The Complete Maternally and Paternally Inherited Mitochondrial Genomes of a Freshwater Mussel Potamilus alatus (Bivalvia: Unionidae)

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.

Morphology of Mitochondria in Syncytial Annelid Female Germ-Line Cyst Visualized by Serial Block-Face SEM

“…Additionally, as was shown in the previous study, in late oogenesis in E. albidus a large vitellogenic oocyte surrounds the rest of the o spring [81,82]. is is especially important because, as is well known, all mitochondria in future organisms are inherited from only the oocyte [83] with only a few exceptions that occur in some bivalves [84,85].…”

The complete mitochondrial genome of parasitic nematode Camallanus cotti: extreme discontinuity in the rate of mitogenomic architecture evolution within the Chromadorea class

“…This is common, and believed to be a consequence of lesser evolutionary constraints on tRNA sequences [ 59 ]. However, nad4l is a very small gene (234 bp in C. cotti ), which also appears to be under lesser evolutionary constraints as mitogenomes of some groups of animals often exhibit overlaps involving this gene [ 60 , 61 ]. Thus we don’t deem this overlap particularly suspicious.…”

“…Genome was sequenced broadly following the procedure described before [ 60 , 80 ]. After soaking a single adult nematode (≈3.5 cm) in TE buffer (pH 8.0) overnight to remove the ethanol, total genomic DNA was extracted using the Aidlab DNA extraction kit (Aidlab Biotechnologies, Beijing).…”

Sequencing of complete mitochondrial genomes confirms synonymization of Hyalomma asiaticum asiaticum and kozlovi, and advances phylogenetic hypotheses for the Ixodidae

“…sculptum [ 21 ], but metastriate ticks belonging to the Rhipicephalus genus appear to exhibit only an identical (7 bp) atp6 / atp8 overlap [ 20 ]. Both overlaps include very small genes ( atp8 = 162 bp, nad4L = 276 bp), which appear to be under lesser evolutionary constraints, as atp8 is often absent from mitogenomes [ 25 ], whereas the nad4 / nad4L overlap is common in mitogenomes of many different groups of animals [ 17 , 18 , 26 – 28 ]. Although annotation of the nad1 gene is usually very difficult in hard ticks, often producing unusually large gene overlaps [ 21 , 29 ], nad1 genes in the studied two mitogenomes are very similar to closely related Rhipicephalus orthologs ( S1 File ), with an overlap of only 4 bp with the neighbouring tRNA-Glu ( Table 1 ).…”