Stimulation of betacyanin synthesis through exogenous methyl jasmonate and other elicitors in suspension-cultured cells ofPortulaca

Betacyanin production in suspension-cultured cells of Portulaca was significantly enhanced by both abiotic and biotic elicitors. Betacyanin levels increased 1.3 and 1.5-fold over the controls in the presence of two abiotic elicitors (20 μmol/L CuSO4 and 100 μmol/L FeEDTA) and increased 1.8 and 1.6-fold in the presence of two biotic elicitors (0.5 mg/L β-glucan and 0.5 mg/L chitosan). Maximum betacyanin synthesis with the two most effective elicitors was obtained when cultures were treated on day 1 and day 0 by β-glucan and FeEDTA, respectively. A concentration-dependent response was exhibited by cultures treated with exogenous methyl jasmonate (MJ). MJ alone at 0.1 μmol/L caused a 2.6-fold increase in betacyanin synthesis when administered to the suspension culture on day 3. However, no additive effect on betacyanin accumulation was observed in treatments, which combined MJ and β-glucan or FeEDTA. Treatment with ibuprofen (IB), an inhibitor of jasmonate biosynthesis, reduced the level of betacyanin in cells cultured in standard medium at all concentrations tested (25, 50, 100 μmol/L). The effect of IB on betacyanin synthesis in the cells treated with MJ or β-glucan, however, differed with the IB concentration applied. The two higher concentrations (50 and 100 μmol/L) of IB significantly reduced the betacyanin content while the lower concentration (25 μmol/L) did not show an adverse effect on the betacyanin enhancement triggered by MJ or β-glucan. Our findings suggest that, in suspension-cultured cells of Portulaca, an MJ-mediated signal transduction pathway prominently exists in betacyanin synthesis. This pathway seems to act antagonistically towards β-glucan-mediated signaling. As far as we know this is the first report on the elevation of betacyanin level by jasmonate or other elicitors in cell suspension cultures.