ECDYSONE-STIMULATED RNA-SYNTHESIS IN IMAGINAL DISKS OF DROSOPHILA-MELANOGASTER - ASSAY BY INSITU HYBRIDIZATION

Cytoplasmic RNA from imaginal disks of D. melanogaster, labeled by uridine incorporation in organ culture, was assayed by hybridization to cytological preparations of polytene chromosomes. RNA labeled during the early stages (first 4 h) of ecdysone stimulation was compared to RNA labeled in the absence of the hormone. For the poly(A)-containing fraction (oligo-dT bound), several loci hybridized only RNA labeled in the presence of ecdysone; 1 locus hybridized only control RNA. The majority of hybridizing loci were unaffected by the hormone. Of the loci hybridizing RNA not bound to oligo-dT, several appeared specific for the ecdysone-treated sample, though most were labeled more heavily with this RNA than with the control. None of the ecdysone-sensitive loci visualized by in situ hybridization were sites of salivary gland puffs induced by ecdysone on the same time scale.