Ingestion of bacterially expressed dsRNAs can produce specific and potent genetic interference in Caenorhabditis elegans

Genetic interference mediated by double-stranded RNA (RNAi) has been a valu able tool in the analysis of gene function in Caenorhabditis elegans. Here we report an efficient induction of RNAi using bacteria to deliver double-s tranded RNA. This method makes use of bacteria that are deficient in RNaseI II, an enzyme that normally degrades a majority of dsRNAs in the bacterial cell. Bacteria deficient for RNaseIII were engineered to produce high quant ities of specific dsRNA segments. When fed to C. elegans, such engineered b acteria were found to produce populations of RNAi-affected animals with phe notypes that were comparable in expressivity to the corresponding loss-of-f unction mutants. We found the method to be most effective in inducing RNAi for non-neuronal tissue of late larval and adult hermaphrodites, with decre ased effectiveness in the nervous system, in early larval stages, and in ma les. Bacteria-induced RNAi phenotypes could be maintained over the course o f several generations with continuous feeding, allowing for convenient asse ssments of the biological consequences of specific genetic interference and of continuous exposure to dsRNAs. (C) 2001 Elsevier Science B.V. All right s reserved.