The complete mitochondrial DNA sequence of the basal Hexapod Tetrodontophora bielanensis:: Evidence for heteroplasmy and tRNA translocations
The complete mitochondrial DNA sequence of the basal Hexapod Tetrodontophora bielanensis:: Evidence for heteroplasmy and tRNA translocations
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DOI：
10.1093/oxfordjournals.molbev.a003914
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发表时间：
2001-07-01
影响因子：
10.7
通讯作者：
Frati, F
中科院分区：
文献类型：
--
作者：
Nardi, F;Carapelli, A;Frati, F
我们展示了弹尾Tetrodontophora bielanensis（节足目、六足目、弹尾目）的完整15，455-nt线粒体DNA序列。基因内容是典型的大多数后生动物，有13个蛋白质编码基因（PCG），2个基因编码核糖体RNA亚基，和22个tRNA基因。核苷酸序列显示了众所周知的A+T的偏见典型的昆虫mtDNA，其A+T含量低于（72.7%）比其他昆虫物种中观察到的，但仍高于其他节肢动物类群。这种偏向在整个分子中似乎是均匀的，不像其他昆虫类群，它们在所谓的A + T富集区显示出增加的A+T含量。然而，在PCG的第三密码子位置处的偏倚略高（81.4%）。在nad 2和cox 1基因中发现了异常的起始密码子。在后者中，ATTTAA六核苷酸被认为参与起始信号传导。所有的tRNA都可以折叠成典型的三叶草二级结构，但半胱氨酸的tRNA似乎缺少DHU臂。在富含A+ T的区域中发现了长串联重复区域（193 nt），这反过来又被证明有可能形成复杂的二级结构阵列。其中一个结构包含重复序列之间的连接处。富含A+ T的区域也很有趣，因为它在重复次数上表现出异质性。发现了3种单倍型，分别具有2、3和4个相同的重复。确定了分子中蛋白质编码和rRNA基因的顺序，并且与迄今为止研究的所有昆虫的顺序相同。然而，发现了两个tRNA易位，这是前所未有的节肢动物。其中包括位于rrnS和富含A+ T的区域之间的a-ne，以及位于trnM和trnI之间的trnS（ucn）。初步的系统发育分析的基础上的PCG的氨基酸序列未能找到支持单系的六足类。
We present the complete 15,455-nt mitochondrial DNA sequence of the springtail Tetrodontophora bielanensis (Arthropoda, Hexapoda, Collembola). The gene content is typical of most metazoans, with 13 protein-coding genes (PCGs), 2 genes encoding for ribosomal RNA subunits, and 22 tRNA genes. The nucleotide sequence shows the well-known A+T bias typical of insect mtDNA; its A+T content is lower (72.7%) than that observed in other insect species, but still higher than that in other arthropodan taxa. The bias appears to be uniform across the whole molecule, unlike other insect taxa, which show increased A+T content in the so-called A+T-rich region. However, the bias is slightly higher in the third codon positions of the PCGs (81.4%). Anomalous initiation codons have been observed in the nad2 and the cox1 genes. In the latter, the ATTTAA hexanucleotide is suggested to be involved in the initiation signaling. All tRNAs could be folded into the typical cloverleaf secondary structure, but the tRNA for cysteine appears to be missing the DHU arm. Long tandemly repeated regions (193 nt) were found in the A+T-rich region, which in turn was shown to have the possibility of forming a complex array of secondary structures. One of these structures encompassed the junction between the repeats. The A+T-rich region was also interesting in that it showed heteroplasmy in the number of repeats. Three haplotypes were found, possessing 2, 3, and 4 identical repeats, respectively. The order of protein coding and rRNA genes in the molecule was determined and was identical to that of all insects studied so far. However, two tRNA translocations were found which were unprecedented among Arthropoda. These involved the a-ne, which was found between the rrnS and the A+T-rich region, and the trnS(ucn), which was located between trnM and trnI. A preliminary phylogenetic analysis based on the amino acid sequence of the PCGs failed to find support for the monophyly of Hexapoda.