Ecdysone-induced changes in Glycoprotein synthesis and puff activities in Drosophila virilis salivary glands

A Kunitz type protease inhibitor related protein is synthesized in Drosophila prepupal salivary glands and released into the moulting fluid during pupation

From the Drosophila virilis late puff region 31C, we microcloned two neighbouring genes, Kil-1 and Kil-2, that encode putative Kunitz serine protease inhibitor like proteins. The Kil-1 gene is expressed exclusively in prepupal salivary glands. Using a size mutant of the KIL-1 protein and MALDI-TOF analysis, we demonstrate that during pupation this protein is released from the prepupal salivary glands into the pupation fluid covering the surface of the pupa. 3-D-structure predictions are consistent with the known crystal structure of the human Kunitz type protease inhibitor 2KNT. This is the first experimental proof for the extracorporal presence of a distinct Drosophila prepupal salivary gland protein. Possible functions of KIL-1 in the context of the control of proteolytic activities in the pupation fluid are discussed.

Ecdysone-controlled mRNA stability in Drosophila salivary glands: deadenylation-independent degradation of larval glue protein gene message during the larval/prepupal transition

20-Hydroxyecdysone induces poly(A) shortening and the subsequent degradation of transcripts encoding the larval glue protein LGP-1 in Drosophila virilis late third larval instar salivary glands. Degradation concurs with the transient increase of ribonucleolytic activities in the gland cells. In vitro nuclease assays using crude cytoplasmic extracts of ecdysone-treated salivary glands demonstrate degradation to be deadenylation-independent and that the induced ribonucleolytic activities initiate the degradation of the Lgp-1 transcripts in putative single-stranded loop regions. The independence of degradation from deadenylation is also found in vivo in transformed D. melanogaster carrying a modified Lgp-1 gene.

The salivary gland chromosomes of Drosophila virilis: a cytological map, pattern of transcription and aspects of chromosome evolution

By combining information from microscopical observation and photography a graphical map of Drosophila virilis salivary gland chromosomes was constructed. About 1,560 individual bands are shown and patterns of transcription at about 360 sites are indicated. The application of the map is demonstrated by using genetic, morphological and in situ hybridization data to identify the white-Notch regions of D. virilis and Drosophila melanogaster as homologous chromosome segments with constant and variable features.

Drosophila salivary glands exhibit a regional reprogramming of gene expression during the third larval instar

In D. virilis salivary glands transcripts of two early gland protein genes, Egp-1 and Egp-2, which encode putative secretory proteins, accumulate in all cells from the first to mid third larval instar. Subsequently the transcripts disappear from the cytoplasm of the corpus cells, but not from their nuclei, where they accumulate at the chromosomal site of their synthesis. In the collum cells, however, Egp-transcripts continue to be detectable in the cytoplasm until the end of larval life. In the salivary glands of transgenic D. melanogaster the presence of a Egp-1/lacZ fusion protein shows the same regional shift as the cytoplasmic Egp-transcripts in D. virilis. We predict that the expression of Egp-genes is related to an early secretory function of the larval salivary glands which is executed by all cells during earlier larval stages but becomes restricted exclusively to the collum cells during the third larval instar.

Drosophila glue protein gene expression. A proposal for its ecdysone-dependent developmental control

The primary targets of steroid hormones are genes. For the ecdysone-controlled genes of Drosophila larval glue proteins proximal and distal control elements were identified by mutagenesis and sequence comparison. Their presence is required for the correct stage- and tissue-specific expression of these genes. The supposed function of these elements is described in a working model.

High resolution mapping of in situ hybridized biotinylated DNA to surface-spread Drosophila polytene chromosomes

We describe a method of mapping genes or transcripts on polytene chromosomes by transmission electron microscopy. We present several applications which illustrate that, in favorable cases, the method has a resolution of ca. 10 kg, and that high resolution mapping of hybridization sites relative to bands and puffs can be achieved. We mapped sites of transcription for poly-(A) RNA and present evidence which shows that these sites are localized in some bands and puffs, but are also found in interbands.

Effects of ecdysterone in polytene chromosomes of Trichosia pubescens

Injection of ecdysterone into mid-fourth instar larvae of Trichosia pubescens brought about drastic changes in the puffing pattern of the chromosomes of the salivary gland. The puff sequence induced by the hormone is quite similar to that which normally occurs at the end of larval life. Three classes of puffs were observed: the early induced, the late induced, and those repressed by the hormone. Among the late-induced puffs, several were DNA puffs. The protein synthesis inhibition prevents the induction of all late puffs and the process of gene amplification but does not affect the induction of the early puffs.