Enhancing the Survival of Ichneumonid Parasitoid Campoletis chlorideae (Hymenoptera: Ichneumonidae) by Utilizing Haserpin-e Protein to Effectively Manage Lepidopteran Pests

The ichneumonid parasitoid <i>Campoletis chlorideae</i> is an important natural enemy of lepidopteran pests in different agro-ecosystems, specifically targeting early larvae (second- and third-instar). Enhancing the survival of <i>C. chlorideae</i>, especially within hosts, remains a significant technical challenge for large-scale indoor reproduction. This study investigates the use of endogenous serpin-e protein, derived from the host <i>Helicoverpa armigera</i> (Haserpin-e), to improve the survival rate of <i>C. chlorideae</i> in indoor reproduction. The results demonstrated that Haserpin-e protein significantly enhanced cocoon production in <i>C. chlorideae</i>, with no observable adverse effects on the life history traits of both F0 and F1 generations of <i>C. chlorideae</i>. By investigating the mechanism underlying cocoon formation promotion, it was found that Haserpin-e protein reduced the encapsulation, inhibited melanization, as well as suppressed the expression of antimicrobial proteins (AMPs) in <i>H. armigera</i>. This study provides novel insights into improving the survival of <i>C. chlorideae</i> by inhibiting host immune responses through the application of its endogenous Haserpin-e protein during large-scale indoor reproduction efforts. Additionally, this research further elucidates the multifaceted functionality of Haserpin-e proteins by demonstrating their role in regulating innate immune processes in <i>H. armigera</i>, including negatively regulating encapsulation, melanization, and AMP expression.