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51.
The phylogenetic position of the archaebacteria and the place of eukaryotes
in the history of life remain a question of debate. Recent studies based on
some protein-sequence data have obtained unusual phylogenies for these
organisms. We therefore collected the protein sequences that were available
with representatives from each of the major forms of life: the
gram-negative bacteria, gram-positive bacteria, archaebacteria, and
eukaryotes. Monophyletic, unrooted phylogenies based on these sequence data
show that seven of 24 proteins yield a significant
gram-positive-archaebacteria clade/gram-negative- eukaryotic clade. The
phylogenies for these seven proteins cannot be explained by the traditional
three-way split of the eukaryotes, archaebacteria, and eubacteria. Nine of
the 24 proteins yield the traditional gram-positive-gram-negative
clade/archaebacteria-eukaryotic clade. The remaining eight proteins give
phylogenies that cannot be statistically distinguished. These results
support the hypothesis of a chimeric origin for the eukaryotic cell nucleus
formed from the fusion of an archaebacteria and a gram-negative bacteria.
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52.
Phylogenetic analysis of the 90 kD heat shock family of protein sequences and an examination of the relationship among animals, plants, and fungi species 总被引:17,自引:1,他引:16
The heat shock protein (Hsp) sequences, because of their ubiquity and high
degree of conservation, provide useful models for phylogenetic analysis. In
this paper I have carried out a global alignment of all available sequences
(a total of 31) for the 90-kD heat shock protein (Hsp90) family. The
minimum amino acid identity that is seen between presently known Hsp90
homologs is about 40% over the entire length, indicating that it is a
highly conserved protein. Based on the alignment, a number of signature
sequences that either are distinctive of the Hsp90 family or that
distinguish between the cytosolic and the endoplasmic reticular forms of
Hsp90 have been identified. Detailed phylogenetic analyses based on Hsp90
sequences reported here strongly indicate that the cytosolic and the
endoplasmic reticulum (ER) resident forms of Hsp90 constitute paralogous
gene families which arose by a gene duplication event that took place very
early in the evolution of eukaryotic cells. A minimum of two additional
gene duplication events, which took place at a later time, are required to
explain the presence of two different forms of Hsp90 that are found in
fungi and vertebrate species. In a consensus neighbor-joining bootstrap
tree based on Hsp90 sequences, plants and animals species grouped together
989 times of 1,000 (a highly significant score), indicating a closer
relationship between them as compared to fungi. A closer affiliation of
plant and animal species was also observed in the maximum-parsimony tree,
although the relationship was not significantly supported by this method. A
survey of the recent literature on this subject indicates that depending on
the protein sequence and the methods of phylogenetic analysis, the animal
species are indicated as closer relatives to either plants or fungi with
significant statistical support for both topologies. Thus the relationship
among the animal, plant, and fungi kingdoms remains an unresolved issue at
the present time.
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53.
AAM Coelho-Castelo AP Trombone RS Rosada RR Santos Jr VLD Bonato A Sartori CL Silva 《Genetic vaccines and therapy》2006,4(1):1-10
In order to assess a new strategy of DNA vaccine for a more complete understanding of its action in immune response, it is important to determine the in vivo biodistribution fate and antigen expression. In previous studies, our group focused on the prophylactic and therapeutic use of a plasmid DNA encoding the Mycobacterium leprae 65-kDa heat shock protein (Hsp65) and achieved an efficient immune response induction as well as protection against virulent M. tuberculosis challenge. In the present study, we examined in vivo tissue distribution of naked DNA-Hsp65 vaccine, the Hsp65 message, genome integration and methylation status of plasmid DNA. The DNA-Hsp65 was detectable in several tissue types, indicating that DNA-Hsp65 disseminates widely throughout the body. The biodistribution was dose-dependent. In contrast, RT-PCR detected the Hsp65 message for at least 15 days in muscle or liver tissue from immunized mice. We also analyzed the methylation status and integration of the injected plasmid DNA into the host cellular genome. The bacterial methylation pattern persisted for at least 6 months, indicating that the plasmid DNA-Hsp65 does not replicate in mammalian tissue, and Southern blot analysis showed that plasmid DNA was not integrated. These results have important implications for the use of DNA-Hsp65 vaccine in a clinical setting and open new perspectives for DNA vaccines and new considerations about the inoculation site and delivery system. 相似文献
54.
Mitochondrial DNA variation and genetic structure in populations of Drosophila melanogaster 总被引:5,自引:0,他引:5
The understanding of the genetic structure of a species can be improved by
considering together data from different types of genetic markers. In the
past, a number of worldwide populations of Drosophila melanogaster have
been extensively studied for several such markers, including allozymes,
chromosomal inversions, and quantitative characters. Here we present
results from a study of restriction- fragment-length polymorphisms of
mitochondrial DNA (mtDNA) in 92 isofemale lines from many of the same
geographic populations of D. melanogaster. Eleven restriction enzymes were
used, of which four revealed restriction-site polymorphism. A total of 24
different haplotypes were observed, of which 18 were unique to single
populations. In many populations, the unique haplotypes have reached high
frequency without being observed in neighboring populations. A Wagner
parsimony tree reveals that mutationally close variants show geographical
clumping, suggesting local differentiation of mtDNA in populations. The
Old-World and the New-World populations are differentiated, with the
predominant Old-World haplotype being virtually absent from the New World.
These results contrast with those for the nuclear genes, in which many loci
show parallel clines in different continents, and suggest a common origin
of D. melanogaster populations in North America.
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55.