Expression pattern analysis of transmembrane receptor TmToll-8, −9, and −10 in the coleopteran insect Tenebrio molitor following systemic infection

In insects, the production of antimicrobial peptides is considered to be the solo arm of the innate immune response. The Toll and immune deficiency pathways are two major signaling pathways that lead to the production of antimicrobial peptides as final effectors. The dynamic functions of Toll/Toll-like receptors have been thoroughly reviewed in mammals and Drosophila. During the last decade, we have attempted to clarify the immunological roles of different Toll receptor variants and their ligands in Tenebrio molitor. Accordingly, we showed that TmToll-8, −9, and −10 mRNA transcripts are induced following systemic injections of Gram-negative, Gram-positive, and fungal infections. Our data revealed harmonic expression patterns of TmToll-8, −9, and −10 throughout the developmental stages of healthy individuals and in response to infections in the examined tissues (Malpighian tubules, gut, fat bodies, and hemolymph), illustrating similar evolutionary conversions of different Toll receptor variants in T. molitor. Taken together, our findings highlight the immunological actions of TmToll-8, −9, and −10 in response to pathogenic insults in T. molitor.