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Terpenoids (terpenoids) exist in nature of a class of structural units from isoprene the compounds collectively, also called isoprenoids (isoprenoids). These compounds are widely distributed in the Archaea, bacteria, fungi, plants and other living body. Aroma substances in tobacco precursor including three categories, namely CYPRESS alkyl compounds (Cembranoids), carotenoid compounds (Carotenoids) and Cistus compounds (Labdaniods). They are all the tobacco aroma terpenoids, by DOXP / MEP pathway synthesis. 5 - deoxy xylulose phosphate reductoisomerase (DXR) is a key enzyme involved in the biosynthetic pathway of terpenoids DOXP / MEP pathway, which catalyzes the DOXP generate MEP, catalyzed terpenoid precursor IPP generated steps. The role of this enzyme determines the downstream terpenoids yield. At present, a lot of bacteria, protozoa and higher plants DXR genes have been discovered. Different species DXR high homology of the amino acid level. In this study, tobacco (Nicotiana tabacum) leaves the material, the first cloned by RT-PCR and RACE tobacco DXR full-length cDNA sequence (DQ839130). The gene is 1,804 bp, an open reading frame (ORF) of 1,422 bp encoding 473 amino acids, the theoretical molecular weight of approximately 51.2kDa and isoelectric point of 6.04, the N-terminus rich in Pro residues the signal peptide; predicted secondary structure, the irregularly coiled α-helix is ??the major structural elements of the DXR protein; homologous sequences than inferred the DXR amino acid sequence with the Sam's tobacco (Nicotiana benthamiana, AM236596) tomato (Lycopersicon esculentum, AF331705), periwinkle (Catharanthus roseus, AF250235), snapdragon (Antirrhinum majus, AY770406), peppermint (Mentha × piperita, AF116825) DXR consistency respectively 97%, 92%, 84% , 82%, 80%, to confirm that this gene indeed DXR gene. Phylogenetic analysis showed that tobacco the DXR and tomato DXR closest genetic relatives, and the basic reaction of the evolutionary relationship between the 10 different plant DXR. Tobacco DXR gene cloning and analysis has laid a good foundation to further verify the molecular regulation of DXR tobacco terpenoid biosynthetic pathway, as well as constructed transgenic tobacco improved the quality of the tobacco aroma, thereby increasing the content of tobacco aroma substances .
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