|Wright Osment, Maureen|
|Brandt, Sandra - UNIV OF MISSOURI|
Submitted to: Entomological Society of America Annual Meeting North Central Branch
Publication Type: Abstract Only
Publication Acceptance Date: March 24, 1999
Publication Date: N/A
Technical Abstract: The venom of the hymenopteran parasitoid Euplectrus comstockii (Family: Eulophidae) arrests molting and induces premature production of storage proteins in lepidopteran larvae. A higher titer of venom was shown to be required to arrest apolysis than to arrest ecdysis, and the developmental state of the larva within an instar was found to be critical to whether the evenom arrested apolysis or only ecdysis. The arrestment activity of the venom persisted in the host hemolymph for only 12 h post-parasitism. We propose that the degradation of activity is due to a factor present within the hemolymph of the parasitized host, because activity of the venom within the hemolymph of nonparasitized larvae persists beyond this time period. Prior studies revealed that the arrestment activity of the venom was associated with a 66 kDa protein. The presence of this protein, visualized through Western blots using antisera to its 40 kDa subunit, revealed that its presence is closely correlated with the arrestment activity in the hemolymph of parasitized larvae. The mechanism of action of the venom was investigated by culturing larval integument and fat body in vitro with or without venom. In response to 20-hydroxyecdysone, integument from parasitized larvae failed to produce new cuticle in vitro, whereas nonparasitized integument incubated with venom produced a normal cuticle. Results from confocal microscopy of whole mounts of parasitized larvae incubated with antisera to the 40 kDa protein suggest a possible role of the fat body in this arrestment. Therefore, we propose that another host factor, possibly from the fat body, is necessary to arrest cuticle production by integument cultured in vitro.