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 insta r larave. In order to analyse the hormonal regulation of this puff set we have investigated the genetic regulatory hierarchy governing the e xpression of three genes mapping at the 3C polytene region, from which one of the most prominent intermoult puff originates. The results obt ained reveal that the expression of the genes studied, named ng-1, ng- 2 and ng-3, is coordinate and specifically restricted to the Puffing S tage 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 ecdyson e induced BR-C locus. While the ng-gene repression results to be a sec ondary response to ecdysone, the recent identification of functional E cREs 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 beg inning of the third larval instar.