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A limited role in parasitism for Microplitis demolitor polydnavirus
1Department of Entomology, 237 Russell Labs, University of Wisconsin-Madison, Madison, Wisconsin, USA
Journal of Insect Physiology
|May 29, 2003
Summary
Parasitic wasps Microplitis demolitor infect Spodoptera frugiperda larvae with polydnavirus, temporarily disabling immune cells. However, wasp development fails due to early embryo death, not viral activity.
Area of Science:
- Entomology
- Insect Pathology
- Molecular Biology
Background:
- Spodoptera frugiperda larvae are physiologically altered when parasitized by Microplitis demolitor.
- Parasitized S. frugiperda larvae do not yield adult wasps, suggesting unsuccessful parasitism.
- The role of polydnavirus in this host-parasite interaction was previously unclear.
Purpose of the Study:
- To investigate the role of Microplitis demolitor polydnavirus (MdPDV) in the outcome of parasitism in Spodoptera frugiperda.
- To determine if MdPDV's transcriptional activity correlates with S. frugiperda's immune response and wasp development.
Main Methods:
- Monitoring MdPDV expression in S. frugiperda hemocytes post-parasitization.
- Assessing S. frugiperda hemocyte adherence, spreading, and in vitro encapsulation of M. demolitor eggs.
- Observing M. demolitor egg development and embryogenesis within S. frugiperda larvae.
Main Results:
- MdPDV transiently infected and expressed in S. frugiperda hemocytes, peaking in the first three days.
- During viral expression, hemocytes were non-adherent and failed to encapsulate wasp eggs.
- Hemocyte function recovered as viral expression declined, but M. demolitor eggs invariably died within 24 hours, independent of viral activity.
Conclusions:
- MdPDV temporarily disrupts the S. frugiperda encapsulation response but does not cause the failure of M. demolitor development.
- Failure of M. demolitor development in S. frugiperda is due to early embryogenesis arrest, irrespective of viral activity.
- MdPDV DNA persists in hemocytes even after viral expression ceases, indicating long-term molecular presence.
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