Fig. 4: Analysis of TNF-Egr in terminal cell specification.

a–c Lateral views of stage 15 embryos stained with CBP to visualise the tracheal tubes (magenta) and with DSRF for terminal cells (green). TNF-egr mutants show a mild phenotype of extra terminal cells (yellow arrow in a), compared to TNFR-wgn mutants (b). Overexpression of TNFR-wgn prevents terminal cell differentiation in the absence of TNF-egr (blue arrows in (c)). d, e Lateral views of whole embryos stained with TNF-Egr (magenta) and GFP to visualise the tracheal system (green). TNF-Egr is expressed in amnioserosa (yellow arrows) and CNS (blue arrows). f, g Lateral views of stage 14 embryos focused in dorsal branches stained with TNF-Egr (magenta), TNFR-Wgn (green) and GFP (tracheal system, blue). Note the expression of TNF-Egr in amnioserosa cells (yellow arrows in (f, g)) but not in trachea (oulined in (f’)) and some co-localisation of TNF-Egr and TNFR-Wgn (orange arrows in (g’)) in tissues other than the trachea (white arrows in (g’)). h–k Lateral views of embryos overexpressing TNF-Egr, which leads to extra terminal cells (yellow arrows) also in the stalk (white arrow) (h). TNF-Egr does not activate puc-lacZ in tracheal cells (i, inset with puc-lacZ expression alone, white arrow points to expression in the leading edge) or cell death (j). Co-overexpression of TNFR-Wgn suppresses the extra terminal cell phenotype of TNF-Egr overexpression (blue arrows in (k)). l Quantification of the percentage of dorsal branches that lack terminal cells. Co-overexpression of TNFR-Wgn and TNF-Egr is slightly milder than the phenotype produced by TNFR-Wgn alone (together with a control UAS line), likely indicating the genetic interactions. The Error bars indicate SD of mean. n, number of DBs analysed, in brackets number of embryos analysed. ****p < 0.0001; ns not significant, Chi-squared test, two-sided. Scale bar: (d, e) 50 μm, (a–c, h–k) 20 μm, (f, g) 10 μm. Source data and details of statistical tests used and p values are provided as a Source Data file.