GSH Treatment Improved Kenaf (Hibiscus Cannabinus L.) Salt Tolerance And DNA Methylation Involved Mechanisms Analysis

In the present study,used P3A as the experimental material,kenaf seedlings was pre-cultured with exogenous GSH at concentrations of 50,100,150 and 200μmol/L,respectively,and then treated with 200 mmol/L Na Cl,the effects of exogenous GSH pretreatment on the kenaf growth and physiological characteristics under salt stress were investigated.Furthermore,the molecular mechanism of kenaf genomic DNA methylation in response to salt stress under the pretreatment of exogenous GSH was analyzed.The main conclusions are as follows:1.Under salt stress,the growth of Kenaf seedlings were restrained,that is,phenotypic character including plant height,stem diameter,fresh weight,SPAD value,root length,root tip number,root volume and root surface area were significantly reduced;Exogenous GSH pretreatment with different concentrations could significantly alleviate the inhibition of Na Cl stress,and the most suitable concentration for kenaf pretreatment is 100μmol/L.2.Under salt stress,the activities of SOD,POD,and CAT of kenaf seedlings decreased,the content of endogenous GSH decreased,and the contents of H₂O₂and O₂^-in kenaf seedlings increased,resulting in an increase in MDA levels.However,when pretreated with exogenous GSH at different concentrations,the level of endogenous GSH and the activities of SOD,POD,and CAT of kenaf seedlings were significantly increased,while the contents of H₂O₂,O₂^-,and MDA reduced significantly.This indicates that exogenous GSH pretreatment could improve the enzyme activity and the content of antioxidant,and thus alleviate the toxic effect of reactive oxygen species.3.To investigate the effect of exogenous GSH pretreatment on kenaf DNA methylation under salt stress,17 pairs of primers were selected for MSAP analysis of kenaf seedling root genome,and a total of 746 bands were amplified.Compared with the control,the DNA methylation level of the 200 mmol/L Na Cl treatment decreased 12.55%.However,the DNA methylation level of the 100μmol/L GSH+200 mmol/L Na Cl treatment increased 25.34%compared with that of the200 mmol/L Na Cl treatment.This indicates salt stress could decrease the DNA methylation levels,while exogenous GSH pretreatment could increase it.Further analysis on the variation characteristics of kenaf DNA methylation pattern showed that,GSH pretreatment can lead a DNA remethylation and confer the salt tolerance of kenaf.4.A total of 133 specific fragments for DNA methylation were recovered,cloned and sequenced.After sequence analysis,Twelve genes that may be related to plant growth and development and stress response were identified.The results of q PCR showed that the selected five genes had different methylation status and expression levels of the control,200 mmol/L Na Cl treatment group,and 100μmol/L GSH+200 mmol/L Na Cl treatment group,and thus adapted to GSH to alleviate the effect of salt stress on the growth of kenaf.