Nematodes are the most numerous multi-cellular animals on earth representing more than 20,000 described species classified in the phylum Nemata. Free-living terrestrial nematodes have evolved to feed on bacteria, fungi, plants, and other nematodes. The broad ecological niche taken up by nematodes can pose serious agricultural, industrial, and medical problems. One species, Caenorhabditis elegans elegans), has served as a model system for the understanding of nematode biology and as a genetic system to dissect molecular processes that are difficult to research in more complex animal systems. Correct specification of the male and female germ line is essential for sexual reproduction in the C. elegans hermaphrodite. During this process, the suppression of tra-2 activity plays a central role in promoting spermatogenesis -vs- oogenesis. The long term objectives of this proposal are to use C. elegans as model system for the analysis of cell fate specification in the germ line. We have isolated a nematode specific gene, fog-2 (feminization of the germline), which is part of a multi-protein complex that represses the translation of tra-2. As part of this proposal we will use a yeast-two hybrid screen to: 1) identify the binding partners of FOG-2 that function in tra-2 translational control and 2) determine their contribution to hermaphrodite spermatogenesis. The general mechanisms of translational control elucidated by this proposal are likely to applicable to other systems and may prove useful in the generation of novel drugs for nematode specific genes that can be used in their control.