| Summary: | Trehalose is an important carbohydrate substance in insect hemolymph. Chitin is the main component of cuticle and peritrophic matrix in insects. Trehalase (Tre) catalyzes the decomposition of trehalose. Few studies of trehalase in lepidopteran insects have been conducted. Here, the functions of soluble Tre (Tre1) and membrane-bound Tre (Tre2) in the growth and development of <i>Mythimna separata</i> were investigated. We cloned and identified <i>Tre1</i> and <i>Tre2</i> cDNA sequences in <i>M. separata</i>. Analysis expression revealed that <i>MsTre1</i> and <i>MsTre2</i> were highly expressed in midgut and integument, respectively. The expression of <i>MsTre1</i> and <i>MsTre2</i> was highest in the pupal stage. We used RNA interference (RNAi) to inhibit <i>Tre</i> expression in <i>M. separata</i> larvae. Injection of ds<i>MsTre1</i> or ds<i>MsTre2</i> resulted in abnormal phenotypes and impeded normal molting. Silencing of <i>MsTre1</i> and <i>MsTre2</i> resulted in significant changes in the expression of genes in the trehalose and chitin metabolism pathways, significantly increased the trehalose and glycogen content, and significantly decreased MsTre1 and MsTre2 activity, the glucose content, and the chitin content in midgut and integument. Silencing of <i>MsTre1</i> slowed larval molting, and the new cuticle was significantly thinner. These results indicate that RNAi of <i>Tre</i> may be useful for control strategies against <i>M. separata</i>.
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