Two lysozymes are involved in the larva-to-pupa transition and the antibacterial immunity of Lasioderma serricorne (coleoptera: Anobiidae)

Abstract Lysozymes play important roles in the innate immune response against pathogen infections of insects. In this study, i-type and c-type lysozymes (LsLysI and LsLysC) were identified from the cigarette beetle, Lasioderma serricorne. Both genes were highly expressed in late larvae and pupae, especially in the fat body and integument. The expression of LsLysI and LsLysC was induced by 20-hydroxyecdysone. The expression levels of both LsLys genes were significantly upregulated after peptidoglycan (PGN) exposure and gram-positive bacterium Staphylococcus aureus infections. RNA interference (RNAi)-mediated knockdown of LsLysI or/and LsLysC in 5th instar larvae reduced lysozyme levels and disrupted the larva-to-pupa molt. Knockdown of LsLysI or LsLysC alone, and co-suppression of both genes, increased larval mortality by 13.3%, 21.1%, and 43.3% after S. aureus infection. The results demonstrated that LsLysI and LsLysC play key roles in a successful larva-to-pupa transition and in the innate immune response of L. serricorne.