Insect Molecular Biology最新文献

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.

Dual oxidase (Duox) is well-known for its role in immunity and tyrosine cross-linking activity across various biological processes from mammals to holometabolous insects. Nevertheless, its function in hemimetabolous insects remains poorly understood. In this study, we explored the physiological roles of the Duox gene in a hemimetabolous insect, the brown planthopper, one of the most devastating rice pests. A comprehensive analysis of the spatiotemporal expression pattern of the Duox gene was conducted. RNA interference (RNAi)-mediated silencing of the Duox gene led to moulting defects in nymphs, wing abnormalities and impaired feeding in adults and reduced hatchability in eggs. Additionally, Duox knockdown significantly reduced hydrogen peroxide (H₂O₂) levels in premoulting nymphs and female ovaries. These findings highlight the indispensable role of Duox in moulting, hatching, wing expansion and feeding behaviours in the brown planthopper, shedding light on the relationship between H₂O₂ production and cuticle structural stability.

In insects, trehalose is critical for growth and development, as well as environmental stress response, which is mainly transported by trehalose transporters (TRETs). Over nearly two decades, the physiological functions of TRETs in insect growth, development, reproduction and environmental stress response have been well elucidated. However, the role of TRETs in chitin synthesis remains not fully understood. Here, we identified the HcTRET1 gene from Hyphantria cunea, a major Lepidoptera pest in agriculture and forestry. The role of HcTRET1 in growth and development, especially in chitin synthesis, was discussed by dsRNA-mediated HcTRET1 knockdown. Bioassay showed that HcTRET1 knockdown did not affect larval growth, development and survival in H. cunea, but it significantly reduced the pupa formation rate. Additionally, HcTRET1 silencing increased trehalose levels in the fat body but decreased them in the hemolymph, suggesting HcTRET1 plays a key role in trehalose homeostasis. Moreover, HcTRET1 knockdown significantly downregulated the genes for chitin synthesis (HcGFAT, HcUAP and HcCHSA), resulting in a remarkable reduction of chitin content in the epidermis. Moreover, HcTRET1 knockdown significantly reduced the survival of H. cunea larvae at 42°C. Taken together, these results demonstrated that HcTRET1 played a critical role in larva–pupa transition, in vivo trehalose homeostasis, especially in epidermal chitin biosynthesis in H. cunea larvae. In parallel, its important physiological function in response to high-temperature stress has been verified as well. The findings expand our understanding of the physiological functions of TRET1 in insects, providing a new perspective for trehalose transporters to regulate chitin biosynthesis.

The western flower thrips, Frankliniella occidentalis, is the principal thrips vector of Orthotospovirus tomatomaculae (order Bunyavirales, family Tospoviridae), a devastating plant-pathogenic virus commonly referred to as tomato spotted wilt virus (TSWV). The larval gut is the gateway for virus transmission by F. occidentalis adults to plants. In a previous report, gut expression at the transcriptome level was subtle but significant in response to TSWV in L1s. Since it has been well documented that the relationship between the expression of mRNA and associated protein products in eukaryotic cells is often discordant, we performed identical, replicated experiments to identify and quantify virus-responsive larval gut proteins to expand our understanding of insect host response to TSWV. While we documented statistically significant, positive correlations between the abundance of proteins (4189 identified) and their cognate mRNAs expressed in first and second instar guts, there was virtually no alignment of individual genes identified to be differentially modulated by virus infection at the transcriptome and proteome levels. Predicted protein–protein interaction networks associated with clusters of co-expressed proteins revealed wide variation in correlation strength between protein and cognate transcript abundance, which appeared to be associated with the type of cellular processes, cellular compartments and network connectivity represented by the proteins. In total, our findings indicate distinct and dynamic regulatory mechanisms of transcript and protein abundance (expression, modifications and/or turnover) in virus-infected gut tissues. This study provides molecular candidates for future functional analysis of thrips vector competence and underscores the necessity of examining complex virus-vector interactions at a systems level.