Genetic diversity of plant virus populations: towards hypothesis testing in molecular epidemiology.
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Evolution, Molecular↗
Biomedical subjects
M Jacquemond
Publications and source records attributed to M Jacquemond.
Synthesis of (-)-strand RNA from the 3' untranslated region of plant viral genomes expressed in transgenic plants upon infection with related viruses.
When expressed in transgenic tobacco plants, transgene mRNA that includes the 3' untranslated region (3' UTR) of Lettuce mosaic virus served as template for synthesis of complementary (-)-strand RNA following an infection by Tobacco etch virus, Tobacco vein mottle virus or Pepper mottle virus, but not when infected with Cucumber mosaic virus. Deletion of the 3' UTR from the transgene abolished the synthesis of (-)-strand transcripts. Similar results were obtained in transgenic tobacco plants expressing mRNA that includes the RNA3 3' UTR of Cucumber mosaic virus when infected with Tomato aspermy virus. These results show that the viral RNA-dependent RNA polymerase of several potyviruses and Tomato aspermy virus have the ability to recognize heterologous 3' UTRs when included in transgene mRNAs, and to use them as transcription promoters.
3' Untranslated Regions↗
In situ localization of cacao swollen shoot virus in agroinfected Theobroma cacao.
Cacao swollen shoot virus (CSSV) is a small non-enveloped bacilliform virus with a double-stranded DNA genome. A very restricted host range and difficulties in transmitting the virus, either mechanically or via its natural vector, have hindered the study of cacao swollen shoot disease. As an alternative to the particle-bombardment method previously reported, we investigated another approach to infect Theobroma cacao. A greater-than-unit length copy (1.2) of the CSSV DNA genome was cloned into the Agrobacterium binary vector pBin 19 and was transferred into young plants via Agrobacterium tumefaciens. Typical leaf symptoms and stem swelling were observed seven and eleven weeks post inoculation, respectively. Viral DNA, CSSV coat protein and virions were detected in leaves with symptoms. Agroinfected plants were used to study the in situ localization of CSSV and its histopathologic effects in planta. In both leaves and petioles, virions were only seen in the cytoplasm of phloem companion cells and of a few xylem parenchyma cells. Light microscopy showed that stem swelling results from a proliferation of the xylem, phloem and cortex cells.
Badnavirus↗
Recombinants of cucumber mosaic virus (CMV): determinants of host range and symptomatology.
117F and R are subgroup I and II cucumber mosaic virus (CMV) strains, respectively. Whereas I17F induces severe symptoms on all hosts so far tested, R induces generally mild symptoms, except on Nicotiana glutinosa, on which it causes leaf blistering and severe stunting. Pseudorecombinants and recombinants, based on RNAs 1 and 2 from R-CMV, were created by adding either I17F RNA 3 or one of two chimeric RNAs created by exchanging approximate halves of RNA 3 of the two strains. The viruses created were tested on different hosts of the virus. On maize, local necrotic lesions were induced by all strains with the 5' part of RNA 3 from R-CMV, whereas only I17F-CMV induced a systemic infection. The seven solanaceous hosts tested could be classified into two main groups. In the first, RNA 3 was not directly involved in the symptoms that were systemically induced, and the extreme disease severity induced by I17F was correlated with high virus accumulation. In the same hosts, the lesser virulence of R-CMV could reflect a deficiency in long-distance movement, involving RNA 3. The second group included Nicotiana glutinosa where the symptoms induced by R-CMV were determined by the 3' part of RNA 3.
Blotting, Northern↗
Biological properties of pseudorecombinant and recombinant strains created with cucumber mosaic virus and tomato aspermy virus.
Cucumber mosaic virus (CMV) and tomato aspermy virus (TAV) are closely related cucumoviruses. We have made pseudorecombinant viruses in which the RNAs 3 of these two viruses have been exchanged and recombinant viruses containing chimeric RNA 3 molecules, in which the coat proteins and the 3'-end regions of CMV and TAV have been exchanged, giving rise to recombinants designated RT3 and TR3. The replication properties and the cell-to-cell and long-distance movement patterns of these pseudorecombinant and recombinant viruses were examined in different hosts. All the viruses were able to replicate and accumulate RNA 4 in protoplasts. The pseudorecombinants and the R1R2RT3 recombinant infected tobacco systemically, but the R1R2TR3 recombinant was not detectable, even in the inoculated leaves. Comparison of the abilities of the viruses to replicate in protoplasts and intact cucumber plants suggests that cell-to-cell movement factors are also encoded by RNAs 1 and/or 2. Major determinants of symptom severity in Nicotiana glutinosa are localized on the 3' part of RNA 3, and in Nicotiana benthamiana, more severe symptoms were observed with the T1T2R3 strain than with the others tested.
Cucumis sativus↗
The open reading frame 2 product of cacao swollen shoot badnavirus is a nucleic acid-binding protein.
The function of the open reading frame 2 product (p2) of cacao swollen shoot virus (CSSV) and of other badnaviruses is not yet determined. Their carboxyl-termini are lysine and proline rich and also contain alanine residues, amino acids present at the C-termini of histone-like proteins. Full-length CSSV p2 (132 amino acids) or versions truncated at the C-terminus (128, 113, 103, or 101 amino acids) were expressed in Escherichia coli and partially purified. When assayed in nucleic acid-binding tests, p2 was able to interact with CSSV and other double-stranded DNAs and with CSSV and other single-stranded RNA transcripts in sequence-nonspecific manner. Moreover, this binding activity was progressively lost as the C-terminus was gradually deleted.
Amino Acid Sequence↗
Characterization, nucleotide sequence and genome organization of leek white stripe virus, a putative new species of the genus Necrovirus.
White stripe is a disease affecting leek in France with which an isometric virus c. 30 nm in diameter is associated. The most evident symptom is the presence of white stripes on the leaves extending to the stem. Attempts to demonstrate transmission through the soil by sowing or transplanting leek in contaminated soil were unsuccessful. The virus was transmitted by sap inoculation to a narrow range of herbaceous hosts, all of which were infected only locally. Virus purification was from infected leek tissues, where it accumulated in large amounts, as demonstrated by ultrastructural observations. RNA was extracted from purified virus preparations and cDNA clones were prepared. The complete nucleotide sequence of the viral RNA was determined: The genome is 3,662 nucleotides long and contains five open reading frames (ORFs). The first (ORF 1) encodes a putative translation product of M(r) 23,803 (p24) and read through of its amber stop codon results in a protein of M(r) 82,625 (p83) (ORF 2). ORF 3 and ORF 4 encode two small polypeptides of M(r) 11,280 (p11) and M(r) 6,261 (p6), respectively. ORF 5 encodes the capsid protein of M(r) 27,460 (p27). The genome organization and sequence alignments with the corresponding products of necroviruses suggest that the virus isolated from leek is a new species in the genus Necrovirus, for which the name of leek white stripe virus (LWSV) is proposed.
Amino Acid Sequence↗
Sleeping satellites: a risky prospect.
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Biotechnology↗
Replication of cucumber mosaic virus satellite RNA from negative-sense transcripts produced either in vitro or in transgenic plants.
Both positive [(+)] and negative [(-)] sense versions of two satellite RNA (satRNA) genes from cucumber mosaic virus (CMV), the necrogenic I17N and the nonnecrogenic R, have been introduced into the genome of tobacco plants. On infection with satRNA-free CMV, satRNA was amplified in plants expressing each of the four genes. All four genes confer protection against CMV infection. However, co-inoculation of plants with viral RNA and CMV satRNA transcripts synthesized in vitro showed that (-) sense transcripts were less active than the corresponding (+) sense transcripts. This is the first report that (-) sense CMV satRNA transcripts can serve as a template for satRNA replication.
Base Sequence↗
Nucleotide sequence and genomic organization of cacao swollen shoot virus.
Cacao swollen shoot virus is classified as a badnavirus based on its nonenveloped, bacilliform particle morphology and double-stranded DNA genome. A complete copy of the genome was cloned into a plasmid vector and the sequence was determined from 75 overlapping subclones covering both strands. The genome contains 7161 base pairs and possesses an intergenic region and five putative open reading frames (ORF) capable of coding for proteins > 10 kDa. All of the ORFs are present on the plus-strand. ORF 1 (17 kDa) and ORF 2 (14 kDa) encode proteins of unknown function. The large ORF 3 (211 kDa) encodes a polyprotein that can be divided into three regions. Based on distant homologies with viral movement proteins, region 1 may encode a protein involved in cell-to-cell spread, while region 2 encodes the viral capsid protein. Region 3 contains consensus sequences for viral aspartyl proteinase, reverse transcriptase, and ribonuclease H characteristic of pararetroviruses. The last two ORFs (13 and 14 kDa) overlap ORF 3 and are not present in the other badnaviruses described.
Amino Acid Sequence↗
Complete replication of a satellite RNA in vitro by a purified RNA-dependent RNA polymerase.
The 334 nucleotide R satellite RNA was used as a template for purified RNA-dependent RNA polymerase (RdRp) from cucumber mosaic virus-infected tobacco plants. The products of the reaction were dsRNA and positive-strand RNA of the same size as the R satellite RNA. Similar products were obtained when T7 RNA polymerase positive-strand transcripts of a cDNA clone of the satellite RNA, designed to have the same 5' and 3' ends as the satellite RNA, were used as templates. The formation of the positive strands demonstrates complete replication of the satellite RNA. A positive-strand transcript with 65 and 255 additional nucleotides at the 5' and 3' ends of the satellite RNA respectively was also utilized as a template by the RdRp, but only dsRNA was formed. However, no products could be detected when the RdRp was programmed with transcripts corresponding to the negative-strand satellite RNA, either with no additional terminal nucleotides or with 24 and 310 additional nucleotides at the 5' and 3' ends respectively.
Base Sequence↗
Characterization of the genome of cacao swollen shoot virus.
Cacao swollen shoot disease has been known to be caused by a small non-enveloped bacilliform virus for more than 25 years. Purification using a combination of celite filtration, polyethylene glycol concentration and sucrose density gradient centrifugation has yielded concentrated preparations of purified cacao swollen shoot virus (CSSV). Results of nuclease sensitivity tests indicated that the CSSV genome consists of dsDNA which has two single-stranded regions. The approximate size of CSSV DNA calculated from restriction enzyme digests is 7.4 kbp. It is very likely that CSSV is a member of the commelina yellow mottle virus group.
Blotting, Southern↗
The cDNA of cucumber mosaic virus-associated satellite RNA has in vivo biological properties.
Two isolates of cucumber mosaic virus (CMV)-associated satellite RNA, differing in their biological properties, have been reverse transcribed. One was able to induce the tomato necrotic syndrome whereas the other one attenuated fernleaf symptoms on tomato plants after co-inoculation with the helper virus. cDNAs representing partial or full-length copies have been cloned in the plasmid pAT 153 and sequenced. The two RNAs showed a very limited number of variations (2 to 5 substitutions depending on the clones and a one base deletion). Full-length cDNA copies possessed the same biological properties that characterized the parent satellite RNA. Efficiency of the cDNA depended upon its form in the inoculum (circular or linear plasmid or excised cDNA) and upon the form of the helper virus (viral RNAs or virions) with which it seemed to compete for installation and/or expression.
Base Sequence↗
A gene coding for a monomeric form of cucumber mosaic virus satellite RNA confers tolerance to CMV.
A gene whose transcript bears a monomeric form of cucumber mosaic virus (CMV) satellite RNA was introduced into tobacco (Nicotiana tabacum 'Xanthi' nc) plants by using an Ri plasmid-based vector system. On CMV infection, the transcript of the satellite RNA gene was used as a template to yield unit-length satellite RNA, which was efficiently amplified by the virus. Plants bearing the satellite RNA gene displayed long-term tolerance to CMV infection and were also tolerant to CMV infection by aphids, the natural vector of CMV. Implications of these results concerning the mechanism of satellite RNA replication are discussed.
Animals↗