Abstract: 【Objective】 Trehalase, the only enzyme that hydrolyzes one trehalose molecule into two glucose molecules, plays key roles in insect energy metabolism and chitin synthesis. So trehalase could be served as a potential target for insect pest control. In this paper, the molecular characteristics and functions of trehalase genes were explored in an important agricultural pest Locusta migratoria. The results will provide a reasonable basis for the effective management of locusts. 【Method】By searching the transcriptome and genome of L. migratoria, four full-length cDNA of trehalase genes were obtained. Sequence characteristics of these four trehalases were analyzed by using blast, TMHMM and SignalP softwares. Multiple amino acid sequence alignment of trehalases was made using ClustalW. The phylogenetic tree was constructed by MEGA 7. The expression patterns of trehalase genes in different tissues and developmental days were studied in the 5th-instar nymphs by RT-qPCR. The dsRNAs of four trehalase genes were synthesized in vitro, and then injected into the 5th-instar nymphs on day 2, respectively. Control nymphs were injected with dsGFP alone. The whole body after the dsRNA injection for 48 h was used for total RNA extraction and cDNA synthesis. RT-qPCR were performed to determine the transcript levels of four trehalase genesand genes involved in chitin synthesis such as UDP-N-acetylglucosamine pyrophosphorylase gene LmUAP1 andchitin synthase 1 gene LmCHS1. The abnormal nymphs displayed phenotypes were carefully observed. 【Result】 Blast analysis showed that all these four trehalases contained two conservative regions and a glycine enrichment region. A membrane-bound trehalase with a typical transmembrane domain was named LmTreM (GenBank accession number KX371563). A transmembrane like domain was predicted in another trehalase, named LmTreM-like (GenBank accession number KX371565). The two remains were soluble trehalases, named LmTreS1 and LmTreS2, respectively (GenBank accession number KX371564 and FJ795020). Phylogenetic analysis showed that LmTreM and LmTreM-like, LmTreS1 and LmTreS2 were clustered with membrane-bound and soluble trehalases, respectively. RT-qPCR was carried out to analyze the expression patterns of four trehalase genes in different tissues and developmental days in the 5th-instar nymphs of L. migratoria. The results indicated LmTreM, LmTreS1 and LmTreS2 were mainly expressed in specific tissues, and LmTreM-like was consistently expressed in all selected tissues. mRNA transcripts of four trehalase genes were different during the development of 5th-instar nymphs. RNAi results suggested that expressions of four trehalase genes were significantly reduced compared to the control, and the injection of LmTreM, LmTreS1, LmTreS2 and LmTreM-like dsRNA only repressed the expression of the targeted LmTre without reducing that of other LmTres, the expressions of LmUAP1 and LmCHS1 involved in chitin synthesis were not affected. However, nymphs could successfully molt to adults after injected with four trehalase dsRNAs, respectively.【Conclusion】One membrane-bound, one membrane-bound like and two soluble trehalase were found in L. migratoria. The four trehalase genes showed different tissue and developmental expression characteristics, silencing of each of these four trehalase genes in the 5th-instar nymphs could not affect the normal molting to adults.

Key words: Locusta migratoria, trehalase gene, expression characteristics, RT-qPCR, RNA interference