Hormonal cross talk in insect development.

Two hormones, 20-hydroxyecdysone (20E) and juvenile hormone (JH), coordinately orchestrate insect growth and development. 20E initiates all major developmental transitions from egg, to larva, to pupa, to adult, but it is an interaction with the JH signal that transduces 20E pulses into stage-specific responses. Years of research have given us an understanding of 20E signaling pathway. By contrast, the molecular mechanism of JH action remains an enigma. Recent studies provide insight into the molecular background to JH-20E regulatory interplay. Two transcription factors--BR-C and E75A--contribute to the cross-talk between the two hormones. It appears that BR-C is a key target of JH status quo action, and E75A is a part of the mechanism whereby JH prevents BR-C activation.