The role of the hormone ecdysterone in the control of the activity of the Balbiani rings and the other puffs of Drosophila auraria

The activity of the Balbiani rings and the other puffs of Drosophila auraria salivary gland chromosomes from various stages of development was studied in vitro in the presence or the absence of various concentrations of the hormone ecdysterone. It was found that of 81 sites affected by these conditions, 69 (including the BRs) exhibit changes during normal development as well, while the remaining 12 change only under culture conditions. The results indicate that the normal profiles of certain puffs (and the BRs) are approximated more closely by the lower concentrations of the hormone and it is suggested that such low concentrations are necessary to induce the normal course of events in vivo. Various hypotheses concerning the influence of ecdysterone on the puffing patterns are discussed in view of the data presented in this report.