Abstract：Isoprenoid biosynthesis via mvalonate-independent pathway is very important to tobacco resistance and leaf quality. 1-deoxy-D-Xylulose-5-phosphate Reductoisomerases(dxr) is a key enzyme in biosynthesis of isopentenyl diphosphate, which is the precusor for monoterpenoid, diterpenoid and tetratepenoid compounds. To regulate the terpenoid metabolism pathway for tobacco improvement, some important genes such as dxr should be studied firstly. In this paper, dxr gene was cloned successfully from tobacco(Nicotiana tabacum) cultivar K326 leaf by RT-PCR. The cDNA code region was 1 422 bp long and encoding 437 amino acids. Sequence analysis by Clustal W declared that this fragment was highly homologous to dxr gene of other species. It shared 93.6% amino acid homologous to Lycopersicon esculentum, 87.9% to Catharanthus roseus, 86.3% to Antirrhinum majus, 84.6% to Mentha piperita, 84.2% to Zea mays, 82.9% to Arabidopsis thaliana, and 53.5% to Nostoc sp. PCC7120. The expression vector pET21b-dxr was constructed and expressed in Escherichia coli by IPTG. And a fragment about 50 kD was achieved as expect. Expression pattern of dxr gene in tobacco was investigated also by RT-PCR. This gene highly expressed in tobacco flower, leaf, stem and trichome, low expressed in seed and root. These results are helpful to regulate and control the terpenoid composition in tobacco by dxr gene manipulation in further research.
