Submitted to: Annals of the New York Academy of Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 12, 1996
Publication Date: N/A
Interpretive Summary: Lepidopteran insect pests attack numerous vegetable, field, orchard, and forest crops each year in the United States, resulting in reduced productivity and heavy expenditures on chemical insecticides. The necessity of discovering environmentally acceptable and economically feasible alternatives to traditional toxic chemicals for insect control leads to close examination of the biology of the insect. Lepidopterans, such as the gypsy moth, are dependent upon steroid hormones, generically referred to as ecdysteroids, for successful growth and development. Without them, they perish. We have discovered a naturally occurring substance, within the lepidopteran insect itself, which inhibits the production of these essential ecdysteroids. The purification, characterization, and analysis of this inhibitor, an ecdysiostatin, will expedite the development of naturally derived pest control agents. These control agents will be modeled after the insect's own physiology, will be specific for the target pest, and harmless to other organisms.
Prothoracicotropic hormone (PTTH)-like activity (ecdysiotropin) is present in extracts of the larval brain-suboesophageal ganglion complex (brain-SOG) and ventral nerve cord (VNC) ganglia of the gypsy moth, Lymantria dispar, and ecdysiostatic activity is present in extracts of adult L. dispar brain-SOG. PTTH-like activity is detected using an in vitro prothoracic gland bioassay which is modified for detection of ecdysiostatin. Ecdysiotropic activity is distributed among all eleven non-cerebral ganglia associated with the VNC, as well as in brain-SOG. There is some quantitative variability of non-cerebral ecdysiotropic activity among the ganglia with production of RIA-detectable ecdysteroid ranging from less than 200 to greater than 600 pg 20-OH-ecdysone equivalents/hour/gland. Adult ecdysiostatic activity is associated with three fractions which elute from a size exclusion system at a volume corresponding to ca. 900 MW. The most potent fraction contains an ecdysiostatic factor(s) which completely inhibits ecdysteroid production in vitro at 0.08 brain-SOG equivalent/microliter, and has an IC50 of <4x10-3 brain-SOG equivalent/microliter.