus: evidence for acquisition of a dna b component by a monopartite begomovirus.two bipartite begomoviruses, indian cassava mosaic virus (icmv) and sri lankan cassava mosaic virus (slcmv), have been isolated from mosaic-diseased cassava originating from central india and sri lanka, respectively. icmv was transmitted with low efficiency from cassava to nicotiana benthamiana by sap inoculation to give leaf curl symptoms. slcmv was much more virulent in this host, producing severe stunting, leaf curl, and chlorosis. these symptoms were reproduced when their cloned genomic comp ...200211853400
mutation of three cysteine residues in tomato yellow leaf curl virus-china c2 protein causes dysfunction in pathogenesis and posttranscriptional gene-silencing suppression.the nuclear localized c2 protein of the monopartite begomovirus tomato yellow leaf curl virus-china (tylcv-c) contributes to viral pathogenicity. here, we have investigated tylcv-c c2 protein domains that play a role in the phenotype. alignment of the c2 protein with 67 homologues from monopartite and bipartite begomoviruses revealed that a putative zinc-finger motif c36-x1-c38-x7-c46-x6-h53-x4-h58c59 and four potential phosphorylation sites (t52, s61, y68, and s74) are highly conserved. when ex ...200211952122
a distinct bemisia tabaci (gennadius) (hemiptera: sternorrhyncha: aleyrodidae) genotype cluster is associated with the epidemic of severe cassava mosaic virus disease in uganda.during the 1990s, an epidemic of cassava mosaic virus disease caused major losses to cassava production in uganda. two factors associated with the epidemic were the occurrence of a novel recombinant begomovirus, eacmv-ug, and unusually high populations of the whitefly vector, bemisia tabaci. here we present molecular evidence for the occurrence of two cassava-colonizing b. tabaci genotype clusters, ug1 and ug2, one of which, ug2, can be consistently associated with the cmd epidemic in uganda at ...200212074729
co-adaptation between cassava mosaic geminiviruses and their local vector populations.four cassava mosaic geminivirus (cmg) isolates; african cassava mosaic virus from namulonge, uganda (acmv-[nam]), east african cassava mosaic virus from mtwara, tanzania (eacmv-[mtw]), eacmv-uganda from namulonge (eacmv-ug[nam]) and indian cassava mosaic virus from trivandrum, india (icmv-[tri]) were compared for their ability to be transmitted by four colonies of cassava whitefly, bemisia tabaci (gennadius), collected from namulonge (nam), mtwara (mtw), kumasi (kum) and trivandrum (tri). with 2 ...200212076831
differential roles of geminivirus rep and ac4 (c4) in the induction of necrosis in nicotiana benthamiana.summary the replication-associated protein (rep) of two distinct begomoviruses, the bipartite african cassava mosaic virus (acmv) and the monopartite tomato yellow leaf curl virus-china (tylcv-c), elicits a reaction resembling a hypersensitive response (hr), associated with the induction of local necrosis and a systemic burst of hydrogen peroxide production, when expressed from a potato virus x vector in nicotiana benthamiana. transient expression of the acmv rep after agrobacterium infiltration ...200220569353
simultaneous analysis of the bidirectional african cassava mosaic virus promoter activity using two different luciferase genes.the expression of geminivirus genes is controlled by bidirectional promoters which are located in the large intergenic region of the circular dna genomes and specifically regulated by virus encoded proteins. in order to study the simultaneous regulation of both orientations of the dna a and dna b promoters of african cassava mosaic virus (acmv), they were cloned between two different luciferase genes with the firefly luciferase gene in complementary-sense and the renilla luciferase gene in virio ...200111324760
subcellular targeting of the coat protein of african cassava mosaic geminivirus.the coat protein (cp) of geminiviruses is involved in a number of processes during the life cycle of the virus. the predominant function is encapsidation of single-stranded dna and formation of the virus particle to protect viral dna during transmission. the cp of monopartite geminiviruses is absolutely essential for virus movement, whereas cp mutants of bipartite geminiviruses are able to infect some host plants systemically, indicating an involvement of the cp in host specificity. during the l ...200111485405
molecular evidence for diverse populations of cassava-infecting begomoviruses in southern africa.in this paper we describe results obtained from screening field populations of begomoviruses from infected cassava from six countries in southern africa. it was found that african cassava mosaic virus occurs in five of the six countries (except angola), east african cassava mosaic virus is present in five countries (except zambia) and south african cassava mosaic virus was detected only in south africa and swaziland. in addition, we report for the first time in southern africa, the appearance of ...200111699964
recombination, pseudorecombination and synergism of geminiviruses are determinant keys to the epidemic of severe cassava mosaic disease in uganda.the molecular variability of cassava geminiviruses occurring in uganda was investigated in this study. infected cassava plants and whiteflies were collected from cassava plantings in different geographical areas of the country and pcr was used for molecular characterization of the viruses. two complete sequences of dna-a and -b from african cassava mosaic virus (acmv), two dna-a sequences from east african cassava mosaic virus (eacmv), two dna-b sequences of eacmv and the partial dna-a nucleotid ...200111172108
complete nucleotide sequence and host range of south african cassava mosaic virus: further evidence for recombination amongst begomoviruses.complete nucleotide sequences of the dna-a (2800 nt) and dna-b (2760 nt) components of a novel cassava-infecting begomovirus, south african cassava mosaic virus (sacmv), were determined and compared with various new world and old world begomoviruses. sacmv is most closely related to east african cassava mosaic virus (eacmv) in both its dna-a (85% with eacmv-mh and -mk) and -b (90% with eacmv-ug2-mld and eacmv-ug3-svr) components; however, percentage sequence similarities of less than 90% in the ...200111125158
the size of encapsidated single-stranded dna determines the multiplicity of african cassava mosaic virus particles.transgenic nicotiana benthamiana plants harbouring a defective interfering (di) dna of african cassava mosaic virus (acmv) and control plants were inoculated with acmv. virus particles were purified from infected plants, separated in sucrose gradients and fractions were analysed by southern blotting. transgenic plant-derived virus particles taken from the top fractions of sucrose gradients contained di dna, middle fractions contained a mixture of genomic and di dna and bottom fractions contained ...200111172110
expression of the oligomerization domain of the replication-associated protein (rep) of tomato leaf curl new delhi virus interferes with dna accumulation of heterologous geminiviruses.the minimal dna binding domain of the replication-associated protein (rep) of tomato leaf curl new delhi virus was determined by electrophoretic mobility gel shift analysis and co-purification assays. dna binding activity maps to amino acids 1-160 (rep-(1-160)) of the rep protein and overlaps with the protein oligomerization domain. transient expression of rep protein (rep-(1-160)) was found to inhibit homologous viral dna accumulation by 70-86% in tobacco protoplasts and in nicotiana benthamian ...200111342533
expression of functional recombinant antibody molecules in insect cell expression systems.recombinant single-chain variable-fragment molecules (scfv) were constructed from a cell line expressing a monoclonal antibody against african cassava mosaic virus (acmv) and expressed in escherichia coli. dna sequences that encoded the scfv were manipulated to allow scfv expression in insect cell lines. a recombinant baculovirus containing the scfv cdna was constructed and large amounts of scfv were produced in each of three insect cell lines infected with the baculovirus. however, the scfv wer ...200010686153
evidence of synergism between african cassava mosaic virus and a new double-recombinant geminivirus infecting cassava in cameroon.stem cuttings were collected in cameroon from cassava plants displaying cassava mosaic disease (cmd) symptoms. the nature of the viruses present was determined by using the pcr with primers specific for the coat protein (cp) genes of african cassava mosaic virus (acmv) and east african cassava mosaic virus (eacmv). all samples were infected by acmv and eight of the 50 samples were infected by both acmv and an eacmv-like virus. the complete nucleotide sequences of dna-a and -b of representative a ...200010640569
cassava mosaic virus disease in east africa: a dynamic disease in a changing environment.cassava mosaic disease (cmd), now known to be caused by cassava mosaic geminiviruses (family geminiviridae; genus begomovirus), was first reported in east africa in 1894. epidemics occurred in madagascar and uganda in the 1930s and 1940s, and more localised rapid spread of cmd was observed in parts of coastal tanzania in the 1930s and coastal kenya in the 1970s. during the 1990s, a major regional pandemic of an unusually severe form of cmd has expanded to affect parts of at least five countries, ...200011137168
a nanovirus-like dna component associated with yellow vein disease of ageratum conyzoides: evidence for interfamilial recombination between plant dna viruses.yellow vein disease of ageratum conyzoides, a weed species that is widely distributed throughout asia, has been attributed to infection by the geminivirus ageratum yellow vein virus (ayvv). in addition to a single ayvv genomic component (dna a), we have previously demonstrated that infected plants contain chimeric defective viral components, comprising dna a and nongeminiviral sequences, that act as defective interfering dnas. a database search has revealed that the nongeminiviral sequences of o ...199910544139
identification of genes directly and indirectly involved in the insect transmission of african cassava mosaic geminivirus by bemisia tabaci.the inability to transmit progeny virus resulting from the cloned components of an isolate of african cassava mosaic virus originating from kenya (acmv-k) has been shown to be due to defects in both genomic components. this was achieved by the production of infectious pseudorecombinants between acmv-k and the cloned components of a whitefly-transmissible acmv isolate originating from nigeria (acmv-nog). the exchange of gene fragments between acmv-k and acmv-nog has been used to demonstrate that ...199910334034
nucleotide sequence and intergeminiviral homologies of the dna-a of papaya leaf curl geminivirus from india.coat protein gene, rep protein gene and intergenic region of the genome of a whitefly transmitted geminivirus (wtg) causing severe leaf curl in papaya plants were pcr amplified, cloned and sequenced. comparison of the amino acid sequence of the putative coat protein product of papaya leaf curl virus (plcv) with some other mono and bipartite wtgs revealed a maximum of 89.8% homology with indian cassava mosaic virus. the genomic organization of plcv-india is similar to other wtgs with bipartite ge ...19989635134
infectivity of african cassava mosaic virus clones to cassava by biolistic inoculation.clones of an african cassava mosaic virus isolate originating from nigeria (acmv-nog) were shown to be infectious to cassava by biolistic inoculation. the production of pseudorecombinants between acmv-nog and clones of an acmv isolate originating from kenya (acmv-k) indicated that the lack of infectivity of acmv-k to cassava was due to defect(s) in the dna b genomic component; this component encodes two proteins involved in cell-to-cell movement. this is the first demonstration of infectivity of ...19989930204
molecular characterisation of a distinct south african cassava infecting geminivirus.african cassava mosaic virus (acmv) and east african cassava mosaic virus (eacmv) are whitefly-transmitted geminiviruses (wtgs) which are widespread in cassava in africa and cause serious yield losses. recently, a new geminivirus affecting cassava in south africa (sacmv) has been reported. in this work sacmv was found to have dna-a and dna-b components. comparisons of amino acid sequences of the putative coat protein, and nucleotide sequences of the common region and a 687-bp dna b fragment of s ...19989856107
types of variation in dna-a among isolates of east african cassava mosaic virus from kenya, malawi and tanzania.complete nucleotide sequences of the dna-a-like molecules of three east african cassava mosaic virus (eacmv) isolates from kenya (-k, 2801 nt) and malawi (-mh and -mk, both 2804 nt) were determined. these sequences were compared with that published for a tanzanian isolate (-t, 2801 nt) and the partial sequence of a third malawian isolate. intergenic region sequences of all isolates, and deduced amino acid sequences of their ac1 (rep) proteins, each formed a tightly related cluster that was disti ...19989820161
recombination between viral dna and the transgenic coat protein gene of african cassava mosaic geminivirus.nicotiana benthamiana was transformed with three different constructs (pcra1, pcra2 and pjc1) containing the coat protein coding sequence of african cassava mosaic virus (acmv). transformed plants were inoculated with a coat protein deletion mutant of acmv that induces mild systemic symptoms in control plants. several inoculated plants of transgenic lines cra1/3, cra1/4, cra2/1 and cra2/2 developed severe systemic symptoms typical of acmv. dna analysis revealed that, in these plants, recombinati ...19989603342
efficient whitefly transmission of african cassava mosaic geminivirus requires sequences from both genomic components.clones of two subgroup iii geminiviruses, the common strain of tomato golden mosaic virus (cstgmv) and african cassava mosaic virus originating from kenya (acmv-k), were shown to be non-transmissible by whitefiles. lack of transmissibility of cloned acmv-k was investigated by exchanging genomic components with a whitefly-transmissible acmv isolate from nigeria (acmv-nog). neither pseudorecombinant was transmissible, indicating that defects in both genomic components contributed to the lack of tr ...19979225057
transactivation of dianthin transgene expression by african cassava mosaic virus ac2.we have recently described a novel strategy for engineering resistance to african cassava mosaic virus (acmv) in transgenic nicotiana benthamiana plants using a virus-inducible promoter to control the expression of a plant ribosome-inactivating protein (rip) transgene (y. hong et al., virology 220, 119-127, 1996). here, we have used a potato virus x (pvx) vector to express the acmv transactivator protein, ac2, in planta. we confirm that amplification of rip activity in transgenic plants is media ...19979123846
evidence that dna-a of a geminivirus associated with severe cassava mosaic disease in uganda has arisen by interspecific recombination.geminivirus isolates associated with the epidemic of severe cassava mosaic disease in uganda were studied and compared with virus isolates from the part of uganda outside the epidemic area, and with african cassava mosaic virus (acmv) and east african cassava mosaic virus (eacmv). isolates of a novel type [the uganda variant (ugv)] were detected in severely affected plants from the epidemic area, whereas those from plants outside the epidemic area were typical of acmv. the complete nucleotide se ...19979267014
a novel subviral agent associated with a geminivirus: the first report of a dna satellite.numerous plant rna viruses have associated with them satellite (sat) rnas that have little or no nucleotide sequence similarity to either the viral or host genomes but are completely dependent on the helper virus for replication. we report here on the discovery of a 682-nt circular dna satellite associated with tomato leaf curl geminivirus (tlcv) infection in northern australia. this is the first demonstration that satellite molecules are not limited to rna viral systems. the dna satellite (tlcv ...19979192696
resistance to geminivirus infection by virus-induced expression of dianthin in transgenic plants.ribosome-inactivating proteins (rips) are naturally occurring plant toxins that exhibit antiviral activity against a diverse range of plant and animal viruses. here, the action of dianthin, a potent rip isolated from dianthus caryophyllus, has been exploited to engineer resistance to a plant dna virus, african cassava mosaic virus (acmv), in transgenic nicotiana benthamiana. to achieve this, dianthin has been expressed from the acmv virion-sense promoter that is transactivated by the product of ...19968659104
chinese squash leaf curl virus: a new whitefly-transmitted geminivirus.coat protein (cp) gene of the chinese squash leaf curl virus (sqlcv-c) was amplified through pcr, cloned and completely sequenced. based on the comparisons at the levels of both cp gene nucleotide and cp-deduced amino acid sequences with other geminiviruses, sqlcv-c is confirmed to be distinct from the american squash leaf curl virus (sqlcv-e). it is a new geminivirus transmitted by whitefly bemisia tabaci, which infects dicotyledonous plants and is more closely related to the indian cassava mos ...19957755872
mutagenesis of the bc1 and bv1 genes of african cassava mosaic virus identifies conserved amino acids that are essential for spread.the products of three open reading frames encoded by the bipartite geminiviruses have been implicated in viral spread: ac2, bv1 and bc1. alignment of the dna b encoded gene products, bv1 and bc1, from african cassava mosaic virus (acmv) with six other bipartite geminiviruses showed several highly conserved regions. specific amino acids were selected for mutagenic studies to ascertain the tolerance of the virus to change and to identify the regions within these two proteins required for normal fu ...19957730816
complementation of african cassava mosaic virus ac2 gene function in a mixed bipartite geminivirus infection.we have previously demonstrated that african cassava mosaic virus (acmv) dnas a and b efficiently complement the systemic spread of tomato golden mosaic virus (tgmv) dna a when co-agroinoculated onto nicotiana benthamiana. here, we show that a mixture of an acmv dna a ac2 mutant and dna b that is normally unable to systemically infect n. benthamiana can do so at low frequency when co-agroinoculated with tgmv dna a. analysis of viral dna showed that the ac2 mutation was retained during infection. ...19957561766
tomato leaf curl geminivirus from india has a bipartite genome and coat protein is not essential for infectivity.genomes of two isolates of tomato leaf curl geminivirus from india (tolcv-india) have been sequenced. tolcv-india contains a and b components, both of which are required for systemic movement and symptom development. the two isolates have 94% sequence identify but one isolate gave mild symptoms in nicotiana benthamiana and tomato. the genome organization of tolcv-india is similar to other whitefly-transmitted geminiviruses (wtgs) with bipartite genomes. however, it contains an additional orf, av ...19957844539
regulation of african cassava mosaic virus complementary-sense gene expression by n-terminal sequences of the replication-associated protein ac1.fragments of the african cassava mosaic virus (acmv) genome, cloned upstream of the beta-glucuronidase (gus) reporter gene in an expression cassette, were analysed for their ability to direct complementary-sense gene expression in tobacco protoplasts by measuring gus activity. five arbitrary domains (a-e) have been designated that contribute to the expression of ac1 (replication-associated protein) and ac4. consistent with earlier reports, ac1 gene expression was negatively regulated (80% reduct ...19957595345
molecular cloning of indian tomato leaf curl virus genome following a simple method of concentrating the supercoiled replicative form of viral dna.dna-a and dna-b components of the genome of a whitefly transmitted virus causing yellowing and leaf curl in tomato (itlcv) were cloned following a simple procedure for isolation of the double stranded replicative form of viral dna from infected tomato plants. the method is based on extraction of total dna from infected plants followed by concentration of the double stranded replicative form of viral dna by an alkaline denaturation procedure identical to that used for isolation of plasmid dna fro ...19957738150
analysis of african cassava mosaic virus recombinants suggests strand nicking occurs within the conserved nonanucleotide motif during the initiation of rolling circle dna replication.intact clones containing partial repeats of the genomic components of african cassava mosaic (acmv dnas a and b) are infectious when mechanically coinoculated onto nicotiana benthamiana. monomeric genomic components may be generated either by homologous recombination or, when two copies of the origin of replication (ori) are present, by a modified rolling circle replication mechanism in which nascent single-stranded dna is resolved by the introduction of nicks at both oris. dna b partial repeats ...19957831830
lethal mutations within the conserved stem-loop of african cassava mosaic virus dna are rapidly corrected by genomic recombination.the nonanucleotide motif taatattac occurs in the intergenic region of all geminiviruses that have been examined to date. the motif is invariably located within the loop of a potential stem-loop structure that has been implicated in viral dna replication. to investigate the contribution of these sequences to virus proliferation, african cassava mosaic virus (acmv) dna b mutants have been screened for their ability to infect nicotiana benthamiana when co-inoculated with dna a. mutants in which the ...19947964630
expression of tgmv antisense rna in transgenic tobacco inhibits replication of bctv but not acmv geminiviruses.transgenic tobacco plants expressing an antisense rna targeted against tomato golden mosaic virus (tgmv) show reduced/no symptoms and viral dna accumulation upon tgmv infection [5]. the targeted region includes the al1 gene, encoding an essential viral replication protein. this dna sequence is conserved in various other geminiviruses, suggesting they too might show inhibition of replication in these plants. we infected leaf material with african cassava mosaic virus (acmv) and beet curly top vir ...19948111023
the nucleotide sequence and genome structure of mung bean yellow mosaic geminivirus.complete nucleotide sequences of the infectious cloned dna components (dna 1 and dna 2) of mung bean yellow mosaic virus (mymv) were determined. mymv dna 1 and dna 2 consists of 2,723 and 2,675 nucleotides respectively. dna 1 and dna 2 have little sequence similarity except for a region of approximately 200 bases which is almost identical in the two molecules. analysis of open reading frames revealed nine potential coding regions for proteins of mol. wt. > 10,000, six in dna 1 and three in dna 2 ...19938231962
replication of the dna a component of african cassava mosaic virus in a heterologous system.the capacity for autonomous replication of the dna a of african cassava mosaic virus (acmv), a member of the bipartite geminiviruses infecting dicotyledonous plants, has been compared in host and non-host cells. a derivative of the acmv dna a was transfected into tobacco and maize protoplasts. although acmv is not able to infect maize, replication of the dna a in maize protoplasts was observed to occur. the efficiency of replication was 10 to 20% of that seen in tobacco protoplasts. in both plan ...19938277277
rapid production of full-length, infectious geminivirus clones by abutting primer pcr (abp-pcr).the application of the polymerase chain reaction (pcr) method of dna amplification for the isolation of full-length, infectious clones of geminiviruses is described. non-overlapping, abutting 20-mer oligonucleotide primers were used to produce a linear product from the circular geminivirus genomic template. clones of african cassava mosaic virus (acmv) dna a, obtained by this method, were infectious following mechanical inoculation (in the presence of acmv dna b) onto nicotiana benthamiana. norm ...19938360316
cytosine methylation inhibits replication of african cassava mosaic virus by two distinct mechanisms.extrachromosomally replicating viral dna is usually free of cytosine methylation and viral templates methylated in vitro are poor substrates when used in replication assays. we have investigated the mechanism of inhibition of viral replication by dna methylation using as a model the dna a of african cassava mosaic virus. we have constructed two component helper systems which allow for separation of the transcriptional inhibition of viral genes necessary for replication from replication inhibitio ...19937688453
serological relationships and epitope profiles of isolates of okra leaf curl geminivirus from africa and the middle east.a panel of seven murine monoclonal antibodies (mabs) was raised against particles of okra leaf curl virus (olcv), a whitefly-transmitted geminivirus which is prevalent in west africa. the mabs detected at least six distinguishable epitopes, two continuous and four discontinuous. in tests with these mabs, relatively little antigenic variation was found among 24 olcv isolates from burkina faso, chad, ghana, ivory coast, nigeria, oman and saudi arabia, each virus isolate reacting with at least five ...19937506936
detection and possible functions of african cassava mosaic virus dna b gene products.polyclonal antisera raised against synthetic oligopeptides have been used to detect the dna b gene products bv1 and bc1 of the geminivirus african cassava mosaic virus following sds-page fractionation of nicotiana benthamiana extracts. bv1 antiserum detected a soluble protein of 29 kda, consistent with the size predicted from sequence data. bc1 antiserum detected proteins of 37, 39, and 42 kda in addition to variable, less abundant species, all of which are larger than the predicted size of 34 k ...19938517019
specificity of bipartite geminivirus movement proteins.pseudorecombinants produced by exchanging genome components (dnas a and b) of the geminiviruses african cassava mosaic virus (acmv) and indian cassava mosaic virus (icmv), acmv, and tomato golden mosaic virus (tgmv), and tgmv and abutilon mosaic virus (abmv) are not infectious in their common host nicotiana benthamiana. in each case, dna a was unable to trans-replicate the heterogenomic dna b component in a n. benthamiana leaf disc assay. the non-viability of the pseudorecombinants has been expl ...19938372440
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