Main conclusion The rice leaf mitochondrial DNA is more methylated compared to the rice grain mitochondrial DNA. The old rice leaf mitochondrial DNA has also a higher methylation level than the young rice leaf mitochondrial DNA. Abstract The presence of DNA methylation in rice organelles has not been well characterized. We have previously shown that cytosine methylation of chloroplast DNA is different between leaf and grain, and varies between young and old leaves in rice. However, the variation in cytosine methylation of mitochondrial DNA is still poorly characterized. In this study, we have investigated cytosine methylation of mitochondrial DNA in the rice grain and leaf. Based on CpG, CHG, and CHH methylation analyses, the leaf mitochondrial DNA was found to be more methylated compared to the grain mitochondrial DNA. The methylation of the leaf mitochondrial DNA was also higher in old compared to young leaves. Differences in methylation were observed at different cytosine positions of the mitochondrial DNA between grain and leaf, although there were also positions with a similar level of high methylation in all the tissues examined. The differentially methylated cytosine positions in rice mitochondrial DNA were observed mostly in the intergenic region and in some mitochondrial-specific genes involved in ATP production, transcription, and translation. The functional importance of cytosine methylation in the life cycle of rice mitochondria is still to be determined.

中文翻译：

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水稻籽粒和叶组织线粒体 DNA 胞嘧啶甲基化

主要结论 与水稻籽粒线粒体 DNA 相比，水稻叶片线粒体 DNA 甲基化程度更高。老稻叶线粒体DNA的甲基化水平也高于嫩稻叶线粒体DNA。摘要 水稻细胞器中 DNA 甲基化的存在尚未得到很好的表征。我们之前已经表明叶绿体 DNA 的胞嘧啶甲基化在叶片和籽粒之间是不同的，并且在水稻的幼叶和老叶之间也存在差异。然而，线粒体 DNA 胞嘧啶甲基化的变异仍然没有得到很好的表征。在这项研究中，我们研究了水稻籽粒和叶片中线粒体 DNA 的胞嘧啶甲基化。基于 CpG、CHG 和 CHH 甲基化分析，发现与谷物线粒体 DNA 相比，叶线粒体 DNA 的甲基化程度更高。与幼叶相比，老叶线粒体 DNA 的甲基化也更高。在谷粒和叶子之间线粒体 DNA 的不同胞嘧啶位置观察到甲基化的差异，尽管在所有检查的组织中也存在具有相似水平的高甲基化的位置。水稻线粒体 DNA 中差异甲基化的胞嘧啶位置主要在基因间区域和一些参与 ATP 产生、转录和翻译的线粒体特异性基因中观察到。胞嘧啶甲基化在水稻线粒体生命周期中的功能重要性仍有待确定。尽管在所有检查的组织中也存在具有相似水平的高甲基化的位置。水稻线粒体 DNA 中差异甲基化的胞嘧啶位置主要在基因间区域和一些参与 ATP 产生、转录和翻译的线粒体特异性基因中观察到。胞嘧啶甲基化在水稻线粒体生命周期中的功能重要性仍有待确定。尽管在所有检查的组织中也存在具有相似水平的高甲基化的位置。水稻线粒体 DNA 中差异甲基化的胞嘧啶位置主要在基因间区域和一些参与 ATP 产生、转录和翻译的线粒体特异性基因中观察到。胞嘧啶甲基化在水稻线粒体生命周期中的功能重要性仍有待确定。