Abstract
Doubly uniparental inheritance (DUI) of mitochondrial DNA, found only in some bivalve families and characterized by the existence of gender-associated mtDNA lineages that are inherited through males (M-type) or females (F-type), is one of the very few exceptions to the general rule of strict maternal mtDNA inheritance in animals. M-type sequences are often undetected and hence still underrepresented in the GenBank, which hinders the progress of the understanding of the DUI phenomenon. We have sequenced and analyzed the complete M and F mitogenomes of a freshwater mussel, Potamilus alatus. The M-type was 493 bp longer (M = 16 560, F = 16 067 bp). Gene contents, order and the distribution of genes between L and H strands were typical for unionid mussels. Candidates for the two ORFan genes (forf and morf) were found in respective mitogenomes. Both mitogenomes had a very similar A+T bias: F = 61% and M = 62.2%. The M mitogenome-specific cox2 extension (144 bp) is much shorter than in other sequenced unionid mitogenomes (531–576 bp), which might be characteristic for the Potamilus genus. The overall topology of the phylogenetic tree is in very good agreement with the currently accepted phylogenetic relationships within the Unionidae: both studied sequences were placed within the Ambleminae subfamily clusters in the corresponding M and F clades.
Highlights
Uniparental inheritance (DUI), widespread through the class Bivalvia, is one of the most striking exceptions to the general rule of strict maternal inheritance of mitochondrial DNA in animals [1]
M type sequences are underrepresented in the GenBank, with only ten currently available. As this hinders the progress of the understanding of the Doubly uniparental inheritance (DUI) phenomenon, we have identified, sequenced, characterized, compared and phylogenetically analysed both F and M mitogenomes of a freshwater mussel, the pink heelsplitter Potamilus alatus (Unionidae: Ambleminae)
The F genome is somewhat larger than the usual unionid F mitogenomes, whereas the M genome is shorter than most other unionid counterparts [18,20,35,36,37,38,39]. Both genomes contained all 37 genes commonly found in animal mitochondrial DNA (mtDNA) [40]: 13 protein-coding genes, 22 tRNAs and two (12S and 16S) rRNAs
Summary
Uniparental inheritance (DUI), widespread through the class Bivalvia, is one of the most striking exceptions to the general rule of strict maternal inheritance of mitochondrial DNA (mtDNA) in animals [1]. DUI is an ancient system, likely around 500 million years old [2], characterized by the existence of gender-associated mtDNA lineages that are inherited through males (M type) or females (F type). Females are homoplasmic: they have only the F. M and F Mitogenomes of Potamilus alatus. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
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