Cadherin that functions in epithelial morphogenesis and the intestine epithelial immune response (PubMed:16260500, PubMed:16507588, PubMed:24718992, PubMed:25639794). Essential for female fertility (PubMed:16260500, PubMed:16507588). Regulates the length and organization of apical microvilli in developing follicle cells and salivary glands (PubMed:16260500, PubMed:16507588, PubMed:24718992, PubMed:25236597). Function in the follicle cell is essential for egg development as the microvilli secrete eggshell material such as the vitelline membrane (PubMed:16260500, PubMed:16507588, PubMed:25236597). Acts at least in part by regulating the recruitment of the myosin ck to the follicle cell microvilli (PubMed:25236597). Also required to regulate cell rearrangements during salivary tube elongation, possibly by modulating cellular adhesion between the apical surface and apical extracellular matrix during epithelial tube elongation (PubMed:24718992). May also function in cellular adhesion during the development of other tubular epithelia such as the trachea (PubMed:24718992). Possibly functions as an apical membrane determinant which acts in apical membrane expansion during salivary and tracheal epithelial tube elongation (PubMed:24718992). In salivary gland development, this function is independent of the other apical membrane determinants crb and sas (PubMed:24718992). Essential downstream component of a hh-signaling pathway which regulates the Duox-dependent gut epithelial immune response to bacterial uracil; required for endosome formation in the enterocyte and activating norpA-dependent Ca2+ mobilization, which are essential steps in the Duox-dependent production of reactive oxygen species (ROS) in response to intestinal bacterial infection (PubMed:25639794). Interacts (via the cytoplasmic domain) with ck (PubMed:25236597, PubMed:27331610). Interacts (via the cytoplasmic domain) with Cul1 and Ubr3 (PubMed:27331610). Dispersed throughout the enterocyte membrane, but becomes clustered in the brush border membrane in response to uracil. Low expression throughout the imaginal disks of third instar larvae with higher levels of expression at the anterior-posterior boundary (at protein level) (PubMed:15708564). Detected in the germarium and stage 2 and stage 3 egg chambers (at protein level) (PubMed:16507588). From stages 2 to 8, expressed in the follicle cells at the anterior and posterior poles of the egg chambers (at protein level) (PubMed:16260500, PubMed:16507588). From stage 4 to the end of oogenesis, only detected in follicle cells that are in contact with the oocyte (at protein level) (PubMed:16260500, PubMed:16507588). From stage 11 expressed at the apical surface of several embryonic tubular organs including the salivary glands, trachea, foregut and hindgut (PubMed:24718992). Up-regulated in the adult anterior midgut after the ingestion of bacterial uracil. Strong up-regulation detected 1 hour, 2 hours and 16 hours after ingestion, whereas no up-regulation was detected at 4 hours. The extracellular domain is necessary for conferring apical characteristics on the salivary gland membrane (PubMed:24718992). Necessary for regulating salivary gland membrane expansion and tube length, but is not required for cell rearrangement during tube elongation (PubMed:24718992). Sufficient to promote the outgrowth of follicle cell microvilli and the formation of microvilli bundles (PubMed:16260500, PubMed:24718992) Sufficient to promote formation of microvilli-like structures in the salivary glands and the follicle cell microvilli bundles (PubMed:16507588, PubMed:24718992). Dispensable for apical localization (PubMed:24718992). The cytoplasmic domain is necessary for the formation of uracil-induced endosomes. Three calcium ions are usually bound at the interface of each cadherin domain and rigidify the connections, imparting a strong curvature to the full-length ectodomain (By similarity). Females display reduced fertility as well as defective eggshell development (PubMed:16260500). Ovarian follicle cell microvilli are abnormally shaped and display a range of defects including decreased length, reduced number and an irregular distribution pattern, leading to impaired vitelline membrane formation (PubMed:16260500, PubMed:16507588). In the intestines of 3-day old adults there is no formation of endosomes and consequently no DUOX-dependent up-regulation of reactive oxygen species (ROS) in response to the ingestion of bacteria-derived uracil (PubMed:25639794). Embryos display irregular cell rearrangements during salivary gland development with fewer cells surrounding the salivary gland lumens and lumens appear to be elongated (PubMed:24718992).