Required maternally for germline survival and embryogenesis. Forms a complex with gls-1 which promotes the oogenic cell fate by freeing the translational repressor fbf to repress sperm promoting factors. Promotes maturation of primary spermatocytes to mature sperm. Required during hermaphrodite development to promote sperm fate, which is critical for determining the normal number of sperm. Promotion of sperm fate is at the expense of oogenesis, possibly through the negative regulation of fbf. Required during male development for the continued production of sperm and inhibition of oogenesis. Together with gld-2, promotes the transition from mitosis to meiosis. Interacts (via its KH1 domain) with gld-2. Isoform A but not isoform B interacts specifically with fbf-1 and fbf-2 in an RNA-independent manner. Isoform A interacts with gls-1 isoform C. Localizes to P granules. Found also in particles near but not coincident with P granules. Additional isoforms seem to exist. Experimental confirmation may be lacking for some isoforms. Expressed in the germline (at protein level). In adult hermaphrodites, first detected in the transition zone (TZ), weakly expressed in the early mitotic region and in pachytene germ cells, and becomes more abundantly expressed as germ cells enter diakinesis (at protein level). Expressed in primary spermatocytes, but not in secondary spermatocytes or adult sperm (at protein level). Expressed both maternally and zygotically throughout development and in adult hermaphrodites and males (at protein level). Loss of both maternal and zygotic expression causes variable lethality, ranging from arrest during embryonic development to soon after hatching, and sterility due to early germline defects. In these animals the germline precursor cells Z2 and Z3 are smaller, divide more slowly and their descendants remain small and indistinct compared to their wild-type counterparts. In addition, some of these animals show somatic defects, including a protruding vulva, multiple vulvae or a reduction in animal size. In zygotic mutant adult hermaphrodites, most spermatogenic cells are blocked as primary spermatocytes, the number of spermatocytes appears lower than normal and spermatogenesis is delayed by several hours. Zygotic mutant homozygous adult males produce some spermatogenic cells, although these sperm are less well defined morphologically than normal. In addition, loss of maternal and zygotic expression results in adult males that produce enlarged granular cells that appear oocyte-like and show chromosomal bivalents typical of oocytes. In zygotic mutants the mitotic region is longer and has more nuclei than normal, the mitotic region/TZ boundary is shifted from 20 to an average of 27 or 28 nuclei and the boundaries between mitotic region and TZ and TZ and pachytene region are not sharp as in wild-type. The deletion mutant gld-3 (q730) makes no detectable GLD-3; it is predicted to generate an mRNA with a premature stop codon, which should be subject to NMD. The deletion mutant gld-3 (q741) removes the fbf-binding site from isoform A, but leaves the gld-2-binding site intact. Animals homozygous for gld-3 (7q41) enter meiosis, but are feminized. In addition, gld-3 protein that retains its gld-2-binding region, does not have the dramatic mitosis/meiosis delay seen in gld-3 null mutants. By contrast, sex determination was not normal; gld-3 (q741) males produced oocytes. Therefore, promotes meiosis primarily via its interaction with gld-2 whereas the sperm/oocyte decision relies on its interaction with fbf.