Figure 3.

Timely transition in pachytene progression in the him-6 mutant. (A) Immunoflouorescence images of whole-mount gonads, extending from the distal premeiotic tip to the end of the pachytene region. In both the wild-type and him-6 mutant, phosphorylation of nuclear envelope protein SUN-1 (SUN-1 S8Pi) and association of the DSB-promoting protein DSB-2 with chromatin show similar dynamics: They are detected in germ-cell nuclei at the onset of meiotic prophase and then decline and disappear from most nuclei during mid-pachytene. As SUN-1 S8Pi and DSB-2 persist until late pachytene in multiple mutants that fail to make crossover-eligible recombination intermediates (Rosu et al. 2013; Woglar et al. 2013) (see B), this finding is consistent with the conclusion that him-6 mutants are proficient for generating crossover intermediates. Scale bar, 10 μm. (B) Bar graph showing quantitation of the percentage of the meiotic zone occupied by SUN-1 S8-Pi-positive nuclei in germ lines of indicated genotypes. The presence/absence of SUN-1 S8-Pi signals was assessed in the portion of the germ line extending from the onset of meiotic prophase to the end of the pachytene region. The extent of the SUN-1 S8-Pi-positive zone was defined as the number of contiguous rows of nuclei in which all rows contained two or more nuclei with SUN-1 S8-Pi staining/total rows of nuclei in the scored region. Data are represented as mean ±SD. Whereas the SUN-1 S8-Pi-positive zones were significantly extended in the cosa-1 and cosa-1; him-6 mutants relative to wild type and the him-6 single mutant (P < 0.0001, two-tailed Mann–Whitney tests), no significant difference was observed between wild type and the him-6 mutant (P = 0.10). Numbers of germ lines scored: wild type, 18; him-6, 21; cosa-1, 20; cosa-1; him-6, 17.