Figure 3.

LAB-1 localizes to the AIR-2-free domain of the bivalent in late prophase I. (A) AIR-2 and phospho Histone H3 (pH3) localization in wild-type and lab-1(tm1791) diakinesis bivalents (−1 oocytes). Bar, 0.5 μm. (B) AIR-2 localization on the short (S) or both short and long (S + L) arms of bivalents in −1 oocytes at diakinesis of different genotypes. Bar, 1 μm. (C) Expression of a GFP∷LAB-1∷HA transgene, detected with an anti-GFP antibody, partially rescues the lab-1(tm1791) phenotypes. Error bars represent standard deviation of the mean. Bar, 1 μm. (D) LAB-1 and AIR-2 (top) or LAB-1 and phospho Histone H3 (bottom) localization on bivalents in −1 oocytes at diakinesis in gsp-2(tm301) gonads. Bar, 0.5 μm. (E) Schematic representation of chromosome-associated REC-8 during meiosis I segregation. Upon fertilization, bivalents align at the metaphase plate and rotate to assume a position perpendicular to the cell cortex prior to homolog segregation. REC-8 in the region distal to the chiasma (short arms) progressively weakens until it is completely removed by separase in the metaphase to anaphase transition. The subset of REC-8 present on the long arms of the bivalent is spared from separase activity and sustains sister chromatid cohesion as chromatids enter meiosis II. (F) REC-8 and LAB-1 localization on a bivalent from a fertilized oocyte in wild type. Bar, 0.5 μm. (G) AIR-2 and REC-8 localization on metaphase I bivalents of wild-type and lab-1(tm1791) worms. Bar, 0.5 μm. (H) AIR-2 and REC-8 localization on anaphase I chromosomes of wild-type and lab-1(tm1791) worms. Bar, 2 μm.