Fig. 5. pntP2 expression in the tubules is regulated by Wg. The expression of pnt is driven by two promoters, P1 and P2, resulting in the expression of the isoforms PntP1 and PntP2 (Scholz et al., 1993). The isoform expressed more strongly in the tubules is PntP2. (A) A stage 10 (4.75 hours) pntP2-lacZ embryo stained for Ac (green) and ß-gal (purple, overlay; white) shows that pntP2 is expressed in a wider domain than the PNC. (B-E) In situ hybridisation for pntP2, showing expression on the posterior side of the tubules (arrow in B, late stage 10; C, stage 11; arrowheads indicate the anterior side). (D) In wg^cx4 mutant embryos, pntP2 expression fails in the tubules but is unaltered in the mesoderm (m; posterior side of tubule is indicated with an arrow, early stage 11). (E) Ectopic expression of wg by activating hs-wg from 3.5 to 4.5 hours results in elevated levels of pntP2 expression throughout the tubules (arrow indicates the posterior and arrowhead the anterior side of the tubule, late stage 10). e, epidermis; m, mesoderm; AMT, anterior Malpighian tubules; HG, hind gut; MTs, Malpighian tubules; PMG, posterior midgut; PMT, posterior Malpighian tubules.

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