Preface

The Last Unicellular Common Ancestor (LUCA) has existed more than 1 billion years ago. During that time, the plant and animal kingdoms have evolved separately and adopted a multicellular system, with sophisticated pathways of development and capability for perfect adaptation to the environment. Today, in the era of genomics it is known that many developmental processes of plants and animals are similar, although they have evolved independently. The carriers of the logic in these two major lineages are different and show a complicated network of ancient protein and nucleic acid domains, but at the same time a very high conservation and similarity of chromatin proteins and regulatory mechanisms is observed. This, however, does not exclude differences of structure and functions of chromatin that exist between plants and animals. They have evolved very efficient and flexible but different adaptation mechanisms to the local environment in order to ensure survival and reproduction. The specific differences connected to lineage-specific features may provide strong information on the general mechanisms underlying the complexity and regulatory and integratory role of chromatin in all eukaryotes. During a movement towards their final differentiated states, various changes occur in cells due to genetic and environmental factors. Resulted altered properties of the cells have been memorized after each cell division. Recent technological advances allow genome-wide analysis of DNA and histone modifications, which affect their structures, and have the potential to reveal the regulation mechanisms in plants on the level above nucleotide sequence. Those chemical changes allow the manifestation of multiple phenotypes encoded in the same DNA sequence. In this way, chromatin modifications contribute to variation at multiple levels, ranging from the expression of individual genes, to the differentiation of cell types, to population-level phenotypic diversity. In other words, that is epigenetics.