Figure 1.

Remodeling of the Extracellular Matrix Precedes Wing Elongation

(A) Time-lapse imaging of the apical extracellular matrix (ECM) component Dumpy-YFP (Dp-YFP, aECM) and basal ECM component Collagen IV-GFP (Collagen IV α2-subunit, Vkg-GFP, bECM), which distribute homogeneously in the developing wing from 2 to 4 hr (h) after puparium formation (APF), but are degraded from 5 hr APF, concomitant with peripodial membrane release. The entire wing disc is shown for Dp-YFP, and only the basal surface for Vkg-GFP. Scale bar, 50 μm.

(B) Cross-sections of developing wings at 4 and 7 hr APF. At 4 hr APF, Dp-GFP and Vkg-GFP cover the apical and the basal surface of the wing epithelia, respectively and Vkg-GFP also surrounds the basal side of the peripodial membrane. At 7 hr APF the matrix has been removed and only some traces of Vkg-GFP are still detected. Nuclei (DNA) are shown in blue. Scale bar, 50 μm.

(C) High-magnification view of epithelial cells showing that, at 4 hr APF, columnar epithelial cells distributed in a pseudo-stratified epithelium are in contact with apical Dp-YFP and basal Vkg-GFP (orange arrowhead), whereas by 7 hr APF the matrix is absent and cells adopt a more cuboidal morphology. The layer of Vkg-GFP that covers the basal surface of the peripodial membrane at 4 hr APF is indicated by a white arrowhead. Scale bar, 25 μm.

(D) Quantification of the percentage of epithelium covered with apical Dp-YFP and basal Vkg-GFP in developing wings from 2 to 7 hr APF. Average and SD are presented; n > 4 for each developmental stage. Statistically significant differences are indicated (^∗p < 0.05, ^∗∗∗p < 0.001).

(E) Quantification of wing blade area and epithelial cell height from 4 to 7 hr APF. Average, SD, and individual data points are presented; n > 8 for each developmental stage. Statistically significant differences are indicated (^∗p < 0.05, ^∗∗p < 0.005, ^∗∗∗p < 0.001).