Effects of 60Co-γ radiation and PEG stress on physiological indexes and genomic DNA methylation levels of alfalfa tissue culture seedlings
[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 in-creasing 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 resis-tance 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 methyla-tion 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.
alfalfa tissue culture seedlingPEG stress60Co-γ radiationphysiological and biochemical charac-teristicsDNA methylation
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