Insect Metamorphosis Research Articles

Adhesion and shrinkage transform the rounded pupal horn into an angular adult horn in Japanese rhinoceros beetle.

Clarifying the mechanisms underlying shape alterations during insect metamorphosis is important for understanding exoskeletal morphogenesis. The large horn of the Japanese rhinoceros beetle Trypoxylus dichotomus is the result of drastic metamorphosis, wherein it appears as a rounded shape during pupation and then undergoes remodeling into an angular adult shape. However, the mechanical mechanisms underlying this remodeling process remain unknown. In this study, we investigated the remodeling mechanisms of the Japanese rhinoceros beetle horn by developing a physical simulation. We identified three factors contributing to remodeling by biological experiments - ventral adhesion, uneven shrinkage, and volume reduction - which were demonstrated to be crucial for transformation using a physical simulation. Furthermore, we corroborated our findings by applying the simulation to the mandibular remodeling of stag beetles. These results indicated that physical simulation applies to pupal remodeling in other beetles, and the morphogenic mechanism could explain various exoskeletal shapes.

MicroRNA miR-285 modulates the metamorphosis in Galeruca daurica by targeting Br-C.

Galeruca daurica has become a new pest on the Inner Mongolia grasslands since an abrupt outbreak in 2009 caused serious damage. As a pupa indicator during insect metamorphosis, the early response gene of the ecdysone signaling pathway, Broad-Complex (Br-C), plays a vital role in the growth and development of insects. MicroRNAs (miRNAs) are small non-coding RNAs which mediate various biological activities, but it is unknown whether and how Br-C is regulated by miRNAs. Temporal expression profiles revealed that miR-285 and Br-C basically displayed an opposite trend during larval-adult development, and Br-C was sharply up-regulated on the last day of final-instar larvae while miR-285 was significantly down-regulated. Both dual-luciferase reporter assay and miRNA-mRNA interaction assay indicated that miR-285 interacts with the coding sequence of Br-C and represses its expression. Not only overexpression but also downexpression of miR-285 led to the failure of larval to pupal to adult metamorphosis. In addition, both overexpression of miR-285 and silence of Br-C inhibited the expression of Br-C and other ecdysone signaling pathway genes, including E74, E75, ECR, FTZ-F1, and HR3. On the contrary, suppressing miR-285 obtained opposite results. Further experiments showed that 20-hydroxyecdysone down-regulated miR-285 and up-regulated Br-C and above-mentioned genes, whereas juvenile hormone alalogue (JHA) resulted in opposite effects. Our results reveal that miR-285 is involved in mediating the metamorphosis in G. daurica by targeting Br-C in the ecdysone signaling pathway. miR-285 and its target Br-C could be as a potential target for G. daurica management. © 2024 Society of Chemical Industry.

A CTL − Lys immune function maintains insect metamorphosis by preventing gut bacterial dysbiosis and limiting opportunistic infections

BackgroundGut bacteria are beneficial to the host, many of which must be passed on to host offspring. During metamorphosis, the midgut of holometabolous insects undergoes histolysis and remodeling, and thus risks losing gut bacteria. Strategies employed by holometabolous insects to minimize this risk are obscure. How gut bacteria affect host insects after entering the hemocoel and causing opportunistic infections remains largely elusive.ResultsWe used holometabolous Helicoverpa armigera as a model and found low Lactobacillus load, high level of a C-type lectin (CTL) gene CD209 antigen-like protein 2 (CD209) and its downstream lysozyme 1 (Lys1) in the midgut of the wandering stage. CD209 or Lys1 depletion increased the load of midgut Lactobacillus, which further translocate to the hemocoel. In particular, CD209 or Lys1 depletion, injection of Lactobacillus plantarum, or translocation of midgut L. plantarum into the hemocoel suppressed 20-hydroxyecdysone (20E) signaling and delayed pupariation. Injection of L. plantarum decreased triacylglycerol and cholesterol storage, which may result in insufficient energy and 20E available for pupariation. Further, Lysine-type peptidoglycan, the major component of gram-positive bacterial cell wall, contributed to delayed pupariation and decreased levels of triacylglycerols, cholesterols, and 20E, in both H. armigera and Drosophila melanogaster.ConclusionsA mechanism by which (Lactobacillus-induced) opportunistic infections delay insect metamorphosis was found, namely by disturbing the homeostasis of lipid metabolism and reducing 20E production. Moreover, the immune function of CTL − Lys was characterized for insect metamorphosis by maintaining gut homeostasis and limiting the opportunistic infections.

Anna Letitia Barbauld's Insect Poetics

AbstractThis article reads Anna Letitia Barbauld's affective encounter in ‘The Caterpillar’ (1825) in the light of her broader entomological writing for both adults and children. It investigates the recommendations for attention to the small and the particular in her didactic work alongside the narratives of insect subjectivity and insect metamorphosis in her occasional and lyric verse to assess the poet's contribution to an ecological mode of writing in this period. This uncovers a key tension in Barbauld's communication of insect worlds, reflected in the conclusion of ‘The Caterpillar’, where the affective encounter exposes the inescapable otherness of the human observer.

Identification of potent inhibitors targeting Tribolium castaneum GSTe2 via structure-based screening and molecular dynamics simulation

Red flour beetle, Tribolium castaneum, has a major negative impact during storage of agricultural products and reveals the negative impacts on human health. Insect-specific epsilon glutathione S-transferase (GSTs) which requires reduced glutathione (GSH) as an essential substrate not only develop insecticide resistance but also play important role in insect metamorphosis. Inhibition of the insect metamorphosis and the development of insecticide resistance could play an important role in pest control, so T. castaneum GSTe2 (TcGSTe2) in our previous study could be an important target protein for this purpose. This study aimed to find a potential TcGSTe2 inhibitors through in silico mothods, including molecular modeling, molecular docking, ADMET assay, followed by molecular dynamics (MD) simulation, principal component analysis and MM/PBSA analysis. The results showed that ZINC000169293362 and ZINC000095566957 were selected as potential TcGSTe2 inhibitors with high-binding affinity and without any toxicity from 3618 of GSH-like compounds obtained from ZINC database. MD simulation results revealed that TcGSTe2-ZINC000169293362 had more stability than that of reference GSH. Moreover, TcGSTe2-ZINC000169293362 and TcGSTe2-ZINC000095566957 showed lower binding free energy (−27.53 ± 0.16 kcal/mol and −18.83 ± 0.15 kcal/mol, respectively) compared with TcGSTe2-GSH (−8.90 ± 0.30 kcal/mol). This study could provide new insight into reduction of insecticide resistance and be used to design new inhibitors of insect GSTs. Communicated by Ramaswamy H. Sarma

Performing the Insect and Its Mysterious Metamorphosis

Insect metamorphosis fascinated Greek philosophers, bewildered Christian theologians, affirmed the beliefs of Chinese moralists, and continues to mystify science. Yet dramas representing human-animal transformations rarely involve insects. When they do appear, they usually serve as metaphors satirizing human flaws, but are also demeaning to the insect in their simplistic representation. In some 21st-century performances, however, that approach is evolving to better appreciate the multifarious intricacies of insect life.

Barns hållbarhetsfrågor i digitala och fysiska gränssnitt - transduktionskedja som ett didaktiskt verktyg

In this article, we show empirically how preschool childrens’ creative, physical, and digital leaps, provide new perspectives concerning childrens’ engagement in ecology related questions in the domain of Sustainability Education. The metamorphosis of insects is explored by children digitally, embodied and 'hands-on', and the children move through the digital and analogue interfaces. Childrens’ embodied explorations through instant encounters with nature has an obvious place where the digital world and nature become intersected forming a whole. We introduce a transduction chain, a didactic design-theoretic analysis tool, which supports teachers and researchers to get to hold of childrens’ digital and analogue meaning-making sign use. We draw attention to the preschool children's contribution in the area, which is made visible through transduction processes. We do not yet have the answers to the complex questions of sustainability, implying the need of all citizens’ participation and contributions. In anthropocene, it is also important to strengthen agency processes by paying attention to children's own course of actions and proposals. In light of this study, preschool teachers need to provide rich opportunities where children can explore and process what is happening around them.

Molecular identification and functional analysis of chitinase genes reveal their importance in the metamorphosis of Sarcophaga peregrina (Diptera: Sarcophagidae).

Chitinases play a crucial role in insect metamorphosis by facilitating chitin degradation. Sarcophaga peregrina (Robineau-Desvoidy, 1830) (Diptera: Sarcophagidae) is a typical holometabolous insect and an important hygiene pest that causes myiasis in humans and other mammals and acts as a vector for various parasitic agents, including bacteria, viruses, and parasites. Enhancing the understanding of the metamorphosis in this species has significance for vector control. In this study, we identified a total of 12 chitinase genes in S. peregrina using bioinformatic analysis methods. Based on transcriptome data, SpIDGF2 and SpCht10 were selected for further functional investigation. The down-regulation of these genes by RNA interference led to developmental delays, disruptions in molting, and differences in cuticle composition during the pupal stage. These findings underscore the pivotal role of chitinase genes in the metamorphic process and offer valuable insights for effective control strategies.

Cytoplasmic FKBPs are involved in molting and metamorphosis through regulating the nuclear localization of EcR.

Molting and metamorphosis are important physiological processes in insects that are tightly controlled by ecdysone receptor (EcR) through the 20-hydroxyecdysone (20E) signaling pathway. EcR is a steroid nuclear receptor (SR). Several FK506-binding proteins (FKBPs) have been identified from the mammal SR complex, and are thought to be involved in the subcellular trafficking of SR. However, their roles in insects are poorly understood. To explore whether FKBPs are involved in insect molting or metamorphosis, we injected an FKBP inhibitor (FK506) into a lepidopteran insect, Spodoptera litura, and found that molting was inhibited in 61.11% of the larvae, and that the time for larvae to pupate was significantly extended. A total of 10 FKBP genes were identified from the genome of S.litura and were clustered into 2 distinct groups, according to their subcellular localization, with FKBP13 and FKBP14 belonging to the endoplasmic reticulum (ER) group and with the other members belonging to the cytoplasmic (Cy) group. All the CyFKBPs were significantly upregulated in the prepupal or pupal stages, with the opposite being observed for the ER group members. FK506 completely blocked the transfer of EcR to the nucleus under 20E induction, and significantly downregulated the transcriptional expression of many 20E signaling genes. A similar phenomenon was observed after RNA interference of 2 CyFKBPs (FKBP45 and FKBP12b), but not for FKBP13. Taken together, our data indicate that the cytoplasmic FKBPs, especially FKBP45 and FKBP12b, mediate the nuclear localization of EcR, thereby regulating the 20E signaling and ultimately affecting molting and metamorphosis in insects.

Regulation and remodeling of microbial symbiosis in insect metamorphosis

Many insects are dependent on microbial mutualists, which are often harbored in specialized symbiotic organs. Upon metamorphosis, insect organs are drastically reorganized. What mechanism regulates the remodeling of the symbiotic organ upon metamorphosis? How does it affect the microbial symbiont therein? Here, we addressed these fundamental issues of symbiosis by experimentally manipulating insect metamorphosis. The stinkbug Plautia stali possesses a midgut symbiotic organ wherein an essential bacterial symbiont resides. By RNAi of master regulator genes for metamorphosis, Kr-h1 over nymphal traits and E93 over adult traits, we generated precocious adults and supernumerary nymphs of P. stali, thereby disentangling the effects of metamorphosis, growth level, developmental stage, and other factors on the symbiotic system. Upon metamorphosis, the symbiotic organ of P. stali was transformed from nymph type to adult type. The supernumerary nymphs and the precocious adults, respectively, developed nymph-type and adult-type symbiotic organs not only morphologically but also transcriptomically, uncovering that metamorphic remodeling of the symbiotic organ is under the control of the MEKRE93 pathway. Transcriptomic, cytological, and biochemical analyses unveiled that the structural and transcriptomic remodeling of the symbiotic organ toward adult emergence underpins its functional extension to food digestion in addition to the original role of symbiont retention for essential nutrient production. Notably, we found that the symbiotic bacteria in the adult-type symbiotic organ up-regulated genes for production of sulfur-containing essential amino acids, methionine and cysteine, that are rich in eggs and sperm, uncovering adult-specific symbiont functioning for host reproduction and highlighting intricate host-symbiont interactions associated with insect metamorphosis.

Knockout of nuclear receptor HR38 gene impairs pupal-adult development in silkworm Bombyx mori.

Nuclear receptors are ligand-regulated transcription factors that play important role in regulating insect metamorphosis through the ecdysone signalling pathway. In this study, we investigated the nuclear receptor HR38 gene in Bombyx mori (BmHR38), belonging to the NR4A subfamily. BmHR38 mRNA was highly expressed in the head and epidermis at the pupal stage. The expression of the BmHR38 gene was influenced by different doses of 20E at different times. A BmHR38 deletion mutant silkworm was generated using the clustered regularly interspaced short palindromic repeat (CRISPR)/Cas9 system. Compared with the wild-type B. mori, the BmHR38 deletion mutant resulted in abnormal development during the pupal stage, leading to either failed eclosion or the formation of abnormal adult wings. After silencing of BmHR38 in the pupal stage, the phenotype of pupa or moth had no significant change, but it did result in reduced egg production. The mRNA levels of USP, E75 and E74 were significantly increased, while the transcript levels of FTZ-F1 were suppressed after RNA interference. Furthermore, interference with BmHR38 also inhibited the expressions of chitin metabolism genes, including Chs1, Chs2, Chi, Chi-h and CDA. Our results suggest that BmHR38 is essential for pupal development and pupa-adult metamorphosis in B. mori by regulating the expression of NRs and chitin metabolism genes.

Synthesis of 1,4-benzodioxan derivatives and the evaluation of their biological activity as a novel juvenile hormone signaling inhibitor.

Juvenile hormone (JH) signaling inhibitors may be used as insect growth regulators because of their ability to control metamorphosis and reproduction in insects by regulating the action of JH. We identified ethyl (E)-3-(4-{[7- (4-methoxycarbonylbenzyloxy)-1,4-benzodioxan-6-yl]methyl}phenyl)prop-2-enoate (EMBP) and observed its strong precocious metamorphosis-inducing activity against silkworm larvae. To further elucidate its mechanism of action, we investigated the effect of EMBP on the JH-mediated signaling pathway in vitro and in vivo. In a reporter assay using a Bombyx mori cell line, EMBP strongly suppressed the induction of reporter gene expression by Juvenile hormone I (JH I) in a concentration-dependent manner. A parallel rightward shift was observed in the dose-response curve of JH I after treatment with EMBP, indicating that EMBP competitively inhibited JH. Moreover, we monitored developmental changes in the JH-responsive gene, Krüppel homolog 1 (Kr-h1), and ecdysone-responsive gene, Broad-Complex (BRC), in EMBP-treated silkworm larvae. EMBP suppressed only the expression of Kr-h1 in third-instar larvae. Our results demonstrated that EMBP specifically regulates the JH-mediated Kr-h1 signaling pathway. EMBP could be used as a lead compound in the development of new insect growth regulators. © 2023 Society of Chemical Industry.

Further evidences of an emerging stingless bee-yeast symbiosis.

Symbiotic interactions between microorganisms and social insects have been described as crucial for the maintenance of these multitrophic systems, as observed for the stingless bee Scaptotrigona depilis and the yeast Zygosaccharomyces sp. SDBC30G1. The larvae of S. depilis ingest fungal filaments of Zygosaccharomyces sp. SDBC30G1 to obtain ergosterol, which is the precursor for the biosynthesis of ecdysteroids that modulate insect metamorphosis. In this work, we find a similar insect-microbe interaction in other species of stingless bees. We analyzed brood cell samples from 19 species of stingless bees collected in Brazil. The osmophilic yeast Zygosaccharomyces spp. was isolated from eight bee species, namely Scaptotrigona bipunctata, S. postica, S. tubiba, Tetragona clavipes, Melipona quadrifasciata, M. fasciculata, M. bicolor, and Partamona helleri. These yeasts form pseudohyphae and also accumulate ergosterol in lipid droplets, similar to the pattern observed for S. depilis. The phylogenetic analyses including various Zygosaccharomyces revealed that strains isolated from the brood cells formed a branch separated from the previously described Zygosaccharomyces species, suggesting that they are new species of this genus and reinforcing the symbiotic interaction with the host insects.

Bruceine D Acts as a Potential Insecticide by Antagonizing 20E-EcR/USP Signal Transduction.

Bruceine D (BD) is an effective insecticidal compound found in the Chinese herb Brucea javanica (L.) Merr. BD inhibits the growth and metamorphosis of Plutella xylostella and Drosophila melanogaster; however, its target protein and the molecular mechanism of insecticidal activity remain unclear. In this study, proteins with high affinity for BD were screened using surface plasmon resonance and high-performance liquid chromatography coupled with matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry, revealing the ecdysone receptor (EcR) is the main target of BD. In vivo results showed that BD inhibited insect growth and metamorphosis through inhibition of the expression of 20E response genes. In vitro dual luciferase and enhanced green fluorescent protein (EGFP) fluorescence experiments indicated that BD suppressed the transcriptional activation activity of EcR by blocking the ecdysone response element (EcRE)-triggered transcriptional cascade, suggesting that BD inhibits the formation of the 20E-EcR-USP-EcRE complex. Moreover, molecular docking demonstrated that BD bound well to EcR. Elucidating the insecticidal mechanism of BD will be helpful in the development of green pesticides to control pests.

Origin of insect wings, metamorphosis, pupae and the maj or insect orders.

Although most discussions on the origin and evolution of insect wings and metamorphosis have assumed that the ancestors of winged insects were terrestrial, it now seems possible that they were actually aquatic. Changing the basic assumptions affects our interpretations of the origin of metamorphosis and our understanding of insect diversity. It is argued that the ancestors of winged insects were similar to primitive mayflies, developing from aquatic larvae into terrestrial adults, and that metamorphosis originated as an inevitable consequence of an amphibiotic life cycle. It is suggested that the first pupae resembled those of Megaloptera.

Genome-wide CRISPR screening reveals key genes and pathways associated with 20-hydroxyecdysone signal transduction in the silkworm (Bombyx mori).

Metamorphosis is a complex developmental process involving multiple pathways and a large number of genes that are regulated by juvenile hormone (JH) and 20-hydroxyecdysone (20E). Despite important progress in understanding various aspects of silkworm biology, the hormone signaling pathway in the silkworm remains poorly understood. Genome-wide screening using clustered regularly interspaced short palindromic repeats (CRISPR) / CRISPR-associated protein 9 (Cas9)-based libraries has recently emerged as a novel method for analyzing genome function, enabling further research into essential genes, drug targets, and virus-host interaction. Previously, we constructed a genome-wide CRISPR/Cas9-based library of the silkworm (Bombyx mori) and successfully revealed the genes involved in biotic or abiotic stress factor responses. In this study, we used our silkworm CRISPR library and large-scale genome-wide screening to analyze the key genes in the silkworm 20E signaling pathway and their mechanisms of action. Functional annotation showed that 20E regulates key proteins in processes that mainly occur in the cytoplasm and nucleus. Pathway enrichment analysis showed that 20E can activate phosphorylation and may affect innate immunity, interfere with intracellular nutrition and energy metabolism, and eventually cause cell apoptosis. The screening results were experimentally validated by generating cells with knockout alleles of the relevant genes, which had increased tolerance to 20E. Our findings provide a panoramic overview of signaling in response to 20E in the silkworm, underscoring the utility of genome-wide CRISPR mutant libraries in deciphering hormone signaling pathways and the mechanisms that regulate metamorphosis in insects.

Genome-wide analysis of long noncoding RNAs and their association in regulating the metamorphosis of the Sarcophaga peregrina (Diptera: Sarcophagidae).

The flesh fly, Sarcophaga peregrina (Diptera: Sarcophagidae), is an important hygiene pest, that causes myiasis in humans and other mammals, typically livestock, and as a vector for various parasitic agents, including bacteria, viruses, and parasites. The role of long non-coding RNAs (lncRNAs) in regulating gene expression during metamorphosis of the flesh fly has not been well established. In this study, we performed genome-wide identification and characterization of lncRNAs from the early pupal stage (1-days pupae), mid-term pupal stage (5-days pupae), and late pupal stage (9-days pupae) of S. peregrina by RNA-seq, and a total of 6921 lncRNAs transcripts were identified. RT-qPCR and enrichment analyses revealed the differentially expressed lncRNAs (DE lncRNAs) that might be associated with insect metamorphosis development. Furthermore, functional analysis revealed that the DE lncRNA (SP_lnc5000) could potentially be involved in regulating the metamorphosis of S. peregrina. RNA interference of SP_lnc5000 caused reduced expression of metamorphosis-related genes in 20-hydroxyecdysone (20E) signaling (Br-c, Ftz-F1), cuticle tanning pathway (TH, DOPA), and chitin related pathway (Cht5). Injection of dsSP_lnc5000 in 3rd instar larvae of S. peregrina resulted in deformed pupae, stagnation of pupal-adult metamorphosis, and a decrease in development time of pupal, pupariation rates and eclosion rates. Hematoxylin-eosin staining (H&E), scanning electron microscope (SEM) observation and cuticle hydrocarbons (CHCs) analysis indicated that SP_lnc5000 had crucial roles in the metamorphosis developmental by modulating pupal cuticular development. We established that the lncRNA SP_lnc5000 potentially regulates the metamorphosis of S. peregrina by putatively affecting the structure and composition of the pupal cuticle. This study enhances our understanding of lncRNAs as regulators of metamorphosis in S. peregrina, and provide valuable insights into the identification of potential targets for vector control and the development of effective strategies for controlling the spread of myiasis and parasitic diseases.

Population Dynamics of Intestinal Enterococcus Modulate Galleria mellonella Metamorphosis.

Microbes found in the digestive tracts of insects are known to play an important role in their host's behavior. Although Lepidoptera is one of the most varied insect orders, the link between microbial symbiosis and host development is still poorly understood. In particular, little is known about the role of gut bacteria in metamorphosis. Here, we explored gut microbial biodiversity throughout the life cycle of Galleria mellonella, using amplicon pyrosequencing with the V1 to V3 regions, and found that Enterococcus spp. were abundant in larvae, while Enterobacter spp. were predominant in pupae. Interestingly, eradication of Enterococcus spp. from the digestive system accelerated the larval-to-pupal transition. Furthermore, host transcriptome analysis demonstrated that immune response genes were upregulated in pupae, whereas hormone genes were upregulated in larvae. In particular, regulation of antimicrobial peptide production in the host gut correlated with developmental stage. Certain antimicrobial peptides inhibited the growth of Enterococcus innesii, a dominant bacterial species in the gut of G. mellonella larvae. Our study highlights the importance of gut microbiota dynamics on metamorphosis as a consequence of the active secretion of antimicrobial peptides in the G. mellonella gut. IMPORTANCE First, we demonstrated that the presence of Enterococcus spp. is a driving force for insect metamorphosis. RNA sequencing and peptide production subsequently revealed that antimicrobial peptides targeted against microorganisms in the gut of Galleria mellonella (wax moth) did not kill Enterobacteria species, but did kill Enterococcus species, when the moth was at a certain stage of growth, and this promoted moth pupation.

20-hydroxyecdysone Upregulates Ecdysone Receptor (ECR) Gene to Promote Pupation in the Honeybee, Apis mellifera Ligustica.

A heterodimeric complex of two nuclear receptors, the ecdysone receptor (ECR) and ultraspiracle (USP), transduces 20-hydroxyecdysone (20E) signaling to modulate insect growth and development. Here, we aimed to determine the relationship between ECR and 20E during larval metamorphosis and also the specific roles of ECR during larval-adult transition in Apis mellifera. We found that ECR gene expression peaked in the 7-day-old larvae, then decreased gradually from the pupae stage. 20E slowly reduced food consumption and then induced starvation, resulting in small-sized adults. In addition, 20E induced ECR expression to regulate larval development time. Double-stranded RNAs (dsRNAs) were prepared using common dsECR as templates. After dsECR injection, larval transition to the pupal stage was delayed, and 80% of the larvae showed prolonged pupation beyond 18 h. Moreover, the mRNA levels of shd, sro, nvd, and spo, and ecdysteroid titers were significantly decreased in ECR RNAi larvae compared with those in GFP RNAi control larvae. ECR RNAi disrupted 20E signaling during larval metamorphosis. We performed rescuing experiments by injecting 20E in ECR RNAi larvae and found that the mRNA levels of ECR, USP, E75, E93, and Br-c were not restored. 20E induced apoptosis in the fat body during larval pupation, while RNAi knockdown of ECR genes reduced apoptosis. We concluded that 20E induced ECR to modulate 20E signaling to promote honeybee pupation. These results assist our understanding of the complicated molecular mechanisms of insect metamorphosis.

20-Hydroxyecdysone counteracts insulin to promote programmed cell death by modifying phosphoglycerate kinase 1

BackgroundThe regulation of glycolysis and autophagy during feeding and metamorphosis in holometabolous insects is a complex process that is not yet fully understood. Insulin regulates glycolysis during the larval feeding stage, allowing the insects to grow and live. However, during metamorphosis, 20-hydroxyecdysone (20E) takes over and regulates programmed cell death (PCD) in larval tissues, leading to degradation and ultimately enabling the insects to transform into adults. The precise mechanism through which these seemingly contradictory processes are coordinated remains unclear and requires further research. To understand the coordination of glycolysis and autophagy during development, we focused our investigation on the role of 20E and insulin in the regulation of phosphoglycerate kinase 1 (PGK1). We examined the glycolytic substrates and products, PGK1 glycolytic activity, and the posttranslational modification of PGK1 during the development of Helicoverpa armigera from feeding to metamorphosis.ResultsOur findings suggest that the coordination of glycolysis and autophagy during holometabolous insect development is regulated by a balance between 20E and insulin signaling pathways. Glycolysis and PGK1 expression levels were decreased during metamorphosis under the regulation of 20E. Insulin promoted glycolysis and cell proliferation via PGK1 phosphorylation, while 20E dephosphorylated PGK1 via phosphatase and tensin homolog (PTEN) to repress glycolysis. The phosphorylation of PGK1 at Y194 by insulin and its subsequent promotion of glycolysis and cell proliferation were important for tissue growth and differentiation during the feeding stage. However, during metamorphosis, the acetylation of PGK1 by 20E was key in initiating PCD. Knockdown of phosphorylated PGK1 by RNA interference (RNAi) at the feeding stage led to glycolysis suppression and small pupae. Insulin via histone deacetylase 3 (HDAC3) deacetylated PGK1, whereas 20E via acetyltransferase arrest-defective protein 1 (ARD1) induced PGK1 acetylation at K386 to stimulate PCD. Knockdown of acetylated-PGK1 by RNAi at the metamorphic stages led to PCD repression and delayed pupation.ConclusionsThe posttranslational modification of PGK1 determines its functions in cell proliferation and PCD. Insulin and 20E counteractively regulate PGK1 phosphorylation and acetylation to give it dual functions in cell proliferation and PCD.