Abstract: 3-Hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) is a key enzyme of the mevalonate pathway. Obtaining HMGR gene information is the basis of studying the relationship between cantharidin biosynthesis and the mevalonate pathway. In this study, a fulllength cDNA of the HMGR gene was cloned from the blister beetle Epicauta mannerheimi (Maklin) by RACE technology, which was named EmHMGR (GeneBank accession no. JQ690539). The full-length of EmHMGR is 3 118 bp with an ORF of 2 526 bp, containing a 5′-untranslated region (5′-UTR) of 178 bp and a 3′UTR of 414 bp. It encodes a deduced protein of 842-amino acid residues, with a predicted molecular mass of 92.8 kDa and isoeletric point (pI) of 6.0. Its predicted molecular formula is C₄₁₃₅H₆₆₀₄N₁₀₉₈O₁₂₁₆S₅₀. Bioinformatical analysis showed that its instability index is 43.37 and the GRAVY 0.091, suggesting that EmHMGR is an unstable hydrophobic protein. The deduced protein EmHMGR has the conserved functional domain of HMGR_ClassⅠ and the sterol-sensing domain, and shares more than 50% amino acid identity with HMGRs from other insects. Phylogenetic analysis showed that EmHMGR has the closest relationship with HMGRs of chrysomelids. This study provides the basis for further research on the biosynthetic pathway of cantharidin in the blister beetles.

Key words: Epicauta mannerheimi, 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR), RACE, cloning, bioinformatical analysis, mevalonate pathway