( May 20 2002 ...)RNA Interference and Gene Silencing: History and Overview

Post-transcriptional gene silencing (PTGS), which was initially considered a bizarre phenomenon limited to petunias and a few other plant species, is now one of the hottest topics in molecular biology (1). In the last few years, it has become clear that PTGS occurs in both plants and animals and has roles in viral defense and transposon silencing mechanisms. Perhaps most exciting, however, is the emerging use of PTGS and, in particular, RNA interference (RNAi) PTGS initiated by the introduction of double-stranded RNA (dsRNA) as a tool to knock out expression of specific genes in a variety of organisms (reviewed in 1-3).

How was RNAi discovered? How does it work? Perhaps more importantly, how can it be harnessed for functional genomics experiments? This article will briefly answer these questions and provide you with resources to find in depth information on PTGS and RNAi research.

A Bizarre Phenomenon is Discovered: Cosuppression and PTGS in Plants
More than a decade ago, a surprising observation was made in petunias. While trying to deepen the purple color of these flowers, Rich Jorgensen and colleagues introduced a pigment-producing gene under the control of a powerful promoter. Instead of the expected deep purple color, many of the flowers appeared variegated or even white. Jorgensen named the observed phenomenon "cosuppression", since the expression of both the introduced gene and the homologous endogenous gene was suppressed (1-5).

First thought to be a quirk of petunias, cosuppression has since been found to occur in many species of plants. It has also been observed
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