Fig. 6. Ttk controls tracheal tube size. (A,B) Portions of dorsal trunk (DT) in longitudinal views (upper panels) or in cross-sections (lower panels) of wild type (WT; A) and ttk mutants (B). Thickness of the tubes is measured. (C,D) Stage 16 embryos showing accumulation of CBP in the DT. ttk mutants show an abnormal intraluminal chitin filament (D). (E-G) Expression pattern of mmy in stage 14 embryos. Notice the increased levels of expression in ttk mutants (F) and the absence of expression when ttk is generally overexpressed (G). (H,K) Stage 16 embryos. Verm is abnormally accumulated in ttk mutants (K). (I,J,L,M) Stage 16 embryos. Accumulation of septate junction (SJ) markers (FasIII and Cora; green) in ttk mutants (L,M) is only slightly affected (L) or is comparable to wild type (M). (N,O) Stage 16 embryos injected with a 10 kDa rhodamine-labelled dextran. ttk embryos (O) are permeable to the dye, which fills the tracheal lumen (arrows), whereas the wild-type trachea is impermeable (N). All panels except E-G,N and O show projections of confocal sections of laterally viewed embryos.