Molecular analysis of mite mitochondrial genome structure

后生动物线粒体基因组的基因内容通常是保守的。与此相反，这些基因的重排，37个基因和大的非编码区（LNR），观察到恙螨属的纤颤螨。在其他螨目螨类（Ascoschoengastia sp.和Walchia hayashii）中也大量发生了这些基因的重复、甚至不同方向的迁移和基因复制。我们发现，苍白纤恙螨的mt基因组有一个额外的大亚基rRNA基因（rrnL），一个小亚基rRNA的假基因（PrrnS），和三个额外的LNR，除了37个基因和一个典型的后生动物的LNR。此外，还对L. pallidum与假定的节肢动物祖先有很大的不同。为了发现纤恙螨中新基因含量和基因排列的程度，我们对其他四个物种的全部mt基因组进行了测序，它们是：红恙螨、德氏纤恙螨、Ascoschoengastia sp.、和Walchia hayashii，以及部分L.fletcheri、L.scutellare、L.intermedium、L.chaingraiensis、L.imphalum、L.fujii和Leptotrombidium sp.的线粒体基因组结构与Leptotrombidium完全不同。其它纤恙螨属的物种与纤恙螨属共享或部分共享所有基因排列。苍白球，除了trnQ（对于tRNA-谷氨酰胺）。然而，与苍白军团菌不同，这些其他物种没有额外的rrnL或PrrnS，只有一个额外的LNR。通过与节肢动物祖先细恙螨的比较，我们认为：（1）苍白细恙螨的mt基因组类型是由其他3种细恙螨的mt基因类型进化而来的;（2）细恙螨mt基因含量和基因排列的进化涉及3种分子机制。

The gene content of a mitochondrial (mt) genome is usually conserved in Metazoa. In contrast, the re-arrangement of these genes, 37 genes and large noncoding region (LNR), was observed in chigger mites of the genus Leptotombidium. Recombination of theses genes, relocation in even different direction, and gene duplication were also occurred substantially in the other acariformes mite (Ascoschoengastia sp. and Walchia hayashii). We found 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 mt genomes of four other species, L.akamushi, L.deliense, Ascoschoengastia sp., and Walchia hayashii, and partially L.fletcheri, L.scutellare, L.intermedium, L.chaingraiensis, L.imphalum, L.fujii, and Leptotrombidium sp. The mit genomes of Ascoschoengastia sp. and W.hayashii were entirely distinct structures from that of Leptotrombidium. The other Leptotrombidium species share the or partial arrangement of all genes with L. pallidum, except trnQ (for tRNA-glutamine). Unlike L.pallidum, however, these other 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.