Wu_2025_Insect.Biochem.Mol.Biol_187_104470

Carboxylesterases are commonly found in the venom of parasitoids, yet their physiological roles as venom proteins in parasitoids remain to be elucidated. This study identified 19 carboxylesterase genes within the genome of Sclerodermus guani, with Sgie3 showing specific and abundant expression in the venom gland, implicating it as a key venom constituent with a vital role in host regulation. Functional characterization demonstrated that Sgie3 displays hydrolytic activity towards triglycerides in vitro. Injection of Sgie3 induces triglyceride increase and reduction in lipid droplet size in Tenebrio molitor pupae, the host of S. guani, resulting in dose-dependent developmental arrest effects in the pupae. Lipidomic analysis indicated that Sgie3 injection altered 436 lipid metabolites after one day, notably enriched in glycerophospholipid, arachidonic acid, alpha-linolenic acid, glycerolipid metabolism, as well as fatty acid elongation and degradation, and fatty acid autophagy pathways. These findings highlight the specific role of Sgie3 in modulating host lipid metabolism, providing insights into how parasitoids employ venom to manipulate host nutritional metabolism to support the successful development of their offsprings.