Simultaneous Detection and Distribution of Five Juvenile Hormones in 58 Insect Species and the Absolute Configuration in 32 Insect Species

UDP-glycosyltransferases-mediated vitellogenin protein biogenesis reveals juvenile hormone I-specific dominance in Spodoptera frugiperda reproductive programming

Juvenile hormone (JH) critically regulates reproduction in Spodoptera frugiperda (FAW) via its signaling cascade. We dissected isoform-specific roles of JH I, II, and III by using hormone injection, RNAi, and RNA-seq. Systematic modulation of JH variants revealed distinct roles in ovarian development, egg production, and vitellogenin (Vg) dynamics. Transcriptomic profiling identified JH I as the most potent inducer of reproductive pathways, specifically enriching the steroid hormone biosynthesis pathway. Within this pathway, two UDP-glycosyltransferases (UGT), SfUGT2 and SfUGT2-like, were identified as key regulators of Vg synthesis through RNAi knockdown and functional validation (qPCR, Western blot). Silencing either gene reduced Vg levels and impaired ovarian maturation. JH I exhibited the strongest induction of SfUGT2/SfUGT2-like expression, correlating with its superior reproductive activation. Notably, JH III synergistically amplified JH I/II-induced Vg accumulation and egg production, as evidenced by co-treatment assays. This cooperative interplay highlights a tiered regulatory network among JH isoforms, and provide novel insights into the endocrine regulation of reproduction in FAW, also highlight the potential for targeted manipulation of JH signaling for pest control strategies.

Differential regulation of reproduction and molting by juvenile hormone in aphids

Insects rely on juvenile hormones to regulate various physiological processes, including reproduction and molting; currently eight forms of this hormone are known. In most insects, only JH Ⅲ is synthesized. Meanwhile, aphids produce JH Ⅲ and JH Ⅲ skipped bisepoxide (JHSB3). However, it remains unclear whether these compounds play distinct roles in functional regulation. In this study, we demonstrated that the tested concentrations of JH Ⅲ effectively increased the number of aphid offspring, whereas high concentrations of JHSB3 affected the molting process. Drip experiments showed that 10 mg/L JH Ⅲ increased the number of offspring from 39.38 ± 8.03 to 56.50 ± 13.17, whereas 10 mg/L JHSB3 resulted in a 60.00 %± 5.77 % failure rate in molting before adulthood. Transcriptomic analysis also revealed that in the JH Ⅲ treatment group, 9 genes and 7 pathways associated with reproduction were expressed, but not genes or pathways associated with molting. In addition, 16 genes and 9 pathways associated with molting as well as 5 genes and 4 pathways associated with reproduction were identified in the JHSB3 treatment group. JH Ⅲ promotes reproduction in aphids by enhancing Vg expression, whereas JHSB3 affects molting by inhibiting the synthesis of molting hormone-related enzymes. The results indicate that JH Ⅲ and JHSB3 exhibit diverse functions in Aphis craccivora. The findings have significant implications for further studies on the physiological functions of different JHs.

Regulation of Insect Hormones in Different Types of Diapause in Chilo Partellus (Swinhoe)

Maize stem borer, Chilo partellus (Swinhoe) is a key pest of maize and sorghum. It undergoes both in estivation and hibernation depending on prevailing environmental conditions. Present investigations were aimed to decipher the regulation of ecdysone, 20-hydroxyecdysone (20E) and juvenile hormone III (JH III) during different stages (prediapause, diapause and post-diapause/pupae) of hibernation and estivation as compared to counterpart nondiapause C. partellus. Significant variations were found in the ecdysone, 20E and JH III titers in the hemolymph of different stages of hibernation and estivation over the nondiapause C. partellus. At the prediapause stages of hibernation and estivation, the 20E was greater than the ecdysone. However, the ecdysone and 20E downregulated, while JH III upregulated during prediapause stages of hibernation and estivation as compared to nondiapause larvae. During diapause, 20E decreased in hibernation, and increased in estivation as compared to their respective prediapause stages. The JH III significantly upregulated in diapause stages of hibernation and estivation over the nondiapause larvae. However, it was significantly greater in prediapause and diapause stages of estivation as compared to hibernation strain. During post-diapause stage, the ecdysone and 20E titers were greater in estivation than in the hibernation and nondiapause strains, while JH III was greater in nondiapause than in the hibernation and estivation strains. These findings suggest the crucial role of these hormones in establishing switch between different stages of diapause and metamorphosis in C. partellus, which could further be useful to strategize sustainable management of C. partellus.

Nanomaterial-mediated RNAi reveals the effect of the oral secretory protein serine protease inhibitor on the growth of Conogethes punctiferalis larvae

The oral secretions of herbivorous insects play a pivotal role in insect-plant interactions and the regulation of insect physiology. Unlike the saliva of Hemiptera species, Lepidopteran oral secretions include both saliva and regurgitated gut fluids; yet research on their composition remains limited. This study focuses on yellow peach moth (YPM), Conogethes punctiferalis, a pest increasingly damaging maize. A total of 103 proteins were identified from oral secretions collected from larvae reared on corn and artificial diets, comprising 67 enzymes, 30 non-enzymes, and 6 unknowns. The identified enzyme proteins were primarily trypsin, lipase, and serine protease inhibitors (serpins). Further genomic investigation revealed 36 serpin genes in the YPM genome, distributed in clusters across various chromosomes, with some genes exhibiting partial synteny to homologous sequences in Ostrinia furnacalis. Among the identified serpin genes, the SpI gene (jg17839), which encoded the most abundant protein in YPM oral secretions, was found to exhibit peak expression in fifth-instar larvae and culticle tissues. Silencing of the SpI gene through nanomaterial-mediated RNA interference significantly reduced larval length, weight, pupation rates, and pupal weight, while also increased larval mortality. Moreover, interfering with SpI expression elevated juvenile hormone levels in the larvae. These findings indicate that the abundant SpI protein in YPM oral secretions plays a vital role in larval growth and development by modulating internal hormone levels. This study enriches the database of lepidopteran oral secretion components, fostering a deeper understanding of their physiological roles and informing eco-friendly pest control strategies targeting these proteins in YPM.

Nutritional Resources Regulate the Reproduction or Migration of Spodoptera frugiperda through Juvenile Hormones and 20-Hydroxyecdysone

Spodoptera frugiperda is a significant agricultural pest that migrates annually based on the growth stages of its host plants. However, the role of host plant growth stages in the residency or migration of S. frugiperda remains unclear. We allowed S. frugiperda to feed on maize leaves and seeds, and results showed that maize seeds had higher amino acids, carbohydrates, and triglyceride (TG). S. frugiperda that fed on seeds had longer adult stages; larger wings; higher TG, juvenile hormone II (JH II), and JH III; and more developed flight muscles, indicating tendencies toward migration. Interestingly, maize leaves were richer in sterols. S. frugiperda that fed on leaves exhibited longer larval stages, higher 20-hydroxyecdysone (20E) and JH I, faster egg maturation, and earlier oviposition, suggesting tendencies toward residency. These findings suggest that the nutritional composition of host plants influences S. frugiperda for migration or reproduction, offering new insights into its invasion and establishment patterns.

The moulting arthropod: a complete genetic toolkit review

Exoskeletons are a defining character of all arthropods that provide physical support for their segmented bodies and appendages as well as protection from the environment and predation. This ubiquitous yet evolutionarily variable feature has been instrumental in facilitating the adoption of a variety of lifestyles and the exploitation of ecological niches across all environments. Throughout the radiation that produced the more than one million described modern species, adaptability afforded by segmentation and exoskeletons has led to a diversity that is unrivalled amongst animals. However, because of the limited extensibility of exoskeleton chitin and cuticle components, they must be periodically shed and replaced with new larger ones, notably to accommodate the growing individuals encased within. Therefore, arthropods grow discontinuously by undergoing periodic moulting events, which follow a series of steps from the preparatory pre-moult phase to ecdysis itself and post-moult maturation of new exoskeletons. Each event represents a particularly vulnerable period in an arthropod's life cycle, so processes must be tightly regulated and meticulously executed to ensure successful transitions for normal growth and development. Decades of research in representative arthropods provide a foundation of understanding of the mechanisms involved. Building on this, studies continue to develop and test hypotheses on the presence and function of molecular components, including neuropeptides, hormones, and receptors, as well as the so-called early, late, and fate genes, across arthropod diversity. Here, we review the literature to develop a comprehensive overview of the status of accumulated knowledge of the genetic toolkit governing arthropod moulting. From biosynthesis and regulation of ecdysteroid and sesquiterpenoid hormones, to factors involved in hormonal stimulation responses and exoskeleton remodelling, we identify commonalities and differences, as well as highlighting major knowledge gaps, across arthropod groups. We examine the available evidence supporting current models of how components operate together to prepare for, execute, and recover from ecdysis, comparing reports from Chelicerata, Myriapoda, Crustacea, and Hexapoda. Evidence is generally highly taxonomically imbalanced, with most reports based on insect study systems. Biases are also evident in research on different moulting phases and processes, with the early triggers and late effectors generally being the least well explored. Our synthesis contrasts knowledge based on reported observations with reasonably plausible assumptions given current taxonomic sampling, and exposes weak assumptions or major gaps that need addressing. Encouragingly, advances in genomics are driving a diversification of tractable study systems by facilitating the cataloguing of putative genetic toolkits in previously under-explored taxa. Analysis of genome and transcriptome data supported by experimental investigations have validated the presence of an "ultra-conserved" core of arthropod genes involved in moulting processes. The molecular machinery has likely evolved with elaborations on this conserved pathway backbone, but more taxonomic exploration is needed to characterise lineage-specific changes and novelties. Furthermore, linking these to transformative innovations in moulting processes across Arthropoda remains hampered by knowledge gaps and hypotheses based on untested assumptions. Promisingly however, emerging from the synthesis is a framework that highlights research avenues from the underlying genetics to the dynamic molecular biology through to the complex physiology of moulting.

Aphis craccivora (Hemiptera: Aphididae) synthesizes juvenile hormone III via a pathway involving epoxidation followed by esterification, potentially providing an epoxidation active site for the synthesis of juvenile hormone SB3

Juvenile hormones (JHs) play a crucial role in regulating development and reproduction in insects. Most insects predominantly synthesize JH III, which typically involves esterification followed by epoxidation, lepidopteran insects use a pathway of epoxidation followed by esterification. Although hemipteran insects have JH III and JH skipped bisepoxide III (JH SB3), the synthesis pathway and key epoxidases remain unclear. This study was conducted on Aphis craccivora, and demonstrated that corpora allata, microsomes, Ac-CYP15C1, and Ac-JHAMT catalyze JH III production in vitro, establishing the pathway of epoxidation followed by esterification. These findings were further confirmed through RNA interference and molecular docking. The presence of JH III and JH SB3 in A. craccivora was identified, and their synthesis pathway was elucidated as follows: Ac-CYP15C1 oxidizes farnesic acid to JH A, followed by methylation to JH III by Ac-JHAMT, possibly providing an epoxidation site on the second carbon for JH SB3. This alteration may significantly contribute to the differentiation and functional diversification of JH types in insects.

Effects of pyriproxyfen on development and hormone of the aphis, Aphis craccivora (Hemiptera: Aphididae)

Pyriproxyfen (PPF) has been shown to affect the pupal stage and ecdysone levels in holometabolous insects, such as silkworms and mealworms. It remains unknown whether it affects hemimetabolous insects with their hormone levels in insects lacking a pupal stage. In this laboratory study, bioassays were conducted to investigate the effects of varying doses of PPF on Aphis craccivora Koch (Hemiptera: Aphididae). Ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was used to determine the types and titers of juvenile hormone (JH) and 20-hydroxyecdysone (20E). Additionally, the effects of PPF on A. craccivora reproduction and molting, as well as its influence on relevant gene expression, were examined. The results revealed LC50 and LC90 values of 3.84 and 7.49 mg/l for PPF, respectively, after 48 h of exposure. The results demonstrated a significant reduction in the titer of JH III and a significant increase in the titer of 20E following treatment with PPF. However, there was no significant decrease observed in the titer of JH III skipped bisepoxide (JH SB3). A sublethal concentration of PPF was found to inhibit Krüppel homolog 1 (kr-h1) gene expression and reduce aphid reproduction, but it did not significantly impact ecdysone receptor expression and aphid molting. The results of this study demonstrate that PPF exhibits a lethal effect on aphids, thereby providing an effective means of control. Additionally, sublethal concentrations of PPF have been found to inhibit the JH in aphids, resulting in a decline in their reproductive ability and achieving the desired control objectives.

Precise Regulation of Juvenile Hormone III R-Stereoisomer Synthesis by Apis mellifera through Specifically Binding Methyl-(2E,6E)-farnesoate and Strictly Controlling Its Titer

Juvenile hormone III (JH III) is a crucial hormone synthesized exclusively as R-stereoisomer in most insects. Herein, we established a mature Tris-HCl culture system for essential biochemical reactions and applied stable instrumental detection methods to analyze JH III, methyl farnesoate (MF) and juvenile hormone acid (JHA) using UPLC-MS/MS. Our results revealed that the R-JH III terminal synthesis pathway in Apis mellifera follows the "esterify then epoxidize" sequence, with precise methyl-(2E,6E)-farnesoate titer regulation and its spatial cis-trans isomerism, achieving selective R-JH III synthesis. Furthermore, we observed that the preferred generation of S/R-JH III chiral enantiomers varied depending on the spatial cis-trans isomerism of different MFs. Our results suggest that S-JH III could theoretically exist in insects, offering a novel perspective for understanding the synthesis mechanism of diverse complex juvenile hormones in different insect species.

A short neuropeptide F analog (sNPF), III-2 may particularly regulate juvenile hormone III to influence Spodoptera frugiperda metamorphosis and development

Allatostatin (AS) or Allatotropin (AT) is a class of insect short neuropeptide F (sNPF) that affects insect growth and development by inhibiting or promote the synthesis of juvenile hormone (JH) in different insects. III-2 is a novel sNPF analog derived from a group of nitroaromatic groups connected by different amino acids. In this study, we found that III-2 showed high insecticidal activity against S. frugiperda larvae with a LC50 of 18.7 mg L-1. As demonstrated by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), III-2 particularly facilitated JH III and hindered 20E synthesis in S. frugiperda. The results of RNA-Seq and quantitative real-time polymerase chain reaction (qPCR) showed that III-2 treatment promoted the expression of key genes such as SfCYP15C1 in JH synthesis pathway and inhibited the expression of SfCYP314A1 and other genes in the 20E synthetic pathway. Significant differences were also observed in the expression of the genes related to cuticle formation. We report for the first time that sNPF compounds specifically interfere with the synthesis and secretion of a certain JH in insects, thus affecting the ecdysis and growth of insects, and leading to death. This study may provide a new plant conservation concept for us to seek the targeted control of certain insects based on specific interference with different JH.