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Oguchi K, Miura T. Body part-specific development in termite caste differentiation: crosstalk between hormonal actions and developmental toolkit genes. CURRENT OPINION IN INSECT SCIENCE 2024; 63:101183. [PMID: 38428818 DOI: 10.1016/j.cois.2024.101183] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2023] [Revised: 02/24/2024] [Accepted: 02/25/2024] [Indexed: 03/03/2024]
Abstract
In social insects, interactions among colony members trigger caste differentiation with morphological modifications. During caste differentiation in termites, body parts and caste-specific morphologies are modified during postembryonic development under endocrine controls such as juvenile hormone (JH) and ecdysone. In addition to endocrine factors, developmental toolkit genes such as Hox- and appendage-patterning genes also contribute to the caste-specific body part modifications. These toolkits are thought to provide spatial information for specific morphogenesis. During social evolution, the complex crosstalks between physiological and developmental mechanisms should be established, leading to the sophisticated caste systems. This article reviews recent studies on these mechanisms underlying the termite caste differentiation and addresses implications for the evolution of caste systems in termites.
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Affiliation(s)
- Kohei Oguchi
- Misaki Marine Biological Station, The University of Tokyo, Miura, Kanagawa 238-0225, Japan
| | - Toru Miura
- Misaki Marine Biological Station, The University of Tokyo, Miura, Kanagawa 238-0225, Japan.
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2
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Salazar-Salazar LR, Pinzón-Florian OP. Ecology, behavior and bionomics: functional response of Heterotermes tenuis Hagen (Insecta: Blattaria: Isoptera: Rhinotermitidae) in forests of the Colombian Orinoquía. BMC ZOOL 2023; 8:24. [PMID: 37884987 PMCID: PMC10601117 DOI: 10.1186/s40850-023-00184-7] [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: 10/05/2022] [Accepted: 09/06/2023] [Indexed: 10/28/2023] Open
Abstract
BACKGROUND Land use intensification may affect diversity, abundance, and functional morphological traits (FMT) related to dispersal, food acquisition, digestion, and nesting in some insects, possibly impacting their ecological role. Most studies of termites on the effects of afforestation focus on diversity and abundance, but changes in FMT have yet to be studied. AIM To better understand the response mechanisms to land use intensification, we compared the FMT of the worker and soldier caste of Heterotermes tenuis among Pinus caribaea plantations of four different ages and gallery forests of the Colombian Orinoquía. METHODOLOGY We measured thirty-eight FMTs in the worker and soldier castes of H. tenuis from gallery forests and pine plantations. Then, we used a Community-Weighted Mean (CWM), a PERMANOVA, and a nonmetric multidimensional scaling (NMDS) to estimate the possible effect of land use type on the FMT of both castes. We selected the FMTs with the lowest intraspecific coefficient of variation (CV) from each caste to compare their size among the land use types and pine plantation ages. RESULTS Land use type had a more significant impact on the FMT size of pine plantation workers than the age of the afforestation. FMT of the worker caste tends to be larger in gallery forests than in pine plantations, while the results were inconclusive for soldiers. CONCLUSION The results suggested a homogenization mainly of the feeding FMT of the worker caste of H. tenuis in pine plantations associated with the increase in the softwood food resource of P. caribaea.
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Soldier Caste-Specific Protein 1 Is Involved in Soldier Differentiation in Termite Reticulitermes aculabialis. INSECTS 2022; 13:insects13060502. [PMID: 35735839 PMCID: PMC9224846 DOI: 10.3390/insects13060502] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Revised: 05/22/2022] [Accepted: 05/23/2022] [Indexed: 01/27/2023]
Abstract
Termite soldiers are a unique caste among social insects, and their differentiation can be induced by Juvenile hormone (JH) from workers through two molts (worker–presoldier–soldier). However, the molecular mechanism underlying the worker-to-soldier transformation in termites is poorly understood. To explore the mechanism of soldier differentiation induced by JH, the gene soldier caste-specific protein 1 (RaSsp1, NCBI accession no: MT861054.1) in R. aculabialis was cloned, and its function was studied. This gene was highly expressed in the soldier caste, and the protein RsSsp1 was similar to the JHBP (JH-binding protein) domain-containing protein by Predict Protein online. In addition, JHIII could be anchored in the hydrophobic cage of RaSsp1 as the epoxide of the JHBP-bound JH according to the protein ligand molecular docking online tool AutoDock. The functional studies indicated that knocking down of the RaSsp1 shorted the presoldier’s head capsule, reduced mandible size, delayed molting time and decreased molting rate (from worker to presoldier) at the beginning of worker gut-purging. Furthermore, knocking down of the RaSsp1 had a more pronounced effect on soldier differentiation (from presoldier to soldier), and manifested in significantly shorter mandibles, rounder head capsules, and lower molting rate (from worker to presoldier) at the beginning of presoldier gut-purging. Correspondingly, the expressions of JH receptor Methoprene-tolerant (Met), the JH-inducible transcription factor Krüppel homolog1 (Kr-h1) and ecdysone signal genes Broad-complex (Br-C) were downregulated when knocking down the RaSsp1 at the above two stages. All these results that RaSsp1 may be involved in soldier differentiation from workers by binding and transporting JH.
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Molecular underpinnings of division of labour among workers in a socially complex termite. Sci Rep 2021; 11:18269. [PMID: 34521896 PMCID: PMC8440649 DOI: 10.1038/s41598-021-97515-w] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Accepted: 08/20/2021] [Indexed: 02/08/2023] Open
Abstract
Division of labour characterizes all major evolutionary transitions, such as the evolution of eukaryotic cells or multicellular organisms. Social insects are characterized by reproductive division of labour, with one or a few reproducing individuals (queens) and many non-reproducing nestmates (workers) forming a colony. Among the workers, further division of labour can occur with different individuals performing different tasks such as foraging, brood care or building. While mechanisms underlying task division are intensively studied in social Hymenoptera, less is known for termites, which independently evolved eusociality. We investigated molecular mechanisms underlying task division in termite workers to test for communality with social Hymenoptera. We compared similar-aged foraging workers with builders of the fungus-growing termite Macrotermes bellicosus using transcriptomes, endocrine measures and estimators of physiological condition. Based on results for social Hymenoptera and theory, we tested the hypotheses that (i) foragers are in worse physiological conditions than builders, (ii) builders are more similar in their gene expression profile to queens than foragers are, and (iii) builders invest more in anti-ageing mechanism than foragers. Our results support all three hypotheses. We found storage proteins to underlie task division of these similar-aged termite workers and these genes also characterize reproductive division of labour between queens and workers. This implies a co-option of nutrient-based pathways to regulate division of labour across lineages of termites and social Hymenoptera, which are separated by more than 133 million years.
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Korb J, Greiner C, Foget M, Geiler A. How Can Termites Achieve Their Unparalleled Postembryonic Developmental Plasticity? A Test for the Role of Intermolt-Specific High Juvenile Hormone Titers. Front Ecol Evol 2021. [DOI: 10.3389/fevo.2021.619594] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Termites are “social cockroaches” and amongst the most phenotypically plastic insects. The different castes (i.e., two types of reproductives, workers, and soldiers) within termite societies are all encoded by a single genome and present the result of differential postembryonic development. Besides the default progressive development into winged sexuals of solitary hemimetabolous insects, termites have two postembryonic, non-terminal molts (stationary and regressive; i.e., molts associated, respectively, with no change or reduction of size/morphological differentiation) which allow them to retain workers, and two terminal developmental types to become soldiers and replacement reproductives. Despite this unique plasticity, especially the mechanisms underlying the non-terminal development are poorly understood. In 1982, Nijhout and Wheeler proposed a model how this diversity might have evolved. They proposed that varying juvenile hormone (JH) titers at the start, mid-phase, and end of each intermolt period account for the developmental diversity. We tested this rarely addressed model in the lower termite Cryptotermes secundus using phase-specific pharmacological manipulations of JH titers. Our results partially support the Nijhout and Wheeler model. These data are supplemented with gene expression studies of JH-related genes that characterize different postembryonic developmental trajectories. Our study provides new insights into the evolution of the unique postembryonic developmental plasticity of termites that constitutes the foundation of their social life.
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Ye C, Song Z, Wu T, Zhang W, Saba NU, Xing L, Su X. Endocuticle is involved in caste differentiation of the lower termite. Curr Zool 2021; 67:489-499. [PMID: 34616947 PMCID: PMC8489109 DOI: 10.1093/cz/zoab005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Accepted: 01/19/2021] [Indexed: 12/30/2022] Open
Abstract
Caste differentiation in termites is one of the most conspicuous examples of facultative polyphenism in animals. It is clear that specific cuticular formation occurs in hard exocuticles during caste differentiation. However, the developmental pattern of the soft endocuticle in the differentiation pathways of castes is unknown. To reveal whether the endocuticle is involved in caste differentiation, we compared the exocuticle and endocuticle thickness of individuals in 2 pathways (nymph line and worker line) of caste differentiation in the termite Reticulitermes aculabialis. The endocuticle protein genes were identified by transcriptome analysis and the expression patterns of these genes were confirmed in caste differentiation. We found that the endocuticle structure showed dynamic changes in 2 pathways, and the first difference in endocuticle structure occurred after larvae differentiation bifurcated into workers and nymphs. The thinning of the endocuticle was a significant event from nymphs developing into alates with the thickest exocuticle and thinnest endocuticle. The thickest endocuticle layers were found in the heads of the workers and the ultrastructure of the endocuticle in the heads was more complex than that in the thorax–abdomens. Six endocuticle protein genes were identified and annotated as endocuticle structural glycoproteins SgAbd-2, SgAbd-9, and Abd-5. The expression levels of endocuticle protein genes changed dramatically during caste development and the expression levels in neotenic reproductives (secondary reproductives) were significantly higher than those in alates (primary reproductives). These results reveal the roles of endocuticles in caste differentiation and adaptation to the environment.
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Affiliation(s)
- Chenxu Ye
- Shaanxi Key Laboratory for Animal Conservation, Northwest University, Xi'an 710069, China.,College of Life Sciences, Northwest University, Xi'an 710069, China
| | - Zhuanzhuan Song
- College of Life Sciences, Northwest University, Xi'an 710069, China
| | - Taoyu Wu
- College of Life Sciences, Northwest University, Xi'an 710069, China
| | - Wenxiu Zhang
- College of Life Sciences, Northwest University, Xi'an 710069, China
| | - Noor Us Saba
- Shaanxi Key Laboratory for Animal Conservation, Northwest University, Xi'an 710069, China.,College of Life Sciences, Northwest University, Xi'an 710069, China
| | - Lianxi Xing
- Shaanxi Key Laboratory for Animal Conservation, Northwest University, Xi'an 710069, China.,College of Life Sciences, Northwest University, Xi'an 710069, China
| | - Xiaohong Su
- Shaanxi Key Laboratory for Animal Conservation, Northwest University, Xi'an 710069, China.,College of Life Sciences, Northwest University, Xi'an 710069, China
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7
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Miura T, Maekawa K. The making of the defensive caste: Physiology, development, and evolution of the soldier differentiation in termites. Evol Dev 2020; 22:425-437. [PMID: 32291940 DOI: 10.1111/ede.12335] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2019] [Revised: 02/11/2020] [Accepted: 03/08/2020] [Indexed: 12/29/2022]
Abstract
Termites (Blattodea, Termitoidea, or Isoptera) constitute one of the major lineages of eusocial insects. In termite societies, multiple types of functional individuals, that is, castes, perform divisions of labors to coordinate social behaviors. Among other castes, the soldier caste is distinctive since it is sterile and exclusively specialized into defensive behavior with largely modified morphological features. Therefore, many of the previous studies have been focused on soldiers, in terms of ecology, behavior, and evolution as well as developmental and physiological mechanisms. This article overviews the accumulation of studies especially focusing on the developmental and physiological mechanisms underlying the soldier differentiation in termites. Furthermore, the evolutionary trajectories that have led the acquisition of soldier caste and have diversified the soldier characteristics in association with the social evolution are discussed.
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Affiliation(s)
- Toru Miura
- Department of Biological Sciences, Misaki Marine Biological Station, School of Science, The University of Tokyo, Japan
| | - Kiyoto Maekawa
- Department of Biology, Faculty of Science, Academic Assembly, University of Toyama, Toyama, Japan
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8
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Cesar CS, Giacometti D, Costa-Leonardo AM, Casarin FE. Drywood Pest Termite Cryptotermes brevis (Blattaria: Isoptera: Kalotermitidae): a Detailed Morphological Study of Pseudergates. NEOTROPICAL ENTOMOLOGY 2019; 48:822-833. [PMID: 31197677 DOI: 10.1007/s13744-019-00687-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2018] [Accepted: 04/11/2019] [Indexed: 06/09/2023]
Abstract
The Kalotermitidae Cryptotermes brevis (Walker) presents colonies that lack a true worker caste. They have totipotent worker-like individuals named pseudergates. Few studies have characterized the morphology of immature instars, including pseudergates. In order to identify these instars and characterize the pseudergates, we conducted a comparison between morphometric and morphological variations among immature individuals of C. brevis colonies. Juvenile hormone analog (JHA) was used in the first instar nymphs to induce regressive molts and compare morphological differences between nymphs and pseudergates. Results showed the existence of three larval instars and four nymphal instars. These immatures were morphologically characterized. Individuals classified as third instar larvae presented white body, 10 to 12 antennal articles, absent or small non-pigmented compound eyes, and absence of wing buds. Pseudergates presented pigmented abdomen and sclerotized cuticle, 10 to 12 antennal articles, and absent or small compound eyes, and few specimens had large pigmented compound eyes and absence of wing buds. First instar nymphs had pigmented abdomen and sclerotized cuticle, 10 to 12 antennal articles, both large non-pigmented and pigmented compound eyes, the presence of wing buds. Bioassays using JHA on first instar nymphs resulted in a large percentage of nymph-soldier intercastes. We concluded that abdomen pigmentation and sclerotized cuticle are good characters to differentiate pseudergates from larvae and the absence of wing buds is a good character to differentiate pseudergates from nymphs. Our findings not only contribute to the basic biological and morphological information of this species but also help to identify correctly pseudergates in further studies that involve applied bioassays.
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Affiliation(s)
- C S Cesar
- Dept of Ecology and Evolutionary Biology, Lab de Termitologia, Federal Univ of São Paulo (UNIFESP), Diadema, SP, Brasil.
- Dept of Ecology, Univ of São Paulo, São Paulo, SP, Brasil.
| | - D Giacometti
- Dept of Ecology and Evolutionary Biology, Lab de Termitologia, Federal Univ of São Paulo (UNIFESP), Diadema, SP, Brasil
| | - A M Costa-Leonardo
- Dept of Biological Sciences, Instituto de Biociências, São Paulo State Univ (UNESP), Rio Claro, SP, Brasil
| | - F E Casarin
- Dept of Ecology and Evolutionary Biology, Lab de Termitologia, Federal Univ of São Paulo (UNIFESP), Diadema, SP, Brasil
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9
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Santos CG, Humann FC, Hartfelder K. Juvenile hormone signaling in insect oogenesis. CURRENT OPINION IN INSECT SCIENCE 2019; 31:43-48. [PMID: 31109672 DOI: 10.1016/j.cois.2018.07.010] [Citation(s) in RCA: 108] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Accepted: 07/15/2018] [Indexed: 06/09/2023]
Abstract
Juvenile hormone (JH) plays a crucial role in insect reproduction, but its molecular mode of action only became clear within the last decade. We here review recent findings revealing the intricate crosstalk between JH and ecdysone signaling with nutrient sensing pathways in Drosophila melanogaster, Aedes aegypti, Tribolium castaneum and Locusta migratoria. The finding for a critical role of ecdysis triggering hormone (ETH) in both molting and ooogenesis now also highlights the importance of an integrated view of development and reproduction. Furthermore, insights from non-model insects, especially so social Hymenoptera and termites, where JH function gradually becomes decoupled from reproduction and plays a role in division of labor, emphasize the need to consider life cycle and life history strategies when studying insect reproductive physiology.
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Affiliation(s)
- Carolina Gonçalves Santos
- Departamento de Biologia Celular e Molecular e Bioagentes Patogênicos, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil.
| | | | - Klaus Hartfelder
- Departamento de Biologia Celular e Molecular e Bioagentes Patogênicos, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil
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Jongepier E, Kemena C, Lopez-Ezquerra A, Belles X, Bornberg-Bauer E, Korb J. Remodeling of the juvenile hormone pathway through caste-biased gene expression and positive selection along a gradient of termite eusociality. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2018; 330:296-304. [PMID: 29845724 DOI: 10.1002/jez.b.22805] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2018] [Revised: 04/25/2018] [Accepted: 05/03/2018] [Indexed: 11/10/2022]
Abstract
The evolution of division of labor between sterile and fertile individuals represents one of the major transitions in biological complexity. A fascinating gradient in eusociality evolved among the ancient hemimetabolous insects, ranging from noneusocial cockroaches through the primitively social lower termites-where workers retain the ability to reproduce-to the higher termites, characterized by lifetime commitment to worker sterility. Juvenile hormone (JH) is a prime candidate for the regulation of reproductive division of labor in termites, as it plays a key role in insect postembryonic development and reproduction. We compared the expression of JH pathway genes between workers and queens in two lower termites (Zootermopsis nevadensis and Cryptotermes secundus) and a higher termite (Macrotermes natalensis) to that of analogous nymphs and adult females of the noneusocial cockroach Blattella germanica. JH biosynthesis and metabolism genes ranged from reproductive female-biased expression in the cockroach to predominantly worker-biased expression in the lower termites. Remarkably, the expression profile of JH pathway genes sets the higher termite apart from the two lower termites, as well as the cockroach, indicating that JH signaling has undergone major changes in this eusocial termite. These changes go beyond mere shifts in gene expression between the different castes, as we find evidence for positive selection in several termite JH pathway genes. Thus, remodeling of the JH pathway may have played a major role in termite social evolution, representing a striking case of convergent molecular evolution between the termites and the distantly related social hymenoptera.
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Affiliation(s)
- Evelien Jongepier
- Institute for Evolution and Biodiversity, University of Münster, Münster, Germany
| | - Carsten Kemena
- Institute for Evolution and Biodiversity, University of Münster, Münster, Germany
| | | | - Xavier Belles
- Institut de Biologia Evolutiva, CSIC-University Pompeu Fabra, Barcelona, Spain
| | - Erich Bornberg-Bauer
- Institute for Evolution and Biodiversity, University of Münster, Münster, Germany
| | - Judith Korb
- Evolutionary Biology & Ecology, University of Freiburg, Freiburg, Germany
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11
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Korb J. Chemical Fertility Signaling in Termites: Idiosyncrasies and Commonalities in Comparison with Ants. J Chem Ecol 2018; 44:818-826. [PMID: 29616376 DOI: 10.1007/s10886-018-0952-2] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Revised: 02/15/2018] [Accepted: 03/21/2018] [Indexed: 11/25/2022]
Abstract
Termites evolved eusociality independently from social Hymenoptera. As a common trait, reproductive monopoly is maintained through chemical communication. The queen (and in termites also a king) prevents workers from reproduction by conveying their reproductive status. In termites all soldiers are sterile, but workers' potential to reproduce differs between species. It ranges from totipotency in wood-dwelling lower termites where workers are a transient stage from which all other castes develop, to sterile workers in some higher termites. Intermediate are species in which workers can develop into replacement sexuals within the nest but not into winged sexuals. I summarize the patchy picture about fertility signaling that we currently have for termites, pointing also to potential conflicts over reproduction that differ from those in social Hymenoptera. Recent findings imply that, similar to many social Hymenoptera, wood-dwelling termites that live in confined nests use long-chain cuticular hydrocarbons (CHCs) as fertility signals. Yet other compounds are important as well, comprising proteinaceous secretions and especially volatiles. For a subterranean termite, two volatiles have been identified as primer pheromones that prevent reproductive differentiation of workers. It requires more data to test whether wood-dwelling termites use CHCs, while species with larger colonies and less confined nests use volatiles, or whether all species rely on multicomponent signals. Ultimately, we need more effort to model and test potential conflicts over reproduction between queens, kings and workers. Here results from social Hymenoptera cannot be transferred to termites as the latter are diploid and commonly inbred. This review illustrates promising future research avenues.
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Affiliation(s)
- Judith Korb
- Evolutionary Biology & Ecology, University of Freiburg, Hauptstrasse 1, D-79104, Freiburg, Germany.
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12
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Su X, Yang X, Li J, Xing L, Liu H, Chen J. The transition path from female workers to neotenic reproductives in the termite Reticulitermes labralis. Evol Dev 2017; 19:218-226. [PMID: 28869353 DOI: 10.1111/ede.12229] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Termite workers are characterized by unique flexibility in that a worker can develop in one of three ways: remain a worker, become a soldier within two successive moults, or become a neotenic reproductive (NR) within a single moult. However, is it true that workers can transform into NRs within a single moult? Actually, the developmental pathways of workers turning into NRs remains unclear. In this study, we show for the first time that the female workers of Reticulitermes labralis develop into NRs after a pre-NRs stage. We found that a female worker became a NR after two successive moults, whereas the male workers copulated directly with queens without undergoing any moults. After the first moult led the female workers into the pre-NR stage, the length of their abdomens, seventh sternites and ovaries significantly increased. After the second moult from the pre-NRs stage into NRs, the follicle cells returned to normal, and a few oocytes and follicle cells underwent apoptosis. These results demonstrated that the female pre-NR type was a transitional type during the development of female workers to the NR caste, and the starting point for oogenesis resumption was the NR stage. We confirmed there were fundamental differences in the reproductive pathway of the male and female workers. Therefore, we determined that the transformation process of the female NRs from workers may be a very complex process, and the reproductive biology of the workers has great potential to provide important and spectacular insights into the evolution strategy of termites.
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Affiliation(s)
- Xiaohong Su
- Shaanxi Key Laboratory for Animal Conservation, Northwest University, Xi'an, China.,Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education, Northwest University, Xi'an, China.,College of Life Sciences, Northwest University, Xi'an, China
| | - Xiaojuan Yang
- College of Life Sciences, Northwest University, Xi'an, China
| | - Jing Li
- College of Life Sciences, Northwest University, Xi'an, China
| | - Lianxi Xing
- Shaanxi Key Laboratory for Animal Conservation, Northwest University, Xi'an, China.,Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education, Northwest University, Xi'an, China.,College of Life Sciences, Northwest University, Xi'an, China
| | - He Liu
- College of Life Sciences, Northwest University, Xi'an, China
| | - Jiaoling Chen
- College of Life Sciences, Northwest University, Xi'an, China
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13
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Korb J, Belles X. Juvenile hormone and hemimetabolan eusociality: a comparison of cockroaches with termites. CURRENT OPINION IN INSECT SCIENCE 2017; 22:109-116. [PMID: 28805632 DOI: 10.1016/j.cois.2017.06.002] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2017] [Revised: 05/17/2017] [Accepted: 06/09/2017] [Indexed: 06/07/2023]
Abstract
Termites are social Dictyoptera that evolved eusociality independently from social Hymenoptera. They are characterized by unique developmental plasticity that is the basis of caste differentiation and social organization. As developmental plasticity is a result of endocrine regulation, in order to understand the evolution of termite sociality it is helpful to compare the endocrine underpinning of development between termites and cockroaches. Nijhout and Wheeler (1982) proposed that varying JH titers determine caste differentiation in termites. Based on current results, we extend this model by adding the importance of social interactions. High JH titers in the presence of soldiers lead to regressive development (decrease in body size, apparent regression in development), while an absence of soldiers induces (pre-)soldier differentiation. On the opposite side, low JH titers in colonies headed by reproductives result in progressive molts toward adults, while an absence of reproductives induces development of replacement reproductives. In cockroaches, transcription factors involved in JH signaling, including the adult specifier E93 (the co-called MEKRE93 pathway) regulate the morphogenetic transition between the nymph and the adult. In termites, we speculate that castes might be determined by social effects playing a modulatory action of JH in the MEKRE93 pathway.
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Affiliation(s)
- Judith Korb
- Evolutionary Biology & Ecology, University of Freiburg, Hauptstrasse 1, D-79104 Freiburg, Germany.
| | - Xavier Belles
- Institute of Evolutionary Biology, CSIC-Universitat Pompeu Fabra, Passeig Marítim 37, 08003 Barcelona, Spain
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14
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Su X, Liu H, Yang X, Chen J, Zhang H, Xing L, Zhang X. Characterization of the transcriptomes and cuticular protein gene expression of alate adult, brachypterous neotenic and adultoid reproductives of Reticulitermes labralis. Sci Rep 2016; 6:34183. [PMID: 27690209 PMCID: PMC5044703 DOI: 10.1038/srep34183] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2016] [Accepted: 09/08/2016] [Indexed: 01/22/2023] Open
Abstract
The separation of primary reproductive and secondary reproductive roles based on the differentiation of alate adults and neotenic reproductives is the most prominent characteristic of termites. To clarify the mechanism underlying this differentiation, we sequenced the transcriptomes of alate adults (ARs), brachypterous neotenics (BNs) and adultoid reproductives (ANs) from the last instar nymphs of Reticulitermes labralis. A total of 404,152,188 clean sequencing reads was obtained and 61,953 unigenes were assembled. Of the 54 identified cuticular protein (CP) genes of the reproductives, 22 were classified into the CPR family and 7 were classified into the CPG family. qRT-PCR analyses of the 6 CP genes revealed that the CP genes involved in exocuticle sclerotization were highly expressed in the ARs and RR-1 involved in soft endocuticle was highly expressed in the ARs and ANs. These results suggest that the alate adults might increase cuticular component deposition to adapt to new or changing environments and that the development of reproductive individuals into primary or secondary reproductives is controlled by the expression of cuticular protein genes involved in the hardening of the exocuticle. In addition, the AN caste is a transitional type between the BN and AR castes in the process of evolution.
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Affiliation(s)
- Xiaohong Su
- Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education, Northwest University, Xi'an, China.,Shaanxi Key Laboratory for Animal Conservation, Northwest University, Xi'an, China.,College of Life Sciences, Northwest University, Xi'an, China
| | - He Liu
- College of Life Sciences, Northwest University, Xi'an, China
| | - Xiaojuan Yang
- College of Life Sciences, Northwest University, Xi'an, China
| | - Jiaoling Chen
- College of Life Sciences, Northwest University, Xi'an, China
| | - Honggui Zhang
- College of Life Sciences, Northwest University, Xi'an, China
| | - Lianxi Xing
- Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education, Northwest University, Xi'an, China.,Shaanxi Key Laboratory for Animal Conservation, Northwest University, Xi'an, China.,College of Life Sciences, Northwest University, Xi'an, China
| | - Xiaojing Zhang
- College of Life Sciences, Northwest University, Xi'an, China
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15
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Induction of a reproductive-specific cuticular hydrocarbon profile by a juvenile hormone analog in the termite Zootermopsis nevadensis. CHEMOECOLOGY 2016. [DOI: 10.1007/s00049-016-0219-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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16
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Masuoka Y, Maekawa K. Gene expression changes in the tyrosine metabolic pathway regulate caste-specific cuticular pigmentation of termites. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2016; 74:21-31. [PMID: 27125584 DOI: 10.1016/j.ibmb.2016.04.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Revised: 04/20/2016] [Accepted: 04/23/2016] [Indexed: 06/05/2023]
Abstract
In social insects, all castes have characteristic phenotypes suitable for their own tasks and to engage in social behavior. The acquisition of caste-specific phenotypes was a key event in the course of social insect evolution. However, understanding of the genetic basis and the developmental mechanisms that produce these phenotypes is still very limited. In particular, termites normally possess more than two castes with specific phenotypes (i.e. workers, soldiers, and reproductives), but proximate developmental mechanisms are far from being fully understood. In this study, we focused on the pigmentation of the cuticle as a model trait for caste-specific phenotypes, during the molts of each caste; workers, soldiers, presoldiers (intermediate stage of soldiers), and alates (primary reproductives) in Zootermopsis nevadensis. Expression patterns of cuticular tanning genes (members of the tyrosine metabolic pathway) were different among each molt, and high expression levels of several "key genes" were observed during each caste differentiation. For the differentiation of castes with well-tanned cuticles (i.e. soldiers and alates), all focal genes except DDC in the former were highly expressed. On the other hand, high expression levels of yellow and aaNAT were observed during worker and presoldier molts, respectively, but most other genes in the pathway were expressed at low levels. RNA interference (RNAi) of these key genes affected caste-specific cuticular pigmentation, leading to soldiers with yellowish-white heads and pigmented mandibular tips, presoldiers with partly pigmented head cuticles, and alates with the yellow head capsules. These results suggest that the pigmentation of caste-specific cuticles is achieved by the regulation of gene expression in the tyrosine metabolic pathway.
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Affiliation(s)
- Yudai Masuoka
- Graduate School of Science and Engineering, University of Toyama, Toyama, Japan
| | - Kiyoto Maekawa
- Graduate School of Science and Engineering, University of Toyama, Toyama, Japan.
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17
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Masuoka Y, Maekawa K. Ecdysone signaling regulates soldier-specific cuticular pigmentation in the termiteZootermopsis nevadensis. FEBS Lett 2016; 590:1694-703. [DOI: 10.1002/1873-3468.12219] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2016] [Revised: 05/11/2016] [Accepted: 05/18/2016] [Indexed: 01/04/2023]
Affiliation(s)
- Yudai Masuoka
- Graduate School of Science and Engineering; University of Toyama; Japan
| | - Kiyoto Maekawa
- Graduate School of Science and Engineering; University of Toyama; Japan
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18
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Sillam-Dussès D, Hanus R, Poulsen M, Roy V, Favier M, Vasseur-Cognet M. The role of the glucose-sensing transcription factor carbohydrate-responsive element-binding protein pathway in termite queen fertility. Open Biol 2016; 6:160080. [PMID: 27249798 PMCID: PMC4892437 DOI: 10.1098/rsob.160080] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Accepted: 04/25/2016] [Indexed: 12/04/2022] Open
Abstract
Termites are among the few animals that themselves can digest the most abundant organic polymer, cellulose, into glucose. In mice and Drosophila, glucose can activate genes via the transcription factor carbohydrate-responsive element-binding protein (ChREBP) to induce glucose utilization and de novo lipogenesis. Here, we identify a termite orthologue of ChREBP and its downstream lipogenic targets, including acetyl-CoA carboxylase and fatty acid synthase. We show that all of these genes, including ChREBP, are upregulated in mature queens compared with kings, sterile workers and soldiers in eight different termite species. ChREBP is expressed in several tissues, including ovaries and fat bodies, and increases in expression in totipotent workers during their differentiation into neotenic mature queens. We further show that ChREBP is regulated by a carbohydrate diet in termite queens. Suppression of the lipogenic pathway by a pharmacological agent in queens elicits the same behavioural alterations in sterile workers as observed in queenless colonies, supporting that the ChREBP pathway partakes in the biosynthesis of semiochemicals that convey the signal of the presence of a fertile queen. Our results highlight ChREBP as a likely key factor for the regulation and signalling of queen fertility.
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Affiliation(s)
- David Sillam-Dussès
- Laboratoire d'Ethologie Expérimentale et Comparée, Université Paris 13, EA4443, 93430 Villetaneuse, France UMR IRD 242, UPEC, CNRS 7618, UPMC 113, INRA 1392, PARIS 7 113, Institut d'Ecologie et des Sciences de l'Environnement de Paris, 93140 Bondy, France Sorbonne Paris Cité, Paris, France Sorbonne Universités, Paris, France
| | - Robert Hanus
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, 16610 Prague, Czech Republic
| | - Michael Poulsen
- Centre for Social Evolution, Section for Ecology and Evolution, Department of Biology, University of Copenhagen, 2100 Copenhagen East, Denmark
| | - Virginie Roy
- UMR IRD 242, UPEC, CNRS 7618, UPMC 113, INRA 1392, PARIS 7 113, Institut d'Ecologie et des Sciences de l'Environnement de Paris, 93140 Bondy, France Sorbonne Paris Cité, Paris, France Sorbonne Universités, Paris, France
| | - Maryline Favier
- Institut National de la Santé et de la Recherche Médicale, Unité 1016, Institut Cochin, 75014 Paris, France
| | - Mireille Vasseur-Cognet
- UMR IRD 242, UPEC, CNRS 7618, UPMC 113, INRA 1392, PARIS 7 113, Institut d'Ecologie et des Sciences de l'Environnement de Paris, 93140 Bondy, France Sorbonne Paris Cité, Paris, France Sorbonne Universités, Paris, France Institut National de la Santé et de la Recherche Médicale, Unité 1016, Institut Cochin, 75014 Paris, France
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19
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Korb J. Genes Underlying Reproductive Division of Labor in Termites, with Comparisons to Social Hymenoptera. Front Ecol Evol 2016. [DOI: 10.3389/fevo.2016.00045] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
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20
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Toga K, Hanmoto S, Suzuki R, Watanabe D, Miura T, Maekawa K. Sexual difference in juvenile-hormone titer in workers leads to sex-biased soldier differentiation in termites. JOURNAL OF INSECT PHYSIOLOGY 2016; 87:63-70. [PMID: 26868724 DOI: 10.1016/j.jinsphys.2016.02.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Revised: 02/01/2016] [Accepted: 02/06/2016] [Indexed: 06/05/2023]
Abstract
In termites, the soldier caste, with its specialized defensive morphology, is one of the most important characteristics for sociality. Most of the basal termite species have both male and female soldiers, and the soldier sex ratio is almost equal or only slightly biased. However, in the apical lineages (especially family Termitidae), there are many species that have soldiers with strongly biased sex ratio. Generally in termites, since high juvenile hormone (JH) titer is required for soldier differentiation from a worker via a presoldier stage, it was hypothesized that the biased soldier-sex ratio was caused by differences in JH sensitivity and/or JH titer between male and female workers. Therefore, we focused on the presoldier differentiation and the worker JH titer in species with only male soldiers (Nasutitermes takasagoensis) and with both male and female soldiers (Reticulitermes speratus) in natural conditions. In the former species, there are four types of workers; male minor, male medium, female medium and female major workers, and presoldiers differentiate from male minor workers. First, we tried to artificially induce presoldiers from male and female workers. In N. takasagoensis, the presoldier differentiation rate and mortality was significantly higher in male minor workers. Morphological analyses showed that both male and female induced presoldiers possessed normal soldier-specific morphologies. It was suggested that female workers, from which soldiers do not differentiate under natural conditions, also maintained the physiological and developmental potential for soldier differentiation. In R. speratus, however, no differences were observed in solder differentiation rate and mortality between male and female workers. Second, the JH titers of each sex/type of workers were quantified by high performance liquid chromatography-mass spectrometry in two different seasons (April and December). The results showed that, in N. takasagoensis, JH titer in male minor workers was consistently higher than those in other worker types. In R. speratus, in contrast, there were no significant differences in JH titers between male and female workers. These results suggested that, in N. takasagoensis, male minor workers maintain JH titers at a high level throughout a year, and this may cause the male-biased presoldier differentiation.
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Affiliation(s)
- Kouhei Toga
- Graduate School of Science and Engineering, University of Toyama, Toyama, Japan; Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
| | - Shutaro Hanmoto
- Graduate School of Science and Engineering, University of Toyama, Toyama, Japan
| | - Ryutaro Suzuki
- Graduate School of Science and Engineering, University of Toyama, Toyama, Japan
| | - Dai Watanabe
- Graduate School of Environmental Science, Hokkaido University, Sapporo, Japan
| | - Toru Miura
- Graduate School of Environmental Science, Hokkaido University, Sapporo, Japan
| | - Kiyoto Maekawa
- Graduate School of Science and Engineering, University of Toyama, Toyama, Japan.
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21
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Su XH, Chen JL, Zhang XJ, Xue W, Liu H, Xing LX. Testicular development and modes of apoptosis during spermatogenesis in various castes of the termite Reticulitermes labralis (Isoptera:Rhinotermitidae). ARTHROPOD STRUCTURE & DEVELOPMENT 2015; 44:630-638. [PMID: 26344723 DOI: 10.1016/j.asd.2015.08.009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2015] [Revised: 08/13/2015] [Accepted: 08/25/2015] [Indexed: 06/05/2023]
Abstract
The separation of reproductive and non-reproductive roles based on caste differentiation is the most prominent characteristic of termites. However, little is known about the mechanism of male reproductive division that underlies caste differentiation. In the present study, testicular development and stage-specific apoptotic patterns were investigated and compared during spermatogenesis in reproductives, workers and soldiers of the termite Reticulitermes labralis. The results showed that male workers were divided into two types, the workers with spermatozoa (WS) and the workers without spermatozoa (WN). Spermatogenesis in WN and soldiers arrested at the spermatocyte stage. Moreover, there were significant differences in testicular size and spermatogenesis among the various castes. The mode of apoptosis in late instar WS was similar to the reproductives, as demonstrated by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling (TUNEL) analysis. First, the majority of apoptotic cells were spermatogonia, and the spermatogonia of both late instar WS and reproductives exhibited lower apoptotic rates compared with late instar WN and soldiers. Second, the spermatocytes and spermatids showed very little apoptosis in the late instar WS and reproductives, and no TUNEL signal was detected in any of the examined spermatozoa. Our findings suggest that the male workers undergo a basal developmental schema comprising two undifferentiated larval instars, followed by a bifurcated development into either (i) the sexual lineage, in which the workers are able to provide normal spermatozoa to queens, or (ii) the neuter lineage, in which the male workers lose reproductive options. The level of testicular development may explain the significant discrepancies in reproductive capacity among the reproductives, workers and soldiers and reveal the reproductive division in male workers. These differences are controlled by apoptosis during early spermatogenesis.
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Affiliation(s)
- Xiao Hong Su
- College of Life Sciences, Northwest University, Xi'an, China.
| | - Jiao Ling Chen
- College of Life Sciences, Northwest University, Xi'an, China
| | - Xiao Jing Zhang
- College of Life Sciences, Northwest University, Xi'an, China
| | - Wei Xue
- College of Life Sciences, Northwest University, Xi'an, China
| | - He Liu
- College of Life Sciences, Northwest University, Xi'an, China
| | - Lian Xi Xing
- College of Life Sciences, Northwest University, Xi'an, China
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22
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Su XH, Xue W, Liu H, Chen JL, Zhang XJ, Xing LX, Liu MH. The development of adultoid reproductives and brachypterous neotenic reproductives from the last instar nymphs in Reticulitermes labralis (Isoptera: Rhinotermitidae): a comparative study. JOURNAL OF INSECT SCIENCE (ONLINE) 2015; 15:147. [PMID: 26494776 PMCID: PMC4622179 DOI: 10.1093/jisesa/iev130] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/20/2015] [Accepted: 09/29/2015] [Indexed: 06/05/2023]
Abstract
Secondary reproductives develop primarily from nymphs. However, they have been rarely studied; in particular, the development of adultoid reproductives (AR) with floppy wings is still unclear. In this study, the change in juvenile hormone (JH) levels, vitellogenin gene expression, and oogenesis during the development of AR and brachypterous neotenic reproductives (BN) from the last instar nymphs of Reticulitermes labralis are investigated and compared. The results showed that the AR derived from the last instar nymphs by molting, and they were more similar to neotenic reproductives in morphology. In addition, the paired AR were not able to survive in the absence of workers. In R. labralis, the process of the last instar nymphs developing into AR and BN took an increase in JH level as a starting point. The JH level of the last instar nymphs molting into BN was approximately 1.5-fold higher than that of the AR. Additionally, The JHIII level of BN peaked on day 5, and that of AR peaked on day 10, which induced the onset of vitellogenesis in BN and AR, respectively. After molting, the vitellogenin gene expression levels of both BN and AR initially increased and then declined, and the expression levels in the BN were significantly higher than those in the AR. In addition, the oocytes of BN matured earlier than those of the AR, and the number of eggs laid by the BN was higher than the number laid by the AR. Our results demonstrate that, in R. labralis, the last instar nymphs can develop into AR, which are significantly different from BN in their development.
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Affiliation(s)
- Xiao Hong Su
- Biology Department, College of Life Sciences, Northwest University, Xi'an, China
| | - Wei Xue
- Biology Department, College of Life Sciences, Northwest University, Xi'an, China
| | - He Liu
- Biology Department, College of Life Sciences, Northwest University, Xi'an, China
| | - Jiao Ling Chen
- Biology Department, College of Life Sciences, Northwest University, Xi'an, China
| | - Xiao Jing Zhang
- Biology Department, College of Life Sciences, Northwest University, Xi'an, China
| | - Lian Xi Xing
- Biology Department, College of Life Sciences, Northwest University, Xi'an, China
| | - Ming Hua Liu
- Biology Department, College of Life Sciences, Northwest University, Xi'an, China
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23
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Saiki R, Gotoh H, Toga K, Miura T, Maekawa K. High juvenile hormone titre and abdominal activation of JH signalling may induce reproduction of termite neotenics. INSECT MOLECULAR BIOLOGY 2015; 24:432-441. [PMID: 25847681 DOI: 10.1111/imb.12169] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Revised: 01/30/2015] [Accepted: 02/03/2015] [Indexed: 06/04/2023]
Abstract
Termite castes are a key example of polyphenism, in which reproductive division of labour is clearly seen in colonies. The reproductive castes in termites include primary and neotenic reproductives; primary reproductives found a new colony whereas neotenics succeed them in the reproductive role when the primary reproductives die or become senescent. Neotenics usually differentiate from nymphs or workers by developing functional gonads while retaining juvenile characteristics; however, the developmental mechanism during neotenic differentiation remains poorly understood. Juvenile hormone (JH) mediates a number of aspects of developmental regulation in caste differentiation in termites. In the present study we quantified JH titres in neotenic reproductives of Reticulitermes speratus, and compared these with other developmental stages. In addition, expression changes in JH signalling gene homologues (Methoprene-tolerant [Met], Krüppel-homolog1, Broad-Complex) in the head, thorax and abdomen were investigated during neotenic differentiation. Finally, we examined the function of Met in reproduction of neotenics by RNA interference (RNAi). Our results showed that the JH titres of neotenics were significantly higher than those of nymphs and workers. JH signalling genes were highly expressed in neotenic abdomens, compared with those in workers and nymphs. Met RNAi resulted in the inhibition of vitellogenin gene expression in newly moulted neotenics. These results suggest that the fertility of neotenics might be controlled by a large increase of JH titres and body-part-specific activation of JH signalling pathways.
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Affiliation(s)
- R Saiki
- Department of Biology, Graduate School of Science and Engineering, University of Toyama, Toyama, 930-8555, 3190, Gofuku, Japan
| | - H Gotoh
- Department of Entomology, Washington State University, Pullman, WA, 99164, USA
- Laboratory of Ecological Genetics, Graduate School of Environmental Science, Hokkaido University, Sapporo, Hokkaido, 060-0810, Japan
- Laboratory of Sericulture and Entomoresources, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Aichi, 466-8550, Japan
| | - K Toga
- Department of Biology, Graduate School of Science and Engineering, University of Toyama, Toyama, 930-8555, 3190, Gofuku, Japan
- Laboratory of Sericulture and Entomoresources, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Aichi, 466-8550, Japan
| | - T Miura
- Laboratory of Ecological Genetics, Graduate School of Environmental Science, Hokkaido University, Sapporo, Hokkaido, 060-0810, Japan
| | - K Maekawa
- Department of Biology, Graduate School of Science and Engineering, University of Toyama, Toyama, 930-8555, 3190, Gofuku, Japan
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24
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Chouvenc T, Basille M, Li HF, Su NY. Developmental instability in incipient colonies of social insects. PLoS One 2014; 9:e113949. [PMID: 25423502 PMCID: PMC4244189 DOI: 10.1371/journal.pone.0113949] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Accepted: 11/03/2014] [Indexed: 12/02/2022] Open
Abstract
Social insect colonies can provide homeostatic conditions that buffer the incidence of environmental fluctuations on individuals, which have contributed to their ecological success. Coptotermes (Isoptera: Rhinotermitidae) is a highly invasive termite genus and several species have important economic impact in many areas of the world. Mature Coptotermes colonies with millions of individuals can provide optimal environmental condition and nurturing capacity for the developing brood. However, it was previously suggested that contrary to mature colonies, incipient colonies may be exposed to critical stress, which may explain for the low success rate of establishment within the first year of the life of a termite colony. We here investigated the stress imposed on individuals of incipient colonies by comparing the developmental instability of individuals between incipient and mature colonies of two Coptotermes species, C. formosanus Shiraki and C. gestroi (Wasmann). We assessed the developmental instability by measuring the asymmetry of morphological traits from the head capsule of the soldier caste. Soldiers from incipient colonies of both species displayed strong asymmetrical traits in comparison to soldiers from mature colonies. We suggest that homeostatic conditions for optimal development are reached as the colony matures, and confirmed that the incipient colony remains a critical bottleneck where individuals are exposed to high developmental stress.
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Affiliation(s)
- Thomas Chouvenc
- Department of Entomology and Nematology, Fort Lauderdale Research and Education Center, University of Florida, Institute of Food and Agricultural Sciences, Fort Lauderdale, Florida, United States of America
| | - Mathieu Basille
- Department of Wildlife Ecology and Conservation, Fort Lauderdale Research and Education Center, University of Florida, Institute of Food and Agricultural Sciences, Fort Lauderdale, Florida, United States of America
| | - Hou-Feng Li
- Entomology Department, National Chung Hsing University, Taichung City, Taiwan
| | - Nan-Yao Su
- Department of Entomology and Nematology, Fort Lauderdale Research and Education Center, University of Florida, Institute of Food and Agricultural Sciences, Fort Lauderdale, Florida, United States of America
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25
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Saiki R, Yaguchi H, Hashimoto Y, Kawamura S, Maekawa K. Reproductive Soldier-like Individuals Induced by Juvenile Hormone Analog Treatment in Zootermopsis nevadensis (Isoptera, Archotermopsidae). Zoolog Sci 2014; 31:573-81. [PMID: 25186928 DOI: 10.2108/zs140083] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Eusocial insects have highly sophisticated societies, showing a conspicuous division of labor associated with different phenotypes. These castes show specific morphologies adapted to discrete tasks. Termite castes are divided into reproductives, workers, and soldiers. Individuals with soldier-like heads as well as developed gonads have been recorded in several primitive families, and are called reproductive soldiers. In some termite species, however, a trade-off-like developmental relationship has been shown between soldier and imaginal characteristics. Thus, while the mechanism that regulates the development of both characteristics in the same individual is interesting, the details are still unclear. We focused on juvenile hormone (JH), which is involved not only in termite caste differentiation, but also in the gonad development of many insects, and we aimed to clarify the effects of JH on the differentiation of reproductive soldiers in Zootermopsis nevadensis. We succeeded in the induction of individuals with reproductive soldier-like gross morphologies by JH analog (JHA) application to several developmental stages. We also observed that gonad development was significantly promoted by JHA application after molts in the induced reproductive soldier-like individuals, but not in natural soldiers. Finally, we confirmed that the gene expression level of vitellogenin was extremely high in the induced reproductive soldier-like individuals following JHA treatment after the molt. These results suggested that soldiers do not have regulatory mechanisms for gonad development involving JH, and the regulation of reproductive soldiers development is different from that of soldiers. Reproductive soldiers may have evolved independently from the soldier caste rather than from an intermediate stage of soldier evolution.
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Affiliation(s)
- Ryota Saiki
- Graduate School of Science and Engineering, University of Toyama, 3190 Gofuku, Toyama 930-8555, Japan
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26
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Hoffmann K, Gowin J, Hartfelder K, Korb J. The scent of royalty: a p450 gene signals reproductive status in a social insect. Mol Biol Evol 2014; 31:2689-96. [PMID: 25053804 DOI: 10.1093/molbev/msu214] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Cooperation requires communication; this applies to animals and humans alike. The main communication means differ between taxa and social insects (ants, termites, and some bees and wasps) lack the cognitive abilities of most social vertebrates. Central to the regulation of the reproductive harmony in insect societies is the production of a royalty scent which signals the fertility status of the reproducing queen to the nonreproducing workers. Here, we revealed a central genetic component underlying this hallmark of insect societies in the termite Cryptotermes secundus. Communication between queens and workers relied upon the expression of a gene, Neofem4, which belongs to the cytochrome P450 genes. We inhibited Neofem4 in queens by RNA interference. This resulted in the loss of the royalty scent in queens and the workers behaved as though the queen were absent. The queen's behavior was not generally affected by silencing Neofem4. This suggests that the lack of the royalty scent lead to workers not recognizing her anymore as queen. P450 genes are known to be involved in the production of chemical signals in cockroaches and their expression has been linked to a major fertility regulator, juvenile hormone. This makes P450 genes, both a suitable and available evolutionary substrate in the face of natural selection for production of a queen substance. Our data suggest that in an organism without elaborate cognitive abilities communication has been achieved by the exploitation of a central gene that links the fertility network with the chemical communication pathway. As termites and social Hymenoptera seem to share the same class of compounds in signaling fertility, this role of P450 genes might be more widespread across social insects.
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Affiliation(s)
| | - Johannes Gowin
- Behavioral Biology, University of Osnabrueck, Osnabrueck, Germany Evolutionary Biology & Ecology, University of Freiburg, Freiburg, Germany
| | - Klaus Hartfelder
- Departamento de Biologia Celular e Molecular e Bioagentes Patogênicos, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brazil
| | - Judith Korb
- Behavioral Biology, University of Osnabrueck, Osnabrueck, Germany Evolutionary Biology & Ecology, University of Freiburg, Freiburg, Germany
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27
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Watanabe D, Gotoh H, Miura T, Maekawa K. Social interactions affecting caste development through physiological actions in termites. Front Physiol 2014; 5:127. [PMID: 24782780 PMCID: PMC3988372 DOI: 10.3389/fphys.2014.00127] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2013] [Accepted: 03/14/2014] [Indexed: 11/13/2022] Open
Abstract
A colony of social insects is not only an aggregation of individuals but also a functional unit. To achieve adaptive social behavior in fluctuating environmental conditions, in addition to coordination of physiological status in each individual, the whole colony is coordinated by interactions among colony members. The study on the regulation of social-insect colonies is termed "social physiology." Termites, a major group of social insects, exhibit many interesting phenomena related to social physiology, such as mechanisms of caste regulation in a colony. In their colonies, there are different types of individuals, i.e., castes, which show distinctive phenotypes specialized in specific colony tasks. Termite castes comprise reproductives, soldiers and workers, and the caste composition can be altered depending on circumstances. For the regulation of caste compositions, interactions among individuals, i.e., social interactions, are thought to be important. In this article, we review previous studies on the adaptive meanings and those on the proximate mechanisms of the caste regulation in termites, and try to understand those comprehensively in terms of social physiology. Firstly, we summarize classical studies on the social interactions. Secondly, previous studies on the pheromone substances that mediate the caste regulatory mechanisms are overviewed. Then, we discuss the roles of a physiological factor, juvenile hormone (JH) in the regulation of caste differentiation. Finally, we introduce the achievements of molecular studies on the animal sociality (i.e., sociogenomics) in terms of social physiology. By comparing the proximate mechanisms of social physiology in termites with those in hymenopterans, we try to get insights into the general principles of social physiology in social animals.
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Affiliation(s)
- Dai Watanabe
- Laboratory of Ecological Genetics, Graduate School of Environmental Science, Hokkaido UniversitySapporo, Hokkaido, Japan
- Department of Biology, Graduate School of Science and Engineering, University of ToyamaToyama, Japan
| | - Hiroki Gotoh
- Laboratory of Ecological Genetics, Graduate School of Environmental Science, Hokkaido UniversitySapporo, Hokkaido, Japan
- Department of Entomology, Washington State UniversityPullman, WA, USA
| | - Toru Miura
- Laboratory of Ecological Genetics, Graduate School of Environmental Science, Hokkaido UniversitySapporo, Hokkaido, Japan
| | - Kiyoto Maekawa
- Department of Biology, Graduate School of Science and Engineering, University of ToyamaToyama, Japan
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Amsalem E, Malka O, Grozinger C, Hefetz A. Exploring the role of juvenile hormone and vitellogenin in reproduction and social behavior in bumble bees. BMC Evol Biol 2014; 14:45. [PMID: 24618396 PMCID: PMC4007805 DOI: 10.1186/1471-2148-14-45] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2013] [Accepted: 02/21/2014] [Indexed: 12/12/2022] Open
Abstract
Background The genetic and physiological pathways regulating behavior in solitary species are hypothesized to have been co-opted to regulate social behavior in social species. One classic example is the interaction between vitellogenin (an egg-yolk and storage protein) and juvenile hormone, which are positively correlated in most insect species but have modified interactions in highly eusocial insects. In some of these species (including some termites, ants, and the honey bee), juvenile hormone and vitellogenin levels are negatively correlated and juvenile hormone has shifted its role from a gonadotropin to a regulator of maturation and division of labor in the primarily sterile workers. The function of vitellogenin also seems to have broadened to encompass similar roles. Thus, the functions and molecular interactions of juvenile hormone and vitellogenin are hypothesized to have undergone changes during the evolution of eusociality, but the mechanisms underlying these changes are unknown. Bumble bees offer an excellent model system for testing how the relationship between juvenile hormone and vitellogenin evolved from solitary to social species. Bumble bee colonies are primitively eusocial and comprised of a single reproductive queen and facultatively sterile workers. In Bombus terrestris, juvenile hormone retains its ancestral role as a gonadotropin and is also hypothesized to regulate aggressive behavior. However, the function of vitellogenin and its interactions with juvenile hormone have not yet been characterized. Results By characterizing vitellogenin RNA expression levels (vg) in B. terrestris we show that vg is not associated with task and only partially associated with worker age, queen presence, and caste (queen vs worker). The correlations of vg with ovarian activation were not consistent across experiments, but both vg and ovarian activation were significantly associated with levels of aggression experienced by workers. Treatment with juvenile hormone did not affect vg levels in queenless groups. Conclusions We suggest that social interactions affect vg levels more strongly than a worker’s reproductive physiological state, and that juvenile hormone and vg are uncoupled in this species. Thus, although juvenile hormone maintains its traditional role as gonadotropin in B. terrestris, vg has already been co-opted into a novel role, consistent with the model that Bombus represents an intermediate stage in the evolution of eusociality.
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Affiliation(s)
- Etya Amsalem
- Department of Entomology, Center for Pollinator Research, Center for Chemical Ecology, The Pennsylvania State University, University Park, PA 16802, USA.
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Cornette R, Hayashi Y, Koshikawa S, Miura T. Differential gene expression in response to juvenile hormone analog treatment in the damp-wood termite Hodotermopsis sjostedti (Isoptera, Archotermopsidae). JOURNAL OF INSECT PHYSIOLOGY 2013; 59:509-518. [PMID: 23481672 DOI: 10.1016/j.jinsphys.2013.02.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2012] [Revised: 01/29/2013] [Accepted: 02/07/2013] [Indexed: 06/01/2023]
Abstract
Termite societies are characterized by a highly organized division of labor among conspicuous castes, groups of individuals with various morphological specializations. Termite caste differentiation is under control of juvenile hormone (JH), but the molecular mechanism underlying the response to JH and early events triggering caste differentiation are still poorly understood. In order to profile candidate gene expression during early soldier caste differentiation of the damp-wood termite, Hodotermopsis sjostedti, we treated pseudergates (workers) with a juvenile hormone analog (JHA) to induce soldier caste differentiation. We then used Suppressive Subtractive Hybridization to create two cDNA libraries enriched for transcripts that were either up- or downregulated at 24h after treatment. Finally, we used quantitative PCR to confirm temporal expression patterns. Hexamerins represent a large proportion of the genes upregulated following JHA treatment and have an expression pattern that shows roughly an inverse correlation to intrinsic JH titers. This data is consistent with the role of a JH "sink", which was demonstrated for hexamerins in another termite, Reticulitermes flavipes. A putative nuclear protein was also upregulated a few hours after JHA treatment, which suggests a role in the early response to JH and subsequent regulation of transcriptional events associated with soldier caste differentiation. Some digestive enzymes, such as endogenous beta-endoglucanase and chymotrypsin, as well as a protein associated to digestion were identified among genes downregulated after JHA treatment. This suggests that JH may directly influence the pseudergate-specific digestive system.
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Affiliation(s)
- Richard Cornette
- Laboratory of Ecological Genetics, Graduate School of Environmental Science, Hokkaido University, Sapporo, Hokkaido 060-0810, Japan
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Toga K, Hojo M, Miura T, Maekawa K. Expression and function of a limb-patterning gene Distal-less in the soldier-specific morphogenesis in the nasute termite Nasutitermes takasagoensis. Evol Dev 2013; 14:286-95. [PMID: 23017076 DOI: 10.1111/j.1525-142x.2012.00545.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
One of the major foci in evolutionary developmental biology is to understand developmental mechanisms that underlie the acquisition of morphological novelties. Termite soldiers, the highly specialized defensive caste, show exaggerated species-specific morphologies, mostly enlarged mandibles. Soldiers of the subfamily Nasutitermitinae (Termitidae), however, possess a novel structure for defense in their heads, that is a horn-like frontal projection (nasus) from which defensive chemicals are discharged. Just prior to the molt into presoldiers (the preceding stage to soldiers) from workers, a nasus disc, or a nasus primordium, is observed under the worker head cuticle. In order to understand the developmental underpinnings of this evolutionarily novel structure, the role of a homeobox gene Distal-less (Dll) during nasus development was examined in this study, using a nasute termite Nasutitermes takasagoensis. Histological observations showed that complex developmental processes comprising epidermal evagination and invagination through changes in cell shape and cell proliferation formed the projection and the gland. Immunohistochemistry showed that Dll was localized in the developing nasus disc, but not in the frontal-gland primordium. Consistent with this finding, Dll RNA interference only repressed nasus growth not the frontal-gland formation. Taken together, the co-option of Dll is suggested to contribute to the acquisition of a novel defensive structure in a termite lineage, coupled with the acquisition of adaptive defensive behaviors.
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Affiliation(s)
- Kouhei Toga
- Graduate School of Science and Engineering, University of Toyama, Toyama, 930-8555, Japan
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Tarver MR, Coy MR, Scharf ME. Cyp15F1: a novel cytochrome P450 gene linked to juvenile hormone-dependent caste differention in the termite Reticulitermes flavipes. ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY 2012; 80:92-108. [PMID: 22550027 DOI: 10.1002/arch.21030] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Termites are eusocial insects that jointly utilize juvenile hormone (JH), pheromones, and other semiochemicals to regulate caste differentiation and achieve caste homeostasis. Prior EST sequencing from the symbiont-free gut transcriptome of Reticulitermes flavipes unexpectedly revealed a number of unique cytochrome P450 (Cyp) transcripts, including fragments of a Cyp15 family gene (Cyp15F1) with homology to other insect Cyp15s that participate in JH biosynthesis. The present study investigated the role of Cyp15F1 in termite caste polyphenism and specifically tested the hypothesis that it plays a role in JH-dependent caste differentiation. After assembling the full-length Cyp15F1 cDNA sequence, we (i) determined its mRNA tissue expression profile, (ii) investigated mRNA expression changes in response to JH and the caste-regulatory primer pheromones γ-cadinene (CAD) and γ-cadinenal (ALD), and (iii) used RNA interference (RNAi) in combination with caste differentiation bioassays to investigate gene function at the phenotype level. Cyp15F1 has ubiquitous whole-body expression (including gut tissue); is rapidly and sustainably induced from 3 h to 48 h by JH, CAD, and ALD; and functions at least in part by facilitating JH-dependent soldier caste differentiation. These findings provide the second example of a termite caste regulatory gene identified through the use of RNAi, and significantly build upon our understanding of termite caste homeostatic mechanisms. These results also reinforce the concept of environmental caste determination in termites by revealing how primer pheromones, as socioenvironmental factors, can directly influence Cyp15 expression and caste differentiation.
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Affiliation(s)
- Matthew R Tarver
- Entomology and Nematology Department, University of Florida, Gainesville, Florida, USA
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Korb J, Hoffmann K, Hartfelder K. Molting dynamics and juvenile hormone titer profiles in the nymphal stages of a lower termite, Cryptotermes secundus (Kalotermitidae)--signatures of developmental plasticity. JOURNAL OF INSECT PHYSIOLOGY 2012; 58:376-383. [PMID: 22245373 DOI: 10.1016/j.jinsphys.2011.12.016] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2011] [Revised: 12/17/2011] [Accepted: 12/21/2011] [Indexed: 05/31/2023]
Abstract
Termites are social cockroaches and this sociality is founded on a high plasticity during development. Three molting types (progressive, stationary and regressive molts) are fundamental to achieve plasticity during alate/sexual development, and they make termites a major challenge to any model on endocrine regulation in insect development. As the endocrine signatures underpinning this plasticity are barely understood, we studied the developmental dynamics and their underlying juvenile hormone (JH) titers in a wood-dwelling termite, Cryptotermes secundus, which is characterized by an ancestral life style of living in dead wood and individuals being totipotent in development. The following general pattern elements could be identified during winged sexual development (i) regressive molts were accompanied by longer intermolt periods than other molting types, (ii) JH titers decreased gradually during the developmental transition from larva (immatures without wing buds), to nymph (immatures with wing buds), to winged adult, (iii) in all nymphal stages, the JH titer rose before the next molt and dropped thereafter within the first week, (iv) considerable variation in JH titers occurred in the midphase of the molting cycle of the 2nd and 3rd nymphal instar, inferring that this variation may reflect the underlying endocrine signature of each of the three molting types, (v) the 4th nymphal instar, the shortest of all, seems to be a switch point in development, as nymphs in this stage mainly developed progressively. When comparing these patterns with endocrine signatures seen in cockroaches, the developmental program of Cryptotermes can be interpreted as a co-option and repetitive use of hormonal dynamics of the post dorsal-closure phase of cockroach embryonic development.
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Affiliation(s)
- Judith Korb
- Biologie I, Universität Regensburg, Germany.
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Leniaud L, Darrouzet E, Dedeine F, Ahn K, Huang Z, Bagnères AG. Ontogenic potentialities of the worker caste in two sympatric subterranean termites in France. Evol Dev 2011; 13:138-48. [PMID: 21410870 DOI: 10.1111/j.1525-142x.2011.00464.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In termites, the capacity of workers to differentiate into neotenic reproductives is an important characteristic that deserves particular attention. To gain insight into the differentiation pathway, the potentialities of workers and the endocrinal changes during the formation of neotenics were compared in two sympatric termites, Reticulitermes flavipes and Reticulitermes grassei. After 1 year of development, 100% of R. flavipes worker groups produced neotenics against only 63% of R. grassei groups. The average production of female neotenics was significantly higher in R. flavipes worker groups compared with R. grassei groups and R. flavipes produced a greater proportion of female neotenics. Moreover, R. flavipes produced more offspring, not only because there were more females, but also because R. flavipes females were more productive. Moreover, the offspring produced by R. flavipes grew faster than the offspring of R. grassei. Both ecdysteroid and juvenile hormone (JH) titers varied significantly during the development of neotenics. The two species showed similar ecdysteroid titer variation patterns. However, the JH titer variation patterns strongly differed: in R. grassei, the concentration of JH increased in maturing neotenics then dropped in mature neotenics, whereas in R. flavipes, the level of JH was significantly higher than in R. grassei and remained constantly high in mature neotenics. Overall, these results suggest that these two species differ strongly in many life-history traits as well as in the physiological control of their caste differentiation system. Possible origins and mechanisms of such interspecific variations are discussed, as well as their evolutionary and ecological consequences.
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Affiliation(s)
- Laurianne Leniaud
- CNRS UMR 6035, Faculté des Sciences et Techniques, Université François Rabelais, Parc Grandmont, Tours, France
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Neoh KB, Lee CY. Developmental stages and caste composition of a mature and incipient colony of the drywood termite, Cryptotermes dudleyi (Isoptera: Kalotermitidae). JOURNAL OF ECONOMIC ENTOMOLOGY 2011; 104:622-628. [PMID: 21510214 DOI: 10.1603/ec10346] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The caste composition and sex ratio in a mature and an incipient colony of Cryptotermes dudleyi Banks (Isoptera: Kalotermitidae) was studied. Biometric descriptors of both immature and sexual castes were developed. Morphometric analysis revealed that there are four larval instars, a pseudergate, and three nymphal instars in the development of C. dudleyi. To differentiate between the fourth larval instars and the pseudergate, pronotal width and tibial length must be taken into account, because the head width overlaps between the two groups. The number of antennal segments increases in parallel with instar development. The mature colony was headed by a pair of physogastric nymphoid neotenics; the colony also contained multiple pairs of nonphysogastric de-alates and wing-torn alates. The majority of eggs and larvae were confined to galleries that connected to locations where nymphoid neotenics were found, whereas in general only pseudergates and nymphs were found together with de-alates and wing-torn alates. In contrast, the incipient colony contained only a pair of primary reproductives. Nymphs formed a major group in both mature and incipient colonies, as did pseudergates. The sex ratio of the mature colony was slightly but significantly biased in favor of females, whereas it was skewed toward males in the incipient colony. The data also suggested that the soldier caste was female skewed.
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Affiliation(s)
- Kok-Boon Neoh
- Urban Entomology Laboratory, Vector Control Research Unit, School of Biological Sciences, Universiti Sains Malaysia, 11800 Penang, Malaysia
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Chan KK, Abel DS, Stay B. Fine structure of corpora allata of castes with different rates of juvenile hormone production in the termite Reticulitermes flavipes. ARTHROPOD STRUCTURE & DEVELOPMENT 2011; 40:26-38. [PMID: 20849977 DOI: 10.1016/j.asd.2010.09.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2010] [Accepted: 09/03/2010] [Indexed: 05/29/2023]
Abstract
The aim of this work is to describe corpora allata (CA) of several castes of the termite Reticulitermes flavipes that have different rates of juvenile hormone (JH) synthesis, with respect to differences in fine structure, volume, and intensity of allatostatin immunoreactivity in their innervation. The castes chosen are workers and their potential derivatives, apterous secondary reproductives and pre-soldiers (the precursors of soldiers). These castes, at the stages chosen, produce JH at low, high and intermediate rates respectively. Hormone production is positively correlated with volume and negatively correlated with intensity of allatostatin immunoreactivity in axons within the glands. Characteristics of fine structure that correlate with increased activity are increase in abundance and width of mitochondria, decrease in ability to fix and visualize smooth endoplasmic reticulum. These features have previously been described for CA of cockroaches and other insects. Glycogen in the CA of all of the castes studied, especially the large amounts in highly active glands of physogastric apterous reproductive females, is the most striking difference between the CA cells of R. flavipes and previously described CA of cockroaches, in which glycogen is absent throughout the reproductive cycles. This suggests that glycogen is an important source of energy for hormone production by termite CA.
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Affiliation(s)
- Kuen K Chan
- Department of Biology, University of Iowa, Iowa City, IA 52242, USA
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36
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Tarver MR, Zhou X, Scharf ME. Socio-environmental and endocrine influences on developmental and caste-regulatory gene expression in the eusocial termite Reticulitermes flavipes. BMC Mol Biol 2010; 11:28. [PMID: 20416061 PMCID: PMC2873311 DOI: 10.1186/1471-2199-11-28] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2009] [Accepted: 04/23/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Strict regulation of caste differentiation, at the molecular level, is thought to be important to maintain social structure in insect societies. Previously, a number of extrinsic and intrinsic factors have been shown to influence caste composition in termite colonies. One important factor is the influence of nestmates; in particular, soldier termites are known to inhibit hormone-dependent worker-to-soldier differentiation. However, soldier influences on nestmates at the molecular level are virtually unknown. Here, to test the hypothesis that soldiers can influence nestmate gene expression, we investigated the impact of four treatments on whole-body gene expression in totipotent Reticulitermes flavipes workers: (i) juvenile hormone III (JHIII; a morphogenetic hormone), (ii) soldier head extracts (SHE), (iii) JHIII+SHE, and (iv) live soldiers. RESULTS Using quantitative-real-time PCR we determined the expression patterns of 49 previously identified candidate genes in response to the four treatments at assay days 1, 5, and 10. Thirty-eight total genes from three categories (chemical production/degradation, hemolymph protein, and developmental) showed significant differential expression among treatments. Most importantly, SHE and live soldier treatments had a significant impact on a number of genes from families known to play roles in insect development, supporting previous findings and hypotheses that soldiers regulate nestmate caste differentiation via terpene primer pheromones contained in their heads. CONCLUSIONS This research provides new insights into the impacts that socio-environmental factors (JH, soldiers, primer pheromones) can have on termite gene expression and caste differentiation, and reveals a number of socially-relevant genes for investigation in subsequent caste differentiation research.
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Affiliation(s)
- Matthew R Tarver
- Department of Entomology and Nematology, University of Florida, Gainesville, FL, USA
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Wheeler MM, Tarver MR, Coy MR, Scharf ME. Characterization of four esterase genes and esterase activity from the gut of the termite Reticulitermes flavipes. ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY 2010; 73:30-48. [PMID: 19802899 DOI: 10.1002/arch.20333] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Four esterase genes and general esterase activity were investigated in the gut of the termite Reticulitermes flavipes. Two genes (RfEst1 and RfEst2) share significant translated identity with a number of insect JH esterases. The two remaining genes (RfEst3 and RfEst4) apparently code for much shorter proteins with similarity to fungal phenolic acid esterases involved in hemicellulose solubilization. All four genes showed consistently high midgut expression. This result was further supported by colorimetric activity assays and Native polyacrylamide gel electrophoresis, which showed significant esterase activity and a number of isoforms in the midgut. The greatest esterase activity and isoform composition were detected when alpha-naphthyl propionate was used as a substrate. Moreover, esterase activity and diverse isoforms were present in gut mitochondrial, microsomal, and cytosolic sub-cellular protein fractions, as well as in the hindgut lumen. These findings reveal an agreement between gut esterase gene expression and activity distributions, and support the idea that R. flavipes gut esterase activity is host (not symbiont)-derived. In addition, these findings support the hypotheses that termite gut esterases may play important roles in lignocellulose digestion and caste differentiation. This study provides important baseline data that will assist ongoing functional-genomic efforts to identify novel genes with roles in semiochemical, hormone, and lignocellulose processing in the termite gut.
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Affiliation(s)
- Marsha M Wheeler
- Entomology and Nematology Department, University of Florida, Gainesville, FL 32611-0620, USA
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Nalepa CA. Altricial development in subsocial cockroach ancestors: foundation for the evolution of phenotypic plasticity in termites. Evol Dev 2010; 12:95-105. [DOI: 10.1111/j.1525-142x.2009.00394.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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