nos-1 and nos-2, two genes related to Drosophila nanos, regulate primordial germ cell development and survival in Caenorhabditis elegans

In Drosophila, the posterior determinant nanos is required for embryonic pa tterning and for primordial germ cell (PGC) development. We have identified three genes in Caenorhabditis elegans that contain a putative zinc-binding domain similar to the one found in nanos, and show that two of these genes function during PGC development, Like Drosophila nanos, C. elegans nos-1 a nd nos-2 are not generally required for PGC fate specification, but instead regulate specific aspects of PGC development. nos-2 is expressed in PGCs a round the time of gastrulation from a maternal RNA associated with P granul es, and is required for the efficient incorporation of PGCs into the somati c gonad. nos-1 is expressed in PGCs after gastrulation, and is required red undantly with nos-2 to prevent PGCs from dividing in starved animals and to maintain germ cell viability during larval development. In the absence of nos-1 and nos-2, germ cells cease proliferation at the end of the second la rval stage, and die in a manner that is partially dependent on the apoptosi s gene ced-4, Our results also indicate that putative RNA-binding proteins related to Drosophila Pumilio are required for the same PGC processes as no s-1 and nos-2. These studies demonstrate that evolutionarily distant organi sms utilize conserved factors to regulate early germ cell development and s urvival, and that these factors include members of the nanos and pumilio ge ne families.