Candidatus Phytoplasma Aurantifolia Affects the TIA Pathway Genes and Metabolites Temporally in Catharanthus Roseus

Catharanthus roseus as an exclusive producer of rare terpenoid indole alkaloids (TIA) is considered as one of the main sources for the production of anticancer agents like vinblastine through the TIA pathway. It also produces some other important metabolites such as ajmalicine with anti-hypertension activity. According to low yield of important indole alkaloids, TIAs enrichment by use of elicitors are highly marked in research and industry. Due to high potential of biotic elicitors in stimulating the overaccumulation of secondary metabolites, we aimed to explore the feasibility of using phytoplasma and study its temporal effect on the chief TIA pathway genes and alkaloids in C. roseus leaves at 15, 30, 45 and 60- days post infection. Artificial infection was done through lateral transplantation of infected scion with Candidatus Phytoplasma aurantifolia on healthy plants. The infection was confirmed as the phenotypical symptoms appeared on plants by PCR. Afterward, the expression analysis of STR, SGD, DAT and Prx1 genes were performed by qRT-PCR. Moreover, the accumulation of related TIAs including ajmalicine, catharanthine and vinblastine were analyzed by use of HPLC technique. The results showed the enhanced expression of STR(~ 4.7-fold), SGD(~ 8.5-folds), DAT(7-folds) and Prx1(~ 3.5 fold) at different time points compared to healthy control plants. Nevertheless, the biochemical analysis approved the overaccumulation of ajmalicine (0.13 mg/g DW), Catharanthine (0.77 mg/g DW) and vinblastine (0.2 mg/g DW) at 45, 60- and 30-days post infection. In conclusion, phytoplasma as a potent biotic elicitor affects positively on TIA pathway genes and alkaloids in C. roseus leaves. However, its effect is temporally depended.