A 24 kDa parasitism-specific protein (PSP24) occurs in the hemolymph of larvae and pharate pupae of the Caribbean fruit fly, Anastrepha suspensa (Diptera: Tephritidae) after parasitization of larvae by the wasp Diachasmimorpha longicaudata (Dl) (Hymenoptera: Braconidae). PSP24 occurs as isoforms of pI 6.3 and 6.7 in the host’s hemolymph along with an antigenically related 10 kDa protein (PSP10). The proteins are highly glycosylated and have the same N-terminus amino acids and 5’ nucleotide sequences in their cDNAs but differ toward their 3’ ends. Their sequence similarities suggest that they are either members of the same gene family or the result of post-translational modification of the PSP24 message. The protein is encoded by both A. suspensa and Dl genes and its expression is induced in the host by the entomopoxvirus (DlEPV) from the poison glands of the female wasp. The objectives of the present study are to (1) determine whether PSP24-like proteins are expressed in Dl as they are in parasitized A. suspensa and (2) determine the effect of PSP24 on A. suspensa cells in vitro. Using a rabbit anti-PSP24 polyclonal serum and Western blot hybridization techniques, we now show that PSP24 is highly expressed in wasp larvae and in the poison gland reservoir of females, where DlEPV also occurs. PSP24-like proteins are released from wasp larvae cultured in vitro from embryonated eggs. We also detected DlEPV in male wasps by probing (i) Western blots of their proteins with a mouse anti-DlEPV polyclonal serum and (ii) dot blots of their DNA with digoxigenin (DIG-) labeled DlEPV genomic DNA. The co-occurrence of DlEPV and PSP24 in the wasps and the induction of the proteins in the host by DlEPV, suggest that PSP24 may serve some beneficial role in both wasp and host. Progress on the effects of PSP24 on A. suspensa cells in vitro, independent of DlEPV infection will be reported.

Index terms: Anastrepha suspensa, Caribbean fruit fly, parasitoid, fruit fly cell line, virus-induced proteins.

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