Project description:Background: Differences in levels of gene expression among individuals are an important source of phenotypic variation within populations. Recent microarray studies have revealed that expression variation is abundant in many species, including Drosophila melanogaster. However, previous expression surveys in this species generally focused on a small number of laboratory strains established from derived populations. Thus, these studies were not ideal for population genetic analyses. Results: We surveyed gene expression variation in adult males of 16 D. melanogaster strains from two natural populations, including an ancestral African population and a derived European population. Levels of expression polymorphism were nearly equal in the two populations, but a higher number of differences was detected when comparing strains between populations. Expression variation was greatest for genes associated with few molecular functions or biological processes, as well as those expressed predominantly in males. Our analysis also identified genes that differed in expression level between the European and African populations, which may be candidates for adaptive regulatory evolution. Genes involved in flight musculature and fatty acid metabolism were over-represented in the list of candidates. Conclusions: Overall, stabilizing selection appears to be the major force governing gene expression variation within populations. However, positive selection may be responsible for much of the between-population expression divergence. The nature of the genes identified to differ in expression between populations may reveal which traits were important for local adaptation to the European and African environments. Keywords: Natural variation
Project description:Background: Differences in levels of gene expression among individuals are an important source of phenotypic variation within populations. Recent microarray studies have revealed that expression variation is abundant in many species, including Drosophila melanogaster. However, previous expression surveys in this species generally focused on a small number of laboratory strains established from derived populations. Thus, these studies were not ideal for population genetic analyses. Results: We surveyed gene expression variation in adult males of 16 D. melanogaster strains from two natural populations, including an ancestral African population and a derived European population. Levels of expression polymorphism were nearly equal in the two populations, but a higher number of differences was detected when comparing strains between populations. Expression variation was greatest for genes associated with few molecular functions or biological processes, as well as those expressed predominantly in males. Our analysis also identified genes that differed in expression level between the European and African populations, which may be candidates for adaptive regulatory evolution. Genes involved in flight musculature and fatty acid metabolism were over-represented in the list of candidates. Conclusions: Overall, stabilizing selection appears to be the major force governing gene expression variation within populations. However, positive selection may be responsible for much of the between-population expression divergence. The nature of the genes identified to differ in expression between populations may reveal which traits were important for local adaptation to the European and African environments. We used dual channel microarrays to compare genome-wide expression profiles in adult males from 16 inbred strains derived from two natural populations. In total 80 hybidizations were performed including dye-swaps. The hybridization scheme consisted of a balanced loop design, which allowed an unbiased comparison of relative expression levels within and between populations.
Project description:We used RNA-seq to examine coding and non-coding gene expression variation in the larval fat body of an ancestral African and a derived European Drosophila melanogaster population across three developmental stages spanning ten hours of larval development.
Project description:Background: Changes in gene regulation are thought to be crucial for the adaptation of organisms to their environment. Transcriptome analyses can be used to identify candidate genes for ecological adaptation, but can be complicated by variation in gene expression between tissues, sexes, or individuals. Here we use high-throughput RNA sequencing of a single Drosophila melanogaster tissue to detect brain-specific differences in gene expression between the sexes and between two populations, one from the ancestral species range in sub-Saharan Africa and one from the recently colonized species range in Europe. Results: Relatively few genes (<100) displayed sexually dimorphic expression in the brain, but there was an enrichment of sex-biased genes, especially male-biased genes, on the X chromosome. Over 340 genes differed in brain expression between flies from the African and European populations, with the between-population divergence being highly correlated between males and females. The differentially expressed genes include those involved in stress response, olfaction, and detoxification. Expression differences were associated with transposable element insertions at two genes implicated in insecticide resistance (Cyp6g1 and CHKov1). Conclusions: Analysis of the brain transcriptome revealed many genes differing in expression between populations that were not detected in previous studies using whole flies. There was little evidence for sex-specific regulatory adaptation in the brain, as most expression differences between populations were observed in both males and females. The enrichment of genes with sexually dimorphic expression on the X chromosome is consistent with dosage compensation mechanisms affecting sex-biased expression in somatic tissues. mRNA profiles of Drosophila melanogaster brains from adult males and females from a European and an African population (2 biological replicates each)
Project description:To investigate the effect of sex on within- and between-population variation in gene expression, we performed a microarray analysis of adult females from 16 strains of Drosophila melanogaster, including eight strains from the putative ancestral range in sub-Saharan Africa and eight strains from a European population. The results were compared to those of a previous study of adult male gene expression variation among the same strains (GSE8843).
Project description:We used RNA-seq to investigate gene expression variation in Malpighian tubules, which have a function analogous to that of human kidneys. In order to characterize population differentiation, we sequenced the Malpighian tubule transcriptomes of flies derived from two populations, one from sub-Saharan Africa (Zimbabwe) and one from Europe (the Netherlands). Males and females were examined separately. Overall, we found a high amount of differential expression between sexes (2,308 genes) and populations (2,474 genes). Although most of the differentially expressed genes were consistent between sexes and populations, there were 615 genes showed sex-biased expression in only one population and 557 genes showed population-biased expression in only one sex. mRNA expression profiles of Drosophila melanogaster Malpighian tubules from adult males and females from a European and an African population (2 biological replicates per sex and population)
Project description:We used RNA-seq in a derived European Drosophila melanogaster population from Germany (MU) to examine coding gene expression variation in the larval fat body during the late wandering third instar stage.