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At least 19 recordsLinked to original sources

Replacement of the coat protein gene of plum pox potyvirus with that of zucchini yellow mosaic potyvirus: characterization of the hybrid potyvirus.

Infectious hybrid virus was generated by replacing part of the coat protein gene of plum pox potyvirus with that of the zucchini yellow mosaic potyvirus. This viable hybrid contains 84.5% of zucchini yellow mosaic potyvirus coat protein gene while the rest of the sequence was derived from plum pox potyvirus. Changing the coat protein gene between these two viruses had no effect on the experimental host range. Pathogenicity, stability and replication capacity of the hybrid virus were nearly identical to the parent viruses.

Amino Acid Sequence↗

Comparison and differentiation of potyvirus isolates and identification of strain-, virus-, subgroup-specific and potyvirus group-common epitopes using monoclonal antibodies.

A panel of monoclonal antibodies (MAbs) generated against an admixture of 12 potyvirus isolates was used to compare and differentiate diverse potyviruses. Both native and denatured virions of strains of bean yellow mosaic (BYMV), potato virus Y, tobacco etch, pea seed-borne mosaic, iris severe mosaic, iris mild mosaic and asparagus virus-1 potyviruses were used as immunogen and as antigen for screening of the hybridoma cell lines. Thirty cell lines secreting potyvirus-specific antibodies reactive in indirect antigen-coated plate (ACP-) ELISA were selected for detailed analysis. All 30 MAbs reacted with at least one strain of BYMV; 11 MAbs reacted with between one and eight of the nine BYMV strains and an additional three MAbs reacted only with isolates within the BYMV subgroup (BYMV, pea mosaic virus and clover yellow vein virus). The remaining 16 MAbs reacted with a BYMV isolate and with at least one of the other 43 potyvirus isolates tested. MAb PTY 1 reacted with all 55 potyvirus isolates tested (representing at least 33 different and distinct aphid-transmissible potyviruses). The potyvirus cross-reactive MAbs generally gave higher reactivity values in ACP-ELISA with dissociated virus than with polyclonal antibody-trapped intact virions in triple antibody sandwich ELISA (i.e. were cryptotope-specific). The BYMV strain- and virus-specific MAbs reacted strongly with both types of antigens (i.e. were metatope-specific). At least 25 distinct epitopes (12 cryptotopes and 13 metatopes) could be identified from the MAb-antigen reactivity patterns. The distribution of these epitopes between virus isolates can be used to detect and differentiate potyviruses in infected plant extracts and to examine virus architectures. Some of these epitopes are shared by potyvirus isolates not previously shown to be serologically related. The broad spectrum-reacting MAb PTY 1 recognizes a cryptotope conserved on all of the aphid-transmissible potyviruses examined and should be a valuable tool for the detection and assay of these potyviruses.

Antibodies, Monoclonal↗

Ultrastructural localization of nonstructural and coat proteins of 19 potyviruses using antisera to bacterially expressed proteins of plum pox potyvirus.

Antisera to the bacterially expressed nonstructural proteins (NSP) HC-Pro, CI, NIa, and NIb and the coat protein (CP) of plum pox potyvirus (PPV) were used for analysing the composition of virus-induced cytoplasmic and nuclear inclusions by electron microscopy. The antisera reacted with NSP and CP of PPV on immunogold-labelled ultrathin sections. Antiserum to CP reacted with virions of seven out of 18 other potyviruses. CP was distributed throughout the cytoplasm of infected cells. Antisera to PPV NSP specifically reacted with virus-specific cytoplasmic and/or nuclear inclusions induced by 17 different potyviruses. NSP were furthermore localized in confined cytoplasmic areas in between complex accumulations of virus-specific inclusions. Cylindrical inclusions induced by the potyviruses were proven to consist of CI protein. Most other cytoplasmic or nuclear inclusions were shown to be composed of two or more NSP. An unexpected composition of virus-induced inclusions was observed for the crystalline nuclear inclusions of tobacco etch virus. Here, in addition to the expected presence of NIa and NIb, HC-Pro could be demonstrated. Furthermore, amorphous cytoplasmic inclusions induced by papaya ringspot virus contained the expected HC-Pro but additionally NIa, NIb and CI. Beet mosaic virus-induced nuclear inclusions ('satellite bodies') contained in their electron-dense matrix NIa, NIb, Hc-Pro and CI and in their lacunae CP in bundles of virion-like filaments. The results indicate that all cytoplasmic or nuclear inclusions of potyviruses have to be regarded as deposition sites of excessively produced viral NSP.

Capsid↗

Expression of the potyvirus coat protein mediated by recombinant vaccinia virus and assembly of potyvirus-like particles in mammalian cells.

The coat protein of the potyvirus, Johnsongrass mosaic virus (JGMV), was expressed using a recombinant vaccinia virus (VV) system. Ultra-thin section electron microscopy demonstrated that the coat protein assembled into potyvirus-like particles (PVLPs) in recombinant VV infected cells. Infection of cells with two additional VV recombinants expressing coat protein plus N-terminal and N- and C-terminal extensions also resulted in the formation of PVLPs. These results suggest that the ability of VV to express the potyvirus coat protein at sufficient levels to allow PVLP formation in vitro, could make VV a suitable vector for the delivery of PVLPs displaying vaccine antigens in vivo without the need for particle purification and/or inclusion of adjuvant. Use of such a vaccine strategy would also benefit from the proven advantages of poxviruses as vaccines such as stability in a freeze dried form, resistance to environmental factors and the potential for oral administration.

Animals↗

Analysis of the sequence diversity of the P1, HC, P3, NIb and CP genomic regions of several yam mosaic potyvirus isolates: implications for the intraspecies molecular diversity of potyviruses.

Partial sequences from serologically characterized yam mosaic potyvirus (YMV) isolates were determined in conserved (helper-component proteinase, HC; nuclear inclusion b, NIb) and variable (first protein, P1; third protein, P3; and coat protein, CP) regions of the potyviral genome in order to investigate the intraspecies molecular diversity of YMV. Multiple sequence alignments and pairwise comparisons were used to quantify the sequence polymorphism in these regions. Two levels of diversity were observed among YMV isolates: above 90% nucleotide (nt) sequence identities were found between YMV isolates of the same group (intragroup) regardless of the region considered, whereas identities between isolates from different groups (intergroup) were lower and depended upon the protein chosen. For instance, the average intergroup nt sequence identity between YMV isolates was about 65% in the P1 protein and the N terminus of the CP while there was more than 80% nt identity in the HC, P3 and NIb proteins. Thus P3 appeared to be conserved between YMV isolates even though this region was variable between potyvirus species. Similar analysis of the intraspecies molecular diversity of other potyviruses (potato virus Y, zucchini yellow mosaic virus, plum pox virus, pea seed-borne mosaic virus) led to the same results: (i) two levels of intraspecies molecular diversity were found (intragroup and intergroup); (ii) intraspecies molecular diversity differed from interspecies molecular diversity in the P3, P1 and N-terminal regions.

Amino Acid Sequence↗

The nucleotide sequence of Watermelon mosaic virus (WMV, Potyvirus) reveals interspecific recombination between two related potyviruses in the 5' part of the genome.

Watermelon mosaic virus (WMV, Potyvirus) is a potyvirus with a worldwide distribution, mostly in temperate and mediterranean regions. According to the partial sequences that were available, WMV appeared to share high sequence similarity with Soybean mosaic virus (SMV), and it was almost considered as a strain of SMV in spite of its different and much broader host range. Like SMV, it was also related to legume-infecting potyviruses belonging to the " Bean common mosaic virus (BCMV) subgroup". In this paper we obtained the full-length sequence of WMV, and we confirmed that this virus is very closely related to SMV in most of its genome; however, there is evidence for an interspecific recombination in the P1 protein, as the P1 of WMV was 135 amino-acids longer than that of SMV, and the N-terminal half of the P1 showed no relation to SMV but was 85% identical to BCMV. This suggests that WMV has emerged through an ancestral recombination event, and supports the distinction of WMV and SMV as separate taxonomic units.

5' Untranslated Regions↗

Relatedness of the nucleotide sequence of the 3'-terminal region of clover yellow vein potyvirus RNA to bean yellow mosaic potyvirus RNA.

The sequence of the 3'-terminal 1,357 nucleotides of clover yellow vein potyvirus RNA was determined. A coat protein gene was identified and its predicted amino acid sequence deduced. It had 273 residues with a molecular weight of 31,019. The amino acid and nucleotide sequences of the virus were compared with those of five other potyviruses. The homology between these viruses indicated that clover yellow vein virus was a distinct virus, but had a closer affinity to bean yellow mosaic virus than to the four other potyviruses.

Amino Acid Sequence↗

Detection of an unidentified potyvirus from Roystonea regia palm using the polymerase chain reaction and degenerate, potyvirus specific, primers and potential problems arising from the amplification of host plant DNA sequences.

Degenerate potyvirus-specific primers were used in the PCR to amplify cDNA representing a 335 nucleotide region of the coat protein gene in RNA purified from an uncharacterised potyvirus isolated from Roystonea regia palms in Queensland, Australia. The RNA was also detected by PCR in total nucleic acid extracts from infected Nicotiana benthamiana, N. clevelandii and Vicia faba. The method also successfully detected pea seed-borne mosaic virus in Pisum sativum. In addition the procedure amplified DNA's of approximately 200 bp and 420 bp, of non-viral origin, from total nucleic acid extracts of healthy Nicotiana spp, indicating that size of the PCR products needs to be included as a criterion for identifying virus specific products when this method is used.

Base Sequence↗

Towards a protein interaction map of potyviruses: protein interaction matrixes of two potyviruses based on the yeast two-hybrid system.

A map for the interactions of the major proteins from Potato virus A (PVA) and Pea seed-borne mosaic virus (PSbMV) (members of the genus POTYVIRUS:, family POTYVIRIDAE:) was generated using the yeast two-hybrid system (YTHS). Interactions were readily detected with five PVA protein combinations (HC-HC, HC-CI, VPg-VPg, NIa-NIb and CP-CP) and weak but reproducible interactions were detected for seven additional combinations (P1-CI, P3-NIb, NIaPro-NIb, VPg-NIa, VPg-NIaPro, NIaPro-NIa and NIa-NIa). In PSbMV, readily detectable interactions were found in five protein combinations (HC-HC, VPg-VPg, VPg-NIa, NIa-NIa and NIa-NIb) and weaker but reproducible interactions were detected for three additional combinations (P3-NIa, NIa-NIaPro and CP-CP). The self-interactions of HC, VPg, NIa and CP and the interactions of VPg-NIa, NIa-NIaPro and NIa-NIb were, therefore, common for the two potyviruses. The multiple protein interactions revealed in this study shed light on the co-ordinated functions of potyviral proteins involved in virus movement and replication.

Hybridization, Genetic↗

Coat protein of potyviruses. 6. Amino acid sequences suggest watermelon mosaic virus 2 and soybean mosaic virus-N are strains of the same potyvirus.

The amino acid sequence of the coat protein of watermelon mosaic virus 2 (WMV 2) was determined by a combination of peptide and nucleic acid sequencing. The coat protein of WMV 2 contained 281 amino acid residues including a single cysteine at position 132 and a blocked amino terminus. Comparison with the coat protein sequences of 20 strains of ten distinct potyviruses showed sequence homologies ranging from 43% to 69% except for the N strain of soybean mosaic virus (SMV-N), where the sequence homology with WMV 2 was 83%. This degree of homology and the location of sequence differences between WMV 2 and SMV-N is much closer to that observed between strains of the same virus than that found between distinct potyviruses. These data suggest that WMV 2 and SMV-N may be strains of the same virus.

Amino Acid Sequence↗

Potyvirus taxonomy: potyviruses that affect solanaceous crops.

Serology has been the main, or at least an important, tool for differentiating potyviruses that affect solanaceous crops. At present, analysis of the genome by hybridization techniques has supported the differentiation of viruses demonstrated by serology. Phylogenetic groupings, based on nucleic acid sequences, should be combined with serological detection to make the groupings more usable.

Plant Viruses↗

Pathogen-derived resistance to a potyvirus: immune and resistant phenotypes in transgenic tobacco expressing altered forms of a potyvirus coat protein nucleotide sequence.

Transgenic Nicotiana tabacum 'Burley 49' plants containing one of six different forms of the tobacco etch virus (TEV) coat protein (CP) nucleotide sequence have been generated. In whole plant studies, R1 and R2 progeny were inoculated mechanically with TEV, and the appearance and severity of symptoms were recorded. Symptom phenotype was altered, ranging from near wild type susceptibility to apparent immunity. Protoplasts derived from wild type and transgenic Burley 49 plant lines were transfected with TEV RNA. Protoplasts from transgenic plants expressing full-length or truncated forms of TEV CP supported virus replication. Protoplasts from certain transgenic plants, producing plus- or minus-sense CP transcripts but no CP, did not support virus replication at wild type levels. A model is proposed to account for these observations.

Amino Acid Sequence↗

Sequencing and characterization of the coat protein and 3' non-coding region of a new sweet potato potyvirus.

A cDNA library was constructed from viral genomic RNA purified from sweet potato plants affected by "Sweet Potato Chlorotic Dwarf disease" in an attempt to clarify the etiology of this viral complex in Argentina. By sequence analysis, some of the obtained clones were found to belong to sweet potato feathery mottle potyvirus (SPFMV), to a closterovirus and to a new potyvirus. A cDNA clone of 1,103 bp representing the coat protein cistron and 3' non-coding region of the newly identified potyvirus was further characterized. The sequence contained an ORF of 855 nucleotides with a coding capacity of 285 amino acids, followed by a 3' untranslated tail of 248 nucleotides. The core and C-terminal regions have sequences well conserved among potyviruses. Furthermore, amino acid sequence comparisons of the capsid protein with those of other described potyviruses showed 63% homology with SPFMV, 68 to 70% with two different isolates of sweet potato latent potyvirus (SPLV), 57% with sweet potato G potyvirus (SPGV) and 73% with potato virus Y (PVY). These data allowed us to propose the inclusion of this virus as a new member of the family Potyviridae, genus Potyvirus with the designation sweet potato mild speckling potyvirus (SPMSV).

Amino Acid Sequence↗

Complete nucleotide sequence of the genomic RNA of a Japanese yam mosaic virus, a new potyvirus in Japan.

We determined the complete nucleotide sequence of a potyvirus purified from a Japanese yam plant. The genomic RNA of this virus is 9,757 nucleotides (nts) in length, excluding the 3'-terminal poly(A) tail. It contains a single open reading frame (ORF) encoding a polyprotein of 3130 amino acids (aa) with a calculated Mr of 356,793. The genomic organization of this potyvirus is similar to that of other members of the genus Potyvirus and nine potential cleavage sites for the viral proteinase were found by comparison of its sequence with those available for other potyviruses. The nucleotide sequence and genome characteristics show that this isolate is a new potyvirus species. Its polyprotein differs substantially from Yam mosaic virus (YMV) (50% amino acid sequence identity) and fourteen other potyvirus species examined (44-59% identity). Although this potyvirus has been classified as YMV, our results suggest that the potyvirus infectious to the Japanese yam plant in Japan is distinct from YMV. Therefore, we propose that the Japanese yam potyvirus should be designated as Japanese yam mosaic virus (JYMV).

Amino Acid Sequence↗

Identification and classification of potyviruses on the basis of coat protein sequence data and serology. Brief review.

The identification and classification of potyviruses has been in a very unsatisfactory state due to the large size of the group, the apparent vast variation among the members and the lack satisfactory taxonomic parameters that will distinguish distinct viruses from strains. In the past, use of classical methods, such as host range and symptomatology, cross-protection, morphology of cytoplasmic inclusions and conventional serology, revealed a "continuum" implying that the "species" and "strain" concepts cannot be applied to potyviruses. In contrast nucleic acid and amino acid sequence data of coat proteins has clearly demonstrated that potyviruses can be divided into distinct members and strains. This sequence data in combination with information of the structure of the potyvirus particle has been used to develop simple techniques such as HPLC peptide profiling, serology (using polyclonal antibody probes obtained by cross-adsorption with core protein from trypsin treated particles) and cDNA hybridization. These findings, along with immunochemical analyses of overlapping synthetic peptides have established the molecular basis for potyvirus serology; explained many of the problems associated with the application of conventional serology; and provided a sound basis for the identification and classification of potyviruses. As a result, the virus/strain status of some potyviruses has been redefined, requiring a change in the potyvirus nomenclature. These new developments necessitate a re-evaluation of the earlier literature on symptomatology, cross-protection, cytoplasmic inclusion body morphology and serology.

Amino Acid Sequence↗

Characterization of petunia flower mottle virus (PetFMV), a new potyvirus infecting Petunia x hybrida.

With the introduction of cutting-grown Petunia x hybrida plants on the European market, a new potyvirus which showed no serological reaction with antisera against any other potyviruses infecting petunias was discovered. Infected leaves contained flexuous rod-shaped virus particles of 750-800 nm in length and inclusion bodies (pinwheel structures) typical for potyviruses in ultrathin leaf sections. The purified coat protein with a Mr of approximately 36 kDa could be detected in Western immunoblots with a specific antibody to the coat protein of the petunia-infecting virus. The 3' end of the viral genome encompassing the 3' non-coding region, the coat protein gene, and part of the NIb gene was amplified from infected leaf material by IC/PCR using degenerate and specific primers. Sequences of PCR-generated cDNA clones were compared to other known sequences of potyviruses. Maximum homology of 56% was found in the 3' non-coding region between the petunia isolate and other potyviruses. A maximum homology of 69% was found between the amino acid sequence of the coat protein of the petunia isolate and corresponding sequences of other potyviruses. These data indicate that the petunia-infecting virus is a previously undescribed potyvirus and the name petunia flower mottle virus (PetFMV) is suggested.

Amino Acid Sequence↗

Potyviruses, chaos or order?

At first potyviruses were easily distinguished by biological and serological properties because only a few were known and information on their host ranges was limited. The first evidence of serological cross reaction between two of these viruses was reported in 1951 and was further corroborated for three obviously distinct members of the group in 1960. In 1968 attention was drawn to the fact that some legume and non-legume potyviruses have much wider host ranges than previously known and that within the potyvirus group there is as much biological variation within viruses and overlap between viruses as there is in serology. The concept of continuity within the group was soon supported by others and became known as the "continuum hypothesis." Results with highly sensitive serological methods using polyclonal antisera were conflicting, and nucleic acid hybridization techniques did not unambiguously discriminate between potyviruses. Recent results, obtained with antibodies directed toward epitopes located in the N-termini of the coat proteins of potyviruses, suggest that there are ways to more definitely group strains of one potyvirus and distinguish them from other potyviruses. However, there are exceptions to this rule, as in the case of bean yellow mosaic virus and clover yellow vein virus which are clearly distinct in host range, inclusion bodies, and migration velocity of coat protein, but which still react with antibodies to the N-terminal epitopes of one virus. So the question remains of whether coat-protein properties, especially the serological reactivity of N-termini, which do not alter overall virus integrity when lost, sufficiently represent the genome of a pathogenic virus entity as a single criterion for classification.

Capsid↗