RNA interference to reveal roles of β-N-acetylglucosaminidase gene during molting process in Locusta migratoria

β-N-acetylglucosaminidases are crucial enzymes involved in chitin degrada- tion in insects. We identified a β-N-acetylglucosaminidase gene （LmNAG1） from Locusta migratoria. The full-length complementary DNA （cDNA） of LmNAG1 consists of 2 667 nucleotides, including an open reading frame （ORF） of 1 845 nucleotides encoding 614 amino acid residues, and 233- and 589-nucleotide non-coding regions at the 5＇- and 3＇- ends, respectively. Phylogenetic analysis grouped the cDNA-deduced LmNAG1 protein with the enzymatically characterized β-N-acetylglucosaminidases in group I. Analyses of stage- and tissue-dependent expression patterns of LmNAG1 were carried out by real- time quantitative polymerase chain reaction. Our results showed that LmNAG1 transcript level in the integument was significantly high in the last 2 days of the fourth and fifth instar nymphs. LmNAG1 was highly expressed in foregut and hindgut. RNA interference of LmNAG1 resulted in an effective silence of the gene and a significantly reduced total LmNAG enzyme activity at 48 and 72 h after the injection of LmNAG1 double-stranded RNA （dsRNA）. As compared with the control nymphs injected with GFP dsRNA, 50% of the dsLmNAGl-injected nymphs were not able to molt successfully and eventually died. Our results suggest that LmNAG1 plays an essential role in molting process ofL. migratoria.