araucan and caupolican, Two Members of the Novel Iroquois Complex, Encode Homeoproteins That Control Proneural and Vein-Forming Genes

Abstract

In Drosophila imaginal wing discs, the achaete-scute (ac-sc) proneural genes and rhomboid (veinlet) are expressed in highly resolved patterns that prefigure the positions of sensory organs and wing veins, respectively. It is thought that these patterns are generated by a combination of factors (a prepattern) regulating these genes. We provide evidence for the existence of this prepattern by identifying two of its factors, Araucan and Caupolican. They are members of a novel family of homeoproteins, with homologs in vertebrates. Araucan and Caupolican, present in domains of the imaginal discs larger than those expressing ac-sc and rhomboid, are necessary for expression of these genes in the overlapping domains. Araucan and Caupolican appear to be positive, direct regulators of ac-sc.

mirror encodes a novel PBX-class homeoprotein that functions in the definition of the dorsal-ventral border in the Drosophila eye.

“…2E). The similarity of mrr to ara and caup and its coincident location at 69D (within 50 kb of caup; Gomez-Skarmeta et al 1996) suggests that mrr is a new member of the Iroquois complex.…”

“…2C). In the aminoterminal region there is a highly conserved Notch interaction domain, which has been proposed to be involved in protein-protein interactions (Gomez-Skarmeta et al 1996) (Fig. 2D).…”

“…Three observations are consistent with this model. First, a potential Mrr-binding site (based on the defined DNA binding site of Ara; Gomez-Skarmeta et al 1996) is present in the mrr upstream region (H. McNeill, unpubl.). Second, mrr expression includes both a gradient that is strongest in the most dorsal regions and a sharp termination at the equator (see Fig.…”

Genetic Interaction of Lobe With Its Modifiers in Dorsoventral Patterning and Growth of the Drosophila Eye

“…Wg signaling in turn promotes the expression of members of the Iroquois complex (Iro-C), namely araucan (ara), caupolican (caup), and mirror (mirr) (Heberlein et al 1998). pnr and members of Iro-C act as selectors for the dorsal eye fate (Gomez-Skarmeta et al 1996;McNeill et al 1997;Cavodeassi et al 1999). The boundary between the dorsal and ventral compartments is the site of Notch (N) signaling, which is required for cell proliferation and differentiation of the eye (Cho and Choi 1998;Dominguez and de Celis 1998;Papayannopoulos et al 1998;Dominguez and Casares 2005).…”

“…, an amorph allele of emc (Brown et al 1995); Bar 1 (B 1 )/FM7, a dominant gain-offunction mutation generated by duplication of the 16A region containing BarH1 and BarH2 genes, referred to as Bar (B); Df(1)Bar , a deficiency in which both B genes are deleted (Higashijima et al 1992); sgg 1 /FM7a Dp(1;2;4) w 1 , a lethal recessive X-ray allele of sgg (Bourouis et al 1990); Df (2L) BSC7/CyO, UAS-pnr D4 (Haenlin et al 1997); y w; FRT82, pnr vx6 / TM6B (Heitzler et al 1996); UAS-pnr ENR , a dominant-negative form of pnr, which contains the repressor domain from Engrailed (amino acids 2-298) (Klinedinst and Bodmer 2003); UAS-ush (Fossett et al 2001); Df (3L) Iro-C DFM3 FRT80/TM6B, a deficiency for ara, caup, and promoter for mirr, UAS-ara (Gomez-Skarmeta et al 1996); UAS-mirr (McNeill et al 1997); y w ey-FLP (Newsome et al 2000); and pnr-GAL4 . All stocks are described in FlyBase (http:/ /flybase.bio.indiana.edu).…”