Plant insects and mites uptake double-stranded RNA upon its exogenous application on tomato leaves

Abstract

Exogenously applied double-stranded RNA (dsRNA) molecules onto tomato leaves, moved rapidly from local to systemic leaves and were uptaken by agricultural pests namely aphids, whiteflies and mites. Four small interfering RNAs, deriving from the applied dsRNA, were molecularly detected in plants, aphids and mites but not in whiteflies. Double-stranded RNA (dsRNA) acts as the elicitor molecule of the RNA silencing (RNA interference, RNAi), the endogenous and evolutionary conserved surveillance system present in all eukaryotes. DsRNAs and their subsequent degradation products, namely the small interfering RNAs (siRNAs), act in a sequence-specific manner to control gene expression. Exogenous application of dsRNAs onto plants elicits resistance against plant viruses. In the present work, exogenously applied dsRNA molecules, derived from Zucchini yellow mosaic virus (ZYMV) HC-Pro region, onto tomato plants were detected in aphids (Myzus persicae), whiteflies (Trialeurodes vaporariorum) and mites (Tetranychus urticae) that were fed on treated as well as systemic tomato leaves. Furthermore, four siRNAs, deriving from the dsRNA applied, were detected in tomato and the agricultural pests fed on treated tomato plants. More specifically, dsRNA was detected in agricultural pests at 3 and 10 dpt (days post treatment) in dsRNA-treated leaves and at 14 dpt in systemic leaves. In addition, using stem-loop RT-PCR, siRNAs were detected in agricultural pests at 3 and 10 dpt in aphids and mites. Surprisingly, in whiteflies carrying the applied dsRNA, siRNAs were not molecularly detected. Our results showed that, upon exogenous application of dsRNAs molecules, these moved rapidly within tomato and were uptaken by agricultural pests fed on treated tomato. As a result, this non-transgenic method has the potential to control important crop pests via RNA silencing of vital genes of the respective pests.

Beyond insects: current status and achievements of RNA interference in mite pests and future perspectives

“…In addition, dsRNA could be detected inside mites after feeding on a dsRNA‐coated leaf, providing evidence of dsRNA transmission from a dsRNA‐coated plant leaf to mites . Also, when mites were immersed directly in a solution of fluorescently labeled dsRNA, the presence of the dsRNA could be observed in the mite gut .…”

“…30 In addition, dsRNA could be detected inside mites after feeding on a dsRNA-coated leaf, providing evidence of dsRNA transmission from a dsRNA-coated plant leaf to mites. 39 Also, when mites were immersed directly in a solution of fluorescently labeled dsRNA, the presence of the dsRNA could be observed in the mite gut. 21 It is still not clear how the dsRNA is taken up by and transported through the mites, but the effective RNAi silencing by these two strategies indicates that using sprayable dsRNA products may have potential in future mite pest control ( Fig.…”

Genetically Modified Organism-Free RNA Interference: Exogenous Application of RNA Molecules in Plants

“…Similar to insects, mites have been targeted for RNAi by various methods, such as feeding on leaves floating on dsRNA solution, dsRNAexpressing transgenic plants, and dsRNA-containing artificial diet, as discussed elsewhere (Suzuki et al, 2017;Niu et al, 2018). To the best of our knowledge, the only study wherein mites took up dsRNA that was exogenously applied in plants involved mechanical inoculation of tomato leaves with in vitro-transcribed dsRNA (targeting the otherwise irrelevant zucchini yellow mosaic virus helper component proteinase) and the concomitant detection by stem loop reverse transcription PCR of the corresponding siRNAs in the two-spotted spider mite Tetranychus urticae at 3 and 10 dpa (Gogoi et al, 2017). However, in that case it was not possible to determine whether the mite absorbed the applied dsRNA or the plant-produced siRNAs.…”

Double-Stranded RNAs in Plant Protection Against Pathogenic Organisms and Viruses in Agriculture

“…Over the past few years, numerous studies have shown that dsRNAs that are complementary to a number of important insect pest genes can become an effective inducer of SIGS and increase insect mortality, decrease their growth rate and fertility, and reduce their sensitivity to insecticides [87]. Treatment of leaves with artificially synthesized dsRNAs targeted at the genes involved in insect development significantly increases mortality and inhibits insect growth [88][89][90][91][92]. This effect can be achieved by irrigating the roots of plants by dsRNA, which leads to effective suppression of the target gene and abnormal development of insect pests [74,76,93].…”