Molecular cloning and functional characterization of the gene encoding hydroxy-2-methyl-2-(E)-butenyl 4-diphosphate reductase gene from Artemisia annua L / 药学学报

Artemisinin is the first choice for malaria treatment. The plastidial MEP pathway provides 5-carbon precursors (IPP and its isomer DMAPP) for the biosynthesis of isoprenoid (including artemisinin). Hydroxy-2-methyl-2-(E)-butenyl 4-diphosphate reductase (HDR) is the last enzyme involved in the MEP pathway, which catalyzes HMBPP to form IPP and DMAPP. In this study, we isolated the full-length cDNA of HDR from Artemisia annua L. (AaHDR2) and performed functional analysis. According to gene expression analysis of AaHDR2 (GenBank:KX058541) and AaHDR1 reported ever (GenBank:ADC84348.1) by qPCR, we found that AaHDR1 and AaHDR2 had much higher expression level in trichomes than that in roots, stems, leaves and flowers. AaHDR2 had much higher expression level in flowers than that in leaves. Further, the plant hormones such as MeJA and ABA respectively up-regulated the expression level of AaHDR1 and AaHDR2 significantly, but GA3 up-regulated the expression level of AaHDR2 only. The gene expression analysis of AaHDR1 and AaHDR2 showed that AaHDR2 had a greater contribution than AaHDR1 to isoprenoid biosynthesis (including artemisinin). We used AaHDR2 for the following experiments. Bioinformatic analysis indicated that AaHDR2 belonged to the HDR family and the functional complementation assay showed that AaHDR2 did have the enzymatic function of HDR, using E. coli mutant MG1655araHDR as host cell. The subcellular localization assay showed that AaHDR2 fused with GFP at its N-terminal specifically targeted in chloroplasts. Finally, AaHDR2 was overexpressed in Arabidopsis thaliana. The AaHDR2-overexpressing plants produced the isoprenoids including chlorophyll a, chlorophyll b and carotenoids at significantly higher levels than the wild-type Arabidopsis plants. In summary, AaHDR2 might be a candidate gene for genetic improvement of the isoprenoid biosynthesis.

Cloning and bioinformatics analysis of 1-hydroxy-2-methyl-2-(E)-butenyl 4-diphosphate reductase（PcHDR1）gene in Phlegmarirus carinatus / 中国中药杂志

The open reading frame of 1-hydroxy-2-methyl-2-(E)-butenyl 4-diphosphate reductase (HDR) was cloned from Phlegmarirus carinatus by RT-PCR method and the sequence was analyzed by bioinformatics tools. After searching the transcriptome dataset of P. carinatus, one unique sequence encoding 1-hydroxy-2-methyl-2-(E)-butenyl 4-diphosphate reductase was discovered. The primers were designed according to the cDNA sequence of 1-hydroxy-2-methyl-2-(E)-butenyl 4-diphosphate reductase from the dataset. And then, the open reading frame (ORF) of 1-hydroxy-2-methyl-2-(E)-butenyl 4-diphosphate reductase, named as PcHDR1 (GenBank Accession number：JQ957845), was cloned by RT-PCR strategy with the template of mixed RNA extracted from roots, stem and leaf of P. carinatus. The bioinformatic analysis of this gene and its corresponding protein was performed. The ORF of PcHDR1 consisted of 1 437 base pairs (bp), encoding one polypeptide with 478 amino acids. The sequence comparison showed that PcHDR1 is closest with GbHDR (Ginkgo biloba),and the sequence homology was up to 78%. Bioinformatics prediction and analysis indicated that PcHDR1 protein contained a conserved domain of LytB, without transmembrane region and signal peptides. This study cloned and analyzed 1-hydroxy-2-methyl-2-(E)-butenyl 4-diphosphate reductase from P. carinatus. The result will provide a foundation for exploring the function of PcHDR1 involved in terpene biosynthesis in P. carinatus plants.

Cloning and analysis of 1-hydroxy-2-methyl-2-(E)-butenyl-4-diphosphate reductase genes HsHDR1 and HsHDR2 in Huperzia serrate

We cloned and analyzed the two genes of the 1-hydroxy-2-methyl-2-(E)-butenyl-4-diphosphate reductase (HDR) gene family from Huperzia serrate. The two transcripts coding HDR, named HsHDR1 and HsHDR2, were discovered in the transcriptome dataset of H. serrate and were cloned by reverse transcription-polymerase chain reaction (RT-PCR). The physicochemical properties, protein domains, protein secondary structure, and 3D structure of the putative HsHDR1 and HsHDR2 proteins were analyzed. The full-length cDNA of the HsHDR1 gene contained 1431 bp encoding a putative protein with 476 amino acids, whereas the HsHDR2 gene contained 1428 bp encoding a putative protein of 475 amino acids. These two proteins contained the conserved domain of 1-hydroxy-2-methyl-2-(E)-butenyl-4-diphosphate reductase (PF02401), but without the transmembrane region and signal peptide. The most abundant expression of HsHDR1 and HsHDR2 was detected in H. serrate roots, followed by the stems and leaves. Our results provide a foundation for exploring the function of HsHDR1 and HsHDR2 in terpenoid and sterol biosynthesis in Huperziaceae plants.