TmCactin plays an important role in Gram-negative and -positive bacterial infection by regulating expression of 7 AMP genes in Tenebrio molitor

Abstract

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.

In silico identification, characterization and expression analysis of attacin gene family in response to bacterial and fungal pathogens in Tenebrio molitor

“…The regulatory expression of seven AMP genes by the NF‐kB factor Cactin and innate immunity against both Gram‐positive and Gram‐negative bacteria has improved the understanding of the Toll pathway in the beetle (Jo et al . ). Tenecin 1 was the first AMP identified from T. molitor showing activity against fungi as well as Gram‐positive and Gram‐negative bacteria (Lee et al .…”

“…The signal recognition molecules, the intracellular signaling components and the transcription factors relaying the signal into the nucleus for the expression of AMP genes have been studied in the beetle, especially in relation to Toll and IMD pathways (Patnaik et al 2013;Patnaik et al 2014;Seo et al 2016). The regulatory expression of seven AMP genes by the NF-kB factor Cactin and innate immunity against both Gram-positive and Gram-negative bacteria has improved the understanding of the Toll pathway in the beetle (Jo et al 2017). Tenecin 1 was the first AMP identified from T. molitor showing activity against fungi as well as Gram-positive and Gram-negative bacteria (Lee et al 1998).…”

Molecular cloning and characterization of SOCS2 from the mealworm beetle Tenebrio molitor

“…In T. molitor , the Toll pathway is under investigation for furthering the understanding of humoral immunity with reference to the synthesis of AMPs (Jo et al . ). Focused studies on the immune‐ deficiency (IMD) and JAK/STAT pathways have been performed in the insect model.…”

“…The present study was conducted in the coleopteran species Tenebrio molitor, which is considered to be a convenient model for scientific studies involving innate immunity. In T. molitor, the Toll pathway is under investigation for furthering the understanding of humoral immunity with reference to the synthesis of AMPs (Jo et al 2017). Focused studies on the immune-deficiency (IMD) and JAK/STAT pathways have been performed in the insect model.…”

TmPGRP-SA regulates Antimicrobial Response to Bacteria and Fungi in the Fat Body and Gut of Tenebrio molitor

“…However, the effect of TmPGRP-SA expression on each of the TmSpz genes remains unclear. Concordantly, the intracellular protein cassettes of the Toll pathway comprising TmMyD88 [31], Pelle, and Tube are essential for transducing the signal to TmCactin [32], a positive regulator that interacts with TmCactus, for ensuring the nuclear translocation of TmDorX2 [33] and robust transcription of the TmAMP gene. In agreement with this, earlier immune studies in other invertebrates such as D. melanogaster, Manduca sexta, and Marsupenaeus japonicus have revealed the same mechanism of indirect Toll activation [22,34,35].…”