ANTENNA TO LEG TRANSFORMATION - DYNAMICS OF DEVELOPMENTAL COMPETENCE

We explore the transformation of antenna to leg in Drosophila melanoga ster, using ectopically expressed transgenes with heat shock promoters : heat shock Antennapedia, heat shock Ultrabithorax, and heat shock mo use Hox A5. We determined the frequency of transformation of several l eg markers in response to Antennapedia protein delivered by heat shock at different times and doses. We also studied stage-specific response s to the transgene, heat shock mouse Hox A5. Results show that each ma rker has its own stage and dose-specific pattern of response. The same marker could pass through a period of high-dose inhibition followed b y a dose-independent response and then a positive dose-dependent phase . The heat shock-induced transgenes and spineless aristapedia transfor med the apterous enhancer trap antenna disc expression pattern toward the pattern found in leg discs. These results are considered in relati on to developmental competence-the ability of developing tissue to res pond to internal or external influences. The results suggest that all genes tested interact with the same competence system and that at leas t two classes of mechanisms are associated with antenna to leg transfo rmation: one comprises global mechanisms that permit transformation ov er approximately 24 hr; the second class of mechanisms act very locall y and are responsible for changes in dose response on the order of 4-8 hr. (C) 1996 Wiley-Liss, Inc.