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111.
Mitochondrial gene order is not conserved in arthropods: prostriate and metastriate tick mitochondrial genomes 总被引:25,自引:15,他引:10
The entire mitochondrial genome was sequenced in a prostriate tick, Ixodes
hexagonus, and a metastriate tick, Rhipicephalus sanguineus. Both genomes
encode 22 tRNAs, 13 proteins, and two ribosomal RNAs. Prostriate ticks are
basal members of Ixodidae and have the same gene order as Limulus
polyphemus. In contrast, in R. sanguineus, a block of genes encoding NADH
dehydrogenase subunit 1 (ND1), tRNA(Leu)(UUR), tRNA(Leu)(CUN), 16S rDNA,
tRNA(Val), 12S rDNA, the control region, and the tRNA(Ile) and tRNA(Gln)
have translocated to a position between the tRNA(Glu) and tRNA(Phe) genes.
The tRNA(Cys) gene has translocated between the control region and the
tRNA(Met) gene, and the tRNA(Leu)(CUN) gene has translocated between the
tRNA(Ser)(UCN) gene and the control region. Furthermore, the control region
is duplicated, and both copies undergo concerted evolution. Primers that
flank these rearrangements confirm that this gene order is conserved in all
metastriate ticks examined. Correspondence analysis of amino acid and codon
use in the two ticks and in nine other arthropod mitochondrial genomes
indicate a strong bias in R. sanguineus towards amino acids encoded by
AT-rich codons.
相似文献
112.
Bradley RD; Adkins RM; Honeycutt RL; McDonald JH 《Molecular biology and evolution》1998,15(6):709-717
Using the strictly neutral model as a null hypothesis, we tested for
deviations from expected levels of nucleotide polymorphism at the alcohol
dehydrogenase locus (Adh-1) within and among four species of pocket gophers
(Geomys bursarius major, G. knoxjonesi, G. texensis llanensis, and G.
attwateri). The complete protein-encoding region was examined, and 10
unique alleles, representing both electromorphic and cryptic alleles, were
used to test hypotheses (e.g., the neutral model) concerning the
maintenance of genetic variation. Nineteen variable sites were identified
among the 10 alleles examined, including 9 segregating sites occurring in
synonymous positions and 10 that were nonsynonymous. Several statistical
methods, including those that test for within-species variation as well as
those that examine variation within and among species, failed to reject the
null hypothesis that variation (both within and between species of Geomys)
at the Adh locus is consistent with the neutral theory. However, there was
significant heterogeneity in the ratio of polymorphism to divergence across
the gene, with polymorphisms clustered in the first half of the coding
region and fixed differences clustered in the second half of the gene. Two
alternative hypotheses are discussed as possible explanations for this
heterogeneity: an old balanced polymorphism in the first half of the gene
or a recent selective sweep in the second half of the gene.
相似文献
113.
Fernando Rodrigues da Silva Mário Almeida‐Neto Vitor Hugo Mendonça do Prado Célio Fernando Baptista Haddad Denise de Cerqueira Rossa‐Feres 《Journal of Biogeography》2012,39(9):1720-1732
Aim The diversity of reproductive modes among amphibians constitutes a striking example of how differences in the biology of species provide important explanations for species distribution patterns on a broad scale. We hypothesize that sites with a higher humidity level will support more modes of reproduction than drier sites and will consequently exhibit a higher phylogenetic diversity. Furthermore, if there is a gradient in the tolerance of reproductive modes to desiccation, there will be a nested pattern in the composition of reproductive modes among sites. Location Twenty‐seven forest sites in the Brazilian Atlantic Forest. Methods Through a path analysis approach, we evaluated the direct and indirect effects of the humidity level on the number of reproductive modes, as well as the relative importance of both variables on amphibian phylogenetic diversity. A nestedness analysis was used to quantify the extent to which the compositions of both species and reproductive modes in drier sites correspond to subsets of those in sites with higher annual precipitation. Results We found that the reproductive modes present in drier sites are non‐random subsets of those present in sites with higher humidity levels. Because reproductive modes are phylogenetically conserved among amphibians, sites with a greater number of reproductive modes supported greater phylogenetic diversity. Sites with high precipitation throughout the year provided suitable environmental conditions for a larger number of reproductive modes, whereas sites with low precipitation and typical seasonal climates supported only those reproductive modes specialized to resist desiccation. Main conclusions Our results show that humidity‐related variables are key environmental factors related to both the richness of reproductive modes and phylogenetic diversity. Our results support the hypothesis that the higher phylogenetic diversity found in moister sites reflects differences in the tolerance to desiccation among different reproductive modes. Given that reproductive modes are associated with susceptibility to desiccation, their incorporation into explanatory models may trigger a significant advance in the understanding of the mechanisms regulating the species richness and composition of amphibian communities. 相似文献
114.
115.
Kassab BH de Carvalho DD Oliveira MA Baptista GR Pereira GA Novello JC 《Protein expression and purification》2004,35(2):344-352
The lactose-binding lectin from Bothrops jararacussu venom (BJcuL) is a homodimer belonging to group VII of the c-type animal lectins. BJcuL has also been shown to serve as an interesting tool for combating tumor progression by inhibiting cancer and endothelial cell growth. However, detailed structural studies of BJcuL and its biological mechanisms of cytotoxicity are yet to be reported, perhaps because of the non-availability of recombinant proteins in necessary quantities. Intending to increase the present information about structural and consequently the understating of biological studies, the cDNA coding for BJcuL from a venom gland has been cloned and sequenced. The mature protein-coding region was amplified by PCR with specific oligonucleotides, and subcloned into the pET-15b vector to express the recombinant BJcuL in Escherichia coli BL21 (DE3). The deduced amino acid sequence exhibits a high degree of sequence identity with c-type lectins (CTLs) and c-type lectin-like domains (CTLDs). An insoluble and inactive 18.5-kDa protein was overexpressed after 1.0mM IPTG induction. The recombinant BJcuL was recovered and denatured in a buffer with 6M urea and purified on a nickel-affinity column. Protein refolding was carried out on this column, during procedure purification, followed by dialysis against CTBS and then by gel filtration for separation of the active dimmer. The refolding process of rBJcuL and the analysis of its structure were confirmed by biological assay, circular dichroism, and MALDI-TOF. 相似文献
116.
Molecular dynamics simulation (MD) constitutes an alternative to time-consuming experiments for studying conformational changes. We apply MD on a redox system where experimental information exists for the fully oxidized and fully reduced states: tetraheme cytochrome c3. Instead of doing one simulation for each state, we apply 10 4-ns replicas for both states, which provides robust statistics to characterize the redox changes. Besides these long simulations, we perform 120 short ones (50 ps), where an equilibrated oxidized state is perturbed to a reduced state. This allows the application of a nonequilibrium method, the subtraction technique, which makes it possible to characterize the different timescales of conformational changes. Reduction induces conformational changes in the N-terminus and on the loops spanning residues 36-42 and 88-93, which correlate very well with experiments, demonstrating the applicability of this methodology. We also analyze the effect of reduction on hydrogen bonds, solvent accessible surface and bound water, the changes being found to involve the hemes and propionate groups. Redox-induced protonation is also investigated, by protonating the propionates D from hemes I and IV. Although this change in the former does not have major conformational consequences, it induces in the latter conformational changes beyond the ones obtained with reduction. 相似文献
117.
Thiol-linked DNA-gold nanoparticles were used in a novel colorimetric method to detect the presence of specific mRNA from a total RNA extract of yeast cells. The method allowed detection of expression of the FSY1 gene that encodes a specific fructose/H+ symporter in Saccharomyces bayanus PYCC 4565. FSY1 is strongly expressed when the yeast is grown in fructose as the sole carbon source, while cells cultivated in glucose as the sole carbon source repress gene expression. The presence of FSY1 mRNA is detected based on color change of a sample containing total RNA extracted from the organism and gold nanoparticles derivatized with a 15-mer of complementary single stranded DNA upon addition of NaCl. If FSY1 mRNA is present, the solution remains pink, changing to blue-purple in the absence of FSY1 mRNA. Direct detection of specific expression was possible from only 0.3 microg of unamplified total RNA without any further enhancement. This novel method is inexpensive, very easy to perform as no amplification or signal enhancement steps are necessary and takes less than 15 min to develop after total RNA extraction. No temperature control is necessary and color change can be easily detected visually. 相似文献
118.
The participation of the recently described uvsZ1 mutation in checkpoint control and the identification of epistatic relations between uvsZ1 mutation and uvsD153 and uvsJ1 mutations are provided. The effect of mutation uvsZ1 in mitotic exchanges into paba-bi (chromosome I) and cho-nic (chromosome VII) genetic intervals has also been evaluated. The mutation uvsZ1 was epistatic with regard to uvsD153 and uvsJ1 mutations, with no involvement with checkpoint control. In contrast to mutations in UvsB and UvsF groups, the uvsZ1 mutation failed to cause any changes in the frequencies of mitotic crossing-over. The distinct phenotypic traits given by mutation uvsZ1 suggest the presence of complex interactions among the different DNA repair pathways. Interaction may be an additional cell strategy of DNA damage response. 相似文献
119.
120.
Ludmila Correa Muniz Ana Maria Baptista Menezes Maria Cecília Formoso Assun??o Fernando Cesar Wehrmeister Jeovany Martínez-Mesa Helen Gon?alves Marlos Rodrigues Domingues Denise Petrucci Gigante Bernardo Lessa Horta Fernando C. Barros 《PloS one》2015,10(4)