| The erosion of soil salinization in Xinjiang extend 11 million hectares,accounting for one-third of the saline soil area throughout the country.The earth’s land salinization is also rising, which severely affects agricultural productivity. Salt stress mainly includes the osmotic stress, ion toxicity and a series of secondary stress induced by high salt, these stress may lead to the plant growth inhibition, the increase in energy consumption, thus accelerating the aging and death. However such toxiciy inevitably damages the genomic DNA of plant cells. Plants in order to adapt to the salt stress, and reduce the harm of adversity, stimulating DNA damage stress signalling pathways, and regulation of gene expression.Therefore, how to explore the salt-tolerant plants through their own defense system to resist external stress on the body damage, has become a hotspot in the field of agricultural research.Halostachys caspica(Bieb.) C. A. Mey is a extremely salt-tolerant plants that grows on semi-desert salt-alkaloid land, the leaves and stalks of H. caspica has evolved into assimilating branches, in order to reduce moisture loss. It is an ideal candidate for investigating the mechanisms of salt tolerance in plants. In our previous study on the physiological and biochemical characteristics and salt tolerance genes function in Halostachys caspica,we found our research lack of comprehensive and system acquaintance.So our group began to involve in this research area by RNA-seq technology at transcriptional level for receive complete species information.In this study we chose 16 genes from DNA damage stress pathway. Combining real time quantitative PCR technique to analyze the expression pattern of these genes, we proposed signaling pathways about DNA damage and repair under salt stress. Detect genome DNA methylation level under salt stress, analysis the relationship between salt stress, DNA methylation level and damage stress relate genes expression, to do further research on plants salt tolerance mechanism. The main experimental results were summarized as follows:1. The expression patttern of 16 DNA damage and repair related gene, as analyzed after treating seedling of H. caspica shoot and root with different concentrations(100,300,500,700 mmol/L) Na Cl solution under different time. 9 genes in shoot, i.e.Hc Cif7(Chromosome transmission fidelity 7), Hc Rad17(Radiation sensitive17),Hc Mlh3(Mut L homolog3), Hc Msh3(mismatch repair(MMR) genes, Msh3),Hc Dmc1(Disruption of meiotic control 1), Hc Pig1(Programmed cell death(PCD) in male gametogenesis), Hc Rev3(Recovery protein 3), Hc Rev1(Recovery protein 1), Hc DNA Pol λ(DNA polymerase λ), and 7 genes in root, i.e. Hc Sim(Serine trans hydroxy methyltransferase), Hc Vtc2(Vitamin C defective 2), Hc Thil(Thiazolebiosynthetic enzyme), Hc Ros1(Repressor of silencing1), Hc Xbp2(Homolog of xeroderma pigmentosum complementation group B 2), Hc Rps3(Resistance to pseudomonas syringae 3), Hc Bip2(Binding immunoglobulin protein 2). The results showed that only Hc Pig1 gene was down-regulated with the increase of salt stress concentration.The rest of the genes were up-regulated with the increase of salt stress concentration.and the extension of time, they presented as concentration and time dependent.2. Combining q RT-PCR results and the current documentation of these genes the signaling pathway networks on DNA damage and repair under salt stress weres proposed. The results showed that under salt stress H. caspica mainly employed by pathways of nucleotide excision repair, base excision repair, strand break repair,nonhomologous end-joining, translesion synthesis DNA damage repair, mismatch repair and homologous recombination for DNA damage repair.3. According to the transcriptome data of H. caspica under salt stress, c DNA fragments of two genes about Hc Dmc1、 Hc Thil were isolated. Through bioinformatics software analyse these genes nucleic acid sequence, homology analysis of these genes amino acid sequences and those from other plant species,functional structure domain and the active site indicated that these genes have specific domain of damage repair gene motifies and active site, through different damagerepair pathways for H. caspica resist salt stress.4. Adopt genomic DNA methylation detection kit to test different concentrations(100,300,500,700 mmol/L) salt stress treatment H. caspica seedling branches and roots genomic DNA methylation level.The results showed that with the increase of concentration of salt stress, prolonged, the genomic DNA methylation level trend downward, at the same time the genomic DNA methylation level in branch higher than root. This paper mainly studied the demethylase gene Ros1(Repressor Of Silencing 1) mediated DNA demethylation. And found that the genomic DNA methylation level and Ros1 gene relative expression of H. caspica under salt stress showed a negative correlation. |
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