Effects of TmTak1 silencing on AMP production as an Imd pathway component in Tenebrio molitor

Abstract

Mealworms beetles, Tenebrio molitor, are the limelight next-generation food for humans due to their high nutrient contents. Since Tenebrio molitor is used as feed for pets and livestock in addition to their ability to decompose polystyrene and plastic waste, it is recognized as an insect with an industrial core value. Therefore, it is important to study the immune mechanism related to the development and infection of mealworms for mass breeding purposes. The immune deficiency (Imd) signaling is one of the main pathways with pivotal roles in the production of antimicrobial peptides (AMPs). Transforming growth factor-β activated kinase (TAK1) is one of the Imd pathway components, forms a complex with TAK1 binding protein 2 (TAB2) to ultimately help activate the transcription factor Relish and eventually induce host to produce AMPs. Relatively, little has been revealed about TAK1 in insect models, especially in the T. molitor. Therefore, this study was conducted to elucidate the function of TmTak1 in T. molitor. Our results showed that the highest and lowest mRNA expression of TmTak1 were found in egg and young larvae respectively. The tissue-specific expression patterns were reported in the gut of T. molitor larvae and the fat bodies of adults. Systemic microbial challenge illustrated TmTak1 high expression following the fungal infection in all dissected tissues except for the whole body. However, silencing TmTak1 experiments showed that the survivability of T. molitor larvae affected significantly following Escherichia coli infection. Accordingly, AMP induction after TmTak1 knock down was mainly reported in the integument and the fat bodies.