Fig. 7. Sog protein diffuses into the provein territory. Staining with the 8B anti-Sog antiserum reveals that Sog protein is initially expressed in a patchy intervein pattern at 18-22 hours apf (A). At this stage, there are more labeled intervein cells on the dorsal than ventral surface. (B) At 22-26 hours apf, Sog staining is still patchy but expands evenly to all intervein cells towards the end of this period. Staining is also visible in provein domains on the dorsal surface of the wing. (C) At 26-30 hours apf, Sog protein is present throughout the entire provein domain on the dorsal surface of veins, with increased staining at the provein/intervein border. (D) Later (>30 hours apf), anti-Sog staining again becomes restricted to intervein cells. Hemocytes running through the center of the vein also label. Staining fades away in subsequent stages. (E) High magnification of the L3 vein of a 24-26 hours apf pupal wing shows that Sog protein is present in provein cells on the dorsal surface of the wing except for the most central cells. This pattern is not synchronous for all veins. (F) On the corresponding ventral surface of the same region no provein (bar) staining is observed. (G) High magnification of the L3 vein of a wing as in C, showing Sog protein localized over the entire vein competent domain of all veins on the dorsal surface, but excluded from the provein regions of veins on the ventral (H) surface. Arrows indicate increased staining at the provein/intervein border. Note that the texture of reticular staining in intervein regions (asterisk) on the dorsal surface is different from the more punctate staining on the ventral surface of the wing. (I-N) High magnification confocal images of a 22-26 hours apf wild-type wing double labeled for Sog (red) and ßPS integrin (green). This optical section, which is focused on the basolateral region of the dorsal wing epithelium, reveals that Sog (I,K) and integrin receptors (J,M) are co-localized, staining the cell perimeter. Sog staining is also observed inside intervein cells and entering the provein area (arrows, I,K), where integrins are absent. No Sog staining inside the provein area is observed on the ventral wing epithelium (L-N), as shown by the double arrows (L,N).

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