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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: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [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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2
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Feigin C, Li S, Moreno J, Mallarino R. The GRN concept as a guide for evolutionary developmental biology. JOURNAL OF EXPERIMENTAL ZOOLOGY. PART B, MOLECULAR AND DEVELOPMENTAL EVOLUTION 2023; 340:92-104. [PMID: 35344632 PMCID: PMC9515236 DOI: 10.1002/jez.b.23132] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Revised: 03/08/2022] [Accepted: 03/11/2022] [Indexed: 12/13/2022]
Abstract
Organismal phenotypes result largely from inherited developmental programs, usually executed during embryonic and juvenile life stages. These programs are not blank slates onto which natural selection can draw arbitrary forms. Rather, the mechanisms of development play an integral role in shaping phenotypic diversity and help determine the evolutionary trajectories of species. Modern evolutionary biology must, therefore, account for these mechanisms in both theory and in practice. The gene regulatory network (GRN) concept represents a potent tool for achieving this goal whose utility has grown in tandem with advances in "omic" technologies and experimental techniques. However, while the GRN concept is widely utilized, it is often less clear what practical implications it has for conducting research in evolutionary developmental biology. In this Perspective, we attempt to provide clarity by discussing how experiments and projects can be designed in light of the GRN concept. We first map familiar biological notions onto the more abstract components of GRN models. We then review how diverse functional genomic approaches can be directed toward the goal of constructing such models and discuss current methods for functionally testing evolutionary hypotheses that arise from them. Finally, we show how the major steps of GRN model construction and experimental validation suggest generalizable workflows that can serve as a scaffold for project design. Taken together, the practical implications that we draw from the GRN concept provide a set of guideposts for studies aiming at unraveling the molecular basis of phenotypic diversity.
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Affiliation(s)
- Charles Feigin
- Department of Molecular Biology, Princeton University, Princeton, New Jersey, USA,School of BioSciences, The University of Melbourne, Parkville, Victoria, Australia
| | - Sha Li
- Department of Molecular Biology, Princeton University, Princeton, New Jersey, USA
| | - Jorge Moreno
- Department of Molecular Biology, Princeton University, Princeton, New Jersey, USA
| | - Ricardo Mallarino
- Department of Molecular Biology, Princeton University, Princeton, New Jersey, USA
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3
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Schaal KA, Yu YTN, Vasse M, Velicer GJ. Allopatric divergence of cooperators confers cheating resistance and limits effects of a defector mutation. BMC Ecol Evol 2022; 22:141. [PMID: 36510120 PMCID: PMC9746145 DOI: 10.1186/s12862-022-02094-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Accepted: 11/23/2022] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND Social defectors may meet diverse cooperators. Genotype-by-genotype interactions may constrain the ranges of cooperators upon which particular defectors can cheat, limiting cheater spread. Upon starvation, the soil bacterium Myxococcus xanthus cooperatively develops into spore-bearing fruiting bodies, using a complex regulatory network and several intercellular signals. Some strains (cheaters) are unable to sporulate effectively in pure culture due to mutations that reduce signal production but can exploit and outcompete cooperators within mixed groups. RESULTS In this study, interactions between a cheater disrupted at the signaling gene csgA and allopatrically diversified cooperators reveal a very small cheating range. Expectedly, the cheater failed to cheat on all natural-isolate cooperators owing to non-cheater-specific antagonisms. Surprisingly, some lab-evolved cooperators had already exited the csgA mutant's cheating range after accumulating fewer than 20 mutations and without experiencing cheating during evolution. Cooperators might also diversify in the potential for a mutation to reduce expression of a cooperative trait or generate a cheating phenotype. A new csgA mutation constructed in several highly diverged cooperators generated diverse sporulation phenotypes, ranging from a complete defect to no defect, indicating that genetic backgrounds can limit the set of genomes in which a mutation creates a defector. CONCLUSIONS Our results demonstrate that natural populations may feature geographic mosaics of cooperators that have diversified in their susceptibility to particular cheaters, limiting defectors' cheating ranges and preventing them from spreading. This diversification may also lead to variation in the phenotypes generated by any given cooperation-gene mutation, further decreasing the chance of a cheater emerging which threatens the persistence of cooperation in the system.
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Affiliation(s)
- Kaitlin A. Schaal
- grid.5801.c0000 0001 2156 2780Institute of Integrative Biology, ETH Zürich, 8092 Zurich, Switzerland
| | - Yuen-Tsu Nicco Yu
- grid.5801.c0000 0001 2156 2780Institute of Integrative Biology, ETH Zürich, 8092 Zurich, Switzerland
| | - Marie Vasse
- grid.5801.c0000 0001 2156 2780Institute of Integrative Biology, ETH Zürich, 8092 Zurich, Switzerland ,grid.121334.60000 0001 2097 0141Institute MIVEGEC (UMR 5290 CNRS, IRD, UM), 34394 Montpellier, France
| | - Gregory J. Velicer
- grid.5801.c0000 0001 2156 2780Institute of Integrative Biology, ETH Zürich, 8092 Zurich, Switzerland
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4
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Ewe CK, Sommermann EM, Kenchel J, Flowers SE, Maduro MF, Joshi PM, Rothman JH. Feedforward regulatory logic controls the specification-to-differentiation transition and terminal cell fate during Caenorhabditis elegans endoderm development. Development 2022; 149:dev200337. [PMID: 35758255 PMCID: PMC10656426 DOI: 10.1242/dev.200337] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Accepted: 05/13/2022] [Indexed: 11/20/2023]
Abstract
The architecture of gene regulatory networks determines the specificity and fidelity of developmental outcomes. We report that the core regulatory circuitry for endoderm development in Caenorhabditis elegans operates through a transcriptional cascade consisting of six sequentially expressed GATA-type factors that act in a recursive series of interlocked feedforward modules. This structure results in sequential redundancy, in which removal of a single factor or multiple alternate factors in the cascade leads to a mild or no effect on gut development, whereas elimination of any two sequential factors invariably causes a strong phenotype. The phenotypic strength is successfully predicted with a computational model based on the timing and levels of transcriptional states. We found that one factor in the middle of the cascade, END-1, which straddles the distinct events of specification and differentiation, functions in both processes. Finally, we reveal roles for key GATA factors in establishing spatial regulatory state domains by repressing other fates, thereby defining boundaries in the digestive tract. Our findings provide a paradigm that could account for the genetic redundancy observed in many developmental regulatory systems.
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Affiliation(s)
- Chee Kiang Ewe
- Department of MCD Biology and Neuroscience Research Institute, University of California Santa Barbara, Santa Barbara, CA 93106, USA
| | - Erica M. Sommermann
- Department of MCD Biology and Neuroscience Research Institute, University of California Santa Barbara, Santa Barbara, CA 93106, USA
| | - Josh Kenchel
- Program in Biomolecular Science and Engineering, University of California Santa Barbara, Santa Barbara, CA 93106, USA
- Chemical and Biomolecular Engineering Department, University of California Los Angeles, Los Angeles, CA 90095, USA
| | - Sagen E. Flowers
- Department of MCD Biology and Neuroscience Research Institute, University of California Santa Barbara, Santa Barbara, CA 93106, USA
| | - Morris F. Maduro
- Molecular, Cell and Systems Biology Department, University of California Riverside, Riverside, CA 92521, USA
| | - Pradeep M. Joshi
- Department of MCD Biology and Neuroscience Research Institute, University of California Santa Barbara, Santa Barbara, CA 93106, USA
| | - Joel H. Rothman
- Department of MCD Biology and Neuroscience Research Institute, University of California Santa Barbara, Santa Barbara, CA 93106, USA
- Program in Biomolecular Science and Engineering, University of California Santa Barbara, Santa Barbara, CA 93106, USA
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5
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Perkins ML, Gandara L, Crocker J. A synthetic synthesis to explore animal evolution and development. Philos Trans R Soc Lond B Biol Sci 2022; 377:20200517. [PMID: 35634925 PMCID: PMC9149795 DOI: 10.1098/rstb.2020.0517] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Identifying the general principles by which genotypes are converted into phenotypes remains a challenge in the post-genomic era. We still lack a predictive understanding of how genes shape interactions among cells and tissues in response to signalling and environmental cues, and hence how regulatory networks generate the phenotypic variation required for adaptive evolution. Here, we discuss how techniques borrowed from synthetic biology may facilitate a systematic exploration of evolvability across biological scales. Synthetic approaches permit controlled manipulation of both endogenous and fully engineered systems, providing a flexible platform for investigating causal mechanisms in vivo. Combining synthetic approaches with multi-level phenotyping (phenomics) will supply a detailed, quantitative characterization of how internal and external stimuli shape the morphology and behaviour of living organisms. We advocate integrating high-throughput experimental data with mathematical and computational techniques from a variety of disciplines in order to pursue a comprehensive theory of evolution. This article is part of the theme issue ‘Genetic basis of adaptation and speciation: from loci to causative mutations’.
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Affiliation(s)
- Mindy Liu Perkins
- Developmental Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Lautaro Gandara
- Developmental Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Justin Crocker
- Developmental Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
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6
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McDonald JMC, Reed RD. Patterns of selection across gene regulatory networks. Semin Cell Dev Biol 2022; 145:60-67. [PMID: 35474149 DOI: 10.1016/j.semcdb.2022.03.029] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2021] [Revised: 01/31/2022] [Accepted: 03/23/2022] [Indexed: 12/29/2022]
Abstract
Gene regulatory networks (GRNs) are the core engine of organismal development. If we would like to understand the origin and diversification of phenotypes, it is necessary to consider the structure of GRNs in order to reconstruct the links between genetic mutations and phenotypic change. Much of the progress in evolutionary developmental biology, however, has occurred without a nuanced consideration of the evolution of functional relationships between genes, especially in the context of their broader network interactions. Characterizing and comparing GRNs across traits and species in a more detailed way will allow us to determine how network position influences what genes drive adaptive evolution. In this perspective paper, we consider the architecture of developmental GRNs and how positive selection strength may vary across a GRN. We then propose several testable models for these patterns of selection and experimental approaches to test these models.
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Affiliation(s)
- Jeanne M C McDonald
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY, United States.
| | - Robert D Reed
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY, United States.
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7
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Kremnev SV. Evolutionary and Ontogenetic Plasticity of Conserved Signaling Pathways in Animals’ Development. Russ J Dev Biol 2022. [DOI: 10.1134/s1062360422020114] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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8
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Streit A. Opinion: What do rescue experiments with heterologous proteins tell us and what not? Parasitol Res 2022; 121:1131-1135. [PMID: 34351494 PMCID: PMC8986660 DOI: 10.1007/s00436-021-07247-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Accepted: 07/12/2021] [Indexed: 11/30/2022]
Abstract
The recent progress in sequencing technology allowed the compilation of gene lists for a large number of organisms, though many of these organisms are hardly experimentally tractable when compared with well-established model organisms. One popular approach to further characterize genes identified in a poorly tractable organism is to express these genes in a model organism, and then ask what the protein does in this system or if the gene is capable of replacing the homologous endogenous one when the latter is mutated. While this is a valid approach for certain questions, I argue that the results of such experiments are frequently wrongly interpreted. If, for example, a gene from a parasitic nematode is capable of replacing its homologous gene in the model nematode Caenorhabditis elegans, it is often concluded that the gene is most likely involved in the same biological process in its own organism as the C. elegans gene is in C. elegans. This conclusion is not valid. All this experiment tells us is that the chemical properties of the parasite protein are similar enough to the ones of the C. elegans protein that it can perform the function of the C. elegans protein in C. elegans. Here I discuss this misconception and illustrate it using the analog of similar electric switches (components) controlling various devices (processes).
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Affiliation(s)
- Adrian Streit
- Department of Integrative Evolutionary Biology, Max Planck Institute for Developmental Biology, Max-Planck-Ring 9, 72076, Tübingen, Germany.
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9
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Hansen CL, Pelegri F. Primordial Germ Cell Specification in Vertebrate Embryos: Phylogenetic Distribution and Conserved Molecular Features of Preformation and Induction. Front Cell Dev Biol 2021; 9:730332. [PMID: 34604230 PMCID: PMC8481613 DOI: 10.3389/fcell.2021.730332] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Accepted: 08/25/2021] [Indexed: 11/24/2022] Open
Abstract
The differentiation of primordial germ cells (PGCs) occurs during early embryonic development and is critical for the survival and fitness of sexually reproducing species. Here, we review the two main mechanisms of PGC specification, induction, and preformation, in the context of four model vertebrate species: mouse, axolotl, Xenopus frogs, and zebrafish. We additionally discuss some notable molecular characteristics shared across PGC specification pathways, including the shared expression of products from three conserved germline gene families, DAZ (Deleted in Azoospermia) genes, nanos-related genes, and DEAD-box RNA helicases. Then, we summarize the current state of knowledge of the distribution of germ cell determination systems across kingdom Animalia, with particular attention to vertebrate species, but include several categories of invertebrates - ranging from the "proto-vertebrate" cephalochordates to arthropods, cnidarians, and ctenophores. We also briefly highlight ongoing investigations and potential lines of inquiry that aim to understand the evolutionary relationships between these modes of specification.
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Affiliation(s)
| | - Francisco Pelegri
- Laboratory of Genetics, University of Wisconsin-Madison, Madison, WI, United States
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10
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Ewe CK, Alok G, Rothman JH. Stressful development: integrating endoderm development, stress, and longevity. Dev Biol 2020; 471:34-48. [PMID: 33307045 DOI: 10.1016/j.ydbio.2020.12.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2020] [Revised: 12/02/2020] [Accepted: 12/03/2020] [Indexed: 10/22/2022]
Abstract
In addition to performing digestion and nutrient absorption, the intestine serves as one of the first barriers to the external environment, crucial for protecting the host from environmental toxins, pathogenic invaders, and other stress inducers. The gene regulatory network (GRN) governing embryonic development of the endoderm and subsequent differentiation and maintenance of the intestine has been well-documented in C. elegans. A key regulatory input that initiates activation of the embryonic GRN for endoderm and mesoderm in this animal is the maternally provided SKN-1 transcription factor, an ortholog of the vertebrate Nrf1 and 2, which, like C. elegans SKN-1, perform conserved regulatory roles in mediating a variety of stress responses across metazoan phylogeny. Other key regulatory factors in early gut development also participate in stress response as well as in innate immunity and aging and longevity. In this review, we discuss the intersection between genetic nodes that mediate endoderm/intestine differentiation and regulation of stress and homeostasis. We also consider how direct signaling from the intestine to the germline, in some cases involving SKN-1, facilitates heritable epigenetic changes, allowing transmission of adaptive stress responses across multiple generations. These connections between regulation of endoderm/intestine development and stress response mechanisms suggest that varying selective pressure exerted on the stress response pathways may influence the architecture of the endoderm GRN, thereby leading to genetic and epigenetic variation in early embryonic GRN regulatory events.
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Affiliation(s)
- Chee Kiang Ewe
- Department of MCD Biology and Neuroscience Research Institute, University of California Santa Barbara, Santa Barbara, CA, USA.
| | - Geneva Alok
- Department of MCD Biology and Neuroscience Research Institute, University of California Santa Barbara, Santa Barbara, CA, USA.
| | - Joel H Rothman
- Department of MCD Biology and Neuroscience Research Institute, University of California Santa Barbara, Santa Barbara, CA, USA.
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11
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Natural cryptic variation in epigenetic modulation of an embryonic gene regulatory network. Proc Natl Acad Sci U S A 2020; 117:13637-13646. [PMID: 32482879 DOI: 10.1073/pnas.1920343117] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Gene regulatory networks (GRNs) that direct animal embryogenesis must respond to varying environmental and physiological conditions to ensure robust construction of organ systems. While GRNs are evolutionarily modified by natural genomic variation, the roles of epigenetic processes in shaping plasticity of GRN architecture are not well understood. The endoderm GRN in Caenorhabditis elegans is initiated by the maternally supplied SKN-1/Nrf2 bZIP transcription factor; however, the requirement for SKN-1 in endoderm specification varies widely among distinct C. elegans wild isotypes, owing to rapid developmental system drift driven by accumulation of cryptic genetic variants. We report here that heritable epigenetic factors that are stimulated by transient developmental diapause also underlie cryptic variation in the requirement for SKN-1 in endoderm development. This epigenetic memory is inherited from the maternal germline, apparently through a nuclear, rather than cytoplasmic, signal, resulting in a parent-of-origin effect (POE), in which the phenotype of the progeny resembles that of the maternal founder. The occurrence and persistence of POE varies between different parental pairs, perduring for at least 10 generations in one pair. This long-perduring POE requires piwi-interacting RNA (piRNA) function and the germline nuclear RNA interference (RNAi) pathway, as well as MET-2 and SET-32, which direct histone H3K9 trimethylation and drive heritable epigenetic modification. Such nongenetic cryptic variation may provide a resource of additional phenotypic diversity through which adaptation may facilitate evolutionary changes and shape developmental regulatory systems.
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