Abiotic Stress-Induced Epigenetic Alteratioils In Plants

As an important form of epigenetic modifications, DNA cytosine methylation widely exists in animals and plants, and plays functions in maintaining genome stability and regulating gene expression. Understanding on DNA methylation level changes and its transgenerational inheritance under stress is meaningful to explore the possible relationship between epigenetic regulation and plant stress response. In this study, two sorghum inbred lines were used as materials and were treated with0.4mM of SNP which is the NO exogeneous donor. The methylation-senstiive amplified polymorphism (MSAP) marker was used to analyze the levels, patterns, and transmission of the NO-induced DNA methylation changes. At the same time, some biochemical/physiological characteristics and several phenotypic traits in progenies of the NO-treated sorghum plants were investigated. We have obtained the following main results:1. DNA methylation levels only showed slight alterations (towards reduction) on the sorghum leaves after NO stress, which is statistically insignificant from the mock controls. In contrast, substantial DNA methylation patterns changes occurred in the NO-treated plants, in which CG hypomethylation is the most frequent pattern change. Clear difference was noted between the two inbred genotypes, with genotype A showed more changes than the D genotype.2. The altered DNA methylation patterns were inherited to their selfed progenies (S1) at frequencies ranging from7.1%to77.8%depending on individual plants. The rest loci showed either recovery or further pattern changes mainly showing further DNA hypomethylation.3. Sequence analysis of a subset of the variable MSAP bands indicated that DNA methylation changes have occured in known-function genes, transposons and some unknown function sequences.4. The NO treatment caused clear variations in several phenotypic traits in the SO and S1sorghum plants.5. The selfed S2generations showed enhanced tolerance to salt stress, but not to drought and nitrogen-deficiency stresses.Based on the above results, implications of NO stress-induced epigenetic variations with regard to the resistance mechanism of plants and potentiality for epigenetic mutagenesis in sorghum breeding are discussed. DNA methylation is a major component of the epigenetic regulation machinary in eukaryotes. Accumulating evidence in both animals and plants indicates that envrionmental stress may cause alteration in inrinsic methylation patterns.The salt and alkaline condition is a common environmental stress. Mechanisms by which plants are tolerant to this stress including the active function of specific genes and their regulation. In this study, by using two methods, methylation-sensitive ISSR and Southern blot, we found that the treatment by alkaline and salt, along or together, induces alteration in DNA methylation patterns in rice. Furthermore, the altered methylation patterns are heritable across biological generations, though both reversion (to that of wild type) and further alterations were aosl detetced. Alteration may also occur in plant progenies, which did not occur in their parent wherby the treatments applied.The changing trend is not identical between the two kinds of treatments, suggesting that different responses and tolerance mechanisms may have evolved in the rice genome to cope with alkaline and salt stresses.The progeny of stressed rice enhanced resistant to salt stress.