担当区分：筆頭著者,　責任著者   掲載種別：研究論文（学術雑誌）   出版者・発行元：Frontiers Media {SA}  

<jats:p>Termite colonies, composed of large numbers of siblings, develop an important caste-based division of labor; individuals in these societies interact via intra- or intercaste chemical communications. For more than 50 years, termites have been known to use a variety of pheromones to perform tasks necessary for maintenance of their societies, similar to eusocial hymenopterans. Although trail-following pheromones have been chemically identified in various termites, other types of pheromones have not been elucidated chemically or functionally. In the past decade, however, chemical compositions and biological functions have been successfully identified for several types of termite pheromones; accordingly, the details of the underlying pheromone communications have been gradually revealed. In this review, we summarize both the functions of all termite pheromones identified so far and the chemical interactions among termites and other organisms. Subsequently, we argue how termites developed their sophisticated pheromone communication. We hypothesize that termites have diverted defensive and antimicrobial substances to pheromones associated in caste recognition and caste-specific roles. Furthermore, termites have repeatedly used a pre-existing pheromone or have added supplementary compounds to it in accordance with the social context, leading to multifunctionalization of pre-existing pheromones and emergence of new pheromones. These two mechanisms may enable termites to transmit various context-dependent information with a small number of chemicals, thus resulting in formation of coordinated, complex, and rational chemical communication systems.</jats:p>

DOI： 10.3389/fevo.2020.595614

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1007/s10886-020-01182-6

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担当区分：筆頭著者,　責任著者   掲載種別：研究論文（学術雑誌）   出版者・発行元：Springer Science and Business Media {LLC}  

Social behaviours in termites are regulated by sophisticated chemical communication systems. The majority of subterranean termites continuously forage for new wood resources to expand their nesting areas; an aggregation pheromone is presumed to regulate this process. However, the chemical components of this pheromone have never been determined. We identified the chemical properties of the aggregation pheromone that signals nestmate presence and induces arrest in the termite Reticulitermes speratus. The results of gas chromatography-mass spectrometry analyses and bioassays indicated that R. speratus worker release the pheromone to their nesting site. The pheromone consists of an aromatic compound (2-phenylundecane), cuticular hydrocarbons (pentacosane and heptacosane), fatty acids (palmitic acid and trans-vaccenic acid), and cholesterol; the pheromone induces long-term aggregation at new nesting and feeding sites. Although 2-phenylundecane alone attracted workers, the combination of all six compounds showed greater arrestant activity than 2-phenylundecane alone. This suggests that 2-phenylundecane functions as an attractant, whereas the remaining five components function as arrestants. Our results indicate that foraging worker termites produce a multi-component aggregation pheromone by combining a volatile hydrocarbon and non-volatile lipids with cuticular hydrocarbons. This pheromone enables rapid, long-lasting aggregation of termite workers, which contributes to efficient feeding and colonisation of new wood. Our work furthers the understanding of chemical communication systems underlying social assembly in social insects.

DOI： 10.1038/s41598-020-64388-4

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担当区分：筆頭著者   掲載種別：研究論文（学術雑誌）   出版者・発行元：Elsevier {BV}  

DOI： 10.1016/j.isci.2019.06.041

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担当区分：筆頭著者   掲載種別：研究論文（学術雑誌）   出版者・発行元：Impact Journals, {LLC}  

DOI： 10.18632/aging.101578

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担当区分：筆頭著者,　責任著者   掲載種別：研究論文（学術雑誌）   出版者・発行元：Springer Nature America, Inc  

DOI： 10.1007/s13355-018-0589-1

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その他リンク： http://link.springer.com/content/pdf/10.1007/s13355-018-0589-1.pdf

担当区分：筆頭著者,　責任著者   掲載種別：研究論文（学術雑誌）   出版者・発行元：Wiley  

DOI： 10.1111/1744-7917.12640

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掲載種別：研究論文（学術雑誌）   出版者・発行元：University of Chicago Press  

DOI： 10.1086/697238

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掲載種別：研究論文（学術雑誌）   出版者・発行元：The Royal Society  

DOI： 10.1098/rsbl.2018.0025

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Springer Nature  

DOI： 10.1007/s13355-018-0545-0

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その他リンク： http://link.springer.com/content/pdf/10.1007/s13355-018-0545-0.pdf

担当区分：筆頭著者,　責任著者   掲載種別：研究論文（学術雑誌）   出版者・発行元：The Royal Society  

Division of labour in eusocial insects is characterized by efficient communication systems based on pheromones. Among such insects, termites have evolved specialized sterile defenders, called soldiers. Because they are incapable of feeding themselves, it has been suggested that soldiers are sustained by workers and emit the pheromone arresting workers. However, such a soldier pheromone has not been identified in any termite species, and the details of the soldier–worker interaction remain to be explored. Here, we identified a soldier-specific volatile sesquiterpene as a worker arrestant, which also acts as a primer pheromone regulating soldier differentiation and fungistatic agent in a termite
<italic>Reticulitermes speratus</italic>
. Chemical analyses revealed that (−)-
<italic>β</italic>
-elemene is the major component of soldier extract, and its authentic standard exhibited arrestant activity to workers and inhibited the differentiation from workers to soldiers. This compound also showed fungistatic activity against entomopathogenic fungi. These suggest that (−)-
<italic>β</italic>
-elemene secreted by soldiers acts not only as a worker arrestant but also as one component of inhibitory primer pheromone and an anti-pathogenic agent. Our study provides novel evidence supporting the multi-functionality of termite soldier pheromone and provides new insights into the role of soldiers and the evolutionary mechanisms of pheromone compounds.

DOI： 10.1098/rspb.2017.1134

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その他リンク： https://royalsocietypublishing.org/doi/full-xml/10.1098/rspb.2017.1134

担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Public Library of Science  

Insects protect themselves from microbial infections through innate immune responses, including pathogen recognition, phagocytosis, the activation of proteolytic cascades, and the synthesis of antimicrobial peptides. Termites, eusocial insects inhabiting microbe-rich wood, live in closely-related family groups that are susceptible to shared pathogen infections. To resist pathogenic infection, termite families have evolved diverse immune adaptations at both individual and societal levels, and a strategy of trade-offs between reproduction and immunity has been suggested. Although termite immune-inducible genes have been identified, few studies have investigated the differential expression of these genes between reproductive and neuter castes, and between sexes in each caste. In this study, we compared the expression levels of immune-related genes among castes, sexes, and ages in a Japanese subterranean termite, Reticulitermes speratus. Using RNA-seq, we found 197 immune-related genes, including 40 pattern recognition proteins, 97 signalling proteins, 60 effectors. Among these genes, 174 showed differential expression among castes. Comparing expression levels between males and females in each caste, we found sexually dimorphic expression of immune-related genes not only in reproductive castes, but also in neuter castes. Moreover, we identified age-related differential expression of 162 genes in male and/or female reproductives. In addition, although R. speratus is known to use the antibacterial peptide C-type lysozyme as an egg recognition pheromone, we determined that R. speratus has not only C-type, but also P-type and I-type lysozymes, as well as other termite species. Our transcriptomic analyses revealed immune response plasticity among all castes, and sex-biased expression of immune genes even in neuter castes, suggesting a sexual division of labor in the immune system of R. speratus. This study heightens the understanding of the evolution of antimicrobial strategies in eusocial insects, and of sexual roles in insect societies as a whole.

DOI： 10.1371/journal.pone.0175417

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Public Library of Science  

役割によって異なるシロアリの化学受容体の発現 : 高度な分業体制を支えるコミュニケーション機構解明へ期待. 京都大学プレスリリース. 2016-02-17.The sophisticated colony organization of eusocial insects is primarily maintained through the utilization of pheromones. The regulation of these complex social interactions requires intricate chemoreception systems. The recent publication of the genome of Zootermopsis nevadensis opened a new avenue to study molecular basis of termite caste systems. Although there has been a growing interest in the termite chemoreception system that regulates their sophisticated caste system, the relationship between division of labor and expression of chemoreceptor genes remains to be explored. Using high-throughput mRNA sequencing (RNA-seq), we found several chemoreceptors that are differentially expressed among castes and between sexes in a subterranean termite Reticulitermes speratus. In total, 53 chemoreception-related genes were annotated, including 22 odorant receptors, 7 gustatory receptors, 12 ionotropic receptors, 9 odorant-binding proteins, and 3 chemosensory proteins. Most of the chemoreception-related genes had caste-related and sex-related expression patterns; in particular, some chemoreception genes showed king-biased or queen-biased expression patterns. Moreover, more than half of the genes showed significant age-dependent differences in their expression in female and/or male reproductives. These results reveal a strong relationship between the evolution of the division of labor and the regulation of chemoreceptor gene expression, thereby demonstrating the chemical communication and underlining chemoreception mechanism in social insects.

DOI： 10.1371/journal.pone.0146125

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