Biotechnology Research Lab, Miami Dade College Miami, FL, USA.
Front Plant Sci. 2013 May 7;4:128. doi: 10.3389/fpls.2013.00128. eCollection 2013.
The number of plant mitochondrial genomes sequenced exceeds two dozen. However, for a detailed comparative study of different phylogenetic branches more plant mitochondrial genomes should be sequenced. This article presents sequencing data and comparative analysis of mitochondrial DNA (mtDNA) of the legume Vicia faba. The size of the V. faba circular mitochondrial master chromosome of cultivar Broad Windsor was estimated as 588,000 bp with a genome complexity of 387,745 bp and 52 conservative mitochondrial genes; 32 of them encoding proteins, 3 rRNA, and 17 tRNA genes. Six tRNA genes were highly homologous to chloroplast genome sequences. In addition to the 52 conservative genes, 114 unique open reading frames (ORFs) were found, 36 without significant homology to any known proteins and 29 with homology to the Medicago truncatula nuclear genome and to other plant mitochondrial ORFs, 49 ORFs were not homologous to M. truncatula but possessed sequences with significant homology to other plant mitochondrial or nuclear ORFs. In general, the unique ORFs revealed very low homology to known closely related legumes, but several sequence homologies were found between V. faba, Beta vulgaris, Nicotiana tabacum, Vitis vinifera, and even the monocots Oryza sativa and Zea mays. Most likely these ORFs arose independently during angiosperm evolution (Kubo and Mikami, 2007; Kubo and Newton, 2008). Computational analysis revealed in total about 45% of V. faba mtDNA sequence being homologous to the Medicago truncatula nuclear genome (more than to any sequenced plant mitochondrial genome), and 35% of this homology ranging from a few dozen to 12,806 bp are located on chromosome 1. Apparently, mitochondrial rrn5, rrn18, rps10, ATP synthase subunit alpha, cox2, and tRNA sequences are part of transcribed nuclear mosaic ORFs.
已测序的植物线粒体基因组数量超过二十余个。然而，为了对不同系统发育枝进行详细的比较研究，还需要更多的植物线粒体基因组测序。本文呈现了菜豆属植物 Vicia faba 的线粒体 DNA (mtDNA)测序数据和比较分析结果。经估算，宽叶豌豆品种 Broad Windsor 的线粒体环状主染色体大小约为 588000bp，基因组复杂度为 387745bp，包含 52 个保守的线粒体基因；其中 32 个基因编码蛋白质，3 个 rRNA 和 17 个 tRNA 基因。6 个 tRNA 基因与叶绿体基因组序列高度同源。除 52 个保守基因外，还发现了 114 个独特的开放阅读框（ORF），其中 36 个与任何已知蛋白均无显著同源性，29 个与 Medicago truncatula 核基因组及其他植物线粒体 ORF 同源，49 个 ORF 与 M. truncatula 无同源性，但与其他植物线粒体或核 ORF 具有序列同源性。总体而言，独特的 ORF 与已知的亲缘关系密切的豆科植物的同源性非常低，但在 V. faba、Beta vulgaris、Nicotiana tabacum、Vitis vinifera 甚至单子叶植物 Oryza sativa 和 Zea mays 之间发现了一些序列同源性。这些 ORF 很可能是在被子植物进化过程中独立产生的（Kubo and Mikami，2007；Kubo and Newton，2008）。计算分析显示，V. faba mtDNA 序列中约有 45%与 Medicago truncatula 核基因组同源（比任何已测序的植物线粒体基因组都多），其中 35%的同源性长度从几十到 12806bp 不等，位于 1 号染色体上。显然，线粒体 rrn5、rrn18、rps10、ATP 合酶亚基 alpha、cox2 和 tRNA 序列是转录核镶嵌 ORF 的一部分。
