Trehalose‐6‐phosphate synthase (TPS), an enzyme that hydrolyzes two glucose molecules to yield trehalose, plays a pivotal role in various physiological processes. In this study, we cloned the trehalose‐6‐phosphate synthase gene ( HvTPS) and investigated its expression patterns in various tissues and developmental stages in Heortia vitessoides Moore (Lepidoptera: Crambidae). HvTPS was highly expressed in the fat body and after pupation or before molting. We knocked down TPS in H. vitessoides by RNA interference and found that 3.0 μ g of ds HvTPS resulted in optimal interference at 24 h and 36 h post‐injection and caused a sharp decline in the survival rate during the 5th instar larval–pupal stage and obviously abnormal or lethal phenotypes. Additionally, compared to the controls, TPS activity and trehalose contents were significantly lower and the glucose content was significantly higher 24 h or 36 h after injection with 3.0 μg of ds HvTPS . Furthermore, the silencing of HvTPS suppressed the expression of six key genes in the chitin biosynthesis pathway and one key gene related to lipid catabolism. The expression levels of two genes associated with lipid biosynthesis were upregulated. These results strongly suggest that HvTPS is essential for the normal growth and development of H. vitessoides and provide a reference for further studies of the utility of key genes involved in chitin and lipid biosynthesis for controlling insect development.

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β‐N‐acetylglucosaminidase (NAG) is a key enzyme in insect chitin metabolism and plays an important role in many physiological activities of insects. The HvNAG1 gene was identified from the Heortia vitessoides Moore (Lepidoptera: Crambidae) cDNA library and its expression patterns were determined using quantitative real‐time polymerase chain reaction. The results indicated that HvNAG1 mRNA levels were high in the midgut and before molting, and 20E could induce its expression. Subsequently, the HvNAG1 gene was knocked down via RNA interference to identify its functions. We found that 3 μg of dsNAG1 resulted in optimal interference at 48 and 72 hr after injection, causing a decrease in NAG1 protein content, which resulted in abnormal or lethal phenotypes, and a sharp decrease in the survival rate. These results indicate that HvNAG1 plays a key role in the molting process of H. vitessoides. However, the silencing of HvNAG1 had no significant effect on the chitin metabolism‐related genes tested in this study. Our present study provides a reference for further research on the utility of key genes involved in the chitin metabolic pathway in the insect molting process.

To elucidate the role of glutathione S-transferases (GSTs) in Heortia vitessoides Moore (Lepidoptera: Crambidae), one of the most destructive defoliating pests in Aquilaria sinensis (Lour.) Gilg (Thymelaeaceae) forests, 16 GST cDNAs were identified in the transcriptome of adult H. vitessoides. All cDNAs included a complete open reading frame and were designated HvGSTd1–HvGSTu2. A phylogenetic analysis showed that the 16 HvGSTs were classified into seven different cytosolic classes; three in delta, two in epsilon, three in omega, three in sigma, one in theta, two in zeta, and two in unclassified. The expression patterns of these HvGSTs in various larval and adult tissues, following exposure to half the lethal concentrations (LC50s) of chlorantraniliprole and beta-cypermethrin, were determined using real-time quantitative polymerase chain reaction (RT-qPCR). The expression levels of the 16 HvGSTs were found to differ among various larval and adult tissues. Furthermore, the RT-qPCR confirmed that the transcription levels of nine (HvGSTd1, HvGSTd3, HvGSTe2, HvGSTe3, HvGSTo3, HvGSTs1, HvGSTs3, HvGSTu1, and HvGSTu2) and six (HvGSTd1, HvGSTd3, HvGSTe2, HvGSTo2, HvGSTs1, and HvGSTu1) HvGST genes were significantly higher in the fourth-instar larvae following exposure to the insecticides chlorantraniliprole and beta-cypermethrin, respectively. These genes are potential candidates involved in the detoxification of these two insecticides. Further studies utilizing the RNA interference approach are required to enhance our understanding of the functions of these genes in this forest pest.

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