Deletion mutant of PGE(2) receptor using CRISPR-Cas9 exhibits larval immunosuppression and adult infertility in a lepidopteran insect, Spodoptera exigua

Prostaglandins (PGs) mediate various physiological processes in insects and other invertebrates, but there is very little information on PG receptors. This study identified a PGE(2) receptor (SePGE(2)R) in the lepidopteran insect, Spodoptera exigua, and addressed its functional association with cellular immunity, development, and reproduction. SePGE(2)R is expressed in most developmental stages and tissues. After SePGE(2)R expression knock down by RNA interference (RNAi), larval nodule formation (clears bacterial infections from circulating hemolymph) was severely suppressed coupled with reduced F-actin growth in hemocytes. Treating female adults with RNAi prevented nurse cell dumping in follicles and interfered with oocyte development. SePGE(2)R was heterologously expressed in Sf9 cells, in which the endogenous S. frugiperda SePGE(2)R was knocked down by small interfering RNA. This transiently expressed SePGE(2)R responded to PGE(2), but not other PGs, with dose-dependent up-regulation of intracellular cAMP concentrations. Treating S. exigua larvae with PGE(2) led to activation of a trimeric Gas subunit, protein kinase A (PKA), and Rho family small intracellular G proteins in hemocytes. A deletion mutant of SePGE(2)R was generated using CRISPR/Cas9 which exhibited severely retarded larval development and adult reproduction. We infer that PGE(2)R mediates insect immune and reproductive processes via a PKA signal pathway.