Figure 1. Germline organization and meiotic nuclear morphology in P. pacificus are superficially similar to C. elegans.

(A) Projection image of the distal arm of a P. pacificus hermaphrodite gonad stained with DAPI. Scale bar, 30 μm. Insets show representative nuclei from the premeiotic region (PM), transition zone (TZ), pachytene (Pach), diplotene (Dip), diffuse stage (Diff), and diakinesis. Scale bar, 5 μm. (B) Distal region of a P. pacificus germline following injection of fluorescent nucleotides to label replicating DNA. Scale bar, 30 μm. (C) Metaphase I oocyte expressing CENP-C::V5, stained with anti-V5, DAPI, and anti-tubulin. Scale bar, 10 μm. (D) Mitotic chromosomes (DAPI) in the premeiotic germline of adult hermaphrodites and a 2–4 cell stage embryo and expressing CENP-C::V5 (magenta). Scale bar, 2 μm.

Figure 1—figure supplement 1. Multiple sequence alignments of homologs of proteins analyzed in this study.

Sequences from species other than nematodes were obtained from Uniprot; nematode sequences were from Wormbase (wormbase.org) and pristionchus.org (see Figure 1—figure supplement 1—source data 1, Figure 1—figure supplement 2—source data 1, Figure 1—figure supplement 3—source data 1, Figure 1—figure supplement 4—source data 1, Figure 1—figure supplement 5—source data 1, Figure 1—figure supplement 6—source data 1, Figure 1—figure supplement 7—source data 1, Figure 1—figure supplement 8—source data 1). For Pristionchus pacificus (Ppa) proteins, ‘El Paco’ gene predictions were refined by our own alignments and in some cases, RNA sequence data. For broadly conserved proteins, homologs from Caenorhabditis elegans (Cele), humans (Hsap), mouse Mus musculus (Mmus), Arabidopsis thaliana (Athal), the budding yeast Saccharomyces cerevisiae (Scer), the fission yeast Schizosaccharomyces pombe (Spom), and, where available, the fruit fly Drosophila melanogaster (Dmel) were included. Recognizable homologs of the meiotic cyclin COSA-1/CNTD-1 are restricted to metazoans and are not found in Drosophila. Homologs of SYP-4 are only found in nematodes, so an expanded group of nematode sequences was included in the alignment, including three Caenorhabditis species, C. elegans (Cele), C. briggsae (Cbri), C. remanei (Crem), plus Haemonchus contortus (Hcon), and Dictyocaulus viviparus (Dviv). Multiple sequence alignments were computed using MAFFT (Katoh et al., 2019) with default settings and displayed using Jalview (Waterhouse et al., 2009).

Figure 1—figure supplement 2. Multiple sequence alignment of Rad51/RAD-51 proteins.

Figure 1—figure supplement 3. Multiple sequence alignment of Rad51/RAD-51 proteins.

Figure 1—figure supplement 4. Multiple sequence alignment of Mnd1/MND-1 proteins.

Figure 1—figure supplement 5. Multiple sequence alignment of Hop2/HOP-2 proteins.

Figure 1—figure supplement 6. Multiple sequence alignment of meiotic HORMA domain proteins homologous to P. pacificus HOP-1.

Figure 1—figure supplement 7. Multiple sequence alignment of SYP-4 homologs from several nematode species.

Figure 1—figure supplement 8. Multiple sequence alignment of COSA-1/Cntd1 proteins from metazoans.