Abstract
The sequences of the control region (D-loop) of mitochondrial DNA ( mtDNA) were obtained from five species of sturgeon. The sequences obtained had lengths between 795-813 bp. The motifs of the conserved sequence block (CBS) and termination-associated sequence (TAS) were identified in the sequences. Examination of the molecular phylogeny using maximum likelihood, maximum parsimony and Bayesian analysis shows that sturgeons form two clades representing biogeographic distribution, and the Huso is not monophyletic. Heteroplasmy in 150 fishes was due to a variable number of tandem repeats. Length of the central repeat units ranges from 78 to 82 bp with repeat sequence copies between four and six. The repeat units, followed by an imperfect repeat unit, are in high similarity between species, with 82.93% between Amur sturgeon and starlet and 90.59% between Siberian sturgeon and Russian sturgeon. Furthermore, comparing with other repeat sequences published, different species have the same repeat unit and intramolecular recombination event may happen in the repeat unit. All of these indicate that the repeat units are related to the evolution of sturgeon and arose prior to species divergence after which recombination happened.
Highlights
Abstract:The sequences of the control region (D-loop) of mitochondrial DNA were obtained from five species of sturgeon
Examination of the molecular phylogeny using maximum likelihood, maximum parsimony and Bayesian analysis shows that sturgeons form two clades representing biogeographic distribution, and the Huso is not monophyletic
Comparing with other repeat sequences published, different species have the same repeat unit and intramolecular recombination event may happen in the repeat unit
Summary
Abstract:The sequences of the control region (D-loop) of mitochondrial DNA ( mtDNA) were obtained from five species of sturgeon. Heteroplasmic band pattern (number of repeats) a:达氏鳇(4 拷贝);b:小体鲟(4 拷贝);c:史氏鲟(4 拷贝);d、e:俄罗斯鲟(5 拷贝, 4 拷贝);f、g、h:西伯利亚鲟(4 拷贝, 5 拷 贝, 6 拷贝)。 a: H. dauricus (4 copies); b: Acipenser ruthenus (4 copies); c: A. schrenckii (4 copies); d, e: A. gueldenstaedtii (5 copies, 4 copies); f, g, h: A. baerii (4 copies, 5 copies, 6 copies). MtDNA 控制区包含重复序列的拷贝数不一样, 反映在电泳上就是条带数不同。只出现 1 条条带的 个体为同质性(homoplasmic)个体,出现 2 条以上 条带的个体为异质性(heteroplasmic)个体。本研 究中被检测的 150 个个体全部出现多条条带,说明 这 5 种鲟鱼的线粒体 DNA 均具异质性,而且俄罗 斯鲟和西伯利亚鲟出现两种类型的异质性个体,说 明不同个体间 mtDNA D-loop 包含重复序列的拷贝 数也不一样。迄今为止,线粒体 DNA 异质性在很 多物种都有发现,无脊椎动物中的扇贝(Placopecten magellanicus)(Snyder et al, 1987)、果蝇(Drosophila melanogaster)(Fauron & Wolstenholme, 1976)、象 皮虫(Pissodes nemorensis)(Boyce et al, 1989)、蟋 蟀(Gryllus firmus)(Harrison et al, 1985),脊椎动 物,如两栖类(Yang et al, 1994)、爬行类(Densmore et al, 1985; Ray & Densmore, 2003; Wallis, 1987),鸟 类(Mundy et al, 1996)、哺乳类(Boursot, 1987; Casane et al, 1994; Hayasaka, 1991)等,在人类中也 有发现(Comas et al, 1995)。在鲟鱼以外的鱼类中 已 发 现 mtDNA 存在异质性特征的有黑鲈 (Dicentrarchus zabrax)(Cesaroni et al, 1997)、美 洲西鲱(Alosa sapidissima)(Bentzen et al, 1988)、 弓鳍鱼(Amia calva)(Bermingham et al, 1986)、遮 目鱼(Chanos chanos)(Ravago et al, 2002)、三斑 圆雀鲷(Dascyllus trimaculatus)(Chen et al, 2004)、 大西洋鳕(Gadus morhua)(Arnason & Rand, 1992)、 小鲤(Cyprinella spiloptera)(Broughton & Dowling, 1994)、平鲉(Sebastes mentella)(Bentzen et al, 1998) 等。
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