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Pyenson BC, Rehan SM. Gene regulation supporting sociality shared across lineages and variation in complexity. Genome 2024; 67:99-108. [PMID: 38096504 DOI: 10.1139/gen-2023-0054] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2024]
Abstract
Across evolutionary lineages, insects vary in social complexity, from those that exhibit extended parental care to those with elaborate divisions of labor. Here, we synthesize the sociogenomic resources from hundreds of species to describe common gene regulatory mechanisms in insects that regulate social organization across phylogeny and levels of social complexity. Different social phenotypes expressed by insects can be linked to the organization of co-expressing gene networks and features of the epigenetic landscape. Insect sociality also stems from processes like the emergence of parental care and the decoupling of ancestral genetic programs. One underexplored avenue is how variation in a group's social environment affects the gene expression of individuals. Additionally, an experimental reduction of gene expression would demonstrate how the activity of specific genes contributes to insect social phenotypes. While tissue specificity provides greater localization of the gene expression underlying social complexity, emerging transcriptomic analysis of insect brains at the cellular level provides even greater resolution to understand the molecular basis of social insect evolution.
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Affiliation(s)
| | - Sandra M Rehan
- Department of Biology, York University, Toronto, ON M3J 1P3, Canada
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Mikhailova AA, Rinke S, Harrison MC. Genomic signatures of eusocial evolution in insects. Curr Opin Insect Sci 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] [What about the content of this article? (0)] [Affiliation(s)] [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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Fujiwara K, Karasawa A, Hanada T, Tobo M, Kaneko T, Usui M, Maekawa K. Caste-specific expressions and diverse roles of takeout genes in the termite Reticulitermes speratus. Sci Rep 2023; 13:8422. [PMID: 37225771 DOI: 10.1038/s41598-023-35524-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Accepted: 05/19/2023] [Indexed: 05/26/2023] Open
Abstract
Acquisition of novel functions caused by gene duplication may be important for termite social evolution. To clarify this possibility, additional evidence is needed. An important example is takeout, encoding juvenile hormone binding protein. We identified 25 takeouts in the termite Reticulitermes speratus genome. RNA-seq revealed that many genes were highly expressed in specific castes. Two novel paralogs (RsTO1, RsTO2) were tandemly aligned in the same scaffold. Real-time qPCR indicated that RsTO1 and RsTO2 were highly expressed in queens and soldiers, respectively. Moreover, the highest RsTO1 expression was observed in alates during queen formation. These patterns were different from vitellogenins, encoding egg-yolk precursors, which were highly expressed in queens than alates. In situ hybridization showed that RsTO1 mRNA was localized in the alate-frontal gland, indicating that RsTO1 binds with secretions probably used for the defence during swarming flight. In contrast, increased RsTO2 expression was observed approximately 1 week after soldier differentiation. Expression patterns of geranylgeranyl diphosphate synthase, whose product functions in the terpenoid synthesis, were similar to RsTO2 expression. In situ hybridization indicated RsTO2-specific mRNA signals in the soldier-frontal gland. RsTO2 may interact with terpenoids, with a soldier-specific defensive function. It may provide additional evidence for functionalization after gene duplication in termites.
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Affiliation(s)
- Kokuto Fujiwara
- Graduate School of Science and Engineering, University of Toyama, Gofuku, Toyama, 930-8555, Japan
| | - Akimi Karasawa
- Department of Biology, Faculty of Science, University of Toyama, Gofuku, Toyama, 930-8555, Japan
| | - Takumi Hanada
- Graduate School of Science and Engineering, University of Toyama, Gofuku, Toyama, 930-8555, Japan
| | - Mutsuaki Tobo
- Graduate School of Science and Engineering, University of Toyama, Gofuku, Toyama, 930-8555, Japan
| | - Tousuke Kaneko
- Department of Biology, Faculty of Science, University of Toyama, Gofuku, Toyama, 930-8555, Japan
| | - Mizuna Usui
- Department of Biology, Faculty of Science, University of Toyama, Gofuku, Toyama, 930-8555, Japan
| | - Kiyoto Maekawa
- Faculty of Science, Academic Assembly, University of Toyama, Gofuku, Toyama, 930-8555, Japan.
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Suzuki R, Masuoka Y, Suzuki RH, Maekawa K. Efficient RNA interference method during caste differentiation with hormone treatment in the termite Reticulitermes speratus (Isoptera: Rhinotermitidae). Front Insect Sci 2023; 3:1188343. [PMID: 38469474 PMCID: PMC10926471 DOI: 10.3389/finsc.2023.1188343] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/17/2023] [Accepted: 04/24/2023] [Indexed: 03/13/2024]
Abstract
Unveiling the proximate mechanism of caste differentiation is crucial for understanding insect social evolution, and gene function analysis is an important tool in this endeavor. The RNA interference (RNAi) technique is useful in termites, but its knockdown effects may differ among species. One of the most important model species in the field of termite sociogenomics is Reticulitermes speratus Kolbe (Isoptera: Rhinotermitidae). Presoldier and worker differentiation of this species can be artificially induced by juvenile hormone and 20-hydroxyecdysone application, respectively. However, appropriate RNAi technique of genes expressed during caste differentiation has never been considered. To clarify this issue, first, we injected nine different volumes of nuclease-free water (NFW, 0-404.8 nL) into workers and found that survival and caste differentiation rates were strongly reduced by the application of the top three largest volumes. Second, we injected double-stranded (ds) RNA of ecdysone receptor homolog (RsEcR) (2.0 µg/151.8 nL NFW) into workers with hormone treatments. The expression levels of RsEcR were significantly reduced at 9 days after dsRNA injection. RsEcR RNAi strongly affected both molting events during presoldier and worker differentiation induced by hormone treatments. The present results highlight the need for caution regarding injection volumes for RNAi experiments using hormone treatments. We suggest that the injection of dsRNA solution (2 µg; approximately 100-200 nL) is suitable for RNAi experiments during caste differentiation induced by hormone application in R. speratus.
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Affiliation(s)
- Ryutaro Suzuki
- Graduate School of Science and Engineering, University of Toyama, Toyama, Japan
- Ishikawa Insect Museum, Hakusan, Japan
| | - Yudai Masuoka
- Graduate School of Science and Engineering, University of Toyama, Toyama, Japan
- Institute of Agrobiological Sciences, National Agriculture and Food Research Organization, Tsukuba, Japan
| | - Ryohei H. Suzuki
- Graduate School of Science and Engineering, University of Toyama, Toyama, Japan
- Research and Development Headquarters, Earth Corporation, Ltd. Ako, Japan
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Matsunami M, Watanabe D, Fujiwara K, Hayashi Y, Shigenobu S, Miura T, Maekawa K. Transcriptomics on Social Interactions in Termites: Effects of Soldier Presence. Front Ecol Evol 2022. [DOI: 10.3389/fevo.2022.924151] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The organization of social insect colonies requires sophisticated mechanisms to regulate caste composition according to colony demands. In termites, the soldier caste is responsible for the inhibition of soldier differentiation, but the mechanism underlying the regulation of soldier differentiation is still unclear. In this study, we performed transcriptome analyses to identify genes expressed in workers that fluctuated in the presence of soldiers in the subterranean termite Reticulitermes speratus. First, soldier differentiation was artificially induced via juvenile hormone (JH) application, and the inhibitory effects of soldier differentiation on soldier presence were evaluated. Second, transcriptomes were prepared from workers with or without soldiers under JH treatment, and expression analyses were performed to identify differentially expressed genes (DEGs) for each treatment. The expression levels of several DEGs were verified by quantitative real-time PCR. The results indicated that only a small number of DEGs were upregulated by the presence of soldiers. A homology search of DEGs and gene ontology (GO) analysis of the DEGs showed that some genes were responsible for the regulation of hormone levels, social interaction, and response to xenobiotic substances, suggesting that they could be involved in developmental arrest and pheromonal regulation in workers. Moreover, GO analysis indicated that the expression of many genes, including those involved in hormone metabolic processes, fluctuated with JH application. Suppression of soldier differentiation in the presence of soldiers could be accomplished by the expression of a large number of genes required for soldier differentiation.
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