WITHDRAWN: TcJAMYC: A bHLH transcription factor that activates paclitaxel biosynthetic pathway genes in yew

Abstract

Abstract:Paclitaxel (Taxol ®) is a highly modified diterpene anti-cancer agent produced by the gymnosperm Taxus. Taxus suspension cell cultures have the potential to provide a sustainable source of paclitaxel, but the paclitaxel biosynthetic pathway is not fully characterized, making metabolic engineering efforts difficult. Methyl jasmonate (MJ) is used to elicit paclitaxel production in suspension cultures. Here we show that the promoters of five genes encoding enzymes of the paclitaxel biosynthetic pathway are activated by MJ elicitation.Thus, elicitation of paclitaxel production by MJ is regulated at least in part at the level of transcription. A transcription factor that positively activates the promoters of paclitaxel biosynthetic genes has been cloned. This transcription factor, TcJAMYC, possesses a high degree of similarity to AtMYC2 and JAMYC2, which are known to regulate the expression of jasmonate inducible genes in other systems. TcJAMYC binds to E-boxes found in the promoters of the paclitaxel pathway genes, and these promoters are transiently activated by TcJAMYC overexpression. Addition of MJ attenuates the effect of TcJAMYC on the pathway promoters, suggesting that TcJAMYC could be engineered into Taxus cells to avoid the negative regulation of MJ-induced genes that follows initial MJinduced positive regulation.This strategy could prolong the expression of paclitaxel pathway genes, and increase paclitaxel production.

Regulatory Mechanisms of bHLH Transcription Factors in Plant Adaptive Responses to Various Abiotic Stresses

“…This cis-acting element is usually located in the promoter of genes involved in multiple physiological pathways. Nims et al (2009) found that the yew bHLH TcJAMYC can bind to the E-box in the promotor of paclitaxel-related genes to activate their transcriptional expression. Huang et al (2013) demonstrated that the Poncirus trifoliata PtrbHLH can bind to an E-box in the promoter region of the POD gene.…”