Eliciting Effect of Catharanthine on the Biosynthesis of Vallesiachotamine and Isovallesiachotamine in Catharanthus roseus Cambial Meristematic Cells

Vallesiachotamine and isovallesiachotamine are pharmacologically active monoterpene indole alkaloids produced by Catharanthus roseus. However, the biosynthetic pathway for these two alkaloids has not been characterized. The results of our experiments demonstrated that catharanthine induced the biosynthesis of vallesiachotamine and isovallesiachotamine in C. roseus cambial meristematic cells (CMCs) in a time- and dosage-dependent manner. The highest yields of vallesiachotamine and isovallesiachotamine (i.e., 1.49 mg l−1 and 1.08 mg l−1, respectively) were observed in CMCs treated with 10 mg catharanthine l−1 for 12 h. The cells growth was inhibited by 20 mg catharanthine l−1 (i.e., 16.3% decrease in dry-cell weight). A quantitative reverse transcription polymerase chain reaction analysis revealed that catharanthine regulated the biosynthesis of vallesiachotamine and isovallesiachotamine by up-regulating the expression of specific genes, including STR (strictosidine synthase), SGD (strictosidine β-D-glucosidase) and ORCA3 (transcription factor octadecanoid-responsive Catharanthus AP2/ERF-domain 3). Finally, considering the up-regulated expression of STR and SGD was consistent with the accumulation of vallesiachotamine and isovallesiachotamine, a potential vallesiachotamine and isovallesiachotamine biosynthetic pathway was proposed.