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At least 1,207 records · Page 67Linked to original sources
PubMed1981

Electron microscopic studies of bacteriophage phi X174 intact and "eclipsing' particles, and the genome by the staining, and shadowing method.

Bacteriophage phi X174 particles were observed with a new method, a combination of staining and shadowing. Previously we used this technique to obtain clear visualization of the shape of cytoplasmic-polyhedrosis virus, especially the spikes of this particle. The phi X174 particle was observed to be an icosahedral particle of 25 nm in diameter carrying a spike at each vertex. The spike was a pentagonal frustum with a base of 9 nm and a height of 6 nm. When the phage was treated with calcium on the supporting film, the genome extruded from the particle. With the staining and shadowing method, it was clearly observed that the spike was the extruding channel of the genome. The genome extrusion occurred not only a single spike of the particle but also at two or more spikes. This implied that all 12 spikes of the particle had the same abilities to act as the channel of genome extrusion. The released genomes showed various thicknesses and shapes such as bending, looping, or branching, which were thought to reflect to compact form of DNA in a virus particle. The similarly between the spikes of bacteriophage phi X174 and those of cytoplasmic-polyhedrosis virus from silk worm was also discussed.

Bacteriophage phi X 174↗
PubMed1988

Coupled transcription-translation of silkworm cytoplasmic polyhedrosis virus injected into oocytes of the frog, Xenopus laevis.

The cytoplasmic polyhedrosis virus of the silkworm, Bombyx mori, contains a ten-segmented, double-stranded RNA genome and five species of polypeptides, V1 (Mr 146,000), V2 (Mr 140,000), V3 (Mr 128,000)), V4 (Mr 62,000), and V5 (Mr 32,000). The virus contains an RNA-dependent RNA polymerase that transcribes the duplex genome RNA to form mRNA either in the infected animals or under appropriate conditions in vitro. We co-microinjected the virus, [alpha-32P]GTP and actinomycin D into oocytes of the frog, Xenopus laevis, and found that at least eight species of mRNA were formed in the oocytes. Virus-injected oocytes were labeled with [35S]methionine and cell extracts were treated with rabbit anti-cytoplasmic polyhedrosis virus immunoglobulin G. Analysis of the immunoprecipitates by sodium dodecyl sulfate polyacrylamide gel electrophoresis revealed that V1, V2, and V3 were produced in the virus-injected oocytes whereas V4 and V5 were not. By injecting the separated double-stranded genome segments immediately after heat-denaturation into oocytes, it was found that V1 was coded for by segment 1 with a chain length of 4.2 kilobase pairs, V2 by segment 2 or 3, whose chain lengths are both 4.0 kilobase pairs, and V3 by segment 4 with a chain length of 3.2 kilobase pairs. These results demonstrate that the Xenopus oocyte is a very useful system for the coupled transcription-translation of double-stranded RNA viruses.

Animals↗
PubMed2001

Analysis of the capsid processing strategy of Thosea asigna virus using baculovirus expression of virus-like particles.

Thosea asigna virus (TaV), a putative member of the genus Betatetravirus of the family Tetraviridae, is predicted to have a novel capsid expression strategy compared with other characterized tetraviruses. The capsid precursor protein is cleaved twice to generate three proteins. Two of the proteins, L (58.3 kDa) and S (6.8 kDa), are incorporated into the TaV virion. The third, non-structural protein, produced from the N terminus of the precursor protein, is up to 17 kDa in size and is of unknown function. The TaV capsid precursor protein sequence without the 17 kDa N-terminal region was modelled against the solved structure from Nudaurelia omega virus (N omega V) using SwissModel. The TaV model was very similar to the solved structure determined for subunit A of N omega V and had features that are conserved between tetraviruses and nodaviruses, including the positioning of the cleavage site between the L and S capsid proteins. The production of virus-like particles (VLPs) using the baculovirus expression system was used to analyse the capsid processing strategy employed by TaV. VLPs were formed in both the presence and absence of the 17 kDa N-terminal region of the capsid precursor. VLPs were not formed when the L and S regions were expressed from separate promoters, indicating that cleavage between the L and S capsid proteins was an essential part of TaV capsid assembly. Expression of the TaV 17 kDa protein in bacteria did not produce intracellular tubules similar to those formed by bacterial expression of the p17 protein from Helicoverpa armigera stunt virus.

Animals↗
PubMedDate not supplied

The CO2 sensitivity induced by two rhabdoviruses, Piry and Chandipura, in Drosophila melanogaster.

Piry and Chandipura viruses induce CO2 sensitivity after multiplication in D. melanogaster. Flies infected with Piry virus react to CO2 like flies infected with sigma virus: after a post-infection delay the flies become sensitive; sister batches exposed later on remain persistently CO2 sensitive. Flies infected with Chandipura virus react to CO2 like flies infected with VSV: flies become sensitive, but sister batches exposed later on recover and fail to show any CO2 sensitivity, although they remain infected with virus. These are consistent with the hypothesis that at the CO2 site (nervious system) a definite rhythm of production of budding sites, which transform the plasma membrane, is necessary for the CO2 sensitivity. Meanwhile, flies inoculated with Chandipura virus present a distinctive feature: below a definite temperature the flies do not become CO2 sensitive although it is still possible to observe a slight multiplication. The results from shift-up and shift-down experiments suggest that there is a cyrosensitive event in the viral multiplication. The experiments on the survival of infectious centers show that this event is implicated in the maturation step. With a study of the influence of previous CO2 exposure on CO2 sensitivity, when the expression of the viral functions are restricted by temperature, CO2 is whown to have a protective action probably produced by a cellular repair mechanism of non lethal lesions. When compared with VSV strains Brazil and New-Jersey, Piry and Chandipura viruses are moderately adapted to Drosophila. Like VSV, SVC virus and PFR, the Piry and Chandipura viruses have not been found in the progeny of infected flies, while with sigma virus "l'héritier has shown that CO2 sensitivity is hereditary.

Animals↗
PubMed1990

Expression of hepatitis B virus core and precore antigens in insect cells and characterization of a core-associated kinase activity.

The hepatitis B virus core open reading frame with and without the precore domain was expressed in insect cells using a baculovirus expression system. Precore antigen was not properly processed in insect cells and was present in highly insoluble cytoplasmic aggregates. Core antigen without the precore domain formed core particles with a diameter of 28 nm that were secreted into the medium. Both core and precore antigens were phosphorylated in insect cells. The immune response in mice to both antigens yielded antibodies with a high degree of preferential reactivity for the homologous immunizing polypeptide. A kinase activity that phosphorylated core antigen was associated with highly purified core particles. The kinase activity resembled that previously demonstrated for core particles purified from the cytoplasm of infected hepatocytes and detergent-treated Dane particles. Partial resistance of the phosphate-label to phosphatase treatment suggested that some of the phosphorylated sites are in the interior of the particle. The presence of kinase activity in recombinant core particles demonstrated that this activity is not derived from another hepatitis B virus-encoded polypeptide, and the lack of a kinase consensus sequence in the core open reading frame suggests that the kinase is of cellular origin.

Animals↗
PubMed1991

Synthesis of Newcastle disease virus (NDV)-like envelopes in insect cells infected with a recombinant baculovirus expressing the haemagglutinin-neuraminidase of NDV.

Electron microscopical examination of negatively stained extracellular fluids (ECF) from Spodoptera frugiperda cell cultures infected with a recombinant baculovirus expressing the Newcastle disease virus (NDV) haemagglutinin-neuraminidase (HN) revealed NDV-like envelopes which resembled the envelopes of authentic NDV. Immunogold staining with anti-NDV HN monoclonal antibodies demonstrated HN antigen in spikes on the NDV-like envelopes. The ECF from the recombinant-infected cultures also contained baculovirus particles which resembled standard baculovirus particles except that some showed polar protrusions of the envelope. It was concluded that the HN of NDV, in the absence of the matrix protein, might be able to initiate and control the production of viral envelopes which are morphologically identical to those of authentic NDV.

Animals↗
PubMed2006

Pigeonpea (Cajanus cajan L. Millsp.).

Pigeonpea [Cajanus cajan (L.) Millsp.], also known as redgram, is one of the major grain legume (pulses) crops grown in the semiarid tropics (SAT) extending between 30 degrees N and 30 degrees S; it is the second most important food legume of India. It is cultivated in about 50 countries of Asia, Africa, and the Americas for a variety of uses (food, fodder, fuel wood, rearing lac insects, hedges, wind breaks, soil conservation, green manure, roofing, and so on). The constraints of enhancing its productivity include the damage caused by various fungi, bacteria, viruses, and insect pests. Conventional plant breeding methods have not been successful for the improvement of pigeonpea because of genetic variation and incompatibility among the wild varieties. Genetic engineering technology can therefore be used as an additional tool for the introduction of agronomically useful traits into established varieties. The development of plant transformation techniques has been a major breakthrough in overcoming constraints to achieve precision in genetic manipulation. The development of efficient plant regeneration protocols is a prerequisite for recombinant technology to carry out genetic transformation. This chapter describes an Agrobacterium-mediated transformation protocol for pigeonpea, a simple, efficient, and reproducible method that is applicable across diverse genotypes of pigeonpea.

Agrobacterium tumefaciens↗