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Bolton PE, Ryder TB, Dakin R, Houtz JL, Moore IT, Balakrishnan CN, Horton BM. Neurogenomic landscape associated with status-dependent cooperative behaviour. Mol Ecol 2024:e17327. [PMID: 38511765 DOI: 10.1111/mec.17327] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2023] [Revised: 01/04/2024] [Accepted: 03/07/2024] [Indexed: 03/22/2024]
Abstract
The neurogenomic mechanisms mediating male-male reproductive cooperative behaviours remain unknown. We leveraged extensive transcriptomic and behavioural data on a neotropical bird species (Pipra filicauda) that performs cooperative courtship displays to understand these mechanisms. In this species, the cooperative display is modulated by testosterone, which promotes cooperation in non-territorial birds, but suppresses cooperation in territory holders. We sought to understand the neurogenomic underpinnings of three related traits: social status, cooperative display behaviour and testosterone phenotype. To do this, we profiled gene expression in 10 brain nuclei spanning the social decision-making network (SDMN), and two key endocrine tissues that regulate social behaviour. We associated gene expression with each bird's behavioural and endocrine profile derived from 3 years of repeated measures taken from free-living birds in the Ecuadorian Amazon. We found distinct landscapes of constitutive gene expression were associated with social status, testosterone phenotype and cooperation, reflecting the modular organization and engagement of neuroendocrine tissues. Sex-steroid and neuropeptide signalling appeared to be important in mediating status-specific relationships between testosterone and cooperation, suggesting shared regulatory mechanisms with male aggressive and sexual behaviours. We also identified differentially regulated genes involved in cellular activity and synaptic potentiation, suggesting multiple mechanisms underpin these genomic states. Finally, we identified SDMN-wide gene expression differences between territorial and floater males that could form the basis of 'status-specific' neurophysiological phenotypes, potentially mediated by testosterone and growth hormone. Overall, our findings provide new, systems-level insights into the mechanisms of cooperative behaviour and suggest that differences in neurogenomic state are the basis for individual differences in social behaviour.
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Affiliation(s)
- Peri E Bolton
- Department of Biology, East Carolina University, Greenville, North Carolina, USA
- Department of Vertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington, District of Columbia, USA
| | - T Brandt Ryder
- Migratory Bird Center, Smithsonian National Zoological Park, Washington, District of Columbia, USA
- Bird Conservancy of the Rockies, Fort Collins, Colorado, USA
| | - Roslyn Dakin
- Migratory Bird Center, Smithsonian National Zoological Park, Washington, District of Columbia, USA
- Department of Biology, Carleton University, Ottawa, Ontario, Canada
| | - Jennifer L Houtz
- Department of Biology, Millersville University, Millersville, Pennsylvania, USA
- Department of Biology, Allegheny College, Meadville, Pennsylvania, USA
| | - Ignacio T Moore
- Department of Biological Sciences, Virginia Tech, Blacksburg, Virginia, USA
| | | | - Brent M Horton
- Department of Biology, Millersville University, Millersville, Pennsylvania, USA
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2
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Prichard MR, Grogan KE, Merritt JR, Root J, Maney DL. Allele-specific cis-regulatory methylation of the gene for vasoactive intestinal peptide in white-throated sparrows. GENES, BRAIN, AND BEHAVIOR 2022; 21:e12831. [PMID: 36220804 PMCID: PMC9744568 DOI: 10.1111/gbb.12831] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Revised: 08/05/2022] [Accepted: 08/31/2022] [Indexed: 11/06/2022]
Abstract
White-throated sparrows (Zonotrichia albicollis) offer a unique opportunity to connect genotype with behavioral phenotype. In this species, a rearrangement of the second chromosome is linked with territorial aggression; birds with a copy of this "supergene" rearrangement are more aggressive than those without it. The supergene has captured the gene VIP, which encodes vasoactive intestinal peptide, a neuromodulator that drives aggression in other songbirds. In white-throated sparrows, VIP expression is higher in the anterior hypothalamus of birds with the supergene than those without it, and expression of VIP in this region predicts the level of territorial aggression regardless of genotype. Here, we aimed to identify epigenetic mechanisms that could contribute to differential expression of VIP both in breeding adults, which exhibit morph differences in territorial aggression, and in nestlings, before territorial behavior develops. We extracted and bisulfite-converted DNA from samples of the hypothalamus in wild-caught adults and nestlings and used high-throughput sequencing to measure DNA methylation of a region upstream of the VIP start site. We found that the allele inside the supergene was less methylated than the alternative allele in both adults and nestlings. The differential methylation was attributed primarily to CpG sites that were shared between the alleles, not to polymorphic sites, which suggests that epigenetic regulation is occurring independently of the genetic differentiation within the supergene. This work represents an initial step toward understanding how epigenetic differentiation inside chromosomal inversions leads to the development of alternative behavioral phenotypes.
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Affiliation(s)
| | - Kathleen E. Grogan
- Department of PsychologyEmory UniversityAtlantaGeorgiaUSA
- Present address:
Departments of Anthropology and BiologyUniversity of CincinnatiCincinnatiOhioUSA
| | - Jennifer R. Merritt
- Department of PsychologyEmory UniversityAtlantaGeorgiaUSA
- Present address:
Zuckerman Mind Brain Behavior Institute and Department of Ecology, Evolution and Environmental BiologyColumbia UniversityNew YorkNew YorkUSA
| | - Jessica Root
- Department of PsychologyEmory UniversityAtlantaGeorgiaUSA
- Present address:
Department of Pharmacology and Chemical BiologyEmory UniversityAtlantaGeorgiaUSA
| | - Donna L. Maney
- Department of PsychologyEmory UniversityAtlantaGeorgiaUSA
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3
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Jeong H, Baran NM, Sun D, Chatterjee P, Layman TS, Balakrishnan CN, Maney DL, Yi SV. Dynamic molecular evolution of a supergene with suppressed recombination in white-throated sparrows. eLife 2022; 11:e79387. [PMID: 36040313 PMCID: PMC9427109 DOI: 10.7554/elife.79387] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2022] [Accepted: 08/17/2022] [Indexed: 12/11/2022] Open
Abstract
In white-throated sparrows, two alternative morphs differing in plumage and behavior segregate with a large chromosomal rearrangement. As with sex chromosomes such as the mammalian Y, the rearranged version of chromosome two (ZAL2m) is in a near-constant state of heterozygosity, offering opportunities to investigate both degenerative and selective processes during the early evolutionary stages of 'supergenes.' Here, we generated, synthesized, and analyzed extensive genome-scale data to better understand the forces shaping the evolution of the ZAL2 and ZAL2m chromosomes in this species. We found that features of ZAL2m are consistent with substantially reduced recombination and low levels of degeneration. We also found evidence that selective sweeps took place both on ZAL2m and its standard counterpart, ZAL2, after the rearrangement event. Signatures of positive selection were associated with allelic bias in gene expression, suggesting that antagonistic selection has operated on gene regulation. Finally, we discovered a region exhibiting long-range haplotypes inside the rearrangement on ZAL2m. These haplotypes appear to have been maintained by balancing selection, retaining genetic diversity within the supergene. Together, our analyses illuminate mechanisms contributing to the evolution of a young chromosomal polymorphism, revealing complex selective processes acting concurrently with genetic degeneration to drive the evolution of supergenes.
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Affiliation(s)
- Hyeonsoo Jeong
- School of Biological Sciences, Georgia Institute of TechnologyAtlantaUnited States
| | - Nicole M Baran
- School of Biological Sciences, Georgia Institute of TechnologyAtlantaUnited States
- Department of Psychology, Emory UniversityAtlantaUnited States
- Department of Ecology, Evolution, Marine Biology, University of California, Santa BarbaraSanta BarbaraUnited States
| | - Dan Sun
- School of Biological Sciences, Georgia Institute of TechnologyAtlantaUnited States
- Department of Medicine Huddinge, Karolinska InstitutetStockholmSweden
| | - Paramita Chatterjee
- School of Biological Sciences, Georgia Institute of TechnologyAtlantaUnited States
| | - Thomas S Layman
- School of Biological Sciences, Georgia Institute of TechnologyAtlantaUnited States
| | | | - Donna L Maney
- Department of Psychology, Emory UniversityAtlantaUnited States
| | - Soojin V Yi
- School of Biological Sciences, Georgia Institute of TechnologyAtlantaUnited States
- Department of Ecology, Evolution, Marine Biology, University of California, Santa BarbaraSanta BarbaraUnited States
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4
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Evolutionary Ecology of Fixed Alternative Male Mating Strategies in the Ruff (Calidris pugnax). DIVERSITY 2022. [DOI: 10.3390/d14040307] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
A few empirical examples document fixed alternative male mating strategies in animals. Here we focus on the polymorphism of male mating strategies in the ruff (Calidris pugnax, Aves Charadriiformes). In ruffs, three fixed alternative male mating strategies coexist and are signaled by extreme plumage polymorphism. We first present relevant data on the biology of the species. Then we review the available knowledge of the behavioral ecology of ruffs during the breeding season, and we detail the characteristics of each of the three known fixed male mating strategies. We next turn to the results of exceptional quality accumulated on both the structural and functional genomics of the ruff over the past few years. We show how much these genomic data can shed new, mechanistic light on the evolution and maintenance of the three fixed alternative male mating strategies. We then look if there is sufficient indication to support frequency-dependent selection as a key mechanism in maintaining these three strategies. Specifically, we search for evidence of equal fitness among individuals using each of the three strategies. Finally, we propose three lines of research avenues that will help to understand the eco-evolutionary dynamics of phenotypic differences within natural populations of this iconic model species.
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5
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Holland PWH, Jiggins CD, Liedvogel M, Warren G, Wurm Y. Functional genomics of supergene-controlled behavior in the white-throated sparrow. Fac Rev 2022; 10:75. [PMID: 35146495 DOI: 10.12703/r-01-000003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Supergenes are regions of suppressed recombination that may span hundreds of genes and can control variation in key ecological phenotypes. Since genetic analysis is made impossible by the absence of recombination between genes, it has been difficult to establish how individual genes within these regions contribute to supergene-controlled phenotypes. The white-throated sparrow is a classic example in which a supergene controls behavioral differences as well as distinct coloration that determines mate choice. A landmark study now demonstrates that differences between supergene variants in the promoter sequences of a hormone receptor gene change its expression and control changes in behavior. To unambiguously establish the link between genotype and phenotype, the authors used antisense oligonucleotides to alter the level of gene expression in a focal brain region targeted through a cannula. The study showcases a powerful approach to the functional genomic manipulation of a wild vertebrate species.
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Affiliation(s)
| | | | - Miriam Liedvogel
- Institute of Avian Research 'Vogelwarte Helgoland'; Max Planck Institute for Evolutionary Biology
| | | | - Yannick Wurm
- Queen Mary University of London; Alan Turing Institute
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6
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Hollander-Cohen L, Meir I, Shulman M, Levavi-Sivan B. Identifying the Interaction of the Brain and the Pituitary in Social - and Reproductive - State of Tilapia by Transcriptome Analyses. Neuroendocrinology 2022; 112:1237-1260. [PMID: 35381588 DOI: 10.1159/000524437] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Accepted: 03/23/2022] [Indexed: 12/26/2022]
Abstract
INTRODUCTION As in all vertebrates, reproduction in fish is regulated by gonadotrophin-releasing hormone (GnRH) control on gonadotrophic hormones (GtHs) activity. However, the neuroendocrine factors that promote GnRH and GtH activity are unknown. In Nile tilapia (Oreochromis niloticus), sexual activity and reproduction ability depend on social rank; only dominant males and females reproduce. Here, this characteristic of dominant fish allows us to compare brain and pituitary gene expression in animals that do and do not reproduce, aiming to reveal mechanisms that regulate reproduction. METHODS An extensive transcriptome analysis was performed, combining two sets of transcriptomes: a novel whole-brain and pituitary transcriptome of established dominant and subordinate males, together with a cell-specific transcriptome of luteinizing hormone (LH) and follicle-stimulating hormone cells. Pituitary incubation assay validated the direct effect of steroid application on chosen genes and GtH secretion. RESULTS In most dominant fish, as determined behaviorally, the gonadosomatic index was higher than in subordinate fish, and the leading upregulated pituitary genes were those coding for GtHs. In the brain, various neuropeptide genes, including isotocin, cholecystokinin, and MCH, were upregulated; these may be related to reproductive status through effects on behavior and feeding. In a STRING network analysis combining the two transcriptome sets, brain aromatase, highly expressed in LH cells, is the most central gene with the highest number of connections. In the pituitary incubation assay, testosterone and estradiol increased the secretion of LH and specific gene transcription. CONCLUSIONS The close correlation between behavioral dominance and reproductive capacity in tilapia allows unraveling novel genes that may regulate the hypothalamic-pituitary-gonadal axis, highlighting aromatase as the main factor affecting the brain and pituitary in maintaining a sexually active organism.
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Affiliation(s)
- Lian Hollander-Cohen
- Department of Animal Sciences, The Robert H. Smith Faculty of Agriculture, Food, and Environment, Hebrew University of Jerusalem, Rehovot, Israel,
| | - Inbar Meir
- Department of Animal Sciences, The Robert H. Smith Faculty of Agriculture, Food, and Environment, Hebrew University of Jerusalem, Rehovot, Israel
| | - Miriam Shulman
- Department of Animal Sciences, The Robert H. Smith Faculty of Agriculture, Food, and Environment, Hebrew University of Jerusalem, Rehovot, Israel
| | - Berta Levavi-Sivan
- Department of Animal Sciences, The Robert H. Smith Faculty of Agriculture, Food, and Environment, Hebrew University of Jerusalem, Rehovot, Israel
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7
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Loveland JL, Lank DB, Küpper C. Gene Expression Modification by an Autosomal Inversion Associated With Three Male Mating Morphs. Front Genet 2021; 12:641620. [PMID: 34149796 PMCID: PMC8213371 DOI: 10.3389/fgene.2021.641620] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Accepted: 04/22/2021] [Indexed: 11/22/2022] Open
Abstract
Chromosomal inversions are structural rearrangements that frequently provide genomic substrate for phenotypic diversity. In the ruff Philomachus pugnax, three distinct male reproductive morphs (Independents, Satellites and Faeders) are genetically determined by a 4.5 Mb autosomal inversion. Here we test how this stable inversion polymorphism affects gene expression in males during the lekking season. Gene expression may be altered through disruptions at the breakpoints and the accumulation of mutations due to suppressed recombination. We used quantitative PCR to measure expression of 11 candidate inversion genes across three different tissues (liver, adrenal glands and gonads) and tested for allelic imbalance in four inversion genes across 12 males of all three morphs (8 Independents, 2 Satellites, 2 Faeders). We quantified transcripts of CENPN, an essential gene disrupted by the inversion at the proximal breakpoint, at different exons distributed near and across the breakpoint region. Consistent with dosage dependent gene expression for the breakpoint gene CENPN, we found that expression in Independents was broadly similar for transcripts segments from inside and outside the inversion regions, whereas for Satellites and Faeders, transcript segments outside of the inversion showed at least twofold higher expression than those spanning over the breakpoint. Within the inversion, observed expression differences for inversion males across all four genes with allele-specific primers were consistent with allelic imbalance. We further analyzed gonadal expression of two inversion genes, HSD17B2 and SDR42E1, along with 12 non-inversion genes related to steroid metabolism and signaling in 25 males (13 Independents, 7 Satellites, 5 Faeders). Although we did not find clear morph differentiation for many individual genes, all three morphs could be separated based on gene expression differences when using linear discriminant analysis (LDA), regardless of genomic location (i.e., inside or outside of the inversion). This was robust to the removal of genes with the highest loadings. Pairwise correlations in the expression of genes showed significant correlations for 9–18 pairs of genes within morphs. However, between morphs, we only found a single association between genes SDR42E1 and AROM for Independents and Satellites. Our results suggest complex and wide-ranging changes in gene expression caused by structural variants.
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Affiliation(s)
- Jasmine L Loveland
- Research Group for Behavioural Genetics and Evolutionary Ecology, Max Planck Institute for Ornithology, Seewiesen, Germany
| | - David B Lank
- Department of Biological Sciences, Simon Fraser University, Burnaby, BC, Canada
| | - Clemens Küpper
- Research Group for Behavioural Genetics and Evolutionary Ecology, Max Planck Institute for Ornithology, Seewiesen, Germany
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8
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Gutiérrez-Valencia J, Hughes PW, Berdan EL, Slotte T. The Genomic Architecture and Evolutionary Fates of Supergenes. Genome Biol Evol 2021; 13:6178796. [PMID: 33739390 PMCID: PMC8160319 DOI: 10.1093/gbe/evab057] [Citation(s) in RCA: 37] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/14/2021] [Indexed: 12/25/2022] Open
Abstract
Supergenes are genomic regions containing sets of tightly linked loci that control multi-trait phenotypic polymorphisms under balancing selection. Recent advances in genomics have uncovered significant variation in both the genomic architecture as well as the mode of origin of supergenes across diverse organismal systems. Although the role of genomic architecture for the origin of supergenes has been much discussed, differences in the genomic architecture also subsequently affect the evolutionary trajectory of supergenes and the rate of degeneration of supergene haplotypes. In this review, we synthesize recent genomic work and historical models of supergene evolution, highlighting how the genomic architecture of supergenes affects their evolutionary fate. We discuss how recent findings on classic supergenes involved in governing ant colony social form, mimicry in butterflies, and heterostyly in flowering plants relate to theoretical expectations. Furthermore, we use forward simulations to demonstrate that differences in genomic architecture affect the degeneration of supergenes. Finally, we discuss implications of the evolution of supergene haplotypes for the long-term fate of balanced polymorphisms governed by supergenes.
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Affiliation(s)
- Juanita Gutiérrez-Valencia
- Department of Ecology, Environment and Plant Sciences, Science for Life Laboratory, Stockholm University, Sweden
| | - P William Hughes
- Department of Ecology, Environment and Plant Sciences, Science for Life Laboratory, Stockholm University, Sweden
| | - Emma L Berdan
- Department of Ecology, Environment and Plant Sciences, Science for Life Laboratory, Stockholm University, Sweden
| | - Tanja Slotte
- Department of Ecology, Environment and Plant Sciences, Science for Life Laboratory, Stockholm University, Sweden
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9
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Maney DL, Merritt JR, Prichard MR, Horton BM, Yi SV. Inside the supergene of the bird with four sexes. Horm Behav 2020; 126:104850. [PMID: 32937166 PMCID: PMC7725849 DOI: 10.1016/j.yhbeh.2020.104850] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Revised: 09/04/2020] [Accepted: 09/06/2020] [Indexed: 02/07/2023]
Abstract
The white-throated sparrow (Zonotrichia albicollis) offers unique opportunities to understand the adaptive value of supergenes, particularly their role in alternative phenotypes. In this species, alternative plumage morphs segregate with a nonrecombining segment of chromosome 2, which has been called a 'supergene'. The species mates disassortatively with respect to the supergene; that is, each breeding pair consists of one individual with it and one without it. This species has therefore been called the "bird with four sexes". The supergene segregates with a behavioral phenotype; birds with it are more aggressive and less parental than birds without it. Here, we review our efforts to identify the genes inside the supergene that are responsible for the behavioral polymorphism. The gene ESR1, which encodes estrogen receptor α, differs between the morphs and predicts both territorial and parental behavior. Variation in the regulatory regions of ESR1 causes an imbalance in expression of the two alleles, and the degree to which this imbalance favors the supergene allele predicts territorial singing. In heterozygotes, knockdown of ESR1 causes a phenotypic switch, from more aggressive to less aggressive. We recently showed that another gene important for social behavior, vasoactive intestinal peptide (VIP), is differentially expressed between the morphs and predicts territorial singing. We hypothesize that ESR1 and VIP contribute to behavior in a coordinated way and could represent co-adapted alleles. Because the supergene contains more than 1000 individual genes, this species provides rich possibilities for discovering alleles that work together to mediate life-history trade-offs and maximize the fitness of alternative complex phenotypes.
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Affiliation(s)
- Donna L Maney
- Department of Psychology, Emory University, Atlanta, GA, USA.
| | | | | | - Brent M Horton
- Department of Biology, Millersville University, Millersville, PA, USA
| | - Soojin V Yi
- School of Biological Sciences, Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA, USA
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10
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Merritt JR, Grogan KE, Zinzow-Kramer WM, Sun D, Ortlund EA, Yi SV, Maney DL. A supergene-linked estrogen receptor drives alternative phenotypes in a polymorphic songbird. Proc Natl Acad Sci U S A 2020; 117:21673-21680. [PMID: 32817554 PMCID: PMC7474689 DOI: 10.1073/pnas.2011347117] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Behavioral evolution relies on genetic changes, yet few behaviors can be traced to specific genetic sequences in vertebrates. Here we provide experimental evidence showing that differentiation of a single gene has contributed to the evolution of divergent behavioral phenotypes in the white-throated sparrow, a common backyard songbird. In this species, a series of chromosomal inversions has formed a supergene that segregates with an aggressive phenotype. The supergene has captured ESR1, the gene that encodes estrogen receptor α (ERα); as a result, this gene is accumulating changes that now distinguish the supergene allele from the standard allele. Our results show that in birds of the more aggressive phenotype, ERα knockdown caused a phenotypic change to that of the less aggressive phenotype. We next showed that in a free-living population, aggression is predicted by allelic imbalance favoring the supergene allele. Finally, we identified cis-regulatory features, both genetic and epigenetic, that explain the allelic imbalance. This work provides a rare illustration of how genotypic divergence has led to behavioral phenotypic divergence in a vertebrate.
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Affiliation(s)
| | | | | | - Dan Sun
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA 30332
| | - Eric A Ortlund
- Department of Biochemistry, Emory University, Atlanta, GA 30322
| | - Soojin V Yi
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA 30332
| | - Donna L Maney
- Department of Psychology, Emory University, Atlanta, GA 30322
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11
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Supergene evolution via stepwise duplications and neofunctionalization of a floral-organ identity gene. Proc Natl Acad Sci U S A 2020; 117:23148-23157. [PMID: 32868445 DOI: 10.1073/pnas.2006296117] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Heterostyly represents a fascinating adaptation to promote outbreeding in plants that evolved multiple times independently. While l-morph individuals form flowers with long styles, short anthers, and small pollen grains, S-morph individuals have flowers with short styles, long anthers, and large pollen grains. The difference between the morphs is controlled by an S-locus "supergene" consisting of several distinct genes that determine different traits of the syndrome and are held together, because recombination between them is suppressed. In Primula, the S locus is a roughly 300-kb hemizygous region containing five predicted genes. However, with one exception, their roles remain unclear, as does the evolutionary buildup of the S locus. Here we demonstrate that the MADS-box GLOBOSA2 (GLO2) gene at the S locus determines anther position. In Primula forbesii S-morph plants, GLO2 promotes growth by cell expansion in the fused tube of petals and stamen filaments beneath the anther insertion point; by contrast, neither pollen size nor male incompatibility is affected by GLO2 activity. The paralogue GLO1, from which GLO2 arose by duplication, has maintained the ancestral B-class function in specifying petal and stamen identity, indicating that GLO2 underwent neofunctionalization, likely at the level of the encoded protein. Genetic mapping and phylogenetic analysis indicate that the duplications giving rise to the style-length-determining gene CYP734A50 and to GLO2 occurred sequentially, with the CYP734A50 duplication likely the first. Together these results provide the most detailed insight into the assembly of a plant supergene yet and have important implications for the evolution of heterostyly.
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12
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Horton BM, Michael CM, Prichard MR, Maney DL. Vasoactive intestinal peptide as a mediator of the effects of a supergene on social behaviour. Proc Biol Sci 2020; 287:20200196. [PMID: 32259472 PMCID: PMC7209063 DOI: 10.1098/rspb.2020.0196] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2020] [Accepted: 03/13/2020] [Indexed: 12/15/2022] Open
Abstract
Supergenes, or linked groups of alleles that are inherited together, present excellent opportunities to understand gene-behaviour relationships. In white-throated sparrows (Zonotrichia albicollis), a supergene on the second chromosome associates with a more aggressive and less parental phenotype. This supergene includes the gene for vasoactive intestinal peptide (VIP), a neuropeptide known to play a causal role in both aggression and parental behaviour. Here, using a free-living population, we compared the levels of VIP mRNA between birds with and without the supergene. We focused on the anterior hypothalamus and infundibular region, two brain regions containing VIP neurons known to play a causal role in aggression and parental behaviour, respectively. First, we show that the supergene enhances VIP expression in the anterior hypothalamus and that expression positively predicts vocal aggression independently of genotype in both sexes. Next, we show that the supergene reduces VIP expression in the infundibular region, which suggests reduced secretion of prolactin, a pro-parental hormone. Thus, the patterns of VIP expression in these two regions are consistent with the enhanced aggression and reduced parental behaviour of birds with the supergene allele. Our results illustrate mechanisms by which elements of genomic architecture, such as supergenes, can contribute to the evolution of alternative behavioural phenotypes.
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Affiliation(s)
- Brent M. Horton
- Department of Biology, Millersville University, Millersville, PA, USA
- Department of Psychology, Emory University, Atlanta, GA, USA
| | | | | | - Donna L. Maney
- Department of Psychology, Emory University, Atlanta, GA, USA
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