A practical approach to the understanding and teaching of RNA silencing in plants

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