Interference of the insect growth regulator methoprene in the process of larval‐pupal differentiation

Abstract

AbstractStudies with epidermal cells of a number of insects showed that a sequence of physiological events takes place prior to and during the process of commitment of the epidermal cells from the larval to the pupal stage. At the onset of metamorphosis RNA synthesis, including that of RNA, was suppressed for about 30 h just prior to the wandering stage. At the completion of the wandering stage, pupally committed epidermal cells synthesize a new type of RNA termed hetero‐disperse nuclear RNA (hnRNA). It is suggested that this RNA species could play a role in the permanent shutting‐off of larval‐specific genes. Methoprene, a juvenile hormone analogue (JHA), delayed the larval‐pupal transformation and prevented these changes in RNA synthesis when applied prior to the appearance of the hnRNA, but had no effect when applied after this period. Treatment with the JHA in the early last larval instar prevented not only the normal rise in ecdysteroid titer, but also the increase in the activity of chitinolytic enzymes. Treatment of young pupae had no effect on either the ecdysteroids titer or on enzyme activity. A causal relationship between molting hormone titer and the activity of chitinolytic enzymes is proposed. © 1993 Wiley‐Liss, Inc.