Dietary Stimuli, Intestinal Bacteria and Peptide Hormones Regulate Female Drosophila Defecation Rate

Abstract

Peptide hormones control Drosophila gut motility, but the intestinal stimuli and the gene networks coordinating this trait remain poorly defined. Here, we customized an assay to quantify female Drosophila defecation rate as a proxy of intestinal motility. We found that bacterial infection with the human opportunistic bacterial pathogen Pseudomonas aeruginosa (strain PA14) increases defecation rate in wild-type female flies, and we identified specific bacteria of the fly microbiota able to increase defecation rate. In contrast, dietary stress, imposed by either water-only feeding or high ethanol consumption, decreased defecation rate and the expression of enteroendocrine-produced hormones in the fly midgut, such as Diuretic hormone 31 (Dh31). The decrease in defecation due to dietary stress was proportional to the impact of each stressor on fly survival. Furthermore, we exploited the Drosophila Genetic Reference Panel wild type strain collection and identified strains displaying high and low defecation rates. We calculated the narrow-sense heritability of defecation rate to be 91%, indicating that the genetic variance observed using our assay is mostly additive and polygenic in nature. Accordingly, we performed a genome-wide association (GWA) analysis revealing 17 candidate genes linked to defecation rate. Downregulation of four of them (Pmp70, CG11307, meso18E and mub) in either the midgut enteroendocrine cells or in neurons reduced defecation rate and altered the midgut expression of Dh31, that in turn regulates defecation rate via signaling to the visceral muscle. Hence, microbial and dietary stimuli, and Dh31-controlling genes, regulate defecation rate involving signaling within and among neuronal, enteroendocrine, and visceral muscle cells.

Intestinal Immune Deficiency and Juvenile Hormone Signaling Mediate a Metabolic Trade-off in Adult Drosophila Females

“…Although systemic immune response has been shown to compromise reproduction in Diptera [ 1 , 27 , 28 ], the interplay between intestinal host defense, including midgut motility, permeability and regeneration, and fecundity remains unexplored. To examine whether adult females balance fecundity with intestinal motility, which is an aspect of intestinal host defense to infection, we used three RNAi lines primarily found to control intestinal defecation rate [ 29 ]. The downregulation of CG11307 via the VDRC lines 108230/KK and 3005/GD) and of Myosuppressin (Ms) via the 108760/KK line in enteroendocrine cells (EEs) using the prospero V1 -Gal4 (pros-G4) driver decreased fly survival upon intestinal infection ( Figure 1 A).…”

“…The former relies on toll and Imd pathway induction and the release of AMPs from the fat body and hemocytes into the hemolymph, while intestinal immunity requires Imd and JAK/STAT pathway signaling in enterocytes to produce luminally secreted AMPs [ 5 , 39 ]. Moreover, intestinal epithelium integrity and regeneration and intestinal motility are parameters of host defense directly relevant to intestinal infection [ 18 , 29 ]. Intestinal motility inhibition by downregulating CG11307 and Myosuppressin in EEs decreased host defense to intestinal infection, but also female reproductive output.…”

“…Intestinal motility inhibition by downregulating CG11307 and Myosuppressin in EEs decreased host defense to intestinal infection, but also female reproductive output. CG11307 and Ms are lowly expressed in the midgut EEs compared to other gut motility regulators [ 40 , 41 ] but their downregulation in the midgut EEs effectively reduces the defecation rate [ 29 ]. Thus, CG11307 and Ms are bona fide intestinal motility regulators contributing to the intestinal host defense to infection, without counterbalancing fecundity.…”