FIGURE 7.

U7 and SLBP are required for histone pre-mRNA processing during oogenesis. (A) w¹¹¹⁸ control egg chamber hybridized with a histone H3 coding probe. In this and subsequent panels, white and black asterisks indicate individual nurse cells with and without H3 mRNA, respectively, and arrows indicate follicle cells. (B) w¹¹¹⁸ control egg chamber hybridized with an H3-ds probe. Note the lack of staining because H3-ds only detects misprocessed, poly A⁺ histone H3 mRNA. (C,D) U7¹⁴ mutant egg chambers hybridized with H3 coding and H3-ds probes, respectively. (E,F) Early stage Slbp¹⁰ mutant egg chambers, each from an individual ovariole, hybridized with the H3 coding and H3-ds probes, respectively. The brackets indicate a stage 2 or 3 egg chamber with staining in the nurse cells undergoing endocycles. Note the absence of H3-ds probe in the older egg chambers (asterisk in F). (G) Slbp¹⁰ mutant egg chamber stained with the H3 probe indicating production of H3 mRNA in both nurse and follicle cells. (H) Slbp¹⁰ mutant egg chamber hybridized with an H3-ds probe, with focus on the follicle cells. The arrow indicates a follicle cell expressing misprocessed, poly A⁺ histone mRNA. (I,J) Mosaic egg chambers containing Slbp¹⁵ mutant germ cells hybridized with a histone H3 coding probe (I) or an H3-ds probe (J). Because this is a mosaic egg chamber, the follicle cells are phenotypically wild-type and do not stain with the H3-ds probe because they express only wild-type H3 mRNA (arrow in I). All egg chambers except E and F stage 9. Anterior at left and posterior at right in all panels.