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1.
Molecular population genetics of male accessory gland proteins in the Drosophila simulans complex 总被引:2,自引:0,他引:2
Accessory gland proteins are a major component of Drosophila seminal fluid. These proteins have a variety of functions and may be subject to sexual selection and/or antagonistic evolution between the sexes. Most population genetic data from these proteins are from D. melanogaster and D. simulans. Here, we extend the population genetic analysis of Acp genes to the other simulans complex species, D. mauritiana and D. sechellia. We sequenced population samples of seven Acp's from D. mauritiana, D. sechellia, and D. simulans. We investigated the population genetics of these genes on individual simulans complex lineages and compared Acp polymorphism and divergence to polymorphism and divergence from a set of non-Acp loci in the same species. Polymorphism and divergence data from the simulans complex revealed little evidence for adaptive protein evolution at individual loci. However, we observed a dramatically inflated index of dispersion for amino acid substitutions in the simulans complex at Acp genes, but not at non-Acp genes. This pattern of episodic bursts of protein evolution in Acp's provides the strongest evidence to date that the population genetic mechanisms driving Acp divergence are different from the mechanisms driving evolution at most Drosophila genes. 相似文献
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Adaptive evolution of recently duplicated accessory gland protein genes in desert Drosophila 总被引:1,自引:1,他引:0
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The relationship between animal mating system variation and patterns of protein polymorphism and divergence is poorly understood. Drosophila provides an excellent system for addressing this issue, as there is abundant interspecific mating system variation. For example, compared to D. melanogaster subgroup species, repleta group species have higher remating rates, delayed sexual maturity, and several other interesting differences. We previously showed that accessory gland protein genes (Acp's) of Drosophila mojavensis and D. arizonae evolve more rapidly than Acp's in the D. melanogaster subgroup and that adaptive Acp protein evolution is likely more common in D. mojavensis/D. arizonae than in D. melanogaster/D. simulans. These findings are consistent with the idea that greater postcopulatory selection results in more adaptive evolution of seminal fluid proteins in the repleta group flies. Here we report another interesting evolutionary difference between the repleta group and the D. melanogaster subgroup Acp's. Acp gene duplications are present in D. melanogaster, but their high sequence divergence indicates that the fixation rate of duplicated Acp's has been low in this lineage. Here we report that D. mojavensis and D. arizonae genomes contain several very young duplicated Acp's and that these Acp's have experienced very rapid, adaptive protein divergence. We propose that rapid remating of female desert Drosophila generates selection for continuous diversification of the male Acp complement to improve male fertilization potential. Thus, mating system variation may be associated with adaptive protein divergence as well as with duplication of Acp's in Drosophila. 相似文献
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M Aguadé 《Genetics》1999,152(2):543-551
Nucleotide sequence variation at the Acp29AB gene region has been surveyed in Drosophila melanogaster from Spain (12 lines), Ivory Coast (14 lines), and Malawi (13 lines) and in one line of D. simulans. The approximately 1.7-kb region studied encompasses the Acp29AB gene that codes for a male accessory gland protein and its flanking regions. Seventy-seven nucleotide and 8 length polymorphisms were detected. Nonsynonymous polymorphism was an order of magnitude lower than synonymous polymorphism, but still high relative to other non-sex-related genes. In D. melanogaster variation at this region revealed no major genetic differentiation between East and West African populations, while differentiation was highly significant between the European and the two African populations. Comparison of polymorphism and divergence at synonymous and nonsynonymous sites showed an excess of fixed nonsynonymous changes, which indicates that the evolution of the Acp29AB protein has been driven by directional selection at least after the split of the D. melanogaster and D. simulans lineages. The pattern of variation in extant populations of D. melanogaster favors a scenario where the fixation of advantageous replacement substitutions occurred in the early stages of speciation and balancing selection is maintaining variation in this species. 相似文献
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Positive selection driving the evolution of a gene of male reproduction, Acp26Aa, of Drosophila: II. Divergence versus polymorphism 总被引:5,自引:1,他引:4
The evolution of the gene for a male ejaculatory protein, Acp26Aa, has been
shown to be driven by positive selection when nonsibling species in the
Drosophila melanogaster subgroup are compared. To know if selection has
been operating in the recent past and to understand the details of its
dynamics, we obtained DNA sequences of Acp26Aa and the nearby Acp26Ab gene
from 39 D. melanogaster chromosomes. Together with the 10 published
sequences, we analyzed 49 sequences from five populations in four
continents. The southern African population is somewhat differentiated from
all other populations, but its nucleotide diversity is lower at these two
loci. We find the following results for Acp26Aa: (1) The R: S (replacement
: silent changes) ratio is significantly higher in the between-species
comparisons than in the within-species data by the McDonald and Kreitman
test. Positive selection is probably responsible for the excess of amino
acid replacements between species. (2) However, within-species nucleotide
diversity is high. Neither the Tajima test nor the Fu and Li test indicates
a reduction in nucleotide diversity due to positive selection in the recent
past. (3) The newly derived nucleotides in D. melanogaster are at high
frequency significantly more often than predicted by the neutral
equilibrium. Since the nearby Acp26Ab gene does not show these patterns,
these observations cannot be attributed to the characteristics of this
chromosomal region. We suggest that positive selection is active, but may
be weak, for each amino acid change in the Acp26Aa gene.
相似文献
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Drosophila seminal proteins have an unusually high rate of molecular sequence evolution, suggesting either a high rate of neutral substitution or rapid adaptive evolution. To further quantify patterns of polymorphism and divergence in genes encoding seminal proteins, also called accessory gland proteins (Acp's), we conducted a sequencing survey of 10 Acp genes in samples of Drosophila melanogaster and D. simulans (Acp29AB, Acp32CD, Acp33A, Acp36DE, Acp53Ea, Acp62F, Acp63F, Acp76A, Acp95EF, and Acp98AB). Mean heterozygosity at replacement sites in D. simulans was 0.0074 for Acp genes and 0.0013 for a set of 19 non-Acp genes, and mean melanogaster-simulans divergence at replacement sites was 0.0497 for Acp genes and 0.0107 at non-Acp genes. The elevated divergence of Acp genes is thus accompanied by elevated within-species polymorphism. In addition to the already-reported departures of Acp26A, Acp29AB, and Acp70A from neutrality, our data reject neutrality at Acp29AB and Acp36DE in the direction of excess replacements in interspecific comparisons. 相似文献
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In Drosophila melanogaster and Drosophila simulans, positive Darwinian selection drives high rates of evolution of male reproductive genes, and accessory gland proteins (Acps) in particular. Here, we tested whether 13 X-linked male-specific genes, 4 Acps and 9 non-Acps, are under selective forces in the Drosophila pseudoobscura species group, much as those in the D. melanogaster group. We observed a statistically significant correlation in relative rates of nonsynonymous evolution between the two species groups tested. One Acp examined had a higher rate of nonsynonymous substitution than predicted by a neutral model in both species groups, suggesting its divergence was driven by positive Darwinian selection. To further test for the signature of selection, we examined polymorphism of three Acps within D. pseudoobscura. From this test, no Acp individually bore the signature of positive selection, but the 3 Acps together possessed an excess of nonsynonymous differences between species, relative to polymorphism within species. We conclude that faster evolution of Acps in the D. pseudoobscura group appears to be driven by positive selection, as previously suggested in the D. melanogaster group. 相似文献
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Sexually dimorphic traits are often subject to diversifying selection. Genes with a male-biased gene expression also are probably affected by sexual selection and have a high rate of protein evolution. We used SAGE to measure sex-biased gene expression in Drosophila pseudoobscura. Consistent with previous results from D. melanogaster, a larger number of genes were male biased (402 genes) than female biased (138 genes). About 34% of the genes changed the sex-related expression pattern between D. melanogaster and D. pseudoobscura. Combining gene expression with protein divergence between both species, we observed a striking difference in the rate of evolution for genes with a male-biased gene expression in one species only. Contrary to expectations, D. pseudoobscura genes in this category showed no accelerated rate of protein evolution, while D. melanogaster genes did. If sexual selection is driving molecular evolution of male-biased genes, our data imply a radically different selection regime in D. pseudoobscura. 相似文献
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Many genes pertaining to male reproductive functions have been shown to evolve rapidly between species, and evidence increasingly suggest the influence of positive Darwinian selection. The accessory gland protein gene (Acp26Aa) of Drosophila is one such example. In order to understand the mechanism of selection, it is often helpful to examine the pattern of polymorphism. We report here that the level of amino acid polymorphism in the N-terminal quarter of Acp26Aa is high in Drosophila melanogaster and is unprecedented in its sibling species Drosophila mauritiana. We postulate that (1) this N-terminal segment may play a role in sperm competition, and (2) D. mauritiana may have been under much more intense sexual selection than other species. Both postulates have important ramifications and deserve to be tested rigorously. 相似文献
11.
Mueller JL Ravi Ram K McGraw LA Bloch Qazi MC Siggia ED Clark AG Aquadro CF Wolfner MF 《Genetics》2005,171(1):131-143
Drosophila melanogaster males transfer seminal fluid proteins along with sperm during mating. Among these proteins, ACPs (Accessory gland proteins) from the male's accessory gland induce behavioral, physiological, and life span reduction in mated females and mediate sperm storage and utilization. A previous evolutionary EST screen in D. simulans identified partial cDNAs for 57 new candidate ACPs. Here we report the annotation and confirmation of the corresponding Acp genes in D. melanogaster. Of 57 new candidate Acp genes previously reported in D. melanogaster, 34 conform to our more stringent criteria for encoding putative male accessory gland extracellular proteins, thus bringing the total number of ACPs identified to 52 (34 plus 18 previously identified). This comprehensive set of Acp genes allows us to dissect the patterns of evolutionary change in a suite of proteins from a single male-specific reproductive tissue. We used sequence-based analysis to examine codon bias, gene duplications, and levels of divergence (via dN/dS values and ortholog detection) of the 52 D. melanogaster ACPs in D. simulans, D. yakuba, and D. pseudoobscura. We show that 58% of the 52 D. melanogaster Acp genes are detectable in D. pseudoobscura. Sequence comparisons of ACPs shared and not shared between D. melanogaster and D. pseudoobscura show that there are separate classes undergoing distinctly dissimilar evolutionary dynamics. 相似文献
12.
Molecular evolution of a duplication: the sex-peptide (Acp70A) gene region of Drosophila subobscura and Drosophila madeirensis 总被引:2,自引:2,他引:0
In Drosophila melanogaster, the Acp70A gene, which is involved in the
postmating reactions of the female, is a single-copy gene. However, in
Drosophila subobscura, the gene is duplicated and both copies are
transcribed. To study the molecular evolution of the duplication, a 2.1- kb
fragment encompassing both copies of the duplication was sequenced for 10
lines of D. subobscura and one line of Drosophila madeirensis. Estimates of
the divergence between the two copies of the duplicated region and between
the two species studied, D. subobscura and D. madeirensis, revealed that
both copies of the Acp70a gene had evolved independently since their
duplication. The ratio of nonsynonymous to silent divergence between copies
was generally higher than one. The McDonald and Kreitman test revealed an
excess of nonsynonymous changes fixed since the duplication and before the
split of the D. subobscura and D. madeirensis lineages. These results point
to natural selection driving protein evolution after the duplication.
Specifically, adaptive evolution appears to have caused the initial
differentiation between copies of the N-terminal parts of the proteins,
while purifying selection could be responsible for the high conservation of
the C- terminal parts.
相似文献
13.
Both positive selection and negative selection have been shown to drive the evolution of coding regions. It is of interest to know if the corresponding 5' regions of genes may be subjected to selection of comparable intensities. For such a comparison, we chose the Accessory gland protein (Acp) genes as our test case. About 700 bp and 600 bp for the 5' and coding regions, respectively, of eight previously unstudied genes were sequenced from 21 isogenic lines of D. melanogaster and one line from D. simulans. The ratio of divergence at the amino-acid replacement sites (A) over that at the synonymous sites (S) was twice the ratio for common polymorphism. Interestingly, the 5' region shows the same trend, with the 5'/S divergence ratio being 1.8 times higher than the 5'/S ratio for common polymorphism. There are several possible explanations for the 5'/S ratios, including demography, negative selection, and positive selection. Under normal conditions, positive selection is the most likely explanation. If that is true, about 45 to 50 percent of all fixed differences at both the replacement and 5' sites were adaptive, even though the substitution rate in the former is only half that of the latter (K(A)/K(S) approximately 0.3 vs. K(5')/K(S) approximately 0.6). As previous analyses have indicated, the inclusion of slightly deleterious polymorphism confounds the inference of positive selection. The analysis of published polymorphism data covering 97 verified 5' regions of Drosophila suggests more pronounced selective constraint on the 5' untranslated region and the core promoter (together corresponding to approximately 200 bp in this data set) when compared to the more distal portion of the 5' region of genes. 相似文献
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Studies of morphology, interspecific hybridization, protein/DNA sequences, and levels of gene expression have suggested that sex-related characters (particularly those involved in male reproduction) evolve rapidly relative to non-sex-related characters. Here we report a general comparison of evolutionary rates of sex-biased genes using data from cDNA microarray experiments and comparative genomic studies of Drosophila. Comparisons of nonsynonymous/synonymous substitution rates (d(N)/d(S)) between species of the D. melanogaster subgroup revealed that genes with male-biased expression had significantly faster rates of evolution than genes with female-biased or unbiased expression. The difference was caused primarily by a higher d(N) in the male-biased genes. The same pattern was observed for comparisons among more distantly related species. In comparisons between D. melanogaster and D. pseudoobscura, genes with highly biased male expression were significantly more divergent than genes with highly biased female expression. In many cases, orthologs of D. melanogaster male-biased genes could not be identified in D. pseudoobscura through a Blast search. In contrast to the male-biased genes, there was no clear evidence for accelerated rates of evolution in female-biased genes, and most comparisons indicated a reduced rate of evolution in female-biased genes relative to unbiased genes. Male-biased genes did not show an increased ratio of nonsynonymous/synonymous polymorphism within D. melanogaster, and comparisons of polymorphism/divergence ratios suggest that the rapid evolution of male-biased genes is caused by positive selection. 相似文献
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The no-on-transient A (nonA) gene encodes a putative RNA-binding protein, and mutations in this gene are known to affect vision, male courtship song and viability in Drosophila melanogaster. Here we have sequenced the coding region of the nonA gene of Drosophila littoralis and compared it with those of Drosophila virilis and D. melanogaster. All portions of nonA appeared to be conserved between D. littoralis and D. virilis, while the 5' region of the gene of these two species showed high divergence from that of a more distantly-related species, D. melanogaster. The same was true for the glycine repeat regions. No significant deviation from neutrality was observed in the analysis of intraspecific nucleotide variation in 5' or 3' region of the nonA gene in D. littoralis population. Also, comparison of D. littoralis sequences with homologous sequence of D. virilis suggests that the gene is evolving neutrally in D. virilis group. Divergence of the 5' regions between D. virilis group species and D. melanogaster could be a result of positive selection, but this finding is obscured by the long divergence time of the species groups. 相似文献
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M Aguadé 《Genetics》1998,150(3):1079-1089
The Acp26Aa and Acp26Ab genes that code for male accessory gland proteins are tandemly arranged in the species of the Drosophila melanogaster complex. An approximately 1.6-kb region encompassing both genes has been sequenced in 10, 24, and 18 lines from Spain, Ivory Coast, and Malawi, respectively; the previously studied 10 lines from North Carolina have also been included in the analyses. A total of 110 nucleotide and 4 length polymorphisms were detected. Silent variation for the whole Acp26A region was slightly higher in African than in non-African populations, while for both genes nonsynonymous variation was similar in all populations studied. Based on Fst estimates no major genetic differentiation was detected between East and West Africa, while in general non-African populations were strongly differentiated from both African populations. Comparison of polymorphism and divergence at synonymous and nonsynonymous sites revealed that directional selection acting on amino acid replacement changes has driven the evolution of the Acp26Aa protein in the last 2.5 myr. 相似文献
20.
An essential component of the immune system of animals is the production of antimicrobial peptides (AMPs). In vertebrates and termites the protein sequence of some AMPs evolves rapidly under positive selection, suggesting that they may be coevolving with pathogens. However, antibacterial peptides in Drosophila tend to be highly conserved. We have inferred the selection pressures acting on Drosophila antifungal peptides (drosomycins) from both the divergence of drosomycin genes within and between five species of Drosophila and polymorphism data from Drosophila simulans and D. melanogaster. In common with Drosophila antibacterial peptides, there is no evidence of adaptive protein evolution in any of the drosomycin genes, suggesting that they do not coevolve with pathogens. It is possible that this reflects a lack of specific fungal and bacterial parasites in Drosophila populations. The polymorphism data from both species differed from neutrality at one locus, but this was not associated with changes in the protein sequence. The synonymous site diversity was greater in D. simulans than in D. melanogaster, but the diversity both upstream of the genes and at nonsynonymous sites was similar. This can be explained if both upstream and nonsynonymous mutations are slightly deleterious and are removed more effectively from D. simulans due to its larger effective population size. 相似文献