Shao Renfu, Barker Stephen C, Mitani Harumi, Takahashi Mamoru, Fukunaga Masahito
Faculty of Pharmacy and Pharmaceutical Sciences, Fukuyama University, Fukuyama, Hiroshima, 729-0292, Japan.
J Mol Evol. 2006 Aug;63(2):251-61. doi: 10.1007/s00239-005-0196-y. Epub 2006 Jul 7.
The gene content of a mitochondrial (mt) genome, i.e., 37 genes and a large noncoding region (LNR), is usually conserved in Metazoa. The arrangement of these genes and the LNR is generally conserved at low taxonomic levels but varies substantially at high levels. We report here a variation in mt gene content and gene arrangement among chigger mites of the genus Leptotrombidium. We found previously that the mt genome of Leptotrombidium pallidum has an extra gene for large-subunit rRNA (rrnL), a pseudo-gene for small-subunit rRNA (PrrnS), and three extra LNRs, additional to the 37 genes and an LNR typical of Metazoa. Further, the arrangement of mt genes of L. pallidum differs drastically from that of the hypothetical ancestor of the arthropods. To find to what extent the novel gene content and gene arrangement occurred in Leptotrombidium, we sequenced the entire or partial mt genomes of three other species, L. akamushi, L. deliense, and L. fletcheri. These three species share the arrangement of all genes with L. pallidum, except trnQ (for tRNA-glutamine). Unlike L. pallidum, however, these three species do not have extra rrnL or PrrnS and have only one extra LNR. By comparison between Leptotrombidium species and the ancestor of the arthropods, we propose that (1) the type of mt genome present in L. pallidum evolved from the type present in the other three Leptotrombidium species, and (2) three molecular mechanisms were involved in the evolution of mt gene content and gene arrangement in Leptotrombidium species.
后生动物中线粒体（mt）基因组的基因组成，即37个基因和一个大的非编码区（LNR），通常是保守的。这些基因和LNR的排列在低分类水平上一般是保守的，但在高分类水平上则有很大差异。我们在此报告纤恙螨属恙螨的mt基因组成和基因排列存在变异。我们先前发现，苍白纤恙螨的mt基因组除了后生动物典型的37个基因和一个LNR外，还有一个额外的大亚基rRNA（rrnL）基因、一个小亚基rRNA假基因（PrrnS）和三个额外的LNR。此外，苍白纤恙螨mt基因的排列与节肢动物假定祖先的排列有很大不同。为了确定这种新的基因组成和基因排列在纤恙螨属中出现的程度，我们对另外三个物种——红纤恙螨、地里纤恙螨和弗氏纤恙螨的全部或部分mt基因组进行了测序。这三个物种与苍白纤恙螨共享所有基因的排列，除了trnQ（用于tRNA-谷氨酰胺）。然而，与苍白纤恙螨不同的是，这三个物种没有额外的rrnL或PrrnS，并且只有一个额外的LNR。通过比较纤恙螨属物种和节肢动物的祖先，我们提出：（1）苍白纤恙螨中存在的mt基因组类型是从其他三种纤恙螨属物种中存在的类型进化而来的；（2）三种分子机制参与了纤恙螨属物种mt基因组成和基因排列的进化。
