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Wilburn DB, Kunkel CL, Feldhoff RC, Feldhoff PW, Searle BC. Recurrent Co-Option and Recombination of Cytokine and Three Finger Proteins in Multiple Reproductive Tissues Throughout Salamander Evolution. Front Cell Dev Biol 2022; 10:828947. [PMID: 35281090 PMCID: PMC8904931 DOI: 10.3389/fcell.2022.828947] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2021] [Accepted: 02/01/2022] [Indexed: 11/13/2022] Open
Abstract
Reproductive proteins evolve at unparalleled rates, resulting in tremendous diversity of both molecular composition and biochemical function between gametes of different taxonomic clades. To date, the proteomic composition of amphibian gametes is largely a molecular mystery, particularly for Urodeles (salamanders and newts) for which few genomic-scale resources exist. In this study, we provide the first detailed molecular characterization of gametes from two salamander species (Plethodon shermani and Desmognathus ocoee) that are models of reproductive behavior. Long-read PacBio transcriptome sequencing of testis and ovary of both species revealed sex-specific expression of many genes common to vertebrate gametes, including a similar expression profile to the egg coat genes of Xenopus oocytes. In contrast to broad conservation of oocyte genes, major testis transcripts included paralogs of salamander-specific courtship pheromones (PRF, PMF, and SPF) that were confirmed as major sperm proteins by mass spectrometry proteomics. Sperm-specific paralogs of PMF and SPF are likely the most abundant secreted proteins in P. shermani and D. ocoee, respectively. In contrast, sperm PRF lacks a signal peptide and may be expressed in cytoplasm. PRF pheromone genes evolved independently multiple times by repeated gene duplication of sperm PRF genes with signal peptides recovered through recombination with PMF genes. Phylogenetic analysis of courtship pheromones and their sperm paralogs support that each protein family evolved for these two reproductive contexts at distinct evolutionary time points between 17 and 360 million years ago. Our combined phylogenetic, transcriptomic and proteomic analyses of plethodontid reproductive tissues support that the recurrent co-option and recombination of TFPs and cytokine-like proteins have been a novel driving force throughout salamander evolution and reproduction.
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Affiliation(s)
- Damien B. Wilburn
- Department of Biomedical Informatics, The Ohio State University, Columbus, OH, United States
- *Correspondence: Damien B. Wilburn,
| | - Christy L. Kunkel
- Department of Biology, John Carroll University, Cleveland Heights, OH, United States
| | - Richard C. Feldhoff
- Department of Biochemistry and Molecular Genetics, University of Louisville, Louisville, KY, United States
| | - Pamela W. Feldhoff
- Department of Biochemistry and Molecular Genetics, University of Louisville, Louisville, KY, United States
| | - Brian C. Searle
- Department of Biomedical Informatics, The Ohio State University, Columbus, OH, United States
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2
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Schulte LM, Martel A, Cruz-Elizalde R, Ramírez-Bautista A, Bossuyt F. Love bites: male frogs (Plectrohyla, Hylidae) use teeth scratching to deliver sodefrin precursor-like factors to females during amplexus. Front Zool 2021; 18:59. [PMID: 34823558 PMCID: PMC8613984 DOI: 10.1186/s12983-021-00445-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Accepted: 11/09/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Efficient transfer of chemical signals is important for successful mating in many animal species. Multiple evolutionary lineages of animals evolved direct sex pheromone transmission during traumatic mating-the wounding of the partner with specialized devices-which helps to avoid signal loss to the environment. Although such direct transmission modes of so-called allohormone pheromones are well-documented in invertebrates, they are considered rare in vertebrates. Males of several species of the frog genus Plectrohyla (Hylidae, Anura) have elongated teeth and develop swollen lips during the breeding season. Here we investigated the possibility that these structures are used to scratch the females' skin and apply allohormone pheromones during traumatic mating in several Plectrohyla species. RESULTS Our behavioural observations revealed that males press their upper jaw onto the females' dorsum during amplexus, leaving small skin scratches with their teeth. Histological examinations of the males' lips identified specialized mucus glands, resembling known amphibian pheromone glands. Whole-transcriptome sequencing of these breeding glands showed high expression of sodefrin precursor-like factor (SPF) proteins, which are known to have a pheromone function in multiple amphibian species. CONCLUSIONS Our study suggests SPF delivery via traumatic mating in several anuran species: the males have specialized breeding glands in the lips for production and secretion and use their elongated teeth as wounding devices for application. We hypothesize that these SPF proteins end up in the females' circulatory system, where understanding their exact function will require further molecular, physiological and behavioural testing.
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Affiliation(s)
- Lisa M Schulte
- Department of Wildlife-/Zoo-Animal-Biology and Systematics, Faculty of Biological Sciences, Goethe University Frankfurt, Max-von-Laue-Str. 13, 60438, Frankfurt/Main, Germany.
| | - An Martel
- Wildlife Health, Ghent University, Salisburylaan 133, 9820, Merelbeke, Belgium
| | - Raciel Cruz-Elizalde
- Laboratorio de Zoología, Facultad de Ciencias Naturales, Universidad Autónoma de Querétaro, Avenida de Las Ciencias S/N, Santa Fe Juriquilla, C. P. 76230, Querétaro, Mexico
| | - Aurelio Ramírez-Bautista
- Laboratorio de Ecología de Poblaciones, Centro de Investigaciones Biológicas, Instituto de Ciencias Básicas E Ingeniería, Universidad Autónoma del Estado de Hidalgo, Km 4.5 carretera Pachuca-Tulancingo, 42184, Mineral de La Reforma, Hidalgo, Mexico
| | - Franky Bossuyt
- Amphibian Evolution Lab, Biology Department, Vrije Universiteit Brussel (VUB), Pleinlaan 2, 1050, Brussels, Belgium
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Herrboldt MA, Steffen MA, McGouran CN, Bonett RM. Pheromone Gene Diversification and the Evolution of Courtship Glands in Plethodontid Salamanders. J Mol Evol 2021; 89:576-587. [PMID: 34392385 DOI: 10.1007/s00239-021-10026-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2020] [Accepted: 07/28/2021] [Indexed: 11/30/2022]
Abstract
Proteinaceous pheromones that diversify through gene duplication can result in shifts in courtship cocktails that may serve as a mechanism for reproductive isolation. The molecular evolution of pheromones has been extensively studied in salamanders, but how these genes and associated novel courtship glands have codiversified has not been evaluated. In this study we used transcriptional analyses to examine the relationship between pheromone diversification and gland type in three divergent lineages of plethodontid salamanders. Our results revealed that plethodontid salamanders express up to eight divergent Sodefrin Precursor-like Factor genes (spf, representing both alpha and beta subfamilies) along with Plethodontid Modulating Factor (pmf) and Plethodontid Receptivity Factor (prf). Expression of pheromone genes is tissue specific with pmf, prf, and some spf genes restricted to the mental gland. In contrast, the caudal gland shows strong expression of the other spf genes. We found evidence for punctuated changes in pheromone cocktail composition related to the loss of metamorphosis, and subsequent extreme reduction of the mental gland, in a paedomorphic lineage. Our study provides insight into how pheromone diversification can be partitioned into unique glands, which may lead to cocktail specificity in behavioral modules during courtship.
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Affiliation(s)
- Madison A Herrboldt
- Department of Biological Science, University of Tulsa, Tulsa, OK, 74104, USA.
| | - Michael A Steffen
- Department of Biological Science, University of Tulsa, Tulsa, OK, 74104, USA
| | - Carissa N McGouran
- Department of Biological Science, University of Tulsa, Tulsa, OK, 74104, USA
| | - Ronald M Bonett
- Department of Biological Science, University of Tulsa, Tulsa, OK, 74104, USA
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4
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Abstract
Pheromonal communication is an ancient and pervasive sensory modality in urodelan amphibians. One family of salamander pheromones (the sodefrin precursor-like factor (SPF) family) originated 300 million years ago, at the origin of amphibians. Although salamanders are often thought of as relatively simple animals especially when compared to mammals, the pheromonal systems are varied and complex with nuanced effects on behavior. Here, we review the function and evolution of pheromonal signals involved in male-female reproductive interactions. After describing common themes of salamander pheromonal communication, we describe what is known about the rich diversity of pheromonal communication in each salamander family. Several pheromones have been described, ranging from simple, invariant molecules to complex, variable blends of pheromones. While some pheromones elicit overt behavioral responses, others have more nuanced effects. Pheromonal signals have diversified within salamander lineages and have experienced rapid evolution. Once receptors have been matched to pheromonal ligands, rapid advance can be made to better understand the olfactory detection and processing of salamander pheromones. In particular, a large number of salamander species deliver pheromones across the skin of females, perhaps reflecting a novel mode of pheromonal communication. At the end of our review, we list some of the many intriguing unanswered questions. We hope that this review will inspire a new generation of scientists to pursue work in this rewarding field.
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Affiliation(s)
- Sarah K Woodley
- Department of Biological Sciences, Duquesne University, 600 Forbes Avenue, Pittsburgh, PA, 15282, USA.
| | - Nancy L Staub
- Biology Department, Gonzaga University, Spokane, WA, 99203, USA
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Bossuyt F, Schulte LM, Maex M, Janssenswillen S, Novikova PY, Biju SD, Van de Peer Y, Matthijs S, Roelants K, Martel A, Van Bocxlaer I. Multiple Independent Recruitment of Sodefrin Precursor-Like Factors in Anuran Sexually Dimorphic Glands. Mol Biol Evol 2020; 36:1921-1930. [PMID: 31238339 DOI: 10.1093/molbev/msz115] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Chemical signaling in animals often plays a central role in eliciting a variety of responses during reproductive interactions between males and females. One of the best-known vertebrate courtship pheromone systems is sodefrin precursor-like factors (SPFs), a family of two-domain three-finger proteins with a female-receptivity enhancing function, currently only known from salamanders. The oldest divergence between active components in a single salamander species dates back to the Late Paleozoic, indicating that these proteins potentially gained a pheromone function earlier in amphibian evolution. Here, we combined whole transcriptome sequencing, proteomics, histology, and molecular phylogenetics in a comparative approach to investigate SPF occurrence in male breeding glands across the evolutionary tree of anurans (frogs and toads). Our study shows that multiple families of both terrestrially and aquatically reproducing frogs have substantially increased expression levels of SPFs in male breeding glands. This suggests that multiple anuran lineages make use of SPFs to complement acoustic and visual sexual signaling during courtship. Comparative analyses show that anurans independently recruited these proteins each time the gland location on the male's body allowed efficient transmission of the secretion to the female's nares.
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Affiliation(s)
- Franky Bossuyt
- Amphibian Evolution Lab, Biology Department, Vrije Universiteit Brussel, Brussels, Belgium
| | - Lisa M Schulte
- Amphibian Evolution Lab, Biology Department, Vrije Universiteit Brussel, Brussels, Belgium.,Department of Wildlife-/Zoo-Animal-Biology and Systematics, Faculty of Biological Sciences, Goethe University Frankfurt, Frankfurt/Main, Germany
| | - Margo Maex
- Amphibian Evolution Lab, Biology Department, Vrije Universiteit Brussel, Brussels, Belgium
| | - Sunita Janssenswillen
- Amphibian Evolution Lab, Biology Department, Vrije Universiteit Brussel, Brussels, Belgium
| | - Polina Yu Novikova
- Department of Plant Biotechnology and Bioinformatics, Center for Plant Systems Biology, Ghent University, Ghent, Belgium
| | - S D Biju
- Systematics Lab, Department of Environmental Studies, University of Delhi, Delhi, India
| | - Yves Van de Peer
- Department of Plant Biotechnology and Bioinformatics, Center for Plant Systems Biology, Ghent University, Ghent, Belgium
| | - Severine Matthijs
- Amphibian Evolution Lab, Biology Department, Vrije Universiteit Brussel, Brussels, Belgium
| | - Kim Roelants
- Amphibian Evolution Lab, Biology Department, Vrije Universiteit Brussel, Brussels, Belgium
| | - An Martel
- Wildlife Health Ghent, Department of Pathology, Bacteriology, and Avian Diseases, Ghent University, Merelbeke, Belgium
| | - Ines Van Bocxlaer
- Amphibian Evolution Lab, Biology Department, Vrije Universiteit Brussel, Brussels, Belgium
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6
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Pelletier TA, Denton RD. A pheromone by any other gene would smell as sweet. Mol Ecol 2018; 27:311-312. [PMID: 29561075 DOI: 10.1111/mec.14412] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2017] [Revised: 10/25/2017] [Accepted: 10/26/2017] [Indexed: 11/28/2022]
Abstract
Reproductive isolation is the result of either the inability to produce viable and fertile offspring or the avoidance of mating altogether. While these mechanisms can evolve either over time via genetic drift or natural selection, the genetic result is usually a complex set of traits that are often linked. Explaining how reproductive isolation proceeds from the initiation of divergence to the complete prevention of mating is often a difficult task, as the underlying genes for traits associated with reproductive isolation can change via molecular evolution and subsequent protein coding alterations or through alterations of gene expression regulation. In this issue of Molecular Ecology, Treer, Maex, VanBocxlaer, Proost, and Bossuyt () use transcriptomic, proteomic and phylogenetic analyses to show that species-specific sex pheromones are the result of gradual sequence divergence on the same set of proteins in two closely related newt species (Ichthyosaura alpestris and Lissotriton helveticus). This study shows that salamander pheromone systems provide an enticing opportunity to connect the evolution of reproductive isolation to the changes in genes that underlie a key phenotype.
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Affiliation(s)
- Tara A Pelletier
- Department of Ecology, Evolution & Organismal Biology, The Ohio State University, Columbus, OH, USA
| | - Robert D Denton
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT, USA
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Maex M, Treer D, De Greve H, Proost P, Van Bocxlaer I, Bossuyt F. Exaptation as a Mechanism for Functional Reinforcement of an Animal Pheromone System. Curr Biol 2018; 28:2955-2960.e5. [DOI: 10.1016/j.cub.2018.06.074] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Revised: 06/27/2018] [Accepted: 06/28/2018] [Indexed: 10/28/2022]
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Treer D, Maex M, Van Bocxlaer I, Proost P, Bossuyt F. Divergence of species-specific protein sex pheromone blends in two related, nonhybridizing newts (Salamandridae). Mol Ecol 2017; 27:508-519. [PMID: 29087032 DOI: 10.1111/mec.14398] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2017] [Revised: 08/17/2017] [Accepted: 08/24/2017] [Indexed: 12/01/2022]
Abstract
In animals that use chemical communication during courtship and reproduction, speciation is often associated with divergence of their sex pheromones. In multicomponent pheromone systems, divergence can be obtained either by adding or deleting components, or by altering the relative contribution of individual components to the mixture. Protein pheromone systems can additionally evolve by amino acid sequence divergence to produce pheromones with a species-specific effect. The sodefrin precursor-like factor (SPF) pheromone system, a blend of proteins that essentially enhances receptivity in salamanders, has had a long and dynamic evolution of gene duplications, but the mechanisms that govern interspecific divergence and the role they play in reproductive isolation remain elusive. Here, we use transcriptomics and proteomics to characterize the SPF protein repertoire of the alpine newt (Ichthyosaura alpestris), and compare it to the previously identified repertoire of SPF proteins of the palmate newt (Lissotriton helveticus), a related but nonhybridizing species. Subsequent phylogenetic analyses indicate that, despite the availability of multiple SPF gene copies, both species predominantly express the same subset of orthologs. Our study demonstrates that species specificity in the SPF protein pheromone system can be established by gradual sequence divergence of the same set of proteins alone.
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Affiliation(s)
- Dag Treer
- Amphibian Evolution Lab, Biology Department, Vrije Universiteit Brussel (VUB), Brussels, Belgium
| | - Margo Maex
- Amphibian Evolution Lab, Biology Department, Vrije Universiteit Brussel (VUB), Brussels, Belgium
| | - Ines Van Bocxlaer
- Amphibian Evolution Lab, Biology Department, Vrije Universiteit Brussel (VUB), Brussels, Belgium
| | - Paul Proost
- Laboratory of Molecular Immunology, Department of Microbiology and Immunology, Rega Institute, Katholieke Universiteit Leuven (K.U. Leuven), Leuven, Belgium
| | - Franky Bossuyt
- Amphibian Evolution Lab, Biology Department, Vrije Universiteit Brussel (VUB), Brussels, Belgium
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9
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Denoël M. On the identification of paedomorphic and overwintering larval newts based on cloacal shape: review and guidelines. Curr Zool 2017; 63:165-173. [PMID: 29491974 PMCID: PMC5804162 DOI: 10.1093/cz/zow054] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2016] [Accepted: 04/15/2016] [Indexed: 11/14/2022] Open
Abstract
Paedomorphosis is an alternative process to metamorphosis in which adults retain larval traits at the adult stage. It is frequent in newts and salamanders, where larvae reach sexual maturity without losing their gills. However, in some populations, larvae overwinter in water, while remaining immature. These alternative ontogenetic processes are of particular interest in various research fields, but have different causes and consequences, as only paedomorphosis allows metamorphosis to be bypassed before maturity. It is thus relevant to efficiently identify paedomorphs versus overwintering larvae. In this context, the aim of this article was 3-fold: firstly, to perform a meta-analysis of the identification procedures carried out in the literature; secondly, to determine the effectiveness of body size to make inferences about adulthood by surveying natural newt populations of Lissotriton helveticus and Ichthyosaura alpestris, and thirdly, to propose easy guidelines for an accurate distinction between large larvae and paedomorphs based on an external sexual trait, which is essential for reproduction-the cloaca. More than half of the studies in the literature do not mention the diagnostic criteria used for determining adulthood. The criteria mentioned were the presence of mature gonads (10%), eggs laid (4%), courtship behavior (10%), and external morphological sexual traits (39%) including the cloaca (24%). Body-size thresholds should not be used as a proxy for paedomorphosis, because overwintering larvae can reach a larger size than paedomorphs within the same populations. In contrast, diagnosis based on cloacal external morphology is recommended, as it can be processed by the rapid visual assessment of all caught specimens, thus providing straightforward data at the individual level for both sexes.
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Affiliation(s)
- Mathieu Denoël
- Laboratory of Fish and Amphibian Ethology, Behavioural Biology Unit, FOCUS, University of Liège, 22 Quai van Benden, 4020 Liège, Belgium
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10
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Van Bocxlaer I, Maex M, Treer D, Janssenswillen S, Janssens R, Vandebergh W, Proost P, Bossuyt F. Beyond sodefrin: evidence for a multi-component pheromone system in the model newt Cynops pyrrhogaster (Salamandridae). Sci Rep 2016; 6:21880. [PMID: 26935790 PMCID: PMC4776240 DOI: 10.1038/srep21880] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2015] [Accepted: 01/18/2016] [Indexed: 11/09/2022] Open
Abstract
Sodefrin, a decapeptide isolated from the male dorsal gland of the Japanese fire belly newt Cynops pyrrhogaster, was the first peptide pheromone identified from a vertebrate. The fire belly salamander and sodefrin have become a model for sex pheromone investigation in aquatically courting salamanders ever since. Subsequent studies in other salamanders identified SPF protein courtship pheromones of around 20 kDa belonging to the same gene-family. Although transcripts of these proteins could be PCR-amplified in Cynops, it is currently unknown whether they effectively use full-length SPF pheromones next to sodefrin. Here we combined transcriptomics, proteomics and phylogenetics to investigate SPF pheromone use in Cynops pyrrhogaster. Our data show that not sodefrin transcripts, but multiple SPF transcripts make up the majority of the expression profile in the dorsal gland of this newt. Proteome analyses of water in which a male has been courting confirm that this protein blend is effectively secreted and tail-fanned to the female. By combining phylogenetics and expression data, we show that independent evolutionary lineages of these SPF’s were already expressed in ancestral Cynops species before the origin of sodefrin. Extant Cynops species continue to use this multi-component pheromone system, consisting of various proteins in addition to a lineage-specific peptide.
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Affiliation(s)
- Ines Van Bocxlaer
- Amphibian Evolution Lab, Biology Department, Vrije Universiteit Brussel (VUB), Pleinlaan 2, B-1050 Brussels, Belgium
| | - Margo Maex
- Amphibian Evolution Lab, Biology Department, Vrije Universiteit Brussel (VUB), Pleinlaan 2, B-1050 Brussels, Belgium
| | - Dag Treer
- Amphibian Evolution Lab, Biology Department, Vrije Universiteit Brussel (VUB), Pleinlaan 2, B-1050 Brussels, Belgium
| | - Sunita Janssenswillen
- Amphibian Evolution Lab, Biology Department, Vrije Universiteit Brussel (VUB), Pleinlaan 2, B-1050 Brussels, Belgium
| | - Rik Janssens
- Laboratory of Molecular Immunology, Department of Microbiology and Immunology, KU Leuven - University of Leuven, Minderbroedersstraat 10 - box 1030, B-3000 Leuven, Belgium
| | - Wim Vandebergh
- Amphibian Evolution Lab, Biology Department, Vrije Universiteit Brussel (VUB), Pleinlaan 2, B-1050 Brussels, Belgium
| | - Paul Proost
- Laboratory of Molecular Immunology, Department of Microbiology and Immunology, KU Leuven - University of Leuven, Minderbroedersstraat 10 - box 1030, B-3000 Leuven, Belgium
| | - Franky Bossuyt
- Amphibian Evolution Lab, Biology Department, Vrije Universiteit Brussel (VUB), Pleinlaan 2, B-1050 Brussels, Belgium
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Maex M, Van Bocxlaer I, Mortier A, Proost P, Bossuyt F. Courtship Pheromone Use in a Model Urodele, the Mexican Axolotl (Ambystoma mexicanum). Sci Rep 2016; 6:20184. [PMID: 26842386 DOI: 10.1038/srep20184] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2015] [Accepted: 12/23/2015] [Indexed: 11/08/2022] Open
Abstract
Sex pheromones have been shown to constitute a crucial aspect of salamander reproduction. Until now, courtship pheromones of Salamandridae and Plethodontidae have been intensively studied, but information on chemical communication in other urodelan families is essentially lacking. The axolotl (Ambystoma mexicanum, Ambystomatidae) has a courtship display that suggests a key role for chemical communication in the orchestration of its sexual behavior, but no sex pheromones have yet been characterized from this species. Here we combined whole transcriptome analyses of the male cloaca with proteomic analyses of water in which axolotls were allowed to court to show that male axolotls secrete multiple ca. 20 kDa glycosylated sodefrin precursor-like factor (SPF) proteins during courtship. In combination with phylogenetic analyses, our data show that the male cloaca essentially secretes a courtship-specific clade of SPF proteins that is orthologous to salamandrid courtship pheromones. In addition, we identified an SPF protein for which no orthologs have been described from other salamanders so far. Overall, our study advocates a central role for SPF proteins during the courtship display of axolotls and adds knowledge on pheromone use in a previously unexplored deep evolutionary branch of salamander evolution.
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Abstract
Pheromones are an important component of sexual communication in courting salamanders, but the number of species in which their use has been demonstrated with behavioral evidence remains limited. Here we developed a behavioral assay for demonstrating courtship pheromone use in the aquatically courting Iberian ribbed newt Pleurodeles waltl. By performing an in-depth study of the courtship behavior, we show that females invariably open their cloaca (cloacal gaping) before engaging in pinwheel behavior, the circling movement that is the prelude to spermatophore uptake. In contrast, cloacal gaping was not observed in failed courtships, where females escaped or displayed thanatosis. Since gaping mainly occurred during male amplexus and cloacal imposition, which is the obvious period of pheromone transfer, we next investigated whether male courtship water (i.e., water holding courtship pheromones) alone was able to induce this reaction in females. These tests showed that courtship water induced cloacal gaping significantly more than water, even in the absence of a male. Cloacal gaping thus provides a simple and robust test for demonstrating courtship pheromone use in the Iberian ribbed newt. Since opening the cloaca is an essential prerequisite for spermatophore pick-up in all internally fertilizing salamanders, we hypothesize that variations on this assay will also be useful in several other species.
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Affiliation(s)
| | - Franky Bossuyt
- Amphibian Evolution Lab, Biology Department, Vrije Universiteit, Brussel, Belgium
- * E-mail:
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13
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Wilburn DB, Swanson WJ. From molecules to mating: Rapid evolution and biochemical studies of reproductive proteins. J Proteomics 2015; 135:12-25. [PMID: 26074353 DOI: 10.1016/j.jprot.2015.06.007] [Citation(s) in RCA: 72] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2015] [Revised: 06/09/2015] [Accepted: 06/10/2015] [Indexed: 01/10/2023]
Abstract
UNLABELLED Sexual reproduction and the exchange of genetic information are essential biological processes for species across all branches of the tree of life. Over the last four decades, biochemists have continued to identify many of the factors that facilitate reproduction, but the molecular mechanisms that mediate this process continue to elude us. However, a recurring observation in this research has been the rapid evolution of reproductive proteins. In animals, the competing interests of males and females often result in arms race dynamics between pairs of interacting proteins. This phenomenon has been observed in all stages of reproduction, including pheromones, seminal fluid components, and gamete recognition proteins. In this article, we review how the integration of evolutionary theory with biochemical experiments can be used to study interacting reproductive proteins. Examples are included from both model and non-model organisms, and recent studies are highlighted for their use of state-of-the-art genomic and proteomic techniques. SIGNIFICANCE Despite decades of research, our understanding of the molecular mechanisms that mediate fertilization remain poorly characterized. To date, molecular evolutionary studies on both model and non-model organisms have provided some of the best inferences to elucidating the molecular underpinnings of animal reproduction. This review article details how biochemical and evolutionary experiments have jointly enhanced the field for 40 years, and how recent work using high-throughput genomic and proteomic techniques have shed additional insights into this crucial biological process.
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Affiliation(s)
- Damien B Wilburn
- Department of Genome Sciences, University of Washington, United States.
| | - Willie J Swanson
- Department of Genome Sciences, University of Washington, United States
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Janssenswillen S, Willaert B, Treer D, Vandebergh W, Bossuyt F, Van Bocxlaer I. High pheromone diversity in the male cheek gland of the red-spotted newt Notophthalmus viridescens (Salamandridae). BMC Evol Biol 2015; 15:54. [PMID: 25888438 PMCID: PMC4379952 DOI: 10.1186/s12862-015-0333-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Accepted: 03/09/2015] [Indexed: 01/18/2023] Open
Abstract
BACKGROUND Male salamanders (Urodela) often make use of pheromones that are produced in sexually dimorphic glands to persuade the female into courtship and mating. The mental gland of lungless salamanders (Plethodontidae) and dorsal cloacal glands (or abdominal glands) of newts (Salamandridae) have been particularly well studied in that respect. In both families, sodefrin precursor-like factor (SPF) proteins have been identified as major components of the courtship pheromone system. However, similar to plethodontids, some newts also make use of subtle head glands during courtship, but few pheromones have been characterized from such structures. Males of red-spotted newts (Notophthalmus viridescens, Salamandridae) have both cloacal and cheek (genial) glands, and are known to apply secretions to the female's nose by both tail-fanning and cheek-rubbing. Here we combined transcriptomic and phylogenetic analyses to investigate the presence, diversity and evolution of SPF proteins in the cloacal and cheek glands of this species. RESULTS Our analyses indicate that the cheek glands of male N. viridescens produce a similar amount and diversity of SPF isoforms as the cloacal glands in this species. Expression in other tissues was much lower, suggesting that both male-specific courtship glands secrete SPF pheromones during courtship. Our phylogenetic analyses show that N. viridescens expresses a combination of isoforms that stem from four highly diverged evolutionary lineages of SPF variants, that together form a basis for the broad diversity of SPF precursors in the breeding glands. CONCLUSIONS The similar SPF expression of cheek and cloacal glands suggests that this protein family is used for pheromone signalling through cheek rubbing in the red-spotted newt. Since several male salamandrids in other genera have comparable head glands, SPF application via other glands than the cloacal glands may be more widespread than currently appreciated in salamandrids.
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Affiliation(s)
- Sunita Janssenswillen
- Biology Department, Amphibian Evolution Lab, Vrije Universiteit Brussel (VUB), Pleinlaan 2, B-1050, Brussels, Belgium.
| | - Bert Willaert
- Biology Department, Amphibian Evolution Lab, Vrije Universiteit Brussel (VUB), Pleinlaan 2, B-1050, Brussels, Belgium.
| | - Dag Treer
- Biology Department, Amphibian Evolution Lab, Vrije Universiteit Brussel (VUB), Pleinlaan 2, B-1050, Brussels, Belgium.
| | - Wim Vandebergh
- Biology Department, Amphibian Evolution Lab, Vrije Universiteit Brussel (VUB), Pleinlaan 2, B-1050, Brussels, Belgium.
| | - Franky Bossuyt
- Biology Department, Amphibian Evolution Lab, Vrije Universiteit Brussel (VUB), Pleinlaan 2, B-1050, Brussels, Belgium.
| | - Ines Van Bocxlaer
- Biology Department, Amphibian Evolution Lab, Vrije Universiteit Brussel (VUB), Pleinlaan 2, B-1050, Brussels, Belgium.
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