Epigenetics – A Historical Perspective

The term ‘epigenetics’ refers to heritable and reversible changes to a gene that do not alter its DNA sequence but that affect its competence or efficiency of expression. The three contexts in which epigenetic changes are predominantly studied today are their contribution to the developmental program of an organism, their part in the response of an organism to changing environmental conditions and their contribution to evolutionary flux via the production of new epigenetic variants. Jean-Baptiste Lamarck's theory about the inheritance of acquired characteristics initiated the discussion about the role of heritable epigenetic changes in evolution, and Conrad Waddington's epigenetic landscape model provided a new definition of epigenesis, the development of the phenotype, as the combination of genetic expression and tissue interaction. Plant research has played a crucial role in the identification of epigenetic concepts and mechanisms, especially via the analysis of plant transposons and transgenes that helped to discover the importance of chromatin states and small RNAs.