Figure 8.

C-terminal region of Yb is required for PIWI but not HH expression in niche cells. (A) DAPI image of Yb⁷²/Yb⁷² ovarioles carrying a transgene with a C-terminal deletion (pAS10). These ovarioles show improved follicle cell (FC) proliferation, implicating improved hh signaling, which is essential for follicle stem cell division (Forbes et al., 1996). (B and C) Consistent with this, the cap cell (CC) expression of hh is fully restored in Yb⁷²/Yb⁷² mutants by introducing a C-terminally deleted Yb (pAS9 in B and pAS10 in C). This suggests that the C-terminal region of Yb is not required for HH expression. (D and E) A Yb⁷²/Yb⁷² germarium, carrying a pAS10 transgene and an myc-piwi gene, stained for DAPI (D) and myc-PIWI (E), respectively, is shown. The expression of piwi in TF and cap cells is not restored. This is also the case when any other mutant transgene in Fig. 6 is introduced into the Yb⁷²/Yb⁷² mutants (see Fig. 6 for summary). Thus, the full-length Yb protein is required for piwi expression. GC, germline cell; NC, nurse cell. Bars, 20 µm.