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Cervantes S, Kesälahti R, Kumpula TA, Mattila TM, Helanterä H, Pyhäjärvi T. Strong Purifying Selection in Haploid Tissue-Specific Genes of Scots Pine Supports the Masking Theory. Mol Biol Evol 2023; 40:msad183. [PMID: 37565532 PMCID: PMC10457172 DOI: 10.1093/molbev/msad183] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Revised: 06/16/2023] [Accepted: 08/10/2023] [Indexed: 08/12/2023] Open
Abstract
The masking theory states that genes expressed in a haploid stage will be under more efficient selection. In contrast, selection will be less efficient in genes expressed in a diploid stage, where the fitness effects of recessive deleterious or beneficial mutations can be hidden from selection in heterozygous form. This difference can influence several evolutionary processes such as the maintenance of genetic variation, adaptation rate, and genetic load. Masking theory expectations have been confirmed in single-cell haploid and diploid organisms. However, in multicellular organisms, such as plants, the effects of haploid selection are not clear-cut. In plants, the great majority of studies indicating haploid selection have been carried out using male haploid tissues in angiosperms. Hence, evidence in these systems is confounded with the effects of sexual selection and intraspecific competition. Evidence from other plant groups is scarce, and results show no support for the masking theory. Here, we have used a gymnosperm Scots pine megagametophyte, a maternally derived seed haploid tissue, and four diploid tissues to test the strength of purifying selection on a set of genes with tissue-specific expression. By using targeted resequencing data of those genes, we obtained estimates of genetic diversity, the site frequency spectrum of 0-fold and 4-fold sites, and inferred the distribution of fitness effects of new mutations in haploid and diploid tissue-specific genes. Our results show that purifying selection is stronger for tissue-specific genes expressed in the haploid megagametophyte tissue and that this signal of strong selection is not an artifact driven by high expression levels.
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Affiliation(s)
- Sandra Cervantes
- Department of Ecology and Genetics, University of Oulu, Oulu, Finland
- Biocenter Oulu, University of Oulu, Oulu, Finland
| | - Robert Kesälahti
- Department of Ecology and Genetics, University of Oulu, Oulu, Finland
| | - Timo A Kumpula
- Biocenter Oulu, University of Oulu, Oulu, Finland
- Laboratory of Cancer Genetics and Tumor Biology, Research Unit of Translational Medicine, University of Oulu, Oulu, Finland
| | - Tiina M Mattila
- Human Evolution, Department of Organismal Biology, Uppsala University, Uppsala, Sweden
| | - Heikki Helanterä
- Department of Ecology and Genetics, University of Oulu, Oulu, Finland
| | - Tanja Pyhäjärvi
- Department of Forest Sciences, University of Helsinki, Helsinki, Finland
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2
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Li LL, Xiao Y, Wang X, He ZH, Lv YW, Hu XS. The Ka /Ks and πa /πs Ratios under Different Models of Gametophytic and Sporophytic Selection. Genome Biol Evol 2023; 15:evad151. [PMID: 37561000 PMCID: PMC10443736 DOI: 10.1093/gbe/evad151] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Revised: 08/06/2023] [Accepted: 08/08/2023] [Indexed: 08/11/2023] Open
Abstract
Alternation of generations in plant life cycle provides a biological basis for natural selection occurring in either the gametophyte or the sporophyte phase or in both. Divergent biphasic selection could yield distinct evolutionary rates for phase-specific or pleiotropic genes. Here, we analyze models that deal with antagonistic and synergistic selection between alternative generations in terms of the ratio of nonsynonymous to synonymous divergence (Ka/Ks). Effects of biphasic selection are opposite under antagonistic selection but cumulative under synergistic selection for pleiotropic genes. Under the additive and comparable strengths of biphasic allelic selection, the absolute Ka/Ks for the gametophyte gene is equal to in outcrossing but smaller than, in a mixed mating system, that for the sporophyte gene under antagonistic selection. The same pattern is predicted for Ka/Ks under synergistic selection. Selfing reduces efficacy of gametophytic selection. Other processes, including pollen and seed flow and genetic drift, reduce selection efficacy. The polymorphism (πa) at a nonsynonymous site is affected by the joint effects of selfing with gametophytic or sporophytic selection. Likewise, the ratio of nonsynonymous to synonymous polymorphism (πa/πs) is also affected by the same joint effects. Gene flow and genetic drift have opposite effects on πa or πa/πs in interacting with gametophytic and sporophytic selection. We discuss implications of this theory for detecting natural selection in terms of Ka/Ks and for interpreting the evolutionary divergence among gametophyte-specific, sporophyte-specific, and pleiotropic genes.
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Affiliation(s)
- Ling-Ling Li
- College of Forestry and Landscape Architecture, South China Agricultural University, Guangzhou 510642, China
- Guangdong Key Laboratory for Innovative Development and Utilization of Forest Plant Germplasm, South China Agricultural University, Guangzhou 510642, China
| | - Yu Xiao
- College of Forestry and Landscape Architecture, South China Agricultural University, Guangzhou 510642, China
- Guangdong Key Laboratory for Innovative Development and Utilization of Forest Plant Germplasm, South China Agricultural University, Guangzhou 510642, China
| | - Xi Wang
- College of Forestry and Landscape Architecture, South China Agricultural University, Guangzhou 510642, China
- Guangdong Key Laboratory for Innovative Development and Utilization of Forest Plant Germplasm, South China Agricultural University, Guangzhou 510642, China
| | - Zi-Han He
- College of Forestry and Landscape Architecture, South China Agricultural University, Guangzhou 510642, China
- Guangdong Key Laboratory for Innovative Development and Utilization of Forest Plant Germplasm, South China Agricultural University, Guangzhou 510642, China
| | - Yan-Wen Lv
- College of Forestry and Landscape Architecture, South China Agricultural University, Guangzhou 510642, China
- Guangdong Key Laboratory for Innovative Development and Utilization of Forest Plant Germplasm, South China Agricultural University, Guangzhou 510642, China
| | - Xin-Sheng Hu
- College of Forestry and Landscape Architecture, South China Agricultural University, Guangzhou 510642, China
- Guangdong Key Laboratory for Innovative Development and Utilization of Forest Plant Germplasm, South China Agricultural University, Guangzhou 510642, China
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Abstract
Many animal species are haplodiploid: their fertilized eggs develop into diploid females and their unfertilized eggs develop into haploid males. The unique genetic features of haplodiploidy raise the prospect that these systems can be used to disentangle the population genetic consequences of haploid and diploid selection. To this end, sex-specific reproductive genes are of particular interest because, while they are shared within the same genome, they consistently experience selection in different ploidal environments. However, other features of these genes, including sex-specific expression and putative involvement in postcopulatory sexual selection, are potentially confounding factors because they may also impact the efficacy of selection asymmetrically between the sexes. Thus, to properly interpret evolutionary genomic patterns, it is necessary to generate a null expectation for the relative amount of polymorphism and divergence we expect to observe among sex-specific genes in haplodiploid species, given differences in ploidal environment, sex-limited expression, and their potential role in sexual selection. Here, we derive the theoretical expectation for the rate of evolution of sex-specific genes in haplodiploid species, under the assumption that they experience the same selective environment as genes expressed in both sexes. We find that the null expectation is that reproductive genes evolve more rapidly than constitutively expressed genes in haplodiploid genomes. However, despite the aforementioned differences, the null expectation does not differ between male- and female-specific reproductive genes, when assuming additivity. Our theoretical results provide an important baseline expectation that should be used in molecular evolution studies comparing rates of evolution among classes of genes in haplodiploid species.
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Affiliation(s)
| | - Garett P. Slater
- Department of Entomology, Purdue University, West Lafayette, IN 47907, USA
| | - Katherynne Shores
- Department of Biological Sciences, Mississippi State University, MS 39762, USA
| | - Brock A. Harpur
- Department of Entomology, Purdue University, West Lafayette, IN 47907, USA
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Abstract
Many species have separate haploid and diploid phases. Theory predicts that each phase should experience the effects of evolutionary forces (like selection) differently. In the haploid phase, all fitness-affecting alleles are exposed to selection, whereas in the diploid phase, those same alleles can be masked by homologous alleles. This predicts that selection acting on genes expressed in haploids should be more effective than diploid-biased genes. Unfortunately, in arrhenotokous species, this prediction can be confounded with the effects of sex-specific expression, as haploids are usually reproductive males. Theory posits that, when accounting for ploidal- and sex-specific expression, selection should be equally efficient on haploid- and diploid-biased genes relative to constitutive genes. Here, we used a multiomic approach in honey bees to quantify the evolutionary rates of haploid-biased genes and test the relative effects of sexual- and haploid-expression on molecular evolution. We found that 16% of the honey bee’s protein-coding genome is highly expressed in haploid tissue. When accounting for ploidy and sex, haploid- and diploid-biased genes evolve at a lower rate than expected, indicating that they experience strong negative selection. However, the rate of molecular evolution of haploid-biased genes was higher than diploid-based genes. Genes associated with sperm storage are a clear exception to this trend with evidence of strong positive selection. Our results provide an important empirical test of theory outlining how selection acts on genes expressed in arrhenotokous species. We propose the haploid life history stage affects genome-wide patterns of diversity and divergence because of both sexual and haploid selection.
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Affiliation(s)
| | - Amy L. Dapper
- Department of Biological Sciences, Mississippi State University, 219 Harned Hall, 295 Lee Blvd, Mississippi State, Mississippi 39762, USA
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5
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Abstract
Sexual selection drives the evolution of many striking behaviors and morphologies and should leave signatures of selection at loci underlying these phenotypes. However, although loci thought to be under sexual selection often evolve rapidly, few studies have contrasted rates of molecular sequence evolution at such loci across lineages with different sexual selection contexts. Furthermore, work has focused on separate sexed animals, neglecting alternative sexual systems. We investigate rates of molecular sequence evolution in hermaphroditic flatworms of the genus Macrostomum. Specifically, we compare species that exhibit contrasting sperm morphologies, strongly associated with multiple convergent shifts in the mating strategy, reflecting different sexual selection contexts. Species donating and receiving sperm in every mating have sperm with bristles, likely to prevent sperm removal. Meanwhile, species that hypodermically inject sperm lack bristles, potentially as an adaptation to the environment experienced by hypodermic sperm. Combining functional annotations from the model, Macrostomum lignano, with transcriptomes from 93 congeners, we find genus-wide faster sequence evolution in reproduction-related versus ubiquitously expressed genes, consistent with stronger sexual selection on the former. Additionally, species with hypodermic sperm morphologies had elevated molecular sequence evolution, regardless of a gene's functional annotation. These genome-wide patterns suggest reduced selection efficiency following shifts to hypodermic mating, possibly due to higher selfing rates in these species. Moreover, we find little evidence for convergent amino acid changes across species. Our work not only shows that reproduction-related genes evolve rapidly also in hermaphroditic animals, but also that well-replicated contrasts of different sexual selection contexts can reveal underappreciated genome-wide effects.
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Affiliation(s)
- R Axel W Wiberg
- Department of Environmental Sciences, Zoological Institute, University of Basel, Basel, Switzerland
| | - Jeremias N Brand
- Department of Environmental Sciences, Zoological Institute, University of Basel, Basel, Switzerland
| | - Lukas Schärer
- Department of Environmental Sciences, Zoological Institute, University of Basel, Basel, Switzerland
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Gutiérrez-Valencia J, Fracassetti M, Horvath R, Laenen B, Désamore A, Drouzas AD, Friberg M, Kolář F, Slotte T. Genomic Signatures of Sexual Selection on Pollen-Expressed Genes in Arabis alpina. Mol Biol Evol 2021; 39:6456311. [PMID: 34878144 PMCID: PMC8788238 DOI: 10.1093/molbev/msab349] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Fertilization in angiosperms involves the germination of pollen on the stigma, followed by the extrusion of a pollen tube that elongates through the style and delivers two sperm cells to the embryo sac. Sexual selection could occur throughout this process when male gametophytes compete for fertilization. The strength of sexual selection during pollen competition should be affected by the number of genotypes deposited on the stigma. As increased self-fertilization reduces the number of mating partners, and the genetic diversity and heterozygosity of populations, it should thereby reduce the intensity of sexual selection during pollen competition. Despite the prevalence of mating system shifts, few studies have directly compared the molecular signatures of sexual selection during pollen competition in populations with different mating systems. Here we analyzed whole-genome sequences from natural populations of Arabis alpina, a species showing mating system variation across its distribution, to test whether shifts from cross- to self-fertilization result in molecular signatures consistent with sexual selection on genes involved in pollen competition. We found evidence for efficient purifying selection on genes expressed in vegetative pollen, and overall weaker selection on sperm-expressed genes. This pattern was robust when controlling for gene expression level and specificity. In agreement with the expectation that sexual selection intensifies under cross-fertilization, we found that the efficacy of purifying selection on male gametophyte-expressed genes was significantly stronger in genetically more diverse and outbred populations. Our results show that intra-sexual competition shapes the evolution of pollen-expressed genes, and that its strength fades with increasing self-fertilization rates.
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Affiliation(s)
- Juanita Gutiérrez-Valencia
- Department of Ecology, Environment, and Plant Sciences, Science for Life Laboratory, Stockholm University, Stockholm, Sweden
| | - Marco Fracassetti
- Department of Ecology, Environment, and Plant Sciences, Science for Life Laboratory, Stockholm University, Stockholm, Sweden
| | - Robert Horvath
- Department of Ecology, Environment, and Plant Sciences, Science for Life Laboratory, Stockholm University, Stockholm, Sweden
| | - Benjamin Laenen
- Department of Ecology, Environment, and Plant Sciences, Science for Life Laboratory, Stockholm University, Stockholm, Sweden
| | - Aurélie Désamore
- Department of Ecology, Environment, and Plant Sciences, Science for Life Laboratory, Stockholm University, Stockholm, Sweden
| | - Andreas D Drouzas
- Laboratory of Systematic Botany and Phytogeography, School of Biology, Aristotle University of Thessaloniki, Thessaloniki, Greece
| | - Magne Friberg
- Department of Biology, Lund University, Lund, Sweden
| | - Filip Kolář
- Department of Botany, Faculty of Science, Charles University, Prague, Czech Republic
| | - Tanja Slotte
- Department of Ecology, Environment, and Plant Sciences, Science for Life Laboratory, Stockholm University, Stockholm, Sweden
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7
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Linde AM, Eklund DM, Cronberg N, Bowman JL, Lagercrantz U. Rates and patterns of molecular evolution in bryophyte genomes, with focus on complex thalloid liverworts, Marchantiopsida. Mol Phylogenet Evol 2021; 165:107295. [PMID: 34438050 DOI: 10.1016/j.ympev.2021.107295] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Revised: 06/30/2021] [Accepted: 08/19/2021] [Indexed: 10/20/2022]
Abstract
Plants commonly referred to as "bryophytes" belong to three major lineages of non-vascular plants: the liverworts, the hornworts and the mosses. They are unique among land plants in having a dominant haploid generation and a short-lived diploid sporophytic generation. The dynamics of selection acting on a haploid genome differs from those acting on a diploid genome: new mutations are directly exposed to selection. The general aim of this paper is to investigate the diversification rateof bryophytes - measured as silent site substitution rate representing neutral evolution (mutation rate) and the nonsynonymous to synonymous substitution rate ratio (dN/dS) representing selective evolution - and compare it with earlier studies on vascular plants. Results show that the silent site substitution rate is lower for liverworts as compared to angiosperms, but not as low as for gymnosperms. The selection pressure, measured as dN/dS, isnot remarkably lower for bryophytes as compared to other diploid dominant plants as would be expected by the masking hypothesis, indicating that other factors are more important than ploidy.
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Affiliation(s)
- Anna-Malin Linde
- Department of Plant Ecology and Evolution, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, SE-75236 Uppsala, Sweden
| | - D Magnus Eklund
- Department of Plant Ecology and Evolution, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, SE-75236 Uppsala, Sweden
| | - Nils Cronberg
- Biodiversity, Department of Biology, Lund University, Ecology Building, SE-223 62 Lund, Sweden.
| | - John L Bowman
- School of Biological Sciences, Monash University, Clayton, VIC 3800, Australia
| | - Ulf Lagercrantz
- Department of Plant Ecology and Evolution, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, SE-75236 Uppsala, Sweden
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8
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Moyle LC, Wu M, Gibson MJS. Reproductive Proteins Evolve Faster Than Non-reproductive Proteins Among Solanum Species. Front Plant Sci 2021; 12:635990. [PMID: 33912206 PMCID: PMC8072272 DOI: 10.3389/fpls.2021.635990] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Accepted: 03/01/2021] [Indexed: 05/13/2023]
Abstract
Elevated rates of evolution in reproductive proteins are commonly observed in animal species, and are thought to be driven by the action of sexual selection and sexual conflict acting specifically on reproductive traits. Whether similar patterns are broadly observed in other biological groups is equivocal. Here, we examine patterns of protein divergence among wild tomato species (Solanum section Lycopersicon), to understand forces shaping the evolution of reproductive genes in this diverse, rapidly evolving plant clade. By comparing rates of molecular evolution among loci expressed in reproductive and non-reproductive tissues, our aims were to test if: (a) reproductive-specific loci evolve more rapidly, on average, than non-reproductive loci; (b) 'male'-specific loci evolve at different rates than 'female'-specific loci; (c) genes expressed exclusively in gametophytic (haploid) tissue evolve differently from genes expressed in sporophytic (diploid) tissue or in both tissue types; and (d) mating system variation (a potential proxy for the expected strength of sexual selection and/or sexual conflict) affects patterns of protein evolution. We observed elevated evolutionary rates in reproductive proteins. However, this pattern was most evident for female- rather than male-specific loci, both broadly and for individual loci inferred to be positively selected. These elevated rates might be facilitated by greater tissue-specificity of reproductive proteins, as faster rates were also associated with more narrow expression domains. In contrast, we found little evidence that evolutionary rates are consistently different in loci experiencing haploid selection (gametophytic-exclusive loci), or in lineages with quantitatively different mating systems. Overall while reproductive protein evolution is generally elevated in this diverse plant group, some specific patterns of evolution are more complex than those reported in other (largely animal) systems, and include a more prominent role for female-specific loci among adaptively evolving genes.
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Beaudry FE, Rifkin JL, Barrett SC, Wright SI. Evolutionary Genomics of Plant Gametophytic Selection. Plant Commun 2020; 1:100115. [PMID: 33367268 PMCID: PMC7748008 DOI: 10.1016/j.xplc.2020.100115] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Revised: 10/17/2020] [Accepted: 10/22/2020] [Indexed: 05/26/2023]
Abstract
It has long been recognized that natural selection during the haploid gametophytic phase of the plant life cycle may have widespread importance for rates of evolution and the maintenance of genetic variation. Recent theoretical advances have further highlighted the significance of gametophytic selection for diverse evolutionary processes. Genomic approaches offer exciting opportunities to address key questions about the extent and effects of gametophytic selection on plant evolution and adaptation. Here, we review the progress and prospects for integrating functional and evolutionary genomics to test theoretical predictions, and to examine the importance of gametophytic selection on genetic diversity and rates of evolution. There is growing evidence that selection during the gametophyte phase of the plant life cycle has important effects on both gene and genome evolution and is likely to have important pleiotropic effects on the sporophyte. We discuss the opportunities to integrate comparative population genomics, genome-wide association studies, and experimental approaches to further distinguish how differential selection in the two phases of the plant life cycle contributes to genetic diversity and adaptive evolution.
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Affiliation(s)
- Felix E.G. Beaudry
- Department of Ecology and Evolutionary Biology, The University of Toronto, 25 Willcocks Street, Toronto, ON M5S 3B2, Canada
| | - Joanna L. Rifkin
- Department of Ecology and Evolutionary Biology, The University of Toronto, 25 Willcocks Street, Toronto, ON M5S 3B2, Canada
| | - Spencer C.H. Barrett
- Department of Ecology and Evolutionary Biology, The University of Toronto, 25 Willcocks Street, Toronto, ON M5S 3B2, Canada
| | - Stephen I. Wright
- Department of Ecology and Evolutionary Biology, The University of Toronto, 25 Willcocks Street, Toronto, ON M5S 3B2, Canada
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Becheler R, Guillemin M, Stoeckel S, Mauger S, Saunier A, Brante A, Destombe C, Valero M. After a catastrophe, a little bit of sex is better than nothing: Genetic consequences of a major earthquake on asexual and sexual populations. Evol Appl 2020; 13:2086-2100. [PMID: 32908606 PMCID: PMC7463374 DOI: 10.1111/eva.12967] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 03/04/2020] [Accepted: 03/05/2020] [Indexed: 11/27/2022] Open
Abstract
Catastrophic events can have profound effects on the demography of a population and consequently on genetic diversity. The dynamics of postcatastrophic recovery and the role of sexual versus asexual reproduction in buffering the effects of massive perturbations remain poorly understood, in part because the opportunity to document genetic diversity before and after such events is rare. Six natural (purely sexual) and seven cultivated (mainly clonal due to farming practices) populations of the red alga Agarophyton chilense were surveyed along the Chilean coast before, in the days after and 2 years after the 8.8 magnitude earthquake in 2010. The genetic diversity of sexual populations appeared sensitive to this massive perturbation, notably through the loss of rare alleles immediately after the earthquake. By 2012, the levels of diversity returned to those observed before the catastrophe, probably due to migration. In contrast, enhanced rates of clonality in cultivated populations conferred a surprising ability to buffer the instantaneous loss of diversity. After the earthquake, farmers increased the already high rate of clonality to maintain the few surviving beds, but most of them collapsed rapidly. Contrasting fates between sexual and clonal populations suggest that betting on strict clonality to sustain production is risky, probably because this extreme strategy hampered adaptation to the brutal environmental perturbation induced by the catastrophe.
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Affiliation(s)
- Ronan Becheler
- Centro de Conservación MarinaDepartamento de EcologíaFacultad de Ciencias BiológicasPontificia Universidad Católica de ChileCasillaChile
- UMI 3614Evolutionary Biology and Ecology of AlgaeCNRSSorbonne UniversitéUniversidad Austral de ChilePontificia Universidad Católica de ChileRoscoffFrance
| | - Marie‐Laure Guillemin
- UMI 3614Evolutionary Biology and Ecology of AlgaeCNRSSorbonne UniversitéUniversidad Austral de ChilePontificia Universidad Católica de ChileRoscoffFrance
- Instituto de Ciencias Ambientales y EvolutivasFacultad de CienciasUniversidad Austral de ChileValdiviaChile
| | - Solenn Stoeckel
- UMR1349 Institute for Genetics, Environment and Plant ProtectionINRALe RheuFrance
| | - Stéphane Mauger
- UMI 3614Evolutionary Biology and Ecology of AlgaeCNRSSorbonne UniversitéUniversidad Austral de ChilePontificia Universidad Católica de ChileRoscoffFrance
| | - Alice Saunier
- UMI 3614Evolutionary Biology and Ecology of AlgaeCNRSSorbonne UniversitéUniversidad Austral de ChilePontificia Universidad Católica de ChileRoscoffFrance
- Instituto de Ciencias Ambientales y EvolutivasFacultad de CienciasUniversidad Austral de ChileValdiviaChile
| | - Antonio Brante
- Departamento de EcologíaFacultad de CienciasUniversidad Católica de la Santísima Concepción (UCSC)ConcepciónChile
- Centro de Investigación en Biodiversidad y Ambientes Sustentables (CIBAS)UCSCConcepciónChile
| | - Christophe Destombe
- UMI 3614Evolutionary Biology and Ecology of AlgaeCNRSSorbonne UniversitéUniversidad Austral de ChilePontificia Universidad Católica de ChileRoscoffFrance
| | - Myriam Valero
- UMI 3614Evolutionary Biology and Ecology of AlgaeCNRSSorbonne UniversitéUniversidad Austral de ChilePontificia Universidad Católica de ChileRoscoffFrance
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11
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Harrison MC, Mallon EB, Twell D, Hammond RL. Deleterious Mutation Accumulation in Arabidopsis thaliana Pollen Genes: A Role for a Recent Relaxation of Selection. Genome Biol Evol 2020; 11:1939-1951. [PMID: 31209485 PMCID: PMC6640295 DOI: 10.1093/gbe/evz127] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/11/2019] [Indexed: 12/19/2022] Open
Abstract
In many studies, sex-related genes have been found to evolve rapidly. We therefore expect plant pollen genes to evolve faster than sporophytic genes. In addition, pollen genes are expressed as haploids which can itself facilitate rapid evolution because recessive advantageous and deleterious alleles are not masked by dominant alleles. However, this mechanism is less straightforward to apply in the model plant species Arabidopsis thaliana. For 1 Myr, A. thaliana has been self-compatible, a life history switch that has caused: a reduction in pollen competition, increased homozygosity, and a dilution of masking in diploid expressed, sporophytic genes. In this study, we have investigated the relative strength of selection on pollen genes compared with sporophytic genes in A. thaliana. We present two major findings: 1) before becoming self-compatible, positive selection was stronger on pollen genes than sporophytic genes for A. thaliana and 2) current polymorphism data indicate that selection is weaker on pollen genes compared with sporophytic genes. This weaker selection on pollen genes can in part be explained by their higher tissue specificity, which in outbreeding plants can be outweighed by the effects of haploid expression and pollen competition. These results indicate that since A. thaliana has become self-compatible, selection on pollen genes has become more relaxed. This has led to higher polymorphism levels and a higher build-up of deleterious mutations in pollen genes compared with sporophytic genes.
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12
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Liu Y, Johnson MG, Cox CJ, Medina R, Devos N, Vanderpoorten A, Hedenäs L, Bell NE, Shevock JR, Aguero B, Quandt D, Wickett NJ, Shaw AJ, Goffinet B. Resolution of the ordinal phylogeny of mosses using targeted exons from organellar and nuclear genomes. Nat Commun 2019; 10:1485. [PMID: 30940807 PMCID: PMC6445109 DOI: 10.1038/s41467-019-09454-w] [Citation(s) in RCA: 72] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2018] [Accepted: 03/07/2019] [Indexed: 11/21/2022] Open
Abstract
Mosses are a highly diverse lineage of land plants, whose diversification, spanning at least 400 million years, remains phylogenetically ambiguous due to the lack of fossils, massive early extinctions, late radiations, limited morphological variation, and conflicting signal among previously used markers. Here, we present phylogenetic reconstructions based on complete organellar exomes and a comparable set of nuclear genes for this major lineage of land plants. Our analysis of 142 species representing 29 of the 30 moss orders reveals that relative average rates of non-synonymous substitutions in nuclear versus plastid genes are much higher in mosses than in seed plants, consistent with the emerging concept of evolutionary dynamism in mosses. Our results highlight the evolutionary significance of taxa with reduced morphologies, shed light on the relative tempo and mechanisms underlying major cladogenic events, and suggest hypotheses for the relationships and delineation of moss orders.
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Affiliation(s)
- Yang Liu
- Fairy Lake Botanical Garden & Chinese Academy of Sciences, Shenzhen, 518004, China
- BGI-Shenzhen, Shenzhen, 518120, China
| | | | - Cymon J Cox
- Centro de Ciências do Mar, Universidade do Algarve, Gambelas, 8005-319, Faro, Portugal
| | - Rafael Medina
- Department of Biology, Augustana College, Rock Island, IL, 61201, USA
| | - Nicolas Devos
- Department of Biology, Duke University, Durham, NC, 27708, USA
| | | | - Lars Hedenäs
- Department of Botany, Swedish Museum of Natural History, Stockholm, Box 50007, 10405, Sweden
| | - Neil E Bell
- Royal Botanic Garden Edinburgh, 20A Inverleith Row, Edinburgh, EH3 5LR, UK
| | - James R Shevock
- California Academy of Sciences, San Francisco, CA, 94118, USA
| | - Blanka Aguero
- Department of Biology, Duke University, Durham, NC, 27708, USA
| | - Dietmar Quandt
- Nees Institute for Biodiversity of Plants, University of Bonn, Bonn, 53115, Germany
| | | | - A Jonathan Shaw
- Department of Biology, Duke University, Durham, NC, 27708, USA
| | - Bernard Goffinet
- Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT, 06269, USA.
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13
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Lipinska AP, Serrano-Serrano ML, Cormier A, Peters AF, Kogame K, Cock JM, Coelho SM. Rapid turnover of life-cycle-related genes in the brown algae. Genome Biol 2019; 20:35. [PMID: 30764885 PMCID: PMC6374913 DOI: 10.1186/s13059-019-1630-6] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2018] [Accepted: 01/16/2019] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Sexual life cycles in eukaryotes involve a cyclic alternation between haploid and diploid phases. While most animals possess a diploid life cycle, many plants and algae alternate between multicellular haploid (gametophyte) and diploid (sporophyte) generations. In many algae, gametophytes and sporophytes are independent and free-living and may present dramatic phenotypic differences. The same shared genome can therefore be subject to different, even conflicting, selection pressures during each of the life cycle generations. Here, we analyze the nature and extent of genome-wide, generation-biased gene expression in four species of brown algae with contrasting levels of dimorphism between life cycle generations. RESULTS We show that the proportion of the transcriptome that is generation-specific is broadly associated with the level of phenotypic dimorphism between the life cycle stages. Importantly, our data reveals a remarkably high turnover rate for life-cycle-related gene sets across the brown algae and highlights the importance not only of co-option of regulatory programs from one generation to the other but also of a role for newly emerged, lineage-specific gene expression patterns in the evolution of the gametophyte and sporophyte developmental programs in this major eukaryotic group. Moreover, we show that generation-biased genes display distinct evolutionary modes, with gametophyte-biased genes evolving rapidly at the coding sequence level whereas sporophyte-biased genes tend to exhibit changes in their patterns of expression. CONCLUSION Our analysis uncovers the characteristics, expression patterns, and evolution of generation-biased genes and underlines the selective forces that shape this previously underappreciated source of phenotypic diversity.
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Affiliation(s)
- Agnieszka P Lipinska
- Sorbonne Université, UPMC Univ Paris 06, CNRS, Algal Genetics Group, Integrative Biology of Marine Models, Station Biologique de Roscoff, CS 90074, F-29688, Roscoff, France
| | | | - Alexandre Cormier
- Laboratoire Ecologie et Biologie des Interactions, Equipe Ecologie Evolution Symbiose, Université de Poitiers, UMR CNRS 7267, Poitiers, France
| | | | - Kazuhiro Kogame
- Department of Biological Sciences, Faculty of Sciences, Hokkaido University, Sapporo, 060-0810, Japan
| | - J Mark Cock
- Sorbonne Université, UPMC Univ Paris 06, CNRS, Algal Genetics Group, Integrative Biology of Marine Models, Station Biologique de Roscoff, CS 90074, F-29688, Roscoff, France
| | - Susana M Coelho
- Sorbonne Université, UPMC Univ Paris 06, CNRS, Algal Genetics Group, Integrative Biology of Marine Models, Station Biologique de Roscoff, CS 90074, F-29688, Roscoff, France.
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14
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Abstract
As an immediate consequence of sexual reproduction, biphasic life cycles with alternating diploid and haploid phases are a common characteristic of sexually reproducing eukaryotes. Much of our focus in evolutionary biology has been directed toward dynamics in diploid or haploid populations, but we rarely consider selection occurring during both phases when studying evolutionary processes. One of the reasons for this apparent omission is the fact that many flowering plants and metazoans are predominantly diploid with a very short haploid gametic phase. While this gametic phase may be short, it can play a crucial role in fundamental processes including the rate of adaptation, the load of mutation, and the evolution of features such as recombination. In addition, if selection acts in different directions between the two phases, a genetic conflict will occur, impacting the maintenance of genetic variation. Here we provide an overview of theoretical and empirical studies investigating the importance of selection at the haploid gametic phase in predominantly diploid organisms and discuss future directions to improve our understanding of the underlying dynamics and the general implications of haploid selection.
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15
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Lang D, Ullrich KK, Murat F, Fuchs J, Jenkins J, Haas FB, Piednoel M, Gundlach H, Van Bel M, Meyberg R, Vives C, Morata J, Symeonidi A, Hiss M, Muchero W, Kamisugi Y, Saleh O, Blanc G, Decker EL, van Gessel N, Grimwood J, Hayes RD, Graham SW, Gunter LE, McDaniel SF, Hoernstein SNW, Larsson A, Li FW, Perroud PF, Phillips J, Ranjan P, Rokshar DS, Rothfels CJ, Schneider L, Shu S, Stevenson DW, Thümmler F, Tillich M, Villarreal Aguilar JC, Widiez T, Wong GKS, Wymore A, Zhang Y, Zimmer AD, Quatrano RS, Mayer KFX, Goodstein D, Casacuberta JM, Vandepoele K, Reski R, Cuming AC, Tuskan GA, Maumus F, Salse J, Schmutz J, Rensing SA. The Physcomitrella patens chromosome-scale assembly reveals moss genome structure and evolution. Plant J 2018; 93:515-533. [PMID: 29237241 DOI: 10.1111/tpj.13801] [Citation(s) in RCA: 247] [Impact Index Per Article: 41.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Revised: 11/20/2017] [Accepted: 11/24/2017] [Indexed: 05/18/2023]
Abstract
The draft genome of the moss model, Physcomitrella patens, comprised approximately 2000 unordered scaffolds. In order to enable analyses of genome structure and evolution we generated a chromosome-scale genome assembly using genetic linkage as well as (end) sequencing of long DNA fragments. We find that 57% of the genome comprises transposable elements (TEs), some of which may be actively transposing during the life cycle. Unlike in flowering plant genomes, gene- and TE-rich regions show an overall even distribution along the chromosomes. However, the chromosomes are mono-centric with peaks of a class of Copia elements potentially coinciding with centromeres. Gene body methylation is evident in 5.7% of the protein-coding genes, typically coinciding with low GC and low expression. Some giant virus insertions are transcriptionally active and might protect gametes from viral infection via siRNA mediated silencing. Structure-based detection methods show that the genome evolved via two rounds of whole genome duplications (WGDs), apparently common in mosses but not in liverworts and hornworts. Several hundred genes are present in colinear regions conserved since the last common ancestor of plants. These syntenic regions are enriched for functions related to plant-specific cell growth and tissue organization. The P. patens genome lacks the TE-rich pericentromeric and gene-rich distal regions typical for most flowering plant genomes. More non-seed plant genomes are needed to unravel how plant genomes evolve, and to understand whether the P. patens genome structure is typical for mosses or bryophytes.
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Affiliation(s)
- Daniel Lang
- Plant Biotechnology, Faculty of Biology, University of Freiburg, Schaenzlestr. 1, 79104, Freiburg, Germany
- Plant Genome and Systems Biology, Helmholtz Center Munich, 85764, Neuherberg, Germany
| | - Kristian K Ullrich
- Plant Cell Biology, Faculty of Biology, University of Marburg, Marburg, Germany
| | - Florent Murat
- INRA, UMR 1095 Genetics, Diversity and Ecophysiology of Cereals (GDEC), 5 Chemin de Beaulieu, 63100, Clermont-Ferrand, France
| | - Jörg Fuchs
- Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Corrensstrasse 3, OT Gatersleben, D-06466, Stadt Seeland, Germany
| | - Jerry Jenkins
- HudsonAlpha Institute for Biotechnology, Huntsville, AL, USA
| | - Fabian B Haas
- Plant Cell Biology, Faculty of Biology, University of Marburg, Marburg, Germany
| | - Mathieu Piednoel
- Department of Plant Developmental Biology, Max Planck Institute for Plant Breeding Research, Carl-von-Linné Weg 10, D-50829, Cologne, Germany
| | - Heidrun Gundlach
- Plant Genome and Systems Biology, Helmholtz Center Munich, 85764, Neuherberg, Germany
| | - Michiel Van Bel
- VIB Center for Plant Systems Biology, Technologiepark 927, 9052, Ghent, Belgium
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Technologiepark 927, B-9052, Gent, Belgium
| | - Rabea Meyberg
- Plant Cell Biology, Faculty of Biology, University of Marburg, Marburg, Germany
| | - Cristina Vives
- Center for Research in Agricultural Genomics, CRAG (CSIC-IRTA-UAB-UB), Campus UAB, Bellaterra, Cerdanyola del Vallès, 08193, Barcelona, Spain
| | - Jordi Morata
- Center for Research in Agricultural Genomics, CRAG (CSIC-IRTA-UAB-UB), Campus UAB, Bellaterra, Cerdanyola del Vallès, 08193, Barcelona, Spain
| | | | - Manuel Hiss
- Plant Cell Biology, Faculty of Biology, University of Marburg, Marburg, Germany
| | - Wellington Muchero
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Yasuko Kamisugi
- Centre for Plant Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Omar Saleh
- Plant Biotechnology, Faculty of Biology, University of Freiburg, Schaenzlestr. 1, 79104, Freiburg, Germany
| | - Guillaume Blanc
- Structural and Genomic Information Laboratory (IGS), Aix-Marseille Université, CNRS, UMR 7256 (IMM FR 3479), Marseille, France
| | - Eva L Decker
- Plant Biotechnology, Faculty of Biology, University of Freiburg, Schaenzlestr. 1, 79104, Freiburg, Germany
| | - Nico van Gessel
- Plant Biotechnology, Faculty of Biology, University of Freiburg, Schaenzlestr. 1, 79104, Freiburg, Germany
| | - Jane Grimwood
- HudsonAlpha Institute for Biotechnology, Huntsville, AL, USA
- DOE Joint Genome Institute, Walnut Creek, CA, 94598, USA
| | | | - Sean W Graham
- Department of Botany, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
| | - Lee E Gunter
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Stuart F McDaniel
- Department of Biology, University of Florida, Gainesville, FL, 32611, USA
| | - Sebastian N W Hoernstein
- Plant Biotechnology, Faculty of Biology, University of Freiburg, Schaenzlestr. 1, 79104, Freiburg, Germany
| | - Anders Larsson
- Department of Organismal Biology, Evolutionary Biology Centre, Uppsala University, Uppsala, Sweden
| | - Fay-Wei Li
- Boyce Thompson Institute, Ithaca, NY, 14853, USA
| | | | | | - Priya Ranjan
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Daniel S Rokshar
- DOE Joint Genome Institute, Walnut Creek, CA, 94598, USA
- Department of Molecular and Cell Biology, University of California, Berkeley, CA, 94720, USA
| | - Carl J Rothfels
- University Herbarium and Department of Integrative Biology, University of California, Berkeley, CA, 94720-2465, USA
| | - Lucas Schneider
- Plant Cell Biology, Faculty of Biology, University of Marburg, Marburg, Germany
| | - Shengqiang Shu
- DOE Joint Genome Institute, Walnut Creek, CA, 94598, USA
| | | | - Fritz Thümmler
- Vertis Biotechnologie AG, Lise-Meitner-Str. 30, 85354, Freising, Germany
| | - Michael Tillich
- Max Planck Institute of Molecular Plant Physiology, Am Muehlenberg 1, 14476, Potsdam-Golm, Germany
| | | | - Thomas Widiez
- Department of Plant Biology, University of Geneva, Sciences III, Geneva 4, CH-1211, Switzerland
- Department of Plant Biology & Pathology Rutgers, The State University of New Jersey, New Brunswick, NJ, 08901, USA
| | - Gane Ka-Shu Wong
- Department of Biological Sciences, University of Alberta, Edmonton, AB, T6G 2E9, Canada
- Department of Medicine, University of Alberta, Edmonton, AB, T6G 2E1, Canada
- BGI-Shenzhen, Beishan Industrial Zone, Yantian District, Shenzhen, 518083, China
| | - Ann Wymore
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Yong Zhang
- Shenzhen Huahan Gene Life Technology Co. Ltd, Shenzhen, China
| | - Andreas D Zimmer
- Plant Biotechnology, Faculty of Biology, University of Freiburg, Schaenzlestr. 1, 79104, Freiburg, Germany
| | - Ralph S Quatrano
- Department of Biology, Washington University, St. Louis, MO, USA
| | - Klaus F X Mayer
- Plant Genome and Systems Biology, Helmholtz Center Munich, 85764, Neuherberg, Germany
- WZW, Technical University Munich, Munich, Germany
| | | | - Josep M Casacuberta
- Center for Research in Agricultural Genomics, CRAG (CSIC-IRTA-UAB-UB), Campus UAB, Bellaterra, Cerdanyola del Vallès, 08193, Barcelona, Spain
| | - Klaas Vandepoele
- VIB Center for Plant Systems Biology, Technologiepark 927, 9052, Ghent, Belgium
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Technologiepark 927, B-9052, Gent, Belgium
| | - Ralf Reski
- Plant Biotechnology, Faculty of Biology, University of Freiburg, Schaenzlestr. 1, 79104, Freiburg, Germany
- BIOSS Centre for Biological Signalling Studies, University of Freiburg, Schaenzlestr. 18, 79104, Freiburg, Germany
| | - Andrew C Cuming
- Centre for Plant Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Gerald A Tuskan
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Florian Maumus
- URGI, INRA, Université Paris-Saclay, 78026, Versailles, France
| | - Jérome Salse
- INRA, UMR 1095 Genetics, Diversity and Ecophysiology of Cereals (GDEC), 5 Chemin de Beaulieu, 63100, Clermont-Ferrand, France
| | - Jeremy Schmutz
- HudsonAlpha Institute for Biotechnology, Huntsville, AL, USA
- DOE Joint Genome Institute, Walnut Creek, CA, 94598, USA
| | - Stefan A Rensing
- Plant Cell Biology, Faculty of Biology, University of Marburg, Marburg, Germany
- BIOSS Centre for Biological Signalling Studies, University of Freiburg, Schaenzlestr. 18, 79104, Freiburg, Germany
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16
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Darolti I, Wright AE, Pucholt P, Berlin S, Mank JE. Slow evolution of sex-biased genes in the reproductive tissue of the dioecious plant Salix viminalis. Mol Ecol 2018; 27:694-708. [PMID: 29274186 PMCID: PMC5901004 DOI: 10.1111/mec.14466] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Revised: 11/21/2017] [Accepted: 11/28/2017] [Indexed: 12/13/2022]
Abstract
The relative rate of evolution for sex‐biased genes has often been used as a measure of the strength of sex‐specific selection. In contrast to studies in a wide variety of animals, far less is known about the molecular evolution of sex‐biased genes in plants, particularly in dioecious angiosperms. Here, we investigate the gene expression patterns and evolution of sex‐biased genes in the dioecious plant Salix viminalis. We observe lower rates of sequence evolution for male‐biased genes expressed in the reproductive tissue compared to unbiased and female‐biased genes. These results could be partially explained by the lower codon usage bias for male‐biased genes leading to elevated rates of synonymous substitutions compared to unbiased genes. However, the stronger haploid selection in the reproductive tissue of plants, together with pollen competition, would also lead to higher levels of purifying selection acting to remove deleterious variation. Future work should focus on the differential evolution of haploid‐ and diploid‐specific genes to understand the selective dynamics acting on these loci.
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Affiliation(s)
- Iulia Darolti
- Department of Genetics, Evolution and Environment, University College London, London, UK
| | - Alison E Wright
- Department of Genetics, Evolution and Environment, University College London, London, UK.,Department of Animal and Plant Sciences, University of Sheffield, Sheffield, UK
| | - Pascal Pucholt
- Department of Plant Biology, Linnean Centre for Plant Biology, Swedish University of Agricultural Sciences, Uppsala, Sweden.,Array and Analysis Facility, Department of Medical Science, Uppsala University, Uppsala, Sweden
| | - Sofia Berlin
- Department of Plant Biology, Linnean Centre for Plant Biology, Swedish University of Agricultural Sciences, Uppsala, Sweden
| | - Judith E Mank
- Department of Genetics, Evolution and Environment, University College London, London, UK.,Department of Organismal Biology, Uppsala University, Uppsala, Sweden
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17
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Szövényi P, Ullrich KK, Rensing SA, Lang D, van Gessel N, Stenøien HK, Conti E, Reski R. Selfing in Haploid Plants and Efficacy of Selection: Codon Usage Bias in the Model Moss Physcomitrella patens. Genome Biol Evol 2017; 9:1528-1546. [PMID: 28549175 PMCID: PMC5507605 DOI: 10.1093/gbe/evx098] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/25/2017] [Indexed: 12/15/2022] Open
Abstract
A long-term reduction in effective population size will lead to major shift in genome evolution. In particular, when effective population size is small, genetic drift becomes dominant over natural selection. The onset of self-fertilization is one evolutionary event considerably reducing effective size of populations. Theory predicts that this reduction should be more dramatic in organisms capable for haploid than for diploid selfing. Although theoretically well-grounded, this assertion received mixed experimental support. Here, we test this hypothesis by analyzing synonymous codon usage bias of genes in the model moss Physcomitrella patens frequently undergoing haploid selfing. In line with population genetic theory, we found that the effect of natural selection on synonymous codon usage bias is very weak. Our conclusion is supported by four independent lines of evidence: 1) Very weak or nonsignificant correlation between gene expression and codon usage bias, 2) no increased codon usage bias in more broadly expressed genes, 3) no evidence that codon usage bias would constrain synonymous and nonsynonymous divergence, and 4) predominant role of genetic drift on synonymous codon usage predicted by a model-based analysis. These findings show striking similarity to those observed in AT-rich genomes with weak selection for optimal codon usage and GC content overall. Our finding is in contrast to a previous study reporting adaptive codon usage bias in the moss P. patens.
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Affiliation(s)
- Péter Szövényi
- Department of Systematic and Evolutionary Botany, University of Zurich, Switzerland
| | - Kristian K. Ullrich
- Plant Cell Biology, Faculty of Biology, University of Marburg, Germany
- Present address: Max-Planck-Insitut für Evolutionsbiologie, Plön, Germany
| | - Stefan A. Rensing
- Plant Cell Biology, Faculty of Biology, University of Marburg, Germany
- BIOSS—Centre for Biological Signalling Studies, University of Freiburg, Germany
| | - Daniel Lang
- Plant Genome and Systems Biology, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany
| | - Nico van Gessel
- Plant Biotechnology, Faculty of Biology, University of Freiburg, Germany
| | | | - Elena Conti
- Department of Systematic and Evolutionary Botany, University of Zurich, Switzerland
| | - Ralf Reski
- BIOSS—Centre for Biological Signalling Studies, University of Freiburg, Germany
- Plant Biotechnology, Faculty of Biology, University of Freiburg, Germany
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18
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Abstract
Sexual reproduction leads to an alternation between haploid and diploid phases, whose relative length varies widely across taxa. Previous genetical models showed that diploid or haploid life cycles may be favored, depending on dominance interactions and on effective recombination rates. By contrast, niche differentiation between haploids and diploids may favor biphasic life cycles, in which development occurs in both phases. In this article, we explore the interplay between genetical and ecological factors, assuming that deleterious mutations affect the competitivity of individuals within their ecological niche and allowing different effects of mutations in haploids and diploids (including antagonistic selection). We show that selection on a modifier gene affecting the relative length of both phases can be decomposed into a direct selection term favoring the phase with the highest mean fitness (due to either ecological differences or differential effects of mutations) and an indirect selection term favoring the phase in which selection is more efficient. When deleterious alleles occur at many loci and in the presence of ecological differentiation between haploids and diploids, evolutionary branching often occurs and leads to the stable coexistence of alleles coding for haploid and diploid cycles, while temporal variations in niche sizes may stabilize biphasic cycles.
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19
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Sellis D, Kvitek DJ, Dunn B, Sherlock G, Petrov DA. Heterozygote Advantage Is a Common Outcome of Adaptation in Saccharomyces cerevisiae. Genetics 2016; 203:1401-13. [PMID: 27194750 DOI: 10.1534/genetics.115.185165] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2015] [Accepted: 05/15/2016] [Indexed: 12/31/2022] Open
Abstract
Adaptation in diploids is predicted to proceed via mutations that are at least partially dominant in fitness. Recently, we argued that many adaptive mutations might also be commonly overdominant in fitness. Natural (directional) selection acting on overdominant mutations should drive them into the population but then, instead of bringing them to fixation, should maintain them as balanced polymorphisms via heterozygote advantage. If true, this would make adaptive evolution in sexual diploids differ drastically from that of haploids. The validity of this prediction has not yet been tested experimentally. Here, we performed four replicate evolutionary experiments with diploid yeast populations (Saccharomyces cerevisiae) growing in glucose-limited continuous cultures. We sequenced 24 evolved clones and identified initial adaptive mutations in all four chemostats. The first adaptive mutations in all four chemostats were three copy number variations, all of which proved to be overdominant in fitness. The fact that fitness overdominant mutations were always the first step in independent adaptive walks supports the prediction that heterozygote advantage can arise as a common outcome of directional selection in diploids and demonstrates that overdominance of de novo adaptive mutations in diploids is not rare.
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20
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Kemen AC, Agler MT, Kemen E. Host-microbe and microbe-microbe interactions in the evolution of obligate plant parasitism. New Phytol 2015; 206:1207-28. [PMID: 25622918 DOI: 10.1111/nph.13284] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2014] [Accepted: 12/12/2014] [Indexed: 05/03/2023]
Abstract
Research on obligate biotrophic plant parasites, which reproduce only on living hosts, has revealed a broad diversity of filamentous microbes that have independently acquired complex morphological structures, such as haustoria. Genome studies have also demonstrated a concerted loss of genes for metabolism and lytic enzymes, and gain of diversity of genes coding for effectors involved in host defense suppression. So far, these traits converge in all known obligate biotrophic parasites, but unexpected genome plasticity remains. This plasticity is manifested as transposable element (TE)-driven increases in genome size, observed to be associated with the diversification of virulence genes under selection pressure. Genome expansion could result from the governing of the pathogen response to ecological selection pressures, such as host or nutrient availability, or to microbial interactions, such as competition, hyperparasitism and beneficial cooperations. Expansion is balanced by alternating sexual and asexual cycles, as well as selfing and outcrossing, which operate to control transposon activity in populations. In turn, the prevalence of these balancing mechanisms seems to be correlated with external biotic factors, suggesting a complex, interconnected evolutionary network in host-pathogen-microbe interactions. Therefore, the next phase of obligate biotrophic pathogen research will need to uncover how this network, including multitrophic interactions, shapes the evolution and diversity of pathogens.
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Affiliation(s)
- Ariane C Kemen
- Max Planck Research Group Fungal Biodiversity, Max Planck Institute for Plant Breeding Research, Carl-von-Linne Weg 10, 50829, Cologne, Germany
| | - Matthew T Agler
- Max Planck Research Group Fungal Biodiversity, Max Planck Institute for Plant Breeding Research, Carl-von-Linne Weg 10, 50829, Cologne, Germany
| | - Eric Kemen
- Max Planck Research Group Fungal Biodiversity, Max Planck Institute for Plant Breeding Research, Carl-von-Linne Weg 10, 50829, Cologne, Germany
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21
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Lipinska A, Cormier A, Luthringer R, Peters AF, Corre E, Gachon CMM, Cock JM, Coelho SM. Sexual dimorphism and the evolution of sex-biased gene expression in the brown alga ectocarpus. Mol Biol Evol 2015; 32:1581-97. [PMID: 25725430 DOI: 10.1093/molbev/msv049] [Citation(s) in RCA: 69] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Males and females often have marked phenotypic differences, and the expression of these dissimilarities invariably involves sex differences in gene expression. Sex-biased gene expression has been well characterized in animal species, where a high proportion of the genome may be differentially regulated in males and females during development. Male-biased genes tend to evolve more rapidly than female-biased genes, implying differences in the strength of the selective forces acting on the two sexes. Analyses of sex-biased gene expression have focused on organisms that exhibit separate sexes during the diploid phase of the life cycle (diploid sexual systems), but the genetic nature of the sexual system is expected to influence the evolutionary trajectories of sex-biased genes. We analyze here the patterns of sex-biased gene expression in Ectocarpus, a brown alga with haploid sex determination (dioicy) and a low level of phenotypic sexual dimorphism. In Ectocarpus, female-biased genes were found to be evolving as rapidly as male-biased genes. Moreover, genes expressed at fertility showed faster rates of evolution than genes expressed in immature gametophytes. Both male- and female-biased genes had a greater proportion of sites experiencing positive selection, suggesting that their accelerated evolution is at least partly driven by adaptive evolution. Gene duplication appears to have played a significant role in the generation of sex-biased genes in Ectocarpus, expanding previous models that propose this mechanism for the resolution of sexual antagonism in diploid systems. The patterns of sex-biased gene expression in Ectocarpus are consistent both with predicted characteristics of UV (haploid) sexual systems and with the distinctive aspects of this organism's reproductive biology.
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Affiliation(s)
- Agnieszka Lipinska
- Sorbonne Université, UPMC Univ Paris 06, CNRS, Algal Genetics Group, UMR 8227, Integrative Biology of Marine Models, Station Biologique de Roscoff, CS 90074, F-29688, Roscoff, France
| | - Alexandre Cormier
- Sorbonne Université, UPMC Univ Paris 06, CNRS, Algal Genetics Group, UMR 8227, Integrative Biology of Marine Models, Station Biologique de Roscoff, CS 90074, F-29688, Roscoff, France
| | - Rémy Luthringer
- Sorbonne Université, UPMC Univ Paris 06, CNRS, Algal Genetics Group, UMR 8227, Integrative Biology of Marine Models, Station Biologique de Roscoff, CS 90074, F-29688, Roscoff, France
| | | | - Erwan Corre
- Abims Platform, CNRS-UPMC, FR2424, Station Biologique de Roscoff, Roscoff, France
| | - Claire M M Gachon
- Microbial and Molecular Biology Department, Scottish Marine Institute, Scottish Association for Marine Science, Oban, United Kingdom
| | - J Mark Cock
- Sorbonne Université, UPMC Univ Paris 06, CNRS, Algal Genetics Group, UMR 8227, Integrative Biology of Marine Models, Station Biologique de Roscoff, CS 90074, F-29688, Roscoff, France
| | - Susana M Coelho
- Sorbonne Université, UPMC Univ Paris 06, CNRS, Algal Genetics Group, UMR 8227, Integrative Biology of Marine Models, Station Biologique de Roscoff, CS 90074, F-29688, Roscoff, France
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22
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Tien NS, Sabelis MW, Egas M. Inbreeding depression and purging in a haplodiploid: gender-related effects. Heredity (Edinb) 2015; 114:327-32. [PMID: 25407077 DOI: 10.1038/hdy.2014.106] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Accepted: 09/30/2014] [Indexed: 11/08/2022] Open
Abstract
Compared with diploid species, haplodiploids suffer less inbreeding depression because male haploidy imposes purifying selection on recessive deleterious alleles. However, alleles of genes only expressed in the diploid females are protected in heterozygous individuals. This leads to the prediction that haplodiploids suffer more from inbreeding effects on life-history traits controlled by genes with female-limited expression. To test this, we used a wild population of the haplodiploid mite Tetranychus urticae. First, negative effects of inbreeding were investigated by comparing maturation rate, juvenile survival, oviposition rate and longevity between lines created by three generations of either outbreeding or mother-son inbreeding. Second, purging through inbreeding was investigated by comparing the intensity of inbreeding depression between outbred families with known inbreeding/outbreeding mating histories. Negative effects of inbreeding and evidence for purging were found for the female trait oviposition rate, but not for juvenile survival and longevity. Both male and female maturation rate were negatively affected by inbreeding, most likely due to maternal effects because inbred offspring of outbred mothers was not affected. These results support the hypothesis that, in haplodiploids inbreeding effects and genetic variation due to deleterious recessive alleles may depend on gender.
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Szövényi P, Devos N, Weston DJ, Yang X, Hock Z, Shaw JA, Shimizu KK, McDaniel SF, Wagner A. Efficient purging of deleterious mutations in plants with haploid selfing. Genome Biol Evol 2014; 6:1238-52. [PMID: 24879432 PMCID: PMC4041004 DOI: 10.1093/gbe/evu099] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
In diploid organisms, selfing reduces the efficiency of selection in removing deleterious mutations from a population. This need not be the case for all organisms. Some plants, for example, undergo an extreme form of selfing known as intragametophytic selfing, which immediately exposes all recessive deleterious mutations in a parental genome to selective purging. Here, we ask how effectively deleterious mutations are removed from such plants. Specifically, we study the extent to which deleterious mutations accumulate in a predominantly selfing and a predominantly outcrossing pair of moss species, using genome-wide transcriptome data. We find that the selfing species purge significantly more nonsynonymous mutations, as well as a greater proportion of radical amino acid changes which alter physicochemical properties of amino acids. Moreover, their purging of deleterious mutation is especially strong in conserved regions of protein-coding genes. Our observations show that selfing need not impede but can even accelerate the removal of deleterious mutations, and do so on a genome-wide scale.
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Affiliation(s)
- Péter Szövényi
- Institute of Evolutionary Biology and Environmental Studies, University of Zurich, SwitzerlandInstitute of Systematic Botany, University of Zurich, SwitzerlandSwiss Institute of Bioinformatics, Quartier Sorge-Batiment Genopode, Lausanne, SwitzerlandMTA-ELTE-MTM Ecology Research Group, ELTE, Biological Institute, Hungary
| | | | - David J Weston
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN
| | - Xiaohan Yang
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN
| | - Zsófia Hock
- Institute of Systematic Botany, University of Zurich, Switzerland
| | | | - Kentaro K Shimizu
- Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Switzerland
| | | | - Andreas Wagner
- Institute of Evolutionary Biology and Environmental Studies, University of Zurich, SwitzerlandSwiss Institute of Bioinformatics, Quartier Sorge-Batiment Genopode, Lausanne, SwitzerlandBioinformatics Institute, Agency for Science, Technology and Research (A*STAR), SingaporeThe Santa Fe Institute, Santa Fe NM
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24
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Rensing SA. Gene duplication as a driver of plant morphogenetic evolution. Curr Opin Plant Biol 2014; 17:43-8. [PMID: 24507493 DOI: 10.1016/j.pbi.2013.11.002] [Citation(s) in RCA: 132] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2013] [Revised: 10/30/2013] [Accepted: 11/06/2013] [Indexed: 05/19/2023]
Abstract
Most duplicated genes (paralogs) are quickly erased during evolution, and only some are retained. Yet, gene and genome duplications are connected to the evolution of genetic and, in turn, morphological complexity. Plants are especially prone to experience polyploidizations and to enhance their gene repertoire after such events. Genes encoding proteins involved in transcriptional regulation are of especial interest since they are correlated with the occurrence of genome duplication events and with the rise of plant morphological complexity. Here, I review what we know about paralog retention as a driver for morphogenetic evolution of plants. The main focus is on the evolution of plant genes controlling development (morphogenetic transcription factors).
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Affiliation(s)
- Stefan A Rensing
- Plant Cell Biology, Faculty of Biology, University of Marburg, Karl-von-Frisch-Strasse 8, 35043 Marburg, Germany.
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25
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Arunkumar R, Josephs EB, Williamson RJ, Wright SI. Pollen-specific, but not sperm-specific, genes show stronger purifying selection and higher rates of positive selection than sporophytic genes in Capsella grandiflora. Mol Biol Evol 2013; 30:2475-86. [PMID: 23997108 DOI: 10.1093/molbev/mst149] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Selection on the gametophyte can be a major force shaping plant genomes as 7-11% of genes are expressed only in that phase and 60% of genes are expressed in both the gametophytic and sporophytic phases. The efficacy of selection on gametophytic tissues is likely to be influenced by sexual selection acting on male and female functions of hermaphroditic plants. Moreover, the haploid nature of the gametophytic phase allows selection to be efficient in removing recessive deleterious mutations and fixing recessive beneficial mutations. To assess the importance of gametophytic selection, we compared the strength of purifying selection and extent of positive selection on gametophyte- and sporophyte-specific genes in the highly outcrossing plant Capsella grandiflora. We found that pollen-exclusive genes had a larger fraction of sites under strong purifying selection, a greater proportion of adaptive substitutions, and faster protein evolution compared with seedling-exclusive genes. In contrast, sperm cell-exclusive genes had a smaller fraction of sites under strong purifying selection, a lower proportion of adaptive substitutions, and slower protein evolution compared with seedling-exclusive genes. Observations of strong selection acting on pollen-expressed genes are likely explained by sexual selection resulting from pollen competition aided by the haploid nature of that tissue. The relaxation of selection in sperm might be due to the reduced influence of intrasexual competition, but reduced gene expression may also be playing an important role.
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Affiliation(s)
- Ramesh Arunkumar
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada
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