Fat Body-Multifunctional Insect Tissue

Unravelling the Role of Insulin-Like Peptide Genes in Bombyx mori: Potential Key Regulators of Insect Metabolism

Understanding gene expression in specific tissues and their modulation under environmental stimuli, such as nutritional deficiency, reveals the key physiological regulatory mechanisms of an organism. This study examined the tissue-specific expression of insulin-like peptide (ILP) genes (BmX and BmZ) in Bombyx mori larvae and their responses to hyperglycaemia, food deprivation and hormonal (20-hydroxyecdysone and bovine insulin) treatments. mRNA expression levels of BmX and BmZ were analyzed in the brain, fat body, midgut and ovary. The results revealed that BmX was highly expressed in the fat body, while both genes were abundant in the ovary. Hyperglycaemia increased BmX mRNA expression level in the midgut (3.07-fold) and brain (7.53-fold), while BmZ mRNA expression level was increased in all tissues except the midgut. Nutrient deficiency upregulated BmX mRNA expression level (1.36-fold) in the fat body while reducing it (-0.53-fold) in the midgut. Food deprivation progressively increased (0.77-fold at 24 h and 2.34-fold at 72 h) BmX mRNA expression level in the fat body, while both BmX and BmZ transcripts declined in the midgut. Insulin suppressed BmX (-0.25-fold) and BmZ (-0.91-fold) mRNA expression levels in food-deprived larvae in the fat body, whereas 20E consistently downregulated BmX, BmZ, and BmInR (insulin receptor) mRNA expression levels in all the conditions. These findings revealed the complex interaction of gene expression, tissue specificity, and environmental factors in B. mori larvae and provided insights into adaptive responses to nutritional stress and hormonal regulation in the insect with potential applications in sericulture and agricultural biotechnology.

Hidden target, hidden effects: chlorantraniliprole on the coffee leaf miner (Leucoptera coffeella)

Agricultural insecticide usage presents a complex challenge, particularly when addressing hidden targets such as concealed pest species. Typically, insecticide spraying targets either the host plant or the soil substrate, reaching the target when the pests move or feed, yet their vulnerability when concealed remains low. This study delves into the often-obscure effects of insecticides on hidden herbivore species, focusing specifically on the diamide insecticide chlorantraniliprole and its impact on the concealed insect herbivore, the coffee leaf miner Leucoptera coffeella (Guérin-Mèneville & Perrottet) (Lepidoptera: Lyonetidae). We document the progressive effects of chlorantraniliprole from egg-laying through the insect's development and reproductive output. By examining egg-laying preferences, development, survival, respiration rate, leaf consumption, and polysaccharide and protein accumulation, alongside fecundity, in two field-collected leaf miner populations, we elucidate chlorantraniliprole's broader effects. While the insecticide did not alter the leaf miner's egg-laying preferences, one population exhibited higher larval survival, indicating chlorantraniliprole resistance. This chlorantraniliprole-resistant population displayed a lower respiration rate-indicative of reduced stress-and higher leaf consumption, accompanied by increased sugar and protein accumulation. Although this population showed lower adult longevity, it exhibited higher fecundity. These findings highlight the multifaceted impacts of insecticides, extending beyond survival to affect development, fecundity, and potential fitness. Variations in response among insect populations suggest that resistant insects may outperform susceptible ones even under sublethal exposure, with significant implications for management strategies and future outbreaks.

The role of insulin receptor InR in photoperiod-regulated reproductive diapause of Chrysoperla nipponensis

Insects usually diapause, a process regulated by hormonal signals as an adaptive mechanism developed through long-term evolution to survive unfavorable environmental conditions. Chrysoperla nipponensis is classified as a photoperiod-sensitive insect. Treatments with short-day (SD) and long-day (LD) conditions have distinct effects on ovarian development and lipid accumulation in adults, with SD condition inducing diapause. Injecting bovine insulin promoted ovarian development and egg formation in diapause females, while injecting insulin receptor induced diapause-like traits in reproductive females. This study investigate the biological function of insulin signaling in the reproductive diapause of females of C. nipponensis. Under SD treatment the mRNA expression level of InR1 and InR2, as well as the protein expression level of InR1 were significantly reduced. This reduction led to stagnant ovarian development, increased adipose tissue mass, and a significant rise in triglyceride (TG) content. Silencing InR1 under LD conditions resulted in halted ovarian development and enhanced lipid accumulation, with the expression levels of Akt, Kr-h1, and Vg significantly decreased mirroring those observed under SD conditions. Interestingly, silencing InR2 under LD condition did not affect ovarian development. Furthermore, transcriptome analysis identified six genes (Akt, PkN, Skp2, CycB3, BTrC, and AurkA) associated with reproductive regulation and eight genes (FadΔ11, EchA, EcI, Ugts (2A3, 1-9), AR, Gpdh and Cbr) linked to lipid metabolism, all of which are involved in InR1 mediated regulation of C. nipponensis reproduction.

Towards identification of a holocentromere marker in the lepidopteran model Spodoptera frugiperda

Some insects have holocentric chromosomes, with multiple kinetochores rather than a single centromere. They also lack the CENP-A and CENP-C proteins, suggesting a kinetochore assembly process different from that of monocentric chromosomes. The homolog of CENP-T was recently shown to bind silent chromatin and to play a key role in kinetochore assembly in Bombyx mori, but its role in other insects with holocentric chromosomes is unknown. We identified kinetochore genes and analyzed their expression in Spodoptera frugiperda. We silenced the kinetochore genes cenp-L, cenp-S, cenp-X and ndc80 and searched for chromosome segregation defects in Sf9 cells. All kinetochore genes except cenp-S were more strongly expressed in gonadal than in somatic tissues. Immunofluorescence microscopy and RT-qPCR demonstrated the effective silencing of the target genes by transfection with dsRNA. In Sf9 cells depleted of CENP-L and NDC80, immunofluorescence microscopy revealed increases in mitotic index and in the proportion of cells with unaligned chromosomes or multipolar spindles. The depletion of CENP-S and CENP-X had no effect on mitotic index and no division defects were observed. This suggests that CENP-L and NDC80 play key roles in chromosome segregation, whereas the functions of CENP-S and CENP-X remain unknown. We have begun to characterize the kinetochore proteins (CENP-L, CENP-S, CENP-X, NDC80), a prerequisite for holocentromere identification in S. frugiperda. This study also provides the first information about the role, in Lepidoptera, of CENP-L, a protein essential to the structure of the constitutive centromere-associated network in species with monocentric chromosomes.

Suppression of Adipokinetic hormones enhances Ascovirus HvAV-3h killing speed in Helicoverpa armigera

The emergence of pesticide resistance in Helicoverpa armigera and other pests represents a challenge, necessitating continued development of innovative insecticides. Ascoviruses are a potential insecticide for H. armigera. These double-stranded DNA viruses cause cell death and lethal disease in infected larvae. However, this disease is chronic and prolongs the lifespan of the infected larvae by several weeks. The slow killing speed limits the success of these pathogens in the insecticidal market. Here, we demonstrate that the dsRNA silencing of H. armigera neuropeptide Adipokinetic Hormones (HaAKH) accelerates the killing speed of Heliothis virescens ascovirus 3h (HvAV-3h) against the third-instar larvae of H. armigera. The LT50 was reduced to 3.96 days in larvae with silenced HaAKH1 and 4.7 days in those with silenced HaAKH3. Moreover, the histopathological examinations revealed the destruction of the host's fat body and epidermal tissue shrinkage after HaAKH silencing during HvAV-3h infection. Examining detoxification and antioxidant enzyme activity in HvAV-3h infected larvae showed reduced detoxification mechanisms after HaAKH gene silencing. Furthermore, the silencing of HaAKH resulted in an overall reduction in the fold changes of proline dehydrogenase. In conclusion, this study demonstrates that the ascovirus killing speed can be accelerated by interfering with the host neuropeptide-related gene expression. Moreover, the silencing of H. armigera HaAKH1 and HaAKH3 decreased the antiviral immunity against HvAV-3h.

Genome-wide identification and expression profile analysis of the Ras superfamily genes in eastern honeybee (Apis cerana)

The Ras superfamily, a crucial gene family in eukaryotes, functions as molecular switches that regulate various physiological and biochemical processes within cells. However, research on this topic remains limited concerning Apis cerana, a pollinator of significant economic and ecological importance. Here, 83 Ras superfamily genes in the genome of A. cerana were identified and classified into five distinct families. Phylogenetic analysis revealed that the homologous genes from two closely related species, A. cerana and Apis mellifera, clustered with relatively high bootstrap values. Notably, Rerg was unique to A. cerana compared to A. mellifera and had undergone gene duplication events. Expression profiles indicated diverse expression patterns of the Ras superfamily in the fat body during the holometabolous development of A. cerana. Most genes exhibited high expression levels during the later stages of adipose tissue remodeling; however, a minority were predominantly expressed during the prepupal (PP) and 1-day-old pupae (P1) stages. Among the 8 pairs of genes that had undergone gene duplication, 4 had inconsistent patterns, and 3 pairs were from the Ras family. In particular, Di-Ras2-2 was found to be highly expressed exclusively at the PP, and Rap2a-2 was only highly expressed during newly emerged (Em) stage. The observed differences in expression patterns may reflect adaptations to varying energy metabolism modes or environmental pressures. These findings provided a foundational basis for further investigation into the potential physiological roles of the Ras superfamily in A. cerana and offered valuable insights for analyzing this gene family across other insect species.

A comprehensive cell atlas of fall armyworm (Spodoptera frugiperda) larval gut and fat body via snRNA-Seq

The midgut and fat body of insects control key physiological processes, including growth, digestion, metabolism, and stress response. Single-nucleus RNA sequencing (snRNA-seq) is a promising way to reveal organ complexity at the cellular level, yet data for lepidopteran insects are lacking. We utilized snRNA-seq to assess cellular diversity in the midgut and fat body of Spodoptera frugiperda. Our study identified 20 distinct clusters in the midgut, including enterocytes, enteroendocrine, stem-like cells, and muscle cells, and 27 clusters in the fat body, including adipocytes, hemocytes, and epithelial cells. This dataset, containing all identified cell types in midgut and fat body, is valuable for characterizing the cellular composition of these organs and uncovering new cell-specific biomarkers. This cellular atlas enhances our understanding of cellular heterogeneity of fat and midgut, serving as a basis for future functional and comparative analyses. As the first snRNA-seq study on the midgut and fat body of S. frugiperda, it will also support future research, contribute to lepidopteran studies, and aid in developing targeted pest control strategies.

Identification of Fatty Acid Synthase in Arma chinensis and Its Expression Profiles in Response to Starvation

Fatty acids are the main form of energy production and storage in insects, and fatty acid synthase (FAS) plays a major role in this process. Arma chinensis is a natural enemy used in China to control agricultural pests. While its whole genome has been assembled, its FAS genes remain undescribed. Herein, we aim to identify the FAS genes of A. chinensis and explore their expression during starvation. Phylogenetic analysis identified nine FAS genes (ArmaFas1-ArmaFas9). During the predatory developmental stages, ArmaFas9 expression gradually increased from the 2nd to the 4th instar, peaking at the 5th instar and plateauing at the adult stage. Female adults exhibited the highest expression of ArmaFas9 in their fat body and the lowest expression in their salivary glands, whereas male adults demonstrated the opposite pattern. ArmaFas9 expression was negatively correlated with starvation duration. Compared to the controls, starved adult females exhibited a downward expression trend, whereas starved adult males demonstrated an initial increase, followed by a downward trend after 7 days. Starvation and refeeding increased ArmaFas9 expression. These results demonstrate the important role of ArmaFas9 in A. chinensis growth and development, providing a basis for further studies on lipid synthesis in predatory bugs.

An Overview of the Nutritional Requirements of Honey Bees (Apis mellifera Linnaeus, 1758)

Honey bees are known for their wide global distribution, their ease of handling, and their economic and ecological value. However, they are often exposed to a wide variety of stress factors. Therefore, it is essential for beekeepers to maintain healthy bee colonies. In this context, a balanced diet is recommended to support the growth of strong and healthy honey bee colonies. The purpose of this review is therefore to provide an overview of the nutritional requirements of Apis mellifera and their importance for the maintenance of healthy bee colonies. An adequate diet includes the consumption of sufficient amounts of proteins, carbohydrates, lipids, amino acids, vitamins, minerals, water, and essential sterols, and a diet based on multi-floral pollen is desirable. However, when honey bee colonies are located near agroecosystems with lower resource diversity, both brood rearing and colony longevity may decrease, making them more susceptible to parasites and diseases. On the other hand, efforts have been made to improve the health of honey bee colonies with the help of nutritional supplements consisting of a variety of components. Nevertheless, studies have shown that even with these supplements, a lack of nutrients can still be an issue for honey bee colonies. Furthermore, future research should focus on identifying nutritional supplements that can better replicate natural diet diversity and assessing long-term effects on honey bee colony resilience, especially in low-flowering areas. This review discusses the interaction between nutrient requirements and the effects of supplements on colony health.

Fat Body Metabolome Revealed Glutamine Metabolism Pathway Involved in Prepupal Apis mellifera Responding to Cold Stress

Thermal condition affects the development and growth of ectotherms. The stenothermic honeybee brood, particularly the prepupae, are sensitive to low rearing temperature. The fat body plays important roles in energy reserve and metabolism during the honeybee brood development. To date, the fat body metabolic changes in prepupae responding to cold stress have not been completely understood. In this study, the ultra-performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/MS)-based non-target metabolome was analyzed between the cold-treated (CT, 20 °C, 36 h) and control (CK, 35 °C) fat body in prepupal honeybees. The fat body metabolomic data showed that the levels of 1860 and 254 metabolites were significantly increased and decreased, respectively, in cold-stressed prepupae. These altered metabolites, glutamine, glutamic acid, pyroglutamic acid, and oxidized glutathione, were significantly enriched into glutamine metabolism and glutathione metabolism pathways. Furthermore, the expression levels of glutamine metabolism-related genes, glutaminase (GLS), glutamate dehydrogenase (GDH), and gamma-glutamyl transferase (GGT-1 and GGT-7), were significantly decreased in cold-exposed prepupae compared with the control groups. Meanwhile, the oxidized glutathione (GSSG), but not the reduced glutathione (GSH) content, was increased in the cold-exposed group compared with controls. Collectively, our data revealed the fat body metabolomic changes in larva-to-pupa transition when exposed to cold stress. Our data provided new insights into stenothermic honeybee sensitivity to cold, characterized by perturbation of glutamine metabolism and oxidative stress.

Exploring the role of the microbiome of the H. illucens (black soldier fly) for microbial synergy in optimizing black soldier fly rearing and subsequent applications

The symbiotic microbiome in the insect's gut is vital to the host insect's development, improvement of health, resistance to disease, and adaptability to the environment. The black soldier fly (BSF) can convert organic substrates into a protein- and fat-rich biomass that is viable for various applications. With the support of a selective microbiome, BSF can digest and recycle different organic waste, reduce the harmful effects of improper disposal, and transform low-value side streams into valuable resources. Molecular and systems-level investigations on the harbored microbial populations may uncover new biocatalysts for organic waste degradation. This article discusses and summarizes the efforts taken toward characterizing the BSF microbiota and analyzing its substrate-dependent shifts. In addition, the review discusses the dynamic insect-microbe relationship from the functional point of view and focuses on how understanding this symbiosis can lead to alternative applications for BSF. Valorization strategies can include manipulating the microbiota to optimize insect growth and biomass production, as well as exploiting the role of BSF microbiota to discover new bioactive compounds based on BSF immunity. Optimizing the BSF application in industrial setup and exploiting its gut microbiota for innovative biotechnological applications are potential developments that could emerge in the coming decade.

Susceptibility of Lymantria dispar to Beauveria bassiana under short-term Cd stress: Humoral immunostimulation cannot offset cellular immunotoxicity

Heavy metal is a serious environmental pollutant with all kinds of biotoxic effects. The immunomodulatory effects of Cd stress on Lymantria dispar larvae and its underlying mechanisms were investigated. The susceptibility of Cd-treated larvae to Beauveria bassiana (Bb) was significantly increased by 27.50 %. The hemocyte count, melanization, encapsulation activities, and expression levels of related regulatory genes (e.g. PPO1 and DSCAM) in the Cd and Cd+Bb groups were markedly lower than those in CK and CK+Bb groups. Hemocyte compensation through the apoptosis inhibitor significantly increased the melanization, encapsulation, and the survival rate of larvae in the Cd+Bb group by 100.00 %, 74.03 %, and 18.33 %, respectively. The expression of signal transduction and effector genes (e.g. Gloverin) was significantly elevated in Cd-treated larvae both before and after Bb infection. Silencing Gloverin resulted in a 9.17 % increase in susceptibility of Cd-treated larvae to Bb. Cd exposure induced humoral immunostimulation in larvae through the CncC-Gloverin pathway, as evidenced by that silencing CncC resulted in a 71.07 % decrease in Gloverin expression and a 19.73 % increase in larval mortality in Cd+Bb group. Overall, the humoral immunostimulation induced by Cd stress in L. dispar larvae were insufficient to counteract the cellular immunotoxicity during Bb infection.

Multigenerational expression of antimicrobial peptides in Aedes aegypti exposed to Metarhizium anisopliae: Is trans-generational immune priming involved?

We assessed, for the first time, a multigenerational expression of antimicrobial peptides (AMPs) in Aedes aegypti larvae exposed to the entomopathogenic fungus, Metarhizium anisopliae, and correlated it with a possible involvement in trans-generational immune priming (TGIP). Aedes aegypti larvae were first exposed to blastospores or conidia of M. anisopliae CG 489 for 24 and 48 h, and the relative expression of AMPs were measured using quantitative Real-Time PCR. A suspension of conidia was prepared, and two different survival tests were conducted with different larval generations (F0, F1, and F2). In the first bioassay, the survival curves of the three generations were conducted separately and compared with their respective control groups. In the other bioassay, the survival curves of the F0, F1, and F2 generations were compared simultaneously against a naïve group exposed to Tween 80. In both survival tests, the F0 generation was more susceptible to M. anisopliae than subsequent generations. For molecular analyses related to TGIP, F0, F1, and F2 larvae were exposed to conidia, and their expression of AMPs was compared with their control groups and a naïve group. There was no differential expression of cecropin, defensin A or cathepsin B between generations. Lysozyme C, however, showed an increase in expression across generations, suggesting a role in TGIP. These discoveries may help us develop biological insecticides against mosquito larvae based on entomopathogenic fungi.

Yellow mealworm: effects of adults breeding density on adults and larvae performances from an industrial perspective

A key aspect to optimise the Tenebrio molitor (TM) farm productivity is to find an optimal breeding density for adults. To this purpose, this study investigated, from an industrial perspective, the impact of four breeding densities (D1, D2, D3 and D4, equal to 0.8, 1.1, 1.3 and 1.6 adults/cm2, respectively) on mortality and reproductive performances of TM adults and larvae. Two weeks after pupae emergence, TM adults were randomly assigned to the four groups and housed in 48 breeding crates (60 × 40 × 14.5 cm; 12 crates/group). The trial consisted of 4 consecutive weeks of adult breeding (each week represented one oviposition), and 8 weeks of larvae growth. From each week of oviposition, a batch of larvae was obtained for a total of four batches of larvae (48 crates/batch). Larvae of each batch were grown until 8 weeks of age, corresponding to the period required to reach the selling size. Larvae were kept in the original crates until the 5th weeks of age, after which they were divided into additional crates to ensure a density of 4.2 larvae/cm2 and a final weight of 1 500 g of larvae/crate (0.6 g of larvae/cm2). For each oviposition week, TM adult's mortality, egg hatchability, BW, feed intake, chemical composition and fatty acid profile were evaluated, while ovary weight was measured at weeks 1 and 4. The number of larvae was monitored at week 5 of age while their chemical composition was determined at week 5 and 8. Larvae feed intake and BW were monitored over the 8-weeks growth period. Individual feed intake and BW of adults increased with increasing breeding density (P < 0.0001 and P < 0.05, respectively). With increasing adult breeding density, the number of larvae per crate increased (P < 0.001) while the grams of larvae/gram of adults decreased (R2 = 0.8856). Larvae from groups D2, D3 and D4 showed higher feed intake per crate and higher individual and total final BW than D1 (P < 0.001). However, the feed conversion ratio (FCR) worsened with increasing breeding density (P < 0.001). D4 larvae had higher percentages of protein (P < 0.001), lipids (P < 0.05) and cholesterol (P < 0.001) compared to larvae from other groups. Concluding, a breeding density of 0.8 adults/cm2 maximised both grams of larvae produced/grams of adults and larvae FCR. However, breeding densities above 0.8 adults/cm2 resulted in a higher number of produced larvae per crate with a greater final mass weight making a density of 1.6 adults/cm2 the preferable choice from and industrial perspective.

Phosphoproteomics analyses of Aedes aegypti fat body reveals blood meal-induced signaling and metabolic pathways

The mosquito fat body is the principal source of yolk protein precursors (YPP) during mosquito egg development in female Aedes aegypti. To better understand the metabolic and signaling pathways involved in mosquito reproduction, we investigated changes in the mosquito fat body phosphoproteome at multiple time points after a blood meal. Using LC/MS, we identified 3570 phosphorylated proteins containing 14,551 individual phosphorylation sites. We observed protein phosphorylation changes in cellular pathways required for vitellogenesis, as well as proteins involved in primary cellular functions. Specifically, after a blood meal, proteins involved in ribosome synthesis, transcription, translation, and autophagy showed dynamic changes in their phosphorylation patterns. Our results provide new insight into blood meal-induced fat body dynamics and reveal potential proteins that can be targeted for interference with mosquito reproduction. Considering the devastating impact of mosquitoes on human health, worldwide, new approaches to control mosquitoes are urgently needed.

Characterization of lipases revealed tissue-specific triacylglycerol hydrolytic activity in Spodoptera frugiperda

Lipids perform a diverse and unique array of functions in insects. Lipases are key enzymes in lipid metabolism, and their metabolic products are crucial for development and reproduction of insects. Here, a total of 110 lipase genes were identified in the genome of Spodoptera frugiperda. Cluster analysis indicated that neutral lipases constitute the majority of lipases. Tissue expression profile analysis displayed that most lipase genes were highly expressed in the larval gut of S. frugiperda. Some lipases exhibited a diet-specific expression pattern, which implied their roles in host adaptation. Key domain analysis proved that none of the neutral lipases highly expressed in the gut has an integrated lid domain, while most lipases highly expressed in the fat body contained both the integrated lid domain and β9 loop, indicating the activity loss of neutral lipases in guts. The assay of triacylglycerol (TAG) hydrolytic activity confirmed that the gut had the lowest activity when compared to that of fat body and epidermis. Interestingly, the opposite TAG hydrolytic activity trends across mating were observed between adult males and females, implying that lipase played different roles in the reproduction of both sexes. In conclusion, neutral lipases lost TAG hydrolytic activity in S. frugiperda guts, but retained the activity in fat body. Neutral lipases would play vital roles in many physiological processes in insects, especially in insect reproduction, which provides palpable targets for novel insecticide development to control insect population growth.

Knockdown of CYP6SZ3 and CYP6AEL1 genes increases the susceptibility of Lasioderma serricorne to ethyl formate and benzothiazole

Insect cytochrome P450 monooxygenases (CYPs) play crucial roles in the metabolic detoxification of insecticides. Ethyl formate and benzothiazole have recently regained popularity as fumigants due to rising resistance to phosphine in the stored-product pests. However, the mechanisms underlying tolerance to these two fumigants in Lasioderma serricorne, a major global insect pest of stored products, remain poorly understood. In this study, two CYP genes, named CYP6SZ3 and CYP6AEL1, were identified from L. serricorne, belonging to the CYP6 family and containing five conserved domains characteristic of CYP proteins. Spatiotemporal expression analysis revealed that both genes were predominantly expressed in the larval stage and showed the highest expression in the foregut. Upon exposure to ethyl formate and benzothiazole, both genes were upregulated, with significantly increased transcription levels following treatment. RNA interference-mediated silencing of CYP6SZ3 and CYP6AEL1 led to increased susceptibility and significantly higher mortality of L. serricorne when exposed to these fumigants. Homology modeling and molecular docking analyses showed stable binding of these fumigants to CYP6SZ3 and CYP6AEL1 proteins, with binding free energies from -26.88 to -94.68 kcal mol-1. These findings suggest that the induction of CYP6SZ3 and CYP6AEL1 is likely involved in the detoxification of ethyl formate and benzothiazole in L. serricorne.

Glucose influence cold tolerance in the fall armyworm, Spodoptera frugiperda via trehalase gene expression

The fall armyworm (FAW), Spodoptera frugiperda is a cold-sensitive species that overwinters in temperate climates without diapause. Overwintering in insects involves rapid cold hardening (RCH), supported by trehalose (TRE), which serves as an intermediate between glycogen (GLY) and glucose (GLU). However, both GLU and TRE help maintain homeostasis under stress. TRE is hydrolyzed by the enzyme trehalase (Treh) into GLU. This study retrieved Sf-Treh1a, Sf-Treh1b, and Sf-Treh2 from the FAW transcriptome analysis. RNA interference (RNAi) targeting these three Treh genes resulted in significant downregulation of mRNA levels and altered survival rates in RNAi-treated FAW larvae following RCH treatment. High-pressure liquid chromatography (HPLC) quantification of TRE and GLU in treated groups suggests that GLU is an essential component of the hemolymph for survival adaptation to cold conditions in S. frugiperda. This study reveals limited cold adaptability of FAW, as evidenced by lower glucose concentration levels. We found that FAW requires alternative molecules, in conjunction with glucose and trehalose for freeze tolerance and survivability. Our study aims to discover the molecular mechanisms that contribute to freeze tolerance in FAW by exploring the roles of trehalose, glucose, and glycogen.

Effect of neonicotinoid and fungicide strobilurin in neotropical solitary bee Centris analis

The indiscriminate use of pesticides is one of the factors directly impacting bee populations. However, limited information is available on the pesticide effects on solitary bees, especially in Neotropical countries. In this scenario, this study evaluated the survival and histopathological effects caused by the neonicotinoid insecticide acetamiprid (7 ng/μL) and the fungicide azoxystrobin (10 ng/μL) in the midgut and parietal fat body of the solitary bee Centris analis. Female and male newly-emerged bees were orally exposed for 48 h to the pesticides, or alone or in combination, under laboratory conditions. The exposure to the insecticide reduced the survival of males, while the mixture reduced survival in both sexes. Acetamiprid promoted a reduction in the number of regenerative nests in the midgut, alterations of fat body cells by increasing carbohydrates in trophocytes, and reduction of oenocyte size, and increased the frequency of pericardial cells in the advanced activity stage. Both pesticides caused changes in HSP70 immunolabelling of midgut from males at the end of pesticide exposure. Comparatively, the effects on males were stronger than in females exposed to the same pesticides. Therefore, acetamiprid alone and in mixture with fungicide azoxystrobin can be harmful to males and females of Neotropical solitary bee C. analis showing lethal and sublethal effects at a concentration likely to be found in the environment.

Sublethal Effects Induced by a Cyflumetofen Formulation on Honeybee Apis mellifera L. Workers: Assessment of Midgut, Hypopharyngeal Glands, and Fat Body Integrity

Worldwide, both cultivated and wild plants are pollinated by the honey bee, Apis mellifera. Bee numbers are declining as a result of a variety of factors, including increased pesticide use. Cyflumetofen controls pest mites in some plantations pollinated by bees, which may be contaminated with residual sublethal concentrations of this pesticide, in nectar and pollen. We evaluated the effects of a sublethal concentration of a cyflumetofen formulation on the midgut, hypopharyngeal gland, and fat body of A. mellifera workers orally exposed for 72 h or 10 days. The midgut epithelium of treated bees presented digestive cells with cytoplasm vacuoles and some cell fragmentation, indicating autophagy and cell death. After being exposed to the cyflumetofen formulation for 72 h, the midgut showed a higher injury rate than the control bees, but after 10 days, the organs had recovered. In the hypopharyngeal gland of treated bees, the end apparatus was filled with secretion, suggesting that the acaricide interferes with the secretory regulation of this gland. Histochemical tests revealed differences in the treated bees in both exposure periods in the midgut and hypopharyngeal glands. The acaricide caused cytotoxic effects on the midgut digestive cells, with apical protrusions, plasma membrane rupture, and several vacuoles in the cytoplasm, features of cell degeneration. In the hypopharyngeal glands of the treated bees, the secretory cells presented small electron-dense and large electron-lucent secretory granules. The fat body cells had no changes in comparison with the control bees. In conclusion, the cyflumetofen formulation at sublethal concentrations causes damage to the midgut and the hypopharyngeal glands of honey bee, which may compromise the functions of these organs and colony fitness. Environ Toxicol Chem 2024;43:2455-2465. © 2024 SETAC.

A role of epigenetic mechanisms in regulating female reproductive responses to temperature in a pest beetle

Many species are threatened by climate change and must rapidly respond to survive in changing environments. Epigenetic modifications, such as DNA methylation, can facilitate plastic responses by regulating gene expression in response to environmental cues. Understanding epigenetic responses is therefore essential for predicting species' ability to rapidly adapt in the context of global environmental change. Here, we investigated the functional significance of different methylation-associated cellular processes on temperature-dependent life history in seed beetles, Callosobruchus maculatus Fabricius 1775 (Coleoptera: Bruchidae). We assessed changes under thermal stress in (1) DNA methyltransferase (Dnmt1 and Dnmt2) expression levels, (2) genome-wide methylation and (3) reproductive performance, with (2) and (3) following treatment with 3-aminobenzamide (3AB) and zebularine (Zeb) over two generations. These drugs are well-documented to alter DNA methylation across the tree of life. We found that Dnmt1 and Dnmt2 were expressed throughout the body in males and females, but were highly expressed in females compared with males and exhibited temperature dependence. However, whole-genome methylation did not significantly vary with temperature, and only marginally or inconclusively with drug treatment. Both 3AB and Zeb led to profound temperature-dependent shifts in female reproductive life history trade-off allocation, often increasing fitness compared with control beetles. Mismatch between magnitude of treatment effects on DNA methylation versus life history effects suggest potential of 3AB and Zeb to alter reproductive trade-offs via changes in DNA repair and recycling processes, rather than or in addition to (subtle) changes in DNA methylation. Together, our results suggest that epigenetic mechanisms relating to Dnmt expression, DNA repair and recycling pathways, and possibly DNA methylation, are strongly implicated in modulating insect life history trade-offs in response to temperature change.

The Drosophila Estrogen-Related Receptor promotes triglyceride storage within the larval fat body

The Estrogen-Related Receptor (ERR) family of nuclear receptors (NRs) serve key roles in coordinating triglyceride (TAG) accumulation with juvenile growth and development. In both insects and mammals, ERR activity promotes TAG storage during the post-embryonic growth phase, with loss-of-function mutations in mouse Esrra and Drosophila melanogaster dERR inducing a lean phenotype. However, the role of insect ERRs in controlling TAG accumulation within adipose tissue remains poorly understood, as previous transcriptomic and metabolomic studies relied on whole animal analyses. Here we address this shortcoming by using tissue-specific approaches to examine the role of dERR in regulating lipid metabolism within the Drosophila larval fat body. We find that dERR autonomously promotes TAG accumulation within fat body cells and regulates expression of genes involved in glycolysis, β-oxidation, and mevalonate metabolism. As an extension of these results, we not only discovered that dERR mutant fat bodies exhibit decreased expression of known dHNF4 target genes but also found that dHNF4 activity is decreased in dERR mutants. Overall, our findings indicate that dERR plays a multifaceted role in the larval fat body to coordinate lipid storage with developmental growth and hint at a conserved mechanism by which ERR and HNF4 homologs coordinately regulate metabolic gene expression.

Interactive effects of chlorothalonil and Varroa destructor on Apis mellifera during adult stage

The interaction between environmental factors affecting honey bees is of growing concern due to their potential synergistic effects on bee health. Our study investigated the interactive impact of Varroa destructor and chlorothalonil on workers' survival, fat body morphology, and the expression of gene associated with detoxification, immunity, and nutrition metabolism during their adult stage. We found that both chlorothalonil and V. destructor significantly decreased workers' survival rates, with a synergistic effect observed when bees were exposed to both stressors simultaneously. Morphological analysis of fat body revealed significant alterations in trophocytes, particularly a reduction in vacuoles and granules after Day 12, coinciding with the transition of the bees from nursing to other in-hive work tasks. Gene expression analysis showed significant changes in detoxification, immunity, and nutrition metabolism over time. Detoxification genes, such as CYP9Q2, CYP9Q3, and GST-D1, were downregulated in response to stressor exposure, indicating a potential impairment in detoxification processes. Immune-related genes, including defensin-1, Dorsal-1, and Kayak, exhibited an initially upregulation followed by varied expression patterns, suggesting a complex immune response to stressors. Nutrition metabolism genes, such as hex 70a, AmIlp2, VGMC, AmFABP, and AmPTL, displayed dynamic expression changes, reflecting alterations in nutrient utilization and energy metabolism in response to stressors. Overall, these findings highlight the interactive and dynamic effects of environmental stressor on honey bees, providing insights into the mechanisms underlying honey bee decline. These results emphasize the need to consider the interactions between multiple stressors in honey bee research and to develop management strategies to mitigate their adverse effects on bee populations.

The mlpt smORF gene is essential for digestive physiology and molting during nymphal stages in the kissing bug Rhodnius prolixus

Chagas disease affects around 8 million people globally, with Latin America bearing approximately 10,000 deaths each year. Combatting the disease relies heavily on vector control methods, necessitating the identification of new targets. Within insect genomes, genes harboring small open reading frames (smORFs - < 100 amino acids) present numerous potential candidates. In our investigation, we elucidate the pivotal role of the archetypal smORF-containing gene, mille-pattes/polished-rice/tarsalless (mlpt/pri/tal), in the post-embryonic development of the kissing bug Rhodnius prolixus. Injection of double-stranded RNA targeting mlpt (dsmlpt) during nymphal stages yields a spectrum of phenotypes hindering post-embryonic growth. Notably, fourth or fifth stage nymphs subjected to dsmlpt do not undergo molting. These dsmlpt nymphs display heightened mRNA levels of JHAMT-like and EPOX-like, enzymes putatively involved in the juvenile hormone (JH) pathway, alongside increased expression of the transcription factor Kr-h1, indicating changes in the hormonal control. Histological examination reveals structural alterations in the hindgut and external cuticle of dsmlpt nymphs compared to control (dsGFP) counterparts. Furthermore, significant changes in the vector's digestive physiology were observed, with elevated hemozoin and glucose levels in the posterior midgut of dsmlpt nymphs. Importantly, dsmlpt nymphs exhibit impaired metacyclogenesis of Trypanosoma cruzi, the causative agent of Chagas disease, underscoring the crucial role of proper gut organization in parasite differentiation. Thus, our findings constitute the first evidence of a smORF-containing gene's regulatory influence on vector physiology, parasitic cycle, and disease transmission.

Uridine diphosphate (UDP)-glycosyltransferases (UGTs) are associated with insecticide resistance in the major malaria vectors Anopheles gambiae s.l. and Anopheles funestus

Malaria remains one of the highest causes of morbidity and mortality, with 249 million cases and over 608,000 deaths in 2022. Insecticides, which target the Anopheles mosquito vector, are the primary method to control malaria. The widespread nature of resistance to the most important insecticide class, the pyrethroids, threatens the control of this disease. To reverse the stall in malaria control there is urgent need for new vector control tools, which necessitates understanding the molecular basis of pyrethroid resistance. In this study we utilised multi-omics data to identify uridine-diphosphate (UDP)-glycosyltransferases (UGTs) potentially involved in resistance across multiple Anopheles species. Phylogenetic analysis identifies sequence similarities between Anopheline UGTs and those involved in agricultural pesticide resistance to pyrethroids, pyrroles and spinosyns. Expression of five UGTs was characterised in An. gambiae and An. coluzzii to determine constitutive over-expression, induction, and tissue specificity. Furthermore, a UGT inhibitor, sulfinpyrazone, restored susceptibility to pyrethroids and DDT in An. gambiae, An. coluzzii, An. arabiensis and An. funestus, the major African malaria vectors. Taken together, this study provides clear association of UGTs with pyrethroid resistance as well as highlighting the potential use of sulfinpyrazone as a novel synergist for vector control.

Transcriptional response of laboratory-reared Mexican fruit flies (Anastrepha ludens Loew) to desiccation

Confronting environments with low relative humidity is one of the main challenges faced by insects with expanding distribution ranges. Anastrepha ludens (the Mexican fruit fly) has evolved to cope with the variable conditions encountered during its lifetime, which allows it to colonise a wide range of environments. However, our understanding of the mechanisms underpinning the ability of this species to confront environments with low relative humidity is incomplete. In this sense, omic approaches such as transcriptomics can be helpful for advancing our knowledge on how this species copes with desiccation stress. Considering this, in this study, we performed transcriptomic analyses to compare the molecular responses of laboratory-reared A. ludens exposed and unexposed to desiccation. Data from the transcriptome analyses indicated that the responses to desiccation are shared by both sexes. We identified the up-regulation of transcripts encoding proteins involved in lipid metabolism and membrane remodelling, as well as proteases and cuticular proteins. Our results provide a framework for understanding the response to desiccation stress in one of the most invasive fruit fly species in the world.

The allatotropin/orexin system as an example of immunomodulatory properties of neuropeptides

The central nervous system (CNS) plays a critical role in signal integration in animals and allows the orchestration of life processes to maintain homeostasis. Current research clearly shows that inflammatory processes can also be modulated by the CNS via the neuroendocrine system. One of the neuropeptide families that participate in vertebrates in this process is orexins (OXs). Interestingly, our previous results suggested that a similar dependency may also exist between neuropeptides and immune system activity in insects. Due to the structural homology of orexin and allatotropin receptors and the functional similarity between these two neuropeptide families, the main aim of this research was to perform a complex analysis of the relationships between allatotropin (AT) and the insect immune response. Our results revealed functional similarities between vertebrate OXs and insect ATs. Similar effects were observed in the profile of the expression level of the gene encoding the AT precursor in the Tenebrio molitor nervous system and in the general action of Tenmo-AT on selected immune parameters of the tested beetles. Moreover, for the first time in insects, we confirmed the role of cytokines in the modulation of neuroendocrine system by determining the effect of Spätzle-like protein injection on the expression of genes encoding AT precursor and receptor. All these results are important for understanding the evolutionary basis of hormonal regulation of the immune response.

Silencing NlFAR7 destroyed the pore canals and related structures of the brown planthopper

Fatty acyl-CoA reductase (FAR) is one of the key enzymes, which catalyses the conversion of fatty acyl-CoA to the corresponding alcohols. Among the FAR family members in the brown planthopper (Nilaparvata lugens), NlFAR7 plays a pivotal role in both the synthesis of cuticular hydrocarbons and the waterproofing of the cuticle. However, the precise mechanism by which NlFAR7 influences the formation of the cuticle structure in N. lugens remains unclear. Therefore, this paper aims to investigate the impact of NlFAR7 through RNA interference, transmission electron microscope, focused ion beam scanning electron microscopy (FIB-SEM) and lipidomics analysis. FIB-SEM is employed to reconstruct the three-dimensional (3D) architecture of the pore canals and related cuticle structures in N. lugens subjected to dsNlFAR7 and dsGFP treatments, enabling a comprehensive assessment of changes in the cuticle structures. The results reveal a reduction in the thickness of the cuticle and disruptions in the spiral structure of pore canals, accompanied by widened base and middle diameters. Furthermore, the lipidomics comparison analysis between dsNlFAR7- and dsGFP-treated N. lugens demonstrated that there were 25 metabolites involved in cuticular lipid layer synthesis, including 7 triacylglycerols (TGs), 5 phosphatidylcholines (PCs), 3 phosphatidylethanolamines (PEs) and 2 diacylglycerols (DGs) decreased, and 4 triacylglycerols (TGs) and 4 PEs increased. In conclusion, silencing NlFAR7 disrupts the synthesis of overall lipids and destroys the cuticular pore canals and related structures, thereby disrupting the secretion of cuticular lipids, thus affecting the cuticular waterproofing of N. lugens. These findings give significant attention with reference to further biochemical researches on the substrate specificity of FAR protein, and the molecular regulation mechanisms during N. lugens life cycle.

1H NMR Profiling of Honey Bee Brains across Varying Ages and Seasons

Honey bees (Apis mellifera) provide a useful model for studying aging because of the differences in longevity between the relatively short-lived summer and long-lived winter bees, as well as bees lacking signs of cognitive senescence as they age. Bee brains were dissected from newly emerged, 14-day-, and 28-day- old bees in mid- and late summer, as well as brood nest bees in fall, winter, and spring, before, during, and after overwintering, respectively. Brains were examined with nuclear magnetic resonance (NMR) spectroscopy to analyze their metabolome. Nine variable importance in projection (VIP) variables were identified, primarily amino acids and choline derivatives. Differences in metabolite concentrations were found with different ages of summer bees, mostly between newly emerged and 14-day- old bees, such as a decrease in phenylalanine and an increase in β-alanine, but there were also changes in older adults, such as o-phosphocholine that declined in 28-day- old bees. Differences in brood nest bees were observed, including a decline in tryptophan and an increase in β-alanine. These may provide distinct metabolomic signatures with age and season. Such research holds promise for a better understanding of the complex interplays between bee physiology, development, and aging, which has implications for improving bee health and management.

Exendin-4 Caused Growth Arrest by Regulating Sugar Metabolism in Hyphantria cunea (Lepidoptera: Erebidae) Larvae

Insects' growth and development are highly dependent on energy supply, with sugar metabolism playing a pivotal role in maintaining homeostasis and regulating physiological processes. The present study investigated the effects of exendin-4, a glucagon-like peptide-1 receptor (GLP-1R) agonist, on the growth, development, glycolysis, and energy metabolism of fourth-instar larvae of the fall webworm, Hyphantria cunea. We determined the impact of exendin-4 on larval growth and nutritional indices, analyzed the responses of glycolytic and metabolic pathways, and revealed the underlying regulatory mechanisms. Exendin-4 treatment significantly decreased growth and nutritional indices, influenced the activity of digestive enzymes, and induced changes in metabolite profiles, particularly affecting energy substance metabolism. We observed an increase in the glycogen content and a decrease in glucose and trehalose levels in the hemolymph, suggesting a regulatory effect on blood sugar homeostasis. Furthermore, exendin-4 promoted glycolysis by enhancing the activities and expressions of key glycolytic enzymes, leading to an increase in pyruvate production. This was accompanied by a reduction in ATP levels and the activation of AMP-activated protein kinase (AMPK), which may underlie the growth arrest in larvae. Our findings provide novel insights into the effects of exendin-4 on insect responses from an energy metabolism perspective and may contribute to the development of GLP-1R agonists for pest management.

The effect of pollen monodiets on fat body morphology parameters and energy substrate levels in the fat body and hemolymph of Apis mellifera L. workers

Human activities associated with large-scale farms and the monocultures expose honey bees to one type of food. Moreover, there is an ongoing decline of plant species producing pollen and nectar in Europe. A poorly balanced diet affects a number of processes occurring in a bee's body. The fat body and hemolymph are the tissues that participate in all of them. Therefore, the aim of our study was to determine the effect of hazel, pine, rapeseed, buckwheat, phacelia and goldenrod pollen on the morphological parameters of fat body trophocytes, the diameters of cell nuclei in oenocytes and the concentrations of compounds involved in energy metabolism (glucose, glycogen, triglycerides and protein). In the cage tests, the bees were fed from the first day of life with sugar candy (control group) or candy with a 10% addition of one of the 6 pollen types. Hemolymph and fat body from various locations were collected from 1-, 7- and 14-day-old workers. Pollen produced by plant species such as hazel and pine increased glucose concentrations in the bee tissues, especially in the hemolymph. It can therefore be concluded that they are valuable sources of energy (in the form of simple carbohydrates) which are quickly used by bees. Pollen from plants blooming in the summer and autumn increased the concentrations of proteins, glycogen and triglycerides in the fat body, especially that from the third tergite. The accumulation of these compounds was associated with an increased the length and width of trophocytes as well as with enhanced metabolic activity, which was evidenced in the increasing diameter of oenocyte cell nuclei. It seems a balanced multi-pollen diet is more valuable for bees, but it is important to understand the effects of the particular pollen types in the context of a mono-diet. In the future, this will make it possible to produce mixtures that can ensure homeostasis in the apian body.

Characterization of an agmatine N-acetyltransferase from Bactrocera dorsalis that modulates ovary development

Agmatine N-acetyltransferase (AgmNAT), which catalyzes the formation of N-acetylagmatine from acetyl-CoA and agmatine, is a member of the GCN5-related N-acetyltransferase family. So far, knowledge of the physiological roles of AgmNAT in insects is limited. Here, we identified one gene encoding protein homologous to that of Drosophila AgmNAT using sequence information from an activity-verified Drosophila AgmNAT in a BLAST search of the Bactrocera dorsalis genome. We expressed and purified B. dorsalis AgmNAT in Escherichia coli and used the purified enzyme to define the substrate specificity for acyl-CoA and amine substrates. Our application of the screening strategy to BdorAgmNAT led to the identification of agmatine as the best amine substrate for this enzyme, with the highest kcat/Km value. We successfully obtained a BdorAgmNAT knockout strain based on a wild-type strain (WT) using the CRISPR/Cas9 technique. The ovary development of the BdorAgmNAT knockout mutants was delayed for 10 days compared with the WT specimens. Moreover, mutants had a much smaller mature ovary size and laid far fewer eggs than WT. Loss of function of BdorAgmNAT caused by RNAi with mature WT females did not affect their fecundity. These findings indicate that BdorAgmNAT is critical for oogenesis. Our data provide the first evidence for AgmNAT in regulating ovary development.

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.

Toxic effects of acaricide fenazaquin on development, hemolymph metabolome, and gut microbiome of honeybee (Apis mellifera) larvae

Fenazaquin, a potent insecticide widely used to control phytophagous mites, has recently emerged as a potential solution for managing Varroa destructor mites in honeybees. However, the comprehensive impact of fenazaquin on honeybee health remains insufficiently understood. Our current study investigated the acute and chronic toxicity of fenazaquin to honeybee larvae, along with its influence on larval hemolymph metabolism and gut microbiota. Results showed that the acute median lethal dose (LD50) of fenazaquin for honeybee larvae was 1.786 μg/larva, and the chronic LD50 was 1.213 μg/larva. Although chronic exposure to low doses of fenazaquin exhibited no significant effect on larval development, increasing doses of fenazaquin resulted in significant increases in larval mortality, developmental time, and deformity rates. At the metabolic level, high doses of fenazaquin inhibited nucleotide, purine, and lipid metabolism pathways in the larval hemolymph, leading to energy metabolism disorders and physiological dysfunction. Furthermore, high doses of fenazaquin reduced gut microbial diversity and abundance, characterized by decreased relative abundance of functional gut bacterium Lactobacillus kunkeei and increased pathogenic bacterium Melissococcus plutonius. The disrupted gut microbiota, combined with the observed gut tissue damage, could potentially impair food digestion and nutrient absorption in the larvae. Our results provide valuable insights into the complex and diverse effects of fenazaquin on honeybee larvae, establishing an important theoretical basis for applying fenazaquin in beekeeping.

The Key Role of Amino Acids in Pollen Quality and Honey Bee Physiology-A Review

When studying honey bee nutrition, it is important to pay attention not only to the quantity but also to the quality of pollen for floral visitors. The recommended way to determine the value of pollen is to determine both the protein concentration and the amino acid composition in the insect's hemolymph. In addition, the composition of pollen also includes lipids, sterols and biogenic elements such as carbon, nitrogen, etc. Very high protein concentration is observed in aloe pollen, averaging 51%. Plants with a high protein content, at the level of 27% in Europe, are rapeseed and phacelia. In turn, a plant that is poor in protein (at the level of 11%) is buckwheat. The aforementioned plants are sown over very large areas. Vast acreages in Central and Eastern Europe are occupied by pollen- and nectar-providing invasive plants, such as goldenrod. Therefore, bees are forced to use one food source-a mono diet-which results in their malnutrition. In the absence of natural pollen, beekeepers use other foods for bees; including soy protein, powdered milk, egg yolks, fish meal, etc. However, the colony is the strongest when bees are fed with pollen, as opposed to artificial protein diets. More research is needed on the relationship between bee pollen composition and nutrition, as measured by protein concentration and amino acid composition in apian hemolymph, colony strength, honey yield and good overwintering.

Non-Consumptive Effects of Harmonia axyridis on the Reproduction and Metabolism of Spodoptera frugiperda

An increasing body of research has underscored the significant impact of non-consumptive effects on the dynamics of prey pests, encompassing growth, development, reproduction, and metabolism across various vertebrate and invertebrate taxa, rivaling the influence of consumption effects. In our investigation, we delved into the non-consumptive effects exerted by the natural predatory enemy Harmonia axyridis on the reproductive capacity and metabolism of Spodoptera frugiperda adults. Our findings revealed a substantial decrease in the reproductive ability of S. frugiperda adults when exposed to the non-consumptive effects of H. axyridis. Concurrently, we observed an elevation in hydrogen peroxide (H2O2) content and the activities of antioxidant enzymes such as superoxide dismutases (SODs), catalases (CATs), and peroxidases (PODs). Furthermore, notable alterations were detected in energy metabolism, characterized by heightened triglyceride levels and diminished glycogen and trehalose concentrations. These outcomes underscored the adaptive response of the pest aimed at mitigating non-consumptive adverse effects by augmenting antioxidant enzyme activity to counteract oxidative stress and minimize cellular damage. Nonetheless, this defensive mechanism entails a significant expenditure of energy resources, resulting in shifts in energy utilization. Elevated triglyceride levels and reduced glycogen and trehalose concentrations diminish available resources for reproductive processes, such as egg laying, ultimately culminating in decreased fecundity. This study contributes novel insights into the non-consumptive effects observed in insects, while also furnishing valuable insights into the mechanisms underlying insect stress responses.

Endocrine Control of Lipid Metabolism

Lipids are essential in insects and play pleiotropic roles in energy storage, serving as a fuel for energy-driven processes such as reproduction, growth, development, locomotion, flight, starvation response, and diapause induction, maintenance, and termination. Lipids also play fundamental roles in signal transduction, hormone synthesis, forming components of the cell membrane, and thus are essential for maintenance of normal life functions. In insects, the neuroendocrine system serves as a master regulator of most life activities, including growth and development. It is thus important to pay particular attention to the regulation of lipid metabolism through the endocrine system, especially when considering the involvement of peptide hormones in the processes of lipogenesis and lipolysis. In insects, there are several lipogenic and lipolytic hormones that are involved in lipid metabolism such as insulin-like peptides (ILPs), adipokinetic hormone (AKH), 20-hydroxyecdysone (20-HE), juvenile hormone (JH), and serotonin. Other neuropeptides such as diapause hormone-pheromone biosynthesis activating neuropeptide (DH-PBAN), CCHamide-2, short neuropeptide F, and the cytokines Unpaired 1 and 2 may play a role in inducing lipogenesis. On the other hand, neuropeptides such as neuropeptide F, allatostatin-A, corazonin, leukokinin, tachykinins, limostatins, and insulin-like growth factor (ILP6) stimulate lipolysis. This chapter briefly discusses the current knowledge of the endocrine regulation of lipid metabolism in insects that could be utilized to reveal differences between insects and mammalian lipid metabolism which may help understand human diseases associated with dysregulation of lipid metabolism. Physiological similarities of insects to mammals make them valuable model systems for studying human diseases characterized by disrupted lipid metabolism, including conditions like diabetes, obesity, arteriosclerosis, and various metabolic syndromes.

Exposure of the stingless bee Melipona scutellaris to imidacloprid, pyraclostrobin, and glyphosate, alone and in combination, impair its walking activity and fat body morphology and physiology

The stingless bee Melipona scutellaris performs buzz pollination, effectively pollinating several wild plants and crops with economic relevance. However, most research has focused on honeybees, leaving a significant gap in studies concerning native species, particularly regarding the impacts of pesticide combinations on these pollinators. Thus, this study aimed to evaluate the sublethal effects of imidacloprid (IMD), pyraclostrobin (PYR), and glyphosate (GLY) on the behavior and fat body cell morphology and physiology of M. scutellaris. Foragers were orally exposed to the different pesticides alone and in combination for 48 h. Bees fed with contaminated solution walked less, moved slower, presented morphological changes in the fat body, including vacuolization, altered cell shape and nuclei morphology, and exhibited a higher count of altered oenocytes and trophocytes. In all exposed groups, alone and in combination, the number of cells expressing caspase-3 increased, but the TLR4 number of cells expressing decreased compared to the control groups. The intensity of HSP70 immunolabeling increased compared to the control groups. However, the intensity of the immunolabeling of HSP90 decreased in the IMD, GLY, and I + G (IMD + GLY) groups but increased in I + P-exposed bees (IMD + PYR). Alternatively, exposure to PYR and P + G (PYR + GLY) did not affect the immunolabeling intensity. Our findings demonstrate the hazardous effects and environmental consequences of isolated and combined pesticides on a vital neotropical pollinator. Understanding how pesticides impact the fat body can provide crucial insights into the overall health and survival of native bee populations, which can help develop more environmentally friendly approaches to agricultural practices.

Comparative Transcriptomics of Fat Bodies between Symbiotic and Quasi-Aposymbiotic Adult Females of Blattella germanica with Emphasis on the Metabolic Integration with Its Endosymbiont Blattabacterium and Its Immune System

We explored the metabolic integration of Blattella germanica and its obligate endosymbiont Blattabacterium cuenoti by the transcriptomic analysis of the fat body of quasi-aposymbiotic cockroaches, where the endosymbionts were almost entirely removed with rifampicin. Fat bodies from quasi-aposymbiotic insects displayed large differences in gene expression compared to controls. In quasi-aposymbionts, the metabolism of phenylalanine and tyrosine involved in cuticle sclerotization and pigmentation increased drastically to compensate for the deficiency in the biosynthesis of these amino acids by the endosymbionts. On the other hand, the uricolytic pathway and the biosynthesis of uric acid were severely decreased, probably because the reduced population of endosymbionts was unable to metabolize urea to ammonia. Metabolite transporters that could be involved in the endosymbiosis process were identified. Immune system and antimicrobial peptide (AMP) gene expression was also reduced in quasi-aposymbionts, genes encoding peptidoglycan-recognition proteins, which may provide clues for the maintenance of the symbiotic relationship, as well as three AMP genes whose involvement in the symbiotic relationship will require additional analysis. Finally, a search for AMP-like factors that could be involved in controlling the endosymbiont identified two orphan genes encoding proteins smaller than 200 amino acids underexpressed in quasi-aposymbionts, suggesting a role in the host-endosymbiont relationship.

The Morphological Image of Fat Body and Tergal Gland Cells in Uninseminated Apis mellifera Queen Bees

The morphological changes in fat body cells, tergal gland cells, and the surface areas of the cell nuclei were determined in queen bees of the subspecies Apis mellifera carnica. This study focused on 1-, 8-, and 20-day-old uninseminated females kept in colonies, analyzing cells from three locations in the abdomen: the sternite, and tergites III and V. The oenocytes in the sternites were large, oval/circular with a centrally located nucleus, while in tergites III and V, they were small and triangular in the 1-day-old queens. During the first week of life, these cells in tergites III and V change their shape to oval and increase their sizes. The initially light yellow and then dark yellow granularities in the oenocytes of the fat body appear along with the advancing age of the queens. The trophocytes (sternites, tergites III and V) in the 1-day-old queens were completely filled with droplets of different sizes. In the 8- and 20-day-old queens, the number and size of the droplets decreased in the trophocytes of tergites III and V. The tergal gland cells had a centrally located cell nucleus in the 1-, 8- and 20-day-old queens. The dark granularities in these cells were visible only in the 20-day-old queens. Different morphological images of the fat body at the sternite, and tergites III and V, and the difference in the size of the oenocyte cell nuclei may indicate various functions of the fat body depending on its location. Characterization of the changes in the morphology of the fat body, taking into account its segmental character, and the tergal glands requires further research in older queens, e.g., one-year-old, brooding queens.

Integrated stress response signaling acts as a metabolic sensor in fat tissues to regulate oocyte maturation and ovulation

Reproduction is an energy-intensive process requiring systemic coordination. However, the inter-organ signaling mechanisms that relay nutrient status to modulate reproductive output are poorly understood. Here, we use Drosophila melanogaster as a model to establish the integrated stress response (ISR) transcription factor, Atf4, as a fat tissue metabolic sensor that instructs oogenesis. We demonstrate that Atf4 regulates lipase activity to mediate yolk lipoprotein synthesis in the fat body. Depletion of Atf4 in the fat body also blunts oogenesis recovery after amino acid deprivation and re-feeding, suggestive of a nutrient-sensing role for Atf4. We also discovered that Atf4 promotes secretion of a fat-body-derived neuropeptide, CNMamide, which modulates neural circuits that promote egg-laying behavior (ovulation). Thus, we posit that ISR signaling in fat tissue acts as a "metabolic sensor" that instructs female reproduction-directly by impacting yolk lipoprotein production and follicle maturation and systemically by regulating ovulation.

The immune response mechanism of Nilaparvata lugens against a combined infection of rice ragged stunt virus and Metarhizium anisopliae

BACKGROUND

Previous studies of brown planthopper (BPH), Nilaparvata lugens, showed that carrying the plant pathogenic virus, rice ragged stunt virus (RRSV), enhanced the lethality of the entomopathogenic fungus, Metarhizium anisopliae (YTTR). The underlying mechanism for this was not established but a serine protease cascade was hypothesized to be involved.

RESULTS

Two immune response genes, NlKPI and NlVenomase, were identified and shown to be involved. The synthesized double-strand RNA (dsRNA) techniques used in this study to explore gene function revealed that treatment with dsRNA to silence either gene led to a higher BPH mortality from M. anisopliae infection than the dsRNA control treatment. NlKPI and NlVenomase play vital roles in BPH immunity to defend against alien pathogens. Both genes participate in the immune response process of BPH against co-infection with RRSV and M. anisopliae YTTR by regulating the expression of antimicrobial peptides and phenoloxidase activity.

CONCLUSION

Our study provided new targets for BPH biocontrol and laid a solid foundation for further research on the interaction of virus-insect-EPF (entomopathogenic fungus). © 2023 Society of Chemical Industry.

Exposure to sublethal concentrations of imidacloprid, pyraclostrobin, and glyphosate harm the behavior and fat body cells of the stingless bee Scaptotrigona postica

Pesticide use in agriculture threatens non-target insects such as bees. Considering the ecological and economic relevance of native bees, such as Scaptotrigona postica, and the insufficient studies on the effects of pesticides on their behavior and physiology, improving the current knowledge on this issue is essential. Therefore, this study investigated the sublethal effects of imidacloprid, pyraclostrobin, and glyphosate on the behavior and fat body cells of S. postica. Pesticide ingestion decreased the walking distance and mean velocity of bees compared to the control and solvent control groups. The oenocytes of the control groups were spherical, with central nuclei containing decondensed chromatin, and the trophocytes presented irregular morphology, with cells varying in shape and the cytoplasm filled with vacuoles and granules. However, bees exposed to pesticides showed extensive cytoarchitectural disruption in the fat body, such as vacuolization and shape changes in oenocytes and altered nuclei morphology in trophocytes. Moreover, pesticide exposure increased the number of atypical oenocytes and altered trophocytes, except for the PYR group, which showed a lower number of atypical oenocytes. Caspase-positive labeling significantly increased in all exposed bee groups. Alternatively, TLR4 labeling was significantly decreased in the exposed groups compared to the control groups. There was a significant increase in HSP90 immunolabeling in all exposed groups compared to the control. These findings reinforce the importance of research on the sublethal effects of low pesticide concentrations on key neotropical pollinators and prove that these toxic substances can impair their detoxification and immune defense.

Histopathological observations and comparative transcriptome analysis of Ophiocordyceps sinensis infection of Hepialus xiaojinensis in the early stage

Hepialus xiaojinensis is a Lepidopteran insect and one of the hosts for the artificial cultivation of Cordyceps. Ophiocordyceps sinensis can infect and coexist with H. xiaojinensis larvae for a long time. Little studies focused on the interaction process through its early infection stage. In this research, we particularly study the interaction of infected and uninfected larvae in the 3rd (OS-3, CK-3) and 4th (OS-4, CK-4) instars. O. sinensis was distributed within the larvae and accompanied by pathological changes in some tissue structures. In response to O. sinensis infection, OS-3 enhanced the antioxidant defense ability, while OS-4 decreased. The transcriptome analysis showed that OS-3 resisted the invasion of O. sinensis by the immune and nervous systems. Correspondingly, OS-4 reduced immune response and utilized more energy for growth and development. This study provides a comprehensive resource for analyzing the mechanism of H. xiaojinensis and O. sinensis interaction.

Effects of the insecticide imidacloprid on the post-embryonic development of the honey bee Apis mellifera (Hymenoptera: Apidae)

The widespread use of pesticides in agriculture has been linked to declines in bee populations worldwide. Imidacloprid is a widely used systemic insecticide that can be found in the pollen and nectar of plants and has the potential to negatively impact the development of bee larvae. We investigated the effects of oral exposure to a realistic field concentration (20.5 ng g-1) of imidacloprid on the midgut and fat body of Apis mellifera worker larvae. Our results showed that larvae exposed to imidacloprid exhibited changes in the midgut epithelium, including disorganization of the brush border, nuclear chromatin condensation, cytoplasm vacuolization, and release of cell fragments indication cell death. Additionally, histochemical analysis revealed that the midgut brush border glycocalyx was disorganized in exposed larvae. The fat body cells of imidacloprid-exposed larvae had a decrease in the size of lipid droplets from 50 to 8 μm and increase of 100 % of protein content, suggesting possible responses to the stress caused by the insecticide. However, the expression of de cdc20 gene, which plays a role in cell proliferation, was not affected in the midgut and fat body of treated larvae. These results suggest that imidacloprid negatively affects non-target organs during the larval development of A. mellifera potentially impacting this important pollinator species.

Lipidomic features of honey bee and colony health during limited supplementary feeding

Honey bee nutritional health depends on nectar and pollen, which provide the main source of carbohydrates, proteins and lipids to individual bees. During malnutrition, insect metabolism accesses fat body reserves. However, this process in bees and its repercussions at the colony level are poorly understood. Using untargeted lipidomics and gene expression analysis, we examined the effects of different feeding treatments (starvation, sugar feeding and sugar + pollen feeding) on bees and correlated them with colony health indicators. We found that nutritional stress led to an increase in unsaturated triacylglycerols and diacylglycerols, as well as a decrease in free fatty acids in the bee fat body. Here, we hypothesise that stored lipids are made available through a process where unsaturations change lipid's structure. Increased gene expression of three lipid desaturases in response to malnutrition supports this hypothesis, as these desaturases may be involved in releasing fatty acyl chains for lipolysis. Although nutritional stress was evident in starving and sugar-fed bees at the colony and physiological level, only starved colonies presented long-term effects in honey production.

Metoprolol elicits neurobehavioral insufficiency and oxidative damage in nontarget Nauphoeta cinerea nymphs

Metoprolol, a drug for hypertension and cardiovascular diseases, has become a contaminant of emerging concern because of its frequent detection in various environmental matrices globally. The dwindling in the biodiversity of useful insects owing to increasing presence of environmental chemicals is currently a great interest to the scientific community. In the current research, the toxicological impact of ecologically relevant concentrations of metoprolol at 0, 0.05, 0.1, 0.25, and 0.5 μg/L on Nauphoeta cinerea nymphs following exposure for 42 consecutive days was evaluated. The insects' behavior was analyzed with automated video-tracking software (ANY-maze, Stoelting Co, USA) while biochemical assays were done using the midgut, head and fat body. Metoprolol-exposed nymphs exhibited significant diminutions in the path efficiency, mobility time, distance traveled, body rotation, maximum speed and turn angle cum more episodes, and time of freezing. In addition, the heat maps and track plots confirmed the metoprolol-mediated wane in the exploratory and locomotor fitness of the insects. Compared with control, metoprolol exposure decreased acetylcholinesterase activity in insects head. Antioxidant enzymes activities and glutathione level were markedly decreased whereas indices of inflammation and oxidative injury to proteins and lipids were significantly increased in head, midgut and fat body of metoprolol-exposed insects. Taken together, metoprolol exposure induces neurobehavioral insufficiency and oxido-inflammatory injury in N. cinerea nymphs. These findings suggest the potential health effects of environmental contamination with metoprolol on ecologically and economically important nontarget insects.

Solanaceae Glycoalkaloids Disturb Lipid Metabolism in the Tenebrio molitor Beetle

Glycoalkaloids (GAs) are produced naturally by plants and affect insect survivability and fertility. These compounds can be considered potential bioinsecticides; however, the mechanisms and effects of their action remain undiscovered. As lipids are essential molecules for the proper functioning of an insect organism, this research aimed to determine the effects of GAs on the lipid metabolism of the Tenebrio molitor beetle. Solanine, chaconine, tomatine, and tomato leaf extract were applied to larvae by injection at two concentrations, 10-8 and 10-5 M. Then, the tissue was isolated after 2 and 24 h to determine the levels of free fatty acids, sterols and esters using the GC-MS technique. Moreover, the triacylglyceride level and the activity of the key β-oxidation enzyme, 3-hydroxyacyl-CoA dehydrogenase (HADH), were measured. The results indicate that GAs affect the content and composition of lipid compounds in the beetles' haemolymph and fat body. The effects depend on the GA concentrations, incubation time, and kind of tissue. Moreover, the tested compounds decrease HADH activity, especially in the fat body, which may affect energy production. To our knowledge, this is the first study concerning lipid metabolism in T. molitor after GA application. Our results provide some insights into that topic.

Biting Midges (Diptera: Ceratopogonidae) as Vectors of Viruses

Biting midges of the genus Culicoides occur almost globally and can regionally and seasonally reach high abundances. Most species are hematophagous, feeding on all groups of vertebrates, including humans. In addition to being nuisance pests, they are able to transmit disease agents, with some viruses causing high morbidity and/or mortality in ruminants, horses and humans. Despite their impact on animal husbandry, public health and tourism, knowledge on the biology and ecology of culicoid biting midges and their interactions with ingested pathogens or symbiotic microorganisms is limited. Research is challenging due to unknown larval habitats, the insects' tiny size, the inability to establish and breed most species in the laboratory and the laborious maintenance of colonies of the few species that can be reared in the laboratory. Consequently, the natural transmission of pathogens has experimentally been demonstrated for few species while, for others, only indirect evidence of vector potential exists. Most experimental data are available for Culicoides sonorensis and C. nubeculosus, the only species kept in western-world insectaries. This contribution gives an overview on important biting midge vectors, transmitted viruses, culicoid-borne viral diseases and their epidemiologies and summarizes the little knowledge on interactions between biting midges, their microflora and culicoid-borne arboviruses.

Bees exposed to climate change are more sensitive to pesticides

Bee populations are exposed to multiple stressors, including land-use change, biological invasions, climate change, and pesticide exposure, that may interact synergistically. We analyze the combined effects of climate warming and sublethal insecticide exposure in the solitary bee Osmia cornuta. Previous Osmia studies show that warm wintering temperatures cause body weight loss, lipid consumption, and fat body depletion. Because the fat body plays a key role in xenobiotic detoxification, we expected that bees exposed to climate warming scenarios would be more sensitive to pesticides. We exposed O. cornuta females to three wintering treatments: current scenario (2007-2012 temperatures), near-future (2021-2050 projected temperatures), and distant-future (2051-2080). Upon emergence in spring, bees were orally exposed to three sublethal doses of an insecticide (Closer, a.i. sulfoxaflor; 0, 4.55 and 11.64 ng a.i./bee). We measured the combined effects of wintering and insecticide exposure on phototactic response, syrup consumption, and longevity. Wintering treatment by itself did not affect winter mortality, but body weight loss increased with increasing wintering temperatures. Similarly, wintering treatment by itself hardly influenced phototactic response or syrup consumption. However, bees wintered at the warmest temperatures had shorter longevity, a strong fecundity predictor in Osmia. Insecticide exposure, especially at the high dose, impaired the ability of bees to respond to light, and resulted in reduced syrup consumption and longevity. The combination of the warmest winter and the high insecticide dose resulted in a 70% longevity decrease. Smaller bees, resulting from smaller pollen-nectar provisions, had shorter longevity suggesting nutritional stress may further compromise fecundity in O. cornuta. Our results show a synergistic interaction between two major drivers of bee declines, and indicate that bees will become more sensitive to pesticides under the current global warming scenario. Our findings have important implications for pesticide regulation and underscore the need to consider multiple stressors to understand bee declines.