Analysis Of The DNA Methylation Of Mongolia Astragalus And Suaeda Salsa L Under Higher Salt Stress

With the increase of soil salinization all over the world, various plants have established a set of protective measures in the process of evolution in order to survive in the saline environment. The results showed that physiological and biochemical indexes and DNA methylation in plants would change under salt stress.Mongolia Astragalus is one of the rare traditional Chinese herbal medicines in China, distributed in both temperate and warm temperate regions in China, especially widely in the Northeast and North China. Suaeda salsa L, rich in amino acids and carotene, is a typical saline indicator plant, distributed mainly in northeastern, northwestern and northern regions in China, especially in alkaline soil around rivers and lakes, and so on. Six physiological and biochemical indexes of Mongolia Astragalus under salt stress were determined in this work. DNA methylation on Mongolia Astragalus and Suaeda salsa L was conducted by methylation-sensitive amplification polymorphism (MSAP) and high performance liquid chromatography (HPLC) and the relationship between the two and salt stress was analyzed in this study. The main results were summarized as follows:1. Six physiological and biochemical indexes, namely the MDA content, free proline content, SOD activity, POD activity, CAT activity and soluble protein content, were measured and analyzed after treating seeds of Mongolia Astragalus with different concentrations (0%, 0.1%, 0.3%, 0.5%, 0.8%, 1.0%, 1.2%) NaCl solution. The results showed that SOD activity, CAT activity and soluble protein content rised with the increase of salt concentration, but the MDA content, free proline content and POD activity decreased after the adaptation and buffering process of Mongolia Astragalus to salt stress when treatment with 0%-0.1% NaCl.2. DNA was extracted with high-salt SDS, high-salt CTAB, and high-salt low pH value methods. The results show that high quality genomic DNA can be extracted by high-salt CTAB method.3. The variation patterns of DNA methylation in genomes of Mongolia Astragalus and Suaeda salsa L under the condition of higher salt stress were studied using MSAP technique. The results showed that 179 methylation sits of amplification products by 22 selective primer combinations were detected in Mongolia Astragalus. The overall results showed that higher salt could induce DNA demethylation in the CCGG sequence of genome in Mongolia Astragalus and 147 methylation sits of amplification products by 18 selective primer combinations were detected in Suaeda salsa L. The results indicated that it was a significantly negative correlation (R=-0.92) between NaCl concentrations and the level of all DNA methylation in Suaeda salsa L.4. The content of C and 5mC in genomic DNA hydrolyzates was investigated with HPLC. HPLC conditions were Hypersil C18 BDS column, mobile phase consisting of 10% methanol-5mM pentane sodium-0.2% triethylamine at a flow rate of 0.8ml /min, and the detection wavelength of 273nm.The features of DNA methylation in Mongolia Astragalus were described as follows: DNA methylation pattern was reduced with the increase of salt concentration.