Doubly Uniparental Inheritance of mtDNA: An Unappreciated Defiance of a General Rule.

We recount the basic observations about doubly uniparental inheritance (DUI) of mtDNA in bivalvian mollusks with an emphasis on those that were obtained from work in Mytilus and appeared after the review by Zouros (Evol Biol 40:1-31, 2013). Using this information, we present a new model about DUI that is a revised version of previously suggested models. The model can be summarized as follows.

A protein binding site in the M mitochondrial genome of Mytilus galloprovincialis may be responsible for its paternal transmission.

Sea mussels (genus Mytilus) have two mitochondrial genomes in obligatory co-existence, one that is transmitted through the egg and the other through the sperm. The phenomenon, known as Doubly Uniparental Inheritance (DUI) of mitochondrial DNA (mtDNA), is presently known to occur in more than 40 molluscan bivalve species. Females and the somatic tissues of males contain mainly the maternal (F) genome.

Does the ORF in the control region of Mytilus mtDNA code for a protein product?

The control region of the mtDNA of Mytilus is known to contain sequences that determine whether the genome will be paternally or maternally transmitted. An open reading frame (ORF) in this region raised suspicion that it may code for a protein involved in this mechanism. An analysis of the mtDNA transcriptome failed to produce evidence for this hypothesis.

The rRNA and tRNA transcripts of maternally and paternally inherited mitochondrial DNAs of Mytilus galloprovincialis suggest presence of a "degradosome" in mussel mitochondria and necessitate the re-annotation of the l-rRNA/CR boundary.

Species of the genus Mytilus carry two mitochondrial genomes in obligatory coexistence; one transmitted though the eggs (the F type) and one through the sperm (the M type). We have studied the 3' and 5' ends of rRNA and tRNA transcripts using RT-PCR and RNA circularization techniques in both the F and M genomes of Mytilus galloprovincialis. We have found polyadenylated and non-adenylated transcripts for both ribosomal and transfer RNAs.

The mRNAs of maternally and paternally inherited mtDNAs of the mussel Mytilus galloprovincialis: start/end points and polycistronic transcripts.

Transcription of the mitochondrial genomes of the Mediterranean mussel Mytilus galloprovincialis has been studied by RT-PCR and RNA circularization. This species has an egg-transmitted (F) and a sperm-transmitted (M) mitochondrial genome, in accordance with the doubly uniparental inheritance (DUI) pattern of mtDNA transmission. The primary transcript is cleaved into ten transcripts, eight of which are monocistronic, one is tricistronic and one is most likely, but not certainly, bicistronic.

Homologous recombination between highly diverged mitochondrial sequences: examples from maternally and paternally transmitted genomes.

Homologous recombination is restricted to sequences of low divergence. This is attributed to the mismatch repairing system (MMR), which does not allow recombination between sequences that are highly divergent. This acts as a safeguard against recombination between nonhomologous sequences that could result in genome imbalance.

The atypical presence of the paternal mitochondrial DNA in somatic tissues of male and female individuals of the blue mussel species Mytilus galloprovincialis.

Background: In animals mtDNA inheritance is maternal except in certain molluscan bivalve species which have a paternally inherited mitochondrial genome (genome M) along with the standard maternal one (genome F). Normally, the paternal genome occurs in the male gonad, but it can be often found, as a minority, in somatic tissues of males and females. This may happen in two ways.

Correlation of the 4977 bp mitochondrial DNA deletion with human sperm dysfunction.

Background: Several studies have examined the association between mitochondrial DNA (mtDNA) deletions, in particular the "common" 4977-bp deletion, and human sperm dysfunction, but have produced contradictory results.

Findings: Here we show that PCR slippage and primer miss-match to nuclear DNA may lead to overestimates in the frequency of deletions. Our investigation resolves this issue and gives strong negative correlation between the proportion of the "common" deletion and sperm motility.

The control region of maternally and paternally inherited mitochondrial genomes of three species of the sea mussel genus Mytilus.

Species of the mussel genus Mytilus possess maternally and paternally transmitted mitochondrial genomes. In the interbreeding taxa Mytilus edulis and M. galloprovincialis, several genomes of both types have been fully sequenced.

Nucleotide content gradients in maternally and paternally inherited mitochondrial genomes of the mussel Mytilus.

Several studies have shown that in vertebrate mtDNAs the nucleotide content at fourfold degenerate sites is well correlated with the site's time of exposure to the single-strand state, as predicted from the asymmetrical model of mtDNA replication. Here we examine whether the same explanation may hold for the regional variation in nucleotide content in the maternal and paternal mtDNAs of the mussel Mytilus galloprovincialis. The origin of replication of the heavy strand (O(H)) of these genomes has been previously established.

A mitochondrial genome with a reversed transmission route in the Mediterranean mussel Mytilus galloprovincialis.

Species of the marine mussel genus Mytilus are known to contain two mitochondrial genomes, one transmitted maternally (the F genome) and the other paternally (the M genome). The two genomes have diverged by more than 20% in DNA sequence. Here we present the complete sequence of a third genome, genome C, which we found in the sperm of a Mytilus galloprovincialis male.

Inference of evolutionary patterns of the land snail Albinaria in the Aegean archipelago: is vicariance enough?

Mitochondrial DNA sequences from 16S rRNA and ATPase8 genes were used to investigate phylogeographic patterns of the land snail Albinaria (Gastropoda: Clausiliidae) in the Aegean archipelago. Forty-two populations of Albinaria were analyzed, mainly A. turrita, A.

No evidence for presence of maternal mitochondrial DNA in the sperm of Mytilus galloprovincialis males.

Species of the mussel family Mytilidae have a special mitochondrial DNA (mtDNA) transmission system, known as doubly uniparental inheritance (DUI), which consists of a maternally inherited (F) and a paternally inherited (M) mitochondrial genome. Females are normally homoplasmic for the F genome and males are heteroplasmic mosaics, with their somatic tissues dominated by the maternal and their gonads dominated by the paternal genome. Several studies have indicated that the maternal genome may often be present in the male germ line.

Multiple events are responsible for an insertion in a paternally inherited mitochondrial genome of the mussel Mytilus galloprovincialis.

In a sperm-transmitted mtDNA of Mytilus galloprovincialis we found an insertion that is not present in the typical genome and whose origin can be explained by a sequence of three events: a tandem duplication, a nonhomologous recombination, and a deletion. Unless such events are extremely rare in this species, the identical gene arrangement of the two gender-specific genomes should imply strong selection for same gene order and size.

The complete maternal and paternal mitochondrial genomes of the Mediterranean mussel Mytilus galloprovincialis: implications for the doubly uniparental inheritance mode of mtDNA.

The maternal (F) and paternal (M) mitochondrial genomes of the mussel Mytilus galloprovincialis have diverged by about 20% in nucleotide sequence but retained identical gene content and gene arrangement and similar nucleotide composition and codon usage bias. Both lack the ATPase8 subunit gene, have two tRNAs for methionine and a longer open-reading frame for cox3 than seen in other mollusks. Between the F and M genomes, tRNAs are most conserved followed by rRNAs and protein-coding genes, even though the degree of divergence varies considerably among the latter.

Evidence that the large noncoding sequence is the main control region of maternally and paternally transmitted mitochondrial genomes of the marine mussel (Mytilus spp.).

Both the maternal (F-type) and paternal (M-type) mitochondrial genomes of the Mytilus species complex M. edulis/galloprovincialis contain a noncoding sequence between the l-rRNA and the tRNA(Tyr) genes, here called the large unassigned region (LUR). The LUR, which is shorter in M genomes, is capable of forming secondary structures and contains motifs of significant sequence similarity with elements known to have specific functions in the sea urchin and the mammalian control region.

MITOCHONDRIAL PHYLOGEOGRAPHY OF THE LAND SNAIL ALBINARIA IN CRETE: LONG-TERM GEOLOGICAL AND SHORT-TERM VICARIANCE EFFECTS.

The land snail genus Albinaria exhibits an extreme degree of morphological differentiation in Greece, especially in the island of Crete. Twenty-six representatives of 17 nominal species and a suspected hybrid were examined by sequence analysis of a PCR-amplified mitochondrial DNA fragment of the large rRNA subunit gene. Maximum parsimony and neighbor-joining phylogenetic analyses demonstrate a complex pattern of speciation and differentiation and suggest that Albinaria species from Crete belong to at least three distinct monophyletic groups, which, however, are not monophyletic with reference to the genus as a whole.