Ecdysone-stimulated RNA synthesis in salivary glands of drosophila melanogaster: assay by in situ hybridization.

3H-RNA was isolated from nuclei and cytoplasm of Drosophila melanogaster larval salivary glands after labeling in organ culture in the presence or absence of ecdysone. Hybridization to the sites of the ecdysone-induced puffs 74EF and 75B could be detected only if the RNA was labeled in the presence of ecdysone, while hybridization to the ecdysone-repressed puff 68C was found primarily in the cytoplasmic RNA sample labeled in the absence of ecdysone. Hybridization at the site of an ecdysone-insensitive puff, 50CD, was readily detectable in all RNA samples. RNA hybridizing to the unpuffed region 60D seemed to be restricted to the nucleus of salivary gland cells and was present at only a low level in cytoplasmic RNA samples. The data indicate that in situ hybridization can be used to detect specific hormone-induced changes in transcription.