Implicated in the regulation of ecdysone-triggered gene hierarchies. Probably plays a key role in mediating the regulation of the larval molt by 20-OH-ecdysone. In mid instar larvae salivary glands, levels are low during puff stage 1, increase during puff stages 2-4 and diminish from stage 5 onwards. In prepupae, isoform A is the predominant form during puff stage 19 and the transition to stage 20. By stage 3 it is present in the gut, Malpighian tubules and the fat body, levels persist beyond stage 11. The expression of this protein is developmentally regulated and is correlated with the 20-OH-ecdysone induced activity of puff 75B. Belongs to the nuclear hormone receptor family. NR1 subfamily.