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Excess amino acid polymorphism in mitochondrial DNA: contrasts among genes from Drosophila, mice, and humans 总被引:13,自引:3,他引:10
Recent studies of mitochondrial DNA (mtDNA) variation in mammals and
Drosophila have shown an excess of amino acid variation within species
(replacement polymorphism) relative to the number of silent and replacement
differences fixed between species. To examine further this pattern of
nonneutral mtDNA evolution, we present sequence data for the ND3 and ND5
genes from 59 lines of Drosophila melanogaster and 29 lines of D. simulans.
Of interest are the frequency spectra of silent and replacement
polymorphisms, and potential variation among genes and taxa in the
departures from neutral expectations. The Drosophila ND3 and ND5 data show
no significant excess of replacement polymorphism using the
McDonald-Kreitman test. These data are in contrast to significant
departures from neutrality for the ND3 gene in mammals and other genes in
Drosophila mtDNA (cytochrome b and ATPase 6). Pooled across genes, however,
both Drosophila and human mtDNA show very significant excesses of amino
acid polymorphism. Silent polymorphisms at ND5 show a significantly higher
variance in frequency than replacement polymorphisms, and the latter show a
significant skew toward low frequencies (Tajima's D = -1.954). These
patterns are interpreted in light of the nearly neutral theory where mildly
deleterious amino acid haplotypes are observed as ephemeral variants within
species but do not contribute to divergence. The patterns of polymorphism
and divergence at charge-altering amino acid sites are presented for the
Drosophila ND5 gene to examine the evolution of functionally distinct
mutations. Excess charge-altering polymorphism is observed at the carboxyl
terminal and excess charge-altering divergence is detected at the amino
terminal. While the mildly deleterious model fits as a net effect in the
evolution of nonrecombining mitochondrial genomes, these data suggest that
opposing evolutionary pressures may act on different regions of
mitochondrial genes and genomes.
相似文献
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Sofia Duarte Isabel Fernandes Maria João Nogueira Fernanda Cássio Cláudia Pascoal 《Fungal Ecology》2013,6(3):187-191
Temperature is a key factor in determining the structure and performance of fungal assemblages on decomposing plant litter in streams. However, little is known of how temperature affects interspecific relationships among fungi. We compared the growth of four aquatic hyphomycetes co-occurring in temperate streams, in monocultures and all species combinations when exposed to five temperatures from 11 to 27 °C. In monocultures, maximum growth rates of Heliscus submersus, Lunulospora curvula and Varicosporium elodeae occurred at 27 °C whereas Articulospora tetracladia had the lowest growth rate. At 27 °C, the increase in species diversity had no effect on the growth of V. elodeae, increased the growth of H. submersus and L. curvula, and decreased the growth of A. tetracladia. Results suggest that within a species' optimal temperature range the growth of that species increases with higher fungal diversity, while outside this range growth decreases with diversity. 相似文献
5.
Susana Pascoal Joana Esteves de Lima Jonathan D. Leslie Simon M. Hughes Leonor Saúde 《PloS one》2013,8(6)
Background
Accurate regulation of Notch signalling is central for developmental processes in a variety of tissues, but its function in pectoral fin development in zebrafish is still unknown.Methodology/Principal Findings
Here we show that core elements necessary for a functional Notch pathway are expressed in developing pectoral fins in or near prospective muscle territories. Blocking Notch signalling at different levels of the pathway consistently leads to the formation of thin, wavy, fragmented and mechanically weak muscles fibres and loss of stress fibres in endoskeletal disc cells in pectoral fins. Although the structural muscle genes encoding Desmin and Vinculin are normally transcribed in Notch-disrupted pectoral fins, their proteins levels are severely reduced, suggesting that weak mechanical forces produced by the muscle fibres are unable to stabilize/localize these proteins. Moreover, in Notch signalling disrupted pectoral fins there is a decrease in the number of Pax7-positive cells indicative of a defect in myogenesis.Conclusions/Significance
We propose that by controlling the differentiation of myogenic progenitor cells, Notch signalling might secure the formation of structurally stable muscle fibres in the zebrafish pectoral fin. 相似文献6.
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Time control is a crucial issue during embryonic development.Nevertheless, little is known about how embryonic cells measuretime. Until recently, the only molecular clock known to operateduring vertebrate embryonic development was the somitogenesisclock, exclusively functioning in coordinating the precise timingof each new pair of somites formed from the presomitic mesoderm.We have recently evidenced that a similar molecular clock alsounderlies the timing at which autopod chondrogenic precursorsare laid down to form a skeletal limb element. In addition,we herein suggest that the molecular clock is not the only parallelismthat can be established between somitogenesis and limb-bud development.In an evolutionary perspective, we support the previously proposedidea that the molecular mechanisms involved in the segmentationof the body axis may have been partially reused in the mesodermof the lateral plate, thereby allowing the emergence of pairedappendages. 相似文献
8.
Arias-Real Rebeca Gutirrez-Cnovas Cayetano Muoz Isabel Pascoal Cludia Menndez Margarita 《Ecosystems》2022,25(4):780-794
Ecosystems - Investigating the influence of biodiversity on ecosystem functioning over environmental gradients is needed to anticipate ecosystem responses to global change. However, our... 相似文献
9.
Sara Santarossa Alexandra R. Sitarik Christine Cole Johnson Jia Li Susan V. Lynch Dennis R. Ownby Alex Ramirez Germaine LM. Yong Andrea E. Cassidy-Bushrow 《Journal of Exercise Nutrition & Biochemistry》2021,25(4):24
[Purpose] To determine whether physical activity (PA), primarily the recommended 60 minutes of moderate-to-vigorous PA, is associated with gut bacterial microbiota in 10-year-old children.[Methods] The Block Physical Activity Screener, which provides minutes/day PA variables, was used to determine whether the child met the PA recommendations. 16S rRNA sequencing was performed on stool samples from the children to profile the composition of their gut bacterial microbiota. Differences in alpha diversity metrics (richness, Pielou’s evenness, and Faith’s phylogenetic diversity) by PA were determined using linear regression, whereas beta diversity (unweighted and weighted UniFrac) relationships were assessed using PERMANOVA. Taxon relative abundance differentials were determined using DESeq2.[Results] The analytic sample included 321 children with both PA and 16S rRNA sequencing data (mean age [SD] =10.2 [0.8] years; 54.2% male; 62.9% African American), where 189 (58.9%) met the PA recommendations. After adjusting for covariates, meeting the PA recommendations as well as minutes/day PA variables were not significantly associated with gut richness, evenness, or diversity (p ≥ 0.19). However, meeting the PA recommendations (weighted UniFrac R2 = 0.014, p = 0.001) was significantly associated with distinct gut bacterial composition. These compositional differences were partly characterized by increased abundance of Megamonas and Anaerovorax as well as specific Christensenellaceae_R-7_group taxa in children with higher PA.[Conclusion] Children who met the recommendations of PA had altered gut microbiota compositions. Whether this translates to a reduced risk of obesity or associated metabolic diseases is still unclear. 相似文献
10.
The contribution of fungi and bacteria to the decomposition of alder leaves was examined at two reference and two polluted sites in the Ave River (northwestern Portugal). Leaf mass loss, microbial production from incorporation rates of radiolabeled compounds into biomolecules, fungal biomass from ergosterol concentration, sporulation rates, and diversity of aquatic hyphomycetes associated with decomposing leaves were determined. The concentrations of organic nutrients and of inorganic nitrogen and phosphorus in the stream water was elevated and increased at downstream sites. Leaf decomposition rates were high (0.013 day(-1) < k < 0.042 day(-1)), and the highest value was estimated at the most downstream polluted site, where maximum values of microbial production and fungal biomass and sporulation were found. The slowest decomposition occurred at the other polluted site, where, along with the nutrient enrichment, the lowest current velocity and dissolved-oxygen concentration in water were observed. At this site, fungal production, biomass, and sporulation were depressed, suggesting that stimulation of fungal activity by increased nutrient concentrations might be offset by other factors. Although bacterial production was higher at polluted sites, fungi accounted for more than 94% of the total microbial net production. Fungal yield coefficients varied from 10.2 to 13.6%, while those of bacteria were less than 1%. The contribution of fungi to overall leaf carbon loss (29.0 to 38.8%) greatly exceeded that of bacteria (4.2 to 13.9%). 相似文献