| Summary: | <i>β</i>-<i>N</i>-acetylglucosaminidases (NAGs) are carbohydrate enzymes that degrade chitin oligosaccharides into <i>N</i>-acetylglucosamine monomers. This process is important for chitin degradation during insect development and metamorphosis. We identified and evaluated a <i>β</i>-<i>N</i>-acetylglucosaminidase 2 gene (<i>LsNAG2</i>) from the cigarette beetle, <i>Lasioderma serricorne</i> (Fabricius). The full-length open reading frame of <i>LsNAG2</i> was 1776 bp and encoded a 591 amino acid protein. The glycoside hydrolase family 20 (GH20) catalytic domain and an additional GH20b domain of the LsNAG2 protein were highly conserved. Phylogenetic analysis revealed that LsNAG2 clustered with the group II NAGs. Quantitative real-time PCR analyses showed that <i>LsNAG2</i> was expressed in all developmental stages and was most highly expressed in the late larval and late pupal stages. In the larval stage, <i>LsNAG2</i> was predominantly expressed in the integument. Knockdown of <i>LsNAG2</i> in fifth instar larvae disrupted larval−pupal molting and reduced the expression of four chitin synthesis genes (trehalase 1 (<i>LsTRE1</i>), UDP-<i>N</i>-acetylglucosamine pyrophosphorylase 1 and 2 (<i>LsUAP1</i> and <i>LsUAP2</i>), and chitin synthase 1 (<i>LsCHS1</i>)). In late pupae, <i>LsNAG2</i> depletion resulted in abnormal adult eclosion and wing deformities. The expression of five wing development-related genes (teashirt (<i>LsTSH</i>), vestigial (<i>LsVG</i>), wingless (<i>LsWG</i>), ventral veins lacking (<i>LsVVL</i>), and distal-less (<i>LsDLL</i>)) significantly declined in the <i>LsNAG2</i>-depleted beetles. These findings suggest that <i>LsNAG2</i> is important for successful molting and wing development of <i>L. serricorne</i>.
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