Molecular cloning and characterization of 1-hydroxy-2-methyl-2-(E)-butenyl-4-diphosphate reductase gene from Ginkgo biloba.

Ginkgo biloba contains terpene triclactones of high pharmaceutical value such as ginkgolides. 1-hydroxy-2-methyl-2-(E)-butenyl-4-diphosphate (HMBPP) reductase (HDR) is proved to be the terminal-acting enzyme in the plastid MEP pathway which provides isoprenoid precursors for the biosynthesis of ginkgolides. The full-length cDNA encoding HDR, designated as GbHDR (Genbank Accession Number DQ364231), was isolated for the first time from G. biloba by RACE method. GbHDR contained a 1,422-bp open reading frame encoding 474 amino acids. The deduced GbHDR protein, showing high identity to HDRs of other plant species, was predicted to possess a chloroplast transit peptide at the N-terminal and four conserved cysteine residues. Two-dimensional structural analysis showed that GbHDR had a similar secondary structure with HDR from Arabidopsis thaliana. Southern blot analysis indicated that GbHDR belonged to a small gene family. Transcription pattern analysis revealed that GbHDR had high transcription in roots, and low in leaves and stems. The cloning of GbHDR gene will enable us to further understand the role of GbHDR involved in terpene triclatones biosynthetic pathway in G. biloba at molecular level.