Steroid receptors and orphan receptors in Drosophila development.

Drosophila steroid receptors and related receptor-like proteins show remarkable conservation of structure and function relative to vertebrate homologues. While those proteins are involved in numerous embryonic and post-embryonic developmental processes, a striking number of receptor-like proteins are clustered in regulatory hierarchies under the control of the insect molting hormone ecdysone. This has suggested a number of models based on competitive, cooperative and inter-regulatory interactions between these proteins.