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United States Department of Agriculture

Agricultural Research Service

Title: Characteristics of the Developmental Arrestant in the Venom of the Ectoparasitoid Wasp Euplectrus Comstockii

Authors
item Coudron, Thomas
item Brandt, Sandra - UNIV OF MISSOURI

Submitted to: Toxicon
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 5, 1996
Publication Date: N/A

Interpretive Summary: Wasps that feed upon other insects (hosts) for their food source control their hosts so as not to become separated from them and in order to maximize the nutritional resources of the host to best fit their own needs. These control efforts result in changes in the host mobility, development, and biochemical composition. Some wasps accomplish these changes by injecting venom into the host. The venom then impacts the host physiology to bring about the changes. Often the venom is a complex mixture of chemicals. The venom of the ectoparasite Euplectrus comstockii is of particular interest because it causes a number of pest insects to stop growing at the very small caterpillar stage. The active ingredient within the venom was isolated, and found to be a mid-sized protein that is reasonably stable. These chemical characteristics indicate the active ingredient will be amenable to genetic engineering, which is an ideal quality for today's agricultural biotechnology efforts.

Technical Abstract: Parasitic Hymenoptera regulate their hosts in order to provide a suitable source of nutrition and dwelling for their offspring. Few regulatory factors, known to cause a specific effect on the host, have been structurally characterized. The larval ectoparasitoid Euplectrus comstockii Howard (Hymenoptera: Eulophidae) arrests larval-larval ecdysis in its lepidopteran hosts. Prior to oviposition the female wasp injects a venom into the hemocoel of the host and that venom alone is effective in causing the arrestment. A venom gland/reservoir structure connected to the lower reproductive tract of the wasp contains a complex mixture of proteins. There are no obvious similarities among the electrophoretic banding pattern (native or denatured) for venom proteins of E. comstockii and several other parasitic hymenopteran species. Venomous protein, separated by electrophoretic techniques, with a native molecular weight of ca. 66 kDa, was capable of arresting larval-larval ecdysis in fourth insta larvae of Trichoplusia ni (Lepidoptera: Noctuidae). Nanogram quantities of the protein were sufficient to cause arrestment. The activity of the protein was temperature, pH, organic solvent, and protease sensitive.

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