Spatial expression of the hsr-omega (93D) gene in different tissues of Drosophila melanogaster and identification of promoter elements controlling its developmental expression

Abstract

Developmental expression of the heat shock inducible non-protein coding hsromega gene in several larval and adult tissues of Drosophila melanogaster was examined by in situ hybridization to transcripts in intact organs and by X-gal staining in the germline transformants carrying the lacZ reporter gene under the control of hsromega promoter. This gene is expressed in a specific spatial pattern in all the larval and adult tissue types examined; however, its transcripts were specifically absent in certain gonadal cell types like the male as well as female gonial cells and in follicle cells and oocytes in ovary. All polytenised tissues like the prothoracic and salivary glands, certain regions of larval gut and the Malpighian tubules showed a greater abundance of hsr-omega transcripts with a strong hybridization in nuclei. Our results with promoter deletion variant germline transformants suggest that a region between -346bp to -844bp upstream contains major regulatory element/s for developmental expression of this gene in most of the larval and adult tissues examined; however, this region is not sufficient for its normal expression in male and female reproductive systems. An analysis of the base sequence of the hsr-omega promoter (upto -844bp) reveals putative ecdysone receptor element half-sites and two GAGA factor binding sites which may be involved in its developmental expression and its ready inducibility. The widespread expression in most tissue types and the known lethality associated with its homozygous deletion, suggest that the variety of non-protein coding transcripts of the hsromega gene have vital "house-keeping" functions.