Prepupal larval mosaics in Drosophila melanogaster

Abstract

THE metamorphosis of insects provides a model system for the study of hormone action. In Drosophila, metamorphosis is initiated by the formation of a puparium with a rigid cuticle that becomes tanned early in the prepupal period. Subsequently many larval tissues degenerate and the imaginal tissues develop to produce the adult insect. These processes are initiated in Drosophila by the steroid moulting hormone, β-ecdysone¹. We are interested in the mechanisms by which β-ecdysone elicits adult development. The recovery of mutants which cannot respond to the hormone would facilitate investigation into the nature of the action of β-ecdysone. We have isolated systematically a series of late larval and prepupal X-linked lethals (ref. 2 and unpublished results of I.K. et al.), about 15% of which are non-pupariating (npr) lethals in which metamorphosis is not initiated. We have investigated whether the npr condition is a result of the autonomous inability of the mutant target tissues to respond normally to β-ecdysone or rather is a stage-specific failure in the production of the hormone. Our results indicate that in most npr lethals the tissue cannot respond to the hormone. Futhermore, we estimate that there are 100–200 such lethals in the genome of D. melanogaster.