Enhanced glucotropaeolin production in hairy root cultures of Tropaeolum majus L. by combining elicitation and precursor feeding

We have studied the effects of precursor amino acids (phenylalanine and cystein), elicitors (salicylic and acetylsalicylic acids, methyl jasmonate, beta-aminobutyric acid, yeast extract), PAL-inhibitor (1-amino-2-phenylethylphosphonic acid) applied alone or in combination on glucotropaeolin production and myrosinase activity in hairy root cultures of Tropaeolum majus. Short, 24-h treatment, and subsequent transfer of hairy roots to the fresh medium enabled avoiding detrimental effect of studied stimulators on biomass growth. In control cultures the highest glucotropaeolin content, 58.1 +/- 6.7 mg g(-1)DW, was detected on the 3rd day after transfer of the roots to the fresh medium but glucotropaeolin yield (mg 100 ml(-1) stop culture volume) had been increasing until the 9th day after transfer as a result of continuous biomass growth. Glucotropaeolin content and yield were 2-fold enhanced after treatment with precursor amino acids or PAL-inhibitor alone, but their combination additively led to 4-fold increase in glucotropaeolin production. Among the studied elicitors acetylsalicylic acid induced the highest, 3-fold increase in glucotropaeolin production, it also enhanced myrosinase activity, but to a smaller extend (by about 50%). Acetylsalicylic acid also potentiated induced by precursors, PAL-inhibitor, methyl jasmonate and yeast extract production of glucotropaeolin. The highest, 4.8-fold increase in glucotropaeolin production was found after combined acetylsalicylic acid and precursors treatment. Additive effect of acetylsalicylic acid-combined treatment on myrosinase activity was not detected. The obtained results indicate that amino acid precursors, phenylalanine and cystein, availability may be a limiting factor in the process of stimulation of glucotropaeolin production in T. majus hairy root cultures.