NaCl胁迫下多倍体西瓜离子吸收及DNA甲基化调控机制研究

The production of watermelon is seriously affected by soil salinization and secondary salinization which restrict the quality and efficiency of sustainable development of watermelon in China. Our previous study found that the polyploid watermelon including triploid and tetraploid had better salt tolerance than its isogonics diploid, but the mechanism of salt resistance of polyploid watermelon is not clear. In this research, the different ploidy watermelon include the same genotype diploid, triploid, tetraploid and the diploid which is reverse mutation formed by tetraploid will be used as materials. The grafting interaction methods will be studied using different ploidy watermelon as rootstock, the Na+, K+ contents and ion absorption changes in different organizations of each watermelon plants after NaCl stress will be measured, and the ion absorption type of salt stress of the different ploidy watermelon will be determined; the level of DNA methylation and the change of methylation patterns using MSAP technology will be researched, the related genes of polyploidy salt tolerant based on MSAP will be screened, and the important genes in real-time fluorescence quantitative and differential expression of salt tolerance genes regulation of DNA methylation in different ploidy watermelon will be analyzed. The salt tolerance advantage mechanism of polyploidy watermelon from the aspects of ion absorption and epigenetics under salt stress will be carried out. This study will provide theoretical basis and some useful information for polyploid breeding and resistance breeding of watermelon.

土壤盐碱化和次生盐渍化是影响西瓜生产的一个重要因素，严重制约着我国西瓜优质高效可持续发展。申请人发现多倍体西瓜较其同基因型二倍体耐盐，但多倍体西瓜耐盐机理尚不明确。本项目拟以同基因型的二倍体、三倍体、四倍体西瓜和由四倍体回复突变形成的二倍体为材料，采用不同倍性西瓜互做砧木进行嫁接的方法，研究NaCl胁迫后不同类型西瓜植株各组织Na+、K+含量及离子吸收的变化，确定不同倍性西瓜盐胁迫离子吸收类型差异；并结合MSAP技术研究DNA甲基化水平和甲基化模式的变化，在MSAP基础上筛选与倍性相关的耐盐基因，并对重要的耐盐基因进行实时荧光定量分析，研究DNA甲基化调控水平上不同倍性西瓜耐盐基因的差异表达。研究结果将从离子吸收和表观遗传学方面解析多倍体西瓜的耐盐优势机理，为多倍体西瓜育种和抗逆育种提供理论依据。

土壤盐碱化和次生盐渍化是影响西瓜生产的一个重要因素，严重制约着我国西瓜优质高效可持续发展，了解西瓜的耐盐机理并培育耐盐的西瓜新品种对西瓜产业发展具有重要意义。生产经验发现多倍体西瓜抗枯萎病、耐低温、耐盐、耐淹水等逆境胁迫能力都强于其同源二倍体；多倍体西瓜中次生代谢物质如番茄红素、瓜氨酸、可溶性糖等高于二倍体，而这些次生代谢物质是与植物抗逆密切相关的。本研究从多倍体西瓜耐盐机制着手，探索多倍体西瓜的耐盐机理。. 本项目通过对多倍体和二倍体西瓜幼苗根系结构的观察和比较分析，找到了与多倍体西瓜耐盐能力相关的细胞学特征，即四倍体西瓜根系粗壮。采用不同倍性西瓜互做砧木进行嫁接的方法，测定NaCl胁迫后Na+、K+含量及离子吸收规律，确定了NaCl胁迫后西瓜幼苗的离子吸收类型为根系吸收型。之后又比较了盐胁迫后不同类型材料间光合作用、抗氧化酶活性和内源激素含量的差异，从生理生化指标上进一步证明四倍体西瓜的高耐盐能力，最后结合不同倍性西瓜NaCl胁迫后DNA甲基化变化及耐盐基因表达量的差异，初步确定了四倍体西瓜耐盐的机理为：DNA甲基化介导的四倍体西瓜根系中亚油酸合成途径基因的高表达导致了其耐盐能力的提高。. 本项目从细胞结构、离子吸收、DNA甲基化和基因表达水平解释了多倍体西瓜的耐盐机理，这些结果可以为多倍体西瓜育种和抗逆育种提供理论依据。