Biology subjects

Radzvilavicius, A.

Publications and source records attributed to Radzvilavicius, A..

5 recordsLinked to original sources

bioRxiv2021

Sexually antagonistic evolution of mitochondrial and nuclear linkage

Across eukaryotes, genes encoding bioenergetic machinery are located in both mitochondrial and nuclear DNA, and incompatibilities between the two genomes can be devastating. Mitochondria are often inherited maternally, and theory predicts sex-specific fitness effects of mitochondrial mutational diversity. Yet how evolution acts on linkage patterns between mitochondrial and nuclear genomes is poorly understood. Using novel mito-nuclear population genetic models, we show that the interplay between nuclear and mitochondrial genes maintains mitochondrial haplotype diversity within populations, and it selects both for sex-independent segregation of mitochondrion-interacting genes and for paternal leakage. These effects of genetic linkage evolution can eliminate male-harming fitness effects of mtDNA mutational diversity. With maternal mitochondrial inheritance, females maintain a tight mitochondrial-nuclear match, but males accumulate mismatch mutations because of the weak statistical associations between the two genomic components. Sex-independent segregation of mitochondria-interacting loci improves the mito-nuclear match. In a sexually antagonistic evolutionary process, male nuclear alleles evolve to increase the rate of recombination, while females evolve to suppress it. Paternal leakage of mitochondria can evolve as an alternative mechanism to improve the mito-nuclear linkage. Our modelling framework provides an evolutionary explanation for the observed paucity of mitochondrion-interacting genes on mammalian sex chromosomes and for paternal leakage in protists, plants, fungi, and some animals.

evolutionary biology↗

bioRxiv2021

Organelle bottlenecks facilitate evolvability by traversing heteroplasmic fitness valleys

Bioenergetic organelles - mitochondria and plastids - retain their own genomes, and these organelle DNA (oDNA) molecules are vital for eukaryotic life. Like all genomes, oDNA must be able to evolve to suit new environmental challenges. However, mixed oDNA populations can challenge cellular bioenergetics, providing a penalty to the appearance and adaptation of new mutations. Here we show that organelle bottlenecks, mechanisms increasing cell-to-cell oDNA variability during development, can overcome this mixture penalty and facilitate the adaptation of beneficial mutations. We show that oDNA heteroplasmy and bottlenecks naturally emerge in evolutionary simulations subjected to fluctuating environments, demonstrating that this evolvability is itself evolvable. Usually thought of as a mechanism to clear damaging mutations, organelle bottlenecks therefore also resolve the tension between intracellular selection for pure oDNA populations and the bet-hedging need for evolvability and adaptation to new environments. This general theory suggests a reason for the maintenance of organelle heteroplasmy in cells, and may explain some of the observed diversity in organelle maintenance and inheritance across taxa.

genetics↗

bioRxiv2020

Paternal leakage of organelles can improve adaptation to changing environments

Sexual eukaryotes have diverse mechanisms preventing the biparental inheritance of mitochondria and plastids, and reducing the coexistence of dissimilar organelle DNA (heteroplasmy). Nevertheless, paternal leakage often occurs in plants, fungi, protists and animals, and this leaves the possibility that heteroplasmy can in some contexts be advantageous. Theoretical models developed in the past revealed that maternal inheritance improves selection against deleterious mitochondrial mutations, but none of them have explained the observed variation in the extent of paternal leakage. Here we show that paternal leakage regulated by nuclear loci can evolve to maintain advantageous organelle diversity in fluctuating environments. Strict maternal inheritance reduces organelle variance within the cell, but this loss of diversity can be detrimental when environments are shifting rapidly. Our model reveals that high levels of paternal leakage can evolve in these types of rapidly changing environments and that strict maternal inheritance evolves only when the environment is changing slowly. DataMatlab/Octave implementation of the model is available at Https://github.com/StochasticBiology/PaternalLeakageEvolution.

ecology↗

bioRxiv2018

Evolution of empathetic moral evaluation

Social norms can promote cooperation in human societies by assigning reputations to individuals based on their past actions. A good reputation indicates that an individual is worthy of help and is likely to reciprocate. A large body of research has established the norms of moral assessment that promote cooperation and maximize social welfare, assuming reputations are objective. But if there is no centralized institution to provide objective moral evaluation, then opinions about an individuals reputation may differ across a population. Here we use evolutionary game theory to study the effects of empathy - the capacity to make moral evaluations from the perspective of another person. We find that empathetic moral evaluation tends to foster cooperation by reducing the rate of unjustified defection. The norms of moral evaluation previously considered most socially beneficial depend on high levels of empathy, whereas different norms are required to maximize social welfare in populations unwilling or incapable of empathy. We demonstrate that empathy itself can evolve through social contagion and attain evolutionary stability under most social norms. We conclude that a capacity for empathetic moral evaluation represents a key component to sustaining cooperation in human societies: cooperation requires getting into the mindset of others whose views differ from our own.

evolutionary biology↗

bioRxiv2017

Mitigating Mitochondrial Genome Erosion Without Recombination

Mitochondria are ATP-producing organelles of bacterial ancestry that played a key role in the origin and early evolution of complex eukaryotic cells. Most modern eukaryotes transmit mitochondrial genes uniparentally, often without recombination among genetically divergent organelles. While this asymmetric inheritance maintains the efficacy of purifying selection at the level of the cell, the absence of recombination could also make the genome susceptible to Mullers ratchet. How mitochondria escape this irreversible defect accumulation is a fundamental unsolved question. Occasional paternal leakage could in principle promote recombination, but it would also compromise the purifying-selection benefits of uniparental inheritance. We assess this tradeoff using a stochastic population-genetic model. In the absence of recombination, uniparental inheritance of freely segregating genomes mitigates mutational erosion, while paternal leakage exacerbates the ratchet effect. Mitochondrial fusion-fission cycles ensure independent genome segregation, improving purifying selection. Paternal leakage provides opportunity for recombination to slow down the mutation accumulation, but always at a cost of increased steady-state mutation load. Our findings indicate that random segregation of mitochondrial genomes under uniparental inheritance can effectively combat the mutational meltdown, and that homologous recombination under paternal leakage might not be needed.

genetics↗