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Heatmap for the 50-class clustering of RNA-seq transcriptomes. Gene expression, normalized across samples to percentages, ranging from absent (pale yellow) to overexpressed (deep red). Cluster sizes are indicated on the right. Trees at the top and left correspond to hierarchical clusterings of the samples and of cluster-averaged expression, respectively. Type of samples with similar expression patterns (juveniles, soldiers, and male and female reproductives) and unique samples (egg, male and female alates), labelled at the bottom, indicate grouping for differential expression analysis.
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Although eusociality evolved independently within several orders of insects, research into the
molecular underpinnings of the transition towards social complexity has been confined primarily to
Hymenoptera (for example, ants and bees). Here we sequence the genome and stage-specific
transcriptomes of the dampwood termite Zootermopsis nevadensis (Bla...
Citations
... However, past examinations of genome-wide molecular evolution in termites have typically been based on a single termite representative [3,5], or have lacked comparisons with cockroach relatives [6]. Although a number of termite genomes have been sequenced [20][21][22][23], genomes are available for only two cockroach species, the pests Periplaneta americana (Blattidae [24]) and Blattella germanica (Ectobiidae [21]). A lack of genomic resources hinders our ability to perform in-depth comparisons of termites and cockroaches to examine the consequences of eusociality on genome evolution. ...
Genetic changes that enabled the evolution of eusociality have long captivated biologists. More recently, attention has focussed on the consequences of eusociality on genome evolution. Studies have reported higher molecular evolutionary rates in eusocial hymenopteran insects compared with their solitary relatives. To investigate the genomic consequences of eusociality in termites, we analysed nine genomes, including newly sequenced genomes from three non-eusocial cockroaches. Using a phylogenomic approach, we found that termite genomes have experienced lower rates of synonymous substitutions than those of cockroaches, possibly as a result of longer generation times. We identified higher rates of non-synonymous substitutions in termite genomes than in cockroach genomes, and identified pervasive relaxed selection in the former (24–31% of the genes analysed) compared with the latter (2–4%). We infer that this is due to reductions in effective population size, rather than gene-specific effects (e.g. indirect selection of caste-biased genes). We found no obvious signature of increased genetic load in termites, and postulate efficient purging of deleterious alleles at the colony level. Additionally, we identified genomic adaptations that may underpin caste differentiation, such as genes involved in post-translational modifications. Our results provide insights into the evolution of termites and the genomic consequences of eusociality more broadly.
... Additionally, certain social immune behaviors of termites can also influence pathogen infestation [11]. Furthermore, genomic studies of social insects have revealed that termites and cockroaches possess a complete immune gene pool [38][39][40], equipping them to defend against external threats. This renders biological control of termites less effective and more challenging in practice. ...
Odontotermes formosanus (Shiraki) is a subterranean termite species known for causing severe damage to trees and structures such as dams. During the synergistic evolution of O. formosanus with pathogenic bacteria, the termite has developed a robust innate immunity. Termicin is a crucial antimicrobial peptide in termites, significantly contributing to the defense against external infections. Building upon the successful construction and expression of the dsRNA-HT115 engineering strains of dsOftermicin1 and dsOftermicin2 in our laboratory, this work employs the ultrasonic breaking method to establish an inactivated dsOftermicins-HT115 technological system capable of producing a substantial quantity of dsRNA. This approach also addresses the limitation of transgenic strains which cannot be directly applied. Treatment of O. formosanus with dsOftermicins produced by this method could enhance the virulence of both Bt and Bb to the termites. This study laid the theoretical groundwork for the development of novel termite immunosuppressants and for the advancement and application of termite biological control strategies.
... First, we used the illuminautils library v1.4.1 (86) to remove noise from raw reads with the program iu-filter-qualityminoche (87). Then, we identified host sequences by mapping our reads with Bowtie 2 v2.2.5 (88) against a database composed of the three termite genomes available at the time of the analysis: Zootermopsis nevadensis (89), Cryptotermes secundus (90), and Macrotermes natalensis (91). Subsequently, we removed the host reads by retaining only the unmapped reads using SAMtools v1.7 (92). ...
Bacterial endosymbionts of eukaryotic hosts typically experience massive genome reduction, but the underlying evolutionary processes are often obscured by the lack of free-living relatives. Endomicrobia, a family-level lineage of host-associated bacteria in the phylum Elusimicrobiota that comprises both free-living representatives and endosymbionts of termite gut flagellates, are an excellent model to study evolution of intracellular symbionts. We reconstructed 67 metagenome-assembled genomes (MAGs) of Endomicrobiaceae among more than 1,700 MAGs from the gut microbiota of a wide range of termites. Phylogenomic analysis confirmed a sister position of representatives from termites and ruminants, and allowed to propose eight new genera in the radiation of Endomicrobiaceae. Comparative genome analysis documented progressive genome erosion in the new genus Endomicrobiellum, which comprises all flagellate endosymbionts characterized to date. Massive gene losses were accompanied by the acquisition of new functions by horizontal gene transfer, which led to a shift from a glucose-based energy metabolism to one based on sugar phosphates. The breakdown of glycolysis and many anabolic pathways for amino acids and cofactors in several subgroups was compensated by the independent acquisition of new uptake systems, including an ATP/ADP antiporter, from other gut microbiota. The putative donors are mostly flagellate endosymbionts from other bacterial phyla, including several, hitherto unknown lineages of uncultured Alphaproteobacteria, documenting the importance of horizontal gene transfer in the convergent evolution of these intracellular symbioses. The loss of almost all biosynthetic capacities in some lineages of Endomicrobiellum suggests that their originally mutualistic relationship with flagellates is on its decline.
IMPORTANCE
Unicellular eukaryotes are frequently colonized by bacterial and archaeal symbionts. A prominent example are the cellulolytic gut flagellates of termites, which harbor diverse but host-specific bacterial symbionts that occur exclusively in termite guts. One of these lineages, the so-called Endomicrobia, comprises both free-living and endosymbiotic representatives, which offers the unique opportunity to study the evolutionary processes underpinning the transition from a free-living to an intracellular lifestyle. Our results revealed a progressive gene loss in energy metabolism and biosynthetic pathways, compensated by the acquisition of new functions via horizontal gene transfer from other gut bacteria, and suggest the eventual breakdown of an initially mutualistic symbiosis. Evidence for convergent evolution of unrelated endosymbionts reflects adaptations to the intracellular environment of termite gut flagellates.
... Besides allogrooming and secretion of antimicrobial proteins, various antimicrobial organic compounds are used as protective substances: for example, α-pinene and limonene from Nasutitermes species (Zhao et al. 2004), trinervitane and n-hexanoic acid from Zootermopsis species (Rosengaus et al. 2004), and naphthalene, an antiseptic and an anthelmintic (Middleditch et al. 1981) found in the inner wall of the nest of Coptotermes formosanus Shiraki (Chen et al. 1998). Antifungal and antibacterial proteins (lysozymes, termicin, spingerin, and Gram-negative-binding proteins) have also been identified in many termite species (Bulmer and Crozier 2006;Terrapon et al. 2014;Mitaka et al. 2017a). However, as none of these substances is effective against all pathogenic microorganisms, termites must have multiple antimicrobial substances with different antimicrobial spectra to combat the various types of pathogenic microorganisms in the environment. ...
Social insects live in closely related family groups but face risks of intrusion and infection by pathogenic and parasitic microbes. To cope with the microbes invading their nests and feeding sites, social insects produce various types of antimicrobial substances. Subterranean termites occupy microbe-rich decaying wood and soil at high density, expanding their nest area by exploring and feeding on wood outward from the royal chamber (room for kings and queens). Although antimicrobial agents have been identified in many termite species, few studies have investigated those used by foraging workers in decaying wood under development, which is richer in microbes than the well-sterilized royal chamber and its surroundings. Here, we report that phenylacetic acid, an antifungal aromatic compound, is secreted by foraging workers of the Japanese subterranean termite Reticulitermes speratus. The compound was detected by gas chromatography–mass spectrometry analysis of ethyl acetate extracts of shelter papers infested with the workers, and antimicrobial tests demonstrated that it inhibits the germination and/or mycelial growth of the entomopathogenic fungi (Metarhizium anisopliae and Beauveria bassiana) and the termite egg-mimicking fungus Athelia termitophila. Our study provides new insights into the antimicrobial defense mechanisms of termites, including by combining different types of antimicrobial substances secreted by different castes, and thus the survival strategy of entomopathogenic and parasitic fungi in termite nests.
... germanica, D. punctata, P. americana), five termites (Z. nevadensis, C.secundus, R. speratus, C. formosanus, M. natalensis), and two outgroup species (Eriosoma lanigerum, Frankliniella occidentalis) for this study (Biello et al., 2021;Fouks et al., 2022;Harrison et al., 2018;Itakura et al., 2020;Li et al., 2018;Poulsen et al., 2014;Rotenberg et al., 2020;Shigenobu et al., 2022;Terrapon et al., 2014). All proteomes were filtered for possible pseudogenes and only the longest isoforms were kept, using DW-Helper scripts (https://domain-world.zivgitlabpages.unimuenster.de/dw-helper/index.html). ...
... One of the characteristics of eusociality is the division of labour with genomes producing distinct castes that differ in morphology, behaviour, and physiology. These differences can be reflected in caste-specific patterns of gene expression and splicing Scharf et al., 2005;Terrapon et al., 2014). In two of four termites, we observed an enrichment of differential expression among rearranged genes. ...
Domains as functional protein units and their rearrangements along the phylogeny can shed light on the functional changes of proteomes associated with the evolution of complex traits like eusociality. This complex trait is associated with sterile soldiers and workers, and long-lived, highly fecund reproductives. Unlike in Hymenotpera (ants, bees, and wasps), the evolution of eusociality within Blattodea, where termites evolved from within cockroaches, was accompanied by a reduction in proteome size, raising the question of whether functional novelty was achieved with existing rather than novel proteins. To address this, we investigated the role of domain rearrangements during the evolution of termite eusociality. Analysing domain rearrangements in the proteomes of three solitary cockroaches and five eusocial termites, we inferred more than 5000 rearrangements over the phylogeny of Blattodea. The 90 novel domain arrangements that emerged at the origin of termites were enriched for several functions related to longevity, such as protein homeostasis, DNA repair, mitochondrial activity, and nutrient sensing. Many domain rearrangements were related to changes in developmental pathways, important for the emergence of novel castes. Along with the elaboration of social complexity, including permanently sterile workers and larger, foraging colonies, we found 110 further domain arrangements with functions related to protein glycosylation and ion transport. We found an enrichment of caste-biased expression and splicing within rearranged genes, highlighting their importance for the evolution of castes. Furthermore, we found increased levels of DNA methylation among rearranged compared to non-rearranged genes suggesting fundamental differences in their regulation. Our findings indicate an importance of domain rearrangements in the generation of functional novelty necessary for termite eusociality to evolve.
... [50], Zootermopsis nevadensis (GCF_000696155.1) [51], Drosophila melanogaster (GCF_000001215.4) [52], Rhopalosiphum maidis (GCF_003676215.2) [53], Tribolium castaneum (GCF_ 000002335.3) ...
Collembola is a highly diverse and abundant group of soil arthropods with chromosome numbers ranging from 5 to 11. Previous karyotype studies indicated that the Tomoceridae family possesses an exceptionally long chromosome. To better understand chromosome size evolution in Collembola, we obtained a chromosome-level genome of Yoshiicerus persimilis with a size of 334.44 Mb and BUSCO completeness of 97.0% (n = 1013). Both genomes of Y. persimilis and Tomocerus qinae (recently published) have an exceptionally large chromosome (ElChr greater than 100 Mb), accounting for nearly one-third of the genome. Comparative genomic analyses suggest that chromosomal elongation occurred independently in the two species approximately 10 million years ago, rather than in the ancestor of the Tomoceridae family. The ElChr elongation was caused by large tandem and segmental duplications, as well as transposon proliferation, with genes in these regions experiencing weaker purifying selection (higher dN/dS) than conserved regions. Moreover, inter-genomic synteny analyses indicated that chromosomal fission/fusion events played a crucial role in the evolution of chromosome numbers (ranging from 5 to 7) within Entomobryomorpha. This study provides a valuable resource for investigating the chromosome evolution of Collembola.
... Using the newly assembled transcriptomes as well as the previously generated data 10 , we built the reference orthologous gene groups originally identi ed by Song et al. 10 using the following reference genomes on OrthoDB v7 48-50 : Acyrthosiphon pisum (Hemiptera) 51 , Nasonia vitripennis (Hymenoptera) 52 , Pediculus humanus (Psocodea) 53 , Rhodnius prolixus (Hemiptera) 54 , and Zootermopsis nevadensis (Blattodea) 55 . These taxa were chosen based on annotation and sequence quality and because of the lack of availability of reference genomes in Orthoptera or other closely related polyneopteran orders at the beginning of this project. ...
Phylogenomic data are revolutionizing the field of insect phylogenetics. One of the most tenable and cost-effective methods of generating phylogenomic data is target enrichment, which has resulted in novel phylogenetic hypotheses and revealed new insights into insect evolution. Orthoptera is the most diverse insect order within Polyneoptera and includes many evolutionarily and ecologically interesting species. Still, the order as a whole has lagged behind other major insect orders in terms of transitioning to phylogenomics. In this study, we developed an Orthoptera-specific target enrichment (OR-TE) from 80 transcriptomes across Orthoptera. The probe set targets 1,828 loci from genes exhibiting a wide range of evolutionary rates. The utility of this new probe set was validated by generating phylogenomic data from 36 orthopteran species that had not previously been subjected to phylogenomic studies. The OR-TE probe set captured an average of 1,009 loci across the tested taxa, resolving relationships across broad phylogenetic scales. Our detailed documentation of the probe design and bioinformatics process is intended to facilitate the widespread adoption of this tool.
... In queens, all three fecundity-related Vgs (Neofem3 (Vg1) (1), Neofem3 (Vg1) (2), and Vg2) were overexpressed, while only Vg2 was more highly expressed in workers (compared to larvae) (Fig. 2). This implies that the two Vg1 in Z. angusticollis, which seem to be the result of a gene duplication of Neofem3 of C. secundus 43 , are reproductive-specific. This is in line with results for C. secundus, in which Neofem3 is also only upregulated in reproductives and across all body parts 44 . ...
... removing adapter sequences and keeping only paired-end reads with a minimum length of 120 bp 64,65 . As there is no sequenced genome of Zootermopsis angusticollis available, we mapped the trimmed reads with hisat2 to the genome of the sister species Zootermopsis nevadensis, v. 2.2 43 . While other strategies such as Trinity-based de novo transcriptome assembly could have been employed, this was not a good alternative in our study, given our focus on gene expression, rather than transcript variants and alternative splicing. ...
Social insect castes (e.g., queens, workers) are prime examples of phenotypic plasticity (i.e., different phenotypes arising from the same genotype). Yet, the mechanisms that give rise to highly fertile, long-lived queens versus non-reproducing, short-lived workers are not well understood. Recently, a module of co-expressed genes has been identified that characterizes queens compared to workers of the termite Cryptotermes secundus (Kalotermitidae): the Queen Central Module (QCM). We tested whether the QCM is shared in termite species, in which queens gradually develop via early larval and late larval instars, the latter functioning as totipotent workers (linear development). Similar as in C. secundus, gene expression profiles revealed an enrichment of QCM genes in Zootermopsis angusticollis queens, a species from another termite family (Archotermopsidae). The expression of these QCM genes became gradually enriched during development from early larval instars via workers to queens. Thus, our results support the hypothesis of a conserved genetic toolkit that characterizes termite queens with gradual linear development. Our data also imply a strong caste-specific tissue specificity with the QCM signal being restricted to head-prothorax tissues in termite queens. This tissue-specific expression of key aging-related genes might have facilitated the evolution of a long lifespan in termite queens.
... This is achieved by the production of antimicrobial agents, such as α-pinene and limonene from Nasutitermes species (Zhao et al. 2004), trinervitane and n-hexanoic acid from Zootermopsis species (Rosengaus et al. 2004), and naphthalene, an antiseptic and an anthelmintic (Middleditch et al. 1981) found in the inner wall of the nest of Coptotermes formosanus Shiraki (Chen et al. 1998). Antifungal and antibacterial proteins (lysozymes, termicin, spingerin, and Gram-negative-binding proteins) have also been identi ed in many termite species (Bulmer and Crozier 2006;Terrapon et al. 2014; Mitaka et al. 2017a). However, as none these substances is effective against all pathogenic microorganisms, termites must have multiple antimicrobial substances with different antimicrobial spectra to combat the various types of pathogenic microorganisms in the environment. ...
Social insects live in closely related family groups but face risks of intrusion and infection by pathogenic and parasitic microbes. To cope with the microbes invading their nests and feeding sites, social insects produce various types of antimicrobial substances. Subterranean termites occupy microbe-rich decaying wood and soil at high density, expanding their nest area by exploring and feeding on wood outward from the royal chamber (room for kings and queens). Although antimicrobial agents have been identified in many termite species, few studies have investigated those used by foraging workers in unexplored decaying wood, which is richer in microbes than the well-sterilized royal chamber and its surroundings. Here we report that phenylacetic acid, an antifungal aromatic compound, is secreted by foraging workers of the Japanese subterranean termite Reticulitermes speratus . The compound was detected by gas chromatography-mass spectrometry analysis of ethyl acetate extracts of shelter papers infested with the workers, and antimicrobial tests demonstrated that it inhibits the mycelial growth of the entomopathogenic fungus Metarhizium anisopliae and the termite egg-mimicking fungus Athelia termitephila . Our study provides new insights into the antimicrobial defense mechanisms of termites, including by combining different types of antimicrobial substances secreted by different castes, and thus the survival strategy of entomopathogenic and parasitic fungi in termite nests.
... The latest developments in the research on the functional genomics of termites have been useful in precisely understanding the distinctive and fascinating aspects of termite biology [37], like understanding aggression and differences between castes on a genetic level [38]. These developments have allowed us to comprehend their behavioral and evolutionary adaptability in many biological circumstances involving eusociality, and also to understand chemosensory systems [28,[39][40][41][42][43][44][45]. Nonetheless, despite their great ecological, evolutionary, as well as economic importance, subterranean termites are a genetic and genomically unexplored group of insects [46]. ...
... The research on termites is mainly focused on chemical ecology, as well as pheromone biology; however, there are only six species of termites in which the chemosensory genes have been identified, three of which are Zootermopsis nevadensis [42], Cryptotermes secundus [47], and Reticulitermes speratus [48], having 85, 42, and 22 ORs in their genomes, respectively. In another study, the chemosensory genes of three termite species from three distinct lineages, Neotermes cubanus, Prorhinotermes simplex, and Inquilinitermes inquilinus, were identified using the antennae of the worker termites by employing transcriptome screening, resulting in a large number of ORs, GRs, SNMPs, OBPs, and CSPs [49]. ...
... All of the putatively identified genes have not been previously reported in O. formosanus, except OforOR2 [62]. Our results are based on de novo assembly data obtained via RNA-seq and comparable to Reticulitermes speratus, in which 31 OBPs identified and Z. nevadensis with 29 OBPs identified [42,50]. There are 52 OBP genes in D. melanogaster [63]; however, the highest number of 109 OBPs was observed in B. germanica, showing the variability of the number of OBPs among social insects [64]. ...
Simple Summary
In order to sense the numerous chemical signals from their surroundings, insects have developed complex olfactory systems and olfactory mechanisms involving a wide range of chemosensory genes. Olfaction therefore plays an integral role in directing and regulating all insect behaviors and activities. Termites possess significant ecological significance due to their eusocial nature; that is, they use intricate chemical communication mechanisms to coordinate colony organization and regulate social behavior. In this study, a transcriptomic analysis of Odontotermes formosanus workers was performed to uncover candidate chemosensory genes. Forty-two candidate chemosensory genes were identified, and the relative expression profiles of these candidate genes were investigated. This study reveals new directions for the study of chemosensory genes and uncovers the molecular underpinnings of the functional olfactory system in termites, which will lead to the green pest management of termites in the future.
Abstract
Termites are eusocial insects. Chemical signals between colony members are crucial to the smooth running of colony operations, but little is known about their olfactory system and the roles played by various chemosensory genes in this process. Chemosensory genes are involved in basic olfactory perception in insects. Odontotermes formosanus (Shiraki) is one of the most damaging pests to agricultural crops, forests, and human-made structures. To better understand the olfactory system and the genes involved in olfactory processing in O. formosanus, we produced a transcriptome of worker termites. In this study, we identified 13 OforOBPs, 1 OforCSP, 15 OforORs, 9 OforGRs, and 4 OforSNMPs. Multiple sequence alignments were used in the phylogenetic study, which included data from other termite species and a wide variety of insect species. Moreover, we also investigated the mRNA expression levels using qRT-PCR. The significantly high expression levels of OforCSP1, OforOBP2, OforOR1, and OforSNMP1 suggest that these genes may play important roles in olfactory processing in termite social behavior, including caste differentiation, nestmate and non-nestmate discrimination, and the performance of colony operations among members. Our research establishes a foundation for future molecular-level functional studies of chemosensory genes in O. formosanus, which might lead to the identification of novel targets for termite integrated pest management.
