Cloning and expression profile of 1-deoxy-D-xylulose 5-phosphate reductoisomerase gene from an oil-bearing rose

Abstract

The components of rose essential oil are mainly monoterpene alcohols, predominantly synthesized through the methylerythritol 4-phosphate (MEP) pathway in plants. 1-Deoxy-D-xylulose 5-phosphate reductoisomerase (DXR) is specified to be a first committed enzyme of the MEP pathway. In order to understand better the role of DXR in the rose essential oil biosynthesis at the molecular level, the full-length cDNA of DXR sequence (designated as RhDXR) was isolated from an oil-bearing rose hybrid Rosa cv. Zizhi and characterized, and the expression profile of it was investigated. Essential oils of rose cv. Zizhi and the other five oil-bearing roses were distilled to evaluate the relationship between the expression of DXR gene and oil yield rate. The full-length cDNA of RhDXR was 1915 bp in length, comprised an open reading frame of 1419 bp, encoding an enzyme of 472 amino acids. A comparative analysis with DXRs of selected species from bacteria to higher plants revealed three conserved domains: a conserved cleavage site for plastids, an extended Prorich region, and a highly conserved NADPH oxidase-binding motif existing in the N-terminal region, like in other higher plant species. The relative expression levels of the DXR gene were determined in various tissues: receptacle, leaf, sepal, pistil, stamen, and petal (in the order of decreasing expression level), and at different flowering stages (flower bud, flower in half bloom, and flower in full bloom). Six cultivars could be classified into two groups according to flower color, and within each group there was a positive correlation between the expression level of DXR gene and oil yield rate.