Molecular cloning and functional identification of a novel borneol dehydrogenase from Artemisia annua L.

• A specific borneol dehydrogenase gene AaBDH was cloned from A. annua.
• Full-length cDNA of AaBDH was obtained and analyzed.
• AaBDH protein was produced and purified.
• The catalytic property of AaBDH was characterized.
• The relationship between AaBDH and camphor level in planta was investigated.

In order to investigate the physiological functions and biosynthesis regulation of borneol or comphore in Artermisia annua L., which is the major source of the anti-malaria drug artemisinin, the full length cDNA of the gene encoding a borneol dehydrogenase (AaBDH) was cloned from A. annua for the first time by using RACE (rapid amplification of cDNA ends). The completed open read frame of AaBDH was 1415 bp and it encoded a 885-amino acid protein with a predicted molecular mass of 31.04 kDa and a pI of 6.16. AaBDH showed 68–70% of amino acid identity to alcohol dehydrogenases from Solanum lycopersicum, Ppulus trichocarpa, Morus notabili and Ricinus communis. While it shared 51% and 58% of identity with artemisia alcohol dehydrogenase ADH2 from A. annua and borneol dedrogenase LiBDH from Lavandula x intermedia, respectively. The recombinant protein was obtained by heterogeneous expression of AaBDH in a strain of Escherichia coli BL 21 and purified by affinity chromatography. The function of AaBDH was characterized by using of in vitro enzymatic assays, and the results showed that AaBDH had the ability to specifically convert borneol into camphor in the presence of NAD+ (nicotinamide adenine dinucleotide) or NADP+ (nicotinamide adenine dinucleotide phosphate). The cloning of AaBDH laid a significant foundation for further investigation on physiological functions and biosynthesis regulation of plant monoterpenoids.