A GONAD-DERIVED SURVIVAL SIGNAL FOR VULVAL PRECURSOR CELLS IN 2 NEMATODE SPECIES

Intercellular cell survival signals play a major role in animal develo pment [1], In the nematode Caenorhabditis elegans, however, the stereo typed cell deaths that occur reproducibly during development are regul ated in a cell-autonomous fashion (or, in a few cases, by a death-indu cing signal) [2], We show here the existence of a cell-survival signal acting on the vulval precursor cells in two nematodes, Turbatrix acet i and Halicephalobus sp. JB128, In C. elegans [3], as in many other ne matode species [4-7], ablation of the gonad causes ail vulval precurso r cells to adopt a default epidermal fate: a gonadal signal is require d for the induction of vulval fates, In the nematodes T. aceti and Hal icephalobus sp. JB128, however, we found that ablation of the gonad in the L1 larval stage caused all vulval precursor cells to undergo prog ramed cell death, Thus, in intact Turbatrix and Halicephalobus, a surv ival signal from the gonad prevents activation of the cell-death progr am in vulval precursor cells. Our results demonstrate the existence of intercellular cell-survival signals in nematodes and uncover an evolu tionary variation in the role of the gonad in nematode vulval developm ent.