Role‐reversal of gender‐associated mitochondrial DNA affects mitochondrial function in Mytilus edulis (Bivalvia: Mytilidae)

Abstract

Mussel species of the genus Mytilus possess an unusual system of mitochondrial DNA (mtDNA) transmission termed doubly uniparental inheritance. They are characterized by the presence of two highly divergent gender-associated mtDNA genomes (often with>20 and>10% divergences in DNA and amino acid sequences, respectively) that are inherited either maternally (F mtDNA) or paternally (M mtDNA). Females are typically homoplasmic for the F mtDNA and males are heteroplasmic with the F mtDNA being most common in all tissues except the gonad that is dominated by the M mtDNA. Collectively, males are polymorphic for two classes of M mtDNAs known as the "standard male" and "recently masculinized" M types (SM and RM, respectively). The coding portions of the RM mtDNA genome differ from the SM mtDNA by as much as the maternally inherited F mtDNA genome differs from the SM type. Because the SM and RM types exhibit considerable amino acid sequence divergence, we hypothesized that these differences could affect mitochondrial respiratory chain complex enzyme activities. To test this hypothesis, the activity of the major mitochondrial respiratory chain complexes (complexes II, I+III and IV) as well as the activity of citrate synthase were measured on gonad samples from males containing either the SM or RM mtDNA. Our data demonstrate that the mitochondrial subunits encoded by the RM mtDNA are associated with higher enzymatic activities than the gene products of the SM mtDNA.

Mitochondrial genomes and Doubly Uniparental Inheritance: new insights from Musculista senhousia sex-linked mitochondrial DNAs (Bivalvia Mytilidae)

“…No. AB055625 and AB055624) (see also [59]). In other mollusks, a relatively small number of mitochondrial genes are transcribed from the second strand.…”

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

“…Comparisons of F and M mtDNA sequences of Mytilus species have shown that the M mitogenome evolves more quickly than the F mitogenome242829. From these studies, it appears that both genomes experience purifying selection, but this selection is relatively relaxed for the M mtDNA in Mytilus spp 24282930…”

Interactions between nuclear genes and a foreign mitochondrial genome in the redbelly dace Chrosomus eos

“…According to Melvin et al (2008), an amino acid change is considered likely to affect complex IV activity if its property is changed and/or if the site is in close contact with another subunit. Indeed, substitutions able to modify interactions between nuclear and mitochondrial subunits at positions of structural importance to enzyme function are known to modify enzymatic activity (Barrientos et al, 2000;Melvin et al, 2008;Breton et al, 2009). Therefore, the change at residue 41 on the COX3 mitochondrial subunit could potentially explain the difference of complex IV activity observed between wild type and cybrids.…”