TcJAMYC5 positively regulates paclitaxel biosynthesis in Taxus chinensis var. Mairei

Paclitaxel is an important natural anticancer drug. Its biosynthesis is very complex and 18 enzymes likely involved have been characterized. However, the regulatory mechanism of these enzyme genes still remains to be elucidated. Here we identified a novel transcription factor in the MYC family of Taxus chinensis TcJAMYC5 function in paclitaxel biosynthesis. TcJAMYC5 was highly expressed in the roots and regulated by MeJA. Transient overexpression of TcJAMYC5 in T. chinensis cambial meristematic cells resulted in a significant increase in paclitaxel and bacctin III content and upregulated expression of nearly all of paclitaxel biosynthesis related genes except T13αOH. Suppression of TcJAMYC5 expression in cambial meristematic cells resulted in a significant decrease in paclitaxel content. TcJAMYC5 could bind to promoters of paclitaxel biosynthesis pathway enzyme genes TASY, DBTNBT and T5αH for directly activating their expression. Taken together, we conclude that TcJAMYC5 is an activator that improves the accumulation of paclitaxel in T. chinensis through a MeJA-medicated signaling pathway.