Proteins synthesized and secreted by larvae of the ectoparasitic wasp, Eulophus pennicornis.

A microscopic examination of Eulophus pennicornis larvae on their host Lacanobia oleracea, revealed that peristaltic waves travelled from the anterior to posterior end of the feeding wasp larvae, and vice versa. In addition, when wasp larvae were immersed in PBS in vitro, they released a variety of proteins, with molecular weights ranging from (at least) 14 to 200 kDa. Amongst these was a protein with an estimated molecular weight similar to that of the 27 kDa parasitism-specific protein (PSP) detected in plasma from parasitized L. oleracea [Richards and Edwards, Insect Biochem Mol Biol 29:557-569 (1999)]. Similar results were obtained when the wasp larvae were incubated on balls of cotton wool soaked in tissue culture medium or sucrose, i.e., conditions that resemble their natural feeding behaviour. These results (and others) indicate that the wasp larvae release proteins, putatively through their mouth. Protein synthesis studies using (35)S-methionine indicated that the wasp larvae synthesize and secrete a variety of proteins in vitro, including one with a molecular weight corresponding to that of the L. oleracea 27 kDa PSP. As expected, only a portion of the total proteins synthesized by the parasitoid larvae were subsequently secreted. In addition, the autoradiogram of secreted proteins contained significantly fewer bands than silver-stained SDS gels of proteins released into PBS or onto cotton wool. Thus, some of the additional bands detected on the latter gels are thought to represent proteins that were not of wasp origin. Instead, these proteins released by the wasp larvae are speculated to be derived from their gut and, as such, probably represent proteins derived from host haemolymph and ingested during feeding. This possibility was supported by an electrophoretic analysis of homogenate supernatants prepared from wasp larvae with or without their gut contents. These studies indicated that the gut contents of the larval parasitoid contributes several distinct bands to the total protein profile. The ability of E. pennicornis larvae to synthesize, secrete, and release proteins is discussed with reference to those produced by endoparasitoid larvae. Published 2001 Wiley-Liss, Inc.