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At least 19 recordsLinked to original sources
PubMed1991

Mutational analysis of the small intergenic region of maize streak virus.

Maize streak virus (MSV) is a leafhopper-transmitted geminivirus containing one molecule of circular single-stranded DNA of about 2.7 kb. We have tested the infectivity of MSV mutants. A deletion of 29 bases in the small intergenic region (SIR) did not affect the infectivity of MSV. Mutants containing insertions of oligonucleotides of up to 32 bases at the AsnI site in SIR were also infectious. However, the infection efficiency of the insertion mutants decreased as the size of the oligonucleotides increased. This reduced virulence may be due to a decreased efficiency of 3'-end formation of the complementary sense mRNA(s). The stability of MSV mutants in infected maize plants was analyzed by polymerase chain reaction (PCR). Some oligonucleotide-insertion mutants were completely stable while others obtained deletions. Infectivity of the mutants, however, did not require deletion formation. Deletion rearrangement was shown to be dependent on the sequence of the inserted oligonucleotide. The AsnI site is the only site known to permit insertion of nonviral DNA without abolishing MSV infectivity. The system described may allow the use of MSV as a delivery vector to introduce at least small segments of DNA into maize.

Base Sequence↗
PubMed2000

Eight decades of maize streak virus research.

Maize streak virus (MSV) (genus Mastrevirus; family Geminiviridae) causes what is considered the most important and widespread disease of maize in sub-Saharan Africa. Maize streak was named by Storey in 1925. Since his classical work on the virus and its leafhopper vectors of the genus Cicadulina China, MSV has been the subject of intensive research. Aspects concerning the geographical distribution, virus diversity, molecular characterization, vector-virus relationships and resistance breeding are reviewed. Special emphasis is placed on recent studies of MSV ecology and epidemiology in West Africa.

Africa↗
PubMed1993

Replication of maize streak virus mutants in maize protoplasts: evidence for a movement protein.

We have used protoplasts derived from a maize (Black Mexican Sweet) suspension culture to study the replication of maize streak virus (MSV) wild-type (wt) and mutant DNA genomes. Following inoculation with plasmids containing multimeric copies of MSV, both single-stranded (ss) and double-stranded MSV DNA forms were produced, in proportions relative to those seen in infected plants. The immunodetection of coat protein (PV2) and geminate particles confirmed that the protoplasts were able to support the entire multiplication cycle of MSV and therefore were suitable for the study of MSV gene function. Inoculation of protoplasts with V1 gene mutants which are unable to produce systemic infections in plants resulted in DNA replication and encapsidation indistinguishable from that obtained with wt constructs implicating the protein in virus movement. Computer analysis of the V1 protein (PV1) indicated a potential trans-membrane or membrane-embedded domain. Following inoculation of protoplasts with V2 mutants, ssDNA was not detected; the inability of these mutants to spread in plants may be due to a lack of ssDNA, PV2, or a combination of the two. The requirements for systemic infection of MSV are discussed.

Base Sequence↗
PubMed2006

Successful application of FTA Classic Card technology and use of bacteriophage phi29 DNA polymerase for large-scale field sampling and cloning of complete maize streak virus genomes.

Leaf samples from 155 maize streak virus (MSV)-infected maize plants were collected from 155 farmers' fields in 23 districts in Uganda in May/June 2005 by leaf-pressing infected samples onto FTA Classic Cards. Viral DNA was successfully extracted from cards stored at room temperature for 9 months. The diversity of 127 MSV isolates was analysed by PCR-generated RFLPs. Six representative isolates having different RFLP patterns and causing either severe, moderate or mild disease symptoms, were chosen for amplification from FTA cards by bacteriophage phi29 DNA polymerase using the TempliPhi system. Full-length genomes were inserted into a cloning vector using a unique restriction enzyme site, and sequenced. The 1.3-kb PCR product amplified directly from FTA-eluted DNA and used for RFLP analysis was also cloned and sequenced. Comparison of cloned whole genome sequences with those of the original PCR products indicated that the correct virus genome had been cloned and that no errors were introduced by the phi29 polymerase. This is the first successful large-scale application of FTA card technology to the field, and illustrates the ease with which large numbers of infected samples can be collected and stored for downstream molecular applications such as diversity analysis and cloning of potentially new virus genomes.

Bacillus Phages↗
PubMed1990

Serotyping and strain identification of maize streak virus isolates.

Four strains of maize streak virus, namely the Panicum maximum, Digitaria setigera and sugarcane strains, have been identified from 19 isolates by ELISA using polyclonal antisera cross-absorbed with particles of the maize strain. The results suggest there is an epitope of the maize strain which is not dependent on the capsid being intact and which is common to all the members of the group; other strain-specific epitopes are probably conformation-dependent. A specific epitope (probably internal) occurs on the coat protein of a maize strain isolate, D(R)D, grown in D. velutina, that is also present on the coat protein of the D. setigera (previously reported as D. sanguinalis) strain. Specific internal epitopes also occur in the coat proteins of sugarcane and P. maximum strains. The use of indirect ELISA was necessary for accurate serotyping. The serological reactivities of particles of all the members of each type were identical irrespective of the host from which they were extracted. Sap extracts proved to be more reliable sources of antigen than virus preparations, which could vary in their serological reactivity. Nevertheless, serological differentiation index values determined in tests using either type of antigen proved reliable and consistent.

Edible Grain↗
PubMed2004

Isolation and characterization of subgenomic DNAs encapsidated in "single" T = 1 isometric particles of Maize streak virus.

"Single" T = 1 isometric particles of Maize streak virus (MSV) have been isolated from infected maize leaves. Biochemical and genetic characterizations show that these particles contain subgenomic (sg) MSV DNA encapsidated by the MSV coat protein. The largest sg DNA is 1.56 kb, slightly larger than half genome size, although sg DNAs as small as 0.2 kb were also cloned. The sg DNAs are not infectious, and they do not appear to play a role in the pathogenicity of MSV. This is the first report of sg DNAs for MSV and, to our knowledge, the first time that encapsidated sg DNAs have been characterized at the sequence level for any geminivirus. These data will assist in our investigations into the role of genomic DNA in the formation of the unique geminate capsid architecture of the Geminiviridae.

Capsid Proteins↗
PubMed1992

Mutational analysis of the 'conserved region' of maize streak virus suggests its involvement in replication.

Maize streak virus as well as other geminiviruses contain a potential hairpin structure with the conserved sequence TAATATTAC in the loop. We assessed the possible involvement of this structure in replication and symptom induction of the virus. A series of insertion and deletion mutants were analyzed by agroinfection. Deletion of the hairpin or insertions in the conserved sequence abolished symptom development. Viral DNA could not be detected in the infected tissue. However, a mutant with a point mutation in the 'conserved' sequence, isolated after inoculation of maize plants with an insertion mutant, was able to replicate and to induce symptoms.

Agrobacterium tumefaciens↗
PubMed1989

Evolutionary relationship of three southern African maize streak virus isolates.

The aligned restriction endonuclease maps of three sequenced maize streak virus isolates, three restriction-mapped southern African maize streak virus isolates, and two other sequenced geminiviruses were used as a means of calculating the sequence divergence between these viruses. The degree of divergence was used to construct a phylogenetic tree for the viruses; this tree agrees well with predictions from sequence comparisons, and so the method can be used to study the relationship of geminivirus isolates without the labor and expense of sequencing each one.

Africa, Southern↗
PubMed1995

Vectors based on maize streak virus can replicate to high copy numbers in maize plants.

The genome of maize streak virus (MSV) consists of one molecule of circular, single-stranded DNA of 2.7 kb. A reporter gene (bar) coding for phosphinothricin acetyl-transferase was inserted into the small non-coding region of the MSV genome. The recombinant bar-containing MSV vectors were introduced into maize seedlings via agroinfection. The chimeric viral DNA was found to replicate to high copy numbers in maize leaves resistant to the application of the herbicide Basta. This establishes the usefulness of MSV as an efficient replicating vector in cells of maize plants.

Acetyltransferases↗
PubMed1984

Physical structure and genetic organisation of the genome of maize streak virus (Kenyan isolate).

The structure of the maize streak virus genome (Kenyan isolate, MSV-K), as determined from the sequence of clones obtained from DNA isolated from virus particles, is composed of one major DNA component of about 2.6 kb. MSV virion DNA is partially double-stranded, composed of a full-length virion (V) strand and a short (70-80b) primer (P) strand. The primer strand has a fixed 5'-end capped with alkaline labile material, presumably 1-2 ribonucleotides. The MSV genome has two major coding regions oriented on opposite strands and flanked by two small intergenic regions. The coding region on the P strand is composed of two major open reading frames (ORFs), arranged in tandem and in the same reading frame. Because the predicted protein derived from a composite of these two ORFs closely corresponds to the product from a single ORF in the cassava latent virus genome, it is likely that this region encodes two proteins with common amino-termini, one a read-through product of the amber codon terminator in the first ORF. The intergenic regions contain potential transcription start and stop signals oriented in the direction of the two opposing coding regions. Considerable DNA sequence heterogeneity was observed, mostly silent or conservative third base substitutions in coding regions and base substitutions, small insertions and small, close-range transpositions in intergenic regions.

Base Sequence↗
PubMed2005

A three-nucleotide mutation altering the Maize streak virus Rep pRBR-interaction motif reduces symptom severity in maize and partially reverts at high frequency without restoring pRBR-Rep binding.

Geminivirus infectivity is thought to depend on interactions between the virus replication-associated proteins Rep or RepA and host retinoblastoma-related proteins (pRBR), which control cell-cycle progression. It was determined that the substitution of two amino acids in the Maize streak virus (MSV) RepA pRBR-interaction motif (LLCNE to LLCLK) abolished detectable RepA-pRBR interaction in yeast without abolishing infectivity in maize. Although the mutant virus was infectious in maize, it induced less severe symptoms than the wild-type virus. Sequence analysis of progeny viral DNA isolated from infected maize enabled detection of a high-frequency single-nucleotide reversion of C(601)A in the 3 nt mutated sequence of the Rep gene. Although it did not restore RepA-pRBR interaction in yeast, sequence-specific PCR showed that, in five out of eight plants, the C(601)A reversion appeared by day 10 post-inoculation. In all plants, the C(601)A revertant eventually completely replaced the original mutant population, indicating a high selection pressure for the single-nucleotide reversion. Apart from potentially revealing an alternative or possibly additional function for the stretch of DNA that encodes the apparently non-essential pRBR-interaction motif of MSV Rep, the consistent emergence and eventual dominance of the C(601)A revertant population might provide a useful tool for investigating aspects of MSV biology, such as replication, mutation and evolution rates, and complex population phenomena, such as competition between quasispecies and population turnover.

Base Sequence↗
PubMed2001

Sequence diversity and virulence in Zea mays of Maize streak virus isolates.

Full genomic sequences were determined for 12 Maize streak virus (MSV) isolates obtained from Zea mays and wild grass species. These and 10 other publicly available full-length sequences were used to classify a total of 66 additional MSV isolates that had been characterized by PCR-restriction fragment length polymorphism and/or partial nucleotide sequence analysis. A description is given of the host and geographical distribution of the MSV strain and subtype groupings identified. The relationship between the genotypes of 21 fully sequenced virus isolates and their virulence in differentially MSV-resistant Z. mays genotypes was examined. Within the only MSV strain grouping that produced severe symptoms in maize, highly virulent and widely distributed genotypes were identified that are likely to pose the most serious threat to maize production in Africa. Evidence is presented that certain of the isolates investigated may be the products of either intra- or interspecific recombination.

Geminiviridae↗
PubMed1984

The nucleotide sequence of maize streak virus DNA.

The nucleotide sequence of the DNA of maize streak virus (MSV) has been determined. The data were accommodated into one DNA circle of 2687 nucleotides, in contrast to previously characterised geminiviruses which have been shown to possess two circles of DNA. Comparison of the nucleotide sequences of the DNA of MSV with those of cassava latent virus (CLV) and tomato golden mosaic virus (TGMV) showed no detectable homology. Analysis of open reading frames revealed seven potential coding regions for proteins of mol. wt. greater than or equal to 10 000, three in the viral (+) sense and four in the complementary (-) sense. The position of likely transcription signals on the MSV DNA sequence would suggest a bidirectional strategy of transcription as proposed for CLV and TGMV. Nine inverted repeat sequences which have a potential of forming hairpin structures of delta G greater than or equal to -14 kcal/mol have been detected. Three of these hairpin structures are in non-coding regions and could be involved in the regulation of transcription and/or replication.

Base Sequence↗
PubMed1984

A putative primer for second-strand DNA synthesis of maize streak virus is virion-associated.

We have isolated, from maize streak virus (MSV) preparations, a population of 'nested' DNA molecules. These molecules have ribonucleotides covalently linked to the DNA species' discrete 5' deoxyribonucleotide terminus. The major species has a DNA sequence of 80 nucleotides which is complementary to a region 5' of two hairpin structures on the MSV genome, almost exclusively in an intergenic region. These molecules have been used to prime the synthesis in vitro of a complementary strand to virion DNA, initiating this reaction at one site on the genome.

Base Sequence↗
PubMed2001

Investigation of the potential of maize streak virus to act as an infectious gene vector in maize plants.

There has been a great deal of interest in the possibility that geminiviruses might be used as infectious gene vectors for expression of foreign proteins in plants. However, generic mastreviruses such as Maize streak virus (MSV) have no sequences which are dispensable for systemic infection of plants, and there is a strict limitation on the size of viral DNA which can be moved systemically. We attempted to complement the movement functions deleted from a wild-type-sized, replication-proficient gene replacement vector, by co-infecting plants with it and either wild type MSV, or a replication-deficient but putatively movement-proficient viral construct. While ssDNA formation by the gene replacement vector could be complemented in trans by co-transfected wild type virus, true systemic movement of either the vector, or of co-complementing constructs, did not occur. However, recombination between the two complementing viral constructs frequently occurred to generate wild-type virus genomes. The results therefore suggest that formation of ssDNA and size of the viral replicon are not the sole determinants of whether the MSV movement proteins can mobilise viral sequences and move them systemically in plants.

Blotting, Southern↗
PubMed1985

Bidirectional transcription of maize streak virus DNA and identification of the coat protein gene.

Three RNA transcripts encoded by maize streak virus DNA were detected in polyadenylated RNA from virus-infected maize leaves. Two of the transcripts, a major 0.9 kb and a minor 1.05 kb RNA, were mapped on the virion (+) sense DNA and the other minor transcript of 1.2 kb was mapped on the complementary (-) sense DNA, demonstrating that transcription of MSV DNA was bidirectional. The two virion sense transcripts were 3' coterminal at nucleotide 1114 but had 5' termini at nucleotides 2682 and 163 respectively. Virus-specific polyadenylated RNA translated in vitro to produce a 28,000 MW polypeptide, specifically immunoprecipitable by antiserum raised against whole virus. The mRNA for this protein was mapped by hybrid-arrested translation to the long open reading frame in virion sense DNA whose potential amino acid composition, calculated from nucleotide sequence data, closely agreed with that determined experimentally for the coat protein.

Capsid↗
PubMed2001

Cell-cycle, phase-specific activation of Maize streak virus promoters.

It is believed that geminiviral DNA replication is coupled to the cell-cycle regulatory complex of the plant cell and that the virus-early (complementary or C sense) gene products REP and REPA may be able to manipulate the regulation of the cycle. In this study, we examined expression from the promoters of Maize streak virus (MSV) in transgenic maize plants and cells to determine whether they showed cell-cycle specificity. Histochemical staining of plant roots containing "long and short" C-sense promoter sequences upstream of the GUS (beta-glucuronidase) reporter gene showed that promoter activity was restricted to the meristematic region of the roots and was enhanced by 2,4-dichlorophenoxy acetic acid (2,4-D) treatment. Analysis of reporter gene and cell-cycle-specific gene transcript levels coupled with flow cytometric data in synchronized transgenic maize cells revealed that all of the MSV promoters showed cell-cycle specificity. The coat protein gene promoter showed highest activity in early G2, whereas the C-sense promoter sequences produced two peaks of activity in the S and G2 cell-cycle phases.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1991

Host range and symptoms are determined by specific domains of the maize streak virus genome.

We have cloned two distinct symptomatic variants of the geminivirus streak virus from maize plants infected with the Nigerian strain (MSV-N). Following "agroinoculation" to maize plants MSV-Nm produces narrow, mildly chlorotic discontinuous streaks, whereas MSV-Ns-infected tissue has wide, severely chlorotic streaks. Symptom appearance is delayed following MSV-Nm inoculation. MSV-Nm has a narrow host range within the Gramineae comprising a fraction of that of the wide host range isolate MSV-Ns. The two isolates are highly homologous and have identical restriction enzyme maps. In order to localize the determinants of pathogenicity we constructed, in vitro, hybrid genomes by restriction enzyme fragment exchange. The determinants of host range, severity of chlorosis, streak length, and timing of symptom appearance map to a fragment which includes the large intergenic region and the 5' terminus of the complementary sense C1 gene. Streak width is determined by the virion-sense portion of the genome, which is consistent with the observation that the virion-sense gene products (V1 and V2) are required for spread of the virus.

Cloning, Molecular↗