Fig. 3: Analysis of JNK pathway role in terminal cell specification.

a Scheme of the proposed Egr-Wgn-JNK signalling pathway. b Quantification of the percentage of dorsal branches that show the indicated phenotypes. Error bars indicate SD of mean. n, number of DBs analysed, in brackets number of embryos analysed. ****p < 0.0001; 0.001 <**p < 0.01, *p < 0.05; Chi-squared test, two-sided. Magenta asterisks refer to the p values comparing each mutant condition to the control. Purple asterisks refer to the p values comparing each mutant condition to the TNFR-wgn downregulation condition. c–f, m, n Lateral views of stage 15 embryos stained with CBP to visualise the tracheal tubes (magenta) and with DSRF to visualise the terminal cells (green). JNK pathway downregulation produce a mild tracheal effect (white arrow in (c)). Note the presence of terminal cells in embryos with overexpressed/overactivated JNK or Traf2 (yellow arrows in (d–f)). Overexpression of hep cannot rescue the excess of terminal cells (white arrows) produced by TNFR-wgn depletion (m). Downregulation of JNK cannot rescue the lack of terminal cells (blue arrows) produced by an excess of TNFR-wgn (n). g, h Lateral views of stage 14 embryos stained with GFP or β-Galactosidase (magenta) to visualise the JNK activity reporters, with CBP to visualise the tracheal tubes (white) and with DSRF to visualise the terminal cells (green). Note that the reporters are not expressed in the trachea. i–l Lateral views of stage 14/15 embryos stained in magenta with β-Galactosidase (i, j) to visualise the puc-lacZ reporter or with Dcp1 (k, l) to visualise cell death and in green to visualise the trachea. Note that puc-lacZ and cell death are activated upon JNK overactivation (yellow arrows in (i’), inset in (k)) but not upon TNFR-wgn overexpression (j’ and inset in (l)). Asterisks in (j’) indicate staining background in the lumen of the trachea. White arrows in (h–j) point to puc-lacZ expression in the leading edge. Scale bar: 20 μm. Source data and details of statistical tests used and p values are provided as a Source Data file.