serpe02821 LCBP1KG07819 double mutants display an enhanced tracheal phenotype. The dorsal trunk begins to elongate excessively at stage 15 and by stage 16 is approximately 40% longer than normal and highly convoluted. Similar effects are observed in other branches including the transverse connective, although the effects are not as pronounced in smaller-caliber branches, such as the dorsal branch. While the apical (inner) cell surfaces are elongated in serpe02821 LCBP1KG07819 mutants the basal (outer) side of tracheal cells does not appear to be similarly elongated and does not follow the tortuous path of the lumen. The tracheal pericellular-diffusion barrier is not compromised in serpe02821 LCBP1KG07819 mutants.
serpe02821 LCBP1KG07819 double mutants exhibit morphological defects in chitin structure, apparent by stage 14, several hours before the elongated-tube phenotype begins to manifest. In contrast to wild-type, in serpe02821 LCBP1KG07819 trachea the fibrous structure of the chitin cylinder is abolished and the surface of the cylinder is irregular. Also, the small gap between the chitin cylinder and the apical surface is absent in serpe02821 LCBP1KG07819 mutants. This double mutant also affects embryo body shape, presumably through altering the structure and rigidity of epidermal cuticle.
The phenotype of hemizygous serpe02821 LCBP1KG07819 embryos (in trans to Df(3L)Exel6135) is indistinguishable from homozygous serpe02821 LCBP1KG07819 embryos. In contrast to the dramatic effects of the mutations on tracheal length and shape, there is little or no effect of the mutations on the diameter of the tubes. The dorsal trunk exhibits its characteristic posterior to anterior taper and is of normal caliber except for slight constrictions that are occasionally observed near dorsal trunk fusion joints.