Effect of Strong Light Stress on Growth, Physiological and Biochemical and Gene Expression of Key Enzymes in Atractylodes lancea / 中国实验方剂学杂志

Objective::To explore the effect of strong light stress on the growth, physiological and biochemical and key enzyme gene expression of the Atractylodes lancea, in order to provide the scientific basis for the standardized cultivation of the A. lancea. Method::The two-year-old A. lancea seedlings were taken as experimental materials. Poplar forest (light transmittance between 18.26%-36.04%) was taken as control group(ck). Different density shading networks were used to simulate different degrees of high light stress (51.10%, 80.73%, 100%) in late July. The growth state of A. lancea was observed. On the 0th, 5th, 10th, 15th, 20th days, the physiological and biochemical indexes of malondialdehyde (MDA) content, cell membrane permeability, proline (Pro) content, antioxidant enzyme activity and chlorophyll content in the leaves of A. lancea were measured. The relative expression levels of 3-hydroxy-3-methylglutarate monoacyl coenzyme A reductase (3-hydroxy-3-methylglutaryl coenzyme A, HMGR) and farnesyl pyrophosphate synthase gene (farnesyl pyrophosphate synthase, FPPS) in leaves of A. lancea under intense light stress were determined by real-time fluorescence quantitative PCR(Real-time PCR). Result::After strong light stress, the color of the leaves of A. lancea changed from dark green to light green and yellowish green, and the burn of leaves became more and more serious. The contents of MDA, conductivity and Pro showed an upward trend with the increase of transmittance. Peroxidase (POD), superoxide dismutase (SOD) and catalase (CAT) tended to increase first and then decrease. The chlorophyll content decreased with the increase of light transmittance. The relative expression of HMGR in leaves of A. lancea decreased with the increase of light transmittance, while FPPS increased first and then decreased. Conclusion::The results showed that A. lanceaa could alleviate the inhibition of strong light stress by increasing the activity of antioxidant enzymes and regulating the content of osmotic pressure under certain strong light stress. Excessively strong intensity light stress leads to disequilibrium of metabolic mechanism of A. lancea, and seriously inhibits the plant growth.

Prokaryotic expression, function verification and immunoassay activity of farnesyl pyrophosphate synthase of Alisma orientale (Sam.) Juzep / 药学学报

Farnesyl pyrophosphate synthase of Alisma orientale (Sam.) Juzep. (AoFPPS) is considered as one of the important rate-limiting enzymes in the biosynthetic pathway of protostane triterpenes. In order to investigate the expression and function of AoFPPS, the gene (accession No. HQ724508) was cloned into a bacterial expression vector pCzn1, then the combined plasmid pCzn1-AoFPPS was transformed into Escherichia coli BL21, and a fusion protein was obtained after induction. The fusion protein was purified by Ni resin, and the function was verified through in vitro enzymatic reaction. High performance liquid chromatography (HPLC) analysis revealed that the products were able to catalyze the synthesis of farnesyl pyrophosphate (FPP). High purity recombinant protein was used to immunize New Zealand rabbits to generate a polyclonal antibody. The titer of the antibody was determined by enzyme linked immunosorbent assay (ELISA), and Western blot results demonstrated that the antibody could specifically recognize the AoFPPS protein in A. orientale (Sam.) Juzep. So,the method of rapid immunoassay to detect AoFPPS was established. This study lays the foundation for further study of the AoFPPS gene expression, regulation and mechanism of action in A. orientale (Sam.) Juzep., and it also provides a scientific basis on improving the quality of Alismatis Rhizoma using the plant genetic engineering.

Prokaryotic expression, functional identification of squalene synthase in Alisma orientale and its immunoassay study / 中国中药杂志

Squalene synthase of Alisma orientale catalyzes farnesyl diphosphate (FPP) to form squalene, which is the key regulatory enzyme of the carbon source flow to protostane triterpenes biosynthesis. For further research on the function and expression of AoSS gene, the open reading frame (ORF) of squalene synthase gene (accession no. JX866770) from A. orientale was subcloned into a prokaryotic expression vector pCzn1 and induced the expression of AoSS gene in Escherichia coli BL21(Roseta). The fusion protein was mainly in the form of inclusion bodies and purified to obtain high purity protein. By verifying its functionality through vitro enzymatic reaction, the results showed that the catalytic protein had the catalytic activity of FPP into squalene. In order to research the expression of AoSS in A. orientale, the purified protein was used to immunized rabbits to prepare polyclonal antibody which was then purified, the titer of the antibody was greater than 1∶51 200 by ELISA detection, and displayed good specificity by Western blotting. The prepared antibody was used for immunoassay of AoSS in different organs of A. orientale, and the results showed that the AoSS expression level was the highest in tubers, followed by leaves, and lowest in root. Successful construction of prokaryotic expression vector, validation of gene functions and establishment of rapid immunoassay lay the foundation for further researches on the function and regulation of AoSS gene, and also provide scientific basis on the application of the protostane triterpenes of A. orientale in the field of synthetic biology.

Molecular cloning of farnesyl pyrophosphate synthase from Alisma orientale (Sam.) Juzep. and its distribution pattern and bioinformatics analysis / 药学学报

Triterpenes, which have large application potential in the treatment of cancer, are the main active components of genuine medicinal material Alisma orientale (Sam.) Juzep. Farnesyl pyrophosphate synthase (FPPS) is one of the important rate-limiting enzymes in the synthetic pathway of triterpenes. In this study the FPPS full length cDNA of the A. orientale, was cloned via homology-based cloning approach and rapid amplification of cDNA ends (RACE). The full length of the FPPS cDNA was 1 531 bp (accession no. HQ724508), which contained a full 1 032 bp ORF that encoded 343 amino acids. The deduced protein sequence exhibited five conserved motifs, two of which is riched of Asp (DDXXD). The result of real-time quantitative PCR (QRT-PCR) showed that FPPS gene was expressed in different organs of A. orientale. The expression increased from October to the first ten-day period of December, and then decreased. The FPPS gene expression was higher in leaves but lower in leafstalk, tuber and root. HPLC analysis of active components 23-acetyl-alismol B of A. orientale. during different periods indicated that its change trend should be consistent with FPPS gene expression. It can be primarily deduced that FPPS gene should be an important control point in the synthetic pathway of Alisma terpenes. This study may facilitate the quality of medicinal plants through gene engineering in the future.