Small DNA Methylation, Big Player in Plant Abiotic Stress Responses and Memory

Abstract

DNA methylation is a conserved epigenetic mark that plays important roles in maintaining genome stability and regulating gene expression. As sessile organisms, plants have evolved sophisticated regulatory systems to endure or respond to diverse adverse abiotic environmental challenges, i.e., abiotic stresses, such as extreme temperatures (cold and heat), drought and salinity. Plant stress responses are often accompanied by changes in chromatin modifications at diverse responsive loci, such as 5-methylcytosine (5mC) and N6-methyladenine (6mA) DNA methylation. Some abiotic stress responses are memorized for several hours or days through mitotic cell divisions and quickly reset to baseline levels after normal conditions are restored, which is referred to as somatic memory. In some cases, stress-induced chromatin marks are meiotically heritable and can impart the memory of stress exposure from parent plants to at least the next stress-free offspring generation through the mechanisms of transgenerational epigenetic inheritance, which may offer the descendants the potential to be adaptive for better fitness. In this review, we briefly summarize recent achievements regarding the establishment, maintenance and reset of DNA methylation, and highlight the diverse roles of DNA methylation in plant responses to abiotic stresses. Further, we discuss the potential role of DNA methylation in abiotic stress-induced somatic memory and transgenerational inheritance. Future research directions are proposed to develop stress-tolerant engineered crops to reduce the negative effects of abiotic stresses.

Dynamics of H3K27me3 Modification on Plant Adaptation to Environmental Cues

“…DNA methylation at the carbon-5 position of cytosine (5mC) is a well-understood epigenetic mark that is relevant to gene repression and genome stability, involved in diverse biological processes, as well as in response to environmental cues [4,5]. Histone modifications, including methylation, acetylation, phosphorylation, ubiquitination, sumoylation, biotinylation, glycosylation, and ADP-ribosylation, are also conserved epigenetic marks in eukaryotes [6].…”

“…An increasing number of recent studies have revealed that epigenetic mechanisms are also implicated in plants' responses to environmental stresses; in particular, the roles of DNA methylation have been extensively discussed in several reviews [3,4]. By contrast, functions of H3K27me3 in plants' adaption to environmental cues have not been well documented.…”

Deciphering the Epigenetic Alphabet Involved in Transgenerational Stress Memory in Crops

“…Plants respond to stress exposure by changing the expression of a wide range of genes [76][77][78][79]. When plants are primed, they memorize the obtained experiences and are better prepared for a recurring event by rapid and/or strong induction of responsive genes.…”

“…Some lines of evidence indicate that epigenetic marks have different capacities of long-term inheritance [108]. DNA methylation marks are more stably transmitted through mitosis and meiosis as compared to other epigenetic regulators, thereby they are better candidates for potential transgenerational inheritance of beneficial crop traits [79,109]. On the contrary, post-translational histone modifications are more likely to be reset during meiosis [109,110], which make them less suitable for breeding purposes.…”

The Relationship between Cadmium Toxicity and the Modulation of Epigenetic Traits in Plants

“…These processes are dependent on the gene expression of 2 of 12 certain genes and thus are controlled by genetic programming. DNA methylation is one of the more common epigenetic traits and it has been found to be important as it is involved in processes such as the induction of phenotypic alterations and maintaining genome stability when plants are under abiotic stress [15,16]. At times these alterations have been observed to improve the tolerance of the plants to specific abiotic stresses.…”