Synergistic host-parasitoid antimicrobial peptide interactions ensure the survival of parasitized hosts

Host-parasite interaction is always involved in the immune response. It is well known that parasitic wasps introduce various factors to suppress host immune responses, thereby facilitating parasitoid progeny development while compromising host survival. However, little is understood about how parasitic wasps, especially endoparasitoids, survive pathogen threats when they develop in hosts. Antimicrobial peptides (AMPs) are important immune effectors that are active against pathogens and essential for the survival of organisms. Here, we investigated the immune response of the host <i>Plutella xylostella</i> and its endoparasitic wasp <i>Cotesia vestalis</i> during the process of parasitism, focusing on AMPs. We found that the suppression of parasitism on host AMPs diminished as the process went on and selected AMPs responded differently in parasitized hosts following bacterial challenges. We then demonstrated that the host-expressed gloverin was extremely sensitive to pathogen infection after parasitism and was vital for host survival. Furthermore, we found that parasitoid teratocytes expressed antimicrobial peptides, especially hymenopteacin, which were significantly upregulated following bacterial infection. With a broad antimicrobial spectrum, the presence of hymenopteacin in the hemolymph of parasitized hosts significantly decreased bacterial load and increased the survival of the parasitized host. Our study provides a systematic perspective on host-parasitoid immune interaction by highlighting the significance of AMPs.