Physiological Conditions and dsRNA Application Approaches for Exogenously induced RNA Interference in Arabidopsis thaliana

Regulation of Anthocyanin Accumulation in Tomato Solanum lycopersicum L. by Exogenous Synthetic dsRNA Targeting Different Regions of SlTRY Gene

RNA interference (RNAi) is a regulatory and protective mechanism that plays a crucial role in the growth, development, and control of plant responses to pathogens and abiotic stresses. In spray-induced gene silencing (SIGS), exogenous double-stranded RNAs (dsRNA) are used to efficiently regulate target genes via plant surface treatment. In this study, we aimed to evaluate the effect of specific exogenous dsRNAs on silencing different regions (promoter, protein-coding and intron) of the target SlTRY tomato gene, encoding an R3-type MYB repressor of anthocyanin biosynthesis. We also assessed the impact of targeting different SlTRY regions on the expression of genes involved in anthocyanin and flavonoid biosynthesis. This study demonstrated the critical importance of selecting the appropriate gene target region for dsRNA action. The highest inhibition of the SlTRY gene expression and activation of anthocyanin biosynthesis was achieved by dsRNA complementary to the protein-coding region of SlTRY gene, compared with dsRNAs targeting the SlTRY promoter or intron regions. Silencing the SlTRY gene increased the content of anthocyanins and boosted levels of other substances in the phenylpropanoid pathway, such as caffeoyl putrescine, chlorogenic acid, ferulic acid glucoside, feruloyl quinic acid, and rutin. This study is the first to examine the effects of four different dsRNAs targeting various regions of the SlTRY gene, an important negative regulator of anthocyanin biosynthesis.

Impact of Exogenous dsRNA on miRNA Composition in Arabidopsis thaliana

The application of double-stranded RNAs (dsRNAs) to plant surfaces has emerged as a promising tool for manipulating gene expression in plants and pathogens, offering new opportunities for crop improvement. While research has shown the capability of exogenous dsRNAs to silence genes, the full spectrum of their impact, particularly on the intricate network of microRNAs (miRNAs), remains largely unexplored. Here, we show that the exogenous application of chalcone synthase (CHS)-encoding dsRNA to the rosette leaves of Arabidopsis thaliana induced extensive alterations in the miRNA profile, while non-specific bacterial neomycin phosphotransferase II (NPTII) dsRNA had a minimal effect. Two days after treatment, we detected 60 differentially expressed miRNAs among the 428 miRNAs found in the A. thaliana genome. A total of 59 miRNAs were significantly changed after AtCHS-dsRNA treatment compared with water and NPTII-dsRNA, and 1 miRNA was significantly changed after AtCHS-dsRNA and NPTII-dsRNA compared with the water control. A comprehensive functional enrichment analysis revealed 17 major GO categories enriched among the genes potentially targeted by the up- and downregulated miRNAs. These categories included processes such as aromatic compound biosynthesis (a pathway directly related to CHS activity), heterocycle biosynthesis, RNA metabolism and biosynthesis, DNA transcription, and plant development. Several predicted targets of upregulated and downregulated miRNAs, including APETALA2, SCL27, SOD1, GRF1, AGO2, PHB, and PHV, were verified by qRT-PCR. The analysis showed a negative correlation between the expression of miRNAs and the expression of their predicted targets. Thus, exogenous plant gene-specific dsRNAs induce substantial changes in the plant miRNA composition, ultimately affecting the expression of a wide range of genes. These findings have profound implications for our understanding of the effects of exogenously induced RNA interference, which can have broader effects beyond targeted mRNA degradation, affecting the expression of other genes through miRNA regulation.

Simultaneous Application of Several Exogenous dsRNAs for the Regulation of Anthocyanin Biosynthesis in Arabidopsis thaliana

Plant surface treatment with double-stranded RNAs (dsRNAs) has gained recognition as a promising method for inducing gene silencing and combating plant pathogens. However, the regulation of endogenous plant genes by external dsRNAs has not been sufficiently investigated. Also, the effect of the simultaneous application of multiple gene-specific dsRNAs has not been analyzed. The aim of this study was to exogenously target five genes in Arabidopsis thaliana, namely, three transcription factor genes (AtCPC, AtMybL2, AtANAC032), a calmodulin-binding protein gene (AtCBP60g), and an anthocyanidin reductase gene (AtBAN), which are known as negative regulators of anthocyanin accumulation. Exogenous dsRNAs encoding these genes were applied to the leaf surface of A. thaliana either individually or in mixtures. The mRNA levels of the five targets were analyzed using qRT-PCR, and anthocyanin content was evaluated through HPLC-MS. The results demonstrated significant downregulation of all five target genes by the exogenous dsRNAs, resulting in enhanced expression of chalcone synthase (AtCHS) gene and increased anthocyanin content. The simultaneous foliar application of the five dsRNAs proved to be more efficient in activating anthocyanin accumulation compared to the application of individual dsRNAs. These findings hold considerable importance in plant biotechnology and gene function studies.

Exogenously Induced Silencing of Four MYB Transcription Repressor Genes and Activation of Anthocyanin Accumulation in Solanum lycopersicum

RNA interference (RNAi) is a natural post-transcriptional regulatory mechanism that can be artificially induced by exogenous application of double-stranded RNAs (dsRNAs) to the plant surfaces. Recent studies show that it is possible to silence plant genes and change plant properties using plant RNA spraying and other approaches for dsRNA delivery. In this study, we investigated the effect of exogenous gene-specific dsRNAs on the silencing of four tomato genes encoding MYB-family transcription repressors of anthocyanin biosynthesis in the leaves of tomato Solanum lycopersicum L. We found that the exogenous application of dsRNAs encoding for the SlMYBATV1, SlMYB32, SlMYB76, and SlTRY genes downregulated mRNA levels of these endogenous repressors of anthocyanin production, upregulated the expression of anthocyanin biosynthesis-related genes, and enhanced anthocyanin content in the leaves of S. lycopersicum. The data demonstrated that exogenous gene-specific dsRNAs can induce post-transcriptional gene silencing in tomato leaves by direct foliar application of dsRNAs. This approach may be used for plant secondary metabolism induction and as a silencing tool for gene function studies without the need to produce genetically modified plants.

Recent Advances in Nanoparticle-Mediated Co-Delivery System: A Promising Strategy in Medical and Agricultural Field

Drug and gene delivery systems mediated by nanoparticles have been widely studied for life science in the past decade. The application of nano-delivery systems can dramatically improve the stability and delivery efficiency of carried ingredients, overcoming the defects of administration routes in cancer therapy, and possibly maintaining the sustainability of agricultural systems. However, delivery of a drug or gene alone sometimes cannot achieve a satisfactory effect. The nanoparticle-mediated co-delivery system can load multiple drugs and genes simultaneously, and improve the effectiveness of each component, thus amplifying efficacy and exhibiting synergistic effects in cancer therapy and pest management. The co-delivery system has been widely reported in the medical field, and studies on its application in the agricultural field have recently begun to emerge. In this progress report, we summarize recent progress in the preparation and application of drug and gene co-delivery systems and discuss the remaining challenges and future perspectives in the design and fabrication.

Critical points for the design and application of RNA silencing constructs for plant virus resistance

Control of plant virus diseases is a big challenge in agriculture as is resistance in plant lines to infection by viruses. Recent progress using advanced technologies has provided fast and durable alternatives. One of the most promising techniques against plant viruses that is cost-effective and environmentally safe is RNA silencing or RNA interference (RNAi), a technology that could be used alone or along with other control methods. To achieve the goals of fast and durable resistance, the expressed and target RNAs have been examined in many studies, with regard to the variability in silencing efficiency, which is regulated by various factors such as target sequences, target accessibility, RNA secondary structures, sequence variation in matching positions, and other intrinsic characteristics of various small RNAs. Developing a comprehensive and applicable toolbox for the prediction and construction of RNAi helps researchers to achieve the acceptable performance level of silencing elements. Although the attainment of complete prediction of RNAi robustness is not possible, as it also depends on the cellular genetic background and the nature of the target sequences, some important critical points have been discerned. Thus, the efficiency and robustness of RNA silencing against viruses can be improved by considering the various parameters of the target sequence and the construct design. In this review, we provide a comprehensive treatise regarding past, present and future prospective developments toward designing and applying RNAi constructs for resistance to plant viruses.

Foliar Application of dsRNA Targeting Endogenous Potato (Solanum tuberosum) Isoamylase Genes ISA1, ISA2, and ISA3 Confers Transgenic Phenotype

Isoamylase (ISA) is a debranching enzyme found in many plants, which hydrolyzes (1-6)-α-D glucosidic linkages in starch, amylopectin, and β-dextrins, and is thought to be responsible for starch granule formation (ISA1 and ISA2) and degradation (ISA3). Lipid-modified PEI (lmPEI) was synthesized as a carrier for long double-stranded RNA (dsRNA, 250-bp), which targets the three isoamylase isoforms. The particles were applied to the plant via the foliar spray and were differentially effective in suppressing the expressions of ISA1 and ISA2 in the potato leaves, and ISA3 in the tubers. Plant growth was not significantly impaired, and starch levels in the tubers were not affected as well. Interestingly, the treated plants had significantly smaller starch granule sizes as well as increased sucrose content, which led to an early sprouting phenotype. We confirm the proposal of previous research that an increased number of small starch granules could be responsible for an accelerated turnover of glucan chains and, thus, the rapid synthesis of sucrose, and we propose a new relationship between ISA3 and the starch granule size. The implications of this study are in achieving a transgenic phenotype for endogenous plant genes using a systemic, novel delivery system, and foliar applications of dsRNA for agriculture.

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.

Nanovector-mediated exogenous delivery of dsRNA induces silencing of target genes in very young tomato flower buds

RNA interference (RNAi) is a post-translational regulatory mechanism that controls gene expression in plants. This process can be artificially induced by double-stranded RNA (dsRNA) molecules with sequence homology to target mRNAs. Exogenously applied dsRNA on leaves has been shown to silence virulence genes of fungi and viruses, conferring protection to plants. Coupling dsRNA to nanoparticles has been demonstrated to prolong the silencing effect. The ability of exogenous dsRNA to silence endogenous genes in plants is currently under debate, mainly due to the difficulty in delivering dsRNA into plant tissues and organs. Our study aims to develop a method based on the exogenous application of dsRNA on tomato flowers for silencing endogenous genes controlling ovary growth. Two methods of dsRNA delivery into tomato flower buds (i.e., pedicel soaking and injection) were compared to test their efficacy in silencing the tomato Aux/IAA9 (SlIAA9) gene, which encodes for a known repressor of ovary growth. We examined the silencing effect of dsRNA alone and coupled to layered double hydroxide (LDHs) nanoparticles. We found that injection into the pedicel led to the silencing of SlIAA9 and the efficacy of the method was confirmed by choosing a different ovary growth repressor gene (SlAGAMOUS-like 6; SlAGL6). The coupling of dsRNA to LDHs increased the silencing effect in the case of SlIAA9. Silencing of the two repressors caused an increase in ovary size only when flower buds were treated with dsRNA coupled to LDHs. RNA-Seq of small RNAs showed that induction of RNAi was caused by the processing of injected dsRNA. In this work, we demonstrate for the first time that exogenous dsRNA coupled to LDHs can induce post-transcriptional gene silencing in the young tomato ovary by injection into the flower pedicel. This method represents a silencing tool for the study of the molecular changes occurring during the early stages of ovary/fruit growth as a consequence of downregulation of target genes, without the need to produce transgenic plants stably expressing RNAi constructs.

RNAi as a Foliar Spray: Efficiency and Challenges to Field Applications

RNA interference (RNAi) is a powerful tool that is being increasingly utilized for crop protection against viruses, fungal pathogens, and insect pests. The non-transgenic approach of spray-induced gene silencing (SIGS), which relies on spray application of double-stranded RNA (dsRNA) to induce RNAi, has come to prominence due to its safety and environmental benefits in addition to its wide host range and high target specificity. However, along with promising results in recent studies, several factors limiting SIGS RNAi efficiency have been recognized in insects and plants. While sprayed dsRNA on the plant surface can produce a robust RNAi response in some chewing insects, plant uptake and systemic movement of dsRNA is required for delivery to many other target organisms. For example, pests such as sucking insects require the presence of dsRNA in vascular tissues, while many fungal pathogens are predominately located in internal plant tissues. Investigating the mechanisms by which sprayed dsRNA enters and moves through plant tissues and understanding the barriers that may hinder this process are essential for developing efficient ways to deliver dsRNA into plant systems. In this review, we assess current knowledge of the plant foliar and cellular uptake of dsRNA molecules. We will also identify major barriers to uptake, including leaf morphological features as well as environmental factors, and address methods to overcome these barriers.

Exogenous dsRNA Induces RNA Interference of a Chalcone Synthase Gene in Arabidopsis thaliana

Recent investigations have shown the possibility of artificial induction of RNA interference (RNAi) via plant foliar treatments with naked double-stranded RNA (dsRNA) to silence essential genes in plant fungal pathogens or to target viral RNAs. Furthermore, several studies have documented the downregulation of plant endogenous genes via external application of naked gene-specific dsRNAs and siRNAs to the plant surfaces. However, there are limited studies on the dsRNA processing and gene silencing mechanisms after external dsRNA application. Such studies would assist in the development of innovative tools for crop improvement and plant functional studies. In this study, we used exogenous gene-specific dsRNA to downregulate the gene of chalcone synthase (CHS), the key enzyme in the flavonoid/anthocyanin biosynthesis pathway, in Arabidopsis. The nonspecific NPTII-dsRNA encoding the nonrelated neomycin phosphotransferase II bacterial gene was used to treat plants in order to verify that any observed effects and processing of AtCHS mRNA were sequence specific. Using high-throughput small RNA (sRNA) sequencing, we obtained six sRNA-seq libraries for plants treated with water, AtCHS-dsRNA, or NPTII-dsRNA. After plant foliar treatments, we detected the emergence of a large number of AtCHS- and NPTII-encoding sRNAs, while there were no such sRNAs after control water treatment. Thus, the exogenous AtCHS-dsRNAs were processed into siRNAs and induced RNAi-mediated AtCHS gene silencing. The analysis showed that gene-specific sRNAs mapped to the AtCHS and NPTII genes unevenly with peak read counts at particular positions, involving primarily the sense strand, and documented a gradual decrease in read counts from 17-nt to 30-nt sRNAs. Results of the present study highlight a significant potential of exogenous dsRNAs as a promising strategy to induce RNAi-based downregulation of plant gene targets for plant management and gene functional studies.

The Specificity of Transgene Suppression in Plants by Exogenous dsRNA

The phenomenon of RNA interference (RNAi) is widely used to develop new approaches for crop improvement and plant protection. Recent investigations show that it is possible to downregulate plant transgenes, as more prone sequences to silencing than endogenous genes, by exogenous application of double-stranded RNAs (dsRNAs) and small interfering RNAs (siRNAs). However, there are scarce data on the specificity of exogenous RNAs. In this study, we explored whether plant transgene suppression is sequence-specific to exogenous dsRNAs and whether similar effects can be caused by exogenous DNAs that are known to be perceived by plants and induce certain epigenetic and biochemical changes. We treated transgenic plants of Arabidopsis thaliana bearing the neomycin phosphotransferase II (NPTII) transgene with specific synthetic NPTII-dsRNAs and non-specific dsRNAs, encoding enhanced green fluorescent protein (EGFP), as well as with DNA molecules mimicking the applied RNAs. None of the EGFP-dsRNA doses resulted in a significant decrease in NPTII transgene expression in the NPTII-transgenic plants, while the specific NPTII-dsRNA significantly reduced NPTII expression in a dose-dependent manner. Long DNAs mimicking dsRNAs and short DNA oligonucleotides mimicking siRNAs did not exhibit a significant effect on NPTII transgene expression. Thus, exogenous NPTII-dsRNAs induced a sequence-specific and RNA-specific transgene-suppressing effect, supporting external application of dsRNAs as a promising strategy for plant gene regulation.

Exploring the Effectiveness and Durability of Trans-Kingdom Silencing of Fungal Genes in the Vascular Pathogen Verticillium dahliae

Host-induced gene silencing (HIGS) based on trans-kingdom RNA interference (RNAi) has been successfully exploited to engineer host resistance to pests and pathogens, including fungi and oomycetes. However, revealing the mechanisms underlying trans-kingdom RNAi between hosts and pathogens lags behind applications. The effectiveness and durability of trans-kingdom silencing of pathogenic genes are uncharacterized. In this study, using our transgenic 35S-VdH1i cotton plants in which dsVdH1-derived small RNAs (siVdH1) accumulated, small RNA sequencing analysis revealed that siVdH1s exclusively occur within the double-stranded (ds)VdH1 region, and no transitive siRNAs were produced beyond this region in recovered hyphae of Verticillium dahliae (V. dahliae). Accordingly, we found that VdH1 silencing was reduced over time in recovered hyphae cultured in vitro, inferring that once the fungus got rid of the 35S-VdH1i cotton plants would gradually regain their pathogenicity. To explore whether continually exporting dsRNAs/siRNAs from transgenic plants into recipient fungal cells guaranteed the effectiveness and stability of HIGS, we created GFP/RFP double-labeled V. dahliae and transgenic Arabidopsis expressing dsGFP (35S-GFPi plants). Confocal images visually demonstrate the efficient silencing of GFP in V. dahliae that colonized host vascular tissues. Taken together, our results demonstrate that HIGS effectively triggers long-lasting trans-kingdom RNAi during plant vasculature V. dahliae interactions, despite no amplification or transitivity of RNAi being noted in this soil-borne fungal pathogen.

Spray-induced gene silencing targeting a glutathione S-transferase gene improves resilience to drought in grapevine

Along with the ongoing climate change, drought events are predicted to become more severe. In this context, the spray-induced gene silencing (SIGS) technique could represent a useful strategy to improve crop stress resilience. A previous study demonstrated that the Arabidopsis mutants for a glutathione S-transferase (GST) gene had increased abscisic acid (ABA) levels and a more activated antioxidant system, both features that improved drought resilience. Here, we used SIGS to target a putative grape GST gene (VvGST40). Then, ecophysiological, biochemical and molecular responses of 'Chardonnay' cuttings were analysed during a drought and recovery time-course. Gas exchange, ABA and t-resveratrol concentration as well as expression of stress-related genes were monitored in not treated controls, dsRNA-VvGST40- and dsRNA-GFP- (negative control of the technique) treated plants, either submitted or not to drought. VvGST40-treated plants revealed increased resilience to severe drought as attested by the ecophysiological data. Analysis of target metabolites and antioxidant- and ABA-related transcripts confirmed that VvGST40-treated plants were in a priming status compared with controls. SIGS targeting an endogenous gene was successfully applied in grapevine, confirming the ability of this technique to be exploited not only for plant protection issues but also for functional genomic studies.

Tuning Beforehand: A Foresight on RNA Interference (RNAi) and In Vitro-Derived dsRNAs to Enhance Crop Resilience to Biotic and Abiotic Stresses

Crop yield is severely affected by biotic and abiotic stresses. Plants adapt to these stresses mainly through gene expression reprogramming at the transcriptional and post-transcriptional levels. Recently, the exogenous application of double-stranded RNAs (dsRNAs) and RNA interference (RNAi) technology has emerged as a sustainable and publicly acceptable alternative to genetic transformation, hence, small RNAs (micro-RNAs and small interfering RNAs) have an important role in combating biotic and abiotic stresses in plants. RNAi limits the transcript level by either suppressing transcription (transcriptional gene silencing) or activating sequence-specific RNA degradation (post-transcriptional gene silencing). Using RNAi tools and their respective targets in abiotic stress responses in many crops is well documented. Many miRNAs families are reported in plant tolerance response or adaptation to drought, salinity, and temperature stresses. In biotic stress, the spray-induced gene silencing (SIGS) provides an intelligent method of using dsRNA as a trigger to silence target genes in pests and pathogens without producing side effects such as those caused by chemical pesticides. In this review, we focus on the potential of SIGS as the most recent application of RNAi in agriculture and point out the trends, challenges, and risks of production technologies. Additionally, we provide insights into the potential applications of exogenous RNAi against biotic stresses. We also review the current status of RNAi/miRNA tools and their respective targets on abiotic stress and the most common responsive miRNA families triggered by stress conditions in different crop species.

External dsRNA Downregulates Anthocyanin Biosynthesis-Related Genes and Affects Anthocyanin Accumulation in Arabidopsis thaliana

Exogenous application of double-stranded RNAs (dsRNAs) and small-interfering RNAs (siRNAs) to plant surfaces has emerged as a promising method for regulation of essential genes in plant pathogens and for plant disease protection. Yet, regulation of plant endogenous genes via external RNA treatments has not been sufficiently investigated. In this study, we targeted the genes of chalcone synthase (CHS), the key enzyme in the flavonoid/anthocyanin biosynthesis pathway, and two transcriptional factors, MYBL2 and ANAC032, negatively regulating anthocyanin biosynthesis in Arabidopsis. Direct foliar application of AtCHS-specific dsRNAs and siRNAs resulted in an efficient downregulation of the AtCHS gene and suppressed anthocyanin accumulation in A. thaliana under anthocyanin biosynthesis-modulating conditions. Targeting the AtMYBL2 and AtANAC032 genes by foliar dsRNA treatments markedly reduced their mRNA levels and led to a pronounced upregulation of the AtCHS gene. The content of anthocyanins was increased after treatment with AtMYBL2-dsRNA. Laser scanning microscopy showed a passage of Cy3-labeled AtCHS-dsRNA into the A. thaliana leaf vessels, leaf parenchyma cells, and stomata, indicating the dsRNA uptake and spreading into leaf tissues and plant individual cells. Together, these data show that exogenous dsRNAs were capable of downregulating Arabidopsis genes and induced relevant biochemical changes, which may have applications in plant biotechnology and gene functional studies.

Spray-Induced Silencing of Pathogenicity Gene MoDES1 via Exogenous Double-Stranded RNA Can Confer Partial Resistance Against Fungal Blast in Rice

Over the past years, RNA interference (RNAi) has been used as a promising combat strategy against a wide range of pests and pathogens in ensuring global food security. It involves the induction of highly specific posttranscriptional regulation of target essential genes from an organism, via the application of precursor long, non-coding double-stranded RNA (dsRNA) molecules that share sequence-complementarity with the mRNAs of the targets. Fungal blast disease caused by Magnaporthe oryzae is one of the most deadly diseases of rice and wheat incurring huge losses in global crop yield. To date, the host-induced gene silencing (HIGS) and virus-induced gene silencing (VIGS) aspects of RNAi have been successfully exploited in developing resistance against M. oryzae in rice. Spray-induced gene silencing (SIGS) is a current, potential, non-transformative, and environment-friendly pest and pathogen management strategy, where naked or nanomaterial-bound dsRNA are sprayed on leaves to cause selective knockdown of pathogenicity genes. Although it relies on the ability of fungal pathogens to uptake sprayed RNA, its efficiency varies largely across phytopathogens and their genes, targeted for silencing. Here, we report a transient dsRNA supplementation system for the targeted knockdown of MoDES1, a host-defense suppressor pathogenicity gene from M. oryzae. We validate the feasibility of in vivo SIGS and post-uptake transfer of RNA signals to distal plant parts in rice-M. oryzae pathosystem through a GFP-based reporter system. A protocol for efficient silencing via direct foliar spray of naked dsRNA was optimized. As proof-of-concept, we demonstrate the phenotypic impacts of in vitro dsDES1 treatment on growth, conidiation, ROS-scavenging ability, and pathogenic potential of M. oryzae. Furthermore, our extrapolatory dsDES1 spray experiments on wounded leaves and whole rice plants indicate resultant silencing of MoDES1 that conferred significant resistance against the fungal blast disease. The evaluation of primary and secondary host defense responses provides evidence supporting the notion that spray of sequence-specific dsRNA on wounded leaf tissue can cause systemic and sustained silencing of a M. oryzae target gene. For the first time, we establish a transgene-free SIGS approach as a promising crop protection strategy against the notorious rice-blast fungus.