Cloning and Expression Characteristics of Sorbitol Dehydrogenase Gene EiSD under Temperature Stress in Epicauta impressicornis

Epicauta impressicornis Pic. (Coleoptera: Meloidae), an insect of profound medicinal significance, synthesizes cantharidin, a compound known for its anticancer effects. To investigate the expression characteristics of the EiSD gene in E. impressicornis and its temperature adaptability. In this study, we cloned E. impressicornis’ sorbitol dehydrogenase gene (EiSD) (GenBank accession number: PV394100), and analyzed its bioinformatic characterization, and profiled its expression across developmental stages, tissues, and under various temperatures stress conditions. EiSD has a 1,071 bp ORF that encodes 356 amino acids, with a molecular weight of 38.90 kDa, an isoelectric point of 6.42, and a half-life of 30 h. Phylogenetic analysis showed that it is highly conserved and closely related to the SD of Tribolium castaneum (Herbst). Real-time quantitative PCR (RT-qPCR) revealed that EiSD expression peaks in the thorax, and is lowest in the 5th instar larvae and at 12, 18, and 36 °C. The results suggest that EiSD is essential for withstanding low and extreme temperatures. Its low expression under extreme temperature stress likely modulates the sorbitol metabolic pathway, leading to cryoprotectant sorbitol accumulation that supports larval diapaused and stress resistance.