Microplitis mediator venom protein LC-MSMS

Insects mount an innate immune response to defend against the foreign invading microorganisms and parasites. To be successful parasites, endoparasitoid wasps need to be able to suppress the immune responses of their hosts. This allows the wasp eggs to hatch and the larvae to develop inside the host. However, the molecular mechanism underlying the interaction between wasp and its host remains largely unknown. In this study, we identified the reprolysin type metalloprotease venom component MmV189, which was designated venom regulatory factor-1 (VRF1). VRF1 plays a critical role in the interaction between the wasp Microplitis mediator and its lepidopteran host Helicoverpa armigera (the cotton bollworm). Proteomics analysis based on isobaric tags for relative and absolute quantitation (iTRAQ) revealed that at least twelve wasp venom proteins were released into the host hemolymph, causing significant changes in 511 host proteins at 24 h post parasitization. Taking an approach of integrated transcriptome and proteome analysis, we identified 313 putative proteins from the wasp venom reservoirs, 25 of which belong to the family of metalloproteases. Proenzyme of VRF1 was firstly cleaved in the host hemolymph after parasitization and then entered the hemocytes. Additionally, depletion of VRF1 in M. mediator by dsRNA-mediated knockdown significantly reduced the percentage of cocoon formation. Furthermore, we showed possible binding of VRF1 to Dorsal, a H. armigera nuclear factor kappa B (NF-κB), using yeast two-hybrid and pull-down assays, and confirmed the cleavage of Dorsal by VRF1. Moreover, we found that VRF1 acts as a protease to process Dorsal in the host hemocytes and suppress the induction of antimicrobial peptides (AMPs). Taken together, our findings identify a novel mechanism by which a component of endoparasitoid wasp venom interferes with host immune signaling cascades.