Fig. 3: Bc/Bt spores do not trigger midgut innate immune response.
From: Ingestion of Bacillus cereus spores dampens the immune response to favor bacterial persistence
a ROS monitoring one-hour post-acute feeding with SA-11 spores or vegetative cells. ROS production in the midgut is visualized by the HOCl-specific R19S probe (orange). DAPI (blue) marks the nuclei. b SA-11 loads in midguts knocked down for the expression of Duox in enterocytes 0.5 or 4 h after acute feeding with vegetative cells or spores. The horizontal axis indicates the mean number of CFUs. Dots correspond to independent experiments of five pooled midguts. c DptA-Cherry expression (red) in the anterior R1 midgut region (upper panel) and in the posterior R5 midgut region (bottom panel) of Drosophila fed for 30 min with H2O, Ecc15, SA-11 vegetative cells (Btvg) or SA-11 spores (Btsp) and observed 24 h later. In each panel anterior is to the left. Measured quantities are shown on the right graphs. The results are given as the relative expression compared with the control (H2O). At least three independent experiments were performed and each dot correspond to one midgut. d AttD-Gal4 UAS-Cherry expression (red, AttD>Cherry) in the anterior R1 midgut region (upper panel) and in posterior R4 midgut region (bottom panel) of Drosophila fed for 30 min with H2O, Ecc15, SA-11 vegetative cells (Btvg), or SA-11 spores (Btsp) and observed 24 h later. Measured quantities are shown on the right graphs. The results are given as the relative expression compared with the control (H2O). At least three independent experiments were performed and each dot correspond to one midgut. e qRT-PCR analyses of AMP expression in midgut upon acute feeding with SA-11 or Bc spores. UC corresponds to flies fed with water. For RT-qPCR results, mRNA levels in unchallenged wild-type flies were set to 100 and all other values were expressed as a percentage of this value. RT-qPCR results are shown as mean ± SEM. Dots correspond to independent experiments of 10 pooled female flies. f Bacterial load in the midguts of ∆AMP14 mutant flies 0.5 or 4 h after acute feeding with SA-11 spores. The horizontal axis indicates the mean number of CFUs per midgut. Each dot corresponds to an independent biological replicate where each replicate is the mean of five midguts. g Representative confocal images showing SA-11R/G spore germination in the anterior and posterior midgut of WT (Canton S) and ∆AMP14 mutant flies 2 h after acute feeding with spores. DAPI (blue) marks the nuclei. Spores are in red, vegetative cells in green. The yellow fluorescence corresponds to germinating spores. Error bars correspond to the SEM. The two-sided Mann–Whitney test was applied in b–d and f. A two-sided Student’s t-tests were used to analyze data in e. *p ≤ 0.05, **p ≤ 0.01, ***p ≤ 0.001, ns non-significant (exact P values are provided in the source data). Source data are provided as a Source Data file.
