Archives of Insect Biochemistry and Physiology最新文献

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.

The insect pest Chilo partellus (C. Swinhoe 1885), commonly known as the spotted stem borer, poses a significant threat to Sorghum bicolor (L. Moench 1794), a major cereal crop. This study investigates the complex interaction between C. partellus and different sorghum genotypes, with a focus on the contrasting effects on larval mass and mortality when reared on resistant versus susceptible sorghum varieties. Notably, larvae fed on susceptible sorghum exhibited enhanced growth performance. Our analysis revealed qualitative and quantitative differences in digestive protease expression in response to host plant genotype, with the highest overall protease activity observed in larvae fed on resistant sorghum. Furthermore, protease isoforms demonstrated distinct responses to synthetic non-host proteinaceous protease inhibitors, indicating variable inhibitor sensitivities. Transcriptomic analysis revealed a diverse array of hydrolase and protease genes expressed in C. partellus larvae reared on natural sorghum. The expression profiles of the newly identified chymotrypsins (CpaChy1-4) varied according to the resistance status of the host sorghum genotype. Phylogenetic analysis positioned these novel CpaChys within a clade closely related to chymotrypsins identified in Ostrinia nubilalis. In silico binding studies suggested that CpaChy1 and CpaChy2 are less likely to interact with sorghum-derived serine protease inhibitors compared to the other identified chymotrypsins. Unraveling the molecular mechanisms underlying these diet-specific protease adaptations in C. partellus is critical for advancing our understanding of the insect's ability to adapt to different host plant defenses.

Insect nymphal/larval instars vary widely across insect taxa and at the intraspecific level, they are orchestrated by two hormones, juvenile hormones (JH) and 20-hydroxyecdysone (20E). For insects whose nympha/larva molting events are more than 3, lack of JH signal causes premature metamorphosis and additional JH exposure induces supernumerary juvenile molts. In Drosophila melanogaster, the number of larval molts is fixed at two (dimolter) and is not affected by either JH or 20E signals. Larvae of a subset of Coleopterans are trimolters. Whether JH signal governs the number of larval molts in these Coleopteran trimolters deserves investigation. In the current study, we found that Methoprene-tolerant (Met) gene was actively transcribed from the first instar to pupal stages in an herbivorous ladybird Henosepilachna vigintioctomaculata. An injection of dsMet at the second, third and fourth (final) larval stages successfully knocked down the target gene, and disrupted the expression of both JH and 20E signaling genes. RNA interference for Met at the second instar larval stage reduced the number of larval molts from 3 to 2, and consequently caused premature metamorphosis and miniature pupae, as well as the impairment of larval-pupal transition. Contrarily, depletion of Met at the third and fourth instar larval periods arrested the larval development at the prepupal stage. Our findings suggest that JH signaling orchestrates the number of larval molts at the second instar stage in the H. vigintioctomaculata larvae.

The diamondback moth (Plutella xylostella), a major lepidopteran pest with a wide host range, presents persistent challenges to sustainable agriculture due to its high adaptability to cruciferous host plants. Although glyoxylate/hydroxypyruvate reductases (GRHPRs) have been well-characterized in plants and humans, their functional role in insects, particularly in host plant adaptation, remains largely unexplored. In this study, we characterized PxGRHPR2, a member of the GRHPR gene family, using a bioinformatics analysis, expression profiling, and CRISPR/Cas9-mediated gene knockout. RT-qPCR analysis showed that PxGRHPR2 was predominantly expressed in larval stage, with the highest transcript levels observed in the second instar and larval midgut tissues. Three homozygous PxGRHPR2 knockout strains were successfully generated using CRISPR/Cas9 system. Mutation of PxGRHPR2 led to significant reductions in larval weight, survival, and eclosion rates when larvae were fed on radish seedlings, whereas no such effects were observed under artificial diet conditions. These findings suggest that PxGRHPR2 plays a critical role in detoxification and metabolic regulation, thereby facilitating host plant adaptability in P. xylostella. Overall, this study provides new insights into insect−plant interactions and identifies PxGRHPR2 as a potential molecular target for developing sustainable pest management strategies.

Various physiological activities of the honeybee abdomen depend on muscle contraction, mainly regulated by calcium ions. Thus, the dynamic changes of calcium ions are crucial for unraveling the molecular mechanism of muscle contraction but remain unclear. Considering that calcium ions bind to troponin on thin filaments to induce the formation of actomyosin cross-bridges, fluorescence labeling technology can be employed to investigate the dynamic regulatory effect of calcium ions on muscle fibers. Here we show that the calcium ion concentration first increased and then gradually decayed under the simulation of L-glutamic acid, leading to a gradual decay of the changes in the length of muscle fibers until they were almost unchanged, at which point the maximum contraction was reached. The contraction rate of the muscle fibers was fastest at the beginning and then decreased as the calcium ion concentration decreased. The maximum extent of muscle fiber shortening sizes was about 20 μm, with the initial size of about 225 μm. A model of half sarcomere contraction stimulated by calcium ions was established to further verify the effects of calcium ions on muscle fiber contraction, and the consistent tendency with the experiment demonstrated good agreement on the regulatory effect of calcium ions on muscle fiber contraction. This finding provides a deeper understanding of the dynamic process of muscle contraction in insects and an important reference for the design of integrated soft-body actuators, especially ion-regulated actuators.