Innate Immune Response of TmToll-3 Following Systemic Microbial Infection in Tenebrio molitor

Abstract

Although Toll-like receptors have been widely identified and functionally characterized in mammalian models and Drosophila, the immunological function of these receptors in other insects remains unclear. Here, we explored the relevant innate immune response of Tenebrio molitor (T. molitor) Toll-3 against Gram-negative bacteria, Gram-positive bacteria, and fungal infections. Our findings indicated that TmToll-3 expression was mainly induced by Candida albicans infections in the fat bodies, gut, Malpighian tubules, and hemolymph of young T. molitor larvae. Surprisingly, Escherichia coli systemic infection caused mortality after TmToll-3 knockdown via RNA interference (RNAi) injection, which was not observed in the control group. Further analyses indicated that in the absence of TmToll-3, the final effector of the Toll signaling pathway, antimicrobial peptide (AMP) genes and relevant transcription factors were significantly downregulated after E. coli 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 TmToll-3 in T. molitor in response to systematic infections.

Current status of innate immune responses in Malpighian tubules of insects: A review focusing on the Toll signaling pathway

“…The expression of TmToll‐3 was induced in response to C. albicans infections within MTs. Furthermore, when TmToll‐3 was experimentally silenced, the expression of AMP genes and the associated transcription factors was considerably downregulated, particularly after exposure to E. coli (Ali Mohammadie Kojour et al 2023). In another study, the expression levels of TmToll‐7 were assessed during development and within specific tissues.…”

Chromosome-level genome assembly of the medicinal insect Blaps rhynchopetera (Coleoptera: Tenebrionidae) using Nanopore and Hi-C technologies

“…The suppression of this protein's function leads to the impairment of the larval glands' defensive capabilities [55] . Furthermore, the research conducted by Weifeng Ding et al [57] revealed that differentially expressed genes between the defensive glands and muscle tissues of B. rhynchopetera were enriched in P450 metabolism. Notably, the downstream products of the "Metabolism of xenobiotics by cytochrome P450" gene exhibit structural similarity to certain substances previously reported in the defensive secretions of B. rhynchopetera [8] .…”

Recent trends in insect gut immunity

“…In addition, TmToll-2 expression was elevated in young larvae gut after E. coli, S. aureus , and C. albicans invasion ( 164 ). C. albicans infection in young T. molitor larvae induced TmToll-3 within the gut; however, AMP gene transcription factors were downregulated by E. coli infection ( 165 ).…”

“…In addition, TmToll-2 expression was elevated in young larvae gut after E. coli, S. aureus, and C. albicans invasion (164). C. albicans infection in young T. molitor larvae induced TmToll-3 within the gut; however, AMP gene transcription factors were downregulated by E. coli infection (165). The potent production and proliferation of specialized daughter cells intestinal stem cells are crucial in gut cell self-renewal following infection (136).…”