Coordination of LysC and Ctl24 in PGN-derived intestinal immunity.
(A) Requirement of LysC for PGN, but not muropeptides, to induce intestinal immunity. PGN or muropeptides (5 μg) were administered into shrimp intestine at 24 h after dsRNA application. AlfB1 expression (left panel) and FoxO nucleus level (right panel) was detected 6 h later. (B) Requirement of Ctl24 to counteract the intestinal immunity induced by either of PGN and muropeptides. (C) Model of the coordination among immune effectors in intestinal immunity. LysC cleaves intestinal bacterial PGN into muropeptides, which activate both FoxO and Relish to induce the expression of three immune effectors. Coating of bacteria by Ctl24 inhibits the PGN-processing ability of LysC, and inhibits the bactericidal activity of AlfB1. The bar charts show the mean ± SD from three replicates. The images are representative of three repeats. Statistical analysis was performed using the Students’ t test. *, 0.01 < p < 0.05; **, 0.001 < p < 0.01; ***, p < 0.001.