Abstract: 【Aim】 This study aims to ascertain the change patterns of sorbitol content and the mRNA expression level of sorbitol dehydrogenase gene ( SmSDH) in Sitodiplosis mosellana(Géhin) larvae at different diapause stages and to explore the relationship between diapause and sorbitol content and the expression level of SmSDH in S. mosellana. 【Methods】 Colorimetry and real-time quantitative PCR were respectively used to analyze the sorbitol content and mRNA transcription level of SmSDH2aand SmSDH2b in pre-diapause, diapause and post-diapause larvae of S. mosellana collected from a field insectary in Yangling, Shaanxi during May 2013 to March 2014. 【Results】 The sorbitol content in pre-diapause larvaeof S. mosellana was the highest (9.41 μg/mg). During diapause, the sorbitol content in December was the highest, which was 8.50 μg/mg. The sorbitol content in post-diapause larvae was 3.25-3.49 μg/mg, significantly lower than those in pre-diapause and diapause larvae (P<0.05). Change trends of the mRNA transcription levels of SmSDH2a and SmSDH2b in the process of diapause were similar and closely consistent with the decreasing trend of diapause intensity. Namely, the relative expression levels of SmSDH2a and SmSDH2b reduced significantly after the larvae entered diapause (P<0.05) and maintained at a low level during diapause. The relative expression levels of SmSDH2a and SmSDH2b gradually increased and reached the highest after diapause termination. No obvious difference was found in sorbitol content and the relative expression level of SmSDH2a between no-cocooned and cocooned larvae, but the expression level of SmSDH2b in no-cocooned larvae was higher than that in cocooned larvae at the same diapause stage. 【Conclusion】 Sorbitol and SmSDH are involved in diapause ofS. mosellana and play important roles in diapause maintenance and termination.

Key words: Sitodiplosis mosellana, diapause, sorbitol, sorbitol dehydrogenase, gene expression