SOMA-GERM CELL-INTERACTIONS IN CAENORHABDITIS-ELEGANS - MULTIPLE EVENTS OF HERMAPHRODITE GERMLINE DEVELOPMENT REQUIRE THE SOMATIC SHEATH TEND SPERMATHECAL LINEAGES

Germ cells complete multiple events to form functional oocytes and spe rm. In the Caenorhabditis elegans hermaphrodite, germ cells develop in proximity to the somatic gonad sheath and spermathecal cells. We pres ent evidence from cellular laser ablation studies indicating that cell s of the somatic sheath and spermathecal lineages play critical roles in four events of hermaphrodite germline development. (1) Cells of the sheath and spermathecal lineage support germline proliferation; ablat ion of sheath/spermathecal precursor cells reduces mitotic proliferati on. (2) These cells also play a role in the exit of germ cells from th e pachytene stage of meiotic prophase and/or gamete differentiation; a blation can result in undifferentiated germ cells arrested in pachyten e. (3) Proximal sheath and distal spermatheca cells are required for o vulation of the oocyte. During wild-type ovulation, the mature oocyte is expelled from the gonad arm by contraction of the proximal myoepith elial sheath and dilation of the distal spermatheca. Ablation of these cells traps mature oocytes in the gonad arm where they endomitoticall y replicate their DNA (the Emo phenotype). (4) Cells of the sheath and spermathecal lineage also appear to promote the male germ cell fate s ince ablation of one sheath/spermathecal precursor cell can feminize t he hermaphrodite germ line. These somatic ablation-induced germline ph enotypes demonstrate that the somatic gonad is required for multiple e vents in C. elegans germline development. Further, these results sugge st that soma to germline cell-cell interactions in C. elegans are phys iological in character (i.e., contraction during ovulation) as well as regulatory. (C) 1997 Academic Press.