Endochitinase Knockdown Assayed in Sarcophaga bullata

Parasitoid wasps use venom to manipulate the immunity and metabolism of their host insects in a variety of ways to provide resources for their offspring. Yet, how venom proteins are recruited and evolve remain open questions. A more recently recognized source of eukaryotic innovation is lateral gene transfer (LGT). In this study, an LGT between two eukaryotes is described, in which a microsporidal endochitinase is recruited into the venom of parasitoid wasps in the superfamily Chalcidoidea. Endochitinases are widespread in bacteria and plants where they are used in nutrient acquisition or defense, but are typically not found in metazoans. An endochitinase LGT is present in at least 15 species of chalcidoid wasps representing four families, suggesting that endochitinase was transferred near or before the origin of Chalcidoidea. Furthermore, the gene is highly expressed in the venom gland of at least seven species, indicating that it may have a role in the complex host manipulations performed by parasitoid wasp venom. An RNA interference knockdown of venom endochitinase in Nasonia vitripennis followed by the injection of endochitinase-depleted venom in a host, showed a targeted set of nine genes significantly affected in the host. The knock down results suggest a function in immunity against fungal pathogens. In addition to microsporidia and chalcidoid wasps, the endochitinase gene is present in bacteria, plants, oomycetes, and mosquitoes and its phylogeny suggests multiple lateral gene transfers in its evolutionary history.