Plant epigenetics and the ‘intelligent’ priming system to combat biotic stress

Plants and animals are morphologically different and have distinct evolutionary lineages. However, both share the same epigenetic mechanisms and much of the evidence is provided by research in plants that relates to animals as well. Adjustments in DNA methylation patterns and histones are epigenetic changes that are heritable. Precisely, three different systems exist in plant cells to silence genes: DNA methylation, histone modification, and RNA-associated silencing. Such mechanisms are significant as plants are sessile living beings possessing rich sources of nutrients that invite continuous threats by microbes and herbivores. As a part of the defense strategy, plants have to “learn” and “memorize” their past experiences. The control of gene expression helps plants enable their responses to several biotic stresses, overviewed in this chapter. When such responses are generated without a delay, it is termed as “priming.” Research on Arabidopsis thaliana (L.), a model plant, has furnished important insights on how these mechanisms occur. Further, knowledge on plant epigenetics to some extent has been applied successfully for the benefit of agriculture. Uses of somatic embryogenesis and heterosis or hybrid vigor have been discussed as “applied epigenetics.”