<i>Drosophila</i> host defense after oral infection by an entomopathogenic <i>Pseudomonas</i> species

TLDR

Drosophila is a valuable model for host–pathogen studies, yet most work uses injected bacteria that bypass natural infection, and no true Drosophila pathogens have been identified. The study identifies Pseudomonas entomophila as a natural oral pathogen that induces systemic antimicrobial peptide expression in Drosophila. Using this strain, the authors profiled larval transcriptome changes during infection to assess modulation of gene expression. Pe infection is highly pathogenic, destroying gut cells, and elicits dramatic larval gene expression changes, uncovering many previously unreported immunity and pathogenesis genes.

Abstract

Drosophila has been shown to be a valuable model for the investigation of host–pathogen interactions. Study of the Drosophila immune response has been hampered, however, by the lack of true Drosophila pathogens. In nearly all studies reported, the bacteria used were directly injected within the body cavity of the insect, bypassing the initial steps of a natural interaction. Here, we report the identification of a previously uncharacterized bacterial species, Pseudomonas entomophila ( Pe ), which has the capacity to induce the systemic expression of antimicrobial peptide genes in Drosophila after ingestion. In contrast to previously identified bacteria, Pe is highly pathogenic to both Drosophila larvae and adults, and its persistence in larvae leads to a massive destruction of gut cells. Using this strain, we have analyzed the modulation of the larval transcriptome upon bacterial infection. We found that natural infection by Pe induces a dramatic change in larval gene expression. In addition to immunity genes, our study identifies many genes associated with Pe pathogenesis that have been previously unreported.