Control of plant cell differentiation by histone modification and DNA methylation.

How cells differentiate and acquire diverse arrays of determined states in multicellular organisms is a fundamental and yet unanswered question in biology. Molecular genetic studies over the last few decades have identified many transcriptional regulators that activate or repress gene expression to promote cell differentiation in plant development. What has recently emerged as an additional important regulatory layer is the control at the epigenetic level by which locus-specific DNA methylation and histone modification alter the chromatin state and limit the expression of key developmental regulators to specific windows of time and space. Accumulating evidence suggests that histone acetylation is commonly linked with active transcription and this mechanism is adopted to control sequential progression of cell differentiation. Histone H3 trimethylation at lysine 27 and DNA methylation are both associated with gene repression, and these mechanisms are often utilised to promote and/or maintain the differentiated status of plant cells.