Gene silencing, also called RNA interference (RNAi) is a specific
mechanism of RNA degradation involved in gene regulation, development
and defense in eukaryotic organisms. It became an important subject in
the teaching programs of molecular biology, genetics and biotechnology
courses in the last years. The aim of this work is to provide simple
and inexpensive assays to understand and teach gene silencing using
plants as model systems. The use of transient and permanent transgenic
plants for expressing reporter genes, like those derived from jellyfish
green fluorescent protein (gfp) encoding gene, provides a nice,
colorful and conclusive image of gene silencing. Three experimental
approaches to evidence RNA silencing are depicted. In the first
approach gene silencing is demonstrated after transient expression of
reporter genes in non-transgenic plants. In the second, silencing is
triggered against a reporter gene stably integrated into a transgenic
plant. The third approach involves the triggering of RNA silencing
against endogenous genes using viral vectors. In addition we illustrate
systemic gene silencing showing how the silencing signal is spread over
a plant and finally it is also demonstrated the suppression of gene
silencing. The first group of experiments is recommended to be tough on
undergraduate courses, the following two sections are recommended for
graduate courses. Hopefully, it will help students to understand this
important phenomenon and to unravel the importance of gene silencing as
a key gene regulation mechanism and as a molecular and biotechnological
tool