Molecular cloning and functional characterization of borneol dehydrogenase from the glandular trichomes of Lavandula x intermedia

► A borneol dehydrogenase cDNA (LiBDH) was isolated from Lavandula x intermedia glandular trichomes. ► LiBDH was purified and functionally characterized in vitro. ► LiBDH specifically converts borneol to camphor. ► LiBDH transcripts were specifically expressed in the secretory cells of floral glandular trichomes. Several varieties of Lavandula x intermedia (lavandins) are cultivated for their essential oils (EOs) for use in cosmetic, hygiene and personal care products. These EOs are mainly constituted of monoterpenes including camphor, which contributes an off odor reducing the olfactory appeal of the oil. We have recently constructed a cDNA library from the glandular trichomes (the sites of EO synthesis) of L. x intermedia plants. Here, we describe the cloning of a borneol dehydrogenase cDNA (LiBDH) from this library. The 780bp open reading frame of the cDNA encoded a 259 amino acid short chain alcohol dehydrogenase with a predicted molecular mass of ca. 27.5kDa. The recombinant LiBDH was expressed in Escherichia coli, purified by Ni-NTA agarose affinity chromatography, and functionally characterized in vitro. The bacterially produced enzyme specifically converted borneol to camphor as the only product with Km and kcat values of 53μM and 4.0×10−4s−1, respectively. The LiBDH transcripts were specifically expressed in glandular trichomes of mature flowers indicating that like other Lavandula monoterpene synthases the expression of this gene is regulated in a tissue-specific manner. The cloning of LiBDH has far reaching implications in improving the quality of Lavandula EOs through metabolic engineering.