Towards an understanding of the molecular basis of effective RNAi against a global insect pest, the whitefly Bemisia tabaci

Abstract

In planta RNAi against essential insect genes offers a promising route to control insect crop pests, but is constrained for many insect groups, notably phloem sap-feeding hemipterans, by poor RNAi efficacy. This study conducted on the phloem-feeding whitefly Bemisia tabaci reared on tomato plants investigated the causes of low RNAi efficacy and routes to ameliorate the problem. Experiments using tomato transgenic lines containing ds-GFP (green fluorescent protein) revealed that full-length dsRNA is phloem-mobile, ingested by the insects, and degraded in the insect. We identified B. tabaci homologs of nuclease genes (dsRNases) in other insects that degrade dsRNA, and demonstrated that degradation of ds-GFP in B. tabaci is suppressed by administration of dsRNA against these genes. dsRNA against the nuclease genes was co-administered with dsRNA against two insect genes, an aquaporin AQP1 and sucrase SUC1, that are predicted to protect B. tabaci against osmotic collapse. When dsRNA constructs for AQP1, SUC1, dsRNase1 and dsRNase2 were stacked, insect mortality was significantly elevated to 50% over 6 days on artificial diets. This effect was accompanied by significant reduction in gene expression of the target genes in surviving diet-fed insects. This study offers proof-of-principle that the efficacy of RNAi against insect pests can be enhanced by using dsRNA to suppress the activity of RNAi-suppressing nuclease genes, especially where multiple genes with related physiological function but different molecular function are targeted.

Delivery of gene‐specific dsRNA by microinjection and feeding induces RNAi response in Sri Lanka weevil, Myllocerus undecimpustulatus undatus Marshall

“…Similarly, no apparent lethal phenotype following V-ATPase A knockdown was observed in Aedes aegypti larvae fed with V-ATPase A dsRNA/chitosan nanoparticles and A. aegypti adults fed with V-ATPase A dsRNA. 40,41 In contrast, reduction in V-ATPase A expression in D. virgifera virgifera, 42 Bemisia tabaci 43 and Tuta absoluta 44 resulted in significant insect mortality.…”

Synthetic biology approach for plant protection using dsRNA

“…Consistent with the central role of dsRNA in triggering RNAi, numerous studies have shown that plants treated with virus‐specific dsRNA or single‐stranded RNA (ssRNA) molecules that fold into hairpin conformation showed antiviral resistance (Carbonell et al ., ; Gan et al ., ; Konakalla et al ., ; Tenllado and Diaz‐Ruiz, ; Tenllado et al ., ,b; Yin et al ., ). dsRNAs were also shown to be effective against fungi (Koch et al ., ; Wang et al ., , ) and insects (Baum et al ., ; Ghosh et al ., ; Li et al ., ; Luo et al ., ), thus providing important implications for dsRNA‐triggered RNAi as an emerging novel approach for crop protection. RNAi has been deployed for plant protection since it was discovered.…”

Expression of exogenous dsRNA by Lecanicillium attenuatum enhances its virulence to Dialeurodes citri

“…Studies have also shown that insects have dsRNA‐degrading enzymes (dsRNase) that affect interference efficiency. Therefore, inhibition of dsRNase expression is conducive to the success of insect RNAi …”