The role of a novel Wo l b a c h i a (Rickettsiales: Anaplasmataceae) synthetic peptide, WolFar, in regulating prostaglandin levels in the hemolymph of Acheta domesticus (Orthoptera: Gryllidae)

Abstract

Prostaglandins and other eicosanoids are known as regulating agents for cellular immune responses to pathogen threats in an insect's hemolymph. A novel synthetic peptide, WolFar, was customized from a conserved region of the Wolbachia surface protein (WSP), isolated from an economically important endoparasitoid species, Fopius arisanus. WolFar consists of nine amino acids (SYY VRL QYN) and was tested on the house cricket, Acheta domesticus. Three concentrations of peptides, 0.83 mmol/L (100%), 0.63 mmol/L (75%), and 0.42 mmol/L (50%), were injected and observed for 72 h. The regulation of prostaglandin E 2 (PGE 2 ) in the hemolymph of A. domesticus was determined using ELISA and by observation of nodules in the internal system of A. domesticus. The results showed that there were significant increases in PGE 2 in response to peptide injection at 24, 48, and 72 h after treatment. Furthermore, higher concentrations of peptide were directly proportional to the level of PGE 2 activity. These findings were supported by the abundance of nodules that formed in the internal system and fat body of A. domesticus, detectable at 72 h into the treatment. This indicates that WolFar is able to stimulate the immune system of insects and can be further developed as a potential biopesticide.