A Halloween gene shadow is a potential target for RNA ‐interference‐based pest management in the small brown planthopper Laodelphax striatellus

BACKGROUND L aodelphax striatellus is an economically important rice pest in China. Ecdysteroid hormone 20‐hydroxyecdysone regulates insect development and reproduction. The cytochrome P450 monooxygenase Shadow (Sad) plays a critical role in ecdysteroidogenesis. Here, tests were conducted to establish whether Lssad was a potential target gene for RNA ‐interference‐based management of L. striatellus.RESULTS L ssad was cloned and characterised. LsSad had Helix‐C, Helix‐I, Helix‐K, PERF and haem‐binding motifs. Lssad is expressed at a higher level in the thorax, where prothoracic glands are located, compared with the level in the head or abdomen. It showed two expression peaks in day 2 and day 4–5 fourth‐instar nymphs, and two troughs in day 1 fourth and fifth instars. Oral delivery of double‐stranded RNA ( dsRNA ) of Lssad at the nymph stage successfully knocked down the expression of the target gene, reduced the expression level of ecdysone receptor ( L sEcR ) gene, caused nymphal lethality and delayed development in a dose‐dependent manner. Ingestion of 20‐hydroxyecdysone in Lssad ‐d sRNA ‐exposed nymphs did not increase Lssad expression level, but almost completely rescued the L sEcR mRNA level and relieved the negative effects on survival and development. CONCLUSIONS The ecdysteroidogenic pathway is conserved in L. striatellus . Lssad can serve as a possible target for dsRNA ‐based pesticides for planthopper control. © 2014 Society of Chemical Industry