[Hydrogen peroxide is involved in the signal transduction of salicylic acid-induced salvianolic acid B biosynthesis in Salvia miltiorrhiza cell cultures]

Hydrogen peroxide (H2O2), one of reactive oxygen species, is widely generated in many biological systems, and it mediates various physiological and biochemical process in plants. To investigate the role of H2O2 as a signaling molecule in the process of salicylic acid (SA)-induced Salvianolic acid B (Sal B) accumulation, we separately inspected the cultured cells of Salvia miltiorrhiza with SA, H2O2, catalase (CAT), 2-(4-carboxy-2-phenyl)-4,4,5,5-tetramethylimidazoline-l-oxyl-3-oxide (DMTU) and Imidazole (IMD) to investigate the influence on the activity of phenylalanine ammonia-lyase (PAL) and tyrosine aminotransferase (TAT) and the accumulation of Sal B. Treatment of S. miltiorrhiza cells with SA resulted in an increase of H2O2, the increase of PAL and TAT and accumulation of Sal B. Exogenous application of 10-30 mmol/L H2O2 was found to effectively increase PAL and TAT activity as well as the Sal B content. CAT, a H2O2 scavenger, eliminated the Sal B-accumulating effects of exogenous H2O2 and SA. These indicated that H2O2 may serve as an upstream signaling molecule in the SA-induced accumulation of Sal B signal transduction pathway. Disposed by DMTU, a chemical trap for H2O2, as observed to be effective in inhibiting SA-induced accumulation of Sal B. IMD strongly inhibits the activity of NADPH oxidase, which is one of the main sources of H2O2 formation in plant cells. IMD treatment strongly inhibited the accumulation of Sal B in cultured cells of S. miltiorrhiza, but the effects of IMD, can be partially reversed by the exogenous SA. The accumulation of Sal B was blocked once the generation of H2O2 by NADPH oxidase was inhibited, and H2O2 served as signaling molecule mediated the SA-induced Sal B accumulation.