GLS-1 and Germline Development Figure 4. Oogenesis Defects in gls-1 Mutants. (A, B) Extruded germ line of a gls-1/nDf23 hemizygote animal raised at 20uC stained for nuclear morphology. (B) Enlargement of proximal end in A. sp, mature sperm; arrows, abnormal endoreduplicating oocyte nuclei. Dashed lines mark a group of cells with small decondensed nuclei of various sizes that do not match typical meiotic germ cell nuclei. (C) Distal germ line of a gls-1/nDf23 hemizygote animal. e. pachy., early pachytene. l. pachy., late pachytene. 1usp, primary spermatocytes in late prophase I. (D, E) Proximal germ lines of wild-type and a gls-1 homozygote progeny from a gls-1/+ mother raised at 25uC in the last larval stage. Distal to the left, proximal (prox.) to the right. Numbers denote oocyte nuclei. Note, gls-1(ef8) germ lines have multiple rows of oocytes. Arrowhead, diplotene oocyte. Other additional labels as in A. (F–I) Most proximal end of a gls-1(ef8) homozygous germ line from the progeny of a gls-1/+ mother raised at 25uC in the last larval stage. Small decondensed nuclei of various sizes and showing mitotic behavior are located between dashed white lines. Arrow, metaphase plate. (F) DAPI staining. (G) anti-RME-2 (H) SP56 staining (I) P granules. doi:10.1371/journal.pgen.1000494.g004 40). We conclude that, for oogenesis defects, both gls-1 mutations behave as genetic alleles at elevated temperatures. gls-1 Acts Redundantly with fbf-1 and nos-3 to Promote the Female Fate of Germ Cells To investigate the relationships between gls-1 and gld-3 and to understand their molecular interactions we first focused on their seemingly opposing roles in germline sex determination. Zygotic gld-3 is required for the sperm fate; gld-3(0) mutants display a feminized germ line in both sexes [5,20]. In contrast, gls-1 mutations masculinized the hermaphrodite germ line (Table 1). Other known regulators of the sperm-to-oocyte switch include three PUF proteins (FBF-1, FBF-2 and PUF-8) and NOS-3. The former are required for suppressing the sperm fate by translation- ally repressing several sperm promoting genes of the sex PLoS Genetics | www.plosgenetics.org 7 May 2009 | Volume 5 | Issue 5 | e1000494