Drosophila embryos as a Model System to Study Bacterial Infection In Vivo

  • Kiri Tan

Student thesis: Doctoral ThesisPhD

Abstract

The fruit fly Drosophila melanogaster is recognised as the most widely established genetic model of immunity of the contemporary scientific era, exhibiting a high degree of conservation between Drosophila and mammalian innate immunity genes. However, whilst the majority of Drosophila immunity studies have previously been performed in adults and larvae, the embryo has recently emerged as a potentially viable model system; aiding in vivo studies and providing a more amendable system to undertake live imaging, hence evading many of the caveats associated with current immunity models. This project aimed to further develop the Drosophila embryo as a more potent and insightful immunity model, focusing on the immune response to bacterial infection. Initial results demonstrated that the Stage 15 Drosophila embryo was able to mount a relatively robust immune response to bacterial infection. This included induction of antimicrobial peptide (AMP) genes upon a range of bacterial stimuli; a response which was able to effectively discriminate between differential types of bacterial infection via the characterised Drosophila systemic immunity pathways. Live-imaging studies also showed that the cellular immune response was functional within the Stage 15 embryo. Subsequently, immune competence was shown to arise at approximately mid-embryogenesis, under the control of 20-hydroxyecdysone (20-HE) signalling, as demonstrated by the partial rescue of AMP expression and bacterial clearance in early stage embryos upon 20-HE co-administration with infective agents. Further analysis of the global transcriptional response of the Drosophila embryo to infection and damage via microarray studies confirmed the immune potential of this system, but also permitted the identification of genes upregulated uniquely upon Gram-positive or Gram-negativ infection. Moreover, wounding via sterile laser ablation induced significant upregulation of a subset of AMP genes an a network of cuticular genes, providing an insight into the embryonic damage response. Parallel analysis of the hemocyte transcriptional profile upon infection and damage elucidated that these immune cells may play a role in the regulation of the immune response via 20-HE signalling and production of ROS, although this remains subject to further validation. As such, transcriptional profile analysis of the embryo has been successful in identifying candidate genes for further validation and study.
Date of Award6 Apr 2014
LanguageEnglish
Awarding Institution
  • University of Bath
SupervisorWilliam Wood (Supervisor) & Isabella Vlisidou (Supervisor)

Keywords

  • Drosophila
  • immunity
  • innate
  • antimicrobials
  • competence
  • ecdysone

Cite this

Drosophila embryos as a Model System to Study Bacterial Infection In Vivo
Tan, K. (Author). 6 Apr 2014

Student thesis: Doctoral ThesisPhD