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RNA interference (RNAi) is a naturally occurring mechanism that leads to the “silencing” of genes. In consequence, the respective protein is no longer synthesised. In nature, this mechanism is used for the regulation of specific genes and is also applied as a defence against viruses. RNA interference (RNAi) is a form of post transcriptional gene regulation in which non translated double stranded RNA (dsRNA) molecules called small interfering RNA (siRNA) mediate sequence specific degradation of target messenger RNA (mRNA). RNA silencing is a novel gene regulatory mechanism that limits the transcript level by either suppressing transcription (TGS) or by activating a sequence- Specific RNA degradation process [PTGS/RNA interference (RNAi)]. The silencing effect was first observed in plants in 1990, when the Jorgensen laboratory introduced exogenous transgenes into petunias in an attempt to up-regulate the activity of a gene for chalcone synthase, an enzyme involved in the production of specific pigments. The natural function of RNAi is referring to the mechanism involved in cellular defense against viruses, genomic containment of retro-transposons, and post-transcriptional regulation of gene expression. RNAi can specifically silence individual genes, creating knockout phenotypes, either in transformants that can produce the required hairpin RNAs, or upon infection with recombinant RNA viruses that carry the target gene (VIGS, viral-induced gene silencing). RNAi is a multistep process involving the generation of small interfering RNAs (siRNAs) in vivo through the action of the RNase III endonuclease „Dicer‟. The resulting 21- to 23-nt siRNAs mediate degradation of their complementary RNA.
Keywords: RNA, RNA Interference, Pigments, Viruses.