Genetic studies along with biochemical and cell biology analyses in plant model systems have influenced human health research and have enabled researchers to understand how proteins are recruited to chromatin and how they regulate their target genes and to elucidate their functions. Accordingly, it has become evident that almost all human genes that were assumed or known to participate in disease have orthologs in the model plant Arabidopsis thaliana and in many other plants (e.g. the common bean, Phaseolus vulgaris). Also, it is now recognized that many defence mechanisms in Arabidopsis are under epigenetic control, similarly to the mechanisms regulated by members of the animal Polycomb Group (PcG)/Trithorax Group (TrxG) complexes involved in the regulation of disease and cancer, though it is not clear how plant pathogens manipulate, for example, host post-translational modifications (PTMs) and how they use these PTMs to solve their own biological requirements. Despite the fact that a number of stress responses include epigenetic components, we are just beginning to elucidate the mechanisms and molecular interactions. Thus, it is imperative to broaden our knowledge in such areas of research.