Histone variants and modifications in plant gene regulation.

Genomes are packaged by complexing DNA with histone proteins, which provides an opportunity to regulate gene expression by dynamically impeding access of transcriptional regulatory proteins and RNA polymerases to DNA. The incorporation of histone variants into nucleosomes and addition of post-translational modifications to histones can alter the physical properties of nucleosomes and thereby serve as a mechanism for regulating DNA exposure. Chromatin-based gene regulation has profound effects on developmental processes including regulation of the vegetative to reproductive transition, as well as responses to pathogens and abiotic factors. Incorporation of the histone variant H2A.Z and methylation of histone H3 lysine residues 4 and 27 have emerged as key elements in the regulation of genes involved in each of these processes.