Exogenous Application of RNAi-Inducing Double-Stranded RNA Inhibits Aphid-Mediated Transmission of a Plant Virus

Abstract

Plant viruses are difficult to control, and they decrease both the quality and yield of crops, thus threatening global food security. A new approach that uses topical application of double-stranded RNA (dsRNA) to induce antiviral RNA-interference has been shown to be effective at preventing virus infection in a range of plants following mechanical inoculation. In this study, topical application of dsRNA was effective against mechanical inoculation and aphid-mediated inoculation with the potyvirus bean common mosaic virus (BCMV). Topical application of dsRNAs targeting either the coding region of the potyviral nuclear inclusion b (NIb) protein (BCMVNIb-dsRNA) or the coat protein (CP) coding region (BCMVCP-dsRNA) protected Nicotiana benthamiana and cowpea (Vigna unguiculata) plants against mechanical inoculation with BCMV. BCMVCP-dsRNA was selected for subsequent aphid transmission experiments. BCMVCP-dsRNA was loaded onto layered double hydroxide nanoparticles to form BCMVCP-BioClay which is a more stable formulation for delivering dsRNA than naked dsRNA. BCMVCP-BioClay was shown to be successful in protecting plants against BCMV transmission by the aphid Myzus persicae. Spraying detached N. benthamiana leaves with BCMVCP-BioClay 5 days prior to exposure to viruliferous aphids protected the leaves from infection by BCMV. Importantly, spraying of intact N. benthamiana and cowpea plants with BCMVCP-BioClay 5 days prior to exposure to viruliferous aphids protected plants of both species from BCMV infection. This study demonstrates that topical application of dsRNA using BioClay protects plants from aphid-mediated virus transmission, which is an important first step toward developing practical application of this approach in crop protection.

Manipulation of Jasmonate Signaling by Plant Viruses and Their Insect Vectors

“…Currently, the emergence and reemergence of insect-transmitted plant viruses in the past decades have been mainly driven by planthoppers, whiteflies, aphids and thrips [116][117][118][119][120]. We and many other groups in the world have developed several biotechnological methods to improve crop resistance against these vector-borne viruses with the expression of virus-targeting RNA interference [121][122][123]. Due to the difficulties in the further usage of these genetically modified plants in the field, the most effective method for insect-borne plant virus management is likely to control the population of insect vectors.…”

SIGS vs HIGS: a study on the efficacy of two dsRNA delivery strategies to silence Fusarium FgCYP51 genes in infected host and non‐host plants

“…Similarly, both Brassica napus (rapeseed) and Arabidopsis plants were protected by dsRNA sprays against B. cinerea and Sclerotinia sclerotiorum (McLoughlin et al , ). Of note, higher efficacy under field studies directed to control viral diseases was achieved when dsRNA was merged in a composition with non‐toxic, degradable, layered double hydroxide (LDH) clay nanosheets (Mitter et al , ; Worrall et al , ). However, not all fungi are amenable to HIGS or SIGS strategies, as exemplarily shown by the insensitivity of Zymoseptoria tritici to dsRNA that targets essential fungal genes, including ZtCYP51 (Kettles et al ., ).…”

Bacterium-Mediated RNA Interference: Potential Application in Plant Protection

“…These issues have been addressed to some degree through the development of compounds and materials that bind RNA molecules to increase their stability, adhesion to plant tissues, and subsequent uptake. Notable innovations in this area include the use of layered double hydroxide clay nanosheets [9], carrier peptides [11], surfactants [25] and cationic nanoparticles [39]. However, it is worth noting that widespread application of these agents has been lacking in plants and are often confined to single pests or pathogen model systems.…”

“…Antiviral exoRNAi studies have, to date, only applied RNAi molecules either by spray [9,12,52] or abrasive-assisted mechanical inoculation [45,[53][54][55][56][57][58][59], and while it is highly likely that other delivery mechanisms have this capacity, they remain to be tested. Numerous genes are appropriate as antiviral targets in both host-induced gene silencing (HIGS) and exoRNAi systems, with those encoding viral replicases [8], coat proteins [56], or viral RNAi suppressors [45] being the most common.…”

“…Exogenous application overcomes some of the constraints associated with transforming plants by having dsRNA synthesized outside of the target. dsRNA produced from both biological [8] and chemical sources [9] can be applied to plants through foliar application, such as spraying [10], or infiltration [11]. In this manner, both biologically and chemically produced dsRNA can induce the silencing of plant, viral [12], fungal [13], and invertebrate genes [14].…”