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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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