Comparative Genomics of Marine Mussels (Mytilus spp.) Gender Associated mtDNA: Rapidly Evolving atp8

Abstract

The unusual mode of mitochondrial DNA inheritance, with two separate: maternal (F) and paternal (M) lineages, gives unique opportunities to study the evolution of the mitochondrial genome. This system was first discovered in the marine mussels Mytilus. The three related species: Mytilus edulis, Mytilus galloprovincialis and Mytilus trossulus form a complex in which the divergence of M and F lineages pre-dates the speciation. The complete mitochondrial genomes of both lineages were known for all species except Pacific M. trossulus. Here we report, for the first time, the complete sequences of both mitochondrial genomes of Pacific M. trossulus, filling the gap. While the reported M and F genomes are highly diverged (26%), they have similar organisation. The only difference is the translocation of one tRNA gene into the long, mosaic control region of the F genome. Consistent presence of an ORF which most likely represents the atp8 gene was confirmed in both genomes. The predicted protein has characteristics expected of the functional atp8 even though the M and F versions are markedly different in length. Comparative analysis involving all three species led to the conclusion that the cause of a faster evolution of atp8 and Mytilus mtDNA in general is most likely the Compensation-Draft Feedback process coupled with relatively relaxed selection in the M lineage. Thus, we postulate that the adaptive changes may have played a role in the emergence of highly diverged, barely recognizable atp8 in Mytilus mussels.

Rapid evolution of the compact and unusual mitochondrial genome in the ctenophore, Pleurobrachia bachei

“…Among the animal groups that have been sampled, atp8 has been independently lost from the mtDNA genomes in some bivalve molluscs (Ren et al, 2010) but is found in others (e.g. in Mytilus see (Breton et al, 2010); (Smietanka et al, 2010)), secernentean nematodes (Lavrov and Brown, 2001), and platyhelminths (Le et al, 2000)). All 5 species of chaetognaths studied so far have also lost both their atp6 and 8 genes (Faure and Casanova, 2006; Helfenbein et al, 2004; Miyamoto et al, 2010).…”

Mitogenomics of southern hemisphere blue mussels (Bivalvia: Pteriomorphia): Insights into the evolutionary characteristics of the Mytilus edulis complex

“…Previous phylogenetic studies about the evolutionary relationships among Mytilus spp. have suggested that Southern Hemisphere mussels could be closely related to those mussels in the M. edulis complex of the Northern Hemisphere in which M. edulis and M. galloprovincialis are sister taxa, whereas M. trossulus is more distantly related518212223.…”

Next-generation sequencing of Dreissena polymorpha transcriptome sheds light on its mitochondrial DNA

“…Other than the structural uncertainty, this genome is reasonably complete, with the possible exception of atp8. This is not surprising given the difficulties associated with detection of this gene (Breton et al, 2010;Ś mietanka et al, 2010). The possibility that one of the anonymous ORFs is in fact encoding atp8 cannot be dismissed; however, there is also no positive argument supporting such a claim.…”