The basic pathway of RNA silencing is similar in many animals and plants. An RNA dependent RNA polymerase generates double stranded RNA from a single stranded precursor. The double stranded RNA is cleaved into 21-25nt fragments by nucleases of the Dicer family. These RNA fragments, known as mico (mi)RNAs and short interfering (si)RNAs, are separated into single stranded molecules and one of the two strands then becomes bound to an Argonaute nuclease. This RNA then forms base paired duplex structures with longer RNAs and thereby guides Argonaute to its target. Argonautes are sometimes referred to as Slicer. RNA silencing is therefore a combination of Dicing and Slicing.
We describe the mechanism of RNA silencing as part of a DEFRA-funded desk study on risks associated with RNA silencing in transgenic plants: http://www.plantsci.cam.ac.uk/Baulcombe/Schwach/. - do something with this link!
We are currently using three model systems in our research: Arabidopsis is a model higher plant with a completely sequenced genome; tomato is a model crop plant whose genome is being sequenced and for which there are extensive germplasm resources; Chlamydomonas reinhardtii is a model unicellular alga with a completely sequenced genome, a silencing system that is similar in many respects to that of higher plants. We have several projects that are designed to unravel the mechanisms of silencing in these three plants.