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Ewart KM, Ho SYW, Chowdhury AA, Jaya FR, Kinjo Y, Bennett J, Bourguignon T, Rose HA, Lo N. Pervasive relaxed selection in termite genomes. Proc Biol Sci 2024; 291:20232439. [PMID: 38772424 DOI: 10.1098/rspb.2023.2439] [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: 10/30/2023] [Accepted: 05/02/2024] [Indexed: 05/23/2024] Open
Abstract
Genetic changes that enabled the evolution of eusociality have long captivated biologists. More recently, attention has focussed on the consequences of eusociality on genome evolution. Studies have reported higher molecular evolutionary rates in eusocial hymenopteran insects compared with their solitary relatives. To investigate the genomic consequences of eusociality in termites, we analysed nine genomes, including newly sequenced genomes from three non-eusocial cockroaches. Using a phylogenomic approach, we found that termite genomes have experienced lower rates of synonymous substitutions than those of cockroaches, possibly as a result of longer generation times. We identified higher rates of non-synonymous substitutions in termite genomes than in cockroach genomes, and identified pervasive relaxed selection in the former (24-31% of the genes analysed) compared with the latter (2-4%). We infer that this is due to reductions in effective population size, rather than gene-specific effects (e.g. indirect selection of caste-biased genes). We found no obvious signature of increased genetic load in termites, and postulate efficient purging of deleterious alleles at the colony level. Additionally, we identified genomic adaptations that may underpin caste differentiation, such as genes involved in post-translational modifications. Our results provide insights into the evolution of termites and the genomic consequences of eusociality more broadly.
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Affiliation(s)
- Kyle M Ewart
- School of Life and Environmental Sciences, University of Sydney, Sydney, New South Wales, Australia
| | - Simon Y W Ho
- School of Life and Environmental Sciences, University of Sydney, Sydney, New South Wales, Australia
| | - Al-Aabid Chowdhury
- School of Life and Environmental Sciences, University of Sydney, Sydney, New South Wales, Australia
| | - Frederick R Jaya
- Ecology & Evolution, Research School of Biology, Australian National University, Acton, Australian Capital Territory, Australia
| | - Yukihiro Kinjo
- Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
- Okinawa International University, Okinawa, Japan
| | - Juno Bennett
- School of Life and Environmental Sciences, University of Sydney, Sydney, New South Wales, Australia
| | - Thomas Bourguignon
- Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
| | - Harley A Rose
- School of Life and Environmental Sciences, University of Sydney, Sydney, New South Wales, Australia
| | - Nathan Lo
- School of Life and Environmental Sciences, University of Sydney, Sydney, New South Wales, Australia
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Mikhailova AA, Rinke S, Harrison MC. Genomic signatures of eusocial evolution in insects. CURRENT OPINION IN INSECT SCIENCE 2024; 61:101136. [PMID: 37922983 DOI: 10.1016/j.cois.2023.101136] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 10/27/2023] [Accepted: 10/28/2023] [Indexed: 11/07/2023]
Abstract
The genomes of eusocial insects allow the production and regulation of highly distinct phenotypes, largely independent of genotype. Although rare, eusociality has evolved convergently in at least three insect orders (Hymenoptera, Blattodea and Coleoptera). Despite such disparate origins, eusocial phenotypes show remarkable similarity, exhibiting long-lived reproductives and short-lived sterile workers and soldiers. In this article, we review current knowledge on genomic signatures of eusocial evolution. We confirm that especially an increased regulatory complexity and the adaptive evolution of chemical communication are common to several origins of eusociality. Furthermore, colony life itself can shape genomes of divergent taxa in a similar manner. Future research should be geared towards generating more high-quality genomic resources, especially in hitherto understudied clades, such as ambrosia beetles and termites. The application of more sophisticated tools such as machine learning techniques may allow the detection of more subtle convergent genomic footprints of eusociality.
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Affiliation(s)
- Alina A Mikhailova
- Institute for Evolution and Biodiversity, University of Münster, Hüfferstrasße 1, 48149 Münster, Germany
| | - Sarah Rinke
- Institute for Evolution and Biodiversity, University of Münster, Hüfferstrasße 1, 48149 Münster, Germany
| | - Mark C Harrison
- Institute for Evolution and Biodiversity, University of Münster, Hüfferstrasße 1, 48149 Münster, Germany.
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Berger J, Legendre F, Zelosko KM, Harrison MC, Grandcolas P, Bornberg-Bauer E, Fouks B. Eusocial Transition in Blattodea: Transposable Elements and Shifts of Gene Expression. Genes (Basel) 2022; 13:1948. [PMID: 36360186 PMCID: PMC9689775 DOI: 10.3390/genes13111948] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2022] [Revised: 10/19/2022] [Accepted: 10/20/2022] [Indexed: 11/07/2023] Open
Abstract
(1) Unravelling the molecular basis underlying major evolutionary transitions can shed light on how complex phenotypes arise. The evolution of eusociality, a major evolutionary transition, has been demonstrated to be accompanied by enhanced gene regulation. Numerous pieces of evidence suggest the major impact of transposon insertion on gene regulation and its role in adaptive evolution. Transposons have been shown to be play a role in gene duplication involved in the eusocial transition in termites. However, evidence of the molecular basis underlying the eusocial transition in Blattodea remains scarce. Could transposons have facilitated the eusocial transition in termites through shifts of gene expression? (2) Using available cockroach and termite genomes and transcriptomes, we investigated if transposons insert more frequently in genes with differential expression in queens and workers and if those genes could be linked to specific functions essential for eusocial transition. (3) The insertion rate of transposons differs among differentially expressed genes and displays opposite trends between termites and cockroaches. The functions of termite transposon-rich queen- and worker-biased genes are related to reproduction and ageing and behaviour and gene expression, respectively. (4) Our study provides further evidence on the role of transposons in the evolution of eusociality, potentially through shifts in gene expression.
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Affiliation(s)
- Juliette Berger
- Institut de Systématique, Évolution, Biodiversité (ISYEB), Muséum National d’Histoire Naturelle, CNRS, Sorbonne Université, EPHE, Université des Antilles, CP50, 57 rue Cuvier, 75005 Paris, France
| | - Frédéric Legendre
- Institut de Systématique, Évolution, Biodiversité (ISYEB), Muséum National d’Histoire Naturelle, CNRS, Sorbonne Université, EPHE, Université des Antilles, CP50, 57 rue Cuvier, 75005 Paris, France
| | - Kevin-Markus Zelosko
- Institute for Evolution and Biodiversity, Molecular Evolution and Bioinformatics, Westfälische Wilhelms-Universität, Hüfferstrasse 1, 48149 Münster, Germany
| | - Mark C. Harrison
- Institute for Evolution and Biodiversity, Molecular Evolution and Bioinformatics, Westfälische Wilhelms-Universität, Hüfferstrasse 1, 48149 Münster, Germany
| | - Philippe Grandcolas
- Institut de Systématique, Évolution, Biodiversité (ISYEB), Muséum National d’Histoire Naturelle, CNRS, Sorbonne Université, EPHE, Université des Antilles, CP50, 57 rue Cuvier, 75005 Paris, France
| | - Erich Bornberg-Bauer
- Institute for Evolution and Biodiversity, Molecular Evolution and Bioinformatics, Westfälische Wilhelms-Universität, Hüfferstrasse 1, 48149 Münster, Germany
- Department of Protein Evolution, Max Planck Institute for Developmental Biology, Max-Planck-Ring 5, 72076 Tübingen, Germany
| | - Bertrand Fouks
- Institute for Evolution and Biodiversity, Molecular Evolution and Bioinformatics, Westfälische Wilhelms-Universität, Hüfferstrasse 1, 48149 Münster, Germany
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Differential Selection on Caste-Associated Genes in a Subterranean Termite. INSECTS 2022; 13:insects13030224. [PMID: 35323522 PMCID: PMC8955789 DOI: 10.3390/insects13030224] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/09/2021] [Revised: 02/18/2022] [Accepted: 02/23/2022] [Indexed: 11/29/2022]
Abstract
Analyzing the information-rich content of RNA can help uncover genetic events associated with social insect castes or other social polymorphisms. Here, we exploit a series of cDNA libraries previously derived from whole-body tissue of different castes as well as from three behaviourally distinct populations of the Eastern subterranean termite Reticulitermes flavipes. We found that the number (~0.5 M) of single nucleotide variants (SNVs) was roughly equal between nymph, worker and soldier caste libraries, but dN/dS (ratio of nonsynonymous to synonymous substitutions) analysis suggested that some of these variants confer a caste-specific advantage. Specifically, the dN/dS ratio was high (~4.3) for genes expressed in the defensively specialized soldier caste, relative to genes expressed by other castes (~1.7−1.8) and regardless of the North American population (Toronto, Raleigh, Boston) from which the castes were sampled. The populations, meanwhile, did show a large difference in SNV count but not in the manner expected from known demographic and behavioural differences; the highly invasive unicolonial population from Toronto was not the least diverse and did not show any other unique substitution patterns, suggesting any past bottleneck associated with invasion or with current unicoloniality has become obscured at the RNA level. Our study raises two important hypotheses relevant to termite sociobiology. First, the positive selection (dN/dS > 1) inferred for soldier-biased genes is presumably indirect and of the type mediated through kin selection, and second, the behavioural changes that accompany some social insect urban invasions (i.e., ‘unicoloniality’) may be detached from the loss-of-diversity expected from invasion bottlenecks.
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