二氧化硫胁迫诱发的拟南芥DNA甲基化修饰及转录调控作用

项目名称： 二氧化硫胁迫诱发的拟南芥DNA甲基化修饰及转录调控作用

项目编号： No.30870454

项目类型： 面上项目

立项/批准年度： 2009

项目学科： 轻工业、手工业

项目作者： 仪慧兰

作者单位： 山西大学

项目金额： 30万元

中文摘要： 为研究植物对环境胁迫的适应机制，在获得拟南芥基因表达谱的基础上，我们研究了SO2胁迫对拟南芥基因组DNA甲基化的影响。用甲基化敏感扩增多态性技术分析DNA中CCGG位点的甲基化特征，12对随机引物扩增出703条带，其中37%的差异带显示胁迫组胞嘧啶甲基化特征改变，发生甲基化的位点多于去甲基化位点，总甲基化水平增高。胁迫组上调表达基因MHL1, ACS6和NIT2启动子区和编码区甲基化特征改变，RD29A和CDD7甲基化特征未变。甲基化定量分析发现，ACS6和NIT2基因启动子区总甲基化水平降低，不同位点甲基化水平升高或降低，无重新甲基化；RD29A和CDD7启动子区保持非甲基化状态不变。因此，胁迫响应基因的上调表达与启动子区低甲基化有关。SO2诱发的胞内ROS增高与NIT2基因转录上调和启动子区甲基化变异有关，还诱发microRNA参与基因的转录调控。逆境中DNA甲基化特征改变可能对植物基因转录调节和基因组稳定具有作用。SO2诱发胞内ROS增高可介导多种细胞学过程，包括气孔运动、转录响应、表观遗传学修饰、细胞程序性死亡等，ROS、钙离子、生长素等参与调节植株对逆境的适应。

中文关键词： 拟南芥；二氧化硫；DNA甲基化；转录调节；逆境适应

英文摘要： In order to further understanding the regulaiton mechanism and the importance of DNA methylation in plant adaptation to environment challenges, DNA methylation alterations in 4-week-old Aradopsis plants were detected after exposed to 30 mg/m3 sulfur dioxide (SO2) for 72 h. By using methylation sensitive amplification polymorphism technique, 12 pairs of AFLP primers were employed to generate 703 amplified bands, which included 37% different bands showing more hypermethylated sites and less hypomethylated sites in CCGG context in SO2-exposed plants, suggesting that the DNA methylation level of global genome were obviously promoted after SO2 exposure. DNA methylation alterations occurred in either promoter regions or encoding regions in up-regulated genes MHL1, ACS6 and NIT2, but did not occur in the promoter regions of RD29A and CDD7 genes. Quantitative analysis of DNA methylation in NIT2 and ACS6 promoter regions showed that cytosine residues were hypomethylated in both CG and CHH (where H is C, A or T) contexts after plant exposed to 30 mg﹒m-3 SO2 , and the methylation levels of the promoters decreased. DNA hypomethylation of NIT2 and ACS6 promoter regions is associated with high gene transcript levels in SO2-exposed plants, suggeting that NIT2 and ACS6 expression was directly regulated by promoter DNA methylation. These data suggest that SO2-induced epigenetic change may be closely related to the gene activation in plant response to SO2 stress. Increased ROS is associated with DNA methylation alteration and transcription activation of NIT2 gene afte SO2 exposure. Some evidences revealed that both DNA methylation and microRNAs play some roles in gene transcription regulation. The changes in DNA methylation and gene transcription pattern in SO2-exposed plants may provide an efficient protection against other abiotic and biotic stress. ROS production in SO2-treated plants also involved in stomatal movement, transcription response, epigenetic modification and programmed cell death. Intracellular ROS and Ca2+ as well as plant hormone auxin and ethylene involved in plant adaptation to SO2 stress. Our report may help to reveal a possible role of this epigenetic mechanism in plants adaptation to environmental stress.

英文关键词： Arabidopsis; sulfur dioxide; DNA methylaiton; transcription regulation；plant adaptation