Epigenetic Landscape and Regulation of Secondary Metabolite Accumulation Implicated in Anticancer and Nutraceuticals

Plants are important sources for obtaining diverse secondary metabolites which have pharmaceutical importance. Out of multiple factors that modulate their accumulation in vitro and in vivo, epigenetic factors play critical roles, adding an extra layer of regulation. This review focuses on (a) dynamic changes that occur in DNA methylation, histone acetylation, and the role of small RNAs in transcriptional and post-transcriptional modulation that alter secondary metabolism in plants under abiotic stress and (b) the role of epigenetics in secondary metabolite accumulation in the plant cell cultures. Such epigenetic factors are manipulated by applying inhibitors of DNA methylation like 5-azacytidine or histone deacetylation such as trichostatin A in intact plants as well as in cultured plant cells and hairy roots for enhanced production. This article synthesizes current findings on epigenetic engineering for improved synthesis of anticancer compounds and nutraceuticals and lists out limitations and challenges that the pharmaceutical industry is facing for their large scale production and commercialization. Main conclusion: Through epigenetic changes such as DNA methylation, histone acetylation, and non-coding RNAs, plants dynamically fine-tune specific gene expressions to adjust to environmental stresses and mediate secondary metabolite accumulation as a chemical combat mechanism.