Abstract

1-Hydroxy-2-methyl-2-(E)-butenyl 4-diphosphate reductase (HDR, EC 1.17.1.2) catalyses the last committed step of MEP pathway, which provides precursors for biosynthesis of isoprenoids in plant. This research is the first report of cloning full-length cDNA encoding HDR from sweet potato [Ipomoea batatas (L.) Lam], which is designated as IbHDR (Genbank Accession Number: HQ596402). The full length of IbHDR was 1725 bp, containing a 1383 bp open reading frame which encoded 461 putative amino acids. The deduced IbHDR protein was predicted to possess a chloroplast transit peptide at the N-terminal and showed extensive homology with HDRs from other plant species. Quantitative PCR revealed that transcription level of IbHDR was highest in tender leaves while lowest in old leaves. Accumulation analysis indicated that carotenoids content was highest in old leaves, followed by tender leaves. Other tissues demonstrated similar carotenoids accumulation which was approximate 7-fold lower than that in old leaves. Cloning and characterization of IbHDR gene will facilitate the further understanding of the function of IbHDR at the genetic level. This report also will be helpful to elevate carotenoid content in sweet potato cultivators by applying metabolic engineering strategy.

Key words: Ipomoea batatas, 1-Hydroxy-2-methyl-2-(E)-butenyl 4-diphosphate reductase, transcription pattern, carotenoids.