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PubMed1998

Watermelon bud necrosis tospovirus is a distinct virus species belonging to serogroup IV.

The nucleocapsid protein gene of a tospovirus infecting watermelon in India was cloned and sequenced. Sequence analyses showed that the gene was most closely related to those of watermelon silver mottle tospovirus (WSMV) from Taiwan and peanut bud necrosis tospovirus (PBNV) from India, the two definitive species of serogroup IV. Amino acid sequence similarity was 84% and 82% with WSMV and PBNV, respectively. On the basis of the sequence divergence and the previously determined host range differences, the watermelon tospovirus, designated as watermelon bud necrosis tospovirus, should be considered as a distinct species belonging to serogroup IV.

Amino Acid Sequence↗
PubMed1990

Firefly luciferase, synthesized to very high levels in caterpillars infected with a recombinant baculovirus, can also be used as an efficient reporter enzyme in vivo.

Trichoplusia ni and Spodoptera littoralis larvae were infected with a recombinant AcNPV, having the viral polyhedrin gene replaced with the cDNA encoding firefly luciferase. Both S. littoralis and T. ni synthesized very high levels of luciferase representing greater than or equal to 25% and greater than or equal to 15%, respectively of the total Coomassie blue stainable protein. Luciferase was apparently not secreted into the hemolymph but was contained within the body tissue. Expression in S. littoralis larvae suggests that luciferase can be an excellent reporter enzyme to study virus infection, dissemination and expression in different tissues, host range determination, insect physiology and also to monitor the release of recombinant virus in the environment when used as a biocide.

Animals↗
PubMed1988

The genes encoding the DNA binding protein and the 23K protease of adenovirus types 40 and 41.

The adenovirus (Ad) single-stranded DNA binding protein (DBP) is a multifunctional protein. It is thought to consist of two domains, the amino-terminal domain involved in host-range determination and the carboxyl-terminal domain functioning in DNA replication and DNA binding. We have determined the nucleotide sequences of the DBP genes of Ad40 and Ad41, two human adenoviral serotypes that differ significantly from other adenoviruses. Regions of structural and functional importance in the corresponding proteins could be identified by comparison of the amino acid sequences with those of other known DBPs. In addition, the nucleotide sequences of the DBP early promoters, of the 23K protease genes, and of parts of the hexon and 100K protein genes have been determined. It can be deduced from the nucleotide sequences, that the Ad40 and Ad41 DBPs are relatively small (473 and 474 amino acids (a.a.), respectively, versus 529 a.a. for the Ad5 DBP). This is caused by the presence of very small amino-terminal domains of 119 a.a. (Ad40) and 120 a.a. (Ad41), as compared to 173 a.a. for the corresponding Ad5 domain. Only a few amino acids in this domain have been conserved in all known DBPs. The carboxyl-terminal domains show a higher degree of sequence conservation. In this domain, four strongly conserved regions can be identified, one of which might form a metal-binding site. The 23K proteases of both Ad40 and Ad41 show a strong homology to the Ad2 and Ad5 proteins, with the exception of the carboxyl-terminal end of the proteins. The 23K protease gene of Ad41 has an open reading frame that extends beyond the polyadenylation signal, in contrast to the Ad40 gene that ends well in front of the signal.

Adenoviruses, Human↗
PubMed1985

Identification of pTiC58 plasmid-encoded proteins for virulence in Agrobacterium tumefaciens.

Analyses were made of the host-dependent-variation (hdv) locus of the virulence (vir) region of the pTiC58 plasmid of Agrobacterium tumefaciens. The hdv locus is comprised of at least four genes that encode polypeptides of 13, 15, 29, and 28 kDa. Insertion of transposon Tn5 in the first gene abolishes the expression of all four genes in vitro and in vivo. Nucleotide sequence analysis of the hdv locus revealed four open reading frames tandemly arranged with spacer sequences having no promoter-like sequences and lacking the ability to bind A. tumefaciens RNA polymerase. These studies suggest that the hdv locus is comprised of at least four genes arranged in an operon in the vir region. The protein products of these genes are likely to function in some aspect of the host-range determination of A. tumefaciens.

Amino Acid Sequence↗
PubMed1989

Cloned avirulence genes from the tomato pathogen Pseudomonas syringae pv. tomato confer cultivar specificity on soybean.

Three different cosmid clones were isolated from a genomic library of the tomato pathogen Pseudomonas syringae pv. tomato, which, when introduced into the soybean pathogen P. syringae pv. glycinea, caused a defensive hypersensitive response (HR) in certain soybean cultivars. Each clone was distinguished by the specific cultivars that reacted hypersensitively and by the intensity of the HR elicited. Unlike wild-type P. syringae pv. tomato isolates, which elicit the HR on all soybean cultivars, all three clones exhibited cultivar specificities analogous to avirulence genes previously cloned from P. syringae pv. glycinea. However, the collective phenotypes of the three clones accounted for HRs on all tested soybean cultivars. One of the three P. syringae pv. tomato clones contained an avirulence gene homologous to avrA, which was previously cloned from P. syringae pv. glycinea race 6. The other two P. syringae pv. tomato clones expressed unique HR patterns on various soybean cultivars, which were unlike those caused by any known P. syringae pv. glycinea race or previously cloned P. syringae pv. glycinea avr gene. Further characterization of the second P. syringae pv. tomato clone indicated that the avirulence phenotype resided on a 5.6-kilobase HindIII fragment that, in Southern blot analyses, hybridized to an identical-size fragment in various P. syringae pathovars, including all tested glycinea races. These results demonstrate that avirulence genes may be distributed among several P. syringae pathovars but may be modified so that the HR is not elicited in a particular host plant. Furthermore, the data raise the possibility that avirulence genes may function in host-range determination at levels above race-cultivar specificity.

Journal Article↗
PubMed1995

Mutation or increased copy number of nodE has no effect on the spectrum of chitolipooligosaccharide nod factors made by Rhizobium leguminosarum bv. trifolii.

The bacterial gene nodE is the key determinant of host specificity in the Rhizobium leguminosarum-legume symbiosis and has been proposed to determined unique polyunsaturated fatty acyl moieties in chitolipooligosaccharides (CLOS) made by the bacterial symbiont. We evaluated nodE function by examining CLOS structures made by wild-type R. leguminosarum bv. trifolii ANU843, an isogenic nodE::Tn5 mutant, and a recombinant strain containing multiple copies of the pSym nod region of ANU843. 1H-NMR, electrospray ionization mass spectrometry, fast atom bombardment mass spectrometry, flame ionization detection-gas chromatography, gas chromatography/mass spectrometry, and high performance liquid chromatography/UV photodiode array analyses revealed that these bacterial strains made the same spectrum of CLOS species. We also found that ions in the mass spectra which were originally assigned to nodE-dependent CLOS species containing unique polyunsaturated fatty acids (Spaink, H. P., Bloemberg, G. V., van Brussel, A. A. N., Lugtenberg, B. J. J., van der Drift, K. M. G. M., Haverkamp, J., and Thomas-Oates, J. E. (1995) Mol. Plant-Microbe Interact. 8, 155-164) were actually due to sodium adducts of the major nodE-independent CLOS species. No evidence for nodE-dependent CLOSs was found for these strains. These results indicate a need to revise the current model to explain how nodE determines host range in the R. leguminosarum-legume symbiosis.

Acyltransferases↗
PubMed1998

The presence and characterization of a virF gene on Agrobacterium vitis Ti plasmids.

Octopine and nopaline strains of Agrobacterium tumefaciens differ in their ability to induce tumors on Nicotiana glauca. The presence of a virF locus on the octopine Ti plasmid makes N. glauca a host plant for these strains, indicating that the VirF protein is a host-range determinant. Here we show the presence of a virF locus not only on the Agrobacterium vitis octopine/cucumopine plasmids pTiAg57 and pTiTm4, but also on the nopaline Ti plasmids pTiAT1, pTiAT66a, and pTiAT66b. On the octopine Ti plasmids from A. tumefaciens the virF gene is located between the virE locus and the left border of the T-region. In contrast, the virF gene on Ti plasmids of A. vitis is located at the very left end of the vir-region near the virA locus. The virF gene of pTiAg57 has been sequenced and codes for a protein of 202 amino acids with a molecular mass of 22,280 Da. Comparison showed that the virF gene from A. vitis strain Ag57 is almost identical to that from A. tumefaciens octopine strains. The transcription of the pTiAg57 virF is inducible by the plant phenolic compound acetosyringone through the presence of a vir-box consensus sequence in its promoter region. The VirF protein from pTiAg57 can complement octopine A. tumefaciens strains deleted for virF as shown by tumor formation on N. glauca.

Agrobacterium tumefaciens↗
PubMed1988

Molecular and biochemical studies of the evolution, infection and transmission of insect bunyaviruses.

Members of the Bunyaviridae family of RNA viruses (bunyaviruses, hantaviruses, nairoviruses, phleboviruses and uukuviruses) have been studied at the molecular and genetic level to understand the basis of their evolution and infection in vertebrate and invertebrate (arthropod) hosts. With the exception of the hantaviruses, these viruses infect and are transmitted by a variety of blood-sucking arthropods (mosquitoes, phlebotomines, gnats, ticks, etc.). The viruses are responsible for infection of various vertebrate species, occasionally causing human disease, morbidity and mortality (e.g. Rift Valley fever, Crimean-Congo haemorrhagic fever, Korean haemorrhagic fever). Genetic and molecular analyses of bunyaviruses have established the coding assignments of the three viral RNA species and documented which viral gene products determine host range and virulence. Ecological studies, with molecular techniques, have provided evidence for bunyavirus evolution in nature through genetic drift (involving the accumulation of point mutations) and shift (RNA-segment reassortment).

Animals↗
PubMed1985

Phosphopeptide fingerprints of nucleoproteins of various influenza A virus strains grown in different host cells.

MDCK, HeLa, L or primary chick embryo cells were infected with different influenza A virus strains and labelled with [32P]orthophosphate. The nucleoprotein was immunoprecipitated and digested by trypsin. The resulting tryptic fingerprints were strain-specific and dependent on the host cell in which the virus strains had been propagated. Virus mutants had different fingerprints. It is suggested that specific cellular protein phosphokinases are involved in virus replication and that these may determine host range and cell tropism by site-specific phosphorylation of viral phosphoproteins.

Animals↗
PubMed1989

Location and characterization of two functions on RP1 that inhibit the fertility of the IncW plasmid R388.

Two fertility-inhibition functions which reduce R388 (IncW) transfer were detected on RP1 (60 kb, IncP). The respective genes, fiwA and fiwB, were mapped by transposon insertion mutagenesis to the regions between coordinates 32.8 to 31.7 kb (fiwA), and 59.8 to 0.8 kb (fiwB). The fiwA function occurs in a non-essential region of RP1 whereas fiwB is straddled by essential plasmid-maintenance and host-range determinants and apparently coincides (or overlaps) with the gene for tellurite-resistance.

DNA Transposable Elements↗
PubMed2006

Replication of bovine respiratory syncytial virus in murine cells depends on type I interferon-receptor functionality.

Bovine respiratory syncytial virus (BRSV) is able to counteract the alpha/beta interferon (IFN-alpha/beta)-mediated antiviral response for efficient replication in a host-specific manner. Mice models have been developed for experimental infection with human, but not bovine, respiratory syncytial virus strains. Here, it is shown that BRSV can replicate efficiently on primary cell cultures derived from type I IFN receptor-deficient, but not from wild-type IFN-competent, mice. However, BRSV infection was not enhanced in mice devoid of the type I IFN receptor. These results show that type I IFN is a major host-range determinant for infection at the cellular level, but that other factors control virus replication and pathology in vivo.

Animals↗
PubMed1994

Acquisition and rearrangement of sequence motifs in the evolution of bacteriophage tail fibres.

Molecular analysis reveals a surprising sharing of short gene segments among a variety of large double-stranded DNA bacteriophages of enteric bacteria. Ancestral genomes from otherwise unrelated phages, including lambda, Mu, P1, P2 and T4, must have exchanged parts of their tail-fibre genes. Individual genes appear as mosaics with parts derived from a common gene pool. Therefore, horizontal gene transfer emerges as a major factor in the evolution of a specific part of phage genomes. Current concepts of homologous recombination cannot account for the formation of such chimeric genes and the recombinational mechanisms responsible are not known. However, recombination sites for DNA invertases and recombination site-like sequences are present at the boundaries of gene segments conferring the specificity for the host receptor. This, together with the properties of the DNA inversion mechanism, suggests that these site-specific recombination enzymes could be responsible for the exchange of host-range determinants.

Base Sequence↗
PubMed2003

Growth dynamics of Salmonella enterica strains on alfalfa sprouts and in waste seed irrigation water.

Alfalfa sprouts and other seed sprouts have been implicated in numerous outbreaks of salmonellosis. The source of these epidemics appears to have been low-level contamination of seeds by Salmonella bacteria that developed into clinically significant populations during the seed germination process. To test the possibility that Salmonella enterica strains carry host range determinants that allow them to grow on alfalfa, strains isolated from alfalfa or other sources were surveyed for their ability to grow on germinating alfalfa seeds. An S. enterica serovar Cubana strain originally isolated from contaminated alfalfa sprouts multiplied most rapidly during the initial 24 h of the seed germination process. Germinating alfalfa seeds supported the multiplication of S. enterica cells prior to the emergence of the root radicle at 72 h. Thereafter, much lower rates of multiplication were apparent. The ability of S. enterica to grow on germinating alfalfa seeds was independent of the serovar, isolation source, or virulence of the strain. Isolates obtained from alfalfa attained population levels similar to those observed for strains isolated from contaminated meat products or stools. Each of the strains could be detected in the waste irrigation water, with populations being strongly correlated with those detected on the germinating alfalfa seeds. The S. enterica strains were capable of utilizing the waste irrigation water as a sole carbon and nitrogen source. S. enterica strains thus appear to grow saprophytically on soluble organics released from seeds during early phases of germination. The ability to detect S. enterica in the waste irrigation water early in the germination process indicates that this method may be used as a simple way to monitor the contamination of sprouts during commercial operations.

Animals↗
PubMed1986

Molecular cloning and expression of Rhizobium fredii USDA 193 nodulation genes: extension of host range for nodulation.

DNA hybridization with the cloned nodulation region of Rhizobium meliloti as a probe revealed DNA homology with four HindIII fragments, 12.5, 6.8, 5.2, and 0.3 kilobases (kb) in size, of the symbiotic plasmid pRjaUSDA193. Both hybridization and complementation studies suggest that the common nodulation genes nodABC and nodD of R. fredii USDA 193 are present on the 5.2-kb HindIII and 2.8-kb EcoRI fragments, respectively, of the Sym plasmid. Both fragments together could confer nodulation ability on soybeans when present in Sym plasmid-cured (Sym-) and wild-type (Sym+) Rhizobium strains or in a Ti plasmid-cured Agrobacterium tumefaciens strain. Furthermore, the 2.8-kb EcoRI fragment alone was able to form nodulelike structures on Glycine max L. cv. "Peking" (soybean). Microscopic examination of these nodules revealed bacterial invasion of the cells, probably via root hair penetration. Bacterial strains harboring plasmids carrying the 5.2- and 2.8-kb nod fragments elicited root-hair-curling responses on infection. These data suggest that the genes responsible for host range determination and some of the early events of nodulation may be coded for by the 5.2-kb HindIII and 2.8-kb EcoRI fragments.

Cloning, Molecular↗
PubMed2002

Genomic analysis of Clostridium perfringens bacteriophage phi3626, which integrates into guaA and possibly affects sporulation.

Two temperate viruses, phi3626 and phi8533, have been isolated from lysogenic Clostridium perfringens strains. Phage phi3626 was chosen for detailed analysis and was inspected by electron microscopy, protein profiling, and host range determination. For the first time, the nucleotide sequence of a bacteriophage infecting Clostridium species was determined. The virus belongs to the Siphoviridae family of the tailed phages, the order Caudovirales. Its genome consists of a linear double-stranded DNA molecule of 33,507 nucleotides, with invariable 3'-protruding cohesive ends of nine residues. Fifty open reading frames were identified, which are organized in three major life cycle-specific gene clusters. The genes required for lytic development show an opposite orientation and arrangement compared to the lysogeny control region. A function could be assigned to 19 gene products, based upon bioinformatic analyses, N-terminal amino acid sequencing, or experimental evidence. These include DNA-packaging proteins, structural components, a dual lysis system, a putative lysogeny switch, and proteins that are involved in replication, recombination, and modification of phage DNA. The presence of genes encoding a putative sigma factor related to sporulation-dependent sigma factors and a putative sporulation-dependent transcription regulator suggests a possible interaction of phi3626 with onset of sporulation in C. perfringens. We found that the phi3626 attachment site attP lies in a noncoding region immediately downstream of int. Integration of the viral genome occurs into the bacterial attachment site attB, which is located within the 3' end of a guaA homologue. This essential housekeeping gene is functionally independent of the integration status, due to reconstitution of its terminal codons by phage sequence.

Attachment Sites, Microbiological↗
PubMed1979

Avian sarcoma virus-transformed quail clones defective in the production of focus-forming virus.

Quail embryo fibroblasts were infected at low multiplicity with avian sarcoma virus, and transformed cells were selected by their ability to form colonies in agar. Five clones that failed to produce focus-forming virus were examined for (i) intactness of the integrated proviral DNA, (ii) intracellular viral RNA production, (iii) intracellular viral antigen production, (iv) production of virus particles, and (v) rescue of a functional src gene and of parental host range determinants by superinfection with Rous-associated virus-60, an avian leukosis virus of subgroup E. Deletions in the integrated viral DNA were apparent in three of the five nonproducer clones. In one clone producing focus-forming virus, analysis of the integrated viral DNA revealed an insertion in the region of the genome that codes for src.

Animals↗
PubMed1987

In vitro recombinants of ground squirrel and woodchuck hepatitis viral DNAs produce infectious virus in squirrels.

Hepatitis B viruses of humans, woodchucks, ground squirrels, and ducks are similar biochemically but differ with respect to host range and pathogenicity. To pursue the genetic basis of these properties in the absence of a cell culture system for virus growth, we exploited the demonstrated infectivity of cloned hepatitis B virus DNA in whole animals. We constructed several recombinant molecules in vitro between cloned infectious genomes of woodchuck hepatitis virus (WHV) and ground squirrel hepatitis virus (GSHV) and assayed the recombinants for infectivity after intrahepatic injection in ground squirrels, which support growth of GSHV but not WHV. Two of the recombinants molecules initiated productive infection; in one recombinant genome, 76% of the coding region for the major surface glycoprotein of GSHV and for the overlapping portion of the presumptive gene for DNA polymerase was replaced by WHV DNA; in the other, 29% of the same coding domain was replaced by WHV DNA. These findings demonstrate the feasibility of generating viable recombinants of hepatitis B viruses from different animal species and suggest that the major host range determinants are not encoded within the surface antigen gene of these viruses.

Amino Acid Sequence↗
PubMed1993

Apoptosis reduces both the in vitro replication and the in vivo infectivity of a baculovirus.

Apoptotic programmed cell death occurs when the insect cell line SF-21, derived from Spodoptera frugiperda, is infected with mutants of the baculovirus Autographa californica nuclear polyhedrosis virus (AcMNPV) which lack a functional p35 gene. However, infection of the Trichoplusia ni TN-368 cell line with p35 mutants does not result in apoptosis (R. Clem, M. Fechheimer, and L. Miller, Science 254:1388-1390, 1991). We have examined the effect of apoptosis on AcMNPV infections in cell lines and larvae of these two insect species. Production of viral progeny was significantly lower in SF-21 cells infected with p35 mutants than in cells infected with wild-type (wt) or revertant viruses. Viral gene expression was abnormal in SF-21 cells infected with p35 mutants; there was a delay in the transcription and translation of early and late viral genes, a lack of expression of very late genes, and a total cessation of protein synthesis late in the apoptotic process. In vivo analysis revealed that the dose of budded virus required for 50% lethality in S. frugiperda larvae was approximately 1,000-fold higher for p35 mutants than for wt or revertant viruses. In contrast, the replication and infectivity of p35 mutant viruses was equivalent to that of wt AcMNPV during infection of both TN-368 cells and T. ni larvae. Thus, the data indicate that a host apoptotic response provides protection against viral infection at the organismal level and that the p35 gene constitutes a host range determinant for AcMNPV infection.

Animals↗