Figure 5.

Functional mapping of tubule regions. (A) Alkaline phosphatase staining of lower tubule. Tubules were fixed and stained for alkaline phosphatase. This shows a perfect overlap with line c507 (cf. Fig. 2G). (B and C) Short-term (10 min) labeling with 10 μg/ml rhodamine 123 identifies the main segment of both posterior (B) and anterior (C) tubules as the region responsible for transport of this organic molecule. (D) Initial and transitional segments express V-ATPase at a far lower level than the main segment, as detected by a reporter gene inserted into the vha55 gene in the P-element lethal line vha55^j2e5 (28). This corresponds to the boundary reported by lines 155Y, c709, and c776 in Fig. 2 A and B. (E) A boundary midway along the ureter is marked by a change in the size of nuclei labeled in line vha55^j2e5. This corresponds to the boundary reported by lines c649 and c601 in Fig. 2 H and I. (F) Within the main segment, only principal cell nuclei (cf. Fig. 4B) are labeled in line vha55^j2e5. (G) Within the main segment, only principal cell nuclei (cf. Fig. 4B) are labeled in P-element line l(2)k02508, a recessive lethal insertion within the gene encoding the body-enriched vha68–2 V-ATPase A subunit (36). (H) The tiny cells (cf. Figs. 3F and 4C) are labeled by antibodies to horseradish peroxidase, which recognize an epitope on a Drosophila nervous system-specific Na⁺,K⁺ ATPase β-subunit (37).