Project description:Despite being essential for fertility, genome defence pathway genes often evolve rapidly. However, little is known about the molecular basis of this adaptation. Here, we characterize the evolution of a protein interaction network within the PIWI-interacting small RNA (piRNA) genome defence pathway in Drosophila at unprecedented scale and evolutionary resolution. We uncover pervasive rapid evolution of a protein interaction network anchored at the Heterochromatin Protein 1 (HP1) paralog Rhino. Using complementary phylogenetic analysis, high-throughput yeast-two-hybrid matrix screening, and in vivo interaction analyses in cross-species transgenic flies, we characterized at least three distinct evolutionary protein interaction trajectories across ~40 million years of Drosophila evolution. The comprehensive cross-species interaction data set covering 11 piRNA pathway proteins of five Drosophila species revealed several protein interactions that are fully conserved, indicating functional conservation despite overall rapid amino acid sequence change. Other interactions are preserved through co-evolution and were detected only between proteins in closely related and within species. We also identified sets of species-restricted protein interactions which, through rewiring of a Rhino-anchored transcription factor network, may preserve critical roles in enabling and adapting piRNA production from heterochromatic loci. In sum, our analyses dissected principles of interaction evolution in an adaptively evolving protein-protein interaction network uncovering evolutionary and functional insight into germline piRNA production across Drosophila species. Our work provides key experimental evidence in support of a fundamental model proposing that intermolecular interaction innovation is a major molecular mechanism of evolutionary adaptation in protein-coding genes.
Project description:Ribosomes can read through stop codons in a regulated manner, elongating rather than terminating the nascent peptide. Stop codon readthrough is essential to diverse viruses, and phylogenetically predicted to occur in a few hundred genes in Drosophila melanogaster, but the importance of regulated readthrough in eukaryotes remains largely unexplored. Here, we present a ribosome profiling assay (deep sequencing of ribosome-protected mRNA fragments) for Drosophila melanogaster, and provide the first genome-wide experimental analysis of readthrough. Readthrough is far more pervasive than expected: the vast majority of readthrough events evolved within D. melanogaster and were not predicted phylogenetically. The resulting C-terminal protein extensions show evidence of selection, contain functional subcellular localization signals, and their readthrough is regulated, arguing for their importance. We further demonstrate that readthrough occurs in yeast and humans. Readthrough thus provides general mechanisms both to regulate gene expression and function, and to add plasticity to the proteome during evolution. 12 samples of Drosophila ribosome profiling and poly(A)+ mRNA-seq, including technical replicates in S2 cells, and biological replicates of 0-2 hour embryos
Project description:Sexually dimorphic traits are subject to diversifying selection. Also genes with a male biased gene expression are probably affected by sexual selection and have a high rate of protein evolution. We used SAGE to measure sex biased gene expression in Drosophila pseudoobscura. Consistent with previous results from D. melanogaster, a larger number of genes were male biased (402 genes) than female biased (138 genes). About 34% of the genes changed the sex related expression pattern between D. melanogaster and D. pseudoobscura. Combining gene expression with protein divergence between both species, we observed a striking difference in rate of evolution for genes with a male biased gene expression in one species only. Contrary to expectations, D. pseudoobscura genes in this category showed no accelerated rate of protein evolution, while D. melanogaster genes did. If sexual selection is driving molecular evolution of male biased genes, our data imply a radically different selection regime in D. pseudoobscura. Keywords: SAGE
Project description:Ribosomes can read through stop codons in a regulated manner, elongating rather than terminating the nascent peptide. Stop codon readthrough is essential to diverse viruses, and phylogenetically predicted to occur in a few hundred genes in Drosophila melanogaster, but the importance of regulated readthrough in eukaryotes remains largely unexplored. Here, we present a ribosome profiling assay (deep sequencing of ribosome-protected mRNA fragments) for Drosophila melanogaster, and provide the first genome-wide experimental analysis of readthrough. Readthrough is far more pervasive than expected: the vast majority of readthrough events evolved within D. melanogaster and were not predicted phylogenetically. The resulting C-terminal protein extensions show evidence of selection, contain functional subcellular localization signals, and their readthrough is regulated, arguing for their importance. We further demonstrate that readthrough occurs in yeast and humans. Readthrough thus provides general mechanisms both to regulate gene expression and function, and to add plasticity to the proteome during evolution.
Project description:FAR-RED ELONGATED HYPOCOTYL 3 (FHY3) and its homolog FAR-RED IMPAIRED RESPONSE 1 (FAR1) are two transposase-derived transcription factors initially identified as the key components in phytochrome A signaling and recently shown to function in the circadian clock. However, whether FHY3 and FAR1 are involved in other processes of plant development remains largely unknown. Here, we explored chromatin immunoprecipitation-based sequencing (ChIP-seq) analysis to identify 1745 and 1171 FHY3 direct binding target genes in darkness and far-red light conditions, respectively in the Arabidopsis thaliana genome. This analysis revealed that FHY3 preferentially binds to the gene promoters through the previously identified typical FHY3/FAR1 binding motif. Interestingly, FHY3 also binds to two novel motifs in the 178-bp repeats of the Arabidopsis centromere regions in vivo. Comparison between the ChIP-seq and microarray data indicates that FHY3 regulates the expression of 196 and 85 genes in dark and far-red respectively by directly binding to their promoters. FHY3 also co-regulates a number of common target genes with PHYTOCHROME INTERACTING FACTOR 3-LIKE 5 (PIL5) and ELONGATED HYPOCOTYL 5 (HY5). Moreover, our genome-wide identification of FHY3 direct target genes ultimately led to the discovery and validation of a new role of FHY3 in controlling chloroplast development, by directly activating the expression of ACCUMULATION AND REPLICATION OF CHLOROPLASTS5 (ARC5), a key gene regulating chloroplast constriction and division. Taken together, our data suggest that FHY3 is involved in regulating multiple facets of plant development, thus providing new insights into the functions of this type of transposase-derived transcription factors.
Project description:MicroRNAs (miRNAs) are small, endogenously expressed RNAs that regulate mRNAs post-transcriptionally. The class of miRNA genes, like other gene classes, should experience birth, death and persistence of its members. We carried out deep sequencing of miRNAs from three species of Drosophila, and obtained 107,000 sequences that map to no fewer than 300 loci that were not previously known. We observe a large class of miRNA genes that are evolutionarily young, with a rate of birth of 12 new genes per million years (Myr). Most of these new miRNAs originated from non-miRNA sequences. Among the new genes, we estimate that 96% disappeared quickly in the course of evolution; only 4% of new miRNA genes were retained by natural selection. Furthermore, only 60% of these retained genes became integrated into the transcriptome in the long run (60 Myr). This small fraction (2.5%) of surviving miRNAs may later on become moderately or highly expressed. Our results suggest that there is a high birth rate of new miRNA genes, accompanied by a comparably high death rate. The estimated net gain of long-lived miRNA genes, which is not strongly affected by either the depth or the breadth (number of tissues) of sequencing, is 0.3 genes per Myr in Drosophila Keywords: 454 microRNA deep sequencing
Project description:Sexually dimorphic traits are subject to diversifying selection. Also genes with a male biased gene expression are probably affected by sexual selection and have a high rate of protein evolution. We used SAGE to measure sex biased gene expression in Drosophila pseudoobscura. Consistent with previous results from D. melanogaster, a larger number of genes were male biased (402 genes) than female biased (138 genes). About 34% of the genes changed the sex related expression pattern between D. melanogaster and D. pseudoobscura. Combining gene expression with protein divergence between both species, we observed a striking difference in rate of evolution for genes with a male biased gene expression in one species only. Contrary to expectations, D. pseudoobscura genes in this category showed no accelerated rate of protein evolution, while D. melanogaster genes did. If sexual selection is driving molecular evolution of male biased genes, our data imply a radically different selection regime in D. pseudoobscura. Keywords: SAGE Male and female SAGE libraries of D. pseudoobscura were developed for analyzing the gene expression pattern.
Project description:Genes with sex-biased expression often show rapid molecular evolution between species. Previous population genetic and comparative genomic studies of Drosophila melanogaster and D. simulans revealed that male-biased genes have especially high rates of adaptive evolution. To test if this is also the case for other lineages within the melanogaster group, we investigated gene expression in D. ananassae, a species that occurs in structured populations in tropical and subtropical regions. We used custom-made microarrays and published microarray data to characterize the sex-biased expression of 129 D. ananassae genes whose D. melanogaster orthologs had been classified previously as male-biased, female-biased, or unbiased in their expression and had been studied extensively at the population-genetic level.
Project description:Differences in the selective pressures experienced by males and females are believed to be ubiquitous in dioecious organisms and are expected to result in the evolution of sexually antagonistic alleles, thereby driving the evolution of sexual dimorphism. Negative genetic correlation for fitness between the sexes has been documented, however, the identity, number and location of loci causing this relationship are unknown. Here we show that a large proportion of Drosophila melanogaster transcripts are associated with the interaction between genomic haplotype and gender and that at least 8% of loci in the fly genome are currently evolving under sexually antagonistic selection.