Silencing of juvenile hormone epoxide hydrolase gene in Spodoptera litura (Lepidoptera: Noctuidae) by oral delivery of double-stranded RNA

Spodoptera litura being polyphagous is the major constraints for the production of many agricultural crops. The extensive use of insecticides for its management leads to development of resistance and environmental hazards. So, there is a need for an alternative, efficient and environmentally safe strategy for management of S. litura. RNA interference (RNAi) is one of them, it is an efficient reverse genetics tool, utilized successfully for functional validation of genes involved in insect development. In the present study a partial cDNA region of a Sljheh gene from S. litura, was cloned and sequenced. The result showed that the putative Sljheh gene shares the similar conserved signature as other JHEHs involved in JH degradation. The expression analysis data revealed that Sljheh is highly expressed in final instar larva and newly emerged adult female. To validate the functional role of Sljheh, double-stranded RNA (dsRNA) was synthesized from the cloned region of the cognate gene and delivered to S. litura larva through oral feeding. Feeding bioassays of dsRNA at 1 µg/larva dose showed 20% larval-pupal intermolt mortality as well as malformed pupae whereas no such abnormalities and mortality were observed in the control. Moreover, longer larval duration, reduced daily weight gain, reduction in pupal size were observed. The result showed a successful down regulation of the Sljheh gene with 1 µg/larva of dsRNA. Present study confirms the functional role of JHEH in S. litura and RNAi through orally-delivered dsRNA and hence, is potentially promising for pest control in future.