Jasmonic acid stimulates the oxidative responses and triterpene production in Jatropha curcas cell suspension cultures through mevalonate as biosynthetic precursor

Abstract

Jatropha curcas has considerable potential for production of biodiesel and secondary metabolites with medicinal uses. Herein, J. curcas cell suspension cultures were established to study the effect of jasmonic acid (JA) elicitation on triterpene production and oxidative responses. Cell cultures grown in dark conditions reached maximum biomass accumulation at the 12th day of culture (14.3 ± 0.45 g DW L⁻¹) with a specific growth rate μ = 0.131 d⁻¹. Elicitation with JA (200 or 400 μM) on 4-days-old cell cultures caused reduction in biomass and triterpene contents. In contrast, application of 200 μM JA at the 7th day of culture triggered triterpene accumulation by three times (1180 ± 12.3 μg g⁻¹ DW, at day 2) with respect to control, without significant changes in biomass and viability. After 2 days of elicitation, betulin increased up to 7.3-fold (from 110.6 ± 20.7 to 808.7 ± 55.4 μg g⁻¹ DW), while betulinic acid reached the maximum amount at day 6 after elicitation (245.6 ± 3.7 to 835 ± 41.5 μg g⁻¹ DW). Lupeol presented a moderate increase (167.9 ± 51.0–288.8 ± 7.3 μg g⁻¹ DW) along 8 days after elicitation. In correlation with triterpene production, JA application induced oxidative responses evaluated by an increase in the H₂O₂ levels up to three times and of malondialdehyde by 59 %. At day 4 after elicitation, catalase showed higher increase (122 %) than peroxidases (63 %) and ascorbate peroxidase (26 %). Incorporation of radioactive labels from (R,S)-[2-¹⁴C]mevalonic acid in triterpenes and sterols confirmed its role as metabolic precursor.