Abstract: 【Aim】 3-Hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) is a rate-limiting enzyme of juvenile hormone (JH) synthesis. This study aims to explore the potential roles of HMGR gene in diapause and metamorphosis of Sitodiplosis mosellana, an insect species undergoing obligatory larval diapause. 【Methods】 The full-length cDNA of HMGR gene was cloned from S. mosellana pre-diapause larvae by RT-PCR and RACE technologies. The sequence characteristics of the nucleotide and amino acid sequences of the cloned HMGR were analyzed by bioinformatics programs. The mRNA expression levels of HMGR in the 3rd instar larva of S. mosellana in different stages of diapause (pre-diapause, diapause, post-diapause quiescent and post-diapause development) and different developmental stages (the 1st-2nd instar larva, pre-pupa, early pupa, middle pupa and late pupa, as well as male adult and female adult) were determined by qPCR. 【Results】 The full-length cDNA sequence of HMGR was obtained from S. mosellana and named SmHMGR, which was deposited at GenBank under the accession number MG876766. SmHMGR is 2 548 bp in length and contains a 2 328 bp ORF, encoding a protein of 775 amino acids with a predicted molecular weight of 84.16 kD and a theoretical pI of 8.29. The deduced amino acid sequence contains the conserved HMG-CoA-reductase-classⅠ domain and other motifs of the HMGR protein family. Multiple sequence alignment and phylogenetic analysis showed that SmHMGR has the highest similarity and the closest relationship to HMGRs from the Nematocera including Anopheles darling. The expression level of SmHMGR increased as the larvae entered the early 3rd instar before diapause, maintained high after diapause, and peaked in the post-diapause quiescence phase (from December to the next January). The expression level of SmHMGR was lower in the pupal stage than in the larval stage, the lowest in the pre-pupal stage, and significantly higher in female adults than in pupae and male adults. 【Conclusion】 SmHMGR expression is related to the development of S. mosellana, and might play key roles in diapause induction, maintenance and post-diapause quiescence as well as in adult reproduction, whereas the metamorphosis from larva to pupa might be correlated with its reduced expression.

Key words:  Sitodiplosis mosellana')"> Sitodiplosis mosellana, 3-hydroxy-3-methylglutaryl coenzyme A reductase, gene cloning, diapause, developmental metamorphosis