Yellow Strain Research Articles

Molecular characterization of SLG and S -related genes in a self-compatible Brassica campestris L. var. yellow sarson

From a stigma cDNA library of a self-compatible strain, designated C636, of Brassica campestris var. yellow sarson, we isolated three cDNA clones that showed a high degree of sequence similarity with cDNAs encoding either SLG or SLR’s. These three cDNA clones were designated SLG (C636), SLR1 (C636), and SLR2 (C636), respectively. Restriction fragment length polymorphism (RFLP) linkage analyses of a segregating F2 progeny of a hybrid between C636 and the self-incompatible S8-homozygote revealed that SLG (C636) was linked to the S locus, whereas SLR1 (C636) and SLR2 (C636) were not. The latter two genes were not linked to each other. The transcripts of SLG (C636), SLR1 (C636), and SLR2 (C636) were detected in stigmas, but not in anthers, of C636. However, the steady-state level of the SLG (C636) transcript was significantly lower than that of the SLG transcript in the self-incompatible S9-homozygote. No SRK transcripts were detected in the stigma tissue of C636, whereas an RNA band of the expected size of the SRK transcript was detected in the self-incompatible S9-homozygote. The SLG protein was detected in C636 and in three other self-compatible yellow sarson strains by immunoblot analysis; however, the amounts were lower than those of SLGs in self-incompatible strains. We conclude that one reason for the breakdown of self-compatibility in C636 yellow sarson is the down-regulation of the SLG gene and/or failure of the expression of the SRK gene.

Molecular detection and characterization of yellow fever virus in blood and liver specimens of a non-vaccinated fatal human case

A yellow fever virus of a South American genotype was identified in the liver and blood samples of a non-vaccinated European patient after his return from Brazil. ELISA tests were negative for IgG and positive for IgM against yellow fever. Yellow fever proteins in the formalin-fixed and paraffin-embedded liver biopsy were detected by immunohistochemical procedures. Viral RNA extracted from the liver tissue was also detected using an RT-semi-nested PCR procedure and molecular hybridization. Alignment of the sequence obtained from a gene fragment amplified by RT-semi-nested PCR directly from a blood sample with those of African and South American yellow fever virus strains identified a Brazilian topotype as being responsible for the disease. RT-semi-nested PCR may be used advantageously for clinical specimens for rapid and specific diagnosis, and with archival biopsy material for retrospective studies.

Sequence and RFLP analysis of the elongation factor Tu gene used in differentiation and classification of phytoplasmas.

Primers designed from sequences of the gene encoding the elongation factor Tu (tuf gene) of several culturable mollicutes amplified most of the tuf gene from phytoplasmas of the aster yellows, stolbur and X-disease groups. About 85% of the tuf gene from two aster yellows strains and a tomato stolbur phytoplasma was sequenced. The nucleotide sequence similarity between these related phytoplasmas was between 87.8 and 97.0%, whereas the homology with other mollicutes was 66.3-72.7%. The similarity of the deduced amino acid sequence was significantly higher, ranging from 96.0 to 99.4% among the phytoplasmas and 78.5% to 83.3% between phytoplasmas and the culturable mollicutes examined. From the nucleotide sequences of the phytoplasma strains, two pairs of primers were designed; one amplified the phytoplasmas of most phylogenetic groups that were established, the other was specific for the aster yellows and stolbur groups. The phytoplasmas of the various groups that were amplified could be distinguished by RFLP analysis using Sau3AI, Alul and HpaII. The aster yellows group could be divided into five Sau3AI RFLP groups. These results showed that the tuf gene has the potential to be used to differentiate and classify phytoplasmas. Southern blot analysis revealed that the tuf gene is present as a single copy.

Influence of prey density, species and developmental stages on the predatory behaviour ofAmblyseius longispinosus (Acari: Phytoseiidae)

The influence of prey density, species and developmental stages on the predatory behaviour ofAmblyseius longispinosus (Evans) was studied. A 24 h exposure revealed that gravid females were more voracious compared to young females. The trends in the number of eggs and larvae consumed by each young and gravid female predator were about the same, showing an increase with density of the red and the yellow strains ofT. urticae levelling off at a prey density of 40 per predator. The highest mean number of eggs consumed in 24 h was 16.7 for the young female and 33.3 for the gravid female, and a mean high of 17 larvae in 24 h for the young female and 27.8 for the gravid female. With adult prey, however, the predators reached satiation point at a lower density of five to ten adult prey per female. In general, the response curves were adequately described by the Holling’s Type II model. Under continuous exposure for five days, a significant reduction in consumption was observed with the gravid female from the second day onwards, to a level similar to the number of eggs and larvae consumed by a young female predator.

Purification and characterization of flavoproteins and cytochromes from the yellow bioluminescence marine bacterium Vibrio fischeri strain Y1.

Several flavoproteins and cytochromes that occur as major components in extracts of the yellow bioluminescence Y1 strain of the marine bacterium Vibrio fischeri have been purified and characterized with respect to their mass (SDS/PAGE and matrix-assisted laser-desorption/ionization MS), chromatographic properties, N-terminal sequence, and spectroscopy (absorption, fluorescence emission and anisotropy decay). The investigated proteins were as follows: yellow fluorescence protein (YFP) with bound riboflavin, FMN or 6,7-dimethyl-8-ribityllumazine; a blue fluorescence protein (BFP) with bound 6,7-dimethyl-8-ribityllumazine, riboflavin, or 6-methyl-7-oxo-8-ribityllumazine; thioredoxin reductase with FAD as ligand; and two c-type diheme cytochromes, c551 and c554. We present evidence that the riboflavin-bound YFP has an N-terminal sequence corresponding to that published for the dimeric YFP. We show that an equilibrium replacement of the riboflavin can be made with excess lumazine derivative and that lumazine-bound YFP has different bioluminescence properties to those of the lumazine protein from Photobacterium leiognathi. BFP is a different protein again, and in the bacterial lysate it occurs in multiple forms, ligated to either riboflavin, lumazine, or the 7-oxolumazine derivative. The N-terminal sequence for BFP shows similarities to those of the YFP proteins and to lumazine protein and riboflavin synthase from Photobacterium. BFP in any form has no bioluminescence or riboflavin-synthase activity. A 70-kDa fluorescent flavoprotein with FAD as ligand has an N-terminal sequence highly similar to those of thioredoxin reductases from Haemophilus influenzae and Escherichia coli. Cytochrome contaminations in previous preparations of YFP have been removed and are identified as the two c-type cytochromes c551 and c554. Both inhibit the NADH-induced bioluminescence in the reductase/luciferase system with the luciferases from P. leiognathi and V. fischeri. The N-terminal amino acid sequence of the cytochrome (c551) corresponds to a diheme cytochrome c4. The spectral properties of c554 are similar to those of other c5 cytochromes, and both c554 and c551 have absorption spectra similar to those of the respective cytochromes from the gram-negative bacteria Pseudomonas and Azotobacter.

Homogeneity of yellow fever virus strains isolated during an epidemic and a post-epidemic period in West Africa.

Three strains of yellow fever virus (YFV) were isolated in 1982 in The Ivory Coast, one from a human case and two from Aedes luteocephalus, during and subsequent to an epidemic. The complete genomic sequence of the human strain was determined and compared to that of the 1927 Asibi strain of YFV. The divergence observed was on average of 8.3%, ranging from 5.5 to 11.7% in the coding region. The transitions to transversions ratio was 5.9. Most mutations (84.3%) occurred on the third position of the codons, with synonymous mutations representing 92.5%. However, when partial sequences representing 60% of each genome were compared, homology between the three Ivory Coast strains was greater than 99%. These results demonstrate the homogeneity of the virus strains circulating in different hosts and vectors in a limited geographical region and validate the concept of topotype in viral quasi-species.

Identification of a New Wheat Yellow Mosaic Virus Strain with Specific Pathogenicity towards Major Wheat Cultivars Grown in Hokkaido.

Identification of a New Wheat Yellow Mosaic Virus Strain with Specific Pathogenicity towards Major Wheat Cultivars Grown in Hokkaido.

The microflora of Tilsit cheese. Part 2. Development of a surface smear starter culture

AbstractSingle strains of bacteria isolated from the surface of commercial Tilsit cheeses were screened for their ability to produce typical Tilsit flavour and colour and for fast growth in milk. Three milk based model systems were developed for screening. Shake liquid milk cultures were suitable to determine production of colour and volatile flavour compounds. Milk agar plates were used to study synergistic and antagonistic effects between isolates. With mini cheeses in centrifuge bottles, cheese conditions were simulated under sterile conditions. Volatile aroma production and pigmentation of the surface flora were studied with this system. Additional growth studies in other growth media with various combinations of strains revealed some of the possible roles of surface bacteria. Brevibacterium linens promoted growth of yellow coryneform bacteria. A pigmented Arthrobacter strain was responsible for the production of a yellow coloured watersoluble pigment, a precursor for the typical red‐brown colour of Tilsit cheese. In mixed culture with pigmented or non‐pigmented strains of B. linens, the yellow colour turned into red‐brown. A proteolytic Staphylococcus strain seemed to be important for the initiation of surface starter growth. Staphylococci showed fast growth at pH 5.5 and below. They also promoted growth of the yellow Arthrobacter strain.Based on these results, a defined surface starter was developed consisting of 5 strains. The yeast Debaryomyces hansenii was used for deacidification of the cheese rind. A combination of a non‐pigmented, proteolytic B. linens, a yellow Arhrobacter strain, a cream‐coloured coryneform bacterium, and a proteolytic Staphylococcus sciuri were used for cheese ripening. Experimental cheeses were produced on a 10 kg scale. The defined starter grew fast on the cheese surfaces, and produced the typical taste and flavour and colour of Tilsit cheese.

Detection and differentiation of phytoplasmas in Australia

In a polymerase chain reaction (PCR) diagnostic test, phytoplasma (formerly known as plant-pathogenic mycoplasma-like organism or MLO) ribosomal DNA was detected in total DNA extracts prepared from 56 out of 63 plants collected from geographically diverse locations across Australia. The list of phytoplasma hosts consisted of 38 different species in 16 different families. Restriction site analysis of the PCR-amplified DNA accessions was used to divide the phytoplasmas into 2 groups. The majority of the tomato big bud group and sweet potato little leaf group phytoplasmas were closely related to a phytoplasma originally obtained from Crotalaria in Thailand, which is a member of the faba bean phyllody strain cluster. In contrast, phytoplasmas associated with Australian grapevine yellows and papaya dieback were most similar to members of the aster yellows strain cluster. Twelve phytoplasmas were compared by Southern blot hybridisation with DNA cloned from the sweet potato little leaf phytoplasma strain V4. The restriction fragment length polymorphism pattern of all phytoplasmas compared was identical except for 2 sweet potato little leaf phytoplasmas.

Unusual sequence relationships between two isolates of citrus tristeza virus.

The complete, 19,226 nt sequence of the RNA genome from VT, a seedling yellows strain of citrus tristeza virus (CTV), was determined and found to have a genome organization identical with that of the previously determined CTV-T36 isolate, except that ORF 1 of CTV-VT was 70 nt shorter due to two widely separated 18 nt deletions. Sequence comparison of CTV-VT and CTV-T36 revealed approximately 89% identity throughout the ten 3' ORFs, but only 60-70% identity throughout ORF 1. The 5' nontranslated regions were only 60% identical whereas the 3' nontranslated regions were 97% identical. The transition between regions of similarity and deviation was gradual, suggesting that the sequence similarities and differences compared to CTV-T36 were unlikely to have arisen from a recent recombination event between a close T36 relative and a distantly related CTV isolate. This is the first attempt to compare in detail the variation between the genomes of two strains of a member of the closterovirus group. The observed deviation between the large RNA genomes of the two CTV strains is greater than that among different viruses of most other groups, raising the question of how to define the taxonomy of these viruses.

Isoenzyme diversity in Xanthomonas campestris pv. mangiferaeindicae

A collection of 26 strains of Xanthomonas campestris pv. mangiferaeindicae isolated from three different host species in eight countries was investigated for variation in isozyme patterns. Three enzyme systems were analysed: esterase (EST), phosphoglucomutase (PGM) and superoxide dismutase (SOD). Four groups of strains were identified: nonpigmented strains isolated from mango and pepper‐tree in Australia, Comores, India, Reunion Island, South Africa, and Taiwan; nonpigmented Brazilian strains from mango; nonpigmented strains from ambarella isolated in the French West Indies; heterogeneous yellow pigmented strains from mango (Brazil and Reunion Island). The value of isozyme profiling as markers of the pathogenicity groups in X. c. pv. mangiferaeindicae is discussed.

Use of the yellow fever virus vaccine strain 17D for the study of strategies for the treatment of yellow fever virus infections

We have employed the attenuated vaccine strain 17D of yellow fever virus (YFV) to evaluate the inhibitory effect of a selected series of compounds on YFV in Vero cells. Use of the vaccine strain does not require high-level microbiological containment facilities and should allow extensive screening. In addition, YFV may serve as a model for other flaviviruses including hepatitis C virus (HCV), and thus strategies for the treatment of YFV infections may apply to flavivirus infections in general. In the present study, several compounds belonging to different classes of nucleoside analogues and polyanions were evaluated for their inhibitory effect on the replication of YFV. Compounds that are targeted at: (i) IMP dehydrogenase (ribavirin, EICAR, tiazofurin, selenazofurin and mycophenolic acid), (ii) OMP decarboxylase (pyrazofurin and 6-azauridine), (iii) CTP synthetase (carbodine and cyclopentenyl cytosine), (iv) dihydrofolate reductase (methotrexate) and the (v) sulfated polymers (dextran sulfate and PAVAS) proved inhibitory to the replication of YFV. Mycophenolic acid (EC 50: 0.08 μg/ml), EICAR (EC 50: 0.8 μ/ml) and methotrexate (EC 50: 0.07 μg/ml) were the most effective. The finding that EICAR and mycophenolic acid, despite their potent anti-YFV activity, had little or no effect on the replication of the bunyavirus Punta Toro or herpes simplex virus in Vero cells, indicates that their anti-YFV activity is rather specific and does not merely result from cytotoxicity. Inhibitors of S-adenosylhomocysteine hydrolase (SAH hydrolase) and thymidylate synthase were found to be devoid of anti-YFV activity.

Genomic reassortment of barley mild mosaic virus: evidence for the involvement of RNA1 in pathogenicity

A reverse transcription-polymerase chain reaction (RT-PCR) was developed for specific detection of RNA1 and RNA2 of two barely mild mosaic virus strains (BaMMV-Ka1 and BaMMV-Na1) and a barley yellow mosaic virus strain (BaYMV-II-1). Mechanical inoculation of barley cultivars with a mixture of BaMMV-Ka1 and BaMMV-Na1, followed by RT-PCR to detect RNA components in infected plants, revealed that the RNAs of the two strains were exchangeable in vivo to generate all nine possible combinations containing at least one RNA1 and one RNA2. Infected plants with mixed or reassorted RNAs were selected and used as inocula for further analysis of cultivar reactions. The results demonstrate that the pathogenicity and symptomatology are determined solely by RNA1. In contrast, following inoculation with mixtures of BaYMV-II-1 and either BaMMV-Ka1 or BaMMV-Na1, no heterologous combinations of their RNAs were observed.

First isolation of thermophilic aerobic non-sporulating heterotrophic bacteria from deep-sea hydrothermal vents

Thermophilic aerobic non-sporulating heterotrophic bacteria were isolated for the first time from deep-sea hydrothermal vents. Samples were taken at Snakepit (Mid-Atlantic Ridge) and Guaymas Basin (Gulf of California). Isolates consisting of pleomorphic rods, single cells or pairs, formed filaments of variable length, and grew at 70°C or some up to 80°C. They were halotolerant and unable to grow anaerobically, except some strains in the presence of nitrate. A numerical classification based on phenotypic features was performed on the isolates, including three reference strains Rhodothermus marinus (R-10), Thermus aquaticus (YT-1) and Thermus scotoductus (X-1) and one yellow pigmented Thermus strain. Results from unweighted average linkage (UPGMA) clustering applied to a similarity matrix derived from the simple matching (S SM) coefficient showed the formation of five main clusters which were defined for at least 80% similarity, whereas only three isolates remained outside of the clusters. One reference strain (X-1) clustered with one isolate at a level of 83% and between 76–78% with other clusters. The other reference strains showed less than 55% similarity with the deep-sea isolates.

First isolation of thermophilic aerobic non-sporulating heterotrophic bacteria from deep-sea hydrothermal vents

Thermophilic aerobic non-sporulating heterotrophic bacteria were isolated for the first time from deep-sea hydrothermal vents. Samples were taken at Snakepit (Mid-Atlantic Ridge) and Guaymas Basin (Gulf of California). Isolates consisting of pleomorphic rods, single cells or pairs, formed filaments of variable length, and grew at 70°C or some up to 80°C. They were halotolerant and unable to grow anaerobically, except some strains in the presence of nitrate. A numerical classification based on phenotypic features was performed on the isolates, including three reference strains Rhodothermus marinus (R-10), Thermus aquaticus (YT-1) and Thermus scotoductus (X-1) and one yellow pigmented Thermus strain. Results from unweighted average linkage (UPGMA) clustering applied to a similarity matrix derived from the simple matching (SSM) coefficient showed the formation of five main clusters which were defined for at least 80% similarity, whereas only three isolates remained outside of the clusters. One reference strain (X-1) clustered with one isolate at a level of 83% and between 76–78% with other clusters. The other reference strains showed less than 55% similarity with the deep-sea isolates.

Barley Yellow Dwarf Virus Strain Incidence in Small Grain Cereals in Northeast Spain

AbstractBarley yellow dwarf virus (BYDV) was detected in forage cereals and small grain cereals by indirect enzyme‐linked immunosorbent assay. Samples of forage cereals collected in the winters of 1987/1988, 1988/1989 and 1989/1990 showed that this crop is a reservoir of BYDV during the end of summer and autumn. PAV‐like and MAV‐like isolates, in single or mixed infection, were the most common. The proportion of isolates in the infected samples was relatively stable, Samples of winter cereals collected in the springs of 1988, 1989 and 1990 showed that PAV‐ and MAV‐like isolates were widespread. The proportion of samples infected with PAV‐like isolates was much more variable than that of MAV‐like isolates. The incidence of PAV‐like isolates in winter cereals is more dependent on the population of Rhopalosiphum padi during the winter and early spring, than is the incidence of MAV‐like isolates on Sitobion avenae density. In northeast Spain (Lleida basin) forage cereals are a constant source of PAV‐ and MAV‐ like isolates from which BYDV inoculum is introduced into winter cereals.

Electrophoretic mobility of different in pathogenicity strains of Tobamovirus group

Twenty four Tobamovirus strains divided according to their ability to overcome the resistance genes in tobacco and tomato as well as in their severity of systemic symptoms were tested. Significant differences between means of particle mobility of the virus groups were found especially about yellow mosaic strains which were distinguishable enough by the electrophoretic analysis.

Detection of beet necrotic yellow vein virus strains, variants and mixed infections by examining single-strand conformation polymorphisms of immunocapture RT-PCR products.

Single-strand conformation polymorphism analysis was found to be a powerful tool for rapidly assigning large numbers of beet necrotic yellow vein virus (BNYVV) isolates to a known strain group as well as for detecting mixed infections, minor variants or new strain groups. The prevalence of the B-type in Germany and France and the A-type in most other countries was confirmed. Minor variants with a very restricted distribution were detected occasionally. New rhizomania outbreaks in Great Britain were caused either by the A- or B-type or mixtures of both suggesting introduction of BNYVV from several sites abroad. An entirely different BNYVV type (P-type) was identified in a small area in France. Evidence for further strain groups in China was also obtained.

Thermostabilization of live virus vaccines by heavy water (D 2O)

Eradication of poliomyelitis is based on the mass administration of oral poliovirus vaccine (OPV). Delivery of effective vaccines in the developing world, especially in tropical areas, is compromised when refrigeration cannot be assured. The OPV, prepared with three live attenuated polioviruses (Sabin strains, serotypes 1, 2 and 3), is considered to be the most thermolabile of vaccines in the World Health Organization's Expanded Programme on Immunization. To be effective, the initial concentration (potency) of each of the three component serotypes, measured in tissue culture infective doses, should not decrease by more than 0.5 log 10 before vaccine delivery. High concentration (1 M) of MgCl 2 is currently used as stabilizer for OPV. The stabilizing effect of D 2O was tested here on OPV strains. By diluting the viral suspension with D 2O-based salt and buffer solutions, in a manner similar to that involved in OPV production, an 87% concentration of D 2O in the final viral preparation was achieved. In severe conditions of testing (incubation for 3 days at 45°C), the Sabin 3 virus lost an average of 2.7 log 10 potency in the presence of 87% D 2O as compared to 3.0 log 10 in H 2O-based 1 M MgCl 2, and to 5.7 log 10 in the H 2O-based control solutions. When tested in a combined 87% D 2O and 1 M MgCl 2 treatment, the Sabin 3 virus lost only 1.3 log 10 potency after 3 days at 45°C. Similar thermostabilizing effects were obtained for Sabin 1 and Sabin 2 strains, but the level of stabilization was slightly lower. Tested in standard conditions at 37°C for 7 days, the infectivity of the three D 2O MgCl 2-treated OPV strains remained in the limit of requirements (≤0.5 log 10). The stabilizing effect of D 2O was also demonstrated on yellow fever 17D vaccine virus strain. D 2O, alone or in combination with other stabilizers such as MgCl 2, could thus be considered as a candidate for the improvement of live virus vaccine thermostability.

The Yellow Bioluminescence Bacterium, Vibrio fischeri Y1, Contains a Bioluminescence-Active Riboflavin Protein in Addition to the Yellow Fluorescence FMN Protein

The yellow bioluminescence Y1 strain of Vibrio fischeri can produce a 22 kDa protein with either FMN or riboflavin as a bound fluorophore. Both forms are active for shifting the bioluminescence spectral maximum. The fluorescence spectral distribution of the two proteins differs slightly and the in vivo emission appears to be an equal mixture of the two. The bioluminescence activity of the riboflavin Y1 protein contrasts with the inactivity of the related Photobacterium type.