Mutation accumulation in Tetrahymena

Brito, Patrícia H.; Guilherme, Elsa; Soares, Helena; Gordo, Isabel

doi:10.1186/1471-2148-10-354

Cited by 21 publications

(24 citation statements)

References 54 publications

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“…Thus, it is possible that SB210 has a lower mutation rate than other strains of the same species. The choice of starting strain may also help explain the difference in transfer failure between our study and that of Brito et al (2010). Studies of mutational parameters in other isolates could reveal the degree of variation in these traits among individuals within a species.…”

Section: Discussionmentioning

confidence: 91%

“…In an earlier MA study in T. thermophila, Brito et al (2010) used the rate of clonal extinction as a measure of fitness effects of somatic mutations. They found that 1.25 MA lines per bottleneck went extinct and interpreted this as evidence for the rapid accumulation of deleterious mutations in the somatic genome.…”

Section: Discussionmentioning

confidence: 99%

“…We found no evidence that our MA lines accumulated any deleterious somatic mutations over the course of 1000 generations. However, our experimental design, involving multiple single-cell transfer cultures at each bottleneck event, did not allow us to detect the kinds of lethal somatic mutations hypothesized by Brito et al (2010).…”

Section: Discussionmentioning

confidence: 99%

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Accumulation of Spontaneous Mutations in the CiliateTetrahymena thermophila

2013

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Knowledge of the rate and fitness effects of mutations is essential for understanding the process of evolution. Mutations are inherently difficult to study because they are rare and are frequently eliminated by natural selection. In the ciliate Tetrahymena thermophila, mutations can accumulate in the germline genome without being exposed to selection. We have conducted a mutation accumulation (MA) experiment in this species. Assuming that all mutations are deleterious and have the same effect, we estimate that the deleterious mutation rate per haploid germline genome per generation is U = 0.0047 (95% credible interval: 0.0015, 0.0125), and that germline mutations decrease fitness by s = 11% when expressed in a homozygous state (95% CI: 4.4%, 27%). We also estimate that deleterious mutations are partially recessive on average (h = 0.26; 95% CI: -0.022, 0.62) and that the rate of lethal mutations is ,10% of the deleterious mutation rate. Comparisons between the observed evolutionary responses in the germline and somatic genomes and the results from individual-based simulations of MA suggest that the two genomes have similar mutational parameters. These are the first estimates of the deleterious mutation rate and fitness effects from the eukaryotic supergroup Chromalveolata and are within the range of those of other eukaryotes. MUTATIONS are the ultimate source of variation responsible for evolutionary change. Thus, knowledge of the rate and fitness consequences of spontaneous mutations is essential to understanding evolution (Charlesworth 1996). These parameters have been estimated in a handful of species and have provided many important insights into the evolutionary process (reviewed in Lynch et al. 1999;Halligan and Keightley 2009;Lynch 2010). For example, the observation that the deleterious mutation rate is less than one per genome per generation in several species suggests that the mutational deterministic hypothesis is insufficient to explain the widespread maintenance of sexual reproduction (Kondrashov 1988; Halligan and Keightley 2009). However, among eukaryotes, these mutational parameters have been estimated only in Opisthokonta (animals, fungi, and relatives) and Archaeplastida (red and green algae, land plants, and relatives), leaving the majority of eukaryotic diversity unexamined.Mutation accumulation (MA) is the best experimental tool with which to study mutation rates and fitness effects. Typically, MA experiments consist of allowing spontaneous mutations to arise and fix in parallel, replicate populations over many generations. Small populations are used to reduce the effectiveness of natural selection in determining the fate of new mutations. The quality of the estimates of mutational parameters derived from MA experiments is constrained by the biology of the organism used. Organisms with long-generation times experience a slow rate of MA [e.g., one experiment on Arabidopsis thaliana (Shaw et al. 2000), which has a generation time of 10 weeks, lasted only 17 generations], leading to imp...

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Section: Discussionmentioning

confidence: 91%

Section: Discussionmentioning

confidence: 99%

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Accumulation of Spontaneous Mutations in the CiliateTetrahymena thermophila

2013

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“…1 ). An approach that has been applied to different organisms, including Drosophila melanogaster [Haag-Liautard et al, 2007, 2008, Caenorhabditis elegans [Davies et al, 1999;Denver et al, 2000;Estes et al, 2004;Keightley and Caballero, 1997;Vassilieva and Lynch, 1999] and S. cerevisiae [Dickinson, 2008;Joseph and Hall, 2004;Wloch et al, 2001;Zeyl and DeVisser, 2001], Tetrahymena [Brito et al, 2010], E. coli [Kibota and Lynch, 1996;Trindade et al, 2010] and some viruses [de la Iglesia and Elena, 2007;Elena and Moya, 1999;Lazaro et al, 2003;Li and Roossinck, 2004]. The assumption underlying an MA experiment is that, when the population size ( N e ) is kept extremely low, genetic drift overwhelms natural selection and mutations accumulate at the rate at which they appear (i.e.…”

Section: Ma In Bacteriamentioning

confidence: 99%

Fitness Effects of Mutations in Bacteria

2011

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Mutation is the primary source of variation in any organism. Without it, natural selection cannot operate and organisms cannot adapt to novel environments. Mutation is also generally a source of defect: many mutations are not neutral but cause fitness decreases in the organisms where they arise. In bacteria, another important source of variation is horizontal gene transfer. This source of variation can also cause beneficial or deleterious effects. Determining the distribution of fitness effects of mutations in different environments and genetic backgrounds is an active research field. In bacteria, knowledge of these distributions is key for understanding important traits. For example, for determining the dynamics of microorganisms with a high genomic mutation rate (mutators), and for understanding the evolution of antibiotic resistance, and the emergence of pathogenic traits. All of these characteristics are extremely relevant for human health both at the individual and population levels. Experimental evolution has been a valuable tool to address these questions. Here, we review some of the important findings of mutation effects in bacteria revealed through laboratory experiments.

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“…3). These results, while contracting expectations from ramifications of the theory of mutation accumulation of aging, do have a basis for experimental support since mutations can accumulate on the germ line in clonal species, as shown in protozoans (Brito et al 2010), fungi (Griffiths 1992;Taylor et al 2015) and some long-lived clonal plants (Ally et al 2010). Furthermore, sexual reproduction has been shown to slow down the accumulation of mutations in other modular species like fungi (Bruggeman et al 2003).…”

Section: Discussionmentioning

confidence: 64%

Implications of clonality for ageing research

Salguero‐Gómez

2017

Evol Ecol

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Senescence, an organismal performance decline with age, has historically been considered a universal phenomenon by evolutionary biologists and zoologist. Yet, increasing fertility and survival with age are nothing new to plant ecologists, among whom it is common knowledge that senescence is not universal. Recently, these two realities have come into a confrontation, begging for the rephrasing of the classical question that has led ageing research for decades: ''why do we senesce?'' to a more practical ''what are the mechanisms by which some organisms escape from senescence?'' Plants are amenable to examining this question because of their rich repertoire of life history strategies. These include the existence of permanent seed banks, vegetative dormancy and ability to produce clones, among others. Here, I use a large number of high resolution demographic models from 181 species that reflect life history strategies and their trade-offs among herbaceous perennials, succulents and shrubs measured under field conditions worldwide to examine whether senescence rates of ramets from clonal plants differ from those of whole plants reproducing either strictly sexually, or with a combination of sexual and clonal mechanisms. Contrary to the initial expectation from the mutation accumulation theory of senescence, ramets of clonal plants were more likely to exhibit senescence than those species employing sexual reproduction. I discuss why these comparisons between ramets and genets are useful, as well as its implications and future directions for ageing research.

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Mutation accumulation in Tetrahymena

Cited by 21 publications

References 54 publications

Accumulation of Spontaneous Mutations in the CiliateTetrahymena thermophila

Accumulation of Spontaneous Mutations in the CiliateTetrahymena thermophila

Fitness Effects of Mutations in Bacteria

Implications of clonality for ageing research

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