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PubMed2000

Host range and symptom variation of pseudorecombinant virus produced by two distinct bipartite geminiviruses.

Within the whitefly group only the species Bemisia tabaci (Gennadius) is the vector. Most whitefly-transmitted geminiviruses possess bipartite DNA genomes, DNAs A and B. Although they are closely related to each other, the production of viable pseudorecombinants between bipartite geminiviruses by reassortment of infectious cloned components is generally limited to strains of a particular virus. Following exchange of cloned genomic components of Sida golden mosaic virus (SiGMV/Hoyv) and Abutilon mosaic virus (AbMV), the pseudorecombinant viruses were infectious in various host plants. The symptom type of pseudorecombinant virus was in most cases determined by DNA B. However, in some host plants also DNA A of the pseudorecombinant virus was involved in the symptom phenotype.

Base Sequence↗

PubMed1985

F factor inhibition of conjugal transfer of broad-host-range plasmid RP4: requirement for the protein product of pif operon regulatory gene pifC.

By the use of deletions, point mutations, and gene fusions, we show that the protein product of the F factor pifC gene is responsible for F factor inhibition of plasmid RP4 conjugal transfer. Deletion analysis of pif sequences carried by pSC101-F chimeric plasmids demonstrated that removal of all or part of the pifC coding sequence greatly decreased or abolished the ability of these plasmids to inhibit RP4 transfer. Amber mutations in the pifC gene eliminated inhibition in an Su- host strain but not in and Su+ (supF) host. Plasmids carrying nonpolar pifC mutations did not decrease the efficiency of RP4 transfer when present in trans. Whereas pifC+ plasmids inhibited RP4 transfer, the presence of RP4 in the same cell as F' lac increased F'lac Pif activity approximately 1,000-fold. This effect most likely resulted from the binding of the pifC product to RP4 DNA and concomitant derepression of the F factor pif operon. PifC inhibited trans mobilization of pMS204, a nonconjugative plasmid carrying the RP4 oriT locus, by the RP1 derivative pUB307. pMS204 had no trans effect on pif operon expression, whereas pUB307 increased F'lac Pif expression, as did RP4. Our results suggest that the pifC product inhibits expression of one or more RP4 genes, the products of which are required for conjugal transfer of RP4 and are required in trans for mobilization of nonconjugal RP4 oriT containing plasmids.

Base Sequence↗

PubMed1999

Thermodynamic properties and DNA binding of the ParD protein from the broad host-range plasmid RK2/RP4 killing system.

ParD is a small, acidic protein from the partitioning system of the plasmid RK2/RP4. The ParD protein exhibits specific DNA binding activity and, as the antidote component of a toxin-antidote plasmid addiction system, ParD forms a tight complex in solution with its toxin antagonist, the ParE protein. Unopposed ParE acts as a toxin that causes growth retardation and killing of plasmid cured cells. ParD negatively autoregulates its expression by binding to an operator sequence in the parDE promoter region. This DNA binding activity is crucial for the regulation of the relative abundance of toxin and antidote which ultimately determines life or death for the bacterial host and its daughter cells. In light scattering studies and gel filtration chromatography we observed the existence of a stable dimer of ParD in solution. The stoichiometry of ParD-DNA complex formation appeared to be 4:1, the molecular mass of the complex was 72.1 kDa. The alpha-helical content of ParD as determined by CD-spectrometry was 35%. The protein exhibited high thermostability with a T(M) of 64 degrees C and deltaH of 25 kcal/mol as shown by differential scanning calorimetry. Upon complex formation the T(M) increased by 10 degrees C. The thermal unfolding of the ParD protein was highly reversible as observed in repeated DSC scans of the same sample. The recovery of the native fold was proven by CD-spectroscopy.

Bacterial Proteins↗

PubMed2002

Allelic variation of a Beauveria bassiana (Ascomycota: Hypocreales) minisatellite is independent of host range and geographic origin.

The minisatellite locus, BbMin1, was isolated from a partial Beauveria bassiana genomic library that consisted of poly(GA) flanked inserts. Polymerase chain reaction (PCR) of the BbMin1 repeat demonstrated allele size variation among 95 B. bassiana isolates. Amplification was also observed from single isolates of Beauveria amorpha, Beauveria brongniartii, and Beauveria caledonica. Eight alleles were identified at the haploid locus, where repeat number fluctuated between one and fourteen. AMOVA and theta (Fst) indicated that fixation of repeat number has not occurred within pathogenic ecotypes or geographically isolated samples of B. bassiana. Selective neutrality of allele size, the rate of BbMin1 mutation, and the age of the species may contribute to host and geographic independence of the marker. Presence of alleles with a large number of repeat units may be attributed to the rare occurrence of somatic recombination or DNA replication error. The molecular genetic marker was useful for the identification of genetic types of B. bassiana and related species.

Analysis of Variance↗

PubMed2002

NolX of Sinorhizobium fredii USDA257, a type III-secreted protein involved in host range determination, Iis localized in the infection threads of cowpea (Vigna unguiculata [L.] Walp) and soybean (Glycine max [L.] Merr.) nodules.

Sinorhizobium fredii USDA257 forms nitrogen-fixing nodules on soybean (Glycine max [L.] Merr.) in a cultivar-specific manner. This strain forms nodules on primitive soybean cultivars but fails to nodulate agronomically improved North American cultivars. Soybean cultivar specificity is regulated by the nolXWBTUV locus, which encodes part of a type III secretion system (TTSS). NolX, a soybean cultivar specificity protein, is secreted by TTSS and shows homology to HrpF of the plant pathogen Xanthomonas campestris pv. vesicatoria. It is not known whether NolX functions at the bacterium-plant interface or acts inside the host cell. Antibodies raised against S. fredii USDA257 NolX were used in immunocytochemical studies to investigate the subcellular localization of this protein. Immunostaining of paraffin-embedded sections of developing soybean and cowpea (Vigna unguiculata [L.] Walp) nodules revealed localization of NolX in the infection threads. Protein A-gold immunocytochemical localization studies utilizing affinity-purified NolX antibodies revealed specific deposition of gold particles in the fibrillar material inside infection threads. Similar immunogold localization studies failed to detect NolX in thin sections of mature soybean and cowpea nodules. The results from this study indicate that NolX is expressed in planta only during the early stages of nodule development.

Bacterial Proteins↗

PubMed2002

Extending chestnut blight hypovirus host range within diaporthales by biolistic delivery of viral cDNA.

Biolistic bombardment was used to successfully transform three phytopathogenic fungal species with an infectious cDNA clone of the prototypic hypovirus, CHV1-EP713, a genetic element responsible for the virulence attenuation (hypovirulence) of the chestnut blight fungus, Cryphonectria parasitica. The fungal species included two strains each of C. parasitica and Valsa ceratosperma, as well as one strain of Phomopsis G-type (teleomorph Diaporthe Nitschke); all are members of the order Diaporthales but classified into three different genera. A subset of transformants for each of the fungal species contained CHV1-EP713 dsRNA derived from chromosomally integrated viral cDNA. As has been reported for CHV1-EP713 infection of the natural host C parasitica, biolistic introduction of CHV1-EP713 into the new fungal hosts V ceratosperma and Phomopsis G-type resulted in altered colony morphology and, more importantly, reduced virulence. These results suggest a potential for hypoviruses as biological control agents in plant-infecting fungal pathogens other than the chestnut blight fungus and closely related species. In addition, the particle delivery technique offers a convenient means of transmitting hypoviruses to potential host fungi that provides new avenues for fundamental mycovirus research and may have practical applications for conferring hypovirulence directly on infected plants in the field.

Ascomycota↗

PubMed1993

Envelope-binding domain in the cationic amino acid transporter determines the host range of ecotropic murine retroviruses.

Infection of rodent cells by ecotropic type C retroviruses requires the expression of a cationic amino acid transporter composed of multiple membrane-spanning domains. By exchanging portions of cDNAs encoding the permissive mouse and nonpermissive human transporters and examining their abilities to specify virus infection upon expression in human 293 cells, we have identified the amino acid residues in the extracellular loop connecting the fifth and sixth membrane-spanning segments of the mouse transporter that are required for both envelope gp70 binding and infection. These findings strongly suggest that the role of the mouse transporter in determining infection is to provide an envelope-binding site. This role is analogous to those of host membrane proteins composed of a single membrane-spanning domain that serve as binding proteins or receptors for other enveloped viruses such as human immunodeficiency virus, Epstein-Barr virus, and murine and human coronaviruses.

3T3 Cells↗

PubMedDate not supplied

Mutational analysis of the movement protein of odontoglossum ringspot virus to identify a host-range determinant.

Tobacco mosaic virus (TMV) which contains the movement protein (MP) of odontoglossum ringspot tobamovirus (ORSV) in place of the TMV MP systemically infects orchids but causes local infection in tobacco unless the carboxy-terminal 48 amino acids of the MP are deleted (C. A. Holt, C. A. Fenczik, S. J. Casper, and R. N. Beachy; Virology, in press, 1995). Frameshift mutations were created within the 3' ends of the MP gene that led to truncations of the ORSV MP by 11, 19, 28, 37, and 48 amino acids; each of the mutant MP genes was inserted into the cloned cDNA of TMV in place of the TMV MP and infectious transcripts were produced. Virus containing mutant MPs were used to infect vanilla orchids, a systemic host of ORSV, and tobacco plants. Removal of 11 amino acids from the ORSV MP prevented spread of the chimeric virus in orchids while restoring the ability to cause a systemic infection on tobacco. Further deletions of the MP affected the size of virus-induced necrotic local lesions on tobacco cv. Xanthi NN and the systemic spread and accumulation of virus in cv. Xanthi nn, a systemic host of TMV. However, each virus replicated to equivalent levels in protoplasts. A mechanism by which the ORSV MP limits the spread of the chimeric virus is proposed.

Amino Acid Sequence↗

PubMed2001

A broad host range replicon with different requirements for replication initiation in three bacterial species.

Plasmid RK2 is unusual in its ability to replicate stably in a wide range of Gram-negative bacteria. The replication origin (oriV) and a plasmid-encoded initiation protein (TrfA; expressed as 33 and 44 kDa forms) are essential for RK2 replication. To examine initiation events in bacteria unrelated to Escherichia coli, the genes encoding the replicative helicase, DnaB, of Pseudomonas putida and Pseudomonas aeruginosa were isolated and used to construct protein expression vectors. The purified proteins were tested for activity along with E.coli DnaB at RK2 oriV. Each helicase could be recruited and activated at the RK2 origin in the presence of the host-specific DnaA protein and the TrfA protein. Escherichia coli or P.putida DnaB was active with either TrfA-33 or TrfA-44, while P.aeruginosa DnaB required TrfA-44 for activation. Moreover, unlike the E.coli DnaB helicase, both Pseudomonas helicases could be delivered and activated at oriV in the absence of an ATPase accessory protein. Thus, a DnaC-like accessory ATPase is not universally required for loading the essential replicative helicase at a replication origin.

Amino Acid Sequence↗

PubMed2000

Mutational analysis of the tra locus of the broad-host-range Streptomyces plasmid pIJ101.

The tra gene of Streptomyces lividans plasmid pIJ101 encodes a 621-amino-acid protein that can mediate both plasmid transfer and the interbacterial transfer of chromosomal genes (i.e., chromosome-mobilizing ability [Cma]) during mating. Here we report the results of in-frame insertional mutagenesis studies aimed at defining regions of Tra required for these functions. While hexameric linker insertions throughout the tra gene affected plasmid and chromosomal gene transfer, insertions in a 200-amino-acid region of the Tra protein that contains presumed nucleotide-binding motifs and that is widely conserved among a functionally diverse family of bacterial and plasmid proteins (K. J. Begg, S. J. Dewar, and W. D. Donachie, J. Bacteriol. 177:6211-6222, 1995) had especially prominent effects on both functions. Insertions near the N terminus of Tra reduced Cma for either circular or linear host chromosomes to a much greater extent than pIJ101 plasmid transfer. Our results suggest that Cma involves Tra functions incremental to those needed for plasmid DNA transfer.

Amino Acid Sequence↗

PubMed2003

Evidence of the establishment of Cotesia flavipes (Hymenoptera: Braconidae), a parasitoid of cereal stemborers, and its host range expansion in Ethiopia.

Three lepidopteran cereal stemborers, Chilo partellus (Swinhoe) (Crambidae), Busseola fusca Fuller, and Sesamia calamistis Hampson (Noctuidae) were collected from maize and sorghum in Ethiopia. The noctuid stemborers are indigenous to Africa while C. partellus is an introduced species from Asia. In 1999, the Asian stemborer parasitoid, Cotesia flavipes Cameron (Braconidae) was found to be widespread in Ethiopia, even though it had never been released in the country. In addition to attacking Chilo partellus, Cotesia flavipes was reared from B. fusca and S. calamistis. The origin of C. flavipes in Ethiopia may have been Somalia where it was released in 1997 near the border with eastern Ethiopia. Percent parasitism of borers by C. flavipes was higher in eastern Ethiopia than other surveyed regions, and parasitism was higher in 2000 than 1999. Parasitism was higher when cereals were intercropped with other plants and when wild grass hosts of stemborers were present.

Animals↗

PubMed1971

Analysis of host range restriction in Escherichia coli treated with toluene.

Escherichia coli cells treated with toluene replicate DNA when they are provided with deoxyribonucleoside 5'-triphosphates, ATP, Mg(++), and K(+). However, when deoxycytidine 5'-triphosphate is replaced by hydroxymethyl deoxycytidine 5'-triphosphate, incorporation of nucleotides into acid-precipitable material by toluenetreated strains restrictive to nonglucosylated T-even phage is reduced to less than 5% of that normally observed. Even when dCTP is present in the reaction mixture, a similar effect of the hydroxymethyl analogue on DNA replication is observed. In contrast, toluene-treated E. coli K12r6(-)r2,4(-), a strain permissive to the nonglucosylated T-even phage, incorporates hydroxymethyl deoxycytosine into its DNA, and replication proceeds at only a slightly reduced rate in the presence of the hydroxymethyl deoxycytidine 5'-triphosphate. The presence of the hydroxymethyl deoxycytidine 5'-triphosphate in the reaction mixture does not lead to degradation of preexisting DNA of the restrictive host, but it does lead to an irreversible inhibition of further DNA replication; the inhibition is observed only when the hydroxymethyl deoxycytidine 5'-triphosphate is present during replication. Thus phage-specific enzymes are not necessary for the incorporation of hydroxymethylcytosine into phage DNA, and the restrictive mechanism, present in the host cell before infection, can recognize hydroxymethylcytosine residues in its own DNA, as well as the DNA of the T-even phage.

Adenosine Triphosphate↗

PubMed1987

A locus encoding host range is linked to the common nodulation genes of Bradyrhizobium japonicum.

By using cloned Rhizobium meliloti, Rhizobium leguminosarum, and Rhizobium sp. strain MPIK3030 nodulation (nod) genes as hybridization probes, homologous regions were detected in the slow-growing soybean symbiont Bradyrhizobium japonicum USDA 110. These regions were found to cluster within a 25-kilobase (kb) region. Specific nod probes from R. meliloti were used to identify nodA-, nodB-, nodC-, and nodD-like sequences clustered on two adjacent HindIII restriction fragments of 3.9 and 5.6 kb. A 785-base-pair sequence was identified between nodD and nodABC. This sequence contained an open reading frame of 420 base pairs and was oriented in the same direction as nodABC. A specific nod probe from R. leguminosarum was used to identify nodIJ-like sequences which were also contained within the 5.6-kb HindIII fragment. A nod probe from Rhizobium sp. strain MPIK3030 was used to identify hsn (host specificity)-like sequences essential for the nodulation of siratro (Macroptilium atropurpureum) on a 3.3-kb HindIII fragment downstream of nodIJ. A transposon Tn5 insertion within this region prevented the nodulation of siratro, but caused little or no delay in the nodulation of soybean (Glycine max).

Amino Acid Sequence↗

PubMed1991

Pathogenicity, host range and temperature tolerance of Crypticola clavulifera (Oomycetes: Lagenidiales) in the laboratory.

The Oomycete fungus Crypticola clavulifera was pathogenic for laboratory-reared and field-collected larval Diptera, including the mosquitoes Aedes aegypti, Ae. notoscriptus, Anopheles farauti No. 1 and 3, Culex annulirostris, Cx. quinquefasciatus and the chironomid midge Chironomus tepperi. Zoospores were produced in water held at 15, 20 and 25 degrees C and were pathogenic for Ae. aegypti larvae, but at 30 and 35 degrees C zoospores were not produced.

Aedes↗

PubMed1991

The receptor repertoire defines the host range for attaching Escherichia coli strains that recognize globo-A.

Escherichia coli strains which colonize the human urinary tract express lectins specific for different members of the globoseries of glycolipids, e.g., globotetraosylceramide and globo-A. This study investigated the importance of globo-A expression for attachment to human uroepithelial cells, colonization of the urinary tract, and severity of urinary tract infection. The expression of receptor-active glycolipids by erythrocytes and epithelial cells was analyzed by thin-layer chromatography and bacterial overlay as well as by bacterial binding to those cells. The epithelial expression of the globo-A receptor was restricted to individuals of blood group A with a positive secretor state. Consequently, globo-A binding E. coli strains attached only to epithelial cells from these individuals. In contrast, globoside-recognizing strains attached in similar numbers to uroepithelial cells regardless of the ABH blood group and secretor state of the donor. The role of host receptor expression for infection with globo-A-specific E. coli was analyzed in 1,473 children with urinary tract infections. All those infected with strains exclusively expressing globo-A-specific adhesins were found to be of blood group A, compared with 45% in the population at large (P less than 0.006). The inflammatory response (fever, C-reactive protein, erythrocyte sedimentation rate) of individuals infected with these strains was lower than that in individuals with infections caused by globoside binding strains. The results demonstrate the importance of fitness between host receptors and bacterial adhesins for infection and suggest that minor receptor epitope differences have profound effects on the disease process.

ABO Blood-Group System↗

PubMed1998

The role of transferrin-receptor variation in the host range of Trypanosoma brucei.

Trypanosoma brucei is a unicellular parasite transmitted between African mammals by tsetse flies. T. brucei multiplies freely in the bloodstream of many different mammals, and survives by antigenic variation of the main component of its surface coat, variant surface glycoprotein (VSG). Trypanosomes take up transferrin through a heterodimeric transferrin receptor, the genes for which are expressed in telomeric expression sites along with the VSG gene. There are up to 20 of these expression sites per trypanosome nucleus, but usually only one is active at a time. Different expression sites encode transferrin receptors that are similar but not identical. Here we show that these small differences between transferrin receptors can have profound effects on the binding affinity for transferrins from different mammals, and on the ability of trypanosomes to grow in the sera of these mammals. Our results suggest that the ability to switch between different transferrin-receptor genes allows T. brucei to cope with the large sequence diversity in the transferrins of its hosts.

Animals↗

PubMed1986

Molecular cloning of the plasmid RP4 primase region in a multi-host-range tacP expression vector.

Plasmid RP4 primase was overproduced by utilizing autoregulated high-level expression vector systems in Escherichia coli and in four other Gram-negative bacterial species. Analysis of the products in E. coli revealed that in addition to the two primase polypeptides of 118 and 80 kDa the pri region of RP4 encodes two smaller proteins of 16.5 and 8.6 kDa. The transcript for the four RP4-specified products is polycistronic. The vector system used in E. coli is based on the plasmid pKK223-3 (Brosius and Holy, 1984), a ColE1-type replicon which contains a polylinker sequence flanked on one side by the controllable tac promoter and on the other side by two strong transcriptional terminators. The gene for the lac repressor (lacIQ) was inserted to render the use of the plasmid independent from repressor-overproducing strains. The gene cartridge essential for high-level expression and selection was combined with the RSF1010 replicon to generate a vector plasmid functioning in a wide variety of Gram-negative hosts. The versatility of the vector family was extended by constructing derivatives that contain the polylinker in inverted orientation relative to the tac promoter. Therefore, the orientation of the cloned fragment can be chosen by 'forced cloning' into the appropriately selected vector.

Cloning, Molecular↗

PubMed1952

Acute hepatitis associated with mouse leukemia. II. Etiology and host range of the causal agent in mice.

The etiological agent of the acute hepatitis encountered in weanling mice of the Princeton strain is a virus found in the liver, spleen, kidneys, heart's blood, urine, and intestinal contents of experimentally infected animals. Older Princeton mice and weanlings from four other strains (Swiss, Webster's BSVS, C albino) and Bagg) proved to be less susceptible than Princeton weanlings. The virus was demonstrable in Berkefeld V filtrates of liver suspensions and in supernatants after centrifugation at 10,000 G. In whole liver suspensions it was detectable in decreasing amounts through a dilution of 10(-7). Aureomycin and terramycin had no detectable effect on the activity of the virus in weanlings.

Animals↗