Genetic and epigenetic regulation of stress responses in natural plant populations.

Plants have developed intricate mechanisms involving gene regulatory systems to adjust to stresses. Phenotypic variation in plants under stress is classically attributed to DNA sequence variants. More recently, it was found that epigenetic modifications - DNA methylation-, chromatin- and small RNA-based mechanisms - can contribute separately or together to phenotypes by regulating gene expression in response to the stress effect. These epigenetic modifications constitute an additional layer of complexity to heritable phenotypic variation and the evolutionary potential of natural plant populations because they can affect fitness. Natural populations can show differences in performance when they are exposed to changes in environmental conditions, partly because of their genetic variation but also because of their epigenetic variation. The line between these two components is blurred because little is known about the contribution of genotypes and epigenotypes to stress tolerance in natural populations. Recent insights in this field have just begun to shed light on the behavior of genetic and epigenetic variation in natural plant populations under biotic and abiotic stresses. This article is part of a Special Issue entitled: Plant gene regulation in response to abiotic stress.