Humphreys-Pereira Danny A, Elling Axel A
Department of Plant Pathology, Washington State University, Pullman, WA 99164, USA.
Department of Plant Pathology, Washington State University, Pullman, WA 99164, USA.
Gene. 2015 Apr 15;560(2):173-83. doi: 10.1016/j.gene.2015.01.065. Epub 2015 Feb 2.
The mitochondrial (mt) genomes of the plant-parasitic root-knot nematodes Meloidogyne arenaria, Meloidogyne enterolobii and Meloidogyne javanica were sequenced and compared with those of three other root-knot nematode species in order to explore the mt genome plasticity within Meloidogyne. The mt genomes of M. arenaria, M. enterolobii and M. javanica are circular, with an estimated size of 18.8, 18.9 and 19.6 kb, respectively. Compared to other nematodes these mt genomes are larger, due to the presence of large non-coding regions. The mt genome architecture within the genus Meloidogyne varied in the position of trn genes and in the position, length and nucleotide composition of non-coding regions. These variations were observed independent of the species' natural environments or reproductive modes. M. enterolobii showed three main non-coding regions whereas Meloidogyne chitwoodi, Meloidogyne incognita, M. javanica and M. arenaria had two non-coding regions, and Meloidogyne graminicola had a unique large non-coding region interrupted by two trn genes. trn genes were positioned in different regions of the mt genomes in M. chitwoodi, M. enterolobii and M. graminicola, whereas the trn gene order was identical between M. arenaria, M. incognita and M. javanica. Importantly, M. graminicola had extra copies of trnV and trnS2. High divergence levels between the two copies of each trn might indicate duplication events followed by random loss and mutations in the anticodon. Tree-based methods based on amino acid sequences of 12 mt protein-coding genes support the monophyly for the tropical and mitotic parthenogenetic species, M. arenaria, M. enterolobii, M. incognita and M. javanica and for a clade that includes the meiotic parthenogenetic species, M. chitwoodi and M. graminicola. A comparison of the mt genome architecture in plant-parasitic nematodes and phylogenetic analyses support that Pratylenchus is the most recent ancestor of root-knot nematodes.
对植物寄生根结线虫南方根结线虫、花生根结线虫和爪哇根结线虫的线粒体（mt）基因组进行了测序，并与其他三种根结线虫物种的线粒体基因组进行了比较，以探索根结线虫属内线粒体基因组的可塑性。南方根结线虫、花生根结线虫和爪哇根结线虫的线粒体基因组呈环状，估计大小分别为18.8、18.9和19.6 kb。与其他线虫相比，这些线粒体基因组更大，这是由于存在大的非编码区。根结线虫属内的线粒体基因组结构在trn基因的位置以及非编码区的位置、长度和核苷酸组成方面存在差异。这些差异与物种的自然环境或繁殖方式无关。花生根结线虫有三个主要的非编码区，而禾本科根结线虫、南方根结线虫、爪哇根结线虫和南方根结线虫有两个非编码区，而稻根结线虫有一个独特的大非编码区，被两个trn基因打断。在禾本科根结线虫、花生根结线虫和稻根结线虫中，trn基因位于线粒体基因组的不同区域，而在南方根结线虫、南方根结线虫和爪哇根结线虫中，trn基因顺序相同。重要的是，稻根结线虫有额外的trnV和trnS2拷贝。每个trn的两个拷贝之间的高度差异可能表明复制事件后反密码子发生随机丢失和突变。基于12个线粒体蛋白质编码基因氨基酸序列的树状方法支持热带和有丝分裂孤雌生殖物种南方根结线虫、花生根结线虫、南方根结线虫和爪哇根结线虫以及包括减数分裂孤雌生殖物种禾本科根结线虫和稻根结线虫的一个分支的单系性。对植物寄生线虫线粒体基因组结构的比较和系统发育分析支持短体线虫是根结线虫的最新祖先。
