Abstract: [Objective] The DNA methylation, which is regulated by methylation and demethylation coordinately, directly affects the expression of stress-related genes.DNA demethylation in plants is mainly mediated by demethylase gene Ros1 (Repressor of silencing 1) to finish the base excision repair.Analysis of the dynamic changes of the DNA methylation of Halostachys caspica and gene expression changes of Ros1 will be helpful to elucidate the molecular mechanism of DNA methylation in response to salt stress.[Method]qRT-PCR was used to measure the degree of genomic DNA methylation in assimilation shoots and roots of H.caspica,the correlation between DNA methylation and HcRos1 gene expression was also analyzed.[Result]The results showed that the degree of genomic DNA methylation in assimilation shoots and roots of H.caspica increased firstly and then decreased under the same concentration of NaCl stress treated with different times, and DNA methylation in assimilating shoots was higher than in roots and reached the highest at 24 h.However,the degree of genomic DNA methylation in assimilation shoots and roots of H.caspica also increased firstly and then decreased under the different concentrations of NaCl stress treated with the same time, DNA methylation in assimilating shoots was higher than in roots and reached the highest under concentration of 100 mmol/L NaCl.The gene expression of HcRos1 did not changed under low concentration of NaCl stress, but increased significantly under concentration of 700 mmol/L at 72 h.[Conclusion]Correlation analysis demonstrated that the expression of HcRos1 was negatively correlated with the degree of DNA methylation.Salt stress can increase the expression of HcRos1, reduce the methylation degree of genomic DNA and enhance the salt tolerance of plants.

摘要： [目的]甲基化和去甲基化协同调控的DNA甲基化直接影响逆境胁迫相关基因的表达,植物的DNA去甲基化主要由去甲基化酶基因Ros1(Repressor of Silencing 1)介导的碱基切除修复实现.开展盐穗木(Halostachys caspica)DNA甲基化程度与HcRos1表达动态变化的分析,有助于阐明DNA甲基化应答盐胁迫的分子机制.[方法]利用qRT-PCR测定盐胁迫下盐穗木幼苗同化枝和根基因组DNA的甲基化程度,探讨DNA的甲基化程度与去甲基化酶基因HcRos1表达的相关性.[结果]在相同NaCl浓度胁迫不同时间下盐穗木同化枝和根中DNA甲基化程度呈现先升高后降低的趋势,盐穗木同化枝中的DNA甲基化程度大多高于根中的基因组甲基化程度,且均在24 h达到最高DNA甲基化程度.而在不同浓度NaCl胁迫处理24 h时,盐穗木同化枝和根中DNA甲基化程度也是先升高后降低的趋势,盐穗木同化枝中的基因组甲基化程度高于根中的基因组甲基化程度,且多在100 mmol/L达到最高DNA甲基化程度.HcRos1的基因表达量在低浓度NaCl胁迫下变化不大,但在700 mmol/L NaCl胁迫72 h时则显著升高.[结论]HcRos1表达量与DNA甲基化水平呈明显的负相关, 盐胁迫能够提高HcRos1的表达,降低基因组DNA的甲基化程度,增强植物的耐盐性.