Project description:The differential production of pheromones is a major barrier to mating between species in Drosophila. Individuals from morphologically similar sister species can produce different sets of cuticular hydrocarbons that allow potential mates to identify them as a suitable partner. In order to elucidate cis-regulatory mechanisms behind speciation, we looked for allele-specific expression in hydrocarbon-producing oenocytes from F1 hybrids of the sister species D. simulans and D. sechellia. By focusing on cis-regulatory changes specific to female oenocytes, we rapidly identified a small number of candidate genes. Oour RNA-seq approach proved to be far more efficient than QTL mapping in identifying candidate genes, and it can be used to pinpoint the genetic basis for a wide range of traits differing due to cis-regulatory divergence between any interfertile species.
Project description:Despite holding a central role for fertilisation success, reproductive traits often show elevated rates of evolution and diversification. The rapid evolution of seminal fluid proteins (Sfps) within populations is predicted to cause mis-signalling between the male ejaculate and female reproductive tract between populations resulting in postmating prezygotic (PMPZ) isolation. Crosses between populations of Drosophila montana show PMPZ isolation in the form of reduced fertilisation success in both noncompetitive and competitive contexts. Here we test whether male ejaculate proteins deriving from either the accessory glands or the ejaculatory bulb differ between populations using liquid chromatography tandem mass spectrometry. We find more than 150 differentially abundant proteins between populations which may contribute to PMPZ isolation. These proteins include a number of proteases and peptidases, and several orthologs of D. melanogaster Sfps, all known to mediate fertilisation success and which mimic PMPZ isolation phenotypes. Males of one population typically produced greater quantities of Sfps and the strongest PMPZ isolation occurs in this direction. The accessory glands and ejaculatory bulb have different functions and the ejaculatory bulb contributes more to population differences than the accessory glands. Proteins with a secretory signal, but not Sfps, evolve faster than non-secretory proteins although the conservative criteria used to define Sfps may have impaired the ability to identify rapidly evolving proteins. We take advantage of quantitative proteomics data from three Drosophila species to determine shared and unique functional enrichments of Sfps that could be subject to selection between taxa and subsequently mediate PMPZ isolation. Our study provides the first high throughput quantitative proteomic evidence showing divergence of reproductive proteins implicated in the emergence of PMPZ isolation between populations.
Project description:This SuperSeries is composed of the following subset Series: GSE34280: Clonal Selection Drives Genetic Divergence of Metastatic Medulloblastoma [Affymetrix SNP6 Arrays] GSE34355: Clonal Selection Drives Genetic Divergence of Metastatic Medulloblastoma [Illumina Infinium HumanMethylation27 Beadchip v1.2] Refer to individual Series
Project description:Fertility depends, in part, on interactions between male and female reproductive proteins inside the female reproductive tract (FRT) that mediate postmating changes in female behavior, morphology, and physiology. Coevolution between interacting proteins within species may drive reproductive incompatibilities between species, yet the mechanisms underlying postmating-prezygotic isolating barriers remain poorly resolved. Here, we used quantitative proteomics in sibling Drosophila species to investigate the molecular composition of the FRT environment and its role in mediating species-specific postmating responses. We found that (1) FRT proteomes in D. simulans and D. mauritiana virgin females express unique combinations of secreted proteins and are enriched for distinct functional categories, (2) mating induces substantial changes to the FRT proteome in D. mauritiana but not in D. simulans, and (3) the D. simulans FRT proteome exhibits limited postmating changes irrespective of whether females mate with conspecific or heterospecific males, suggesting an active female role in mediating reproductive interactions. Our study suggests that divergence in the FRT extracellular environment and postmating response contribute to previously described patterns of postmating-prezygotic isolation and the maintenance of species boundaries.
Project description:Gene-expression divergence between species shapes morphological evolution, but the molecular basis is largely unknown. Here we show cis- and trans-regulatory elements and chromatin modifications on gene-expression diversity in genetically tractable Arabidopsis allotetraploids. In Arabidopsis thaliana and Arabidopsis arenosa, both cis and trans with predominant cis-regulatory effects mediate gene-expression divergence. The majority of genes with both cis- and trans-effects are subjected to compensating interactions and stabilizing selection. Interestingly, chromatin modifications correlate with cis - and trans -regulation. In F1 allotetraploids, Arabidopsis arenosa trans factors predominately affect allelic expression divergence. Arabidopsis arenosa trans factors tend to upregulate Arabidopsis thaliana alleles, whereas Arabidopsis thaliana trans factors up- or down-regulate Arabidopsis arenosa alleles. In resynthesized and natural allotetraploids, trans effects drive expression of both homoeologous loci into the same direction. We provide evidence for natural selection and chromatin regulation in shaping gene-expression diversity during plant evolution and speciation. Examination of gene expression in 5 tetraploid Arabidopsis using mRNA-seq
Project description:Hybrid seed lethality as a consequence of interspecies or interploidy hybridizations is a major mechanism of reproductive isolation in plants. This mechanism is manifested in the endosperm, a dosage sensitive tissue supporting embryo growth. Deregulated expression of imprinted genes like ADMETOS (ADM) underpin the interploidy hybridization barrier in Arabidopsis thaliana, however, the mechanisms of their action remained unknown. In this study we show that ADM interacts with the AT-hook domain protein AHL10 and the SET domain-containing SU(VAR)3-9 homolog SUVH9 and ectopically recruits the heterochromatic mark H3K9me2 to AT-rich transposable elements (TEs), causing deregulated expression of neighboring genes. Several hybrid incompatibility genes identified in Drosophila encode for heterochromatin-interacting proteins, which has led to the suggestion that hybrid incompatibilities evolve as consequence of interspecies divergence of selfish DNA elements and their regulation. Our data showing that imbalance of dosage-sensitive chromatin regulators underpins hybrid incompatibility in Arabidopsis strongly support this view, demonstrating that reproductive isolation as a consequence of epigenetic regulation of TEs is a conserved feature in animals and plants.
Project description:Species-specific regulation of gene expression contributes to the development and maintenance of reproductive isolation and to species differences in ecologically important traits. A better understanding of the evolutionary forces which shape regulatory variation and divergence can be developed by comparing expression differences among species and interspecific hybrids. Once expression differences are identified, the underlying genetics of regulatory variation or divergence can be explored. With the goal of associating cis and/or trans components of regulatory divergence with differences in gene expression, overall and allele-specific expression levels were assayed genome-wide in female adult heads of D. melanogaster, D. simulans and their F1 hybrids. A greater proportion of cis differences than trans differences were identified for genes expressed in heads and, in accordance with previous studies, cis differences also explained a larger number of species differences in overall expression level. Regulatory divergence was found to be prevalent among genes associated with defense, olfaction, and among genes downstream of the Drosophila sex determination hierarchy. In addition, two genes, with critical roles in sex determination and micro RNA processing, Sxl and loqs, were identified as misexpressed in hybrid female heads, potentially contributing to hybrid incompatibility.
Project description:Both cis- and trans-acting changes could accumulate and participate in complex interactions, so to isolate the cis-regulatory component of patterning evolution, we measured allele-specific spatial gene expression patterns in Drosophila melanogaster × D. simulans hybrid embryos. RNA-seq of cryosectioned slices revealed 55 genes with strong spatially-varying allele-specific expression, and several hundred more with weaker but significant spatial divergence. Combined with mathematical modeling and regulatory locus editing, we determine the SNP responsible for the allele-specific expression observed in the gene hunchback.
Project description:Gene-expression divergence between species shapes morphological evolution, but the molecular basis is largely unknown. Here we show cis- and trans-regulatory elements and chromatin modifications on gene-expression diversity in genetically tractable Arabidopsis allotetraploids. In Arabidopsis thaliana and Arabidopsis arenosa, both cis and trans with predominant cis-regulatory effects mediate gene-expression divergence. The majority of genes with both cis- and trans-effects are subjected to compensating interactions and stabilizing selection. Interestingly, chromatin modifications correlate with cis - and trans -regulation. In F1 allotetraploids, Arabidopsis arenosa trans factors predominately affect allelic expression divergence. Arabidopsis arenosa trans factors tend to upregulate Arabidopsis thaliana alleles, whereas Arabidopsis thaliana trans factors up- or down-regulate Arabidopsis arenosa alleles. In resynthesized and natural allotetraploids, trans effects drive expression of both homoeologous loci into the same direction. We provide evidence for natural selection and chromatin regulation in shaping gene-expression diversity during plant evolution and speciation.