Abstract
Venom proteins act in the immunological interactions between parasitoids and their host insects. The effect of venom proteins on host immunity is not fully understood in pupal parasitoids. We identified the functions of a venom protein, calreticulin (PvCRT), in the pupal ectoparasitoid Pachycrepoideus vindemiae. Here, we report that PvCRT features a signal peptide and two conserved “calreticulin” domains. Multiple sequence alignments show that PvCRT shares 83.54% amino acid identity with CRT from both Pteromalus puparum and Nasonia vitripennis, which infers a close relationship among these three species. Using qPCR analysis, we found a lower expression level of PvCRT (0.27-fold) in the venom apparatus compared to the corresponding carcass. Immunohistochemical localization revealed that PvCRT was ubiquitously expressed in venom gland. The expression of the PvCRT gene in Drosophila transgenic lines via the UAS/Gal4 binary expression system reduced the self-encapsulation phenotype of tu(1)Sz1 mutants. Additionally, studies on humoral immunity indicate that PvCRT does not affect the antimicrobial immune responses of the host. This work on an ectoparasitoid will increase our understanding of venom–mediated host-parasitoid interactions.
Highlights
Parasitoids are a valuable group of natural enemies used to manage arthropod pests
Thevindemiae hosts previously indicating that a cosmopolitan wasp, attacks parasitized the pupariaby ofother manyparasitoids, cyclorrhaphous vindemiae has the potential for expanding its host range vindemiae parasitize the
They successfully develop from the hosts previously parasitized by other parasitoids, indicating invasive spotted wing drosophila, which provides one of the most promising biological resources to that P. vindemiae has the potential for expanding its host range [46]
Summary
Female wasps lay eggs either inside (endoparasitoid) or on the surface (ectoparasitoid) of their hosts where their larvae develop [1]. The host dies during the late stage of parasitoid development. The variations in the developmental strategies of endoparasitoids and ectoparasitoids suggest that parasitoids manipulate the physiology of their hosts in different ways [2]. Parasitic factors, including venom proteins [3,4], polydnaviruses (PDVs) [5], virus-like particles (VLPs) [6] and ovarian secretions [7,8] are injected into the host while the eggs are laid. Depending on the specific host/parasitoid relationship, some or all of these factors operate to manipulate host development and immunity, which are necessary for successful parasitism
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