DSB-2 and SUN-1 S8P are coordinately regulated by common upstream regulator CHK-2.

<p>Immunofluorescence images of gonads of indicated genotypes from the distal pre-meiotic region to end of pachytene, stained with DAPI and antibodies that recognize DSB-2 and SUN-1 S8P. Scale bar, 15 µm. (A) SUN-1 S8P is detected at the NE in meiotic prophase nuclei in the <i>dsb-2</i> mutant germ line, indicating that although these features are coordinated during wild-type meiosis, acquisition of meiotic SUN-1 S8P does not depend on DSB-2. However, the SUN-1 S8P zone is extended in the <i>dsb-2</i> mutant, indicating that the timing of its removal is affected. DSB-2 staining is absent from chromatin, indicating antibody specificity. (B) Main panel: Immunofluorescence images showing that localization of DSB-2 on chromatin and SUN-1 S8P staining at the NE are both severely reduced in the <i>chk-2</i> mutant in the indicated meiotic region. Note: SUN-1 S8P signal remains present on some pre-meiotic nuclei and on late diakinesis oocytes in <i>chk-2</i> mutants (data not shown; <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1003674#pgen.1003674-Penkner1" target="_blank">[23]</a>). Inset: Western blot of whole-worm protein lysates from the indicated genotypes (60 worms per lane) stained with anti-DSB-2 antibodies. The arrow indicates the DSB-2 protein (32 kD), which is absent in the <i>dsb-2</i> mutant but is still present in the <i>chk-2</i> mutant; the asterisk indicates a non-specific band that serves as a loading control. (C) The presence of DSB-2 on chromatin and SUN-1 S8P at the NE are correlated in the <i>him-19</i> mutant, in which only a small subset of nuclei are positive for these marks.