The DAZ -family genes encode RNA-binding proteins conserved among animals, which play important roles in meiosis and gametogenesis. We have previously shown that C. elegans
daz-1 , a member of the family, is necessary for oogenesis but not for spermatogenesis. However, the molecular function of the
daz-1 gene product is still unclear. To approach its role in gametogenesis, we analyzed
daz-1 homologs in C. briggsae and C. remanei , two nematodes closely related to C. elegans . When function of
Cb-daz-1 was depleted by RNAi, hermaphrodites became sterile, continuing spermatogenesis in adulthood without switching to oogenesis. This "Mog" (masculinization of germline) phenotype was different from the pachytene arrest during oogenesis observed in the C. elegans
daz-1 mutant, suggesting a role for
Cb-daz-1 in germline sex determination. This result led us to investigate the possible involvement of C. elegans
daz-1 in germline sex determination. When
daz-1 was depleted in C. elegans mutants showing a weak Mog phenotype such as
fem-3(gf) and
fbf-1 , their Mog phenotype was strongly enhanced, resulting in a complete defect in sperm-to-oocyte switch. This suggests that C. elegans
daz-1 potentially participates in the regulation of germline sex determination. On the other hand, we isolated
fbf-1 ,
fbf-2 and
gld-1 mRNA as possible targets of DAZ-1 by immunoprecipitation. By immno-blotting , a decrease of FBF and GLD-1 protein was detected in
daz-1 mutant. We examined their functional interaction using a
gld-1 gain-of-function mutation and a
gld-3 deletion mutation. GLD-3 has been proposed to antagonize FBF activity, suggesting that the
gld-3 mutant is likely to mimic a high FBF activity state. We found that oogenesis was partially recovered in the
daz-1 gld-3 double mutant compared to the
daz-1 single mutant. This recovery was further enhanced by combining
gld-1(gf Fog) . These genetic interactions support the possibility that
daz-1 may act positively on both fbf and
gld-1 pathways for faithful germline sex determination. Further,
daz-1 may control the
fbf-1/fbf-2 and
gld-1 activities in multiple aspects in germ cell development.