Evolutionary streamlining of GPCRs in Hymenoptera and their protentional functional roles in host exploitation

Parasitic wasps (Hymenoptera) are important biological control agents, yet studies on the function and evolution of their G protein-coupled receptors (GPCRs) remain limited. To address this gap, we systematically identified GPCRs in seven representative hymenopteran species based on evolutionary relationships, and found notable contraction compared to basal hymenopterans. Furthermore, phylogenetic analysis revealed extensive contraction in Family A GPCRs and methuselah-like (mthl) genes. Among the species analyzed, Gregopimpla kuwanae was selected for detailed experimental studies due to its relatively large size and suitability for laboratory manipulation. Temporal gene expression analysis in G. kuwanae showed that opsins and biogenic amine receptors exhibit low expression during the larval stages, likely reflecting adaptations associated with its parasitic lifestyle. Moreover, transcriptomic comparisons before and after initial host feeding in G. kuwanae showed 63 GPCRs showing higher expression before feeding, suggesting their involvement in host detection and feeding initiation. Notably, we found that short neuropeptide F (sNPF) and its receptor are highly expressed in females before their initial host-feeding experience, and RNAi knockdown of either gene significantly reduced both feeding motivation and intake, confirming their key function in parasitic feeding behavior. Together, our study elucidates how a streamlined GPCR repertoire supports essential life-history traits in parasitic wasps and provides a framework for leveraging these receptors in targeted biological-control strategies.