Department of Biology, Acadia University, Wolfville, NS, Canada.
Department of Biology, Dalhousie University, Halifax, NS, Canada.
BMC Genomics. 2018 Mar 27;19(1):221. doi: 10.1186/s12864-018-4583-3.
Doubly uniparental inheritance (DUI) of mitochondrial DNA in bivalves is a fascinating exception to strictly maternal inheritance as practiced by all other animals. Recent work on DUI suggests that there may be unique regions of the mitochondrial genomes that play a role in sex determination and/or sexual development in freshwater mussels (order Unionoida). In this study, one complete mitochondrial genome of the hermaphroditic swan mussel, Anodonta cygnea, is sequenced and compared to the complete mitochondrial genome of the gonochoric duck mussel, Anodonta anatina. An in silico assessment of novel proteins found within freshwater bivalve species (known as F-, H-, and M-open reading frames or ORFs) is conducted, with special attention to putative transmembrane domains (TMs), signal peptides (SPs), signal cleavage sites (SCS), subcellular localization, and potential control regions. Characteristics of TMs are also examined across freshwater mussel lineages.
In silico analyses suggests the presence of SPs and SCSs and provides some insight into possible function(s) of these novel ORFs. The assessed confidence in these structures and functions was highly variable, possibly due to the novelty of these proteins. The number and topology of putative TMs appear to be maintained among both F- and H-ORFs, however, this is not the case for M-ORFs. There does not appear to be a typical control region in H-type mitochondrial DNA, especially given the loss of tandem repeats in unassigned regions when compared to F-type mtDNA.
In silico analyses provides a useful tool to discover patterns in DUI and to navigate further in situ analyses related to DUI in freshwater mussels. In situ analysis will be necessary to further explore the intracellular localizations and possible role of these open reading frames in the process of sex determination in freshwater mussel.
双单亲遗传（DUI）的线粒体 DNA 在双壳类动物中是一个令人着迷的例外，因为所有其他动物都严格遵循母系遗传。最近关于 DUI 的研究表明，线粒体基因组中可能存在一些独特的区域，这些区域在淡水贻贝类（Unionoida 目）的性别决定和/或性发育中发挥作用。在这项研究中，我们对雌雄同体的 Swan 贻贝（Anodonta cygnea）的完整线粒体基因组进行了测序，并与雌雄异体的 Duck 贻贝（Anodonta anatina）的完整线粒体基因组进行了比较。对在淡水双壳类物种中发现的新型蛋白质（称为 F-、H-和 M-开放阅读框或 ORFs）进行了计算机评估，特别关注潜在的跨膜结构域（TMs）、信号肽（SPs）、信号切割位点（SCS）、亚细胞定位和潜在的调控区。还检查了 TMs 在淡水贻贝类中的特征。
计算机分析表明存在 SPs 和 SCS，并为这些新型 ORFs 的可能功能提供了一些见解。这些结构和功能的置信度高度可变，可能是由于这些蛋白质的新颖性所致。F-和 H-ORFs 中的推定 TM 数量和拓扑似乎得到了维持，但 M-ORFs 并非如此。在 H 型线粒体 DNA 中似乎没有典型的调控区，特别是与 F 型 mtDNA 相比，未分配区域中的串联重复序列丢失。
计算机分析为发现 DUI 中的模式以及为 DUI 在淡水贻贝类中的进一步原位分析提供了有用的工具。需要进行原位分析，以进一步探讨这些开放阅读框在淡水贻贝性别决定过程中的细胞内定位和可能作用。
