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Zhao L, Zhou W, He J, Li DZ, Li HT. Positive selection and relaxed purifying selection contribute to rapid evolution of male-biased genes in a dioecious flowering plant. eLife 2024; 12:RP89941. [PMID: 38353667 PMCID: PMC10942601 DOI: 10.7554/elife.89941] [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] [Indexed: 02/16/2024] Open
Abstract
Sex-biased genes offer insights into the evolution of sexual dimorphism. Sex-biased genes, especially those with male bias, show elevated evolutionary rates of protein sequences driven by positive selection and relaxed purifying selection in animals. Although rapid sequence evolution of sex-biased genes and evolutionary forces have been investigated in animals and brown algae, less is known about evolutionary forces in dioecious angiosperms. In this study, we separately compared the expression of sex-biased genes between female and male floral buds and between female and male flowers at anthesis in dioecious Trichosanthes pilosa (Cucurbitaceae). In floral buds, sex-biased gene expression was pervasive, and had significantly different roles in sexual dimorphism such as physiology. We observed higher rates of sequence evolution for male-biased genes in floral buds compared to female-biased and unbiased genes. Male-biased genes under positive selection were mainly associated with functions to abiotic stress and immune responses, suggesting that high evolutionary rates are driven by adaptive evolution. Additionally, relaxed purifying selection may contribute to accelerated evolution in male-biased genes generated by gene duplication. Our findings, for the first time in angiosperms, suggest evident rapid evolution of male-biased genes, advance our understanding of the patterns and forces driving the evolution of sexual dimorphism in dioecious plants.
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Affiliation(s)
- Lei Zhao
- Germplasm Bank of Wild Species & Yunnan Key Laboratory of Crop Wild Relatives Omics, Kunming Institute of Botany, Chinese Academy of SciencesKunming, YunnanChina
| | - Wei Zhou
- Germplasm Bank of Wild Species & Yunnan Key Laboratory of Crop Wild Relatives Omics, Kunming Institute of Botany, Chinese Academy of SciencesKunming, YunnanChina
| | - Jun He
- Germplasm Bank of Wild Species & Yunnan Key Laboratory of Crop Wild Relatives Omics, Kunming Institute of Botany, Chinese Academy of SciencesKunming, YunnanChina
| | - De-Zhu Li
- Germplasm Bank of Wild Species & Yunnan Key Laboratory of Crop Wild Relatives Omics, Kunming Institute of Botany, Chinese Academy of SciencesKunming, YunnanChina
- Kunming College of Life Science, University of Chinese Academy of SciencesKunmingChina
| | - Hong-Tao Li
- Germplasm Bank of Wild Species & Yunnan Key Laboratory of Crop Wild Relatives Omics, Kunming Institute of Botany, Chinese Academy of SciencesKunming, YunnanChina
- Kunming College of Life Science, University of Chinese Academy of SciencesKunmingChina
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Deng D, Xing S, Liu X, Ji Q, Zhai Z, Peng W. Transcriptome analysis of sex-biased gene expression in the spotted-wing Drosophila, Drosophila suzukii (Matsumura). G3 GENES|GENOMES|GENETICS 2022; 12:6588685. [PMID: 35587603 PMCID: PMC9339319 DOI: 10.1093/g3journal/jkac127] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Accepted: 05/11/2022] [Indexed: 11/16/2022]
Abstract
Sexual dimorphism occurs widely throughout insects and has profound influences on evolutionary path. Sex-biased genes are considered to account for most of phenotypic differences between sexes. In order to explore the sex-biased genes potentially associated with sexual dimorphism and sexual development in Drosophila suzukii, a major devastating and invasive crop pest, we conducted whole-organism transcriptome profiling and sex-biased gene expression analysis on adults of both sexes. We identified transcripts of genes involved in several sex-specific physiological and functional processes, including transcripts involved in sex determination, reproduction, olfaction, and innate immune signals. A total of 11,360 differentially expressed genes were identified in the comparison, and 1,957 differentially expressed genes were female-biased and 4,231 differentially expressed genes were male-biased. The pathway predominantly enriched for differentially expressed genes was related to spliceosome, which might reflect the differences in the alternative splicing mechanism between males and females. Twenty-two sex determination and 16 sex-related reproduction genes were identified, and expression pattern analysis revealed that the majority of genes were differentially expressed between sexes. Additionally, the differences in sex-specific olfactory and immune processes were analyzed and the sex-biased expression of these genes may play important roles in pheromone and odor detection, and immune response. As a valuable dataset, our sex-specific transcriptomic data can significantly contribute to the fundamental elucidation of the molecular mechanisms of sexual dimorphism in fruit flies, and may provide candidate genes potentially useful for the development of genetic sexing strains, an important tool for sterile insect technique applications against this economically important species.
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Affiliation(s)
- Dan Deng
- Hunan Provincial Key Laboratory of Animal Intestinal Function and Regulation, State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan International Joint Laboratory of Animal Intestinal Ecology and Health, Hunan Normal University , Changsha 410081, China
| | - Shisi Xing
- Hunan Provincial Key Laboratory of Animal Intestinal Function and Regulation, State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan International Joint Laboratory of Animal Intestinal Ecology and Health, Hunan Normal University , Changsha 410081, China
| | - Xuxiang Liu
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Key Lab of Biopesticide and Chemical Biology, Ministry of Education, Institute of Biological Control, Fujian Agriculture and Forestry University , Fuzhou 350002, China
| | - Qinge Ji
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Key Lab of Biopesticide and Chemical Biology, Ministry of Education, Institute of Biological Control, Fujian Agriculture and Forestry University , Fuzhou 350002, China
| | - Zongzhao Zhai
- Hunan Provincial Key Laboratory of Animal Intestinal Function and Regulation, State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan International Joint Laboratory of Animal Intestinal Ecology and Health, Hunan Normal University , Changsha 410081, China
| | - Wei Peng
- Hunan Provincial Key Laboratory of Animal Intestinal Function and Regulation, State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan International Joint Laboratory of Animal Intestinal Ecology and Health, Hunan Normal University , Changsha 410081, China
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3
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Whittle CA, Kulkarni A, Extavour CG. Evolutionary dynamics of sex-biased genes expressed in cricket brains and gonads. J Evol Biol 2021; 34:1188-1211. [PMID: 34114713 DOI: 10.1111/jeb.13889] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Accepted: 05/31/2021] [Indexed: 12/14/2022]
Abstract
Sex-biased gene expression, particularly sex-biased expression in the gonad, has been linked to rates of protein sequence evolution (nonsynonymous to synonymous substitutions, dN/dS) in animals. However, in insects, sex-biased expression studies remain centred on a few holometabolous species. Moreover, other major tissue types such as the brain remain underexplored. Here, we studied sex-biased gene expression and protein evolution in a hemimetabolous insect, the cricket Gryllus bimaculatus. We generated novel male and female RNA-seq data for two sexual tissue types, the gonad and somatic reproductive system, and for two core components of the nervous system, the brain and ventral nerve cord. From a genome-wide analysis, we report several core findings. Firstly, testis-biased genes had accelerated evolution, as compared to ovary-biased and unbiased genes, which was associated with positive selection events. Secondly, although sex-biased brain genes were much less common than for the gonad, they exhibited a striking tendency for rapid protein sequence evolution, an effect that was stronger for the female than male brain. Further, some sex-biased brain genes were linked to sexual functions and mating behaviours, which we suggest may have accelerated their evolution via sexual selection. Thirdly, a tendency for narrow cross-tissue expression breadth, suggesting low pleiotropy, was observed for sex-biased brain genes, suggesting relaxed purifying selection, which we speculate may allow enhanced freedom to evolve adaptive protein functional changes. The findings of rapid evolution of testis-biased genes and male and female-biased brain genes are discussed with respect to pleiotropy, positive selection and the mating biology of this cricket.
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Affiliation(s)
- Carrie A Whittle
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA
| | - Arpita Kulkarni
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA.,Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA, USA
| | - Cassandra G Extavour
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA.,Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA, USA
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4
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Patlar B, Jayaswal V, Ranz JM, Civetta A. Nonadaptive molecular evolution of seminal fluid proteins in Drosophila. Evolution 2021; 75:2102-2113. [PMID: 34184267 PMCID: PMC8457112 DOI: 10.1111/evo.14297] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2021] [Revised: 06/02/2021] [Accepted: 06/09/2021] [Indexed: 12/20/2022]
Abstract
Seminal fluid proteins (SFPs) are a group of reproductive proteins that are among the most evolutionarily divergent known. As SFPs can impact male and female fitness, these proteins have been proposed to evolve under postcopulatory sexual selection (PCSS). However, the fast change of the SFPs can also result from nonadaptive evolution, and the extent to which selective constraints prevent SFPs rapid evolution remains unknown. Using intra‐ and interspecific sequence information, along with genomics and functional data, we examine the molecular evolution of approximately 300 SFPs in Drosophila. We found that 50–57% of the SFP genes, depending on the population examined, are evolving under relaxed selection. Only 7–12% showed evidence of positive selection, with no evidence supporting other forms of PCSS, and 35–37% of the SFP genes were selectively constrained. Further, despite associations of positive selection with gene location on the X chromosome and protease activity, the analysis of additional genomic and functional features revealed their lack of influence on SFPs evolving under positive selection. Our results highlight a lack of sufficient evidence to claim that most SFPs are driven to evolve rapidly by PCSS while identifying genomic and functional attributes that influence different modes of SFPs evolution.
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Affiliation(s)
- Bahar Patlar
- Department of Biology, University of Winnipeg, Winnipeg, MB, R3B 2E9, Canada
| | - Vivek Jayaswal
- School of Mathematics and Statistics, The University of Sydney, Sydney, NSW, 2006, Australia
| | - José M Ranz
- Department of Ecology and Evolutionary Biology, University of California Irvine, Irvine, California, 92697
| | - Alberto Civetta
- Department of Biology, University of Winnipeg, Winnipeg, MB, R3B 2E9, Canada
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Congrains C, Zucchi RA, de Brito RA. Phylogenomic approach reveals strong signatures of introgression in the rapid diversification of neotropical true fruit flies (Anastrepha: Tephritidae). Mol Phylogenet Evol 2021; 162:107200. [PMID: 33984467 DOI: 10.1016/j.ympev.2021.107200] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2020] [Revised: 01/30/2021] [Accepted: 05/03/2021] [Indexed: 01/08/2023]
Abstract
New sequencing techniques have allowed us to explore the variation on thousands of genes and elucidate evolutionary relationships of lineages even in complex scenarios, such as when there is rapid diversification. That seems to be the case of species in the genus Anastrepha, which shows great species diversity that has been divided into 21 species groups, several of which show wide geographical distribution. The fraterculus group has several economically important species and it is also an outstanding model for speciation studies, since it includes several lineages that have diverged recently possibly in the presence of interspecific gene flow. Our main goal is to test whether we can infer phylogenetic relationships of recently diverged taxa with gene flow, such as what is expected for the fraterculus group and determine whether certain genes remain informative even in this complex scenario. An analysis of thousands of orthologous genes derived from transcriptome datasets of 10 different lineages across the genus, including some of the economically most important pests, revealed signals of incomplete lineage sorting, vestiges of ancestral introgression between more distant lineages and ongoing gene flow between closely related lineages. Though these patterns affect the phylogenetic signal, the phylogenomic inferences consistently show that the morphologically identified species here investigated are in different evolutionary lineages, with the sole exception involving Brazilian lineages of A. fraterculus, which has been suggested to be a complex assembly of cryptic species. A tree space analysis suggested that genes with greater phylogenetic resolution have evolved under similar selection pressures and are more resilient to intraspecific gene flow, which would make it more likely that these genomic regions may be useful for identifying fraterculus group lineages. Our findings help establish relationships among the most important Anastrepha species groups, as well as bring further data to indicate that the diversification of fraterculus group lineages, and even other lineages in the genus Anastrepha, has been strongly influenced by interspecific gene flow.
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Affiliation(s)
- Carlos Congrains
- Departamento de Genética e Evolução, Universidade Federal de São Carlos, São Carlos, SP, Brazil.
| | - Roberto A Zucchi
- Escola Superior de Agricultura "Luiz de Queiroz" - ESALQ, Universidade de São Paulo - USP, Piracicaba, SP, Brazil
| | - Reinaldo A de Brito
- Departamento de Genética e Evolução, Universidade Federal de São Carlos, São Carlos, SP, Brazil
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Scannapieco AC, Conte CA, Rivarola M, Wulff JP, Muntaabski I, Ribone A, Milla F, Cladera JL, Lanzavecchia SB. Transcriptome analysis of Anastrepha fraterculus sp. 1 males, females, and embryos: insights into development, courtship, and reproduction. BMC Genet 2020; 21:136. [PMID: 33339505 PMCID: PMC7747455 DOI: 10.1186/s12863-020-00943-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Anastrepha fraterculus sp. 1 is considered a quarantine pest in several American countries. Since chemical control applied in an integrated pest management program is the only strategy utilized against this pest, the development of pesticide-free methods, such as the Sterile Insect Technique, is being considered. The search for genes involved in sex-determination and differentiation, and in metabolic pathways associated with communication and mating behaviour, contributes with key information to the development of genetic control strategies. The aims of this work were to perform a comprehensive analysis of A. fraterculus sp. 1 transcriptome and to obtain an initial evaluation of genes associated with main metabolic pathways by the expression analysis of specific transcripts identified in embryos and adults. RESULTS Sexually mature adults of both sexes and 72 h embryos were considered for transcriptome analysis. The de novo transcriptome assembly was fairly complete (62.9% complete BUSCO orthologs detected) with a total of 86,925 transcripts assembled and 28,756 GO annotated sequences. Paired-comparisons between libraries showed 319 transcripts differently expressed between embryos and females, 1242 between embryos and males, and 464 between sexes. Using this information and genes searches based on published studies from other tephritid species, we evaluated a set of transcripts involved in development, courtship and metabolic pathways. The qPCR analysis evidenced that the early genes serendipity alpha and transformer-2 displayed similar expression levels in the analyzed stages, while heat shock protein 27 is over-expressed in embryos and females in comparison to males. The expression of genes associated with courtship (takeout-like, odorant-binding protein 50a1) differed between males and females, independently of their reproductive status (virgin vs mated individuals). Genes associated with metabolic pathways (maltase 2-like, androgen-induced gene 1) showed differential expression between embryos and adults. Furthermore, 14,262 microsatellite motifs were identified, with 11,208 transcripts containing at least one simple sequence repeat, including 48% of di/trinucleotide motifs. CONCLUSION Our results significantly expand the available gene space of A. fraterculus sp. 1, contributing with a fairly complete transcript database of embryos and adults. The expression analysis of the selected candidate genes, along with a set of microsatellite markers, provides a valuable resource for further genetic characterization of A. fraterculus sp. 1 and supports the development of specific genetic control strategies.
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Affiliation(s)
- Alejandra Carla Scannapieco
- Instituto de Genética "E. A. Favret" (IGEAF) gv Instituto de Agrobiotecnología y Biología Molecular (IABIMO), Instituo Nacional de Tecnología Agropecuaria (INTA) - Consejo de Investigaciones Científicas y Técnicas (CONICET), Hurlingham, Buenos Aires, Argentina
| | - Claudia Alejandra Conte
- Instituto de Genética "E. A. Favret" (IGEAF) gv Instituto de Agrobiotecnología y Biología Molecular (IABIMO), Instituo Nacional de Tecnología Agropecuaria (INTA) - Consejo de Investigaciones Científicas y Técnicas (CONICET), Hurlingham, Buenos Aires, Argentina
| | - Máximo Rivarola
- Instituto de Biotecnología, IABIMO, INTA - CONICET, Hurlingham, Buenos Aires, Argentina
| | - Juan Pedro Wulff
- Instituto de Genética "E. A. Favret" (IGEAF) gv Instituto de Agrobiotecnología y Biología Molecular (IABIMO), Instituo Nacional de Tecnología Agropecuaria (INTA) - Consejo de Investigaciones Científicas y Técnicas (CONICET), Hurlingham, Buenos Aires, Argentina
| | - Irina Muntaabski
- Instituto de Genética "E. A. Favret" (IGEAF) gv Instituto de Agrobiotecnología y Biología Molecular (IABIMO), Instituo Nacional de Tecnología Agropecuaria (INTA) - Consejo de Investigaciones Científicas y Técnicas (CONICET), Hurlingham, Buenos Aires, Argentina
| | - Andrés Ribone
- Instituto de Biotecnología, IABIMO, INTA - CONICET, Hurlingham, Buenos Aires, Argentina
| | - Fabián Milla
- Instituto de Genética "E. A. Favret" (IGEAF) gv Instituto de Agrobiotecnología y Biología Molecular (IABIMO), Instituo Nacional de Tecnología Agropecuaria (INTA) - Consejo de Investigaciones Científicas y Técnicas (CONICET), Hurlingham, Buenos Aires, Argentina
| | - Jorge Luis Cladera
- Instituto de Genética "E. A. Favret" (IGEAF) gv Instituto de Agrobiotecnología y Biología Molecular (IABIMO), Instituo Nacional de Tecnología Agropecuaria (INTA) - Consejo de Investigaciones Científicas y Técnicas (CONICET), Hurlingham, Buenos Aires, Argentina
| | - Silvia Beatriz Lanzavecchia
- Instituto de Genética "E. A. Favret" (IGEAF) gv Instituto de Agrobiotecnología y Biología Molecular (IABIMO), Instituo Nacional de Tecnología Agropecuaria (INTA) - Consejo de Investigaciones Científicas y Técnicas (CONICET), Hurlingham, Buenos Aires, Argentina.
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Bao R, Friedrich M. Genomic signatures of globally enhanced gene duplicate accumulation in the megadiverse higher Diptera fueling intralocus sexual conflict resolution. PeerJ 2020; 8:e10012. [PMID: 33083121 PMCID: PMC7560327 DOI: 10.7717/peerj.10012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Accepted: 08/31/2020] [Indexed: 12/03/2022] Open
Abstract
Gene duplication is an important source of evolutionary innovation. To explore the relative impact of gene duplication during the diversification of major insect model system lineages, we performed a comparative analysis of lineage-specific gene duplications in the fruit fly Drosophila melanogaster (Diptera: Brachycera), the mosquito Anopheles gambiae (Diptera: Culicomorpha), the red flour beetle Tribolium castaneum (Coleoptera), and the honeybee Apis mellifera (Hymenoptera). Focusing on close to 6,000 insect core gene families containing maximally six paralogs, we detected a conspicuously higher number of lineage-specific duplications in Drosophila (689) compared to Anopheles (315), Tribolium (386), and Apis (223). Based on analyses of sequence divergence, phylogenetic distribution, and gene ontology information, we present evidence that an increased background rate of gene duplicate accumulation played an exceptional role during the diversification of the higher Diptera (Brachycera), in part by providing enriched opportunities for intralocus sexual conflict resolution, which may have boosted speciation rates during the early radiation of the megadiverse brachyceran subclade Schizophora.
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Affiliation(s)
- Riyue Bao
- Hillman Cancer Center, University of Pittsburgh, Pittsburgh, PA, USA.,Department of Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Markus Friedrich
- Department of Biological Sciences, Wayne State University, Detroit, MI, USA.,School of Medicine, Department of Anatomy and Cell Biology, Wayne State University, Detroit, MI, USA
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Whittle CA, Extavour CG. Selection shapes turnover and magnitude of sex-biased expression in Drosophila gonads. BMC Evol Biol 2019; 19:60. [PMID: 30786879 PMCID: PMC6383255 DOI: 10.1186/s12862-019-1377-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Accepted: 01/23/2019] [Indexed: 12/18/2022] Open
Abstract
BACKGROUND Sex-biased gene expression is thought to drive the phenotypic differences in males and females in metazoans. Drosophila has served as a primary model for studying male-female differences in gene expression, and its effects on protein sequence divergence. However, the forces shaping evolution of sex-biased expression remain largely unresolved, including the roles of selection and pleiotropy. Research on sex organs in Drosophila, employing original approaches and multiple-species contrasts, provides a means to gain insights into factors shaping the turnover and magnitude (fold-bias) of sex-biased expression. RESULTS Here, using recent RNA-seq data, we studied sex-biased gonadal expression in 10,740 protein coding sequences in four species of Drosophila, D. melanogaster, D. simulans, D. yakuba and D. ananassae (5 to 44 My divergence). Using an approach wherein we identified genes with lineage-specific transitions (LSTs) in sex-biased status (amongst testis-biased, ovary-biased and unbiased; thus, six transition types) standardized to the number of genes with the ancestral state (S-LSTs), and those with clade-wide expression bias status, we reveal several key findings. First, the six categorical types of S-LSTs in sex-bias showed disparate rates of turnover, consistent with differential selection pressures. Second, the turnover in sex-biased status was largely unrelated to cross-tissue expression breadth, suggesting pleiotropy does not restrict evolution of sex-biased expression. Third, the fold-sex-biased expression, for both testis-biased and ovary-biased genes, evolved directionally over time toward higher values, a crucial finding that could be interpreted as a selective advantage of greater sex-bias, and sexual antagonism. Fourth, in terms of protein divergence, genes with LSTs to testis-biased expression exhibited weak signals of elevated rates of evolution (than ovary-biased) in as little as 5 My, which strengthened over time. Moreover, genes with clade-wide testis-specific expression (44 My), a status not observed for any ovary-biased genes, exhibited striking acceleration of protein divergence, which was linked to low pleiotropy. CONCLUSIONS By studying LSTs and clade-wide sex-biased gonadal expression in a multi-species clade of Drosophila, we describe evidence that interspecies turnover and magnitude of sex-biased expression have been influenced by selection. Further, whilst pleiotropy was not connected to turnover in sex-biased gonadal expression, it likely explains protein sequence divergence.
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Affiliation(s)
- Carrie A Whittle
- Department of Organismic and Evolutionary Biology, Harvard University, 16 Divinity Avenue, Cambridge, MA, 02138, USA
| | - Cassandra G Extavour
- Department of Organismic and Evolutionary Biology, Harvard University, 16 Divinity Avenue, Cambridge, MA, 02138, USA.
- Department of Molecular and Cellular Biology, Harvard University, 16 Divinity Avenue, Cambridge, MA, 02138, USA.
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