Fig. 2

Dpp expression and activity in the midgut. a Dpp-GAL4 driving UAS-GFP as a marker for Dpp expressing midgut cells (Dpp > GFP). GFP-positive cells (green) can be found along the anterior midgut (arrows). Inset shows higher magnification. Scale bar represents 100 μm. b Dpp > GFP (green) is expressed in the larval intestinal stem cells (ISC)/enteroblasts (EB) and not in the Prospero-labeled enteroendocrine (EE) cells. Higher magnification inset shows the GFP and Pros cells do not colocalize. DNA is stained by Hoechst (blue). Scale bar represents 50 μm. c Schematic representation of larval midgut cells. The larval midgut cells include intestinal stem cells (ISC), enteroblasts (EB), enteroendocrine (EE), and enterocytes (EC) cells. Other cell types include adult midgut progenitors (AMP), and the basement membrane (BM) and visceral muscle (VM). d In control, dpp-lacZ and omb-LacZ expression of LacZ reporter for Dpp signaling can be detected by β-GAL activity in the midgut at −4 h RPF. X-gal activity is present in distinct cells along the gastric caeca (arrow) and along the midgut. Scale bar represents 100 μm. e β-GAL immunolocalization in dpp-LacZ midguts at −4 h RPF marks distinct cells along the gastric caeca and along the midgut body. Scale bar represents 20 μm. f Nuclear localization of phospho-Smad (red) and DNA (blue) in midgut ECs is high in −16 h RFP, with reduced levels in −8 h RPF and low-nuclear levels in −4 h RPF. Scale bar represents 10 μm