Project description:High-throughput sequencing of Drosophila pseudoobscura and Drosophila simulans small RNAs. ~18-26nt RNAs were isolated from total RNA using PAGE, ligation to adapters requires 5' monophosphate and 3' OH.
Project description:Multicellular development is largely determined by transcriptional regulatory programs that orchestrate the expression of thousands of protein-coding and noncoding genes. To decipher the genomic regulatory code that specifies these programs, and to investigate globally the developmental relevance of noncoding transcription, we profiled genome-wide promoter activity throughout embryonic development in 5 Drosophila species. We show that core promoters, generally not thought to play a significant regulatory role, in fact impart broad restrictions on the developmental timing of gene expression on a genome-wide scale. We propose a hierarchical model of transcriptional regulation during development in which core promoters define broad windows of opportunity for expression, by defining a limited range of transcription factors from which they are able to receive regulatory inputs. This two-tiered mechanism globally orchestrates developmental gene expression, including noncoding transcription on a scale that defies our current understanding of ontogenesis. Indeed, noncoding transcripts are far more prevalent than ever reported before, with ~4,000 long noncoding RNAs expressed during embryogenesis. Over 1,500 are functionally conserved throughout the melanogaster subgroup, and hundreds are under strong purifying selection. Overall, this work introduces a hierarchical model for the developmental regulation of transcription, and reveals the central role of noncoding transcription in animal development.
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
