Polarised EGF signalling is required for MpT elongation.

<p>(A–C, E) Stage 16 embryos stained for MpTs (Cut). (A) Wild type embryo. (B) <i>EGFR^ts</i> embryo raised at restrictive temperature during period of elongation. (C) <i>ctB>EGFR^DN</i>, (E) <i>ctB>EGFR^act</i>. Perturbation of EGF signalling disrupts tubule elongation. (D, D′, F, F′) Beginning and end point still images from <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1002013#pbio.1002013.s013" target="_blank">Movies S6</a> and <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1002013#pbio.1002013.s015" target="_blank">S8</a> in <i>ctB>EGFR^DN</i> (D) and <i>ctB>EGFR^act</i> (F) embryos, right panels show 4-D reconstruction, stars in (D, D′) indicate TC. Circumferential cell rows (coloured) achieve no (D,D′) or highly reduced (F,F′) cell intercalation (arrowheads). (G) Graph to show tubule elongation in wild type embryos and in those with perturbed EGFR signalling. Tubule length is significantly reduced in <i>ctB>EGFR^DN</i> (<i>p</i> = 4×10⁻⁶<0.05) and <i>ctB>EGFR^act</i> (<i>p</i> = 1×10⁻⁴<0.05) compared to WT. (H, I) Stage 16 <i>ctB>sSpi</i> (H) and <i>ase>sSpi</i> (I) embryos stained for Cut. (H′, I′) Enlarged views showing aMpTs.