Molecular analysis of mite mitochondrial genome structure

线粒体基因组的基因内容在后生动物中通常是保守的。相反，37个基因和较大的非编码区(LNR)的重排在纤毛虫属恙螨螨类中被观察到。这些基因的重组、甚至不同方向的重新定位和基因复制也大量地发生在其他粉螨(Ascoschoengastia sp.)中。和Walchia hayashii)。我们发现梅毒细毛虫的mt基因组中有一个大亚基rRNA(RrnL)的额外基因，一个小亚基rRNA(PrrnS)的伪基因，以及三个额外的LNRs，除了37个基因和一个典型的后生动物的LNR。此外，梅毒螺旋体mt基因的排列与节肢动物假想祖先的mt基因排列有很大的不同。为了发现Leptotrombidium中新的基因含量和基因排列在多大程度上发生，我们对其他四个物种的mt全基因组进行了测序：L.akamushi，L.deliense，Ascoschoengastia sp.，Walchia hayashii，以及L.fletcheri，L.scutelare，L.interdium，L.chaingraiensis，L.imphalum，L.fujii和Leptotrombidium sp.Ascoschoengastia sp.的MIT基因组和W.hayashii是与Leptotrombidium完全不同的结构。除trnQ(tRNA-谷氨酰胺)外，其他种与梅毒Leptotrombidium具有相同或部分的基因排列。然而，与梅毒乳杆菌不同的是，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的比较，我们认为：(1)梅毒螺旋藻的mt基因组类型是由其他3个种的mt基因组类型进化而来的；(2)Leptotrombidium物种mt基因含量和基因排列的进化涉及三种分子机制。

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.