Wang Qin-Mei, Wang Li, Zhou Yongbin, Cui Jianguo, Wang Yuzhang, Zhao Chengming
Plant Cell Rep. 2016 Jan;35(1):167-84. doi: 10.1007/s00299-015-1877-7.
Leaf patterns (yellow, green and striped) of Clivia miniata var. variegata might be caused by differential DNA methylation in CCGG sites in response to heterogeneous environmental pressure. Clivia miniata is an important ornamental plant.Clivia miniata var. variegata (Cmvv) is a variegated leaf mutant of C. miniata. Typical Cmvv has attractive green and yellow-stripped leaves. The study has revealed that an explant of Cmvv, even a full-green explant, could regenerate plants of three different types: yellow, green, ands triped; normal-appearing chloroplasts were found in guard cells but not in mesophyll cells of all the three types of Cmvv using confocal laser scanning microscopy (CLSM).Thus, we speculated that cells of the three types of Cmvv had an identical mutation and the mutation might disturb mesophyll cell chloroplast biogenesis after symplastic isolation of guard cells. Using CLSM and methylation sensitive amplification polymorphism (MSAP), we found that (a) striped leaves of Cmvv are due to sectorial decreases in chlorophyll levels and the decreases are associated with CG hypermethylation; (b) extent of epigenetic divergence among the three types of Cmvv leaves is positively correlated with intensity of leaf-color difference; and (c) green stripes of two plants are clustered in one group based on the MSAP profiles, but green and yellow stripes of a plant are not. Sequencing analysis indicated that CG hypermethylation in gene bodies of CPSAR1 and ycf2 might lead to gene silencing and yellow leaves/stripes of Cmvv. All together, it is possible that cytosine methylation involved regulating leaf color of Cmvv, also striped pattern of Cmvv might be caused by differential DNA methylation in response to heterogeneous environmental pressure. Furthermore, a novel leaf-color epigenetic hypothesis was proposed in this article.
花叶君子兰（Clivia miniata var. variegata）的叶片图案（黄色、绿色和条纹状）可能是由于CCGG位点的DNA甲基化差异，以响应异质环境压力所致。君子兰是一种重要的观赏植物。花叶君子兰（Cmvv）是君子兰的一个叶色变异突变体。典型的Cmvv具有吸引人的绿色和黄色条纹叶片。该研究表明，Cmvv的外植体，即使是全绿外植体，也能再生出三种不同类型的植株：黄色、绿色和条纹状；使用共聚焦激光扫描显微镜（CLSM）在所有三种类型的Cmvv的保卫细胞中发现了正常外观的叶绿体，但在叶肉细胞中未发现。因此，我们推测这三种类型的Cmvv细胞具有相同的突变，并且该突变可能在保卫细胞共质体分离后干扰叶肉细胞叶绿体的生物发生。使用CLSM和甲基化敏感扩增多态性（MSAP），我们发现：（a）Cmvv的条纹叶是由于叶绿素水平的局部降低，且这种降低与CG超甲基化有关；（b）三种类型的Cmvv叶片之间表观遗传差异程度与叶色差异强度呈正相关；（c）基于MSAP图谱，两株植物的绿色条纹聚为一组，但一株植物的绿色和黄色条纹则不然。测序分析表明，CPSAR1和ycf2基因体中的CG超甲基化可能导致基因沉默以及Cmvv的黄叶/条纹。总之，胞嘧啶甲基化可能参与调控Cmvv的叶色，Cmvv的条纹图案也可能是由于响应异质环境压力的DNA甲基化差异所致。此外，本文还提出了一种新的叶色表观遗传假说。
