ABSTRACT
Objective: To select reference genes suitable for the expression analysis of Bupleurum chinense, and analyze the relationship between the content of saikosaponin and the gene expression of key enzymes in different tissues of B. chinense. Methods The roots, stems, leaves and fruits of B. chinense were used as test materials, and five commonly used internal reference genes of Actin, α-tubublin, β-tubulin, Cyclophilin and EF-1α were selected as candidates by real-time quantitative PCR. Based on the selected internal reference gences, tissue expression pattern of ACAT, FPS, HMGR, IPPI, PMD, PMK, SE, SS, β-AS, UGT1, UGT3, UGT6, UGT8, UGT10, P450-7 and P450-12 genes in B. chinense was analyzed. The content of saikosaponin a, saikosaponin c and saikosaponin d were determined by HPLC, and correlation analysis was performed by SPSS. Results:The EF-1α gene with the best stability in the five candidate genes (EF-1α, Cyclophilin, Actin, β-tubulin, α-tubublin) was selected as the internal reference gene. The expression levels of 16 key enzymes in the roots of B. chinense were measured. The results showed that ACAT, PMK, IPPI, SS, SE, UGT1, UGT3, UGT6, and UGT8 were the highest in the aboveground parts, the levels of HMGR, β-AS, P450-7 and P450-12 were higher in the roots than those in the aboveground parts, but PMD, FPS and UGT10 were not significantly different in the tissues. The content of saponins in the root was much higher than that in the aerial parts (stem, leaf and fruit) by HPLC. The results of correlation analysis showed that 16 key enzyme genes in the upstream ACAT, HMGR, PMD, SE and so on were significantly correlated with downstream P450-7, P450-12, UGT3, UGT6 and UGT8 (P < 0.05). It showed that the key enzyme genes were closely related to each other and regulated the synthesis of saikosaponin in common. The correlation analysis between the 16 key enzyme genes and the content of saikosaponin showed: HMGR, P450-7, p450-12 and the total of three saponins were significantly positively correlated (P < 0.01), and β-AS was significantly correlated with the total content of three saponins (P < 0.05), and HMGR, P450-7, P450-12, and β-AS were significantly correlated with the monomer saponins a, c, d (P < 0.05). These four genes jointly regulated the synthesis of saikosaponin and had an important effect on the accumulation of saponin. Conclusion:The HMGR, β-AS, P450-7 and P450-12 genes in the saikosaponin synthesis pathway have a consistent distribution in saikosaponin synthesis and play an important role in the regulation of saponin synthesis.
ABSTRACT
Objective: To select suitable references genes of Bupleurum scorzonerifolium for tissue expression analyses, and study the tissue expression characteristics of the key enzyme genes of saikosaponins biosynthesis. Methods: Five candidate reference genes including Actin, α-tubulin, β-tubulin, Cyclophilin, and EF-1α were chosen. The stability of these candidate reference genes was investigated by using four softwares (Delta CT, BestKeeper, NormFinder, and GeNorm). The stability of these candidate reference genes was tested and verified by real-time quantitative PCR. Used the stable reference gene, the tissue expression characteristics of the saikosaponins biosynthesis key enzyme genes (HMGR, IPPI, FPS, SS, and β-AS) was analyzed by qRT-PCR. Results: The average expression stability of the five candidate reference genes from high to low was β-tubulin > Cyclophilin > Actin > EF-1α > α-tubulin. Β-tubulin was the most suitable reference gene for tissue expression analysis in B. scorzonerifolium. HMGR expression level was roots > stems and fruits > leaves, IPPI expression level was roots > stems > fruits and leaves, FPS expression level was leaves > roots > stems and fruits, SS expression level was leaves > fruits > roots > stems, β-AS expression level was leaves > roots > fruits > stems. HMGR was significant positive correlated with IPPI, and FPS was significant positive correlated with β-AS (P < 0.05). Conclusion: β-tubulin gene was confirmed as the most suitable reference gene in different tissues of B. scorzonerifolium. It provided a methodological basis for the tissue expression analysis on the functional genes of B. scorzonerifolium. The expression pattern of five key enzyme genes of saikosaponins biosynthesis in different tissues had obvious differentiation, which might be involved in regulating the flow of saikosaponins synthesis and accumulation in various tissues of B. scorzonerifolium.
ABSTRACT
One strain of endophytic fungus ZPRa-R-1 was obtained for the capacity of promoting production of salidroside in Rhodiola crenulata. To explain the mechanism of salidroside biosynthesis in host plant, eight housekeeping genes were evaluated, and the evaluation method was created for the expression activities of four key enzyme genes PAL (phenylalanine ammonia-lyase), TyDC (tyrosine decarboxylase), TAT (tyrosine transaminase), UDPGT (UDP-glucosyltransferase) referenced double reference genes in biosynthesis pathway of salidroside in R. crenulata. Stabilities of housekeeping genes were confirmed by real-time fluorescent quantitative PCR technology and three softwares including geNorm, NormFinder and BestKeeper, then relative expressions of key enzyme genes were analysized by the 2-ΔΔCt method. The results showed that the most stable gene was GAPDH, followed by PCS, and the most appropriate reference of internal genes were combination with two genes in R. crenulata inoculated with endophytic fungus ZPRa-R-1. Under symbiosis conditions, regularity changes of key enzyme genes affected by endophytic fungus ZPRa-R-1 were as follows:the relative expression activity of PAL attached to peak value, which was 4.9 times as that of control group when inoculated ten days. The relative expression of TyDC reached the maximum value, which was 2.8 times of that control after inoculating 12 days. The relative expression of UDPGT actually reach 17.1 times than that of control after inoculating 8 days. However, the relative expression of TAT was not affected by this fungus. The changes of four key enzyme genes are positively correlated with the changes of salidroside content in R. crenulata.