Cloning and expression regulation of 1-deoxy-D-xylulose-5-phosphate reductoisomerase cDNA from Alpinia officinarum / 中国中药杂志

The rhizome of Alpinia officinarum is a widely used Chinese herbal medicine. The essential oil in A. officinarum rhizome is mainly composed of 1, 8-cineole and other monoterpenes, as the major bioactive ingredients. In plants, monoterpenes are synthesized through the methylerythritol phosphate (MEP) pathway in the plastids, and 1-deoxy-D-xylulose 5-phosphate reductoisomerase (DXR) is an enzyme catalyzing a committed step of the MEP pathway. In the present study, the full-length cDNA encoding DXR was cloned from the rhizome of A. officinarum, using homology-based RT-PCR and rapid amplification of cDNA ends (RACE) techniques. The new cDNA was designated as AoDXR and submitted to GenBank to be assigned with an accession number HQ874658. The full-length cDNA of AoDXR was 1 670 bp containing a 1 419 bp open reading frame encoding a polypeptide of 472 amino acids with a calculated molecular mass of 51.48 kDa and an isoelectric point of 6.15. Bioinformatic analyses revealed that AoDXR showed extensive homology with DXRs from other plant species and contained a conserved plastids transit peptide, a Pro-rich region and two highly conserved NADPH-binding motifs in its N-terminal region characterized by all plant DXRs. The phylogenetic analysis revealed that AoDXR belonged to angiosperm DXRs. The structural modeling of AoDXR showed that AoDXR had the typical V-shaped structure of DXR proteins. The tissue expression pattern analysis indicated that AoDXR expressed strongly in leaves, weak in rhizomes of A. officinarum. Exogenous methyl jasmonate (MeJA) could enhance the expression of AoDXR and the production of 1, 8-cineole in A. officinarum rhizomes. The cloning and characterization of AoDXR will be helpful to reveal the molecular regulation mechanism of monoterpene biosynthesis in A. officinarum and provides a candidate gene for metabolic engineering in improving the medicinal quality of A. officinarum rhizome.

3′-terminus shifted bases degeneracy primers increasing sensitivity of polymerase chain reaction / 第二军医大学学报

To reduce the risk of 3′-terminal mismatch between primers and template and increase the sensitivity of polymerase chain reaction (PCR) in the detection of variable region of DNA. Methods: A pair of special primer(WU,WD) was designed to amplify a fragment of HBV DNA P gene by PCR. Other 2 similar pairs of primer (MU1, MD1, MU2, MD2) were obtained by knocking off 1 or 2 bases at the 3′-terminal of WU and WD. (1) Special primers (WU, WD) and degeneracy primers(WU, WD, MU1, MU2, MD1, MD2) were used to amplify 27 samples respectively by PCR under the same condition. The sensitivity of each PCR was compared. (2) Using degeneracy primers, serum HBV DNA was amplified from 4 patients who were resistant to lamivudine. The PCR products were sequenced to evaluate the effect of the 3′-terminal mismatch of primers upon PCR. Results: (1) The sensitivity of special primers and degeneracy primers were 70.4%(19/27) and 85.2%(23/27) respectively (P<0.05). (2) The sequencing analysis of the PCR products suggested that the 3′-terminal mismatch of primers caused false negative in the PCR detection. Conclusion: When amplifying the variable region of DNA, the false negative result can be avoided by using 3′-terminus shifted degeneracy primers.

3′-terminus shifted bases degeneracy primers increasing sensitivity of polymerase chain reaction / 第二军医大学学报

To reduce the risk of 3′-terminal mismatch between primers and template and increase the sensitivity of polymerase chain reaction (PCR) in the detection of variable region of DNA. Methods: A pair of special primer(WU,WD) was designed to amplify a fragment of HBV DNA P gene by PCR. Other 2 similar pairs of primer (MU1, MD1, MU2, MD2) were obtained by knocking off 1 or 2 bases at the 3′-terminal of WU and WD. (1) Special primers (WU, WD) and degeneracy primers(WU, WD, MU1, MU2, MD1, MD2) were used to amplify 27 samples respectively by PCR under the same condition. The sensitivity of each PCR was compared. (2) Using degeneracy primers, serum HBV DNA was amplified from 4 patients who were resistant to lamivudine. The PCR products were sequenced to evaluate the effect of the 3′-terminal mismatch of primers upon PCR. Results: (1) The sensitivity of special primers and degeneracy primers were 70.4%(19/27) and 85.2%(23/27) respectively (P<0.05). (2) The sequencing analysis of the PCR products suggested that the 3′-terminal mismatch of primers caused false negative in the PCR detection. Conclusion: When amplifying the variable region of DNA, the false negative result can be avoided by using 3′-terminus shifted degeneracy primers.