Juvenile hormone biosynthetic genes are critical for regulating reproductive diapause in the cabbage beetle

Identification of Histone and N-Terminal Acetyltransferases Required for Reproduction and Embryonic Development of Yellow Fever Mosquito, Aedes aegypti

Histone acetylation levels maintained by histone acetyltransferases (HATs) and histone deacetylases play important roles in maintaining local chromatin accessibility and expression of genes that regulate many biological processes, including development and reproduction. N-terminal acetylation of proteins catalyzed by N-terminal acetyltransferases (NATs) also regulates gene expression. We identified 25 HATs/NATs genes in the yellow fever mosquito, Aedes aegypti, and investigated their function in female reproduction using RNA interference (RNAi). Among the HATs/NATs studied, the knockdown of AANAT1 (Arylamine N-acetyltransferase), NAA40 (N-alpha-acetyltransferase 40), NAA80 (N-alpha-acetyltransferase 80), KAT7 (Histone lysine acetyltransferase 7), ACNAT (Acyl-CoA N-acyltransferase), and MCM3AP (Minichromosome maintenance complex component 3 associated protein) significantly reduced egg laying and caused severe problems in oocyte development compared to that in control insects injected with dsGFP. Gene expression analysis using RT-qPCR revealed that vitellogenin and its receptor genes are downregulated in mosquitoes injected with dsAANAT1, dsNAA40, dsNAA80, dsKAT7, dsACNAT, and dsMCM3AP compared to that in control animals. Also, the knockdown of HATs/NATs genes ATAT1 (Alpha-tubulin N-acetyltransferase 1), AANAT1, TAFIID (Transcription initiation factor TFIID subunit 1), HATB (Histone acetyltransferase type B) and NAT9 (N-acetyltransferase 9) decreased more than 50% egg hatch by blocking embryonic development. These results suggest that the acetylation of proteins, especially histones mediated by NATs and HATs, plays an important role in regulating female reproduction and embryonic development of Ae. aegypti.

Comparative transcriptome analysis provides a glance into the regulation of the Krüppel homolog 1 on the reproduction and diapause of the predatory ladybeetle, Coccinella septempunctata

As a typical natural predator of agricultural pests, the lady beetle, Coccinella septempunctata, has been commercially mass-reared and widely employed in in pest management. The lady beetles can enter a long-term reproductive diapause phase in response to short photoperiods and low temperatures, for maintaining population during the overwintering process. Insect diapause is a physiological adaptative strategy that is characterized by a cessation of ovarian development, lipid accumulation and extended lifespan. Diapause regulating improve the long-term storage of C. septempunctata and release of natural enemies at the right time. In our previous research, as a main output of the juvenile hormone pathway, Krüppel homolog 1 (Kr-h1) was a key component of reproduction and diapause in C. septempunctata. However, the molecular mechanisms underlying the regulation of C. septempunctata reproduction and diapause by Kr-h1 transcription factor remains unknown. In this study, we utilized RNA-Sequencing to investigate the transcriptomic changes in C. septempunctata following RNA interference targeting the Kr-h1 gene. DEGs analysis revealed significant transcriptional alterations between the Kr-h1 knockdown group and the control group. Noteworthy findings include the downregulation of three genes related to reproduction (follicle cell protein,vitelline membrane protein, and vitellogenin) in the dsKr-h1 group, while genes involved in lipid metabolism, such as lipase and fatty acid synthase, were upregulated. These results suggested that Kr-h1 plays a critical role in the regulation of both reproductive processes and lipid metabolism in C. septempunctata. Our findings provided valuable insights into the molecular mechanisms regulating reproduction and diapause in C. septempunctata and contributed to the expanding understanding of the role of CsKr-h1 in insect physiology.

The PBAP chromatin remodeling complex mediates summer diapause via H3K4me3-driven juvenile hormone regulation in Colaphellus bowringi

Diapause, a developmental arrest mechanism, helps animals to survive seasonal changes via endocrine regulation. While obligate diapause is genetically programmed, facultative diapause is typically triggered by environmental cues such as photoperiod. In insects, this often leads to reproductive diapause characterized by reduced juvenile hormone (JH) signaling, resulting in ovarian arrest and lipid accumulation. However, the molecular link between photoperiod and hormonal control remains poorly understood. In this study, we investigated the cabbage beetle Colaphellus bowringi as our model system. This species exhibits a photoperiodic response, where short-day (SD) conditions promote reproduction, whereas long-day (LD) conditions induce diapause. Our research identified the PBAP chromatin remodeling complex as a key regulator of LD-induced summer diapause entry. Through RNAi screening of 56 transcriptional regulators that were differentially expressed between SD and LD females, we identified BAP170, a PBAP-specific component, as a key mediator of diapause. Knockdown of bap170 in SD females induced reproductive diapause traits, which were reversed by treatment with methoprene, a JH analog, suggesting that the PBAP complex regulates diapause by influencing JH production. We further demonstrated that the PBAP complex modulates JH biosynthesis via SET1/COMPASS-mediated trimethylation of H3K4. Transcriptome analysis and a second RNAi screen identified calmodulin, a calcium-binding messenger protein gene, as a direct target of PBAP-SET1/COMPASS-H3K4me3 signaling in the corpora allata (CA), the primary source of JH. These findings reveal how the chromatin remodeling machinery translates photoperiod signals into endocrine responses governing seasonal adaptation.

Krüppel homolog 1 mediates juvenile hormone action to suppress photoperiodic reproductive diapause-related phenotypes in the female Chrysoperla nipponensis (Neuroptera: Chrysopidae)

Juvenile hormone (JH) has been revealed to be a critical factor in regulating photoperiod reproductive diapause in various insect species, however, little information is known about the detailed mechanisms. In this study, we investigated the roles of JH signaling in photoperiod reproductive diapause in a green lacewing, Chrysoperla nipponensis (Okamoto), which is a potentially important biological control predator. Our results showed that the short-day condition induces a diapause state including JH synthesis suppression, ovarian development arrest, and triglyceride accumulation. The interference of JH response genes, Krüppel homolog 1 (Kr-h1), in reproductive females exhibited a diapause-related phenotype such as ovarian development arrest and larger triglyceride storage. Exogenous JH III suppresses diapause to promote ovarian development and inhibit triglyceride synthesis. However, exogenous JH III fails to rescue the Kr-h1-silenced phenotype. Accordingly, our results demonstrate the critical role of Kr-h1 in regulating JH signaling to promote reproduction.

Juvenile hormone regulates reproductive diapause through both canonical and noncanonical pathways in the bean bug Riptortus pedestris

Diapause is an adaptive developmental arrest commonly utilized by animals to cope with seasonal changes. Central to this process are hormonal events that bridge photoperiodic cues and physiological changes. In insect reproductive diapause, the absence of juvenile hormone (JH) serves as the primary endocrine event that governs key diapause traits, including ovarian developmental arrest and lipid accumulation. Conventionally, it is believed that the effects of JH are conveyed through the receptor Methoprene-tolerant (Met) and its transcriptional factor Krüppel homolog 1 (Kr-h1). However, our study with the bean bug Riptortus pedestris reveals that JH independently regulates lipid accumulation, bypassing Met and Kr-h1 pathways. R. pedestris enters reproduction under long-day (LD) conditions, while diapause occurs under short-day (SD) conditions. Treatment of SD females with the JH mimic methoprene stimulated reproductive activities, enhancing ovary development and reducing lipid accumulation. In contrast, silencing genes essential for JH biosynthesis in LD females led to pronounced diapause characteristics, including ovarian developmental arrest and substantial lipid accumulation. Interestingly, disruptions in the JH action genes, either Met or Kr-h1, solely affected ovary development, leaving lipid accumulation unchanged, indicating an independent pathway for regulating JH in lipid accumulation. This was further confirmed by RNA interference experiments in SD females, where knockdown of Met or Kr-h1 did not alter the effects of methoprene on lipid reduction. Collectively, these results suggest that JH controls ovary development through the established Met-Kr-h1 pathway, while it modulates lipid accumulation through an alternative, yet to be identified noncanonical pathway during reproductive diapause in R. pedestris.

Seven up regulates reproductive diapause initiation via juvenile hormone biosynthesis in the cabbage beetle Colaphellus bowringi

Reproductive diapause is an insect survival strategy in which reproduction temporarily halts in response to adverse environmental changes. This process is characterized by arrested ovarian development and lipid accumulation in females. A reduction in juvenile hormone (JH) biosynthesis is known to initiate reproductive diapause, but its regulatory mechanism remains unclear. Seven up (Svp), a transcription factor from the nuclear receptor family, plays a crucial role in various developmental processes in insects. In this study, using the cabbage beetle Colaphellus bowringi as a model, we observed higher expression of Svp in the heads of female adults under reproductive photoperiodic conditions (short-day [SD]) compared to diapause conditions (long-day [LD]). RNA interference-mediated knockdown of Svp in SD females induced typical diapause phenotypes, including ovarian arrest and lipid accumulation. The application of methoprene (ME), a JH receptor agonist, reversed these diapause phenotypes and restored reproduction, indicating that Svp's regulation of reproductive diapause is dependent on JH signaling. Additionally, Svp knockdown led to the downregulation of JH pathway genes and a reduction in JH titers. Further evidence suggested that Svp regulates the expression of JHAMT1, a critical gene in JH biosynthesis, which determines diapause entry in C. bowringi. These findings suggest that diapause-inducing photoperiods suppress Svp expression, blocking JH production and triggering diapause. This work reveals a critical transcription factor that regulates reproductive diapause initiation through modulating JH production, providing a potential target for controlling pests capable of entering reproductive diapause.

Functional analysis of AgJHAMT gene related to developmental period in Aphis gossypii Glover

Aphis gossypii is one of the most economically important agricultural pests that cause serious crop losses worldwide, and the indiscriminate chemical application causes resistance development in A. gossypii, a major obstacle to successful control. In this study, we selected the up-regulated expression gene AgJHAMT, which was enriched into juvenile hormone pathway though transcriptome sequencing analysis of the cotton aphids that fed on transgenic cotton lines expressing dsAgCYP6CY3 (the TG cotton). The AgJHAMT gene was overexpressed in cotton aphids which fed on the TG cotton, and its expression profile during the nymphs was clarified. Then, silencing AgJHAMT could advance the developmental period of cotton aphids by 0.5 days compared with control groups. The T and t values of cotton aphids in the dsJHAMT treatment group (6.88 ± 0.15, 1.65 ± 0.06) were significantly shorter than that of the sprayed H2O control group (7.6 ± 0.14, 1.97 ± 0.09) (P < 0.05), respectively. The fast growth caused by AgJHAMT silencing was rescued by applying the JH analogue, methoprene. Overall, these findings clarified the function of AgJHAMT in the developmental period of A. gossypii. This study contributes to further clarify the molecular mechanisms of delaying the growth and development of cotton aphids by the transgenic cotton lines expressing dsAgCYP6CY3.

Key roles of insulin receptor InR1 in initiating reproductive diapause in males of the cabbage beetle Colaphellus bowringi (Coleoptera: Chrysomelidae)

BACKGROUND

Reproductive diapause serves as a valuable strategy enabling insects to survive unfavorable seasonal conditions. However, forcing insects into diapause when the environment is conducive to their well-being can cause them to miss out on seasonal opportunities for reproduction. This outcome not only reduces insect populations but also minimizes crop losses caused by insect feeding. Therefore, altering the timing of diapause initiation presents a potential strategy for managing pests. In this study, we examined the possible role of the Insulin Receptor 1 (InR1) in controlling reproductive diapause entry in the male cabbage beetle, Colaphellus bowringi.

RESULTS

Compared to short-day (SD) conditions, long-day (LD) conditions led to reproductive diapause of C. bowringi males, characterized by arrested gonad development, increased Triglyceride (TG) accumulation, and upregulated expression of diapause protein 1 and genes associated with lipogenesis and stress tolerance. Upon employing RNA interference to knock down InR1 under SD conditions, males destined for reproduction were compelled into diapause, evidenced by arrested gonadal development, accumulation of TG, and elevated expression of diapause-related genes. Intriguingly, despite the common association of the absence of juvenile hormone (JH) with reproductive diapause in females, the knockdown of InR1 in males did not significant affect the expression of JH biosynthesis and JH response gene.

CONCLUSION

The study highlight InR1 is a key factor involved in regulating male reproductive diapause in C. bowringi. Consequently, targeting insulin signaling could be a viable approach to perturb diapause timing, offering a promising strategy for managing pests with reproductive diapause capabilities. © 2024 Society of Chemical Industry.

Molecular identification of two thioredoxin genes and their function in antioxidant defense in Arma chinensis diapause

Thioredoxin (Trx), an important part of thioredoxin systems, plays crucial role in maintaining the intracellular redox balance by scavenging reactive oxygen species (ROS). However, few Trxs have been functionally characterized in Arma chinensis, especially in diapause. In this study, diapause induction condition promoted hydrogen peroxide accumulation and increased CAT enzymatic activity and ascorbate content, suggesting that A. chinensis was exposed to high level of ROS. Therefore, we identified AcTrx2 and AcTrx-like, and investigated the relationship with antioxidant defense. It was found that AcTrx2 expression was significantly induced, whereas AcTrx-like expression was the highest on day 10 under diapause conditions. The expression of AcTrx2 and AcTrx-like in fat body, a central metabolic organ of resisting oxidative stress, was significantly increased under diapause conditions, and was significantly improved by 5/15°C (diapause temperature). We investigated the knockdown of AcTrx2 and AcTrx-like in A. chinensis and found that some selected antioxidant genes were upregulated, indicating that the upregulated genes may be functional compensation for AcTrx2 and AcTrx-like silencing. We also found that the enzymatic activities of SOD and CAT, and the metabolite contents of hydrogen peroxide, ascorbate increased after AcTrx2 and AcTrx-like knockdown. These results suggested the AcTrx2 and AcTrx-like may play critical roles in antioxidant defense of A. chinensis diapause.

Functional analysis of adipokinetic hormone signaling in reproductive diapause of Coccinella septempunctata

BACKGROUND

The ladybeetle, Coccinella septempunctata, an important predator, is widely used to control aphids, whiteflies, mites, thrips, and lepidopteran pests. Diapause control technology is key to extending C. septempunctata shelf-life and commercialization. Lipid accumulation is a major feature of reproductive diapause, but the function of AKH signaling as a regulator of lipid mobilization in reproductive diapause remains unclear. This study aimed to identify and characterize AKH and AKHR genes, and clarify their functions in reproductive diapause.

RESULTS

The relative expression levels of CsAKH and CsAKHR were the highest in the head and fat body, respectively, and were significantly decreased under diapause conditions, both in developmental stages and tissues (head, midgut, fat body, and ovary). Furthermore, CsAKH and CsAKHR expression was increased significantly after juvenile hormone (JH) injection, but CsMet silencing significantly inhibited CsAKH and CsAKHR expression, whereas CsMet knockdown blocked the induction effect of JH. CsAKH and CsAKHR knockdown significantly reduced water content, increased lipid storage, and promoted the expression of genes related to lipid synthesis, but significantly blocked ovarian development, and induced forkhead box O (FOXO) gene expression in C. septempunctata under reproduction conditions. By contrast, injection of AKH peptide significantly inhibited FOXO expression, reduced lipid storage, and increased water content in C. septempunctata under diapause conditions.

CONCLUSION

These results indicate that CsAKH and CsAKHR are involved in the regulation of lipid accumulation and ovarian development during diapause in C. septempunctata, and provide a promising target for manipulating C. septempunctata diapause. © 2024 Society of Chemical Industry.

Lipids in Insect Reproduction: Where, How, and Why

Modern insects have inhabited the earth for hundreds of millions of years, and part of their successful adaptation lies in their many reproductive strategies. Insect reproduction is linked to a high metabolic rate that provides viable eggs in a relatively short time. In this context, an accurate interplay between the endocrine system and the nutrients synthetized and metabolized is essential to produce healthy offspring. Lipids guarantee the metabolic energy needed for egg formation and represent the main energy source consumed during embryogenesis. Lipids availability is tightly regulated by a complex network of endocrine signals primarily controlled by the central nervous system (CNS) and associated endocrine glands, the corpora allata (CA) and corpora cardiaca (CC). This endocrine axis provides hormones and neuropeptides that significatively affect tissues closely involved in successful reproduction: the fat body, which is the metabolic center supplying the lipid resources and energy demanded in egg formation, and the ovaries, where the developing oocytes recruit lipids that will be used for optimal embryogenesis. The post-genomic era and the availability of modern experimental approaches have advanced our understanding of many processes involved in lipid homeostasis; therefore, it is crucial to integrate the findings of recent years into the knowledge already acquired in the last decades. The present chapter is devoted to reviewing major recent contributions made in elucidating the impact of the CNS/CA/CC-fat body-ovary axis on lipid metabolism in the context of insect reproduction, highlighting areas of fruitful research.

Regulation of forkhead box O transcription factor by insulin signaling pathway controls the reproductive diapause of the lady beetle, Coccinella septempunctata

In biological control programs, knowledge about diapause regulation in natural enemy insects provides important insight for improving long-term storage, transportation, and field adoption of these biological control agents. As a natural predator of agricultural pests, the lady beetle Coccinella septempunctata has been commercially mass-cultured and widely employed in pest management. In some insects, insulin signaling, in conjunction with the downstream transcription factor Forkhead box O (FoxO), are master regulators of multiple physiological processes involved in diapause, but it is unclear whether insulin signaling and FoxO affect the diapause of C. septempunctata. In this study, we use a combination of approaches to demonstrate that insulin signaling and FoxO mediate the diapause response in C. septempunctata. In diapausing beetles, application of exogenous insulin and knocking down expression of CsFoxo with RNA interference (RNAi) both rescued beetles from developmental arrest. In non-diapausing beetles, knocking down expression of the insulin receptor (CsInR) with RNA interference (RNAi) arrested ovarian development and decreased juvenile hormone (JH) content to levels comparable to the diapause state. Taken together, these results suggest that a shutdown of insulin signaling prompts the activation of the downstream FoxO gene, leading to the diapause phenotype.

MYST family histone acetyltransferases regulate reproductive diapause initiation

Histone acetylation, a crucial epigenetic mechanism, has been suggested to play a role in diapause regulation, but this has not been confirmed through gene loss-of-function studies. In this work, we investigated the involvement of MYST family genes, which are key writers of histone acetylation, in initiating reproductive diapause using the cabbage beetle Colaphellus bowringi as a model. We identified C. bowringi orthologs of MYST, including Tip60, KAT6A, KAT7, and KAT8, from previous transcriptomes. Analyses of phylogenetic trees and protein domains indicated that these MYST proteins are structurally conserved across animal species. Expression of these MYST genes was found to be enriched in heads and ovaries of C. bowringi. Under reproductive photoperiod conditions, RNAi targeting MYST genes, especially KAT8, suppressed ovarian growth and yolk deposition, resembling the characteristics of diapausing ovaries. Additionally, KAT8 knockdown led to the upregulation of diapause-related genes, such as heat shock proteins and diapause protein 1, and the emergence of diapause-like guts. Moreover, KAT8 knockdown reduced the expression of a crucial enzyme involved in juvenile hormone (JH) biosynthesis, likely due to decreased H4K16ac levels. Consequently, our findings suggest that MYST family genes, specifically KAT8, influence the JH signal, thereby regulating the initiation of reproductive diapause.

Farnesol dehydrogenase from Helicoverpa armigera (Hübner) as a promising target for pest management: molecular docking, in vitro and insect bioassay studies using geranylgeraniol as potential inhibitor

Juvenile hormone (JH) plays pivotal roles in several critical developmental processes in insects, including metamorphosis and reproduction. JH-biosynthetic pathway enzymes are considered highly promising targets for discovering novel insecticides. The oxidation of farnesol to farnesal, catalysed by farnesol dehydrogenase (FDL), represents a rate-limiting step in JH biosynthesis. Here, we report farnesol dehydrogenase (HaFDL) from H. armigera as a promising insecticidal target. The inhibitory potential of natural substrate analogue geranylgeraniol (GGol) was tested in vitro, wherein it showed a high binding affinity (kd 595 µM) for HaFDL in isothermal titration calorimetry (ITC) and subsequently exhibited dose-dependent enzyme inhibition in GC-MS coupled qualitative enzyme inhibition assay. Moreover, the experimentally determined inhibitory activity of GGol was augmented by the in silico molecular docking simulation which showed that GGol formed a stable complex with HaFDL, occupied the active site pocket and interacted with key active site residues (Ser147 and Tyr162) as well as other residues that are crucial in determining the active site architecture. Further, the diet-incorporated oral feeding of GGol caused detrimental effects on larval growth and development, exhibiting a significantly reduced rate of larval weight gain (P < 0.01), aberrant pupal and adult morphogenesis, and a cumulative mortality of ~ 63%. To the best of our knowledge, the study presents the first report on evaluating GGol as a potential inhibitor for HaFDL. Overall, the findings revealed the suitability of HaFDL as a potential insecticidal target for the management H. armigera.

Quantitative transcriptomic and proteomic analyses reveal the potential maintenance mechanism of female adult reproductive diapause in Chrysoperla nipponensis

BACKGROUND

The green lacewing Chrysoperla nipponensis is an important natural enemy of many insect pests and exhibits reproductive diapause to overwinter. Our previous studies showed that adult C. nipponensis enters reproductive diapause under a short-day photoperiod. However, the molecular mechanism underlying diapause maintenance in C. nipponensis is still unknown.

RESULTS

The total lipid and triglyceride content showed the reservation and degradation of energy during diapause in C. nipponensis. Thus, we performed combined transcriptomic and proteomic analyses of female reproductive diapause in C. nipponensis at three ecophysiological phases (initiation, maintenance and termination). A total of 64 388 unigenes and 5532 proteins were identified from the transcriptome and proteome. In-depth dissection of the gene-expression dynamics revealed that differentially expressed genes and proteins were predominately involved in the lipid and carbohydrate metabolic pathways, in particular fatty acid metabolism, metabolic pathways and the citrate cycle. Among of these genes, TIM, CLK, JHAMT2, PMK, HMGS, HMGR, FKBP39, Kr-h1, Phm, ECR, IR1, ILP3, ILP4, mTOR, ACC, LSD1 and LSD2 were differentially expressed in diapause and non-diapause female adults of C. nipponensis. The expression patterns of these genes were consistent with the occurrence of vitellogenesis and expression of either Vg or VgR.

CONCLUSION

Our findings indicated that diapause adult C. nipponensis accumulate energy resources to overwinter. Transcriptomic and proteomic analyses suggested candidate key genes involved in the maintenance of C. nipponensis during adult reproductive diapause. Taken together, these results provide in-depth knowledge to understand the maintenance mechanism of C. nipponensis during adult reproductive diapause. © 2023 Society of Chemical Industry.

Cathepsin L Contributes to Reproductive Diapause by Regulating Lipid Storage and Survival of Coccinella septempunctata (Linnaeus)

Cathepsin L protease, which belongs to the papain-like cysteine proteases family, is an important player in many physiological and pathological processes. However, little was known about the role of cathepsin L in ladybird beetles (Coccinella septempuctata Linnaeus) during diapause. Here, we analyzed the characteristics of cathepsin L (CsCatL) in the females of C. septempunctata and its role during the diapause of the ladybeetle. CsCatL was cloned and identified from beetle specimens by rapid amplification of cDNA-ends (RACE). The cDNA sequence of CsCatL was 971 bp in length, including an 843 bp open reading frame encoding a protein of 280 amino acids. It was identified as the cathepsin L group by phylogenetic analysis. Knockdown of CsCatL by RNA interference led to decreased expression levels of fatty acid synthase 2 (fas 2) genes and suppressed lipid accumulation. Furthermore, silencing the CsCatL gene distinctly reduced diapause-related features and the survival of female C. spetempunctata under diapause-inducing conditions. The results suggested that the CsCatL gene was involved in fatty acid biosynthesis and played a crucial role in the survival of adult C. septempunctata during the diapause preparation stage.

Structural characterization and functional analysis of juvenile hormone acid methyltransferase JHAMT3 from the silkworm, Bombyx mori

Juvenile hormone acid methyltransferase (JHAMT) is a rate-limiting enzyme of juvenile hormone (JH) biosynthesis in insects. It transfers the methyl group of S-adenosyl methionine to either the carboxyl group of JH acids or farnesoic acid to produce JH. Six JHAMT paralogues have been identified in the silkworm (Bombyx mori); among them, JHAMT1 and JHAMT2 display a methyltransferase activity. Here, the three-dimensional crystal structure of inactive JHAMT3 and the binary complex of JHAMT3 with its cofactor S-adenosyl-l-homocysteine were determined through X-ray crystallization. Comparative structural analysis revealed that JHAMT3 adopted a similar structural pattern to that of functional JHAMT2, which comprised one core Rossmann fold domain and one substrate-binding domain. Similar to JHAMT2, JHAMT3 underwent a conformational change at the Rossmann fold domain because of cofactor binding, which promoted ligand accommodation. However, it exhibited a relatively rigid substrate-binding pocket compared with that of JHAMT2. JHAMT3 was also highly expressed in the silk gland of fourth- and fifth-instar B. mori larvae. The results of expression profiling combined with activity analysis suggested that JHAMT3 might function as a binding protein of JH acids for the regulation of JH acid titers. These findings provide a structural basis for enhancing the understanding of the physiological function of JHAMT3 and a rational framework for the development of potent and specific inhibitors of JHAMT family members.

Ovarian transcriptome and metabolic responses of RNAi-mediated farnesyl pyrophosphate synthase knockdown in Neocaridina denticulata sinensis

Methyl farnesoate (MF) is considered the equivalent of JH in crustaceans and plays an essential role in many crucial physiological processes. It is believed that farnesyl pyrophosphate synthase (FPPS) plays an essential role in the biosynthesis of mevalonate, which is a branch of the JH/MF pathway. The full-length cDNA of FPPS (NdFPPS) from Neocaridina denticulata sinensis was isolated and characterized, and the deduced amino acid of NdFPPS contained a polyprenyl_synt domain. In addition to its ubiquitous tissue expression, NdFPPS was significantly expressed in the ovary. In vivo gene silencing with dsRNA interference was performed to further investigate the function of NdFPPS. An ovarian transcriptomic analysis of dsNdFPPS experimental and control groups was used to compare, annotate, and classify differentially expressed genes (DEGs). A total of 9230 DEGs were identified in the experimental and control groups based on FPKM values, of which 5082 were up-regulated genes and 4148 were down-regulated genes. 761 GO terms and 102 KEGG pathways were enriched for the DEGs. Our results suggest that NdFPPS might play an important role in ovarian development, however, further functional study is needed to elucidate physiological role of NdFPPS in reproduction.

MAPK Signaling Pathway Is Essential for Female Reproductive Regulation in the Cabbage Beetle, Colaphellus bowringi

The mitogen-activated protein kinase (MAPK) signaling pathway is a well-conserved intracellular signal transduction pathway, and has important roles in mammalian reproduction. However, it is unknown whether MAPK also regulates insect reproductive mechanisms. Therefore, we investigated the role of the MAPK signaling pathway in ovarian growth and oviposition in the cabbage beetle Colaphellus bowringi, an economically important pest of Cruciferous vegetables. As an initial step, 14 genes from the extracellular regulated protein kinase (ERK), c-Jun N-terminal kinase (JNK), and p38 MAPK (P38) cascades were knocked down using RNA interference (RNAi). The results revealed that RNAi knockdown of MAPK-ERK kinase (MEK), ERK, Kinase suppressor of RAS 2 (KSR2), and P38 induced ovarian development stagnation, low fecundity, and decreased longevity, which indicate that ERK and P38 signaling pathways are important for female C. bowringi survival and reproduction. The potential regulatory role of ERK and P38 pathways in the female reproductive process was investigated using quantitative real-time PCR. We found that ERK pathway possibly regulated ecdysone biosynthesis and P38 pathway possibly involved in the germline stem cell (GSC) development and differentiation. Our findings demonstrated the importance of the MAPK signaling pathway in the female reproduction of insects, and further enhanced the molecular mechanism of female reproductive regulation in insects.

Enhanced Degradation of Juvenile Hormone Promotes Reproductive Diapause in the Predatory Ladybeetle Coccinella Septempunctata

Improved knowledge on the regulation of reproductive diapause in Coccinella septempunctata, an important predator of aphids, is crucial for improving shelf-life and mass production of the ladybeetles. In many insects, the absence of juvenile hormone (JH) is a central regulator of reproductive diapause. JH is principally degraded by JH esterase (JHE) and JH epoxide hydrolase (JHEH). Previous studies have shown that genes encoding these enzymes were upregulated in early diapause of C. septempunctata, but whether increased JH degradation contributes to the reduction of JH levels and facilitates reproductive diapause remains unknown. Here, we investigate the role of JH and JH degradation genes during reproductive diapause in C. septempunctata females. Applying methoprene, a JH analogue, to the diapause preparation females clearly elevated JH signaling and reversed diapause program, suggesting that a lower level of JH is critical for the induction of reproductive diapause in the ladybeetle. Full-length cDNA sequences of JHE and JHEH were cloned and characterized, and their deduced proteins contain all the conserved active domains and typical motifs as identified in other insects. The expressions of JHE and JHEH were both significantly increased in diapause preparation and remained at a high level for a period throughout diapause, and then decreased after the termination of diapause. Knocking down these JH degradation genes clearly increased the expression levels of JH-inducible genes Krüppel-homolog 1 (Kr-h1) and vitellogenin (Vg), indicating an elevated JH level. Simultaneously, silencing JH degradation genes distinctly reduced diapause-related features and promotes reproduction, indicated by accelerated ovary growth, yolk deposition, and suppressed lipid accumulation. These results indicate that the enhanced JH degradation plays a critical role in regulating reproductive diapause of C. septempunctata.

Endocrine Regulation of Lifespan in Insect Diapause

Diapause is a physiological adaptation to conditions that are unfavorable for growth or reproduction. During diapause, animals become long-lived, stress-resistant, developmentally static, and non-reproductive, in the case of diapausing adults. Diapause has been observed at all developmental stages in both vertebrates and invertebrates. In adults, diapause traits weaken into adaptations such as hibernation, estivation, dormancy, or torpor, which represent evolutionarily diverse versions of the traditional diapause traits. These traits are regulated through modifications of the endocrine program guiding development. In insects, this typically includes changes in molting hormones, as well as metabolic signals that limit growth while skewing the organism's energetic demands toward conservation. While much work has been done to characterize these modifications, the interactions between hormones and their downstream consequences are incompletely understood. The current state of diapause endocrinology is reviewed here to highlight the relevance of diapause beyond its use as a model to study seasonality and development. Specifically, insect diapause is an emerging model to study mechanisms that determine lifespan. The induction of diapause represents a dramatic change in the normal progression of age. Hormones such as juvenile hormone, 20-hydroxyecdysone, and prothoracicotropic hormone are well-known to modulate this plasticity. The induction of diapause-and by extension, the cessation of normal aging-is coordinated by interactions between these pathways. However, research directly connecting diapause endocrinology to the biology of aging is lacking. This review explores connections between diapause and aging through the perspective of endocrine signaling. The current state of research in both fields suggests appreciable overlap that will greatly contribute to our understanding of diapause and lifespan determination.