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Majane AC, Cridland JM, Blair LK, Begun DJ. Evolution and genetics of accessory gland transcriptome divergence between Drosophila melanogaster and D. simulans. Genetics 2024; 227:iyae039. [PMID: 38518250 PMCID: PMC11151936 DOI: 10.1093/genetics/iyae039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2023] [Revised: 08/27/2023] [Accepted: 02/15/2024] [Indexed: 03/24/2024] Open
Abstract
Studies of allele-specific expression in interspecific hybrids have provided important insights into gene-regulatory divergence and hybrid incompatibilities. Many such investigations in Drosophila have used transcriptome data from complex mixtures of many tissues or from gonads, however, regulatory divergence may vary widely among species, sexes, and tissues. Thus, we lack sufficiently broad sampling to be confident about the general biological principles of regulatory divergence. Here, we seek to fill some of these gaps in the literature by characterizing regulatory evolution and hybrid misexpression in a somatic male sex organ, the accessory gland, in F1 hybrids between Drosophila melanogaster and D. simulans. The accessory gland produces seminal fluid proteins, which play an important role in male and female fertility and may be subject to adaptive divergence due to male-male or male-female interactions. We find that trans differences are relatively more abundant than cis, in contrast to most of the interspecific hybrid literature, though large effect-size trans differences are rare. Seminal fluid protein genes have significantly elevated levels of expression divergence and tend to be regulated through both cis and trans divergence. We find limited misexpression (over- or underexpression relative to both parents) in this organ compared to most other Drosophila studies. As in previous studies, male-biased genes are overrepresented among misexpressed genes and are much more likely to be underexpressed. ATAC-Seq data show that chromatin accessibility is correlated with expression differences among species and hybrid allele-specific expression. This work identifies unique regulatory evolution and hybrid misexpression properties of the accessory gland and suggests the importance of tissue-specific allele-specific expression studies.
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Affiliation(s)
- Alex C Majane
- Department of Evolution and Ecology, University of California, Davis, CA 95616, USA
| | - Julie M Cridland
- Department of Evolution and Ecology, University of California, Davis, CA 95616, USA
| | - Logan K Blair
- Department of Evolution and Ecology, University of California, Davis, CA 95616, USA
| | - David J Begun
- Department of Evolution and Ecology, University of California, Davis, CA 95616, USA
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2
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Longan ER, Fay JC. The distribution of beneficial mutational effects between two sister yeast species poorly explains natural outcomes of vineyard adaptation. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.06.03.597243. [PMID: 38895255 PMCID: PMC11185594 DOI: 10.1101/2024.06.03.597243] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/21/2024]
Abstract
Domesticated strains of Saccharomyces cerevisiae have adapted to resist copper and sulfite, two chemical stressors commonly used in winemaking. S. paradoxus, has not adapted to these chemicals despite being consistently present in sympatry with S. cerevisiae in vineyards. This contrast represents a case of apparent evolutionary constraints favoring greater adaptive capacity in S. cerevisiae. In this study, we used a comparative mutagenesis approach to test whether S. paradoxus is mutationally constrained with respect to acquiring greater copper and sulfite resistance. For both species, we assayed the rate, effect size, and pleiotropic costs of resistance mutations and sequenced a subset of 150 mutants isolated from our screen. We found that the distributions of mutational effects displayed by the two species were very similar and poorly explained the natural pattern. We also found that chromosome VIII aneuploidy and loss of function mutations in PMA1 confer copper resistance in both species, whereas loss of function mutations in REG1 were only a viable route to copper resistance in S. cerevisiae. We also observed a single de novo duplication of the CUP1 gene in S. paradoxus but none in S. cerevisiae. For sulfite, loss of function mutations in RTS1 and KSP1 confer resistance in both species, but mutations in RTS1 have larger average effects in S. paradoxus. Our results show that even when the distributions of mutational effects are largely similar, species can differ in the adaptive paths available to them. They also demonstrate that assays of the distribution of mutational effects may lack predictive insight concerning adaptive outcomes.
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Affiliation(s)
- Emery R. Longan
- University of Rochester, Department of Biology, Rochester, NY, 14620 USA
| | - Justin C. Fay
- University of Rochester, Department of Biology, Rochester, NY, 14620 USA
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3
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Balogun EJ, Ness RW. The Effects of De Novo Mutation on Gene Expression and the Consequences for Fitness in Chlamydomonas reinhardtii. Mol Biol Evol 2024; 41:msae035. [PMID: 38366781 PMCID: PMC10910851 DOI: 10.1093/molbev/msae035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2023] [Revised: 02/01/2024] [Accepted: 02/13/2024] [Indexed: 02/18/2024] Open
Abstract
Mutation is the ultimate source of genetic variation, the bedrock of evolution. Yet, predicting the consequences of new mutations remains a challenge in biology. Gene expression provides a potential link between a genotype and its phenotype. But the variation in gene expression created by de novo mutation and the fitness consequences of mutational changes to expression remain relatively unexplored. Here, we investigate the effects of >2,600 de novo mutations on gene expression across the transcriptome of 28 mutation accumulation lines derived from 2 independent wild-type genotypes of the green algae Chlamydomonas reinhardtii. We observed that the amount of genetic variance in gene expression created by mutation (Vm) was similar to the variance that mutation generates in typical polygenic phenotypic traits and approximately 15-fold the variance seen in the limited species where Vm in gene expression has been estimated. Despite the clear effect of mutation on expression, we did not observe a simple additive effect of mutation on expression change, with no linear correlation between the total expression change and mutation count of individual MA lines. We therefore inferred the distribution of expression effects of new mutations to connect the number of mutations to the number of differentially expressed genes (DEGs). Our inferred DEE is highly L-shaped with 95% of mutations causing 0-1 DEG while the remaining 5% are spread over a long tail of large effect mutations that cause multiple genes to change expression. The distribution is consistent with many cis-acting mutation targets that affect the expression of only 1 gene and a large target of trans-acting targets that have the potential to affect tens or hundreds of genes. Further evidence for cis-acting mutations can be seen in the overabundance of mutations in or near differentially expressed genes. Supporting evidence for trans-acting mutations comes from a 15:1 ratio of DEGs to mutations and the clusters of DEGs in the co-expression network, indicative of shared regulatory architecture. Lastly, we show that there is a negative correlation with the extent of expression divergence from the ancestor and fitness, providing direct evidence of the deleterious effects of perturbing gene expression.
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Affiliation(s)
- Eniolaye J Balogun
- Department of Biology, William G. Davis Building, University of Toronto, Mississauga L5L-1C6, Canada
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto M5S-3B2, Canada
| | - Rob W Ness
- Department of Biology, William G. Davis Building, University of Toronto, Mississauga L5L-1C6, Canada
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4
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Cui L, Yang B, Xiao S, Gao J, Baud A, Graham D, McBride M, Dominiczak A, Schafer S, Aumatell RL, Mont C, Teruel AF, Hübner N, Flint J, Mott R, Huang L. Dominance is common in mammals and is associated with trans-acting gene expression and alternative splicing. Genome Biol 2023; 24:215. [PMID: 37773188 PMCID: PMC10540365 DOI: 10.1186/s13059-023-03060-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Accepted: 09/18/2023] [Indexed: 10/01/2023] Open
Abstract
BACKGROUND Dominance and other non-additive genetic effects arise from the interaction between alleles, and historically these phenomena play a major role in quantitative genetics. However, most genome-wide association studies (GWAS) assume alleles act additively. RESULTS We systematically investigate both dominance-here representing any non-additive within-locus interaction-and additivity across 574 physiological and gene expression traits in three mammalian stocks: F2 intercross pigs, rat heterogeneous stock, and mice heterogeneous stock. Dominance accounts for about one quarter of heritable variance across all physiological traits in all species. Hematological and immunological traits exhibit the highest dominance variance, possibly reflecting balancing selection in response to pathogens. Although most quantitative trait loci (QTLs) are detectable as additive QTLs, we identify 154, 64, and 62 novel dominance QTLs in pigs, rats, and mice respectively that are undetectable as additive QTLs. Similarly, even though most cis-acting expression QTLs are additive, gene expression exhibits a large fraction of dominance variance, and trans-acting eQTLs are enriched for dominance. Genes causal for dominance physiological QTLs are less likely to be physically linked to their QTLs but instead act via trans-acting dominance eQTLs. In addition, thousands of eQTLs are associated with alternatively spliced isoforms with complex additive and dominant architectures in heterogeneous stock rats, suggesting a possible mechanism for dominance. CONCLUSIONS Although heritability is predominantly additive, many mammalian genetic effects are dominant and likely arise through distinct mechanisms. It is therefore advantageous to consider both additive and dominance effects in GWAS to improve power and uncover causality.
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Affiliation(s)
- Leilei Cui
- National Key Laboratory for Pig Genetic Improvement and Production Technology, Jiangxi Agricultural University, Nanchang, 330045, People's Republic of China
- UCL Genetics Institute, University College London, London, WC1E 6BT, UK
- Human Aging Research Institute and School of Life Science, Nanchang University, and Jiangxi Key Laboratory of Human Aging, Jiangxi, China
- School of Life Sciences, Nanchang University, Nanchang, China
| | - Bin Yang
- National Key Laboratory for Pig Genetic Improvement and Production Technology, Jiangxi Agricultural University, Nanchang, 330045, People's Republic of China
| | - Shijun Xiao
- National Key Laboratory for Pig Genetic Improvement and Production Technology, Jiangxi Agricultural University, Nanchang, 330045, People's Republic of China
| | - Jun Gao
- National Key Laboratory for Pig Genetic Improvement and Production Technology, Jiangxi Agricultural University, Nanchang, 330045, People's Republic of China
| | - Amelie Baud
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Barcelona, Spain
| | - Delyth Graham
- BHF Glasgow Cardiovascular Research Centre, University of Glasgow, Glasgow, G12 8TA, UK
| | - Martin McBride
- BHF Glasgow Cardiovascular Research Centre, University of Glasgow, Glasgow, G12 8TA, UK
| | - Anna Dominiczak
- BHF Glasgow Cardiovascular Research Centre, University of Glasgow, Glasgow, G12 8TA, UK
| | - Sebastian Schafer
- Cardiovascular and Metabolic Disorders Program, Duke-National University of Singapore Medical School, Singapore, Singapore
| | - Regina Lopez Aumatell
- Department of Medicine and Life Sciences, Universitat Pompeu Fabra, Barcelona, Spain
| | - Carme Mont
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, UK
| | - Albert Fernandez Teruel
- Departamento de Psiquiatría y Medicina Legal, Universitat Autonoma de Barcelona, Barcelona, Spain
| | - Norbert Hübner
- Genetics and Genomics of Cardiovascular Diseases Research Group, Max Delbrück Center (MDC) for Molecular Medicine in the Helmholtz Association, Berlin, Germany
- DZHK (German Center for Cardiovascular Research) Partner Site Berlin, Berlin, Germany
- Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Jonathan Flint
- Department of Psychiatry and Behavioral Sciences, Brain Research Institute, University of California, Los Angeles, CA, USA
| | - Richard Mott
- UCL Genetics Institute, University College London, London, WC1E 6BT, UK.
| | - Lusheng Huang
- National Key Laboratory for Pig Genetic Improvement and Production Technology, Jiangxi Agricultural University, Nanchang, 330045, People's Republic of China.
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5
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Kovuri P, Yadav A, Sinha H. Role of genetic architecture in phenotypic plasticity. Trends Genet 2023; 39:703-714. [PMID: 37173192 DOI: 10.1016/j.tig.2023.04.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2022] [Revised: 04/06/2023] [Accepted: 04/11/2023] [Indexed: 05/15/2023]
Abstract
Phenotypic plasticity, the ability of an organism to display different phenotypes across environments, is widespread in nature. Plasticity aids survival in novel environments. Herein, we review studies from yeast that allow us to start uncovering the genetic architecture of phenotypic plasticity. Genetic variants and their interactions impact the phenotype in different environments, and distinct environments modulate the impact of genetic variants and their interactions on the phenotype. Because of this, certain hidden genetic variation is expressed in specific genetic and environmental backgrounds. A better understanding of the genetic mechanisms of phenotypic plasticity will help to determine short- and long-term responses to selection and how wide variation in disease manifestation occurs in human populations.
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Affiliation(s)
- Purnima Kovuri
- Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, IIT Madras, Chennai, India; Centre for Integrative Biology and Systems mEdicine (IBSE), IIT Madras, Chennai, India; Robert Bosch Centre for Data Science and Artificial Intelligence (RBCDSAI), IIT Madras, Chennai, India
| | - Anupama Yadav
- Center for Cancer Systems Biology (CCSB), Dana-Farber Cancer Institute, Boston, MA, USA; Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA, USA; Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA, USA
| | - Himanshu Sinha
- Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, IIT Madras, Chennai, India; Centre for Integrative Biology and Systems mEdicine (IBSE), IIT Madras, Chennai, India; Robert Bosch Centre for Data Science and Artificial Intelligence (RBCDSAI), IIT Madras, Chennai, India.
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6
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Puixeu G, Macon A, Vicoso B. Sex-specific estimation of cis and trans regulation of gene expression in heads and gonads of Drosophila melanogaster. G3 (BETHESDA, MD.) 2023; 13:jkad121. [PMID: 37259621 PMCID: PMC10411594 DOI: 10.1093/g3journal/jkad121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2023] [Revised: 05/17/2023] [Accepted: 05/17/2023] [Indexed: 06/02/2023]
Abstract
The regulatory architecture of gene expression is known to differ substantially between sexes in Drosophila, but most studies performed so far used whole-body data and only single crosses, which may have limited their scope to detect patterns that are robust across tissues and biological replicates. Here, we use allele-specific gene expression of parental and reciprocal hybrid crosses between 6 Drosophila melanogaster inbred lines to quantify cis- and trans-regulatory variation in heads and gonads of both sexes separately across 3 replicate crosses. Our results suggest that female and male heads, as well as ovaries, have a similar regulatory architecture. On the other hand, testes display more and substantially different cis-regulatory effects, suggesting that sex differences in the regulatory architecture that have been previously observed may largely derive from testis-specific effects. We also examine the difference in cis-regulatory variation of genes across different levels of sex bias in gonads and heads. Consistent with the idea that intersex correlations constrain expression and can lead to sexual antagonism, we find more cis variation in unbiased and moderately biased genes in heads. In ovaries, reduced cis variation is observed for male-biased genes, suggesting that cis variants acting on these genes in males do not lead to changes in ovary expression. Finally, we examine the dominance patterns of gene expression and find that sex- and tissue-specific patterns of inheritance as well as trans-regulatory variation are highly variable across biological crosses, although these were performed in highly controlled experimental conditions. This highlights the importance of using various genetic backgrounds to infer generalizable patterns.
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Affiliation(s)
- Gemma Puixeu
- Institute of Science and Technology Austria, Am Campus 1, Klosterneuburg 3400, Austria
| | - Ariana Macon
- Institute of Science and Technology Austria, Am Campus 1, Klosterneuburg 3400, Austria
| | - Beatriz Vicoso
- Institute of Science and Technology Austria, Am Campus 1, Klosterneuburg 3400, Austria
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7
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Snyman M, Xu S. The effects of mutations on gene expression and alternative splicing. Proc Biol Sci 2023; 290:20230565. [PMID: 37403507 PMCID: PMC10320348 DOI: 10.1098/rspb.2023.0565] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2023] [Accepted: 06/12/2023] [Indexed: 07/06/2023] Open
Abstract
Understanding the relationship between mutations and their genomic and phenotypic consequences has been a longstanding goal of evolutionary biology. However, few studies have investigated the impact of mutations on gene expression and alternative splicing on the genome-wide scale. In this study, we aim to bridge this knowledge gap by utilizing whole-genome sequencing data and RNA sequencing data from 16 obligately parthenogenetic Daphnia mutant lines to investigate the effects of ethyl methanesulfonate-induced mutations on gene expression and alternative splicing. Using rigorous analyses of mutations, expression changes and alternative splicing, we show that trans-effects are the major contributor to the variance in gene expression and alternative splicing between the wild-type and mutant lines, whereas cis mutations only affected a limited number of genes and do not always alter gene expression. Moreover, we show that there is a significant association between differentially expressed genes and exonic mutations, indicating that exonic mutations are an important driver of altered gene expression.
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Affiliation(s)
- Marelize Snyman
- Department of Biology, University of Texas at Arlington, Arlington, TX 76019, USA
| | - Sen Xu
- Department of Biology, University of Texas at Arlington, Arlington, TX 76019, USA
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8
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Cutter AD. Speciation and development. Evol Dev 2023; 25:289-327. [PMID: 37545126 DOI: 10.1111/ede.12454] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2023] [Revised: 06/13/2023] [Accepted: 07/20/2023] [Indexed: 08/08/2023]
Abstract
Understanding general principles about the origin of species remains one of the foundational challenges in evolutionary biology. The genomic divergence between groups of individuals can spawn hybrid inviability and hybrid sterility, which presents a tantalizing developmental problem. Divergent developmental programs may yield either conserved or divergent phenotypes relative to ancestral traits, both of which can be responsible for reproductive isolation during the speciation process. The genetic mechanisms of developmental evolution involve cis- and trans-acting gene regulatory change, protein-protein interactions, genetic network structures, dosage, and epigenetic regulation, all of which also have roots in population genetic and molecular evolutionary processes. Toward the goal of demystifying Darwin's "mystery of mysteries," this review integrates microevolutionary concepts of genetic change with principles of organismal development, establishing explicit links between population genetic process and developmental mechanisms in the production of macroevolutionary pattern. This integration aims to establish a more unified view of speciation that binds process and mechanism.
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Affiliation(s)
- Asher D Cutter
- Department of Ecology & Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada
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9
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Wittkopp PJ. Contributions of mutation and selection to regulatory variation: lessons from the Saccharomyces cerevisiae TDH3 gene. Philos Trans R Soc Lond B Biol Sci 2023; 378:20220057. [PMID: 37004723 PMCID: PMC10067266 DOI: 10.1098/rstb.2022.0057] [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: 12/07/2022] [Accepted: 02/16/2023] [Indexed: 04/04/2023] Open
Abstract
Heritable variation in gene expression is common within and among species and contributes to phenotypic diversity. Mutations affecting either cis- or trans-regulatory sequences controlling gene expression give rise to variation in gene expression, and natural selection acting on this variation causes some regulatory variants to persist in a population for longer than others. To understand how mutation and selection interact to produce the patterns of regulatory variation we see within and among species, my colleagues and I have been systematically determining the effects of new mutations on expression of the TDH3 gene in Saccharomyces cerevisiae and comparing them to the effects of polymorphisms segregating within this species. We have also investigated the molecular mechanisms by which regulatory variants act. Over the past decade, this work has revealed properties of cis- and trans-regulatory mutations including their relative frequency, effects, dominance, pleiotropy and fitness consequences. Comparing these mutational effects to the effects of polymorphisms in natural populations, we have inferred selection acting on expression level, expression noise and phenotypic plasticity. Here, I summarize this body of work and synthesize its findings to make inferences not readily discernible from the individual studies alone. This article is part of the theme issue 'Interdisciplinary approaches to predicting evolutionary biology'.
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Affiliation(s)
- Patricia J. Wittkopp
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI 48109, USA
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA
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10
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Gao Z, Yang X, Chen J, Rausher MD, Shi T. Expression inheritance and constraints on cis- and trans-regulatory mutations underlying lotus color variation. PLANT PHYSIOLOGY 2023; 191:1662-1683. [PMID: 36417237 PMCID: PMC10022630 DOI: 10.1093/plphys/kiac522] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2022] [Accepted: 11/17/2022] [Indexed: 06/16/2023]
Abstract
Both cis- and trans-regulatory mutations drive changes in gene expression that underpin plant phenotypic evolution. However, how and why these two major types of regulatory mutations arise in different genes and how gene expression is inherited and associated with these regulatory changes are unclear. Here, by studying allele-specific expression in F1 hybrids of pink-flowered sacred lotus (Nelumbo nucifera) and yellow-flowered American lotus (N. lutea), we reveal the relative contributions of cis- and trans-regulatory changes to interspecific expression rewiring underlying petal color change and how the expression is inherited in hybrids. Although cis-only variants influenced slightly more genes, trans-only variants had a stronger impact on expression differences between species. In F1 hybrids, genes under cis-only and trans-only regulatory effects showed a propensity toward additive and dominant inheritance, respectively, whereas transgressive inheritance was observed in genes carrying both cis- and trans-variants acting in opposite directions. By investigating anthocyanin and carotenoid coexpression networks in petals, we found that the same category of regulatory mutations, particularly trans-variants, tend to rewire hub genes in coexpression modules underpinning flower color differentiation between species; we identified 45 known genes with cis- and trans-regulatory variants significantly correlated with flower coloration, such as ANTHOCYANIN 5-AROMATIC ACYLTRANSFERASE (ACT), GLUTATHIONE S-TRANSFERASE F11 (GSTF11), and LYCOPENE Ε-CYCLASE (LCYE). Notably, the relative abundance of genes in different categories of regulatory divergence was associated with the inferred magnitude of constraints like expression level and breadth. Overall, our study suggests distinct selective constraints and modes of gene expression inheritance among different regulatory mutations underlying lotus petal color divergence.
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Affiliation(s)
- Zhiyan Gao
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan 430074, China
- Center of Conservation Biology, Core Botanical Gardens, Chinese Academy of Sciences, Wuhan 430074, China
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xingyu Yang
- Wuhan Institute of Landscape Architecture, Wuhan 430081, China
| | - Jinming Chen
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan 430074, China
- Center of Conservation Biology, Core Botanical Gardens, Chinese Academy of Sciences, Wuhan 430074, China
| | - Mark D Rausher
- Department of Biology, Duke University, Durham, North Carolina 27708, USA
| | - Tao Shi
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan 430074, China
- Center of Conservation Biology, Core Botanical Gardens, Chinese Academy of Sciences, Wuhan 430074, China
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11
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Mechanisms of regulatory evolution in yeast. Curr Opin Genet Dev 2022; 77:101998. [PMID: 36220001 PMCID: PMC10117219 DOI: 10.1016/j.gde.2022.101998] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2022] [Revised: 08/30/2022] [Accepted: 09/01/2022] [Indexed: 02/06/2023]
Abstract
Studies of regulatory variation in yeast - at the level of new mutations, polymorphisms within a species, and divergence between species - have provided great insight into the molecular and evolutionary processes responsible for the evolution of gene expression in eukaryotes. The increasing ease with which yeast genomes can be manipulated and expression quantified in a high-throughput manner has recently accelerated mechanistic studies of cis- and trans-regulatory variation at multiple evolutionary timescales. These studies have, for example, identified differences in the properties of cis- and trans-acting mutations that affect their evolutionary fate, experimentally characterized the molecular mechanisms through which cis- and trans-regulatory variants act, and illustrated how regulatory networks can diverge between species with or without changes in gene expression.
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12
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Behling AH, Winter DJ, Ganley ARD, Cox MP. Cross-kingdom transcriptomic trends in the evolution of hybrid gene expression. J Evol Biol 2022; 35:1126-1137. [PMID: 35830478 PMCID: PMC9546207 DOI: 10.1111/jeb.14059] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2021] [Accepted: 06/13/2022] [Indexed: 11/29/2022]
Abstract
Hybridization is a route to speciation that occurs widely across the eukaryote tree of life. The success of allopolyploids (hybrid species with increased ploidy) and homoploid hybrids (with unchanged ploidy) is well documented. However, their formation and establishment is not straightforward, with a suite of near‐instantaneous and longer term biological repercussions faced by the new species. Central to these challenges is the rewiring of gene regulatory networks following the merger of distinct genomes inherited from both parental species. Research on the evolution of hybrid gene expression has largely involved studies on a single hybrid species or a few gene families. Here, we present the first standardized transcriptome‐wide study exploring the fates of genes following hybridization across three kingdoms: animals, plants and fungi. Within each kingdom, we pair an allopolyploid system with a closely related homoploid hybrid to decouple the influence of increased ploidy from genome merger. Genome merger, not changes in ploidy, has the greatest effect on posthybridization expression patterns across all study systems. Strikingly, we find that differentially expressed genes in parent species preferentially switch to more similar expression in hybrids across all kingdoms, likely as a consequence of regulatory trans‐acting cross‐talk within the hybrid nucleus. We also highlight the prevalence of gene loss or silencing among extremely differentially expressed genes in hybrid species across all kingdoms. These shared patterns suggest that the evolutionary process of hybridization leads to common high‐level expression outcomes, regardless of the particular species or kingdom.
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Affiliation(s)
- Anna H Behling
- School of Natural Sciences, Massey University, Palmerston North, New Zealand
| | - David J Winter
- School of Natural Sciences, Massey University, Palmerston North, New Zealand
| | - Austen R D Ganley
- School of Biological Sciences, University of Auckland, Auckland, New Zealand
| | - Murray P Cox
- School of Natural Sciences, Massey University, Palmerston North, New Zealand
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13
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Coton C, Talbot G, Louarn ML, Dillmann C, Vienne D. Evolution of enzyme levels in metabolic pathways: A theoretical approach. J Theor Biol 2022; 538:111015. [PMID: 35016894 DOI: 10.1016/j.jtbi.2022.111015] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Revised: 12/03/2021] [Accepted: 01/03/2022] [Indexed: 10/19/2022]
Abstract
The central role of metabolism in cell functioning and adaptation has given rise to countless studies on the evolution of enzyme-coding genes and network topology. However, very few studies have addressed the question of how enzyme concentrations change in response to positive selective pressure on the flux, considered a proxy of fitness. In particular, the way cellular constraints, such as resource limitations and co-regulation, affect the adaptive landscape of a pathway under selection has never been analyzed theoretically. To fill this gap, we developed a model of the evolution of enzyme concentrations that combines metabolic control theory and an adaptive dynamics approach, and integrates possible dependencies between enzyme concentrations. We determined the evolutionary equilibria of enzyme concentrations and their range of neutral variation, and showed that they differ with the properties of the enzymes, the constraints applied to the system and the initial enzyme concentrations. Simulations of long-term evolution confirmed all analytical and numerical predictions, even though we relaxed the simplifying assumptions used in the analytical treatment.
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Affiliation(s)
- Charlotte Coton
- Université Paris-Saclay, INRAE, CNRS, AgroParisTech, GQE - Le Moulon, 91190, Gif-sur-Yvette, France.
| | - Grégoire Talbot
- Université Paris-Saclay, INRAE, CNRS, AgroParisTech, GQE - Le Moulon, 91190, Gif-sur-Yvette, France
| | - Maud Le Louarn
- Université Paris-Saclay, INRAE, CNRS, AgroParisTech, GQE - Le Moulon, 91190, Gif-sur-Yvette, France
| | - Christine Dillmann
- Université Paris-Saclay, INRAE, CNRS, AgroParisTech, GQE - Le Moulon, 91190, Gif-sur-Yvette, France
| | - Dominique Vienne
- Université Paris-Saclay, INRAE, CNRS, AgroParisTech, GQE - Le Moulon, 91190, Gif-sur-Yvette, France.
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14
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Brown KE, Kelly JK. Genome-wide association mapping of transcriptome variation in Mimulus guttatus indicates differing patterns of selection on cis- versus trans-acting mutations. Genetics 2022; 220:iyab189. [PMID: 34791192 PMCID: PMC8733635 DOI: 10.1093/genetics/iyab189] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Accepted: 09/28/2021] [Indexed: 11/14/2022] Open
Abstract
We measured the floral bud transcriptome of 151 fully sequenced lines of Mimulus guttatus from one natural population. Thousands of single nucleotide polymorphisms (SNPs) are implicated as transcription regulators, but there is a striking difference in the allele frequency spectrum of cis-acting and trans-acting mutations. Cis-SNPs have intermediate frequencies (consistent with balancing selection) while trans-SNPs exhibit a rare-alleles model (consistent with purifying selection). This pattern only becomes clear when transcript variation is normalized on a gene-to-gene basis. If a global normalization is applied, as is typically in RNAseq experiments, asymmetric transcript distributions combined with "rarity disequilibrium" produce a superabundance of false positives for trans-acting SNPs. To explore the cause of purifying selection on trans-acting mutations, we identified gene expression modules as sets of coexpressed genes. The extent to which trans-acting mutations influence modules is a strong predictor of allele frequency. Mutations altering expression of genes with high "connectedness" (those that are highly predictive of the representative module expression value) have the lowest allele frequency. The expression modules can also predict whole-plant traits such as flower size. We find that a substantial portion of the genetic (co)variance among traits can be described as an emergent property of genetic effects on expression modules.
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Affiliation(s)
- Keely E Brown
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS 66045, USA
| | - John K Kelly
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS 66045, USA
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15
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Tomanek I, Guet CC. Adaptation dynamics between copy-number and point mutations. eLife 2022; 11:82240. [PMID: 36546673 PMCID: PMC9833825 DOI: 10.7554/elife.82240] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Accepted: 12/20/2022] [Indexed: 12/24/2022] Open
Abstract
Together, copy-number and point mutations form the basis for most evolutionary novelty, through the process of gene duplication and divergence. While a plethora of genomic data reveals the long-term fate of diverging coding sequences and their cis-regulatory elements, little is known about the early dynamics around the duplication event itself. In microorganisms, selection for increased gene expression often drives the expansion of gene copy-number mutations, which serves as a crude adaptation, prior to divergence through refining point mutations. Using a simple synthetic genetic reporter system that can distinguish between copy-number and point mutations, we study their early and transient adaptive dynamics in real time in Escherichia coli. We find two qualitatively different routes of adaptation, depending on the level of functional improvement needed. In conditions of high gene expression demand, the two mutation types occur as a combination. However, under low gene expression demand, copy-number and point mutations are mutually exclusive; here, owing to their higher frequency, adaptation is dominated by copy-number mutations, in a process we term amplification hindrance. Ultimately, due to high reversal rates and pleiotropic cost, copy-number mutations may not only serve as a crude and transient adaptation, but also constrain sequence divergence over evolutionary time scales.
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Affiliation(s)
- Isabella Tomanek
- Institute of Science and Technology AustriaKlosterneuburgAustria
| | - Călin C Guet
- Institute of Science and Technology AustriaKlosterneuburgAustria
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16
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Duveau F, Vande Zande P, Metzger BP, Diaz CJ, Walker EA, Tryban S, Siddiq MA, Yang B, Wittkopp PJ. Mutational sources of trans-regulatory variation affecting gene expression in Saccharomyces cerevisiae. eLife 2021; 10:67806. [PMID: 34463616 PMCID: PMC8456550 DOI: 10.7554/elife.67806] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Accepted: 08/03/2021] [Indexed: 12/15/2022] Open
Abstract
Heritable variation in a gene’s expression arises from mutations impacting cis- and trans-acting components of its regulatory network. Here, we investigate how trans-regulatory mutations are distributed within the genome and within a gene regulatory network by identifying and characterizing 69 mutations with trans-regulatory effects on expression of the same focal gene in Saccharomyces cerevisiae. Relative to 1766 mutations without effects on expression of this focal gene, we found that these trans-regulatory mutations were enriched in coding sequences of transcription factors previously predicted to regulate expression of the focal gene. However, over 90% of the trans-regulatory mutations identified mapped to other types of genes involved in diverse biological processes including chromatin state, metabolism, and signal transduction. These data show how genetic changes in diverse types of genes can impact a gene’s expression in trans, revealing properties of trans-regulatory mutations that provide the raw material for trans-regulatory variation segregating within natural populations.
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Affiliation(s)
- Fabien Duveau
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, United States.,Laboratory of Biology and Modeling of the Cell, Ecole Normale Supérieure de Lyon, CNRS, Université Claude Bernard Lyon, Université de Lyon, Lyon, France
| | - Petra Vande Zande
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, United States
| | - Brian Ph Metzger
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, United States
| | - Crisandra J Diaz
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, United States
| | - Elizabeth A Walker
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, United States
| | - Stephen Tryban
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, United States
| | - Mohammad A Siddiq
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, United States
| | - Bing Yang
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, United States
| | - Patricia J Wittkopp
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, United States.,Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, United States
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17
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Molecular and evolutionary processes generating variation in gene expression. Nat Rev Genet 2020; 22:203-215. [PMID: 33268840 DOI: 10.1038/s41576-020-00304-w] [Citation(s) in RCA: 121] [Impact Index Per Article: 30.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/21/2020] [Indexed: 12/18/2022]
Abstract
Heritable variation in gene expression is common within and between species. This variation arises from mutations that alter the form or function of molecular gene regulatory networks that are then filtered by natural selection. High-throughput methods for introducing mutations and characterizing their cis- and trans-regulatory effects on gene expression (particularly, transcription) are revealing how different molecular mechanisms generate regulatory variation, and studies comparing these mutational effects with variation seen in the wild are teasing apart the role of neutral and non-neutral evolutionary processes. This integration of molecular and evolutionary biology allows us to understand how the variation in gene expression we see today came to be and to predict how it is most likely to evolve in the future.
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18
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Abstract
New species arise as the genomes of populations diverge. The developmental 'alarm clock' of speciation sounds off when sufficient divergence in genetic control of development leads hybrid individuals to infertility or inviability, the world awoken to the dawn of new species with intrinsic post-zygotic reproductive isolation. Some developmental stages will be more prone to hybrid dysfunction due to how molecular evolution interacts with the ontogenetic timing of gene expression. Considering the ontogeny of hybrid incompatibilities provides a profitable connection between 'evo-devo' and speciation genetics to better link macroevolutionary pattern, microevolutionary process, and molecular mechanisms. Here, we explore speciation alongside development, emphasizing their mutual dependence on genetic network features, fitness landscapes, and developmental system drift. We assess models for how ontogenetic timing of reproductive isolation can be predictable. Experiments and theory within this synthetic perspective can help identify new rules of speciation as well as rules in the molecular evolution of development.
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Affiliation(s)
- Asher D Cutter
- Department of Ecology & Evolutionary Biology, University of TorontoTorontoCanada
| | - Joanna D Bundus
- Department of Integrative Biology, University of Wisconsin – MadisonMadisonUnited States
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19
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Biddle JF, Ragsdale EJ. Regulators of an ancient polyphenism evolved through episodic protein divergence and parallel gene radiations. Proc Biol Sci 2020; 287:20192595. [PMID: 32098612 PMCID: PMC7062019 DOI: 10.1098/rspb.2019.2595] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2019] [Accepted: 02/03/2020] [Indexed: 12/18/2022] Open
Abstract
Polyphenism is a form of developmental plasticity that transduces environmental cues into discontinuous, often disparate phenotypes. In some cases, polyphenism has been attributed to facilitating morphological diversification and even the evolution of novel traits. However, this process is predicated on the origins and evolutionary maintenance of genetic mechanisms that specify alternate developmental networks. When and how regulatory loci arise and change, specifically before and throughout the history of a polyphenism, is little understood. Here, we establish a phylogenetic and comparative molecular context for two dynamically evolving genes, eud-1 and seud-1, which regulate polyphenism in the nematode Pristionchus pacificus. This species is dimorphic in its adult feeding-structures, allowing individuals to become microbivores or facultative predators depending on the environment. Although polyphenism regulation is increasingly well understood in P. pacificus, the polyphenism is far older than this species and has diversified morphologically to enable an array of ecological functions across polyphenic lineages. To bring this taxonomic diversity into a comparative context, we reconstructed the histories of eud-1 and seud-1 relative to the origin and diversification of polyphenism, finding that homologues of both genes have undergone lineage-specific radiations across polyphenic taxa. Further, we detected signatures of episodic diversifying selection on eud-1, particularly in early diplogastrid lineages. Lastly, transgenic rescue experiments suggest that the gene's product has functionally diverged from its orthologue's in a non-polyphenic outgroup. In summary, we provide a comparative framework for the molecular components of a plasticity switch, enabling studies of how polyphenism, its regulation, and ultimately its targets evolve.
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Affiliation(s)
| | - Erik J. Ragsdale
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
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20
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Zhang M, Tang YW, Qi J, Liu XK, Yan DF, Zhong NS, Tao NQ, Gao JY, Wang YG, Song ZP, Yang J, Zhang WJ. Effects of parental genetic divergence on gene expression patterns in interspecific hybrids of Camellia. BMC Genomics 2019; 20:828. [PMID: 31703692 PMCID: PMC6842218 DOI: 10.1186/s12864-019-6222-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Accepted: 10/24/2019] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND The merging of two divergent genomes during hybridization can result in the remodeling of parental gene expression in hybrids. A molecular basis underling expression change in hybrid is regulatory divergence, which may change with the parental genetic divergence. However, there still no unanimous conclusion for this hypothesis. RESULTS Three species of Camellia with a range of genetic divergence and their F1 hybrids were used to study the effect of parental genetic divergence on gene expression and regulatory patterns in hybrids by RNA-sequencing and allelic expression analysis. We found that though the proportion of differentially expressed genes (DEGs) between the hybrids and their parents did not increase, a greater proportion of DEGs would be non-additively (especially transgressively) expressed in the hybrids as genomes between the parents become more divergent. In addition, the proportion of genes with significant evidence of cis-regulatory divergence increased, whereas with trans-regulatory divergence decreased with parental genetic divergence. CONCLUSIONS The discordance within hybrid would intensify as the parents become more divergent, manifesting as more DEGs would be non-additively expressed. Trans-regulatory divergence contributed more to the additively inherited genes than cis, however, its contribution to expression difference would be weakened as cis mutations accumulated over time; and this might be an important reason for that the more divergent the parents are, the greater proportion of DEGs would be non-additively expressed in hybrid.
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Affiliation(s)
- Min Zhang
- Co-Innovation Center for Sustainable Forestry in Southern China, College of Biology and the Environment, Nanjing Forestry University, Nanjing, 210037, China.,Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, School of Life Sciences, Fudan University, Shanghai, 200438, China
| | - Yi-Wei Tang
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, School of Life Sciences, Fudan University, Shanghai, 200438, China
| | - Ji Qi
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, School of Life Sciences, Fudan University, Shanghai, 200438, China
| | - Xin-Kai Liu
- Palm Eco-Town Development Co, Ltd, Guangzhou, 510627, Guangdong, China
| | - Dan-Feng Yan
- Palm Eco-Town Development Co, Ltd, Guangzhou, 510627, Guangdong, China
| | - Nai-Sheng Zhong
- Palm Eco-Town Development Co, Ltd, Guangzhou, 510627, Guangdong, China
| | - Nai-Qi Tao
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, School of Life Sciences, Fudan University, Shanghai, 200438, China
| | - Ji-Yin Gao
- Palm Eco-Town Development Co, Ltd, Guangzhou, 510627, Guangdong, China.,Research Institute of Subtropical Forest, Chinese Academy of Forestry, Fuyang, 311400, Zhejiang, China
| | - Yu-Guo Wang
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, School of Life Sciences, Fudan University, Shanghai, 200438, China
| | - Zhi-Ping Song
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, School of Life Sciences, Fudan University, Shanghai, 200438, China
| | - Ji Yang
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, School of Life Sciences, Fudan University, Shanghai, 200438, China
| | - Wen-Ju Zhang
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, School of Life Sciences, Fudan University, Shanghai, 200438, China.
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21
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Empirical measures of mutational effects define neutral models of regulatory evolution in Saccharomyces cerevisiae. Proc Natl Acad Sci U S A 2019; 116:21085-21093. [PMID: 31570626 DOI: 10.1073/pnas.1902823116] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Understanding how phenotypes evolve requires disentangling the effects of mutation generating new variation from the effects of selection filtering it. Tests for selection frequently assume that mutation introduces phenotypic variation symmetrically around the population mean, yet few studies have tested this assumption by deeply sampling the distributions of mutational effects for particular traits. Here, we examine distributions of mutational effects for gene expression in the budding yeast Saccharomyces cerevisiae by measuring the effects of thousands of point mutations introduced randomly throughout the genome. We find that the distributions of mutational effects differ for the 10 genes surveyed and are inconsistent with normality. For example, all 10 distributions of mutational effects included more mutations with large effects than expected for normally distributed phenotypes. In addition, some genes also showed asymmetries in their distribution of mutational effects, with new mutations more likely to increase than decrease the gene's expression or vice versa. Neutral models of regulatory evolution that take these empirically determined distributions into account suggest that neutral processes may explain more expression variation within natural populations than currently appreciated.
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22
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Metzger BPH, Wittkopp PJ. Compensatory trans-regulatory alleles minimizing variation in TDH3 expression are common within Saccharomyces cerevisiae. Evol Lett 2019; 3:448-461. [PMID: 31636938 PMCID: PMC6791293 DOI: 10.1002/evl3.137] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Revised: 08/07/2019] [Accepted: 08/09/2019] [Indexed: 11/06/2022] Open
Abstract
Heritable variation in gene expression is common within species. Much of this variation is due to genetic differences outside of the gene with altered expression and is trans-acting. This trans-regulatory variation is often polygenic, with individual variants typically having small effects, making the genetic architecture and evolution of trans-regulatory variation challenging to study. Consequently, key questions about trans-regulatory variation remain, including the variability of trans-regulatory variation within a species, how selection affects trans-regulatory variation, and how trans-regulatory variants are distributed throughout the genome and within a species. To address these questions, we isolated and measured trans-regulatory differences affecting TDH3 promoter activity among 56 strains of Saccharomyces cerevisiae, finding that trans-regulatory backgrounds varied approximately twofold in their effects on TDH3 promoter activity. Comparing this variation to neutral models of trans-regulatory evolution based on empirical measures of mutational effects revealed that despite this variability in the effects of trans-regulatory backgrounds, stabilizing selection has constrained trans-regulatory differences within this species. Using a powerful quantitative trait locus mapping method, we identified ∼100 trans-acting expression quantitative trait locus in each of three crosses to a common reference strain, indicating that regulatory variation is more polygenic than previous studies have suggested. Loci altering expression were located throughout the genome, and many loci were strain specific. This distribution and prevalence of alleles is consistent with recent theories about the genetic architecture of complex traits. In all mapping experiments, the nonreference strain alleles increased and decreased TDH3 promoter activity with similar frequencies, suggesting that stabilizing selection maintained many trans-acting variants with opposing effects. This variation may provide the raw material for compensatory evolution and larger scale regulatory rewiring observed in developmental systems drift among species.
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Affiliation(s)
- Brian P H Metzger
- Department of Ecology and Evolutionary Biology University of Michigan Ann Arbor Michigan 48109.,Department of Ecology and Evolution University of Chicago Chicago Illinois 60637
| | - Patricia J Wittkopp
- Department of Ecology and Evolutionary Biology University of Michigan Ann Arbor Michigan 48109.,Department of Molecular, Cellular, and Developmental Biology University of Michigan Ann Arbor Michigan 48109
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23
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Levis NA, Pfennig DW. Plasticity‐led evolution: A survey of developmental mechanisms and empirical tests. Evol Dev 2019; 22:71-87. [DOI: 10.1111/ede.12309] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- Nicholas A. Levis
- Department of Biology University of North Carolina Chapel Hill North Carolina
| | - David W. Pfennig
- Department of Biology University of North Carolina Chapel Hill North Carolina
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24
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Koch EM. The Effects of Demography and Genetics on the Neutral Distribution of Quantitative Traits. Genetics 2019; 211:1371-1394. [PMID: 30782599 PMCID: PMC6456309 DOI: 10.1534/genetics.118.301839] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Accepted: 02/15/2019] [Indexed: 11/18/2022] Open
Abstract
Neutral models for quantitative trait evolution are useful for identifying phenotypes under selection. These models often assume normally distributed phenotypes. This assumption may be violated when a trait is affected by relatively few variants or when the effects of those variants arise from skewed or heavy tailed distributions. Molecular phenotypes such as gene expression levels may have these properties. To accommodate deviations from normality, models making fewer assumptions about the underlying genetics and patterns of variation are needed. Here, we develop a general neutral model for quantitative trait variation using a coalescent approach. This model allows interpretation of trait distributions in terms of familiar population genetic parameters because it is based on the coalescent. We show how the normal distribution resulting from the infinitesimal limit, where the number of loci grows large as the effect size per mutation becomes small, depends only on expected pairwise coalescent times. We then demonstrate how deviations from normality depend on demography through the distribution of coalescence times as well as through genetic parameters. In particular, population growth events exacerbate deviations while bottlenecks reduce them. We demonstrate the practical applications of this model by showing how to sample from the neutral distribution of [Formula: see text], the ratio of the variance between subpopulations to that in the overall population. We further show it is likely impossible to distinguish sparsity from skewed or heavy tailed mutational effects using only sampled trait values. The model analyzed here greatly expands the parameter space for neutral trait models.
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Affiliation(s)
- Evan M Koch
- Department of Ecology and Evolution, University of Chicago, Illinois 60637
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25
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Zhou P, Hirsch CN, Briggs SP, Springer NM. Dynamic Patterns of Gene Expression Additivity and Regulatory Variation throughout Maize Development. MOLECULAR PLANT 2019; 12:410-425. [PMID: 30593858 DOI: 10.1016/j.molp.2018.12.015] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Revised: 12/14/2018] [Accepted: 12/18/2018] [Indexed: 05/26/2023]
Abstract
Gene expression variation is a key component underlying phenotypic variation and heterosis. Transcriptome profiling was performed on 23 different tissues or developmental stages of two maize inbreds, B73 and Mo17, as well as their F1 hybrid. The obtained large-scale datasets provided opportunities to monitor the developmental dynamics of differential expression, additivity for gene expression, and regulatory variation. The transcriptome can be divided into ∼30 000 genes that are expressed in at least one tissue of one inbred and an additional ∼10 000 ″silent" genes that are not expressed in any tissue of any genotype, 90% of which are non-syntenic relative to other grasses. Many (∼74%) of the expressed genes exhibit differential expression in at least one tissue. However, the majority of genes with differential expression do not exhibit consistent differential expression in different tissues. These genes often exhibit tissue-specific differential expression with equivalent expression in other tissues, and in many cases they switch the directionality of differential expression in different tissues. This suggests widespread variation for tissue-specific regulation of gene expression between the two maize inbreds B73 and Mo17. Nearly 5000 genes are expressed in only one parent in at least one tissue (single parent expression) and 97% of these genes are expressed at mid-parent levels or higher in the hybrid, providing extensive opportunities for hybrid complementation in heterosis. In general, additive expression patterns are much more common than non-additive patterns, and this trend is more pronounced for genes with strong differential expression or single parent expression. There is relatively little evidence for non-additive expression patterns that are maintained in multiple tissues. The analysis of allele-specific expression allowed classification of cis- and trans-regulatory variation. Genes with cis-regulatory variation often exhibit additive expression and tend to have more consistent regulatory variation throughout development. In contrast, genes with trans-regulatory variation are enriched for non-additive patterns and often show tissue-specific differential expression. Taken together, this study provides a deeper understanding of regulatory variation and the degree of additive gene expression throughout maize development. The dynamic nature of differential expression, additivity, and regulatory variation imply abundant variability for tissue-specific regulatory mechanisms and suggest that connections between transcriptome and phenome will require expression data from multiple tissues.
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Affiliation(s)
- Peng Zhou
- Department of Plant and Microbial Biology, University of Minnesota, Saint Paul, MN 55108, USA
| | - Candice N Hirsch
- Department of Agronomy and Plant Genetics, University of Minnesota, Saint Paul, MN 55108, USA
| | - Steven P Briggs
- Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA
| | - Nathan M Springer
- Department of Plant and Microbial Biology, University of Minnesota, Saint Paul, MN 55108, USA.
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26
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Nandamuri SP, Conte MA, Carleton KL. Multiple trans QTL and one cis-regulatory deletion are associated with the differential expression of cone opsins in African cichlids. BMC Genomics 2018; 19:945. [PMID: 30563463 PMCID: PMC6299527 DOI: 10.1186/s12864-018-5328-z] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2018] [Accepted: 11/28/2018] [Indexed: 01/22/2023] Open
Abstract
Background Dissecting the genetic basis of phenotypic diversity is one of the fundamental goals in evolutionary biology. Despite growing evidence for gene expression divergence being responsible for the evolution of complex traits, knowledge about the proximate genetic causes underlying these traits is still limited. African cichlids have diverse visual systems, with different species expressing different combinations of seven cone opsin genes. Using opsin expression variation in African cichlids as a model for gene expression evolution, this study aims to investigate the genetic architecture of opsin expression divergence in this group. Results Results from a genome-wide linkage mapping on the F2 progeny of an intergeneric cross, between two species with differential opsin expression show that opsins in Lake Malawi cichlids are controlled by multiple quantitative trait loci (QTLs). Most of these QTLs are located in trans to the opsins except for one cis-QTL for SWS1 on LG17. A closer look at this major QTL revealed the presence of a 691 bp deletion in the promoter of the SWS1 opsin (located 751 bp upstream of the start site) that is associated with a decrease in its expression. Phylogenetic footprinting indicates that the region spanning the deletion harbors a microRNA miR-729 and a conserved non-coding element (CNE) that also occurs in zebrafish and other teleosts. This suggests that the deletion might contain ancestrally preserved regulators that have been tuned for SWS1 gene expression in Lake Malawi. While this deletion is not common, it does occur in several other species within the lake. Conclusions Differential expression of cichlid opsins is associated with multiple overlapping QTL, with all but one in trans to the opsins they regulate. The one cis-acting factor is a deletion in the promoter of the SWS1 opsin, suggesting that ancestral polymorphic deletions may contribute to cichlid’s visual diversity. In addition to expanding our understanding of the molecular landscape of opsin expression in African cichlids, this study sheds light on the molecular mechanisms underlying phenotypic variation in natural populations. Electronic supplementary material The online version of this article (10.1186/s12864-018-5328-z) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Sri Pratima Nandamuri
- Department of Biology, University of Maryland, 1210 Biology / Psychology Bldg #144, College Park, MD, 20742, USA
| | - Matthew A Conte
- Department of Biology, University of Maryland, 1210 Biology / Psychology Bldg #144, College Park, MD, 20742, USA
| | - Karen L Carleton
- Department of Biology, University of Maryland, 1210 Biology / Psychology Bldg #144, College Park, MD, 20742, USA.
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27
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Lauer S, Avecilla G, Spealman P, Sethia G, Brandt N, Levy SF, Gresham D. Single-cell copy number variant detection reveals the dynamics and diversity of adaptation. PLoS Biol 2018; 16:e3000069. [PMID: 30562346 PMCID: PMC6298651 DOI: 10.1371/journal.pbio.3000069] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Accepted: 11/14/2018] [Indexed: 12/13/2022] Open
Abstract
Copy number variants (CNVs) are a pervasive source of genetic variation and evolutionary potential, but the dynamics and diversity of CNVs within evolving populations remain unclear. Long-term evolution experiments in chemostats provide an ideal system for studying the molecular processes underlying CNV formation and the temporal dynamics with which they are generated, selected, and maintained. Here, we developed a fluorescent CNV reporter to detect de novo gene amplifications and deletions in individual cells. We used the CNV reporter in Saccharomyces cerevisiae to study CNV formation at the GAP1 locus, which encodes the general amino acid permease, in different nutrient-limited chemostat conditions. We find that under strong selection, GAP1 CNVs are repeatedly generated and selected during the early stages of adaptive evolution, resulting in predictable dynamics. Molecular characterization of CNV-containing lineages shows that the CNV reporter detects different classes of CNVs, including aneuploidies, nonreciprocal translocations, tandem duplications, and complex CNVs. Despite GAP1's proximity to repeat sequences that facilitate intrachromosomal recombination, breakpoint analysis revealed that short inverted repeat sequences mediate formation of at least 50% of GAP1 CNVs. Inverted repeat sequences are also found at breakpoints at the DUR3 locus, where CNVs are selected in urea-limited chemostats. Analysis of 28 CNV breakpoints indicates that inverted repeats are typically 8 nucleotides in length and separated by 40 bases. The features of these CNVs are consistent with origin-dependent inverted-repeat amplification (ODIRA), suggesting that replication-based mechanisms of CNV formation may be a common source of gene amplification. We combined the CNV reporter with barcode lineage tracking and found that 102-104 independent CNV-containing lineages initially compete within populations, resulting in extreme clonal interference. However, only a small number (18-21) of CNV lineages ever constitute more than 1% of the CNV subpopulation, and as selection progresses, the diversity of CNV lineages declines. Our study introduces a novel means of studying CNVs in heterogeneous cell populations and provides insight into their dynamics, diversity, and formation mechanisms in the context of adaptive evolution.
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Affiliation(s)
- Stephanie Lauer
- Center for Genomics and Systems Biology, Department of Biology, New York University, New York, New York, United States of America
- Department of Biology, New York University, New York, New York, United States of America
| | - Grace Avecilla
- Center for Genomics and Systems Biology, Department of Biology, New York University, New York, New York, United States of America
- Department of Biology, New York University, New York, New York, United States of America
| | - Pieter Spealman
- Center for Genomics and Systems Biology, Department of Biology, New York University, New York, New York, United States of America
- Department of Biology, New York University, New York, New York, United States of America
| | - Gunjan Sethia
- Center for Genomics and Systems Biology, Department of Biology, New York University, New York, New York, United States of America
- Department of Biology, New York University, New York, New York, United States of America
| | - Nathan Brandt
- Center for Genomics and Systems Biology, Department of Biology, New York University, New York, New York, United States of America
- Department of Biology, New York University, New York, New York, United States of America
| | - Sasha F. Levy
- Joint Initiative for Metrology in Biology, National Institute of Standards and Technology, Stanford University, Stanford, California, United States of America
| | - David Gresham
- Center for Genomics and Systems Biology, Department of Biology, New York University, New York, New York, United States of America
- Department of Biology, New York University, New York, New York, United States of America
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28
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Support for the Dominance Theory in Drosophila Transcriptomes. Genetics 2018; 210:703-718. [PMID: 30131345 PMCID: PMC6216581 DOI: 10.1534/genetics.118.301229] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2018] [Accepted: 08/10/2018] [Indexed: 12/14/2022] Open
Abstract
Interactions among divergent elements of transcriptional networks from different species can lead to misexpression in hybrids through regulatory incompatibilities, some with the potential to generate sterility. While the possible contribution of faster-male evolution to this misexpression has been explored, the role of the hemizygous X chromosome (i.e., the dominance theory for transcriptomes) remains yet to be determined. Here, we study genome-wide patterns of gene expression in females and males of Drosophila yakuba, Drosophila santomea and their hybrids. We used attached-X stocks to specifically test the dominance theory, and we uncovered a significant contribution of recessive alleles on the X chromosome to hybrid misexpression. Our analyses also suggest a contribution of weakly deleterious regulatory mutations to gene expression divergence in genes with sex-biased expression, but only in the sex toward which the expression is biased (e.g., genes with female-biased expression when analyzed in females). In the opposite sex, we found stronger selective constraints on gene expression divergence. Although genes with a high degree of male-biased expression show a clear signal of faster-X evolution of gene expression, we also detected slower-X evolution in other gene classes (e.g., female-biased genes). This slower-X effect is mediated by significant decreases in cis- and trans-regulatory divergence. The distinct behavior of X-linked genes with a high degree of male-biased expression is consistent with these genes experiencing a higher incidence of positively selected regulatory mutations than their autosomal counterparts.
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29
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Signor SA, Nuzhdin SV. The Evolution of Gene Expression in cis and trans. Trends Genet 2018; 34:532-544. [PMID: 29680748 PMCID: PMC6094946 DOI: 10.1016/j.tig.2018.03.007] [Citation(s) in RCA: 163] [Impact Index Per Article: 27.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2017] [Revised: 03/06/2018] [Accepted: 03/27/2018] [Indexed: 10/17/2022]
Abstract
There is abundant variation in gene expression between individuals, populations, and species. The evolution of gene regulation and expression within and between species is thought to frequently contribute to adaptation. Yet considerable evidence suggests that the primary evolutionary force acting on variation in gene expression is stabilizing selection. We review here the results of recent studies characterizing the evolution of gene expression occurring in cis (via linked polymorphisms) or in trans (through diffusible products of other genes) and their contribution to adaptation and response to the environment. We review the evidence for buffering of variation in gene expression at the level of both transcription and translation, and the possible mechanisms for this buffering. Lastly, we summarize unresolved questions about the evolution of gene regulation.
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Affiliation(s)
- Sarah A Signor
- Molecular and Computational Biology, University of Southern California, Los Angeles, CA 90089, USA.
| | - Sergey V Nuzhdin
- Molecular and Computational Biology, University of Southern California, Los Angeles, CA 90089, USA
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30
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Li XC, Fay JC. Cis-Regulatory Divergence in Gene Expression between Two Thermally Divergent Yeast Species. Genome Biol Evol 2018; 9:1120-1129. [PMID: 28431042 PMCID: PMC5554586 DOI: 10.1093/gbe/evx072] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/13/2017] [Indexed: 12/19/2022] Open
Abstract
Gene regulation is a ubiquitous mechanism by which organisms respond to their environment. While organisms are often found to be adapted to the environments they experience, the role of gene regulation in environmental adaptation is not often known. In this study, we examine divergence in cis-regulatory effects between two Saccharomycesspecies, S. cerevisiaeand S. uvarum, that have substantially diverged in their thermal growth profile. We measured allele specific expression (ASE) in the species’ hybrid at three temperatures, the highest of which is lethal to S. uvarumbut not the hybrid or S. cerevisiae. We find that S. uvarumalleles can be expressed at the same level as S. cerevisiaealleles at high temperature and most cis-acting differences in gene expression are not dependent on temperature. While a small set of 136 genes show temperature-dependent ASE, we find no indication that signatures of directional cis-regulatory evolution are associated with temperature. Within promoter regions we find binding sites enriched upstream of temperature responsive genes, but only weak correlations between binding site and expression divergence. Our results indicate that temperature divergence between S. cerevisiaeand S. uvarumhas not caused widespread divergence in cis-regulatory activity, but point to a small subset of genes where the species’ alleles show differences in magnitude or opposite responses to temperature. The difficulty of explaining divergence in cis-regulatory sequences with models of transcription factor binding sites and nucleosome positioning highlights the importance of identifying mutations that underlie cis-regulatory divergence between species.
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Affiliation(s)
- Xueying C Li
- Molecular Genetics and Genomics Program, Division of Biological and Biomedical Sciences, Washington University, St. Louis, MO
| | - Justin C Fay
- Department of Genetics, Washington University, St. Louis, MO.,Center for Genome Sciences and System Biology, Washington University, St. Louis, MO
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31
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Effects of mutation and selection on plasticity of a promoter activity in Saccharomyces cerevisiae. Proc Natl Acad Sci U S A 2017; 114:E11218-E11227. [PMID: 29259117 DOI: 10.1073/pnas.1713960115] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Phenotypic plasticity is an evolvable property of biological systems that can arise from environment-specific regulation of gene expression. To better understand the evolutionary and molecular mechanisms that give rise to plasticity in gene expression, we quantified the effects of 235 single-nucleotide mutations in the Saccharomyces cerevisiae TDH3 promoter (PTDH3 ) on the activity of this promoter in media containing glucose, galactose, or glycerol as a carbon source. We found that the distributions of mutational effects differed among environments because many mutations altered the plastic response exhibited by the wild-type allele. Comparing the effects of these mutations with the effects of 30 PTDH3 polymorphisms on expression plasticity in the same environments provided evidence of natural selection acting to prevent the plastic response in PTDH3 activity between glucose and galactose from becoming larger. The largest changes in expression plasticity were observed between fermentable (glucose or galactose) and nonfermentable (glycerol) carbon sources and were caused by mutations located in the RAP1 and GCR1 transcription factor binding sites. Mutations altered expression plasticity most frequently between the two fermentable environments, with mutations causing significant changes in plasticity between glucose and galactose distributed throughout the promoter, suggesting they might affect chromatin structure. Taken together, these results provide insight into the molecular mechanisms underlying gene-by-environment interactions affecting gene expression as well as the evolutionary dynamics affecting natural variation in plasticity of gene expression.
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32
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Noble LM, Chelo I, Guzella T, Afonso B, Riccardi DD, Ammerman P, Dayarian A, Carvalho S, Crist A, Pino-Querido A, Shraiman B, Rockman MV, Teotónio H. Polygenicity and Epistasis Underlie Fitness-Proximal Traits in the Caenorhabditis elegans Multiparental Experimental Evolution (CeMEE) Panel. Genetics 2017; 207:1663-1685. [PMID: 29066469 PMCID: PMC5714472 DOI: 10.1534/genetics.117.300406] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2017] [Accepted: 10/10/2017] [Indexed: 01/27/2023] Open
Abstract
Understanding the genetic basis of complex traits remains a major challenge in biology. Polygenicity, phenotypic plasticity, and epistasis contribute to phenotypic variance in ways that are rarely clear. This uncertainty can be problematic for estimating heritability, for predicting individual phenotypes from genomic data, and for parameterizing models of phenotypic evolution. Here, we report an advanced recombinant inbred line (RIL) quantitative trait locus mapping panel for the hermaphroditic nematode Caenorhabditis elegans, the C. elegans multiparental experimental evolution (CeMEE) panel. The CeMEE panel, comprising 507 RILs at present, was created by hybridization of 16 wild isolates, experimental evolution for 140-190 generations, and inbreeding by selfing for 13-16 generations. The panel contains 22% of single-nucleotide polymorphisms known to segregate in natural populations, and complements existing C. elegans mapping resources by providing fine resolution and high nucleotide diversity across > 95% of the genome. We apply it to study the genetic basis of two fitness components, fertility and hermaphrodite body size at time of reproduction, with high broad-sense heritability in the CeMEE. While simulations show that we should detect common alleles with additive effects as small as 5%, at gene-level resolution, the genetic architectures of these traits do not feature such alleles. We instead find that a significant fraction of trait variance, approaching 40% for fertility, can be explained by sign epistasis with main effects below the detection limit. In congruence, phenotype prediction from genomic similarity, while generally poor ([Formula: see text]), requires modeling epistasis for optimal accuracy, with most variance attributed to the rapidly evolving chromosome arms.
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Affiliation(s)
- Luke M Noble
- Center for Genomics and Systems Biology, Department of Biology, New York University, New York 10003
| | - Ivo Chelo
- Instituto Gulbenkian de Ciência, P-2781-901 Oeiras, Portugal
| | - Thiago Guzella
- Institut de Biologie, École Normale Supérieure, Centre National de la Recherche Scientifique (CNRS) UMR 8197, Institut National de la Santé et de la Recherche Médicale (INSERM) U1024, F-75005 Paris, France
| | - Bruno Afonso
- Instituto Gulbenkian de Ciência, P-2781-901 Oeiras, Portugal
- Institut de Biologie, École Normale Supérieure, Centre National de la Recherche Scientifique (CNRS) UMR 8197, Institut National de la Santé et de la Recherche Médicale (INSERM) U1024, F-75005 Paris, France
| | - David D Riccardi
- Center for Genomics and Systems Biology, Department of Biology, New York University, New York 10003
| | - Patrick Ammerman
- Center for Genomics and Systems Biology, Department of Biology, New York University, New York 10003
| | - Adel Dayarian
- Kavli Institute for Theoretical Physics, University of California, Santa Barbara, California 93106
| | - Sara Carvalho
- Instituto Gulbenkian de Ciência, P-2781-901 Oeiras, Portugal
| | - Anna Crist
- Institut de Biologie, École Normale Supérieure, Centre National de la Recherche Scientifique (CNRS) UMR 8197, Institut National de la Santé et de la Recherche Médicale (INSERM) U1024, F-75005 Paris, France
| | | | - Boris Shraiman
- Kavli Institute for Theoretical Physics, University of California, Santa Barbara, California 93106
- Department of Physics, University of California, Santa Barbara, California 93106
| | - Matthew V Rockman
- Center for Genomics and Systems Biology, Department of Biology, New York University, New York 10003
| | - Henrique Teotónio
- Institut de Biologie, École Normale Supérieure, Centre National de la Recherche Scientifique (CNRS) UMR 8197, Institut National de la Santé et de la Recherche Médicale (INSERM) U1024, F-75005 Paris, France
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33
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Wong ES, Schmitt BM, Kazachenka A, Thybert D, Redmond A, Connor F, Rayner TF, Feig C, Ferguson-Smith AC, Marioni JC, Odom DT, Flicek P. Interplay of cis and trans mechanisms driving transcription factor binding and gene expression evolution. Nat Commun 2017; 8:1092. [PMID: 29061983 PMCID: PMC5653656 DOI: 10.1038/s41467-017-01037-x] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Accepted: 08/09/2017] [Indexed: 12/23/2022] Open
Abstract
Noncoding regulatory variants play a central role in the genetics of human diseases and in evolution. Here we measure allele-specific transcription factor binding occupancy of three liver-specific transcription factors between crosses of two inbred mouse strains to elucidate the regulatory mechanisms underlying transcription factor binding variations in mammals. Our results highlight the pre-eminence of cis-acting variants on transcription factor occupancy divergence. Transcription factor binding differences linked to cis-acting variants generally exhibit additive inheritance, while those linked to trans-acting variants are most often dominantly inherited. Cis-acting variants lead to local coordination of transcription factor occupancies that decay with distance; distal coordination is also observed and may be modulated by long-range chromatin contacts. Our results reveal the regulatory mechanisms that interplay to drive transcription factor occupancy, chromatin state, and gene expression in complex mammalian cell states.
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Affiliation(s)
- Emily S Wong
- European Molecular Biology Laboratory, European Bioinformatics Institute, Wellcome Genome Campus, Hinxton, Cambridge, CB10 1SD, UK
| | - Bianca M Schmitt
- University of Cambridge, Cancer Research UK-Cambridge Institute, Li Ka Shing Centre, Cambridge, CB2 0RE, UK
| | | | - David Thybert
- European Molecular Biology Laboratory, European Bioinformatics Institute, Wellcome Genome Campus, Hinxton, Cambridge, CB10 1SD, UK
| | - Aisling Redmond
- University of Cambridge, Cancer Research UK-Cambridge Institute, Li Ka Shing Centre, Cambridge, CB2 0RE, UK
| | - Frances Connor
- University of Cambridge, Cancer Research UK-Cambridge Institute, Li Ka Shing Centre, Cambridge, CB2 0RE, UK
| | - Tim F Rayner
- University of Cambridge, Cancer Research UK-Cambridge Institute, Li Ka Shing Centre, Cambridge, CB2 0RE, UK
| | - Christine Feig
- University of Cambridge, Cancer Research UK-Cambridge Institute, Li Ka Shing Centre, Cambridge, CB2 0RE, UK
| | | | - John C Marioni
- European Molecular Biology Laboratory, European Bioinformatics Institute, Wellcome Genome Campus, Hinxton, Cambridge, CB10 1SD, UK
- University of Cambridge, Cancer Research UK-Cambridge Institute, Li Ka Shing Centre, Cambridge, CB2 0RE, UK
| | - Duncan T Odom
- University of Cambridge, Cancer Research UK-Cambridge Institute, Li Ka Shing Centre, Cambridge, CB2 0RE, UK.
- Wellcome Trust Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge, CB10 1SA, UK.
| | - Paul Flicek
- European Molecular Biology Laboratory, European Bioinformatics Institute, Wellcome Genome Campus, Hinxton, Cambridge, CB10 1SD, UK.
- Wellcome Trust Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge, CB10 1SA, UK.
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34
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Rhoné B, Mariac C, Couderc M, Berthouly-Salazar C, Ousseini IS, Vigouroux Y. No Excess of Cis-Regulatory Variation Associated with Intraspecific Selection in Wild Pearl Millet (Cenchrus americanus). Genome Biol Evol 2017; 9:388-397. [PMID: 28137746 PMCID: PMC5381623 DOI: 10.1093/gbe/evx004] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/25/2017] [Indexed: 12/15/2022] Open
Abstract
Several studies suggest that cis-regulatory mutations are the favorite target of evolutionary changes, one reason being that cis-regulatory mutations might have fewer deleterious pleiotropic effects than protein-coding mutations. A review of the process also suggests that this bias towards adaptive cis-regulatory variation might be less pronounced at the intraspecific level compared with the interspecific level. In this study, we assessed the contribution of cis-regulatory variation to adaptation at the intraspecific level using populations of wild pearl millet (Cenchrus americanus ssp. monodii) sampled along an environmental gradient in Niger. From RNA sequencing of hybrids to assess allele-specific expression, we identified genes with cis-regulatory divergence between two parental accessions collected in contrasted environmental conditions. This revealed that ∼15% of transcribed genes showed cis-regulatory variation. Intersecting the gene set exhibiting cis-regulatory variation with the gene set identified as targets of selection revealed no excess of cis-acting mutations among the selected genes. We additionally found no excess of cis-regulatory variation among genes associated with adaptive traits. As our approach relied on methods identifying mainly genes submitted to strong selection pressure or with high phenotypic effect, the contribution of cis-regulatory changes to soft selection or polygenic adaptive traits remains to be tested. However our results favor the hypothesis that enrichment of adaptive cis-regulatory divergence builds up over time. For short evolutionary time-scales, cis-acting mutations are not predominantly involved in adaptive evolution associated with strong selective signal.
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Affiliation(s)
- Bénédicte Rhoné
- Unité Mixte de Recherche Diversité Adaptation et Développement des Plantes (UMR DIADE), Institut de Recherche pour le Développement, Montpellier, France.,Laboratoire de Biométrie et Biologie Evolutive, Université Lyon 1, CNRS, Lyon, France
| | - Cédric Mariac
- Unité Mixte de Recherche Diversité Adaptation et Développement des Plantes (UMR DIADE), Institut de Recherche pour le Développement, Montpellier, France
| | - Marie Couderc
- Unité Mixte de Recherche Diversité Adaptation et Développement des Plantes (UMR DIADE), Institut de Recherche pour le Développement, Montpellier, France
| | - Cécile Berthouly-Salazar
- Unité Mixte de Recherche Diversité Adaptation et Développement des Plantes (UMR DIADE), Institut de Recherche pour le Développement, Montpellier, France.,Laboratoire Mixte International Adaptation des Plantes et Microorganismes Associés aux Stress Environnementaux (LMI LAPSE), Centre de Recherche de Bel Air, Dakar, Sénégal
| | - Issaka Salia Ousseini
- Unité Mixte de Recherche Diversité Adaptation et Développement des Plantes (UMR DIADE), Institut de Recherche pour le Développement, Montpellier, France.,Laboratoire Mixte International Adaptation des Plantes et Microorganismes Associés aux Stress Environnementaux (LMI LAPSE), Centre de Recherche de Bel Air, Dakar, Sénégal.,Biology Department, Unité Mixte de Recherche Diversité Adaptation et Développement des plantes (UMR DIADE), Université Montpellier, France.,Université Abdou Moumouni de Niamey, Niger
| | - Yves Vigouroux
- Unité Mixte de Recherche Diversité Adaptation et Développement des Plantes (UMR DIADE), Institut de Recherche pour le Développement, Montpellier, France.,Laboratoire Mixte International Adaptation des Plantes et Microorganismes Associés aux Stress Environnementaux (LMI LAPSE), Centre de Recherche de Bel Air, Dakar, Sénégal.,Biology Department, Unité Mixte de Recherche Diversité Adaptation et Développement des plantes (UMR DIADE), Université Montpellier, France
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35
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Cis- and Trans-regulatory Effects on Gene Expression in a Natural Population of Drosophila melanogaster. Genetics 2017; 206:2139-2148. [PMID: 28615283 DOI: 10.1534/genetics.117.201459] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Accepted: 06/06/2017] [Indexed: 12/30/2022] Open
Abstract
Cis- and trans-regulatory mutations are important contributors to transcriptome evolution. Quantifying their relative contributions to intraspecific variation in gene expression is essential for understanding the population genetic processes that underlie evolutionary changes in gene expression. Here, we have examined this issue by quantifying genome-wide, allele-specific expression (ASE) variation using a crossing scheme that produces F1 hybrids between 18 different Drosophila melanogaster strains sampled from the Drosophila Genetic Reference Panel and a reference strain from another population. Head and body samples from F1 adult females were subjected to RNA sequencing and the subsequent ASE quantification. Cis- and trans-regulatory effects on expression variation were estimated from these data. A higher proportion of genes showed significant cis-regulatory variation (∼28%) than those that showed significant trans-regulatory variation (∼9%). The sizes of cis-regulatory effects on expression variation were 1.98 and 1.88 times larger than trans-regulatory effects in heads and bodies, respectively. A generalized linear model analysis revealed that both cis- and trans-regulated expression variation was strongly associated with nonsynonymous nucleotide diversity and tissue specificity. Interestingly, trans-regulated variation showed a negative correlation with local recombination rate. Also, our analysis on proximal transposable element (TE) insertions suggested that they affect transcription levels of ovary-expressed genes more pronouncedly than genes not expressed in the ovary, possibly due to defense mechanisms against TE mobility in the germline. Collectively, our detailed quantification of ASE variations from a natural population has revealed a number of new relationships between genomic factors and the effects of cis- and trans-regulatory factors on expression variation.
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36
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Metzger BPH, Wittkopp PJ, Coolon JD. Evolutionary Dynamics of Regulatory Changes Underlying Gene Expression Divergence among Saccharomyces Species. Genome Biol Evol 2017; 9:843-854. [PMID: 28338820 PMCID: PMC5604594 DOI: 10.1093/gbe/evx035] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/21/2017] [Indexed: 12/11/2022] Open
Abstract
Heritable changes in gene expression are important contributors to phenotypic differences within and between species and are caused by mutations in cis-regulatory elements and trans-regulatory factors. Although previous work has suggested that cis-regulatory differences preferentially accumulate with time, technical restrictions to closely related species and limited comparisons have made this observation difficult to test. To address this problem, we used allele-specific RNA-seq data from Saccharomyces species and hybrids to expand both the evolutionary timescale and number of species in which the evolution of regulatory divergence has been investigated. We find that as sequence divergence increases, cis-regulatory differences do indeed become the dominant type of regulatory difference between species, ultimately becoming a better predictor of expression divergence than trans-regulatory divergence. When both cis- and trans-regulatory differences accumulate for the same gene, they more often have effects in opposite directions than in the same direction, indicating widespread compensatory changes underlying the evolution of gene expression. The frequency of compensatory changes within and between species and the magnitude of effect for the underlying cis- and trans-regulatory differences suggests that compensatory changes accumulate primarily due to selection against divergence in gene expression as a result of weak stabilizing selection on gene expression levels. These results show that cis-regulatory differences and compensatory changes in regulation play increasingly important roles in the evolution of gene expression as time increases.
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Affiliation(s)
- Brian P H Metzger
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI.,Department of Ecology and Evolution, University of Chicago, Chicago, IL
| | - Patricia J Wittkopp
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI.,Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI
| | - Joseph D Coolon
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI.,Department of Biology, Wesleyan University, Middletown, CT
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37
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Regulatory Architecture of Gene Expression Variation in the Threespine Stickleback Gasterosteus aculeatus. G3-GENES GENOMES GENETICS 2017; 7:165-178. [PMID: 27836907 PMCID: PMC5217106 DOI: 10.1534/g3.116.033241] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Much adaptive evolutionary change is underlain by mutational variation in regions of the genome that regulate gene expression rather than in the coding regions of the genes themselves. An understanding of the role of gene expression variation in facilitating local adaptation will be aided by an understanding of underlying regulatory networks. Here, we characterize the genetic architecture of gene expression variation in the threespine stickleback (Gasterosteus aculeatus), an important model in the study of adaptive evolution. We collected transcriptomic and genomic data from 60 half-sib families using an expression microarray and genotyping-by-sequencing, and located expression quantitative trait loci (eQTL) underlying the variation in gene expression in liver tissue using an interval mapping approach. We identified eQTL for several thousand expression traits. Expression was influenced by polymorphism in both cis- and trans-regulatory regions. Trans-eQTL clustered into hotspots. We did not identify master transcriptional regulators in hotspot locations: rather, the presence of hotspots may be driven by complex interactions between multiple transcription factors. One observed hotspot colocated with a QTL recently found to underlie salinity tolerance in the threespine stickleback. However, most other observed hotspots did not colocate with regions of the genome known to be involved in adaptive divergence between marine and freshwater habitats.
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38
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A New Mechanism for Mendelian Dominance in Regulatory Genetic Pathways: Competitive Binding by Transcription Factors. Genetics 2016; 205:101-112. [PMID: 27866169 DOI: 10.1534/genetics.116.195255] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2016] [Accepted: 11/04/2016] [Indexed: 12/11/2022] Open
Abstract
We report a new mechanism for allelic dominance in regulatory genetic interactions that we call binding dominance. We investigated a biophysical model of gene regulation, where the fractional occupancy of a transcription factor (TF) on the cis-regulated promoter site it binds to is determined by binding energy (-ΔG) and TF dosage. Transcription and gene expression proceed when the TF is bound to the promoter. In diploids, individuals may be heterozygous at the cis-site, at the TF's coding region, or at the TF's own promoter, which determines allele-specific dosage. We find that when the TF's coding region is heterozygous, TF alleles compete for occupancy at the cis-sites and the tighter-binding TF is dominant in proportion to the difference in binding strength. When the TF's own promoter is heterozygous, the TF produced at the higher dosage is also dominant. Cis-site heterozygotes have additive expression and therefore codominant phenotypes. Binding dominance propagates to affect the expression of downstream loci and it is sensitive in both magnitude and direction to genetic background, but its detectability often attenuates. While binding dominance is inevitable at the molecular level, it is difficult to detect in the phenotype under some biophysical conditions, more so when TF dosage is high and allele-specific binding affinities are similar. A body of empirical research on the biophysics of TF binding demonstrates the plausibility of this mechanism of dominance, but studies of gene expression under competitive binding in heterozygotes in a diversity of genetic backgrounds are needed.
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39
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Verta JP, Landry CR, MacKay J. Dissection of expression-quantitative trait locus and allele specificity using a haploid/diploid plant system - insights into compensatory evolution of transcriptional regulation within populations. THE NEW PHYTOLOGIST 2016; 211:159-171. [PMID: 26891783 DOI: 10.1111/nph.13888] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2015] [Accepted: 01/06/2016] [Indexed: 06/05/2023]
Abstract
Regulation of gene expression plays a central role in translating genotypic variation into phenotypic variation. Dissection of the genetic basis of expression variation is key to understanding how expression regulation evolves. Such analyses remain challenging in contexts where organisms are outbreeding, highly heterozygous and long-lived such as in the case of conifer trees. We developed an RNA sequencing (RNA-seq)-based approach for both expression-quantitative trait locus (eQTL) mapping and the detection of cis-acting (allele-specific) vs trans-acting (non-allele-specific) eQTLs. This method can be potentially applied to many conifers. We used haploid and diploid meiotic seed tissues of a single self-fertilized white spruce (Picea glauca) individual to dissect eQTLs according to linkage and allele specificity. The genetic architecture of local eQTLs linked to the expressed genes was particularly complex, consisting of cis-acting, trans-acting and, surprisingly, compensatory cis-trans effects. These compensatory effects influence expression in opposite directions and are neutral when combined in homozygotes. Nearly half of local eQTLs were under compensation, indicating that close linkage between compensatory cis-trans factors is common in spruce. Compensated genes were overrepresented in developmental and cell organization functions. Our haploid-diploid eQTL analysis in spruce revealed that compensatory cis-trans eQTLs segregate within populations and evolve in close genetic linkage.
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Affiliation(s)
- Jukka-Pekka Verta
- Centre d'étude de la forêt, Département des sciences du bois et de la forêt, Université Laval, Québec, QC, Canada G1V 0A6
- Institut de Biologie Intégrative et des Systèmes, Université Laval, Québec, QC, Canada G1V 0A6
| | - Christian R Landry
- Institut de Biologie Intégrative et des Systèmes, Université Laval, Québec, QC, Canada G1V 0A6
- Département de Biologie, Université Laval, Québec, QC, Canada G1V 0A6
| | - John MacKay
- Centre d'étude de la forêt, Département des sciences du bois et de la forêt, Université Laval, Québec, QC, Canada G1V 0A6
- Institut de Biologie Intégrative et des Systèmes, Université Laval, Québec, QC, Canada G1V 0A6
- Department of Plant Sciences, University of Oxford, Oxford, OX1 3RB, UK
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40
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Ehrenreich IM, Pfennig DW. Genetic assimilation: a review of its potential proximate causes and evolutionary consequences. ANNALS OF BOTANY 2016; 117:769-79. [PMID: 26359425 PMCID: PMC4845796 DOI: 10.1093/aob/mcv130] [Citation(s) in RCA: 110] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2015] [Revised: 05/07/2015] [Accepted: 06/29/2015] [Indexed: 05/24/2023]
Abstract
BACKGROUND Most, if not all, organisms possess the ability to alter their phenotype in direct response to changes in their environment, a phenomenon known as phenotypic plasticity. Selection can break this environmental sensitivity, however, and cause a formerly environmentally induced trait to evolve to become fixed through a process called genetic assimilation. Essentially, genetic assimilation can be viewed as the evolution of environmental robustness in what was formerly an environmentally sensitive trait. Because genetic assimilation has long been suggested to play a key role in the origins of phenotypic novelty and possibly even new species, identifying and characterizing the proximate mechanisms that underlie genetic assimilation may advance our basic understanding of how novel traits and species evolve. SCOPE This review begins by discussing how the evolution of phenotypic plasticity, followed by genetic assimilation, might promote the origins of new traits and possibly fuel speciation and adaptive radiation. The evidence implicating genetic assimilation in evolutionary innovation and diversification is then briefly considered. Next, the potential causes of phenotypic plasticity generally and genetic assimilation specifically are examined at the genetic, molecular and physiological levels and approaches that can improve our understanding of these mechanisms are described. The review concludes by outlining major challenges for future work. CONCLUSIONS Identifying and characterizing the proximate mechanisms involved in phenotypic plasticity and genetic assimilation promises to help advance our basic understanding of evolutionary innovation and diversification.
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Affiliation(s)
- Ian M Ehrenreich
- Molecular and Computational Biology Section, University of Southern California, Los Angeles, CA 90089, USA and
| | - David W Pfennig
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA
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41
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Comprehensive Analysis of the SUL1 Promoter of Saccharomyces cerevisiae. Genetics 2016; 203:191-202. [PMID: 26936925 DOI: 10.1534/genetics.116.188037] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2016] [Accepted: 02/21/2016] [Indexed: 11/18/2022] Open
Abstract
In the yeast Saccharomyces cerevisiae, beneficial mutations selected during sulfate-limited growth are typically amplifications of the SUL1 gene, which encodes the high-affinity sulfate transporter, resulting in fitness increases of >35% . Cis-regulatory mutations have not been observed at this locus; however, it is not clear whether this absence is due to a low mutation rate such that these mutations do not arise, or they arise but have limited fitness effects relative to those of amplification. To address this question directly, we assayed the fitness effects of nearly all possible point mutations in a 493-base segment of the gene's promoter through mutagenesis and selection. While most mutations were either neutral or detrimental during sulfate-limited growth, eight mutations increased fitness >5% and as much as 9.4%. Combinations of these beneficial mutations increased fitness only up to 11%. Thus, in the case of SUL1, promoter mutations could not induce a fitness increase similar to that of gene amplification. Using these data, we identified functionally important regions of the SUL1 promoter and analyzed three sites that correspond to potential binding sites for the transcription factors Met32 and Cbf1 Mutations that create new Met32- or Cbf1-binding sites also increased fitness. Some mutations in the untranslated region of the SUL1 transcript decreased fitness, likely due to the formation of inhibitory upstream open reading frames. Our methodology-saturation mutagenesis, chemostat selection, and DNA sequencing to track variants-should be a broadly applicable approach.
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42
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Guerrero RF, Posto AL, Moyle LC, Hahn MW. Genome-wide patterns of regulatory divergence revealed by introgression lines. Evolution 2016; 70:696-706. [PMID: 26842879 DOI: 10.1111/evo.12875] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2015] [Accepted: 01/24/2016] [Indexed: 01/03/2023]
Abstract
Understanding the genetic basis for changes in transcriptional regulation is an important aspect of understanding phenotypic evolution. Using interspecific introgression lines, we infer the mechanisms of divergence in genome-wide patterns of gene expression between the nightshades Solanum pennellii and S. lycopersicum (domesticated tomato). We find that cis- and trans-regulatory changes have had qualitatively similar contributions to divergence in this clade, unlike results from other systems. Additionally, expression data from four tissues (shoot apex, ripe fruit, pollen, and seed) suggest that introgressed regions in these hybrid lines tend to be downregulated, while background (nonintrogressed) genes tend to be upregulated. Finally, we find no evidence for an association between the magnitude of differential expression in NILs and previously determined sterility phenotypes. Our results contradict previous predictions of the predominant role of cis- over trans-regulatory divergence between species, and do not support a major role for gross genome-wide misregulation in reproductive isolation between these species.
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Affiliation(s)
- Rafael F Guerrero
- Department of Biology, Indiana University, Bloomington, Indiana, 47405.
| | - Amanda L Posto
- Department of Biology, Indiana University, Bloomington, Indiana, 47405
| | - Leonie C Moyle
- Department of Biology, Indiana University, Bloomington, Indiana, 47405
| | - Matthew W Hahn
- Department of Biology, Indiana University, Bloomington, Indiana, 47405.,School of Informatics and Computing, Indiana University, Bloomington, Indiana, 47405
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43
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Metzger BPH, Duveau F, Yuan DC, Tryban S, Yang B, Wittkopp PJ. Contrasting Frequencies and Effects of cis- and trans-Regulatory Mutations Affecting Gene Expression. Mol Biol Evol 2016; 33:1131-46. [PMID: 26782996 DOI: 10.1093/molbev/msw011] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Heritable differences in gene expression are caused by mutations in DNA sequences encoding cis-regulatory elements and trans-regulatory factors. These two classes of regulatory change differ in their relative contributions to expression differences in natural populations because of the combined effects of mutation and natural selection. Here, we investigate how new mutations create the regulatory variation upon which natural selection acts by quantifying the frequencies and effects of hundreds of new cis- and trans-acting mutations altering activity of the TDH3 promoter in the yeast Saccharomyces cerevisiae in the absence of natural selection. We find that cis-regulatory mutations have larger effects on expression than trans-regulatory mutations and that while trans-regulatory mutations are more common overall, cis- and trans-regulatory changes in expression are equally abundant when only the largest changes in expression are considered. In addition, we find that cis-regulatory mutations are skewed toward decreased expression while trans-regulatory mutations are skewed toward increased expression. We also measure the effects of cis- and trans-regulatory mutations on the variability in gene expression among genetically identical cells, a property of gene expression known as expression noise, finding that trans-regulatory mutations are much more likely to decrease expression noise than cis-regulatory mutations. Because new mutations are the raw material upon which natural selection acts, these differences in the frequencies and effects of cis- and trans-regulatory mutations should be considered in models of regulatory evolution.
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Affiliation(s)
- Brian P H Metzger
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor
| | - Fabien Duveau
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor
| | - David C Yuan
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor Department of Biology, Stanford University
| | - Stephen Tryban
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor
| | - Bing Yang
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor
| | - Patricia J Wittkopp
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor
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44
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Hodgins-Davis A, Rice DP, Townsend JP. Gene Expression Evolves under a House-of-Cards Model of Stabilizing Selection. Mol Biol Evol 2015; 32:2130-40. [PMID: 25901014 PMCID: PMC4592357 DOI: 10.1093/molbev/msv094] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Divergence in gene regulation is hypothesized to underlie much of phenotypic evolution, but the role of natural selection in shaping the molecular phenotype of gene expression continues to be debated. To resolve the mode of gene expression, evolution requires accessible theoretical predictions for the effect of selection over long timescales. Evolutionary quantitative genetic models of phenotypic evolution can provide such predictions, yet those predictions depend on the underlying hypotheses about the distributions of mutational and selective effects that are notoriously difficult to disentangle. Here, we draw on diverse genomic data sets including expression profiles of natural genetic variation and mutation accumulation lines, empirical estimates of genomic mutation rates, and inferences of genetic architecture to differentiate contrasting hypotheses for the roles of stabilizing selection and mutation in shaping natural expression variation. Our analysis suggests that gene expression evolves in a domain of phenotype space well fit by the House-of-Cards (HC) model. Although the strength of selection inferred is sensitive to the number of loci controlling gene expression, the model is not. The consistency of these results across evolutionary time from budding yeast through fruit fly implies that this model is general and that mutational effects on gene expression are relatively large. Empirical estimates of the genetic architecture of gene expression traits imply that selection provides modest constraints on gene expression levels for most genes, but that the potential for regulatory evolution is high. Our prediction using data from laboratory environments should encourage the collection of additional data sets allowing for more nuanced parameterizations of HC models for gene expression.
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Affiliation(s)
- Andrea Hodgins-Davis
- Department of Ecology and Evolutionary Biology, Yale University Department of Biostatistics, School of Public Health, Yale University
| | - Daniel P Rice
- Department of Ecology and Evolutionary Biology, Yale University Department of Organismic and Evolutionary Biology, Harvard University
| | - Jeffrey P Townsend
- Department of Ecology and Evolutionary Biology, Yale University Department of Biostatistics, School of Public Health, Yale University Program in Computational Biology and Bioinformatics, Yale University
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45
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Rodríguez-Mega E, Piñeyro-Nelson A, Gutierrez C, García-Ponce B, Sánchez MDLP, Zluhan-Martínez E, Álvarez-Buylla ER, Garay-Arroyo A. Role of transcriptional regulation in the evolution of plant phenotype: A dynamic systems approach. Dev Dyn 2015; 244:1074-1095. [PMID: 25733163 DOI: 10.1002/dvdy.24268] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2014] [Revised: 02/24/2015] [Accepted: 02/24/2015] [Indexed: 12/20/2022] Open
Abstract
A growing body of evidence suggests that alterations in transcriptional regulation of genes involved in modulating development are an important part of phenotypic evolution, and this can be documented among species and within populations. While the effects of differential transcriptional regulation in organismal development have been preferentially studied in animal systems, this phenomenon has also been addressed in plants. In this review, we summarize evidence for cis-regulatory mutations, trans-regulatory changes and epigenetic modifications as molecular events underlying important phenotypic alterations, and thus shaping the evolution of plant development. We postulate that a mechanistic understanding of why such molecular alterations have a key role in development, morphology and evolution will have to rely on dynamic models of complex regulatory networks that consider the concerted action of genetic and nongenetic components, and that also incorporate the restrictions underlying the genotype to phenotype mapping process. Developmental Dynamics 244:1074-1095, 2015. © 2015 Wiley Periodicals, Inc.
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Affiliation(s)
- Emiliano Rodríguez-Mega
- Laboratorio de Genética Molecular, Desarrollo, Evolución y Epigenética de Plantas, Universidad Nacional Autónoma de México, 3er Circuito Exterior junto al Jardín Botánico, Ciudad Universitaria, México
| | - Alma Piñeyro-Nelson
- Department of Plant and Microbial Biology, University of California, Berkeley, California
| | - Crisanto Gutierrez
- Centro de Biología Molecular Severo Ochoa, CSIC-UAM, Nicolás Cabrera 1, Cantoblanco, 28049, Madrid, Spain
| | - Berenice García-Ponce
- Laboratorio de Genética Molecular, Desarrollo, Evolución y Epigenética de Plantas, Universidad Nacional Autónoma de México, 3er Circuito Exterior junto al Jardín Botánico, Ciudad Universitaria, México
| | - María De La Paz Sánchez
- Laboratorio de Genética Molecular, Desarrollo, Evolución y Epigenética de Plantas, Universidad Nacional Autónoma de México, 3er Circuito Exterior junto al Jardín Botánico, Ciudad Universitaria, México
| | - Estephania Zluhan-Martínez
- Laboratorio de Genética Molecular, Desarrollo, Evolución y Epigenética de Plantas, Universidad Nacional Autónoma de México, 3er Circuito Exterior junto al Jardín Botánico, Ciudad Universitaria, México
| | - Elena R Álvarez-Buylla
- Laboratorio de Genética Molecular, Desarrollo, Evolución y Epigenética de Plantas, Universidad Nacional Autónoma de México, 3er Circuito Exterior junto al Jardín Botánico, Ciudad Universitaria, México
| | - Adriana Garay-Arroyo
- Laboratorio de Genética Molecular, Desarrollo, Evolución y Epigenética de Plantas, Universidad Nacional Autónoma de México, 3er Circuito Exterior junto al Jardín Botánico, Ciudad Universitaria, México.,Centro de Biología Molecular Severo Ochoa, CSIC-UAM, Nicolás Cabrera 1, Cantoblanco, 28049, Madrid, Spain
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46
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Sensitivity of quantitative traits to mutational effects and number of loci. Theor Popul Biol 2015; 102:85-93. [PMID: 25840144 DOI: 10.1016/j.tpb.2015.03.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Revised: 03/20/2015] [Accepted: 03/24/2015] [Indexed: 12/18/2022]
Abstract
When models of quantitative genetic variation are built from population genetic first principles, several assumptions are often made. One of the most important assumptions is that traits are controlled by many genes of small effect. This leads to a prediction of a Gaussian trait distribution in the population, via the Central Limit Theorem. Since these biological assumptions are often unknown or untrue, we characterized how finite numbers of loci or large mutational effects can impact the sampling distribution of a quantitative trait. To do so, we developed a neutral coalescent-based framework, allowing us to gain a detailed understanding of how number of loci and the underlying mutational model impacts the distribution of a quantitative trait. Through both analytical theory and simulation we found the normality assumption was highly sensitive to the details of the mutational process, with the greatest discrepancies arising when the number of loci was small or the mutational kernel was heavy-tailed. In particular, skewed mutational effects will produce skewed trait distributions and fat-tailed mutational kernels result in multimodal sampling distributions, even for traits controlled by a large number of loci. Since selection models and robust neutral models may produce qualitatively similar sampling distributions, we advise extra caution should be taken when interpreting model-based results for poorly understood systems of quantitative traits.
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47
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Wang XG, Huang JM, Feng MY, Ju ZH, Wang CF, Yang GW, Yuan JD, Zhong JF. Regulatory mutations in the A2M gene are involved in the mastitis susceptibility in dairy cows. Anim Genet 2015; 45:28-37. [PMID: 25237709 DOI: 10.1111/age.12099] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Mutations, such as single nucleotide polymorphisms (SNPs), in the 5′-flanking and microRNA (miRNA) regulatory regions may result in altered gene expression levels and cause diseases. Alpha-2-macroglobulin (A2M) has the function of binding host or foreign peptides and particles, and thereby serves as a defense barrier against pathogens in the plasma and tissues of animals. To investigate the functional markers of the A2M gene associated with mastitis, the promoter was characterized and SNPs that affect promoter activity or binding affinity with the target miRNA were identified using the luciferase reporter assay and real-time quantitative PCR method. Results showed that the core promoter of A2M was found between the bases g.-2641 and g.-2479. Four novel SNPs (g.-724A>G, g.-665G>A, g.-535C>G and g.-520_-519insA) in the promoter region were completely linked. The activity of the mutant haplotype (GAGA) increased by 177% compared with that of the wild haplotype (AGC-). Bta-miR-2898 was upregulated by 6.25-fold in the mammary gland tissues of mastitis-infected cows compared with that of the healthy cows. One SNP (c.4659_4661delC) located in the 3′-untranslated region of the A2M gene may affect the binding affinity with the target bta-miR-2898. Five SNPs exhibited tight linkage. Association analysis showed that the milk somatic cell score for cows with the mutant haplotype (GAGA-) was lower than that for cows with the wild haplotype. Thus, the mutant type can be used as a potential functional marker for a mastitis resistance breeding program in dairy cows. Our findings provided the molecular basis for A2M transcriptional and post-transcriptional regulations. A close relationship between regulatory mutations and mastitis susceptibility of cows also was established.
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48
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Selection on noise constrains variation in a eukaryotic promoter. Nature 2015; 521:344-7. [PMID: 25778704 PMCID: PMC4455047 DOI: 10.1038/nature14244] [Citation(s) in RCA: 99] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2014] [Accepted: 01/19/2015] [Indexed: 01/19/2023]
Abstract
Genetic variation segregating within a species reflects the combined activities of mutation, selection, and genetic drift. In the absence of selection, polymorphisms are expected to be a random subset of new mutations; thus, comparing the effects of polymorphisms and new mutations provides a test for selection1–4. When evidence of selection exists, such comparisons can identify properties of mutations that are most likely to persist in natural populations2. Here, we investigate how mutation and selection have shaped variation in a cis-regulatory sequence controlling gene expression by empirically determining the effects of polymorphisms segregating in the TDH3 promoter among 85 strains of Saccharomyces cerevisiae and comparing their effects to a distribution of mutational effects defined by 236 point mutations in the same promoter. Surprisingly, we find that selection on expression noise (i.e., variability in expression among genetically identical cells5) appears to have had a greater impact on sequence variation in the TDH3 promoter than selection on mean expression level. This is not necessarily because variation in expression noise impacts fitness more than variation in mean expression level, but rather because of differences in the distributions of mutational effects for these two phenotypes. This study shows how systematically examining the effects of new mutations can enrich our understanding of evolutionary mechanisms and provides rare empirical evidence of selection acting on expression noise.
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49
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Graze RM, McIntyre LM, Morse AM, Boyd BM, Nuzhdin SV, Wayne ML. What the X has to do with it: differences in regulatory variability between the sexes in Drosophila simulans. Genome Biol Evol 2015; 6:818-29. [PMID: 24696400 PMCID: PMC4007535 DOI: 10.1093/gbe/evu060] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
The mechanistic basis of regulatory variation and the prevailing evolutionary forces shaping that variation are known to differ between sexes and between chromosomes. Regulatory variation of gene expression can be due to functional changes within a gene itself (cis) or in other genes elsewhere in the genome (trans). The evolutionary properties of cis mutations are expected to differ from mutations affecting gene expression in trans. We analyze allele-specific expression across a set of X substitution lines in intact adult Drosophila simulans to evaluate whether regulatory variation differs for cis and trans, for males and females, and for X-linked and autosomal genes. Regulatory variation is common (56% of genes), and patterns of variation within D. simulans are consistent with previous observations in Drosophila that there is more cis than trans variation within species (47% vs. 25%, respectively). The relationship between sex-bias and sex-limited variation is remarkably consistent across sexes. However, there are differences between cis and trans effects: cis variants show evidence of purifying selection in the sex toward which expression is biased, while trans variants do not. For female-biased genes, the X is depleted for trans variation in a manner consistent with a female-dominated selection regime on the X. Surprisingly, there is no evidence for depletion of trans variation for male-biased genes on X. This is evidence for regulatory feminization of the X, trans-acting factors controlling male-biased genes are more likely to be found on the autosomes than those controlling female-biased genes.
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Affiliation(s)
- Rita M. Graze
- Department of Molecular Genetics and Microbiology, University of Florida
- Department of Biological Sciences, Auburn University
- *Corresponding author: E-mail:
| | - Lauren M. McIntyre
- Department of Molecular Genetics and Microbiology, University of Florida
- Department of Statistics, University of Florida
| | - Alison M. Morse
- Department of Molecular Genetics and Microbiology, University of Florida
| | - Bret M. Boyd
- Florida Museum of Natural History, University of Florida
| | - Sergey V. Nuzhdin
- Section of Molecular and Computational Biology, Department of Biological Sciences, University of Southern California
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50
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Somel M, Rohlfs R, Liu X. Transcriptomic insights into human brain evolution: acceleration, neutrality, heterochrony. Curr Opin Genet Dev 2014; 29:110-9. [PMID: 25233113 DOI: 10.1016/j.gde.2014.09.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2014] [Revised: 08/31/2014] [Accepted: 09/01/2014] [Indexed: 01/09/2023]
Abstract
Primate brain transcriptome comparisons within the last 12 years have yielded interesting but contradictory observations on how the transcriptome evolves, and its adaptive role in human cognitive evolution. Since the human-chimpanzee common ancestor, the human prefrontal cortex transcriptome seems to have evolved more than that of the chimpanzee. But at the same time, most expression differences among species, especially those observed in adults, appear as consequences of neutral evolution at cis-regulatory sites. Adaptive expression changes in the human brain may be rare events involving timing shifts, or heterochrony, in specific neurodevelopmental processes. Disentangling adaptive and neutral expression changes, and associating these with human-specific features of the brain require improved methods, comparisons across more species, and further work on comparative development.
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Affiliation(s)
- Mehmet Somel
- Department of Biology, Middle East Technical University, Ankara, Turkey.
| | - Rori Rohlfs
- Department of Integrative Biology, University of California, Berkeley, CA, USA
| | - Xiling Liu
- Key Laboratory of Computational Biology, CAS-MPG Partner Institute for Computational Biology, Shanghai Institutes for Biological Sciences, Shanghai, China
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