Insulin signaling in the long-lived reproductive caste of ants

The pace and shape of ant ageing

Ants have been proposed as good models to study ageing and the effects of extrinsic mortality because of their long lifespans and plasticity of ageing within species. We discuss how age-dependent extrinsic mortality might influence queen lifespan, and how the effect of age-independent extrinsic mortality needs further study, accounting for different density-dependence scenarios. Based on a critical review of the available demographic data, we discuss the selective forces underlying ant ageing. We discuss differences and similarities between the life-history strategy of ants and the reproductive strategies iteroparity and semelparity. We consider how late-life fitness gains for the "superorganism" select for a delay of actuarial, and reproductive senescence, and we suggest future research directions.

Metabolic and transcriptional regulation of reproductive diapause in Arma chinensis

Diapause enables insects to survive unfavorable conditions through metabolic and developmental adjustments. We investigated metabolic regulation during reproductive diapause in the predatory stinkbug Arma chinensis using transcriptomic and metabolomic analyses. Our study revealed 9,254 differentially expressed genes and 493 significantly changed metabolites across diapause stages. Key metabolic pathways including glutathione metabolism, TCA cycle, glycolysis, and lipid metabolism underwent substantial reorganization. The pre-diapause phase showed increased energy consumption and lipid accumulation, while the maintenance phase exhibited restructuring of amino acid and glucose metabolism. We identified stage-specific metabolic signatures and potential regulatory mechanisms, including the roles of glutathione metabolism in redox regulation and insulin signaling in diapause control. This comprehensive characterization of metabolic reprogramming during A. chinensis diapause provides insights for improving biocontrol agent production and storage strategies.

Ecological change and conflict reduction led to a social circulatory system in ants

Behavioral innovations can be ecologically transformative for lineages that perform them and for their associated communities. Many ecologically dominant, superorganismal, and speciose ant lineages use mouth-to-mouth social regurgitation behavior - stomodeal trophallaxis - to share exogenous and endogenous materials within colonies. This behavior is less common in other species-poor, less cooperative ant lineages. How and why trophallaxis evolved and fixed in only some ant clades remains unclear, and whether this trait could be indicative of superorganismality has yet to be established. Here we show that trophallaxis evolved in two main events, in non-doryline formicoids around 130 Ma and in some ponerines around 90 Ma, lineages that today encompass 86% of all ant species. We found that trophallaxis evolved in lineages that began drinking sugary liquids and that had reduced intra-colonial conflict by constraining worker reproductive potential. Evolution of trophallaxis increased net diversification. Causal models indicate that trophallaxis required low reproductive conflict and contributed to the large colony sizes of the ants that use it. This suggests that the evolution of social regurgitation was enabled by both social conflict reduction and opportunistic inclusion of nectar and honeydew in the ant diet during the shifts in terrestrial ecosystems toward flowering plants.

From Egg to Adult: A Developmental Table of the Ant Monomorium pharaonis

Ants are one of the most ecologically and evolutionarily successful groups of animals and exhibit a remarkable degree of phenotypic diversity. This success is largely attributed to the fact that all ants are eusocial and live in colonies with a reproductive division of labor between morphologically distinct queen and worker castes. Yet, despite over a century of studies on caste determination and evolution in ants, we lack a complete ontogenetic series from egg to adult for any ant species. We, therefore, present a developmental table for the Pharaoh ant Monomorium pharaonis, a species whose colonies simultaneously produce reproductive queens and completely sterile workers. In total, M. pharaonis embryonic, larval, and pupal development lasts 45 days. During embryogenesis, the majority of developmental events are conserved between M. pharaonis and the fruit fly Drosophila melanogaster. We discovered, however, two types of same-stage embryos before gastrulation: (1) embryos with internalized germ cells; and (2) embryos with germ cells outside of the blastoderm at the posterior pole. Moreover, we also found two-types of embryos following germ band extension: (1) embryos with primordial germ cells that will develop into reproductive queens; and (2) embryos with no germ cells that will develop into completely sterile workers. Together, these data show that queen and worker castes are already determined and differentiated by early embryogenesis. During larval development, we confirmed that reproductive and worker larvae proceed through three larval instars. Using anatomical and developmental markers, we can further discern the development of gyne (unmated queen) larvae, male larvae, and worker larvae as early as the 1st instar. Overall, we hope that the ontogenetic series we present here will serve as a blueprint for the generation of future ant developmental tables.

Termites and other social insects as emerging model organisms of ageing research: how to achieve a long lifespan and a high fecundity

Social insects (termites, ants and some bees and wasps) are emerging model organisms of ageing research. In this Commentary, I outline which advantages they offer compared with other organisms. These include the co-occurrence of extraordinarily long-lived, highly fecund queens together with short-lived workers within colonies that share the same genetic background. I then summarize which new insights have been gained so far from social insect studies. Research on social insects has led to the development of a universal mechanistic framework underlying the regulation of ageing and other life-history trade-offs in insects: the TI-J-LiFe network (short for TOR/IIS-juvenile hormone-lifespan/fecundity). Because of its conservative nature, this network can be extended to also incorporate vertebrates. Current data for social insect models suggest that molecular re-wirings along the I-J-Fe (IIS-juvenile hormone-fecundity) axis of the network can explain the concurrent long lifespans and high fecundity of queens. During social evolution, pathways that foster a high fecundity have apparently been uncoupled from mechanisms that shorten lifespan in solitary insects. Thus, fecundity-related vitellogenesis is uncoupled from life-shortening high juvenile hormone (JH)-titres in the honeybee and from insulin/insulin-like growth factor signalling (IIS) activity in ants. In termites, similarly, vitellogenesis seems tissue-specifically unlinked from JH signalling and IIS activity might have lost life-shortening consequences. However, as in solitary animals, the downstream processes (Li of the TI-J-LiFe network) that cause actual ageing (e.g. oxidative stress, transposable element activity, telomere attrition) seem to differ between species and environments. These results show how apparently hard-wired mechanisms underlying life-history trade-offs can be overcome during evolution.

Juvenile hormone as a key regulator for asymmetric caste differentiation in ants

Caste differentiation involves many functional traits that diverge during larval growth and metamorphosis to produce adults irreversibly adapted to reproductive division of labor. Investigating developmental differentiation is important for general biological understanding and has increasingly been explored for social phenotypes that diverge in parallel from similar genotypes. Here, we use Monomorium pharaonis ants to investigate the extent to which canalized worker development can be shifted toward gyne (virgin-queen) phenotypes by juvenile hormone (JH) treatment. We show that excess JH can activate gyne-biased development in workers so that wing-buds, ocelli, antennal and genital imaginal discs, flight muscles, and gyne-like fat bodies and brains emerge after pupation. However, ovary development remained unresponsive to JH treatment, indicating that JH-sensitive germline sequestration happens well before somatic differentiation. Our findings reveal important qualitative restrictions in the extent to which JH treatment can redirect larval development and that these constraints are independent of body size. Our findings corroborate that JH is a key hormone for inducing caste differentiation but show that this process can be asymmetric for higher colony-level germline versus somatic caste differentiation in superorganisms as defined a century ago by Wheeler. We quantified gene expression changes in response to JH treatment throughout development and identified a set of JH-sensitive genes responsible for the emergence of gyne-like somatic traits. Our study suggests that the gonadotropic role of JH in ovary maturation has shifted from the individual level in solitary insects to the colony level in an evolutionary-derived and highly polygynous superorganism like the pharaoh ant.

Neuropeptides specify and reprogram division of labor in the leafcutter ant Atta cephalotes

Social insects offer powerful models to investigate the mechanistic foundation of elaborate individual behaviors comprising a cooperative community. Workers of the leafcutter ant genus Atta provide an extreme example of behavioral segregation among many phenotypically distinct worker types. We utilize the complex worker system of Atta cephalotes to test the molecular underpinnings of behavioral programming and, in particular, the extent of plasticity to reprogramming. We identify specific neuropeptides as mediators of worker division of labor in A. cephalotes , finding two neuropeptides associated with characteristic behaviors of leafcutting and of brood care. Manipulation via genetic knockdown or by injection of these neuropeptides led to stark loss or gain of each behavior and to transcriptomic shifts in the predicted direction, that is, towards gene pathways expressed in the natural caste. We also compare specific A. cephalotes worker transcriptomes with those of orthologous workers of the eusocial mammal, the naked mole rat H. gaber , revealing global similarities between caste-biased expression and link to specific roles of our studied neuropeptides in ants. This work underscores the essential function of neuropeptides in establishing complex social behavior and a remarkable plasticity among individual behavioral types.

Histone Deacetylase 3 Is Involved in Maintaining Queen Hallmarks of a Termite

The role of epigenetics in regulating caste polyphenism in social insects has been debated. Here, we tested the importance of histone de/acetylation processes for the maintenance of queen hallmarks like a high fecundity and a long lifespan. To this end, we performed RNA interference experiments against histone deacetylase 3 (HDAC3) in the termite Cryptotermes secundus. Fat body transcriptomes and chemical communication profiles revealed that silencing of HDAC3 leads to signals indicative of queen hallmarks. This includes fostering of queen signalling, defence against ageing and a reduction of life-shortening IIS (insulin/insulin-like growth factor signalling) and endocrine JH (juvenile hormone) signalling via Kr-h1 (Krüppel-homologue 1). These observed patterns were similar to those of a protein-enriched diet, which might imply that histone acetylation conveys nutritional effects. Strikingly, in contrast to solitary insects, reduced endocrine JH signalling had no negative effect on fecundity-related vitellogenesis in the fat bodies. This suggests an uncoupling of longevity pathways from fecundity in fat bodies, which can help explain queens' extraordinary lifespans combined with high fecundity.

Insulin receptor participates in the peripheral olfactory processes of honey bees (Apis cerana cerana)

Insulin receptors (InR) are an integral component of the insulin/insulin-like growth factor signaling pathway, which plays a vital role in insect development, lifespan, reproduction, and olfactory sensitivity. However, whether InR participate in the peripheral olfactory system of insects remains unclear. Recently, we found that 2-heptanone (2-HT) affects AcerInR expression, the gene for an InR protein, in Apis cerana cerana. We then examined the spatiotemporal expression profile of the gene in A. cerana cerana. The mRNA of AcerInR was primarily expressed in the antennae, wings, and legs of forager bees, which are probable chemosensory tissues. The results of fluorescence competitive binding assays, combined with site-directed mutagenesis, demonstrated that AcerOBP6 and AcerOBP14 exhibit strong binding affinities to 2-HT. Furthermore, after foragers were fed with double-stranded AcerInR, the expression levels of AcerOBP6 and AcerOBP14 decreased significantly, as did the electroantennogram responsiveness to 2-HT and some other odorants. In conclusion, our findings provide a foundation for understanding the involvement of AcerInR in the odor perception of A. cerana cerana. Moreover, they offer novel insights into the olfactory recognition mechanism in insects.

Transcription Factor CcFoxO Mediated the Transition from Summer Form to Winter Form in Cacopsylla chinensis

Amid global climate change featuring erratic temperature fluctuations, insects adapt via seasonal polyphenism, essential for population sustainability and reproductive success. Cacopsylla chinensis, influenced by environment variations, displays a distinct summer form and winter form distinguished by significant morphological variations. Previous studies have highlighted the role of temperature receptor CcTPRM in orchestrating the transition in response to 10 °C temperature. Nevertheless, the contribution of the transcription factor FoxO in this process has remained ambiguous. Here, we aimed to explore the correlation between C. chinensis FoxO (CcFoxO) and cold stress responses, while identifying potential energetic substances for monitoring physiological shifts during this transition from summer to winter form under cold stress by using RNAi. Initially, CcFoxO emerges as responsive to low temperatures (10 °C) and is regulated by CcTRPM. Subsequent investigations reveal that CcFoxO facilitates the accumulation of triglycerides and glycogen, thereby influencing the transition from summer form to winter form by affecting cuticle pigment content, cuticle chitin levels, and cuticle thickness. Thus, the knockdown of CcFoxO led to high mortality and failed transition. Overall, our findings demonstrate that CcFoxO governs seasonal polyphenism by regulating energy storage. These insights not only enhance our comprehension of FoxO functionality but also offer avenues for environmentally friendly management strategies for C. chinensis.

An evolutionarily conserved pathway mediated by neuroparsin-A regulates reproductive plasticity in ants

Phenotypic plasticity displayed by an animal in response to different environmental conditions is supposedly crucial for its survival and reproduction. The female adults of some ant lineages display phenotypic plasticity related to reproductive role. In pharaoh ant queens, insemination induces substantial physiological/behavioral changes and implicates remarkable gene regulatory network (GRN) shift in the brain. Here, we report a neuropeptide neuroparsin A (NPA) showing a conserved expression pattern associated with reproductive activity across ant species. Knock-down of NPA in unmated queen enhances ovary activity, whereas injection of NPA peptide in fertilized queen suppresses ovary activity. We found that NPA mainly affected the downstream gene JHBP in the ovary, which is positively regulated by NPA and suppression of which induces elevated ovary activity, and shadow which is negatively regulated by NPA. Furthermore, we show that NPA was also employed into the brain-ovary axis in regulating the worker reproductive changes in other distantly related species, such as Harpegnathos venator ants.

Orco-dependent survival of odorant receptor neurons in ants

Olfaction is essential for complex social behavior in insects. To discriminate complex social cues, ants evolved an expanded number of odorant receptor (Or) genes. Mutations in the obligate odorant co-receptor gene orco lead to the loss of ~80% of the antennal lobe glomeruli in the jumping ant Harpegnathos saltator. However, the cellular mechanism remains unclear. Here, we demonstrate massive apoptosis of odorant receptor neurons (ORNs) in the mid to late stages of pupal development, possibly due to ER stress in the absence of Orco. Further bulk and single-nucleus transcriptome analysis shows that, although most orco-expressing ORNs die in orco mutants, a small proportion of them survive: They express ionotropic receptor (Ir) genes that form IR complexes. In addition, we found that some Or genes are expressed in mechanosensory neurons and nonneuronal cells, possibly due to leaky regulation from nearby non-Or genes. Our findings provide a comprehensive overview of ORN development and Or expression in H. saltator.

Phenomenon of reproductive plasticity in ants

Ant colonies are organized in castes with distinct behaviors that together allow the colony to strive. Reproduction relies on one or a few queens that stay in the nest producing eggs, while females of the worker caste do not reproduce and instead engage in colony maintenance and brood caretaking. Yet, in spite of this clear separation of functions, workers can become reproductive under defined circumstances. Here, we review the context in which workers become reproductive, exhibiting asexual or sexual reproduction depending on the species. Remarkably, the activation of reproduction in these workers can be quite stable, with changes that include behavior and a dramatic extension of lifespan. We compare these changes between species that do or do not have a queen caste. We discuss how the mechanisms underlying reproductive plasticity include changes in hormonal functions and in epigenetic configurations. Further studies are warranted to elucidate not only how reproductive functions have been gradually restricted to the queen caste during evolution but also how reproductive plasticity remains possible in workers of some species.

Gene regulation supporting sociality shared across lineages and variation in complexity

Across evolutionary lineages, insects vary in social complexity, from those that exhibit extended parental care to those with elaborate divisions of labor. Here, we synthesize the sociogenomic resources from hundreds of species to describe common gene regulatory mechanisms in insects that regulate social organization across phylogeny and levels of social complexity. Different social phenotypes expressed by insects can be linked to the organization of co-expressing gene networks and features of the epigenetic landscape. Insect sociality also stems from processes like the emergence of parental care and the decoupling of ancestral genetic programs. One underexplored avenue is how variation in a group's social environment affects the gene expression of individuals. Additionally, an experimental reduction of gene expression would demonstrate how the activity of specific genes contributes to insect social phenotypes. While tissue specificity provides greater localization of the gene expression underlying social complexity, emerging transcriptomic analysis of insect brains at the cellular level provides even greater resolution to understand the molecular basis of social insect evolution.

Let's talk about sex: Mechanisms of neural sexual differentiation in Bilateria

In multicellular organisms, sexed gonads have evolved that facilitate release of sperm versus eggs, and bilaterian animals purposefully combine their gametes via mating behaviors. Distinct neural circuits have evolved that control these physically different mating events for animals producing eggs from ovaries versus sperm from testis. In this review, we will describe the developmental mechanisms that sexually differentiate neural circuits across three major clades of bilaterian animals-Ecdysozoa, Deuterosomia, and Lophotrochozoa. While many of the mechanisms inducing somatic and neuronal sex differentiation across these diverse organisms are clade-specific rather than evolutionarily conserved, we develop a common framework for considering the developmental logic of these events and the types of neuronal differences that produce sex-differentiated behaviors. This article is categorized under: Congenital Diseases > Stem Cells and Development Neurological Diseases > Stem Cells and Development.

MiR-143-3p/FNDC5 axis: a novel regulator of insulin sensitivity

PURPOSE

Insulin resistance is a key hallmark in type 2 diabetes. In recent decades, there have been numerous studies of the causes of insulin resistance. microRNAs (miRNAs) participate in the regulation of multiple aspects of energy metabolism and miR-143-3p has been shown to induce insulin resistance. We aimed to predict the downstream targets of miR-143-3p and found a miR-143-3p binding site on the 3'-untranslated region of FNDC5 (Fibronectin type III domain containing 5) mRNA.

METHODS

We first confirmed that FNDC5 mRNA is a target of miR-143-3p using a double luciferase experiment, then constructed a prokaryotic expression system for the mature form of FNDC5, irisin, and expressed and purified irisin protein. We transfected a miR-143-3p mimic into HepG2-NTCP (Na+-taurocholate cotransporting polypeptide) cells using an NTCP targeting vector, then 24 h later, the glucose concentration of the culture medium, western blot analysis was analyzed. We next co-incubated the cells transfected with the miR-143-3p mimic with irisin for 12 h following by the assay of glucose uptake and AKT phosphorylation.

RESULTS

The glucose concentration of the culture medium was higher than that associated with control miRNA-transfected cells (p < 0.01). Western blot analysis showed that the miR-143-3p mimic significantly reduced the expression of FNDC5 (p < 0.05) and the phosphorylation of AKT (Protein kinase B) (p < 0.05), implying impaired insulin signaling. which increased the glucose uptake (p < 0.0001) and AKT phosphorylation in the cells (p < 0.05).

CONCLUSION

We conclude that FNDC5 is a direct target of miR-143-3p and that miR-143-3p induces insulin resistance by reducing its expression.

A Chemical Counterpart to the Resolution Step of Nature's Intein-Mediated Protein Splicing

In the course of an attempted total chemical synthesis of the ant insulin-like peptide-2 (ILP2) protein molecule, specific cleavage of a backbone peptide bond in a branched ester-linked polypeptide chain with concomitant peptide splicing was observed. The side reaction was investigated in model compounds. Here, we postulate a chemical mechanism for this novel polypeptide backbone cleavage reaction as a chemical counterpart to the resolution step of biochemical intein-mediated protein splicing.

Metabolic plasticity sustains the robustness of Caenorhabditis elegans embryogenesis

Embryogenesis is highly dependent on maternally loaded materials, particularly those used for energy production. Different environmental conditions and genetic backgrounds shape embryogenesis. The robustness of embryogenesis in response to extrinsic and intrinsic changes remains incompletely understood. By analyzing the levels of two major nutrients, glycogen and neutral lipids, we discovered stage-dependent usage of these two nutrients along with mitochondrial morphology changes during Caenorhabditis elegans embryogenesis. ATGL, the rate-limiting lipase in cellular lipolysis, is expressed and required in the hypodermis to regulate mitochondrial function and support embryogenesis. The embryonic lethality of atgl-1 mutants can be suppressed by reducing sinh-1/age-1-akt signaling, likely through modulating glucose metabolism to maintain sustainable glucose consumption. The embryonic lethality of atgl-1(xd314) is also affected by parental nutrition. Parental glucose and oleic acid supplements promote glycogen storage in atgl-1(xd314) embryos to compensate for the impaired lipolysis. The rescue by parental vitamin B12 supplement is likely through enhancing mitochondrial function in atgl-1 mutants. These findings reveal that metabolic plasticity contributes to the robustness of C. elegans embryogenesis.

Palmitoleic acid as a coordinating molecule between the invasive pinewood nematode and its newly associated fungi

Symbiotic microorganisms are ubiquitous on the body surface or internal tissues of invertebrates, providing them with benefits. Developing symbiotic relationships requires synchronization of developmental stages and physical proximity of partners. Therefore, the identification of metabolites that coordinate the reproduction of symbiotic partners is essential. This study demonstrates that palmitoleic acid (C16: 1) coordinates bilateral propagation by regulating the synchronization of reproduction between the invasive pinewood nematode (PWN) and its newly associated blue-stain fungus, Sporothrix sp.1. When the PWN fed on Sporothrix sp.1, there was a significant increase in lipid metabolism gene expression and metabolite abundance. Through further investigations, it highlighted a significant enhancement in the reproduction of the PWN through direct acquisition of C16: 1, which was abundantly present in Sporothrix sp.1. Furthermore, the PWN biosynthesized C16: 1 through the involvement of the stearoyl-CoA 9-desaturase gene fat-5 and its hormone nuclear receptor nhr-80, which was clarified to promote the egg-laying capacity of females. Moreover, it is worth noting that the production of C16: 1 was significantly higher by the associated fungus Sporothrix sp.1 to enhance sporulation during the spore formation phase compared to the hypha growth phase. Thus, by coordinating the fecundity and spore production, the key lipid metabolite C16: 1 facilitates the rapid and successful colonization of a mutually beneficial symbiotic relationship between the invasive PWN and the native Sporothrix sp.1 within the host. This finding emphasizes the significant role of metabolite sharing and its function in promoting partner synchronization within symbiotic relationships.

Development, regeneration and aging: a bizarre love triangle

The Jacques Monod Conference on 'Growth and regeneration during development and aging' was organized by Claude Desplan and Allison Bardin in May 2023. The conference took place in Roscoff, France, where participants shared recent conceptual advances under the general motto that developmental processes do not end with embryogenesis. The meeting covered various aspects of how development relates to fitness, regeneration and aging across a refreshing diversity of evolutionarily distant organisms.

Social isolation shortens lifespan through oxidative stress in ants

Social isolation negatively affects health, induces detrimental behaviors, and shortens lifespan in social species. Little is known about the mechanisms underpinning these effects because model species are typically short-lived and non-social. Using colonies of the carpenter ant Camponotus fellah, we show that social isolation induces hyperactivity, alters space-use, and reduces lifespan via changes in the expression of genes with key roles in oxidation-reduction and an associated accumulation of reactive oxygen species. These physiological effects are localized to the fat body and oenocytes, which perform liver-like functions in insects. We use pharmacological manipulations to demonstrate that the oxidation-reduction pathway causally underpins the detrimental effects of social isolation on behavior and lifespan. These findings have important implications for our understanding of how social isolation affects behavior and lifespan in general.

Caste Transition and Reversion in Harpegnathos saltator Ant Colonies

Living organisms possess the ability to respond to environmental cues and adapt their behaviors and physiologies for survival. Eusocial insects, such as ants, bees, wasps, and termites, have evolved advanced sociality: living together in colonies where individuals innately develop into reproductive and non-reproductive castes. These castes exhibit remarkably distinct behaviors and physiologies that support their specialized roles in the colony. Among ant species, Harpegnathos saltator females stand out with their highly plastic caste phenotypes that can be easily manipulated in a laboratory environment. In this protocol, we provide detailed instructions on how to generate H. saltator ant colonies, define castes based on behavioral and physiological phenotypes, and experimentally induce caste switches, including the transition from a non-reproductive worker to a reproductive gamergate and vice versa (known as reversion). The unusual features of H. saltator make it a valuable tool to investigate cellular and molecular mechanisms underlying phenotypic plasticity in eusocial organisms. Key features H. saltator is one of few ant species showing remarkable caste plasticity with striking phenotypic changes, being a useful subject for studying behavioral plasticity. Caste switches in H. saltator can be easily manipulated in a controlled laboratory environment by controlling the presence of reproductive females in a colony. The relatively large size of H. saltator females allows researchers to dissect various tissues of interest and conduct detailed phenotypic analyses.

Evolution: How sweat bees gained and lost eusociality

Eusocial insects divide labor between reproductive and non-reproductive individuals. The molecular mechanisms underlying the evolution of these castes have remained mysterious. A comparative genomic study of sweat bees points to a familiar factor as a regulator of behavioral specialization: juvenile hormone.

Long ant life span is maintained by a unique heat shock factor

Eusocial insect reproductive females show strikingly longer life spans than nonreproductive female workers despite high genetic similarity. In the ant Harpegnathos saltator (Hsal), workers can transition to reproductive "gamergates," acquiring a fivefold prolonged life span by mechanisms that are poorly understood. We found that gamergates have elevated expression of heat shock response (HSR) genes in the absence of heat stress and enhanced survival with heat stress. This HSR gene elevation is driven in part by gamergate-specific up-regulation of the gene encoding a truncated form of a heat shock factor most similar to mammalian HSF2 (hsalHSF2). In workers, hsalHSF2 was bound to DNA only upon heat stress. In gamergates, hsalHSF2 bound to DNA even in the absence of heat stress and was localized to gamergate-biased HSR genes. Expression of hsalHSF2 in Drosophila melanogaster led to enhanced heat shock survival and extended life span in the absence of heat stress. Molecular characterization illuminated multiple parallels between long-lived flies and gamergates, underscoring the centrality of hsalHSF2 to extended ant life span. Hence, ant caste-specific heat stress resilience and extended longevity can be transferred to flies via hsalHSF2. These findings reinforce the critical role of proteostasis in health and aging and reveal novel mechanisms underlying facultative life span extension in ants.

Regulation of the immune system by the insulin receptor in health and disease

The signaling pathways downstream of the insulin receptor (InsR) are some of the most evolutionarily conserved pathways that regulate organism longevity and metabolism. InsR signaling is well characterized in metabolic tissues, such as liver, muscle, and fat, actively orchestrating cellular processes, including growth, survival, and nutrient metabolism. However, cells of the immune system also express the InsR and downstream signaling machinery, and there is increasing appreciation for the involvement of InsR signaling in shaping the immune response. Here, we summarize current understanding of InsR signaling pathways in different immune cell subsets and their impact on cellular metabolism, differentiation, and effector versus regulatory function. We also discuss mechanistic links between altered InsR signaling and immune dysfunction in various disease settings and conditions, with a focus on age related conditions, such as type 2 diabetes, cancer and infection vulnerability.

Multi-Omics Reveals the Effect of Population Density on the Phenotype, Transcriptome and Metabolome of Mythimna separata

Population-density-dependent polymorphism is important in the biology of some agricultural pests. The oriental armyworm (Mythimna separata) is a lepidopteran pest (family Noctuidae). As the population density increases, its body color becomes darker, and the insect eats more and causes greater damage to crops. The molecular mechanisms underlying this phase change are not fully clear. Here, we used transcriptomic and metabolomic methods to study the effect of population density on the differentiation of second-day sixth instar M. separata larvae. The transcriptomic analysis identified 1148 differentially expressed genes (DEGs) in gregarious-type (i.e., high-population-density) armyworms compared with solitary-type (low-population-density) armyworms; 481 and 667 genes were up- and downregulated, respectively. The metabolomic analysis identified 137 differentially accumulated metabolites (DAMs), including 59 upregulated and 78 downregulated. The analysis of DEGs and DAMs showed that activation of the insulin-like signaling pathway promotes the melanization of gregarious armyworms and accelerates the decomposition of saccharides, which promotes the gregarious type to take in more food. The gregarious type is more capable of digesting and absorbing proteins and decreases energy consumption by inhibiting transcription and translation processes. The phase change traits of the armyworm are thus attributable to plasticity of its energy metabolism. These data broaden our understanding of the molecular mechanisms of insect-density-dependent polymorphism.

Differential expression of some termite neuropeptides and insulin/IGF-related hormones and their plausible functions in growth, reproduction and caste determination

Background

Insulin-like growth factor (IGF) and other insulin-like peptides (ilps) are important hormones regulating growth and development in animals. Whereas most animals have a single female and male adult phenotype, in some insect species the same genome may lead to different final forms. Perhaps the best known example is the honeybee where females can either develop into queens or workers. More extreme forms of such polyphenism occur in termites, where queens, kings, workers and soldiers coexist. Both juvenile hormone and insulin-like peptides are known to regulate growth and reproduction as well as polyphenism. In termites the role of juvenile hormone in reproduction and the induction of the soldier caste is well known, but the role of IGF and other ilps in these processes remains largely unknown. Here the various termite ilps are identified and hypotheses regarding their functions suggested.

Methods

Genome assemblies and transcriptome short read archives (SRAs) were used to identify insulin-like peptides and neuropeptides in termites and to determine their expression in different species, tissues and castes.

Results and Discussion

Termites have seven different ilps, i.e. gonadulin, IGF and an ortholog of Drosophila insulin-like peptide 7 (dilp7), which are commonly present in insects, and four smaller peptides, that have collectively been called short IGF-related peptides (sirps) and individually atirpin, birpin, cirpin and brovirpin. Gonadulin is lost from the higher termites which have however amplified the brovirpin gene, of which they often have two or three paralogs. Based on differential expression of these genes it seems likely that IGF is a growth hormone and atirpin an autocrine tissue factor that is released when a tissue faces metabolic stress. Birpin seems to be responsible for growth and in the absence of juvenile hormone this may lead to reproductive adults or, when juvenile hormone is present, to soldiers. Brovirpin is expressed both by the brain and the ovary and likely stimulates vitellogenesis, while the function of cirpin is less clear.