Epigenetic Regulation of Abiotic Stress Tolerance in Plants

Abstract

Sequence specific, genome-wide changes are being reported in plants which often correlate with regulation of gene expression at transcription levels. Many of such changes occur during stress exposure, and both gene expression and chromatin changes may revert to the pre-stress state shortly thereafter. There are reports for stress-induced chromatin changes that are transmitted to the progenies. Such changes alter gene expression without having any change in the DNA sequence. These epigenetic changes include modification in DNA base, histones and small non-coding RNAs. Some of the cytosine residues in nuclear genome may get methylated at 5' position by the action of DNA methyl transferase. Histones are also subjected to post-translational modifications which affect transcription, replication, chromosome condensation/segregation, as well as DNA repair. Methylation of a promoter may repress gene transcription, while methylation of coding region of a gene may cause post-transcriptional gene silencing. Epigenetic changes may also be inherited over the generations in the form of epialleles, which are considered as a source of genetic variability for crop improvement. The roles of epigenetic changes in plant's response to stress are becoming increasingly evident, suggesting that epigenetic mechanisms play important role in stress tolerance, acclimatization, adaptation and evolution processes. Therefore, it is worth investigating the epigenetic mechanisms of gene regulation in plants, and their possible exploitation in crop improvement.

Epigenomics of Plant’s Responses to Environmental Stress

“…Similar findings were reported in rice [87] and in moss [88]. Thus, a better understanding of epigenetic machinery of gene regulation might not only provide the basic information for regulation of genes, but it may also facilitate possible epigenetic engineering of crop plants towards enhanced tolerance to environmental stresses [17]. Transcription of an Onsen family of Copia retrotransposons was reported to increase under extreme temperatures, and the effect persisted for seven days which supported the involvement of epigenetics in the process [90].…”

“…DNA base modification is a tissue-specific, dynamic, sequence-context dependent process, and unraveling the complex patterns of the modifications may answer several biological questions. Methylcytosine (5-mC), which is also known as the 5 th base, was reported long before the DNA was accepted as the genetic material [17,26]. In addition to the 5-mC, DNA has also been found to contain 5-hydroxymethylcytosine (5-hmC), 5-formylcytosine (5-fC), 5-carboxycytosine (5-caC) and N 6 -methyladenine (6-mA) in small amounts.…”

“…Growing evidences indicate that cytosine methylation and ncRNAs are involved in controlling gene expression at transcriptional as well as post-transcriptional levels influenced by various abiotic and biotic factors [17]. Though many epigenetic modifications are known to be reversible, they have been found to be associated with activation as well as inactivation of genes [60].…”

Epigenomics of Plant’s Responses to Environmental Stress

“…Growing evidence indicates that chromatin modifications and small inhibitory RNA (siRNA) are involved in controlling gene expression at transcriptional as well as post-transcriptional levels influenced by various abiotic and biotic factors [17]. Though many epigenetic modifications are known to be reversible, they have been found to be associated with activation as well as inactivation of genes [60].…”

Epigenomics of Plant’s Responses to Environmental Stress

“…DNA base modification is a tissue-specific, dynamic, sequencecontext dependent process, and unraveling the complex patterns of the modifications may answer several biological questions. Methylcytosine (5-mC), which is also known as the 5 th base, was reported long before the DNA was accepted as the genetic material [17,26]. In addition to the 5-mC, DNA has also been found to contain 5-hydroxymethylcytosine (5-hmC), 5-formylcytosine (5-fC), 5-carboxycytosine (5-caC) and N 6 -methyladenine (6-mA) in small amounts.…”