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Nancy E. Beckage
Professor of Entomology and Cell Biology
Email: nbeckage@ucr.edu
Biochemical host-parasite and host-pathogen relationships.
Insect proteins, immunity, endocrinology and virology.
My laboratory has focused its efforts in deciphering the complexities of biochemical and molecular host-pathogen and hostparasite relationships, with special emphasis on wasp parasitoids that kill their hosts. The wasp parasitoid Cotesia congregata injects a polydnavirus (polydisperse DNA virus) into its host, the tobacco hormworm (Manduca sexta). The wasp genome contains integrated viral sequences, and the viruses replicate only in the female wasp's ovarian calyx tissue. The viruses cause host immunosuppression (the equivalent of an insect AIDS-like virus), allowing the parasitoids to mature without invoking a host immune response. The polydnavirus triggers apoptosis of host hemocytes, thus causing the host to be immunosuppressed during the initial stages of parasitic infection. Integration of viral sequences in the genomic DNA of the wasp itself is under study. Future studies are being directed at deciphering the role of virus-encoded proteins in causing host immunosuppression.
Another area of special interest concerns the role of the parasitoid's polydnavirus in the successful interaction between the parasites and their host via expression of PDV gene products. A major hemolymph protein is induced to appear in the host beginning immediately following parasitization and this protein is a polydnavirus transcript. Host hemocytes, fat body, and other tissues participate in its synthesis to varying degrees. Viral DNAs persist in the host for the duration of parasitism. We are now exploring the biological role of the protein in causing host immunosuppression and other physiological changes.
Endocrine relationships between the partners also are being examined, with particular emphasis on mechanisms of host developmental arrest involving endocrine and neuroendocrine disruption. Parasitized larvae show enhanced accumulation of neuropeptides in neurosecretory cells of the endocrine system. Hundreds of species of wasp parasitoids cause a similar host arrest, hence their utility as biological control agents. A common mechanism, such as disruption of neuropeptide release, may account for many species' ability to cause developmental arrest of their host insect in a pre-metamorphic state. The hemolymph ecdysteroid titer of the host peaks shortly before the wasps emerge.
Wasp endo- and ectoparasitoids clearly have evolved the capacity to interact with their host via a variety of complex hormonal and biochemical interactions. This is particularly true of parsitoids that ultimately induce developmental arrest and cause death of the host. Behavioral effects pf parasitism are also seen.
Selected Publications:
- Beckage, N.E. (1997) Parasites and Pathogens: Effects on Host Hormones and Behavior. Editor. Chapman & Hall.
- Reed, D. & N.E. Beckage. (1997) Inhibition of testicular growth and development in Manduca sexta larvae parasitized by the braconid wasp Cotesia congregata. J. Insect Physiol. 41:29-38.
- Alleyne, M. & N.E. Beckage. (1997) Parasitism-induced effects on host growth and metabolic efficiency in tobacco hornworm larvae parasitized by Cotesia congregata. J. Insect Physiol. 43:407-424.
- Adamo, S.A., C.E. Linn & N.E.Beckage. (1997) Correlation between changes in host behaviour and octopamine levels in the tobacco hornworm, Manduca sexta, parasitized by the gregarious braconid parasitoid wasp Cotesia congregata. J. Exp. Biol. 200:117-127.
- Beckage, N.E. (1996) Interactions of Viruses with Invertebrate Cells. Invited chapter for book entitled "New Directions in Invertebrate Immunology" Edited by K. Soderhall, S. Iwanaga & G.R. Vasta, pp. 375-399. SOS Publications. Fair Haven, N.J.
- Lavine, M.D. & N.E. Beckage. (1996) Temporal pattern of parasitism-induced immunosuppression in Manduca sexta larvae parasitized by Cotesia congregata. J. Insect Physiol. 42: 41-51.
- Lavine, M. D. & N. E. Beckage. (1995) Polydnaviruses: Potent mediators of host insect immune dysfunction. Parasitology Today 11:368-378.
- Zitnan, D., S. J. Kramer, T. G. Kingan & N. E. Beckage. (1995) Parasitism-induced accumulation of multiple neuropeptides in the brain and central nervous system of Manduca sexta parasitized by Cotesia congregata. J. Comp. Neurol. 356:83-100.
- Harwood, S. H., A. J. Grosovsky, J. W. Davis, E. A. Cowles & N. E. Beckage. (1994) An abundantly expressed host hemolymph glycoprotein isolated from newly parasitized Manduca sexta larvae is a polydnavirus gene project. Virology 205:381-392.
- Beckage, N.E. (1993) Endocrine and neuroendocrie host-parasite relationships. Receptor 3:233-245.
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