Cactin was originally identified as an interactor of the Drosophila IκB factor Cactus and shown to play a role in controlling embryonic polarity and regulating the NF-κB signaling pathway. While subsequent studies have identified the roles for Cactin in the mammalian immune response, the immune function of Cactin in insects has not been described yet. Here, we identified a Cactin gene from the mealworm beetle, Tenebrio molitor (TmCactin) and characterized its functional role in innate immunity. TmCactin was highly expressed in prepupa to last instar stages, and its expression was high in the integument and Malpighian tubules of last instar larvae and adults. TmCactin was induced in larvae after infection with different pathogens and detectable within 3 hours of infection. The highest levels of TmCactin expression were detected at 9 hours post infection. TmCactin RNAi significantly decreased the survival rates of larvae after challenge with Escherichia coli and Staphylococcus aureus, but had no significant effect after challenge with Candida albicans. Furthermore, TmCactin RNAi significantly reduced the expression of seven antimicrobial peptide genes (AMPs) after bacterial challenge. Our results suggest that TmCactin may serve as an important regulator of innate immunity, mediating AMP responses against both Gram-positive and Gram-negative bacteria in T. molitor.

No abstract

No abstract

Target of rapamycin (TOR) is an evolutionarily conserved serine–threonine kinase that affects various cellular functions including growth, development, ageing, immunity and autophagy. Inhibition in TOR activity stimulates autophagy, a self‐eating process that ensures survival by maintaining metabolic homeostasis and energy retention at both cellular and organismal levels. To understand the interplay between TOR and autophagy during development and immunity, we screened and identified a TOR homologue from the coleopteran insect, Tenebrio molitor (TmTOR). The full‐length cDNA of TmTOR contained an open reading frame (ORF) of 7,197 bp encoding a protein of 2,398 amino acids, and a 5′‐ and 3′‐ untranslated region (UTR) of 156 and 457 bp, respectively. Deduced amino acid sequence of TmTOR shows characteristic Huntington, EF3A, ATM, TOR (HEAT) repeat, focal adhesion kinase targeting (FAT), rapamycin‐binding, phosphatidylinositol 3‐/4‐kinase and FRAP, ATM and TRRAP C‐terminal (FATC) domains known to be conserved among TOR orthologs. TmTOR showed high sequence identity (92%) with Tribolium castaneum TOR (TcTOR) and the two were placed in the same cluster of the phylogenetic tree. TmTOR shows high mRNA expression level in the fat body and integument of T. molitor larvae. Significantly, a reduced expression of TmTOR mRNA during pupation correlated to an increase in the area of autolysosomes. Intriguingly, T. molitor larvae showed an increase in TmTOR transcripts upon a challenge with various bacterial pathogens. This suggests a negative role of TmTOR in the regulation of autophagy during development.