The follicular epithelium is under anisotropic apical tension.Figure 3Epithelial cell size and shape is affected by decreased proliferation. Representative images of epithelial cells taken from egg chambers with aspect ratios of approximately 1.4 (A). Epithelial cell size and shape is affected by decreased proliferation. Cell outlines are marked with Basigin::YFP. Scale bars =­ 5 μm. Cells become significantly larger (B) Cell area shown on a log4 scale in (B). Number of cells analyzed: w1118 1.0-1.2 n= 14, 1.2-1.4 n=114, 1.4-1.6 n=160 Statistical significance calculated using a Mann-Whitney test. Data information: Bars represent mean and standard deviation. Epithelial cell size and shape is affected by decreased proliferation. Cell outlines are marked with Basigin::YFP. Scale bars =­ 5 μm. Cells become more aligned with the tissue elongation axis when proliferation is stopped using String-shRNA (C). Number of cells analyzed: w1118 1.0-1.2 n= 14, 1.2-1.4 n=114, 1.4-1.6 n=160; String-shRNA 1.0-1.2, n=10, 1.2-1.4 n=19, 1.4-1.6 n=17. Statistical significance calculated using a Mann-Whitney test. Data information: Bars represent mean and standard deviation. D, E) The follicular epithelium 'thins out' over the egg chamber equator when proliferation is blocked. Cartoon demonstrates the tissue cell shape observed in the follicular epithelium in control (w1118) and String-shRNA treated egg chambers. Quantification of the phenomenon shown in (D) reveals that cells are shorter over the equator than at the anterior pole in elongated egg chambers when proliferation is blocked. Statistical significance calculated using unpaired t-test with Welch's correction. Number of cells analyzed: w1118 1.0-1.2 n= 21, 1.2-1.4 n=11, 1.4-1.6 n=10; String-shRNA 1.0-1.2, n=9, 1.2-1.4 n=11, 1.4-1.6 n=13. Data information: Bars represent mean and standard deviation. F) Recoil is observed when cuts are made in apical cortex with a 2-photon laser with egg chambers in saggital view. Images show cortex before and after cutting. Scale bars = 10 μm. Yellow arrows indicate edges of ablated region. G) Recoil is higher when cuts are made at the apical cortex at the equator of egg chambers, rather than at the poles. Quantification of experiment shown in (F). Statistical significance tested by Mann-Whitney test. Number of laser cuts: equator n=30, pole n=20. Data information Laser ablation experiments performed on tissue from sqhAX3, sqh::GFP flies. H) Recoil is observed when larger cuts are made in apical cortex with a UV laser. Images show cortex before and after cutting. Red lines indicate the lines over which recoil was calculated, parallel to the axes of the egg chamber. Scale bars = 5 μm. Yellow arrows indicate edges of ablated region. I) Recoil tends to be higher towards the AP (elongation) axis compared to the the UD (rotation) axis. Graph shows the ratio of recoil speed plotted on a log2 scale in the AP versus the UD axis. Red line at x=1 indicates equal recoil in both axes. Values above 1 indicate higher recoil speeds in the AP axis lower than 1 indicate higher recoil in the UD axis. AP/UD Ratio Median = 1.242 ; Mean = 2.1. Wilcoxon Signed Rank Test to test for significance of the recoil ratio AP/UD shows that the median is significantly different from 1 to p = 0.0172. Number of cuts = 20. Bar represents median.Laser ablation experiments performed on tissue from sqhAX3, sqh::GFP flies.