Role of the RNA silencing machinery in the regulation of FLC.

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The Dean laboratory is interested in understanding what controls the timing of flowering in a wide range of plants. We are using a model plant Arabidopsis thaliana to identify all the genes involved in controlling flowering as in this plant it is easy to clone the gene based on just having a mutation (a lesion) in that gene and no other information. Over the years we have shown that a key player in the regulation of flowering is a protein called FLC. FLC prevents flowering by stopping the activation of a set of genes needed to make flowers. FLC levels are reduced by a winter period which is why many plants flower in the spring. It is also reduced by a set of genes grouped together in the so-called autonomous promotion pathway. We have recently also found FLC levels are regulated by a new gene regulatory pathway involving very small RNA molecules. Studies on virus resistance in plants and development in worms has revealed that RNA molecules between 21 and 24 nucleotides long act as messengers to zap longer RNA molecules containing the same sequence. They also get embedded in large protein complexes and guide them to the genetic material in the cell (chromatin = DNA looped around proteins called histones) finding DNA with a matching sequence. The processes involving small RNAs have been called RNA silencing pathways and are used in human therapeutics to switch off genes under the name RNAi or RNA interference. How RNA silencing is activated and how it leads to regulation of the chromatin structure of regular genes is not known. We want to dissect these processes by analysing FLC regulation. This system is likely to produce concepts relevant to gene regulation throughout biology.