Plant chromatin - Learning from similarities and differences

The availability of the complete sequence of Arabidopsis genomic DNA has allowedin-depth comparative analyses of plant proteins homologous to components of yeast and animal complexes involved in chromatin remodelling. These studies have uncovered an astonishing diversity of plant proteins that are potentially involved in ATP-dependent modulation of nucleosome structure and in post- translational modification of the core histone tails. Of the small fraction of these proteins that have been studied; all were shown to play important roles in plant development. These broad comparative analyses have provided insights into plant-specific features of evolutionarily conserved chromatin processes. An interesting example is the scarcity or absence from many plant DNA-dependent ATPases, histone acetyl transferases and histone methyltransferases of the protein-protein recognition modules (like bromo- and chromodomains), which are highly conserved in yeast and animals. The comparison in plants and animals of the phenotypic effects of disturbances in the native ratio of linker histone variants has shed some light on the possible functions of these abundant and still mysterious chromatin components. Of general importance for deciphering the biochemical modification code underlying the epigenetic organisation of chromatin was a recent discovery of a link between histone H3 lysine 9 methylation and DNA methylation in Arabidopsis. Although not yet as advanced as in yeast and animals, chromatin research in plants has moved rapidly to a stage at which major progress in understanding the chromatin-based regulation of plant development will soon be possible. © 2003 Elsevier Ltd.