HORMONAL-REGULATION OF THE DROSOPHILA-MELANOGASTER NG-GENES

Intermoult puffs constitute the first set of ecdysone-responsive puffs detected on salivary gland chromosomes of D. melanogaster third instar larave. In order to analyse the hormonal regulation of this puff set we have investigated the genetic regulatory hierarchy governing the expression of three genes mapping at the 3C polytene region, from which one of the most prominent intermoult puff originates. The results obtained reveal that the expression of the genes studied, named ng-1, ng-2 and ng-3, is coordinate and specifically restricted to the Puffing Stage 1 (PS 1). The repression of these genes appears to be related to the PS1/PS2 transition and is dependent on the activity of the ecdysone induced BR-C locus. While the ng-gene repression results to be a secondary response to ecdysone, the recent identification of functional EcREs within the ng-1,2 coding region suggests that the induction of ng-genes might be part of the early ecdysone primary response at the beginning of the third larval instar.