Fig. 1. Expression of phosphorylated Src42A (pSrc) in the adherens junctions of epithelial tissues. (A) Schematic diagrams of Src42A and Src64B. Three functional domains (SH3, SH2 and the kinase domain), the myristoylation (M) site at glycine 2 (G2), the catalytic lysine in the kinase domain, and the sites of activating (Y400/434) and inhibitory (Y511/547) tyrosine phosphorylation are indicated. (B-D) Staining pattern of anti-phospho Src (pSrc) antibody during tracheal development. (B) Embryos were stained for pSrc (gray scale), and tracheal cells were labeled green with trh-lacZ. pSrc was localized to the apical cell-cell junction of the ectoderm and in invaginating tracheal primordia in stage 11. (B') y-z section shows that tracheal cells (arrow) express a higher level of pSrc than ectoderm (arrowhead). (C) pSrc and E-cadherin are co-localized in the AJs of stage 11 tracheal primordia (btl>gfp-moe, green). (D) Src expression in a control (Src42A^26-1/+) embryo at stage 14, showing broad cell membrane staining by anti-Src42A antibody and highly restricted AJ staining by anti-pSrc (arrow indicates trachea; arrowhead, epidermis). (E) Both signals were greatly reduced in Src42A^26-1 mutant embryos. (F) Src42A overexpression in the trachea (btl>Src42A^GS) greatly increased the pSrc signal (arrow). (G) Src64B overexpression in the trachea (btl> Src64B^GS) did not increase the pSrc signal. (H) Src activation in the parasegmental furrow. Optical section of the embryonic ectoderm at stage 9 labeled with pSrc (green) and Arm (magenta). Nuclei were visualized by DAPI (blue). Grayscale images of the two channels are shown below. Scale bars: in C, 10 µm for B,C; in H, 100 µm.