SOLO and SMC1 are enriched at centromeres and interact genetically.

DNA was visualized with DAPI. Scale bars: 5 µm. (A–C) Localization of SOLO-Venus expressed from its native promoter. SOLO-Venus was detected with anti-GFP antibody. (A) SOLO-Venus formed bright foci and bound to chromosome arms in a whole-mount germarium. Females were deficient for the native solo gene but carried four copies of UPS-SOLO::Venus ({UPS-SOLO::Venus}; Df(2L)A267/solo^Z2-0198; {UPS-SOLO::Venus}. SOLO foci were visible in mitotic cells in the posterior area of region 1 (white arrowhead) while no SOLO signals were seen in the anterior-most area of germarium that contains stem cells and early cystoblasts (red arrowheads). (B, C) Df(2L)A267/solo^Z2-0198; {UPS-SOLO::Venus} females. SOLO formed bright foci at centromeres. CID was stained with anti-CID antibody. (B) SOLO and CID signals co-aligned in the nuclei of germ cells within region 2b but not in surrounding somatic follicle cells. (C) SOLO and CID signals co-aligned in the nuclei of germ cells but not somatic follicle cells in a stage 5 egg chamber. The oocyte (arrow) was identified by DNA amount (diploid) and position (posterior end of the cyst). The nurse cells are polyploid (arrowhead). The inset shows an enlarged view of the oocyte (arrow). (D) SOLO co-aligned with the cohesin component SMC1. Expression of Venus::SOLO was induced by nos-Gal4::VP16 in {UASp-Venus::SOLO}/{nos-Gal4::VP16} females and stained with anti-GFP antibody. SMC1 was stained with anti-SMC1 antibody. No SOLO or SMC1 foci were found in the anterior-most tip of the germarium where stem cells and early cystoblasts reside (red arrowheads). SOLO and SMC1 localized to centromeres but did not form linear structures in the posterior of region 1 (arrows). SOLO and SMC1 formed linear structures on chromosome arms and bright foci at centromeres in region 2a (white arrowheads). (E) Dependence of SMC1 staining on SOLO. Bright SMC1 foci were completely absent in solo (solo^Z2-3534/Df) germaria although some diffuse and linear SMC1 staining was still present. The insets are magnifications of pro-oocytes marked by the arrowheads and show linear staining in both WT and solo pro-oocytes.