The promoter of DNA puff gene II/9-1 of Sciara coprophila is inducible by ecdysone in late prepupal salivary glands of Drosophila melanogaster.

Abstract

DNA puffs occur in Sciarid salivary gland chromosomes; they are sites of DNA amplification and intense transcription and they appear to encode secreted structural proteins needed for pupation. In this report we have used P-element transformation of Drosophila to study regulation of a Sciara DNA puff gene. We found that a 718-bp promoter fragment of DNA puff gene II/9-1 from Sciara coprophila directs expression of the bacterial reporter gene CAT in late prepupal salivary glands of transgenic Drosophila melanogaster. The identical tissue and analogous stage specificity indicate that some aspects of the ecdysone response are evolutionarily conserved between Drosophila and Sciara. When transgenic salivary glands are cultured in vitro, CAT activity is rapidly induced by ecdysone, suggesting direct control of gene expression by the ecdysone receptor. Putative stage-specific factors limit expression of the chimeric Sciara-CAT gene in transgenic Drosophila to late prepupae but not to third instar larvae when ecdysone titers are also high.

Ras signaling modulates activity of the ecdysone receptor EcR during cell migration in the drosophila ovary

“…While reduced amplification of the chorion loci in EcR-DN egg chambers is sufficient to explain reduced chorion protein accumulation and gene expression, it has been shown that sequence elements that regulate Cp18 amplification are discrete from sequences controlling transcription (Austin et al, 1999). Recent work from the Sciarid fly Sciara coprophila (Foulk et al, 2006) has shown that EcR, which regulates transcription of the II/9a genes (Bienz-Tadmor et al, 1991), also binds to the ORC site in the II/9a locus, suggesting that the mechanism of hormonal control of amplification may be conserved in insects. Thus, EcR regulation of amplification and transcriptional activation of the Cp18 gene via its nearby EcRE likely are stimulated independently by ecdysone.…”

The DNA puff BhB10-1 gene is differentially expressed in various tissues of Bradysia hygida late larvae and constitutively transcribed in transgenic Drosophila

“…The transformed sequences so far tested are not amplified in the salivary gland of transgenic Drosophila, indicating that amplification and transcription of DNA puff genes are processes that can be uncoupled (7,8).…”

“…The analysis of transgenic lineages of Drosophila carrying promoter sequences of the II/9-1 gene of Sciara coprophila and the BhC4-1 gene of B. hygida has indicated that the factors necessary for tissue-specific and developmentally regulated expression of sciarid DNA puff genes may be conserved in Drosophila (7,8). The transformed sequences so far tested are not amplified in the salivary gland of transgenic Drosophila, indicating that amplification and transcription of DNA puff genes are processes that can be uncoupled (7,8).…”

Replication initiates at a confined region during DNA amplification in Sciara DNA puff II/9A.

“…Unlike RNA puffs in Drosophila, DNA puffs in the fungus fly, Sciara coprophila, not only are sites of active transcription (GabrusewyczGarcia and Kleinfeld 1966), but also of DNA amplification (Crouse and Keyl 1968;Rasch 1970a). Whereas the developmental cues that trigger chorion gene amplification and transcription in Drosophila are unknown, cytological puffing and the molecular events of DNA amplification and transcription in Sciarid DNA puffs are controlled by the insect steroid molting hormone, ecdysone (Crouse 1968;Bienz-Tadmor et al 1991;C. Liang, N. Wu, D. Alam, H.S.…”