Université de Montréal, Département de Sciences Biologiques, Montréal, H2V 2S9, Quebéc, Canada.
Università di Bologna, Dipartimento di Scienze Biologiche, Geologiche ed Ambientali (BiGeA), Bologna, 40126, Italy.
Sci Rep. 2017 May 8;7(1):1551. doi: 10.1038/s41598-017-01708-1.
Doubly uniparental inheritance (DUI) describes a mode of mtDNA transmission widespread in gonochoric freshwater mussels (Bivalvia: Palaeoheterodonta: Unionida). In this system, both female- and male-transmitted mtDNAs, named F and M respectively, coexist in the same species. In unionids, DUI is strictly correlated to gonochorism and to the presence of the atypical open reading frames (ORFans) F-orf and M-orf, respectively inside F and M mtDNAs, which are hypothesized to participate in sex determination. However, DUI is not found in all three Unionida superfamilies (confirmed in Hyrioidea and Unionoidea but not in Etherioidea), raising the question of its origin in these bivalves. To reconstruct the co-evolution of DUI and of ORFans, we sequenced the mtDNAs of four unionids (two gonochoric with DUI, one gonochoric and one hermaphroditic without DUI) and of the related gonochoric species Neotrigonia margaritacea (Palaeoheterodonta: Trigoniida). Our analyses suggest that rearranged mtDNAs appeared early during unionid radiation, and that a duplicated and diverged atp8 gene evolved into the M-orf associated with the paternal transmission route in Hyrioidea and Unionoidea, but not in Etherioidea. We propose that novel mtDNA-encoded genes can deeply influence bivalve sex determining systems and the evolution of the mitogenomes in which they occur.
双倍单亲遗传 (DUI) 描述了一种在雌雄异体淡水贻贝类（双壳纲：古异齿亚纲：贻贝目）中广泛存在的 mtDNA 传递模式。在这个系统中，雌性和雄性传递的 mtDNA 分别命名为 F 和 M，它们共存于同一物种中。在贻贝类中，DUI 与雌雄异体和存在非典型的开放阅读框 (ORFans) F-orf 和 M-orf 严格相关，分别位于 F 和 M mtDNA 内，它们被假设参与性别决定。然而，DUI 并非在所有三个贻贝超科（Hyrioidea 和 Unionoidea 中得到证实，但在 Etherioidea 中没有）中发现，这引发了 DUI 在这些双壳类动物中的起源问题。为了重建 DUI 和 ORFans 的共同进化，我们对 4 种贻贝（2 种具有 DUI 的雌雄异体，1 种具有 DUI 的雌雄异体和 1 种无 DUI 的雌雄同体）和相关的雌雄异体物种 Neotrigonia margaritacea（古异齿亚纲：Trigoniida）的 mtDNA 进行了测序。我们的分析表明，重排的 mtDNA 在贻贝辐射早期出现，并且一个复制和分化的 atp8 基因演变成与 Hyrioidea 和 Unionoidea 中的父系传递途径相关的 M-orf，但在 Etherioidea 中没有。我们提出，新的 mtDNA 编码基因可以深刻影响双壳类动物的性别决定系统和它们发生的线粒体基因组的进化。
