两栖动物线粒体基因组重排概述

 

熊荣川 邓欢欢 译

 

脊椎动物线粒体基因的排列通常较为保守。从硬骨鱼类到真兽亚纲哺乳动物，所有37个基因以相同的顺序排列，但是也有一些类群的线粒体基因有重排现象（例如在有袋目哺乳动物、鸟类、爬行类、圆口类及鱼类）。然而，对于两栖动物，线粒体基因的重排在很多类群内都有发现。例如，在美国南部一些相互亲缘关系很近的蚓螈类就观察到重排的tRNA。在有尾目，基因或者控制区的重排及复制出现在无肺螈科。在无尾目，较原始的类群（古蛙亚目）的线粒体基因排列和典型的脊椎动物一致。然而，系统树上聚在无尾目（新蛙亚目）下的树蛙科和蛙科的物种，其基因排列和经典排列有差异。在大多数的新蛙亚目类群中，4个tRNA从传统上的位置转座到了12S rRNA的上游形成LTPF tRNA基因簇。另外，进一步的基因重排在新蛙亚目的一个重要支系蛙总科中被报道。蛙科中目前已有6个物种的线粒体基因组报道；除了黑斑蛙外，另外5种有区别于彼此的重排。尤其是马达加斯加蛙类（曼蛙属Mantella）表现出了高度重排。新蛙类线粒体基因大小从16kbp(Microhyla heymonsi)到23kbp(Mantella madagascariensis)不等。新蛙类线粒体DNA大小的多变主要是由D-loop的不同长度引起的，它通常包含有较长较多的重复序列。这些基因重排的例子使得新蛙类成为研究脊椎动物线粒体不稳定机制的一个极好模型。

 

 

原文(Igawa et al., 2008)：

 

Mitochondrial gene arrangements are generally conserved in vertebrates. All 37 genes are arranged in the same relative order in almost all vertebrate species from teleost fishes to eutherian mammals (Anderson et al., 1981; Roe et al., 1985; Tzeng et al., 1992; Boore, 1999), though some taxa has rearranged mt gene orders [e.g., in marsupials, birds, reptiles, lampreys, and fishes (see Boore, 1999)]. As for amphibians, however, mitochondrial gene rearrangements have been found in a number of taxa. For example, tRNA gene rearrangements were observed within closely related South American caecilians (San Mauro et al., 2006). In Caudata, gene rearrangements and duplication of genes or control regions were also found in mtDNAs of plethodontid salamanders (Mueller and Boore, 2005). In anurans, the mt gene arrangements of basal groups (archaeobatrachians) are completely identical to those of typical vertebrates (Roe et al., 1985; San Mauro et al., 2004; Gissiet al., 2006). However, in hyloid and ranoid frogs in the phylogenetically nested anuran group (suborder Neobatrachia), the gene arrangement diverged from the typical one. In most neobatrachian mtDNAs, four tRNA genes translocated from typical positions, and these tRNA genes formed a cluster upstream of the 12S rRNA gene (LTPF tRNA cluster; Sumida et al., 2001; Zhang et al., 2005a). In addition, further gene rearrangements have been reported in a major neobatrachian clade, the epifamily Ranoidae. Within Ranoidae, complete mtDNA sequences of six species have been reported so far (Sumida et al., 2001; Sano et al., 2004, 2005; Zhang et al., 2005b; Liu et al., 2005; Kurabayashi et al., 2006) and five of these except R. nigromaculata possess additional rearrangements that are different from each other. Especially, mtDNAs of genus Madagascan frogs (genus Mantella) show extended rearrangements (Kurabayashi et al., 2006). In addition, the neobatrachian mt genomes vary in length ranging from about 16 kbp (Microhyla heymonsi) to 23 kbp (Mantella madagascariensis). The size variations of neobatrachian mtDNA are mainly caused by length differences of D-loops, which usually contain long and many repeated sequences. These many instances of gene rearrangements make neobatrachian frogs an excellent model for examining the mechanisms of such vertebrate mitochondrial instability.

 

 

参考文献：

 

 

Igawa Takeshi, Kurabayashi Atsushi, Usuki Chisako, Fujii Tamotsu,Sumida Masayuki (2008). "Complete mitochondrial genomes of three neobatrachian anurans: A case study of divergence time estimation using different data and calibration settings." Gene 407(1-2): 116-129.

 

 

 

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