GLD-1, A CYTOPLASMIC PROTEIN ESSENTIAL FOR OOCYTE DIFFERENTIATION, SHOWS STAGE-SPECIFIC AND SEX-SPECIFIC EXPRESSION DURING CAENORHABDITIS-ELEGANS GERMLINE DEVELOPMENT

GLD-1, a putative RNA binding protein, is essential for oocyte develop ment in Caenorhabditis elegans. A gld-1 null mutation abolishes hermap hrodite oogenesis and confers a tumorous germline phenotype in which p resumptive female germ cells exit the meiotic pathway and return to th e mitotic cell cycle. Here we demonstrate that gld-l(null) germ lines express female-specific, but not male-specific, molecular markers, ind icating that gld-l acts downstream of sexual fate specification to reg ulate oocyte differentiation. Immunolocalization studies identify GLD- 1 as a cytoplasmic germline protein that displays differential accumul ation during germline development. first, germ cells that are in the m itotic cell cycle contain low levels of GLD-1 that likely reflect a no nessential gld-l function (negative regulation of proliferation in the mitotic germ line) revealed in previous genetic studies. Second, entr y of presumptive oocytes into the meiotic pathway is accompanied by a strong increase in GLD-1 expression/accumulation. GLD-1 levels are hig h through the pachytene stage but fall to background as germ cells exi t pachytene and complete oogenesis. The meiotic prophase accumulation pattern is consistent with GLD-l's essential role in oocyte differenti ation, which may be to repress the translation of a subset of maternal RNAs synthesized during early oogenesis until late oogenesis when GLD -1 is absent. (C) 1996 Academic Press, Inc.