Prevalence of Local Immune Response against Oral Infection in a Drosophila/Pseudomonas Infection Model
Figure 5
The Local Immune Response Plays a Critical Role against P. entomophila
(A) Time course analysis of Diptericin expression measured by RT-qPCR in Drosophila fat body and gut extracted from females following natural infection with wild-type P. entomophila, aprA, and gacA mutants. Infection with wild-type P. entomophila and the aprA mutant induced a rapid and sustained Diptericin expression unlike the gacA mutant. Fat bodies (carcasses) and digestive tracts were dissected from adults collected at different time intervals after oral infection. Diptericin expression was normalized to rp49 mRNA. 100% value corresponds to the level of Dpt mRNA obtained 4 h after infection with wild-type P. entomophila. rp49: ribosomal protein 49; Dpt, Diptericin
(B) P. entomophila induces Diptericin expression in the cardia of adult Drosophila. Histochemical staining of β-galactosidase activity shows that Dpt-lacZ is expressed in the anterior midgut at the level of the proventriculus of infected flies carrying the Dpt-lacZ reporter gene (left panel). Similar results were obtained with a Dpt-GFP transgene (right panel). Adults were collected 24 h after infection. The control pictures display the cardia of uninfected flies. A constitutive expression was observed in the anterior part of the cardia. Dpt, Diptericin.
(C) Survival of wild-type flies (n = 60) to P. entomophila after previous infection with Ecc15. Flies were first infected with Ecc15 either orally (OD600 = 100) or by septic injury (OD600 = 200). 20 h after this Ecc15 infection, flies were fed with P. entomophila. Survival curves demonstrate that Drosophila flies primed with Ecc15 were protected from a subsequent P. entomophila infection only when Ecc15 was orally administrated. Log-rank analysis demonstrated a statistically significant difference in survival to P. entomophila infection of flies primed with Ecc15 by septic injury (SI) or natural infection (NI) (p < 0.0001).
(D) Survival of wild-type and Rel flies (n = 60) to P. entomophila after previous infection with Ecc15 evf-. Flies were first infected with Ecc15 evf- orally (OD600 = 100). 20 h after this Ecc15 infection, flies were fed with P. entomophila. Survival curves demonstrate that wild-type, but not Rel Drosophila flies primed with Ecc15 evf-, were protected from a subsequent P. entomophila infection. This experiment was repeated three times and gave similar results. Log-rank analysis demonstrated a statistically significant difference in survival to P. entomophila infection of flies primed with Ecc15 evf- by natural infection (NI) and flies without previous priming (p < 0.0001).
(E) Rel flies expressing a UAS-Rel transgene in the midgut under the control of the gut-specific cad-Gal4 driver survive better to P. entomophila infection than Rel mutant flies. Survival experiments were performed on 30 flies orally infected with P. entomophila (OD600 = 50). This experiment was repeated three times and yielded similar results. Log-rank analysis demonstrated a statistically significant difference in survival of UAS-Rel/caudal-Gal4; Rel flies, and UAS-Rel/Rel; Rel flies to P. entomophila infection (p < 0.01).