Use of Forward Genetic Screens to Identify Genes Required for RNA-Directed DNA Methylation in Arabidopsis thaliana

摘要

RNA-directed DNA methylation is a small RNA-mediated epigenetic modification that contributes to transcriptional silencing of transposons and repetitive sequences in plants. We have conducted several forward genetic screens to identify factors required for RNA-directed DNA methylation and transcriptional gene silencing in Arabidopsis thaliana. Here, we review the findings from these screens and report on two new mutants, dmsl2 and dmsl3, that are defective in Pol V-specific subunits NRPE5 and NRPE9b. Cumulative results from genetic screens performed in our laboratory and those of other investigators have revealed that RNA-directed DNA methylation requires a complex transcriptional machinery comprising a number of plant-specific factors, many of which were functionally uncharacterized before being implicated in this pathway. Future challenges include unraveling the detailed mechanism and full range of functions of RNA-directed DNA methylation.