Du Jingjing, Wang Junwei, Shan Sicong, Mi Tian, Song Yulong, Xia Yu, Ma Shoucai, Zhang Gaisheng, Ma Lingjian, Niu Na
College of Agronomy, Northwest A & F University, Xianyang 712100, China.
Key Laboratory of Crop Heterosis of Shaanxi Province, Xianyang 712100, China.
Int J Mol Sci. 2023 Sep 28;24(19):14697. doi: 10.3390/ijms241914697.
Chlorophyll is an indispensable photoreceptor in plant photosynthesis. Its anabolic imbalance is detrimental to individual growth and development. As an essential epigenetic modification, DNA methylation can induce phenotypic variations, such as leaf color transformation, by regulating gene expression. Albino line XN1376B is a natural mutation of winter wheat cultivar XN1376; however, the regulatory mechanism of its albinism is still unclear. In this study, we found that low temperatures induced albinism in XN1376B. The number of chloroplasts decreased as the phenomenon of bleaching intensified and the fence tissue and sponge tissue slowly dissolved. We identified six distinct (protochlorophyllide oxidoreductase) genes in the wheat genome, and was deemed to be related to the phenomenon of albinism based on the expression in different color leaves (green leaves, white leaves and returned green leaves) and the analysis of promoters' cis-acting elements. TaPOR2D was localized to chloroplasts. overexpression (TaPOR2D-OE) enhanced the chlorophyll significantly in Arabidopsis, especially at two weeks; the amount of chlorophyll was 6.46 mg/L higher than in WT. The methylation rate of the promoter in low-temperature albino leaves is as high as 93%, whereas there was no methylation in green leaves. Correspondingly, three DNA methyltransferase genes (, and ) were up-regulated in white leaves. Our study clarified that the expression of is associated with its promoter methylation at a low temperature; it affects the level of chlorophyll accumulation, which probably causes the abnormal development of plant chloroplasts in albino wheat XN1376B. The results provide a theoretical basis for in-depth analysis of the regulation of development of plant chloroplasts and color variation in wheat XN1376B leaves.
叶绿素是植物光合作用中不可或缺的光感受器。其合成代谢失衡对个体生长发育有害。作为一种重要的表观遗传修饰，DNA甲基化可通过调节基因表达诱导表型变异，如叶片颜色转变。白化系XN1376B是冬小麦品种XN1376的自然突变体；然而，其白化现象的调控机制仍不清楚。在本研究中，我们发现低温诱导XN1376B白化。随着白化现象加剧，叶绿体数量减少，栅栏组织和海绵组织逐渐溶解。我们在小麦基因组中鉴定出6个不同的原叶绿素酸酯氧化还原酶（POR）基因，基于其在不同颜色叶片（绿色叶片、白色叶片和返绿叶片）中的表达以及启动子顺式作用元件分析，认为TaPOR2D与白化现象有关。TaPOR2D定位于叶绿体。TaPOR2D过表达（TaPOR2D - OE）显著提高了拟南芥中的叶绿素含量，尤其是在两周时；叶绿素含量比野生型高6.46 mg/L。低温白化叶片中TaPOR2D启动子的甲基化率高达93%，而绿色叶片中没有甲基化。相应地，三个DNA甲基转移酶基因（TaMET1、TaCMT3和TaDRM2）在白色叶片中上调表达。我们的研究表明，TaPOR2D的表达与其启动子在低温下的甲基化有关；它影响叶绿素积累水平，这可能导致白化小麦XN1376B中植物叶绿体的异常发育。这些结果为深入分析小麦XN1376B叶片中植物叶绿体发育调控和颜色变异提供了理论依据。
