Submitted to: Archives of Insect Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 26, 1997
Publication Date: N/A
Interpretive Summary: The gypsy moth is a destructive pest of Northern forests and shade trees. It reproduces at a very high rate, it is difficult to control with known insecticidal agents in the field, and it has few known predators. Increased knowledge of how reproductive processes are controlled in this insect may lead to development of new methods for control of this pest. Very little is known about the physiology and endocrinology of male insects, although we have shown that one peptide from the brain (LTE) can initiate and maintain steroid syntheses by moth testes. In this paper we have shown that there are at least 15 other brain peptide hormones that can regulate the output of steroid hormones by the testes of gypsy moths. The structures of 9 of these additional active hormones have been determined; 5 sequences are chemically similar to LTE (the LTE family) and 4 are quite different. In a database search, the former were similar to the inhibitory peptides, but the latter 4 were similar to zinc finger proteins (which are active in hormone mechanisms) and several virus proteins. This information will be useful to scientists in determining how these hormones function in insects and will lead to new approaches for development in gypsy moth control by manipulation of their reproductive processes.
Technical Abstract: Lymantria testis ecdysiotropin (LTE) was isolated from the most prominent peptide peak corresponding to an active fraction obtained by high pressure liquid chromatographic (HPLC) separation of a homogenate of 13,000 Lymantria dispar pupal brains. In this work we examined the other active fractions from a second HPLC separation of an additional 2,300 pupal brains. Bioassay of the ecdysteroidogenic effects of each peak on L. dispar testes allowed detection of 20 peptide peaks with testis ecdysiotropic activity in addition to LTE. Of these, 10 peptides were purified and sequenced. All of them were comparable to LTE in molecular weight. The amino acid sequences of 5 of the peptides were similar enough to LTE to be considered to be members of an LTE family. However, the other 5 peptides had no significant homology with LTE or with each other. A BLAST database search indicated LTE family homology with portions of inhibitory peptides such as those inhibiting cytolysis. In contrast, non-LTE ecdysiotropic peptides were strikingly homologous to portions of vertebrate and invertebrate zinc finger peptides and to vertebrate and invertebrate virus proteins.