972 resultados para Two potyvirus isolates


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Efetuou-se a clonagem e seqüenciamento do gene que codifica a proteína capsidial de dois isolados do vírus do mosaico da alface (Lettuce mosaic virus, LMV) provenientes do estado de São Paulo, previamente caracterizados como pertencentes aos patótipos II (AF198, incapaz de infetar cultivares com os genes de resistência mo1¹ ou mo1²) e IV (AF199, capaz de quebrar a resistência propiciada pelos genes mo1¹ e mo1²), com base na virulência em cultivares diferenciadoras. Análise comparativa das seqüências de nucleotídeos de isolados provenientes da Europa, América do Norte, Oriente Médio e os dois isolados brasileiros não permitiu sua separação em estirpes, pois as porcentagens de homologia foram sempre superiores a 95%. Entretanto, análise filogenética dos isolados sugere uma origem comum entre o isolado AF-198 e os isolados LMV-R e LMV-0 (patótipo II, provenientes dos Estados Unidos e da França, respectivamente). O isolado AF199 apresentou uma alta homologia de seqüência com os isolados LMV-Aud e LMV-13, ambos provenientes da França. Esses isolados também são relacionados a isolados provenientes do Chile, embora uma origem comum não seja proposta. Eventos independentes de mutação podem estar ocorrendo em diferentes partes do mundo, propiciando o surgimento de novas estirpes de LMV capazes de quebrar a resistência conferida pelos genes mo1¹ e mo1².

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The genomes of an Australian and a Canadian isolate of potato leafroll virus have been cloned and sequenced. The sequences of both isolates are similar (about 93%), but the Canadian isolate (PLRV-C) is more closely related (about 98% identity) to a Scottish (PLRV-S) and a Dutch isolate (PLRV-N) than to the Australian isolate (PLRV-A). The 5'-terminal 18 nucleotide residues of PLRV-C, PLRV-A, PLRV-N and beet western yellows virus have 17 residues in common. In contrast, PLRV-S shows no obvious similarity in this region. PLRV-A and PLRV-C genomic sequences have localized regions of marked diversity, in particular a 600 nucleotide residue sequence in the polymerase gene. These data provide a world-wide perspective on the molecular biology of PLRV strains and their comparison with other luteoviruses and related RNA plant viruses suggests that there are two major subgroups in the plant luteoviruses.

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BacilliformOryctes baculovirus particles have been visualized in electron micrographs of midgut sections from virus infectedOryctes rhinoceros beetles. Morphologically the Indian isolate (Oryctes baculovirus, KI) resembled the previously reportedOryctes baculovirus, isolate PV505. The constituent proteins of baculovirus KI have been analysed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and by Western blots using polyclonal antibodies raised against the complete viral particles, as probes. A total of forty eight viral proteins have been identified. Fourteen viral proteins were located on the viral envelope. Among the proteins constituting the nucleocapsid, three were located internally within the capsid. A 23.5 kDa protein was tightly associated with viral DNA in the nucleocapsid core. Two envelope and seven capsid proteins stained positive for glycosylation. Comparison between the viral proteins of KI and PV505 revealed differences in SDS-PAGE profiles and glycosylation patterns. Immunoblotting of KI and PV505 proteins with anti KI antiserum demonstrated antigenic differences between the two viral isolates.

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An assay was developed for quantitation of the antigenic relationship between viruses, by modification of the indirect ELISA. The principle of this method is to estimate the epitopes not shared between the related viruses, after titration of the antibodies specific to the common epitopes as in a blocking ELISA. In practice, varying concentrations of purified virus are preincubated with a fixed dilution of heterologous or homologous antiserum and the unbound antibodies present in the mixture are back titrated with virus particles bound to microtitre plates. The antigenic relationship is described in terms of differentiation index (DI) and total antigenic reactivity (TAR). This method has been used to quantitate cross-reactivity between two geographically different isolates of Oryctes baculovirus.

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Mixed infections in cucurbits are frequently observed in natural conditions between viruses from the Potyvirus genus and Cucumber mosaic virus (CMV), which significantly decreases productivity. The objectives of the present study was to compare the host range of PRSV-W, WMV, and ZYMV isolates and evaluate the effects of mixed infections with CMV in zucchini plants (Cucurbita pepo L.). Host range studies comprising 23 plant species confirmed some similarities and biological differences among the isolates of PRSV-W, ZYMV, and WMV. RT-PCR confirmed the amplification of DNA fragments of the PRSV-W, WMV, and ZYMV coat protein gene (cp) and cytoplasm inclusion gene (ci). The virus interaction studies in zucchini Caserta plants indicated synergistic interactions, particularly among species from the Potyvirus genus, and some CMV interference with some virus combinations.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Rice grassy stunt virus is a member of the genus Tenuivirus, is persistently transmitted by a brown planthopper, and has occurred in rice plants in South, Southeast, and East Asia (similar to North and South America). We determined the complete nucleotide (nt) sequences of RNAs 1 (9760 nt), 2 (4069 nt), 3 (3127 nt), 4 (2909 nt), 5 (2704 nt), and 6 (2590 nt) of a southern Philippine isolate from South Cotabato and compared them with those of a northern Philippine isolate from Laguna (Toriyama et al., 1997, 1998). The numbers of nucleotides in the terminal untranslated regions and open reading frames were identical between the two isolates except for the 5′ untranslated region of the complementary strand of RNA 4. Overall nucleotide differences between the two isolates were only 0.08% in RNA 1, 0.58% in RNA 4, and 0.26% in RNA 5, whereas they were 2.19% in RNA 2, 8.38% in RNA 3, and 3.63% in RNA 6. In the intergenic regions, the two isolates differed by 9.12% in RNA 2, 11.6% in RNA 3, and 6.86% in RNA 6 with multiple consecutive nucleotide deletion/insertions, whereas they differed by only 0.78% in RNA 4 and 0.34% in RNA 5. The nucleotide variation in the intergenic region of RNA 6 within the South Cotabato isolate was only 0.33%. These differences in accumulation of mutations among individual RNA segments indicate that there was genetic reassortment in the two geographical isolates; RNAs 1, 4, and 5 of the two isolates came from a common ancestor, whereas RNAs 2, 3, and 6 were from two different ancestors.

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In an epidemiological study of symptomatic human rotaviruses in Mysore, India during 1993 and 1994, isolates MP409 and MP480 were isolated from two children suffering from severe, acute dehydrating diarrhea. Both isolates exhibited 'long' RNA pattern and subgroup I specificity suggesting the likelihood of their animal origin. Both isolates did not react with monoclonal antibodies (MAbs) specific for serotypes G1 to G6 as well as CIO. To determine the genetic origin of these isolates, complete nucleotide sequences of genes encoding the outer capsid proteins VP4 and VP7, nonstructural proteins NSP1 and NSP3 and viral enterotoxin protein NSP4 from MP409 and partial sequences of genes from MP480 were determined. Comparison of the 5' and 3' terminal sequences of 250 nucleotides revealed complete identity of the gene sequences in both strains suggesting that MP409 and MP480 are two different isolates of a single strain. Comparison of the nucleotide and deduced amino acid sequences of VP4, VP7, NSP1 and NSP3 of MP409 with published sequences of strains belonging to different serotypes revealed that both outer capsid proteins VP4 and VP7 and NSP1 are highly related to the respective proteins from the P6[1], G8 type bovine rotavirus A5 isolated from a calf with diarrhoea in Thailand and that the NSP3 is highly homologous to that of bovine rotaviruses. The NSP 1 protein showed greatest sequence identity with NSP4s belonging to the KUN genetic group to which NSP4s from human G2 type strains and bovine rotaviruses belong. MP409 and MP480 likely signify interspecies transmission of P6[1], G8 type strains from cattle to humans and represent the first P6[1] type rotaviruses isolated in humans. These and our previous studies on the asymptomatic neonatal strain I321 are of evolutionary and epidemiological significance in the context of close association of majority of the Indian population with cattle.

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Two Saprolegnia isolates, JY isolated from silver crucian carp (Carassius auratus gibelio Bloch) and BMY isolated from zebra fish (Brachydanio rerio Hamilton) came from infections occurring concurrently in different locations in China. To confirm whether the two isolates were from the same Saprolegnia clone, comparative studies have been carried out based on their morphological, physiological and molecular characteristics. Observations showed that morphologically (both asexual and sexual organs) the two isolates were broadly similar and both isolates under-went repeated zoospore emergence. Comparing 704 base pairs of internal transcribed spacer (ITS) region and the 5.8S rDNA, we found isolates JY and BMY shared an identical ITS sequence with a minor variation (99.6 % similarity). Forty available sequences for representatives Saprolegnia spp. belonged to four phylogenetically separate clades. The two studied isolates fell within clade I that comprised a group of isolates which showed almost an identical ITS sequence but had been identified as a number of different morphological species. our findings suggest that isolates JY and BMY appear to belong to the S. ferax clade and this clade (1) contains a number of closely related phylogenetic species. This is distinct from the more common fish pathogenic isolates, which belong to the S. parasitica clade (III) and are characterized by having cysts decorated by bundles of long hooked hairs and two further clades (II and IV) containing largely saprotrophic or soil born species. (C) 2009 Published by Elsevier Ltd on behalf of The British Mycological Society.

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Ongoing Cryptococcus gattii outbreaks in the Western United States and Canada illustrate the impact of environmental reservoirs and both clonal and recombining propagation in driving emergence and expansion of microbial pathogens. C. gattii comprises four distinct molecular types: VGI, VGII, VGIII, and VGIV, with no evidence of nuclear genetic exchange, indicating these represent distinct species. C. gattii VGII isolates are causing the Pacific Northwest outbreak, whereas VGIII isolates frequently infect HIV/AIDS patients in Southern California. VGI, VGII, and VGIII have been isolated from patients and animals in the Western US, suggesting these molecular types occur in the environment. However, only two environmental isolates of C. gattii have ever been reported from California: CBS7750 (VGII) and WM161 (VGIII). The incongruence of frequent clinical presence and uncommon environmental isolation suggests an unknown C. gattii reservoir in California. Here we report frequent isolation of C. gattii VGIII MATα and MATa isolates and infrequent isolation of VGI MATα from environmental sources in Southern California. VGIII isolates were obtained from soil debris associated with tree species not previously reported as hosts from sites near residences of infected patients. These isolates are fertile under laboratory conditions, produce abundant spores, and are part of both locally and more distantly recombining populations. MLST and whole genome sequence analysis provide compelling evidence that these environmental isolates are the source of human infections. Isolates displayed wide-ranging virulence in macrophage and animal models. When clinical and environmental isolates with indistinguishable MLST profiles were compared, environmental isolates were less virulent. Taken together, our studies reveal an environmental source and risk of C. gattii to HIV/AIDS patients with implications for the >1,000,000 cryptococcal infections occurring annually for which the causative isolate is rarely assigned species status. Thus, the C. gattii global health burden could be more substantial than currently appreciated.

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Gentisate-1,2-dioxygenase genes (gdoA), with homology to a number of bacterial dioxygenases, and genes encoding a putative coenzyme A (CoA)-synthetase subunit (acdB) and a CoA-thioesterase (tieA) were identified in two haloarchaeal isolates. In Haloarcula sp. D1, gdoA was expressed during growth on 4-hydroxybenzoate but not benzoate, and acdB and tieA were not expressed during growth on any of the aromatic substrates tested. In contrast, gdoA was expressed in Haloferax sp. D1227 during growth on benzoate, 3-hydroxybenzoate, cinnamate and phenylpropionate, and both acdB and tieA were expressed during growth on benzoate, cinnamate and phenylpropionate, but not on 3-hydroxybenzoate. This pattern of induction is consistent with these genes encoding steps in a CoA-mediated benzoate pathway in this strain.

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The efficacies of putative fasciolicides and vaccines against Fasciola hepatica are frequently monitored in clinical and field trials by determination of fluke egg output in host faeces and by worm counts in the host liver at autopsy. Less often used are parameters based on fluke size and histology, yet these can provide important indications of specific effects on the development of particular germ-line or somatic tissues, especially in relation to the timing and profligacy of egg production. In this study. F. hepatica metacercariae of two distinct isolates, the triclabendazole (TCBZ)-sensitive Cullompton isolate and the TCBZ-resistant Oberon isolate, were administered to rats as single-isolate or mixed-isolate infections. At autopsy 16 weeks later individual adult flukes were counted, measured and the reproductive organs were examined histologically. The degree of development of the testis tubules in each fluke was represented by a numerical score, based on the proportion of the histological section profiles occupied by testis tissue. The level of anti-F. hepatica antibody in the serum of each rat was determined by ELISA. It was found that Cullompton flukes were significantly larger than Oberon flukes, and that significantly more Cullompton metacercariae developed to adults than Oberon metacercariae. The Cullompton flukes showed histological evidence of aspermy and spermatogenic arrest, which was reflected in quantitatively reduced testicular development, as compared with the Oberon isolate. In Cullompton flukes, parthenogenetic egg development is implied. The size of Cullompton and Oberon flukes was significantly related to the number of adult flukes recovered, to the number of metacercariae administered, and to the percentage success of infection. The testis development score in both isolates was significantly related to the number of adult flukes recovered but not to the number of metacercariae administered, or to the percentage success of infection. Fluke size was positively related to testis score for both isolates, and a significant negative relationship was found between percentage success of infection and metacercarial dose. The results are interpreted in terms of differing interactions between various numbers of young flukes and host immunity during invasion of and migration in the hepatic parenchyma, and of fluke intra-specific (possibly pheromonal) stimulatory effects in the final stages of development, within the host bile ducts. No significant relationships were found between host antibody levels and fluke size or testis score. False positive serological reactions were found in some rats that had been infected, but found to harbour no flukes at autopsy. Clearly the act of eliminating the flukes involved generation of an immune response. (C) 2011 Elsevier B.V. All rights reserved.