The research described here is directed at understanding a gene-silencing phenomenon known as RNAi. During RNAi, dsRNA directs the post-transcriptional sequence-specific inhibition of gene expression. Recent studies have begun to reveal how dsRNA is converted into a potent gene-silencing agent, and how related mechanisms are important in germline maintenance and developmental gene regulation in a variety of animals and plants. The proposed studies will employ an integrated set of molecular, biochemical and genetic methods using the nematode Caenorhabditis elegans as a model system and will address the following questions; (i) How is RNAi initiated? (ii) How do RNAi and mechanistically related developmental pathways, direct distinct outcomes; mRNA destruction vs. translation inhibition? and (iii) what gene products function in RNAi and related pathways? The findings from these studies will advance our understanding of RNAi and of related pathways in other organisms including humans and may lead to improved genetic interference technologies. Moreover, because the genetic mechanisms of RNAi are related to ancient gene-regulatory mechanisms, the proposed studies will lead to new insights of potential importance to our understanding of human development and disease. [unreadable] [unreadable]