A pattern recognition receptor C-type lectin TcCTL14 contributes to immune response and development in the red flour beetle, Tribolium castaneum.

Evidence is accumulating that pattern recognition receptor C-type lectins (CTLs) play essential roles in recognition of pathogens. TcCTL14 (accession no. TC00871) contains the most domains among all CTLs of Tribolium castaneum. Yet the biological function of TcCTL14 remains unclear. In this study, TcCTL14 exhibiting typical motif and domain of CTLs, was cloned from T. castaneum. The expression pattern analysis showed that TcCTL14 was highly expressed in late pupae and central nervous system, and was up-regulated after treatment with Escherichia coli and Staphylococcus aureus, respectively. Analysis of binding affinity revealed that recombinant TcCTL14 not only could bind to lipopolysaccharide (LPS) and peptidoglycan (PGN) in a dose dependent fashion, but possibly could bind to and agglutinate different bacterium in a Ca 2+ dependent fashion. Knockdown of TcCTL14 before injection with bacterium led to the NF-κB transcription factors of Toll/IMD and 4 antimicrobial peptides (AMPs) down-regulation. Intriguingly, knockdown of TcCTL14 also caused suppressed metamorphosis, reduced fecundity, and delayed embryogenesis of T. castaneum. Further observation discovered that knockdown of TcCTL14 inhibited the development of ovaries and embryos. The detection of signaling pathways revealed that TcCTL14 may be involved in metamorphosis and fecundity by impacting the 20-hydroxyecdysone and vitellogenin, respectively. Overall, these results indicate that TcCTL14 may contribute to immune response by agglutination or regulating the expression of AMPs by Toll/IMD pathway, and is required for T. castaneum development including metamorphosis, fecundity, and embryogenesis. These findings will improve the functional cognition of pattern recognition receptor CTLs in insects and provide the new strategy for pest control. This article is protected by copyright. All rights reserved.