Topical application of double-stranded RNA molecules deriving from Tomato yellow leaf curl virus reduces cognate virus infection in tomato

Abstract

Tomato yellow leaf curl virus (TYLCV), a whitefly-transmitted single-stranded DNA (ssDNA) virus, causes the most important viral disease of tomato worldwide. TYLCV-mediated disease is mainly controlled via extensive insecticide sprays aiming at the whitefly vector. RNA-based vaccination was proven to be a non-transgenic approach leading to efficient plant virus control. In this work, double-stranded RNA (dsRNA) molecules deriving from sequences of the C4 and V2 genes of TYLCV-Mild were produced in vitro and topically applied onto tomato plants along with the virus (via agroinfiltration). DsC4 and dsV2 application reduced disease incidence to 23 and 46 %, respectively, while TYLCV positive control reached 64 %. Bioinformatics analysis of the virus-specific small interfering RNAs (vsiRNAs) from TYLCV-infected tomato revealed 'hot' and 'cold' spots in the TYLCV-Mild genome. Interestingly, the viral C-strand had twofold siRNA reads when compared to that of the V-strand. Overall, vsiRNAs of negative and positive polarity were almost equal (53.5 vs. 46.6 %); vsiRNAs of negative polarity prevailed at the V-strand. Stem-loop RT-PCR validated the presence of six vsiRNAs (hot or cold spots) in TYLCV-Mild-infected and dsRNA-treated tomato. The exogenously applied dsRNA was found to rapidly move systemically in tomato and was detected for 54 days post treatment (dpt). The applied dsRNA molecules were successfully processed by the Dicer-like proteins (DCLs) in tomato since small interfering RNAs (siRNAs) deriving from the dsRNA were detected for at least 54 dpt. This consists the first report of dsRNA-based vaccination applied against a monopartite geminivirus.

Direct Foliar Application of dsRNA Derived From the Full-Length Gene of NSs of Groundnut Bud Necrosis Virus Limits Virus Accumulation and Symptom Expression

“…To date, the studies on the topical application of dsRNA have been conducted against at least 14 plant viruses having positive sense ssRNA as their genome ( Taliansky et al, 2021 ). To some extent, the approach was also found to be effective against ssDNA virus (genus Begomovirus ), however, not much information is available as only three studies are available that showed limited or no effect against Begomovirus ( Namgiala et al, 2019 ; Rego-Machado et al, 2020 ; Melita et al, 2021 ). Recently, two studies had shown the efficacy of topically applied dsRNA against the type member of the genus Orthotospovirus , TSWV, a negative/ambisense ssRNA virus ( Tabein et al, 2020 ; Konakalla et al, 2021 ).…”

Graphene Quantum Dots (GQD)-Mediated dsRNA Delivery for the Control of Fusarium Head Blight Disease in Wheat

“…RNAi has demonstrated its efficacy in silencing or suppressing the expression of critical genes in fungal pathogens. For example, studies have successfully deployed exogenous dsRNA to suppress fungal pathogens such as Fusarium o xysporum, bacterial pathogens such as Pectobacterium carotovorum , and viral pathogens such as tomato yellow leaf curl virus …”

“…For example, studies have successfully deployed exogenous dsRNA to suppress fungal pathogens such as Fusarium oxysporum, 28 bacterial pathogens such as Pectobacte-rium carotovorum 29 , and viral pathogens such as tomato yellow leaf curl virus. 30 Fusarium head blight (FHB), caused by the pathogen F. graminearum, is a fungal disease of wheat that causes a reduction in the yield and quality of grains by producing mycotoxins. Fusarium species obtain nutrients from both living and dead tissues and are characterized as hemibiotrophic pathogens in nature.…”

Hairpin-RNA Spray Confers Resistance to Mungbean Yellow Mosaic India Virus in Mungbean

“…Topical dsRNA application also shows promise against monopartite geminiviruses such as Tomato yellow leaf curl virus (TYLCV) (56) and Chilli leaf curl virus (ChiLCV) (57).…”

“…Recently, the approach was successfully employed in blackgram plants against MYMV (55). Topical dsRNA application also shows promise against monopartite geminiviruses such as Tomato yellow leaf curl virus (TYLCV) (56) and Chilli leaf curl virus (ChiLCV) (57).…”