Université de Poitiers, UMR CNRS 7267, Ecologie et Biologie des Interactions, Equipe Ecologie Evolution Symbiose, 40 Avenue du Recteur Pineau, 86022 Poitiers CEDEX, France.
Genome. 2012 Mar;55(3):234-44. doi: 10.1139/g2012-008. Epub 2012 Feb 29.
Metazoan mitochondrial DNA (mtDNA) is generally composed of circular monomeric molecules. However, a few exceptions do exist and among them two terrestrial isopods Armadillidium vulgare and Porcellionides pruinosus have an atypical mtDNA composed of linear monomers associated with circular "head-to-head" dimers: a very unusual structure for animal mtDNA genome. To assess the distribution of this atypical mtDNA among isopods, we performed RFLP and Southern blot analyses on mtDNA of 16 terrestrial (Oniscidea family) and two aquatic isopod species: the marine Sphaeroma serratum (suborder Flabellifera, sister group of Oniscidea) and the freshwater Asellus aquaticus (Asellota, early derived taxon of isopod). The atypical mtDNA structure was observed in 15 terrestrial isopod species and A. aquaticus, suggesting a wide distribution of atypical mtDNA among isopods. However, a typical metazoan mtDNA structure was detected in the marine isopod S. serratum and the Oniscidea Ligia oceanica . Our results suggest two possible scenarios: an early origin of the atypical mtDNA in isopods followed by reversion to the typical ancestral mtDNA structure for several species, or a convergent appearance of the atypical mtDNA structure in two isopod suborders. We compare this distribution of the atypical mtDNA structure with the presence of a heteroplasmy also observed in the mtDNA of several terrestrial isopod species. We discuss if this transmitted heteroplasmy is vectored by the atypical mtDNA and its impact on the maintenance of the atypical mtDNA in isopods.
后生动物线粒体 DNA（mtDNA）通常由圆形单体分子组成。然而，也存在一些例外，其中两种陆生等足目动物 Armadillidium vulgare 和 Porcellionides pruinosus 的 mtDNA 是非典型的，由与圆形“头对头”二聚体相关的线性单体组成：这是动物 mtDNA 基因组的一种非常不寻常的结构。为了评估这种非典型 mtDNA 在等足目动物中的分布，我们对 16 种陆生（等足目科）和两种水生等足目动物的 mtDNA 进行了 RFLP 和 Southern 印迹分析：海洋 Sphaeroma serratum（瓣足目，等足目姐妹群）和淡水 A. aquaticus（Asellota，等足目早期衍生类群）。在 15 种陆生等足目动物和 A. aquaticus 中观察到了非典型 mtDNA 结构，表明非典型 mtDNA 在等足目动物中广泛分布。然而，在海洋等足目 S. serratum 和等足目 Ligia oceanica 中检测到了典型的后生动物 mtDNA 结构。我们的结果表明有两种可能的情况：非典型 mtDNA 可能在等足目动物中早期起源，然后几种物种的 mtDNA 结构恢复为典型的祖先 mtDNA 结构，或者两种等足目亚目同时出现非典型 mtDNA 结构。我们将这种非典型 mtDNA 结构的分布与在几种陆生等足目动物的 mtDNA 中观察到的异质性进行了比较。我们讨论了这种传递的异质性是否由非典型 mtDNA 载体，并讨论了其对等足目动物中非典型 mtDNA 维持的影响。
