Department of Forest Ecosystems and Society, Oregon State University, Corvallis, OR 97331, USA.
Planta. 2013 Jun;237(6):1483-93. doi: 10.1007/s00425-013-1858-4. Epub 2013 Feb 28.
The Arabidopsis thaliana DDM1 (Decreased DNA Methylation) gene is necessary for the maintenance of DNA methylation and heterochromatin assembly. In Arabidopsis, ddm1 mutants exhibit strong but delayed morphological phenotypes. We used RNA interference (RNAi) to suppress transcripts of two orthologous DDM1 paralogs in Populus trichocarpa and examined effects on whole plant phenotypes during perennial growth and seasonal dormancy. The RNAi-PtDDM1 transgenic poplars showed a wide range of DDM1 transcript suppression; the most strongly suppressed line had 37.5 % of the expression of the non-transgenic control. Genomic cytosine methylation (mC %) was 11.1 % in the non-transgenic control, compared with 9.1 % for the transgenic event with lowest mC %, a reduction of 18.1 %. An evaluation of greenhouse growth directly after acclimation of in vitro grown plants showed no developmental or growth rate abnormalities associated with the decrease in PtDDM1 expression. However, after a dormancy cycle and growth outdoors, a mottled leaf phenotype appeared in some of the transgenic insertion events that had strongly reduced PtDDM1 expression and DNA methylation. The phenotypic consequences of reduced DDM1 activity and DNA methylation appears to increase with cumulative plant propagation and growth.
拟南芥 DDM1（去甲基化）基因是维持 DNA 甲基化和异染色质组装所必需的。在拟南芥中，ddm1 突变体表现出强烈但延迟的形态表型。我们使用 RNA 干扰（RNAi）来抑制杨树（Populus trichocarpa）中两个同源 DDM1 旁系同源物的转录本，并在多年生生长和季节性休眠期间研究其对整个植物表型的影响。RNAi-PtDDM1 转基因杨树表现出广泛的 DDM1 转录本抑制；受抑制最强的品系的表达水平仅为非转基因对照的 37.5%。非转基因对照的基因组胞嘧啶甲基化（mC%）为 11.1%，而甲基化最低的转基因事件为 9.1%，降低了 18.1%。对体外生长植物适应后的温室生长进行评估表明，与 PtDDM1 表达减少相关的发育或生长速率异常。然而，在经历一个休眠周期并在户外生长后，一些强烈降低 PtDDM1 表达和 DNA 甲基化的转基因插入事件出现斑驳的叶片表型。减少 DDM1 活性和 DNA 甲基化的表型后果似乎随着植物繁殖和生长的累积而增加。
