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Broitman-Maduro G, Maduro MF. Evolutionary Change in Gut Specification in Caenorhabditis Centers on the GATA Factor ELT-3 in an Example of Developmental System Drift. J Dev Biol 2023; 11:32. [PMID: 37489333 PMCID: PMC10366740 DOI: 10.3390/jdb11030032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2023] [Revised: 07/04/2023] [Accepted: 07/06/2023] [Indexed: 07/26/2023] Open
Abstract
Cells in a developing animal embryo become specified by the activation of cell-type-specific gene regulatory networks. The network that specifies the gut in the nematode Caenorhabditis elegans has been the subject of study for more than two decades. In this network, the maternal factors SKN-1/Nrf and POP-1/TCF activate a zygotic GATA factor cascade consisting of the regulators MED-1,2 → END-1,3 → ELT-2,7, leading to the specification of the gut in early embryos. Paradoxically, the MED, END, and ELT-7 regulators are present only in species closely related to C. elegans, raising the question of how the gut can be specified without them. Recent work found that ELT-3, a GATA factor without an endodermal role in C. elegans, acts in a simpler ELT-3 → ELT-2 network to specify gut in more distant species. The simpler ELT-3 → ELT-2 network may thus represent an ancestral pathway. In this review, we describe the elucidation of the gut specification network in C. elegans and related species and propose a model by which the more complex network might have formed. Because the evolution of this network occurred without a change in phenotype, it is an example of the phenomenon of Developmental System Drift.
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Affiliation(s)
- Gina Broitman-Maduro
- Department of Molecular, Cell, and Systems Biology, University of California-Riverside, Riverside, CA 92521, USA
| | - Morris F Maduro
- Department of Molecular, Cell, and Systems Biology, University of California-Riverside, Riverside, CA 92521, USA
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2
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Santos-Moreno J, Tasiudi E, Kusumawardhani H, Stelling J, Schaerli Y. Robustness and innovation in synthetic genotype networks. Nat Commun 2023; 14:2454. [PMID: 37117168 PMCID: PMC10147661 DOI: 10.1038/s41467-023-38033-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2022] [Accepted: 04/13/2023] [Indexed: 04/30/2023] Open
Abstract
Genotype networks are sets of genotypes connected by small mutational changes that share the same phenotype. They facilitate evolutionary innovation by enabling the exploration of different neighborhoods in genotype space. Genotype networks, first suggested by theoretical models, have been empirically confirmed for proteins and RNAs. Comparative studies also support their existence for gene regulatory networks (GRNs), but direct experimental evidence is lacking. Here, we report the construction of three interconnected genotype networks of synthetic GRNs producing three distinct phenotypes in Escherichia coli. Our synthetic GRNs contain three nodes regulating each other by CRISPR interference and governing the expression of fluorescent reporters. The genotype networks, composed of over twenty different synthetic GRNs, provide robustness in face of mutations while enabling transitions to innovative phenotypes. Through realistic mathematical modeling, we quantify robustness and evolvability for the complete genotype-phenotype map and link these features mechanistically to GRN motifs. Our work thereby exemplifies how GRN evolution along genotype networks might be driving evolutionary innovation.
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Affiliation(s)
- Javier Santos-Moreno
- Department of Fundamental Microbiology, University of Lausanne, Biophore Building, 1015, Lausanne, Switzerland
- Department of Medicine and Life Sciences, Pompeu Fabra University, 00803, Barcelona, Spain
| | - Eve Tasiudi
- Department of Biosystems Science and Engineering, ETH Zurich and SIB Swiss Institute of Bioinformatics, Basel, Switzerland
| | - Hadiastri Kusumawardhani
- Department of Fundamental Microbiology, University of Lausanne, Biophore Building, 1015, Lausanne, Switzerland
| | - Joerg Stelling
- Department of Biosystems Science and Engineering, ETH Zurich and SIB Swiss Institute of Bioinformatics, Basel, Switzerland.
| | - Yolanda Schaerli
- Department of Fundamental Microbiology, University of Lausanne, Biophore Building, 1015, Lausanne, Switzerland.
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3
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DiFrisco J, Love AC, Wagner GP. The hierarchical basis of serial homology and evolutionary novelty. J Morphol 2023; 284:e21531. [PMID: 36317664 DOI: 10.1002/jmor.21531] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2022] [Revised: 10/26/2022] [Accepted: 10/29/2022] [Indexed: 11/05/2022]
Abstract
Given the pervasiveness of gene sharing in evolution and the extent of homology across the tree of life, why is everything not homologous with everything else? The continuity and overlapping genetic contributions to diverse traits across lineages seem to imply that no discrete determination of homology is possible. Although some argue that the widespread overlap in parts and processes should be acknowledged as "partial" homology, this threatens a broad base of presumed comparative morphological knowledge accepted by most biologists. Following a long scientific tradition, we advocate a strategy of "theoretical articulation" that introduces further distinctions to existing concepts to produce increased contrastive resolution among the labels used to represent biological phenomena. We pursue this strategy by drawing on successful patterns of reasoning from serial homology at the level of gene sequences to generate an enriched characterization of serial homology as a hierarchical, phylogenetic concept. Specifically, we propose that the concept of serial homology should be applied primarily to repeated but developmentally individualized body parts, such as cell types, differentiated body segments, or epidermal appendages. For these characters, a phylogenetic history can be reconstructed, similar to families of paralogous genes, endowing the notion of serial homology with a hierarchical, phylogenetic interpretation. On this basis, we propose a five-fold theoretical classification that permits a more fine-grained mapping of diverse trait-types. This facilitates answering the question of why everything is not homologous with everything else, as well as how novelty is possible given that any new character possesses evolutionary precursors. We illustrate the fecundity of our account by reference to debates over insect wing serial homologs and vertebrate paired appendages.
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Affiliation(s)
| | - Alan C Love
- Department of Philosophy, University of Minnesota, Minneapolis, Minnesota, USA.,Minnesota Center for Philosophy of Sciences, University of Minnesota, Minneapolis, Minnesota, USA
| | - Günter P Wagner
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut, USA.,Yale Systems Biology Institute, Yale University, New Haven, Connecticut, USA.,Department of Obstetrics, Gynecology and Reproductive Sciences, Yale Medical School, New Haven, Connecticut, USA.,Department of Obstetrics and Gynecology, Wayne State University, Detroit, Michigan, USA
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4
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Nishida H, Matsuo M, Konishi S, Ohno N, Manni L, Onuma TA. Germline development during embryogenesis of the larvacean, Oikopleura dioica. Dev Biol 2021; 481:188-200. [PMID: 34755656 DOI: 10.1016/j.ydbio.2021.10.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Revised: 10/08/2021] [Accepted: 10/24/2021] [Indexed: 11/18/2022]
Abstract
Germ cells develop into eggs and sperms and represent a lineage that survives through multiple generations. Germ cell specification during embryogenesis proceeds through one of two basic modes: either the cell-autonomous mode or the inductive mode. In the cell-autonomous mode, specification of germ cell fate involves asymmetric partitioning of the specialized maternal cytoplasm, known as the germplasm. Oikopleura dioica is a larvacean (class Appendicularia) and a chordate. It is regarded as a promising animal model for studying chordate development because of its short life cycle (5 days) and small genome size (∼60 Mb). We show that their embryos possess germplasm, as observed in ascidians (class Ascidiacea). The vegetal cytoplasm shifted towards the future posterior pole before the first cleavage occurred. A bilateral pair of primordial germ cells (PGC, B11 cells) was formed at the posterior pole at the 32-cell stage through two rounds of unequal cleavage. These B11 cells did not undergo further division before hatching of the tadpole-shaped larvae. The centrosome-attracting body (CAB) is a subcellular structure that contains the germplasm and plays crucial roles in germ cell development in ascidians. The presence of CAB with germplasm was observed in the germline lineage cells of larvaceans via electron microscopy and using extracted embryos. The CAB appeared at the 8-cell stage and persisted until the middle stage of embryogenesis. The antigen for the phosphorylated histone 3 antibody was localized to the CAB and persisted in the PGC until hatching after the CAB disappeared. Maternal snail mRNA, which encodes a transcription factor, was co-localized with the antigen for the H3S28p antibody. Furthermore, we found a novel PGC-specific subcellular structure that we call the germ body (GB). This study thus highlights the conserved and non-conserved features of germline development between ascidians and larvaceans. The rapid development and short life cycle (five days) of O. dioica would open the way to genetically analyze germ cell development in the future.
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Affiliation(s)
- Hiroki Nishida
- Department of Biological Sciences, Graduate School of Science, Osaka University, Toyonaka, Osaka, 560-0043, Japan.
| | - Masaki Matsuo
- Department of Biological Sciences, Graduate School of Science, Osaka University, Toyonaka, Osaka, 560-0043, Japan
| | - Shohei Konishi
- Department of Biological Sciences, Graduate School of Science, Osaka University, Toyonaka, Osaka, 560-0043, Japan
| | - Nobuhiko Ohno
- Division of Ultrastructural Research, National Institute for Physiological Sciences, Okazaki, 444-8787, Japan; Division of Histology and Cell Biology, Department of Anatomy, Jichi Medical University, Shimotsuke, Tochigi, 329-0498, Japan
| | - Lucia Manni
- Dipartimento di Biologia, Università degli Studi di Padova, via U. Bassi 58/B, I-35121, Padova, Italy
| | - Takeshi A Onuma
- Department of Biological Sciences, Graduate School of Science, Osaka University, Toyonaka, Osaka, 560-0043, Japan
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5
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Manrubia S, Cuesta JA, Aguirre J, Ahnert SE, Altenberg L, Cano AV, Catalán P, Diaz-Uriarte R, Elena SF, García-Martín JA, Hogeweg P, Khatri BS, Krug J, Louis AA, Martin NS, Payne JL, Tarnowski MJ, Weiß M. From genotypes to organisms: State-of-the-art and perspectives of a cornerstone in evolutionary dynamics. Phys Life Rev 2021; 38:55-106. [PMID: 34088608 DOI: 10.1016/j.plrev.2021.03.004] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Accepted: 03/01/2021] [Indexed: 12/21/2022]
Abstract
Understanding how genotypes map onto phenotypes, fitness, and eventually organisms is arguably the next major missing piece in a fully predictive theory of evolution. We refer to this generally as the problem of the genotype-phenotype map. Though we are still far from achieving a complete picture of these relationships, our current understanding of simpler questions, such as the structure induced in the space of genotypes by sequences mapped to molecular structures, has revealed important facts that deeply affect the dynamical description of evolutionary processes. Empirical evidence supporting the fundamental relevance of features such as phenotypic bias is mounting as well, while the synthesis of conceptual and experimental progress leads to questioning current assumptions on the nature of evolutionary dynamics-cancer progression models or synthetic biology approaches being notable examples. This work delves with a critical and constructive attitude into our current knowledge of how genotypes map onto molecular phenotypes and organismal functions, and discusses theoretical and empirical avenues to broaden and improve this comprehension. As a final goal, this community should aim at deriving an updated picture of evolutionary processes soundly relying on the structural properties of genotype spaces, as revealed by modern techniques of molecular and functional analysis.
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Affiliation(s)
- Susanna Manrubia
- Department of Systems Biology, Centro Nacional de Biotecnología (CSIC), Madrid, Spain; Grupo Interdisciplinar de Sistemas Complejos (GISC), Madrid, Spain.
| | - José A Cuesta
- Grupo Interdisciplinar de Sistemas Complejos (GISC), Madrid, Spain; Departamento de Matemáticas, Universidad Carlos III de Madrid, Leganés, Spain; Instituto de Biocomputación y Física de Sistemas Complejos (BiFi), Universidad de Zaragoza, Spain; UC3M-Santander Big Data Institute (IBiDat), Getafe, Madrid, Spain
| | - Jacobo Aguirre
- Grupo Interdisciplinar de Sistemas Complejos (GISC), Madrid, Spain; Centro de Astrobiología, CSIC-INTA, ctra. de Ajalvir km 4, 28850 Torrejón de Ardoz, Madrid, Spain
| | - Sebastian E Ahnert
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Philippa Fawcett Drive, Cambridge CB3 0AS, UK; The Alan Turing Institute, British Library, 96 Euston Road, London NW1 2DB, UK
| | | | - Alejandro V Cano
- Institute of Integrative Biology, ETH Zurich, Zurich, Switzerland; Swiss Institute of Bioinformatics, Lausanne, Switzerland
| | - Pablo Catalán
- Grupo Interdisciplinar de Sistemas Complejos (GISC), Madrid, Spain; Departamento de Matemáticas, Universidad Carlos III de Madrid, Leganés, Spain
| | - Ramon Diaz-Uriarte
- Department of Biochemistry, Universidad Autónoma de Madrid, Madrid, Spain; Instituto de Investigaciones Biomédicas "Alberto Sols" (UAM-CSIC), Madrid, Spain
| | - Santiago F Elena
- Instituto de Biología Integrativa de Sistemas, I(2)SysBio (CSIC-UV), València, Spain; The Santa Fe Institute, Santa Fe, NM, USA
| | | | - Paulien Hogeweg
- Theoretical Biology and Bioinformatics Group, Utrecht University, the Netherlands
| | - Bhavin S Khatri
- The Francis Crick Institute, London, UK; Department of Life Sciences, Imperial College London, London, UK
| | - Joachim Krug
- Institute for Biological Physics, University of Cologne, Köln, Germany
| | - Ard A Louis
- Rudolf Peierls Centre for Theoretical Physics, University of Oxford, Oxford, UK
| | - Nora S Martin
- Theory of Condensed Matter Group, Cavendish Laboratory, University of Cambridge, Cambridge, UK; Sainsbury Laboratory, University of Cambridge, Cambridge, UK
| | - Joshua L Payne
- Institute of Integrative Biology, ETH Zurich, Zurich, Switzerland; Swiss Institute of Bioinformatics, Lausanne, Switzerland
| | | | - Marcel Weiß
- Theory of Condensed Matter Group, Cavendish Laboratory, University of Cambridge, Cambridge, UK; Sainsbury Laboratory, University of Cambridge, Cambridge, UK
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6
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Coulcher JF, Roure A, Chowdhury R, Robert M, Lescat L, Bouin A, Carvajal Cadavid J, Nishida H, Darras S. Conservation of peripheral nervous system formation mechanisms in divergent ascidian embryos. eLife 2020; 9:e59157. [PMID: 33191918 PMCID: PMC7710358 DOI: 10.7554/elife.59157] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Accepted: 11/13/2020] [Indexed: 01/23/2023] Open
Abstract
Ascidians with very similar embryos but highly divergent genomes are thought to have undergone extensive developmental system drift. We compared, in four species (Ciona and Phallusia for Phlebobranchia, Molgula and Halocynthia for Stolidobranchia), gene expression and gene regulation for a network of six transcription factors regulating peripheral nervous system (PNS) formation in Ciona. All genes, but one in Molgula, were expressed in the PNS with some differences correlating with phylogenetic distance. Cross-species transgenesis indicated strong levels of conservation, except in Molgula, in gene regulation despite lack of sequence conservation of the enhancers. Developmental system drift in ascidians is thus higher for gene regulation than for gene expression and is impacted not only by phylogenetic distance, but also in a clade-specific manner and unevenly within a network. Finally, considering that Molgula is divergent in our analyses, this suggests deep conservation of developmental mechanisms in ascidians after 390 My of separate evolution.
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Affiliation(s)
- Joshua F Coulcher
- Sorbonne Université, CNRS, Biologie Intégrative des Organismes Marins (BIOM)Banyuls-sur-MerFrance
| | - Agnès Roure
- Sorbonne Université, CNRS, Biologie Intégrative des Organismes Marins (BIOM)Banyuls-sur-MerFrance
| | - Rafath Chowdhury
- Sorbonne Université, CNRS, Biologie Intégrative des Organismes Marins (BIOM)Banyuls-sur-MerFrance
| | - Méryl Robert
- Sorbonne Université, CNRS, Biologie Intégrative des Organismes Marins (BIOM)Banyuls-sur-MerFrance
| | - Laury Lescat
- Sorbonne Université, CNRS, Biologie Intégrative des Organismes Marins (BIOM)Banyuls-sur-MerFrance
| | - Aurélie Bouin
- Sorbonne Université, CNRS, Biologie Intégrative des Organismes Marins (BIOM)Banyuls-sur-MerFrance
| | - Juliana Carvajal Cadavid
- Sorbonne Université, CNRS, Biologie Intégrative des Organismes Marins (BIOM)Banyuls-sur-MerFrance
| | - Hiroki Nishida
- Department of Biological Sciences, Graduate School of Science, Osaka UniversityToyonakaJapan
| | - Sébastien Darras
- Sorbonne Université, CNRS, Biologie Intégrative des Organismes Marins (BIOM)Banyuls-sur-MerFrance
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7
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Colgan W, Leanza A, Hwang A, DeBiasse MB, Llosa I, Rodrigues D, Adhikari H, Barreto Corona G, Bock S, Carillo-Perez A, Currie M, Darkoa-Larbi S, Dellal D, Gutow H, Hokama P, Kibby E, Linhart N, Moody S, Naganuma A, Nguyen D, Stanton R, Stark S, Tumey C, Velleca A, Ryan JF, Davidson B. Variable levels of drift in tunicate cardiopharyngeal gene regulatory elements. EvoDevo 2019; 10:24. [PMID: 31632631 PMCID: PMC6790052 DOI: 10.1186/s13227-019-0137-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2019] [Accepted: 09/13/2019] [Indexed: 12/29/2022] Open
Abstract
BACKGROUND Mutations in gene regulatory networks often lead to genetic divergence without impacting gene expression or developmental patterning. The rules governing this process of developmental systems drift, including the variable impact of selective constraints on different nodes in a gene regulatory network, remain poorly delineated. RESULTS Here we examine developmental systems drift within the cardiopharyngeal gene regulatory networks of two tunicate species, Corella inflata and Ciona robusta. Cross-species analysis of regulatory elements suggests that trans-regulatory architecture is largely conserved between these highly divergent species. In contrast, cis-regulatory elements within this network exhibit distinct levels of conservation. In particular, while most of the regulatory elements we analyzed showed extensive rearrangements of functional binding sites, the enhancer for the cardiopharyngeal transcription factor FoxF is remarkably well-conserved. Even minor alterations in spacing between binding sites lead to loss of FoxF enhancer function, suggesting that bound trans-factors form position-dependent complexes. CONCLUSIONS Our findings reveal heterogeneous levels of divergence across cardiopharyngeal cis-regulatory elements. These distinct levels of divergence presumably reflect constraints that are not clearly associated with gene function or position within the regulatory network. Thus, levels of cis-regulatory divergence or drift appear to be governed by distinct structural constraints that will be difficult to predict based on network architecture.
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Affiliation(s)
| | - Alexis Leanza
- Thomas Jefferson University Sidney Kimmel Medical College, Philadelphia, USA
| | - Ariel Hwang
- University of North Carolina, Chapel Hill, USA
| | | | | | | | | | | | | | | | | | | | - Daniel Dellal
- Icahn School of Medicine at Mount Sinai, New York, USA
| | | | | | - Emily Kibby
- University of Colorado Boulder, Boulder, USA
| | | | | | | | | | | | - Sierra Stark
- University of California San Francisco, San Francisco, USA
| | | | | | - Joseph F. Ryan
- Whitney Laboratory for Marine Bioscience, St. Augustine, USA
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8
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Reding K, Chen M, Lu Y, Cheatle Jarvela AM, Pick L. Shifting roles of Drosophila pair-rule gene orthologs: segmental expression and function in the milkweed bug Oncopeltus fasciatus. Development 2019; 146:dev181453. [PMID: 31444220 PMCID: PMC6765130 DOI: 10.1242/dev.181453] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Accepted: 08/12/2019] [Indexed: 01/21/2023]
Abstract
The discovery of pair-rule genes (PRGs) in Drosophila revealed the existence of an underlying two-segment-wide prepattern directing embryogenesis. The milkweed bug Oncopeltus fasciatus, a hemimetabolous insect, is a more representative arthropod: most of its segments form sequentially after gastrulation. Here, we report the expression and function of orthologs of the complete set of nine Drosophila PRGs in Oncopeltus Seven Of-PRG-orthologs are expressed in stripes in the primordia of every segment, rather than every other segment; Of-runt is PR-like and several orthologs are also expressed in the segment addition zone. RNAi-mediated knockdown of Of-odd-skipped, paired and sloppy-paired impacted all segments, with no indication of PR-like register. We confirm that Of-E75A is expressed in PR-like stripes, although it is not expressed in this way in Drosophila, demonstrating the existence of an underlying PR-like prepattern in Oncopeltus These findings reveal that a switch occurred in regulatory circuits, leading to segment formation: while several holometabolous insects are 'Drosophila-like', using PRG orthologs for PR patterning, most Of-PRGs are expressed segmentally in Oncopeltus, a more basally branching insect. Thus, an evolutionarily stable phenotype - segment formation - is directed by alternate regulatory pathways in diverse species.
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Affiliation(s)
- Katie Reding
- Department of Entomology, 4291 Fieldhouse Drive, University of Maryland, College Park, MD 20742, USA
| | - Mengyao Chen
- Department of Entomology, 4291 Fieldhouse Drive, University of Maryland, College Park, MD 20742, USA
| | - Yong Lu
- Department of Entomology, 4291 Fieldhouse Drive, University of Maryland, College Park, MD 20742, USA
| | - Alys M Cheatle Jarvela
- Department of Entomology, 4291 Fieldhouse Drive, University of Maryland, College Park, MD 20742, USA
| | - Leslie Pick
- Department of Entomology, 4291 Fieldhouse Drive, University of Maryland, College Park, MD 20742, USA
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9
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Khatri BS, Goldstein RA. Biophysics and population size constrains speciation in an evolutionary model of developmental system drift. PLoS Comput Biol 2019; 15:e1007177. [PMID: 31335870 PMCID: PMC6677325 DOI: 10.1371/journal.pcbi.1007177] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Revised: 08/02/2019] [Accepted: 06/13/2019] [Indexed: 02/06/2023] Open
Abstract
Developmental system drift is a likely mechanism for the origin of hybrid incompatibilities between closely related species. We examine here the detailed mechanistic basis of hybrid incompatibilities between two allopatric lineages, for a genotype-phenotype map of developmental system drift under stabilising selection, where an organismal phenotype is conserved, but the underlying molecular phenotypes and genotype can drift. This leads to number of emergent phenomenon not obtainable by modelling genotype or phenotype alone. Our results show that: 1) speciation is more rapid at smaller population sizes with a characteristic, Orr-like, power law, but at large population sizes slow, characterised by a sub-diffusive growth law; 2) the molecular phenotypes under weakest selection contribute to the earliest incompatibilities; and 3) pair-wise incompatibilities dominate over higher order, contrary to previous predictions that the latter should dominate. The population size effect we find is consistent with previous results on allopatric divergence of transcription factor-DNA binding, where smaller populations have common ancestors with a larger drift load because genetic drift favours phenotypes which have a larger number of genotypes (higher sequence entropy) over more fit phenotypes which have far fewer genotypes; this means less substitutions are required in either lineage before incompatibilities arise. Overall, our results indicate that biophysics and population size provide a much stronger constraint to speciation than suggested by previous models, and point to a general mechanistic principle of how incompatibilities arise the under stabilising selection for an organismal phenotype. The process of speciation is of fundamental importance to the field of evolution as it is intimately connected to understanding the immense bio-diversity of life. There is still relatively little understanding of the underlying genetic mechanisms that give rise to hybrid incompatibilities with results suggesting that divergence in transcription factor DNA binding and gene expression play an important role. A key finding from the field of evo-devo is that organismal phenotypes show developmental system drift, where species maintain the same phenotype, but diverge in developmental pathways; this is an important potential source of hybrid incompatibilities. Here, we explore a theoretical framework to understand how incompatibilities arise due to developmental system drift, using a tractable biophysically inspired genotype-phenotype for spatial gene expression. Modelling the evolution of phenotypes in this way has the key advantage that it mirrors how selection works in nature, i.e. that selection acts on phenotypes, but variation (mutation) arise at the level of genotypes. This results, as we demonstrate, in a number of non-trivial and testable predictions concerning speciation due to developmental system drift, which would not be obtainable by modelling evolution of genotypes or phenotypes alone.
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Affiliation(s)
| | - Richard A. Goldstein
- Division of Infection & Immunity, University College London, London, United Kingdom
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10
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Morris ZS, Vliet KA, Abzhanov A, Pierce SE. Heterochronic shifts and conserved embryonic shape underlie crocodylian craniofacial disparity and convergence. Proc Biol Sci 2019; 286:20182389. [PMID: 30963831 PMCID: PMC6408887 DOI: 10.1098/rspb.2018.2389] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2018] [Accepted: 01/25/2019] [Indexed: 12/29/2022] Open
Abstract
The distinctive anatomy of the crocodylian skull is intimately linked with dietary ecology, resulting in repeated convergence on blunt- and slender-snouted ecomorphs. These evolutionary shifts depend upon modifications of the developmental processes which direct growth and morphogenesis. Here we examine the evolution of cranial ontogenetic trajectories to shed light on the mechanisms underlying convergent snout evolution. We use geometric morphometrics to quantify skeletogenesis in an evolutionary context and reconstruct ancestral patterns of ontogenetic allometry to understand the developmental drivers of craniofacial diversity within Crocodylia. Our analyses uncovered a conserved embryonic region of morphospace (CER) shared by all non-gavialid crocodylians regardless of their eventual adult ecomorph. This observation suggests the presence of conserved developmental processes during early development (before Ferguson stage 20) across most of Crocodylia. Ancestral state reconstruction of ontogenetic trajectories revealed heterochrony, developmental constraint, and developmental systems drift have all played essential roles in the evolution of ecomorphs. Based on these observations, we conclude that two separate, but interconnected, developmental programmes controlling craniofacial morphogenesis and growth enabled the evolutionary plasticity of skull shape in crocodylians.
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Affiliation(s)
- Zachary S. Morris
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA
| | - Kent A. Vliet
- Department of Biology, University of Florida, 876 Newell Drive, Gainesville, FL 32611, USA
| | - Arhat Abzhanov
- Department of Life Sciences, Imperial College London, Silwood Park Campus, Buckhurst Road, Ascot, Berkshire SL5 7PY, UK
- Natural History Museum, Cromwell Road, London SW7 5BD, UK
| | - Stephanie E. Pierce
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA
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11
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Babbitt GA, Coppola EE, Alawad MA, Hudson AO. Can all heritable biology really be reduced to a single dimension? Gene 2016; 578:162-8. [DOI: 10.1016/j.gene.2015.12.043] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Revised: 12/16/2015] [Accepted: 12/17/2015] [Indexed: 12/23/2022]
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12
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Niklas KJ, Bondos SE, Dunker AK, Newman SA. Rethinking gene regulatory networks in light of alternative splicing, intrinsically disordered protein domains, and post-translational modifications. Front Cell Dev Biol 2015; 3:8. [PMID: 25767796 PMCID: PMC4341551 DOI: 10.3389/fcell.2015.00008] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Accepted: 01/26/2015] [Indexed: 11/16/2022] Open
Abstract
Models for genetic regulation and cell fate specification characteristically assume that gene regulatory networks (GRNs) are essentially deterministic and exhibit multiple stable states specifying alternative, but pre-figured cell fates. Mounting evidence shows, however, that most eukaryotic precursor RNAs undergo alternative splicing (AS) and that the majority of transcription factors contain intrinsically disordered protein (IDP) domains whose functionalities are context dependent as well as subject to post-translational modification (PTM). Consequently, many transcription factors do not have fixed cis-acting regulatory targets, and developmental determination by GRNs alone is untenable. Modeling these phenomena requires a multi-scale approach to explain how GRNs operationally interact with the intra- and intercellular environments. Evidence shows that AS, IDP, and PTM complicate gene expression and act synergistically to facilitate and promote time- and cell-specific protein modifications involved in cell signaling and cell fate specification and thereby disrupt a strict deterministic GRN-phenotype mapping. The combined effects of AS, IDP, and PTM give proteomes physiological plasticity, adaptive responsiveness, and developmental versatility without inefficiently expanding genome size. They also help us understand how protein functionalities can undergo major evolutionary changes by buffering mutational consequences.
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Affiliation(s)
- Karl J Niklas
- Plant Biology Section, School of Integrative Plant Science, Cornell University Ithaca, NY, USA
| | - Sarah E Bondos
- Department of Molecular and Cellular Medicine, Texas A&M Health Science Center College Station, TX, USA
| | - A Keith Dunker
- Center for Computational Biology and Bioinformatics, School of Medicine, Indiana University Indianapolis, IN, USA
| | - Stuart A Newman
- Department of Cell Biology and Anatomy, New York Medical College Valhalla, NY, USA
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