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Morita M, Ugwu SI, Kohda M. Variations in the breeding behavior of cichlids and the evolution of the multi-functional seminal plasma protein, seminal plasma glycoprotein 120. BMC Evol Biol 2018; 18:197. [PMID: 30572831 PMCID: PMC6302530 DOI: 10.1186/s12862-018-1292-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2018] [Accepted: 11/09/2018] [Indexed: 11/27/2022] Open
Abstract
Background Seminal plasma proteins are associated with successful fertilization. However, their evolutionary correlation with fertilization mechanisms remains unclear. Cichlids from Lake Tanganyika show a variety-rich spawning behavior that is associated with the transfer of the sperm to the egg for fertilization. One of these behaviors, called “oral fertilization,” emerged during their speciation. In oral fertilization, females nuzzle the milt from male genitalia and pick up the released eggs in their mouths, which are then fertilized inside the oral cavity. Thus, the success of the fertilization is dependent on the retention of sperm in the oral cavity during spawning. Sperm aggregation and immobilization in viscous seminal plasma may help retain the sperm inside the oral cavity, which ultimately determines the success of the fertilization. Seminal plasma glycoprotein 120 (SPP120) is one of the major seminal plasma proteins present in cichlids. SPP120 has been implicated to immobilize sperm and increase the milt viscosity. However, the functional linkage between oral fertilization and seminal plasma proteins has not been investigated. Results During trials of simulated oral fertilization, it was observed that milt viscosity contributed to fertilization success by facilitating longer retention of the milt inside the mouth during spawning. Glycosylation of SPP120 was associated with high milt viscosity. Its glycosylation was specifically present in the milt of cichlid species exhibiting oral fertilization. Moreover, recombinant SPP120 from several the oral fertilization species strongly immobilized/aggregated sperm. Therefore, the functions of SPP120 (immobilization/aggregation and its glycosylation) may contribute to success of oral fertilization, and these functions of SPP120 are more prominent in oral fertilization species. In addition, comparative phylogenetic analyses showed a positive evolutionary correlation between SPP120 function and oral fertilization. Hence, these evolutions may have occurred to keep up with the transition in the mode of fertilization. In addition, rapid evolution in the molecular sequence might be associated with functional modifications of SPP120. Conclusion These results suggest that SPP120 might be associated with oral fertilization. In other words, reproductive traits that define the interaction between sperms and eggs could be the evolutionary selective force that cause the rapid functional modification of the fertilization-related reproductive protein, SPP120. Electronic supplementary material The online version of this article (10.1186/s12862-018-1292-0) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Masaya Morita
- Sesoko Station, Tropical Biosphere Research Center, University of the Ryukyus, Sesoko, Motobu, Okinawa, 905-0227, Japan.
| | - Stanley Ifeanyi Ugwu
- Sesoko Station, Tropical Biosphere Research Center, University of the Ryukyus, Sesoko, Motobu, Okinawa, 905-0227, Japan
| | - Masanori Kohda
- Laboratory of Animal Sociology, Department of Biology and Geosciences, Graduate School of Sciences, Osaka City University, Sumiyoshi, Osaka, 558-8585, Japan
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2
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Zhong H, Zhang H, Tang Z, Guo Z, Yan J, Xiao J, Luo Y, Zhou Y. Evidence for natural selection of immune genes from Parachromis managuensis by transcriptome sequencing. BIOTECHNOL BIOTEC EQ 2018. [DOI: 10.1080/13102818.2018.1519377] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022] Open
Affiliation(s)
- Huan Zhong
- Guangxi Key Laboratory of Aquatic Genetic Breeding and Healthy Aquaculture, Guangxi Academy of Fishery Sciences, Nanning, PR China
| | - Hong Zhang
- Guangxi Key Laboratory of Beibu Gulf Marine Biodiversity Conservation, Qinzhou University, Qinzhou, PR China
| | - Zhanyang Tang
- Guangxi Key Laboratory of Aquatic Genetic Breeding and Healthy Aquaculture, Guangxi Academy of Fishery Sciences, Nanning, PR China
| | - Zhongbao Guo
- Guangxi Key Laboratory of Aquatic Genetic Breeding and Healthy Aquaculture, Guangxi Academy of Fishery Sciences, Nanning, PR China
| | - Jinpeng Yan
- Department of Cell Biology, School of Life Sciences, Central South University, Changsha, PR China
| | - Jun Xiao
- Guangxi Key Laboratory of Aquatic Genetic Breeding and Healthy Aquaculture, Guangxi Academy of Fishery Sciences, Nanning, PR China
| | - Yongju Luo
- Guangxi Key Laboratory of Aquatic Genetic Breeding and Healthy Aquaculture, Guangxi Academy of Fishery Sciences, Nanning, PR China
| | - Yi Zhou
- Guangxi Key Laboratory of Aquatic Genetic Breeding and Healthy Aquaculture, Guangxi Academy of Fishery Sciences, Nanning, PR China
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Ugwu SI, Shiba K, Inaba K, Morita M. A Unique Seminal Plasma Protein, Zona Pellucida 3-Like Protein, has Ca 2+ -Dependent Sperm Agglutination Activity. Zoolog Sci 2018; 35:161-171. [PMID: 29623792 DOI: 10.2108/zs170150] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Identification of seminal proteins provides a means of investigating their roles. Despite their importance in the study of protein function, such as regulation of sperm motility, it is difficult to select candidates from the large number of proteins. Analyzing the rate of molecular evolution is a useful strategy for selecting candidates, and expressing the protein allows the examination of its function. In the present study, we investigated seminal plasma proteins of the cichlid Oreochromis mossambicus, which exhibits a unique mode of fertilization and a rapidly evolving gene that encodes a seminal plasma protein, zona-pellucida 3-like (ZP3-like), which does not belong to the same molecular family as other ZPs. Seminal plasma proteins of O. mossambicus were separated by two-dimensional electrophoresis, and 19 major proteins were identified by mass spectrometry (MALDI-Tof Mass). Because proteins that are under positive selection often impact sperm function, the rates of molecular evolution of these proteins were analyzed in terms of non-synonymous/synonymous substitutions (ω). Among the 19 proteins, positive selection was supported for five genes; functional assays were carried out on four of the proteins encoded by these genes. Of the four positively selected proteins, only ZP3-like protein agglutinated sperm in a dose- and Ca2+ -dependent manner. The other three proteins did not affect sperm motility. Because of the unique fertilization type, in which fertilization occurs in the buccal cavity, the need to retain sperm within the cavity during spawning, and the agglutination of sperm, which may be partly assisted by ZP3-like protein, may contribute to fertilization success. Fertilization in the buccal cavity may be related to its rapid molecular evolution.
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Affiliation(s)
- Stanley Ifeanyi Ugwu
- 1 Sesoko Station, Tropical Biosphere Research Center, University of the Ryukyus, 3422 Sesoko, Motobu, Okinawa 905-0227, Japan
| | - Kogiku Shiba
- 2 Shimoda Marine Research Center, University of Tsukuba, 5-10-1 Shimoda City, Shizuoka 415-0025, Japan
| | - Kazuo Inaba
- 2 Shimoda Marine Research Center, University of Tsukuba, 5-10-1 Shimoda City, Shizuoka 415-0025, Japan
| | - Masaya Morita
- 1 Sesoko Station, Tropical Biosphere Research Center, University of the Ryukyus, 3422 Sesoko, Motobu, Okinawa 905-0227, Japan
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4
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A structured interdomain linker directs self-polymerization of human uromodulin. Proc Natl Acad Sci U S A 2016; 113:1552-7. [PMID: 26811476 DOI: 10.1073/pnas.1519803113] [Citation(s) in RCA: 67] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Uromodulin (UMOD)/Tamm-Horsfall protein, the most abundant human urinary protein, plays a key role in chronic kidney diseases and is a promising therapeutic target for hypertension. Via its bipartite zona pellucida module (ZP-N/ZP-C), UMOD forms extracellular filaments that regulate kidney electrolyte balance and innate immunity, as well as protect against renal stones. Moreover, salt-dependent aggregation of UMOD filaments in the urine generates a soluble molecular net that captures uropathogenic bacteria and facilitates their clearance. Despite the functional importance of its homopolymers, no structural information is available on UMOD and how it self-assembles into filaments. Here, we report the crystal structures of polymerization regions of human UMOD and mouse ZP2, an essential sperm receptor protein that is structurally related to UMOD but forms heteropolymers. The structure of UMOD reveals that an extensive hydrophobic interface mediates ZP-N domain homodimerization. This arrangement is required for filament formation and is directed by an ordered ZP-N/ZP-C linker that is not observed in ZP2 but is conserved in the sequence of deafness/Crohn's disease-associated homopolymeric glycoproteins α-tectorin (TECTA) and glycoprotein 2 (GP2). Our data provide an example of how interdomain linker plasticity can modulate the function of structurally similar multidomain proteins. Moreover, the architecture of UMOD rationalizes numerous pathogenic mutations in both UMOD and TECTA genes.
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Genome-Wide Identification of Genes Probably Relevant to the Uniqueness of Tea Plant (Camellia sinensis) and Its Cultivars. Int J Genomics 2015; 2015:527054. [PMID: 26543846 PMCID: PMC4620235 DOI: 10.1155/2015/527054] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Revised: 08/21/2015] [Accepted: 08/23/2015] [Indexed: 11/22/2022] Open
Abstract
Tea (Camellia sinensis) is a popular beverage all over the world and a number of studies have focused on the genetic uniqueness of tea and its cultivars. However, molecular mechanisms underlying these phenomena are largely undefined. In this report, based on expression data available from public databases, we performed a series of analyses to identify genes probably relevant to the uniqueness of C. sinensis and two of its cultivars (LJ43 and ZH2). Evolutionary analyses showed that the evolutionary rates of genes involved in the pathways were not significantly different among C. sinensis, C. oleifera, and C. azalea. Interestingly, a number of gene families, including genes involved in the pathways synthesizing iconic secondary metabolites of tea plant, were significantly upregulated, expressed in C. sinensis (LJ43) when compared to C. azalea, and this may partially explain its higher content of flavonoid, theanine, and caffeine. Further investigation showed that nonsynonymous mutations may partially contribute to the differences between the two cultivars of C. sinensis, such as the chlorina and higher contents of amino acids in ZH2. Genes identified as candidates are probably relevant to the uniqueness of C. sinensis and its cultivars should be good candidates for subsequent functional analyses and marker-assisted breeding.
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6
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Glasauer SMK, Neuhauss SCF. Whole-genome duplication in teleost fishes and its evolutionary consequences. Mol Genet Genomics 2014; 289:1045-60. [PMID: 25092473 DOI: 10.1007/s00438-014-0889-2] [Citation(s) in RCA: 511] [Impact Index Per Article: 51.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2013] [Accepted: 07/15/2014] [Indexed: 12/18/2022]
Abstract
Whole-genome duplication (WGD) events have shaped the history of many evolutionary lineages. One such duplication has been implicated in the evolution of teleost fishes, by far the most species-rich vertebrate clade. After initial controversy, there is now solid evidence that such event took place in the common ancestor of all extant teleosts. It is termed teleost-specific (TS) WGD. After WGD, duplicate genes have different fates. The most likely outcome is non-functionalization of one duplicate gene due to the lack of selective constraint on preserving both. Mechanisms that act on preservation of duplicates are subfunctionalization (partitioning of ancestral gene functions on the duplicates), neofunctionalization (assigning a novel function to one of the duplicates) and dosage selection (preserving genes to maintain dosage balance between interconnected components). Since the frequency of these mechanisms is influenced by the genes' properties, there are over-retained classes of genes, such as highly expressed ones and genes involved in neural function. The consequences of the TS-WGD, especially its impact on the massive radiation of teleosts, have been matter of controversial debate. It is evident that gene duplications are crucial for generating complexity and that WGDs provide large amounts of raw material for evolutionary adaptation and innovation. However, it is less clear whether the TS-WGD is directly linked to the evolutionary success of teleosts and their radiation. Recent studies let us conclude that TS-WGD has been important in generating teleost complexity, but that more recent ecological adaptations only marginally related to TS-WGD might have even contributed more to diversification. It is likely, however, that TS-WGD provided teleosts with diversification potential that can become effective much later, such as during phases of environmental change.
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Affiliation(s)
- Stella M K Glasauer
- Institute of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland
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7
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Zou M, Guo B, Ma X. Characterizing the transcriptome of yellow-cheek carp (Elopichthys bambusa) enables evolutionary analyses within endemic East Asian Cyprinidae. Gene 2014; 547:267-72. [PMID: 24973763 DOI: 10.1016/j.gene.2014.06.056] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2014] [Revised: 06/23/2014] [Accepted: 06/25/2014] [Indexed: 11/30/2022]
Abstract
The identification of genes that may be responsible for the divergence of closely related species is one of the central goals of evolutionary biology. The species of endemic East Asian Cyprinidae diverged less than 8millionyears ago, and the morphological differences among these species are great. However, the genetic basis of their divergence remains unknown. In this report, we investigated the transcriptome of one endemic East Asian cyprinid - the yellow-cheek carp Elopichthys bambusa. A comparison with the publicly available transcriptomes of other endemic East Asian cyprinids, including the silver carp (Hypophthalmichthys molitrix) and blunt-nose black bream (Megalobrama amblycephala), revealed a number of candidate adaptive genes in each species, such as zona pellucida glycoprotein 2 in E. bambusa and zebrafish vitelline envelope protein in M. amblycephala. An enrichment test showed the enrichment of some specific gene ontology (GO) terms for these putatively adaptive genes. Taken together, our work is the first step toward elucidating the genes that may be related to the divergence of endemic East Asian Cyprinidae, and these genes identified as being probably under positive selection should be good candidates for subsequent evolutionary and functional studies.
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Affiliation(s)
- Ming Zou
- College of Fisheries, Huazhong Agricultural University, Wuhan, People's Republic of China; Key Laboratory of Freshwater Animal Breeding, Ministry of Agriculture, People's Republic of China.
| | - Baocheng Guo
- Ecological Genetics Research Unit, Department of Biosciences, University of Helsinki, Helsinki 00014, Finland
| | - Xufa Ma
- College of Fisheries, Huazhong Agricultural University, Wuhan, People's Republic of China; Key Laboratory of Freshwater Animal Breeding, Ministry of Agriculture, People's Republic of China
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8
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Henning F, Meyer A. The evolutionary genomics of cichlid fishes: explosive speciation and adaptation in the postgenomic era. Annu Rev Genomics Hum Genet 2014; 15:417-41. [PMID: 24898042 DOI: 10.1146/annurev-genom-090413-025412] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
With more than 1,500 species, cichlid fishes provide textbook examples of recent and diverse adaptive radiations, rapid rates of speciation, and the parallel evolution of adaptive phenotypes among both recently and distantly related lineages. This extraordinary diversity has attracted considerable interest from researchers across several biological disciplines. Their broad phenotypic variation coupled with recent divergence makes cichlids an ideal model system for understanding speciation, adaptation, and phenotypic diversification. Genetic mapping, genome-wide analyses, and genome projects have flourished in the past decade and have added new insights on the question of why there are so many cichlids. These recent findings also show that the sharing of older DNA polymorphisms is extensive and suggest that linage sorting is incomplete and that adaptive introgression played a role in the African radiation. Here, we review the results of genetic and genomic research on cichlids in the past decade and suggest some potential avenues to further exploit the potential of the cichlid model system to provide a better understanding of the genomics of adaptation and speciation.
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Affiliation(s)
- Frederico Henning
- Department of Biology, University of Konstanz, 78457 Konstanz, Germany;
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9
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Diepeveen ET, Roth O, Salzburger W. Immune-related functions of the Hivep gene family in East African cichlid fishes. G3 (BETHESDA, MD.) 2013; 3:2205-17. [PMID: 24142922 PMCID: PMC3852383 DOI: 10.1534/g3.113.008839] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/30/2013] [Accepted: 10/07/2013] [Indexed: 01/20/2023]
Abstract
Immune-related genes are often characterized by adaptive protein evolution. Selection on immune genes can be particularly strong when hosts encounter novel parasites, for instance, after the colonization of a new habitat or upon the exploitation of vacant ecological niches in an adaptive radiation. We examined a set of new candidate immune genes in East African cichlid fishes. More specifically, we studied the signatures of selection in five paralogs of the human immunodeficiency virus type I enhancer-binding protein (Hivep) gene family, tested their involvement in the immune defense, and related our results to explosive speciation and adaptive radiation events in cichlids. We found signatures of long-term positive selection in four Hivep paralogs and lineage-specific positive selection in Hivep3b in two radiating cichlid lineages. Exposure of the cichlid Astatotilapia burtoni to a vaccination with Vibrio anguillarum bacteria resulted in a positive correlation between immune response parameters and expression levels of three Hivep loci. This work provides the first evidence for a role of Hivep paralogs in teleost immune defense and links the signatures of positive selection to host-pathogen interactions within an adaptive radiation.
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Affiliation(s)
| | - Olivia Roth
- Evolutionary Ecology of Marine Fishes, Helmholtz Centre of Ocean Research Kiel (GEOMAR), D-24105 Kiel, Germany
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10
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Böhne A, Heule C, Boileau N, Salzburger W. Expression and sequence evolution of aromatase cyp19a1 and other sexual development genes in East African cichlid fishes. Mol Biol Evol 2013; 30:2268-85. [PMID: 23883521 PMCID: PMC3773371 DOI: 10.1093/molbev/mst124] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Sex determination mechanisms are highly variable across teleost fishes and sexual development is often plastic. Nevertheless, downstream factors establishing the two sexes are presumably conserved. Here, we study sequence evolution and gene expression of core genes of sexual development in a prime model system in evolutionary biology, the East African cichlid fishes. Using the available five cichlid genomes, we test for signs of positive selection in 28 genes including duplicates from the teleost whole-genome duplication, and examine the expression of these candidate genes in three cichlid species. We then focus on a particularly striking case, the A- and B-copies of the aromatase cyp19a1, and detect different evolutionary trajectories: cyp19a1A evolved under strong positive selection, whereas cyp19a1B remained conserved at the protein level, yet is subject to regulatory changes at its transcription start sites. Importantly, we find shifts in gene expression in both copies. Cyp19a1 is considered the most conserved ovary-factor in vertebrates, and in all teleosts investigated so far, cyp19a1A and cyp19a1B are expressed in ovaries and the brain, respectively. This is not the case in cichlids, where we find new expression patterns in two derived lineages: the A-copy gained a novel testis-function in the Ectodine lineage, whereas the B-copy is overexpressed in the testis of the speciest-richest cichlid group, the Haplochromini. This suggests that even key factors of sexual development, including the sex steroid pathway, are not conserved in fish, supporting the idea that flexibility in sexual determination and differentiation may be a driving force of speciation.
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Affiliation(s)
- Astrid Böhne
- Zoological Institute, University of Basel, Basel, Switzerland
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11
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Fan S, Elmer KR, Meyer A. Genomics of adaptation and speciation in cichlid fishes: recent advances and analyses in African and Neotropical lineages. Philos Trans R Soc Lond B Biol Sci 2012; 367:385-94. [PMID: 22201168 DOI: 10.1098/rstb.2011.0247] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Cichlid fishes are remarkably phenotypically diverse and species-rich. Therefore, they provide an exciting opportunity for the study of the genetics of adaptation and speciation by natural and sexual selection. Here, we review advances in the genomics and transcriptomics of cichlids, particularly regarding ecologically relevant differences in body shape, trophic apparatus, coloration and patterning, and sex determination. Research conducted so far has focused almost exclusively on African cichlids. To analyse genomic diversity and selection in a Neotropical radiation, we conducted a comparative transcriptomic analysis between sympatric, ecologically divergent crater-lake Midas cichlids (Lake Xiloá Amphilophus amarillo and Amphilophus sagittae). We pyrosequenced (Roche 454) expressed sequence tag (EST) libraries and generated more than 178 000 000 ESTs and identified nine ESTs under positive selection between these sister species (Ka/Ks > 1). None of these ESTs were found to be under selection in African cichlids. Of 11 candidate genes for ecomorphological differentiation in African cichlids, none showed signs of selection between A. amarillo and A. sagittae. Although more population-level studies are now needed to thoroughly document patterns of divergence during speciation of cichlids, available information so far suggests that adaptive phenotypic diversification in Neotropical and African cichlids may be evolving through non-parallel genetic bases.
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Affiliation(s)
- Shaohua Fan
- Lehrstuhl für Zoologie und Evolutionsbiologie, Department of Biology, University of Konstanz, Universitätstrasse 10, 78457 Konstanz, Germany
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Fan S, Elmer KR, Meyer A. Positive Darwinian selection drives the evolution of the morphology-related gene, EPCAM, in particularly species-rich lineages of African cichlid fishes. J Mol Evol 2011; 73:1-9. [PMID: 21811860 DOI: 10.1007/s00239-011-9452-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2010] [Accepted: 07/07/2011] [Indexed: 12/23/2022]
Abstract
The study of genetic evolution within the context of adaptive radiations offers insights to genes and selection pressures that result in rapid morphological change. Cichlid fishes are very species-rich and variable in coloration, behavior, and morphology, and so provide a classical model system for studying the genetics of adaptive radiation. In this study, we researched the evolution of the epithelial cell adhesion molecule (EPCAM), a candidate gene for the adaptive evolution of morphology broadly, and skin development specifically, in fishes. We compared EPCAM gene sequences from a rapidly speciating African cichlid lineage (the haplochromines), a species-poor African lineage (Nile tilapia Oreochromis niloticus), and a very young adaptive radiation in the Neotropics (sympatric crater lake Midas cichlids, Amphilophus sp.). Our results, based on a hierarchy of evolutionary analyses of nucleotide substitution, demonstrate that there are different selection pressures on the EPCAM gene among the cichlid lineages. Several waves of positive natural selection were identified not only on the terminal branches, but also on ancestral branches. Interestingly, significant positive or directional selection was found in the haplochromine cichlids only but not the comparatively species-poor tilapia lineage. We hypothesize that the strong signal of selection in the ancestral African cichlid lineage coincided with the transition from riverine to lacustrine habitat. The two neotropical species for which we collected new sequence data were invariant in the EPCAM locus. Our results suggest that functional changes promoted by positive Darwinian selection are widespread in the EPCAM gene during African cichlid evolution.
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Affiliation(s)
- Shaohua Fan
- Lehrstuhl für Zoologie und Evolutionsbiologie, Department of Biology, University of Konstanz, Universitätstrasse 10, 78457 Constance, Germany
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Evidence for positive selection in the gene fruitless in Anastrepha fruit flies. BMC Evol Biol 2010; 10:293. [PMID: 20868501 PMCID: PMC2958917 DOI: 10.1186/1471-2148-10-293] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2010] [Accepted: 09/24/2010] [Indexed: 01/22/2023] Open
Abstract
Background Many genes involved in the sex determining cascade have indicated signals of positive selection and rapid evolution across different species. Even though fruitless is an important gene involved mostly in several aspects of male courtship behavior, the few studies so far have explained its high rates of evolution by relaxed selective constraints. This would indicate that a large portion of this gene has evolved neutrally, contrary to what has been observed for other genes in the sex cascade. Results Here we test whether the fruitless gene has evolved neutrally or under positive selection in species of Anastrepha (Tephritidae: Diptera) using two different approaches, a long-term evolutionary analysis and a populational genetic data analysis. The first analysis was performed by using sequences of three species of Anastrepha and sequences from several species of Drosophila using the ratio of nonsynonymous to synonymous rates of evolution in PAML, which revealed that the fru region here studied has evolved by positive selection. Using Bayes Empirical Bayes we estimated that 16 sites located in the connecting region of the fruitless gene were evolving under positive selection. We also investigated for signs of this positive selection using populational data from 50 specimens from three species of Anastrepha from different localities in Brazil. The use of standard tests of selection and a new test that compares patterns of differential survival between synonymous and nonsynonymous in evolutionary time also provide evidence of positive selection across species and of a selective sweep for one of the species investigated. Conclusions Our data indicate that the high diversification of fru connecting region in Anastrepha flies is due at least in part to positive selection, not merely as a consequence of relaxed selective constraint. These conclusions are based not only on the comparison of distantly related taxa that show long-term divergence time, but also on recently diverged lineages and suggest that episodes of adaptive evolution in fru may be related to sexual selection and/or conflict related to its involvement in male courtship behavior.
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Wallis LJ, Wallis GP. Extreme positive selection on a new highly-expressed larval glycoprotein (LGP) gene in Galaxias fishes (Osmeriformes: Galaxiidae). Mol Biol Evol 2010; 28:399-406. [PMID: 20696791 DOI: 10.1093/molbev/msq208] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
We describe the intron-exon structure and DNA/protein sequences of a new larval glycoprotein (LGP) gene from nine species of galaxiid fish. The gene has a distant similarity to Danio THP (Tamm-Horsfall urinary glycoprotein; uromodulin) and cichlid SPP120 (seminal plasma glycoprotein) due to conserved features of its zona pellucida (ZP) domain, including eight highly conserved cysteines and a consensus furin cleavage site. Using a combination of 454 sequencing of cDNA and exon-primed intron-spanning sequencing of genomic DNA, we obtained full sequences of the coding region (996 bp) and its intervening sequences (1,459 bp). LGP shows an exceptionally strong signal of positive selection over the entire coding region, as evidenced by d(N)/d(S) values >1. Across nine species of Galaxias, 87/332 (26%) amino acid residues are variable, compared with 9/386 (2%) for mitochondrial cytochrome b (cytb) in the same group of species. Across 36 interspecific pairwise comparisons, genetic distances are in all cases larger for coding region than for introns, by a factor of 2.4-fold on average. Reading frame, gene structure, splice sites, and many ZP motifs are conserved across all species. Together with the fact that the gene is expressed in all species, these results argue clearly against the possibility of a pseudogene. We show by 454 sequencing and quantitative polymerase chain reaction that the transcript is abundant (ca. 0.5%) in newly hatched larvae and appears to be almost absent from a range of adult tissues. We postulate that the strong Darwinian evolution exhibited by this protein may reflect some type of immunoprotection at this vulnerable larval stage.
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Affiliation(s)
- Lise J Wallis
- Department of Zoology, University of Otago, Dunedin, New Zealand.
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Elmer KR, Fan S, Gunter HM, Jones JC, Boekhoff S, Kuraku S, Meyer A. Rapid evolution and selection inferred from the transcriptomes of sympatric crater lake cichlid fishes. Mol Ecol 2010; 19 Suppl 1:197-211. [PMID: 20331780 DOI: 10.1111/j.1365-294x.2009.04488.x] [Citation(s) in RCA: 126] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Crater lakes provide a natural laboratory to study speciation of cichlid fishes by ecological divergence. Up to now, there has been a dearth of transcriptomic and genomic information that would aid in understanding the molecular basis of the phenotypic differentiation between young species. We used next-generation sequencing (Roche 454 massively parallel pyrosequencing) to characterize the diversity of expressed sequence tags between ecologically divergent, endemic and sympatric species of cichlid fishes from crater lake Apoyo, Nicaragua: benthic Amphilophus astorquii and limnetic Amphilophus zaliosus. We obtained 24 174 A. astorquii and 21 382 A. zaliosus high-quality expressed sequence tag contigs, of which 13 106 pairs are orthologous between species. Based on the ratio of nonsynonymous to synonymous substitutions, we identified six sequences exhibiting signals of strong diversifying selection (K(a)/K(s) > 1). These included genes involved in biosynthesis, metabolic processes and development. This transcriptome sequence variation may be reflective of natural selection acting on the genomes of these young, sympatric sister species. Based on Ks ratios and p-distances between 3'-untranslated regions (UTRs) calibrated to previously published species divergence times, we estimated a neutral transcriptome-wide substitutional mutation rate of approximately 1.25 x 10(-6) per site per year. We conclude that next-generation sequencing technologies allow us to infer natural selection acting to diversify the genomes of young species, such as crater lake cichlids, with much greater scope than previously possible.
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Affiliation(s)
- K R Elmer
- Department of Biology, University of Konstanz, Germany
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Hulsey CD. Cichlid genomics and phenotypic diversity in a comparative context. Integr Comp Biol 2009; 49:618-29. [DOI: 10.1093/icb/icp071] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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SALZBURGER WALTER. The interaction of sexually and naturally selected traits in the adaptive radiations of cichlid fishes. Mol Ecol 2009; 18:169-85. [DOI: 10.1111/j.1365-294x.2008.03981.x] [Citation(s) in RCA: 193] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Kuraku S, Meyer A. Genomic analysis of cichlid fish 'natural mutants'. Curr Opin Genet Dev 2008; 18:551-8. [PMID: 19095433 DOI: 10.1016/j.gde.2008.11.002] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2008] [Accepted: 11/03/2008] [Indexed: 11/24/2022]
Abstract
In the lakes of East Africa, cichlid fishes have formed adaptive radiations that are each composed of hundreds of endemic, morphologically stunningly diverse, but genetically extremely similar species. In the past 20 years, it became clear that their extreme phenotypic diversity arose within very short time spans, and that phenotypically radically different species are exceptionally similar genetically; hence, they could be considered to be 'natural mutants'. Many species can be hybridized and, therefore, provide a unique opportunity to study the genetic underpinnings of phenotypic diversification. Comparative large-scale genomic analyses are beginning to unravel the patterns and processes that led to the formation of the cichlid species flocks. Cichlids are an emerging evolutionary genomic model system for fundamental questions on the origin of phenotypic diversity.
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Affiliation(s)
- Shigehiro Kuraku
- Lehrstuhl für Zoologie und Evolutionsbiologie, Department of Biology, University of Konstanz, Konstanz, Germany
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A microsatellite-based genetic linkage map of the cichlid fish, Astatotilapia burtoni (Teleostei): a comparison of genomic architectures among rapidly speciating cichlids. Genetics 2008; 182:387-97. [PMID: 18757932 DOI: 10.1534/genetics.108.089367] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Cichlid fishes compose an astonishingly large number of species and formed species flocks in record-breaking time. To facilitate efficient genome scans and comparisons of cichlid genomes, we constructed a medium-density genetic linkage map of microsatellite markers of Astatotilapia burtoni. The mapping cross was derived from two inbred laboratory lines to obtain F(2) progeny by intercrossing. The map revealed 25 linkage groups spanning 1249.3 cM of the genome (size approximately 950 Mb) with an average marker spacing of 6.12 cM. The seven Hox clusters, ParaHox C1, and two paralogs of Pdgfrbeta were mapped to different linkage groups, thus supporting the hypothesis of a teleost-specific genome duplication. The A. burtoni linkage map was compared to the other two available maps for cichlids using shared markers that showed conservation and synteny among East African cichlid genomes. Interesting candidate genes for cichlid speciation were mapped using SNP markers.
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