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Brengdahl MI, Kimber CM, Elias P, Thompson J, Friberg U. Deleterious mutations show increasing negative effects with age in Drosophila melanogaster. BMC Biol 2020; 18:128. [PMID: 32993647 PMCID: PMC7526172 DOI: 10.1186/s12915-020-00858-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Accepted: 08/28/2020] [Indexed: 01/07/2023] Open
Abstract
BACKGROUND In order for aging to evolve in response to a declining strength of selection with age, a genetic architecture that allows for mutations with age-specific effects on organismal performance is required. Our understanding of how selective effects of individual mutations are distributed across ages is however poor. Established evolutionary theories assume that mutations causing aging have negative late-life effects, coupled to either positive or neutral effects early in life. New theory now suggests evolution of aging may also result from deleterious mutations with increasing negative effects with age, a possibility that has not yet been empirically explored. RESULTS To directly test how the effects of deleterious mutations are distributed across ages, we separately measure age-specific effects on fecundity for each of 20 mutations in Drosophila melanogaster. We find that deleterious mutations in general have a negative effect that increases with age and that the rate of increase depends on how deleterious a mutation is early in life. CONCLUSIONS Our findings suggest that aging does not exclusively depend on genetic variants assumed by the established evolutionary theories of aging. Instead, aging can result from deleterious mutations with negative effects that amplify with age. If increasing negative effect with age is a general property of deleterious mutations, the proportion of mutations with the capacity to contribute towards aging may be considerably larger than previously believed.
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Affiliation(s)
| | | | - Phoebe Elias
- IFM Biology, Linköping University, Linköping, Sweden
| | | | - Urban Friberg
- IFM Biology, Linköping University, Linköping, Sweden.
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2
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Hughes KA, Leips J. Pleiotropy, constraint, and modularity in the evolution of life histories: insights from genomic analyses. Ann N Y Acad Sci 2017; 1389:76-91. [PMID: 27936291 PMCID: PMC5318229 DOI: 10.1111/nyas.13256] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Revised: 08/10/2016] [Accepted: 08/22/2016] [Indexed: 12/20/2022]
Abstract
Multicellular organisms display an enormous range of life history (LH) strategies and present an evolutionary conundrum; despite strong natural selection, LH traits are characterized by high levels of genetic variation. To understand the evolution of life histories and maintenance of this variation, the specific phenotypic effects of segregating alleles and the genetic networks in which they act need to be elucidated. In particular, the extent to which LH evolution is constrained by the pleiotropy of alleles contributing to LH variation is generally unknown. Here, we review recent empirical results that shed light on this question, with an emphasis on studies employing genomic analyses. While genome-scale analyses are increasingly practical and affordable, they face limitations of genetic resolution and statistical power. We describe new research approaches that we believe can produce new insights and evaluate their promise and applicability to different kinds of organisms. Two approaches seem particularly promising: experiments that manipulate selection in multiple dimensions and measure phenotypic and genomic response and analytical approaches that take into account genome-wide associations between markers and phenotypes, rather than applying a traditional marker-by-marker approach.
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Affiliation(s)
- Kimberly A. Hughes
- Department of Biological Science, Florida State University, Tallahassee, Florida
| | - Jeff Leips
- Department of Biological Sciences, University of Maryland, Baltimore County, Baltimore, Maryland
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3
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Collet JM, Blows MW, McGuigan K. Transcriptome-wide effects of sexual selection on the fate of new mutations. Evolution 2015; 69:2905-16. [DOI: 10.1111/evo.12778] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2014] [Revised: 09/03/2015] [Accepted: 09/08/2015] [Indexed: 12/20/2022]
Affiliation(s)
- Julie M. Collet
- School of Biological Sciences; The University of Queensland; Queensland 4072 Australia
| | - Mark W. Blows
- School of Biological Sciences; The University of Queensland; Queensland 4072 Australia
| | - Katrina McGuigan
- School of Biological Sciences; The University of Queensland; Queensland 4072 Australia
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4
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Simultaneous Estimation of Additive and Mutational Genetic Variance in an Outbred Population of Drosophila serrata. Genetics 2015; 201:1239-51. [PMID: 26384357 DOI: 10.1534/genetics.115.178632] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Accepted: 09/13/2015] [Indexed: 01/16/2023] Open
Abstract
How new mutations contribute to genetic variation is a key question in biology. Although the evolutionary fate of an allele is largely determined by its heterozygous effect, most estimates of mutational variance and mutational effects derive from highly inbred lines, where new mutations are present in homozygous form. In an attempt to overcome this limitation, middle-class neighborhood (MCN) experiments have been used to assess the fitness effect of new mutations in heterozygous form. However, because MCN populations harbor substantial standing genetic variance, estimates of mutational variance have not typically been available from such experiments. Here we employ a modification of the animal model to analyze data from 22 generations of Drosophila serrata bred in an MCN design. Mutational heritability, measured for eight cuticular hydrocarbons, 10 wing-shape traits, and wing size in this outbred genetic background, ranged from 0.0006 to 0.006 (with one exception), a similar range to that reported from studies employing inbred lines. Simultaneously partitioning the additive and mutational variance in the same outbred population allowed us to quantitatively test the ability of mutation-selection balance models to explain the observed levels of additive and mutational genetic variance. The Gaussian allelic approximation and house-of-cards models, which assume real stabilizing selection on single traits, both overestimated the genetic variance maintained at equilibrium, but the house-of-cards model was a closer fit to the data. This analytical approach has the potential to be broadly applied, expanding our understanding of the dynamics of genetic variance in natural populations.
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Duffy E, Joag R, Radwan J, Wedell N, Hosken DJ. Inbreeding alters intersexual fitness correlations in Drosophila simulans. Ecol Evol 2014; 4:3330-8. [PMID: 25535550 PMCID: PMC4228608 DOI: 10.1002/ece3.1153] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2014] [Revised: 05/20/2014] [Accepted: 06/02/2014] [Indexed: 12/18/2022] Open
Abstract
Intralocus sexual conflict results from sexually antagonistic selection on traits shared by the sexes. This can displace males and females from their respective fitness optima, and negative intersexual correlations (r mf) for fitness are the unequivocal indicator of this evolutionary conflict. It has recently been suggested that intersexual fitness correlations can vary depending on the segregating genetic variation present in a population, and one way to alter genetic variation and test this idea is via inbreeding. Here, we test whether intersexual correlations for fitness vary with inbreeding in Drosophila simulans isolines reared under homogenous conditions. We measured male and female fitness at different times following the establishment of isofemale lines and found that the sign of the association between the two measures varied with time after initial inbreeding. Our results are consistent with suggestions that the type of genetic variation segregating within a population can determine the extent of intralocus sexual conflict and also support the idea that sexually antagonistic alleles segregate for longer in populations than alleles with sexually concordant effects.
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Affiliation(s)
- Eoin Duffy
- Institute of Environmental Science, Jagiellonian University Gronostawa 7, Krakow, Poland
| | - Richa Joag
- Institute of Environmental Science, Jagiellonian University Gronostawa 7, Krakow, Poland
| | - Jacek Radwan
- Institute of Environmental Science, Jagiellonian University Gronostawa 7, Krakow, Poland
| | - Nina Wedell
- Centre for Ecology & Conservation, University of Exeter Tremough, Penryn, TR10 9FE, U.K
| | - David J Hosken
- Centre for Ecology & Conservation, University of Exeter Tremough, Penryn, TR10 9FE, U.K
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6
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Cotto O, Ronce O. MALADAPTATION AS A SOURCE OF SENESCENCE IN HABITATS VARIABLE IN SPACE AND TIME. Evolution 2014; 68:2481-93. [DOI: 10.1111/evo.12462] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2014] [Accepted: 05/17/2014] [Indexed: 11/29/2022]
Affiliation(s)
- Olivier Cotto
- Université Montpellier 2; CNRS, Institut des Sciences de l’Evolution; CC65, Place Eugène Bataillon, 34095 Montpellier cedex 5 France
| | - Ophélie Ronce
- Université Montpellier 2; CNRS, Institut des Sciences de l’Evolution; CC65, Place Eugène Bataillon, 34095 Montpellier cedex 5 France
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7
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Casimiro MC, Crosariol M, Loro E, Li Z, Pestell RG. Cyclins and cell cycle control in cancer and disease. Genes Cancer 2013; 3:649-57. [PMID: 23634253 DOI: 10.1177/1947601913479022] [Citation(s) in RCA: 158] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Cyclin D1 overexpression is found in more than 50% of human breast cancers and causes mammary cancer in transgenic mice. Dysregulation of cyclin D1 gene expression or function contributes to the loss of normal cell cycle control during tumorigenesis. Recent studies have demonstrated that cyclin D1 conducts additional specific functions to regulate gene expression in the context of local chromatin, promote cellular migration, and promote chromosomal instability. It is anticipated that these additional functions contribute to the pathology associated with dysregulated cyclin D1 abundance. This article discusses evidence that examines the functional roles that cyclin D1 may play in cancer with an emphasis on other cyclin family members that also may contribute to cancer and disease in a similar fashion.
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8
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Loyau A, Cornuau JH, Clobert J, Danchin E. Incestuous sisters: mate preference for brothers over unrelated males in Drosophila melanogaster. PLoS One 2012; 7:e51293. [PMID: 23251487 PMCID: PMC3519633 DOI: 10.1371/journal.pone.0051293] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2012] [Accepted: 11/01/2012] [Indexed: 11/20/2022] Open
Abstract
The literature is full of examples of inbreeding avoidance, while recent mathematical models predict that inbreeding tolerance or even inbreeding preference should be expected under several realistic conditions like e.g. polygyny. We investigated male and female mate preferences with respect to relatedness in the fruit fly D. melanogaster. Experiments offered the choice between a first order relative (full-sibling or parent) and an unrelated individual with the same age and mating history. We found that females significantly preferred mating with their brothers, thus supporting inbreeding preference. Moreover, females did not avoid mating with their fathers, and males did not avoid mating with their sisters, thus supporting inbreeding tolerance. Our experiments therefore add empirical evidence for inbreeding preference, which strengthens the prediction that inbreeding tolerance and preference can evolve under specific circumstances through the positive effects on inclusive fitness.
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Affiliation(s)
- Adeline Loyau
- CNRS, Station d'Ecologie Expérimentale du CNRS à Moulis, USR 2936, Saint Girons, France.
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9
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Agrawal AF, Whitlock MC. Mutation Load: The Fitness of Individuals in Populations Where Deleterious Alleles Are Abundant. ANNUAL REVIEW OF ECOLOGY EVOLUTION AND SYSTEMATICS 2012. [DOI: 10.1146/annurev-ecolsys-110411-160257] [Citation(s) in RCA: 137] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Many multicellular eukaryotes have reasonably high per-generation mutation rates. Consequently, most populations harbor an abundance of segregating deleterious alleles. These alleles, most of which are of small effect individually, collectively can reduce substantially the fitness of individuals relative to what it would be otherwise; this is mutation load. Mutation load can be lessened by any factor that causes more mutations to be removed per selective death, such as inbreeding, synergistic epistasis, population structure, or harsh environments. The ecological effects of load are not clear-cut because some conditions (such as selection early in life, sexual selection, reproductive compensation, and intraspecific competition) reduce the effects of load on population size and persistence, but other conditions (such as interspecific competition and load on resource use efficiency) can cause small amounts of load to have strong effects on the population, even extinction. We suggest a series of studies to improve our understanding of the effects of mutation load.
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Affiliation(s)
- Aneil F. Agrawal
- Department of Ecology & Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada M5S 3B2
| | - Michael C. Whitlock
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4
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10
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Tayeh A, Estoup A, Laugier G, Loiseau A, Turgeon J, Toepfer S, Facon B. Evolution in biocontrol strains: insight from the harlequin ladybird Harmonia axyridis. Evol Appl 2012; 5:481-8. [PMID: 22949923 PMCID: PMC3407866 DOI: 10.1111/j.1752-4571.2012.00274.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2011] [Accepted: 05/01/2012] [Indexed: 11/30/2022] Open
Abstract
After being used as a biocontrol agent against aphids for decades without harmful consequences, the Asian harlequin ladybird Harmonia axyridis has suddenly become an invasive pest on a worldwide scale. We investigate the impact of captive breeding on several traits of this ladybird such as genetic diversity, fecundity, survival and pathogen resistance. We conducted an experiment in the laboratory to compare the fecundity and the susceptibility to the entomopathogenic fungus Beauveria bassiana of wild and biocontrol adults of H. axyridis. We compiled these new findings with already published data. Altogether, our findings suggest that mass rearing of biological control agents may strongly impact genetic diversity and life-history traits. We discuss how such changes may subsequently affect the fitness of biological control strains in natural environments.
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Affiliation(s)
- Ashraf Tayeh
- Inra, Cbgp (Inra/Ird/Cirad/Montpellier SupAgro)Montpellier, France
| | - Arnaud Estoup
- Inra, Cbgp (Inra/Ird/Cirad/Montpellier SupAgro)Montpellier, France
| | | | - Anne Loiseau
- Inra, Cbgp (Inra/Ird/Cirad/Montpellier SupAgro)Montpellier, France
| | - Julie Turgeon
- Département de biologie, Université LavalQuébec, QC, Canada
| | - Stefan Toepfer
- CABI Europe Switzerland, Plant Protection & Soil Conservation DirectorateHodmezovasarhely, Hungary
| | - Benoit Facon
- Inra, Cbgp (Inra/Ird/Cirad/Montpellier SupAgro)Montpellier, France
- *Correspondence Benoit Facon, Inra, Cbgp (Inra/Ird/Cirad/Montpellier SupAgro), Montpellier, France. Tel.: (33) 499 62 33 22; fax: (33) 499 62 33 45; e-mail:
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11
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Robinson SP, Kennington WJ, Simmons LW. Assortative mating for relatedness in a large naturally occurring population of Drosophila melanogaster. J Evol Biol 2012; 25:716-25. [PMID: 22321157 DOI: 10.1111/j.1420-9101.2012.02466.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Stephen P Robinson
- Centre for Evolutionary Biology, School of Animal Biology (M092), The University of Western Australia, Crawley, WA, Australia.
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12
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Mallet MA, Kimber CM, Chippindale AK. Susceptibility of the male fitness phenotype to spontaneous mutation. Biol Lett 2011; 8:426-9. [PMID: 22090202 DOI: 10.1098/rsbl.2011.0977] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Adult reproductive success can account for a large fraction of male fitness, however, we know relatively little about the susceptibility of reproductive traits to mutation-accumulation (MA). Estimates of the mutational rate of decline for adult fitness and its components are controversial in Drosophila melanogaster, and post-copulatory performance has not been examined. We therefore separately measured the consequences of MA for total male reproductive success and its major pre-copulatory and post-copulatory components: mating success and sperm competitive success. We also measured juvenile viability, an important fitness component that has been well studied in MA experiments. MA had strongly deleterious effects on both male viability and adult fitness, but the latter declined at a much greater rate. Mutational pressure on total fitness is thus much greater than would be predicted by viability alone. We also noted a significant and positive correlation between all adult traits and viability in the MA lines, suggesting pleiotropy of mutational effect as required by 'good genes' models of sexual selection.
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Affiliation(s)
- Martin A Mallet
- Department of Biology, Queen's University, Kingston, Ontario, Canada.
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13
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Abstract
Mutation load is a key parameter in evolutionary theories, but relatively little empirical information exists on the mutation load of populations, or the elimination of this load through selection. We manipulated the opportunity for sexual selection within a mutation accumulation divergence experiment to determine how sexual selection on males affected the accumulation of mutations contributing to sexual and nonsexual fitness. Sexual selection prevented the accumulation of mutations affecting male mating success, the target trait, as well as reducing mutation load on productivity, a nonsexual fitness component. Mutational correlations between mating success and productivity (estimated in the absence of sexual selection) were positive. Sexual selection significantly reduced these fitness component correlations. Male mating success significantly diverged between sexual selection treatments, consistent with the fixation of genetic differences. However, the rank of the treatments was not consistent across assays, indicating that the mutational effects on mating success were conditional on biotic and abiotic context. Our experiment suggests that greater insight into the genetic targets of natural and sexual selection can be gained by focusing on mutational rather than standing genetic variation, and on the behavior of trait variances rather than means.
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Affiliation(s)
- Katrina McGuigan
- School of Biological Sciences, The University of Queensland, St Lucia, Queensland 4072, Australia.
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14
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Experimental mutation-accumulation on the X chromosome of Drosophila melanogaster reveals stronger selection on males than females. BMC Evol Biol 2011; 11:156. [PMID: 21645375 PMCID: PMC3134001 DOI: 10.1186/1471-2148-11-156] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2011] [Accepted: 06/06/2011] [Indexed: 12/11/2022] Open
Abstract
Background Sex differences in the magnitude or direction of mutational effect may be important to a variety of population processes, shaping the mutation load and affecting the cost of sex itself. These differences are expected to be greatest after sexual maturity. Mutation-accumulation (MA) experiments provide the most direct way to examine the consequences of new mutations, but most studies have focused on juvenile viability without regard to sex, and on autosomes rather than sex chromosomes; both adult fitness and X-linkage have been little studied. We therefore investigated the effects of 50 generations of X-chromosome mutation accumulation on the fitness of males and females derived from an outbred population of Drosophila melanogaster. Results Fitness declined rapidly in both sexes as a result of MA, but adult males showed markedly greater fitness loss relative to their controls compared to females expressing identical genotypes, even when females were made homozygous for the X. We estimate that these mutations are partially additive (h ~ 0.3) in females. In addition, the majority of new mutations appear to harm both males and females. Conclusions Our data helps fill a gap in our understanding of the consequences of sexual selection for genetic load, and suggests that stronger selection on males may indeed purge deleterious mutations affecting female fitness.
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15
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MOORAD JA, HALL DW. Age-dependent mutational effects curtail the evolution of senescence by antagonistic pleiotropy. J Evol Biol 2009; 22:2409-19. [DOI: 10.1111/j.1420-9101.2009.01849.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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16
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Abstract
The "middle-class neighborhood" is a breeding design intended to allow new mutations to accumulate by lessening the effects of purifying selection through the elimination of among-line fitness variation. We show that this design effectively applies soft selection to the experimental population, potentially causing biased estimates of mutational effects if social effects contribute to fitness.
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Moorad JA, Promislow DEL. What can genetic variation tell us about the evolution of senescence? Proc Biol Sci 2009; 276:2271-8. [PMID: 19324735 DOI: 10.1098/rspb.2009.0183] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Quantitative genetic approaches have been developed that allow researchers to determine which of two mechanisms, mutation accumulation (MA) or antagonistic pleiotropy (AP), best explain observed variation in patterns of senescence using classical quantitative genetic techniques. These include the creation of mutation accumulation lines, artificial selection experiments and the partitioning of genetic variances across age classes. This last strategy has received the lion's share of empirical attention. Models predict that inbreeding depression (ID), dominance variance and the variance among inbred line means will all increase with age under MA but not under those forms of AP that generate marginal overdominance. Here, we show that these measures are not, in fact, diagnostic of MA versus AP. In particular, the assumptions about the value of genetic parameters in existing AP models may be rather narrow, and often violated in reality. We argue that whenever ageing-related AP loci contribute to segregating genetic variation, polymorphism at these loci will be enhanced by genetic effects that will also cause ID and dominance variance to increase with age, effects also expected under the MA model of senescence. We suggest that the tests that seek to identify the relative contributions of AP and MA to the evolution of ageing by partitioning genetic variance components are likely to be too conservative to be of general value.
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Affiliation(s)
- Jacob A Moorad
- Department of Genetics, University of Georgia, Athens, GA 30602, USA.
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18
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Leips J, Gilligan P, Mackay TFC. Quantitative trait loci with age-specific effects on fecundity in Drosophila melanogaster. Genetics 2005; 172:1595-605. [PMID: 16272414 PMCID: PMC1456283 DOI: 10.1534/genetics.105.048520] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Life-history theory and evolutionary theories of aging assume the existence of alleles with age-specific effects on fitness. While various studies have documented age-related changes in the genetic contribution to variation in fitness components, we know very little about the underlying genetic architecture of such changes. We used a set of recombinant inbred lines to map and characterize the effects of quantitative trait loci (QTL) affecting fecundity of Drosophila melanogaster females at 1 and 4 weeks of age. We identified one QTL on the second chromosome and one or two QTL affecting fecundity on the third chromosome, but these QTL affected fecundity only at 1 week of age. There was more genetic variation for fecundity at 4 weeks of age than at 1 week of age and there was no genetic correlation between early and late-age fecundity. These results suggest that different loci contribute to the variation in fecundity as the organism ages. Our data provide support for the mutation accumulation theory of aging as applied to reproductive senescence. Comparing the results from this study with our previous work on life-span QTL, we also find evidence that antagonistic pleiotropy may contribute to the genetic basis of senescence in these lines as well.
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Affiliation(s)
- Jeff Leips
- Department of Biological Sciences, University of Maryland Baltimore County, Baltimore 21250, USA.
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19
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Rand DM, Fry A, Sheldahl L. Nuclear-mitochondrial epistasis and drosophila aging: introgression of Drosophila simulans mtDNA modifies longevity in D. melanogaster nuclear backgrounds. Genetics 2005; 172:329-41. [PMID: 16219776 PMCID: PMC1456161 DOI: 10.1534/genetics.105.046698] [Citation(s) in RCA: 111] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Under the mitochondrial theory of aging, physiological decline with age results from the accumulated cellular damage produced by reactive oxygen species generated during electron transport in the mitochondrion. A large body of literature has documented age-specific declines in mitochondrial function that are consistent with this theory, but relatively few studies have been able to distinguish cause from consequence in the association between mitochondrial function and aging. Since mitochondrial function is jointly encoded by mitochondrial (mtDNA) and nuclear genes, the mitochondrial genetics of aging should be controlled by variation in (1) mtDNA, (2) nuclear genes, or (3) nuclear-mtDNA interactions. The goal of this study was to assess the relative contributions of these factors in causing variation in Drosophila longevity. We compared strains of flies carrying mtDNAs with varying levels of divergence: two strains from Zimbabwe (<20 bp substitutions between mtDNAs), strains from Crete and the United States (approximately 20-40 bp substitutions between mtDNAs), and introgression strains of Drosophila melanogaster carrying mtDNA from Drosophila simulans in a D. melanogaster Oregon-R chromosomal background (>500 silent and 80 amino acid substitutions between these mtDNAs). Longevity was studied in reciprocal cross genotypes between pairs of these strains to test for cytoplasmic (mtDNA) factors affecting aging. The intrapopulation crosses between Zimbabwe strains show no difference in longevity between mtDNAs; the interpopulation crosses between Crete and the United States show subtle but significant differences in longevity; and the interspecific introgression lines showed very significant differences between mtDNAs. However, the genotypes carrying the D. simulans mtDNA were not consistently short-lived, as might be predicted from the disruption of nuclear-mitochondrial coadaptation. Rather, the interspecific mtDNA strains showed a wide range of variation that flanked the longevities seen between intraspecific mtDNAs, resulting in very significant nuclear x mtDNA epistatic interaction effects. These results suggest that even "defective" mtDNA haplotypes could extend longevity in different nuclear allelic backgrounds, which could account for the variable effects attributable to mtDNA haplogroups in human aging.
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Affiliation(s)
- David M Rand
- Department of Ecology and Evolutionary Biology, Brown University, Providence, Rhode Island 02912, USA.
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20
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Meats A, Holmes HM, Kelly GL. Laboratory adaptation of Bactrocera tryoni (Diptera: Tephritidae) decreases mating age and increases protein consumption and number of eggs produced per milligram of protein. BULLETIN OF ENTOMOLOGICAL RESEARCH 2004; 94:517-524. [PMID: 15541191 DOI: 10.1079/ber2004332] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
A significant reduction in age of mating occurred during the first four generations (G1-G4) of laboratory adaptation of wild Bactrocera tryoni (Froggatt) and this was associated with the earlier attainment of peak egg load although no significant differences were detected in the peak egg load itself. A long term laboratory (LTL) strain had a significantly earlier mating age and higher peak egg load than flies of wild origin or those from the first four laboratory generations. The amount of protein consumed by females in the first week of adult life was significantly higher in the LTL strain than in flies of wild origin or G1-G4 but there were no significant changes (or only slight changes) with laboratory adaptation in the amounts of protein consumed up to the ages of mating and peak egg load. Laboratory adaptation resulted in no significant changes in egg size, egg dry weight, puparial fresh weight and the dry weight of newly emerged females. The large increase in fecundity with laboratory adaptation is associated with a 4- to 5-fold increase in the rate of conversion of dietary protein to eggs (i.e. eggs produced per mg of protein consumed).
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Affiliation(s)
- A Meats
- School of Biological Sciences, University of Sydney, New South Wales 2006, Australia.
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Abstract
The hypothesis that females prefer older males because they have higher mean fitness than younger males has been the centre of recent controversy. These discussions have focused on the success of a female who prefers males of a particular age class when age cues, but not quality cues, are available. Thus, if the distribution of male quality changes with age, such that older males have on average genotypes with higher fitness than younger males, then a female who mates with older males has fitter offspring, which allows the female preference to spread through a genetic correlation. We develop a general model for male display in a species with multiple reproductive bouts that allows us to identify the conditions that promote reliable signalling within an age class. Because males have opportunities for future reproduction, they will reduce their levels of advertising compared with a semelparous species. In addition, because higher-quality males have more future reproduction, they will reduce their advertising more than low-quality males. Thus, the conditions for reliable signalling in a semelparous organism are generally not sufficient to produce reliable signalling in species with multiple reproductive bouts. This result is due to the possibility of future reproduction so that, as individuals age and the opportunities for future reproduction fade, signalling becomes more reliable. This provides a novel rationale for female preference for older mates; older males reveal more information in their sexual displays.
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Affiliation(s)
- Stephen R Proulx
- Department of Zoology, University of Toronto, 25 Harbord Street, Toronto, ON, M5S 3G5, Canada.
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