Insect Biochemistry and Molecular Biology最新文献

Autocrine activation of ecdysteroidogenesis in the prothoracic glands (PGs) of the silkworm, Bombyx mori, was previously demonstrated. In the present study, the signaling cascade involved in this autocrine activation was further investigated. I found that phosphorylation of the translational repressor 4E-binding protein (4E-BP) increased in a time-dependent manner when PGs were incubated in a small volume (10 μl) of medium, compared to those incubated in a larger volume (100 μl). Higher levels of 4E-BP phosphorylation were also observed in PGs incubated either in PG-conditioned medium or under group incubation conditions. Treatment with LY294002 and rapamycin reduced 4E-BP phosphorylation, indicating the involvement of the PI3K/TOR pathway. I further investigated the downstream target genes involved in autocrine activation. Results showed that the expression levels of several sugar transporter (St) and trehalase (Treh) genes were upregulated in PGs incubated in a small volume (10 μl) of medium. Treatment with LY294002 and rapamycin suppressed the autocrine activation of St1 and Treh1 expressions, suggesting that their regulation is mediated via the PI3K/TOR pathway. Time-dependent autocrine activation of Treh enzyme activity was observed, and this effect was blocked by pretreatment with validamycin A, a specific Treh inhibitor, suggesting that the autocrine factor directly enhances Treh activity. Treatment with either validamycin A or the glycolysis inhibitor 2-deoxy-D-glucose (2-DG) suppressed autocrine activation of ecdysteroidogenesis, clearly indicating that both Treh activity and glycolysis are involved. To investigate potential upstream ligands, I examined the gene expressions of bombyxins and epidermal growth factor (Egf) signaling components. Results showed that only bombyxin-Z1 expression was upregulated in a time-dependent manner under an autocrine condition, while other genes remained unchanged. Using a specifically generated anti-bombyxin-Z1 antibody, the presence of bombyxin-Z1 protein was confirmed. To my knowledge, this is the first study to elucidate the signaling cascade involved in autocrine activation of ecdysteroidogenesis in an insect system.

Mosquito-borne diseases persist as a critical global health burden, driving the demand for novel vector control approaches. Here, we identify and characterize Pipiserpin, a female-specific serine protease inhibitor (serpin) in Culex pipiens pallens, and elucidate its role in regulating reproductive fitness. Pipiserpin exhibits tissue-specific expression in the fat body and ovary, peaking post-blood meal, and features a conserved serpin fold with a reactive central loop critical for protease inhibition. RNA interference-mediated knockdown of Pipiserpin severely impaired ovarian follicular development, reducing follicle size by 7.73% and egg production by 68.10%. Mechanistically, Pipiserpin depletion destabilized vitellogenin (Vg)-a key yolk precursor-by 62.79% in the fat body and 73.01% in the ovary, despite unchanged Vg transcription. This phenotype was attributed to unchecked trypsin-mediated Vg degradation, as demonstrated by recombinant Pipiserpin's dose-dependent inhibition of trypsin activity. Crucially, exogenous 20-hydroxyecdysone (20E) supplementation restored Vg protein levels, follicular maturation and fecundity, revealing a compensatory relationship wherein the 20E-Vg hormonal pathway can functionally overcome reproductive defects caused by Pipiserpin depletion. Global transcriptomic profiling of Pipiserpin-depleted mosquitoes identified 221 differentially expressed genes, including upregulated trypsin-like proteases and metabolic pathway components, indicative of disrupted proteolytic balance and compensatory metabolic remodeling. Our findings redefine serpin functionality in arthropods, highlighting Pipiserpin's dual role in post-translational Vg stabilization and crosstalk with developmental signaling. This work positions Pipiserpin as a promising target for RNAi or small-molecule interventions to disrupt mosquito reproduction, offering a sustainable strategy for combating vector-borne diseases by precisely targeting reproduction.

The oriental fruit fly, Bactrocera dorsalis is a serious fruit pest. Trimethylpyrazine (TMP) and tetramethylpyrazine (TTMP) were characterized as its male released sex pheromone, which showed strong attraction to sexually mature females. So far, the molecular basis of the perception of TMP and TTMP by the females has remained unknown. In this study, using BdorIR8a^-/- and BdorOrco^-/- mutants, we demonstrated that the perception of TMP and TTMP is mediated by odorant receptors (ORs). Furthermore, we generated transgenic Drosophila expressing two odorant receptors (BdorOR49a and BdorOR63a previously showed in vitro binding ability to TMP and TTMP, respectively) in T1 neurons. Subsequent single sensillum recordings (SSR) of the transgenic fly demonstrated that BdorOR49a and BdorOR63a are tuned to TMP and TTMP, respectively. Furthermore, knockout of BdorOR49a and knockdown of BdorOR63a in vivo reduced the olfactory sensitivity of the females to TMP and TTMP. Our results indicated that BdorOR49a and BdorOR63a are responsible for the perception of the male released sex pheromones in B. dorsalis.

Insecticides remain indispensable for crop protection and food security, yet their widespread use may contribute to the global decline of beneficial insect populations. Efforts to mitigate these impacts are hampered by a fragmented understanding of how insects metabolise insecticides and how sublethal exposures affect physiology, behaviour, and fitness. Here, we synthesise current understanding of metabolic detoxification and highlight critical gaps: the tissue- and time-dependent dynamics of insecticide entry and processing, the triggers and architecture of xenobiotic transcriptional responses, the role of rapid non-transcriptional regulation, and the population-level consequences of sublethal effects. We also outline emerging experimental strategies for addressing these questions and propose a next-generation research pipeline centred on multi-endpoint phenomics across life stages and sentinel species, integrated with AI-driven predictive toxicology, as a framework for identifying safer chemicals. We propose an integrated framework unifying molecular, physiological, and ecological responses to sublethal exposure to guide the design of insecticides that maintain effective pest control while safeguarding insect biodiversity and the ecosystems it underpins.

RNA interference (RNAi) is a conserved gene-silencing mechanism; however, its efficiency varies among insect taxa and is particularly low in lepidopterans. A Lepidoptera-specific nuclease, RNAi efficiency-related nuclease (REase), has recently been identified as an RNAi suppressor that degrades double-stranded RNA (dsRNA) upon exposure. To investigate the diversity and potential functions of the REase genes, a phylogenetic analysis was conducted across lepidopteran species and a gene expression analysis of Spodoptera exigua was performed. Three lepidopteran-specific REase groups (REase1-3) and one conserved group related to Asteroids were identified, with all previously reported REase genes classified as REase1. REase3 likely originated from an ancestral duplication of an Asteroid, from which REase1 and REase2 subsequently diverged. REase1 and REase2 were broadly distributed across Lepidoptera, although absent in some lineages. Notably, REase1 exhibited extensive copy number variation among species, whereas REase2 and REase3 were mostly in single-copy form. Expression analysis showed that both REase1 and REase2 were strongly upregulated following dsRNA injection, along with core RNAi components such as Dicer2 and Argonaute2. This dsRNA responsiveness, combined with the accelerated evolution of the REases, suggests their involvement in an evolutionary arms race involving fast-evolving immune challenges, such as viruses. Furthermore, the rapid evolution and frequent gene loss of REase paralogs, which are hallmarks of functionally redundant genes, suggest that REase2 acts as an RNAi suppressor, similar to REase1. These findings highlight the evolutionary diversity and possible functional redundancy of the REases and underscore their potential importance in modulating RNAi efficiency in Lepidoptera.