RNA interference targeting ecdysone receptor blocks the larval–pupal transition in Henosepilachna vigintioctopunctata

Abstract

Henosepilachna vigintioctopunctata is a serious insect pest which attacks a large number of nightshades and cucurbits in Asian countries, Brazil and Australia. Prolonged application of traditional pesticides has caused environmental pollution and exerted deleterious effects on human health. Finding new approaches with high target specificity and low environmental contamination has become an urgent task. RNA interference (RNAi) induced by double-stranded RNA (dsRNA) is expected to be applicable to managing this pest. Here we evaluated the effects of Escherichia coli-expressed dsRNAs targeting ecdysone receptor (EcR) gene via dietary delivery in laboratory and foliar spraying in a greenhouse. The target transcript was successfully knocked down when the 4th-instar larvae had fed on potato foliage dipped with dsEcR in a laboratory bioassay. Around 85% of the HvEcR RNAi larvae remained as prepupae or became abnormal pupae, and failed to emerge into adults. Ingestion of dsEcR-immersed foliage by the 3rd-instar larvae effectuated a comparable RNAi response and brought about more severe defects: all the resultant larvae arrested development, remained as prepupae and finally died. For assay in the greenhouse, a dsEcR-contained E. coli suspension was directly sprayed to the foliage of greenhouse-growing potato plants and the 3rd-and 4th-instar larvae were transferred to the leaves. High RNAi efficacy was obtained and identical RNAi phenotypes were observed in treated larvae. In addition, spraying dsEcR reduced leaf damage. Our results indicate a possibility of practical application of dsEcR as an environmentally friendly RNA pesticide to control H. vigintioctopunctata larvae.

Combined Transcriptomic Analysis and RNA Interference Reveal the Effects of Methoxyfenozide on Ecdysone Signaling Pathway of Spodoptera exigua

“…In this study, knockdown of EcRA influenced the expression of genes in the ecdysone signaling pathway. Similarly, the mRNA level of 20E signaling genes was significantly changed after the knockdown of EcR [34][35][36][37][38]. However, the expression of E74 differed from previous research.…”

Lab-to-Field Transition of RNA Spray Applications – How Far Are We?

“…For example, a recent report demonstrated the efficiency of RNA sprays against Henosepilachna vigintioctopunctata (28-spotted ladybird) in the greenhouse (Wu et al, 2021). Spraying E. coliexpressed dsRNAs targeting the ecdysone receptor (EcR) gene onto the foliage of greenhouse-growing potato plants provoked the death of third and fourth instar larvae and reduced leaf damage (Wu et al, 2021). Confirming these results, another study showed exogenous dsRNA application as a promising alternative to chemical pesticides for controlling H. vigintioctopunctata (Lü et al, 2021).…”

“…In addition to the control of viruses and fungi, insect pests are also generally accessible to RNA sprays (Table 1). For example, a recent report demonstrated the efficiency of RNA sprays against Henosepilachna vigintioctopunctata (28-spotted ladybird) in the greenhouse (Wu et al, 2021). Spraying E. coliexpressed dsRNAs targeting the ecdysone receptor (EcR) gene onto the foliage of greenhouse-growing potato plants provoked the death of third and fourth instar larvae and reduced leaf damage (Wu et al, 2021).…”

“…For these purposes, encapsulation is pursued to guarantee and prolong the longevity of RNA sprays in the field. For example, E. coli is not only utilized for cost-effective dsRNA production but also represents a protective envelope for efficient dsRNA delivery (Lü et al, 2020;Máximo et al, 2020;Wang et al, 2021;Wu et al, 2021). Interestingly, encapsulation of dsRNA, if large enough, may prevent cellular uptake (plant intake) and thus shield dsRNA from plant DCL processing, as indicated by previous breakthroughs demonstrating that the expression of dsRNA in chloroplasts (DCL-free organelles) targeting the ßactin gene of L. decemlineata (Colorado potato beetle) caused larval lethality (Zhang et al, 2015).…”

Functional divergence of white genes in Henosepilachna vigintioctopunctata revealed by RNA interference

“…Molecular resources for H. vigintioctopunctata have only recently been developed (Guo et al, 2019;Zhang et al, 2018). Moreover, it has been documented that dsRNA can successfully knock down target genes in H. vigintioctopunctata (Hashiro et al, 2019;Ohde et al, 2009;Wu et al, 2020). This offers a great opportunity to explore the molecular mechanisms of white gene(s) by RNAi.…”