Fig. 2. Autoregulation of Vg in non-DV cells of wing discs. (A1-3) Wing disc with vg¹/vg¹ clones. (A1) Myc marker (P[FRT]42 Myc); loss of Myc marks vg¹/vg¹ cells. (A2) Expression pattern of vg-QE in the same disc. (A3) DAPI staining in the same disc. (A4) Merged image of A1-A3. Note the representative vg¹/vg¹ clones in non-DV cells (arrows), which are positive for DAPI, indicating the survival of the clones. vg-QE is not expressed in these clones, which provides genetic evidence for Vg autoregulation. (B-C) vg¹/vg¹ wing discs stained with anti-Vg antibodies and DAPI (B), and anti-Wg antibodies (C). Note no Vg expression is seen in vg¹/vg¹ wing discs. Wg expression at the DV boundary is also absent. (D,E) Wild-type (D) and vg¹/vg¹ (E) wing discs showing the expression pattern of N23-GAL4. The discs are also stained with DAPI. Note that N23-GAL4, which is expressed only in non-DV cells, still shows separation of dorsal and ventral compartments at the presumptive DV boundary of vg¹/vg¹ discs. Thus, loss of Wg seen in vg¹/vg¹ wing discs is not caused by loss of the DV boundary per se. (F) N23-GAL4/UAS-Vg wing discs stained for vg-QE (red) and Wg (green). Note activation of both vg-QE and Wg (arrow) outside the wing pouch. In all such cases, Wg expression always surrounded but did not overlap vg-QE expression [similar observations have been made by Liu et al. (Liu et al., 2000)]. (G) vg¹/vg¹; N23-GAL4/UAS-Vg stained for vg-QE (red) and Wg (green). Note the very high levels of vg-QE activity in the pouch. No Wg expression was seen in the DV boundary, suggesting that autoregulation of Vg through its quadrant enhancer is independent of Wg. Note also that the size of the wing pouch is nearly normal. (H) vg¹/vg¹ adult wing blade. (I) vg¹/vg¹; N23-GAL4/UAS-Vg adult wing blade showing partial rescue of vg¹ phenotype.

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