Molecular evolution of mitochondrial DNAs in rain frogs (Amphibia:Anura: Breviciptidae:Breviceps): Discovery of the secondary largest vertebrate mitochondrial genome and the cause of genome size increase

概要

Mitochondrial (mt) genomes of multicellular animals (metazoans) are generally
closed-circular and double-stranded DNA molecules approximately 14–20 kbp
in length (D. R. Wolstenholme, 1992; Pereira et. al., 2010; Lavrov & Pett,
2016). However, genome size ranges from 6 to 48kbp (Pereira et. al., 2010; Hou
et. al., 2016), and linear and fragmented mtDNAs have been found in
approximately 9000 animals investigated thus far (Kayal et. al., 2011; Song
et.al.,2019; NCBI organelle genome resourcesAvailable from http://www.
ncbi.nlm. http://nih.gov/genome/browse!/organelles/.). In most metazoans,
this small organelle genome encodes a typical set of 37 genes: 13 protein genes,
involved in the electron transport system of respiration, two rRNA genes (rrns),
and 22 tRNA genes (trns). In addition, animal mt genomes contain one long
noncoding region, harboring several sequence elements related to mt genomic
transcription and replication, named the control region (CR) or alternatively the
D-loop region (Pereira et. al., 2010).
The mt genomic structure of metazoans, particularly vertebrates, tends to be
conserved among closely related taxa. The same mt gene content and gene
arrangement (synteny) are observed from fishes to mammals (e.g.,
(Boore,1999; Warzecha et. al., 2018)). This genomic organization would have
arisen in a common ancestor of vertebrates and has been maintained in a wide
range of vertebrate taxa over 400 million years (Kurabayashi et. al., 2006;
Kumar et. al., 2017).
However, in some vertebrate taxa, increases in gene content due to gene
duplication and rearrangements of mt gene positions are often observed (e.g.,
(Boore,1999; Mueller & Boore, 2005)). In particular, a greater degree of
structural change in mt genomes has been reported for amphibians, especially
modern anurans (neobatrachians) (e.g., (Kurabayashi et. al., 2010; Kakehashi
et. al., 2013)). Among anurans, the members of the basal group (a
paraphyletic group generally called the “Archaeobatrachia”) retain the typical
ancestral (i.e., symplesiomorphic) mt genome organization of vertebrates
(Irisarri et. al., 2012; Zhang et. al., 2013). ...

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