Hydrogen Peroxide and MAPK-Associated Responses During Methyl Jasmonate-Induced Elicitation of Terpenoid Indole Alkaloid in Catharanthus roseus Callus.

Methyl jasmonate (MeJA) is a commonly used elicitor for enhancing secondary metabolite production, including the anticancer terpenoid indole alkaloids (TIAs) vinblastine and vincristine. To investigate the physiological and molecular responses associated with MeJA-induced TIA accumulation, we examined the effect of different MeJA concentrations on vinblastine and vincristine production, gene expression and antioxidant defence in Catharanthus roseus calli. MeJA significantly enhanced relative growth and increased vinblastine and vincristine accumulation, with the highest increases observed at 50 μM MeJA, reaching 159.2% and 183.4% of control, respectively, and upregulated CrMPK3, STR, and DAT expression. The lower concentrations of MeJA showed higher H2O2 accumulation, DPPH free radical-scavenging and flavonoid content. Whereas increased lipid peroxidation and PAL enzyme activity were associated with the higher concentrations (100 and 200 μM). The upregulated expression of CrMPK3, together with the biosynthetic genes STR and DAT, supports the involvement of MAPK in signalling responses that mediate MeJA-elicited TIAs. Pearson correlation and principal component analysis showed that H2O2 accumulation was more closely associated with vinblastine and vincristine accumulation than with the expression of the investigated genes at the experimental time points. These findings suggest that H2O2 accumulation may be associated with downstream metabolic/redox processes accompanying alkaloid accumulation, although an earlier transient role of H2O2 in MeJA signalling cannot be excluded. The enhanced flavonoid accumulation and DPPH scavenging activity further suggest a role for antioxidant responses in maintaining redox homeostasis during MeJA-induced alkaloid accumulation.