Expression of CrMPK3 and alkaloid synthesis genes with antioxidants in callus of Catharanthus roseus in response to polyethylene glycol

Abstract

To improve the yield of secondary metabolites and understand the effects of PEG-induced drought stress on physiological and biochemical characteristics and the relationship between CrMPK3 and some genes of vinblastine biosynthesis pathway, PEG (0, 2.5%, 5%, and 10%) was applied in different exposure times (24 and 72 h) on callus of two cultivars (Alba and Rosea) of Catharanthus roseus. The increase in malondialdehyde and proline contents by increasing PEG concentration in both exposure times in Alba cultivar were more than in Rosea cultivar. Also, the activity of antioxidant enzymes including catalase (CAT), guaiacol peroxidase (GOPX), superoxide dismutase (SOD), glutathione peroxidase (GPX), and ascorbate peroxidase (APX) in the Alba cultivar was higher than the Rosea cultivar. The relative expression of vinblastine biosynthesis genes including STR, DAT, and PRX1 was significantly increased in both cultivars, especially in the medium with 5% PEG. However, the change of T16H gene expression was more minor. Vinblastine content confirmed the expression results of these genes at different concentrations of PEG after 24 and 72 h in both cultivars. The relative expression of CrMPK3 and catalase genes increased significantly in all media containing PEG. The highest expression of CrMPK3 and catalase genes was obtained after 24 and 72 h at 5% PEG in both cultivars, respectively. Finally, PEG can induce the accumulation of vinblastine in calli of C. roseus through a signaling pathway in which MAPK trigger the activation of antioxidant enzymes with up-regulation of the TIAs biosynthesis genes.