<i>obst-A</i> and <i>gasp</i> mutants show defects in luminal tracheal matrix.

<p>(a–d) Confocal microscopy projections of the trachea labeled with a FITC-conjugated chitin-binding probe (ChtB). The filamentous chitin is detected in the wild-type embryos at stage 16 (a). The chitin staining intensity is weaker in the <i>obst-A</i> (b), <i>gasp</i> (c) and <i>obst-A; gasp</i> (d) mutant embryos. (e–h) Optical sections of tracheal tubes stained for Verm. Verm is secreted to the tracheal lumen in wild-type embryos at stage 16 (e). The amount of secreted Verm is reduced in both <i>obst-A</i> (f) and <i>gasp</i> (g) single mutant embryos and <i>obst-A; gasp</i> (h) double mutant embryos. Scale bar: 10 µm.