Fig 5. The aECM component chitin is essential for seamless tube shape and integrity.

(A) Schematic of the kkv gene and the encoded Chitin Synthase protein structure with the position of the sob mutations indicated. (B-B”) kkv^sob404 null terminal cell clone (green) exhibited apical membranes with cystic, irregular morphology. For the areas marqueed in white, the apical membrane is shown enlarged in (B’, B”) as indicated. Terminal cell outlines in B’, B”, C‘, D’ are shown by green dots. In (C) and (D), kkv^sob483 and kkv^sob761 clones, respectively, are shown. In distal terminal branches (B”, D ‘), discrete apical membrane cysts (arrowheads) are interspersed with tube of apparently normal morphology. (C-D’) limited regions of discontinuous apical membrane (C’,D’) were also observed with all kkv alleles. (E) Penetrance of tube phenotypes for the kkv^sob404 null allele and kkv^sob483, a putative recessive antimorphic allele (P<0.0001, Chi-Square test). (Scale Bars: B, C, D 20 μm; B’,B”, C’, D’ 5 μm).