THE ECDYSONE-INDUCIBLE BROAD-COMPLEX AND E74 EARLY GENES INTERACT TO REGULATE TARGET GENE-TRANSCRIPTION AND DROSOPHILA METAMORPHOSIS

Pulses of the steroid hormone ecdysone initiate Drosophila metamorphos is by inducing widespread changes in gene expression. The Broad-Comple x (BR-C) and E74 are induced directly by ecdysone and encode families of transcription factors that regulate ecdysone primary- and secondary -response genes. Genetic analyses have revealed that mutations in the BR-C and E74 are lethal during metamorphosis and that these mutations cause some similar lethal phenotypes and alterations in secondary-resp onse gene transcription. To examine whether the BR-C and E74 function together during development, we have combined representative alleles f rom each BR-C and E74 complementation group. Analysis of the morpholog ical and molecular phenotypes of the double-mutant animals reveals tha t BR-C and E74 alleles act together to produce both novel and synergis tic effects. We find that the BR-C and E74 share functions in puparium formation, pupation and early gene induction. In addition, our eviden ce suggests that the BR-C and E74 transcription factors may directly i nteract to regulate the expression of salivary gland glue and late gen es. This data is consistent with current models which propose that com binations of ecdysone primary-response genes regulate common morphogen etic pathways during insect metamorphosis.