Characterization of Borrelia Species Isolated from Ixodid Ticks,Ixodes ovatus

Thirty-two Borrelia isolates were obtained from the adult stage of ixodid ticks, Ixodes ovatus, collected in various localities in Japan. Borrelial isolates were cultivated and analyzed by polyacrylamide gel electrophoresis, with monoclonal antibodies, by pulsed field gel electrophoresis, and by genomic Southern hybridization. All borrelial isolates showed similar protein profiles and monoclonal antibody reactivities, while plasmid profiles were rather diverse. Genomic hybridization using rRNA gene probes demonstrated the genetic similarities of those isolates. We found no significant differences among the borrelial isolates tested, and the restriction fragment length polymorphism patterns of I. ovatus isolates were quite distinct from those of borrelial strains associated with Lyme disease. Therefore, the isolates of Borrelia obtained from I. ovatus were thought to fall into different genospecies.     

Species of Borrelia distinguished by restriction site polymorphisms in 16S rRNA genes

Abstract Three phyletic groups of Borrelia associated with Lyme disease, B. burgdorferi, B. garinii and group VS461 can be distinguished from each other and other species of Borrelia by Bfa I restriction site polymorphisms in PCR amplified 16S rRNA genes. One strain isolated from an Ixodes pacificus tick in California that was previously unclassifiable was distinguishable from B. burgdorferi by an Mnl I restriction site polymorphism.     

DNA fingerprinting of red clover (Trifolium pratense L.) with Jeffrey's probes: detection of somaclonal variation and other applications

Summary DNA fingerprints generated by the Jeffreys' probes, 33.6 and 33.15, indicated the presence of minisatellite-like sequences in the red clover genome. The fingerprints generated by probe 33.6 gave less background and fewer but better defined bands than those obtained with probe 33.15. Assay of a regenerative somaclonal variant (F49R) by DNA fingerprinting with probe 33.6 detected mutation that was unlinked to the regenerative trait. The fingerprints obtained under the applied conditions also demonstrated genetic stability of consecutive generations of the regenerants in tissue culture. DNA fingerprints of F₁ plants revealed that each polymorphic band was inherited from either one or the other parent. Both probes distinguished individual-specific genotypes in seven cultivars of red clover. Greater variability in DNA fingerprints was detected between (V=0.899) than within (0.417≤V≤0.548) cultivars.     

Comparison of geographically distant populations of Rhizobium isolated from root nodules of Phaseolus vulgaris

Seventy-two rhizobial strains were isolated from the root nodules of french beans ( Phaseolus vulgaris ). They were sampled from two geographically distant field populations and 18 additional different sites in France. They were characterized by a) plasmid profiles, (b) RFLP analysis of total cellular DNA using various chromosomal and symbiotic gene probes (including nif H from Rhizobium etli bv. phaseoli ) and c) their ability to nodulate a potential alternative host, L. leucocephala. Over half of the isolates were ascribed to Rhizobium leguminosarum bv. phaseoli on the basis of the hybridization analysis, the possession of multiple copies of nif H and their inability to nodulate L. leucocephala. The remaining isolates belonged to 2 groups which were shown to be genomically distinct from R. leguminosarum bv. phaseoli, R. etli bv. phaseoli and R. tropici. Most members of these two groups shared with R. tropici the ability to nodulate L. leucocephala and, for isolates of only one of these groups, the presence of one copy of nif H. Members of each of the 3 taxa were widely distributed in France and circumstantial evidence of pSym transfer between them was shown. R. leguminosarum bv. phaseoli and one of the two novel groups co-occurred within the two geographically distant populations. Individual genotypes were conserved between them. The finding of a third taxon at various other locations indicated additional diversity among rhizobia nodulating beans.     

Molecular and chromosomal evolution in anoas (Bovidae: Bubalus spec.)

As a contribution to their taxonomy, population genetic data on zoo-living anoas are reported, and a review of the history of the captive stock is provided. Four different chromosome numbers of 44, 45, 47 and 48 chromosomes have been found, respectively, when karyotyping captive anoas descending from three breeding lines. The number of chromosome arms is 60 throughout, indicating that Robertsonian rearrangements are responsible for this cytogenetic variation. An electrophoretic comparison of isozymes and blood proteins representing 21 genetic loci revealed polymorphism in seven loci: haemoglobin, glyoxalase, superoxide dismutase, phosphoglucomutase, carbonic anhydrase, glucose phosphate isomerase, and an unidentified acid serum protein. Considering the small number of founder specimens and subsequent inbreeding, allozyme variability appears fairly high in anoas. Genetic distances between zoo populations amount to 0.0505 or less. Southern blot hybridizations of restricted DNA from anoas and African buffaloes with a probe from the DRB-like region of the chimpanzee's MHC class II genes also indicate a low degree of genetic differentiation between mountain and lowland anoas. The relevance of these genetic data for the taxonomic classification of mountain and lowland anoas, and for the conservation of anoas by captive breeding is discussed.     

Non-allelic interaction conditioning spikelet sterility in an F2 population of indica/japonica cross in rice

Significant segregation of spikelet fertility occurred in an F₂ population derived from a spikelet fertility-normal F₁ hybrid produced by a cross between Palawan, a japonica variety, and IR42, an indica variety. To identify factors controlling the fertility segregation, we used 104 RFLP markers covering all 12 rice chromosomes to investigate the association of spikelet fertility and marker segregation. We found that the segregation of two sets of gene pairs was significantly (P < 0.001) associated with fertility segregation. The first pair of genes was linked to RFLP marker RG778 on chromosome 12 and RFLP markers RG690/RG369 on chromosome 1. A significant reduction in fertility was observed when the plants were homozygote at RG778 with the indica allele as well as homozygote at RG690/RG369 with the japonica allele. The second pair of genes was linked to RG218 on chromosome 12 and RG650 on chromosome 7, respectively. The recombinant homozygote at these two loci showed a significant reduction on spikelet fertility. The non-allelic interaction effect was further modified by a gene linked to RG778, resulting in even lower fertility. The results of this study provides the first evidence of chromosomal localization of sporophytic sterility genes whose interaction can result in a reduction of spikelet fertility in the F₂ derived from fertility-normal F₁.     

The adaptive significance of colour pattern polymorphism in the Australian scincid lizard Lampropholis delicata

Females of Lampropholis delicata are dimorphic for colour pattern, the difference between morphs being the presence or absence of a distinct white mid-lateral stripe. A less distinct striped morph occurs also in males. We evaluated alternative hypotheses for the maintenance of this polymorphism by examining temporal and spatial variation in morph frequency, testing for differential selection among morphs using data on body size and reproductive traits from preserved specimens, and experimentally manipulating colour pattern in free-ranging lizards of both sexes, to assess the influence of the lateral stripe on survival rates. We found that the relative frequency of striped individuals varied among populations and decreased from north to south in both sexes, coincident with an increasing incidence of regenerated tails. Morph frequencies did not change through time within a population. Striped gravid females appeared to survive better and produced larger clutches than did non-striped females. In our experimental study, the relationship between survival and colour morph differed between the two sexes; males painted with a white lateral stripe had lower survival than control (brown stripe) males, but survival did not differ between striped and control females. The different response in the two sexes may be due partly to differences in temperature and microhabitat selection. We propose that the white lateral stripe decreases susceptibility to predators in gravid females but increases risk of predation in males, especially in combination with low temperatures. The polymorphism might be maintained by: (1) opposing fitness consequences of the stripe in males and females; (2) sex-specific habitat selection; and (3) gene flow in combination with spatial variation in relative fitness of the two morphs.     

SSCP analysis of pig mitochondrial DNA D-loop region polymorphism

The sequence polymorphism that occurs in the mitochondrial DNA (mtDNA) displacement (D)-loop region is useful as a cytoplasmic DNA marker. We cloned the mtDNA D-loop regions of five breeds of pig by polymerase chain reaction (PCR) and determined their sequences. The sequence diversities in D-loop regions among five breeds of pig were located in the starting area of heavy-strand replication. From these sequences, we designed primers for PCR-mediated single-strand conformation polymorphism (PCR-SSCP) analysis that amplified the most polymorphic 227 bp fragment of the D-loop region. The results of PCR-SSCP analysis clearly showed that four types of polymorphism (A to D) are found in Landrace (A), Large White (A, B), Duroc (A), Göttingen miniature pig (B) and Meishan (C, D). The same polymorphisms were also detected from each porcine embryo by this method. Our results show that PCR-SSCP analysis is useful in detecting polymorphisms in the D-loop region of pigs and pig embryos.     

Aggregation and the maintenance of genetic diversity: An individual-based cellular model

Summary A cellular model, where each individual is explicitly defined, is used to describe a population of a mycophagous species ofDrosophila. Patches represent single fungal fruiting bodies which are only available as oviposition sites for a single fly generation. Standard competition equations are used to describe the interaction between larval genotypes at each patch. Dispersal of adults is obligatory and uses a simple model of patch choice to produce aggregated arrivals of adults at fresh patches. The degree to which aggregation of adults and eggs can promote coexistence of genotypes in a one-locus, two-allele system with dominance is explored. When both phenotypes (A- andaa) are aggregated, a polymorphism can be maintained for over 1000 generations even when the selective disadvantage of one phenotype (aa) is great. This model enhances the degree of polymorphism in a population, using aggregation. It does not preclude the operation of other methods which enhance the coexistence of genotypes. Therefore, it is acting to augment the degree of polymorphism maintained in species which exploit patchy and ephemeral habitats, including allDrosophila and a wide range of other organisms.