Assessing the Risks of Topically Applied dsRNA-Based Products to Non-target Arthropods

High-quality reference genome of predatory mite Neoseiulus californicus McGregor (Acari: Phytoseiidae) provides insights into its biological traits and potential RNAi off-target effects

BACKGROUND

Neoseiulus californicus is a predatory mite that can control various spider mites and other small arthropods. Despite its acknowledged effectiveness in the natural enemy market, a crucial knowledge gap exists in understanding the genomic features related to its predatory traits and adaptation. With the increasing emphasis on modern pest management strategies and dynamic environmental changes in plant production trends, constructing a reliable genomic resource for N. californicus becomes imperative.

RESULTS

In this study, we provided a high-quality genome assembly and annotation of N. californicus, with a size of 188.43 Mb and 12 946 predicted genes. We identified genomic features and traits related to its detoxification, stress response, sensory system, mobility, secretory toxins, digestive enzymes and horizontally transferred genes (HGTs) by comparative genomics. We also predicted the potential off-target effects of double-stranded RNA (dsRNA) that could be used to control spider mites, based on public data and the N. californicus genome.

CONCLUSION

Our study provided a valuable genomic resource for a commercialized predatory mite, offering useful insights for the design of integrated pest management (IPM) strategies in the new era. Further studies are needed to explore the functional roles of key gene families in predatory mites, as well as their interactions with their prey and IPM strategies. © 2024 Society of Chemical Industry.

Exogenous dsRNA-Mediated RNAi: Mechanisms, Applications, Delivery Methods and Challenges in the Induction of Viral Disease Resistance in Plants

The increasing challenges posed by plant viral diseases demand innovative and sustainable management strategies to minimize agricultural losses. Exogenous double-stranded RNA (dsRNA)-mediated RNA interference (RNAi) represents a transformative approach to combat plant viral pathogens without the need for genetic transformation. This review explores the mechanisms underlying dsRNA-induced RNAi, highlighting its ability to silence specific viral genes through small interfering RNAs (siRNAs). Key advancements in dsRNA production, including cost-effective microbial synthesis and in vitro methods, are examined alongside delivery techniques such as spray-induced gene silencing (SIGS) and nanocarrier-based systems. Strategies for enhancing dsRNA stability, including the use of nanomaterials like layered double hydroxide nanosheets and carbon dots, are discussed to address environmental degradation challenges. Practical applications of this technology against various plant viruses and its potential to ensure food security are emphasized. The review also delves into regulatory considerations, risk assessments, and the challenges associated with off-target effects and pathogen resistance. By evaluating both opportunities and limitations, this review underscores the role of exogenous dsRNA as a sustainable solution for achieving viral disease resistance in plants.

Leveraging RNA interference technology for selective and sustainable crop protection

Double-stranded RNA (dsRNA) has emerged as key player in gene silencing for the past two decades. Tailor-made dsRNA is now recognized a versatile raw material, suitable for a wide range of applications in biopesticide formulations, including insect control to pesticide resistance management. The mechanism of RNA interference (RNAi) acts at the messenger RNA (mRNA) level, utilizing a sequence-dependent approach that makes it unique in term of effectiveness and specificity compared to conventional agrochemicals. Two primary categories of small RNAs, known as short interfering RNAs (siRNAs) and microRNAs (miRNAs), function in both somatic and germline lineages in a broad range of eukaryotic species to regulate endogenous genes and to defend the genome from invasive nucleic acids. Furthermore, the application of RNAi in crop protection can be achieved by employing plant-incorporated protectants through plant transformation, but also by non-transformative strategies such as the use of formulations of sprayable RNAs as direct control agents, resistance factor repressors or developmental disruptors. This review explores the agricultural applications of RNAi, delving into its successes in pest-insect control and considering its broader potential for managing plant pathogens, nematodes, and pests. Additionally, the use of RNAi as a tool for addressing pesticide-resistant weeds and insects is reviewed, along with an evaluation of production costs and environmental implications.

Silencing ACE1 Gene with dsRNA of Different Lengths Impairs Larval Development in Leptinotarsa decemlineata

In the search for effective strategies to control the Colorado Potato Beetle, RNA interference technology has emerged as a promising method due to its capacity to suppress genes selectively. Factors such as the target gene and double-stranded RNA (dsRNA) length are critical for optimizing gene silencing efficiency. In this study, we designed and synthesized in vitro dsRNAs of varying lengths targeting the ACE1 gene, which encodes the AChE1 isoform of acetylcholinesterase in the beetle. All tested dsRNA lengths (222 bp, 543 bp, 670 bp, and 870 bp) promoted transcript reduction. The 670 bp dsRNA was the most effective, reducing transcript levels by approximately 40% by day seven, followed by the 543 bp dsRNA. No significant differences were observed between the 222 bp and 870 bp dsRNAs. Furthermore, all of the dsRNA lengths resulted in reduced weight gain and increased mortality in larvae, with the 670 bp dsRNA showing the highest mortality rate, leaving only 63% larval survival, a trend that persisted through day nine. These findings emphasize that dsRNA length is a key factor in the silencing response, underscoring the importance of selecting the optimal length while considering the gene's target, stability, and delivery methods. This study contributes to establishing design criteria for dsRNA, aiding in the development of more effective and sustainable pest management strategies.

RNAi-biofungicides: a quantum leap for tree fungal pathogen management

Fungal diseases threaten the forest ecosystem, impacting tree health, productivity, and biodiversity. Conventional approaches to combating diseases, such as biological control or fungicides, often reach limits regarding efficacy, resistance, non-target organisms, and environmental impact, enforcing alternative approaches. From an environmental and ecological standpoint, an RNA interference (RNAi) mediated double-stranded RNA (dsRNA)-based strategy can effectively manage forest fungal pathogens. The RNAi approach explicitly targets and suppresses gene expression through a conserved regulatory mechanism. Recently, it has evolved to be an effective tool in combating fungal diseases and promoting sustainable forest management approaches. RNAi bio-fungicides provide efficient and eco-friendly disease control alternatives using species-specific gene targeting, minimizing the off-target effects. With accessible data on fungal disease outbreaks, genomic resources, and effective delivery systems, RNAi-based biofungicides can be a promising tool for managing fungal pathogens in forests. However, concerns regarding the environmental fate of RNAi molecules and their potential impact on non-target organisms require an extensive investigation on a case-to-case basis. The current review critically evaluates the feasibility of RNAi bio-fungicides against forest pathogens by delving into the accessible delivery methods, environmental persistence, regulatory aspects, cost-effectiveness, community acceptance, and plausible future of RNAi-based forest protection products.

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.

Conjoined partners: efficacy and side effects of grafting and dsRNA application on the microbial endophyte population of grapevine plants inoculated with two esca-related fungal pathogens

Grafting has been exploited since 7000 BC to enhance productivity, disease resistance, and adaptability of cultivated plants to stressful conditions especially in woody crops such as grapevine (Vitis spp.). In contrast, the application of sequence specific double-stranded RNAs (dsRNAs) to control fungal pathogens and insect pests has only been recently developed. The possibility of combining these approaches to enhance plant resilience, reducing reliance on pesticides, offers new perspectives for a more sustainable agriculture. In this study, we assessed the potential of utilizing dsRNAs to enhance resilience against esca-related wood fungal pathogens in grapevine, considering various rootstock-scion combinations. The results showed that the scion genotype modulates the ability of the rootstock to cope with the inoculated wood fungal pathogens, mainly by altering the efficacy of producing stilbene compounds. Additionally, we found that dsRNAs reduced the growth of two inoculated esca-related fungal pathogens but they did not completely stop their colonization. Furthermore, wood microbiome data showed that the scion genotype (always belonging to Vitis vinifera species) was also able to influence the rootstock-associated microbiota, with a major effect on the fungal community. Lastly, adverse effects on non-target microorganisms are reported, raising questions on the environmental fate of dsRNAs and how dsRNAs can directly or indirectly affect plant-associated microbial communities.

Silence is not always golden: A closer look at potential environmental and ecotoxicological impacts of large-scale dsRNA application

RNA interference (RNAi) technology has emerged as a pivotal strategy in sustainable pest management, offering a targeted approach that significantly mitigates the environmental and health risks associated with traditional insecticides. Originally implemented through genetically modified organisms (GMOs) to produce specific RNAi constructs, the technology has evolved in response to public and regulatory concerns over GMOs. This evolution has spurred the development of non-transgenic RNAi applications such as spray-induced gene silencing (SIGS), which employs double-stranded RNA (dsRNA) to silence pest genes directly without altering the plant's genetic makeup. Despite its advantages in specificity and reduced ecological footprint, SIGS faces significant obstacles, particularly the instability of dsRNA in field conditions, which limits its practical efficacy. To overcome these limitations, innovative delivery mechanisms have been developed. These include nanotechnology-based systems, minicells, and nanovesicles, which are designed to protect dsRNA from degradation and enhance its delivery to target organisms. While these advancements have improved the stability and application efficiency of dsRNA, comprehensive assessments of their environmental safety and the potential for increased exposure risks to non-target organisms remain incomplete. This comprehensive review aims to elucidate the environmental fate of dsRNA and evaluate the potential risks associated with its widespread application on non-target organisms, encompassing soil microorganisms, beneficial insects, host plants, and mammals. The objective is to establish a more refined framework for RNAi risk assessment within environmental and ecotoxicological contexts, thereby fostering the development of safer, non-transgenic RNAi-based pest control strategies.

Biosafety aspects of RNAi-based pests control

While the overuse of classical chemical pesticides has had a detrimental impact on the environment and human health, the discovery of RNA interference (RNAi) offered the opportunity to develop new and sustainable approaches for pest management. RNAi is a naturally occurring regulation and defense mechanism that can be exploited to effectively protect crops by silencing key genes affecting the growth, development, behavior or fecundity of pests. However, as with all technologies, there is a range of potential risks and challenges associated with the application of RNAi, such as dsRNA stability, the potential for off-target effects, the safety of non-target organisms, and other application challenges. A better understanding of the molecular mechanisms involved in RNAi and in-depth discussion and analysis of these associated safety risks, is required to limit or mitigate potential adverse effects. © 2024 Society of Chemical Industry.

Arpc2 integrates ecdysone and juvenile hormone metabolism to influence metamorphosis and reproduction in Tribolium castaneum

BACKGROUND

Actin-related protein 2/3 complex regulates actin polymerization and the formation of branched actin networks. However, the function and evolutionary relationship of this complex subunit 2 (Arpc2) has been poorly understood in insects.

RESULTS

To address these issues, we performed comprehensive analysis of Arpc2 in Tribolium castaneum. Phylogenetic analysis revealed that Arpc2 was originated from one ancestral gene in animals but evolved independently between vertebrates and insects after species differentiation. T. castaneum Arpc2 has a 906-bp coding sequence and consists of 4 exons. Arpc2 transcripts were abundantly detected in embryos and pupae but less so in larvae and adults, while it had high expression in the gut, fat body and head but low expression in the epidermis of late-stage larvae. Knockdown of it at the late larval stage inhibited the pupation and resulted in arrested larvae. Silencing it in 1-day pupae impaired eclosion, which caused adult wings to fail to close. Injection of Arpc2 dsRNAs into 5-day pupae made adults have smaller testis and ovary and could not lay eggs. The expression of vitellogenin 1 (Vg1), Vg2 and Vg receptor (VgR) was downregulated after knocking down Arpc2 5 days post-adult emergence. Arpc2 silencing reduced 20-hydroxyecdysone titer by affecting the enzymes of its biosynthesis and catabolism but increased juvenile biosynthesis via upregulating JHAMT3 expression.

CONCLUSION

Our results indicate that Arpc2 is associated with the metamorphosis and reproduction by integrating ecdysone and juvenile hormone metabolism in T. castaneum. This study provides theoretical basis for developing Arpc2 as a potential RNA interference target for pest control. © 2024 Society of Chemical Industry.

Host-Delivered RNA Interference for Durable Pest Resistance in Plants: Advanced Methods, Challenges, and Applications

Insect-pests infestation greatly affects global agricultural production and is projected to become more severe in upcoming years. There is concern about pesticide application being ineffective due to insect resistance and environmental toxicity. Reduced effectiveness of Bt toxins also made the scientific community shift toward alternative strategies to control devastating agricultural pests. With the advent of host-delivered RNA interference, also known as host-induced gene silencing, targeted insect genes have been suppressed through genetic engineering tools to deliver a novel insect-pest resistance strategy for combating a number of agricultural pests. This review recapitulates the possible mechanism of host-delivered RNA interference (HD-RNAi), in particular, the silencing of target genes of insect-pests. We emphasize the development of the latest strategies against evolving insect targets including designing of artificial microRNAs, vector constructs, and the benefit of using plastid transformation to transform target RNA-interfering genes. Advantages of using HD-RNAi over other small RNA delivery modes and also the supremacy of HD-RNAi over the CRISPR-Cas system particularly for insect resistance have been described. However, the broader application of this technology is restricted due to its several limitations. Using artificial miRNA designs, the host-delivered RNAi + Bt combinatorial approach and chloroplast transformation can overcome limitations of RNAi. With careful design and delivery approaches, RNAi promises to be extremely valuable and effective plant protection strategy to attain durable insect-pest resistance in crops.

Exogenous Application of dsRNA in Plant Protection: Efficiency, Safety Concerns and Risk Assessment

The use of double-stranded RNA (dsRNA) for plant protection shows great potential as a sustainable alternative to traditional pesticides. This review summarizes the current state of knowledge on using exogenous dsRNA in plant protection and includes the latest findings on the safety and efficiency of this strategy. The review also emphasizes the need for a cautious and comprehensive approach, considering safety considerations such as off-target effects and formulation challenges. The regulatory landscape in different regions is also discussed, underscoring the need for specific guidelines tailored to dsRNA-based pesticides. The review provides a crucial resource for researchers, regulators, and industry stakeholders, promoting a balanced approach incorporating innovation with thorough safety assessments. The continuous dialog emphasized in this review is essential for shaping the future of dsRNA-based plant protection. As the field advances, collaboration among scientists, regulators, and industry partners will play a vital role in establishing guidelines and ensuring the responsible, effective, and sustainable use of dsRNA in agriculture.

Gene silencing in the aedine cell lines C6/36 and U4.4 using long double-stranded RNA

BACKGROUND

RNA interference (RNAi) is a target-specific gene silencing method that can be used to determine gene functions and investigate host-pathogen interactions, as well as facilitating the development of ecofriendly pesticides. Commercially available transfection reagents (TRs) can improve the efficacy of RNAi. However, we currently lack a product and protocol for the transfection of insect cell lines with long double-stranded RNA (dsRNA).

METHODS

We used agarose gel electrophoresis to determine the capacity of eight TRs to form complexes with long dsRNA. A CellTiter-Glo assay was then used to assess the cytotoxicity of the resulting lipoplexes. We also measured the cellular uptake of dsRNA by fluorescence microscopy using the fluorophore Cy3 as a label. Finally, we analyzed the TRs based on their transfection efficacy and compared the RNAi responses of Aedes albopictus C6/36 and U4.4 cells by knocking down an mCherry reporter Semliki Forest virus in both cell lines.

RESULTS

The TRs from Biontex (K4, Metafectene Pro, and Metafectene SI+) showed the best complexing capacity and the lowest dsRNA:TR ratio needed for complete complex formation. Only HiPerFect was unable to complex the dsRNA completely, even at a ratio of 1:9. Most of the complexes containing mCherry-dsRNA were nontoxic at 2 ng/µL, but Lipofectamine 2000 was toxic at 1 ng/µL in U4.4 cells and at 2 ng/µL in C6/36 cells. The transfection of U4.4 cells with mCherry-dsRNA/TR complexes achieved significant knockdown of the virus reporter. Comparison of the RNAi response in C6/36 and U4.4 cells suggested that C6/36 cells lack the antiviral RNAi response because there was no significant knockdown of the virus reporter in any of the treatments.

CONCLUSIONS

C6/36 cells have an impaired RNAi response as previously reported. This investigation provides valuable information for future RNAi experiments by showing how to mitigate the adverse effects attributed to TRs. This will facilitate the judicious selection of TRs and transfection conditions conducive to RNAi research in mosquitoes.

Lethal and sublethal effects of orally delivered double-stranded RNA on the cabbage stem flea beetle, Psylliodes chrysocephala

BACKGROUND

The cabbage stem flea beetle (Psylliodes chrysocephala) is one of the most important insect pests of oilseed rape (Brassica napus) in northern Europe. The emergence of insecticide-resistant populations and the ban on neonicotinoid seed treatments have made the management of this pest challenging and research is needed to develop alternative strategies such as RNA interference (RNAi). We investigated lethal and sublethal effects of orally delivered double-stranded (ds)RNAs targeting P. chrysocephala orthologs of Sec23 and vacuolar adenosine triphosphatase subunit G (VatpG), which are involved in endoplasmic reticulum-Golgi transport and organelle acidification, respectively.

RESULTS

Feeding bioassays on P. chrysocephala adults showed that the highest concentration (200 ng/leaf disk) of dsSec23 caused mortalities of 76% and 56% in pre-aestivating and post-aestivating beetles, respectively, while the same concentration of dsVatpG led to mortality rates of ~34% in both stages. Moreover, sublethal effects, such as decreased feeding rates and attenuated locomotion were observed. Small RNA sequencing and gene expression measurements following the delivery of dsRNAs demonstrated the generation of ~21 nucleotide-long small interfering RNAs and a systemic RNAi response in P. chrysocephala.

CONCLUSION

We demonstrate that P. chrysocephala is a promising candidate for developing RNAi-based pest management strategies. Further research is necessary to identify more effective target genes and to assess potential non-target effects. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

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.

Outlook on RNAi-Based Strategies for Controlling Culicoides Biting Midges

Culicoides are small biting midges with the capacity to transmit important livestock pathogens around much of the world, and their impacts on animal welfare are likely to expand. Hemorrhagic diseases resulting from Culicoides-vectored viruses, for example, can lead to millions of dollars in economic damages for producers. Chemical insecticides can reduce Culicoides abundance but may not suppress population numbers enough to prevent pathogen transmission. These insecticides can also cause negative effects on non-target organisms and ecosystems. RNA interference (RNAi) is a cellular regulatory mechanism that degrades mRNA and suppresses gene expression. Studies have examined the utility of this mechanism for insect pest control, and with it, have described the hurdles towards producing, optimizing, and applying these RNAi-based products. These methods hold promise for being highly specific and environmentally benign when compared to chemical insecticides and are more transient than engineering transgenic insects. Given the lack of available control options for Culicoides, RNAi-based products could be an option to treat large areas with minimal environmental impact. In this study, we describe the state of current Culicoides control methods, successes and hurdles towards using RNAi for pest control, and the necessary research required to bring an RNAi-based control method to fruition for Culicoides midges.

RNA-Based Control of Fungal Pathogens in Plants

Our duty to conserve global natural ecosystems is increasingly in conflict with our need to feed an expanding population. The use of conventional pesticides not only damages the environment and vulnerable biodiversity but can also still fail to prevent crop losses of 20-40% due to pests and pathogens. There is a growing call for more ecologically sustainable pathogen control measures. RNA-based biopesticides offer an eco-friendly alternative to the use of conventional fungicides for crop protection. The genetic modification (GM) of crops remains controversial in many countries, though expression of transgenes inducing pathogen-specific RNA interference (RNAi) has been proven effective against many agronomically important fungal pathogens. The topical application of pathogen-specific RNAi-inducing sprays is a more responsive, GM-free approach to conventional RNAi transgene-based crop protection. The specific targeting of essential pathogen genes, the development of RNAi-nanoparticle carrier spray formulations, and the possible structural modifications to the RNA molecules themselves are crucial to the success of this novel technology. Here, we outline the current understanding of gene silencing pathways in plants and fungi and summarize the pioneering and recent work exploring RNA-based biopesticides for crop protection against fungal pathogens, with a focus on spray-induced gene silencing (SIGS). Further, we discuss factors that could affect the success of RNA-based control strategies, including RNA uptake, stability, amplification, and movement within and between the plant host and pathogen, as well as the cost and design of RNA pesticides.

Double-stranded RNA (dsRNA) technology to control forest insect pests and fungal pathogens: challenges and opportunities

Climate change alters the seasonal synchronization between plants and respective pests plus pathogens. The geographical infiltration helps to shift their hosts, resulting in novel outbreaks that damage forests and ecology. Traditional management schemes are unable to control such outbreaks, therefore unconventional and competitive governance is needed to manage forest pests and pathogens. RNA interference (RNAi) mediated double-stranded RNA (dsRNA) treatment method can be implemented to protect forest trees. Exogenous dsRNA triggers the RNAi-mediated gene silencing of a vital gene, and suspends protein production, resulting in the death of targeted pathogens and pests. The dsRNA treatment method is successful for many crop insects and fungi, however, studies of dsRNA against forest pests and pathogens are depleting. Pesticides and fungicides based on dsRNA could be used to combat pathogens that caused outbreaks in different parts of the world. Although the dsRNA has proved its potential, the crucial dilemma and risks including species-specific gene selection, and dsRNA delivery methods cannot be overlooked. Here, we summarized the major fungi pathogens and insect pests that have caused outbreaks, their genomic information, and studies on dsRNA fungi-and pesticides. Current challenges and opportunities in dsRNA target decision, delivery using nanoparticles, direct applications, and a new method using mycorrhiza for forest tree protection are discussed. The importance of affordable next-generation sequencing to minimize the impact on non-target species is discussed. We suggest that collaborative research among forest genomics and pathology institutes could develop necessary dsRNA strategies to protect forest tree species.

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.

Towards dsRNA-integrated protection of medical Cannabis crops: considering human safety, recent- and developing RNAi methods, and research inroads

Owing to the expanding industry of medical Cannabis, we discuss recent milestones in RNA interference (RNAi)-based crop protection research and development that are transferable to medical Cannabis cultivation. Recent and prospective increases in pest pressure in both indoor and outdoor Cannabis production systems, and the need for effective nonchemical pest control technologies (particularly crucial in the context of cultivating plants for medical purposes), are discussed. We support the idea that developing RNAi tactics towards protection of medical Cannabis could play a major role in maximizing success in this continuously expanding industry. However, there remain critical knowledge gaps, especially with regard to RNA pesticide biosafety from a human toxicological viewpoint, as a result of the medical context of Cannabis product use. Furthermore, efforts are needed to optimize transformation and micropropagation of Cannabis plants, examine cutting edge RNAi techniques for various Cannabis-pest scenarios, and investigate the combined application of RNAi- and biological control tactics in medical Cannabis cultivation. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Complete protection from Henosepilachna vigintioctopunctata by expressing long double-stranded RNAs in potato plastids

RNA interference (RNAi) has emerged as a powerful technology for pest management. Previously, we have shown that plastid-mediated RNAi (PM-RNAi) can be utilized to control the Colorado potato beetle, an insect pest in the Chrysomelidae family; however, whether this technology is suitable for controlling pests in the Coccinellidae remained unknown. The coccinellid 28-spotted potato ladybird (Henosepilachna vigintioctopunctata; HV) is a serious pest of solanaceous crops. In this study, we identified three efficient target genes (β-Actin, SRP54, and SNAP) for RNAi using in vitro double-stranded RNAs (dsRNAs) fed to HV, and found that dsRNAs targeting β-Actin messenger RNA (dsACT) induced more potent RNAi than those targeting the other two genes. We next generated transplastomic and nuclear transgenic potato (Solanum tuberosum) plants expressing HV dsACT. Long dsACT stably accumulated to up to 0.7% of the total cellular RNA in the transplastomic plants, at least three orders of magnitude higher than in the nuclear transgenic plants. Notably, the transplastomic plants also exhibited a significantly stronger resistance to HV, killing all larvae within 6 d. Our data demonstrate the potential of PM-RNAi as an efficient pest control measure for HV, extending the application range of this technology to Coccinellidae pests.

Potential effects of RNA interference of Asian longhorned beetle on its parasitoid

BACKGROUND

It is important to understand how non-target insects such as parasitoids may be impacted directly or indirectly by RNA interference with double-stranded RNA (dsRNA) that has emerged as a novel pest control tool. We examined the potential effects of a dsRNA targeting an inhibitor of apoptosis (IAP) of the Asian longhorned beetle Anoplophora glabripennis on its gregarious larval ectoparasitoid Ontsira mellipes, directly on adult wasp's survival via injection of 4 μg of dsIAP per wasp, and indirectly on the detectability and suitability of host larvae injected with 2, 4 or 8 μg of dsIAP per larva.

RESULTS

Compared with no injection or injection with a control dsGFP targeting a region of gene coding for a green fluorescence protein (GFP), dsIAP did not affect adult wasp's survival. Ontsira mellipes locates hosts in the wood by sensing their movement. Host larvae did not completely cease movement after the injection of dsIAP and were still detected and parasitized. Clutch size was reduced and only 3.8% of the parasitoid offspring developed into adults on host larvae treated at the highest dose. However, clutch size was not affected and 25.5% of the parasitoid offspring developed into adults on host larvae treated at the lowest dose. The fitness of developed wasps (development time, sex ratio, body size, and fecundity) was not affected when compared to the control treatments. No dsIAP was detected in parasitoid larvae.

CONCLUSION

The results show no direct effect of the dsRNA on its parasitoid, but the potential indirect effect of dsRNA-affected host on the parasitoid, which may be minimized through optimizing dsRNA dosage to promote compatible applications of both management options for this invasive forest pest. © 2022 Society of Chemical Industry. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

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.

Topical delivery of dsRNA in two hemipteran species: Evaluation of RNAi specificity and non-target effects

Double-stranded (ds) RNA-based technologies could provide novel and potential tool for pest management with efficiency and specificity of action. However, before applying this technique in the field, it is necessary to identify effective delivery methods and evaluate the non-target effects that may occur. In this article, we evaluated the effectiveness of dsRNA by topical delivery on a species of great agricultural interest, Halyomorpha halys. The specificity of action of the dsRNA was also investigated in Rhodnius prolixus, an insect phylogenetically close to H. halys. Of the three investigated genes (putative ATPase N2B, ATPase, serine/threonine-protein phosphatase PP1-β catalytic subunit, PP1, and IAP repeat-containing protein 7-B-like, IAP), IAP and ATPase were able to induce higher mortality in H. halys nymphs compared to the control, with specific concentrations for each gene targeted. However, when the same RNAs were topically delivered to both R. prolixus 2nd and 3rd instar nymphs, no gene silencing and mortality were observed. For this reason, to assess dsRNA application-mediated non-target effects, we injected both H. halys and R. prolixus specific dsRNA in R. prolixus 5th instar nymphs. When the dsRNA targeting H. halys IAP was microinjected into R. prolixus 5th instar nymphs, no mortality was observed, suggesting a strong RNAi specificity. Together, these data suggest that the topical delivery could be suitable for the dsRNA to control H. halys population. Furthermore, its specificity of action would allow treatments towards single harmful species with limited non-target effects.

Pesticide soil microbial toxicity: setting the scene for a new pesticide risk assessment for soil microorganisms (IUPAC Technical Report)

Pesticides constitute an integral part of modern agriculture. However, there are still concerns about their effects on non-target organisms. To address this the European Commission has imposed a stringent regulatory scheme for new pesticide compounds. Assessment of the aquatic toxicity of pesticides is based on a range of advanced tests. This does not apply to terrestrial ecosystems, where the toxicity of pesticides on soil microorganisms, is based on an outdated and crude test (N mineralization). This regulatory gap is reinforced by the recent methodological and standardization advances in soil microbial ecology. The inclusion of such standardized tools in a revised risk assessment scheme will enable the accurate estimation of the toxicity of pesticides on soil microorganisms and on associated ecosystem services. In this review we (i) summarize recent work in the assessment of the soil microbial toxicity of pesticides and point to ammonia-oxidizing microorganisms (AOM) and arbuscular mycorrhizal fungi (AMF) as most relevant bioindicator groups (ii) identify limitations in the experimental approaches used and propose mitigation solutions, (iii) identify scientific gaps and (iv) propose a new risk assessment procedure to assess the effects of pesticides on soil microorganisms.

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.

Risk assessment of RNAi-based pesticides to non-target organisms: Evaluating the effects of sequence similarity in the parasitoid wasp Telenomus podisi

RNA interference (RNAi)-based pesticides are promising novel pest management products that might reduce environmental impacts compared to other pesticides. Their sequence-guided mode of action facilitates a high species-selectivity, preventing harm on non-target organisms. However, there is currently no consensus on the minimum needed sequence similarity for efficient RNAi in insects and studies have shown that adverse effects in non-targets cannot always be ruled out a priori. This study investigates the effects of exposing the parasitoid wasp Telenomus podisi to double-stranded RNA (dsRNA) which is lethal to its host, the Neotropical brown stink bug Euschistus heros. Feeding T. podisi with wasp-specific dsRNA targeting the vATPase A and actin-2 genes led to 76.4 ± 9.9% and 76.7 ± 8.8% mortality respectively, demonstrating that dietary RNAi is functional in T. podisi. When feeding T. podisi with E. heros-specific dsRNA targeting the same genes, no lethal or sublethal effects were observed. To link sequence similarity to potential gene silencing effects in the parasitoids, the expression of genes showing the highest degree of similarity (17-21 nucleotide matches) with these two target genes was monitored and was found unaffected by the E. heros-specific dsRNA. Our study confirms that RNAi was in this case highly specific and that for E. heros, RNAi-based pesticides can be used complementary to biological control in an integrated pest management context.

Uniting RNAi Technology and Conservation Biocontrol to Promote Global Food Security and Agrobiodiversity

Habitat loss and fragmentation, and the effects of pesticides, contribute to biodiversity losses and unsustainable food production. Given the United Nation's (UN's) declaration of this decade as the UN Decade on Ecosystem Restoration, we advocate combining conservation biocontrol-enhancing practices with the use of RNA interference (RNAi) pesticide technology, the latter demonstrating remarkable target-specificity via double-stranded (ds)RNA's sequence-specific mode of action. This specificity makes dsRNA a biosafe candidate for integration into the global conservation initiative. Our interdisciplinary perspective conforms to the UN's declaration, and is facilitated by the Earth BioGenome Project, an effort valuable to RNAi development given its utility in providing whole-genome sequences, allowing identification of genetic targets in crop pests, and potentially relevant sequences in non-target organisms. Interdisciplinary studies bringing together biocontrol-enhancing techniques and RNAi are needed, and should be examined for various crop‒pest systems to address this global problem.

RNA Interference Suppression of v-ATPase B and Juvenile Hormone Binding Protein Genes Through Topically Applied dsRNA on Tomato Leaves: Developing Biopesticides to Control the South American Pinworm, Tuta absoluta (Lepidoptera: Gelechiidae)

The South American pinworm Tuta absoluta (Meyrick) (Family: Gelechiidae) is one of the most devastating lepidopteran pests in the developing countries of South America, Africa, and Asia. This pest is classified as the most serious threat for tomato production worldwide. In the present study, we analyzed RNAi-mediated control through exogenously applied dsRNA delivery on tomato. The dsRNA treatments were made to target the juvenile hormone binding protein and the v-ATPase B. Both mRNA targets were cloned, validated by sequencing, and used to produce each dsRNA. After treatments the relative transcript expression was analyzed using qRTPCR to assess to efficacy of RNAi. A leaf-dip assay was used to provide late 2nd instar larvae three feeding access periods: 24, 48, and 72 h, to evaluate the effect of gene silencing of each target. Larvae were fed tomato leaves coated with five different RNAi concentrations (10, 20, 30, 40, and 50 micrograms/centimeter-squared), that suppressed two genes (juvenile hormone protein, JHBP, and vacuolar-type adenosine triphosphatase enzyme, v-ATPase). Treatments with dsRNA showed a significant increase in mortality at 24, 48, and 72 h after ingestion (P < 0.01, α = 0.05), along with reduced leaf damage, and increased feeding deterrence. The results suggest that these two RNAi products may provide a suitable treatment for control of this and other lepidopteran pests.

Mechanisms of Cell Entry by dsRNA Viruses: Insights for Efficient Delivery of dsRNA and Tools for Improved RNAi-Based Pest Control

While RNAi is often heralded as a promising new strategy for insect pest control, a major obstacle that still remains is the efficient delivery of dsRNA molecules within the cells of the targeted insects. However, it seems overlooked that dsRNA viruses already have developed efficient strategies for transport of dsRNA molecules across tissue barriers and cellular membranes. Besides protecting their dsRNA genomes in a protective shell, dsRNA viruses also display outer capsid layers that incorporate sophisticated mechanisms to disrupt the plasma membrane layer and to translocate core particles (with linear dsRNA genome fragments) within the cytoplasm. Because of the perceived efficiency of the translocation mechanism, it is well worth analyzing in detail the molecular processes that are used to achieve this feat. In this review, the mechanism of cell entry by dsRNA viruses belonging to the Reoviridae family is discussed in detail. Because of the large amount of progress in mammalian versus insect models, the mechanism of infections of reoviruses in mammals (orthoreoviruses, rotaviruses, orbiviruses) will be treated as a point of reference against which infections of reoviruses in insects (orbiviruses in midges, plant viruses in hemipterans, insect-specific cypoviruses in lepidopterans) will be compared. The goal of this discussion is to uncover the basic principles by which dsRNA viruses cross tissue barriers and translocate their cargo to the cellular cytoplasm; such knowledge subsequently can be incorporated into the design of dsRNA virus-based viral-like particles for optimal delivery of RNAi triggers in targeted insect pests.

Assessment on effects of transplastomic potato plants expressing Colorado potato beetle β-Actin double-stranded RNAs for three non-target pests

RNA interference has been proved as an efficient technology for pest control through the silencing of essential genes of targeted insects. We had previously shown that the expression of double-stranded RNAs (dsRNAs) in plastids of plants offers a great potential for efficiently controlling Colorado potato beetle (CPB, Leptinotarsa decemlineata) (Coleoptera, Chrysomelidae). However, whether these transplastomic plants have an impact on other non-target pests was not investigated. In this study, we evaluated the potential effects of transplastomic plants expression dsRNAs target CPB β-Actin (referred to as ACT plants) on three other potato pests: Myzus persicae (Hemiptera, Aphididae), Henosepilachna vigintioctopunctata (Coleoptera, Coccinellidae), and Spodoptera litura (Lepidoptera, Noctuidae). Although no effects on M. persicae or S. litura were observed by feeding ACT plants, we found that feeding H. vigintioctopunctata with ACT plants can result in its growth retardation and suppressing the gene expression of HvACT, which has 91.7% identity to CPB β-Actin and shared 66 potential 21-mer matches. Taking together, these results indicated that ACT plants had cross-resistance to H. vigintioctopunctata, another coleopteran insect with the highly conserved nucleotide sequence of β-Actin gene. It also provided an opportunity to simultaneously control L. decemlineata and H. vigintioctopunctata by RNAi induced by intermediate dsRNAs with optimized sequences.

Optimizing Efficient RNAi-Mediated Control of Hemipteran Pests (Psyllids, Leafhoppers, Whitefly): Modified Pyrimidines in dsRNA Triggers

The advantages from exogenously applied RNAi biopesticides have yet to be realized in through commercialization due to inconsistent activity of the dsRNA trigger, and the activity level of RNAi suppression. This has prompted research on improving delivery methods for applying exogenous dsRNA into plants and insects for the management of pests and pathogens. Another aspect to improve RNAi activity is the incorporation of modified 2′-F pyrimidine nucleotides into the dsRNA trigger. Modified dsRNA incorporating 32–55% of the 2′-F- nucleotides produced improved RNAi activity that increased insect mortality by 12–35% greater than non-modified dsRNA triggers of the same sequence. These results were repeatable across multiple Hemiptera: the Asian citrus psyllid (Diaphorina citri, Liviidae); whitefly (Bemisia tabaci, Aleyroididae); and the glassy-winged sharpshooter (Homalodisca vitripennis, Cicadellidae). Studies using siRNA with modified 2′-F- pyrimidines in mammalian cells show they improved resistance to degradation from nucleases, plus result in greater RNAi activity, due to increase concentrations and improved binding affinity to the mRNA target. Successful RNAi biopesticides of the future will be able to increase RNAi repeatability in the field, by incorporating modifications of the dsRNA, such as 2′-F- pyrimidines, that will improve delivery after applied to fruit trees or crop plants, with increased activity after ingestion by insects. Costs of RNA modification have decreased significantly over the past few years such that biopesticides can now compete on pricing with commercial chemical products.

Considerations and Regulatory Approaches in the USA and in the EU for dsRNA-Based Externally Applied Pesticides for Plant Protection

Increasing pest and pathogen challenges as well as having fewer conventional pesticides to employ require innovative and sustainable solutions for plant protection. One group of pesticides that is in the pipeline and is expected to be subject to regulation and risk assessment procedures in the near future, is based on the natural gene silencing mechanism RNA interference (RNAi). These dsRNA-based products can be highly specific for a target organism due to the sequence-specific interaction between effective small interfering RNAs (siRNAs) and a complementary target RNA. General regulatory frameworks for pesticide authorization in the U.S. and in the EU are presented. In addition, production and application procedures and specific characteristics of dsRNA-based pesticides relevant for risk assessment and regulation are considered.

Evaluating toxicity of Varroa mite (Varroa destructor)-active dsRNA to monarch butterfly (Danaus plexippus) larvae

Varroa mites (Varroa destructor) are parasitic mites that, combined with other factors, are contributing to high levels of honey bee (Apis mellifera) colony losses. A Varroa-active dsRNA was recently developed to control Varroa mites within honey bee brood cells. This dsRNA has 372 base pairs that are homologous to a sequence region within the Varroa mite calmodulin gene (cam). The Varroa-active dsRNA also shares a 21-base pair match with monarch butterfly (Danaus plexippus) calmodulin mRNA, raising the possibility of non-target effects if there is environmental exposure. We chronically exposed the entire monarch larval stage to common (Asclepias syriaca) and tropical (Asclepias curassavica) milkweed leaves treated with concentrations of Varroa-active dsRNA that are one- and ten-fold higher than those used to treat honey bee hives. This corresponded to concentrations of 0.025-0.041 and 0.211-0.282 mg/g leaf, respectively. Potassium arsenate and a previously designed monarch-active dsRNA with a 100% base pair match to the monarch v-ATPase A mRNA (leaf concentration was 0.020-0.034 mg/g) were used as positive controls. The Varroa mite and monarch-active dsRNA's did not cause significant differences in larval mortality, larval or pupal development, pupal weights, or adult eclosion rates when compared to negative controls. Irrespective of control or dsRNA treatment, larvae that consumed approximately 7500 to 10,500-mg milkweed leaf within 10 to 12 days had the highest pupal weights. The lack of mortality and sublethal effects following dietary exposure to dsRNA with 21-base pair and 100% base pair match to mRNAs that correspond to regulatory genes suggest monarch mRNA may be refractory to silencing by dsRNA or monarch dsRNase may degrade dsRNA to a concentration that is insufficient to silence mRNA signaling.

Characterization of Halyomorpha halys TAR1 reveals its involvement in (E)-2-decenal pheromone perception

In insects, tyramine receptor 1 (TAR1) has been shown to control several physiological functions, including olfaction. We investigated the molecular and functional profile of the Halyomorpha halys type 1 tyramine receptor gene (HhTAR1) and its role in olfactory functions of this pest. Molecular and pharmacological analyses confirmed that the HhTAR1 gene codes for a true TAR1. RT-qPCR analysis revealed that HhTAR1 is expressed mostly in adult brain and antennae as well as in early development stages (eggs, 1st and 2nd instar nymphs). In particular, among the antennomeres that compose a typical H. halys antenna, HhTAR1 was more expressed in flagellomeres. Scanning electron microscopy investigation revealed the type and distribution of sensilla on adult H. halys antennae: both flagellomeres appear rich in trichoid and grooved sensilla, known to be associated with olfactory functions. Through an RNAi approach, topically delivered HhTAR1 dsRNA induced a 50% downregulation in gene expression after 24 h in H. halys 2nd instar nymphs. An innovative behavioural assay revealed that HhTAR1 RNAi-silenced 2nd instar nymphs were less susceptible to the alarm pheromone component (E)-2 decenal as compared with controls. These results provide critical information concerning the role of TAR1 in olfaction regulation, especially alarm pheromone reception, in H. halys. Furthermore, considering the emerging role of TAR1 as target of biopesticides, this work opens the way for further investigation on innovative methods for controlling H. halys.

dsRNA-Mediated Pest Management of Tuta absoluta Is Compatible with Its Biological Control Agent Nesidiocoris tenuis

Simple Summary

The zoophytophagous mirid bug Nesidiocoris tenuis is an efficient predator of the tomato leafminer, Tuta absoluta. RNA interference (RNAi) targeting the alphaCOP (αCOP) (Coatomer subunit alpha protein) gene of N. tenuis (Nt-αCOP) was proven to be functional in N. tenuis, causing downregulation of gene expression, mortality and sub-lethal effects. In contrast, when N. tenuis were fed with dsRNA (dsTa-αCOP) targeting the ortholog αCOP gene of T. absoluta, no lethal nor sub-lethal effects were observed. These results indicate the compatibility of this biocontrol agent along with RNAi-mediated management in order to suppress T. absoluta efficiently in tomato crop.

Abstract

RNAi-mediated insect pest management has recently shown promising results against the most serious pest of tomato, the tomato leafminer, Tuta absoluta. This study aimed to investigate whether dsRNA (dsTa-αCOP) designed to target the T. absoluta-αCOP gene could cause adverse effects to its biocontrol agent, the mirid predator, Nesidiocoris tenuis. Oral exposure of N. tenuis to dsRNA (dsNt-αCOP) designed to target N. tenuis-αCOP resulted in a 61%, 67% and 55% reduction in its transcript level in comparison to the sucrose, dsGFP and dsTa-αCOP treatments, respectively. In addition, significantly higher mortality of 57% was recorded in dsNt-αCOP-treated N. tenuis when compared to the sucrose (7%), dsGFP (10%) and dsTa-αCOP (10%) treatments. Moreover, the predation rate of ~33–39 Ephestia kuehniella eggs per N. tenuis adult dramatically reduced to almost half in the surviving dsNt-αCOP-treated N. tenuis. This worst-case exposure scenario confirmed for the first time that the RNAi machinery is functional in this species and that the risk of exposure through the oral route is possible. In contrast, dsTa-αCOP did not cause any sub-lethal effects to N. tenuis upon oral exposure. Oral exposure of T. absoluta to dsTa-αCOP resulted in 50% mortality. In the context of a biosafety risk assessment of RNAi-mediated insect management, investigating the effects on non-target organisms is essential in order to include this method as part of an integrated pest management strategy. Based on our laboratory assays, RNAi-mediated control is compatible with the biological control of T. absoluta by its natural enemy N. tenuis, adding the RNAi approach in the armoire of integrated pest management of T. absoluta.

RNAi-Mediated Suppression of Laccase2 Impairs Cuticle Tanning and Molting in the Cotton Boll Weevil (Anthonomus grandis)

The cotton boll weevil, Anthonomus grandis, is the most economically important pest of cotton in Brazil. Pest management programs focused on A. grandis are based mostly on the use of chemical insecticides, which may cause serious ecological impacts. Furthermore, A. grandis has developed resistance to some insecticides after their long-term use. Therefore, alternative control approaches that are more sustainable and have reduced environmental impacts are highly desirable to protect cotton crops from this destructive pest. RNA interference (RNAi) is a valuable reverse genetics tool for the investigation of gene function and has been explored for the development of strategies to control agricultural insect pests. This study aimed to evaluate the biological role of the Laccase2 (AgraLac2) gene in A. grandis and its potential as an RNAi target for the control of this insect pest. We found that AgraLac2 is expressed throughout the development of A. grandis with significantly higher expression in pupal and adult developmental stages. In addition, the immunolocalization of the AgraLac2 protein in third-instar larvae using specific antibodies revealed that AgraLac2 is distributed throughout the epithelial tissue, the cuticle and the tracheal system. We also verified that the knockdown of AgraLac2 in A. grandis resulted in an altered cuticle tanning process, molting defects and arrested development. Remarkably, insects injected with dsAgraLac2 exhibited defects in cuticle hardening and pigmentation. As a consequence, the development of dsAgraLac2-treated insects was compromised, and in cases of severe phenotypic defects, the insects subsequently died. On the contrary, insects subjected to control treatments did not show any visible phenotypic defects in cuticle formation and successfully molted to the pupal and adult stages. Taken together, our data indicate that AgraLac2 is involved in the cuticle tanning process in A. grandis and may be a promising target for the development of RNAi-based technologies.