Figure 6. During Meiosis I, AIR-2 and Other ABI Complex Members Are Concentrated on a Discrete Region of Bivalents. AIR-2 (A), BIR-1 (B), ICP-1 (C and D), phosH3(S28) (E), and phosH3(S10) (F-H) localize to a discrete region of bivalents in diakinesis (A, B, E, and F) and meiosis I (C, D, and G). Wild-type embryos were stained with the indicated antibodies and DAPI to visualize DNA. In metaphase I (C) and anaphase I (G), the alignment of the bivalents on the meiotic spindle indicates that regions of the bivalents that are labeled with AIR-2 and the other antigens correspond to the regions distal to the site of attachment on the meiotic spindle. During metaphase II, phosH3(S10) labels the entire chromosome (H). Localization of REC-8 and phosH3(S10) on individual bivalents from a wild-type oocyte reveals that phosH3(S10) is localized to the chromosome region distal to the chiasma, where cohesion must be released during the first meiotic division (I). In
rec-8(RNAi) oocytes, AIR-2 does not localize to the univalents (J), although the univalents are labeled with phosH3(S10) (K). In
spo-11(
ok79) oocytes, AIR-2 is associated with some but not all of the univalents (L). Drawings depict the arrangement of the chromatids (light and dark blue), cohesion (purple and red), and the distribution of the ABI complex (red).