The ECSIT Mediated Toll3-Dorsal-ALFs Pathway Inhibits Bacterial Amplification in Kuruma Shrimp

PxDorsal Regulates the Expression of Antimicrobial Peptides and Affects the Bt Susceptibility of Plutella xylostella

The insect NF-κB pathway is primarily constituted by nuclear factor κB (NF-κB) and the inhibitor of κB (IκB), which plays a crucial role in the innate immune response. Dorsal and Cactus, as NF-κB and IκB factors, are important downstream regulators of the Toll pathway in Plutella xylostella. In this study, the PxDorsal and PxCactus genes of P. xylostella were cloned, and the molecular docking demonstrated that PxDorsal and PxCactus can interact with each other. RT-qPCR results indicated that PxDorsal and PxCactus were expressed in all stages, and the expression of PxDorsal, PxCactus, and antimicrobial peptides PxGloverin2, PxMoricin3, and PxLysozyme2 were significantly down-regulated under Bacillus thuringiensis (Bt8010) infection. Interestingly, silencing the PxDorsal gene by RNA interference (RNAi) significantly down-regulated the expression of PxGloverin2 and PxMoricin3 and increased the epidermis melanization of P. xylostella larvae fed with Bt8010. Our findings indicate that PxDorsal and PxCactus may interact with each other, and silencing PxDorsal inhibits the expression of downstream antimicrobial peptides, thereby enhance the susceptibility of P. xylostella to Bt8010. This study contributes a theoretical basis for further research on the Toll pathway of P. xylostella to pathogens and offers insights for screening effective biological control targets from the perspective of the immune system.

Peroxiredoxin 4 Interacts With Domeless and Participates in Antibacterial Immune Response Through the JAK/STAT Pathway

The JAK/STAT pathway plays an important role in the development and immune responses of animals. In vertebrates, families of cytokines or growth factors act as activators of the JAK/STAT pathway; however, the activators for the JAK/STAT signaling pathway in arthropods are largely unknown. Herein we report a new ligand, peroxiredoxin 4 (Prx4), for the Domeless in the JAK/STAT pathway of shrimp Marsupenaeus japonicus. Prx4 was induced to secrete into the extracellular surroundings upon Vibrio challenge, which then facilitated the anti-Vibrio activity of shrimp by activating the phosphorylation and nuclear translocation of STAT and the expression of STAT-responsive antimicrobial peptides. Blocking the expression of Prx4 in vivo abrogated the activation of the JAK/STAT pathway by Vibrio infection, while injection of Prx4 protein activated the pathway. The interaction between Prx4 and Domeless was proved by immuno-precipitation and protein pull-down assays. Moreover, two cysteine residues in Prx4 that are critical for the interaction and Prx4’s anti-Vibrio role were identified, and the binding site in Domeless for Prx4 was proved to be the cytokine-binding homology module fragment. Taken together, our study revealed a new function for Prx4 enzyme and established a new enzyme-type ligand for the activation of the JAK/STAT pathway in an aquatic arthropod.