Abstract: 【Aim】 The objective of this study is to explore the roles of glucose oxidase (GOX) in the development, digestion, and immune defense of Mythimna separata.【Methods】 The cDNA sequence of GOX gene from M. separata was cloned by transcriptome sequencing technology. The specific expression patterns of this GOX gene in different developmental stages (1st-6th instar larvae, pupae and 1-day-old adults) and tissues (foregut, midgut, hindgut, labial gland, Malpighian tubules, fat body, and integument) of the day-1 4th instar larvae, and the day-1 4th instar larvae of M. separata fed with maize leaves soaked in different concentrations (0.01%, 0.1%, 1%, and 10%) of glucose solution for 10 s and under starvation and refeeding conditions were detected by qRT.PCR. The role of this GOX gene in the resistance of M. separata to Bacillus thuringiensis was explored by RNAi and bioassay.【Results】 A 2 187 bp cDNA sequence of a novel GOX gene named MsGOX (GenBank accession no.: KY348779) was obtained from M. separata. It has the open reading frame of 1 821 bp in length, encoding a 606-amino acid polypeptide with the predicted molecular weight of 66.4 kD. Developmental expression profile revealed that MsGOX showed different expression levels in M. separata at different developmental stages, with the highest expression level at the 4th instar larval stage, and tissue expression profile showed that MsGOX was expressed in various tissues of the day-1 4th instar larvae，with the highest expression level in labial glands. MsGOX transcription could be induced differently by feeding larvae with different concentrations of glucose. The expression level of MsGOX reached the highest when the glucose concentration was 10%. The expression level of MsGOX in the day-1 4th instar larvae increased gradually with the starvation time increasing, and reached the peak at 24 h after starvation. When the larvae were refed with maize leaves after starvation, the expression level of MsGOX gradually increased. At 48 h after injection of dsMsGOX, the expression level of MsGOX was inhibited by 88.3% as compared to the control (injected with dsEGFP). The larval body weight, body length, and digestibility coefficient at 48 and 72 h after injection of dsMsGOX were significantly reduced, and the corrected mortality rates of larvae infected by B. thuringiensis at 48 and 72 h were enhanced, as compared to those in the control groups at the same time points. 【Conclusion】 MsGOX might participate in digestion and antibacterial processes in the midgut of M. separata. The results provide a basis for further studying the function of MsGOX and exploring novel strategy to control M. separata.

Key words: Mythimna separata, glucose oxidase, expression pattern, RNA interference; Bacillus thuringiensis