TG-dependent protection against <i>P</i>. <i>entomophila</i> infection in the gut.

<p>(A) Survival analysis of gut-specific <i>TG-</i>RNAi flies (<i>NP1>TG IR</i>) and their counterparts (<i>NP1>+</i>) upon oral infection with <i>P</i>. <i>entomophila</i> (<i>Pe</i>) or <i>Ecc15</i>. Statistical analysis was performed using a log-rank test. At least 50 flies were used. N.S., not significant. (B) Cell-death was quantified by propidium iodide staining. Results represent the percentage of dead cells (propidium iodide-positive nuclei) in the midguts of flies infected for 4 h with <i>P</i>. <i>entomophila</i> (<i>Pe</i>). Results represent the mean of 10 independent experiments. Statistical analysis was performed by one-way analysis of variance followed by Bonferroni correction for multiple comparisons to evaluate the pairwise difference. UC, unchallenged. (C) A schematic model of the TG-mediated peritrophic matrix formation. TG crosslinks drosocrystallin (Dcy) on the peritrophic matrix (PM). Crosslinked drosocrystallin is not digested by AprA, and the crosslinked drosocrystallin strengthens the peritrophic matrix to function as a physical barrier against exotoxins of pathogenic microbes.