Abdominal segmentation of the Drosophila embryo requires a hormone receptor-like protein encoded by the gap gene knirps

Abstract

The body pattern along the anterior-posterior axis of the insect embryo is thought to be established by two organizing centres localized at the ends of the egg. Genetic analysis of the polarity-organizing centres in Drosophila has identified three distinct classes of maternal effect genes that organize the anterior, posterior and terminal pattern elements of the embryo. The factors provided by these gene classes specify the patterns of expression of the segmentation genes at defined positions along the longitudinal axis of the embryo. The system responsible for organizing the posterior segment pattern is a group of at least seven maternal genes and the zygotic gap gene knirps (kni). Their mutant phenotype has adjacent segments in the abdominal region of the embryo deleted. Genetic analysis and cytoplasmic transplantation experiments suggested that these maternal genes are required to generate a 'posterior activity' that is thought to activate the expression of kni (reviewed in ref. 2). The molecular nature of the members of the posterior group is still unknown. Here we report the molecular characterization of the kni gene that codes for a member of the steroid/thyroid receptor superfamily of proteins which in vertebrates act as ligand-dependent DNA-binding transcription regulators.

Identification of ecdysone response elements by analysis of the Drosophila Eip28/29 gene.

“…There is precedent in the literature for competitive interactions between steroid receptors and other proteins for binding to HREs (Briiggemeier et al 1990;Crawford and Chapman 1990). It is intriguing to note that the steroid receptor-like proteins encoded by the Diosophila genes E75 (Segraves and Hogness 1990), CPl (Shea et al 1990), tU (Pignoni et al 1990), svp (Mlodzik et al 1990), kni (Nauber et al 1988), kml (Oro et al 1988), and egon (Rothe et al 1989) all have sequences suggesting binding to TGACCT-related half-sites (for a summary, see Pignoni et al 1990). The CFl product has been shown experimentally to bind to such a sequence (Shea et al 1990).…”

Evolution of the nuclear receptor superfamily: early diversification from an ancestral orphan receptor

“…These are the KNI group (Drosophila KNI, KNRL and EGON genes; Nauber et al 1988, Oro et al 1988, Rothe et al 1989, the Caenorhabditis ODR-7 gene (Sengupta et al 1994), the human DAX-1 and SHP-1 genes (Zanaria et al 1994, Seol et al 1996, Swain et al 1996 and the Drosophila Trithorax gene (Stassen et al 1995).…”

Redundant functions of the genes knirps and knirps-related for the establishment of anterior Drosophila head structures.

“…Whole-mount in situ hybridization with kni and knrl cDNAs (13,19), stainings with 4D9 antiengrailed (21) and 22C10 antibodies (22), as well as larval cuticle preparations were done according to standard protocols (23)(24)(25). After staining, embryos were embedded in Araldite, put into capillaries (26), and analyzed under a Zeiss compound microscope with Nomarsky optics.…”

“…kni and knirps-related (knrl) code for sequence-related transcription factors that have the DNA-binding domain in common with vertebrate nuclear hormone receptors (13,14,19). The available evidence suggests that this gene pair arose by tandem duplication and eventual translocation to a site nearby on the same chromosome (14).…”

“…The kni transgene contains a 9.5-kb genomic Sal 1-Hind-III fragment that contains the kni transcription unit and =6.5 kb offlanking sequences (29) cloned into Carnegie 20 (30), as described (20). The knrl transgene includes the coding sequence of the knrl cDNA (13) contained within a 2.1-kb Ban II-Sph I DNA fragment that was inserted between the Nru I site of the untranslated leader of the kni gene (19,29) and the Drosophila a1-tubulin polyadenylylation signal of the CaSpeR vector (31) as described (20). P-element-mediated germ-line transformations were done as described (32); for each transgene several independent lines were established.…”