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71.
Evolutionary relatedness of some primate models of Plasmodium 总被引:1,自引:0,他引:1
Primate--and, specifically, monkey--malaria infections are commonly used
for understanding the pathology of and immune response to the human disease
because they are thought to resemble most closely the host-parasite
relationship found in humans. Plasmodium cynomolgi is used extensively as a
model for the human parasite, P. vivax, and P. knowlesi is used primarily
as a model for the development of erythrocytic-stage vaccines. Both of
these simian parasites can naturally infect man, resulting in mildly
symptomatic episodes of the disease. The phylogenetic relationship between
these two simian parasites and previously characterized Plasmodium species,
including P. vivax, was examined by comparison of the asexually expressed
small- subunit ribosomal RNA genes. Our analysis confirmed that P. vivax is
most closely related to P. cynomolgi and that it remains an appropriate
model of the human pathogen. Furthermore, with P. knowlesi and P. fragile,
these two species form a group of closely related species, distant from
other Plasmodium species. What is considered to be the most ancient of the
human malaria pathogens, P. malariae, was also included in the analysis and
does not group at all with other simian or human parasites.
相似文献
72.
Evolution and phylogenetic information content of the ITS-1 region in the tiger beetle Cicindela dorsalis 总被引:6,自引:0,他引:6
Sequence divergence in the internal transcribed spacer region 1 (ITS-1) of
the ribosomal DNA locus was assessed in subspecies of the coastal North
American tiger beetle, Cicindela dorsalis. The spacer region was amplified
using the polymerase chain reaction and cloned for sequencing. Of a total
of 50 clones obtained from 12 specimens, 42 clones were different in at
least one nucleotide position. In a parsimony analysis of these sequences,
the main phylogenetic distinction was found to separate sequences from the
Gulf of Mexico and the Atlantic Ocean. Within these two assemblages
phylogenetic resolution was low, and the variation within individuals was
almost as high as the variation within the entire lineage. The pattern of
sequence variation suggests the existence of two forms of the ITS-1 that
are maintained on different chromosomes. Polymorphisms of limited
geographical distribution could be detected, and 41 additional clones were
partly sequenced, to assess the geographic distribution of these
polymorphisms in more detail. In a population aggregation analysis, the
geographic pattern of ITS-1 distribution was basically congruent with that
obtained in earlier studies from mitochondrial DNA in the same C. dorsalis
populations.
相似文献
73.
Simultaneous saccharification and fermentation of straw to ethanol using the thermotolerant yeast strain Kluyveromyces marxianus imb3 总被引:1,自引:0,他引:1
The thermotolerant, ethanol-producing yeast strain Kluyveromyces marxianus IMB3 was grown at 45°C on media containing 2, 4 and 6 % (w/v) pulverized barley straw and supplemented with 2% (v/v) cellulase. Maximum ethanol concentrations produced were 2, 3 and 3.6g/l, respectively. When the pulverized straw was replaced by NaOH pretreated straw (at 2, 4 and 6% (w/v); based on original untreated straw), ethanol concentrations increased to maxima of 3.9, 8, and 12g/l, respectively. The ethanol yields amount to 20g ethanol from 100g of straw. 相似文献
74.
Lysine is catabolized via the saccharopine pathway in plants and mammals. In this pathway, lysine is converted to α-aminoadipic-δ-semialdehyde (AASA) by lysine-ketoglutarate reductase/saccharopine dehydrogenase (LKR/SDH); thereafter, AASA is converted to aminoadipic acid (AAA) by α-aminoadipic-δ-semialdehyde dehydrogenase (AASADH). Here, we investigate the occurrence, genomic organization and functional role of lysine catabolic pathways among prokaryotes. Surprisingly, only 27 species of the 1478 analyzed contain the lkr and sdh genes, whereas 323 species contain aasadh orthologs. A sdh-related gene, identified in 159 organisms, was frequently found contiguously to an aasadh gene. This gene, annotated as lysine dehydrogenase (lysdh), encodes LYSDH an enzyme that directly converts lysine to AASA. Pipecolate oxidase (PIPOX) and lysine-6-aminotransferase (LAT), that converts lysine to AASA, were also found associated with aasadh. Interestingly, many lysdh–aasadh–containing organisms live under hyperosmotic stress. To test the role of the lysine-to-AASA pathways in the bacterial stress response, we subjected Silicibacter pomeroyi to salt stress. All but lkr, sdh, lysdh and aasadh were upregulated under salt stress conditions. In addition, lysine-supplemented culture medium increased the growth rate of S. pomeroyi under high-salt conditions and induced high-level expression of the lysdh–aasadh operon. Finally, transformation of Escherichia coli with the S. pomeroyi lysdh–aasadh operon resulted in increased salt tolerance. The transformed E. coli accumulated high levels of the compatible solute pipecolate, which may account for the salt resistance. These findings suggest that the lysine-to-AASA pathways identified in this work may have a broad evolutionary importance in osmotic stress resistance. 相似文献
75.
Paul E. Bellamy Ross A. Hill Peter Rothery Shelley A. Hinsley Robert J. Fuller Richard K. Broughton 《Bird Study》2013,60(3):338-348
Capsule Use of Light Detection and Ranging (LiDAR) data identified suitable Willow Warbler habitat based on mean vegetation height. This habitat model provided maps of distribution and occupation of suitable habitat. Aims To identify habitat associations in woods with different vegetation structure and management systems during a period of low Willow Warbler populations. Methods Locations of all Willow Warblers were mapped during the breeding season in three woods of contrasting management; recent low intervention, actively coppiced woodland and high forest with clear‐fells. Height profile models of each wood were derived from airborne LiDAR. The mean vegetation height at locations with Willow Warblers and a sample from the rest of the wood were used to produce models of optimum habitat and breadth of habitat occupied in each wood. The habitat model was then used to produce maps of suitable habitat. Results The habitat models did not differ between woods, with highest probability of Willow Warbler occurrence in mean vegetation heights of 3.7–5.3 m. Habitat of heights 6–11 m appeared less suitable, being only partly occupied. Habitat maps showed that habitat of suitable height was only occupied when it occurred as large patches; smaller patches (mostly <0.5 ha) and edges along rides and fields were not used. Conclusion The use of LiDAR derived measures of vegetation height identified areas of suitable habitat for Willow Warblers. Willow Warblers occupied areas of low mean vegetation height either as early successional or open canopy woodland in all woods. Height‐based habitat maps can identify areas of suitable habitat within larger expanses of heterogeneous woodland and are a potentially useful tool in assessing changes in extent of what are often temporary patches of habitat. 相似文献
76.
St John JA Braun EL Isberg SR Miles LG Chong AY Gongora J Dalzell P Moran C Bed'hom B Abzhanov A Burgess SC Cooksey AM Castoe TA Crawford NG Densmore LD Drew JC Edwards SV Faircloth BC Fujita MK Greenwold MJ Hoffmann FG Howard JM Iguchi T Janes DE Khan SY Kohno S de Koning AJ Lance SL McCarthy FM McCormack JE Merchant ME Peterson DG Pollock DD Pourmand N Raney BJ Roessler KA Sanford JR Sawyer RH Schmidt CJ Triplett EW Tuberville TD Venegas-Anaya M Howard JT Jarvis ED Guillette LJ Glenn TC 《Genome biology》2012,13(1):415-12
The International Crocodilian Genomes Working Group (ICGWG) will sequence and assemble the American alligator (Alligator mississippiensis), saltwater crocodile (Crocodylus porosus) and Indian gharial (Gavialis gangeticus) genomes. The status of these projects and our planned analyses are described. 相似文献
77.
Sequence variation in the middle part of the small-subunit rRNA was studied
for representatives of the major groups in the family Cicindelidae
(Coleoptera). All taxa exhibited a much expanded segment in variable region
V4 compared to D. melanogaster. This expanded segment was not found in
other groups of beetles, including three taxa in the closely related
Carabidae. Secondary structure predictions indicate that the expanded
segment folds into a single stem-loop structure in all taxa. Despite its
structural conservation, the fragment differs strongly in primary sequence,
even between closely related sister taxa. Several features of these
sequences are consistent with slippage replication as the mechanism that
has generated this sequence variation: the level of internal sequence
repetition as measured by the relative simplicity factor (RSF), its
variation in length between close relatives, and the strong nucleotide bias
compared to the remainder of the gene. With few exceptions, there was also
a correlation between sequence length and the level of sequence repetition,
frequently interpreted as the result of slippage. Phylogenies inferred from
the expansion segment were not consistent with existing hypotheses from
other molecular data for the group. This indicates that DNA sequences in
this region are not homologous throughout the entire Cicindelidae, but it
leaves open the possibility that this expansion segment can be used for
phylogeny reconstruction within subgroups. The implications of a
phylogenetic approach to the understanding of slippage-like evolution are
discussed.
相似文献
78.
Background
An important component of sexual selection arises because females obtain viability benefits for their offspring from their mate choice. Females choosing extra-pair fertilization generally favor males with exaggerated secondary sexual characters, and extra-pair paternity increases the variance in male reproductive success. Furthermore, females are assumed to benefit from 'good genes' from extra-pair sires. How additive genetic variance in such viability genes is maintained despite strong directional selection remains an evolutionary enigma. We propose that sexual selection is associated with elevated mutation rates, changing the balance between mutation and selection, thereby increasing variance in fitness and hence the benefits to be obtained from good genes sexual selection. Two hypotheses may account for such elevated mutation: (1) Increased sperm production associated with sperm competition may increase mutation rate. (2) Mutator alleles increase mutation rates that are revealed by the expression of condition-dependent secondary sexual characters used by choosy females during their mate choice. M Petrie has independently developed the idea that mutator alleles may account for the maintenance of genetic variation in viability despite strong directional selection. 相似文献79.
Hypothesis: For any one time and place a ‘functional signature’ can be derived for a sample of herbaceous vegetation in a way that concisely represents the balance between the different clusters of functional attributes that are present among component species. Methods: We developed a spreadsheet‐based tool for calculating functional signatures within the context of the C‐S‐R system of plant functional types. We used the tool to calculate and compare signatures for specimen British vegetation samples which differed in management regime and location in time. Conclusion: The integrative power of the ‘C‐S‐R signature’ is useful in comparative studies involving widely differing samples. Movements in the signature can be used to indicate degree of resistance, resilience, eutrophication and dereliction. Systems of plant functional types other than C‐S‐R might also be approached in this way. Availability: The tool can be downloaded free of charge from the first author's web pages or from the journal's electronic archive. 相似文献
80.
Nimmy Mohan Sudheesh AP Nimmy Francis Richard Anderson Rakesh S. Laishram 《Nucleic acids research》2015,43(14):7005-7020
Star-PAP is a nuclear non-canonical poly(A) polymerase (PAP) that shows specificity toward mRNA targets. Star-PAP activity is stimulated by lipid messenger phosphatidyl inositol 4,5 bisphoshate (PI4,5P2) and is regulated by the associated Type I phosphatidylinositol-4-phosphate 5-kinase that synthesizes PI4,5P2 as well as protein kinases. These associated kinases act as coactivators of Star-PAP that regulates its activity and specificity toward mRNAs, yet the mechanism of control of these interactions are not defined. We identified a phosphorylated residue (serine 6, S6) on Star-PAP in the zinc finger region, the domain required for PIPKIα interaction. We show that S6 is phosphorylated by CKIα within the nucleus which is required for Star-PAP nuclear retention and interaction with PIPKIα. Unlike the CKIα mediated phosphorylation at the catalytic domain, Star-PAP S6 phosphorylation is insensitive to oxidative stress suggesting a signal mediated regulation of CKIα activity. S6 phosphorylation together with coactivator PIPKIα controlled select subset of Star-PAP target messages by regulating Star-PAP-mRNA association. Our results establish a novel role for phosphorylation in determining Star-PAP target mRNA specificity and regulation of 3′-end processing. 相似文献