Archives of Insect Biochemistry and Physiology最新文献

Proteins are essential for insect development, with methionine (Met) being crucial for protein synthesis. However, the roles of methionine and the methionine-rich storage protein 1 (HaSP1) in Helicoverpa armigera larvae remain unclear. In this study, casein removal (-casein) from the larval diet was employed to simulate protein deficiency. Compared with the normal diet control, the -casein group displayed significant reductions in larval body weight and pupation rate, along with markedly increased mortality. Additionally, the methionine content in the fat body and the expression of HaSP1 were both significantly reduced. During larval development, both methionine levels and HaSP1 expression peaked in the late final instar stage. Both 20-hydroxyecdysone (20E) and juvenile hormone (JH) upregulated HaSP1 in midgut. Further RNA interference (RNAi) experiments indicated that knockdown of HaSP1 resulted in decreased larval body weight, increased mortality, and reduced Met content than the Green Fluorescent Protein (dsGFP) control. Furthermore, Methoprene-tolerant 1 (HaMet1) and Hormone Receptor 3 (HaHR3) expression was significantly downregulated upon HaSP1 knockdown. This study revealed that Met was indispensable for larval development and that HaSP1 governed systemic Met levels, thereby playing a pivotal role in larval growth. The findings provide experimental evidence and a theoretical basis for developing green pest-control pesticides that target key genes in nutrient metabolism.

Silkworms (Bombyx Mori) are traditionally reared on mulberry leaves; however, artificial diets have been developed to enable year-round rearing and automation. The physiological performance and cocoon yield of silkworms fed artificial diets remain inferior to those reared on mulberry leaves. We compared growth and nutrient composition in larvae reared on mulberry leaves (ML) and antibiotic-free artificial diet (ADS), and profiled gut microbiota in ML, ADS, and antibiotic-supplemented artificial diet (ADSA) to assess dietary effects on host physiology and microbial ecology. Proximate analysis revealed that protein accumulation was greater in ML-fed larvae, while ADS-fed larvae showed relatively higher fat content at the late fifth instar. Amino acid profiling showed consistently higher silk-related residues (Gly, Ala, Ser) and the derived Silk Amino Acid Index in ML-fed larvae, indicating enhanced fibroin synthesis potential. Microbiome analysis using 16S rRNA amplicon sequencing demonstrated dominance of Enterococcus mundtii in ADS groups, resulting in reduced alpha diversity and uneven community structure. In contrast, ML-fed larvae harbored diverse taxa, including Methylorubrum and Methylobacterium, while ADSA groups exhibited intermediate profiles with occasional dominance of Bacillus cereus. These findings highlight that artificial diet alters host nutrient metabolism and drives dysbiosis of gut microbiota, underscoring the need for optimized formulations and microbiome-stabilizing strategies, such as probiotics or prebiotics.

Spiromesifen is a nonsystemic insecticide that has been primarily recognized for its efficacy against immature stages of whiteflies and mites. However, its activity against adult and egg stages has been less well characterized. In this study, we evaluated its sublethal effects on the reproduction and egg development of the Mediterranean (MED) cryptic species of Bemisia tabaci (Hemiptera: Aleyrodidae). Leaf-dipping bioassays demonstrated that spiromesifen causes significantly higher mortality in nymphs than in eggs and adults. Beyond direct lethality, adult exposure to spiromesifen-treated tomato leaves reduced oviposition rates and disrupted egg development, inducing abnormal egg morphologies in 39.2% and 58.5% of the eggs, respectively, compared with the untreated control. In addition, as the exposure duration increased, egg hatchability declined proportionally, reaching 50.2% compared with the untreated control. These results indicate that spiromesifen has both lethal and sublethal impacts on B. tabaci, combining direct mortality with reproductive suppression. Such dual effects highlight spiromesifen as a promising tool for integrated pest management (IPM) programs, provided it is used judiciously within resistance management frameworks.

In ectothermic species such as insects, temperature significantly influences development and survival. This study examines the effects of thermal stress on metabolic response of Spodoptera litura (Fabricius), a major agricultural pest, to understand how varying thermal conditions, intensified by climate change, affects its physiology. Eggs and larvae were subjected to 42°C and 46°C for 4 h and 1 h respectively in a single and multiple basis for 2 and 4 consecutive days for eggs and larvae respectively. The study measured water content, protein, carbohydrate, and glycogen levels in adults emerging from these heat stressed stages. Results indicated significant reductions in water content and increase in protein, carbohydrate, and glycogen levels under higher temperatures and repeated stress exposures. Females demonstrated higher resilience, evidenced by higher water and protein content compared to males. The findings suggest that S. litura's physiological adaptations to thermal stress involve complex metabolic adjustments, enhancing thermotolerance. This study provides insights into the potential impacts of climate change on S. litura populations and underscores the necessity for sustainable pest management strategies. Key findings include stage-specific differences in thermal sensitivity, with larvae showing greater susceptibility to heat stress, and the critical role of metabolic plasticity in insect resilience. Understanding these metabolic responses is crucial for predicting pest dynamics and developing effective control measures in a changing climate. This study contributes to the broader knowledge of ectothermic pest adaptation to environmental stressors, emphasizing the integration of physiological data into pest management framework.

High-humidity environments can inhibit the reproduction of faba bean aphids (Megoura crassicauda), reduce their moisture content, and induce the emergence of long-winged aphids. However, little is currently known about the molecular mechanisms through which M. crassicauda adapts to high-humidity stress. To better understand the adaptive mechanisms of M. crassicauda under high relative humidity (RH) conditions, we examined their gene expression under three different RH treatments (60%, 75%, and 90%). Differentially expressed genes (DEGs) and related biological processes were identified using transcriptome analysis. Based on the transcriptomic data, several genes with significant expression differences were identified, and their expression patterns under different humidity conditions were validated by qRT-PCR. In the comparisons of RH 60% versus RH 75%, RH 60% versus RH 90%, and RH 75% versus RH 90%, we observed 44, 552, and 268 upregulated genes, and 17, 1536, and 1075 downregulated genes, respectively. Three key pathways, specifically the PI3K/Akt, AMPK, and insulin signaling pathway, were found to be responsive to high-humidity stress, with a greater number of genes downregulated at RH 90%. Additionally, heat shock proteins (HSPs) and zinc finger proteins (ZFPs) were significantly differentially expressed under high humidity, highlighting their crucial roles in the stress response. These findings provide valuable insights into the genes and metabolic signaling pathways involved in high-humidity stress response, laying the foundation for future research on the molecular mechanisms of M. crassicauda adaptation and identifying potential target genes for pest control.

Culex quinquefasciatus, a primary vector of life-threatening and debilitating diseases, is subjected to persistent insecticidal selection pressure through vector control measures and potential exposure to run-offs from agrochemicals. This study investigated the fitness trade-offs linked to pyrethroid resistance in Culex quinquefasciatus. We selected Culex quinquefasciatus strains against 50% lethal concentration (LC₅₀) of alphacypermethrin (AS strain) and permethrin (PS strain) for 24 generations, followed by 12 generations without selection pressure. A susceptible strain (S strain) was maintained for 36 generations without exposure to pyrethroids. Life history traits, including fecundity, developmental time, and lifespan, were compared among strains. Pyrethroid-selected strains (AS and PS) exhibited reduced fecundity, prolonged developmental duration, and shortened lifespan relative to the susceptible strain. AS and PS strains showed elevated levels of monooxygenase activity and glutathione-S-transferase activity, while no significant changes in the level of esterases than that of the S strain. Moreover, the kdr mutation L1014F was fixed in both the AS and PS strains. These findings indicate that pyrethroid resistance incurs significant biological fitness costs in Culex quinquefasciatus. Exploiting the fitness trade-offs of pyrethroid-resistant mosquitoes through rotational use of insecticides with varied mechanisms may serve to decelerate resistance evolution.

Histone deacetylases (HDACs) are a family of proteins that remove acetyl groups from lysine residues on histone proteins. They play vital roles in development, biological processes, and epigenetic regulation. We identified 12 HDAC genes in the adult red flour beetle, Tribolium castaneum, and studied their functions in female reproduction and embryonic development using RNA interference (RNAi). Knockdown of four out of 12 genes (HDAC4, HDAC6, HDAC8, and Sirt7) caused a significant decrease in the number of eggs laid by females compared to control females injected with dsGFP. Additionally, reduction in the expression of five out of 12 genes (HDAC1, HDAC4, HDAC8, Sirt1, and Sirt7) significantly reduced egg hatching rates. Parental RNAi targeting HDAC8, Sirt1, and Sirt7 disrupted embryonic development. The mRNA levels of Vg1, Vg2, VgR, Kr-h1, and E75 decreased significantly in beetles injected with HDAC4 or Sir7 dsRNA. These results suggest that HDACs are required for female reproduction and embryonic development of T. castaneum.

The tropical fruit passion fruit, which depends on insect pollinators such as the Apis cerana, is susceptible to risks associated with excessive pesticide application. These risks include detrimental effects on pollinating insects and the issue of pesticide residues. To quantify these impacts, a multidimensional experimental design was implemented: (1) Sampling entailed the collection of diverse samples (fruit, leaves, flowers, soil, honey, pollen, bees) from eight orchards spanning Hainan Island at four key time points, from preflowering to postpollination. (2) Residues of 12 targeted chemical substances, comprising neonicotinoids, organophosphorus, pyrethroid, and fungicides, were analyzed through liquid chromatography-mass spectrometry. (3) The acute contact toxicity of four neonicotinoid insecticides to Chinese honeybee workers was determined using the drop method, calculating the 48-h median lethal dose (LD₅₀). (4) Dietary intake risks for passion fruit and honey were evaluated via the target hazard quotient (THQ) and risk quotient (RQ) models, whereas ecological risks to bees were assessed through the hazard quotient (HQ) and spray exposure risk quotient (RQsp). The results revealed pesticide detection rates ranging from 1.41% to 70.59%, with the highest total detection rate in the Baoting region. Thiamethoxam was the most prevalent residue, particularly during the initial phase of pollination. No residues were detected in honey, and flupyradifurone was absent across all samples. The dietary risk was deemed acceptable; however, pesticide use had a discernible impact on bee colonies, particularly in the Wuzhishan region. All four neonicotinoid insecticides exhibited high toxicity to Chinese honeybees, with thiamethoxam being the most potent. The study advises judicious pesticide usage during the flowering period to preserve bee pollination.

Cytochrome P450 (P450s) play a crucial role in insecticide detoxification and metabolic resistance in insects. In this study, we identified and characterized five P450 genes from the transcriptome of Megalurothrips usitatus, a major pest of leguminous crops. Full-length cDNA sequences were cloned and subjected to comprehensive bioinformatic analyses. The encoded proteins exhibited typical hydrophobic properties, with secondary structures dominated by α-helices and random coils. Notably, phosphorylation site prediction revealed a high frequency of serine residues. Phylogenetic analysis demonstrated close evolutionary relationships between these P450s and their orthologs in Frankliniella occidentalis and Thrips palmi. Bioassays revealed that field-collected M. usitatus populations from Haikou had developed moderate resistance to both dinotefuran (LC₅₀ = 844.248 mg/L) and sulfoxaflor (LC₅₀ = 165.991 mg/L). Quantitative real-time PCR analysis showed that CYP6EB24 expression was dramatically upregulated by 8.9-fold (p < 0.0001) and 9.6-fold (p < 0.0001) following exposure to LC₂₅ concentrations of dinotefuran and sulfoxaflor, respectively. Spatiotemporal expression profiling indicated highest CYP6EB24 transcript levels in female adults and thoracic tissues. Correspondingly, cytochrome P450 enzyme activity increased significantly (p < 0.05) after insecticide treatment at LC₅₀ concentrations. These results provide robust experimental evidence that CYP6EB24 plays a pivotal role in the metabolic detoxification of dinotefuran and sulfoxaflor in M. usitatus. Our findings not only advance the understanding of P450-mediated resistance mechanisms in M. usitatus but also establish a foundation for future functional studies of detoxification genes in this economically important pest species.