RNA interference-aided knockdown of a putative saccharopine dehydrogenase leads to abnormal ecdysis in the brown planthopper, Nilaparvata lugens (Stål) (Hemiptera: Delphacidae) P.-J. Wan 1,2 , L. Yang 1,2 , S.-Y. Yuan 1,2 , Y.-H. Tang 1 , Q. Fu 1 * and G.-Q. Li 2 * 1 State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou 310006, China: 2 Education Ministry Key Laboratory of Integrated Management of Crop Diseases and Pests, College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, China Abstract The brown planthopper Nilaparvata lugens is a serious phloem-feeding pest of rice in China. The current study focuses on a saccharopine dehydrogenase (SDH) that cat- alyzes the penultimate reaction in biosynthesis of the amino acid lysine (Lys), which plays a role in insect growth and carnitine production (as a substrate). The protein, provisionally designated as NlylsSDH [a SDH derived from yeast-like symbiont (YLS) in N. lugens], had a higher transcript level in abdomens, compared with heads, wings, legs and thoraces, which agrees with YLS distribution in N. lugens. Ingestion of Nlylssdh targeted double-stranded RNA (dsNlylssdh) for 5, 10 and 15 days decreased the mRNA abundance in the hoppers by 47, 70 and 31%, respectively, comparing with those ingesting normal or dsegfp diets. Nlylssdh knockdown slightly decreased the body weights, significantly delayed the development of females, and killed approximately 30% of the nymphs. Moreover, some surviving adults showed two apparent phenotypic defects: wing deformation and nymphal cuticles remained on tips of the legs and abdomens. The brachypterours/macropterours and sex ratios (female/male) of the adults on the dsRNA diet were lowered compared with the adults on diets without dsRNA. These results suggest that Nlylssdh encodes a func- tional SDH protein. The adverse effect of Nlylssdh knockdown on N. lugens implies the importance of Lys in hopper development. This study provides a proof of concept example that Nlylssdh could serve as a possible dsRNA-based pesticide for planthop- per control. Keywords: Nilaparvata lugens, saccharopine dehydrogenase, lysine, biosynthesis, ecdysis (Accepted 27 February 2015; First published online 24 April 2015) The brown planthopper, Nilaparvata lugens, feeds on the phloem sap of rice plants and is a serious pest in paddy fields throughout Asia. Rice phloem sap contains high levels of glu- cose and starch but low levels of nitrogenous organic com- pounds such as free amino acids. Among these free amino acids, only asparagine, glutamate, glutamine, threonine and valine are abundant (Fukumorita & Chino, 1982). As N. lugens *Author for correspondence Phone: +86-25-84395248 Fax: +86-25-84395248 E-mail: fuqiang@caas.cn and ligq@njau.edu.cn Bulletin of Entomological Research (2015) 105, 390–398 doi:10.1017/S0007485315000231 © Cambridge University Press 2015.