Catharanthus roseus is known as the only source for the low- abundance anticancer agents namely vinblastine and vincristine. Fine tuning of accumulation of such secondary metabolites is highly governed by the regulatory genes. Among these genes,Catharanthus roseus MYC1(CrMYC1) is known as one of the key transcription factors regulating the biosynthesis of terpenoid indole alkaloid metabolites in C. roseus. In this study, CrMYC1 coding sequence (AF283506) was isolated and cloned in PBI121 plant binary vector. Then, CRMYC1 was transiently overexpressed in C. roseus leaves using agroinfiltration method. In addition to molecular analysis for confirming CrMYC1 overexpression, the profile of some chief terpenoid indole alkaloids in control and transgenic plants was evaluated by HPLC to elucidate the role of CrMYC1 in an increased in the anticancer components. The results indicated that overexpression of CrMYC1 transcription factor can increase most important terpenoid indole alkaloids including vinblastine, vincristine, and catharanthine in C. roseus . HPLC analysis of catharanthine and vinblastine contents showed about 3 and 2.5 fold increases, respectively, while the increase in vinecristine was not significant compared to that of the control. Therefore, CrMYC1 is introduced as an efficient candidate for manipulating TIA pathway in C. roseus and increasing at least the most valuable terpenoid indole alkaloids in this plant.

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