EPIGENETIC REPROGRAMMING OF GENE EXPRESSION UNDER ENVIRONMENTAL STRESS CONDITIONS

Abstract

Biotic and abiotic stressors like temperature extremes, drought, salinity and pollutant (environmental stress conditions) and biotic stressors like pathogens (environmental factors) have a great impact on cellular functioning and the survival of organisms. In order to be able to adapt to such dynamic environments organisms use highly complex regulatory systems that can regulate the expression of genes without changing the underlying DNA sequence. DNA methylation, histone modifications, chromatin remodelling, and non-coding RNA activity constitute the primary addicts in mediating these adaptations and are referred to as epigenetic regulation. The review gives a detailed overview of the processes involved in stress-induced epigenetic reprogramming of gene expression in various biological systems. It emphasizes the manner in which environmental signals are converted to epigenetic changes, which regulate the activity of transcription and also play a role in the phenomenon of plasticity. Moreover, the review summarizes the existing evidence on the epigenetic memory and its contribution to allowing sustainable or transgenerational reactions to stress. The nature of epigenetic changes, which are dynamic and reversible, is addressed and their implications in respect to adaptation, resilience and survival, discussed. Lastly, the new directions and challenges of research are described, and integrative approaches should be viewed as the way to improve on the complexity of the epigenetic regulation when faced with environmental stressful circumstances.