Project description:Wolbachia pipientis is a worldwide bacterial parasite of arthropods that infects host germline cells and manipulates host reproduction to increase the ratio of infected females, the transmitting sex of the bacteria. The most common reproductive manipulation, cytoplasmic incompatibility (CI), is expressed as embryonic death in crosses between infected males and uninfected females. Specifically, Wolbachia modify developing sperm in the testes by unknown means to cause a post-fertilization disruption of the sperm chromatin that incapacitates the first mitosis of the embryo. As these Wolbachia-induced changes are stable, reversible, and affect the host cell cycle machinery including DNA replication and chromosome segregation, we hypothesized that the host methylation pathway is targeted for modulation during cytoplasmic incompatibility because it accounts for all of these traits. Here we show that infection of the testes is associated with a 55% increase of host DNA methylation in Drosophila melanogaster, but methylation of the paternal genome does not correlate with penetrance of CI. Overexpression and knock out of the Drosophila DNA methyltransferase Dnmt2 neither induces nor increases cytoplasmic incompatibility. Instead, overexpression decreases Wolbachia titers in host testes by approximately 17%, leading to a similar reduction in CI levels. Finally, strength of CI induced by several different strains of Wolbachia does not correlate with levels of DNA methylation in the host testes. We conclude that DNA methylation mediated by Drosophila's only known methyltransferase is not required for the transgenerational sperm modification that causes CI. Genomic DNA was extracted from pooled samples of Drosophila melanogaster adult testes. One sample from Wolbachia-infected males and one from uninfected males. Bisulfite sequencing was used to determine whether Wolbachia infection affects host DNA methylation in the testes.
Project description:Wolbachia pipientis is a worldwide bacterial parasite of arthropods that infects host germline cells and manipulates host reproduction to increase the ratio of infected females, the transmitting sex of the bacteria. The most common reproductive manipulation, cytoplasmic incompatibility (CI), is expressed as embryonic death in crosses between infected males and uninfected females. Specifically, Wolbachia modify developing sperm in the testes by unknown means to cause a post-fertilization disruption of the sperm chromatin that incapacitates the first mitosis of the embryo. As these Wolbachia-induced changes are stable, reversible, and affect the host cell cycle machinery including DNA replication and chromosome segregation, we hypothesized that the host methylation pathway is targeted for modulation during cytoplasmic incompatibility because it accounts for all of these traits. Here we show that infection of the testes is associated with a 55% increase of host DNA methylation in Drosophila melanogaster, but methylation of the paternal genome does not correlate with penetrance of CI. Overexpression and knock out of the Drosophila DNA methyltransferase Dnmt2 neither induces nor increases cytoplasmic incompatibility. Instead, overexpression decreases Wolbachia titers in host testes by approximately 17%, leading to a similar reduction in CI levels. Finally, strength of CI induced by several different strains of Wolbachia does not correlate with levels of DNA methylation in the host testes. We conclude that DNA methylation mediated by Drosophila's only known methyltransferase is not required for the transgenerational sperm modification that causes CI.
Project description:We report the transcriptional response to Colorado potato beetle herbivory in leaves of the highly beetle resistant Solanum chacoense diploid line USDA8380-1 (80-) and a susceptible F2 individual (EE501F2_093) derived from a cross between 80-1 and a beetle susceptible line S. chacoense M6. Sampling tissue in a time course during adult Colorado potato beetle feeding provides novel insight to the transcriptomic defense response to this important pest.
Project description:Drosophila larvae and adults possess a potent innate immune response, but the response of their eggs is particularly poor. Here we show that eggs of the beetle Tribolium castaneum, in contrast, possess a full range of immune defence mechanisms, based on complete transcriptome comparisons of naïve, sterilely injured, and bacterially challenged eggs. Upon infection, we find massive upregulation of AMPs and differential regulation of 375 other genes including both IMD and Toll signalling components. Importantly, we show that this extensive response depends on the serosa, an extraembryonic epithelium enveloping yolk and embryo. When we delete the serosa using Tc-zen1 RNAi, none of the AMPs and merely 57 other genes are differentially regulated upon infection. Furthermore, unchallenged eggs reveal serosa-biased expression of several bacterial recognition genes. Thus, the serosa is an immune competent frontier epithelium, and its loss in higher flies might account for the poor immune response of Drosophila eggs.