scholarly journals Mitochondria, mutations and sex: a new hypothesis for the evolution of sex based on mitochondrial mutational erosion

2015 ◽  
Author(s):  
Justin Havird ◽  
Matthew D Hall ◽  
Damian Dowling
Keyword(s):  
Mitochondrial Dna ◽  
Mutation Accumulation ◽  
High Rate ◽  
Metabolic Effects ◽  
Evolution Of Sex ◽  
Mitochondrial Mutation ◽  
Sexual Recombination ◽  
Selection For ◽  
New Hypothesis ◽  
Lines Of Evidence

The evolution of sex in eukaryotes represents a paradox, given the “two-fold” fitness cost it incurs. We hypothesize that the mutational dynamics of the mitochondrial genome would have favoured the evolution of sexual reproduction. Mitochondrial DNA (mtDNA) exhibits a high mutation rate across most eukaryote taxa, and several lines of evidence suggest this high rate is an ancestral character. This seems inexplicable given mtDNA-encoded genes underlie the expression of life's most salient functions, including energy conversion. We propose that negative metabolic effects linked to mitochondrial mutation accumulation would have invoked selection for sexual recombination between divergent host nuclear genomes in early eukaryote lineages. This would provide a mechanism by which recombinant host genotypes could be rapidly shuffled and screened for the presence of compensatory modifiers that offset mtDNA-induced harm. Under this hypothesis, recombination provides the genetic variation necessary for compensatory nuclear coadaptation to keep pace with mitochondrial mutation accumulation.

scholarly journals The causes of mutation accumulation in mitochondrial genomes

2009 ◽  
Vol 276 (1660) ◽  
pp. 1201-1209 ◽  
Author(s):  
Maurine Neiman ◽  
Douglas R Taylor
Keyword(s):  
Mutation Accumulation ◽  
High Rate ◽  
Mitochondrial Genomes ◽  
Sequence Evolution ◽  
Deleterious Mutations ◽  
Effective Population ◽  
Mitochondrial Mutation ◽  
Evolutionary Forces ◽  
Body Of Knowledge ◽  
Primary Determinant

A fundamental observation across eukaryotic taxa is that mitochondrial genomes have a higher load of deleterious mutations than nuclear genomes. Identifying the evolutionary forces that drive this difference is important to understanding the rates and patterns of sequence evolution, the efficacy of natural selection, the maintenance of sex and recombination and the mechanisms underlying human ageing and many diseases. Recent studies have implicated the presumed asexuality of mitochondrial genomes as responsible for their high mutational load. We review the current body of knowledge on mitochondrial mutation accumulation and recombination, and conclude that asexuality, per se , may not be the primary determinant of the high mutation load in mitochondrial DNA (mtDNA). Very little recombination is required to counter mutation accumulation, and recent evidence suggests that mitochondrial genomes do experience occasional recombination. Instead, a high rate of accumulation of mildly deleterious mutations in mtDNA may result from the small effective population size associated with effectively haploid inheritance. This type of transmission is nearly ubiquitous among mitochondrial genomes. We also describe an experimental framework using variation in mating system between closely related species to disentangle the root causes of mutation accumulation in mitochondrial genomes.

scholarly journals On the Rate and Linearity of Viability Declines in Drosophila Mutation-Accumulation Experiments: Genomic Mutation Rates and Synergistic Epistasis Revisited

Genetics ◽  
2004 ◽  
Vol 166 (2) ◽  
pp. 797-806 ◽  
Author(s):  
James D Fry
Keyword(s):  
Mutation Rate ◽  
Average Rate ◽  
Natural Populations ◽  
Mutation Accumulation ◽  
High Rate ◽  
Deleterious Mutations ◽  
Order Of Magnitude ◽  
Contamination Event ◽  
Genomic Mutation ◽  
The 1960S

Abstract High rates of deleterious mutations could severely reduce the fitness of populations, even endangering their persistence; these effects would be mitigated if mutations synergize each others’ effects. An experiment by Mukai in the 1960s gave evidence that in Drosophila melanogaster, viability-depressing mutations occur at the surprisingly high rate of around one per zygote and that the mutations interact synergistically. A later experiment by Ohnishi seemed to support the high mutation rate, but gave no evidence for synergistic epistasis. Both of these studies, however, were flawed by the lack of suitable controls for assessing viability declines of the mutation-accumulation (MA) lines. By comparing homozygous viability of the MA lines to simultaneously estimated heterozygous viability and using estimates of the dominance of mutations in the experiments, I estimate the viability declines relative to an appropriate control. This approach yields two unexpected conclusions. First, in Ohnishi’s experiment as well as in Mukai’s, MA lines showed faster-than-linear declines in viability, indicative of synergistic epistasis. Second, while Mukai’s estimate of the genomic mutation rate is supported, that from Ohnishi’s experiment is an order of magnitude lower. The different results of the experiments most likely resulted from differences in the starting genotypes; even within Mukai’s experiment, a subset of MA lines, which I argue probably resulted from a contamination event, showed much slower viability declines than did the majority of lines. Because different genotypes may show very different mutational behavior, only studies using many founding genotypes can determine the average rate and distribution of effects of mutations relevant to natural populations.

A new Liopeltis Fitzinger, 1843 (Squamata: Colubridae) from Pulau Tioman, Peninsular Malaysia

Zootaxa ◽  
2020 ◽  
Vol 4766 (3) ◽  
pp. 472-484
Author(s):  
HANNAH E. SOM ◽  
L. LEE GRISMER ◽  
PERRY L. JR. WOOD ◽  
EVAN S. H. QUAH ◽  
RAFE M. BROWN ◽  
...  
Keyword(s):  
Mitochondrial Dna ◽  
New Species ◽  
Dna Sequence ◽  
Rare Species ◽  
Sequence Data ◽  
Peninsular Malaysia ◽  
Tropical Asia ◽  
Dna Sequence Data ◽  
A New Species ◽  
Lines Of Evidence

Liopeltis is a genus of poorly known, infrequently sampled species of colubrid snakes in tropical Asia. We collected a specimen of Liopeltis from Pulau Tioman, Peninsular Malaysia, that superficially resembled L. philippina, a rare species that is endemic to the Palawan Pleistocene Aggregate Island Complex, western Philippines. We analyzed morphological and mitochondrial DNA sequence data from the Pulau Tioman specimen and found distinct differences to L. philippina and all other congeners. On the basis of these corroborated lines of evidence, the Pulau Tioman specimen is described as a new species, L. tiomanica sp. nov. The new species occurs in sympatry with L. tricolor on Pulau Tioman, and our description of L. tiomanica sp. nov. brings the number of endemic amphibians and reptiles on Pulau Tioman to 12. 

Precise assignment of the heavy-strand promoter of mouse mitochondrial DNA: cognate start sites are not required for transcriptional initiation

1986 ◽  
Vol 6 (9) ◽  
pp. 3262-3267
Author(s):  
D D Chang ◽  
D A Clayton
Keyword(s):  
Mitochondrial Dna ◽  
Dna Sequences ◽  
High Rate ◽  
In Vitro Assays ◽  
Regulatory Sequences ◽  
Sufficient Information ◽  
Mitochondrial Rna ◽  
Loop Region ◽  
Heavy Strand

Transcription of the heavy strand of mouse mitochondrial DNA starts from two closely spaced, distinct sites located in the displacement loop region of the genome. We report here an analysis of regulatory sequences required for faithful transcription from these two sites. Data obtained from in vitro assays demonstrated that a 51-base-pair region, encompassing nucleotides -40 to +11 of the downstream start site, contains sufficient information for accurate transcription from both start sites. Deletion of the 3' flanking sequences, including one or both start sites to -17, resulted in the initiation of transcription by the mitochondrial RNA polymerase from alternative sites within vector DNA sequences. This feature places the mouse heavy-strand promoter uniquely among other known mitochondrial promoters, all of which absolutely require cognate start sites for transcription. Comparison of the heavy-strand promoter with those of other vertebrate mitochondrial DNAs revealed a remarkably high rate of sequence divergence among species.

Escape of mitochondrial DNA to the nucleus in yme1 yeast is mediated by vacuolar-dependent turnover of abnormal mitochondrial compartments

1998 ◽  
Vol 111 (16) ◽  
pp. 2455-2464 ◽  
Author(s):  
C.L. Campbell ◽  
P.E. Thorsness
Keyword(s):  
Alkaline Phosphatase ◽  
Mitochondrial Dna ◽  
High Rate ◽  
Wild Type ◽  
Yeast Saccharomyces Cerevisiae ◽  
Mitochondrial Defects ◽  
Proteinase A ◽  
Abnormal Mitochondria ◽  
Wild Type Yeast

Inactivation of Yme1p, a mitochondrially-localized ATP-dependent metallo-protease in the yeast Saccharomyces cerevisiae, causes a high rate of DNA escape from mitochondria to the nucleus as well as pleiotropic functional and morphological mitochondrial defects. The evidence presented here suggests that the abnormal mitochondria of a yme1 strain are degraded by the vacuole. First, electron microscopy of Yme1p-deficient strains revealed mitochondria physically associated with the vacuole via electron dense structures. Second, disruption of vacuolar function affected the frequency of mitochondrial DNA escape from yme1 and wild-type strains. Both PEP4 or PRC1 gene disruptions resulted in a lower frequency of mitochondrial DNA escape. Third, an in vivo assay that monitors vacuole-dependent turnover of the mitochondrial compartment demonstrated an increased rate of mitochondrial turnover in yme1 yeast when compared to the rate found in wild-type yeast. In this assay, vacuolar alkaline phosphatase, encoded by PHO8, was targeted to mitochondria in a strain bearing disruption to the genomic PHO8 locus. Maturation of the mitochondrially localized alkaline phosphatase pro-enzyme requires proteinase A, which is localized in the vacuole. Therefore, alkaline phosphatase activity reflects vacuole-dependent turnover of mitochondria. This assay reveals that mitochondria of a yme1 strain are taken up by the vacuole more frequently than mitochondria of an isogenic wild-type strain when these yeast are cultured in medium necessitating respiratory growth. Degradation of abnormal mitochondria is one pathway by which mitochondrial DNA escapes and migrates to the nucleus.

Responses to selection for seed weight and seedling vigour in Phalaris

1974 ◽  
Vol 25 (1) ◽  
pp. 33 ◽  
Author(s):  
RJ Clements ◽  
BDH Latter
Keyword(s):  
Seed Weight ◽  
Leaf Size ◽  
High Rate ◽  
Hybrid Population ◽  
Direct Selection ◽  
Seedling Vigour ◽  
Developing Seed ◽  
Selection For ◽  
Leaf Appearance ◽  
Rate Of Leaf Appearance

Significant responses were obtained to three cycles of directional selection for seed weight, seedling weight, leaf size, and rate of leaf appearance in a broadly based P. tuberosa population. The responses were linear in both the high and low directions, and the realized heritabilities of the characters were 0.35, 0.12, 0.61, and 0.38 respectively. Leaf size was positively correlated with seedling weight and negatively correlated with rate of leaf appearance. Selection for high seed weight resulted in marked correlated increases in seedling weight and leaf size, but selection for heavy seedlings or large leaves did not significantly increase seed weight. Selection for light seedling or small leaves, on the other hand, led to a correlated decrease in seed weight. A hybrid population obtained by crossing the parents of the high leaf size line with those of the high rate of leaf appearance line had seedlings nearly as heavy as those of the high seedling weight line and significantly heavier than the mean of the two parent lines. This effect, together with other evidence of the effect of inbreeding on all characters, indicated some degree of directional dominance, particularly for leaf size. Plants in the high seed weight line matured earlier and had fewer heads. However, because they had heavier seeds and more seeds per head, there was no apparent decrease in seed yield per plant in this line, compared with the control population. Areas of the spikelets and leaf sheaths were greater in the high seed weight line, but areas of the flag and penultimate leaves were unchanged, and there was no evidence that increases in seed weight were accompanied by increases in the amount of photosynthetic area available to each developing seed. It was concluded that selection for large leaves is a relatively efficient means of increasing seedling weight, but results in a reduced rate of leaf appearance and possibly a slower rate of tillering. Selection for seed weight, though inefficient, exploits a source of variation largely untapped by direct selection for seedling weight.

scholarly journals Mitochondrial and Metabolic Effects of Nucleoside Reverse Transcriptase Inhibitors (NRTIs) in Mice Receiving One of Five Single- and Three Dual-NRTI Treatments

2003 ◽  
Vol 47 (11) ◽  
pp. 3384-3392 ◽  
Author(s):  
Reine Note ◽  
Caroline Maisonneuve ◽  
Philippe Lettéron ◽  
Gilles Peytavin ◽  
Fatima Djouadi ◽  
...  
Keyword(s):  
Mitochondrial Dna ◽  
Reverse Transcriptase ◽  
Ketone Bodies ◽  
Metabolic Effects ◽  
Reverse Transcriptase Inhibitors ◽  
Nucleoside Reverse Transcriptase Inhibitors ◽  
Aminoisobutyric Acid ◽  
Mitochondrial Fatty Acid ◽  
High Doses ◽  
Cpt I

ABSTRACT Although treatments with nucleoside reverse transcriptase inhibitors (NRTIs) can modify fat metabolism and fat distribution in humans, the mechanisms of these modifications and the roles of diverse NRTIs are unknown. We studied the mitochondrial and metabolic effects of stavudine (d4T), zidovudine (AZT), didanosine (ddI), lamivudine (3TC), zalcitabine (ddC), and three combinations (AZT-3TC, d4T-3TC, and d4T-ddI) in mice treated for 2 weeks with daily doses equivalent to the human dose per body area. Concentrations of AZT and d4T in plasma were lower when these drugs were administered with 3TC or ddI. Whatever the treatment, mitochondrial DNA was not significantly decreased in muscle, heart, brain, or white adipose tissue but was moderately decreased in liver tissue after the administration of AZT, 3TC, or d4T alone. Blood lactate was unchanged, even when NRTIs were administered at supratherapeutic doses. In contrast, the level of plasma ketone bodies increased with the administration of AZT or high doses of d4T but not with ddC, 3TC, or ddI, suggesting that the thymine moiety could be involved. Indeed, the levels of plasma ketone bodies increased in mice treated with β-aminoisobutyric acid, a thymine catabolite. Treatment with AZT, d4T, or β-aminoisobutyric acid increased hepatic carnitine palmitoyltransferase I (CPT-I) mRNA expression and the mitochondrial generation of ketone bodies from palmitate. In conclusion, therapeutic doses of NRTIs have no or moderate effects on mitochondrial DNA and no effects on plasma lactate in mice. However, AZT and high doses of d4T increase the levels of hepatic CPT-I, mitochondrial fatty acid β-oxidation, and ketone bodies, and these catabolic effects are reproduced by β-aminoisobutyric acid, a thymine metabolite.

scholarly journals Post-weaning maternal effects and the evolution of female dominance in the spotted hyena

2009 ◽  
Vol 276 (1665) ◽  
pp. 2291-2298 ◽  
Author(s):  
Heather E. Watts ◽  
Jaime B. Tanner ◽  
Barbara L. Lundrigan ◽  
Kay E. Holekamp
Keyword(s):  
Crocuta Crocuta ◽  
Female Dominance ◽  
Spotted Hyena ◽  
Compensatory Mechanism ◽  
Feeding Apparatus ◽  
Skull Development ◽  
Spotted Hyenas ◽  
Selection For ◽  
Maternal Presence ◽  
New Hypothesis

Mammalian societies in which females dominate males are rare, and the factors favouring the evolution of female dominance have yet to be clearly identified. We propose a new hypothesis for the evolution of female dominance and test its predictions with empirical data from the spotted hyena ( Crocuta crocuta ), a well-studied species characterized by female dominance. We suggest that constraints imposed by the development of a feeding apparatus specialized for bone cracking, in combination with the intensive feeding competition characteristic of spotted hyenas, led to the evolution of female dominance. Specifically, we propose that protracted development of the feeding apparatus in young hyenas led to selection for increased aggressiveness in females as a compensatory mechanism for mothers to secure food access for their young after weaning. Our analyses yielded results consistent with this hypothesis. Morphological and behavioural measurements indicate that skull development is indeed protracted in this species; spotted hyenas do not achieve adult skull size or feeding performance capabilities until after sexual maturity. The period between weaning and completed skull development is particularly challenging, as indicated by high mortality. Finally, maternal presence between weaning and full skull maturity, as well as the relative ability of females to aggressively displace conspecifics from food, are important determinants of offspring survival.

scholarly journals Competing metabolic strategies in a multilevel selection model

2016 ◽  
Vol 3 (11) ◽  
pp. 160544 ◽  
Author(s):  
André Amado ◽  
Lenin Fernández ◽  
Weini Huang ◽  
Fernando F. Ferreira ◽  
Paulo R. A. Campos
Keyword(s):  
High Efficiency ◽  
Evolutionary Process ◽  
Structured Populations ◽  
High Rate ◽  
Energy Usage ◽  
Evolutionary Mechanisms ◽  
Mixed Populations ◽  
Selection For ◽  
Metabolic Strategies ◽  
Low Rate

The evolutionary mechanisms of energy efficiency have been addressed. One important question is to understand how the optimized usage of energy can be selected in an evolutionary process, especially when the immediate advantage of gathering efficient individuals in an energetic context is not clear. We propose a model of two competing metabolic strategies differing in their resource usage, an efficient strain which converts resource into energy at high efficiency but displays a low rate of resource consumption, and an inefficient strain which consumes resource at a high rate but at low yield. We explore the dynamics in both well-mixed and structured populations. The selection for optimized energy usage is measured by the likelihood that an efficient strain can invade a population of inefficient strains. It is found that the parameter space at which the efficient strain can thrive in structured populations is always broader than observed in well-mixed populations.

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