A 24 kD protein occurs in the hemolymph of larvae/pupae (hosts) of the Caribbean fruit fly, Anastrepha suspensa(Diptera: Tephritidae) after parasitism by the wasp Diachasmimorpha longicaudata(Hymenoptera: Braconidae). PSP24 is encoded by host and wasp genes, but not by those of the symbiotic entomopoxvirus, DlEPV, that is found in the poison gland of the wasp and transmitted to the host during parasitism. PSP24 and DlEPV occur in hemocytes of naturally parasitized hosts and in the hemolymph of healthy puparia injected with purified DlEPV. We hypothesized that PSP24: (1) is co-localized with DlEPV within the wasp and host and (2) is released from wasp larvae into the host’s hemolymph. Alternatively, PSP24 is expressed only in the host and occurs independent of DlEPV. Our objectives were to determine whether PSP24: (1) occurred with DlEPV in the wasp adult and immature stages, and in various host tissues, and (2) levels in the host were influenced by wasp development and/or DlEPV morphogenesis. Using PSP24 antisera, we detected PSP24 in Western blots of wasp poison glands, oviposited eggs, and all instars. PSP24 was also in the host fat body and hemocytes. Wasp larvae that hatched from eggs in vitro contained increasing levels of PSP24 with age, as did their culture medium. The enzyme-linked immunosorbent assay (ELISA) of host hemolymph using the anti-PSP24 sera, also detected PSP24 prior to wasp egg hatch, and a sharp sustained peak thereafter, during budding of the virus. Thus, PSP24/DlEPV co-localization and PSP24 release by wasp larvae and induction in other dipterans by DlEPV injection, suggest that PSP24 is probably a type of defensin. Support from the National Science Foundation grants, IBN 9514583 and 9986076 to POL is gratefully acknowledged.
The ESA 2001 Annual Meeting - 2001: An Entomological Odyssey of ESA