Project description:Bacterial and fungal infections induce a potent immune response in Drosophila melanogaster, but it is unclear whether viral infections induce a similar immune response. Using microarrays, we examined the changes in gene expression in Drosophila that occur in response to infection with the sigma virus, a negative-stranded RNA virus (Rhabdoviridae) that occurs in wild populations of D. melanogaster. We detected many changes in gene expression in infected flies, but found no evidence for the activation of the Toll, IMD or Jak-STAT pathways, which control immune responses against other pathogens. We identified a number of functional categories of genes, including serine proteases, ribosomal proteins and chorion proteins that were overrepresented among the differentially expressed genes. We also found that the sigma virus alters the expression of many more genes in males than in females. In contrast to previous results, our data suggest that either Drosophila do not mount an immune response against the sigma virus, or that the immune response is not controlled by known immune pathways. The genes which we identified as differentially expressed after infection are promising candidates for controlling the host’s response to the sigma virus.
Project description:Sigma factors are master regulators of bacterial transcription which direct gene expression of specific subsets of genes. In particular, alternative sigma factors are well-known to be key players of bacterial adaptation to changing environments. To elucidate the regulatory network of sigma factors in P. aeruginosa, an integrative approach including sigma factor-dependent mRNA profiling was performed to define the primary regulon of each sigma factor. Sigma factor hyper-expressing strains harboring the sigma factor gene in trans under control of the araBAD promoter and sigma factor deletion mutants were constructed. Under optimal conditions regarding sigma factor activity and optional induction of sigma factor expression, bacteria were harvested and total RNA was extracted. Upon mRNA enrichment, RNA was fragmented and ligated to specific RNA-adapters containing a hexameric barcode sequence for multiplexing. These RNA-libraries were reverse transcribed and amplified resulting in cDNA libraries which were sequenced on Illumina platforms. Sequence reads were separated according to their barcodes and barcode sequences were removed. The short reads were mapped to the genome sequence of the reference strain P. aeruginosa PA14 wild-type using stampy with default settings. The R package DESeq was used for differential gene expression analysis.