Bnl cleavage determines the range of gradient distribution and signaling. (A–C) Images of αDlg immunostained (white) ASPs (white outline) and wing discs from homozygous wt^endo (n = 52) and m1^endo (n = 64) larvae (A and B); a graphical comparison (C) of their ASP length relative to the wing disc size. (D and E) Average intensity profiles of t-WT^endo (D, n = 3) and M1^endo (E, n = 5) along the ASP D-P axis; lower panels, examples of signal distribution along the ASP D-P axis. Red line, exponential fit trend line; C_max, maximum average intensity; C_1/2, 1/2 C_max; slope for the trend line between C_max and C_1/2. (F) Average intensity profiles of t-WT^endo (n = 9) and M1^endo (n = 12) normalized with recipient ASP length (D-P axes; Materials and methods). (G–I) Images of αdpERK-stained (red) ASPs from homozygous wt^endo (n = 16) and m1^endo (n = 20) larvae (G and H) and graphical comparison (I) of their nuclear dpERK-positive zones along the D-P axes; lower chart: average ratio (± SD) of number of dpERK-positive cells along the D-P axis to the total number of cells in the D-P axis. (J–N) Larval salivary glands expressing CD8:GFP, Bnl:HA₁GFP₃ (18), M1 (11), M2 (20), and M1M2 (18) under bnl-Gal4 as indicated. Red arrow, central branch point. (O) A quantitative assessment of the frequency of terminal branching on salivary gland determined by Sholl analysis under the conditions indicated. Scale bars: 30 µm (A, B, G, and H); 100 µm (J–N).