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1.
The Drosophila olfactory genes OS-E and OS-F are members of a family of genes that encode insect odorant-binding proteins (OBPs). OBPs are believed to transport hydrophobic odorants through the aqueous fluid within olfactory sensilla to the underlying receptor proteins. The recent discovery of a large family of olfactory receptor genes in Drosophila raises new questions about the function, diversity, regulation, and evolution of the OBP family. We have investigated the OS-E and OS-F genes in a variety of Drosophila species. These studies highlight potential regions of functional significance in the OS-E and OS-F proteins, which may include a region required for interaction with receptor proteins. Our results suggest that the two genes arose by an ancient gene duplication, and that in some lineages, one or the other gene has been lost. In D. virilis, the OS-F gene shows a different spatial pattern of expression than in D. melanogaster. One of the OS-F introns shows a striking degree of conservation between the two species, and we identify a putative regulatory sequence within this intron. Finally, a phylogenetic analysis places both OS-E and OS-F within a large family of insect OBPs and OBP-like proteins. 相似文献
2.
Background
Lineage-specific genes, the genes that are restricted to a limited subset of related organisms, may be important in adaptation. In parasitic organisms, lineage-specific gene products are possible targets for vaccine development or therapeutics when these genes are absent from the host genome.Results
In this study, we utilized comparative approaches based on a phylogenetic framework to characterize lineage-specific genes in the parasitic protozoan phylum Apicomplexa. Genes from species in two major apicomplexan genera, Plasmodium and Theileria, were categorized into six levels of lineage specificity based on a nine-species phylogeny. In both genera, lineage-specific genes tend to have a higher level of sequence divergence among sister species. In addition, species-specific genes possess a strong codon usage bias compared to other genes in the genome. We found that a large number of genus- or species-specific genes are putative surface antigens that may be involved in host-parasite interactions. Interestingly, the two parasite lineages exhibit several notable differences. In Plasmodium, the (G + C) content at the third codon position increases with lineage specificity while Theileria shows the opposite trend. Surface antigens in Plasmodium are species-specific and mainly located in sub-telomeric regions. In contrast, surface antigens in Theileria are conserved at the genus level and distributed across the entire lengths of chromosomes.Conclusion
Our results provide further support for the model that gene duplication followed by rapid divergence is a major mechanism for generating lineage-specific genes. The result that many lineage-specific genes are putative surface antigens supports the hypothesis that lineage-specific genes could be important in parasite adaptation. The contrasting properties between the lineage-specific genes in two major apicomplexan genera indicate that the mechanisms of generating lineage-specific genes and the subsequent evolutionary fates can differ between related parasite lineages. Future studies that focus on improving functional annotation of parasite genomes and collection of genetic variation data at within- and between-species levels will be important in facilitating our understanding of parasite adaptation and natural selection. 相似文献3.
Nucleotide variation at the genomic region encompassing the odorant-binding protein genes OS-E and OS-F (OS region) was surveyed in two populations of Drosophila simulans, one from Europe and the other from Africa. We found that the European population shows an atypical and large haplotype structure, which extends throughout the approximately 5-kb surveyed genomic region. This structure is depicted by two major haplotype groups segregating at intermediate frequency in the sample, one haplogroup with nearly no variation, and the other at levels more typical for this species. This pattern of variation was incompatible with neutral predictions for a population at a stationary equilibrium. Nevertheless, neutrality tests contrasting polymorphism and divergence data fail to detect any departure from the standard neutral model in this species, whereas they confirm the non-neutral behavior previously observed at the OS-E gene in D. melanogaster. Although positive Darwinian selection may have been responsible for the observed unusual nucleotide variation structure, coalescent simulation results do not allow rejecting the hypothesis that the pattern was generated by a recent bottleneck in the history of European populations of D. simulans. 相似文献
4.
Singh BN 《Indian journal of experimental biology》2001,39(7):611-622
In Drosophila, chromosomal polymorphism due to paracentric inversions is very common and constitutes an adaptive character. The degree of chromosomal variability varies in different species and also in different populations of the same species. Chromosomal polymorphism in Indian natural populations of three species, D. melaonogaster, D. ananassae and D. bipectinata which belong to the melanogaster species group has been studied and the quantitative data on frequency of inversions have been reported. Behaviour of chromosome inversions has also been studied in laboratory conditions. The present review summarises the work done on inversion polymorphism in Indian populations of three species which clearly demonstrates that these three species vary in their patterns of inversion polymorphism and have evolved different mechanisms for adjustment to their environments although they belong to the same species group. 相似文献
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Molecular evolution in the Drosophila melanogaster species subgroup: frequent parameter fluctuations on the timescale of molecular divergence 下载免费PDF全文
Although mutation, genetic drift, and natural selection are well established as determinants of genome evolution, the importance (frequency and magnitude) of parameter fluctuations in molecular evolution is less understood. DNA sequence comparisons among closely related species allow specific substitutions to be assigned to lineages on a phylogenetic tree. In this study, we compare patterns of codon usage and protein evolution in 22 genes (>11,000 codons) among Drosophila melanogaster and five relatives within the D. melanogaster subgroup. We assign changes to eight lineages using a maximum-likelihood approach to infer ancestral states. Uncertainty in ancestral reconstructions is taken into account, at least to some extent, by weighting reconstructions by their posterior probabilities. Four of the eight lineages show potentially genomewide departures from equilibrium synonymous codon usage; three are decreasing and one is increasing in major codon usage. Several of these departures are consistent with lineage-specific changes in selection intensity (selection coefficients scaled to effective population size) at silent sites. Intron base composition and rates and patterns of protein evolution are also heterogeneous among these lineages. The magnitude of forces governing silent, intron, and protein evolution appears to have varied frequently, and in a lineage-specific manner, within the D. melanogaster subgroup. 相似文献
7.
Rapid evolution of two odorant-binding protein genes, Obp57d and Obp57e, in the Drosophila melanogaster species group 总被引:1,自引:0,他引:1 下载免费PDF全文
Matsuo T 《Genetics》2008,178(2):1061-1072
Genes encoding odorant-binding protein (OBP) form a large family in an insect genome. Two OBP genes, Obp57d and Obp57e, were previously identified to be involved in host-plant recognition in Drosophila sechellia. Here, by comparing the genomic sequences at the Obp57d/e locus from 27 Drosophila species, we found large differences in gene number between species. Phylogenetic analysis revealed that Obp57d and Obp57e in the D. melanogaster species group arose by gene duplication of an ancestral OBP gene that remains single in the obscura species group. Further gain and loss of OBP genes were observed in several lineages in the melanogaster group. Site-specific analysis of evolutionary rate suggests that Obp57d and Obp57e have functionally diverged from each other. Thus, there are two classes of gene number differences in the Obp57d/e region: the difference of the genes that have functionally diverged from each other and the difference of the genes that appear to be functionally identical. Our analyses demonstrate that these two classes of differences can be distinguished by comparisons of many genomic sequences from closely related species. 相似文献
8.
The molecular evolution of the alcohol dehydrogenase and alcohol dehydrogenase-related genes in the Drosophila melanogaster species subgroup 总被引:5,自引:0,他引:5
The DNA sequences of the Adh genes of three members of the Drosophila
melanogaster species subgroup have been determined. This completes the Adh
sequences of the eight species of this subgroup. Two species, D. yakuba and
D. teissieri, possess processed Adh pseudogenes. In all of the species of
the subgroup, a gene of unknown function, Adhr, is located about 300 bp 3'
to Adh. Although this gene is experiencing a higher rate of synonymous
substitution than Adh, it is more constrained at the amino acid level.
Phylogenetic relationships between all eight members of the melanogaster
subgroup have been analyzed using a variety of methods. All analyses
suggested that the D. yakuba and D. teissieri pseudogenes have a single
common ancestor, rather than evolving independently in each species, and
that D. melanogaster is the sister species to D. simulans, D. sechellia,
and D. mauritiana. The evolutionary relationships of the latter three
species remain equivocal.
相似文献
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The nucleotide sequences of the 5'-flanking regions of the duplicated Amy
genes in eight sibling species belonging to the melanogaster species
subgroup are analyzed. In Drosophila melanogaster, a region of about 450 bp
immediately upstream of the translation initiation site of the two
paralogous genes (the proximal and distal genes) has sequence similarities.
However, we could not detect any significant sequence similarity in the
region more upstream than -450. This result indicates that the coding
regions of the ancestral Amy gene were duplicated together with 450 bp of
the 5'-flanking region as one unit. Multiple alignment of these 450-bp
sequences in the proximal and distal genes of all eight species revealed a
mosaic pattern of highly conserved and divergent regions. The conserved
regions included almost all the putative regulatory elements identified in
previous analyses of the sequences. A phylogenetic analysis of the aligned
sequences shows that these 450-bp sequences are clustered into the proximal
and the distal groups. As a whole, the divergence between groups in this
region is very large in contrast to that in the coding regions. Based on
the divergence between groups, the 450-bp region is divided into two
subregions. We found that the ratios of the divergence between groups to
that within groups differ in the two subregions. From these observations,
we discuss a possibility of positive selection acting on the subregion
immediately upstream of the Amy coding region to cause divergence of
regulatory elements of the paralogous genes.
相似文献
13.
Payant V; Abukashawa S; Sasseville M; Benkel BF; Hickey DA; David J 《Molecular biology and evolution》1988,5(5):560-567
Nuclear DNA was extracted from each of the eight species comprising the
Drosophila melanogaster species subgroup. Southern hybridization of this
DNA by using a molecular probe specific for the alpha-amylase coding region
showed that the duplicated structure of the amylase locus, first found in
D. melanogaster, is conserved among all species of the melanogaster
subgroup. Evidence is also presented for the concerted evolution of the
duplicated genes within each species. In addition, it is shown that the
glucose repression of amylase gene expression, which has been extensively
studied in D. melanogaster, is not confined to this species but occurs in
all eight members of the species subgroup. Thus, both the duplicated gene
structure and the glucose repression of Drosophila amylase gene activity
are stable over extended periods of evolutionary time.
相似文献
14.
Revisiting the odorant-binding protein LUSH of Drosophila melanogaster: evidence for odour recognition and discrimination 总被引:3,自引:0,他引:3
LUSH is a soluble odorant-binding protein of the fruit fly Drosophila melanogaster. Mutants not expressing this protein have been reported to lack the avoidance behaviour, exhibited by wild type flies, to high concentrations of ethanol. Very recently, the three-dimensional structure of LUSH complexed with short-chain alcohols has been resolved supporting a role for this protein in binding and detecting small alcohols. Here we report that LUSH does not bind ethanol and that wild type flies are in fact attracted by high concentrations of ethanol. We also report that LUSH binds some phthalates and that flies are repelled by such compounds. Finally, our fluorescence data, interpreted in the light of the three-dimensional structure of LUSH, indicate that the protein undergoes a major conformational change, similar to that reported for the pheromone-binding protein of Bombyx mori, but triggered, in our case, by ligand. 相似文献
15.
Drosophila focal adhesion kinase (Dfak) gene is a single-copy nuclear gene. Previous study revealed that Drosophila melanogaster and Drosophila simulans had lost an intron precisely within the tyrosine kinase (TyK) domain of this gene. However, this did not happen in several other Drosophila species, including Drosophila elegans, Drosophila ficusphila, Drosophila biarmipes, Drosophila jambulina, Drosophila prostipennis, Drosophila takahashii, and Drosophila pseudoobscura. In the current study, homologous sequences of Drosophila sechellia, Drosophila mauritiana, Drosophila yakuba, Drosophila teissieri, Drosophila santomea, and Drosophila erecta were amplified by polymerase chain reaction, and further sequencing analysis indicated that these species were missing a TyK domain intron, indicating they were closely related. The relationship of the D. melanogaster species group was reconstructed using TyK domain nucleotide sequences. The resulting phylogenetic tree revealed that these 8 species were the most related species in the melanogaster group. These results strongly support previously proposed classifications based on morphological and molecular data. 相似文献
16.
LUSH odorant-binding protein mediates chemosensory responses to alcohols in Drosophila melanogaster.
The molecular mechanisms mediating chemosensory discrimination in insects are unknown. Using the enhancer trapping approach, we identified a new Drosophila mutant, lush, with odorant-specific defects in olfactory behavior. lush mutant flies are abnormally attracted to high concentrations of ethanol, propanol, and butanol but have normal chemosensory responses to other odorants. We show that wild-type flies have an active olfactory avoidance mechanism to prevent attraction to concentrated alcohol, and this response is defective in lush mutants. This suggests that the defective olfactory behavior associated with the lush mutation may result from a specific defect in chemoavoidance. lush mutants have a 3-kb deletion that produces a null allele of a new member of the invertebrate odorant-binding protein family, LUSH. LUSH is normally expressed exclusively in a subset of trichoid chemosensory sensilla located on the ventral-lateral surface of the third antennal segment. LUSH is secreted from nonneuronal support cells into the sensillum lymph that bathes the olfactory neurons within these sensilla. Reintroduction of a cloned wild-type copy of lush into the mutant background completely restores wild-type olfactory behavior, demonstrating that this odorant-binding protein is required in a subset of sensilla for normal chemosensory behavior to a subset of odorants. These findings provide direct evidence that odorant-binding proteins are required for normal chemosensory behavior in Drosophila and may partially determine the chemical specificity of olfactory neurons in vivo. 相似文献
17.
Hideki Sezutsu Eiji Nitasaka Tsuneyuki Yamazaki 《Molecular genetics and genomics : MGG》1995,249(2):168-178
LINE-like retrotransposons, the so-called I elements, control the system of I-R (inducer-reactive) hybrid dysgenesis in Drosophila melanogaster. I elements are present in many Drosophila species. It has been suggested that active, complete I elements, located at different sites on the chromosomes, invaded natural populations of D. melanogaster recently (1920–1970). But old strains lacking active I elements have only defective I elements located in the chromocenter. We have cloned I elements from D. melanogaster and the melanogaster subgroup. In D. melanogaster, the nucleotide sequences of chromocentral I elements differed from those on chromosome arms by as much as 7%. All the I elements of D. mauritiana and D. sechellia are more closely related to the chromosomal I elements of D. melanogaster than to the chromocentral I elements in any species. No sequence difference was observed in the surveyed region between two chromosomal I elements isolated from D. melanogaster and one from D. simulans. These findings strongly support the idea that the defective chromocentral I elements of D. melanogaster originated before the species diverged and the chromosomal I elements were eliminated. The chromosomal I elements reinvaded natural populations of D. melanogaster recently, and were possibly introduced from D. simulans by horizontal transmission. 相似文献
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The action spectra of mating activity among the six species of the Drosophila melanogaster species subgroup were compared to understand how light wavelength affects mating activity. The species fell into three groups with respect to the action spectrum of mating activity. We chose one representative species from each of the three types for detailed study: D. melanogaster, D. sechellia and D. yakuba. The mating activities were investigated under three different light intensities of three monochromatic lights stimulus. Each species showed a unique spectral and intensity response. To know the evolutionary meaning of the light wavelength dependency of mating activity, we superimposed the type of action spectrum of mating activity in these six species on a cladogram. Mating inhibition under UV was conserved in evolution among these species. Furthermore we clarified that D. melanogaster showed low mating activity under UV because males courted less under UV. 相似文献
20.
Evolution of eye morphology and rhodopsin expression in the Drosophila melanogaster species subgroup
Posnien N Hopfen C Hilbrant M Ramos-Womack M Murat S Schönauer A Herbert SL Nunes MD Arif S Breuker CJ Schlötterer C Mitteroecker P McGregor AP 《PloS one》2012,7(5):e37346
A striking diversity of compound eye size and shape has evolved among insects. The number of ommatidia and their size are major determinants of the visual sensitivity and acuity of the compound eye. Each ommatidium is composed of eight photoreceptor cells that facilitate the discrimination of different colours via the expression of various light sensitive Rhodopsin proteins. It follows that variation in eye size, shape, and opsin composition is likely to directly influence vision. We analyzed variation in these three traits in D. melanogaster, D. simulans and D. mauritiana. We show that D. mauritiana generally has larger eyes than its sibling species, which is due to a combination of larger ommatidia and more ommatidia. In addition, intra- and inter-specific differences in eye size among D. simulans and D. melanogaster strains are mainly caused by variation in ommatidia number. By applying a geometric morphometrics approach to assess whether the formation of larger eyes influences other parts of the head capsule, we found that an increase in eye size is associated with a reduction in the adjacent face cuticle. Our shape analysis also demonstrates that D. mauritiana eyes are specifically enlarged in the dorsal region. Intriguingly, this dorsal enlargement is associated with enhanced expression of rhodopsin 3 in D. mauritiana. In summary, our data suggests that the morphology and functional properties of the compound eyes vary considerably within and among these closely related Drosophila species and may be part of coordinated morphological changes affecting the head capsule. 相似文献