Long-Range Activation of Systemic Immunity through Peptidoglycan Diffusion in Drosophila
Figure 4
Genital infection induces both systemic and local immune responses.
(A) RT-qPCR analysis of Dpt, Def and CecA expression in the genital tract (gen), the abdominal carcass (corresponding mostly to fat body, FB), the gut (including Malpighian tubules) and in whole flies, following oral infection, septic injury or GI with Ecc15 (6h). (B–D) GI triggers Dpt-lacZ reporter gene expression in the fat body (B), the gut (C) and the genital tract (D). ß-galactosidase stainings were performed on fat body, gut and genital tract from wild-type flies (B,C) or Galn1 flies (deficient for the gene encoding endogenous ß-galactosidase) (D), carrying a Dpt-lacZ reporter gene. Flies were collected 6h after GI, septic injury or oral infection with Ecc15. GI triggers a strong expression of Dpt-lacZ in the fat body of around 20% of adults (B). A low level of ß-galactosidase activity (asterisks) corresponding to the endogenous Gal gene expression was observed in the gut of unchallenged flies (C). Upon GI Dpt-lacZ was induced weakly in the gut in around half of infected flies, while oral bacterial infection triggers a strong expression of the reporter in various gut segments (C). In the genital tract, GI triggers Dpt-lacZ in the ejaculatory bulb and internal ejaculatory duct (arrowheads, D). Note that the Dpt-lacZ reporter gene was also induced in an uncharacterised structure (empty arrowhead, D), attached to the ejaculatory bulb. This structure appears to be a convolution or overgrowth of the external ejaculatory duct leading from the ejaculatory bulb to the terminalia. Although it was not observed in all flies, its presence was not correlated with infection. (E) Def-GFP expression (green) is induced in the internal ejaculatory duct (arrow) 17h after GI with Ecc15. The apodeme (arrowhead) is strongly autofluorescent (yellow). In A the mean of three repeats is shown, error bars are standard error. In B–E, one representative experiment out of 3 repeats is shown.