Development of CS-TPP-dsRNA nanoparticles to enhance RNAi efficiency in the yellow fever mosquito, Aedes aegypti

Synthesis, characterization of chitosan/tripolyphosphate nanoparticles loaded with 4-chloro-2-methylphenoxyacetate sodium salt and its herbicidal activity against Bidens pilosa L

Herbicides are widely used to control weeds in agriculture filed, however, the excessive use of the conventional formulation causes harmful side effects on the environment. To relieve this problem, natural polymer nanoparticles as herbicide carrier were rapidly developed and applied in recent years. In the present study, chitosan/tripolyphosphate (CS/TPP) nanoparticles were synthesized as nanocarrier to load herbicide 4-chloro-2-methylphenoxyacetate sodium salt (MCPA-Na). The encapsulation efficiency (EE) of 51.32% was obtained through measuring indirectly by high performance liquid chromatography (HPLC). The free and MCPA-Na-loaded CS/TPP nanoparticles were characterized by using dynamic light scattering (DLS), zeta potential, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The encapsulation of MCPA-Na in CS/TPP nanoparticles resulted in the change of MCPA-Na release profile in different pH media and displayed effective sustained-release under neutral condition. The evaluation of herbicidal activity against Bidens pilosa L. showed that the efficacy enhancement of MCPA-Na was realized after encapsulation in CS/TPP nanoparticles. The proposed herbicide nanoformulation presented a good potential as a sustainable alternative for weed control in agriculture.

Knock down to level up: Reframing RNAi for invertebrate ecophysiology

Comparative ecophysiologists strive to understand physiological problems in non-model organisms, but molecular tools such as RNA interference (RNAi) are under-used in our field. Here, we provide a framework for invertebrate ecophysiologists to use RNAi to answer questions focused on physiological processes, rather than as a tool to investigate gene function. We specifically focus on non-model invertebrates, in which the use of other genetic tools (e.g., genetic knockout lines) is less likely. We argue that because RNAi elicits a temporary manipulation of gene expression, and resources to carry out RNAi are technically and financially accessible, it is an effective tool for invertebrate ecophysiologists. We cover the terminology and basic mechanisms of RNA interference as an accessible introduction for "non-molecular" physiologists, include a suggested workflow for identifying RNAi gene targets and validating biologically relevant gene knockdowns, and present a hypothesis-testing framework for using RNAi to answer common questions in the realm of invertebrate ecophysiology. This review encourages invertebrate ecophysiologists to use these tools and workflows to explore physiological processes and bridge genotypes to phenotypes in their animal(s) of interest.

Preparation, Optimization, and Anti-Pulmonary Infection Activity of Casein-Based Chrysin Nanoparticles

Introduction

Chrysin has a wide range of biological activities, but its poor bioavailability greatly limits its use. Here, we attempted to prepare casein (cas)-based nanoparticles to promote the biotransfer of chrysin, which demonstrated better bioavailability and anti-infection activity compared to free chrysin.

Methods

Cas-based chrysin nanoparticles were prepared and characterized, and most of the preparation process was optimized. Then, the in vitro and in vivo release characteristics were studied, and anti-pulmonary infection activity was evaluated.

Results

The constructed chrysin-cas nanoparticles exhibited nearly spherical morphology with particle size and ζ potential of 225.3 nm and -33 mV, respectively. These nanoparticles showed high encapsulation efficiency and drug-loading capacity of 79.84% ± 1.81% and 11.56% ± 0.28%, respectively. In vitro release studies highlighted a significant improvement in the release profile of the chrysin-cas nanoparticles (CCPs). In vivo experiments revealed that the relative oral bioavailability of CCPs was approximately 2.01 times higher than that of the free chrysin suspension. Further investigations indicated that CCPs effectively attenuated pulmonary infections caused by Acinetobacter baumannii by mitigating oxidative stress and reducing pro-inflammatory cytokines levels, and the efficacy was better than that of the free chrysin suspension.

Conclusion

The findings underscore the advantageous bioavailability of CCPs and their protective effects against pulmonary infections. Such advancements position CCPs as a promising pharmaceutical agent and candidate for future therapeutic drug innovations.

Challenges of Robust RNAi-Mediated Gene Silencing in Aedes Mosquitoes

In this study, we report the complexities and challenges associated with achieving robust RNA interference (RNAi)-mediated gene knockdown in the mosquitoes Aedes aegypti and Aedes albopictus, a pivotal approach for genetic analysis and vector control. Despite RNAi's potential for species-specific gene targeting, our independent efforts to establish oral delivery of RNAi for identifying genes critical for mosquito development and fitness encountered significant challenges, failing to reproduce previously reported potent RNAi effects. We independently evaluated a range of RNAi-inducing molecules (siRNAs, shRNAs, and dsRNAs) and administration methods (oral delivery, immersion, and microinjection) in three different laboratories. We also tested various mosquito strains and utilized microorganisms for RNA delivery. Our results reveal a pronounced inconsistency in RNAi efficacy, characterized by minimal effects on larval survival and gene expression levels in most instances despite strong published effects for the tested targets. One or multiple factors, including RNase activity in the gut, the cellular internalization and processing of RNA molecules, and the systemic dissemination of the RNAi signal, could be involved in this variability, all of which are barely understood in mosquitoes. The challenges identified in this study highlight the necessity for additional research into the underlying mechanisms of mosquito RNAi to develop more robust RNAi-based methodologies. Our findings emphasize the intricacies of RNAi application in mosquitoes, which present a substantial barrier to its utilization in genetic control strategies.

Nanomaterial-encapsulated dsRNA of ecdysone-induced early gene E75, a potential RNAi-based SIT strategy for pest control against Bactrocera dorsalis

Bactrocera dorsalis is a notorious pest widely distributed across most Asian countries. With the rapid development of pesticide resistance, new pest control methods are urgently needed. RNAi-based sterile insect technique (SIT) is a species-specific pest management strategy for B. dorsalis control. It is of great significance to identify more target genes from B. dorsalis, and improve the RNAi efficiency. In this study, microinjection-based RNAi results showed that six 20E response genes were necessary for male fertility of B. dorsalis, of which E75 was identified as the key target according to the lowest egg-laying number and hatching rate after E75 knockdown. Three nanoparticles chitosan (CS), chitosan‑sodium tripolyphosphate (CS-TPP), and star polycation (SPc) were used to encapsulate dsE75 expressed by HT115 strain. Properties analysis of nanoparticle-dsRNA complexes showed that both CS-TPP-dsRNA and SPc-dsRNA exhibited better properties (smaller size and polydispersity index) than CS-dsRNA. Moreover, oral administration of CS-TPP-dsE75 and SPc-dsE75 by males resulted in more abnormal testis and significantly lower fertility than feeding naked dsE75. Semi-field trials further confirmed that the number of hatched larvae was dramatically reduced in these two groups. Our study not only provides more valuable targets for RNAi-based SIT, but also promotes the application of environment-friendly management against B. dorsalis in the field.

Transcriptomic Identification and Characterization of Trehalose-6-Phosphate Synthase in Fat Body of the Oriental Fruit Fly, Bactrocera dorsalis

The destructive agricultural pest oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), has been causing huge damage to the fruits and vegetable industry. Although many pertinent studies have been conducted on B. dorsalis, the functions of fat body still remain largely unknown. To this end, the comparative transcriptome analysis between fat body and carcass was performed in an attempt to provide insights into functions of fat body of B. dorsalis in the present study. A total of 1431 upregulated and 2511 downregulated unigenes were discovered in the fat body vs carcass comparison, respectively. The enrichment analysis of differentially expressed genes (DEG) revealed that most of the enriched pathways were related to metabolism. The reliability of DEG analysis was validated by qRT-PCR measurements of 12 genes in starch and sucrose metabolism pathway, including the trehalose-6-phosphate synthase (BdTPS) which was highly expressed in eggs, 5 d-old adults, and fat body. The RNAi of BdTPS significantly affected trehalose and chitin metabolism, larval growth, and larva-pupa metamorphosis. Collectively, the findings in this study enriched our understanding of fat body functions in metabolism and demonstrated the indispensable roles of BdTPS in trehalose-related physiological pathways.

Limitations in harnessing oral RNA interference as an antiviral strategy in Aedes aegypti

Mosquitoes, particularly Aedes aegypti, are critical vectors for globally significant pathogenic viruses. This study examines the limitations of oral RNA interference (RNAi) as a strategy to disrupt viral transmission by Ae. aegypti. We hypothesized that double-stranded RNA (dsRNA) targeting the Zika virus (ZIKV) or chikungunya virus (CHIKV) genomes produced by engineered bacterial symbionts could trigger an antiviral response. Mosquitoes mono-colonized with Escherichia coli producing dsZIK or dsCHIK did not display reduced viral titers following exposure to virus-contaminated bloodmeals and failed to generate dsZIK- or dsCHIK-derived small interfering RNAs. To address potential limitations of bacterial dsRNA release, we explored dsRNA inoculation via feeding and injection. Although viral replication was impeded in mosquitoes injected with dsZIK or dsCHIK, no antiviral effect was observed in dsRNA-fed mosquitoes. These findings highlight complexities of implementing oral RNAi as an antiviral strategy in Ae. aegypti and warrant further exploration of local and systemic RNAi mechanisms.

Thiolated chitosan encapsulation constituted mucoadhesive nanovaccine confers broad protection against divergent influenza A viruses

Influenza A virus (IAV) poses a significant threat to human and animal health, necessitating the development of universal influenza vaccines that can effectively activate mucosal immunity. Intranasal immunization has attracted significant attention due to its capacity to induce triple immune responses, including mucosal secretory IgA. However, inducing mucosal immunity through vaccination is challenging due to the self-cleansing nature of the mucosal surface. Thiolated chitosan (TCS) were explored for mucosal vaccine delivery, capitalizing on biocompatibility and bioadhesive properties of chitosan, with thiol modification enhancing mucoadhesive capability. The focus was on developing a universal nanovaccine by utilizing TCS-encapsulated virus-like particles displaying conserved B-cell and T-cell epitopes from M2e and NP proteins of IAV. The optimal conditions for nanoparticle formation were investigated by adjusting the thiol groups content of TCS and the amount of sodium tripolyphosphate. The nanovaccine induced robust immune responses and provided complete protection against IAVs from different species following intranasal immunization. The broad protective effect of nanovaccines can be attributed to the synergistic effect of antibodies and T cells. This study developed a universal intranasal nanovaccine and demonstrated the potential of TCS in the development of mucosal vaccines for respiratory infectious diseases.

Nanoparticle-mediated dsRNA delivery for precision insect pest control: a comprehensive review

Nanoparticle-based delivery systems have emerged as powerful tools in the field of pest management, offering precise and effective means of delivering double-stranded RNA (dsRNA), a potent agent for pest control through RNA interference (RNAi). This comprehensive review aims to evaluate and compare various types of nanoparticles for their suitability in dsRNA delivery for pest management applications. The review begins by examining the unique properties and advantages of different nanoparticle materials, including clay, chitosan, liposomes, carbon, gold and silica. Each material's ability to protect dsRNA from degradation and its potential for targeted delivery to pests are assessed. Furthermore, this review delves into the surface modification strategies employed to enhance dsRNA delivery efficiency. Functionalization with oligonucleotides, lipids, polymers, proteins and peptides is discussed in detail, highlighting their role in improving stability, cellular uptake, and specificity of dsRNA delivery.This review also provides valuable guidance on choosing the most suitable nanoparticle-based system for delivering dsRNA effectively and sustainably in pest management. Moreover, it identifies existing knowledge gaps and proposes potential research directions aimed at enhancing pest control strategies through the utilization of nanoparticles and dsRNA.

RNA Interference in Insects: From a Natural Mechanism of Gene Expression Regulation to a Biotechnological Crop Protection Promise

Insect pests rank among the major limiting factors in agricultural production worldwide. In addition to direct effect on crops, some phytophagous insects are efficient vectors for plant disease transmission. Large amounts of conventional insecticides are required to secure food production worldwide, with a high impact on the economy and environment, particularly when beneficial insects are also affected by chemicals that frequently lack the desired specificity. RNA interference (RNAi) is a natural mechanism gene expression regulation and protection against exogenous and endogenous genetic elements present in most eukaryotes, including insects. Molecules of double-stranded RNA (dsRNA) or highly structured RNA are the substrates of cellular enzymes to produce several types of small RNAs (sRNAs), which play a crucial role in targeting sequences for transcriptional or post-transcriptional gene silencing. The relatively simple rules that underlie RNAi regulation, mainly based in Watson-Crick complementarity, have facilitated biotechnological applications based on these cellular mechanisms. This includes the promise of using engineered dsRNA molecules, either endogenously produced in crop plants or exogenously synthesized and applied onto crops, as a new generation of highly specific, sustainable, and environmentally friendly insecticides. Fueled on this expectation, this article reviews current knowledge about the RNAi pathways in insects, and some other applied questions such as production and delivery of recombinant RNA, which are critical to establish RNAi as a reliable technology for insect control in crop plants.

Encapsulated nanopesticides application in plant protection: Quo vadis?

The increased global food insecurity due to the growing population can be addressed with precision and sustainable agricultural practices. To tackle the issues regarding food insecurity, farmers used different agrochemicals that improved plant growth and protection. Among these agrochemicals, synthetic pesticides used for plant protection in the agricultural field have various disadvantages. Conventional applications of synthetic pesticides have drawbacks such as rapid degradation, poor solubility, and non-target effects, as well as increased pesticide runoff that pollutes the environment. Nanotechnology has evolved as a potential solution to increase agricultural productivity through the development of different nanoforms of agrochemicals such as nanopesticides, nano-fabricated fertilizers, nanocapsules, nanospheres, nanogels, nanofibers, nanomicelles, and nano-based growth promoters. Encapsulation of these pesticides inside the nanomaterials has provided good biocompatibility over conventional application by inhibiting the early degradation of active ingredients (AI), increasing the uptake and adhesion of pesticides, improving the stability, solubility, and permeability of the pesticides, and decreasing the environmental impacts due to the pesticide runoff. In this review, different nanoforms of encapsulated pesticides and their smart delivery systems; nanocarriers in RNA interference (RNAi) based pesticides; environmental fate, practical implications, management of nanopesticides; and future perspectives are discussed.

Effectiveness of chitosan nanohydrogel mediated encapsulation of EcR dsRNA against the whitefly, Bemisia tabaci Asia-I (Gennedius) (Hemiptera: Aleyordidae)

Bemisia tabaci is a global invasive pest causing substantial loss on several economically important crops and has developed a very high level of resistance to insecticides making current management practices ineffective. Thus, the novel pest management strategy like RNA interference (RNAi) has emerged as a potential molecular tool in the management of insect pests particularly B. tabaci. The present study investigated RNAi mediated silencing of the Ecdysone Receptor (EcR) gene in B. tabaci Asia-I using biodegradable Chitosan Nanoparticles (CNPs) hydrogel containing EcR dsRNA. The formation of nanohydrogel and dsRNA loading were characterized by gel retardation assay, scanning electron microscopy (SEM); transmission electron microscopy (TEM) and Fourier transform infrared microscopy (FTIR). The stability of CNPs/dsRNA was assessed by exposure to direct sunlight and UV light for different time periods. The CNPs/dsRNA exhibited increased stability over the untreated control and further confirmed by bioassay studies which yielded mortality over 80% and effectively down regulated the expression of the EcR gene as confirmed by qRT-PCR analysis. These investigations provide potential avenues for advancing innovative pest management strategies using biopolymer CNPs hydrogel, which can enhance the efficiency of dsRNA as a safe and targeted solution in the management of whiteflies.

Chitosan/dsRNA polyplex nanoparticles advance environmental RNA interference efficiency through activating clathrin-dependent endocytosis

Chitosan, as a promising gene nanocarrier for enhancing RNA interference (RNAi) efficiency, displays tremendous application prospects in addressing dsRNA delivery concerns. However, the molecular mechanism of chitosan/dsRNA polyplex nanoparticles (PNs) for advancing dsRNA delivery efficiency remains largely unknown. Here, chitosan/dsRNA PNs were prepared by an electrostatic attraction method. The results showed that the chitosan/dsRNA PNs significantly advance stability, and cellular uptake efficiency of dsRNA, and RNAi efficiency. RNA-Seq and qPCR assays further revealed that chitosan/dsRNA PNs upregulated the key clathrin heavy chain (CHC) gene for activating clathrin-dependent endocytosis (CDE) pathway. Additionally, inhibition of CDE hindered the robust RNAi responses of chitosan/dsRNA PNs using an inhibitor (chlorpromazine) and an RNAi-of-RNAi strategy. Ultimately, microscale thermophoresis assay confirmed that chitosan/dsRNA PNs directly bound to CHC protein, which was a core component in CDE, to advance RNAi efficiency. To our knowledge, our findings firstly illuminate the molecular mechanism how chitosan nanoparticles-based RNAi deliver dsRNA for enhancing RNAi efficiency. Above mechanism will advance the extensive utilization of nanocarrier-based RNAi in pest management and gene delivery.

Improving RNA-based crop protection through nanotechnology and insights from cross-kingdom RNA trafficking

Spray-induced gene silencing (SIGS) is a powerful and eco-friendly method for crop protection. Based off the discovery of RNA uptake ability in many fungal pathogens, the application of exogenous RNAs targeting pathogen/pest genes results in gene silencing and infection inhibition. However, SIGS remains hindered by the rapid degradation of RNA in the environment. As extracellular vesicles are used by plants, animals, and microbes in nature to transport RNAs for cross-kingdom/species RNA interference between hosts and microbes/pests, nanovesicles and other nanoparticles have been used to prevent RNA degradation. Efforts examining the effect of nanoparticles on RNA stability and internalization have identified key attributes that can inform better nanocarrier designs for SIGS. Understanding sRNA biogenesis, cross-kingdom/species RNAi, and how plants and pathogens/pests naturally interact are paramount for the design of SIGS strategies. Here, we focus on nanotechnology advancements for the engineering of innovative RNA-based disease control strategies against eukaryotic pathogens and pests.

RNAi turns 25:contributions and challenges in insect science

Since its discovery in 1998, RNA interference (RNAi), a Nobel prize-winning technology, made significant contributions to advances in biology because of its ability to mediate the knockdown of specific target genes. RNAi applications in medicine and agriculture have been explored with mixed success. The past 25 years of research on RNAi resulted in advances in our understanding of the mechanisms of its action, target specificity, and differential efficiency among animals and plants. RNAi played a major role in advances in insect biology. Did RNAi technology fully meet insect pest and disease vector management expectations? This review will discuss recent advances in the mechanisms of RNAi and its contributions to insect science. The remaining challenges, including delivery to the target site, differential efficiency, potential resistance development and possible solutions for the widespread use of this technology in insect management.

Inefficient uptake of small interfering RNAs is responsible for their inability to trigger RNA interference in Colorado potato beetle cells

There has been limited success in the usage of exogenous small interference RNA (siRNA) or small hairpin RNA (shRNA) to trigger RNA interference (RNAi) in insects. Instead, long double-stranded RNAs (dsRNA) are used to induce knockdown of target genes in insects. Here, we compared the potency of si/sh RNAs and dsRNA in Colorado potato beetle (CPB) cells. CPB cells showed highly efficient RNAi response to dsRNA. However, si/sh RNAs were inefficient in triggering RNAi in CPB cells. Confocal microscopy observations of Cy3 labeled-si/sh RNA cellular uptake revealed reduced si/sh RNA uptake compared to dsRNA. si/sh RNAs were stable in the conditioned media of CPB cells. Although in a small amount, when internalized by CPB cells, the si/sh RNAs were processed by the Dicer enzyme. Lipid-mediated transfection and chimeric dsRNA approaches were used to improve the delivery of si/sh RNAs. Our results suggest that the uptake of si/sh RNAs is inefficient in CPB cells, resulting in ineffective RNAi response. However, with the help of effective delivery methods, si/sh RNA could be a useful option for developing target-specific RNAi-mediated biopesticides.

Advanced nanopesticides: Advantage and action mechanisms

The use of various chemical substances to control pests, diseases, and weeds in the field is a necessary part of the agricultural development process in every country. While the application of pesticides can improve the quality and yield of crops, plant resistance and the harm caused by pesticide residues to the environment and humans have led to the search for greener and safer pesticide formulations to improve the current situation. In recent years, nanopesticides (NPts) have shown great potential in agriculture due to their high efficiency, low toxicity, targeting, resistance, and controlled slow release demonstrated in the experimental stage. Commonly used approaches to prepare NPts include the use of nanoscale metal materials as active ingredients (AI) (ingredients that can play a role in insecticide, sterilization and weeding) or the construction of carriers based on commonly used pesticides to make them stable in nano-sized form. This paper systematically summarizes the advantages and effects of NPts over conventional pesticides, analyzes the formation and functions of NPts in terms of structure, AI, and additives, and describes the mechanism of action of NPts. Despite the feasibility of NPts use, there is not enough comprehensive research on NPts, which must be supplemented by more experiments in terms of biotoxicology and ecological effects to provide strong support for NPts application.

An oral dsRNA delivery system based on chitosan induces G protein-coupled receptor kinase 2 gene silencing for Apolygus lucorum control

RNA interference (RNAi) is recognized as a new and environmentally friendly pest control strategy due to its high specificity. However, the RNAi efficiency is relatively low in many sucking insect pests, such as Apolygus lucorum. Therefore, there is an urgent need to develop new and effective ways of dsRNA delivery. Bacterially expressed or T7 synthesized dsRNA targeting a G Protein-Coupled Receptor Kinase 2 gene was mixed with chitosan in a 1:2 ratio by mass. The size of the chitosan/dsRNA nanoparticles was 69 ± 12 nm, and the TEM and AFM images showed typical spherical or ellipsoidal structures. The chitosan nanoparticles protected the dsRNA from nuclease activity, and pH and temperature-dependent degradation, and the fluorescently-tagged nanoparticles were found to be stable on the surface of green bean plants (48 h) (Phaseolus vulgaris) and were absorbed by midgut epithelial cells and transported to hemolymph. Once fed to the A. lucorum nymph, chitosan/dsRNA could effectively inhibit the expression of the G protein-coupled receptor kinase 2 gene (70%), and led to significantly increase mortality (50%), reduced weight (26.54%) and a prolonged developmental period (8.04%). The feeding-based and chitosan-mediated dsRNA delivery method could be a new strategy for A. lucorum management, providing an effective tool for gene silencing of piercing-sucking insects.

Preparation, characterization and protective effect of chitosan - Tripolyphosphate encapsulated dihydromyricetin nanoparticles on acute kidney injury caused by cisplatin

Dihydromyricetin (DMY) is a natural dihydroflavonol compound known for its diverse pharmacological benefits. However, its limited stability and bioavailability posed significant challenges for further applications. To address these issues, in this study, an ion crosslinking method was utilized to prepare chitosan nanoparticles that were loaded with DMY. The synthesized chitosan nanoparticles (CS-DMY-NPs) were spherical in shape with particle size and ζ potential of 198.7 nm and 45.05 mV, respectively. Furthermore, in vitro release experiments demonstrated that CS-DMY-NPs had sustained release and protective effects in simulated gastric and intestinal fluids. CS-DMY-NPs exhibited better antioxidant activity by ABTS and DPPH radical scavenging activity than free DMY. In vivo study showed that CS-DMY-NPs alleviated cisplatin-induced kidney damage by inhibiting oxidative stress and proinflammatory cytokines, and had better activity compared to DMY (free). Immunofluorescence data showed that CS-DMY-NPs activated the Nrf2 signaling pathways in a dose-dependent manner to combat cisplatin-induced kidney damage. Our results demonstrate that CS-TPP has good compatibility with DMY, and CS-DMY-NPs exhibited better protective effects against cisplatin-induced acute kidney injury (AKI) than free DMY.

Mosquito gene targeted RNAi studies for vector control

Vector-borne diseases are serious public health concern. Mosquito is one of the major vectors responsible for the transmission of a number of diseases like malaria, Zika, chikungunya, dengue, West Nile fever, Japanese encephalitis, St. Louis encephalitis, and yellow fever. Various strategies have been used for mosquito control, but the breeding potential of mosquitoes is such tremendous that most of the strategies failed to control the mosquito population. In 2020, outbreaks of dengue, yellow fever, and Japanese encephalitis have occurred worldwide. Continuous insecticide use resulted in strong resistance and disturbed the ecosystem. RNA interference is one of the strategies opted for mosquito control. There are a number of mosquito genes whose inhibition affected mosquito survival and reproduction. Such kind of genes could be used as bioinsecticides for vector control without disturbing the natural ecosystem. Several studies have targeted mosquito genes at different developmental stages by the RNAi mechanism and result in vector control. In the present review, we included RNAi studies conducted for vector control by targeting mosquito genes at different developmental stages using different delivery methods. The review could help the researcher to find out novel genes of mosquitoes for vector control.

Nanoparticle-Shielded dsRNA Delivery for Enhancing RNAi Efficiency in Cotton Spotted Bollworm Earias vittella (Lepidoptera: Nolidae)

The spotted bollworm Earias vittella (Lepidoptera: Nolidae) is a polyphagous pest with enormous economic significance, primarily affecting cotton and okra. However, the lack of gene sequence information on this pest has a significant constraint on molecular investigations and the formulation of superior pest management strategies. An RNA-seq-based transcriptome study was conducted to alleviate such limitations, and de novo assembly was performed to obtain transcript sequences of this pest. Reference gene identification across E. vittella developmental stages and RNAi treatments were conducted using its sequence information, which resulted in identifying transcription elongation factor (TEF), V-type proton ATPase (V-ATPase), and Glyceraldehyde -3-phosphate dehydrogenase (GAPDH) as the most suitable reference genes for normalization in RT-qPCR-based gene expression studies. The present study also identified important developmental, RNAi pathway, and RNAi target genes and performed life-stage developmental expression analysis using RT-qPCR to select the optimal targets for RNAi. We found that naked dsRNA degradation in the E. vittella hemolymph is the primary reason for poor RNAi. A total of six genes including Juvenile hormone methyl transferase (JHAMT), Chitin synthase (CHS), Aminopeptidase (AMN), Cadherin (CAD), Alpha-amylase (AMY), and V-type proton ATPase (V-ATPase) were selected and knocked down significantly with three different nanoparticles encapsulated dsRNA conjugates, i.e., Chitosan-dsRNA, carbon quantum dots-dsRNA (CQD-dsRNA), and Lipofectamine-dsRNA conjugate. These results demonstrate that feeding nanoparticle-shielded dsRNA silences target genes and suggests that nanoparticle-based RNAi can efficiently manage this pest.

RNA interference to combat the Asian tiger mosquito in Europe: A pathway from design of an innovative vector control tool to its application

The Asian tiger mosquito Aedes albopictus is currently spreading across Europe, facilitated by climate change and global transportation. It is a vector of arboviruses causing human diseases such as chikungunya, dengue hemorrhagic fever and Zika fever. For the majority of these diseases, no vaccines or therapeutics are available. Options for the control of Ae. albopictus are limited by European regulations introduced to protect biodiversity by restricting or phasing out the use of pesticides, genetically modified organisms (GMOs) or products of genome editing. Alternative solutions are thus urgently needed to avoid a future scenario in which Europe faces a choice between prioritizing human health or biodiversity when it comes to Aedes-vectored pathogens. To ensure regulatory compliance and public acceptance, these solutions should preferably not be based on chemicals or GMOs and must be cost-efficient and specific. The present review aims to synthesize available evidence on RNAi-based mosquito vector control and its potential for application in the European Union. The recent literature has identified some potential target sites in Ae. albopictus and formulations for delivery. However, we found little information concerning non-target effects on the environment or human health, on social aspects, regulatory frameworks, or on management perspectives. We propose optimal designs for RNAi-based vector control tools against Ae. albopictus (target product profiles), discuss their efficacy and reflect on potential risks to environmental health and the importance of societal aspects. The roadmap from design to application will provide readers with a comprehensive perspective on the application of emerging RNAi-based vector control tools for the suppression of Ae. albopictus populations with special focus on Europe.

RNAi-mediated mortality of Culex quinquefasciatus using two delivery methods of potential field application

With increasing reports of resistance to traditional insecticides, there is a need for innovative ways for mosquito control. RNAi is a sequence-specific molecular biology technique for gene silencing through degradation of mRNA and prevention of protein translation. Some genes are essential for insect life and their silencing can lead to insect morbidity and/or mortality. Searching for lethal genes in Culex quinquefasciatus, we found dynamin, ROP, HMGR and JHAMT to be lethal targets for RNAi in initial screening through larval soaking in dsRNA solution. Two delivery methods, chitosan nanoparticles and genetically modified yeast cells, were used in this study and proved effective in inducing high larval mortality and low adult emergence. Adult emergence after chitosan nanoparticles/dsRNA treatment was 12.67% ± 1.76 (HMGR), 17.33% ± 1.76 (dynamin), 18.67% ± 0.67 (ROP), and 35.33% ± 0.67 (JHAMT). Genetically modified yeast increased mortalities as adult emergence was 8.33% ± 1.67 (HMGR), 13.33% ± 3.33 (dynamin), and 10% ± 2.89 (JHAMT and ROP). Chitosan nanoparticles retained 75% of its biological activity whereas yeast cells retained >95% of their activities after 7 days of incubation in water. In conclusion, our results showed that these four genes are good targets for C. quinquefasciatus control using RNAi packaged in either chitosan nanoparticles or genetically modified yeast cells.

A dsRNA delivery system based on the rosin-modified polyethylene glycol and chitosan induces gene silencing and mortality in Nilaparvata lugens

BACKGROUND

RNA interference (RNAi) technology has been considered as a promising pest control strategy due to its species selectivity. One of the popular RNAs is exogenous double strand RNA (dsRNA). However, dsRNA is easily degraded by nucleases and is difficult to pass through the insect body walls, and these factors restrict the application of RNAi technology in pest management. Here, the brown planthopper (BPH, Nilaparvata lugens), a major hemipteran pest of rice in Asia countries was used as a model insect, and a dsRNA topical delivery system was constructed.

RESULTS

The carrier part of the delivery system was composed of rosin-modified polyethylene glycol and chitosan, termed ROPE@C. When the N/P ratio was greater than 1:1.25, the dsRNA/ROPE@C complex encouraged full binding of the dsRNA. The gel electrophoresis results showed that ROPE@C improved the stability of dsRNA in the presence of nucleases in gut and lumen contents for at least 6 h and in the temperature range from 4 °C to 37 °C. The dsNlCHSA/ROPE@C/alkyl polyglycoside (APG) nano-formulation directly penetrated the body walls reaching hemocoel within 6 h, and consequently, the relative expression of chitin synthetase A (CHSA) in BPH was reduced by 54.3% and the mortality rate was 65.8%.

CONCLUSION

We developed an appropriate delivery method for dsRNA application in BPH, which is helpful for a large-scale application of RNAi pesticides. © 2022 Society of Chemical Industry.

Recent Progress on Nanocarriers for Topical-Mediated RNAi Strategies for Crop Protection—A Review

To fulfil the growing needs of the global population, sustainability in food production must be ensured. Insect pests and pathogens are primarily responsible for one-third of food losses and harmful synthetic pesticides have been applied to protect crops from these pests and other pathogens such as viruses and fungi. An alternative pathogen control mechanism that is more “friendly” to the environment can be developed by externally applying double-stranded RNAs (dsRNAs) to suppress gene expression. However, the use of dsRNA sprays in open fields is complicated with respect to variable efficiencies in the dsRNA delivery, and the stability of the dsRNA on and in the plants, and because the mechanisms of gene silencing may differ between plants and between different pathogen targets. Thus, nanocarrier delivery systems have been especially used with the goal of improving the efficacy of dsRNAs. Here, we highlight recent developments in nanoparticle-mediated nanocarriers to deliver dsRNA, including layered double hydroxide, carbon dots, carbon nanotubes, gold nanoparticles, chitosan nanoparticles, silica nanoparticles, liposomes, and cell-penetrating peptides, by review of the literature and patent landscape. The effects of nanoparticle size and surface modification on the dsRNA uptake efficiency in plants are also discussed. Finally, we emphasize the overall limitation of dsRNA sprays, the risks associated, and the potential safety concerns for spraying dsRNAs on crops.

Control of Aedes mosquito populations using recombinant microalgae expressing short hairpin RNAs and their effect on plankton

New biocontrol strategies are urgently needed to combat vector-borne infectious diseases. This study presents a low-cost method to produce a potential mosquito insecticide that utilizes the microalgae released into suburban water sources to control mosquito populations. Chlorella microalgae are ubiquitous in local waters, which were chosen as the host for genetic transfection. This species facilitated the recombinant algae to adapt to the prevailing environmental conditions with rapid growth and high relative abundance. The procedure involved microalgae RNAi-based insecticides developed using short hairpin RNAs targeting the Aedes aegypti chitin synthase A (chsa) gene in Chlorella. These insecticides effectively silenced the chsa gene, inhibiting Aedes metamorphosis in the laboratory and simulated-field trials. This study explored the impact of recombinant microalgae on the phytoplankton and zooplankton in suburban waters. High-throughput sequencing revealed that rapid reproduction of recombinant Chlorella indirectly caused the disappearance of some phytoplankton and reduced the protozoan species. This study demonstrated that a recombinant microalgae-based insecticide could effectively reduce the population of Aedes mosquitoes in the laboratory and simulated field trials. However, the impact of this technology on the environment and ecology requires further investigation.

Effect of marker-free transgenic Chlamydomonas on the control of Aedes mosquito population and on plankton

BACKGROUND

More than half of the world's population suffers from epidemic diseases that are spread by mosquitoes. The primary strategy used to stop the spread of mosquito-borne diseases is vector control. Interference RNA (RNAi) is a powerful tool for controlling insect populations and may be less susceptible to insect resistance than other strategies. However, public concerns have been raised because of the transfer of antibiotic resistance marker genes to environmental microorganisms after integration into the recipient genome, thus allowing the pathogen to acquire resistance. Therefore, in the present study, we modified the 3-hydroxykynurenine transaminase (3hkt) and hormone receptor 3 (hr3) RNAi vectors to remove antibiotic resistance marker genes and retain the expression cassette of the inverse repeat sequence of the 3hkt/hr3 target gene. This recombinant microalgal marker-free RNAi insecticide was subsequently added to the suburban water in a simulated-field trial to test its ability to control mosquito population.

METHODS

The expression cassette of the 3hkt/hr3 inverted repeat sequence and a DNA fragment of the argininosuccinate lyase gene without the ampicillin resistance gene were obtained using restriction enzyme digestion and recovery. After the cotransformation of Chlamydomonas, the recombinant algae was then employed to feed Aedes albopictus larvae. Ten and 300 larvae were used in small- and large-scale laboratory Ae.albopictus feeding trials, respectively. Simulated field trials were conducted using Meishe River water that was complemented with recombinant Chlamydomonas. Moreover, the impact of recombinant microalgae on phytoplankton and zooplankton in the released water was explored via high-throughput sequencing.

RESULTS

The marker-free RNAi-recombinant Chlamydomonas effectively silenced the 3hkt/hr3 target gene, resulting in the inhibition of Ae. albopictus development and also in the high rate of Ae. albopictus larvae mortality in the laboratory and simulated field trials. In addition, the results confirmed that the effect of recombinant Chlamydomonas on plankton in the released water was similar to that of the nontransgenic Chlamydomonas, which could reduce the abundance and species of plankton.

CONCLUSIONS

The marker-free RNAi-recombinant Chlamydomonas are highly lethal to the Ae. albopictus mosquito, and their effect on plankton in released water is similar to that of the nontransgenic algal strains, which reduces the abundance and species of plankton. Thus, marker-free recombinant Chlamydomonas can be used for mosquito biorational control and mosquito-borne disease prevention.

Chitosan nanocarriers mediated dsRNA delivery in gene silencing for Helicoverpa armigera biocontrol

Specific gene silencing by RNA interference (RNAi) involving exogenous double stranded RNA (dsRNA) delivery has potential in Helicoverpa armigera control, a resistant insect pest. Here, ionotropically synthesized cationic chitosan nanoparticles (CNPs, 95 nm size, +36 mV charge) showed efficient dsRNA loading (95 %) and effective protection from insect gut nucleases and pH degradation. The CNPs were tagged with fluorescence and found to be stable on leaf surface (24 h) and were internalized by columnar insect gut cells. A single dose of CNPs:dsRNA complex (containing 0.1 μg dsRNA) ingested by H. armigera larvae via artificial/leaf feed effectively silenced lipase and chitinase target genes (2-2.7 fold downregulation) and suppressed their respective enzyme activities (2-5.3 fold). RNAi caused reduced pupation (5-fold) and impaired moth emergence. RNAi effects correlated significantly with 100% insect mortality (PCA 0.97-0.99). Furthermore, specific dsRNA did not affect non-target insects Spodoptera litura and Drosophila melanogaster. Developed CNPs:dsRNA complexes towards RNAi targets can serve as a safe, targeted insecticide for sustainable crop protection.

Simultaneous silencing of juvenile hormone metabolism genes through RNAi interrupts metamorphosis in the cotton boll weevil

The cotton boll weevil (CBW) (Anthonomus grandis) is one of the major insect pests of cotton in Brazil. Currently, CBW control is mainly achieved by insecticide application, which is costly and insufficient to ensure effective crop protection. RNA interference (RNAi) has been used in gene function analysis and the development of insect control methods. However, some insect species respond poorly to RNAi, limiting the widespread application of this approach. Therefore, nanoparticles have been explored as an option to increase RNAi efficiency in recalcitrant insects. Herein, we investigated the potential of chitosan-tripolyphosphate (CS-TPP) and polyethylenimine (PEI) nanoparticles as a dsRNA carrier system to improve RNAi efficiency in the CBW. Different formulations of the nanoparticles with dsRNAs targeting genes associated with juvenile hormone metabolism, such as juvenile hormone diol kinase (JHDK), juvenile hormone epoxide hydrolase (JHEH), and methyl farnesoate hydrolase (MFE), were tested. The formulations were delivered to CBW larvae through injection (0.05-2 µg), and the expression of the target genes was evaluated using RT-qPCR. PEI nanoparticles increased targeted gene silencing compared with naked dsRNAs (up to 80%), whereas CS-TPP-dsRNA nanoparticles decreased gene silencing (0%-20%) or led to the same level of gene silencing as the naked dsRNAs (up to 50%). We next evaluated the effects of targeting a single gene or simultaneously targeting two genes via the injection of naked dsRNAs or dsRNAs complexed with PEI (500 ng) on CBW survival and phenotypes. Overall, the gene expression analysis showed that the treatments with PEI targeting either a single gene or multiple genes induced greater gene silencing than naked dsRNA (∼60%). In addition, the injection of dsJHEH/JHDK, either naked or complexed with PEI, significantly affected CBW survival (18% for PEI nanoparticles and 47% for naked dsRNA) and metamorphosis. Phenotypic alterations, such as uncompleted pupation or malformed pupae, suggested that JHEH and JHDK are involved in developmental regulation. Moreover, CBW larvae treated with dsJHEH/JHDK + PEI (1,000 ng/g) exhibited significantly lower survival rate (55%) than those that were fed the same combination of naked dsRNAs (30%). Our findings demonstrated that PEI nanoparticles can be used as an effective tool for evaluating the biological role of target genes in the CBW as they increase the RNAi response.

Current Scenario of Exogenously Induced RNAi for Lepidopteran Agricultural Pest Control: From dsRNA Design to Topical Application

Invasive insects cost the global economy around USD 70 billion per year. Moreover, increasing agricultural insect pests raise concerns about global food security constraining and infestation rising after climate changes. Current agricultural pest management largely relies on plant breeding-with or without transgenes-and chemical pesticides. Both approaches face serious technological obsolescence in the field due to plant resistance breakdown or development of insecticide resistance. The need for new modes of action (MoA) for managing crop health is growing each year, driven by market demands to reduce economic losses and by consumer demand for phytosanitary measures. The disabling of pest genes through sequence-specific expression silencing is a promising tool in the development of environmentally-friendly and safe biopesticides. The specificity conferred by long dsRNA-base solutions helps minimize effects on off-target genes in the insect pest genome and the target gene in non-target organisms (NTOs). In this review, we summarize the status of gene silencing by RNA interference (RNAi) for agricultural control. More specifically, we focus on the engineering, development and application of gene silencing to control Lepidoptera through non-transforming dsRNA technologies. Despite some delivery and stability drawbacks of topical applications, we reviewed works showing convincing proof-of-concept results that point to innovative solutions. Considerations about the regulation of the ongoing research on dsRNA-based pesticides to produce commercialized products for exogenous application are discussed. Academic and industry initiatives have revealed a worthy effort to control Lepidoptera pests with this new mode of action, which provides more sustainable and reliable technologies for field management. New data on the genomics of this taxon may contribute to a future customized target gene portfolio. As a case study, we illustrate how dsRNA and associated methodologies could be applied to control an important lepidopteran coffee pest.

Synthetic Nanoscale RNAi Constructs as Pesticides for the Control of Locust Migratoria

The low efficiency of RNA interference (RNAi) in insects via the oral administration of double-stranded RNA (dsRNA) is a considerable obstacle preventing its application in insect pest control. The instability of dsRNA and insufficient dsRNA uptake are known to limit the RNAi efficiency. To overcome these limitations, the block copolymer poly(ethylene glycol)-polylysine(thiol) [PEG-PLys(SH)] was designed in this study to form well-defined, core-shell nanoparticles to protect dsRNA from premature degradation and to facilitate its movement through various physiological barriers. The developed material had excellent structural stability and dsRNA-protecting capacity, thereby enabling the prolonged survival of dsRNA in the digestive tract for endocytosis into the midgut cells of the migratory locust, Locusta migratoria. After encapsulation of a dsLmCHS2 payload (a midgut gene), a 60% down-regulation of LmCHS2, accompanied with observations of amorphous and discontinuous linings of the peritrophic matrix and abnormal phenotypes, was observed. In addition, the elaborated nanoscale dsRNA condensates appeared to readily extravasate through the narrow fenestrations in the linings of midgut epithelial cells into the hemolymph and be distributed throughout the body. After encapsulation of a dsLmCHS1 payload (a cuticle gene), a distinctive lethal phenotype with molting failure was observed as a result of a 50% down-regulation in LmCHS1. The persistent leaf adherence of these dsRNA constructs was also capable of resisting continuous rinsing. Therefore, these dsRNA constructs represent a robust type of RNAi pesticide, which has potential as a versatile pesticide against a variety of molecular targets for the control of destructive insects and insects resistant to conventional pesticides.

Advances in nanocarriers to improve the stability of dsRNA in the environment

RNAi technology, known as a revolutionary technology in the history of pesticides, has been identified as a very promising novel approach for crop protection, which is of great significance for achieving the sustainable agricultural development of the United Nations Food and Agriculture Organization. Although many studies have shown that RNA biopesticides have strong application prospects, its stability seriously restricts the commercial use. As the core component of RNAi, double-stranded RNA (dsRNA) is unstable in its natural form. Therefore, how to ensure the stability of dsRNA is one of the most significant challenges in realizing the commercial use of RNA biopesticides. Nanomaterials such as cationic polymers and lipofectamine can improve the stability of dsRNA in the environment, which has been proved. This paper reviews the recent research progress of nanomaterials that can be used to improve the environmental stability of dsRNA, and discusses the advantages and limitations of different nanomaterials combined with dsRNA, which provides reference for the selection of dsRNA nanoformulations.

Protamine-Lipid-dsRNA Nanoparticles Improve RNAi Efficiency in the Fall Armyworm, Spodoptera frugiperda

Developing safe and effective double-stranded RNA (dsRNA) delivery systems remains a major challenge for gene silencing, especially in lepidopteran insects. This study evaluated the protamine sulfate (PS)/lipid/dsRNA nanoparticle (NP) delivery system for RNA interference (RNAi) in cells and larvae of the fall armyworm (FAW), Spodoptera frugiperda, a major worldwide pest. A highly efficient gene delivery formulation was prepared using a cationic biopolymer, PS, and a cationic lipid, Cellfectin (CF), complexed with dsRNA. The NPs were prepared by a two-step self-assembly method. The formation of NPs was revealed by dynamic light scattering and transmission electron microscopy. The formation of CF/dsRNA/PS NPs was spherical in shape and size, ranging from 20 to 100 nm with a positive charge (+23.3 mV). Interestingly, prepared CF/dsRNA/PS NPs could protect dsRNA (95%) from nuclease degradation and thus significantly improve the stability of dsRNA. Formulations prepared by combining EGFP DNA with CF/PS increased transfection efficiency in Sf9 cells compared to PS/EGFP and CF/EGFP NPs. Also, the PS/CF/dsRNA NPs enhanced the endosomal escape for the intracellular delivery of dsRNA. The gene knockdown efficiency was assessed in Sf9 Luciferase (Luc) stable cells after a 72 h incubation with CF/dsRNA/PS, PS/dsRNA, CF/dsRNA, or naked dsRNA. Knockdown of the Luc gene was detected in CF/dsRNA/PS (76%) and PS/dsRNA (42.4%) not CF/dsRNA (19.5%) and naked dsRNA (10.3%) in Sf9 Luc cells. Moreover, CF/dsIAP/PS (25 μg of dsRNA targeting the inhibitor of apoptosis, IAP, gene of FAW) NPs showed knockdown of the IAP gene (39.5%) and mortality (55%) in FAW larvae. These results highlight the potential application of PS/lipid/dsRNA NPs for RNA-mediated control of insect pests.

Juvenile hormone-induced histone deacetylase 3 suppresses apoptosis to maintain larval midgut in the yellow fever mosquito

SignificanceJuvenile hormone (JH), a sesquiterpenoid, regulates many aspects of insect development, including maintenance of the larval stage by preventing metamorphosis. In contrast, ecdysteroids promote metamorphosis by inducing the E93 transcription factor, which triggers apoptosis of larval cells and remodeling of the larval midgut. We discovered that JH suppresses precocious larval midgut-remodeling by inducing an epigenetic modifier, histone deacetylase 3 (HDAC3). JH-induced HDAC3 deacetylates the histone H4 localized at the promoters of proapoptotic genes, resulting in the suppression of these genes. This eventually prevents programmed cell death of midgut cells and midgut-remodeling during larval stages. These studies identified a previously unknown mechanism of JH action in blocking premature remodeling of the midgut during larval feeding stages.

Functionalized LbL Film for Localized Delivery of STAT3 siRNA and Oxaliplatin Combination to Treat Colon Cancer

The aim of the study was to develop and evaluate the efficacy of a functionalized layer-by-layer (LbL) assembled film entrapped with oxaliplatin (OX) and signal transducer and activator of transcription 3 (STAT3) siRNA in the localized treatment of colon cancer. The LbL film was prepared by the sequential layering of chitosan (CS) and alginate to attain desired physical and mechanical properties. The film was functionalized by coating folic acid-conjugated CS on one side. On the other side, polycaprolactone was coated as a backing layer to provide directional drug release. OX was entrapped within the layers of the film, while STAT3 siRNA was complexed with CS to form nanoparticles before entrapment in the LbL film. The CS-siRNA nanoparticles were taken up by the colon carcinoma, Caco-2 cells within 3 h and provided concentration-dependent reduction in STAT3 protein expression. The functionalized LbL film (F-LbL film) selectively adhered to the colon cancer tissue in the mice model, whereas the nonfunctionalized film adhered to the normal colon tissue. The combination of OX and STAT3 siRNA provided significantly greater tumor regression, survival rate, and STAT3 protein suppression after localized delivery through oral administration compared with intravenous administration. Taken together, the F-LbL film can selectively bind to colon tumors for localized delivery of drugs to treat colon cancer.

A novel low-molecular-weight chitosan/gamma-polyglutamic acid polyplexes for nucleic acid delivery into zebrafish larvae

Many challenges, such as virus infection, extreme weather and long cultivation periods, during the development of fish larvae have been observed, especially in aquaculture. Gene delivery is a useful method to express functional genes to defend against these challengers. However, the methods for fish larvae are insufficient. In our earlier report, low-molecular-weight chitosan (LMWCS) showed a strong positive charge and may be useful for polyplex formulation. Herein, we present a simple self-assembly of LMWCS polyplexes (LMWCSrNPs) for gene delivery into zebrafish larvae. Different weight ratios of LMWCS/gamma-polyglutamic acid (γ-PGA)/plasmid DNA were analyzed by gel mobility assay. Delivery efficiency determined by green fluorescent protein (GFP) expression in zebrafish liver (ZFL) cells showed that delivery efficiency at a weight ratio of 20:8:1 was higher than others. Zeta potential and transmission electron microscopy (TEM) analysis showed that the round shape of the particle size varied. In our earlier reports, IRF9S2C could induce interferon-stimulated gene (ISG) expression to induce innate immunity in zebrafish and pufferfish. Further delivery of pcDNA3-IRF9S2C-HA plasmid DNA into ZFL cells and zebrafish larvae by LMWCSrNP successfully induced ISG expression. Collectively, LMWCSrNP could be a novel gene delivery system for zebrafish larvae and might be used to improve applications in aquaculture.

NCs-Delivered Pesticides: A Promising Candidate in Smart Agriculture

Pesticides have been used extensively in the field of plant protection to maximize crop yields. However, the long-term, unmanaged application of pesticides has posed severe challenges such as pesticide resistance, environmental contamination, risk in human health, soil degradation, and other important global issues. Recently, the combination of nanotechnology with plant protection strategies has offered new perspectives to mitigate these global issues, which has promoted a rapid development of NCs-based pesticides. Unlike certain conventional pesticides that have been applied inefficiently and lacked targeted control, pesticides delivered by nanocarriers (NCs) have optimized formulations, controlled release rate, and minimized or site-specific application. They are receiving increasing attention and are considered as an important part in sustainable and smart agriculture. This review discussed the limitation of traditional pesticides or conventional application mode, focused on the sustainable features of NCs-based pesticides such as improved formulation, enhanced stability under harsh condition, and controlled release/degradation. The perspectives of NCs-based pesticides and their risk assessment were also suggested in this view for a better use of NCs-based pesticides to facilitate sustainable, smart agriculture in the future.

Innate and adaptive resistance to RNAi: a major challenge and hurdle to the development of double stranded RNA-based pesticides

RNA interference (RNAi) is a post-transcriptional gene silencing process where short interfering RNAs degrade targeted mRNA. Exploration of gene function through reverse genetics is the major achievement of RNAi discovery. Besides, RNAi can be used as a potential strategy for the control of insect pests. This has led to the idea of developing RNAi-based pesticides. Differential RNAi efficiency in the different insect orders is the biggest biological obstacle in developing RNAi-based pesticides. dsRNA stability, the sensitivity of core RNAi machinery, uptake of dsRNA and amplification and spreading of the RNAi signal are the key factors responsible for RNAi efficiency in insects. This review discusses the physiological and adaptive factors responsible for reduced RNAi in insects that pose a major challenge in developing dsRNA- based pesticides.

RNAi Crop Protection Advances

RNAi technology is a versatile, effective, safe, and eco-friendly alternative for crop protection. There is plenty of evidence of its use through host-induced gene silencing (HIGS) and emerging evidence that spray-induced gene silencing (SIGS) techniques can work as well to control viruses, bacteria, fungi, insects, and nematodes. For SIGS, its most significant challenge is achieving stability and avoiding premature degradation of RNAi in the environment or during its absorption by the target organism. One alternative is encapsulation in liposomes, virus-like particles, polyplex nanoparticles, and bioclay, which can be obtained through the recombinant production of RNAi in vectors, transgenesis, and micro/nanoencapsulation. The materials must be safe, biodegradable, and stable in multiple chemical environments, favoring the controlled release of RNAi. Most of the current research on encapsulated RNAi focuses primarily on oral delivery to control insects by silencing essential genes. The regulation of RNAi technology focuses on risk assessment using different approaches; however, this technology has positive economic, environmental, and human health implications for its use in agriculture. The emergence of alternatives combining RNAi gene silencing with the induction of resistance in crops by elicitation and metabolic control is expected, as well as multiple silencing and biotechnological optimization of its large-scale production.

RNAi-Mediated Screening of Selected Target Genes Against Culex quinquefasciatus (Diptera: Culicidae)

Culex quinquefasciatus, a member of the Culex pipiens complex, is widespread in Saudi Arabia and other parts of the world. It is a vector for lymphatic filariasis, Rift Valley fever, and West Nile virus. Studies have shown the deleterious effect of RNA interference (RNAi)-mediated knockdown of various lethal genes in model and agricultural pest insects. RNAi was proposed as a tool for mosquito control with a focus on Aedes aegypti and Anopheles gambiae. In this study, we examined the effect of RNAi of selected target genes on both larval mortality and adult emergence of Cx. quinquefasciatus through two delivery methods: soaking and nanoparticles. Ten candidate genes were selected for RNAi based on their known lethal effect in other insects. Disruption of three genes, chitin synthase-1, inhibitor of apoptosis 1, and vacuolar adenosine triphosphatase, resulted in the highest mortality among the selected genes using the two treatment methods. Silencing the other seven genes resulted in a medium to low mortality in both assays. These three genes are also active against a wide range of insects and could be used for RNAi-based mosquito control in the future.

Foliar Delivery of siRNA Particles for Treating Viral Infections in Agricultural Grapevines

Grapevine leafroll disease (GLD) is a globally spreading viral infection that causes major economic losses by reducing crop yield, plant longevity and berry quality, with no effective treatment. Grapevine leafroll associated virus-3 (GLRaV-3) is the most severe and prevalent GLD strain. Here, we evaluated the ability of RNA interference (RNAi), a non-GMO gene-silencing pathway, to treat GLRaV-3 in infected Cabernet Sauvignon grapevines. We synthesized lipid-modified polyethylenimine (lmPEI) as a carrier for long double-stranded RNA (dsRNA, 250-bp-long) that targets RNA polymerase and coat protein genes that are conserved in the GLRaV-3 genome. Self-assembled dsRNA-lmPEI particles, 220 nm in diameter, displayed inner ordered domains spaced 7.3±2 nm from one another, correlating to lmPEI wrapping spirally around the dsRNA. The particles effectively protected RNA from degradation by ribonucleases, and Europium-loaded particles applied to grapevine leaves were detected as far as 60-cm from the foliar application point. In three field experiments, a single dose of foliar administration knocked down GLRaV-3 titer, and multiple doses of the treatment kept the viral titer at baseline and triggered recovery of the vine and berries. This study demonstrates RNAi as a promising platform for treating viral diseases in agriculture.

Histone acetyltransferase 1 promotes gemcitabine resistance by regulating the PVT1/EZH2 complex in pancreatic cancer

The poor prognosis of pancreatic cancer is primarily due to the development of resistance to therapies, including gemcitabine. The long noncoding RNA PVT1 (lncRNA PVT1) has been shown to interact with enhancer of zeste 2 polycomb repressive complex 2 subunit (EZH2), promoting gemcitabine resistance in pancreatic cancer. In this study, we found histone acetyltransferase 1 (HAT1) enhanced the tolerance of pancreatic cancer cells to gemcitabine and HAT1-mediated resistance mechanisms were regulated by PVT1 and EZH2. Our results showed that the aberrant HAT1 expression promoted gemcitabine resistance, while silencing HAT1 restored gemcitabine sensitivity. Moreover, HAT1 depletion caused a notable increase of gemcitabine sensitivity in gemcitabine-resistant pancreatic cancer cell lines. Further research found that HAT1 increased PVT1 expression to induce gemcitabine resistance, which enhanced the binding of bromodomain containing 4 (BRD4) to the PVT1 promoter, thereby promoting PVT1 transcription. Besides, HAT1 prevented EZH2 degradation by interfering with ubiquitin protein ligase E3 component n-recognin 4 (UBR4) binding to the N-terminal domain of EZH2, thus maintaining EZH2 protein stability to elevate the level of EZH2 protein, which also promoted HAT1-mediated gemcitabine resistance. These results suggested that HAT1 induced gemcitabine resistance of pancreatic cancer cells through regulating PVT1/EZH2 complex. Given this, Chitosan (CS)-tripolyphosphate (TPP)-siHAT1 nanoparticles were developed to block HAT1 expression and improve the antitumor effect of gemcitabine. The results showed that CS-TPP-siHAT1 nanoparticles augmented the antitumor effects of gemcitabine in vitro and in vivo. In conclusion, HAT1-targeted therapy can improve observably gemcitabine sensitivity of pancreatic cancer cells. HAT1 is a promising therapeutic target for pancreatic cancer.

Zein based-nanoparticles loaded botanical pesticides in pest control: An enzyme stimuli-responsive approach aiming sustainable agriculture

Nanoencapsulation of biopesticides is an important strategy to increase the efficiency of these compounds, reducing losses and adverse effects on non-target organisms. This study describes the preparation and characterisation of zein nanoparticles containing the botanical compounds limonene and carvacrol, responsive to proteolytic enzymes present in the insects guts. The spherical nanoparticles, prepared by the anti-solvent precipitation method, presented in the nanoparticle tracking analysis (NTA) a concentration of 4.7 × 10¹² ± 1.3 × 10¹¹ particles.mL^-1 and an average size of 125 ± 2 nm. The formulations showed stability over time, in addition to not being phytotoxic to Phaseolus vulgaris plants. In vivo tests demonstrated that formulations of zein nanoparticles containing botanical compounds showed higher mortality to Spodoptera frugiperda larvae. In addition, the FTIC probe (fluorescein isothiocyanate) showed wide distribution in the larvae midgut, as well as being identified in the feces. The trypsin enzyme, as well as the enzymatic extract from insects midgut, was effective in the degradation of nanoparticles containing the mixture of botanical compounds, significantly reducing the concentration of nanoparticles and the changes in size distribution. The zein degradation was confirmed by the disappearance of the protein band in the electrophoresis gel, by the formation of the lower molecular weight fragments and also by the greater release of FTIC after enzymes incubation. In this context, the synthesis of responsive nanoparticles has great potential for application in pest management, increasing the selectivity and specificity of the system and contributing to a more sustainable agriculture.

Development of an RNAi-based microalgal larvicide for the control of Aedes aegypti

BACKGROUND

Mosquito-borne diseases affect over half of the human population globally. Multiple studies have shown that chemical insecticides are ineffective because of resistance. Therefore, environmentally safe mosquito population control tools need to be developed. Ribonucleic acid interference (RNAi) is a reverse genetic mechanism recently introduced as a new pest control tool. This technique represents a new class of biorational technology that could combat the increased global incidence of insecticide resistance. The technique has the potential of becoming a critical component of integrated vector control programs.

METHODS

A 3-hydroxykynurenine transaminase (3-HKT) RNAi expression plasmid was constructed, generated and transformed into Chlamydomonas and Chlorella algae. The transgenic algae were then used to feed Ae. aegypti mosquito larvae. The feeding experiments were conducted on a small and large scale with 10 and about 300 larvae, respectively. The mortality rate of the larvae was calculated over 30 days. In addition, histological examination of the insect tissues was performed to examine the extent of tissue damage.

RESULTS

The integumentary system and midguts of larvae fed with transgenic Chlamydomonas were severely damaged. The mortality rate of the larvae fed with transgenic Chlamydomonas ranged from 60 to 100% in small-scale tests. The survival rate of adult mosquitoes was 0.0% in a large-scale feeding experiment when the larvae were fed with transgenic Chlamydomonas. Moreover, when the larvae were fed with transgenic Chlorella, the mortality rate ranged from 6.7% to 43% compared to that fed wild-type Chlorella.

CONCLUSIONS

3HKT RNAi transgenic algae are in some scales lethal to Ae. aegypti. The findings of this study indicate that technology based on microalgae RNAi may provide a new way to control mosquito populations.

Oral delivery of pVAX-OMP and pVAX-hly DNA vaccine using chitosan-tripolyphosphate (Cs-TPP) nanoparticles in Rohu, (Labeo rohita) for protection against Aeromonas hydrophila infection

The present study examines the effectiveness of DNA vaccine against Aeromonas hydrophila through oral route using chitosan-tripolyphosphate (Cs-TPP) nanoparticles encapsulation. The virulent gene of outer membrane protein (OMP) and hemolysin (hly) related to pathogenicity of A. hydrophila was used to construct a DNA vaccine using pVAX1, and the construct was named as pVAX-OMP and pVAX-hly DNA vaccines. The pVAX-OMP and pVAX-hly DNA vaccines were encapsulated by Cs-TPP nanoparticles and size measured by field emission scanning electron microscopy (FE-SEM). The encapsulation efficiency of Cs-TPP nanoparticles was found to be 79.6% for pVAX-OMP DNA and 82.3% for pVAX-hly DNA binding with Cs-TPP nanoparticles. The stability and invitro release profile of plasmid DNA was also determined after encapsulation using DNase and chitosanase. DNA vaccines distribution in tissues was investigated in fish fed with the pVAX-OMP, pVAX-hly and pVAX-OMP+pVAX-hly encapsulated in Cs-TPP nanoparticles and confirmed by PCR and multiplex PCR. The results suggest that Cs-TPP nanoparticles encapsulated DNA vaccine delivered into fish by feeding. After oral vaccination of Labeo rohita were challenged with A. hydrophila by intraperitoneal injection. Relatively, gene expression of c- and g-type lysozyme followed by pro- and anti-inflammatory cytokines (Interlukin-10 and Tumor Growth Factor β) was up-regulated in heart and kidney for pVAX-OMP+pVAX-hly vaccinated group. Moreover, fish fed with pVAX-OMP+pVAX-hly encapsulated in Cs-TPP nanoparticles had a significantly higher survival rate (76.2%) against A. hydrophila. This study concludes that pVAX-OMP and pVAX-hly DNA vaccines can be delivered orally using Cs-TPP nanoparticles for protection against A. hydrophilainfection.

Strategies for enhancing the efficiency of RNA interference in insects

Low RNA interference (RNAi) efficiency in many insect pests has significantly prevented its widespread application for insect pest management. This article provides a comprehensive review of recent research in developing various strategies for enhancing RNAi efficiency. Our review focuses on the strategies in target gene selection and double-stranded RNA (dsRNA) delivery technologies. For target gene selection, genome-wide or large-scale screening strategies have been used to identify most susceptible target genes for RNAi. Other strategies include the design of dsRNA constructs and manipulate the structure of dsRNA to maximize the RNA efficiency for a target gene. For dsRNA delivery strategies, much recent research has focused on the applications of complexed or encapsulated dsRNA using various reagents, polymers, or peptides to enhance dsRNA stability and cellular uptake. Other dsRNA delivery strategies include genetic engineering of microbes (e.g. fungi, bacteria, and viruses) and plants to produce insect-specific dsRNA. The ingestion of the dsRNA-producing organisms or tissues will have lethal or detrimental effects on the target insect pests. This article also identifies obstacles to further developing RNAi for insect pest management and suggests future avenues of research that will maximize the potential for using RNAi for insect pest management. © 2021 Society of Chemical Industry.

Development of Catechin, Poly-l-lysine, and Double-Stranded RNA Nanoparticles

Developing strategies to optimize double-stranded RNA (dsRNA) delivery remains a significant challenge in improving RNA interference (RNAi) in insects. Nanoformulations may provide an avenue for the safe and effective delivery of dsRNA. We investigated nanoparticle-mediated gene silencing using biodegradable polymers, poly-l-lysine (PLL), and polyphenol (-)-epigallocatechin gallate (EGCG) for dsRNA delivery into Spodoptera frugiperda (Sf9) cells. Negatively charged cores were formed by EGCG and dsRNA complexes, and PLL was used to encapsulate the cores. The nanoparticles were characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), and energy-dispersive spectrometry (EDS) analysis. The stability of the nanoparticles was assessed by incubating them in nuclease-containing Sf9 cell conditioned media. The effectiveness of the nanoparticles was investigated in Sf9 cells stably expressing the luciferase gene. The results revealed that the nanoparticles formed were small and spherical. The PLL/EGCG/dsRNA nanoparticles exhibited better stability compared to that of PLL/dsRNA or naked dsRNA. Nanoparticles prepared with dsRNA targeting the luciferase gene induced an efficient knockdown (66.7%) of the target gene. In Sf9 cells, nanoparticles prepared with Cy3- or CyPHer-5E-labeled dsRNA showed higher cellular uptake and endosomal escape, respectively, than the naked dsRNA. The improvement in uptake and cytosolic delivery may have helped to increase the knockdown efficiency. In Sf9 cells, the nanoparticles prepared with dsRNA targeting the inhibitor of apoptosis gene induced apoptosis by knocking down its expression. In conclusion, we demonstrate that PLL/EGCG/dsRNA nanoparticles are stable, highly efficient, and effective in dsRNA delivery and knockdown of the target gene.

Nanoparticle-mediated double-stranded RNA delivery system: A promising approach for sustainable pest management

RNA interference (RNAi) targeting lethal genes in insects has great potential for sustainable crop protection. Compared with traditional double-stranded (ds)RNA delivery systems, nanoparticles such as chitosan, liposomes, and cationic dendrimers offer advantages in delivering dsRNA/small interfering (si)RNA to improve RNAi efficiency, thus promoting the development and practice of RNAi-based pest management strategies. Here, we illustrate the limitations of traditional dsRNA delivery systems, reveal the mechanism of nanoparticle-mediated RNAi, summarize the recent progress and successful applications of nanoparticle-mediated RNAi in pest management, and finally address the prospects of nanoparticle-based RNA pesticides.

Double-stranded RNAs targeting inhibitor of apoptosis gene show no significant cross-species activity

RNA interference (RNAi) has become an integral part of mainstream research due to its versatility and ease of use. However, the potential nontarget effects associated with double-stranded RNAs (dsRNA) are poorly understood. To explore this, we used dsRNAs targeting the inhibitor of apoptosis (iap) gene from nine insect species and assayed their possible nontarget effects. For each assay, we used a control (dsRNA targeting the gene coding for green fluorescent protein, GFP) and a species-specific dsRNA targeting nine iap genes in insect species to evaluate target gene knockdown efficiency, apoptosis phenotype in cells and mortality in insects. Our results revealed that dsIAP efficiently knocks down iap gene expression and induces apoptosis phenotype and mortality in target insect species. In contrast, no significant knockdown of the iap gene expression, apoptosis phenotypes, or mortality were detected in cell lines developed from nontarget insects or nontarget insects treated with dsIAPs. Interestingly, even among closely related insects such as stink bugs, Nezara viridula, Halyomorpha halys, and Murgantia histrionica, with substantial sequence similarity among iap genes from these insects, no significant nontarget effects of dsIAP were observed under the conditions tested. These data demonstrate no significant nontarget effects for dsIAPs and suggest that the threat of nontarget effects of RNAi technology may not be substantial.

Chitosan nanoparticles help double-stranded RNA escape from endosomes and improve RNA interference in the fall armyworm, Spodoptera frugiperda

RNA interference (RNAi) is a promising technology for the development of next-generation insect pest control products. Though RNAi is efficient and systemic in coleopteran insects, it is inefficient and variable in lepidopteron insects. In this study, we explored the possibility of improving RNAi in the fall armyworm (FAW), Spodoptera frugiperda by conjugating double-stranded RNA (dsRNA) with biodegradable chitosan (Chi). dsRNA conjugated with chitosan was protected from degradation by endonucleases present in Sf9 cell-conditioned medium, hemolymph, and midgut lumen contents collected from the FAW larvae. Chi-dsRNA complexes showed reduced accumulation in the endosomes of Sf9 cells and FAW tissues. Exposing chitosan formulated dsRNA in Sf9 cells and the tissues induced a significant knockdown of endogenous genes. Chi-dsIAP fed to FAW larvae induced knockdown of iap gene, growth retardation, and mortality. Processing of dsRNA into small interfering RNA was detected with chitosan-conjugated ³² P-UTP-labeled ds green fluorescent protein in Sf9 cells and FAW larval tissues. Overall, these data suggest that dsRNA conjugated with chitosan helps dsRNA escape from the endosomes and improves RNAi efficiency in FAW cells and tissues.