Note that the leg disc precursor cells are absent. In each of the anterior segments, esg is expressed in a transversely elongated cluster of 9.0 F 0.8 cells (arrowhead). Genotypes are listed in italics and proteins detected in capitals. Panels A, D, and G show the ventral most epidermis of whole embryos, while the remaining panels show close-up views of the ventral tail regions of the embryos. The GDPCs are still arranged as two symmetrical groups on each side of the ventral midline as seen with the antibody staining but appear to be invaginating as a cluster using the enhancer trap.Įffects of Hox genes on the specification of different primordia of the GDPCs. The number of the GDPCs has increased from 20–22 to 30–32 cells by antibody staining (C and F) and to 32–35 cells detectible in the enhancer trap (I). Using the enhancer trap (H), more cells are detected and the cluster appears more unified. With antibody staining, the GDPCs appear in two symmetric groups of cells on each side of the ventral midline with approximately 22 cells, as in earlier stages. The leg disc precursor cells are not in focus. Arrows indicate the thoracic wing and haltere disc precursor cells. There are approximately 22 cells within the cluster at this stage. The GDPCs are a transversely elongated cluster of cells (arrowhead in A) located in the epidermis between the A8 ventral denticle belt and the anal plates. Panels A–C show images of whole embryos, and panels D–I show close-up views of the tail region. Embryos in A–F were stained with anti-ESG antibodies embryos in G–I show cell-membrane-associated GFP expression from an esg enhancer trap line. A ventral view of an embryo is shown in each panel, and anterior of the embryo is to the left. Genital disc precursor cells (GDPCs) in wild-type embryos. By identifying how these different patterning networks regulate the allocation and primordial organization of the 22 embryonic precursors of the compound genital disc, we demonstrate that at least some of the organization of the larval disc originates as positional information in the embryo, thus providing a context for further studies on the development of the genital disc. In addition, we found that the three primordia of the larval genital disc have already been specified in the GDPCs by the coordinated actions of the homeotic (Hox) genes, abdominal-A, Abdominal-B, and caudal. These segment polarity genes are expressed in some, but not all of the GDPCs, indicating that anterior and posterior compartments are not fully established in the GDPCs. Along the anterior-posterior axis, several segment polarity genes (wingless, engrailed, hedgehog, and patched) are required for the proper allocation of the GDPCs. The ventral localization of the GDPCs is further restricted by the action of dorsal patterning genes. The allocation of the GDPCs from the ventral epidermis requires the function of ventral patterning genes, including the EGF receptor and the spitz group of genes. Analysis of mutant and double mutant phenotypes of embryonic patterning genes in the GDPCs, together with their expression patterns in these cells, revealed the following with respect to the origins and specification of the GDPCs. We show that the genital disc precursor cells (GDPCs) are first detectable during mid-embryogenesis as a 22-cell cluster in the ventral epidermis.

The genital imaginal disc is composed of three primordia (female genital, male genital, and anal primordia) that originate from the embryonic tail segments A8, A9, and A10, respectively, and produce the sexually dimorphic genitalia and analia. The adult structures of Drosophila melanogaster are derived from larval imaginal discs, which originate as clusters of cells within the embryonic ectoderm.

Primordia trailblazing 2