Fig. 2. rib mutants have defects in tracheal development. Embryos in the left column are wild-type; embryos in the right column are rib1 homozygotes. A-H, K, and L are lateral views; I and J are dorsal views. 2A12 or anti-CRB was used to visualize the tracheal lumen, and anti-TRH to visualize nuclear TRH in all tracheal cells. The tracheal network is abnormal in rib1 mutants (B). The most obvious difference is a complete loss of the main tracheal tube, the DT (arrow in B). The specification of tracheal placodes and early events of tracheal invagination appear normal in rib mutants (D). (E,F) By late stage 12, many of the tracheal branches in rib mutants have not migrated and lumen size is expanded (F), as compared with wild type (E). Insets in E,F,G,H are of metamere 4 (black arrow). (G,H) At stage 14, the DT (white arrow) is clearly absent in rib mutants (H) and the LT (black arrowhead) and GB (arrow) are stunted. The VB (white arrowhead) is visible out of the plane of focus (H). In late stage rib embryos (J), VBs reach the gut and perform terminal branching (arrows), as in wild type (I). (K,L) In embryos carrying UAS-rib and the tracheal driver btl-Gal4, tracheal phenotypes are rescued. (K) The lumina are less dilated, the two ventral branches are less stunted (black arrow and arrowhead), and DTs are migrating (white arrow). (L) Rescue of DT formation is obvious by late stages (arrow). On average, seven of the nine DT fragments form in these rescued embryos. Wild-type genotypes are rib1/CFL, which were also stained with anti-ßgal (brown staining in C,E,G), or Oregon R (A,I). No differences were observed in the phenotypes of embryos carrying one versus two wild-type alleles of rib.
