The sequence, organization, and evolution of the Locusta migratoria mitochondrial genome
The sequence, organization, and evolution of the Locusta migratoria mitochondrial genome
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DOI：
10.1007/bf00173173
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发表时间：
1995-12-01
影响因子：
3.9
通讯作者：
Gellissen, G
中科院分区：
文献类型：
--
作者：
Flook, PK;Rowell, CHF;Gellissen, G
克隆飞蝗线粒体基因组测序已完成。该序列长度为 15,722 bp，包含 75.3% A+T，是迄今为止确定的 5 种昆虫线粒体序列中的最低值。蛋白质编码基因具有相似的 A+T 含量（74.1%），但其特点是第三个密码子位置的胞嘧啶含量较高。除了两个 tRNA 的重排外，基因内容和组织与果蝇 yakuba 中的相同 基因 tRNA(lys) 和 tRNA(asp)。富含 A+T 的区域具有比其他昆虫更低的 A+T 核苷酸含量，这主要是由于该部分的 5' 端和相邻小 rRNA 基因的开头存在两个富含 G+C 的 155 bp 重复序列。大rRNA基因和小rRNA基因的大小分别为1,314和827 bp，两个序列都可以折叠形成类似于先前预测的果蝇二级结构。 tRNA 基因也已被建模，这些基因与双翅目 tRNA 非常相似，所有反密码子显然在两个物种之间都是保守的。对蝗虫 DNA 的蛋白质编码核苷酸序列与其他五种节肢动物（果蝇、四斑按蚊、冈比亚按蚊、意大利蜜蜂和法国卤虫）的同源序列进行了比较。蝗虫编码的蛋白质的氨基酸组成与果蝇相似，其戴霍夫距离是果蝇与蚊子之间距离的两倍。系统发育分析显示，蝗虫基因在核苷酸和氨基酸水平上与双翅目动物的基因比与蜜蜂的基因更相似。使用甲壳类动物 mtDNA 作为外群对 tRNA 目进行的比较分析支持了这一点。蜜蜂基因组中的这种高度分化已在其他地方注意到，可能是定向突变压力的影响，导致序列进化模式加速。如果全变态动物是单系的一般假设成立，那么这些结果强调了重建系统发育的困难，其中包括具有可变替代率和碱基组成偏差的谱系。还说明了在系统发育分析中使用有关 tRNA 基因顺序的信息时需要谨慎，但是，如果排除蜜蜂序列，其他五个节肢动物序列之间的对应关系支持以前的研究结果，这些研究结果支持在突变率相当时使用 mtDNA 序列在分类学的深层系统发育研究中。
The sequencing of the cloned Locusta migratoria mitochondrial genome has been completed. The sequence is 15,722 bp in length and contains 75.3% A+T, the lowest value in any of the five insect mitochondrial sequences so far determined, The protein coding genes have a similar A+T content (74.1%) but are distinguished by a high cytosine content at the third codon position, The gene content and organization are the same as in Drosophila yakuba except for a rearrangement of the two tRNA genes tRNA(lys) and tRNA(asp). The A+T-rich region has a lower A+T nucleotide content than in other insects, and this is largely due to the presence of two G+C-rich 155-bp repetitive sequences at the 5' end of this section and the beginning of the adjacent small rRNA gene. The sizes of the large and small rRNA genes are 1,314 and 827 bp, respectively, and both sequences can be folded to form secondary structures similar to those previously predicted for Drosophila. The tRNA genes have also been modeled and these show a strong resemblance to the dipteran tRNAs, all anticodons apparently being conserved between the two species. A comparison of the protein coding nucleotide sequences of the locust DNA with the homologous sequences of five other arthropods (Drosophila yakuba, Anopheles quadrimaculatus, Anapheles gambiae, Apis mellifera, and Artemia franciscana) was performed. The amino acid composition of the encoded proteins in Locusta is similar to that of Drosophila, with a Dayhoff distance twice that of the distance between the fruit fly and the mosquitoes. A phylogenetic analysis revealed the locust genes to be more similar to those of the Dipterans than to those of the honeybee at both the nucleotide and amino acid levels. A comparative analysis of tRNA orders, using crustacean mtDNAs as outgroups, supported this. This high level of divergence in the Apis genome has been noted elsewhere and is possibly an effect of directional mutation pressure having resulted in an accelerated pattern of sequence evolution. If the general assumption that the Holometabola are monophyletic holds, then these results emphasize the difficulties of reconstructing phylogenies that include lineages with variable substitution rates and base composition biases. The need to exercise caution in using information about tRNA gene orders in phylogenetic analysis is also illustrated, However, if the honeybee sequence is excluded, the correspondence between the other five arthropod sequences supports the findings of previous studies which have endorsed the use of mtDNA sequences for studies of phylogeny at deep levels of taxonomy when mutation rates are equivalent.