Cloning and analysis of the DXR gene and its promoter in Morinda officinalis / 药学学报

ABSTRACT

The objective of this research was to clone 1-deoxy-D-xylulose 5-phosphate reductoisomerase gene (MoDXR) and its promoter sequence from Morinda officinalis and carry out bioinformatic analysis, cis-acting elements analysis, and prokaryotic expression. On the basis of the MoDXR gene sequence obtained from the M. officinalis transcriptome and with NCBI-ORFfinder analysis, a pair of specific primers were designed, and used for RT-PCR amplification. The promoter region sequence at the 5′ end of MoDXR gene was isolated by the genome walking technique. Localization of MoDXR was carried out by subcellular analysis. The prokaryotic expression plasmid pET-28a-MoDXR was constructed and transfected into Escherichia coli BL21(DE3) chemically-competent cells; the recombiant plasmid expressed fusion protein after the induction by IPTG. The full-length cDNA of MoDXR was 2 015 bp,and open reading frame (ORF) size was 1 425 bp, and it encoded 474 amino acid residues and had a molecular mass of 51.27 kD. Sequence comparison with BlastP to the NCBI database revealed that MoDXR had high sequence similarity with many other DXRs, such as Coffea arabica DXR (CaDXR) and Rauvolfia verticillata DXR (RvDXR). A phylogenetic tree revealed that MoDXR had its closest relationship with DXR from Coffea arabica and Gardenia jasminoides. The subcellular localization revealed that MoDXR protein was located on the chloroplast. Plantcare analysis indicated that the promoter region sequence of MoDXR was 1 493 bp, covering multiple light, stress, and hormone-responsive cis-regulatory elements; protein electrophoresis showed that the expressed protein was the anticipated size. This research lays the foundation for further purification and structural and functional characterization of the MoDXR protein.