Characterization and biological effects of cotesia congregata polydnavirus on host larvae of the tobacco hornworm, manduca sexta

Abstract

The ovaries of endoparasitic species of braconid and ichneumonid wasps contain large numbers of polydnavirus (PDV) virions that replicate in specialized calyx cells of the ovaries and are injected into the host larva during parasitization. In the braconid wasp Cotesia congregata that parasitizes the tobacco hornworm, Manduca sexta, the total amount of viral DNA present in the ovaries was determined to be 25-75 ng. Analysis of viral DNA on 0.4% agarose gels showed that the genome was comprised of 15-20 circles of double-stranded DNA. SDS-PAGE analyses showed that a large number (>30) of structural polypeptides were present in the virions, and analysis of the venom likewise showed that multiple components were present. The major size classes of venom proteins differed from those present in the PDV. However, Western blots using polyclonal PDV antibodies showed that some cross-reacting PDV-like proteins were present in the venom, perhaps explaining the mild PDV-enhancing effect of the venom. Injection of PDV into unparasitized larvae provoked pronounced alterations in their growth, development, pigmentation, and hemolymph proteins. A densely staining band of hemolymph proteins of approximately 18-20 kD appeared in large amounts relative to other hemolymph proteins several days following injection of PDV; this band was undetectable in naturally parasitized larvae. Eggs which had been washed extensively to remove PDVs were encapsulated following injection, but development of the host still was disrupted, usually in the post-wandering prepupal stage. Thus,

Effects of parasitoid associated factors of the endoparasitoid Glyptapanteles liparidis (Hymenoptera: Braconidae)

“…In other well-studied species, parasitoid associated factors cause developmental arrest or mortality during pupation (Dushay & Beckage, 1993;Beckage et al, 1994;Soller & Lanzrein, 1996). Parasitism by the closely related, solitary endoparasitoid, G. porthetriae as well as injection of its purified, PDV-containing calyx fluid induced prolonged larval instars of L. dispar (Nussbaumer et al, 2002).…”

Functional endogenous viral elements in the genome of the parasitoid wasp Cotesia congregata : insights into the evolutionary dynamics of bracoviruses

“…Virus particles were purified from 200 C. congregata ovaries by SpinX filtration (Costar, France), and the DNA packaged in the particles was extracted as previously described [17]. Genomic DNA used for PCR approaches was extracted from over 80 wasps (50 mg) using the Easy-DNA kit (Invitrogen, France).…”

A polydnavirus-encoded protein of an endoparasitoid wasp is an immune suppressor.

“…The result of parasitization by many hymenopteran parasitoids is cellular alteration of host haemocytes, which correlates with a failure to aggregate or spread on a glass surface (Davies et al, 1987 ;Stoltz & Guzo, 1986 ;Strand, 1994). Although polydnavirus injection into caterpillars can induce haemocyte changes similar to those observed in parasitized caterpillars (Asgari et al, 1996 ;Beckage et al, 1994 ;Stoltz & Guzo, 1986 ;Summers & Dib-Hajj, 1995), the question remains whether the virus-coded proteins act in the cytoplasm of infected haemocytes or whether they are secreted into the haemolymph and interact with the surface of other haemocytes.…”