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David J Hosken - One of the best experts on this subject based on the ideXlab platform.
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offspring sex ratios are stable across the life course in Drosophila simulans
Journal of Evolutionary Biology, 2020Co-Authors: Ruth C Archer, Matthew Carey, Tomohito Noda, Stefan J Store, David J HoskenAbstract:Within populations, adult sex ratios influence population growth and extinction risk, mating behaviours and parental care. Sex ratio adjustment can also have pronounced effects on individual fitness. Accordingly, it is important that we understand how often, and why, offspring sex ratios deviate from parity. In Drosophila melanogaster, females appear to improve their fitness by producing fewer sons when paired with older males. However, facultative sex ratio adjustment in D. melanogaster is controversial, and our understanding of how sex ratio skew affects fitness is hampered by pronounced sexual conflict in this species. Additionally, it is unclear whether maternal age or quality interacts with paternal age to influence offspring sex ratios. Here, we test whether offspring sex ratios vary as a function of maternal quality, and maternal and paternal age in Drosophila simulans, a sister species of D. melanogaster that lacks overt sexual conflict. We find that offspring sex ratios are slightly male-biased overall, but constant across the female life course, and independent of female quality, or paternal age. To really understand if, how and when females skew offspring sex ratios, we need studies linking offspring sex ratios to paternal and maternal phenotypes that are predicted to shift optimal investment in sons and daughters.
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the Drosophila simulans y chromosome interacts with the autosomes to influence male fitness
Journal of Evolutionary Biology, 2017Co-Authors: C R Archer, R M Stephens, Manmohan Sharma, David J HoskenAbstract:The Y chromosome should degenerate because it cannot recombine. However, male-limited transmission increases selection efficiency for male-benefit alleles on the Y, and therefore, Y chromosomes should contribute significantly to variation in male fitness. This means that although the Drosophila Y chromosome is small and gene-poor, Y-linked genes are vital for male fertility in Drosophila melanogaster and the Y chromosome has large male fitness effects. It is unclear whether the same pattern is seen in the closely related Drosophila simulans. We backcrossed Y chromosomes from three geographic locations into five genetic backgrounds and found strong Y and genetic background effects on male fertility. There was a significant Y-background interaction, indicating substantial epistasis between the Y and autosomal genes affecting male fertility. This supports accumulating evidence that interactions between the Y chromosome and the autosomes are key determinants of male fitness.
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environmental heterogeneity multivariate sexual selection and genetic constraints on cuticular hydrocarbons in Drosophila simulans
Journal of Evolutionary Biology, 2014Co-Authors: David J Hosken, Manmohan Sharma, Fiona C Ingleby, K Flowers, M F Hawkes, Sarah M Lane, James Rapkin, Clarissa M House, John HuntAbstract:Sexual selection is responsible for the evolution of many elaborate traits, but sexual trait evolution could be influenced by opposing natural selection as well as genetic constraints. As such, the evolution of sexual traits could depend heavily on the environment if trait expression and attractiveness vary between environments. Here, male Drosophila simulans were reared across a range of diets and temperatures, and we examined differences between these environments in terms of (i) the expression of male cuticular hydrocarbons (CHCs) and (ii) which male CHC profiles were most attractive to females. Temperature had a strong effect on male CHC expression, whereas the effect of diet was weaker. Male CHCs were subject to complex patterns of directional, quadratic and correlational sexual selection, and we found differences between environments in the combination of male CHCs that were most attractive to females, with clearer differences between diets than between temperatures. We also show that genetic covariance between environments is likely to cause a constraint on independent CHC evolution between environments. Our results demonstrate that even across the narrow range of environmental variation studied here, predicting the outcome of sexual selection can be extremely complicated, suggesting that studies ignoring multiple traits or environments may provide an over-simplified view of the evolution of sexual traits.
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genotype by environment interactions for cuticular hydrocarbon expression in Drosophila simulans
Journal of Evolutionary Biology, 2013Co-Authors: Fiona C Ingleby, Ian Dworkin, David J Hosken, K Flowers, M F Hawkes, Sarah M Lane, James Rapkin, John HuntAbstract:Genotype-by-environment interactions (G 9 Es) describe genetic variation for phenotypic plasticity. Recent interest in the role of these interactions in sexual selection has identified G 9 Es across a diverse range of species and sexual traits. Additionally, theoretical work predicts that G 9 Es in sexual traits could help to maintain genetic variation, but could also disrupt the reliability of these traits as signals of mate quality. However, empirical tests of these theoretical predictions are scarce. We reared iso-female lines of Drosophila simulans across two axes of environmental variation (diet and temperature) in a fully factorial design and tested for G 9 Es in the expression of cuticular hydrocarbons (CHCs), a multivariate sexual trait in this species. We find sex-specific environmental, genetic and G 9 E effects on CHC expression, with G 9 Es for diet in both male and female CHC profile and a G 9 E for temperature in females. We also find some evidence for ecological crossover in these G 9 Es, and by quantifying variance components, genetic correlations and heritabilities, we show the potential for these G 9 Es to help maintain genetic variation and cause sexual signal unreliability in D. simulans CHC profiles.
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antagonistic responses to natural and sexual selection and the sex specific evolution of cuticular hydrocarbons in Drosophila simulans
Evolution, 2012Co-Authors: Manmohan Sharma, John Hunt, David J HoskenAbstract:Natural and sexual selection are classically thought to oppose one another, and although there is evidence for this, direct experimental demonstrations of this antagonism are largely lacking. Here, we assessed the effects of sexual and natural selection on the evolution of cuticular hydrocarbons (CHCs), a character subject to both modes of selection, in Drosophila simulans. Natural selection and sexual selection were manipulated in a fully factorial design, and after 27 generations of experimental evolution, the responses of male and female CHCs were assessed. The effects of natural and sexual selection differed greatly across the sexes. The responses of female CHCs were generally small, but CHCs evolved predominantly in the direction of natural selection. For males, profiles evolved via sexual and natural selection, as well as through the interaction between the two, with some male CHC components only evolving in the direction of natural selection when sexual selection was relaxed. These results indicate sex-specific responses to selection, and that sexual and natural selection act antagonistically for at least some combinations of CHCs.
Catherine Montchampmoreau - One of the best experts on this subject based on the ideXlab platform.
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local dynamics of a fast evolving sex ratio system in Drosophila simulans
Molecular Ecology, 2013Co-Authors: David Ogereau, Catherine Montchampmoreau, Heloise Bastide, Pierre R Gerard, Michel CazemajorAbstract:By distorting Mendelian transmission to their own advantage, X-linked meiotic drive elements can rapidly spread in natural populations, generating a sex-ratio bias. One expected consequence is the triggering of a co-evolutionary arms race between the sex chromosome that carries the distorter and suppressors counteracting its effect. Such an arms race has been theoretically and experimentally established and can have many evolutionary consequences. However, its dynamics in contemporary populations is still poorly documented. Here, we investigate the fate of the young X-linked Paris driver in Drosophila simulans from sub-Saharan Africa to the Middle East. We provide the first example of the early dynamics of distorters and suppressors: we find consistent evidence that the driving chromosomes have been rising in the Middle East during the last decade. In addition, identical haplotypes are at high frequencies around the two co-evolving drive loci in remote populations, implying that the driving X chromosomes share a recent common ancestor and suggesting that East Africa could be the cradle of the Paris driver. The segmental duplication associated with drive presents an unusual structure in West Africa, which could reflect a secondary state of the driver. Together with our previous demonstration of driver decline in the Indian Ocean where suppression is complete, these data provide a unique picture of the complex dynamics of a co-evolutionary arms race currently taking place in natural populations of D. simulans.
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organization of the sex ratio meiotic drive region in Drosophila simulans
Genetics, 2006Co-Authors: Catherine Montchampmoreau, David Ogereau, Nicole Chaminade, Alexandre Colard, Sylvie AulardAbstract:Sex-ratio meiotic drive is the preferential transmission of the X chromosome by XY males, which occurs in several Drosophila species and results in female-biased progeny. Although the trait has long been known to exist, its molecular basis remains completely unknown. Here we report a fine-mapping experiment designed to characterize the major drive locus on a sex-ratio X chromosome of Drosophila simulans originating from the Seychelles (XSR6). This primary locus was found to contain two interacting elements at least, both of which are required for drive expression. One of them was genetically tracked to a tandem duplication containing six annotated genes (Trf2, CG32712, CG12125, CG1440, CG12123, org-1), and the other to a candidate region located approximately 110 kb away and spanning seven annotated genes. RT-PCR showed that all but two of these genes were expressed in the testis of both sex-ratio and standard males. In situ hybridization to polytene chromosomes revealed a complete association of the duplication with the sex-ratio trait in random samples of X chromosomes from Madagascar and Reunion.
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sex ratio meiotic drive in Drosophila simulans cellular mechanism candidate genes and evolution
Biochemical Society Transactions, 2006Co-Authors: Catherine MontchampmoreauAbstract:The sex-ratio trait, reported in a dozen Drosophila species, is a type of naturally occurring meiotic drive in which the driving elements are located on the X chromosome. Typically, as the result of a shortage of Y-bearing spermatozoa, males carrying a sex-ratio X chromosome produce a large excess of female offspring. The presence of sex-ratio chromosomes in a species can have considerable evolutionary consequences, because they can affect individual fitness and trigger extended intragenomic conflict. Here, I present the main results of the study performed in Drosophila simulans. In this species, the loss of Y-bearing spermatozoa is related to the inability of the Y chromosome sister-chromatids to separate properly during meiosis II. Fine genetic mapping has shown that the primary sex-ratio locus on the X chromosome contains two distorter elements acting synergistically, both of which are required for drive expression. One element has been genetically mapped to a tandem duplication. To infer the natural history of the trait, the pattern of DNA sequence polymorphism in the surrounding chromosomal region is being analysed in natural populations of D. simulans harbouring sex-ratio X chromosomes. Initial results have revealed the recent spread of a distorter allele.
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geographic distribution and inheritance of three cytoplasmic incompatibility types in Drosophila simulans
Genetics, 1991Co-Authors: Catherine Montchampmoreau, J F Ferveur, M JacquesAbstract:Wolbachia-like microorganisms have been implicated in unidirectional cytoplasmic incompatibility between strains of Drosophila simulans. Reduced egg eclosion occurs when females from uninfected strains (type W) are crossed with males from infected strains (type R). Here we characterize a third incompatibility type (type S) which is also correlated with the presence of Wolbachia-like microorganisms. Despite the fact that the symbionts cannot be morphologically distinguished, we observed complete bidirectional incompatibility between R and S strains. This indicates that the determinants of incompatibility are different in the two infected types. S/W incompatibility is unidirectional and similar to R/W incompatibility. A worldwide survey of D. simulans strains showed that type S incompatibility was found only in insular populations which harbor the mitochondrial type SiI. Both W and R types were found among mainland and island populations harboring the worldwide mitochondrial type SiII. Type S incompatibility could be involved in the reinforcement of the geographical isolation of SiI populations.
Ary A Hoffmann - One of the best experts on this subject based on the ideXlab platform.
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rna virome diversity and wolbachia infection in individual Drosophila simulans flies
bioRxiv, 2021Co-Authors: Ayda Susana Ortizbaez, Ary A Hoffmann, Mang Shi, Edward C HolmesAbstract:Abstract The endosymbiont bacterium Wolbachia is associated with multiple mutualistic effects on insect biology, including nutritional and antiviral properties. Wolbachia naturally occurs in Drosophila fly species, providing an operational model host to study how virome composition may be impacted by its presence. Drosophila simulans populations can carry a variety of Wolbachia strains. In particular, the wAu strain of Wolbachia has been associated with strong antiviral protection under experimental conditions. We used D. simulans sampled from the Perth Hills, Western Australia, to investigate the potential virus protective effect of the wAu strain on individual wild-caught flies. Our data revealed no appreciable variation in virus composition and abundance between Wolbachia infected/uninfected individuals associated with the presence/absence of wAu. However, it remains unclear whether wAu might impact viral infection and host survival by increasing tolerance rather than inducing complete resistance. These data also provide new insights into the natural virome diversity of D. simulans. Despite the small number of individuals sampled, we identified a repertoire of RNA viruses, including Nora virus, Galbut virus, Chaq virus, Thika virus and La Jolla virus, that have been identified in other Drosophila species. In addition, we identified five novel viruses from the families Reoviridae, Tombusviridae, Mitoviridae and Bunyaviridae. Overall, this study highlights the complex interaction between Wolbachia and RNA virus infections and provides a baseline description of the natural virome of D. simulans.
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rna virome diversity and wolbachia infection in individual Drosophila simulans flies
Journal of General Virology, 2021Co-Authors: Ayda Susana Ortizbaez, Ary A Hoffmann, Mang Shi, Edward C HolmesAbstract:The endosymbiont bacteria of the genus Wolbachia are associated with multiple mutualistic effects on insect biology, including nutritional and antiviral properties. Members of the genus Wolbachia naturally occur in fly species of the genus Drosophila, providing an operational model host for studying how virome composition may be affected by its presence. Drosophila simulans populations can carry a variety of strains of members of the genus Wolbachia, with the wAu strain associated with strong antiviral protection under experimental conditions. We used D. simulans sampled from the Perth Hills, Western Australia, to investigate the potential virus protective effect of the wAu strain of Wolbachia on individual wild-caught flies. Our data revealed no appreciable variation in virus composition and abundance between individuals infected or uninfected with Wolbachia associated with the presence or absence of wAu. However, it remains unclear whether wAu might affect viral infection and host survival by increasing tolerance rather than inducing complete resistance. These data also provide new insights into the natural virome diversity of D. simulans. Despite the small number of individuals sampled, we identified a repertoire of RNA viruses, including nora virus, galbut virus, thika virus and La Jolla virus, that have been identified in other species of the genus Drosophila. Chaq virus-like sequences associated with galbut virus were also detected. In addition, we identified five novel viruses from the families Reoviridae, Tombusviridae, Mitoviridae and Bunyaviridae. Overall, this study highlights the complex interaction between Wolbachia and RNA virus infections and provides a baseline description of the natural virome of D. simulans.
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rapid spread of a wolbachia infection that does not affect host reproduction in Drosophila simulans cage populations
Evolution, 2018Co-Authors: Peter Kriesner, Ary A HoffmannAbstract:Wolbachia endosymbionts that are maternally inherited can spread rapidly in host populations through inducing sterility in uninfected females, but some Wolbachia infections do not influence host reproduction yet still persist. These infections are particularly interesting because they likely represent mutualistic endosymbionts, spreading by increasing host fitness. Here, we document such a spread in the wAu infection of Drosophila simulans. By establishing multiple replicate cage populations, we show that wAu consistently increased from an intermediate frequency to near fixation, representing an estimated fitness advantage of around 20% for infected females. The effective population size in the cages was estimated from SNP markers to be around a few thousand individuals, precluding large effects of genetic drift in the populations. The exact reasons for the fitness advantage are unclear but viral protection and nutritional benefits are two possibilities.
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rapid sequential spread of two wolbachia variants in Drosophila simulans
PLOS Pathogens, 2013Co-Authors: Peter Kriesner, Ary A Hoffmann, Michael Turelli, Siu F Lee, Andrew R WeeksAbstract:The maternally inherited intracellular bacteria Wolbachia can manipulate host reproduction in various ways that foster frequency increases within and among host populations. Manipulations involving cytoplasmic incompatibility (CI), where matings between infected males and uninfected females produce non-viable embryos, are common in arthropods and produce a reproductive advantage for infected females. CI was associated with the spread of Wolbachia variant wRi in Californian populations of Drosophila simulans, which was interpreted as a bistable wave, in which local infection frequencies tend to increase only once the infection becomes sufficiently common to offset imperfect maternal transmission and infection costs. However, maternally inherited Wolbachia are expected to evolve towards mutualism, and they are known to increase host fitness by protecting against infectious microbes or increasing fecundity. We describe the sequential spread over approximately 20 years in natural populations of D. simulans on the east coast of Australia of two Wolbachia variants (wAu and wRi), only one of which causes significant CI, with wRi displacing wAu since 2004. Wolbachia and mtDNA frequency data and analyses suggest that these dynamics, as well as the earlier spread in California, are best understood as Fisherian waves of favourable variants, in which local spread tends to occur from arbitrarily low frequencies. We discuss implications for Wolbachia-host dynamics and coevolution and for applications of Wolbachia to disease control.
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high throughput pcr assays to monitor wolbachia infection in the dengue mosquito aedes aegypti and Drosophila simulans
Applied and Environmental Microbiology, 2012Co-Authors: Siu F Lee, Ary A Hoffmann, Vanessa L White, Andrew Weeks, Nancy M EndersbyAbstract:We have developed and validated two new fluorescence-based PCR assays to detect the Wolbachia wMel strain in Aedes aegypti and the wRi and wAu strains in Drosophila simulans. The new assays are accurate, informative, and cost-efficient for large-scale Wolbachia screening.
Sylvie Aulard - One of the best experts on this subject based on the ideXlab platform.
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sex ratio meiotic drive shapes the evolution of the y chromosome in Drosophila simulans
Molecular Biology and Evolution, 2019Co-Authors: Sylvie Aulard, Nicole Chaminade, David Ogereau, Quentin Helleu, Cecile Courret, Katie L Burnham, Mohamed ChakirAbstract:The recent emergence and spread of X-linked segregation distorters-called "Paris" system-in the worldwide species Drosophila simulans has elicited the selection of drive-resistant Y chromosomes. Here, we investigate the evolutionary history of 386 Y chromosomes originating from 29 population samples collected over a period of 20 years, showing a wide continuum of phenotypes when tested against the Paris distorters, from high sensitivity to complete resistance (males sire ∼95% to ∼40% female progeny). Analyzing around 13 kb of Y-linked gene sequences in a representative subset of nine Y chromosomes, we identified only three polymorphic sites resulting in three haplotypes. Remarkably, one of the haplotypes is associated with resistance. This haplotype is fixed in all samples from Sub-Saharan Africa, the region of origin of the drivers. Exceptionally, with the spread of the drivers in Egypt and Morocco, we were able to record the replacement of the sensitive lineage by the resistant haplotype in real time, within only a few years. In addition, we performed in situ hybridization, using satellite DNA probes, on a subset of 21 Y chromosomes from six locations. In contrast to the low molecular polymorphism, this revealed extensive structural variation suggestive of rapid evolution, either neutral or adaptive. Moreover, our results show that intragenomic conflicts can drive astonishingly rapid replacement of Y chromosomes and suggest that the emergence of Paris segregation distorters in East Africa occurred less than half a century ago.
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organization of the sex ratio meiotic drive region in Drosophila simulans
Genetics, 2006Co-Authors: Catherine Montchampmoreau, David Ogereau, Nicole Chaminade, Alexandre Colard, Sylvie AulardAbstract:Sex-ratio meiotic drive is the preferential transmission of the X chromosome by XY males, which occurs in several Drosophila species and results in female-biased progeny. Although the trait has long been known to exist, its molecular basis remains completely unknown. Here we report a fine-mapping experiment designed to characterize the major drive locus on a sex-ratio X chromosome of Drosophila simulans originating from the Seychelles (XSR6). This primary locus was found to contain two interacting elements at least, both of which are required for drive expression. One of them was genetically tracked to a tandem duplication containing six annotated genes (Trf2, CG32712, CG12125, CG1440, CG12123, org-1), and the other to a candidate region located approximately 110 kb away and spanning seven annotated genes. RT-PCR showed that all but two of these genes were expressed in the testis of both sex-ratio and standard males. In situ hybridization to polytene chromosomes revealed a complete association of the duplication with the sex-ratio trait in random samples of X chromosomes from Madagascar and Reunion.
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mitotic and polytene chromosomes comparisons between Drosophila melanogaster and Drosophila simulans
Genetica, 2004Co-Authors: Sylvie Aulard, Nicole Chaminade, L. Monti, Francoise LemeunierAbstract:This review deals with the differences between Drosophila melanogaster and Drosophila simulans in their mitotic and polytene chromosomes. The description of the mitotic karyotypes of D. melanogaster and D. simulans is mainly based on the methods that allow to differentiate their euchromatin from their heterochromatin: banding patterns, distribution of satellite DNAs and location of the rDNA. The polytene chromosomes karyotypes are known for many years to differ by a major paracentric inversion on chromosome 3 and minor few differences. The main difference take place in their chromosomal polymorphism: D. melanogaster is highly polymorphic while D. simulans has long been known to be a monomorphic species. In fact, despite worldwide studies of natural populations for both species, only 14 unique inversions have been described for D. simulans while more than 500 inversions are already known for D. melanogaster.
Daniel L Hartl - One of the best experts on this subject based on the ideXlab platform.
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fine scale genetic mapping of a hybrid sterility factor between Drosophila simulans and d mauritiana the varied and elusive functions of speciation genes
BMC Evolutionary Biology, 2010Co-Authors: Luciana O Araripe, Horacio Montenegro, Bernardo Lemos, Daniel L HartlAbstract:Background 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 fertility in hybrid males of Drosophila simulans and D. mauritiana.
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recurrent selection on the winters sex ratio genes in Drosophila simulans
Genetics, 2010Co-Authors: Sarah B. Kingan, Daniel Garrigan, Daniel L HartlAbstract: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 the Winters sex-ratio driver (Distorter on the X or Dox), its progenitor gene (Mother of Dox or MDox), and its suppressor gene (Not Much Yang or Nmy), which have been previously mapped and characterized. We survey three North American populations as well as 13 globally distributed strains and present molecular polymorphism data at the three loci. We find that all three genes show signatures of selection in North America, judging from levels of polymorphism and skews in the site-frequency spectrum. These signatures likely result from the biased transmission of the driver and selection on the suppressor for the maintenance of equal sex ratios. Coalescent modeling indicates that the timing of selection is more recent than the age of the alleles, suggesting that the driver and suppressor are coevolving under an evolutionary “arms race.” None of the Winters sex-ratio genes are fixed in D. simulans, and at all loci we find ancestral alleles, which lack the gene insertions and exhibit high levels of nucleotide polymorphism compared to the derived alleles. In addition, we find several “null” alleles that have mutations on the derived Dox background, which result in loss of drive function. We discuss the possible causes of the maintenance of presence–absence polymorphism in the Winters sex-ratio genes.
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A sex-ratio Meiotic Drive System in Drosophila simulans. II: An X-linked Distorter
PLoS biology, 2007Co-Authors: Yun Tao, Luciana O Araripe, Sarah B. Kingan, Hailian Xiao, Daniel L HartlAbstract:The evolution of heteromorphic sex chromosomes creates a genetic condition favoring the invasion of sex-ratio meiotic drive elements, resulting in the biased transmission of one sex chromosome over the other, in violation of Mendel's first law. The molecular mechanisms of sex-ratio meiotic drive may therefore help us to understand the evolutionary forces shaping the meiotic behavior of the sex chromosomes. Here we characterize a sex-ratio distorter on the X chromosome (Dox) in Drosophila simulans by genetic and molecular means. Intriguingly, Dox has very limited coding capacity. It evolved from another X-linked gene, which also evolved de nova. Through retrotransposition, Dox also gave rise to an autosomal suppressor, not much yang (Nmy). An RNA interference mechanism seems to be involved in the suppression of the Dox distorter by the Nmy suppressor. Double mutant males of the genotype dox; nmy are normal for both sex-ratio and spermatogenesis. We postulate that recurrent bouts of sex-ratio meiotic drive and its subsequent suppression might underlie several common features observed in the heterogametic sex, including meiotic sex chromosome inactivation and achiasmy.
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anomalies in the expression profile of interspecific hybrids of Drosophila melanogaster and Drosophila simulans
Genome Research, 2004Co-Authors: Jose M Ranz, Kalsang Namgyal, Greg Gibson, Daniel L HartlAbstract:When females of Drosophila melanogaster and males of Drosophila simulans are mated, the male progeny are inviable, whereas the female progeny display manifold malformations and are sterile. These abnormalities result from genetic incompatibilities accumulated since the time the lineages of the species diverged, and may have their origin in aberrant gene transcription. Because compensatory changes within species may obscure differences at the regulatory level in conventional comparisons of the expression profile between species, we have compared the gene-expression profile of hybrid females with those of females of the parental species in order to identify regulatory incompatibilities. In the hybrid females, we find abnormal levels of messenger RNA for a large fraction of the Drosophila transcriptome. These include a gross underexpression of genes preferentially expressed in females, accompanying gonadal atrophy. The hybrid females also show significant overexpression of male-biased genes, which we attribute to incompatibilities in the regulatory mechanisms that normally act to control the expression of these genes in females. The net result of the multiple incompatibilities is that the gene-expression profiles of the parental females are more similar to each other than either is to that of the hybrid.
