We describe features of RNA silencing and associated epigenetic imprints that illustrate potential roles for RNA interference (RNAi) in maintenance and transmission of epigenetic states between cells, throughout a plant, and perhaps even across sexual generations. Three types of transgenes can trigger RNAi of homologous endogenous plant genes: (1) "sense" transgenes that overexpress translatabl...

Sweet potato chlorotic stunt virus (SPCSV; family Closteroviridae) encodes a Class 1 RNase III endoribonuclease (RNase3) that suppresses post-transcriptional RNA interference (RNAi) and eliminates antiviral defense in sweetpotato plants (Ipomoea batatas). For RNAi suppression, RNase3 cleaves double-stranded small interfering RNAs (ds-siRNA) and long dsRNA to fragments that are too short to be u...

RNA interference (RNAi) is perhaps best known as a laboratory tool. However, RNAi-related pathways represent an antiviral component of innate immunity in both plants and animals. Since viruses can protect themselves by suppressing RNAi, interaction between RNA viruses and host RNAi may represent an ancient coevolutionary "arms race." This could lead to strong directional selection on RNAi genes...

The design of RNA interference (RNAi) reagents is an essential step for performing loss-of-function studies in many experimental systems. The availability of sequenced and annotated genomes greatly facilitates RNAi experiments in an increasing number of organisms that were previously not genetically tractable. The E-RNAi web-service, accessible at http://www.e-rnai.org/, provides a computationa...

The ability to use double-stranded RNA to inhibit gene expression sequence-specifically (RNA interference, or RNAi) is currently revolutionizing science and medicine alike. Numerous pre-clinical studies are evaluating RNAi as a novel therapeutic modality in the battle against gain-of-function autosomal dominant diseases, cancer, and viral infections. One emerging concern is that RNAi mono-thera...

In the few years since the discovery of RNA interference (RNAi; Fire et al. 1998), it has become clear that this process is ancient. RNAi, the oldest and most ubiquitous antiviral system, appeared before the divergence of plants and animals. Because aspects of RNAi, known as cosuppression, also control the expression of transposable elements and repetitive sequences (Ketting et al. 1999; Tabara...

RNA interference (RNAi) is a natural cellular mechanism that inhibits gene expression in a sequence-specific manner. In the last decade, RNAi has become a cornerstone in basic biological systems research and drug development efforts. The RNAi-based manipulation of mammalian cells facilitates target identification and validation; assists in identifying human disease etiologies; and expedites the...

Dicer ribonucleases of plants and invertebrate animals including Caenorhabditis elegans recognize and process a viral RNA trigger into virus-derived small interfering RNAs (siRNAs) to guide specific viral immunity by Argonaute-dependent RNA interference (RNAi). C. elegans also encodes three Dicer-related helicase (drh) genes closely related to the RIG-I-like RNA helicase receptors which initiat...

RNA-mediated interference (RNAi) is a method to inhibit gene function by introduction of double-stranded RNA (dsRNA). Recently, an RNAi library was constructed that consists of bacterial clones expressing dsRNA, corresponding to nearly 90% of the 19,427 predicted genes of C. elegans. Feeding of this RNAi library to the standard wild-type laboratory strain Bristol N2 detected phenotypes for appr...

The discovery of RNA interference in C. elegans in 1998 has established this nematode as a key model to study RNAi mechanisms. Meanwhile, RNAi has been extensively applied to study a variety of basic biological questions in worms. In C. elegans, the dsRNA required to trigger RNAi can be administered by injection, by soaking, and importantly, by feeding. The delivery of dsRNA through food and th...