Correlation between content of saikosaponin and expression of key enzyme genes in different parts of Bupleurum chinense / 中草药

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.