Fig. 1. Morphogenesis of the Drosophila salivary glands. (A-H) Salivary gland cells (arrow) are stained for FKH in green, the CNS is visualized in red by ELAV staining and the CVM is stained for FASIII, also in red. (A,C,E,G) Lateral and (B,D,F,H) corresponding ventral views of embryos, stages 11 through 14. (A,B) Salivary glands begin as a pair of single-layered epithelial disks, the salivary placodes that invaginate by apical constriction to form slender tubes. (C,D) As they leave the surface these tubes extend dorsally and posteriorly at a 45° angle on either side of the CNS until they reach the visceral mesoderm. (E,F) Then they change paths and migrate actively along the mesoderm until they lie horizontally within the embryo, dorsal and lateral to the CNS. (G,H) By stage 14, the glands encounter the longitudinal visceral mesoderm (not shown) and separate from the circular visceral mesoderm. (I-K) Lateral views of embryos stage 13-15 stained with the salivary gland marker SG2 in green, the mesodermal marker Titin in red and the CVM marker FASIII also in green. In these panels the CVM appears yellow due to FASIII-Titin co-staining; LVM (arrows) is red due to Titin, but not FASIII, staining. (I) At the end of stage 13, cells of the LVM migrate anteriorly and displace the distal end of the salivary gland from the CVM. (J,K) From stage 14, the tip of the salivary gland remains in contact with the LVM.