Fig. 4.

Basal tension depends on ECM. a–h Apical (a, e) and cross-sectional (b, c, f, g) views of a wing imaginal disc before (a–d) and 60 min after (e–h) addition of collagenase to the culture medium are shown. Magnifications of the boxed areas are shown in c and g. d, h Corresponding basal views. Dotted lines indicate position of cross section. Scale bars are 10 μm. i Apical and basal cross-sectional cell area before (0 min) and 60 min after addition of collagenase to the culture medium are shown. Mean and s.e.m. are shown (n = 365 (apical, 0 min), 357 (apical, 60 min), 445 (basal, 0 min), and 354 (basal, 60 min) cells of 4 wing imaginal discs) (***p < 0.001, Student’s t-test). j Average recoil velocity of the two vertices at the end of an ablated cell edge in the pouch region of 72 h AEL wing imaginal discs before and 60 min after addition of collagenase within 0.25 s after ablation. Recoil velocities are shown for ablations of apical and basal cell edges, as indicated. Mean and s.e.m. are shown (n = 15 cuts) (***p < 0.001, Student’s t-test)