Molecular analysis of a developmentally regulated gene which is expressed in the larval salivary gland of Drosophila.

The polytene genome of the larval salivary gland of Drosophila undergoes dramatic alterations in localized transcriptional activity late in third-instar development. One of these changes involves the 20-OH ecdysone-mediated and coordinate repression of a dispersed set of intermolt puff sites. The DNA from one of these loci (that located within the 90BC interval) has been isolated by molecular cloning techniques. This DNA was shown to be present one time per haploid Drosophila genome and to contain a gene (designated the Group V gene) which is developmentally regulated. The Group V transcript was shown to accumulate only during third-instar larval development and to be located exclusively in the salivary gland. These results are consistent with the hypothesis that the Group V gene codes for a salivary gland glue protein.