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Background: Juvenile hormones (JH) play crucial role in regulating development and reproduction in insects. The most common form of JH is JH III, derived from MF through epoxidation by CYP15 enzymes. However, in the higher dipterans, such as the fruitfly, Drosophila melanogaster, a bis-epoxide form of JHB3, accounted most of the JH detected. Moreover, these higher dipterans have lost the CYP15 gene from their genomes. As a result, the identity of the P450 epoxidase in the JH biosynthesis pathway in higher dipterans remains unknown. Results: In this study, we show that Cyp6g2 serves as the major JH epoxidase responsible for the biosynthesis of JHB3 and JH III in D. melanogaster. The Cyp6g2 is predominantly expressed in the corpus allatum (CA), concurring with the expression pattern of jhamt, another well-studied gene that is crucial in the last steps of JH biosynthesis. Mutation in Cyp6g2 leads to severe disruptions in larval-pupal metamorphosis and exhibits reproductive deficiencies, exceeding those seen in jhamt mutants. Notably, Cyp6g2−/−::jhamt2 double mutants all died at the pupal stage but could be rescued through the topical application of JH analogs. JH titer analyses revealed that both Cyp6g2−/− mutant and jhamt2 mutant lacking JHB3 and JH III, while overexpression of Cyp6g2 or jhamt caused a significant increase in JHB3 and JH III titer. Conclusions: These findings collectively established that Cyp6g2 as the major JH epoxidase in the higher dipterans and laid the groundwork for the further understanding of JH biosynthesis. Moreover, these findings pave the way for developing specific Cyp6g2 inhibitors as insect growth regulators or insecticides. [ABSTRACT FROM AUTHOR]

Overwintering conditions affect the physiological state of ectotherms, and therefore, their cold hardiness and survival. A measure of the lethal and sublethal impacts of overwintering conditions on pest populations is crucial to predict population dynamics and to manage pests the following spring. The impact of winter conditions can be most intense for invasive insects undergoing range expansion. Insect herbivores can display plastic host use behaviours that depend on their body condition following winter. The pea leaf weevil, Sitona lineatus L. (Coleoptera: Curculionidae), is an invasive pest of field peas, Pisum sativum L., and faba bean, Vicia faba L. (Fabaceae). Pea leaf weevil has expanded its range in North America to include the Prairie Provinces of Canada. This study investigated the effects of temperature and microhabitat on overwintering survival and cold hardiness of pea leaf weevil in its expanded range. Further, we investigated the sublethal effect of overwintering temperature and duration on post‐overwintering survival, feeding, and oviposition of pea leaf weevil. We also investigated the role of juvenile hormone in modulating body condition of overwintering weevils. The overwintering survival of pea leaf weevil adults increased with soil temperature and varied with region and microhabitat. More weevils survived winters when positioned near tree shelterbelts compared to open alfalfa fields. The supercooling point of pea leaf weevil varied throughout its expanding range but did not differ for weevils held in the two microhabitats. The average threshold lethal temperature of pea leaf weevil at all three sites was −9.4 °C. Weevils that overwintered for a longer duration and at a higher temperature subsequently fed more on faba bean foliage and laid more eggs compared to those which overwintered for a shorter duration at a lower temperature. Our findings highlight that warm winters would increase overwintering survival and post‐overwintering fitness, facilitating further pea leaf weevil invasion northward in the Prairie Provinces of Canada. [ABSTRACT FROM AUTHOR]

The unsustainable and widespread utilization of fossil fuels continues to drive the rapid depletion of global supplies. Biodiesel has emerged as one of the most promising alternatives to conventional diesel, leading to growing research interest in its production. Microbes can facilitate the de novo synthesis of a type of biodiesel in the form of fatty acid methyl esters (FAMEs). In this study, Saccharomyces cerevisiae metabolic activity was engineered to facilitate enhanced FAME production. Initially, free fatty acid concentrations were increased by deleting two acetyl-CoA synthetase genes (FAA1, FAA4) and an acyl-CoA oxidase gene (POX1). Intracellular S-adenosylmethionine (SAM) levels were then enhanced via the deletion of an adenosine kinase gene (ADO1) and the overexpression of a SAM synthetase gene (SAM2). Lastly, the S. cerevisiae strain overproducing free fatty acids and SAM were manipulated to express a plasmid encoding the Drosophila melanogaster Juvenile Hormone Acid O-Methyltransferase (DmJHAMT). Using this combination of engineering approaches, a FAME concentration of 5.79 ± 0.56 mg/L was achieved using these cells in the context of shaking flask fermentation. To the best of our knowledge, this is the first detailed study of FAME production in S. cerevisiae. These results will provide a valuable basis for future efforts to engineer S. cerevisiae strains for highly efficient production of biodiesel. Key points: De novo synthesis of FAMEs was demonstrated in Saccharomyces cerevisiae. FAME production was improved by increasing concentrations of fatty acids and SAM. FAMEs produced in S. cerevisiae mainly included C16 and C18 fatty acid methyl esters. [ABSTRACT FROM AUTHOR]

Diseases transmitted by vectors such as Aedes aegypti and Culex quinquefasciatus (Diptera: Culicidae) have been responsible for endemics and epidemics in several countries, causing irreparable damage to human health. For this reason, vector control is one of the main strategies to prevent the contamination and dissemination of these etiological agents. In this study, the essential oil (EO) of Ocimum basilicum was obtained by hydrodistillation, and the compounds were identified by GC/MS. A nanoemulsion was obtained through a low-energy input method and evaluated by photon correlation spectroscopy. Bioassays were performed against 4th instar larvae of A. aegypti and C. quinquefasciatus. Furthermore, additional in silico studies of biological activity prediction and molecular docking for the acetylcholinesterase enzyme and juvenile hormone protein targets were performed with the 53 identified compounds of the EO. The major compounds identified in greater quantity were linalool (32.66%) and anethole (32.48%). The obtained nanoemulsion had an average size diameter between 244.6 and 280.4 nm and a polydispersity index below 0.250 during the entire storage period. The nanoemulsion was tested at concentrations of 10, 20, 30, 40, and 50 mg/L and the following activity values were observed: LC50 = 42.15 mg/L and 40.94 mg/L and LC90 = 50.35 mg/L and 48.87 mg/L for A. aegypti (24 h and 48 h); LC50 = 39.64 mg/L and 38.08 mg/L and LC90 = 52.58 mg/L and 54.26 mg/L for C. quinquefasciatus (24 h and 48 h). The in silico results showed better activity values for linalool, anethole, carvone, α-selinene, eugenol, and limonene. The α-selinene compound showed the best binding affinity with the insect acetylcholinesterase enzyme (−9.1 Kcal) in molecular docking, showing the importance of antagonist compounds in elucidating the mechanism of action for the investigated targets. Thus, the studied nanoemulsion was considered active against the tested species, becoming a potential alternative as an ecological bioinsecticide due to bioactivity and simplicity of formulation. [ABSTRACT FROM AUTHOR]

Juvenile hormone (JH) acts in the regulation of caste differentiation between queens and workers (i.e., with or without reproductive capacity) during vitellin synthesis and oogenesis in social insects. However, the regulatory mechanisms have not yet been elucidated. Here, we identified a highly expressed microRNA (miRNA), miR‐1175‐3p, in the red imported fire ant, Solenopsis invicta. We found that miR‐1175‐3p is prominently present in the fat bodies and ovaries of workers. Furthermore, miR‐1175‐3p interacts with its target gene, broad‐complex core (Br‐C), in the fat bodies. By utilizing miR‐1175‐3p agomir, we successfully suppressed the expression of the Br‐C protein in queens, resulting in reduced vitellogenin expression, fewer eggs, and poorly developed ovaries. Conversely, decreasing miR‐1175‐3p levels led to the increased expression of Br‐C and vitellogenin in workers, triggering the "re‐development" of the ovaries. Moreover, when queens were fed with JH, the expression of miR‐1175‐3p decreased, whereas the expression of vitellogenin‐2 and vitellogenin‐3 increased. Notably, the suppression of fertility in queens caused by treatment with agomir miR‐1175‐3p was completely rescued by the increased vitellogenin expression induced by being fed with JH. These results suggest the critical role of miR‐1175‐3p in JH‐regulated reproduction, shedding light on the molecular mechanism underlying miRNA‐mediated fecundity in social insects and providing a novel strategy for managing S. invicta. [ABSTRACT FROM AUTHOR]

To gain insights into how juvenile hormone (JH) came to regulate insect metamorphosis, we studied its function in the ametabolous firebrat, Thermobia domestica. Highest levels of JH occur during late embryogenesis, with only low levels thereafter. Loss- of- function and gain-of-function experiments show that JH acts on embryonic tissues to suppress morphogenesis and cell determination and to promote their terminal differentiation. Similar embryonic actions of JH on hemimetabolous insects with short germ band embryos indicate that JH's embryonic role preceded its derived function as the postembryonic regulator of metamorphosis. The postembryonic expansion of JH function likely followed the evolution of flight. Archaic flying insects were considered to lack metamorphosis because tiny, movable wings were evident on the thoraces of young juveniles and their positive allometric growth eventually allowed them to support flight in late juveniles. Like in Thermobia, we assume that these juveniles lacked JH. However, a postembryonic reappearance of JH during wing morphogenesis in the young juvenile likely redirected wing development to make a wing pad rather than a wing. Maintenance of JH then allowed wing pad growth and its disappearance in the mature juvenile then allowed wing differentiation. Subsequent modification of JH action for hemi- and holometabolous lifestyles are discussed. [ABSTRACT FROM AUTHOR]

Differentiation of imaginal epidermal cells of Drosophila melanogaster to form adult cuticles occurs at approximately 40–93 h after puparium formation. Juvenile hormone (JH) given at pupariation results in formation of a second pupal cuticle in the abdomen instead of the adult cuticle. Although the adult cuticle gene Acp65A has been reported to be down‐regulated following JH treatment, the regulatory mechanism remains unclear. Here, we found that the JH primary response gene Krüppel homologue 1 (Kr‐h1) plays a vital role in the repression of adult cuticle formation through the mediation of JH action. Overexpression of Kr‐h1 mimicked—while knocking down of Kr‐h1 attenuated—the inhibitory action of JH on the formation of the adult abdominal cuticle. Further, we found that Kr‐h1 inhibited the transcription of Acp65A by directly binding to the consensus Kr‐h1 binding site (KBS) within the Acp65A promoter region. Moreover, the DNA methyltransferase Dnmt2 was shown to interact with Kr‐h1, combined with the KBS to promote the DNA methylation of sequences around the KBS, in turn inhibiting the transcription of Acp65A. This study advances our understanding of the molecular basis of the "status quo" action of JH on the Drosophila adult metamorphosis. [ABSTRACT FROM AUTHOR]

Simple Summary: Baculovirus infection can prevent the pupation of insects. However, the molecular mechanism of baculovirus preventing the pupation of larvae by regulating the Juvenile hormone (JH) pathway is still unclear. In this study, we examined the interactive relationship of Mamestra brassicae multiple nucleopolyhedroviruses (MbMNPV) and Helicoverpa armigera (H. armigera). We found that MbMNPV infection caused an increased JH titer and inhibited the expression levels of juvenile hormone esterase (JHE) and juvenile hormone epoxide hydrolase (JHEH). Our studies further proved that the JH is mainly degraded by JHE in H. armigera larvae. Knocking down of HaJHE promoted MbMNPV replication. These findings suggest that the infection of H. armigera larvae by MbMNPV leads to an increased JH titer by inhibiting the expression of JHE, which prevents pupation of H. armigera and promotes MbMNPV replication. Baculovirus infection can prevent the pupation of insects. Juvenile hormone (JH) plays a vital role in regulating insect molting and metamorphosis. However, the molecular mechanism of baculovirus preventing the pupation of larvae by regulating the Juvenile hormone (JH) pathway is still unclear. In this study, we found that the Mamestra brassicae multiple nucleopolyhedroviruses (MbMNPV) infection prolonged the larval stage of fourth instar Helicoverpa armigera (H. armigera) by 0.52 d and caused an increase in JH titer. To identify the genes that contribute to the JH increase in H. armigera-MbMNPV interaction, we analyzed mRNA expression profiles of the fat bodies of H. armigera infected by MbMNPV. A total of 3637 differentially expressed mRNAs (DE-mRNAs) were filtered out through RNA-seq analysis. These DE-mRNAs were mainly enriched in Spliceosome, Ribosome biogenesis in eukaryotes, Aminoacyl-tRNA biosynthesis, Mismatch repair, and RNA degradation signaling pathway, which are related to the virus infection. Real-time PCR was used to verify the RNA sequencing results. To find out which genes caused the increase in JH titer, we analyzed all the DE-mRNAs in the transcriptome and found that the JHE and JHEH genes, which were related to JH degradation pathway, were down-regulated. JHE and JHEH genes in the larvae of MbMNPV-infected group were significantly down-regulated compared with the control group by RT-qPCR. We further proved that the JH is degraded by JHE in H. armigera larvae by RNAi, ELISA, RT-qPCR and bioassay, while the hydrolysis of JH by JHEH in H. armigera larvae can almost be ignored. Knocking down of HaJHE promoted the expression of the JH receptor gene Met and the downstream gene Kr-h1, and the replication of MbMNPV. This study clarified that JH is mainly degraded by JHE in H. armigera larvae. The MbMNPV infection of H. armigera larvae leads to the increase of JH titer by inhibiting the expression of JHE. The increase in JH titer promotes the expression of the JH receptor gene Met and the downstream gene Kr-h1, which prevents the pupation of H. armigera, and promotes MbMNPV replication. This study provides new insights into H. armigera and MbMNPV interaction mechanisms. [ABSTRACT FROM AUTHOR]

Simple Summary: This study explores the mechanisms affecting offspring sex ratios in the pea aphid, Acyrthosiphon pisum (Harris), a key issue in evolutionary ecology. It tests the impacts of the presence of both the same and different clones, as well as juvenile hormone III (JH III) levels, on offspring sex allocation. Using red and green clones and the agar method, this study set up three initial treatments using sexuparae and tracked daily offspring number and sex. In a mixed-clone treatment, 1 sexupara of the green clone and 20 oviparous females of either red (1G + 20Rov) or green (1G + 20Gov) clone were transferred onto agar leaves, with a control (1G) established for comparison. After the production of sexuparae, JH III doses were applied to them, and hormone titers and sex allocation in offspring were meticulously measured. The results highlighted marked variations in sex allocation, especially an increase in ovipara number in mixed-clone treatment groups. JH III application reversed this effect, indicating that mixed-clone treatment leads to lowered JH titers, which in turn affects sex allocation. This study concludes that A. pisum sexuparae can modify offspring sex allocation in response to adjacent clones, showing diverse mechanisms of sex allocation, where JH III plays a critical role. The mechanism controlling sex allocation in the pea aphid, Acyrthosiphon pisum (Harris), remains a crucial yet unresolved issue in the field of evolutionary ecology. This study aims to assess the influence of the presence of both self and non-self clones, along with juvenile hormone III (JH III) titer, on the sex allocation of aphid offspring. To this end, red and green clones were utilized as experimental subjects, and the agar method was employed. Initially, three distinct experimental treatments were established using sexuparae, and the daily offspring count and sex allocation in each treatment zone were recorded. Subsequently, an additional experimental condition involving mixed-clone treatments was introduced. This procedure entailed the transfer of a single sexupara and 20 oviparous females from either the red (1G + 20Rov) or green clone (1G + 20Gov) onto a leaf on agar medium. Simultaneously, a control setup with a new sexupara (1G) was established. Three days following sexupara production, a dose of 0, 25, or 50 ng of JH III was applied to the aphids' abdomens. Subsequently, the titers of JH III in the sexuparae across each treatment group were quantified, and the extent of sex allocation was tallied. The findings demonstrated pronounced disparities in sex allocation among the various treatments and, notably, a substantial increase in the total offspring and oviparous number in the mixed-clone treatment group. The effects of mixed-clone treatment on the sex allocation patterns of the sexupara progeny could be determined by the application of exogenous JH III, indicating that JH may mediate the effects of mixed-clone treatment on sex allocation. Consequently, it can be concluded that A. pisum sexuparae possess the capability to modulate their sex allocation in response to the nature of adjacent competitor clones, thereby demonstrating a variety of sex allocation patterns. Throughout this process, JH III plays a pivotal role. [ABSTRACT FROM AUTHOR]

Mevalonate kinase (MevK) is an important enzyme in the mevalonate pathway that catalyzes the phosphorylation of mevalonate into phosphomevalonate and is involved in juvenile hormone biosynthesis. Herein, we present a structure model of MevK from the red flour beetle Tribolium castaneum (TcMevK), which adopts a compact α/β conformation that can be divided into two parts: an N-terminal domain and a C-terminal domain. A narrow, deep cavity accommodating the substrate and cofactor was observed at the junction between the two domains of TcMevK. Computational simulation combined with site-directed mutagenesis and biochemical analyses allowed us to define the binding mode of TcMevK to cofactors and substrates. Moreover, TcMevK showed optimal enzyme activity at pH 8.0 and an optimal temperature of 40 °C for mevalonate as the substrate. The expression profiles and RNA interference of TcMevK indicated its critical role in controlling juvenile hormone biosynthesis, as well as its participation in the production of other terpenoids in T. castaneum. These findings improve our understanding of the structural and biochemical features of insect Mevk and provide a structural basis for the design of MevK inhibitors. [ABSTRACT FROM AUTHOR]

Parental investment is any expenditure of time or energy by parents that increases their offspring survival at the cost of future reproduction. The costs associated with parental investment can be reflected in a deterioration of their physiological condition. In insects, juvenile hormone has been identified as having a role in the control of parental care. However, its effects on parental investment remain unclear for many taxa, especially in species with exclusive paternal care. We evaluated whether juvenile hormone influences postzygotic parental investment in Abedus ovatus, a waterbug with exclusive paternal care. Males provide parental care by carrying eggs on their backs and ventilating them by generating water currents through push‐ups called brood pumping. In an experiment, we applied methoprene (an analog of juvenile hormone) to males at early and late parental care stages and quantified the frequency of brood pumping and the contents of energy reserves (lipids, carbohydrates, and glycogen) at the end of parental care as a measure of physiological condition. We found that methoprene increases the frequency of brood pumping only when the water temperature increases. However, there was no correlation between the parent's energy reserves and methoprene treatments. We found that males who cared for large egg pads had lower amounts of lipids and carbohydrates at the end of parental care, and both effects are greater as the water temperature increases. These results suggest that energy expenditure during parental care is high due to intense muscular activity during brood pumping, which depletes male energy reserves and could affect future reproduction. [ABSTRACT FROM AUTHOR]

Bioinsecticides and transgenic crops based on the bacterial pathogen Bacillus thuringiensis (Bt) can effectively control diverse agricultural insect pests, nevertheless, the evolution of resistance without obvious fitness costs has seriously eroded the sustainable use of these Bt products. Recently, it has been discovered that an increased titer of juvenile hormone (JH) favors an insect host (Plutella xylostella) to enhance fitness whilst resisting the Bt pathogen, however, the underlying regulatory mechanisms of the increased JH titer are obscure. Here, the involvement of N6‐methyladenosine (m6A) RNA modification in modulating the availability of JH in this process is defined. Specifically, it is found that two m6A methyltransferase subunit genes, PxMettl3 and PxMettl14, repress the expression of a key JH‐degrading enzyme JH esterase (JHE) to induce an increased JH titer, mitigating the fitness costs associated with a robust defense against the Bt pathogen. This study identifies an as‐yet uncharacterized m6A‐mediated epigenetic regulator of insect hormones for maintaining fitness during pathogen defense and unveils an emerging Bt resistance‐related m6A methylation atlas in insects, which further expands the functional landscape of m6A modification and showcases the pivotal role of epigenetic regulation in host‐pathogen interactions. [ABSTRACT FROM AUTHOR]

The gene encoding juvenile hormone response (Krüppel homolog1, Kr-hl) in Coccinella septempunctata was investigated by cloning and analysing expression profiles in different developmental stages and tissues by quantitative real-time polymerase chain reaction (PCR). C. septempunctata Kr-hl (CsKr-hl) encoded a 1338 bp open reading frame (ORF) with a predicted protein product of 445 amino acids; the latter showed high similarity to orthologs in other species and contained eight highly-conserved Zn-finger motifs for DNA-binding. CsKr-hl was expressed in different developmental stages of C. septempunctata. The expression levels of CsKr-hl in eggs, 2nd, 3rd, 4th instar larvae, and pupa were 3.31, 2.30, 7.09, 0.58, and 7.48 times the number of 1st instar larvae, respectively. CsKr-hl expression levels in female adults gradually increased at 25–30 days and were significantly higher than expression at 1–20 days. CsKr-hl expression in 20–30 days-old male adults was significantly higher than males aged 1–15 days. CsKr-hl expression levels in heads of male and female adults were significantly higher than expression levels in the thorax, adipose, and reproductive system. Interestingly, CsKr-hl expression levels in the adipose and reproductive system of female adults were significantly higher than in adult male corresponding organs, which suggest that CsKr-hl plays an important role in regulating reproductive development in C. septempunctata. [ABSTRACT FROM AUTHOR]

Simple Summary: Pheromones, such as sex pheromones, aggregation pheromones, and alarm pheromones, are the basis for insect aggregation, mating, and other behaviors. Compared with the structures of sex pheromones, those of aggregation pheromones are more complex, especially in cucujoid grain beetles, which produce macrocyclic lactones as aggregation pheromones. So far, there is limited research studying the biosynthesis of macrocyclic lactones at the molecular level. Two aggregation pheromone components of the rusty grain beetle, Cryptolestes ferrugineus, have been identified to be biosynthesized via the mevalonate (MVA) pathway and fatty acid synthesis (FAS) pathway, with their productions affected by starvation. Therefore, we conducted a comparative transcriptomics analysis of hypothetical pheromone production sites in C. ferrugineus under starvation stress. Additionally, significantly enriched metabolic pathways and down-regulated genes directly involved in the biosynthesis and regulation of aggregation pheromones via the MVA and FAS pathways, respectively, were identified, as well as some juvenile hormone (JH)- and insulin-related genes, which are of great significance for elucidating the synthesis and regulatory mechanisms of cucujoid grain beetle pheromones. Pheromones are the basis of insect aggregation, mating, and other behaviors. Cucujoid grain beetles produce macrocyclic lactones as aggregation pheromones, yet research on their biosynthesis at the molecular level remains limited. The rusty grain beetle, C. ferrugineus, is an important economic species in China. Although two aggregation pheromone components have been identified, their suspected biosynthesis via the MVA pathway and the FAS pathway lacks molecular elucidation. Previous evidence supports that starvation affects the production of aggregation pheromones. Therefore, we constructed comparative transcriptome libraries of pheromone production sites in C. ferrugineus under starvation stress and identified genes related to pheromone biosynthesis and hormone regulation. A total of 2665 genes were significantly differentially expressed, of which 2029 genes were down-regulated in starved beetles. Putative C. ferrugineus genes directly involved in pheromone biosynthesis were identified, as well as some genes related to the juvenile hormone (JH) pathway and the insulin pathway, both of which were depressed in the starved beetles, suggesting possible functions in pheromone biosynthesis and regulation. The identification of genes involved in macrolide lactone biosynthesis in vivo holds great significance, aiding in the elucidation of the synthesis and regulatory mechanisms of cucujoid grain beetle pheromones. [ABSTRACT FROM AUTHOR]

Simple Summary: Chrysoperla nipponensis (Okamoto) is an important predatory insect, primarily preying on various agricultural pests such as aphids. The green lacewing exhibits facultative diapause, which is primarily influenced by the photoperiod. Although previous research has shown the physiological phenotypic responses of diapause-sensitive and pre-diapause periods to photoperiods in C. nipponensis, the corresponding regulatory mechanisms underlying its diapause remain somewhat unclear. In this study, transcriptome sequencing was performed to explore the molecular basis for diapause, and dsRNA-mediated knockdown was used to elucidate the role of juvenile hormone acid methyltransferase 1 (Jhamt1) in regulating diapause in C. nipponensis. Our findings not only provide insights into the transcriptional regulation processes of genes within diapause-sensitive and pre-diapause periods but also unveil the key genes responsible for regulating diapause in C. nipponensis during the pre-diapause phase. Chrysoperla nipponensis (Okamoto) displays typical adult reproductive diapause under short photoperiods; however, our understanding of the molecular mechanism underlying photoperiod-sensitive reproduction remains limited. In this study, we performed transcriptome profiling of four treatments (the diapause-sensitive stage and pre-diapause phase under long and short photoperiods) of C. nipponensis using RNA sequencing (RNA-seq). A total of 71,654 unigenes were obtained from the samples. Enrichment analysis showed that fatty acid metabolism-related pathways were altered under a short photoperiod. Moreover, β-oxidation-related gene expression was active during the diapause-sensitive period under a short photoperiod. The knockdown of juvenile hormone acid methyltransferase 1 (Jhamt1) prolonged the pre-oviposition period but did not affect the reproductive ability of female individuals in C. nipponensis. These findings provided us with a more comprehensive understanding of the molecular mechanisms of photoperiod-sensitive diapause and show that groundwork is crucial for bolstering the long-term storage and biocontrol potential of C. nipponensis. [ABSTRACT FROM AUTHOR]

Simple Summary: Soldiers and workers collectively perform defensive behaviors in termite colonies. To determine the molecular mechanism driving the defensive behaviors of termite soldiers, we tested the effect of the juvenile hormone analogue pyriproxyfen (JHA) and the soldier caste-specific protein 1 (RaSsp1) on the defensive behaviors of Reticulitermes aculabialis soldiers when encountering an ant invasion. The results showed that JHA-feeding may affect defensive behaviors (i.e., bites and head-banging) of soldiers via downregulation of RaSsp1 expression. Feeding JHA may also affect the content of alarm pheromones in soldiers, including limonene, which also influenced the defensive behavior of soldiers. These results suggest that JH and RaSsp1 may play important roles in modulating social defense in termite colonies. Eusocial insects have evolved specific defensive strategies to protect their colonies. In termite colonies, soldiers perform a colony-level defense by displaying mechanical biting, head-banging and mandible opening–closing behaviors. However, few studies have been reported on the factors modulating defensive behaviors in termites. Owing to JH (juvenile hormone) being involved in soldier differentiation, JH was speculated to affect defensive behaviors in termite soldiers. To determine the effect of JH on the defensive behaviors of termite soldiers, we performed a JHA-feeding and RaSsp1-silencing experiment and then tested the changes in defense-related behaviors, alarm pheromones and key JH signaling genes. The observed result was that after feeding workers with JHA, soldiers displayed the following: (1) decreased biting events and increased head-banging events; (2) a reduced expression of RaSsp1 and increased expression of Met (methoprene-tolerant, the nuclear receptor of JH) and Kr-h1 (the JH-inducible transcription factor Krüppel homolog 1); and (3) a decreased concentration of alarm pheromones, including α-pinene, β-pinene and limonene (+, −). Further study showed that soldiers silenced for RaSsp1 also exhibited (1) decreased biting events and increased head-banging events and (2) increased expression of Met and Kr-h1. In addition, soldiers stimulated by the alarm pheromone limonene displayed an increase in the frequency of mandible opening–closing and biting behavior. All of these results show that JHA influenced the defensive behaviors of termite soldiers, possibly via downregulating RaSsp1 expression, up-regulating Met and Kr-h1 and stimulating the secretion of alarm pheromones, suggesting that the JH pathway plays important roles in modulating social behaviors in termite colonies. [ABSTRACT FROM AUTHOR]

Light is an indispensable factor in the healthy growth of living organisms, and alterations in the photoperiod can have consequences for body homeostasis. The eyestalk is a photosensitive organ that secretes various hormones to regulate the Chinese mitten crab (Eriocheir sinensis). However, the photoperiod-dependent eyestalk patterns of gene expression that may underlie changes in body homeostasis are unknown. In this study, we investigated the molecular mechanisms involved in eyestalk transcriptomic responses in E. sinensis under different photoperiod regimes on days 2, 4, and 6. The photoperiods tested were 12, 24, and 0 h light/day. In total, we obtained 110, 958, 348 clean datasets and detected 1809 differentially expressed genes (DEGs). Genes involved in the crustacean hyperglycemic hormone superfamily and juvenile hormones were observed, which play important roles in gonadal development, growth, and immunity in E. sinensis and may also be involved in photoperiod adaptation. In addition, the MAPK signaling pathway was the only signaling pathway identified in the continuous light group but was absent in the continuous darkness group. We suggest that the MAPK pathway is highly responsive to light input during the subjective night and insensitive to light during the middle of the subjective day. These results provide insight into the molecular mechanisms underlying the effects of photoperiod on the immune regulation of E. sinensis. [ABSTRACT FROM AUTHOR]

The corpora allata-corpora cardiaca (CA-CC) is an endocrine gland complex that regulates mosquito development and reproduction through the synthesis of juvenile hormone (JH). Epoxidase (Epox) is a key enzyme in the production of JH. We recently utilized CRISPR/Cas9 to establish an epoxidase-deficient (epox−/−) Aedes aegypti line. The CA from epox−/− mutants do not synthesize epoxidated JH III but methyl farneosate (MF), a weak agonist of the JH receptor, and therefore have reduced JH signalling. Illumina sequencing was used to examine the differences in gene expression between the CA-CC from wild type (WT) and epox−/− adult female mosquitoes. From 18,034 identified genes, 317 were significantly differentially expressed. These genes are involved in many biological processes, including the regulation of cell proliferation and apoptosis, energy metabolism, and nutritional uptake. In addition, the same CA-CC samples were also used to examine the microRNA (miRNA) profiles of epox−/− and WT mosquitoes. A total of 197 miRNAs were detected, 24 of which were differentially regulated in epox−/− mutants. miRNA binding sites for these particular miRNAs were identified using an in silico approach; they target a total of 101 differentially expressed genes. Our results suggest that a lack of epoxidase, besides affecting JH synthesis, results in the diminishing of JH signalling that have significant effects on Ae. aegypti CA-CC transcriptome profiles, as well as its miRNA repertoire. [ABSTRACT FROM AUTHOR]

Insects are rich in various microorganisms, which play diverse roles in affecting host biology. Although most Drosophila species prefer rotten fruits, the agricultural pest Drosophila suzukii attacks ripening fruits before they are harvested. We have reported that the microbiota has positive and negative impacts on the agricultural pest D. suzukii on nutrient‐poor and ‐rich diets, respectively. On nutrient‐poor diets, microbes provide protein to facilitate larval development. But how they impede D. suzukii development on nutrient‐rich diets is unknown. Here we report that Acetobacter pomorum (Apo), a commensal bacterium in many Drosophila species and rotting fruit, has several detrimental effects in D. suzukii. Feeding D. suzukii larvae nutrient‐rich diets containing live Apo significantly delayed larval development and reduced the body weight of emerged adults. Apo induced larval immune responses and downregulated genes of digestion and juvenile hormone metabolism. Knockdown of these genes in germ‐free larvae reproduced Apo‐like weakened phenotypes. Apo was confirmed to secrete substantial amounts of gluconic acid. Adding gluconic acid to the D. suzukii larval diet hindered larval growth and decreased adult body weight. Moreover, the dose of gluconic acid that adversely affected D. suzukii did not negatively affect Drosophila melanogaster, suggesting that D. suzukii is less tolerant to acid than D. melanogaster. Taken together, these findings indicate that D. suzukii is negatively affected by gluconic acid, which may explain why it prefers ripening fruit over Apo‐rich rotting fruit. These results show an insect's tolerance to microbes can influence its ecological niche. [ABSTRACT FROM AUTHOR]

Traumatic brain injury (TBI) can damage the hypothalamus and cause improper activation of the growth hormone (GH) axis, leading to growth hormone deficiency (GHD). GHD is one of the most prevalent endocrinopathies following TBI in adults; however, the extent to which GHD affects juveniles remains understudied. We used postnatal day 17 rats (n = 83), which model the late infantile/toddler period, and assessed body weights, GH levels, and number of hypothalamic somatostatin neurons at acute (1, 7 days post injury (DPI)) and chronic (18, 25, 43 DPI) time points. We hypothesized that diffuse TBI would alter circulating GH levels because of damage to the hypothalamus, specifically somatostatin neurons. Data were analyzed with generalized linear and mixed effects models with fixed effects interactions between the injury and time. Despite similar growth rates over time with age, TBI rats weighed less than shams at 18 DPI (postnatal day 35; P = 0.03, standardized effect size [d] = 1.24), which is around the onset of puberty. Compared to shams, GH levels were lower in the TBI group during the acute period (P = 0.196; d = 12.3) but higher in the TBI group during the chronic period (P = 0.10; d = 52.1). Although not statistically significant, TBIinduced differences in GH had large standardized effect sizes, indicating biological significance. The mean number of hypothalamic somatostatin neurons (an inhibitor of GH) positively predicted GH levels in the hypothalamus but did not predict GH levels in the somatosensory cortex. Understanding TBI-induced alterations in the GH axis may identify therapeutic targets to improve the quality of life of pediatric survivors of TBI. [ABSTRACT FROM AUTHOR]

Reproduction is highly dependent on environmental and physiological factors including nutrition, mating stimuli and microbes. Among these factors, microbes facilitate vital functions for host animals such as nutritional intake, metabolic regulation, and enhancing fertility under poor nutrition conditions. However, detailed molecular mechanisms by which microbes control germline maturation, leading to reproduction, remain largely unknown. In this study, we show that environmental microbes exert a beneficial effect on Drosophila oogenesis by promoting germline stem cell (GSC) proliferation and subsequent egg maturation via acceleration of ovarian cell division and suppression of apoptosis. Moreover, insulin-related signaling is not required; rather, the ecdysone pathway is necessary for microbe-induced increase of GSCs and promotion of egg maturation, while juvenile hormone contributes only to increasing GSC numbers, suggesting that hormonal pathways are activated at different stages of oogenesis. Our findings reveal that environmental microbes can enhance host reproductivity by modulating host hormone release and promoting oogenesis. Environmental microbes enhance Drosophila oogenesis by increasing the number of germline stem cells, suppressing apoptosis and accelerating ovarian cell division through hormonal pathways. [ABSTRACT FROM AUTHOR]

Simple Summary: Several plant species have diterpene compounds with juvenile hormone (JH) disruptor activity in insects. Demethoxycurcumin (DMC) and bisdemethoxycurcumin (BDMC) are two curcuminoid components of turmeric, interfering with the JH-mediated formation of the JH receptor complex. In vitro, DMC and BDMC also inhibit larval and pupal development in Drosophila melanogaster. The results suggest that both DMC and BDMC are JH disruptors that affect insect growth and development by regulating JH-mediated gene expression. Juvenile hormones (JHs) play a central role in insect development, reproduction, and various physiological functions. Curcuminoids generally exhibit a wide range of biological activities, such as antioxidant, anti-inflammatory, antibacterial, and insecticidal, and they exhibit insect growth inhibitory effects. However, research on insecticidal properties of curcuminoids has been limited. Moreover, to the best of our knowledge, studies on JHs of insects and curcuminoids are lacking. Therefore, this study aimed to identify the substances that act as JH disruptors (JHDs) from edible plants. Demethoxycurcumin (DMC) and bisdemethoxycurcumin (BDMC), two curcuminoids from the turmeric plant Curcuma longa L. inhibited the formation of a methoprene-tolerant (Met)–Taiman (Tai) heterodimer complex in Drosophila melanogaster, as shown through in vitro yeast two-hybrid assays. An artificial diet containing 1% (w/v) DMC or BDMC significantly reduced the number of D. melanogaster larvae in a concentration-dependent manner; larval development was disrupted, preventing the progression of larvae to pupal stages, resulting in an absence of adults. Building on the results obtained in this study on curcuminoids, researchers can use our study as a reference to develop eco-friendly pesticides. [ABSTRACT FROM AUTHOR]

Simple Summary: The division of labor among workers is one of the predominant characteristics of social insects, which simply means that workers perform different tasks, such as caring for the brood inside the nest and foraging outside the nest, and which is essential for colony maintenance and development. Previous studies on honeybees have demonstrated that the regulation of behavioral transitions can be influenced by juvenile hormone (JH). The red imported fire ant (RIFA), Solenopsis invicta, is a typical social pest that poses a significant risk to biodiversity, ecosystems, and public health in invaded areas. Understanding the effects of JH on the behavioral transitions of RIFA is necessary, as it may provide valuable experimental data for pest control. In this study, we simulated JH elevation using the juvenile hormone analogue (JHA) methoprene application and evaluated its effect on activity levels, brood care behavior, phototaxis, and threat responsiveness of nurse workers. Our study indicates that the application of JHA reduced brood care behavior and enhanced phototaxis in nurse workers, thereby revealing the role of JH in facilitating behavioral transitions in RIFA from intranidal tasks to extranidal activity. These findings may contribute to a better understanding of the underlying mechanisms behind the division of labor in social insects. The division of labor among workers is a defining characteristic of social insects and plays a pivotal role in enhancing the competitive advantage of their colony. Juvenile hormone (JH) has long been hypothesized to be the essential driver in regulating the division of labor due to its ability to accelerate behavioral transitions in social insects, such as honeybees. The regulation of behavioral transitions by JH in the red imported fire ant (RIFA), Solenopsis invicta, a typical social pest, is unclear. Through video capture and analysis, we investigated the effects of the juvenile hormone analogue (JHA) methoprene on brood care, phototaxis behavior, and threat responsiveness of RIFA nurse workers. Our results showed that the JHA application significantly reduced the time and frequency of brood care behavior by nurse workers while increasing their walking distance and activity time in the light area. Additionally, the application of JHA made ants become excited, indicating a significant improvement in their activity level (movement distance, time, and speed). Furthermore, it was observed that the application of JHA did not affect the threat responsiveness of nurse workers towards stimuli (nestmates or non-nestmates). Our study demonstrates that the application of JHA reduced brood care behavior and enhanced phototaxis in nurse workers, which may reveal the role of JH in facilitating behavioral transitions in RIFA from intranidal tasks to extranidal activity. This study provides an experimental basis for further elucidating the mechanism underlying the division of labor in social insects. [ABSTRACT FROM AUTHOR]

Simple Summary: The regulation of insect growth and development is intricately governed by the levels of juvenile hormone and 20-hydroxyecdysone. Juvenile hormone esterase is a key catabolic enzyme of juvenile hormone that is involved in the growth, development, and metamorphosis of insects. In this study, we identified the juvenile hormone esterase genes Bmjhe1–9 in silkworm and found that Bmjhe6 was specifically expressed in the silk gland. In order to explore the function of Bmjhe6, the expression of Bmjhe6 was down-regulated in an RNA interference experiment. The results showed that the development of the silk gland was changed as well as the juvenile hormone pathway genes. Interestingly, Bmjhe6 was secreted into the silk gland lumen and cocoon silk, which may have new functions. This study provides some theoretical basis for the regulation of tissue growth and development as well as silk protein synthesis by juvenile hormone esterase, and servers as a reference for the study of juvenile hormone esterase in other insects. Juvenile hormone esterase (JHE) is the specific enzyme that degrades juvenile hormone (JH) and regulates the JH titer in insects. JH also regulates the development of the silk gland and the synthesis and secretion of silk proteins in Bombyx mori. Here, we identified nine possible JHE family members, Bmjhe1–9. Notably, Bmjhe6 is specifically expressed in the silk gland. Using semi-quantitative, quantitative real-time RT-PCR and Western blot, it was confirmed that Bmjhe6 was specifically expressed in the middle silk gland (MSG) with high levels in the anterior region of the MSG (A-MSG). The immunofluorescence localization analysis revealed that Bmjhe6 is produced within cells, secreted into the gland lumen, and co-transported with silk proteins into the anterior silk gland (ASG). In vitro hormone induction experiments demonstrated that Bmjhe6 responds to a JH analog, increasing its expression after 12–24 h, whereas 20-hydroxyecdysone inhibited it. In addition, Bmjhe6 knockdown using dsBmjhe6 injections accelerated larval development, resulting in increased larval body and silk gland weight. This induced disordered sericin genes (Ser2, Ser3) expression, and key genes in the JH synthesis pathway (BmKr-h1 and BmMet1) were significantly upregulated along with the transcription factors (SGF-1 and Sage). These results indicate that Bmjhe6 plays an important role in silk gland growth and silk protein synthesis by modulating JH signal. [ABSTRACT FROM AUTHOR]

When Coccinella septempunctata L. was fed on an artificial diet, development was prolonged and survival and reproduction were decreased, thus negatively affecting population growth. Juvenile hormone and moulting hormones are important factors in insect reproduction and development. This study aims to screen out the optimal hormones that can solve the problems such as slow population growth of the C. septempunctata during mass rearing, thus improving their effectiveness as a biological control agent. The effects of juvenile hormone analogues and moulting hormones on C. septempunctata larval growth and adult reproduction were investigated by supplementing an artificial diet with different doses of methoprene, kinoprene, juvenile hormone Ш, fenoxycarb and 20‐hydroxyecdysone. Multiple parameters were measured for C. septempunctata including development, survival, pupation, emergence, pre‐oviposition, fecundity and hatching rates. The addition of juvenile hormone analogues to the diet significantly lengthened larval development times and reduced pupation and emergence. Conversely, juvenile hormone analogues significantly shortened pre‐oviposition period, reduced survival and increased fecundity. The shortest pre‐oviposition period was 9.6 days, and the highest oviposition number was 578 eggs in response to 5 μL kinoprene. The highest hatching rate was 66% in 1.7 mg 20‐hydroxyecdysone treatment. The results of this study provide a theoretical basis for hormone selection and dosage in C. septempunctata artificial diets, thus enhancing the survival, pupation and emergence of larvae and improving the fecundity and hatching rate of ladybird adults. [ABSTRACT FROM AUTHOR]

Understanding the mechanisms governing body size attainment during animal development is of paramount importance in biology. In insects, a crucial phase in determining body size occurs at the larva-pupa transition, marking the end of the larval growth period. Central to this process is the attainment of the threshold size (TS), a critical developmental checkpoint that must be reached before the larva can undergo metamorphosis. However, the intricate molecular mechanisms by which the TS orchestrates this transition remain poor understood. In this study, we investigate the role of the interaction between the Torso and TGFß/activin signaling pathways in regulating metamorphic timing in the red flour beetle, Tribolium castaneum. Our results show that Torso signaling is required specifically during the last larval instar and that its activation is mediated not only by the prothoracicotropic hormone (Tc-Ptth) but also by Trunk (Tc-Trk), another ligand of the Tc-Torso receptor. Interestingly, we show that while Torso activation by Tc-Ptth determines the onset of metamorphosis, Tc-Trk promotes growth during the last larval stage. In addition, we found that the expression of Tc-torso correlates with the attainment of the TS and the decay of juvenile hormone (JH) levels, at the onset of the last larval instar. Notably, our data reveal that activation of TGFß/activin signaling pathway at the TS is responsible for repressing the JH synthesis and inducing Tc-torso expression, initiating metamorphosis. Altogether, these findings shed light on the pivotal involvement of the Ptth/Trunk/Torso and TGFß/activin signaling pathways as critical regulatory components orchestrating the TS-driven metamorphic initiation, offering valuable insights into the mechanisms underlying body size determination in insects. Author summary: Understanding the mechanisms that determine an animal's final body size is a fundamental question in biology. In animals, the majority of growth takes place during the juvenile stage, with adult size being established as they transition into adulthood. Hormones play a pivotal role in orchestrating this complex process. In the case of insects, the metamorphic transition is induced by the interplay between the steroid hormone ecdysone and the sesquiterpenoid juvenile hormone (JH). Our research delved into the roles of the Torso and TGFß/Activin signaling pathways in regulating ecdysone and JH biosynthesis. Remarkably, we discovered that in contrast to other insects, the Torso pathway in Tribolium is activated by not one, but two ligands: the prothoracicotropic hormone that regulates ecdysone production and Trunk that promotes growth in the last larval stage. Additionally, our investigations unveiled the dual functionality of the TGFß/Activin signaling pathway in the initiation of metamorphosis. Firstly, it lowers JH levels, setting in motion the genetic changes required for the metamorphic transition, including the upregulation of Torso and, secondly, facilitating ecdysone production. In summary, our research sheds light on the intricate regulatory network governing metamorphic timing and body size in insects. [ABSTRACT FROM AUTHOR]

Division of labor is a hallmark characteristic of social insect colonies. While it is understood that worker differentiation is regulated through either the queen or her brood, the understanding of the physiology behind task regulation varies within social species. Studies in eusocial insects have shown that juvenile hormone (JH) is associated with division of labor and the onset of foraging tasks. Although, outside of a few key species, this interaction has yet to be elucidated in the red imported fire ant, Solenopsis invicta. In this study, we evaluated the role of a JH analog, S-hydroprene in worker task transition in Solenopsis invicta. S-hydroprene was applied to nurses to observe behavioral changes. S-hyroprene application to nurses did not affect phototaxis, but there was a shift in behavior from internal, nest-based behaviors to external, foraging-based behaviors. These results show that JH may be implicated in worker task transition in S. invicta and may function similarly as it does in other eusocial insects. [ABSTRACT FROM AUTHOR]

In the present study, the spectroscopic investigation of pyriproxyfen (PYR) has been carried out using density functional theory and experimental methods. The FT‐IR, 1H and 13C NMR spectra of PYR were recorded, interpreted and compared with the theoretical spectra. The polarizability and hyperpolarizabilities are responsible for higher lipophilicity which leads to the acute aquatic toxicity of the PYR molecule. The UV‐Visible spectra of PYR exhibited the presence of π→ ${\to }$ π* transition between the π‐orbitals of phenoxyphenyl and pyridyl ring. The standard entropy, heat capacity at constant volume and total energy have been computed to assess the toxicity of the compound. Molecular docking revealed the insecticidal potential of PYR owing to the presence of hydrogen bond interactions between PYR and mosquito juvenile hormone binding protein of aedes aegypti. The biophysical study predicts the possible DNA‐PYR interactions and carcinogenic properties of PYR molecule. [ABSTRACT FROM AUTHOR]

Juvenile hormone (JH) controls the development and reproduction of insects. Therefore, a tight regulation of the expression of JH biosynthetic enzymes is critical. microRNAs (miRNAs) play significant roles in the post-transcriptional regulation of gene expression by interacting with complementary sequences in target genes. Previously, we reported that several miRNAs were differentially expressed during three developmental stages of Aedes aegypti mosquitoes with different JH levels (no JH, high JH, and low JH). One of these miRNAs was aae-miR-34-5p. In this study, we identified the presence of potential target sequences of aae-miR-34-5p in the transcripts of some genes encoding JH biosynthetic enzymes. We analysed the developmental expression patterns of aae-miR-34-5p and the predicted target genes involved in JH biogenesis. Increases in miRNA abundance were followed, with a delay, by decreases in transcript levels of target genes. Application of an inhibitor and a mimic of aae-miR-34-5p led respectively to increased and decreased levels of thiolase transcripts, which is one of the early genes of JH biosynthesis. Female adult mosquitoes injected with an aae-miR-34-5p inhibitor exhibited significantly increased transcript levels of three genes encoding JH biosynthetic enzymes, acetoacetyl-CoA thiolase (thiolase), farnesyl diphosphate phosphatase, and farnesal dehydrogenase. Overall, our results suggest a potential role of miRNAs in JH production by directly targeting genes involved in its biosynthesis. [ABSTRACT FROM AUTHOR]

Honey bees are typical model organisms for the study of caste differentiation, and the juvenile hormone (JH) is a crucial link in the regulatory network of caste differentiation in honey bees. To investigate the mechanism of JH-mediated caste differentiation, we analyzed the effect of the JH response gene AmKr-h1 on this process. We observed that AmKr-h1 expression levels were significantly higher in queen larvae than in worker larvae at the 48 h, 84 h, and 120 h larval stages, and were regulated by JH. Inhibiting AmKr-h1 expression in honey bee larvae using RNAi could lead to the development of larvae toward workers. We also analyzed the transcriptome changes in honey bee larvae after AmKr-h1 RNAi and identified 191 differentially expressed genes (DEGs) and 682 differentially expressed alternative splicing events (DEASEs); of these, many were related to honey bee caste differentiation. Our results indicate that AmKr-h1 regulates caste differentiation in honey bees by acting as a JH-responsive gene. [ABSTRACT FROM AUTHOR]

Simple Summary: Diapause is physiological state of developmental arrest and dormancy, which is genetically determined and mediated by neurohormones. Diapause process is an opportunity for insects to survive seasonal environmental changes. Red mason bee Osmia bicornis is an univoltine species with imaginal diapause, and it is used for crop pollination. Our work shows that obligatory diapause in O. bicornis can be modified by a juvenile hormone analog. Treating pupae or young imagoes in cocoons during the pre-wintering period with a JHA (methoprene) can prevent winter diapause and induce the emergence of adult bees in October when development was accelerated in the laboratory or in November when bees developed outdoors according to their life cycle. More sensitive to methoprene is the imago than the pupa, but earlier application of JH analog can accelerate the emergence of adult bees. Our study suggests that JH levels during the pupal stage and soon after adult eclosion are related to hormonal regulation of winter diapause in O. bicornis. On the other hand, a better understanding of the mechanisms of reproductive diapause can help us improve the management of Osmia bees as commercial pollinators that can be used regardless of the emergence period in nature. Osmia bicornis syn. O. rufa is a univoltine bee species in which adults fly in spring and the offspring overwinter as cocooned imagoes. The flight period of solitary bees is short, so methods of control for development and emergence time are needed to synchronize the activity of managed pollinators with blooming. In our study, we tested the effectiveness of a juvenile hormone analog for the prevention of winter diapause. Bees developed in settled nests outdoors or in the laboratory (22 °C) until the end of the pre-pupa stage, then cocoons were removed from the nest cells and treated with a JH analog—methoprene—during the pupa and young imago stages. Then, bees were activated at 25 °C until the adults left the cocoons. Topical application of methoprene to the cocoon at the pupa or imago stage induced the emergence of some adult bees in the pre-diapause period, while no adults emerged when the bees were not treated with methoprene. Most adults emerged (about 50%) when treated with methoprene on 3-week-old cocooned imagoes. Bees treated in the pupal stage had a lower emergence rate (20–30%), but adult bees emerged earlier. The emergence time of adults for the laboratory group was, on average, from 70 to 91 days, and that for outdoor groups was from 57 to 72 days. [ABSTRACT FROM AUTHOR]

The cricket Velarifictorus aspersus (Walker) (Orthoptera: Gryllidae) exhibits a wing dimorphism mediating two distinct life‐history strategies during early adulthood; long‐winged (LW) females mainly invest resources in flight, whereas short‐winged (SW) females invest more heavily in reproduction than LW females. To understand the relationships among juvenile hormone (JH), flight capacity, and energy accumulation, the daily rhythm of JH titer and flight activity, the concentrations of flight energy substances, and the influence of exogenous JH on flight activity and flight energy substances were investigated in V. aspersus. The results showed that the hemolymph JH titer exhibited a high‐amplitude daily rhythm in 5‐day‐old LW V. aspersus females, and the JH titer rose about 10× at 18:00 hours (6 h before lights off) and dropped to baseline levels after lights off. The females flew inactively (i.e., they floated in the air) from 14:00 to 19:00 hours during the light period, whereas they had a stronger flight capacity in the initial photophase and before lights out. The flight ability of LW females with 20 μg μL−1 JH treatments was significantly improved during periods of flight inactivity. After the peak JH titer, the concentrations of glycogen and trehalose in the flight muscles increased significantly. The LW females treated with JH during the inactive flight period had a significant increase in glycogen after 1 h and trehalose after 3 h. These results suggested that the high‐amplitude daily rhythm of the JH titer was correlated with accumulation of flight energy substance and flight capacity; that is, an elevated JH titer promoted the biosynthesis of flight energy substances, resulting in improvement of flight capacity. [ABSTRACT FROM AUTHOR]

The proteome profiles of the cuticle and haemolymph of two strains of the Chinese Oak silk moth A. pernyi, with cyan and yellow coloured bodies, were compared in order to identify the differentially expressed proteins (DEPs) that determine the differences in the colouration of the two strains. A total of 324 DEPs, including 124 up-regulated and 200 down-regulated proteins, were identified in the cuticles of the cyan and yellow coloured individuals, and 286 DEPs including 79 up-regulated and 207 down-regulated proteins in the haemolymph of the cyan and yellow coloured individuals. Several DEPs associated with the colour of larvae of A. pernyi were screened, including an ommochrome-binding protein, juvenile hormone esterase, protein yellow, L-dopachrome tautomerase yellow-f2 and fumarylacetoacetase, the expression levels in the cuticle and haemolymph of the yellow larvae were higher than those in the cyan coloured larvae, indicating their possible roles underlying the colouration of the yellow larvae of A. pernyi. [ABSTRACT FROM AUTHOR]

This study explores the potential inhibitory activity of alkaloids, a class of natural compounds isolated from Brazilian biodiversity, against the mJHBP enzyme of the Aedes aegypti mosquito. This mosquito is a significant vector of diseases such as dengue, zika, and chikungunya. The interactions between the ligands and the enzyme at the molecular level were evaluated using computational techniques such as molecular docking, molecular dynamics (MD), and molecular mechanics with generalized Born surface area (MMGBSA) free energy calculation. The findings suggest that these compounds exhibit a high binding affinity with the enzyme, as confirmed by the binding free energies obtained in the simulation. Furthermore, the specific enzyme residues that contribute the most to the stability of the complex with the compounds were identified: specifically, Tyr33, Trp53, Tyr64, and Tyr129. Notably, Tyr129 residues were previously identified as crucial in the enzyme inhibition process. This observation underscores the significance of the research findings and the potential of the evaluated compounds as natural insecticides against Aedes aegypti mosquitoes. These results could stimulate the development of new vector control agents that are more efficient and environmentally friendly. [ABSTRACT FROM AUTHOR]

Sexual Selection has been studied predominantly from a functional perspective with relatively limited investigation of the mechanistic basis of female choice. In this study, we evaluated female choice and larvae production in response to attractive or less attractive males and concurrently examined the protein profile in the brains of females, using the mealworm beetle Tenebrio molitor as a model system. Females were found to prefer males with high levels of pheromones, which requires the secretion of juvenile hormone (JH). Male attractiveness was enhanced using the JH analog methoprene, resulting in less female rejection and higher mating frequency and offspring production. Importantly, reproductive success was not due to differences in testis size or sperm production, or viability. Out of the 1833 proteins detected in the brain, only 32 were differentially expressed in females mating with attractive versus less attractive males. These proteins involved memory, metabolism, olfactory detection, reproduction, and movement. Although some brain proteins have been linked to mate choice in vertebrates, most of the differentially expressed molecules found in this study have not been previously reported concerning mate choice. [ABSTRACT FROM AUTHOR]

Division of labor is a hallmark characteristic of social insect colonies. While it is understood that worker differentiation is regulated through either the queen or her brood, the understanding of the physiology behind task regulation varies within social species. Studies in eusocial insects have shown that juvenile hormone (JH) is associated with division of labor and the onset of foraging tasks. Although, outside of a few key species, this interaction has yet to be elucidated in the red imported fire ant, Solenopsis invicta. In this study, we evaluated the role of a JH analog, S-hydroprene in worker task transition in Solenopsis invicta. S-hydroprene was applied to nurses to observe behavioral changes. S-hyroprene application to nurses did not affect phototaxis, but there was a shift in behavior from internal, nest-based behaviors to external, foraging-based behaviors. These results show that JH may be implicated in worker task transition in S. invicta and may function similarly as it does in other eusocial insects. [ABSTRACT FROM AUTHOR]

Various plant species contain terpene secondary metabolites, which disrupt insect growth and development by affecting the activity of juvenile hormone-degrading enzymes, and the juvenile hormone (JH) titers maintained in insects. Nerolidol, a natural sesquiterpenol belonging to the terpenoid group, exhibits structural similarities to insect JHs. However, the impact of nerolidol on insect growth and development, as well as its underlying molecular mechanism, remains unclear. Here, the effects of nerolidol on Spodoptera exigua were investigated under treatment at various sub-lethal doses (4.0 mg/mL, 1.0 mg/mL, 0.25 mg/mL). We found that a higher dose (4.0 mg/mL) of nerolidol significantly impaired the normal growth, development, and population reproduction of S. exigua, although a relatively lower dose (0.25 mg/mL) of nerolidol had no significant effect on this growth and development. Combined transcriptome sequencing and gene family analysis further revealed that four juvenile hormone esterase (JHE)-family genes that are involved in juvenile hormone degradation were significantly altered in S. exigua larvae after nerolidol treatment (4.0 mg/mL). Interestingly, the juvenile hormone esterase-like (JHEL) gene Sexi006721, a critical element responsive to nerolidol stress, was closely linked with the significant augmentation of JHE activity and JH titer in S. exigua (R2 = 0.94, p < 0.01). Taken together, we speculate that nerolidol can function as an analog of JH by modulating the expression of the enzyme genes responsible for degrading JH, resulting in JH disorders and ultimately disrupting the development of insect larvae. This study ultimately provides a theoretical basis for the sustainable control of S. exigua in the field whilst proposing a new perspective for the development of novel biological pesticides. [ABSTRACT FROM AUTHOR]

RNA interference (RNAi) is a technique employed to investigate the functions of various genes in whitefly and other insects. The effectiveness of the RNAi technique depends upon the delivery of dsRNA into the insects and it has been achieved through microinjection, oral feeding, egg soaking, transfection, topical application, spraying with nanoparticles, leaf‐mediated dsRNA feeding or plant‐mediated/ transgenic plants. In Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae), most of the studies on RNAi were conducted on the adult through either injection or oral feeding. There is a need to develop a system to deliver dsRNA in whitefly nymphs because the first instar nymphs after hatching find a suitable place on the leaf and feed on the same place till adult emergence. So, we evaluated nine different techniques using different sponges, tubes, and, Petri plates for feeding nymphs. The detached leaf survived for maximum number of days (8.25 days) with minimum nymphal mortality (12.01%) in the Whitefly Nymphal Feeding System‐1 (WNFS‐1) treatment; therefore, WNFS‐1 was selected for the delivery of dsRNA to B. tabaci nymphs. In WNFS‐1, blue food dye was used to confirm that nymphs were being fed, and the results were evidenced by blue‐coloured bodies. The juvenile hormone esterase (jhe) gene was silenced in order to successfully deliver dsRNA to nymphs using WNFS‐1 and resulting in much higher nymphal mortality (68.36%). Therefore, WNFS‐1 is a reliable method of delivering dsRNA for the purpose of silencing the genes in the nymphal stages of whiteflies. The WNFS system may also be used extensively to evaluate any chemistry (insecticides, hormones, biopesticides, etc.) in nymphs of whitefly. [ABSTRACT FROM AUTHOR]

The efficient production of silkworm silk is crucial to the silk industry. Silk protein synthesis is regulated by the juvenile hormone (JH) and 20-Hydroxyecdysone (20E). Therefore, the genetic regulation of silk production is a priority. JH binding protein (JHBP) transports JH from the hemolymph to target organs and cells and protects it. In a previous study, we identified 41 genes containing a JHBP domain in the Bombyx mori genome. Only one JHBP gene, BmJHBPd2, is highly expressed in the posterior silk gland (PSG), and its function remains unknown. In the present study, we investigated the expression levels of BmJHBPd2 and the major silk protein genes in the high-silk-producing practical strain 872 (S872) and the low-silk-producing local strain Dazao. We found that BmJHBPd2 was more highly expressed in S872 than in the Dazao strain, which is consistent with the expression pattern of fibroin genes. A subcellular localization assay indicated that BmJHBPd2 is located in the cytoplasm. In vitro hormone induction experiments showed that BmJHBPd2 was upregulated by juvenile hormone analogue (JHA) treatment. BmKr-h1 upregulation was significantly inhibited by the overexpression of BmJHBPd2 (BmJHBPd2OE) at the cell level when induced by JHA. However, overexpression of BmJHBPd2 in the PSG by transgenic methods led to the inhibition of silk fibroin gene expression, resulting in a reduction in silk yield. Further investigation showed that in the transgenic BmJHBPd2OE silkworm, the key transcription factor of the JH signaling pathway, Krüppel homolog 1 (Kr-h1), was inhibited, and 20E signaling pathway genes, such as broad complex (Brc), E74A, and ultraspiracle protein (USP), were upregulated. Our results indicate that BmJHBPd2 plays an important role in the JH signaling pathway and is important for silk protein synthesis. Furthermore, our findings help to elucidate the mechanisms by which JH regulates silk protein synthesis. [ABSTRACT FROM AUTHOR]

It is known that 20-hydroxyecdysone is one of the most important hormonal regulators of development, reproduction and adaptation to unfavorable conditions in insects. Here, we show for the first time that exogenous 20-hydroxyecdysone increases the content of two main insect carbohydrates, trehalose and glucose, in Drosophila melanogaster females both in normal conditions and under short-term heat stress. It is found that the levels of both trehalose and glucose increase after 39 min of heat exposure and return to their original levels after 1.5 h. A scheme of hormonal regulation of carbohydrate content under heat stress, involving 20-hydroxyecdysone, juvenile hormone, and dopamine, is suggested. [ABSTRACT FROM AUTHOR]

Wing polymorphism is an evolutionary trait that is widely present in various insects and provides a model system for studying the evolutionary significance of insect dispersal. The brown planthopper (BPH, Nilaparvata lugens) can alter its wing morphs under biotic and abiotic stress. However, whether differential signaling pathways are induced by the 2 types of stress remain largely unknown. Here, we screened a number of candidate genes through weighted gene co‐expression network analysis (WGCNA) and found that ornithine decarboxylase (NlODC), a key enzyme in the synthesis of polyamines, was associated with wing differentiation in BPH and mainly responded to abiotic stress stimuli. We analyzed the Kyoto Encyclopedia of Genes and Genomes enrichment pathways of differentially expressed genes under the 2 stresses by transcriptomic comparison, and found that biotic stress mainly influenced insulin‐related signaling pathways while abiotic stress mainly influenced hormone‐related pathways. Moreover, we found that insulin receptor 1 (NlInR1) may regulate wing differentiation of BPH by responding to both biotic and abiotic stress, but NlInR2 only responded to biotic stress. Similarly, the juvenile hormone epoxide hydrolase associated with juvenile hormone degradation and NlODC may regulate wing differentiation mainly through abiotic stress. A model based on the genes and stresses to modulate the wing dimorphism of BPH was proposed. These findings present a comprehensive molecular mechanism for wing polymorphism in BPH induced by biotic and abiotic stress. [ABSTRACT FROM AUTHOR]

Juvenile hormones (JHs) play a crucial role in the development of the fall armyworm, Spodoptera frugiperda, with varying types and concentrations observed at different stages. However, the interplay between JHs and 20-hydroxyecdysone (20E) in co-ordinating the life cycle of S. frugiperda remains unknown. In this study, by using high-precision UPLC-MS/MS and qRT-PCR, we detected changes in JH and 20E levels and identified important 20E receptor and response genes. Our findings revealed that JH I antagonises JH II, whereas JH II promotes JH III synthesis. High JH I and JH II concentrations in the larval stage strongly affected moulting to the next instar. Furthermore, these hormones inhibit 20E synthesis and reduce its receptor expression, thereby affecting 20E signalling. During pupation, JH II plays a crucial role in stimulating 20E synthesis for larval–pupal transformation. JH I and JH II are essential for eclosion, precisely controlling emergence timing and subsequent reproductive organ maturation. These hormones likely regulate larval development, pupation, and adult reproduction in S. frugiperda. Further studies are warranted to explore the regulatory advantages of JH I and JH II over JH III. [ABSTRACT FROM AUTHOR]

The circadian clock plays an integral role in hormone biosynthesis and secretion. However, how the circadian clock precisely coordinates hormonal homeostasis to maintain normal animal development remains unclear. Here, we show that knocking out the core clock gene Cryptochrome 1 (Cry1) significantly delays the developmental time in Bombyx mori. This study focuses on the ecdysone and juvenile hormone signalling pathways of fifth instar larvae with the longest developmental time delay. We found that the mutant reduced prothoracicotropic hormone synthesis in the brain, and could not produce sufficient ecdysone in the prothoracic gland, resulting in a delayed peak of 20‐hydroxyecdysone titre in the hemolymph of fifth instar larvae, prolonging developmental time. Moreover, further investigation revealed that the mutant enhanced juvenile hormone biosynthesis and signalling pathway and that this higher juvenile hormone titre also resulted in prolonged developmental time in fifth instar larvae. Our results provide insights into the molecular mechanisms by which the circadian clock regulates animal development by maintaining hormonal homeostasis. [ABSTRACT FROM AUTHOR]

The nuclear receptor (NR) superfamily is one of the largest groups of transcription factors in living organisms. Oestrogen related receptor (ERR) is a class of nuclear receptors closely related to oestrogen receptors (ERs). In this study, the Nilaparvata lugens (N. lugens) ERR2 (NlERR2) was cloned, and the expression of NlERR2 was detected by qRT‐PCR to explore the distribution of NlERR2 during development and in different tissues. Using RNAi and qRT‐PCR, the interaction between NlERR2 and related genes of the 20‐hydroxyecdysone (20E) and juvenile hormone (JH) signalling pathways was studied. The results showed that topical application of 20E and juvenile hormone III (JHIII) affected the expression of NlERR2, and NlERR2 could affect the expression of genes related to 20E and JH signalling pathways. Furthermore, NlERR2 and JH/20E hormone signalling‐related genes affect moulting and ovarian development. NlERR2 and NlE93/NlKr‐h1 affect the transcriptional expression of Vg‐related genes. In summary, NlERR2 is related to hormone signalling pathways, which is also related to the expression of Vg and Vg related genes. Brown planthopper is one of the most important rice pests. This study provides an important basis for mining new targets for pest control. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Brassinosteroids (BRs) are steroid hormones that regulate plant growth, development, and stress resistance. In this study, we evaluated the effect of agrochemicals on dark-induced hypocotyl elongation, which is regulated by BRs, to identify novel chemicals that regulate BR action. We found that the juvenile hormone agonist fenoxycarb inhibited dark-induced hypocotyl elongation in Arabidopsis. Treatment with the same class of juvenile hormone agonist, pyriproxyfen, did not affect hypocotyl elongation. Co-treatment with fenoxycarb and BR partly canceled the fenoxycarb-induced hypocotyl suppression. In addition, gene expression analysis revealed that fenoxycarb altered the BR-responsive gene expression. These results indicate that fenoxycarb is a BR action inhibitor. [ABSTRACT FROM AUTHOR]

Derivatives of 1-benzyl-2-methylbenzimidazoles (BMBIs) were synthesized to evaluate their biological activities against Bombyx mori, a lepidopteran model insect. Synthesized BMBIs exhibited two different biological activities: inhibition of development and acute lethality. From a structural perspective, the activity varied with the position of the substitutions on the 1-benzyl moiety; BMBIs with substitutions on the 2 and/or 4 positions had comparatively high activity in comparison with those with substitutions on the 3-position. There was more activity for the inhibition of development with low doses, and more for acute lethality with high doses. The activity was also affected by the applied stage, that is, application in the 4th instar mostly interfered the larval molting or pupation, whereas that in the 3rd instar caused more acute mortality. Taken together, these results suggest that BMBIs have multiple modes of action. [ABSTRACT FROM AUTHOR]

Simple Summary: Most studies have focused on water temperature and photoperiods on the effects of growth and reproduction in fish, but the light spectrum also plays an important role in inducing the synthesis and secretion of growth-/reproduction-related hormones. In this study, the juvenile red spotted grouper was exposed to four light spectra from white, red, blue, or green light-emitting diodes (LEDs) for two months. The fish exposed to white LEDs exhibited the best growth, although the expression levels of growth hormone (GH) showed no significant differences and the pre-pro-somatostatin-I (PSS-I) expression levels significantly increased. Four LED spectra were effective in stimulating food intake as the expression levels of neuropeptide Y significantly increased. The gonadal development advanced from chromatin nucleolar-stage oocytes to perinucleolar-stage oocytes in all four LED groups, while there were no significant differences in FSHβ and LHβ expression. This result suggests that FSHβ and LHβ may not have played important roles in gonadal development when these fish were exposed to the four light spectra. Collectively, our results provide evidence that the natural light condition (white LED condition) is a better choice for the growth of juvenile red spotted grouper in captivity during summer. The light spectrum is a key environmental cue involved in growth and reproduction in teleosts. This study investigated the effects of exposure on juvenile red spotted grouper exposed to white (control), red (590 nm), blue (480 nm), and green (520 nm) light-emitting diodes (LEDs) (12 h light:12 h dark) for two months. The body weight (BW), total length (TL), condition factor (CF), weight gain rate (WGR), gonadosomatic index (GSI), and hepatosomatic index (HSI) were assessed. Gonadal development was observed. The gene expression of growth-related hormones, such as growth hormone (GH), pre-pro-somatostatin-I (PSS-I), neuropeptide Y (NPY), and CCK, and of reproduction-related hormones, such as Kiss1, Kiss2, GPR54, sbGnRH, FSHβ, and LHβ, was analyzed. The results showed that the fish in the white LED group exhibited the best BW, TL, CF, WGR, and HSI after one or two months. The fish exposed to white LEDs showed the best growth after two months, but no significant differences in GH levels were detected. Contrarily, the expression levels of the PSS-I significantly increased (p < 0.05) in fish from the white group, suggesting the complex regulation of GH production and the limited effects of PSS-I on the inhibition of GH synthesis and somatic growth. The significantly increased NPY levels in the four LED groups (p < 0.05) indicated that these four LED spectra were effective in stimulating food intake and energy homeostasis. After two months, the gonads developed from chromatin nucleolar-stage oocytes to perinucleolar-stage oocytes in the four LED groups. The gene expression of Kiss2 and GPR54 in the four LED groups and of sbGnRH in the white and blue LED groups significantly increased when compared to that in the initial group (p < 0.05), while there were no significant differences in FSHβ and LHβ expression in the four LED groups. These results suggest that FSH and LH may not play important roles in gonadal development in juvenile red spotted grouper that are exposed to these four LED spectra. [ABSTRACT FROM AUTHOR]

[Objective] The present paper aimed to investigate the effects of rearing material nutrients and juvenile hormone Ⅲ (JHIII) on the growth and development of Hepialus menyuanicus larvae, and to clarify the direct and indirect relationships between rearing material nutrients and JHIII on the growth and development of larvae using through path analysis. [Method] The newly molted 3rd instar larvae were studied with coconut flour as the rearing substrate, and a two-factor experimental design was used with four rearing materials[J: (Potentilla anserina), H: (Daucus carota), Z: (Polygonum viviparum) and D: (Rheum palmatum) ]and three JHIII titer levels (B1: 13.32 μg/g, B2: 16.56 μg/g and B3: 22.76 μg/g) were reared on larvae, and the reared materials were analyzed for crude protein, crude fiber, soluble sugar, crude ash, water content, carbohydrate and JHIII on larval growth and development (head width, body length, body weight and survival rate) were analyzed by regression analysis and path analysis. [Result] Both rearing materials and JHIII significantly affected the growth and development of larvae with a significant interaction effect (P＜0.05) .Path analysis showed that JHIII had the greatest direct effect on larval head width, body length, body weight and survival rate (P=-2.56, P=-1.89, P=-3.66, P=2.36) .Crude protein had the greatest indirect promoting effect on head width and body length (P=3.99, P=3.79), soluble sugar had the greatest indirect promoting effect on body weight (P=5.40), and crude ash had the greatest indirect inhibitory effect on survival (P=-5.14), and crude protein, soluble sugar, and crude ash all had the greatest indirect effects on head width and body length, body weight, and survival through JHIII (P=2.23, P=1.64, P=2.93, P=-2.86) . [Conclusion] The paper preliminarily finds the simple mechanism of feeding materials affecting the growth and development of larvae.JHIII is a direct factor affecting the growth and development of larvae, while nutrients in rearing materials are an indirect factor and affect larval growth and development through changes in JHIII titer.The nutrients of rearing materials lead to inconsistent growth and development of larvae by affecting the JHIII titer of the larvae.Among them, crude protein, soluble sugar and crude ash promote the growth of head width and body length of larvae, promote the development of body weight and reduce the survival rate of larvae by inhibiting the JHIII titer.The study provides a scientific reference for the artificial domestication and succession rearing of H.menyuanicus. [ABSTRACT FROM AUTHOR]

Simple Summary: Juvenile hormone (JH) is very important to the growth and development of insects, but the role of farnesoic acid O-methyltransferase (FAMeT) on JH titer has not been determined in insects. In this study, BmFAMeT6 overexpression and BmFAMeT6 knockout strains were established by using the Gal4/UAS binary hybrid system and CRISPR/CAS 9 system, respectively. The role of FAMeT in the regulation of insect JH titers and the relationship between farnesoic acid and the synthesis of JH (JH I and JH II) were, first, revealed directly in insects. This provides a new perspective for further understanding the synthesis and regulation of JH in silkworms and other insects. Juvenile hormone (JH) plays a vital role in the growth, development, and reproduction of insects and other arthropods. Previous experiments have suggested that BmFAMeT6 could affect the duration of the silk moth's larval stage. In this study, we established the BmFAMeT6 overexpression strain and BmFAMeT6 knockout strain using the GAL4/UAS binary hybrid system and CRISPR/Cas 9 system, respectively, and found that the larval stage of the overexpression strain was shorter, while the knockout strain was longer. Our results exhibited that both the JH titers and BmKr-h1 levels in the larvae of the third instar were reduced significantly by BmFAMeT6 overexpression, but were increased obviously by BmFAMeT6 knockout. In addition, injection of farnesoic acid induced changes in the JH I and JH II levels in the hemolymphs of larvae. This study is the first to directly reveal the role of BmFAMeT6 in the regulation of insect JH titers and the relationship between farnesoic acid and JH (JH I and JH II). This provides a new perspective on regulating the growth and development of insects such as Bombyx mori. [ABSTRACT FROM AUTHOR]