Cloning and expression of the sorbitol dehydrogenase gene during embryonic development and temperature stress in Artemia sinica.

Sorbitol dehydrogenase (SDH) catalyzes the interconversion of polyols and ketoses, using zinc and NAD(+) as cofactors. SDH converts sorbitol into fructose and plays an important role in the sorbitol metabolic pathway and in the early embryonic development of many invertebrates. Sorbitol usually accumulates in diapause embryos of insects to protect the embryos from frostbite, which indicates the vital function of SDH in the diapause and diapause-termination stages of embryo development. In this study, a 1311-bp full-length cDNA of As-sdh, including a 28-bp 5' UTR and a 59-bp 3' UTR, was cloned from Artemia sinica. This gene encodes 348 amino-acid proteins. Bioinformatic analysis revealed that this gene is highly conserved in arthropods. The expression patterns of As-sdh were investigated during different stages of embryonic development using real-time PCR and in situ hybridization. As-sdh was expressed at relatively high levels during the 0h embryonic stage, and transcript levels were quite high in 5- and 7-day-old embryos. In situ hybridization analysis showed that As-sdh is expressed in a widely dispersed pattern before incubation but is mainly concentrated on the body surface and the inner wall of the alimentary tract after the nauplius stage. Our results suggest that As-sdh is integral to the process of diapause and diapause termination in A. sinica.