Insect Molecular Biology最新文献

Malpighian tubules (MTs) of insects are integral to osmoregulation, detoxification, immunity and stress responses. Cicadas experience an ecological transition from subterranean to aboveground during ontogeny. However, little is known about the morphological/functional differences related to MTs between their nymphal and adult stages and potential molecular mechanisms underlying the transition. We described morphological changes of MTs from nymph to adult, including more elongated and densified microvilli and drastically dissolved secretory vacuoles. These alterations indicate MTs functionally transitioned from multifunctional secretory organs in nymphs to primarily excretory organs in adults. Transcriptomic analyses revealed differentially expressed genes were related to osmoregulation, energy metabolism, detoxification, immunity and protein synthesis, etc., across developmental stages. The upregulation of genes involved in ion transport and energy metabolism in adults suggests that enhanced capabilities for rapid waste excretion and energy acquisition are essential for aboveground adults. Increased expression of detoxification and immune-related genes indicates evolutionary adaptations of MTs to manage dietary toxicity and bolster defence mechanisms in adults. These adaptations facilitate the transition from subterranean nymphs to aboveground adults and enhance cicadas' ability to thrive in diverse ecological niches. Our findings infer the role of hormonal regulation in facilitating functional modifications of MTs to adult emergence during cicadas' growth and development. Results of this study have important implications for the evolution of life-history strategy of insects responding to diet/habitat changes during ontogeny. These findings enhance our understanding of how insects adapt to dietary/habitat shift and emphasise the importance of MTs in physiological responses to environmental challenges.

The microRNAs (miRNAs) play an important role in the regulation of gene expression, influencing the outcome of many biological processes in insects. The introduction of miRNA into the insect body can lead to pest developmental abnormalities indicating that miRNAs are potential targets for pest control. In this study, we employed small RNA sequencing to characterise and analyse the expression of miRNAs in the sugarcane shoot borer Chilo infuscatellus (Snellen). By integrating previously published transcriptome sequencing data, we predicted and identified miRNAs and their target genes involved in the ecdysone metabolic pathway. We confirmed the target relationships between Ci-miR-4, Ci-miR-5 and CiCYP18A1 by RT-qPCR and dual-luciferase reporter assays in vivo and in vitro. Additionally, injection of miRNA mimics reduced the transcripts of CiCYP18A1 and led to abnormal moulting, which is similar to the defect phenotype of depletion of CiCYP18A1 by dsRNA. Furthermore, we also mixed the synthesised Ci-miR-5 mimic into artificial diets and found similar stunting results of the injection method. These results demonstrated that Ci-miR-5 could target CiCYP18A1 to regulate the moulting process and the successful use of an insect miRNA for gene silencing studies in this sugarcane pest. The method provided an effective novel approach for future RNAi-based pest control strategies.

Cyantraniliprole (Cya), a diamide insecticide, is widely utilised for the management of Lepidoptera pests owing to its potent insecticidal efficacy and broad spectrum of activity. The extensive use and prolonged environmental persistence of this insecticide pose a significant threat to the sustainable development of sericulture. This study firstly assessed the lethal toxicity of cyantraniliprole to the 5th instar larvae of Bombyx mori. Exposure to cyantraniliprole (LC₅, LC₁₀ and LC₂₀) resulted in a concentration-dependent reduction in larval weight, pupal weight and survival rate and a prolongation of larval development time. Moreover, cyantraniliprole LC₁₀ resulted in substantial structural damage to the epithelial cells, suppressed the mRNA levels of oxidative phosphorylation genes, perturbed ATP synthesis and led to an imbalance of intracellular reactive oxygen species. Meanwhile, the starvation treatment suggested that the impacts of cyantraniliprole on silkworms cannot be solely ascribed to nutritional deficiencies. Additionally, the results revealed that cytochrome P450s might serve as a pivotal factor in the detoxification metabolism of cyantraniliprole in the midgut of silkworms. The findings of this study offer evidence for the ecological risk posed by environmental residues of cyantraniliprole to non-target organisms and are also of great significance for sericulture production.

Mealybugs are highly aggressive pests that infest various plants and cause substantial economic losses. Histone lysine methyltransferases (KMT) are evolutionarily conserved and proposed to be essential in early embryo development in animals. However, few KMTs have been reported in mealybugs. Here, we identified a novel KMT gene, PsASH2, in the cotton mealybug, Phenacoccus solenopsis Tinsley. This gene was highly expressed in the ovary of female adults. Through RNA interference (RNAi) of PsASH2 by dsRNA microinjection, we found a reduction in the number of male embryos and total embryos in the ovaries of pregnant females. Continuous downregulation of PsASH2 in mated females until their death resulted in few changes in sex ratio but significant decreases in the number of both male and female offspring. Therefore, we believe that PsASH2 plays essential roles in embryo survival for both sexes of the cotton mealybug which may provide a potential target gene for the management of cotton mealybug by disrupting embryo development.

Social insects exhibit reproductive division of labour, governed by both external and internal factors influencing caste determination. In termites with a unique reproductive system known as asexual queen succession (AQS), queens produce neotenic queens via parthenogenesis, while workers and alates arise through sexual reproduction. This inherent caste differentiation bias may have resulted from differences in gene expression potentially influenced by the parent-of-origin effect, as parthenogenetic daughters inherit only maternal genomes, while sexually produced daughters inherit both paternal and maternal genomes. Here, we show that gene expression patterns in developing embryos of the termite Reticulitermes speratus differ significantly between parthenogenetic and sexually produced offspring. However, SNP analysis indicated that these differences were not attributable to the parent-of-origin effect. Through RNA-seq analysis of female embryos post-katatrepsis, we identified 21 genes, including jhbp, nlk, and wge, which are known to be involved in caste differentiation and morphogenesis, with significant expression differences between parthenogenetic and sexually produced daughters. SNP analysis of sexually produced embryos did not reveal any parent-of-origin biased expression except for mitochondrial genes, though 12 genes exhibited colony-specific expression patterns. These findings suggested that early developmental gene expression partly explained caste differentiation biases. Further research is essential to elucidate the molecular mechanisms behind these transgenerational effects, providing insight into the evolution of AQS and complex caste determination in social insects from a gene expression perspective.

Histone acetyltransferases (HATs) catalyse the addition of acetyl groups to histones and other proteins. In contrast, histone deacetylases remove acetyl groups from core histones, and the activity of these enzymes maintains the acetylation levels of these proteins. Histone acetylation levels influence chromatin accessibility and gene expression and regulate many biological processes, including development and reproduction. Recent reports suggest that some N-terminal acetyltransferases (NATs) also regulate gene expression. We identified 29 HAT and NAT genes in the red flour beetle, Tribolium castaneum, and studied their functions in female reproduction using RNA interference (RNAi). Knockdown of seven out of 13 HAT genes (N-acetyltransferase ESCO2) (ESCO1/2), Elongator complex protein 3 (ELP3), Histone acetyltransferase type B catalytic subunit 1 (HAT1), Transcription initiation factor TFIID subunit 1 (TAF1), Protein x-mas-2 (MCM3AP), Histone acetyltransferase Tip60 (KAT5), and Cysteine-rich protein 2-binding protein (KAT14) and 12 out of 16 NAT genes Probable glucosamine 6-phosphate N-acetyltransferase (GNPNAT1), N-alpha-acetyltransferase 10 (NAA10), N-alpha-acetyltransferase 20 (NAA20), N-alpha-acetyltransferase 30 (NAA30), N-alpha-acetyltransferase 40 (NAA40), N-alpha-acetyltransferase 60 (NAA60), N-acetyltransferase 6 (NAA80), RNA cytidine acetyltransferase (NAT10), Diamine acetyltransferase 2 (SATL1), N(alpha)-acetyltransferase 16 (NAA16), Phagocyte signalling-impaired protein (NAA25), N(alpha)-acetyltransferase 35 (NAA35) caused a significant reduction in eggs laid by females compared to the eggs laid by control females injected with dsGFP. Also, knockdown of nine (KAT5, ATAT1, ELP3, HAT1, KAT8A, NAA10, NAA20, GNPNAT1 and TAF1) HAT/NAT genes caused a significant decrease in egg hatching. Parental RNAi of ATAT1 and KAT8 blocked embryogenesis. These data suggest that the acetylation of proteins plays an important role in female reproduction and embryogenesis.

Temperature is one of the most significant abiotic factors influencing vector resistance to pathogens. Research has provided substantial insights into the immunological and oxidative processes affected by temperature. However, our understanding of the complex interplay in mosquito–pathogen interactions remains limited. In this study, we investigated the impact of temperature on alternative splicing in the midgut of Aedes aegypti mosquitoes (adult females) under different thermal conditions. Few genes exhibited differential alternative splicing when comparing low (20°C) and high (36°C) temperatures to standard rearing conditions (28°C). Among these, Trypsin (TRY), Ferritin (FER), Thioredoxin (TRX) and Peptidoglycan recognition protein LC (PGRP-LC) were identified, aligning with previous findings that their expression is temperature-sensitive. Among the genes identified with alternative splicing, we focus on Thioredoxin and PGRP-LC, genes modulated by temperature variations and promising targets for future studies on their role in the competence of Ae. aegypti to transmit Zika. Experimental validation confirmed that TRX, a gene critical for pathogen defence, has a differentially spliced exon under warmer conditions, potentially altering its activity. In contrast, no differential splicing was observed for PGRP-LC across temperature treatments. These findings suggest that temperature-induced alternative splicing may play a role in shaping the mosquito's physiological responses to environmental changes, highlighting a previously underexplored layer of complexity in mosquito–pathogen dynamics.

Nutrient accumulation is essential for insect metamorphosis. As a group of important nutrient-storage proteins, forty-six 30 K proteins (30KPs), including BmLP1-BmLP46, have been identified in the silkworm, Bombyx mori. Most 30KPs are synthesised in the last instar larvae, and the stage-specific expression of 30KPs is believed to be regulated by juvenile hormone (JH)-dependent pathways; however, the specific regulatory mechanism remains unclear. In this study, we found that a 30KP gene Bmlp1 was expressed after Day 3 of the fifth instar, and its expression was down-regulated by JH analogue. We also identified a cis-response element (CRE) on the promoter of Bmlp1. Dfd was determined to bind to this CRE adjacent to another CRE that serves as a binding site for PBX. Dfd is a HOX transcription factor found to exhibit an expression pattern similar to that of PBX. The interaction between PBX and Dfd was confirmed using bimolecular fluorescence complementation and GST pull-down experiments. The expression of Bmlp1 was down-regulated when PBX and Dfd were overexpressed in BmN cells, whereas it was up-regulated when PBX and Dfd were knocked down in BmN cells. Our data show that the transcription factor Dfd, and the cofactor PBX, synergistically regulate the transcription of Bmlp1 in B. mori. This study provides a reference for an in-depth understanding of the regulation of insect development mediated by JH.

Chlorantraniliprole (CAP) is a novel amide insecticide widely used in agriculture. Trace residues of CAP in the environment pose a threat to the development and metamorphosis of silkworm (Bombyx mori). However, the mechanisms by which CAP exposure disrupts insect metamorphosis remain poorly understood. This study investigated the levels of intracellular Ca²⁺ and 20-hydroxyecdysone (20E) following exposure to low concentrations of CAP. The results revealed that CAP exposure both directly caused increased Ca²⁺ levels and indirectly promoted an increase in Ca²⁺ levels by inducing an elevation in 20E levels. Furthermore, increased Ca²⁺ level inhibited the expression of Ftz-f1, leading to abnormal pupation. Our study reveals, for the first time, the sublethal effects of CAP mediated by the Ca²⁺-Ftz-f1 axis. The findings herein provide a reference for evaluating the safety of environmental residues of amide pesticides on insects.

Environmental RNAi (eRNAi) is a recent innovation in insect pest control, and comprehensive risk assessment is needed to ensure the environmental safety and longevity of this technology. As eRNAi relies on the insect's cellular machinery for its mode of action, environmentally mediated plasticity in the activity of cellular processes required for RNAi could influence efficacy and the development of resistance. Here, we investigated the extent to which plant cultivar and temperature influence the efficacy of insecticidal double-stranded RNA (dsRNA) targeting actin in larvae of the Colorado potato beetle, Leptinotarsa decemlineata Say (Coleoptera: Chrysomelidae). Potato cultivar did not significantly affect survival or gene silencing in dsRNA-treated larvae, indicating that efficacy is consistent across potato varieties, at least under laboratory conditions. Temperature did influence RNAi efficacy, with both gene silencing and mortality being reduced when dsRNA treatment occurred at lower temperatures. After 3 days of feeding with dsRNA, gene silencing occurred at all temperatures, but knockdown efficiency was 62% at 30°C and 35% at 18°C. eRNAi efficacy at different temperatures was not related to transcript levels of core RNAi genes, indicating that other mechanisms are responsible for the observed effects. Overall, these results indicate that environmental conditions can influence the efficacy of insecticidal eRNAi and may affect the rate at which insects develop resistance to these technologies.