FURTHER EVIDENCE THAT DIAPAUSE IN THE GYPSY-MOTH, LYMANTRIA-DISPAR, IS REGULATED BY ECDYSTEROIDS - A COMPARISON OF DIAPAUSE AND NONDIAPAUSESTRAINS

A nondiapause strain of the gypsy moth offers an additional tool for e valuating the regulation of diapause in this species. Patterns of prot ein expression in the gut and gut enzyme activity distinguished the tw o strains, Synthesis of a 55 kDa gut protein, previously linked to dia pause, began 14 days after oviposition in both the diapause (D) and no ndiapause (ND) strains. Though synthesis of this protein persisted in the D strain, its synthesis decreased after day 18 in the ND strain, I n the D strain, activity of the proteolytic enzymes (trypsin, chymotry psin, elastase, aminopeptidase) and esterase remained low, while activ ity of all of these enzymes increased dramatically in the ND strain 18 -20 days after oviposition. By contrast, alkaline phosphatase (ALP) ac tivity was high in both strains 15-17 days after oviposition, activity remained high in the D strain but in the ND strain activity then decr eased, Patterns of ALP zymograms were similar in the two strains on da y 15, but later a band of high mobility appeared only in the D strain, When 20-hydroxyecdysone was added to hanging drop cultures containing ND pharate larvae 15 days after oviposition, the larvae assumed the c haracteristics of diapause larvae: the 55 kDa gut protein was synthesi zed, the ALP zymogram revealed the characteristic diapause pattern, an d they failed to ingest culture medium, The fact that 20-hydroxyecdyso ne could elicit these responses in ND individuals further supports pre vious results indicating that ecdysteroids promote the induction and m aintenance of the pharate larval diapause in this species. (C) 1997 El sevier Science Ltd. All rights reserved.