Fig. 3

Serotonin controls gut BdDuox expression in B. dorsalis. a–c Effects of 5-HTP treatment on gut BdDuox and BdNox expression (a) and ROS activity (b, c) in conventionally colonized and axenic flies. ROS activity was measured by DHE (b) and H₂O₂ assay (c). Scale bars in b and e represent 1000 μm. Data of H₂O₂ level were normalized to controls. d–f Regulation of both BdDuox expression (d) and ROS activity (e, f) in the guts of conventionally colonized and axenic flies post dsBdTPH treatment. ROS activity was detected at 96 h post dsRNA injection. Data of H₂O₂ level were normalized to dsGFP-treated controls. To restore the 5-HT level, BdTPH-silenced flies were treated with 1-mM 5-HTP by feeding after dsRNA injection. g–i Gut BdDuox silencing efficiency determination in B. dorsalis by real-time PCR (g) and ROS activity (h, i). ROS activity was detected by DHE (h) and H₂O₂ assay (i) at 24 h post dsRNA injection. Scale bars in h represent 1000 μm. Data of H₂O₂ level were normalized to dsGFP-treated controls. j–m Effect of BdDuox silencing on gut total bacterial load (j) and the burden of S. marcescens (k) and P. alcalifaciens (m) at 24 h post dsRNA injection. Two-tailed unpaired t-test was performed in a, c, d, g, i, j, k, and m; one-way ANOVA followed by Tukey’s multiple comparison test for f. Conv, conventionally colonized flies; Axenic, axenic flies. Error bars indicate ± s.e.m.; *p < 0.05, **p < 0.01, ***p < 0.001. Results represent at least two independent experiments