Juvenile hormone induction of glutathione S-transferase activity in the larval fat body of the common cutworm, Spodoptera litura (Lepidoptera: noctuidae)

The effect of pyriproxyfen, a juvenile hormone analog (JHA), on the pupation of S. litura was examined. A topical application of 100 mu g JHA/larva on the newly ecdysed (0-day) sixth instar larvae resulted in more than 80% pupation, while most of the 1- or 2-day-old larvae similarly treated developed into supernumerary larvae. Glutathione S-transferse (GST) activity in the fat body of 0-day-old sixth instar larvae was significantly induced within 12 h of JHA (100 mu g/larva) treatment. In contrast, no such induction was found when 1- and 2-day-old sixth instar larvae were similarly treated. This induction phenomenon was also observed when 0-day-old sixth instar larvae were treated with the natural JH III. The suppressive effects of alpha-amanitin and cycloheximide suggest that JHA induction of GST activity in these cutworm larvae presumably occurred at the gene transcription level.