A new isopentenyl diphosphate isomerase gene from sweet potato: cloning, characterization and color complementation

Isopentenyl diphosphate isomerase (IDI, EC 5.3.3.2) catalyzes the revisable conversion of 5-carbon isopentenyl diphosphate and its isomer dimethylallyl diphosphate, which are the essential precursors for isoprenoids, including carotenoids. Here we report on the cloning and characterization of a novel cDNA encoding IDI from sweet potato. The full-length cDNA is 1155 bp with an ORF of 892 bp encoding a polypeptide of 296 amino acids, which was designated as IbIDI (GenBank Acc. No: DQ150100). The computational molecular weight is 33.8 kDa and the theoretical isoelectric point is 5.76. The deduced amino acid sequence of IbIDI is similar to the known plant IDIs. The tissue expression analysis revealed that IbIDI expressed at higher level in sweet-potato’s mature leaves and tender leaves than that in tubers, meanwhile, no expression signal could be detected in veins. Recombinant IbIDI was heterologously expressed in engineered Escherichia coli which led to the reconstruction of the carotenoid pathway. In the engineered E. coli, IbIDI could take the role of Arabidopsis IDI gene to produce the orange β-carotene. In summary, cloning and characterization of the novel IDI gene from sweet potato will facilitate our understanding of the molecular genetical mechanism of carotenoid biosynthesis and promote the metabolic engineering studies of carotenoid in sweet potato.