Deletion mutant of PGE2 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 PGE2 receptor (SePGE2R) in the lepidopteran insect, Spodoptera exigua, and addressed its functional association with cellular immunity, development, and reproduction. SePGE2R is expressed in most developmental stages and tissues. After SePGR2R 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. SePGE2R was heterologously expressed in Sf9 cells, in which the endogenous S. frugiperda PGE2R was knocked down by small interfering RNA. This transiently expressed SePGE2R responded to PGE2, but not other PGs, with dose-dependent up-regulation of intracellular cAMP concentrations. Treating S. exigua larvae with PGE2 led to activation of a trimeric Gαs subunit, protein kinase A (PKA), and Rho family small intracellular G proteins in hemocytes. A deletion mutant of SePGE2R was generated using CRISPR/Cas9 which exhibited severely retarded larval development and adult reproduction. We infer that PGE2R mediates insect immune and reproductive processes via a PKA signal pathway.