Gene knockdown by intro-thoracic injection of double-stranded RNA in the brown planthopper, Nilaparvata lugens.

RNA interference (RNAi) is a powerful strategy for gene function study in insects. Here, we described the development of a RNAi technique by microinjection of double-stranded RNA (dsRNA) in the brown planthopper Nilaparvata lugens. Based on the mortality and RNAi efficiency criteria, the conjunctive between prothorax and mesothorax was selected as the injection site and 50 nl as injection volume. Three genes with different expression patterns were selected to evaluate the RNAi efficiency. A comparable 40% decrease of gene expression was observed at the 4th day after injection for the ubiquitously expressed calreticulin and the gut specific cathepsin-B genes, but only 25% decrease at the 5th day for the central nervous system specific Nlbeta2 gene. Double injection could increase the RNAi efficiency, such as from 25% to 53% for Nlbeta2 gene. The gene knockdown technique developed in this study will be an essential post-genomic tool for further investigations in N. lugens.