Project description:Species of the genus Drosophila have served as favorite models in speciation studies, however genetic factors of the interspecific hybrid sterility are underinvestigated to date. Here we performed the analysis of reproductive incompatibilities of hybrid females in crossing Drosophila melanogaster females and Drosophila simulans males. Using transcriptomic data analysis, molecular, cellular and genetic approaches we analyzed differential gene expression, transposable element (TE) activity, piRNA biogenesis and functional defects of oogenesis in hybrids. A premature GSC loss was a most prominent defect of oogenesis in hybrid ovaries. Owing differential expression of genes encoding components of the piRNA pathway rhino and deadlock, functional RDCmel complex in hybrid ovaries was not assembled. At the same time the activity of RDCsim complex was maintained in hybrids, independently from the genomic origin of piRNA clusters. Despite identification of a cohort of overexpressed TEs in hybrid ovaries we found no evidences that their activity can be considered as the main cause of hybrid sterility. We revealed complex pattern of Vasa protein expression in hybrid germline, including partial AT-chX piRNA targeting of vasasim allele and significant developmental delay of vasamel expression. We came to the conclusions that complex multi-locus genetic changes between the species were responsible for hybrid sterility phenotype.
Project description:Space travel presents unlimited opportunities for exploration and discovery, but requires a more complete understanding of the immunological consequences of long-term exposure to the conditions of spaceflight. To understand these consequences better and to contribute to design of effective countermeasures, we used the Drosophila model to compare innate immune responses to bacteria and fungi in flies that were either raised on earth or in outer space aboard the NASA Space Shuttle Discovery (STS-121). Microarrays were used to characterize changes in gene expression that occur in response to infection by bacteria and fungus in drosophila that were either hatched and raised in outer space (microgravity) or on earth (normal gravity).
Project description:Species of the genus Drosophila have served as favorite models in speciation studies, however genetic factors of the interspecific hybrid sterility are underinvestigated to date. Here we performed the analysis of reproductive incompatibilities of hybrid females in crossing Drosophila melanogaster females and Drosophila simulans males. Using transcriptomic data analysis, molecular, cellular and genetic approaches we analyzed differential gene expression, transposable element (TE) activity, piRNA biogenesis and functional defects of oogenesis in hybrids. A premature GSC loss was a most prominent defect of oogenesis in hybrid ovaries. Owing differential expression of genes encoding components of the piRNA pathway rhino and deadlock, functional RDCmel complex in hybrid ovaries was not assembled. At the same time the activity of RDCsim complex was maintained in hybrids, independently from the genomic origin of piRNA clusters. Despite identification of a cohort of overexpressed TEs in hybrid ovaries we found no evidences that their activity can be considered as the main cause of hybrid sterility. We revealed complex pattern of Vasa protein expression in hybrid germline, including partial AT-chX piRNA targeting of vasasim allele and significant developmental delay of vasamel expression. We came to the conclusions that complex multi-locus genetic changes between the species were responsible for hybrid sterility phenotype.
Project description:In many metazons, such as humans and Drosophila, homeodomain proteins comprise the second largest family of sequence specific transcription factors. In Drosophila, homeodomains play an important role in development. Many homeodomain proteins display a high level of homology across metazons, presumably due to importance of their functional roles. We comprehensively characterized the DNA binding preferences of all 84 Drosophila homeodomain transcription factors which contain a single DNA binding domain. Previously, we employed a bacterial one hybrid (B1H) assay to select for 20 to 40 high affinity transcription factor binding sites [Noyes et al. (2008). Cell. 133(7):1277-1289]. In this system, E. coli are transfected with two plasmids. One plasmid encodes the DNA binding domain of a homeodomain fused to two zinc finger domains and the omega subunit of RNAP. The other plasmid is drawn from a library of prey plasmids which contain a 10bp randomized transcription factor binding site (TFBS) region in the promoter of the reporter gene His3. The E. coli strain used is a His3 homolog and omega subunit knock out strain. If a transcription factor has high affinity for a TFBS, more His3 will be produced, leading to the production of more histidine and an increase in the growth rate. If the transcription factor does not bind with sufficient affinity to the TFBS, little or no histidine will be produced resulting in little or no growth. The stringency of the B1H system can be tuned using the chemicals IPTG and 3-AT. IPTG induces production of the chimeric transcription factor, and 3-AT is a competitive inhibitor of the enzyme encoded by His3. One of the advantages of the B1H system is that the transcription factor does not have to be purified and that many experiments can be easily conducted in parallel. In this study, in stead of picking 20 to 40 colonies and sequencing their TFBSs, we used high-throughput Illumina sequencing to sequence the selected sites of all of the colonies growing on a plate. This provided quantitative data regarding the growth rate of cells possessing each selected TFBS variant, which is a function of the affinity of the transcription factor for the binding site. With this quantitative data, we can build more accurate models of transcription factor binding. All 84 of the Drosophila homeodomain proteins that contain a single DNA binding domain were analyzed using the B1H assay. The same selection stringency was used for all experiments (10uM IPTG and 5mM 3-AT). All experiments were run for 36 to 48 hours. 10 mutants were also assayed: 3 Caup, 3 Bcd and 4 En mutants. The bait plasmid omegaUV2zf was used in all but 3 cases. In this instances, a slightly different bait plasmid, omegaUV5zf, with a stronger promoter was used. Thirty different replicates were performed in order to insure that sufficient number of reads were obtained for each protein. In total, 126 experiments were performed.