Parasitism of Lacanobia oleracea (Lepidoptera, noctuidae) by the ectoparasitic wasp Eulophus pennicornis, results in the appearance of a 27 kDa parasitism-specific protein in host plasma

Little is known about the effects of ectoparasitoids and their secretions o n the plasma protein profiles of their insect hosts. To address this defici t, a study has been made of the interactions between an ectoparasitic wasp, Eulophus pennicornis, and its host, the tomato moth, Lacanobia oleracea. I n particular, the quantitative and qualitative effects of parasitism or the experimental injection of wasp venom on host plasma proteins were investig ated. Results demonstrated that both treatments caused an initial increase in L. oleracea total plasma protein concentration up to day 5 of treatment, but whereas the protein concentration remained high in the experimentally envenomated group, a decrease towards day 8 occurred in parasitized insects . Parasitism was also associated with the appearance of a protein with an e stimated molecular weight of 27 kDa. This protein first appeared on day 3 a fter parasitization and its levels subsequently increased. The protein was not detected in any of the unparasitized larvae (including all the various control groups) or in experimentally envenomated L. oleracea larvae. In add ition, the appearance of this protein was not a nonspecific result of nutri tional deprivation, nor was it a general injury, stress, or infection induc ed protein. Its appearance was strictly associated with parasitism of L. ol eracea by E. pennicornis and thus, it may be described as a parasitism-spec ific protein (PSP). The PSP has been partially purified using whole gel elu tion. Gel filtration and SDS PAGE indicated that it has a native molecular weight of 27 kDa and that it does not appear to aggregate to produce higher molecular weight molecules, nor dissociate into lower molecular weight sub units held together by disulphide or covalent bonds. The precise site of sy nthesis of the 27 kDa PSP is not yet known but some evidence leads us to sp eculate that it may be synthesised by the feeding E. pennicornis larvae and introduced into their host. This possibility is discussed in relation to p revious work detailing the effects of parasitism on L. oleracea haemocyte m orphology, function and viability, and the effects of endoparasitoids on ho st plasma proteins. (C) 1999 Elsevier Science Ltd. All rights reserved.