The Stress Memory Of Genetics And Epigenetics Induced By High Hydrostatic Pressurization In Rice

Stress is one of the main factors that affect plant growth, development and regeneration. The limitation of plant is that it cannot take the initiative to avoid adverse environmental impact. It can only respond to environmental stress at the molecular, physiological and biochemical level and develop a series of mechanisms to resist and adapt to environmental changes. Genetic and epigenetic variation may simultaneously or independently enhance tolerance to stress, mainly through changes in developmental and physiological processes of gene expression. The changes of the gene expression lead to the phenotypic variation and better adaptation to the environment.In order to investigate the rice in stress occurred under conditions of genetic and epigenetic variation, the study use produced in Rice(Oryza sativa L.) cultivars JL307 and the progeny of HHP(High Hydrostatic Pressurization) mutant line sd12-14 as experimental materials. Genetic integrity and polymorphism were analyzed using AFLP(Amplified fragment length polymorphism), the results indicates that the variation frequency was less than 1% in the sd12-14. In order to further study the genetic variation, we re-sequenced the genomes of JL307 and sd12-14. By comparing the genomes of JL307 and sd12-14, we identified the base transition and transversion number and ratio. Moreover the rampant mobilization of transposable elements(TEs) was also identified in the sd12-14 genome. Notably, a total of 43 mobilization events representing 5 TE families were found.In order to explore the HHP “memory” in the transcriptional level, we performed genome-wide transcriptional profiling analysis with the Rice Gene Chip. We found that the expression of 902 probe sets was significantly(fold change>2 and <-2, q≤0.05) altered between the progeny of HHP mutant line sd1214 and untreated cultivars LJ307. These differently expressed genes were distributed in cell components, molecular mechanism and biological function. Through the analysis of the metabolic pathway, the differently expressed genes participate in regulation circadian rhythms, glutamic acid metabolism, and phenyl of methane synthesis and so on. Our data shows that, the genome-wide changes in gene expression were significantly screened.Genome-wide methylation status was detected by MSAP(methylation sensitive amplification polymorphism). We have actually found that the DNA cytosine methylation levels are similar. The methylation variation isn’t obvious. The detected ones are dominated by locus-specific demethylation. In order to explore whether the changes of gene expression in microarray analysis is correlated with the methylation of DNA, we detect the promoter methylation variation of the gene expression is more than 4 times by using the method of bisulfite sequencing.The results showed that the changes of gene expression is not directly related with DNA methylation.In summary, the results show that the progeny of HHP mutant line sd12-14 produced genetic and epigenetic variation. These mutations change the expression of genes and lead to the generation of some new phenotypes. Although the study did not find the fact which directly related to the phenotypic change, by microarray analysis we find that these genes may be potential resistance genes.