Project description:A new online resource (flyatlas.org) provides the most comprehensive view yet of expression in multiple tissues of Drosophila. Meta-analysis of the data reveals that a significant fraction ofthe genome is expressed with great tissue specificity in the adult, demonstrating the need for the functional genomic community to embrace a wider range of functional phenotypes. Well-known developmental genes are often re-used in surprising tissues in the adult, suggesting new functions. The homologues of many human genetic disease loci show selective expression in Drosophila tissues with function analogous to the affected tissues in the cognate human disease, providing a useful filter for potential candidate genes. Experiment Overall Design: FlyAtlas is composed of data covering 8 distinct adult tissues (brain, head, midgut, Malpighian tubules,hindgut, testis, ovary, male accessory glands) so far, together with two larval tissues (tubule, fat body), each run with 4 replicates on Affymetrix Dros Genome 2 chips (with probesets for 18770 transcripts), and compared with a matched whole-fly sample.
Project description:Phenotypic evolution can result from gains and losses of genes, mutations in coding sequences, or regulatory mutations affecting gene expression. While the relative importance of these mechanisms is debated, regulatory evolution is recognized as a key driver of phenotypic diversity. In this study, we applied a phylogenetic model to discretized gene expression states (active or inactive) to investigate the evolutionary turnover of organ-specific transcriptomes, which we define as instances where gene expression is activated or deactivated in a particular organ. We focus on transcriptome turnover in two male reproductive organs in 11 species of the Drosophila melanogaster species group. Using the Bayesian inference method zigzag (Thompson et al. 2020), we estimate that testes express a higher proportion of the genome (65--75% of genes, depending on the species) compared to accessory glands (46--64%), with background expression noise producing less than 1% of transcripts in both organs. We find that many conserved genes have gained or lost expression in testes and accessory glands. Our model of joint transcriptome evolution, applied to 8,660 genes conserved as single copy families in all species (singleton genes), revealed similar turnover rates but distinct evolutionary trajectories in the two organs. We estimate that the genes in our data set transition between active and inactive expression states at rates on the order of 10^-9 yr^-1. The two organs experienced accelerated transcriptome turnover on different branches of the Drosophila phylogeny. The accessory glands exhibit greater variation in turnover rates among lineages, suggesting a lower baseline rate with bursts of rapid evolution in a subset of branches on the phylogeny. We do not observe significant differences in turnover rates between X-linked and autosomal genes. Genes that encode transcription factors transition between active and inactive states slower than non-TF genes in the accessory gland, but slightly faster in the testis. The results are robust to the choice of probability cut-offs used to discretize gene expression states, and there is good agreement between the estimates of expression states from zigzag and the inferences from the phylogenetic model. Overall, our study highlights the complex dynamics of transcriptome evolution in male reproductive organs. We discuss the benefits and challenges associated with investigating the evolution of gene expression as a binary trait and suggest potentially fruitful avenues for further methodological development.
Project description:Recent studies have revealed key roles of non-coding RNAs in sex-related pathways, but little is known about the evolutionary forces acting on these non-coding RNAs. We used whole-genome tiling arrays to profile the transcriptome of Drosophila melanogaster tissues and found that 15% of male-biased transcribed fragments (transfrags) are intergenic non-coding RNAs (incRNAs), suggesting a potentially important role for incRNAs in sex-related biological processes. Statistical analysis revealed a paucity of male-biased incRNAs and coding genes on the X chromosome, suggesting that similar evolutionary forces could be affecting the genomic organization of both coding and non-coding genes. Expression profiling across germline and somatic tissues further suggests that both male meiotic sex chromosome inactivation (MSCI) and sexual antagonism contribute to the chromosomal distribution of male-biased incRNAs. Comparative sequence analysis shows that the evolutionary age of male-biased incRNAs is a significant predictor of their chromosomal locations. In addition to identifying abundant sex-biased incRNAs in fly genome, our work unveils a global picture of the complex interplay between non-coding RNAs and sexual chromosome evolution. We used whole-genome tiling arrays to assess sex-biased transcription in D. melanogaster adult whole bodies, and testis, ovary, and accessory gland samples. Gut and thorax, tissues expected to exhibit little or no sex-biased expression, were included as controls. Expression was measured in 2-4 replicates for each tissue.
Project description:We designed this experiment to investigate the transcriptional changes in gonads as a result of sex transformation. Here we performed transcriptional profiling of the ovary transformed into testis from the tra loss of function (XX_tra_lof), testis transformed into ovary from the tra gain of function (XY_tra_gof) and ovary transformed into testis in dsxM gain of function (XX_DsxM_gof/lof) Drosophila melanogaster third instar larvae in biological quadruplicates. In addition, as controls we sequenced ovaries and testes from the female and male wildtype larvae respectively. We constructed polyA+ libraries of the gonads, cleaned off the fatbody and performed 50 bp, stranded single-end RNA-Seq.
Project description:Purpose: Accurate identification of sex-biased genes requires precise measurement of gene expression levels in gonads. This study is designed to provide such data for various Drosophila species to enhance studies of sex-biased gene expression and evolution across the genus. Methods: Virgin flies were collected and aged 6-10 days before dissecting 2-3 replicates of testes or ovaries. Total RNA was extracted using the Arcturus® PicoPure® kit . Illumina® TruSeq® RNA library kits were used to poly-A+ select and reverse-transcribe mRNA, shear cDNA into ~120 bp fragments, and produce libraries for 1x50 bp sequencing on an Illumina GAIIx or HiSeq2000. Illumina®’s Real Time Analysis v1.13 module processed images, called bases, and provided base qualities. Reads were mapped to the current reference genomes using Bowtie v2.1.0 (Langmead and Salzberg, 2012, Nat Meth) with default settings. Differentially expressed genes were detected using Cufflinks v 2.1.0 (Trapnell et al., 2010, Nat Biotech; default settings) or edgeR (Robinson et al., 2010, Bioinformatics; full-quantile GC-content normalization and full-quantile between-sample normalization). Genes were called differentially expressed at a Benjamini-Hochberg false discovery rate of 0.01. Results: Thousands of male- and female-biased genes were detected for each species using both DE detection methods. These results provide a significant improvement in sensitivity of sex-biased gene detection relative to using whole-body RNA-sequencing data. These data provide a foundation for accurate identification of sex-biased genes throughout the Drosophila genus. Testis and ovary samples from Drosophila species were sequenced 1 x 50 bp in duplicate from 6-10 day old virgin, Wolbachia-free adult flies on an Illumina GAIIx or HiSeq2000.
Project description:Data from whole-body, head, thorax, abdomen, ovaries, testes and accessory glands was used to assess possible causes of a non-random distribution of sex-biased genes (sexually dimorphic expression). All samples were derived from virgin adult flies. We measured gene expression of male and female Drosophila serrata from 43 lines (whole-body) and multiple tissues sampled from outbred laboratory stock. All flies were originally samples from Brisbane, Queensland, Australia. Data from two replicates for each sex/line are presented, plus 3-5 replicates per sex/tissue. 24 adult whole-body samples were not used in analyses due to poor quality, giving a total of 176 arrays.