不同浓度磷胁迫对大豆幼苗生长及根系DNA甲基化水平的影响

Effects of different concentrations of phosphorus stresses on soybean(Glycine max L.)seedling growth and DNA methylation in root system

关键词:  大豆  磷胁迫  DNA甲基化  抗氧化酶  甲基化敏感扩增多态性(MSAP)

Key words:  soybean  phosphorus stress  DNA methylation  antioxidant enzymes  methylation sensitive amplification polymorphism(MSAP)

摘要:

为明确不同浓度磷胁迫对大豆幼苗生长及基因组DNA甲基化水平的影响，采用甲基化敏感扩增多态性(MSAP)和实时荧光定量PCR(qRT-PCR)技术分析大豆材料‘CP016’的幼苗在不同浓度磷胁迫下根系DNA甲基化水平和相关基因的表达量变化。结果表明:1)随着磷浓度的逐渐增加，大豆幼苗的株高、鲜重、根长和根表面积呈先升高后降低的趋势，无磷和高磷胁迫(1 000 μmol/L)均显著抑制大豆的生长，低磷胁迫(100 μmol/L)促进地上部生长，极低磷胁迫(10 μmol/L)促进根系生长；2)随着磷浓度的逐渐增加，大豆幼苗根系中的POD和CAT活性呈先降低后升高的趋势，SOD活性、淀粉和蔗糖含量呈先升高后降低的趋势；3)MSAP分析表明，随着磷浓度的增加，大豆幼苗根系DNA甲基化率和全甲基化率逐渐升高。具体来说，在无磷、正常供磷和高磷处理下，大豆幼苗根系的DNA甲基化率分别为43.04%、48.52%和51.05%；4)qRT-PCR分析结果表明，无磷胁迫下，调控大豆幼苗根系POD活性和淀粉合成相关基因以及甲基化酶基因DRM2的表达量显著升高；调控SOD活性和蔗糖合成相关基因以及去甲基化酶基因ROS1的表达量显著降低。本研究表明，无磷和高磷胁迫显著抑制大豆的生长，并使其抗氧化酶系统紊乱，淀粉和蔗糖含量降低，但适度的低磷胁迫可以促进大豆幼苗的生长。无磷和高磷胁迫分别降低和提高大豆幼苗根系的DNA甲基化水平。

Abstract:

To investigate the effects of different concentrations of phosphorus stress on soybean seedling growth and the genomic DNA methylation level, methylation sensitive amplification polymorphism(MSAP)and real-time fluorescence quantitative PCR(qRT-PCR)were used to analyze the DNA methylation level and related gene expression in the root of soybean material ‘CP016' seedlings under different concentrations of phosphorus stress. The results showed that: 1)With the increase of phosphorus concentration, the plant height, fresh weight, root length and root surface area of soybean seedlings increased first and then decreased. Both the phosphorus-free and high phosphorus(1 000 μmol/L)stresses significantly inhibited soybean growth, while the low phosphorus stress(100 μmol/L)promoted the growth of above ground and the extremely low phosphorus stress(10 μmol/L)promoted root growth. 2)With the gradual increase of phosphorus concentration, the POD and CAT activities decreased first and then increased in the root of soybean seedlings, while the SOD activities, starch and sucrose contents increased first and then decreased. 3)The results of MSAP analysis showed that the DNA methylation rate and full methylation rate of soybean seedlings increased gradually with the increase of phosphorus concentration. Specifically, the DNA methylated rates of soybean seedling roots treated with phosphorus-free, normal phosphorus and high phosphorus supply were 43. 04%, 48. 52% and 51. 05%, respectively. 4)The results of qRT-PCR analysis showed that the expression levels of genes that regulate the activity of POD and synthesis of starch, and the methylase gene DRM2 up-regulated significantly, while regulated SOD activity and sucrose synthesis, and ROS1 down-regulated significantly under phosphorus-free stress. In conclusion, this study showed that the phosphorus-free and high phosphorus stress significantly inhibited soybean growth, disturbed its antioxidant enzyme system, and reduced the content of starch and sucrose. However, a certain degree of low phosphorus stress could promote the growth of soybean seedlings. The levels of DNA methylation in the root of soybean seedlings were decreased and increased under phosphorus-free and high phosphorus stress, respectively.