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Ruiz-Trillo I, Kin K, Casacuberta E. The Origin of Metazoan Multicellularity: A Potential Microbial Black Swan Event. Annu Rev Microbiol 2023; 77:499-516. [PMID: 37406343 DOI: 10.1146/annurev-micro-032421-120023] [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] [Indexed: 07/07/2023]
Abstract
The emergence of animals from their unicellular ancestors is a major evolutionary event. Thanks to the study of diverse close unicellular relatives of animals, we now have a better grasp of what the unicellular ancestor of animals was like. However, it is unclear how that unicellular ancestor of animals became the first animals. To explain this transition, two popular theories, the choanoblastaea and the synzoospore, have been proposed. We will revise and expose the flaws in these two theories while showing that, due to the limits of our current knowledge, the origin of animals is a biological black swan event. As such, the origin of animals defies retrospective explanations. Therefore, we should be extra careful not to fall for confirmation biases based on few data and, instead, embrace this uncertainty and be open to alternative scenarios. With the aim to broaden the potential explanations on how animals emerged, we here propose two novel and alternative scenarios. In any case, to find the answer to how animals evolved, additional data will be required, as will the hunt for microscopic creatures that are closely related to animals but have not yet been sampled and studied.
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Affiliation(s)
- Iñaki Ruiz-Trillo
- Institut de Biologia Evolutiva (CSIC-Universitat Pompeu Fabra), Barcelona, Spain;
- ICREA, Barcelona, Spain
| | - Koryu Kin
- Institut de Biologia Evolutiva (CSIC-Universitat Pompeu Fabra), Barcelona, Spain;
| | - Elena Casacuberta
- Institut de Biologia Evolutiva (CSIC-Universitat Pompeu Fabra), Barcelona, Spain;
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Santini S, Schenkelaars Q, Jourda C, Duchesne M, Belahbib H, Rocher C, Selva M, Riesgo A, Vervoort M, Leys SP, Kodjabachian L, Le Bivic A, Borchiellini C, Claverie JM, Renard E. The compact genome of the sponge Oopsacas minuta (Hexactinellida) is lacking key metazoan core genes. BMC Biol 2023; 21:139. [PMID: 37337252 DOI: 10.1186/s12915-023-01619-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2022] [Accepted: 05/09/2023] [Indexed: 06/21/2023] Open
Abstract
BACKGROUND Explaining the emergence of the hallmarks of bilaterians is a central focus of evolutionary developmental biology-evodevo-and evolutionary genomics. For this purpose, we must both expand and also refine our knowledge of non-bilaterian genomes, especially by studying early branching animals, in particular those in the metazoan phylum Porifera. RESULTS We present a comprehensive analysis of the first whole genome of a glass sponge, Oopsacas minuta, a member of the Hexactinellida. Studying this class of sponge is evolutionary relevant because it differs from the three other Porifera classes in terms of development, tissue organization, ecology, and physiology. Although O. minuta does not exhibit drastic body simplifications, its genome is among the smallest of animal genomes sequenced so far, and surprisingly lacks several metazoan core genes (including Wnt and several key transcription factors). Our study also provides the complete genome of a symbiotic Archaea dominating the associated microbial community: a new Thaumarchaeota species. CONCLUSIONS The genome of the glass sponge O. minuta differs from all other available sponge genomes by its compactness and smaller number of encoded proteins. The unexpected loss of numerous genes previously considered ancestral and pivotal for metazoan morphogenetic processes most likely reflects the peculiar syncytial tissue organization in this group. Our work further documents the importance of convergence during animal evolution, with multiple convergent evolution of septate-like junctions, electrical-signaling and multiciliated cells in metazoans.
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Affiliation(s)
- Sébastien Santini
- Aix Marseille Univ, CNRS, IGS, UMR 7256, IMM, IM2B, IOM, Marseille, France
| | - Quentin Schenkelaars
- Aix Marseille Univ, Avignon Univ, CNRS, IRD, IMBE, Marseille, France
- Institut Jacques Monod, CNRS, UMR 7592, Univ Paris Diderot, Sorbonne Paris Cité, Paris, France
| | - Cyril Jourda
- Aix Marseille Univ, CNRS, IGS, UMR 7256, IMM, IM2B, IOM, Marseille, France
- CIRAD, UMR PVBMT, La Réunion, France
| | - Marc Duchesne
- Department of Biological Sciences, University of Alberta, Edmonton, AB, T6G 2E9, Canada
| | - Hassiba Belahbib
- Aix Marseille Univ, CNRS, IGS, UMR 7256, IMM, IM2B, IOM, Marseille, France
| | - Caroline Rocher
- Aix Marseille Univ, Avignon Univ, CNRS, IRD, IMBE, Marseille, France
| | - Marjorie Selva
- Aix Marseille Univ, Avignon Univ, CNRS, IRD, IMBE, Marseille, France
| | - Ana Riesgo
- Department of Biodiversity and Evolutionary Biology, Madrid, Spain
- Department of Life Sciences, Natural History Museum of London, London, SW7 5BD, UK
| | - Michel Vervoort
- Institut Jacques Monod, CNRS, UMR 7592, Univ Paris Diderot, Sorbonne Paris Cité, Paris, France
| | - Sally P Leys
- Department of Biological Sciences, University of Alberta, Edmonton, AB, T6G 2E9, Canada
| | - Laurent Kodjabachian
- Aix Marseille Univ, CNRS, IBDM, UMR 7288, Turing Center for Living Systems, Marseille, France
| | - André Le Bivic
- Aix Marseille Univ, CNRS, IBDM, UMR 7288, Marseille, France
| | | | | | - Emmanuelle Renard
- Aix Marseille Univ, Avignon Univ, CNRS, IRD, IMBE, Marseille, France.
- Aix Marseille Univ, CNRS, IBDM, UMR 7288, Marseille, France.
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MRTF specifies a muscle-like contractile module in Porifera. Nat Commun 2022; 13:4134. [PMID: 35840552 PMCID: PMC9287330 DOI: 10.1038/s41467-022-31756-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2022] [Accepted: 06/30/2022] [Indexed: 12/13/2022] Open
Abstract
Muscle-based movement is a hallmark of animal biology, but the evolutionary origins of myocytes are unknown. Although believed to lack muscles, sponges (Porifera) are capable of coordinated whole-body contractions that purge debris from internal water canals. This behavior has been observed for decades, but their contractile tissues remain uncharacterized with respect to their ultrastructure, regulation, and development. We examine the sponge Ephydatia muelleri and find tissue-wide organization of a contractile module composed of actin, striated-muscle myosin II, and transgelin, and that contractions are regulated by the release of internal Ca2+ stores upstream of the myosin-light-chain-kinase (MLCK) pathway. The development of this contractile module appears to involve myocardin-related transcription factor (MRTF) as part of an environmentally inducible transcriptional complex that also functions in muscle development, plasticity, and regeneration. As an actin-regulated force-sensor, MRTF-activity offers a mechanism for how the contractile tissues that line water canals can dynamically remodel in response to flow and can re-form normally from stem-cells in the absence of the intrinsic spatial cues typical of animal embryogenesis. We conclude that the contractile module of sponge tissues shares elements of homology with contractile tissues in other animals, including muscles, indicating descent from a common, multifunctional tissue in the animal stem-lineage. Myocytes are a key cell type that enable animal movement, but their evolutionary origins remain unclear. Colgren and Nichols describe molecular and functional similarities between a contractile module in tissues of a sponge and muscle tissues in other animals, indicating a common evolutionary origin.
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Booth DS, King N. Genome editing enables reverse genetics of multicellular development in the choanoflagellate Salpingoeca rosetta. eLife 2020; 9:56193. [PMID: 32496191 PMCID: PMC7314544 DOI: 10.7554/elife.56193] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Accepted: 06/03/2020] [Indexed: 12/20/2022] Open
Abstract
In a previous study, we established a forward genetic screen to identify genes required for multicellular development in the choanoflagellate, Salpingoeca rosetta (Levin et al., 2014). Yet, the paucity of reverse genetic tools for choanoflagellates has hampered direct tests of gene function and impeded the establishment of choanoflagellates as a model for reconstructing the origin of their closest living relatives, the animals. Here we establish CRISPR/Cas9-mediated genome editing in S. rosetta by engineering a selectable marker to enrich for edited cells. We then use genome editing to disrupt the coding sequence of a S. rosetta C-type lectin gene, rosetteless, and thereby demonstrate its necessity for multicellular rosette development. This work advances S. rosetta as a model system in which to investigate how genes identified from genetic screens and genomic surveys function in choanoflagellates and evolved as critical regulators of animal biology.
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Affiliation(s)
- David S Booth
- Howard Hughes Medical Institute and Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
| | - Nicole King
- Howard Hughes Medical Institute and Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
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