The control of ecdysterone-regulated puffs in Drosophila salivary glands.

The hormone ecdysterone induces a characteristic sequence of changes in puffing activity in the salivary gland chromosomes of Drosophila melanogaster. A few puffs are induced very rapidly by the hormone and a larger number are only active after a lag period of several hours. To study the interrelationship of the activities of these "early" and "late" puffs, genotypes aneuploid for two early puffs have been constructed. In the duplication genotype the early puffs are active for less time than in the euploids while in the deficient genotype they are active for a longer period. Under appropriate assay conditions duplication of the early puffs results in a greater and more rapid response of some, but not all, late puffs to the hormone. Deletion of the early puffs results in a delayed response of the same late puffs. These data support the idea that the early puffs are autoregulated and that their products control activity at some late puff sites.