Molecular Characterization of the 71E Late Puff in Drosophila melanogasterReveals a Family of Novel Genes

Abstract

Early metamorphic development in Drosophila melanogasteris initiated by pulses of the steroid hormone ecdysone, which are transduced into tissue-specific transcriptional cascades. This process begins with the hormone-dependent activation of a set of transcription factors (early genes) that, in turn, activate set of tissue-specific effector genes (late genes). The 71E cytogenetic region of the salivary gland polytene genome contains several ecdysone-regulated transcription units. Molecular techniques were used to analyze these genes, their transcriptional program and their evolutionary relatedness. We find that this region contains a cluster of ten coordinately regulated late genes ( L71genes) that are organized as five divergently transcribed gene pairs. Maximum parsimony analysis suggests that an ancestral L71gene duplicated to form the first gene pair which was, in turn, duplicated to form the set of gene pairs. The L71gene products form a family of small, chemically basic proteins with a conserved backbone of cysteine residues. In addition, the 71E region contains another gene ( I71-1) with the regulatory and biochemical characteristics of the salivary gland intermolt glue proteins.