A calreticulin-like protein from endoparasitoid venom fluid is involved in host hemocyte inactivation.
During oviposition, most endoparasitoid wasps inject maternal factors into their hosts to interfere with host immune reactions and ensure successful development of their progeny. Since encapsulation is a major cellular defensive response of insects against intruding parasites, parasitoids have developed numerous mechanisms to suppress the host encapsulation capability by interfering with every step in the process, including recognition, adherence and spreading. In previous studies, components of Cotesia rubecula venom were shown to inhibit melanization of host hemolymph by interfering with the prophenoloxidase activation cascade and facilitate expression of polydnavirus genes. Here we report the isolation and characterization of another venom protein with similarity to calreticulin. Results indicate that C. rubecula calreticulin (CrCRT) inhibits hemocyte spreading behavior, thus preventing encapsulation of the developing parasitoid. It is possible that the protein might function as an antagonist competing for binding sites with the host hemocyte calreticulin, which mediates early-encapsulation reactions.
Zhang
Guangmei
G
Insect Molecular Biology Laboratory, Plant and Pest Science, Waite Campus, University of Adelaide, Glen Osmond, SA 5064, Australia.
Schmidt
Otto
O
Asgari
Sassan
S
D000818:Animals; D015153:Blotting, Western; D037282:Calreticulin / Q000235:genetics / Q000276:immunology* / Q000378:metabolism / Q000494:pharmacology; D004247:DNA / Q000737:chemistry / Q000235:genetics; D005260:Female; D006434:Hemocytes / Q000187:drug effects / Q000276:immunology; D006927:Hymenoptera / Q000235:genetics / Q000276:immunology*; D007915:Lepidoptera / Q000276:immunology / Q000469:parasitology*; D008858:Microscopy, Phase-Contrast; D016133:Polymerase Chain Reaction; D011994:Recombinant Proteins / Q000276:immunology / Q000378:metabolism / Q000494:pharmacology; D014862:Wasp Venoms / Q000235:genetics / Q000276:immunology*
D037282:Calreticulin; D011994:Recombinant Proteins; D014862:Wasp Venoms; D004247:DNA