Effects of salicylic acid on synthesis of rosmarinic acid and related enzymes in the suspension cultures of Salvia miltiorrhiza
Rosmarinic acid (RA), a phenolic acid, is one of the important secondary metabolites produced in Salvia miltiorrhiza. To observe the influence of salicylic acid (SA), an elicitor, on the synthesis of RA and related enzymes, we treated the cell suspension cultures of S. miltiorrhiza with SA and L-a-aminooxy-beta-phenylpropionic acid (AOPP), a competitive inhibitor of tyrosine aminotransferase (TAT). Under this condition, the activities of related enzymes, such as phenylalanine ammonia-lyase and TAT were traced and assayed; the accumulative amount of RA was measured. The results showed that the PAL activity reached the peak at 4 h, 124% higher than that of the control, and the content of RA reached its maximum ((5.914 +/- 0.296) mg/g dry weight) at 8 h, after treated by 6.25 mg/L SA on day 6 of the suspension culture. The results of treatment with 0.1 micromol/L AOPP showed that AOPP affected little on the TAT activity, while the PAL activity was significantly influenced, with 44% lower than that of the control at 6 h. Meanwhile, the reduced accumulation of RA ((4.709 +/- 0.204) mg/g dry weight) paralleled with the decrease in PAL activity. The co-treatment by 0.1 micromol/L AOPP and 6.25 mg/L SA relieved the restriction imposed by AOPP on PAL, and made the cell cultures accumulate more RA than sole treatment with AOPP, indicated that SA induced the accumulation of RA in suspension cell culture of S. miltiorrhiza, and the rate-limiting effect of PAL was stronger than TAT.
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- "RA shows a great intensity for free radical scavenging and antioxidant activity. The phenylalanine ammonia-lyase (PAL) is the first enzyme for accumulating phenolic acid compounds in S. miltiorrhiza cell cultures , and SA could induce the production of rosmarinic acid . The aim of this work is to reveal the effects of SA and H2O2 on the accumulation of RA in S. miltiorrhiza cell cultures. "
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ABSTRACT: Salicylic acid (SA) is an elicitor to induce the biosynthesis of secondary metabolites in plant cells. Hydrogen peroxide (H2O2) plays an important role as a key signaling molecule in response to various stimuli and is involved in the accumulation of secondary metabolites. However, the relationship between them is unclear and their synergetic functions on accumulation of secondary metabolites are unknown. In this paper, the roles of SA and H2O2 in rosmarinic acid (RA) production in Salvia miltiorrhiza cell cultures were investigated. The results showed that SA significantly enhanced H2O2 production, phenylalanine ammonia-lyase (PAL) activity, and RA accumulation. Exogenous H2O2 could also promote PAL activity and enhance RA production. If H2O2 production was inhibited by NADPH oxidase inhibitor (IMD) or scavenged by quencher (DMTU), RA accumulation would be blocked. These results indicated that H2O2 is secondary messenger for signal transduction, which can be induced by SA, significantly and promotes RA accumulation.
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ABSTRACT: We studied the influence of the concentration of Ca2+ (0-50 mmol/L) in culture medium on the synthesis of rosmarinic acid (RA) and related enzymes in Salvia miltiorrhiza suspension cultures. Using verpamil (VP, a calcium channel antagonist) and ionophore A23187, we studied the mechanism of secondary metabolites of Salvia miltiorrhiza suspension cultures influenced by the concentration of Ca2+ in the culture medium. The synthesis of intracellular RA in 6-day incubation was significantly dependent on the medium Ca2+ concentration. At the optimal Ca2+ concentration of 10 mmol/L, a maximal RA content of 20.149 mg/g biomass dry weight was reached, which was about 37.3% and 20.4% higher than that at Ca2+ concentrations of 1 and 3 mmol/L, respectively. The variation of the activity of PAL and TAT, two key enzymes of the two branches of RA, could be affected by the concentration of Ca2+ in culture medium. The change of their activity occurred prior to the accumulation of RA, which suggested both of the key enzymes be involved in the synthesis of RA. Meanwhile, the enzymatic action of PAL was more distinct than TAT. The treatment of VP and A23187, respectively, indicated that the influence of RA affected by the concentration of Ca2+ in the culture medium was accomplished by the intracellular Ca2+, and the flow of Ca2+ from the extracellular to the intracellular environment could also participate in this process.
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ABSTRACT: We studied medium alkalinization in Salvia miltiorrhiza suspension cultures treated with salicylic acid and the effect of Ca2+ in this process through application of calcium channel antagonists (Verapamil, LaCl3, LiCl, 2-APB) and ionophore A23187. The results show that salicylic acid could induce significant medium alkalinization in S. miltiorrhiza culture. Verapamil and LaCl3 or LiCl and 2-APB, two different groups of calcium channel antagonist, significantly inhibited the medium alkalinization induced by salicylic acid. However, the suppression effect of verapamil or LaCl3 on medium alkalinization induced by salicylic acid was higher than that of LiCl or 2-APB. When two types of calcium channel inhibitor (LaCl3 and 2-APB) were used together, the medium alkalinization induced by salicylic acid was completely suppressed and even reduced the pH in medium. On the other hand, A23187 could promote the medium alkalinization. Based on the results above, we speculated that salicylic acid could induce significant medium alkalinization in S. miltiorrhiza culture, depending on the calcium from both extracell and intracell. Moreover, calcium from extracell plays a more dominant role in this process. Reveal of relationship in this research between Ca2+ and medium alkalinization can provide theory evidence for mechanism of the plant secondary metabolism.
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