Kim Nam-Soo, Im Min-Ji, Nkongolo Kabwe
Department of Molecular Bioscience College of Biomedical Science Kangwon National University Chuncheon 200701 Korea; Institute of Bioscience and Biotechnology College of Biomedical Science Kangwon National University Chuncheon 200701 Korea.
Department of Molecular Bioscience College of Biomedical Science Kangwon National University Chuncheon 200701 Korea.
Ecol Evol. 2016 Jul 22;6(16):5749-60. doi: 10.1002/ece3.2320. eCollection 2016 Aug.
Red maple (Acer rubum), a common deciduous tree species in Northern Ontario, has shown resistance to soil metal contamination. Previous reports have indicated that this plant does not accumulate metals in its tissue. However, low level of nickel and copper corresponding to the bioavailable levels in contaminated soils in Northern Ontario causes severe physiological damages. No differentiation between metal-contaminated and uncontaminated populations has been reported based on genetic analyses. The main objective of this study was to assess whether DNA methylation is involved in A. rubrum adaptation to soil metal contamination. Global cytosine and methylation-sensitive amplified polymorphism (MSAP) analyses were carried out in A. rubrum populations from metal-contaminated and uncontaminated sites. The global modified cytosine ratios in genomic DNA revealed a significant decrease in cytosine methylation in genotypes from a metal-contaminated site compared to uncontaminated populations. Other genotypes from a different metal-contaminated site within the same region appear to be recalcitrant to metal-induced DNA alterations even ≥30 years of tree life exposure to nickel and copper. MSAP analysis showed a high level of polymorphisms in both uncontaminated (77%) and metal-contaminated (72%) populations. Overall, 205 CCGG loci were identified in which 127 were methylated in either outer or inner cytosine. No differentiation among populations was established based on several genetic parameters tested. The variations for nonmethylated and methylated loci were compared by analysis of molecular variance (AMOVA). For methylated loci, molecular variance among and within populations was 1.5% and 13.2%, respectively. These values were low (0.6% for among populations and 5.8% for within populations) for unmethylated loci. Metal contamination is seen to affect methylation of cytosine residues in CCGG motifs in the A. rubrum populations that were analyzed.
红枫（Acer rubum）是安大略省北部常见的落叶树种，已显示出对土壤金属污染的抗性。先前的报告表明，这种植物在其组织中不会积累金属。然而，与安大略省北部受污染土壤中的生物可利用水平相对应的低水平镍和铜会造成严重的生理损害。基于遗传分析，尚未报道受金属污染和未受污染种群之间的差异。本研究的主要目的是评估DNA甲基化是否参与红枫对土壤金属污染的适应。对来自金属污染和未污染地点的红枫种群进行了全基因组胞嘧啶和甲基化敏感扩增多态性（MSAP）分析。基因组DNA中的全基因组修饰胞嘧啶比率显示，与未受污染种群相比，来自金属污染地点的基因型中胞嘧啶甲基化显著降低。同一区域内另一个金属污染地点的其他基因型似乎对金属诱导的DNA改变具有抗性，即使树木在镍和铜环境中生长≥30年。MSAP分析表明，未受污染（77%）和金属污染（72%）的种群中均存在高水平的多态性。总体而言，共鉴定出205个CCGG位点，其中127个在外部或内部胞嘧啶中发生了甲基化。基于所测试的几个遗传参数，未确定种群之间的差异。通过分子方差分析（AMOVA）比较了未甲基化和甲基化位点的变异。对于甲基化位点，种群间和种群内的分子方差分别为1.5%和13.2%。对于未甲基化位点，这些值较低（种群间为0.6%，种群内为5.8%）。在所分析的红枫种群中，金属污染被认为会影响CCGG基序中胞嘧啶残基的甲基化。
