| rna-primed complementary-sense dna synthesis of the geminivirus african cassava mosaic virus. | the plant dna virus african cassava mosaic virus (acmv) is believed to replicate by a rolling circle mechanism. to investigate complementary-sense dna (lagging strand) synthesis, we have analysed the heterogenous form of complementary-sense dna (h3 dna) from infected nicotiana benthamiana by two-dimensional agarose gel electrophoresis and blot hybridisation. the presence of an rna moeity is demonstrated by comparison of results for nucleic acids resolved on neutral/alkaline and neutral/formamide ... | 1992 | 1475192 |
| the use of african cassava mosaic virus as a vector system for plants. | this paper describes the development of a gene-displacement vector based on dna1, one of two single stranded circular genomic components of a bipartite geminivirus, african cassava mosaic virus (acmv). the dna1 molecules of acmv were cloned as dimers into a plant transformation vector and the constructs have been integrated into tobacco protoplasts by peg-mediated dna transfer. in transgenic plants extrachromosomal copies of dna1 monomers could be detected. deletion of the coat protein-encoding ... | 1992 | 1537557 |
| inhibition of african cassava mosaic virus systemic infection by a movement protein from the related geminivirus tomato golden mosaic virus. | plant viruses encode proteins that mediate their movement through the host plant leading to the establishment of a systemic infection. we have analyzed the effect of tomato golden mosaic virus (tgmv) genes bl1 and br1, which are thought to be involved in the process of virus movement, on the infectivity of african cassava mosaic virus (acmv) in nicotiana benthamiana. recombinant genomes were constructed by replacing the acmv coat protein coding sequence with those of either bl1 or br1. replicati ... | 1992 | 1546454 |
| regulation of the activities of african cassava mosaic virus promoters by the ac1, ac2, and ac3 gene products. | dna fragments comprising each of the promoter regions from the geminivirus african cassava mosaic virus (acmv) were cloned into the puc18-based vector, pg1, producing transcriptional fusions with the beta-glucuronidase gene (gus) and nopaline synthase terminator sequence. the relative activity of each promoter construct was analyzed by a gus expression assay of extracts from nicotiana clevelandii protoplasts coelectroporated with the gus reporter constructs and constructs in which individual acm ... | 1992 | 1585657 |
| african cassava mosaic virus di dna interferes with the replication of both genomic components. | natural infections of the geminivirus african cassava mosaic virus (acmv) are known to be associated with low levels of defective interfering (di) dnas. recently it has been demonstrated that extrachromosomal copies of the di dna, mobilized and amplified from an integrated di dna dimer, can ameliorate acmv symptoms in transformed nicotiana benthamiana, providing a possible means for the control of cassava mosaic disease. to further understand the molecular basis of the interference phenomenon, w ... | 1991 | 1853559 |
| tomato yellow leaf curl virus: a whitefly-transmitted geminivirus with a single genomic component. | the genome of the tomato yellow leaf curl virus (tylcv), a bemisia tabaci-transmitted geminivirus, was cloned. all clones obtained were of one genomic molecule, analogous to dna a of african cassava mosaic virus. nucleotide sequence analysis of the tylcv genome showed that it comprises 2787 nucleotides, encoding six open reading frames, two on the virion strand and four on the complementary strand. all of them have counterparts in other geminiviruses. dimeric copies of the cloned viral genome we ... | 1991 | 1926771 |
| analysis of the potential promoter sequences of african cassava mosaic virus by transient expression of the beta-glucuronidase gene. | dna fragments from promoter regions of the geminivirus, african cassava mosaic virus, were cloned into pg1, a vector based on puc18, producing transcriptional fusions with the beta-glucuronidase (gus) gene and nopaline synthase termination sequence. the activity of each promoter construct was assessed by analysing the transient expression of gus in nicotiana clevelandii protoplasts. the results demonstrated that constructs containing the common region of dna a showed much stronger promoter activ ... | 1991 | 1940874 |
| mutational analysis of complementary-sense genes of african cassava mosaic virus dna a. | we have investigated the ability of african cassava mosaic virus dna a mutants, containing disrupted complementary-sense genes, to infect nicotiana benthamiana and to replicate in nicotiana tabacum protoplasts. three overlapping open reading frames (orfs) with the capacity to encode proteins with an mr greater than 10k (ac1, ac2 and ac3) are highly conserved between geminiviruses that infect dicotyledonous plants and one (ac4) is less well conserved. of these, only ac1 is a prerequisite for dna ... | 1991 | 2033385 |
| dna forms of the geminivirus african cassava mosaic virus consistent with a rolling circle mechanism of replication. | we have analysed dna from african cassava mosaic virus (acmv)-infected nicotiana benthamiana by two-dimensional agarose gel electrophoresis and detected acmv-specific dnas by blot-hybridisation. acmv dna forms including the previously characterised single-stranded, open-circular, linear and supercoiled dnas along with five previously uncharacterised heterogeneous dnas (h1-h5) were resolved. the heterogeneous dnas were characterised by their chromatographic properties on bnd-cellulose and their a ... | 1991 | 2041773 |
| mutagenesis of the ac3 open reading frame of african cassava mosaic virus dna a reduces dna b replication and ameliorates disease symptoms. | small insertions were made independently at each of four unique restriction sites on african cassava mosaic virus (acmv) dna a to disrupt the three overlapping complementary-sense open reading frames (orfs) herein designated ac1, ac2 and ac3. the dna a mutants were assayed for their infectivity by agroinoculation of monomeric constructs to nicotiana benthamiana plants containing chromosomal insertions of acmv dna b. disruption of the ac3 orf alone resulted in a delay and amelioration of disease ... | 1991 | 2045787 |
| nucleotide sequence of the infectious cloned dna components of african cassava mosaic virus (nigerian strain). | | 1990 | 2308831 |
| geminivirus coat protein gene replacement alters insect specificity. | chimeric clones have been constructed in which the coat protein encoded by dna a of the bipartite genome of the geminivirus african cassava mosaic virus (acmv) has been replaced by that of beet curly top virus (bctv). constructs containing the coding region inserted in either orientation were infectious when co-inoculated with acmv dna b onto nicotiana benthamiana, producing symptoms typical of acmv infection. the onset of symptom production was delayed relative to plants inoculated with parenta ... | 1990 | 2353465 |
| defective viral dna ameliorates symptoms of geminivirus infection in transgenic plants. | nicotiana benthamiana was transformed with a single copy of a tandem repeat of subgenomic dna b isolated from plants infected with a kenyan isolate of the bipartite geminivirus african cassava mosaic virus. symptoms in transformed plants were less severe than in nontransformed controls when challenged with virus or cloned dna of kenyan or nigerian isolates. symptom amelioration was associated with the mobilization and amplification of the subgenomic dna, producing a comparable reduction in the a ... | 1990 | 2385593 |
| size reversion of african cassava mosaic virus coat protein gene deletion mutants during infection of nicotiana benthamiana. | mutants of african cassava mosaic virus containing extensive deletions across the coat protein gene that remove up to one-third of the genomic component have been constructed and shown to be infectious when mechanically inoculated onto nicotiana benthamiana by leaf abrasion. using n. tabacum protoplasts we demonstrate that mutant pclv.cp delta 11, containing a 712 bp deletion, is competent for replication in its deleted form. however, systemic spread of pclv. cp delta 11 and other deletion mutan ... | 1989 | 2732690 |
| indian cassava mosaic virus: ultrastructure of infected cells. | ultrastructural examination of leaf tissue of nicotiana benthamiana infected with indian cassava mosaic virus (icmv) revealed abnormalities in phloem and, occasionally, xylem cells. nuclei contained granular inclusion bodies which seemed to be largely composed of virus-like particles and were shown by immunogold labelling (igl) to be rich in icmv coat protein. later in infection, hollow spheres made up of fibrillar material were produced. virus coat protein was not a necessary component of these ... | 1989 | 2794977 |
| 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 ... | 1993 | 7506936 |
| 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. ... | 1995 | 7561766 |
| 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 ... | 1995 | 7595345 |
| 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 ... | 1993 | 7688453 |
| 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 ... | 1995 | 7730816 |
| 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 ... | 1995 | 7738150 |
| 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 ... | 1995 | 7755872 |
| 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 ... | 1995 | 7831830 |
| 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 ... | 1995 | 7844539 |
| 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 ... | 1994 | 7964630 |
| 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 ... | 1994 | 8111023 |
| 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 ... | 1993 | 8231962 |
| nucleotide sequence evidence for the occurrence of three distinct whitefly-transmitted geminiviruses in cassava. | the complete nucleotide sequence of the dna of indian cassava mosaic virus (icmv) and a key part of that of a group b isolate of african cassava mosaic virus from malawi (acmv-m) were determined and compared at the nucleotide and encoded amino acid levels with the published sequences of an acmv group a isolate (acmv-k) and other whitefly-transmitted gemini-viruses (wtgs). the dna of icmv consists of two circular single-stranded molecules, dna-a [2815 nucleotides (nt)] and dna-b (2645 nt), which ... | 1993 | 8245859 |
| 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 ... | 1993 | 8277277 |
| 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 ... | 1993 | 8360316 |
| 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 ... | 1993 | 8372440 |
| complete nucleotide sequence of pepper huasteco virus: analysis and comparison with bipartite geminiviruses. | the complete nucleotide sequence of pepper huasteco geminivirus (phv) isolated in northern mexico was determined. the phv genome consists of two circular ssdna molecules of 2631 bases (phv a) and 2589 bases (phv b). phv has a genome organization typical of a bipartite geminivirus with four open reading frames (orfs) (ar1, al1, al2 and al3) in component a and two (br1 and bl1) in component b. an unexpected orf was found in the complementary sense strand of phv a. this orf, termed al5, is found en ... | 1993 | 8409944 |
| 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 ... | 1993 | 8517019 |
| 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 ... | 1996 | 8659104 |
| 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 ... | 1997 | 9123846 |
| 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 ... | 1997 | 9192696 |
| 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 ... | 1997 | 9225057 |
| 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 ... | 1997 | 9267014 |
| 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 ... | 1998 | 9603342 |
| 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 ... | 1998 | 9635134 |
| 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 ... | 1998 | 9820161 |
| 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 ... | 1998 | 9856107 |
| 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 ... | 1998 | 9930204 |
| 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 ... | 1999 | 10334034 |
| 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 ... | 1999 | 10544139 |
| 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 ... | 2000 | 10640569 |
| 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 ... | 2000 | 10686153 |
| 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 ... | 2001 | 11125158 |
| 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, ... | 2000 | 11137168 |
| 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 ... | 2001 | 11172108 |
| 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 ... | 2001 | 11172110 |
| 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 ... | 2001 | 11324760 |
| 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 ... | 2001 | 11342533 |
| 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 ... | 2001 | 11485405 |
| 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 ... | 2001 | 11699964 |
| 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 ... | 2002 | 11853400 |
| 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 ... | 2002 | 11952122 |
| 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 ... | 2002 | 12074729 |
| 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 ... | 2002 | 12076831 |
| 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 ... | 2003 | 12606075 |
| 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 ... | 2003 | 12886005 |
| 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 ... | 2003 | 14645587 |
| 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 ... | 2004 | 14972538 |
| 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 ... | 2003 | 14994796 |
| 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 ... | 2004 | 15045567 |
| 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 ... | 2004 | 15194750 |
| 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 ... | 2004 | 15220420 |
| 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 ... | 2004 | 15308741 |
| 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 ... | 2004 | 15375675 |
| 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 ... | 2005 | 15503225 |
| 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 ... | 2004 | 15630623 |
| 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 ... | 2004 | 15630624 |
| 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 ... | 2005 | 15784145 |
| 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 ... | 2005 | 15824887 |
| 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 ... | 2005 | 15986172 |
| 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 ... | 2005 | 16006510 |
| 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 ... | 2006 | 16132175 |
| 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 ... | 2006 | 16839615 |
| 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 ... | 2006 | 16963765 |
| cassava mosaic virus disease in east and central africa: epidemiology and management of a regional pandemic. | | 2006 | 17027685 |
| 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 ... | 2007 | 17049959 |
| 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 ... | 2007 | 17109983 |
| 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 ... | 2006 | 17142233 |
| 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 ... | 2005 | 17173627 |
| 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 ... | 2007 | 17412996 |
| 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 ... | 2007 | 17427808 |
| 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 ... | 2007 | 17492253 |
| 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 ... | 2008 | 17761472 |
| 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 ... | 2008 | 18184062 |
| 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 ... | 2008 | 18405995 |
| 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 ... | 2008 | 18559947 |
| 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 ... | 2008 | 18632975 |
| 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 ... | 2008 | 18661095 |
| 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, ... | 2008 | 18789974 |
| 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 ... | 2008 | 18796734 |
| 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 ... | 2008 | 18982246 |
| 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 ... | 2009 | 19264617 |
| 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 ... | 2009 | 19300911 |
| 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 ... | 2009 | 19369323 |
| 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 ... | 2009 | 19665038 |