Botanical Garden, Natural History Museum of Denmark, University of Copenhagen, Copenhagen K, Denmark.
PLoS One. 2013 Apr 24;8(4):e61552. doi: 10.1371/journal.pone.0061552. Print 2013.
In order to study the evolution of mitochondrial genomes in the early branching lineages of the monocotyledons, i.e., the Acorales and Alismatales, we are sequencing complete genomes from a suite of key taxa. As a starting point the present paper describes the mitochondrial genome of Butomus umbellatus (Butomaceae) based on next-generation sequencing data. The genome was assembled into a circular molecule, 450,826 bp in length. Coding sequences cover only 8.2% of the genome and include 28 protein coding genes, four rRNA genes, and 12 tRNA genes. Some of the tRNA genes and a 16S rRNA gene are transferred from the plastid genome. However, the total amount of recognized plastid sequences in the mitochondrial genome is only 1.5% and the amount of DNA transferred from the nucleus is also low. RNA editing is abundant and a total of 557 edited sites are predicted in the protein coding genes. Compared to the 40 angiosperm mitochondrial genomes sequenced to date, the GC content of the Butomus genome is uniquely high (49.1%). The overall similarity between the mitochondrial genomes of Butomus and Spirodela (Araceae), the closest relative yet sequenced, is low (less than 20%), and the two genomes differ in size by a factor 2. Gene order is also largely unconserved. However, based on its phylogenetic position within the core alismatids Butomus will serve as a good reference point for subsequent studies in the early branching lineages of the monocotyledons.
为了研究单子叶植物早期分支谱系（即泽泻目和天南星目）中线粒体基因组的进化，我们正在对一系列关键分类群的完整基因组进行测序。作为一个起点，本论文基于下一代测序数据描述了慈姑科的慈姑（Butomus umbellatus）的线粒体基因组。该基因组被组装成一个圆形分子，长度为 450826bp。编码序列仅占基因组的 8.2%，包括 28 个蛋白质编码基因、4 个 rRNA 基因和 12 个 tRNA 基因。一些 tRNA 基因和 16S rRNA 基因从质体基因组转移而来。然而，线粒体基因组中识别出的质体序列总量仅为 1.5%，从核中转录的 DNA 量也很低。RNA 编辑很丰富，在蛋白质编码基因中预测了总共 557 个编辑位点。与迄今为止测序的 40 个被子植物线粒体基因组相比，慈姑基因组的 GC 含量非常高（49.1%）。慈姑和 Spirodela（天南星科）的线粒体基因组之间的总体相似性很低（不到 20%），而且这两个基因组的大小差异因子为 2。基因顺序也没有得到很好的保守。然而，基于其在核心泽泻目植物中的系统发育位置，慈姑将成为单子叶植物早期分支谱系后续研究的良好参考点。
