Innate Immune Response of Following Systemic Microbial Infection in

Although Toll-like receptors have been widely identified and functionally characterized in mammalian models and , the immunological function of these receptors in other insects remains unclear. Here, we explored the relevant innate immune response of () against Gram-negative bacteria, Gram-positive bacteria, and fungal infections. Our findings indicated that expression was mainly induced by infections in the fat bodies, gut, Malpighian tubules, and hemolymph of young . larvae. Surprisingly, systemic infection caused mortality after knockdown via RNA interference (RNAi) injection, which was not observed in the control group. Further analyses indicated that in the absence of , the final effector of the Toll signaling pathway, antimicrobial peptide (AMP) genes and relevant transcription factors were significantly downregulated after challenge. Our results indicated that the expression of almost all AMP genes was suppressed in silenced individuals, whereas the expression of relevant genes was positively regulated after fungal injection. Therefore, this study revealed the immunological involvement of in in response to systematic infections.