RNAi mediated gene silencing

Double-stranded RNA can be introduced experimentally to silence genes of interest. In plants, silencing can be triggered, for example, by engineering RNA viruses. In worms, silencing can be triggered by injection or feeding of double-stranded RNA (dsRNA). In both these systems, gene silencing triggered by RNAi is systemic and spreads throughout the organism. (A) A silencing signal moves from the veins into a plant's leaf tissue. Green is green fluorescent protein (GFP) fluorescence and red is chlorophyll fluorescence that is seen upon silencing of the GFP gene. (B) C. elegans engineered to express GFP in cell nuclei. Animals on the right have been treated with a control dsRNA, whereas those on the left have been exposed to GFP dsRNA. (C) HeLa cells treated with an siRNA against the gene ORC6 and stained for tubulin (green) and DNA (red). Depletion of ORC6 results in accumulation of multinucleated cells. (D) Adult Drosophila express an RNAi-triggering siRNA homologous to the white gene (left), which results in unpigmented eyes compared with the wild type (right).