Publications

TitleAbstractYear(sorted ascending)
Filter
PMID
Filter
effects of wolbachia on sperm maturation and architecture in drosophila simulans riverside.wolbachia is an intracellular obligate symbiont, that is relatively common in insects and also found in some nematodes. cytoplasmic incompatibility (ci) is the most commonly expressed form, of several sex altering phenotypes caused by this rickettsial-like bacterium. ci is induced when infected males mate with uninfected females, and is likely the result of bacterial-induced modification of sperm grown in a wolbachia-infected environment. several studies have explored the dynamics of wolbachia b ...200717693061
the structure of the 18s rrna, a molecule that might be evolutionarily related to some receptors of innate immunity.comparisons between the sequences of insect and vertebrate 18s rrnas and the sequences of mammalian formyl peptide and some vertebrate chemokine receptor mrnas demonstrated non-random structural similarities between these two groups of rnas. it has been proposed that sections of the more ancient and conserved rrna genes could have participated in the building of these more recent genes involved in immune responses. here we analyze the sequence architecture of the 18s rrna in insects (drosophila ...200718075861
transepithelial transport of salicylate by the malpighian tubules of insects from different orders.the organic anion salicylate is a plant secondary metabolite that protects plants against phytophagous insects. in this study, a combination of salicylate-selective microelectrodes and a radioisotope tracer technique was used to study the transepithelial transport of salicylate by the malpighian tubules of 10 species of insects from five orders. our results show that salicylate is transported into the lumen of the malpighian tubules in all the species evaluated, except rhodnius prolixus. the tra ...200717640663
tetracycline treatment influences mitochondrial metabolism and mtdna density two generations after treatment in drosophila.tetracycline is commonly used to clear wolbachia from infected insects. studies then compare specific biochemical and/or life-history traits between infected and uninfected individuals with the same genetic background. we investigated the potential for tetracycline to influence mitochondrial efficiency and mitochondrial (mt)dna density two generations after treatment in drosophila simulans. we observed that antibiotic treatment resulted in a decline in inorganic phosphate incorporated into atp p ...200718093008
sympatric drosophila simulans flies with distinct mtdna show difference in mitochondrial respiration and electron transport.the role of mitochondrial dna (mtdna) in mitochondrial metabolism is understudied yet humans harboring specific mtdna types age at dissimilar rates, are unequally susceptible to various diseases, and differentially adapt to various environmental conditions. this study compares mitochondrial respiration, proton leak and electron transport of drosophila simulans males with distinct mtdna haplogroups (siii and -iii) that were collected in sympatry in kenya. despite the large divergence among haplog ...200717296496
a female-biased expressed elongase involved in long-chain hydrocarbon biosynthesis and courtship behavior in drosophila melanogaster.drosophila melanogaster produces sexually dimorphic cuticular pheromones that are a key component of the courtship behavior leading to copulation. these molecules are hydrocarbons, with lengths of 23 and 25 carbons in males (mainly with one double bond) and 27 and 29 carbons in females (mainly with two double bonds). here, we describe an elongase gene, elof, with female-biased expression. the 771-bp orf encodes a 257-aa protein that shows the highest sequence identity with mouse ssc1 elongase (3 ...200717360514
symbiotic bacteria in oocyte and ovarian cell mitochondria of the tick ixodes ricinus: biology and phylogenetic position.under natural conditions, eukaryote cells may contain bacteria. arthropods such as ticks, insects or mites are a group particularly favoured by the obligate intracellular bacteria. while arthropods are vectors for some of them, other bacteria inhabit invertebrate host cells having entered mutualistic interactions. such endosymbionts dwell usually in the host cell vacuoles or cytoplasm but have been also reported from tick oocyte mitochondria. the microorganisms contribute to mitochondria degrada ...200717226040
genome-wide patterns of expression in drosophila pure species and hybrid males. ii. examination of multiple-species hybridizations, platforms, and life cycle stages.species often produce sterile hybrids early in their evolutionary divergence, and some evidence suggests that hybrid sterility may be associated with deviations or disruptions in gene expression. in support of this idea, many studies have shown that a high proportion of male-biased genes are underexpressed, compared with non-sex-biased genes, in sterile f1 male hybrids of drosophila species. in this study, we examined and compared patterns of misexpression in sterile f1 male hybrids of drosophil ...200717032727
comparative genomic analysis of allatostatin-encoding (ast) genes in drosophila species and prediction of regulatory elements by phylogenetic footprinting.the role of the yxfgla family of allatostatin (ast) peptides in dipterans is not well-established. the recent completion of sequencing of genomes for multiple drosophila species provides an opportunity to study the evolutionary variation of the allatostatins and to examine regulatory elements that control gene expression. we performed comparative analyses of ast genes from seven drosophila species (drosophila melanogaster, drosophila simulans, drosophila ananassae, drosophila yakuba, drosophila ...200717175069
new candidate genes for sex-comb divergence between drosophila mauritiana and drosophila simulans.a large-effect qtl for divergence in sex-comb tooth number between drosophila simulans and d. mauritiana was previously mapped to 73a-84ab. here we identify genes that are likely contributors to this divergence. we first improved the mapping resolution in the 73a-84ab region using 12 introgression lines and 62 recombinant nearly isogenic lines. to further narrow the list of candidate genes, we assayed leg-specific expression and identified genes with transcript-level evolution consistent with a ...200717565959
lethality in drosophila melanogaster/drosophila simulans species hybrids is not associated with substantial transcriptional misregulation.the cross of drosophila melanogaster females to drosophila simulans males produces lethal f1 hybrid males. these lethal phenotypes can be suppressed by mutations in the d. melanogaster gene hybrid male rescue (hmr), demonstrating that hmr has a major role in causing lethality in this hybridization. we performed parallel crosses to generate viable (hmr-) and lethal (hmr+) hybrid male larvae and used microarrays to compare whole-genome transcriptional profiles between these two samples. this compa ...200717075830
phylogenetic incongruence in the drosophila melanogaster species group.drosophila melanogaster and its close relatives are used extensively in comparative biology. despite the importance of phylogenetic information for such studies, relationships between some melanogaster species group members are unclear due to conflicting phylogenetic signals at different loci. in this study, we use twelve nuclear loci (eleven coding and one non-coding) to assess the degree of phylogenetic incongruence in this model system. we focus on two nodes: (1) the node joining the drosophi ...200717071113
pervasive adaptive evolution among interactors of the drosophila hybrid inviability gene, nup96.nup96 is involved in a lethal hybrid incompatibility between 2 fruit fly species, drosophila melanogaster and drosophila simulans. recurrent adaptive evolution drove the rapid functional divergence of nup96 in both the d. melanogaster and the d. simulans lineages. functional divergence of nup96 between these 2 species is unexpected as nup96 encodes part of the nup107 subcomplex, an architectural component of nuclear pore complexes, the macromolecular channels in nuclear envelopes that mediate nu ...200717056646
recurrent positive selection at bgcn, a key determinant of germ line differentiation, does not appear to be driven by simple coevolution with its partner protein bam.surveys of nucleotide sequence polymorphism in drosophila melanogaster and drosophila simulans were performed at 2 interacting loci crucial for gametogenesis: bag-of-marbles (bam) and benign gonial cell neoplasm (bgcn). at the polymorphism level, both loci appear to be evolving under the expectations of the neutral theory. however, ratios of polymorphism and divergence for synonymous and nonsynonymous mutations depart significantly from neutral expectations for both loci consistent with a previo ...200717056645
recent ltr retrotransposon insertion contrasts with waves of non-ltr insertion since speciation in drosophila melanogaster.ltr and non-ltr retrotransposons exhibit distinct patterns of abundance within the drosophila melanogaster genome, yet the causes of these differences remain unknown. here we investigate whether genomic differences between ltr and non-ltr retrotransposons reflect systematic differences in their insertion history. we find that for 17 ltr and 10 non-ltr retrotransposon families that evolve under a pseudogene-like mode of evolution, most elements from ltr families have integrated in the very recent ...200717592135
canalization of segmentation and its evolution in drosophila.segmentation in drosophila embryogenesis occurs through a hierarchical cascade of regulatory gene expression driven by the establishment of a diffusion-mediated morphogen gradient. here, we investigate the response of this pattern formation process to genetic variation and evolution in egg size. specifically, we ask whether spatial localization of gap genes kruppel (kr) and giant (gt) and the pair-rule gene even-skipped (eve) during cellularization is robust to genetic variation in embryo length ...200717569783
prevalence of positive selection among nearly neutral amino acid replacements in drosophila.we have estimated the selective effects of amino acid replacements in natural populations by comparing levels of polymorphism in 91 genes in african populations of drosophila melanogaster with their divergence from drosophila simulans. the genes include about equal numbers whose level of expression in adults is greater in males, greater in females, or approximately equal in the sexes. markov chain monte carlo methods were used to sample key parameters in the stationary distribution of polymorphi ...200717409186
adaptive evolution of metabolic pathways in drosophila.the adaptive significance of enzyme variation has been of central interest in population genetics. yet, how natural selection operates on enzymes in the larger context of biochemical pathways has not been broadly explored. a basic expectation is that natural selection on metabolic phenotypes will target enzymes that control metabolic flux, but how adaptive variation is distributed among enzymes in metabolic networks is poorly understood. here, we use population genetic methods to identify enzyme ...200717379620
maximum likelihood estimation of ancestral codon usage bias parameters in drosophila.we present a likelihood method for estimating codon usage bias parameters along the lineages of a phylogeny. the method is an extension of the classical codon-based models used for estimating dn/ds ratios along the lineages of a phylogeny. however, we add one extra parameter for each lineage: the selection coefficient for optimal codon usage (s), allowing joint maximum likelihood estimation of s and the dn/ds ratio. we apply the method to previously published data from drosophila melanogaster, d ...200717041152
adaptive protein evolution of x-linked and autosomal genes in drosophila: implications for faster-x hypotheses.patterns of sex chromosome and autosome evolution can be used to elucidate the underlying genetic basis of adaptative change. evolutionary theory predicts that x-linked genes will adapt more rapidly than autosomes if adaptation is limited by the availability of beneficial mutations and if such mutations are recessive. in drosophila, rates of molecular divergence between species appear to be equivalent between autosomes and the x chromosome. however, molecular divergence contrasts are difficult t ...200717884828
species-specific positive selection of the male-specific lethal complex that participates in dosage compensation in drosophila.in many taxa, males and females have unequal ratios of sex chromosomes to autosomes, which has resulted in the invention of diverse mechanisms to equilibrate gene expression between the sexes (dosage compensation). failure to compensate for sex chromosome dosage results in male lethality in drosophila. in drosophila, a male-specific lethal (msl) complex of proteins and noncoding rnas binds to hundreds of sites on the single male x chromosome and up-regulates gene expression. here we use populati ...200717878295
the drosulfakinin 0 (dsk 0) peptide encoded in the conserved dsk gene affects adult drosophila melanogaster crop contractions.we report that the drosulfakinin 0 (dsk 0; nqktmsfnh2) structure and genomic organization are conserved. the dsk 0 c-terminus, sfnh2, is widely distributed in the animal kingdom suggesting it defines a novel peptide family. we also report the first description of dsk 0 activity. dsk 0, i (dsk i, fddyghmrfnh2), and ii (dsk ii, ggddqfddyghmrfnh2) are encoded in sulfakinin (dsk). drosophila erecta, drosophila sechellia, drosophila simulans, and drosophila yakuba shared 62.5-87.5% identity to drosop ...200717632121
systems-level analysis and evolution of the phototransduction network in drosophila.networks of interacting genes are responsible for generating life's complexity and for mediating how organisms respond to their environment. thus, a basic understanding of genetic variation in gene networks in natural populations is important for elucidating how changes at the genetic level map to higher levels of biological organization. here, using the well-characterized phototransduction network in drosophila, we analyze variation in gene expression within and between two closely related spec ...200717360639
adaptive genic evolution in the drosophila genomes.determining the extent of adaptive evolution at the genomic level is central to our understanding of molecular evolution. a suitable observation for this purpose would consist of polymorphic data on a large and unbiased collection of genes from two closely related species, each having a large and stable population. in this study, we sequenced 419 genes from 24 lines of drosophila melanogaster and its close relatives. together with data from drosophila simulans, these data reveal the following. ( ...200717284599
effects of the fourth chromosome on the sterility of hybrids between drosophila simulans and its relatives.genetic analysis of the fourth chromosome of drosophila simulans shows that it has no effect on either male or female fertility in hybrids with two sibling species, d. mauritiana and d. sechellia. the lack of effect holds even when the d. simulans chromosome is homozygous in a foreign genetic background. the absence of major fourth chromosome "sterility genes" in these hybridizations contrasts with the presence of a fourth-chromosome gene causing complete male sterility in hybrids of the more di ...20078014464
starvation resistance is positively correlated with body lipid proportion in five wild caught drosophila simulans populations.stress resistance traits in drosophila often show clinal variation, suggesting that selection affects resistance traits either directly or indirectly. one of the most common causes of stress for animals is the shortage or suboptimal quality of food, and individuals within many species must survive periods of starvation or exposure to nutritionally imbalanced diets. this study determines the relationship between starvation resistance, body lipid content, and lifespan in five recently collected dr ...200818706419
positive and negative selection on noncoding dna in drosophila simulans.there is now a wealth of evidence that some of the most important regions of the genome are found outside those that encode proteins, and noncoding regions of the genome have been shown to be subject to substantial levels of selective constraint, particularly in drosophila. recent work has suggested that these regions may also have been subject to the action of positive selection, with large fractions of noncoding divergence having been driven to fixation by adaptive evolution. however, this wor ...200818515263
recurrent tandem gene duplication gave rise to functionally divergent genes in drosophila.tandem gene duplication is one of the major gene duplication mechanisms in eukaryotes, as illustrated by the prevalence of gene family clusters. tandem duplicated paralogs usually share the same regulatory element, and as a consequence, they are likely to perform similar biological functions. here, we provide an example of a newly evolved tandem duplicate acquiring novel functions, which were driven by positive selection. cg32708, cg32706, and cg6999 are 3 clustered genes residing in the x chrom ...200818408233
divergence times in caenorhabditis and drosophila inferred from direct estimates of the neutral mutation rate.accurate inference of the dates of common ancestry among species forms a central problem in understanding the evolutionary history of organisms. molecular estimates of divergence time rely on the molecular evolutionary prediction that neutral mutations and substitutions occur at the same constant rate in genomes of related species. this underlies the notion of a molecular clock. most implementations of this idea depend on paleontological calibration to infer dates of common ancestry, but taxa wi ...200818234705
evolution of a desaturase involved in female pheromonal cuticular hydrocarbon biosynthesis and courtship behavior in drosophila.drosophila species exhibit polymorphism in female pheromonal cuticular hydrocarbons, with 7-monoenes produced in drosophila simulans and 7,11-dienes in most populations of drosophila melanogaster (5,9-dienes in several african populations). a female-biased desaturase, desatf, expressed only in d. melanogaster is involved in the synthesis of 7,11-dienes. we investigated the role of desatf in 5,9-diene flies. we constructed a 5,9-diene strain knock-down for desatf and showed that desatf is involve ...200818207084
variation in fiber number of a male-specific muscle between drosophila species: a genetic and developmental analysis.we characterize a newly discovered morphological difference between species of the drosophila melanogaster subgroup. the muscle of lawrence (mol) contains about four to five fibers in d. melanogaster and drosophila simulans and six to seven fibers in drosophila mauritiana and drosophila sechellia. the same number of nuclei per fiber is present in these species but their total number of mol nuclei differs. this suggests that the number of muscle precursor cells has changed during evolution. our c ...200817651361
recurrent positive selection of the drosophila hybrid incompatibility gene hmr.lethality in hybrids between drosophila melanogaster and its sibling species drosophila simulans is caused in part by the interaction of the genes hybrid male rescue (hmr) and lethal hybrid rescue (lhr). hmr and lhr have diverged under positive selection in the hybridizing species. here we test whether positive selection of hmr is confined only to d. melanogaster and d. simulans. we find that hmr has continued to diverge under recurrent positive selection between the sibling species d. simulans ...200818755760
evolution of gene expression in the drosophila olfactory system.host plant shifts by phytophagous insects play a key role in insect evolution and plant ecology. such shifts often involve major behavioral changes as the insects must acquire an attraction and/or lose the repulsion to the new host plant's odor and taste. the evolution of chemotactic behavior may be due, in part, to gene expression changes in the peripheral sensory system. to test this hypothesis, we compared gene expression in the olfactory organs of drosophila sechellia, a narrow ecological sp ...200818296696
multiple rescue factors within a wolbachia strain.wolbachia-induced cytoplasmic incompatibility (ci) is expressed when infected males are crossed with either uninfected females or females infected with wolbachia of different ci specificity. in diploid insects, ci results in embryonic mortality, apparently due to the the loss of the paternal set of chromosomes, usually during the first mitotic division. the molecular basis of ci has not been determined yet; however, several lines of evidence suggest that wolbachia exhibits two distinct sex-depen ...200818430940
quantifying the stationarity and time reversibility of the nucleotide substitution process.markov models describing the evolution of the nucleotide substitution process, widely used in phylogeny reconstruction, usually assume the hypotheses of stationarity and time reversibility. although these models give meaningful results when applied to biological data, it is not clear if the 2 assumptions mentioned above hold and, if not, how much sequence evolution processes deviate from them. to this aim, we introduce 2 sets of indices that can be calculated from the nucleotide distribution and ...200818682605
do wolbachia-associated incompatibilities promote polyandry?the genetic incompatibility avoidance hypothesis as an explanation for the polyandrous mating strategies (mating with more than one male) of females of many species has received significant attention in recent years. it has received support from both empirical studies and a meta-analysis, which concludes that polyandrous females enjoy increased reproductive success through improved offspring viability relative to monandrous females. in this study we investigate whether polyandrous female drosoph ...200818067571
investigating latitudinal clines for life history and stress resistance traits in drosophila simulans from eastern australia.latitudinal clines have been demonstrated for many quantitative traits in drosophila and are assumed to be due to climatic selection. however, clinal studies are often performed in species of drosophila that contain common cosmopolitan inversion polymorphisms that also show clinal patterns. these inversion polymorphisms may be responsible for much of the observed clinal variation. here, we consider latitudinal clines for quantitative traits in drosophila simulans from eastern australia. drosophi ...200818811666
validation of manometric microrespirometers for measuring oxygen consumption in small arthropods.scientists have used numerous techniques to measure organismal metabolic rate, including assays of oxygen (o2) consumption and carbon dioxide (co2) production. relatively few studies have directly compared estimates of metabolic rate on the same groups of animals as determined by different assay methods. this study directly compared measures of the metabolic rate of three lines of drosophila simulans as determined either from direct measures of co2 production using infrared gas analysis (irga), ...200818606168
wolbachia infection alters olfactory-cued locomotion in drosophila spp.wolbachia pipientis is an endosymbiotic bacterium present in diverse insect species. although it is well studied for its dramatic effects on host reproductive biology, little is known about its effects on other aspects of host biology, despite its presence in a wide array of host tissues. this study examined the effects of three wolbachia strains on two different drosophila species, using a laboratory performance assay for insect locomotion in response to olfactory cues. the results demonstrate ...200818456851
genetic and functional characterization of the type iv secretion system in wolbachia.a type iv secretion system (t4ss) is used by many symbiotic and pathogenic intracellular bacteria for the successful infection of and survival, proliferation, and persistence within hosts. in this study, the presence and function of the t4ss in wolbachia strains were investigated by a combination of genetic screening and immunofluorescence microscopy. two operons of virb-vird4 loci were found in the genome of wolbachia pipientis strain watab3, from the hymenoptera asobara tabida, and strain wri, ...200818502862
selective sweeps in a 2-locus model for sex-ratio meiotic drive in drosophila simulans.a way to identify loci subject to positive selection is to detect the signature of selective sweeps in given chromosomal regions. it is revealed by the departure of dna polymorphism patterns from the neutral equilibrium predicted by coalescent theory. we surveyed dna sequence variation in a region formerly identified as causing "sex-ratio" meiotic drive in drosophila simulans. we found evidence that this system evolved by positive selection at 2 neighboring loci, which thus appear to be required ...200818071199
rapid r2 retrotransposition leads to the loss of previously inserted copies via large deletions of the rdna locus.r2 non-long terminal repeat retrotransposable elements insert specifically into the 28s rrna genes of a wide range of animals. these elements maintain long-term stable relationships with the host genome. by scoring the variation present at the 5' ends of individual r2 copies, lines of drosophila simulans have been identified with high rates of r2 retrotransposition. comparing the r2 elements present in the parents with that of their progeny after 1 or 30 generations in this report revealed that ...200818003600
a new test for selection applied to codon usage in drosophila simulans and d. mauritiana.in many organisms, synonymous codon usage is biased by a history of natural selection. however, codon bias, itself, does not indicate that selection is ongoing; it may be a vestige of past selection. simple statistical tests have been devised to infer ongoing selection on codon usage by comparing the derived state frequency spectra at polymorphic sites segregating either derived preferred codons or derived unpreferred codons; if selection is effective, the frequency of derived states should be h ...200818288436
the impact of shared ancestral variation on hybrid male lethality--a 16 codon indel in the drosophila simulans lhr gene.the lethal hybrid rescue (lhr) gene causes hybrid male lethality in crosses between drosophila simulans and d. melanogaster. lhr(2) is a d. simulans allele, which rescues hybrid males. it has been recently proposed that a 16 codon insertion, which distinguishes the d. melanogaster and the canonical d. simulans allele, and is lacking in lhr(2), may be responsible for the functional divergence of d. melanogaster and d. simulans lhr alleles. here, we show that the lhr(2) allele lacking the insertio ...200818194231
non-neutral processes drive the nucleotide composition of non-coding sequences in drosophila.the nature of the forces affecting base composition is a key question in genome evolution. there is uncertainty as to whether differences in the gc contents of non-coding sequences reflect differences in mutational bias, or in the intensity of selection or biased gene conversion. we have used a polymorphism dataset for non-coding sequences on the x chromosome of drosophila simulans to examine this question. the proportion of gc-->at versus at-->gc polymorphic mutations in a locus is correlated w ...200818505714
the mariner transposable element in natural populations of drosophila simulans.in cosmopolitan species, geographical variations in copy number and/or level of transposition activity have been observed for several transposable elements (tes). environment, history and population structure can contribute to such variation in ways that are difficult to tease apart. for the mariner element, previous studies of the geographic variation of its somatic activity in natural populations of drosophila simulans have shown contradictory results (latitudinal clines of divergent orientati ...200818461087
the acylphosphatase (acyp) alleles associate with male hybrid sterility in drosophila.hybrid defects are believed to result from genetic incompatibilities between genes that have evolved in separate parental lineages. these genetic dysfunctions on the hybrid genomic background, also known as dobzhansky-muller incompatibilities, can be an incipient signature of speciation, and as such - a subject of active research. here we present evidence that acyp locus (cg16870) that encodes acylphosphatase, a small enzyme that catalyzes the hydrolysis of acylphosphates and participates in ion ...200818440166
a candidate complex approach to study functional mitochondrial dna changes: sequence variation and quaternary structure modeling of drosophila simulans cytochrome c oxidase.a problem with studying evolutionary dynamics of mitochondrial (mt) dna is that classical population genetic techniques cannot identify selected substitutions because of genetic hitchhiking. we circumvented this problem by employing a candidate complex approach to study sequence variation in cytochrome c oxidase (cox) genes within and among three distinct drosophila simulans mtdna haplogroups. first, we determined sequence variation in complete coding regions for all cox mtdna and nuclear loci a ...200818320260
female-driven mechanisms, ejaculate size and quality contribute to the lower fertility of sex-ratio distorter males in drosophila simulans.sex-ratio meiotic drive refers to the preferential transmission of the x chromosome by xy males. the loss of y-bearing sperm is caused by an x-linked distorter and results in female-biased progeny. the fertility of sex-ratio (sr) males expressing the distorter is usually strongly reduced compared to wild-type males, especially when they are in competition. the aim of this study was to identify the post-copulatory mechanisms that lower the fertility of sr males in drosophila simulans. parameters ...200819055718
gene expression disruptions of organism versus organ in drosophila species hybrids.hybrid dysfunctions, such as sterility, may result in part from disruptions in the regulation of gene expression. studies of hybrids within the drosophila simulans clade have reported genes expressed above or below the expression observed in their parent species, and such misexpression is associated with male sterility in multigenerational backcross hybrids. however, these studies often examined whole bodies rather than testes or had limited replication using less-sensitive but global techniques ...200818714377
genomic analysis of the relationship between gene expression variation and dna polymorphism in drosophila simulans.understanding how dna sequence polymorphism relates to variation in gene expression is essential to connecting genotypic differences with phenotypic differences among individuals. addressing this question requires linking population genomic data with gene expression variation.200818700012
estimation of isolation times of the island species in the drosophila simulans complex from multilocus dna sequence data.the drosophila simulans species complex continues to serve as an important model system for the study of new species formation. the complex is comprised of the cosmopolitan species, d. simulans, and two island endemics, d. mauritiana and d. sechellia. a substantial amount of effort has gone into reconstructing the natural history of the complex, in part to infer the context in which functional divergence among the species has arisen. in this regard, a key parameter to be estimated is the initial ...200818560591
epigenetic regulation of retrotransposons within the nucleolus of drosophila.r2 retrotransposable elements exclusively insert into a conserved region of the tandemly organized 28s rrna genes. despite inactivating a subset of these genes, r2 elements have persisted in the ribosomal dna (rdna) loci of insects for hundreds of millions of years. controlling r2 proliferation was addressed in this study using lines of drosophila simulans previously shown to have either active or inactive r2 retrotransposition. lines with active retrotransposition were shown to have high r2 tra ...200818678644
geographic differentiation in the house fly estimated by microsatellite and mitochondrial variation.gene flow over very large geographic scales has been investigated in few species. examples include drosophila melanogaster, drosophila subobscura, drosophila simulans, and the mediterranean fruit fly (ceratitis capitata). the cosmopolitan house fly, a highly vagile, fecund, colonizing species offers an additional exemplar. genotypes at seven microsatellite loci were scored in 14 widely separated natural house fly populations from the nearctic, neotropics, afrotropics, palearctic, and asia. allel ...200816135710
allele-specific expression assays using solexa.allele-specific expression (ase) assays can be used to identify cis, trans, and cis-by-trans regulatory variation. understanding the source of expression variation has important implications for disease susceptibility, phenotypic diversity, and adaptation. while ase is commonly measured via relative fluorescence at a snp, next generation sequencing provides an opportunity to measure ase in an accurate and high-throughput manner using read counts.200919740431
molecular signature of epistatic selection: interrogating genetic interactions in the sex-ratio meiotic drive of drosophila simulans.fine scale analyses of signatures of selection allow assessing quantitative aspects of a species' evolutionary genetic history, such as the strength of selection on genes. when several selected loci lie in the same genomic region, their epistatic interactions may also be investigated. here, we study how the neutral polymorphism pattern was shaped by two close recombining loci that cause 'sex-ratio' meiotic drive in drosophila simulans, as an example of strong selection with potentially strong ep ...200919589187
the pattern of r2 retrotransposon activity in natural populations of drosophila simulans reflects the dynamic nature of the rdna locus.the pattern and frequency of insertions that enable transposable elements to remain active in a population are poorly understood. the retrotransposable element r2 exclusively inserts into the 28s rrna genes where it establishes long-term, stable relationships with its animal hosts. previous studies with laboratory stocks of drosophila simulans have suggested that control over r2 retrotransposition resides within the rdna loci. in this report, we sampled 180 rdna loci of animals collected from tw ...200919229317
sperm dumping as a defense against meiotic drive.sperm from drosophila simulans that carry a sex-ratio distorter is preferentially lost from females' sperm-storage organs. this suggests that sperm dumping is a major factor affecting sperm competition in this species, and may have evolved in response to sex-ratio distorters.200919216726
evolution of the drosophila nuclear pore complex results in multiple hybrid incompatibilities.speciation often involves the evolution of incompatible gene interactions that cause sterility or lethality in hybrids between populations. these so-called hybrid incompatibilities occur between two or more functionally divergent loci. we show that the nucleoporin 160kda (nup160) gene of the fruitfly drosophila simulans is incompatible with one or more factors on the d. melanogaster x chromosome, causing hybrid lethality. nup160 encodes a nuclear pore complex protein and shows evidence of adapti ...200919197064
genomic environment influences the dynamics of the tirant ltr retrotransposon in drosophila.combining genome sequence analysis and functional analysis, we show that some full-length copies of tirant are present in heterochromatic regions in drosophila simulans and that when tested in vitro, these copies have a functional promoter. however, when inserted in heterochromatic regions, tirant copies are inactive in vivo, and only transcription of euchromatic copies can be detected. thus, our data indicate that the localization of the element is a hallmark of its activity in vivo and raise t ...200919141532
identification of quantitative trait loci function through analysis of multiple cuticular hydrocarbons differing between drosophila simulans and drosophila sechellia females.the genetics of sexual isolation, behavioral differences between species that prevent mating, is understood poorly. pheromonal differences between species can influence sexual isolation in many animals and in some cases a single locus can cause large functional changes in pheromonal mating signals. drosophila cuticular hydrocarbons (chcs) can function as pheromones and consequently affect mate recognition. in a previous study of the two major chcs in females that affect mating discrimination bet ...200919654611
high genetic differentiation between an african and a non-african strain of drosophila simulans revealed by segregation distortion and reduced crossover frequency.drosophila simulans strains originating from madagascar and nearby islands in the indian ocean often differ from those elsewhere in the number of sex comb teeth and the degree of morphological anomaly in hybrids with d. melanogaster. here, we report a strong segregation distortion in the f1 intercross between two d. simulans strains originating from madagascar and the us, possibly at both the gametic and zygotic levels. strong bias against alleles of the madagascar strain was observed for all te ...200919590966
effect of intracellular wolbachia on interspecific crosses between drosophila melanogaster and drosophila simulans.wolbachia are bacteria that live inside the cells of a large number of invertebrate hosts and are transmitted from infected females to their offspring. their presence is associated with cytoplasmic incompatibility in several species of drosophila. cytoplasmic incompatibility results when the sperm of infected males fertilize eggs of uninfected females, causing more or less intense embryonic mortality (unidirectional incompatibility). this phenomenon also appears in crosses between populations in ...200919731208
the rosy region of drosophila melanogaster and drosophila simulans. i. contrasting levels of naturally occurring dna restriction map variation and divergence.a 40-kb region around the rosy and snake loci was analyzed for restriction map variation among 60 lines of drosophila melanogaster and 30 lines of drosophila simulans collected together at a single locality in raleigh, north carolina. dna sequence variation in d. simulans was estimated to be 6.3 times greater than in d. melanogaster (heterozygosities per nucleotide of 1.9% vs. 0.3%). this result stands in marked contrast to results of studies of phenotypic variation including proteins (allozymes ...20092900794
the mosaic genome structure of the wolbachia wri strain infecting drosophila simulans.the obligate intracellular bacterium wolbachia pipientis infects around 20% of all insect species. it is maternally inherited and induces reproductive alterations of insect populations by male killing, feminization, parthenogenesis, or cytoplasmic incompatibility. here, we present the 1,445,873-bp genome of w. pipientis strain wri that induces very strong cytoplasmic incompatibility in its natural host drosophila simulans. a comparison with the previously sequenced genome of w. pipientis strain ...200919307581
wolbachia interferes with ferritin expression and iron metabolism in insects.wolbachia is an intracellular bacterium generally described as being a facultative reproductive parasite. however, wolbachia is necessary for oogenesis completion in the wasp asobara tabida. this dependence has evolved recently as a result of interference with apoptosis during oogenesis. through comparative transcriptomics between symbiotic and aposymbiotic individuals, we observed a differential expression of ferritin, which forms a complex involved in iron storage. iron is an essential element ...200919851452
variation in antiviral protection mediated by different wolbachia strains in drosophila simulans.drosophila c virus (dcv) is a natural pathogen of drosophila and a useful model for studying antiviral defences. the drosophila host is also commonly infected with the widespread endosymbiotic bacteria wolbachia pipientis. when dcv coinfects wolbachia-infected d. melanogaster, virus particles accumulate more slowly and virus induced mortality is substantially delayed. considering that wolbachia is estimated to infect up to two-thirds of all insect species, the observed protective effects of wolb ...200919911047
local adaptation of stress related traits in drosophila buzzatii and drosophila simulans in spite of high gene flow.we addressed the question if local adaptation to a thermal gradient is possible in spite of a high gene flow among closely spaced populations of two species of drosophila from the island of la gomera (canary islands). variation in multiple traits related to stress resistance in different life stages was measured in both species in flies collected from five localities at different altitudes and thereby with different climatic conditions. based on microsatellite loci, the populations were not gene ...200921462416
an intron loss of dfak gene in species of the drosophila melanogaster subgroup and phylogenetic analysis.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, h ...200918310070
altered heterochromatin binding by a hybrid sterility protein in drosophila sibling species.hybrid sterility of the heterogametic sex is one of the first postzygotic reproductive barriers to evolve during speciation, yet the molecular basis of hybrid sterility is poorly understood. we show that the hybrid male sterility gene odysseus-site homeobox (odsh) encodes a protein that localizes to evolutionarily dynamic loci within heterochromatin and leads to their decondensation. in drosophila mauritiana x drosophila simulans male hybrids, odsh from d. mauritiana (odshmau) acts as a steriliz ...200919933102
transgenic drosophila simulans strains prove the identity of the speciation gene lethal hybrid rescue.speciation genes are responsible for genetic incompatibilities in hybrids of incipient species and therefore participate in reproductive isolation leading to complete speciation. hybrid males between drosophila melanogaster females and d. simulans males die at late larval or prepupal stages due to a failure in chromosome condensation during mitosis. however a mutant male of d. simulans, named lethal hybrid rescue (lhr), produces viable hybrid males when crossed to females of d. melanogaster. rec ...200920154422
species-specific heterochromatin prevents mitotic chromosome segregation to cause hybrid lethality in drosophila.postzygotic reproductive barriers such as sterility and lethality of hybrids are important for establishing and maintaining reproductive isolation between species. identifying the causal loci and discerning how they interfere with the development of hybrids is essential for understanding how hybrid incompatibilities (his) evolve, but little is known about the mechanisms of how hi genes cause hybrid dysfunctions. a previously discovered drosophila melanogaster locus called zhr causes lethality in ...200919859525
drosophila melanogaster males respond differently at the behavioural and genome-wide levels to drosophila melanogaster and drosophila simulans females.drosophila melanogaster are found in sympatry with drosophila simulans, and matings between the species produce nonfertile hybrid offspring at low frequency. evolutionary theory predicts that females choose mates, so males should alter their behaviour in response to female cues. we show that d. melanogaster males quickly decrease courtship towards d. simulans females. courtship levels are reduced within 5 min of exposure to a heterospecific female, and overall courtship is significantly lower th ...200919765174
molecular population genetics and evolution of drosophila meiosis genes.while many functional elements of the meiotic process are well characterized in model organisms, the genetic basis of most of the natural phenotypic variation observed in meiotic pathways has not been determined. to begin to address this issue, we characterized patterns of polymorphism and divergence in the protein-coding regions of 33 genes across 31 lines of drosophila melanogaster and 6 lines of drosophila simulans. we sequenced genes known to be involved in chromosome segregation, recombinat ...200918984573
incorporating sequence quality data into alignment improves dna read mapping.new dna sequencing technologies have achieved breakthroughs in throughput, at the expense of higher error rates. the primary way of interpreting biological sequences is via alignment, but standard alignment methods assume the sequences are accurate. here, we describe how to incorporate the per-base error probabilities reported by sequencers into alignment. unlike existing tools for dna read mapping, our method models both sequencer errors and real sequence differences. this approach consistently ...201020110255
introgression of drosophila simulans nuclear pore protein 160 in drosophila melanogaster alone does not cause inviability but does cause female sterility.we have been analyzing genes for reproductive isolation by replacing drosophila melanogaster genes with homologs from drosophila simulans by interspecific backcrossing. among the introgressions established, we found that a segment of the left arm of chromosome 2, int(2l)s, carried recessive genes for hybrid sterility and inviability. that nuclear pore protein 160 (nup160) in the introgression region is involved in hybrid inviability, as suggested by others, was confirmed by the present analysis. ...201020647504
recognition and detoxification of the insecticide ddt by drosophila melanogaster glutathione s-transferase d1.gstd1 is one of several insect glutathione s-transferases capable of metabolizing the insecticide ddt. here we use crystallography and nmr to elucidate the binding of ddt and glutathione to gstd1. the crystal structure of drosophila melanogaster gstd1 has been determined to 1.1 a resolution, which reveals that the enzyme adopts the canonical gst fold but with a partially occluded active site caused by the packing of a c-terminal helix against one wall of the binding site for substrates. this hel ...201020417639
transposable and nontransposable elements similar to the i factor involved in inducer-reactive (ir) hybrid dysgenesis in drosophila melanogaster coexist in various drosophila species.the i factor is a transposable element controlling inducer-reactive (ir) hybrid dysgenesis in drosophila melanogaster, which occurs when males from the class of inducer strains are crossed with females from the class of reactive strains. inducer strains contain several copies of the complete 5.4-kilobase (kb) i factor at various sites on the chromosomal arms; reactive strains contain no complete i factor. incomplete and defective i elements occur at constant locations in pericentromeric heteroch ...20102829216
monitoring long-term evolutionary changes following wolbachia introduction into a novel host: the wolbachia popcorn infection in drosophila simulans.wolbachia may act as a biological control agent for pest management; in particular, the wolbachia variant wmelpop (popcorn) shortens host longevity and may be useful for dengue suppression. however, long-term changes in the host and wolbachia genomes can alter wolbachia spread and/or host effects that suppress disease. here, we investigate the phenotypic effects of wmelpop in a non-native host, drosophila simulans, following artificial transinfection approximately 200 generations ago. long-term ...201020219740
infection with the wmel and wmelpop strains of wolbachia leads to higher levels of melanization in the hemolymph of drosophila melanogaster, drosophila simulans and aedes aegypti.introduction of the life-shortening strain of wolbachia pipientis, wmelpop, into the key dengue vector, aedes aegypti, and the anti-pathogen effects in wolbachia-infected hosts highlights the need for more research into its interactions with its original host, drosophila melanogaster, and the novel mosquito host. the visual difference in darkness between the eggs of wmelpop wolbachia-infected and uninfected mosquito hosts after egg deposition led to further investigation into melanization levels ...201021075139
r2 retrotransposons encode a self-cleaving ribozyme for processing from an rrna cotranscript.the non-long terminal repeat (non-ltr) retrotransposon r2 is inserted into the 28s rrna genes of many animals. expression of the element appears to be by cotranscription with the rrna gene unit. we show here that processing of the rrna cotranscript at the 5' end of the r2 element in drosophila simulans is rapid and utilizes an unexpected mechanism. using rna synthesized in vitro, the 5' untranslated region of r2 was shown capable of rapid and efficient self-cleavage of the 28s-r2 cotranscript. t ...201020421411
artificial triple wolbachia infection in aedes albopictus yields a new pattern of unidirectional cytoplasmic incompatibility.obligately intracellular wolbachia bacteria infect numerous invertebrates and often manipulate host reproduction to facilitate the spread of infection. an example of reproductive manipulation is wolbachia-induced cytoplasmic incompatibility (ci), which occurs commonly in insects. this ci has been the focus both of basic scientific studies of naturally occurring invasion events and of applied investigations on the use of wolbachia as a vehicle to drive desired genotypes into insect populations (" ...201020601501
cost of a naturally occurring two-amino acid deletion in cytochrome c oxidase subunit 7a in drosophila simulans.this study aimed to determine whether a naturally occurring (deltatrp85, deltaval86) deletion from a protein subunit of cytochrome c oxidase (complex iv) influenced cytochrome c oxidase activity, mrna expression levels of electron transport chain genes, and aspects of adult female fitness in the fly drosophila simulans. we modeled the tertiary structure of d. simulans cox7a containing the deletion by homology to the bovine cox7a structure and predicted that it would decrease the function of comp ...201020698788
multiple hybridization events between drosophila simulans and drosophila mauritiana are supported by mtdna introgression.the study of speciation has advanced considerably in the last decades because of the increased application of molecular tools. in particular, the quantification of gene flow between recently diverged species could be addressed. drosophila simulans and drosophila mauritiana diverged, probably allopatrically, from a common ancestor approximately 250,000 years ago. however, these species share one mitochondrial dna (mtdna) haplotype indicative of a recent episode of introgression. to study the exte ...201020958812
r2 dynamics in triops cancriformis (bosc, 1801) (crustacea, branchiopoda, notostraca): turnover rate and 28s concerted evolution.the r2 retrotransposon is here characterized in bisexual populations of the european crustacean triops cancriformis. the isolated element matches well with the general aspects of the r2 family and it is highly differentiated from that of the congeneric north american triops longicaudatus. the analysis of 5' truncations indicates that r2 dynamics in t. cancriformis populations show a high turnover rate as observed in drosophila simulans. for the first time in the literature, though, individuals h ...201020628416
hosimary: a new hat transposon group involved in horizontal transfer.a pcr screening approach was used to search for sequences homologous to a previously described hat transposon found in drosophila simulans and drosophila sechellia, named here as hosimary. in this study, 52 drosophilidae species were analyzed and these sequences seem to be restricted to some species of the melanogaster group and zaprionus indianus. these species present variable number of copies and most of those appear to be putatively encoding. the high hosimary sequences similarity among diff ...201020339871
translocation of y-linked genes to the dot chromosome in drosophila pseudoobscura.one of the most striking cases of sex chromosome reorganization in drosophila occurred in the lineage ancestral to drosophila pseudoobscura, where there was a translocation of y-linked genes to an autosome. these genes went from being present only in males, never recombining, and having an effective population size of 0.5n to a state of autosomal linkage, where they are passed through both sexes, may recombine, and their effective population size has quadrupled. these genes appear to be function ...201020147437
fine-scale genetic mapping of a hybrid sterility factor between drosophila simulans and d. mauritiana: the varied and elusive functions of "speciation genes".hybrid male sterility (hms) is a usual outcome of hybridization between closely related animal species. it arises because interactions between alleles that are functional within one species may be disrupted in hybrids. the identification of genes leading to hybrid sterility is of great interest for understanding the evolutionary process of speciation. in the current work we used marked p-element insertions as dominant markers to efficiently locate one genetic factor causing a severe reduction in ...201021144061
female mate preferences in drosophila simulans: evolution and costs.female mate preference is central to sexual selection, and all indirect benefit models require that there is genetic variation in female preference. this has rarely been tested however, with relatively few studies documenting heritable variation in female preference and even fewer that have directly selected on mate preference to unequivocally show that it can evolve. additionally, costs of mate preference are poorly understood even though these have implications for preference evolution. we sel ...201020546089
thermal sensitivity of mitochondrial metabolism in two distinct mitotypes of drosophila simulans: evaluation of mitochondrial plasticity.the overall aim of this study was to (1) evaluate the adaptive value of mitochondrial dna by comparing mitochondrial performance in populations possessing different haplotypes and distribution, and to (2) evaluate the sensitivity of different enzymes of the electron transport system (ets) during temperature-induced changes. we measured the impact of temperature of mitochondrial respiration and several key enzymes of mitochondrial metabolism in two mitotypes (siii and siiii) of drosophila simulan ...201020435817
recurrent selection on the winters sex-ratio genes in drosophila simulans.selfish genes, such as meiotic drive elements, propagate themselves through a population without increasing the fitness of host organisms. x-linked (or y-linked) meiotic drive elements reduce the transmission of the y (x) chromosome and skew progeny and population sex ratios, leading to intense conflict among genomic compartments. drosophila simulans is unusual in having a least three distinct systems of x chromosome meiotic drive. here, we characterize naturally occurring genetic variation at t ...201019897749
early life benefits and later life costs of a two amino acid deletion in drosophila simulans.linking naturally occurring genotypic variation to the organismal phenotype is critical to our understanding of, and ability to, model biological processes such as adaptation to novel environments, disease, and aging. rarely, however, does a simple mutation cause a single simple observable trait. rather it is more common for a mutation to elicit an entangled web of responses. here, we employ biochemistry as the thread to link a naturally occurring two amino acid deletion in a nuclear encoded mit ...201121143473
evolution and inheritance of early embryonic patterning in drosophila simulans and d. sechellia.pattern formation in drosophila is a widely studied example of a robust developmental system. such robust systems pose a challenge to adaptive evolution, as they mask variation that selection may otherwise act upon. yet we find variation in the localization of expression domains (henceforth "stripe allometry") in the pattern formation pathway. specifically, we characterize differences in the gap genes giant and kruppel, and the pair-rule gene even-skipped, which differ between the sibling specie ...201121121913
male attractiveness, fertility and susceptibility to oxidative stress are influenced by inbreeding in drosophila simulans.inbreeding frequently leads to inbreeding depression, a reduction in the trait values of inbred individuals. inbreeding depression has been documented in sexually selected characters in several taxa, and while there is correlational evidence that male fertility is especially susceptible to inbreeding depression, there have been few direct experimental examinations of this. here, we assessed inbreeding depression in male fertility and a range of other male fitness correlates in drosophila simulan ...201121091568
a general method for calculating likelihoods under the coalescent process.analysis of genomic data requires an efficient way to calculate likelihoods across very large numbers of loci. we describe a general method for finding the distribution of genealogies: we allow migration between demes, splitting of demes [as in the isolation-with-migration (im) model], and recombination between linked loci. these processes are described by a set of linear recursions for the generating function of branch lengths. under the infinite-sites model, the probability of any configuratio ...201121900266
empirical evidence for son-killing x chromosomes and the operation of sa-zygotic drive.diploid organisms have two copies of all genes, but only one is carried by each haploid gamete and diploid offspring. this causes a fundamental genetic conflict over transmission rate between alternative alleles. single genes, or gene clusters, only rarely code for the complex phenotypes needed to give them a transmission advantage (drive phenotype). however, all genes on a male's x and y chromosomes co-segregate, allowing different sex-linked genes to code for different parts of the drive pheno ...201121858149
rapid rise and fall of selfish sex-ratio x chromosomes in drosophila simulans: spatiotemporal analysis of phenotypic and molecular data.sex-ratio drive, which has been documented in several drosophila species, is induced by x-linked segregation distorters. contrary to mendel's law of independent assortment, the sex-ratio chromosome (x(sr)) is inherited by more than half the offspring of carrier males, resulting in a female-biased sex ratio. this segregation advantage allows x(sr) to spread in populations, even if it is not beneficial for the carriers. in the cosmopolitan species d. simulans, the paris sex-ratio is caused by rece ...201121498605
females with a mutation in a nuclear-encoded mitochondrial protein pay a higher cost of survival than do males in drosophila.males and females age at different rates in a variety of species, but the mechanisms underlying the difference is not understood. in this study, we investigated sex-specific costs of a naturally occurring mildly deleterious deletion (dtrp85, dval86) in cytochrome c oxidase subunit 7a (cox7a) in drosophila simulans. we observed that females and males homozygous for the mutation had 30% and 26% reduced cox activity, respectively, compared with wild type. furthermore, 4-day-old females had 34%-42% ...201121498433
functional conservatism among drosophila simulans flies experiencing different thermal regimes and mitochondrial dna introgression.drosophila simulans possesses three different mitochondrial haplotypes (sii, ii and iii) that are nonrandomly geographically subdivided with a 3% interhaplogroup variation. the aim of this study was to determine whether perturbation of mitochondrial metabolism and ros management by temperature variation and mtdna introgression would influence the development of aerobic capacity and the intensity of oxidative stress in d. simulans at different ages. environmental temperature divergences during de ...201121462313
thermal sensitivity of mitochondrial functions in permeabilized muscle fibers from two populations of drosophila simulans with divergent mitotypes.in ectotherms, the external temperature is experienced by the mitochondria, and the mitochondrial respiration of different genotypes is likely to change as a result. using high-resolution respirometry with permeabilized fibers (an in situ approach), we tried to identify differences in mitochondrial performance and thermal sensitivity of two drosophila simulans populations with two different mitochondrial types (siii and siiii) and geographical distributions. maximal state 3 respiration rates obt ...201121451139
Refresh
firstprev
12345678
nextlast
Displaying items 501 - 600 of 769