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Paczolt KA, Welsh GT, Wilkinson GS. X chromosome drive is constrained by sexual selection and influences ornament evolution. Proc Biol Sci 2023; 290:20230929. [PMID: 37491962 PMCID: PMC10369026 DOI: 10.1098/rspb.2023.0929] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Accepted: 06/26/2023] [Indexed: 07/27/2023] Open
Abstract
Experimental evolution provides an integrative method for revealing complex interactions among evolutionary processes. One such interaction involves sex-linked selfish genetic elements and sexual selection. X-linked segregation distorters, a type of selfish genetic element, influence sperm transmission to increase in frequency and consequently alter the population sex ratio and the opportunity for sexual selection, while sexual selection may impact the spread of X-linked distorters. Here we manipulated sexual selection by controlling female mating opportunities and the presence of a distorting X chromosome in experimental lines of the stalk-eyed fly, Teleopsis dalmanni, over 11 generations. We find that removal of sexual selection leads to an increase in the frequency of the X-linked distorter and sex ratio across generations and that post-copulatory sexual selection alone is sufficient to limit the frequency of distorters. In addition, we find that male eyestalk length, a trait under pre-copulatory sexual selection, evolves in response to changes in the strength of sexual selection with the magnitude of the response dependent on X chromosome type and the frequency of distorting X chromosomes. These results reveal how a selfish X can interact with sexual selection to influence the evolution of sexually selected traits in multiple ways.
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Affiliation(s)
- Kimberly A. Paczolt
- Department of Biology, University of Maryland at College Park, College Park, MD 20742, USA
| | - Gabrielle T. Welsh
- Department of Biology, University of Maryland at College Park, College Park, MD 20742, USA
| | - Gerald S. Wilkinson
- Department of Biology, University of Maryland at College Park, College Park, MD 20742, USA
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2
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Reinhardt JA, Baker RH, Zimin AV, Ladias C, Paczolt KA, Werren JH, Hayashi CY, Wilkinson GS. Impacts of Sex Ratio Meiotic Drive on Genome Structure and Function in a Stalk-Eyed Fly. Genome Biol Evol 2023; 15:evad118. [PMID: 37364298 PMCID: PMC10319772 DOI: 10.1093/gbe/evad118] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2022] [Revised: 06/02/2023] [Accepted: 06/15/2023] [Indexed: 06/28/2023] Open
Abstract
Stalk-eyed flies in the genus Teleopsis carry selfish genetic elements that induce sex ratio (SR) meiotic drive and impact the fitness of male and female carriers. Here, we assemble and describe a chromosome-level genome assembly of the stalk-eyed fly, Teleopsis dalmanni, to elucidate patterns of divergence associated with SR. The genome contains tens of thousands of transposable element (TE) insertions and hundreds of transcriptionally and insertionally active TE families. By resequencing pools of SR and ST males using short and long reads, we find widespread differentiation and divergence between XSR and XST associated with multiple nested inversions involving most of the SR haplotype. Examination of genomic coverage and gene expression data revealed seven X-linked genes with elevated expression and coverage in SR males. The most extreme and likely drive candidate involves an XSR-specific expansion of an array of partial copies of JASPer, a gene necessary for maintenance of euchromatin and associated with regulation of TE expression. In addition, we find evidence for rapid protein evolution between XSR and XST for testis expressed and novel genes, that is, either recent duplicates or lacking a Dipteran ortholog, including an X-linked duplicate of maelstrom, which is also involved in TE silencing. Overall, the evidence suggests that this ancient XSR polymorphism has had a variety of impacts on repetitive DNA and its regulation in this species.
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Affiliation(s)
| | - Richard H Baker
- Sackler Institute for Comparative Genomics, American Museum of Natural History, New York, New York, USA
| | - Aleksey V Zimin
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland, USA
| | - Chloe Ladias
- Biology Department, State University of New York at Geneseo, Geneseo, New York, USA
| | - Kimberly A Paczolt
- Department of Biology, University of Maryland, College Park, Maryland, USA
| | - John H Werren
- Department of Biology, University of Rochester, Rochester, New York, USA
| | - Cheryl Y Hayashi
- Sackler Institute for Comparative Genomics, American Museum of Natural History, New York, New York, USA
| | - Gerald S Wilkinson
- Department of Biology, University of Maryland, College Park, Maryland, USA
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3
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Feijen HR, Feijen C. A revision of Centrioncus Speiser (Diptera, Diopsidae, Centrioncinae) with descriptions of new species from Angola, Burundi, and Kenya. Zookeys 2023; 1144:1-93. [DOI: 10.3897/zookeys.1144.95619] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2022] [Accepted: 01/05/2023] [Indexed: 02/05/2023] Open
Abstract
A diagnosis is presented for the Centrioncinae, the Afromontane Forest Flies or stalkless Diopsidae, while its taxonomic position within the Diopsidae is discussed. Arguments are presented for an eventual raising of the Centrioncinae to family level. The differential characters for its two genera, Centrioncus Speiser and Teloglabrus Feijen, are tabulated. The diagnosis for Centrioncus is updated and a key to the ten species now recognised (including three new species) is provided. Centrioncus crassifemursp. nov. is described from a single female from Angola. This greatly extends the distribution range for the genus. Centrioncus bururiensissp. nov. is described from Burundi, while Centrioncus copelandisp. nov. originates from the Kasigau Massif of Kenya. Diagnoses, descriptive updates, illustrations and notes are presented for all other Centrioncus. Centrioncus aberrans Feijen, described from Uganda, is now also recorded for western Kenya, Rwanda, and possibly eastern DR Congo. This wide range of C. aberrans is unusual for the Centrioncinae species which have allopatric and usually very restricted distribution ranges. Defining characters of C. aberrans from the various regions were examined in detail, but only minor differences were found. Centrioncus decoronotus Feijen, described from Kenya, is now recorded for several other places in Kenya. A distribution map is given for the Eastern African Centrioncus species. The eastern branch of the Great Rift Valley appears to form a barrier between C. aberrans and C. decoronotus. The type species of the genus, C. prodiopsis Speiser from the Kilimanjaro in Tanzania, was only known from the 1905–1906 type series. After more than 100 years it has now been found again on the Kenya side of Kilimanjaro. Various differential characters of Centrioncus and Diopsidae are discussed, while brief discussions on sex ratio and fungal parasites are given. Centrioncus are known to occur on low shrubs and herbaceous plants in rain forests. Now, the possibility is indicated that they also might occur higher up in the tree canopies.
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Lagunas-Robles G, Purcell J, Brelsford A. Linked supergenes underlie split sex ratio and social organization in an ant. Proc Natl Acad Sci U S A 2021; 118:e2101427118. [PMID: 34772805 PMCID: PMC8609651 DOI: 10.1073/pnas.2101427118] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/23/2021] [Indexed: 12/19/2022] Open
Abstract
Sexually reproducing organisms usually invest equally in male and female offspring. Deviations from this pattern have led researchers to new discoveries in the study of parent-offspring conflict, genomic conflict, and cooperative breeding. Some social insect species exhibit the unusual population-level pattern of split sex ratio, wherein some colonies specialize in the production of future queens and others specialize in the production of males. Theoretical work predicted that worker control of sex ratio and variation in relatedness asymmetry among colonies would cause each colony to specialize in the production of one sex. While some empirical tests supported theoretical predictions, others deviated from them, leaving many questions about how split sex ratio emerges. One factor yet to be investigated is whether colony sex ratio may be influenced by the genotypes of queens or workers. Here, we sequence the genomes of 138 Formica glacialis workers from 34 male-producing and 34 gyne-producing colonies to determine whether split sex ratio is under genetic control. We identify a supergene spanning 5.5 Mbp that is closely associated with sex allocation in this system. Strikingly, this supergene is adjacent to another supergene spanning 5 Mbp that is associated with variation in colony queen number. We identify a similar pattern in a second related species, Formica podzolica. The discovery that split sex ratio is determined, at least in part, by a supergene in two species opens future research on the evolutionary drivers of split sex ratio.
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Affiliation(s)
- German Lagunas-Robles
- Department of Evolution, Ecology and Organismal Biology, University of California, Riverside, CA 92521
| | - Jessica Purcell
- Department of Entomology, University of California, Riverside, CA 92521
| | - Alan Brelsford
- Department of Evolution, Ecology and Organismal Biology, University of California, Riverside, CA 92521;
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Finnegan SR, Mondani M, Fowler K, Pomiankowski A. Meiotic drive does not cause condition-dependent reduction of the sexual ornament in stalk-eyed flies. J Evol Biol 2021; 34:736-745. [PMID: 33559198 DOI: 10.1111/jeb.13770] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Revised: 01/25/2021] [Accepted: 01/27/2021] [Indexed: 12/15/2022]
Abstract
Meiotic drive systems are associated with low-frequency chromosomal inversions. These are expected to accumulate deleterious mutations due to reduced recombination and low effective population size. We test this prediction using the 'sex-ratio' (SR) meiotic drive system of the Malaysian stalk-eyed fly Teleopsis dalmanni. SR is associated with a large inversion (or inversions) on the X chromosome. In particular, we study eyespan in males carrying the SR chromosome, as this trait is a highly exaggerated, sexually dimorphic trait, known to have heightened condition-dependent expression. Larvae were raised in low and high larval food stress environments. SR males showed reduced eyespan under the low and high stress treatments, but there was no evidence of a condition-dependent decrease in eyespan under high stress. Similar but more complex patterns were observed for female eyespan, with evidence of additivity under low stress and heterosis under high stress. These results do not support the hypothesis that reduced sexual ornament size in meiotic drive males is due to a condition-dependent response to the putative increase in mutation load. Instead, reduced eyespan likely reflects compensatory resource allocation to different traits in response to drive-mediated destruction of sperm.
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Affiliation(s)
- Sam Ronan Finnegan
- Department of Genetics, Evolution and Environment, University College London, London, UK
| | - Matteo Mondani
- Department of Genetics, Evolution and Environment, University College London, London, UK
| | - Kevin Fowler
- Department of Genetics, Evolution and Environment, University College London, London, UK
| | - Andrew Pomiankowski
- Department of Genetics, Evolution and Environment, University College London, London, UK.,CoMPLEX, University College London, London, UK
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Meade L, Finnegan SR, Kad R, Fowler K, Pomiankowski A. Maintenance of Fertility in the Face of Meiotic Drive. Am Nat 2020; 195:743-751. [DOI: 10.1086/707372] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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7
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Keais GL, Lu S, Perlman SJ. Autosomal suppression and fitness costs of an old driving X chromosome in Drosophila testacea. J Evol Biol 2020; 33:619-628. [PMID: 31990433 DOI: 10.1111/jeb.13596] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2019] [Revised: 12/18/2019] [Accepted: 01/07/2020] [Indexed: 12/19/2022]
Abstract
Driving X chromosomes (XD s) bias their own transmission through males by killing Y-bearing gametes. These chromosomes can in theory spread rapidly in populations and cause extinction, but many are found as balanced polymorphisms or as "cryptic" XD s shut down by drive suppressors. The relative likelihood of these outcomes and the evolutionary pathways through which they come about are not well understood. An XD was recently discovered in the mycophagous fly, Drosophila testacea, presenting the opportunity to compare this XD with the well-studied XD of its sister species, Drosophila neotestacea. Comparing features of independently evolved XD s in young sister species is a promising avenue towards understanding how XD s and their counteracting forces change over time. In contrast to the XD of D. neotestacea, we find that the XD of D. testacea is old, with its origin predating the radiation of three species: D. testacea, D. neotestacea and their shared sister species, Drosophila orientacea. Motivated by the suggestion that older XD s should be more deleterious to carriers, we assessed the effect of the XD on both male and female fertility. Unlike what is known from D. neotestacea, we found a strong fitness cost in females homozygous for the XD in D. testacea: a large proportion of homozygous females failed to produce offspring after being housed with males for several days. Our male fertility experiments show that although XD male fertility is lower under sperm-depleting conditions, XD males have comparable fertility to males carrying a standard X chromosome under a free-mating regime, which may better approximate conditions in wild populations of D. testacea. Lastly, we demonstrate the presence of autosomal suppression of X chromosome drive. Our results provide support for a model of XD evolution where the dynamics of young XD s are governed by fitness consequences in males, whereas in older XD systems, both suppression and fitness consequences in females likely supersede male fitness costs.
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Affiliation(s)
- Graeme L Keais
- Department of Biology, University of Victoria, Victoria, BC, Canada.,Department of Botany, University of British Columbia, Vancouver, BC, Canada
| | - Sijia Lu
- Department of Biology, University of Victoria, Victoria, BC, Canada
| | - Steve J Perlman
- Department of Biology, University of Victoria, Victoria, BC, Canada
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Finnegan SR, Nitsche L, Mondani M, Camus MF, Fowler K, Pomiankowski A. Does meiotic drive alter male mate preference? Behav Ecol 2019. [DOI: 10.1093/beheco/arz176] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
AbstractMale mate preferences have been demonstrated across a range of species, including the Malaysian stalk-eyed fly, Teleopsis dalmanni. This species is subject to sex-ratio (SR), an X-linked male meiotic driver, which causes the dysfunction of Y-sperm and the production of all-female broods. While there has been work considering female avoidance of meiotic drive males, the mating decisions of drive-bearing males have not been considered previously. Drive males may be less able to bear the cost of choice as SR is associated with a low-frequency inversion that causes reduced organismal fitness. Drive males may also experience weaker selection for preference maintenance if they are avoided by females. Using binary choice trials, across two experiments, we confirmed male preference for large (fecund) females but found no evidence that the strength of male preference differs between drive and standard males. We showed that large eyespan males displayed strong preference for large females, whereas small eyespan males showed no preference. Taken together, these results suggest that, even though meiotic drive is associated with lower genetic quality, it does not directly interfere with male mate preference among available females. However, as drive males tend to have smaller eyespan (albeit only ~5% on average), this will to a minor extent weaken their strength of preference.
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Affiliation(s)
- Sam Ronan Finnegan
- Department of Genetics, Evolution and Environment, University College London, London, UK
- NERC Biomolecular Analysis Facility, Department of Animal and Plant Sciences, University of Sheffield, Western Bank, Sheffield, UK
| | - Leslie Nitsche
- Department of Genetics, Evolution and Environment, University College London, London, UK
| | - Matteo Mondani
- Department of Genetics, Evolution and Environment, University College London, London, UK
| | - M Florencia Camus
- Department of Genetics, Evolution and Environment, University College London, London, UK
| | - Kevin Fowler
- Department of Genetics, Evolution and Environment, University College London, London, UK
| | - Andrew Pomiankowski
- Department of Genetics, Evolution and Environment, University College London, London, UK
- CoMPLEX, University College London, London, UK
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9
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Finnegan SR, White NJ, Koh D, Camus MF, Fowler K, Pomiankowski A. Meiotic drive reduces egg-to-adult viability in stalk-eyed flies. Proc Biol Sci 2019; 286:20191414. [PMID: 31480972 PMCID: PMC6742991 DOI: 10.1098/rspb.2019.1414] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2019] [Accepted: 08/09/2019] [Indexed: 11/12/2022] Open
Abstract
A number of species are affected by Sex-Ratio (SR) meiotic drive, a selfish genetic element located on the X-chromosome that causes dysfunction of Y-bearing sperm. SR is transmitted to up to 100% of offspring, causing extreme sex ratio bias. SR in several species is found in a stable polymorphism at a moderate frequency, suggesting there must be strong frequency-dependent selection resisting its spread. We investigate the effect of SR on female and male egg-to-adult viability in the Malaysian stalk-eyed fly, Teleopsis dalmanni. SR meiotic drive in this species is old, and appears to be broadly stable at a moderate (approx. 20%) frequency. We use large-scale controlled crosses to estimate the strength of selection acting against SR in female and male carriers. We find that SR reduces the egg-to-adult viability of both sexes. In females, homozygous females experience greater reduction in viability (sf = 0.242) and the deleterious effects of SR are additive (h = 0.511). The male deficit in viability (sm = 0.214) is not different from that in homozygous females. The evidence does not support the expectation that deleterious side effects of SR are recessive or sex-limited. We discuss how these reductions in egg-to-adult survival, as well as other forms of selection acting on SR, may maintain the SR polymorphism in this species.
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Affiliation(s)
- Sam Ronan Finnegan
- Department of Genetics, Evolution and Environment, University College London, Gower Street, London WC1E 6BT, UK
| | - Nathan Joseph White
- Department of Genetics, Evolution and Environment, University College London, Gower Street, London WC1E 6BT, UK
- Department of Animal and Plant Sciences, University of Sheffield, Western Bank, Sheffield S10 2NT, UK
| | - Dixon Koh
- Department of Genetics, Evolution and Environment, University College London, Gower Street, London WC1E 6BT, UK
| | - M. Florencia Camus
- Department of Genetics, Evolution and Environment, University College London, Gower Street, London WC1E 6BT, UK
| | - Kevin Fowler
- Department of Genetics, Evolution and Environment, University College London, Gower Street, London WC1E 6BT, UK
| | - Andrew Pomiankowski
- Department of Genetics, Evolution and Environment, University College London, Gower Street, London WC1E 6BT, UK
- CoMPLEX, University College London, Gower Street, London WC1E 6BT, UK
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10
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Meade LC, Dinneen D, Kad R, Lynch DM, Fowler K, Pomiankowski A. Ejaculate sperm number compensation in stalk-eyed flies carrying a selfish meiotic drive element. Heredity (Edinb) 2019; 122:916-926. [PMID: 30467401 PMCID: PMC6781104 DOI: 10.1038/s41437-018-0166-y] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2018] [Revised: 10/19/2018] [Accepted: 11/03/2018] [Indexed: 11/08/2022] Open
Abstract
Meiotic drive genes cause the degeneration of non-carrier sperm to bias transmission in their favour. Males carrying meiotic drive are expected to suffer reduced fertility due to the loss of sperm and associated harmful side-effects of the mechanisms causing segregation distortion. However, sexual selection should promote adaptive compensation to overcome these deleterious effects. We investigate this using SR, an X-linked meiotic drive system in the stalk-eyed fly, Teleopsis dalmanni. Despite sperm destruction caused by drive, we find no evidence that SR males transfer fewer sperm to the female's spermathecae (long-term storage organs). Likewise, migration from the spermathecae to the ventral receptacle for fertilisation is similar for SR and wildtype male sperm, both over short and long time-frames. In addition, sperm number in storage is similar even after males have mated multiple times. Our study challenges conventional assumptions about the deleterious effects of drive on male fertility. This suggests that SR male ejaculate investment per ejaculate has been adjusted to match sperm delivery by wildtype males. We interpret these results in the light of recent theoretical models that predict how ejaculate strategies evolve when males vary in the resources allocated to reproduction or in sperm fertility. Adaptive compensation is likely in species where meiotic drive has persisted over many generations and predicts a higher stable frequency of drive maintained in wild populations. Future research must determine exactly how drive males compensate for failed spermatogenesis, and how such compensation may trade-off with investment in other fitness traits.
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Affiliation(s)
- Lara C Meade
- Department of Genetics, Evolution and Environment, University College London, Gower Street, London, WC1E 6BT, UK
| | - Deidre Dinneen
- Department of Genetics, Evolution and Environment, University College London, Gower Street, London, WC1E 6BT, UK
| | - Ridhima Kad
- Department of Genetics, Evolution and Environment, University College London, Gower Street, London, WC1E 6BT, UK
| | - Dominic M Lynch
- Department of Genetics, Evolution and Environment, University College London, Gower Street, London, WC1E 6BT, UK
| | - Kevin Fowler
- Department of Genetics, Evolution and Environment, University College London, Gower Street, London, WC1E 6BT, UK
| | - Andrew Pomiankowski
- Department of Genetics, Evolution and Environment, University College London, Gower Street, London, WC1E 6BT, UK.
- CoMPLEX, University College London, Gower Street, London, WC1E 6BT, UK.
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11
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Pieper KE, Unckless RL, Dyer KA. A fast-evolving X-linked duplicate of importin-α2 is overexpressed in sex-ratio drive in Drosophila neotestacea. Mol Ecol 2018; 27:5165-5179. [PMID: 30411843 DOI: 10.1111/mec.14928] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2018] [Revised: 10/21/2018] [Accepted: 10/25/2018] [Indexed: 01/31/2023]
Abstract
Selfish genetic elements that manipulate gametogenesis to achieve a transmission advantage are known as meiotic drivers. Sex-ratio X chromosomes (SR) are meiotic drivers that prevent the maturation of Y-bearing sperm in male carriers to result in the production of mainly female progeny. The spread of an SR chromosome can affect host genetic diversity and genome evolution, and can even cause host extinction if it reaches sufficiently high prevalence. Meiotic drivers have evolved independently many times, though only in a few cases is the underlying genetic mechanism known. In this study we use a combination of transcriptomics and population genetics to identify widespread expression differences between the standard (ST) and sex-ratio (SR) X chromosomes of the fly Drosophila neotestacea. We found the X chromosome is enriched for differentially expressed transcripts and that many of these X-linked differentially expressed transcripts had elevated Ka /Ks values between ST and SR, indicative of potential functional differences. We identified a set of candidate transcripts, including a testis-specific, X-linked duplicate of the nuclear transport gene importin-α2 that is overexpressed in SR. We find suggestions of positive selection in the lineage leading to the duplicate and that its molecular evolutionary patterns are consistent with relaxed purifying selection in ST. As these patterns are consistent with involvement in the mechanism of drive in this species, this duplicate is a strong candidate worthy of further functional investigation. Nuclear transport may be a common target for genetic conflict, as the mechanism of the autosomal Segregation Distorter drive system in D. melanogaster involves the same pathway.
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Affiliation(s)
| | - Robert L Unckless
- Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas
| | - Kelly A Dyer
- Department of Genetics, University of Georgia, Athens, Georgia
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12
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Argyridou E, Parsch J. Regulation of the X Chromosome in the Germline and Soma of Drosophila melanogaster Males. Genes (Basel) 2018; 9:genes9050242. [PMID: 29734690 PMCID: PMC5977182 DOI: 10.3390/genes9050242] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2018] [Revised: 04/27/2018] [Accepted: 04/27/2018] [Indexed: 12/22/2022] Open
Abstract
During the evolution of heteromorphic sex chromosomes, the sex-specific Y chromosome degenerates, while the X chromosome evolves new mechanisms of regulation. Using bioinformatic and experimental approaches, we investigate the expression of the X chromosome in Drosophila melanogaster. We observe nearly complete X chromosome dosage compensation in male somatic tissues, but not in testis. The X chromosome contains disproportionately fewer genes with high expression in testis than the autosomes, even after accounting for the lack of dosage compensation, which suggests that another mechanism suppresses their expression in the male germline. This is consistent with studies of reporter genes and transposed genes, which find that the same gene has higher expression when autosomal than when X-linked. Using a new reporter gene that is expressed in both testis and somatic tissues, we find that the suppression of X-linked gene expression is limited to genes with high expression in testis and that the extent of the suppression is positively correlated with expression level.
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Affiliation(s)
- Eliza Argyridou
- Division of Evolutionary Biology, Faculty of Biology, LMU Munich, Grosshaderner Str. 2, 82152 Planegg-Martinsried, Germany.
| | - John Parsch
- Division of Evolutionary Biology, Faculty of Biology, LMU Munich, Grosshaderner Str. 2, 82152 Planegg-Martinsried, Germany.
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