TIME-DEPENDENT AND CONCENTRATION-DEPENDENT RESPONSE OF THE DROSOPHILAANTENNA IMAGINAL DISC TO ANTENNAPEDIA

The response of the antenna imaginal disc to ectopic Antennapedia gene expression was explored in a heat shock Antennapedia (hsAntp) transge nic strain and in strains doubly transgenic for hsAntp and downstream enhancer trap targets. The distal to proximal changes in morphological transformation in response to Antennapedia product at different devel opmental stages were correlated with changing expression patterns of t ransgene targets from antenna to leg-like patterns. Dose-response stud ies indicated changing thresholds of response to Antennapedia. At part icular stages and doses of Antennapedia product, cell differentiation of leg bristles was uncoupled from transformation of the third antenna l segment to tarsus. The results suggest that determination for bristl e type does not depend on a prior determination decision for organ typ e. The results also provide an avenue for exploring the nature of ''co mpetence'' at cellular and molecular levels. (C) 1995 Academic Press, Inc.