Research Faculty of Agriculture, Hokkaido University, Kita 9 Nishi 9, Kita-ku, Sapporo, 060-8589, Japan.
Theor Appl Genet. 2022 Mar;135(3):883-893. doi: 10.1007/s00122-021-04004-9. Epub 2022 Jan 14.
Crosses of parents that differ in their DNA methylation states leads to progressive demethylation in the F hybrids. In plant breeding research, hybrid vigor in F hybrids is known to be a very important phenomenon. Hybrid vigor, or heterosis, refers to the fact that F hybrids from crosses with a certain combination of parents have traits that are superior to those of the parents. In addition, DNA methylation is an important factor that affects gene expression in plant genomes and contributes to hybrid vigor. We introduced the 35S promoter sequence into the cucumber mosaic virus (CMV)-based vector and inoculated the GFP-expressing transgenic Nicotiana benthamiana line 16c with the recombinant virus specifically to induce DNA methylation on the 35S promoter. For plants that had transcriptional gene silencing (TGS) of GFP established by methylation of the 35S promoter (35S-TGS), TGS was fully maintained in their later self-pollinated generations. When the 35S-TGS plants were crossed with 16c, which does not contain DNA methylation in the 35S promoter, the F hybrids unexpectedly became progressively DNA demethylated as the plants grew. We hypothesis that in F hybrids that are produced by a cross between parents with extremely different gene methylation states, the methylation state of the genes in question may shift more and more to hypomethylation as the plants grow. This progressive demethylation phenomenon observed in this study may be important in plant breeding to reactivate the genes which were silenced by DNA methylation.
父母的 DNA 甲基化状态不同导致 F1 杂种中出现渐进性去甲基化。在植物育种研究中，F1 杂种的杂种优势是一个非常重要的现象。杂种优势或杂种优势是指来自具有特定双亲组合杂交的 F1 杂种具有优于双亲的特性。此外，DNA 甲基化是影响植物基因组中基因表达并有助于杂种优势的重要因素。我们将 35S 启动子序列引入基于黄瓜花叶病毒 (CMV)的载体中，并专门用重组病毒接种 GFP 表达的转基因烟草 16c，以诱导 35S 启动子上的 DNA 甲基化。对于通过 35S 启动子甲基化（35S-TGS）建立 GFP 转录基因沉默（TGS）的植物，TGS 在其后期自交后代中得到完全维持。当 35S-TGS 植物与 16c 杂交时，16c 中不存在 35S 启动子的 DNA 甲基化，F1 杂种在生长过程中出人意料地逐渐去甲基化。我们假设，在由基因甲基化状态极不相同的双亲杂交产生的 F1 杂种中，随着植物的生长，所涉及基因的甲基化状态可能越来越向去甲基化方向转变。本研究中观察到的这种渐进性去甲基化现象在植物育种中可能很重要，可以重新激活因 DNA 甲基化而沉默的基因。
