60Co-γ辐射和PEG胁迫对紫花苜蓿组培苗生理指标及基因组DNA甲基化水平的影响

Effects of 60Co-γ radiation and PEG stress on physiological indexes and genomic DNA methylation levels of alfalfa tissue culture seedlings

摘要:

【目的】 探究紫花苜蓿（Medicago Sativa）对⁶⁰Co-γ辐射和聚乙二醇-6000（PEG）模拟干旱胁迫生理及DNA甲基化水平的影响。【方法】 以3种愈伤组织分化组培苗为材料，其中G3和G4为辐射紫花苜蓿种子的变异植株叶片愈伤组织分化组培苗，CK为未辐射苗，对3种组培苗分别进行PEG胁迫，分析其生理指标及基因组DNA甲基化水平的变化。【结果】 紫花苜蓿组培苗对辐射和PEG胁迫的生理响应不同，辐射提高其渗透调节物质（可溶性蛋白、可溶性糖和脯氨酸）含量、过氧化物酶（POD）活性和相对电导率（RC），降低了超氧化物歧化酶（SOD）、过氧化物酶（CAT）活性和丙二醛（MDA）含量； 3种渗透调节物质含量及POD和SOD活性均随PEG胁迫浓度增加呈先增后降变化趋势，CAT活性、 MDA含量和RC均随PEG胁迫浓度增加而增加。隶属函数值综合分析，3种紫花苜蓿组培苗抗旱性强弱为G4＞G3＞CK。【结论】 辐射增加甲基化水平（G4＞CK），PEG胁迫降低甲基化水平。⁶⁰Co-γ辐射可提高紫花苜蓿组培苗抗旱性，可通过DNA甲基化修饰调节对辐射和干旱胁迫响应，诱导的基因组表观遗传变化在紫花苜蓿突变体筛选和适应干旱环境中发挥重要的调控作用。

Abstract:

【Objective】 To explore the effects of alfalfa （Medicago sativa） on physiology and DNA methylation levels under ⁶⁰Co-γ radiation and polyethylene glycol 6000 （PEG-6000） stress.【Method】 Three kinds of callus differentiation tissue culture plantlets were used as materials，among which G3 and G4 were the callus differentiation tissue culture plantlets from the leaves of mutant plants irradiated with alfalfa seeds （CK was not irradiated）. Three types of tissue cultured seedlings were subjected to PEG stress respectively，The changes of physiological indexes and genomic DNA methylation level were analyzed.【Result】 The physiological and biochemical responses of alfalfa tissue culture seedlings to radiation and PEG stress were different. Radiation increased the content of osmoregulatory substances （soluble proteins，soluble sugars，and proline），peroxidase （POD） activity，and relative conductivity （RC），and decreased the activities of superoxide dismutase （SOD），peroxidase （CAT），and malondialdehyde（MDA） content. Content of three osmotic regulating substances，peroxidase and superoxide dismutase activities of the three types of tissue cultured seedlings showed a trend of first increasing and then decreasing with the increase of PEG stress concentration. The catalase activity，malondialdehyde content，and relative conductivity all showed an increasing trend with the increase of PEG constant worry concentration. Accroding to the comprehensive analysis of membership function values for drought resistance coefficients of 8 physiological indicators，the order of drought resistance of the three alfalfa tissue culture seedlings is G4＞G3＞CK.【Conclusion】 Comparing the methylation level of genomic DNA of tissue culture seedlings under radiation treatment and PEG stress，radiation increased the methylation level （G4＜CK），and PEG stress decreased the methylation level. ⁶⁰Co-γ radiation could improve the drought resistance of alfalfa tissue culture seedlings，and regulate the response to radiation and drought stress through DNA methylation modification. The induced epigenetic changes in the genome played an important regulatory role in screening alfalfa mutants and adapting to drought environments.