Protein expression during parasite redirection of host (Trichoplusia ni) biochemistry

Comparison of parasitism by Cotesia glomerata with bacterial infection and wounding in Pieris brassicae: induction of new haemolymph polypeptides and changes in humoral immune response

In Pieris brassicae, parasitism by Cotesia glomerata and bacterial infection are differentiated with respect to haemolymph protein arrays, and production or suppression of antibacterial agents. Bacteriolytic activity in haemolymph from parasitized larvae was slightly, but significantly, higher 24h post-treatment than that of untreated and wounded controls. Micrococcus lysodeikticus- or lipopolysaccharide-(LPS) injected insects exhibited an 11-fold greater response than those parasitized. At 24h post-treatment, antibacterial activity against Escherichia coli was observed in haemolymph from all but untreated larvae. Injection of Grace's medium, M. lysodeikticus or LPS, caused a greater than threefold response than parasitization or wounding. The protein banding patterns of parasitized hosts did not correspond to those of the other treatments. Two parasitoid-induced proteins (38 and 128 kDa) were examined. Both were found in parasitized insects, not in those wounded, injected with Grace's medium, M. lysodeikticus or LPS. Neither protein was bacteriolytic or bacteriostatic in inhibition zone assays.

Characterization of a 212kD protein, released into the host by the larva of the endoparasitoid Chelonus inanitus (Hymenoptera, Braconidae)

Previous studies have shown that the larva of Chelonus inanitus plays an essential role in inducing the precocious onset of metamorphosis in polydnavirus/venom-containing Spodoptera littoralis, and that this effect might be due to proteins released by the parasitoid larva into the host. Here we show that a 212kD protein is the predominant protein released in vitro by late first instar parasitoids. This protein does not accumulate anywhere in the parasitoid body. Polyclonal antibodies specific for the 212kD protein were produced and immunoblot analyses revealed that this protein begins to be released by parasitoid larvae when the precocious onset of metamorphosis is induced in the host. Amino acid sequences of the N-terminus and of internal fragments of the 212kD protein were determined and glycoprotein detection showed that this protein is glycosylated. The availability of specific antibodies and the amino acid sequence information should now allow us to clone and express the 212kD protein and to directly study its functional significance.

Effects of Microplitis croceipes Teratocytes on Host Haemolymph Protein Content and Fat Body Proliferation

Qualitative and quantitative changes in haemolymph proteins in Heliothis virescens were observed in larvae injected with either Microplitis croceipes teratocytes or teratocyte secreted proteins (TSP). Haemolymph protein titres in hosts receiving either 0.5 or 1 larval equivalent (LE) of teratocytes were similar to those of parasitized larvae, whereas a single injection of 4LE of TSP was required to induce a similar response. SDS-PAGE showed that the 82kDa monomer of riboflavin-binding protein and the 74/76kDa monomers of storage proteins were significantly reduced in parasitized larvae and in nonparasitized larvae treated with TSP. Concentrations of a 155kDa monomer (insectacyanin chromoprotein) also were reduced in parasitized larvae and those injected with either teratocytes or TSP. Two monomers (56 and 60kDa) were unique to parasitized larvae. Treated larvae required several days longer than controls to reach a comparable premetamorphic stage (burrowing-digging). Reductions in fat body proliferation similar to those seen in parasitized larvae were observed in larvae treated with either 1LE of teratocytes, or with 2 or 4LEs of TSP. Perivisceral fat body weights from larvae treated with either 0.25 or 0.5LE of teratocytes were significantly reduced, but less so than those which received 1LE. Thus, fat body proliferation in both teratocyte- and TSP-treated larvae was inhibited in a dose-dependent manner. Both light- and transmission electron microscopy observations revealed cytological differences in fat body tissues of larvae injected with either teratocytes or TSP from the condition observed in parasitized larvae and noninjected controls. Gross dissection of periviseral fat body from parasitized, teratocyte-injected and TSP-injected larvae showed tissue much less developed and differing considerably in appearance from controls. Observed differences included reduced size and/or number of lipid bodies and qualitative and quantitative changes in other cytoplasmic organelles.

Characterization of a novel protein associated with the parasitization of lepidopteran hosts by an endoparasitic wasp

We report basic biochemical characteristics of a parasitism-specific protein (PSP) expressed in hosts (Trichopluisa ni) of a parasitic wasp (Chelonus near curvimaculatus). Size exclusion HPLC and SDS-PAGE analysis of cross-linked products indicated the native conformation of the protein is as a monomeric polypeptide with an estimated M(r) of 185,000. Resolution by non-denaturing PAGE revealed two major PSP bands with different charges, PSP-1 and PSP-2, each of which corresponded to several isoforms on native IEF with a pl range of 4.57-5.45. Sequences for the N-terminus region and internal peptides after fragmentation of purified preparations of PSP-1 and PSP-2 did not resemble the sequence of any reported protein. Immunological characterization of PSP using antibodies generated against virus proteins from C. near curvimaculatus female wasps revealed that PSP shares a common epitope(s) with some structural components of the wasp polydnavirus.

Expression of a parasitism-specific protein in lepidopteran hosts of Chelonus sp

The hemolymph of each noctuid species successfully parasitized by Chelonus near curvimaculatus possessed a parasitism-specific protein (PSP) previously identified in host T. ni (Insect Biochem. 19:445;21:845). Expression of PSP occurred in a stage-specific manner in the stadium during which the host undergoes precocious metamorphosis. The appearance of the protein was not due to nutritional stress associated with parasitism of hosts, since starved nonparasitized larvae did not produce the protein, or to low juvenile hormone titers occurring in precociously metamorphosing hosts, but rather was dependent on the presence of the endoparasite larva. Results of an in vivo incorporation experiments with [35S]-methionine showed that synthesis and subsequent appearance of the protein in the hemolymph of parasitized hosts was abrogated by prior surgical removal of endoparasite. Immunoprecipitation analysis of proteins from C. near curvimaculatus larvae cultured in vitro using antibodies specific to PSP indicated that the source of the protein was the endoparasite. Synthesis of PSP by the endoparasitic larvae with its subsequent secretion into the hemocoel of hosts was specific to the advanced stages of parasite development prior to its regression from the host.