Danic-Tchaleu Gwenaelle, Heurtebise Serge, Morga Benjamin, Lapègue Sylvie
IFREMER, Laboratoire de Génétique et Pathologie, F-17390 La Tremblade, France.
BMC Res Notes. 2011 Oct 12;4:400. doi: 10.1186/1756-0500-4-400.
Because of its typical architecture, inheritance and small size, mitochondrial (mt) DNA is widely used for phylogenetic studies. Gene order is generally conserved in most taxa although some groups show considerable variation. This is particularly true in the phylum Mollusca, especially in the Bivalvia. During the last few years, there have been significant increases in the number of complete mitochondrial sequences available. For bivalves, 35 complete mitochondrial genomes are now available in GenBank, a number that has more than doubled in the last three years, representing 6 families and 23 genera. In the current study, we determined the complete mtDNA sequence of O. edulis, the European flat oyster. We present an analysis of features of its gene content and genome organization in comparison with other Ostrea, Saccostrea and Crassostrea species.
The Ostrea edulis mt genome is 16 320 bp in length and codes for 37 genes (12 protein-coding genes, 2 rRNAs and 23 tRNAs) on the same strand. As in other Ostreidae, O. edulis mt genome contains a split of the rrnL gene and a duplication of trnM. The tRNA gene set of O. edulis, Ostrea denselamellosa and Crassostrea virginica are identical in having 23 tRNA genes, in contrast to Asian oysters, which have 25 tRNA genes (except for C. ariakensis with 24). O. edulis and O. denselamellosa share the same gene order, but differ from other Ostreidae and are closer to Crassostrea than to Saccostrea. Phylogenetic analyses reinforce the taxonomic classification of the 3 families Ostreidae, Mytilidae and Pectinidae. Within the Ostreidae family the results also reveal a closer relationship between Ostrea and Saccostrea than between Ostrea and Crassostrea.
Ostrea edulis mitogenomic analyses show a high level of conservation within the genus Ostrea, whereas they show a high level of variation within the Ostreidae family. These features provide useful information for further evolutionary analysis of oyster mitogenomes.
由于线粒体（mt）DNA具有典型的结构、遗传特性和较小的规模，它被广泛用于系统发育研究。尽管某些类群存在相当大的变异，但基因顺序在大多数分类单元中通常是保守的。在软体动物门中尤其如此，特别是在双壳纲中。在过去几年中，可获得的完整线粒体序列数量显著增加。对于双壳类动物，GenBank中现在有35个完整的线粒体基因组，这个数字在过去三年中增加了一倍多，代表6个科和23个属。在本研究中，我们确定了欧洲扁牡蛎O. edulis的完整mtDNA序列。我们对其基因内容和基因组组织特征进行了分析，并与其他牡蛎属、僧帽牡蛎属和太平洋牡蛎属的物种进行了比较。
Ostrea edulis的线粒体基因组长度为16320 bp，在同一条链上编码37个基因（12个蛋白质编码基因、2个rRNA和23个tRNA）。与其他牡蛎科动物一样，O. edulis的线粒体基因组包含rrnL基因的分裂和trnM的重复。O. edulis、密鳞牡蛎Ostrea denselamellosa和弗吉尼亚巨蛎Crassostrea virginica的tRNA基因集均有23个tRNA基因，这与亚洲牡蛎不同，亚洲牡蛎有25个tRNA基因（除了有明巨蛎C. ariakensis有24个）。O. edulis和O. denselamellosa具有相同的基因顺序，但与其他牡蛎科动物不同，并且与太平洋牡蛎属的关系比与僧帽牡蛎属更近。系统发育分析强化了牡蛎科、贻贝科和扇贝科这3个科的分类地位。在牡蛎科中，结果还显示牡蛎属和僧帽牡蛎属之间的关系比牡蛎属和太平洋牡蛎属之间的关系更密切。
Ostrea edulis的线粒体基因组分析表明，牡蛎属内具有高度的保守性，而在牡蛎科内则具有高度的变异性。这些特征为牡蛎线粒体基因组的进一步进化分析提供了有用的信息。
