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(PRR)C-type lectins(CTL)play essential roles in recognition of pathogens.TcCTL14(accession no.TC00871)contains the most domains among all CTL of Tribolium castaneum.Yet the biological function of TcCTL14 remains unclear.In this study,TcCTL14 exhibiting typical motif and domain of CTL was cloned from T.castaneum.The expression pattern analysis showed that TcCTL14 was highly expressed in late pupae and central nervous system,and was upregulated after treatment with Escherichia coli and Staphylococcus aureus,respectively.Analysis of binding affinity revealed that recombinant TcCTL14 not only could bind to lipopolysaccharide and peptidoglycan in a dose-dependent fashion,but possibly could bind to and agglutinate different bacteria in a Ca^(2+)-dependent fashion.Knockdown of TcCTL14 before injection with bacteria led to the downregulation of nuclear factor-κB transcription factors of Toll/IMD and 4 antimicrobial peptides.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 20-hydroxyecdysone and vitellogenin,respectively.Overall,these results indicate that TcCTL14 may contribute to immune response by agglutination or regulating the expression of antimicrobial peptides by the Toll/IMD pathway,and is required for T.castaneum development including metamorphosis,fecundity,and embryogenesis.These findings will improve the functional cognition of PRR CTL in insects and provide the new strategy for pest control.

Comparative study of neuropeptide signaling systems in Hemiptera

Numerous physiological processes in insects are tightly regulated by neuropeptides and their receptors.Although they form an ancient signaling system,there is still a great deal of variety in neuropeptides and their receptors among different species within the same order.Neuropeptides and their receptors have been documented in many hemipteran insects,but the differences among them have been poorly characterized.Commercial grapevines worldwide are plagued by the bug Daktulosphaira vitifoliae(Hemiptera:Sternorrhyncha).Here,33 neuropeptide precursors and 48 putative neuropeptide G protein-coupled receptor(GPCR)genes were identified in D.vitifoliae.Their expression profiles at the probe and feeding stages reflected potential regulatory roles in probe behavior.By comparison,we found that the Releasing Hormone-Related Peptides(GnRHs)system of Sternorrhyncha was differentiated from those of the other 2 suborders in Hemiptera.Independent secondary losses of the adipokinetic hormone/corazoninrelated peptide receptor(ACP)and corazonin(CRZ)occurred during the evolution of Sternorrhyncha.Additionally,we discovered that the neuropeptide signaling systems of Sternorrhyncha were very different from those of Heteroptera and Auchenorrhyncha,which was consistent with Sternorrhyncha's phylogenetic position at the base of the order.This research provides more knowledge on neuropeptide systems and sets the groundwork for the creation of novel D.vitifoliae management strategies that specifically target these signaling pathways.