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

Henosepilachna vigintioctopunctata is a serious insect pest that 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 greenhouse. The target transcript was successfully knocked down when the fourth-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 third-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 greenhouse, a dsEcR-contained E. coli suspension was directly sprayed to the foliage of greenhouse-growing potato plants and the third- and fourth-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 to practical application of dsEcR as an environmentally-friendly RNA pesticide to control H. vigintioctopunctata larvae. This article is protected by copyright. All rights reserved.