THE PLEIOTROPIC FUNCTION OF DELTA DURING POSTEMBRYONIC DEVELOPMENT OFDROSOPHILA-MELANOGASTER

Analysis of the development of Delta (Dl) temperature-sensitive mutant s pulsed at restrictive temperature during larval and pupal stages rev eals multiple phenocritical periods during which reduction of Dl funct ion affects viability and development of adult structures. Dl function is required during the third larval instar for post-pupal viability a nd during the first day of pupal development for viability through ecl osion. Dl function is required biphasically for the development of sen sory bristles. Earlier pulses lead to bristle multiplication and later pulses lead to bristle loss. The exact intervals during which multipl ication and loss are induced vary for different bristles. Dl function is also required for development of most, if not all, cell types in th e retina. Different pulses result in reduction in eye size, scarring, and glossiness, as well as multiplication and loss of interommatidial bristles. We also define intervals during which Dl function is require d for aspects of leg and wing development. Phenocritical periods for D l function are temporally coincident with those previously reported fo r Notch (N), consistent with the hypothesis that the proteins encoded by Dl and N interact throughout development to assure correct specific ation of cell fates in a variety of imaginal tissues.