DNA sequence of a protein lethal to an endoparasitoid, Cotesia kariyai, encoded in genome of entomopoxvirus amd its spectrum on another endoparasitoid, Meteorus pulchricornis

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When the gregarious endoparasitoid Cotesia kariyai (Hymenoptera : Braconidae) parasitizes Mythimna separata(Lepidoptera : Noctuidae) larvae that are infected with an entomopoxvirus (MyseEPV), the embryos and larvae of the parasitoid die inside the host before emergence. Previous studies showed that a toxic factor, lethal to Cotesia kariyai, was present in virion-free plasma (VFP) from M.separata larvae infected with MyseEPV. A polypeptide of 28-kDa was purified and designated as Protein Lethal to C.kariyai (PLCK).In this study, we isolated PLCK from MyseEPV infected larvae and determined DNA sequence of a gene encoding PLCK. ORF of pick is 1265bp, and its homologues were found in genomes of Xestia c-nigram (Lepidotera : Noctuidae) granulovirus and Amsacta moori EPV.It has not been known whether PLCK affects parasitoids other than C.kariyai. In this study we examined the effect of PLCK on Meteorus pulchrcornis (Hymenoptera : Braconidae). Like C.kaniyai, M.pulchricornis is a braconid end … More oparasitoid ; however, it is a generalist, parasitizing not only M.separata larvae, whereas C.kariyai is a specialist as only parasitizes M.separata larvae. We observed larval development and survival of these two parasitoids after exposure to PLCK, both in vivo and in vitro. No C.kariyai larvae emerged from M.separata larvae infected with MyseEPV. However, percentages of emergence, pupation and adult eclosion of M.pulchricornis larvae developed in MyseEPV-infected or VFP-injected M.separata larvae were not significantly different from those in non-infected M.separata larvae or that injected with hemolymph from healthy insects. Similarly, M.pulchricornis larvae survived for seven days in IPL-41 medium containing PLCK, but C.karival died within two days in the same medium, showing pathognomonic symptom as the cuticle detachment from the somatic tissues. We also examined immunohistological localization of PLCK within parasitoid larvae developing in medium containing PLCK, to determine whether PLCK attaches to particular tissues in C. kariyai but not in M.pulchricornis. In summaly, PLCK has no effect on the development and survival of M.pulchricornis, but is lethal to C.kariyai. Less