Uridylation of RNAs has been found to be highly prevalent and conserved among eukaryotes. The untemplated addition of uridines to the 3\u27 end of RNA molecules is catalyzed by poly (U) polymerase (PUP). Uridylation has a fundamental role in RNA decay. The emerging discoveries regarding uridylation emphasize a new layer of gene regulation, and therefore we were curious about the developmental consequences of such gene regulation. Here, we investigated the roles of three Caenorhabditis elegans proteins, with in vitro PUP activity, in germline development. PUP-1/CDE-1 and PUP-2 are known to target certain classes of small non-coding RNA, and the function of PUP-3 remains unknown. We examined the developmental phenotypes of pup mutants and evaluated the expression of PUP proteins in the germ line. We show that PUP-1 and PUP-2 function together to maintain germline identity and ensure germline survival and development under conditions of stress. PUP-1 and PUP-2 have distinct expression patterns within the germ line and localize to distinct subcellular compartments. In contrast, PUP-3 has a distinct role in germline development. PUP-3 abundance is elevated in the pup-1/-2 double mutant germline, and the loss of PUP-3 activity largely suppresses the pup-1/-2 germline phenotype. We propose that germline survival, identity, and development require the correct balance of PUP activity
