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131.
Partial 18S rRNA sequences of five chelicerate arthropods plus a
crustacean, myriapod, insect, chordate, echinoderm, annelid, and
platyhelminth were compared. The sequence data were used to infer phylogeny
by using a maximum-parsimony method, an evolutionary-distance method, and
the evolutionary-parsimony method. The phylogenetic inferences generated by
maximum-parsimony and distance methods support both monophyly of the
Arthropoda and monophyly of the Chelicerata within the Arthropoda. These
results are congruent with phylogenies based on rigorous cladistic analyses
of morphological characters. Results support the inclusion of the
Arthropoda within a spiralian or protostome coelomate clade that is the
sister group of a deuterostome clade, refuting the hypothesis that the
arthropods represent the "primitive" sister group of a protostome coelomate
clade. Bootstrap analyses and consideration of all trees within 1% of the
length of the most parsimonious tree suggest that relationships between the
nonchelicerate arthropods and relationships within the chelicerate clade
cannot be reliably inferred with the partial 18S rRNA sequence data. With
the evolutionary-parsimony method, support for monophyly of the Arthropoda
is found in the majority of the combinations analyzed if the coelomates are
used as "outgroups." Monophyly of the Chelicerata is supported in most
combinations assessed. Our analyses also indicate that the
evolutionary-parsimony method, like distance and parsimony, may be biased
by taxa with long branches. We suggest that a previous study's inference of
the Arthropoda as paraphyletic may be the result of (a) having two few
arthropod taxa available for analysis and (b) including long-branched taxa.
相似文献
132.
The RPC31 gene of Saccharomyces cerevisiae encodes a subunit of RNA polymerase C (III) with an acidic tail. 总被引:13,自引:7,他引:6
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C Mosrin M Riva M Beltrame E Cassar A Sentenac P Thuriaux 《Molecular and cellular biology》1990,10(9):4737-4743
The RPC31 gene encoding the C31 subunit of Saccharomyces cerevisiae RNA polymerase C (III) has been isolated, starting from a C-terminal fragment cloned on a lambda gt11 library. It is unique on the yeast genome and lies on the left arm of chromosome XIV, very close to a NotI site. Its coding sequence perfectly matches the amino acid sequence of two oligopeptides prepared from purified C31. It is also identical to the ACP2 gene previously described as encoding an HMG1-like protein (W. Haggren and D. Kolodrubetz, Mol. Cell. Biol. 8:1282-1289, 1988). Thus, ACP2 and RPC31 are allelic and encode a subunit of RNA polymerase C. The c31 protein has a highly acidic C-terminal tail also found in several other chromatin-interacting proteins, including animal HMG1. Outside this domain, however, there is no appreciable homology to any known protein. The growth phenotypes of a gene deletion, of insertions, and of nonsense mutations indicate that the C31 protein is strictly required for cell growth and that most of the acidic domain is essential for its function. Random mutagenesis failed to yield temperature-sensitive mutants, but a slowly growing mutant was constructed by partial suppression of a UAA nonsense allele of RPC31. Its reduced rate of tRNA synthesis in vivo relative to 5.8S rRNA supports the hypothesis that the C31 protein is a functional subunit of RNA polymerase C. 相似文献
133.
Comparison of the effects of concentration, pH and anion species on astringency and sourness of organic acids 总被引:4,自引:1,他引:3
The separate effects of concentration, pH and anion species on intensity of
sourness and astringency of organic acids were evaluated. Judges rated
sourness and astringency intensity of lactic, malic, tartaric and citric
acid solutions at three levels of constant pH varying in normality and at
three levels of constant concentration varying in pH. To assess the
comparative sourness and astringency of the organic acid anions of study,
binary acid solutions matched in pH and titratable acidity were also rated.
As pH was decreased in equinormal solutions, both sourness and astringency
increased significantly (P < 0.001). By contrast, as the normality of
the equi-pH solutions was increased, only sourness demonstrated significant
increases (P < 0.001) while astringency remained constant or decreased
slightly. At the lowest normality tested, all solutions were more
astringent than sour (P < 0.05). Although lactic acid was found to be
significantly more sour than citric acid (P < 0.05), no other sourness
or astringency differences among the organic acid anions were noted. This
study demonstrates for the first time that astringency elicited by acids is
a function of pH and not concentration or anion species, and confirms that
sourness is independently influenced by concentration, pH and anion species
of the acid.
相似文献
134.
135.
Deuterostome phylogeny and the sister group of the chordates: evidence from molecules and morphology 总被引:13,自引:3,他引:10
Complete coding regions of the 18S rRNA gene of an enteropneust
hemichordate and an echinoid and ophiuroid echinoderm were obtained and
aligned with 18S rRNA gene sequences of all major chordate clades and four
outgroups. Gene sequences were analyzed to test morphological character
phylogenies and to assess the strength of the signal. Maximum- parsimony
analysis of the sequences fails to support a monophyletic Chordata; the
urochordates form the sister taxon to the hemichordates, and together this
clade plus the echinoderms forms the sister taxon to the cephalochordates
plus craniates. Decay, bootstrap, and tree-length distribution analyses
suggest that the signal for inference of dueterostome phylogeny is weak in
this molecule. Parsimony analysis of morphological plus molecular
characters supports both monophyly of echinoderms plus enteropneust
hemichordates and a sister group relationship of this clade to chordates.
Evolutionary parsimony does not support chordate monophyly.
Neighbor-joining, Fitch-Margoliash, and maximum-likelihood analyses support
a chordate lineage that is the sister group to an
echinoderm-plus-hemichordate lineage. The results illustrate both the
limitations of the 18S rRNA molecule alone for high- level phylogeny
inference and the importance of considering both molecular and
morphological data in phylogeny reconstruction.
相似文献
136.
ERVIN ÁRNYAS JUDIT BERECZKI ANDREA TÓTH KATALIN VARGA KATALIN PECSENYE ANDRÁS TARTALLY GYÖRGY KÖVICS DÓRA KARSA ZOLTÁN VARGA 《Ecological Entomology》2009,34(1):90-97
Abstract 1. The influence of infestation of the larval host plant Gentiana cruciata on the egg‐laying preferences of the xerophilous ecotype of Alcon Blue butterfly (Maculinea alcon) was studied in a semi‐dry grassland area (Aggtelek Karst Region, Northern Hungary). 2. We examined whether oviposition patterns of females differed when G. cruciata stems were uninfested compared with when they were infested by an aphid (Aphis gentianae) or a rust (Puccinia gentianae) species. 3. Females laid more than 90% of their eggs on fertile, uninfested G. cruciata stems, although these stems comprised only ~ 50% of the total stems available. Stems infested by aphids were similar to uninfested ones in properties that had a strong correlation with egg numbers, and yet there were significantly fewer eggs on infested stems than on intact ones. 4. Females never laid eggs on parts of Gentiana stems infested by aphids, and the presence of Lasius paralienus ants, which have a mutualistic interaction with Aphis gentianae, did not increase the repulsive effect of aphids. Infection of Gentiana by Puccinia did not influence the egg‐laying behaviour of females, even though the flowers and buds of infested stems exhibited a delayed development. 5. Aphid infestation can influence butterfly oviposition patterns through both direct and indirect effects. The presence of aphids directly excluded oviposition, but our data also indicated the possibility of an indirect effect of aphid infestation. Stems that had no aphids at the last egg counting, but were infested prior to it, had significantly fewer eggs than those that were never infested. 相似文献
137.
CHRISTOPHE PAMPOULIE MAGNÚS ÖRN STEFÁNSSON THÓRA DÖGG JÖRUNDSDÓTTIR BRET S. DANILOWICZ ANNA KRISTÍN DANÍELSDÓTTIR 《Biological journal of the Linnean Society. Linnean Society of London》2008,94(2):315-329
Most studies of the genetic structure of Atlantic cod have focused on small geographical scales. In the present study, the genetic structure of cod sampled on spawning grounds in the North Atlantic was examined using eight microsatellite loci and the Pan I locus. A total of 954 cod was collected from nine different regions: the Baltic Sea, the North Sea, the Celtic Sea, the Irish Sea and Icelandic waters during spring 2002 and spring 2003, from Norwegian waters and the Faroe Islands (North and West spawning grounds) in spring 2003, and from Canadian waters in 1998. Temporal stability among spawning grounds was observed in Icelandic waters and the Celtic Sea, and no significant difference was observed between the samples from the Baltic Sea and between the samples from Faroese waters. F -statistics showed significant differences between most populations and a pattern of isolation-by-distance was described with microsatellite loci. The Pan I locus revealed the presence of two genetically distinguishable basins, the North-west Atlantic composed of the Icelandic and Canadian samples and the North-east Atlantic composed of all other samples. Permutation of allele sizes at each microsatellite locus among allelic states supported a mutational component to the genetic differentiation, indicating a historical origin of the observed variation. Estimation of the time of divergence was approximately 3000 generations, which places the origin of current genetic pattern of cod in the North Atlantic in the late Weichselian (Wisconsinian period), at last glacial maximum. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 94 , 315–329. 相似文献
138.
Knowledge of the mitochondrial DNA (mtDNA) sequence of divergent murine species is critical from both a phylogenetic perspective and in understanding nuclear-mitochondrial interactions, particularly as the latter influences our xenocybrid models of mitochondrial disease. To this end, the sequence of the mitochondrial genome of the murine species Mus terricolor (formerly Mus dunni) is reported and compared with the published sequence for the common laboratory mouse Mus musculus domesticus strain C57BL/6J. These species are of interest because xenomitochondrial cybrid mice were created that harbor M. terricolor mtDNA in a M. m. domesticus nuclear background. Although the total of 1763 nucleotide substitutions represents striking heterogeneity, the majority of these are silent, leading to highly conserved protein sequences with only 159 amino acid differences. Moreover, 58% of these amino acid differences represented conservative substitutions. All of the tRNA genes and rRNA genes have homology of 91% or greater. The control region shows the greatest heterogeneity, as expected, with 85% homology overall. Regions of 100% homology were found for Conserved Sequence Block I, Conserved Sequence Block III and the L-strand origin of replication. Complex I genes showed the greatest degree of difference among protein-coding genes with amino acid homology of 91-97% among the seven mitochondrial genes. Complexes III and IV genes show high homology ranging from 98-100%. From these data, complex I differences appear most critical for the viability of M. m. domesticus: M. terricolor cybrids. Moreover, the sequence information reported here should be useful in identifying critical regions for mitochondrial transfer between species, for furthering the understanding of mitochondrial dynamics and pathology in transmitochondrial organisms, and for the study of Mus genus origins. 相似文献
139.
Liebana E Garcia-Migura L Clouting C Cassar CA Clifton-Hadley FA Lindsay EA Threlfall EJ Chappell SA Davies RH 《Journal of applied microbiology》2002,93(5):732-744
AIMS: To assess the degree of genetic diversity among animal Salmonella Dublin UK isolates, and to compare it with the genetic diversity found among human isolates from the same time period. METHODS AND RESULTS: One hundred isolates (50 human and 50 animal) were typed using plasmid profiling, XbaI-pulsed field gel electrophoresis (PFGE) and PstI-SphI ribotyping. Antimicrobial resistance data to 16 antibiotics was presented, and the presence of class-I integrons was investigated by real-time PCR. Seven different plasmid profiles, 19 ribotypes and 21 PFGE types were detected. A combination of the three methods allowed clear differentiation of 43 clones or strains. Eighteen isolates were resistant to at least one antimicrobial; five of them were multi-resistant and of these, only three presented class I integrons. CONCLUSIONS: Ribotyping data suggest the existence of at least three very different clonal lines; the same distribution in well-defined groups was not evident from the PFGE data. The existence of a variety of clones in both animals and humans has been demonstrated. A few prevalent clones seem to be widely disseminated among different animal species and show a diverse geographical and temporal distribution. The same clones were found in animals and humans, which may infer that both farm and pet animals may act as potential vehicles of infection for humans. Some other clones seem to be less widely distributed. Clustering analysis of genomic fingerprints of Salmonella Dublin and Salm. Enteritidis isolates confirms the existence of a close phylogenetic relationship between both serotypes. SIGNIFICANCE AND IMPACT OF THE STUDY: This paper describes the utility of a multiple genetic typing approach for Salm. Dublin. It gives useful information on clonal diversity among human and animal isolates. 相似文献
140.
Chen J Cassar SC Zhang D Gopalakrishnan M 《Biochemical and biophysical research communications》2005,326(4):887-893
Kcv, the first identified viral potassium channel encoded by the green algae Paramecium bursaria chlorella virus (PBCV-1), conducted K(+) selective currents when expressed in heterologous systems. This K(+) channel was proposed to be important for PBCV-1 infection and replication. In the present study, we identified and functionally characterized a novel K(+) channel Kesv, encoded by Ectocarpus siliculosus virus that infects filamentous marine brown algae. Kesv encodes a protein of 124 amino acids and is 21.8% identical and 37.1% homologous to Kcv. Membrane topology programs predicted that Kesv consists of three transmembrane domains. When expressed in Xenopus oocytes, Kesv induced largely instantaneous, K(+) selective currents that were sensitive to block by Ba(2+) and amantadine. Thus, Kesv along with Kcv, constitutes an emerging family of viral potassium channels, which may play important roles in the life cycle of viruses. 相似文献