THE 4TH KARLSON LECTURE - ECDYSONE-RESPONSIVE GENES

Those of us who study ecdysone action share at least two important lon g-range goals: (i) to understand the developmental specificity of ster oid action in full molecular detail, by integrating ecdysone action wi th our rapidly expanding knowledge of the molecular biology of insect development, and (ii) to better understand the nature of the steroid r esponse and its evolution by taking advantage of the unparalleled oppo rtunities for both genetic and comparative study afforded by the diver sity of the ''ecdysone world''. However, until recently, the molecular fundamentals of the ecdysone system were unknown and our efforts have , of necessity, been devoted to their elucidation. Now that the situat ion has changed: we have a small but varied catalog of ecdysone-respon sive genes for study and it is clear that some of these are tissue- an d stage-specific in their expression. The ecdysone receptor (EcR), lik e other steroid receptors a member of the nuclear receptor family, is now accessible to molecular study, and we have a preliminary understan ding of the DNA sequences (EcREs) that bind receptor and specify a gen e as ecdysone-responsive. With these tools in hand and with the opport unity to turn to larger questions, it is a propitious moment to consid er the nature of those questions and how ecdysone can contribute to th e answers.