NPFR regulates the synthesis and metabolism of lipids and glycogen via AMPK: Novel targets for efficient corn borer management

A self-assembled multicomponent RNA nano-biopesticide for increasing the susceptibility of destructive bean flower thrips to insecticides via dsNrf2

High resistance of bean flower thrips (BFT, Megalurothrips usitatus) has led to the unscientific application of insecticides to cause famous "toxic cowpea" incidents in China. Nuclear factor erythroid 2-related factor 2 (Nrf2) plays an important role in inducing antioxidant responses and drug detoxification. Therefore, the detoxification genes may be suppressed to control insecticide resistance via Nrf2. Herein, we demonstrated that the expression of most detoxification genes and enzyme activity were remarkably suppressed via nrf2 RNAi. Subsequently, a novel hydrophilic-lipophilic diblock polymer (HLDP) was developed to co-assemble with dsNrf2 and sulfoxaflor (SUL) into nanoscale SUL/HLDP/dsNrf2 complex (221.52 nm). Excitingly, the SUL/HLDP/dsNrf2 complex exhibited excellent leaf adhesion performance, with the smaller contact angle, reduced surface tension, amplified contact area, improved retention, and enhanced plant uptake. Meanwhile, theSUL/HLDP/dsNrf2 displayed high delivery efficiency in vitro and in vivo, and its insecticidal activity against BFTs was significantly higher than SUL. Furthermore, the required doses of SUL/HLDP/dsNrf2 to achieve similar insecticidal activity were 50.14% and 58.42% of SUL via immersion and oral feeding, respectively. Overall, this study elucidated the regulatory role of nrf2 in the detoxification and metabolism of BFTs and developed a self-assembled multicomponent RNA nano-biopesticide to increase the susceptibility of BFTs to insecticides.

Engineered nanotransporters for efficient RNAi delivery in plant protection applications

RNA interference (RNAi) is increasingly used for plant protection against pathogens and pests. However, the traditional delivery method causes plant tissue damage, is affected by environmental factors, and faces difficulties in penetrating the barriers of cell walls and the limitations of plant species, ultimately leading to low delivery efficiency. With advances in nanotechnology, nanomaterials (NMs) have been identified as effective carriers for nucleic acid delivery because of their ability to operate independently of external mechanical forces, prevent degradation by bioenzymes, exhibit good biocompatibility, and offer high loading capacity. This review summarizes the application of NM-mediated RNAi against plant pathogens and pests, focusing on how different NMs break through the cell barriers of plants, pathogens, and pests according to their size, morphology, and charge characteristics. Furthermore, we discuss the advantages and improvement strategies of NMs as nucleic acid delivery carriers, alongside assessing their potential application for the management of plant pathogens and pests.

NPF and sNPF can regulate the feeding behaviour and affect the growth and antioxidant levels of the rice brown planthopper, Nilaparvata lugens

Neuropeptide F (NPF) and short neuropeptide F (sNPF) are important neuropeptides and mainly affect feeding behaviour of insects. However, the regulation of insect feeding behaviour by NPF and sNPF appears to differ between species, and it is not clear how NPF and sNPF regulate the food intake of the brown planthopper (Nilaparvata lugens). Therefore, the functions of NPF and sNPF in regulating food intake and affecting the growth and antioxidant levels of N. lugens fed on host rice plants were investigated by knocking down NPF and sNPF respectively and simultaneously knocking down both of them by RNA interference. The results showed that NPF and sNPF were mainly expressed in the head of N. lugens, and N. lugens increased food intake after NPF and sNPF were knocked down, which was reflected in the prolonged duration of N4a and N4b waves in the electrical penetration graph (EPG) experiment after knocking down NPF and sNPF. In addition, knocking down NPF and sNPF led to the increase of body weight and mortality of N. lugens, and also led to the increase of antioxidant level of N. lugens. So it was concluded that NPF and sNPF could regulate food intake, maintain body weight stability and oxidative balance in N. lugens. Our study clarified the molecular mechanism of NPF and sNPF regulating feeding behaviour and affect the growth and antioxidant level of N. lugens.

Nanomaterial-mediated RNAi reveals the effect of the oral secretory protein serine protease inhibitor on the growth of Conogethes punctiferalis larvae

The oral secretions of herbivorous insects play a pivotal role in insect-plant interactions and the regulation of insect physiology. Unlike the saliva of Hemiptera species, Lepidopteran oral secretions include both saliva and regurgitated gut fluids; yet research on their composition remains limited. This study focuses on yellow peach moth (YPM), Conogethes punctiferalis, a pest increasingly damaging maize. A total of 103 proteins were identified from oral secretions collected from larvae reared on corn and artificial diets, comprising 67 enzymes, 30 non-enzymes, and 6 unknowns. The identified enzyme proteins were primarily trypsin, lipase, and serine protease inhibitors (serpins). Further genomic investigation revealed 36 serpin genes in the YPM genome, distributed in clusters across various chromosomes, with some genes exhibiting partial synteny to homologous sequences in Ostrinia furnacalis. Among the identified serpin genes, the SpI gene (jg17839), which encoded the most abundant protein in YPM oral secretions, was found to exhibit peak expression in fifth-instar larvae and culticle tissues. Silencing of the SpI gene through nanomaterial-mediated RNA interference significantly reduced larval length, weight, pupation rates, and pupal weight, while also increased larval mortality. Moreover, interfering with SpI expression elevated juvenile hormone levels in the larvae. These findings indicate that the abundant SpI protein in YPM oral secretions plays a vital role in larval growth and development by modulating internal hormone levels. This study enriches the database of lepidopteran oral secretion components, fostering a deeper understanding of their physiological roles and informing eco-friendly pest control strategies targeting these proteins in YPM.

Complicated gene network for regulating feeding behavior: novel efficient target for pest management

Feeding behavior is a fundamental activity for insects, which is essential for their growth, development and reproduction. The regulation of their feeding behavior is a complicated process influenced by a variety of factors, including external stimuli and internal physiological signals. The current review introduces the signaling pathways in brain, gut and fat body involved in insect feeding behavior, and provides a series of target genes for developing RNA pesticides. Additionally, this review summaries the current challenges for the identification and application of functional genes involved in feeding behavior, and finally proposes the future research direction. © 2024 Society of Chemical Industry.

LdAMPKα2 knockdown accelerated the growth but depressed the chitin biosynthesis in Lymantria dispar larvae

AMPK (AMP-activated protein kinase) is a crucial cellular energy sensor across all eukaryotic species. Its multiple roles in maintaining energy homeostasis, regulating cellular metabolic processes have been widely investigated in mammals. In contrast, the function of AMPK in insects has been less reported. Here, we successfully identified three AMPK subunits from Lymantria dispar (L. dispar), a Lepidoptera pest in forestry. Based on that, in particular, the role of AMPK signaling in regulating larval development, as well as chitin biosynthesis was investigated by the application of RNAi-mediated LdAMPKα2 knockdown. The results indicated that knockdown of LdAMPKα2 significantly increased the body weight of L. dispar larvae, and dramatically upregulated the expression of LdmTOR, LdS6K and LdSREBP1, the key genes in mTOR (mammalian target of rapamycin) signaling pathway. While, it significantly reduced the expression of Ld4EBP, a critical repressor of mTOR pathway. Besides, the glucose level was increased and trehalose level was decreased in L. dispar after LdAMPKα2 silencing. Furthermore, we found that the chitin content in the epidermis, as well as the expressions of four key genes in the chitin biosynthesis pathway, LdGFAT, LdPAGM, LdUAP and LdCHSA, were significantly decreased after LdAMPKα2 knockdown. Taken together, these results revealed that AMPK signaling played a pivotal role in regulating the growth and development, as well as carbohydrate metabolism and chitin biosynthesis in L. dispar larvae. The findings expand our understanding of the comprehensive regulatory role of AMPK signaling in insects.

Advances on polymeric nanocarriers for sustainable agriculture: Enhancing dsRNA/siRNA delivery to combat agricultural pests

The application of exogenous RNA for gene-silencing strategies has gained significant traction in agriculture, offering a highly efficient and eco-friendly alternative to conventional plant protection methods. This success has been driven by advances in biotechnology, from the design of long double-stranded RNA (dsRNA) and small interfering RNA (siRNA) molecules to the development of nanocarrier systems that address the challenge of RNA delivery into plant cells. In particular, polymer-based nanocarriers have emerged as a promising solution for enhancing the stability and delivery efficiency of RNA molecules. This review provides a comprehensive overview of the current state of research on the use of polymeric nanocarriers in RNA interference (RNAi) systems for crop protection. It examines key technological developments that have enabled the effective delivery of dsRNA/siRNA to target organisms, with a focus on the unique advantages polymers offer as carriers. Recent studies highlight significant progress in the preparation, characterization, and application of polymeric nanocarriers for RNA encapsulation and delivery. The review also explores the environmental and health challenges posed by these technologies, emphasizing the need for sustainable approaches in their development. Specifically, the production of nanocarriers must adhere to the principles of green chemistry, prioritizing chemical modification routes that reduce harmful residues, such as toxic solvents. Finally, this paper discusses both the current challenges and future prospects of using polymer-based nanocarriers in sustainable agriculture, offering critical insights into their potential to transform crop protection through RNAi technologies.

Research progress of aphid immunity system: Potential effective target for green pest management

Due to the absence of acquired immunity, insects primarily rely on their innate immune system to resist pathogenic microorganisms and parasitoids in natural habitats. This innate immune system can be classified into cellular immunity and humoral immunity. Cellular immunity is mediated by hemocytes, which perform phagocytosis, aggregation, and encapsulation to fight against invaders, whereas the humoral immunity primarily activates the immune signaling pathways and induces the generation of immune effectors. Existing studies have revealed that the hemipteran aphids lack some crucial immune genes compared to other insect species, indicating the different immune mechanisms in aphids. The current review summarizes the adverse impacts of pathogenic microorganisms and parasitoids on aphids, introduces the cellular and humoral immune systems in insects, and analyzes the differences between aphids and other insect species. Furthermore, our review also discussed the existing prospects and challenges in aphid immunity research, and proposed the potential application of immune genes in green pest management.

Nanocarrier-Based Eco-Friendly RNA Pesticides for Sustainable Management of Plant Pathogens and Pests

The production of healthy agricultural products has increased the demand for innovative and sustainable plant protection technologies. RNA interference (RNAi), described as post-transcriptional gene silencing, offers great opportunities for developing RNA pesticides for sustainable disease and pest control. Compared with traditional synthesized pesticides, RNA pesticides possess many advantages, such as strong targeting, good environmental compatibility, and an easy development process. In this review, we systematically introduce the development of RNAi technology, highlight the advantages of RNA pesticides, and illustrate the challenges faced in developing high-efficiency RNA pesticides and the benefits of nanocarriers. Furthermore, we introduce the process and mechanism of nanocarrier-mediated RNAi technology, summarize the applications of RNA pesticides in controlling plant pathogens and pests, and finally outline the current challenges and future prospects. The current review provides theoretical guidance for the in-depth research and diversified development of RNA pesticides, which can promote the development and practice of nanocarrier-mediated RNAi.

Trypsin-encoding gene function of efficient star polycation nanomaterial-mediated dsRNA feeding delivery system of Grapholita molesta

BACKGROUND

Grapholita molesta is an important and harmful fruit pest worldwide, with widespread feeding hosts. Trypsin, an indispensable hydrolytic digestive protease in the insect gut, is crucial in digestion, growth and development. We analyzed the characteristics of the trypsin-encoding genes, screened for the optimal dose of RNAi mediated by nanocarriers, and investigated various indices of larval growth and development of G. molesta.

RESULTS

Gut content (GC) and RNase A degraded double-stranded RNA (dsRNA), with a faster degradation rate at higher concentrations. Star polycation (SPc) nanomaterials protected dsGFP from degradation by anion-cation binding and did not migrate through agarose gel. The key conserved motifs of the trypsin-encoding genes were similar, exhibiting high homology with those in other lepidopteran insects. An interference efficiency of ≈70% was achieved with SPc nanomaterial-mediated RNA interference with 0.05 μg dsRNA. The efficiency of continuous interference was stable. Trypsin activity, body weight of 8-day-old larvae, pupal weight and emergence rate were significantly reduced, and the larval stage was significantly prolonged.

CONCLUSION

The investigated trypsin gene is a key target gene in the growth and development of G. molesta. We investigated the efficiency and convenience of feeding SPc nanomaterials in a functional study of insects. Our results provide valuable data for the development of efficient trypsin-targeting pesticides. © 2024 Society of Chemical Industry.

Transfer of heavy metals along the food chain: A review on the pest control performance of insect natural enemies under heavy metal stress

Heavy metal contamination represents a critical global environmental concern. The movement of heavy metals through the food chain inevitably subjects insect natural enemies to heavy metal stress, leading to various adverse effects. This review assesses the risks posed by heavy metal exposure to insect natural enemies, evaluates how such exposure impacts their pest control efficacy, and investigates the mechanisms affecting their fitness. Heavy metals transfer and accumulate from soil to plants, then to herbivorous insects, and ultimately to their natural enemies, impeding growth, development, and reproduction of insect natural enemies. Typically, diminished growth and reproduction directly compromise the pest control efficacy of these natural enemies. Nonetheless, within tolerable limits, increased feeding may occur as these natural enemies strive to meet the energy demands for detoxification, potentially enhancing their pest control capabilities. The production of reactive oxygen species and oxidative damage caused by heavy metals in insect natural enemies, combined with disrupted energy metabolism in host insects, are key factors contributing to the reduced fitness of insect natural enemies. In summary, heavy metal pollution emerges as a significant abiotic factor adversely impacting the pest control performance of these beneficial insects.

Spray-induced and nanocarrier-delivered gene silencing system targeting juvenile hormone receptor components: potential application as fertility inhibitors for Adelphocoris suturalis management

BACKGROUND

Adelphocoris suturalis is a destructive pest that attacks > 270 plants, including cotton, maize, soybean, and fruit trees. Adelphocoris suturalis can cause tremendous crop losses when the density exceeds economic thresholds, but because it can be both phytophagous and zoophytophagous it can serve as a natural enemy of other pests when the density is below the economic threshold. Effective control of its population is beneficial for maximizing yield and profits. RNA interference (RNAi) has potential to be a viable alternative to conventional pesticide-based pest management, but the lack of efficient double-stranded RNA (dsRNA) delivery systems and candidate genes are currently limiting factors for field applications.

RESULTS

In this study, RNAi of juvenile hormone (JH) receptor components methoprene-tolerant (Met)/Taiman (Tai) in Adelphocoris suturalis reduced fertility. Based on this reproductive role, we targeted Adelphocoris suturalis Met and Tai for knockdown by coupling nanomaterial-dsRNA complexes with a transdermal spray delivery system. Within 12 h of adult emergence, females were sprayed with star polycation (SPc)-dsRNA formulations and the RNAi effects were assessed over time. RNAi knockdown efficiencies of 39-58% were observed at 5 days post-treatment and abnormal ovarian development was apparent by 10 days post-treatment.

CONCLUSION

Our results show that spray-induced and nanocarrier-delivered gene silencing (SI-NDGS) system targeting JH signal genes effectively impaired oviposition, thus developing a novel RNA fertility inhibitor to control Adelphocoris suturalis populations. These results give new perspective on pest management and suggest broad prospects for field applications. © 2024 Society of Chemical Industry.

An upstream signaling gene calmodulin regulates the synthesis of insect wax via activating fatty acid biosynthesis pathway

Insect wax accumulates on the surface of insect cuticle, which acts as an important protective barrier against rain, ultraviolet light radiation, pathogens, etc. The waxing behavior, wax composition and molecular mechanism underling wax biosynthesis are unclear in dustywings. Herein, the current study determined the vital developmental stage for waxing behavior in dustywings, examined the components of waxy secretions, and identified key regulatory genes for wax biosynthesis. The wax glands were mainly located on the thorax and abdomen of dustywing adults. The adults spread the waxy secretions over their entire body surface. The metabolomics analysis identified 32 lipids and lipid-like molecules, 15 organic acids and derivatives, 7 benzenoids, etc. as the main components of waxy secretions. The fatty acids represented the largest proportion of the category of lipid and lipid-like molecules. The conjoint analysis of metabolomics and transcriptomics identified two crucial genes fatty acyl-CoA reductase (CsFAR) and calmodulin (CsCaM) for wax biosynthesis. The down-regulation of these genes via nanocarrier-mediated RNA interference technology significantly reduced the amount of wax particles. Notably, the RNAi of CsCaM apparently suppressed the expression of most genes in fatty acid biosynthesis pathway, indicating the CsCaM might act as a main upstream regulator of fatty acid biosynthesis pathway.