Figure 6.

  Misexpression of hdc in all tracheal cells can suppress terminal branching. The GAL4 expression system was used to express wild-type and mutant Hdc proteins throughout the developing tracheal system (B,E,F) and selectively in the fusion cells (C,D,F) of hdc⁺ embryos. Expressing UAS–hdc in all tracheal cells with the pantracheal btl–GAL4 driver results in suppression of terminal branching and expression of the terminal marker DSRF (arrow in B). (E) Comparison of the terminal branching suppression phenotype of UAS–hdc and UAS–hdc^Δl. The full-length construct is necessary for suppression. (C) Expression of UAS–hdc with the p127-GAL4 fusion cell-specific driver or the pantracheal btl–GAL4 driver causes extra branching phenotypes similar to the hdc⁵⁰ loss-of-function mutant (arrowheads). Expression of the UAS–hdc^Δ1 construct with the same drivers results in a similar phenotype (D,F). Bar in A–D, 10 μm.