Genetic analyses of DNA methyltransferases in Arabidopsis thaliana.

DNA methylation is a conserved epigenetic silencing mechanism that functions to suppress the proliferation of transposons and regulate the expression of endogenous genes. In plants, mutations that cause severe loss of DNA methylation result in reactivation of transposons as well as developmental abnormalities. We use the flowering plant Arabidopsis thaliana as a model system to study the establishment and maintenance of DNA methylation as well as its role in regulating plant development. The genetic evidence presented here suggests that methylation at CG and non-CG sites functions in a partially redundant and locus-specific manner to regulate a wide range of developmental processes. Results from recent studies also suggested that the dynamic nature of non-CG methylation, which is critically important for its regulatory function, is largely due to its complicated interactions with other epigenetic pathways such as RNAi and histone modifications. Finally, the use of genomic approaches has significantly broadened our understanding of the patterning of DNA methylation on a genomewide scale and has led to the identification of hundreds of candidate genes that are controlled by DNA methylation.