Functional dissection of an early Drosophila chorion gene promoter: expression throughout the follicular epithelium is under spatially composite regulation.

Abstract

We have fused various DNA sequences located upstream of the Drosophila melanogaster s36 chorion gene TATA box to a heterologous basal promoter and reporter gene (hsp70/lacZ). The expression of these constructs, following P‐element‐mediated germline transformation, was examined in 144 independent lines by histological staining of dissected ovaries for beta‐galactosidase activity. A short 84 bp segment of the proximal 5′ flanking DNA was sufficient to confer a wild‐type gene expression pattern, including temporal specificity for early choriogenic follicles. Surprisingly, initial expression was very localized at the anterior and posterior poles of the follicle. The downstream half of that DNA segment permitted expression at both poles, but especially at the anterior tip, while the upstream half only favored expression in the posterior pole; these results suggested the existence of multiple, spatially specific cis‐regulatory elements. When the proximal 84 bp segment was placed 1.5 kb upstream of the basal promoter, beta‐galactosidase activity was observed in an altered spatial pattern, indicating that the cis‐regulatory element(s) that favor expression in the posterior half of the follicle are position independent, while the element(s) that favor expression elsewhere in the follicle are position sensitive. A distal regulatory segment containing redundant DNA element(s) specific for expression in the anterior pole was identified much further upstream of s36. Thus, the expression of this chorion gene throughout the follicular epithelium is actually composite, occurring in distinct spatial domains under the control of corresponding DNA elements.

bullwinkleandsharkregulate dorsal-appendage morphogenesis inDrosophilaoogenesis

“…Although our methods may miss subtle defects in main-body chorion, shark may play a DA-cell-specific role in the production/formation of chorion. Although regulatory sequences and a putative binding protein drive specific spatial expression of chorion-reporter constructs (Tolias and Kafatos, 1990;Tolias et al, 1993), no reported mutants disrupt DA-specific chorion expression.…”

Multiple layers of complexity in cis‐regulatory regions of developmental genes

“…Yet, the first observations of overlapping expression from different enhancers date back from the 1990s (Hoch et al, 1990;Kassis, 1990;Tolias and Kafatos, 1990). In addition to these experimentally validated cases, a computational analysis has predicted the occurrence of ''shadow enhancers'' in many D. melanogaster genes that act in the segmentation cascade (Kazemian et al, 2010).…”

Elements controlling follicular expression of the s36 chorion gene during Drosophila oogenesis.

“…The temporal and spatial regulation of chorion genes is reflected in morphological specializations of the eggshell along the anterior-posterior and dorsal-ventral axes (21,22) and has been documented by molecular studies at both the protein and nucleic acid levels (9,25,28,29,49,50). Detailed studies of the late-expressed siS gene suggest that its temporal control results from specific interactions between cis-regulatory DNA elements and respective positive and negative trans-acting factors, whose presence and/or activity varies during oogenesis (23).Spatial regulation is most obvious for the X-linked cluster of chorion genes and has been studied most extensively with regard to the s36 gene (28,49). Although ultimately expressed throughout the follicular epithelium (with the exception of cell populations immediately surrounding the nurse cell remnants and at the tip of the developing micropyle), this gene is initially expressed during oogenic stage 10b solely in a subpopulation of anterior dorsal follicle cells.…”