Archives of Insect Biochemistry and Physiology最新文献

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.

Mosquitoes spread a range of life-threatening illnesses such as malaria, dengue, zika virus, chikungunya, yellow fever, and many others, and cause up to 1 million deaths and 1 billion infections across the world every year. There has been growing interest in plant-based repellents that display bioactive compounds with insecticidal and repellent activities. In this review, the focus is on a natural monoterpene that has gained therapeutic properties, including antifungal, antibacterial, antioxidant, anticancer, and neuropharmacological activity, including anti-anxiety and sedative activity. The efficacy of linalool was assayed against mosquitoes in larvicidal and repellent bioassays. Larvicidal assays exhibited dose-dependent mortality: 82% at 1%, 87.4% at 2%, and 90.8% at 4% concentration after 24 h. Repellency cage assays exhibited good initial efficacy, with 1% linalool repelling 82.2% of mosquitoes, 2% repelling 81.8%, and 4% repelling 90.8%, very close to DEET's (N,N-diethyl-meta-toluamide) 93.4%. After 210 min, the 4% concentration had 82.2% repellency, while DEET had 89.6%. Tunnel tests revealed 4% linalool provided 90.2% repellency at 1 h and 84% at 3 h. The findings show that linalool, especially at high levels, is extremely effective as a repellent and larvicide. Its activity is as effective as that of DEET, the present synthetic repellent, and hence linalool can be utilized as an effective natural substitute for long-lasting mosquito control.

The taxon Paraneoptera, comprising Condylognatha (Hemiptera e Thysanoptera) and Psocodea (Phthiraptera and Psocoptera), is paraphyletic, according to recent genomic studies. The midgut morphology and digestive physiology of Haematopinus suis (Phtiraptera) are described here and compared with similar data from Hemiptera and Holometabola. H. suis (Phtiraptera) midgut cells, in contrast to Hemiptera, lack microvillar-associated membranes and have a digestive enzyme secretory mechanism of the type microapocrine, like many Holometabola. Also, like Holometabola, and different from Hemiptera, the main endopeptidases of H. suis are serine endopeptidases (trypsin and chymotrypsin), instead of cysteine endopeptidases. The major difference of H. suis in relation to Holometabola is the absence of a peritrophic membrane (PM), thought to be a consequence of the fact of PM cost of production in this minute insect out weights the benefit of midgut compartmentalization. Our data favor the view that Phthiraptera is closer to Holometabola than to Hemiptera, agreeing with the alleged paraphilia of Paraneoptera.