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Title: ALLATOSTIMULATING ACTIVITY OF BRAIN EXTRACTS: COMPARISON OF REPRODUCING AND DIAPAUSING PYRRHOCORIS APTERUS (L) (HETEROPTERA)

Author
item HODKOVA, MAGDALENA - CZECH ACADEMY OF SCIENCES
item OKUDA, TAKAHASHI - MAFF, JAPAN
item Wagner, Renee

Submitted to: European Journal of Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/27/1995
Publication Date: N/A
Citation: N/A

Interpretive Summary: The Colorado potato beetle (CPB) is a major pest of potatoes, both in the US and worldwide. It is difficult to control these insects because they are able to survive during cold weather or food scarcity by entering a state of "hibernation" known as diapause, during which these insects are not able to reproduce. If it were possible to break diapause during unfavorable conditions or to maintain diapause during favorable conditions populations of CPB might be reduced significantly because of the inability to reproduce or survive under harsh conditions. The linden bug is closely related to the milkweed bug and red cotton stainer, and also undergoes diapause during environmentally unfavorable conditions. A new compound, similar to juvenile hormone, but not the same as any known JH, was was isolated from the linden bug. We have shown that this JH is synthesized in the corpora allata, a part of the nervous system, and its synthesis is controlled by factors in the brain which inhibit or stimulate its synthesis. Information obtained from the linden bug and the techniques developed from this work will be directly applied to the CPB. This work is part of a collaborative effort (initially sponsored by OICD) with the Czech Academy of Sciences. Consequently, work done in the Czech Republic will focus on the linden bug, while work done in the US will focus on CPB. As juvenile hormone is directly involved with reproductive function and with diapause, identification of the JH and the brain factors that control its synthesis will be useful in designing insect control agents that are specific and non-toxic. These compounds will help to prevent losses of potato crops by CPB, both in the US and in Europe, where the CPB has become resistant to conventional pesticides.

Technical Abstract: The effect of brain extract on synthetic activity of corpora allata (CA) in vitro was investigated by a radiochemical assay in Pyrrhocoris apterus. Brain extracts were prepared from neuroendocrine complexes of brain-suboesophageal ganglion-corpora cardiaca-corpus allatum dissected from either short-day (diapausing) females or long-day (active) females or males. Both short-day and long-day brain extracts stimulated synthetic activity of the CA from long-day females. The CA from short-day females was refractory to stimulation. The allatostimulating activity of the brain extract was maintained after removal of large proteins by 10,000-molecular weight limit centrifugal ultrafiltration, but was destroyed by treatment with proteinase K. Therefore, the allatostimulating factor appears to be a peptide. The culture medium containing a mixture of synthetic products of the CA was extracted by hexane and subjected to TLC analysis. The brain extract stimulated synthesis of a product from radiolabelled methionine which elutes at the same position on TLC as that of the major yet to be identified product of the CA in four other heteropteran species, which has yet to be identified.