emo-1(
oz1) is a member of a class of hermaphrodite sterile mutations in Caenorhabditis elegans that produce endomitotic oocytes in the gonad arm. Oocytes in
emo-1(
oz1) mutants exhibit multiple defects during oogenesis. After meiotic maturation, ovulation fails, trapping oocytes in the gonad arm where they become endomitotic.
emo-1 encodes a homologue of the Sec61p gamma subunit, a protein necessary for translocation of secretory and transmembrane proteins into the endoplasmic reticulum of yeast and mammalian cells. A putative
emo-1 null mutation,
oz151, displays embryonic lethality. The
oz1 sterile mutation is a transposable element insertion into the
emo-1 3' untranslated region that almost completely eliminates germline mRNA accumulation. Genetic mosaic analysis using the
oz1 allele indicates that
emo-1(+) expression in germ cells is required for fertility. The J67 monoclonal antibody, which recognizes an oocyte surface antigen (Strome, S. 1986. In Gametogenesis and the Early Embryo. J.G. Gall, editor. Alan R. Liss, Inc., New York. 77-95.), does not stain
oz1 oocytes, a finding consistent with defective protein transport in the mutant. We propose that the
emo-1 gene product acts in the transport of secreted and transmembrane proteins in C. elegans oocytes, and is necessary for both oogenesis and the coupling of ovulation with meiotic maturation.